ANALYSIS OF ALTERNATIVES non-confidential report · ANALYSIS OF ALTERNATIVES . ANALYSIS OF...

ANALYSIS OF ALTERNATIVES


non-confidential report

Legal name of applicants: Hoogovens Court Roll Surface Technologies V.O.F.

WAVEC GmbH

Trattamento Cilindri Laminazione S.r.l.

Walzen-Service-Center GmbH

NORD CHROME SAS

RHENAROLL SA

Texturing Technology Limited

NC POLAND Sp.z. o.o.

Submitted by: Hoogovens Court Roll Surface Technologies V.O.F.

Substance: Chromium trioxide, EC No: 215-607-8, CAS No: 1333-82-0

Use title: Functional chrome plating of work rolls used in the steel and

aluminium industry

Use number: 1


Use number:1 Copy right protected – No copying / use allowed i

Disclaimer This document shall not be construed as expressly or implicitly granting a license or any rights to use related to any content or information contained therein. In no event shall applicant be liable in this respect for any damage arising out or in connection with access, use of any content or information contained therein despite the lack of approval to do so.


Use number:1 Copy right protected – No copying / use allowed ii

CONTENTS 1. SUMMARY 1 2. INTRODUCTION .................................................................................................................................................. 10

2.1. The substance ................................................................................................................................... 10 2.2. Use of chromium trioxide in work rolls of metal cold rolling mills ................................................. 10 2.2.1. Flat metal production ............................................................................................................................... 11 2.2.2. Setup of rolling mills ............................................................................................................................... 14 2.2.3. Categories of metal rolling mills ............................................................................................................. 17 2.3. Purpose and benefits of chromium trioxide based chrome coatings of work rolls ........................... 17

3. FUNCTIONAL CHROME PLATING ................................................................................................................... 19 3.1. Functional chrome plating process ................................................................................................... 19 3.1.1. Pre-treatment ........................................................................................................................................... 19 3.1.2. Main treatment......................................................................................................................................... 20 3.1.3. Post-treatment .......................................................................................................................................... 21 3.2. Key functionalities of functional chrome plating ............................................................................. 21 3.2.1. Key functionalities of chromium trioxide based surface pre-treatment ................................................... 21 3.2.2. Key functionalities of metallic chrome coatings ..................................................................................... 22

4. ANNUAL TONNAGE............................................................................................................................................ 30 4.1. Annual tonnage band of chromium trioxide ..................................................................................... 30

5. GENERAL OVERVIEW OF THE ALTERNATIVE DEVELOPMENT AND APPROVAL PROCESS ............ 31 6. IDENTIFICATION OF POSSIBLE ALTERNATIVES ......................................................................................... 36

6.1. Description of efforts made to identify possible alternatives ........................................................... 36 6.1.1. Research and development ...................................................................................................................... 36 6.1.2. Data searches ........................................................................................................................................... 39 6.1.3. Consultations ........................................................................................................................................... 39 6.2. List of possible alternatives .............................................................................................................. 39

7. SUITABILITY AND AVAILABILITY OF POSSIBLE ALTERNATIVES ......................................................... 41 7.1. Concept 1: Work rolls with alternative properties ...................................................................... 41 7.1.1. Alternative 1: Alternative forged steel work roll grades.......................................................................... 42 7.1.2. Alternative 2: Alternative cast steel work roll grades .............................................................................. 53 7.1.3. Alternative 3: Fine micro-structured rolls ............................................................................................... 56 7.2. Concept 2: Alternative coating or surface treatment technology ............................................... 74 7.2.1. Alternative 4: Trivalent chrome plating................................................................................................... 75 7.2.2. Alternative 5: Electro and electroless deposition processes .................................................................... 78 7.2.3. Alternative 6: Nickel and nickel alloy electroplating .............................................................................. 82 7.2.4. Alternative 7: Nanocrystalline cobalt phosphorus alloy coating ............................................................. 86 7.2.5. Alternative 8: High velocity thermal process .......................................................................................... 88 7.2.6. Alternative 6: Electrical Discharge Coating (EDC) ................................................................................. 92 7.3. Pre-treatment .................................................................................................................................... 96 7.3.1. Mineral acids ........................................................................................................................................... 97

8. OVERALL CONCLUSIONS ON SUITABILITY AND AVAILABILITY OF POSSIBLE ALTERNATIVES FOR FUNCTIONAL CHROME PLATING ...................................................................... 100

9. REFERENCE LIST ................................................................................................................................................ 104 APPENDIX 1 – MASTERLIST OF ALTERNATIVES WITH CLASSIFICATION INTO CATEGORIES 1-3

AND SHORT SUMMARY OF THE REASON FOR CLASSIFICATION OF ALTERNATIVES INTO CATEGORY 3 (SELECTION PROCESS) ....................................................................................................... 107

APPENDIX 2 – INFORMATION ON SUBSTANCES USED IN ALTERNATIVES ............................................... 110 APPENDIX 2.1: (SEMI-) HIGH SPEED STEEL ((S)HSS) ........................................................................................ 110 APPENDIX 2.2: LASER CLADDING ........................................................................................................................ 110 APPENDIX 2.3: TRIVALENT CHROME PLATING ................................................................................................ 111 APPENDIX 2.4: ELECTROLESS PLATING ............................................................................................................. 113 APPENDIX 2.5: NICKEL AND NICKEL ALLOY ELECTROPLATING ................................................................ 116 APPENDIX 2.6: NANOCRYSTALLINE COBALT PHOSPHORUS ALLOY COATING ....................................... 118 APPENDIX 2.7: HIGH VELOCITY THERMAL PROCESS ..................................................................................... 119 APPENDIX 2.8 - PRE-TREATMENTS: MINERAL ACIDS ..................................................................................... 120 APPENDIX 3 – SOURCES OF INFORMATION ....................................................................................................... 123


Use number:1 Copy right protected – No copying / use allowed iii

List of Tables:

Table 1: Technical deficiencies of potential alternatives. .......................................................................................... 8 Table 2: Substance of this AoA. .............................................................................................................................. 10 Table 3: Functionalities and benefits of functional chrome plating of work rolls. .................................................. 17 Table 4: Key functionalities of chromium trioxide based pre-treatment. ................................................................ 22 Table 5: Sector specific key functionalities of metallic chrome coatings. ............................................................... 22 Table 6: Surface cleanliness specifications of strip as-cold-rolled, before annealing (“Full Hard”) ....................... 25 Table 7: List of concepts and corresponding alternatives for replacing chromium trioxide. ................................... 40 Table 8: Summary of technical assessment of Concept 1 alternatives (CR: Cold rolling; HR: Hot rolling; TR:

Temper rolling). .......................................................................................................................................... 41 Table 9: Shares of alloyed elements in semi-HSS and HSS (Source: Gaspard et al., 2002a). ................................. 42 Table 10: Example chemical compositions of cast semi-HSS and HSS work rolls (Source: Tremea & Bellicini,

2010a). ........................................................................................................................................................ 53 Table 11: Summary of technical assessment of Concept 2 alternatives (CR: Cold rolling; HR: Hot rolling; TR:

Temper rolling). .......................................................................................................................................... 75 Table 12: Comparison of production costs of the coating: HVOF & functional chrome plating............................. 91 Table 13: Technical deficiencies of potential alternatives. .................................................................................... 102


Use number:1 Copy right protected – No copying / use allowed iv

List of Figures

Figure 1: Simplified overview of different steps that may be involved in functional chrome plating using chromium trioxide. ....................................................................................................................................... 2

Figure 2: Technology Readiness Levels (TRL) and Manufacturing Readiness Levels (MRL) of the five most advanced potential alternatives to functional chrome plating of work rolls in cold rolling (Blue), temper rolling (Yellow) and aluminium hot rolling (Red)........................................................................................ 4

Figure 3: Schematic of relevant steps of the chromium trioxide substitution process in cold and temper rolling metal mills .................................................................................................................................................... 7

Figure 4: Supply chain of chromium trioxide treated work rolls ............................................................................. 11 Figure 5: Plastic deformation and reduction of the flat metal. ................................................................................. 11 Figure 6: Conventional production route for steel strips, excluding steel for packaging applications (tinplate). .... 12 Figure 7: Production route for steel strips for packaging applications (tinplate). .................................................... 13 Figure 8: Aluminium hot rolling process chain from slab casting to packaging of the flat aluminium product. ..... 13 Figure 9: General setup of a mill stand (left) and a 4-high and a 6-high mill stand configuration (BUR: Backup

roll; IMR: Intermediate roll; WR: Work roll). ............................................................................................ 14 Figure 10: Roll operation in a 5-stand tandem mill. ................................................................................................ 15 Figure 11: Example of a cold mill (top) and a temper mill (bottom). ...................................................................... 16 Figure 12: Main data of a 5-stand (all 6 high) tandem cold rolling steel mill (WR= Work Roll; IMR=

Intermediate Roll; BUR= Backup Roll) (Source: Lackinger et al., 2002). ................................................. 16 Figure 13: Simplified overview of different steps that may be involved in functional chrome plating using

chromium trioxide. ..................................................................................................................................... 19 Figure 14: Roll hanging above the functional chrome plating tank (Source: HOCO-RST, 2014)........................... 20 Figure 15: Coolant/Lubricant application and plate-out in the rolling process. ....................................................... 25 Figure 16: Metallic chrome plated roughness (Ra= 2.6 µm) illustration and detailed view as photomicrographs

from a scanning electron microscope showing clearly visible cracks (Source: Hoco-RST, 2014). ............ 28 Figure 17: Overview of and interconnections between individual TRL and MRL as well as estimated time for

passing the respective stage. ....................................................................................................................... 32 Figure 18: Schematic of relevant steps of the chromium trioxide substitution process in cold and temper rolling

metal mills. ................................................................................................................................................. 35 Figure 19: Trials (T1-5) of forged HSS work rolls in the first two stands of a 5-stand cold rolling tandem mill

(steel grades: H300LA and MBW 1500, HSS = forged High Speed Steel rolls, SSt (HV) = standard forged 3% Cr rolls (chrome plated), S = stand (1-5)). ................................................................................ 43

Figure 20: Trials (T1-4) of forged Semi-HSS work rolls in the first two stands of a 5-stand cold rolling tandem mill (steel grades: T1 & T2: S320 and T3 & T4:; DC05, SHSS = forged Semi- High Speed Steel rolls, SSt (HV) = chrome plated standard forged 3% Cr rolls, S = stand (1-5)). ................................................. 44

Figure 21: Electrolytic cleaning line for flat metal products as distributed by Cockerill Maintenance & Ingénierie (Source: CMI Group website, http://www.cmigroupe.com/en/p/electrolytic-cleaning-lines) ... 45

Figure 22: Comparison of the microstructure of forged HSS and standard forged 1-6 % Cr work rolls (Source: Gaspard et al., 2011). .................................................................................................................................. 47

Figure 23: Microstructure of SHSS (M7C3 carbides 2-4%) left and HSS (M7C3 + MC carbides 8%) right (Source: Tremea and Bellicini, 2010a). ...................................................................................................... 54

Figure 24: Schematic of the Continuous Pouring for Cladding (CPC) Process (Source: Hashimoto et al., 2002). . 57 Figure 25: Comparison of the microstructure of CPC manufactured HSS and ESR casted forged 'conventional'

as well as HSS work roll grades (Hashimoto et al., 2002). ......................................................................... 58 Figure 26: Roughness retention of CPC, electro-slag re-melted (ESR) HSS and conventional 5 % Cr work rolls

for tinplate rolling (Source: Hashimoto et al., 2002). ................................................................................. 58 Figure 27: Hardness transect of a CPC treated High Speed Steel (HSS) work roll with a diameter of 580 mm

(Source: Hashimoto et al., 2002). ............................................................................................................... 59 Figure 28: Gas atomization of molten metal (left) and general scheme of a HIP furnace for metal powders

(right) (Source: EPMA, 2013). ................................................................................................................... 62 Figure 29: Principles of 'classical' ESR and ESR cladding (Source: Gaspard et al., 2002a; modified). .................. 67 Figure 30: Laser cladding process (Source: Lester et al., 2013). ............................................................................. 70


Use number:1 Copy right protected – No copying / use allowed v

Figure 31: Room temperature sliding wear tests of laser clad tungsten carbide and high carbon alloy cast steel (Lester, 2013, modified). ............................................................................................................................ 71

Figure 32: Roughness retention of different work roll surface treatments under pilot test temper rolling conditions (Source: Crahay et al., 2015). .................................................................................................... 89

Figure 33: Roughness retention of uncoated and chrome coated EDT work rolls as well as WC- and TiC- EDC work rolls in pilot trial mill testings (Source: Bröcking et al., 2015). ........................................................ 93


Use number:1 Copy right protected – No copying / use allowed vi

Abbreviations

AoA Analysis of Alternatives

Approx. Approximately

ASETSDefense Advanced Surface Engineering Technologies for a Sustainable Defense

CAS Chemical Abstracts Service

CHL Court Holdings Limited affiliates in Europe

CR Cold rolling

Cr(III) Trivalent Chromium

Cr(VI) Hexavalent Chromium

CSR Chemical Safety Report

CTAC Chromium Trioxide Authorisation Consortium

CVD Chemical Vapour Deposition

D-gun Detonation Gun

DLC Diamond Like Carbon

DoD Department of Defense

DU Downstream User

EC European Commission

EDT Electro Discharge Textured

EHS Environmental Health and Safety

EN European Norm

ESTCP Environmental Security Technology Certification Program

EU European Union

HCAT Hard Chrome Alternatives Team

HR Hot rolling

HSS High-Speed Steel

HV Vickers Hardness

HVAF High Velocity Air Fuel

HVOF High velocity oxy-fuel

ISO International Organization for Standardization

MRL Manufacturing Readiness Level

NDCEE National Center for Energy and Environment

OEM Original Equipment Manufacturer

PECVD Plasma Enhanced Chemical Vapour Deposition

PTFE Polytetrafluoroethylene

PVD Physical Vapour Deposition


Use number:1 Copy right protected – No copying / use allowed vii

R&D Research and Development

REACH Registration, Evaluation, Authorisation and Restriction of Chemicals

RoHS Restriction of Hazardous Substances

RPA Department for Environment, Food and Rural Affairs

SDS Safety Data Sheet

SEA Socio Economic Analysis

SHSS Semi High-Speed Steels

SVHC Substance of Very High Concern

TNO Netherlands Organisation for Applied Scientific Research

TR Temper rolling

TRL Technology Readiness Level

TSM Surface Treatment Mechanics, French company


Use number:1 Copy right protected – No copying / use allowed viii

Glossary

Term Definition

Adhesion Parameter describes the tendency of dissimilar particles or surfaces to cling to one another (for example adhesion of coating to substrate, adhesion of paint to coating and/or substrate).

Alternative Potential alternative provided to the respective industry sector for their evaluation.

Bath Typical method for surface treatment of parts. May also be referred to as dipping or immersion. None-bath methods include wiping, spraying, and pen application.

Chemical resistance Parameter is defined as the ability of solid materials to resist damage by chemical exposure.

Coating A coating is a covering that is applied to the surface of an object, usually referred to as the substrate. The purpose of applying the coating may be decorative, functional, or both.

Corrosion protection

Means applied to the metal surface to prevent or interrupt oxidation of the metal part leading to loss of material. This can be a metal conversion coating or anodizing, a pre-treatment, electrolytic or electroless metal/metal alloy coatings, paint, water repellent coating, sealant, liquid, adhesive or bonding material. The corrosion protection provides corrosion resistance to the surface.

Counterpart Structural zone (like assembly, component) to which a given assembly/part is fitted.

Court Holdings Limited

Court Holdings Limited encompasses, inter alia, eight entities in Europe, Nord Chrome S.A.S., Hoogovens Court Roll Surface Technologies V.O.F., Walzen Service Center GmbH, Rhenaroll S.A., Texturing Technology Limited, WAVEC GmbH Germany, Trattamento Cilindri Laminazione S.r.l. and Nord Chrome Poland Sp.z o.o..

Electroplating Electroplating is forming a metal coating on the part by an electrochemical method in an electrolyte containing metal ions and the part is the cathode, an appropriate anode is used and an electrical current is applied.

Etching

Process changing surface morphology as well as removing material. This is a pre-treatment step of the process chain preparing the surface before subsequent plating. This term has significant overlap with the term pickling. As there is no clear demarcation, the term etching is used to cover both etching and pickling as chromium trioxide pre-treatment in this document.

Functional chrome plating

An industrial use, meaning the electrochemical treatment of surfaces (typically metal) to deposit metallic chromium using a solution containing chromium trioxide (amongst other chemicals), to enhance wear resistance, tribological properties, anti-stick properties, corrosion resistance in combination with other important functional characteristics. Functional chrome plating may include use of chromium trioxide in pre-treatment and surface deposits unlimited in thickness but typically between 2 µm to 500 µm. Functional chrome coatings are widely used in many industry sectors.

Implementation After having passed qualification and certification, the third step is to implement or industrialize the qualified material or process in all relevant activities and operations of production, maintenance and the supply chain.

Main treatment The main treatment, functional chrome plating using chromium trioxide, occurs after the pre-treatment and before the post treatment.

Metallic chrome coating Resulting coating layer of the functional chrome plating process.


Use number:1 Copy right protected – No copying / use allowed ix

Term Definition

Pickling

Pickling is the removal of oxides or other compounds from a metal surface by chemical or electrochemical action. The term pickling is not used consistently within the surface finishing industry and is often referred to as the following processes: cleaning, scale removal, scale conditioning, deoxidizing, etching, and passivation of stainless steel. This term has overlap with the term Etching.

Plating Electrolytic process that applies a coating of metal on a substrate.

Post-treatment Post-treatment processes do not involve chromium trioxide and are performed after the main functional chrome plating process.

Pre-treatment Pre-treatment process using chromium trioxide to remove contaminants (e.g. oil, grease, dust), oxides and scale. The pre-treatment process must also provide chemically active surfaces for the subsequent treatment. (See also: Etching).

Process chain

A series of surface treatment process steps. The individual steps are not stand-alone processes. The processes work together as a system, and care should be taken not to assess without consideration of the other steps of the process. In assessing candidate alternatives for chromium trioxide, the whole process chain has to be taken into account

Temperature change resistance / heat resistance

The ability of a coating or substrate to withstand temperature changes and high temperatures.

Tribological properties

Tribological properties relate to friction, lubrication and wear on surfaces in relative motion and are important for moving machine parts.

Wear resistance / abrasion resistance

The ability of a coating to resist the gradual wearing caused by abrasion and friction.


Use number:1 Copy right protected – No copying / use allowed 1

1. SUMMARY

This Analysis of Alternatives (AoA) forms part of the Application for Authorisation (AfA) for the use of chromium trioxide in functional chrome plating of work rolls dedicated to the use in cold rolling (CR) and temper rolling (TR) mills for steel and aluminium, as well as hot rolling (HR) mills for aluminium. Applicants are the eight European entities of Court Holdings Limited, further referred to as 'the applicants' or 'CHL'.

Functional chrome plating using chromium trioxide is a surface treatment process that involves the deposition of a thin metallic chromium layer on the surface of a steel roll. This metallic chrome coating provides the roll with high mechanical and wear resistance as well as favourable tribological properties. Chrome coated rolls deliver high degrees of strip surface cleanliness during the cold and hot rolling process and desired strip surface roughness, texture and appearance in temper rolling operations. Furthermore, the zinc pick-up during rolling operations in hot dip galvanizing lines is lower for chrome coated rolls. The same applies for the aluminium oxide build-up during aluminium rolling operations. Although not each work roll of a metal mill is chrome coated, several rolling operations are reliant on chrome coated rolls, especially in the high quality flat metal segment. The process is therefore specified for particular applications where this combination of performance characteristics is critical. Functional chrome plated work rolls must perform under demanding conditions that involve rapid temperature changes, repetitive wear, very high mechanical contact forces and pressures as well as mechanical impact.

Please note that the use of functional chrome plated work rolls does not refer to the hot rolling of steel, for which they have never been used. Chrome plated work rolls are only used in cold and temper rolling operations for steel and aluminium products as well as for aluminium hot rolling.

40 tonnes of chromium trioxide is used in functional chrome plating per year within the scope of this AfA.

Functional chrome plating with chromium trioxide Surface treatments modify the surface of a substrate so that it performs better under conditions of use. Functional chrome plating using chromium trioxide involves the immersion of the work rolls in a series of treatment baths containing chemical solutions or rinses under specific operating conditions (Figure 1). Chromium trioxide is needed for the main treatment of functional chrome plating to ensure the highest quality of the product, and to meet the requirements of the customers of flat metal products. Chromium trioxide is also used in the (reverse) etching pre-treatment process, which is conducted in the same bath as the main plating process, to prepare the substrate. There are no post-treatment processes for functional chrome plating which involve chromium trioxide.



Figure 1: Simplified overview of different steps that may be involved in functional chrome plating using chromium trioxide.

The surface treatment steps (pre-treatment and main treatment) are inter-related so that they cannot be separated or individually modified without impairing the overall process or performance of the final product. Compatibility and technical performance of the overall system are of fundamental importance during material specification. As of today, no drop-in alternative to chromium trioxide in functional chrome plating, providing all the required properties to the surfaces of work rolls for steel and aluminium cold and temper rolling mills and for aluminium hot rolling mills in the scope of this application, is industrially available.

The characteristics of chromium trioxide, a detailed description of the plating process, and the key functionalities of the plated rolls are discussed in chapter 3.

Furthermore, functional chrome plating using chromium trioxide has been successively refined and improved as a result of many decades of research and experience in the sector, and reliable data is available to support its performance. Data available so far for potential alternatives does not support reliable conclusions regarding their performance as part of complex metal rolling operations, in demanding environments under real rolling conditions. The long-term performance of such potential alternatives can currently only be estimated.

Functional chrome plating is a specialist activity requiring trained personnel and a substantial investment in facilities. The plating shops act as suppliers to customers across the steel and aluminium sector, because it allows them to operate cost effectively and according to high standards.

This summary aims to briefly explain why the use of chromium trioxide in functional chrome plating of work rolls is essential to several metal rolling mills for flat metal production, and describes the steps and effort involved in finding and approving a replacement for chromium trioxide in these applications. A detailed evaluation of potential alternatives is s presented in chapters 6 and 7.

Functional chrome plated work rolls in cold, temper and aluminium hot rolling mills Chromium has been used since the beginning of the 1980s to provide work rolls in metal rolling mills with features to better perform under demanding rolling conditions with reasonable supplementary costs. Functional chrome plating based on chromium trioxide confers substantial advantage over potential alternatives. These include:

- Wear resistance delivering high degrees of roughness retention; - Hardness; - High surface cleanliness of the rolled metal strip; - Appropriate surface appearance of the flat metal product; - Mechanical resistance to incidents; - Stable tribological properties; - Adequate layer thickness to retain applied surface topographies; - Anti-stick properties, and low fatigue debit; - Supports lubrication (due to micro-cracking); - Fast treatment times; and - Good machinability.

The use of chrome coated work rolls with the above-mentioned key functionalities in various metal mills depends on the flat metal product to be rolled and the corresponding specifications matching the customers' requirements. Thereby, each individual metal mill is a well attuned system of several



mill stands, in which the work rolls are integrated (for a detailed description of the metal mill setup see chapter 2). The specifications to be guaranteed, especially regarding the surface cleanliness of cold rolled metal strips and the surface appearance of temper rolled metal strips, are achieved by the selective application of chrome coated work rolls. High wear resistance ensures the retention of the roll surface roughness along extensive rolling campaigns, thus reducing the need for work roll changes and re-work, which is of particular importance due to the immense roll turnover of hundreds to thousands at a single rolling mill per year.

Although not each cold, temper, or aluminium hot rolling mill is reliant on chrome coated work rolls for rolling flat metal in general, for various applications functional chrome coating is indispensable. This mainly refers to the high quality segments the European steel industry depends on to retain its global competitiveness. Highest possible degrees of strip surface cleanliness are essential for subsequent processing steps while the strip surface appearance in terms of brightness and homogeneity need to meet the requirements of ever growing customer demands of e.g. the automotive industry. Changes in the flat metal production would lead to differences in the product, while constant quality is highly requested. The flat metal products – steel and aluminium strips – are used in various different industrial sectors.

Identification and evaluation of potential alternatives An extensive literature survey and consultation was carried out, partly based on the Analysis of Alternatives (AoA) of the CTAC Consortium, to identify and evaluate potential alternatives to chromium trioxide in functional plating of work rolls. In total, 27 potential alternatives were identified. Six of these were clustered as 'concept 1', comprising alternatively manufactured work roll grades. 'Concept 2' encompasses another six potential alternatives, covering alternative coating or surface treatment technologies. The twelve (12) combined concept 1 and 2 alternatives are considered as being the "most promising" alternatives to chromium trioxide-based functional chrome plating, whereas none of those can be regarded an overall replacement. Concept 1 and 2 alternatives are discussed in detail in chapters 7.1 and 7.2.

The evaluation of the remaining 15 alternatives revealed major deficiencies regarding the technical feasibility, economic feasibility and/or the availability as well as the reduction of the overall risk in case of a replacement. Those alternatives are taken into account in Appendix 1, including clear-cut reasoning for screening those alternatives out, and are not discussed in detail.

Alternatives to the etching pre-treatment requiring chromium trioxide are assessed separately in chapter 7.3.1. A chromium trioxide free etching pre-treatment of metals (aluminium and its alloys) based on sulfo nitro ferric acid is commercially available and qualified for some applications and substrates, but not as general replacement for chromium trioxide pre-treatment. The development of a pre-treatment alternative to chromium trioxide depends on the potential alternative to functional chrome plating and is not a standalone process. While an alternative to functional chrome plating is investigated, adequate tailored pre-treatments are evaluated in parallel or after the potential alternatives for the main process has been qualified. Therefore, the time needed for R&D and industrial implementation of an alternative are identical for pre-treatment and main treatment which is a minimum of 12 years.

Table 1 at the end of this section summarises the main deficiencies of potential alternatives to the use of chromium trioxide in functional chrome plating of work rolls assessed in this AoA. Furthermore, Figure 2 depicts the Technology Readiness Level (TRL) as well as the Manufacturing Readiness Level (MRL) of the most advanced potential alternatives (for detailed information on TRL and MRL refer to chapter 5, and for the individual levels of the alternatives to the 'Availability' section of the respective alternative assessed). Please note that only TRL and MRL in combination determine the



overall readiness of a potential alternative, both, from the technological as well as from the manufacturing point of view. According to the OSD Manufacturing Technology Program (2011), manufacturing readiness being paced by technology readiness is not uncommon. The authors mention the manufacturing process to be unable "[…] to mature until the product technology and product design are stable". Therefore, for achieving certain MRL, the alternative should have matured to the associated TRL. In some cases, MRL of alternatives are already advanced, seemingly leapfrogging over respective TRLs. This may be the case when for potential alternatives advanced manufacturing readiness levels are demonstrated, but technical suitability for the applications relevant within this AoA is still lagging behind, thus requiring further development. However, none of the potential alternatives has passed TRL 7.1 yet. Therefore, no alternative assessed in this AoA is currently technically mature for replacing chromium trioxide-based functional chrome plating of work rolls in cold, temper and aluminium hot rolling mills. More than 12 additional years are necessary to reach combined technology and manufacturing readiness for any potential replacement.

Figure 2: Technology Readiness Levels (TRL) and Manufacturing Readiness Levels (MRL) of the five most advanced potential alternatives to functional chrome plating of work rolls in cold rolling (Blue), temper rolling (Yellow) and aluminium hot rolling (Red).

In summary, the analysis shows that there are no technically feasible alternatives to chromium trioxide-based functional chrome plating of work rolls for cold and temper mills, as well as aluminium hot rolling mills. Several potential alternatives are subject to ongoing R&D, but do not currently support the necessary combination of key functionalities to be considered technically feasible alternatives. Some alternatives (e.g. forged or cast (Semi-) High Speed Steels as well as CPC, PM HIP or ESR Cladding are qualified for individual cold rolling applications where less critical criteria



of performance requirements are sufficient but none has all the key properties of functional chrome plating with chromium trioxide in the totality of metal mill stands. Especially the issue of strip surface cleanliness in cold rolling and strip surface appearance in temper rolling is decisive for the difficulty in replacing functional chrome coated work rolls.

Several potential alternatives (e.g. forged HSS, Ti-enhanced and cast (S)HSS work roll grades) were already investigated in internal trials on the industrial mill scale. However, none could prove eligible to replace chrome plated work rolls in the entirety of applications. Identified potential alternatives need to be further developed, including trials in the laboratory, pilot mill and industrial mill scale (Figure 3). The subsequent adaptation of manufacturing processes and approval of the flat metal products take another 5 years minimum. Chrome plated work rolls are an integral part of the flat metal production, especially in the European high quality flat steel segment. The overall process of replacing chromium trioxide-based functional chrome plating – if ever possible – will take at least 12 additional years.

Review period Extensive evaluation of potential alternatives to chromium trioxide-based coating of work rolls in cold and temper steel rolling as well as hot aluminium rolling mills is carried out in the present AoA. Furthermore, economic aspects, as well as aspects of approval and release in flat metal industry are assessed with regard to a future substitution of the substance. The following key points are relevant for deriving the review period:

• No ready-to-use alternative is identified. R&D to identify such an alternative is ongoing, but time and cost intensive due to the fact that the potential alternative's technical feasibility needs to be proven at the industrial mill scale. Process and quality stability are required to be shown in long rolling campaigns and for individual mill types.

• None of the assessed potential alternatives have passed Technology Readiness Level (TRL) 7 yet, and thus have not been proven to be an adequate replacement for chromium trioxide-based functional chrome plating. Furthermore, none of the alternatives have reached Manufacturing Readiness Level (MRL) 10 yet. Based on experience and with reference to the status of R&D programs, alternatives are not foreseen to be commercially available at sufficient capacities for key applications and pre-treatment before 12 years after the sunset date.

• Investment cycles for metal rolling mills are in the range of 30 to 40 years. Major investments in e.g. cleaning lines to uphold competitiveness in the high quality market segments impair calculated long-term returns on investment. The use of chrome plated work rolls is the only opportunity to keep existing, in-service metal rolling mills operating (refer to SEA).

• The socio-economic impacts of a non-granted authorisation, amounting to 95.3 million Euro related to foregone added value for the applicants themselves, 1.2 million Euro related to social impacts due to additional costs to society for unemployment, and 5.7 billion Euro per year for impacts on downstream users (rolling mills), outweigh by far the monetised residual risk to human health and the environment of a granted authorisation of 3.25 million Euro (refer to the SEA).

As a consequence of the above–mentioned key points, a review period of 12 years is selected because it coincides with best case estimates (by the applicants and their customers from the steel and aluminium industry) of the schedule required to industrialise alternatives to chromium trioxide in cold



and temper rolling mills for flat steel and aluminium products, as well as hot rolling mills for aluminium products, if ever possible.



Figure 3: Schematic of relevant steps of the chromium trioxide substitution process in cold and temper rolling metal mills



Table 1: Technical deficiencies of potential alternatives.

Section Alternative Concept Major deficiencies

7.1.1 Alternative forged steel work roll grades /(Semi-) High-Speed Steel /Ti-enhanced

1

- hardness - surface cleanliness - surface appearance - topography - machinability - treatment time - Tempering temperature - economically not feasible

7.1.2 Alternative cast steel work roll grades /(Semi-) High-Speed Steel 1

- hardness - surface cleanliness - surface appearance - topography - machinability - treatment time

7.1.3 Continuous Pouring for Cladding (CPC) 1

- hardness - topography - surface morphology - machinability - treatment time - economically not feasible - not available on the European market

7.1.3 Powder Metallurgy-based Hot Isostatic Pressing (PM HIP) 1

- surface appearance - topography - machinability - treatment time - economically not feasible - large rolls not available

7.1.3 Electro-Slag Remelting Cladding (ESR Cladding) 1

- hardness - surface cleanliness - topography - machinability - treatment time - not available

7.1.3 Laser Cladding 1 - laser cladding as alternate

manufacturing method not available - low technical readiness level

7.2.3.1 Trivalent Chrome Plating 2

- wear resistance - hardness - adhesion to the substrate - low technical readiness level

7.2.4.1 Electroless nickel plating 2

- wear resistance - hardness - adhesion to the substrate - resistance to process conditions


Use number: 1 Copy right protected – No copying / use allowed 9

Section Alternative Concept Major deficiencies - treatment time

- low technical readiness level - soluble nickel compounds may meet

the SVHC criteria under REACH

7.4.1.2 Nickel & nickel alloy electroplating 2

- wear resistance - hardness - surface cleanliness - economically not feasible - soluble nickel compounds may meet

the SVHC criteria under REACH

.2.4.3 (Nano) Co-P plating 2

- wear resistance - hardness - treatment time - cobalt compounds listed on the

REACH candidate list - low technical readiness level

7.2.4.4 High velocity thermal processes 2

- topography - adequate layer thickness - resistance to process conditions - surface morphology - treatment time - economically not feasible - low technical readiness level

7.2.5 Electrical Discharge Coating (EDC) 2

- surface appearance - topography - surface morphology - treatment time - not applicable to work rolls of cold

rolling mills



2. INTRODUCTION

The scope of the present AoA is the use of Chromium trioxide for functional chrome plating of work rolls in metal cold rolling (CR) and temper rolling (TR) mills for the production of flat steel and aluminium products, and additionally in hot rolling (HR) mills for flat aluminium products. Applicants are the eight European entities of Court Holdings Limited, further referred to as 'the applicants' or 'CHL'. In the following chapters, the substance is characterized (chapter 2.1), its use in the coating of work rolls for different metal mills is depicted (chapter 2.2) and the purpose and benefits of metallic chrome coatings for these applications is described (chapter 2.3).

2.1. The substance The substance characterized in Table 2 is subject to this AoA:

Table 2: Substance of this AoA.

Substance Intrinsic property(ies)1 Latest application date2 Sunset date3

Chromium trioxide, CrO3 EC No: 215-607-8 CAS No: 1333-82-0

Carcinogenic (category 1A) Mutagenic (category 1B)

21 March 2016 21 September 2017

1 Referred to in Article 57 of Regulation (EC) No. 1907/2006 ² Date referred to in Article 58(1)(c)(ii) of Regulation (EC) No. 1907/2006 3 Date referred to in Article 58(1)(c)(i) of Regulation (EC) No. 1907/2006

Chromium trioxide is categorized as a Substance of Very High Concern (SVHC) and is listed on Annex XIV of Regulation (EC) No 1907/2006. Adverse effects are evaluated in detail in the chemical safety report (CSR).

2.2. Use of chromium trioxide in work rolls of metal cold rolling mills CHL uses chromium trioxide for functional chrome plating of work rolls that are crucial for the steel and aluminium processing industry. These mills are dedicated to the hot, cold and temper rolling of flat metal products. Please note that the use of functional chrome plated work rolls does not refer to the hot rolling of steel, for which they have never been used. Chrome plated work rolls are only used in cold and temper rolling operations for steel and aluminium products as well as for aluminium hot rolling. The processes including chromium trioxide for functional chrome plating of work rolls – usually high-alloyed steels – are:

- Pre-treatment etching and functional cleaning of the substrate surface; and - Applying a metallic chrome coating in the main treatment process to the work rolls to

enhance wear resistance, metal strip surface cleanliness, surface appearances and tribological properties in combination with other important functional characteristics.

CHL maintains more than 100,000 rolls for European customers every year. The following Figure 4 illustrates the supply chain of chromium trioxide treated work rolls between CHL and its customers. Please note that the present AfA refers to the use of chromium trioxide in the work roll preparing roll shop. Prepared rolls, which do not contain any Cr(VI), are delivered to the steel and aluminium processing industry for the use in metal rolling mills. Produced flat metal in the form of strips or coiled strips are further used by downstream users (DU) of miscellaneous industry sectors e.g. the automotive, packaging or construction industry. Applications include automotive components, bathtubs, food containers, construction and building components, domestic appliances and many others.



Figure 4: Supply chain of chromium trioxide treated work rolls

In order to assess possible alternatives to chromium trioxide for functional chrome plating of work rolls, the following section provides background information on flat metal production including crucial properties and parameters which provide the desired function.

Therefore, in Section 2.2.1. provides a general overview of the production and the different process steps involved. The general setup of steel mills is depicted and the role of chrome coated work rolls is highlighted. Most of these setups are valid for the non-ferrous rolling industry as well.

2.2.1. Flat metal production

Processing of metals comprises a variety of different processes for different applications and shapes as well as corresponding machinery. As indicated, the rolling of flat metal, for shaping and reduction of the gauge of raw metal (Figure 5), is subject to the present AfA.

Figure 5: Plastic deformation and reduction of the flat metal.

For the production of flat metal products, the metal is processed in metal mills producing continuous flat metal, the so-called metal strips, which are coiled up and dedicated to miscellaneous applications, such as e.g. sheet metal in the automotive industry or as packaging steel. In general, rolling of metal can be performed by two different procedures: hot rolling and cold rolling. Thereby, hot rolling refers



to the rolling of metals above the metals' recrystallization temperature, while cold rolling is carried out belowthe metals' recrystallization temperature. . The chrome coated work rolls used in the following process steps for the production of steel and aluminium strips are subject to this AoA.

Hot rolling is always used as a first step in the flat metal production line to shape the metal and reduce its thickness. For several applications, where only moderate gauges are requested (e.g. steel for yellow goods, such as heavy machinery), hot rolling is sufficient and only followed by a pickling step to remove oxides originating from the hot rolling process. Thereafter, the hot rolled metal strips are coiled and further processed. In the present AoA, only the hot rolling of aluminium is relevant, since work rolls in steel hot rolling have never been chrome plated.

Cold rolling of metal results in thinner gauges and improved surface finishes. In addition to that, tighter specifications in terms of dimensional accuracy can be met since shrinking due to cool down effects are avoided by rolling the metal at room temperature. In principle, cold rolling is applied subsequent to hot rolling and pickling. It is used for several applications where additional requirements are to be met, in particular concerning the thickness. Sheet metal for the automotive industry or packaging steels, dedicated to white goods like washing machines or bath tubs, are examples.

Temper rolling of metal strips is carried out after the annealing step mainly due to quality-related considerations. By temper rolling of cold rolled metal, the strip is elongated. Temper rolling ensures the strength and ductility of the product within the customers' specifications. Furthermore, temper rolling eliminates the susceptibility of undesired so-called "Lüder bands" impairing further forming processes on the customers' side. In addition to that, topographical specifications can be established. Thereby, the surface texture of the work roll is transferred to the metal strip during the rolling process. By temper rolling, specific requirements for optimized further processing, gloss, brilliance or paint appearance are met. Furthermore, temper rolling of metal strips improves the strip flatness and shape.

Figure 6: Conventional production route for steel strips, excluding steel for packaging applications (tinplate).

The conventional production route starts with the metal in liquid form and its subsequent continuous casting (Figure 6Error! Reference source not found.). The production routes for the different flat metal products vary. In case of packaging steels, the production route includes an additional cleaning step after cold rolling (Figure 7). The annealed metal strips are either temper rolled or passed through a



double cold reduction mill to produce e.g. tin plate. Double cold reduction mills combine cold rolling and temper rolling steps. The strips are packed on coils after electrolytic coating ("tinning").

In aluminium hot rolling, the continuous casting process is rather exceptional. The aluminium rolling industry makes use of (discontinuous) casting of so-called slabs. However, there is no implication concerning the use of chrome plated work rolls from that point of view. Cast aluminium slabs are pre-annealed and rolled in a single-stand breakdown mill in the first place and subsequently hot rolled in a tandem mill (Figure 8).

Concerning cold rolling operations of flat aluminium products, the process is in general similar to the above mentioned steel cold rolling process (Figure 6), except hot dip galvanising is never conducted. As mentioned above, cold rolling operations are conducted below the recrystallization temperature of the metal. The metal is plastically deformed which results in hardening of the strip. The strength is thereby increased via strain hardening by up to 20%. Processing the metal below its recrystallization temperature, results in a lower reduction in thickness per mill pass compared to hot rolling.

The absolute reduction in thickness during the cold rolling of metal is called the 'draft', expressed in mm, while the relative difference is the so-called 'rolling reduction'. The typical rolling reduction per single rolling pass is up to approx. 30% in case of sheet metal (all sectors except for packaging steel) and approx. 40% for cold rolled tinplate dedicated to packaging. However, in extraordinary cases and more commonly in aluminium rolling, up to 60% rolling reduction in a single pass may be reached.

Figure 7: Production route for steel strips for packaging applications (tinplate).

Figure 8: Aluminium hot rolling process chain from slab casting to packaging of the flat aluminium product.



To retain ductility, the rolled strips are annealed, either in batch or continuous annealing (Figure 4). Steel strips may pass through a hot dip galvanizing line (HDGL) where a zinc coating is applied to the strip improving corrosion resistance and providing a special appearance. HDGL always includes continuous annealing furnaces before, and inline temper rolling after the zinc bath.

After the annealing step, temper rolling of metal strips is conducted (mainly due to quality-related considerations). By temper rolling cold rolled metal the strip is elongated and specific requirements for optimized further processing, gloss, brilliance or paint appearance are met. As a last step in cold rolling and subsequent temper rolling, the metal strip is inspected and packed on a coil for transportation.

2.2.2. Setup of rolling mills

Rolling of flat metal in general is based on passing the metal through a set of at least two rolls, the so-called work rolls, plastically deforming and shaping the metal. The work rolls of metal mills are installed in so-called stands

(Figure 9, left). The number of rolls in one stand varies. Figure 9 (right) shows two examples of possible mill stand configurations. In the 4-high configuration, backup rolls convey the applied rolling forces, adjusted via screw spindles, to the work rolls. While in the 6-high configuration, intermediate rolls are located in between. The resulting vertical stress the roll bite is approximately 1 GPa, which is equivalent to a force of 1000 N per mm², in turn being about 10 tons per cm². Shear stresses reach up to 50 MPa. Depending on mill specifications, the number of backup rolls varies. Since the degree of reduction of a single pass is limited, metal rolling mills may encompass various, sequential stands (Figure 10). Such mills are called tandem mills.

Figure 9: General setup of a mill stand (left) and a 4-high and a 6-high mill stand configuration (BUR: Backup roll; IMR: Intermediate roll; WR: Work roll).



Figure 10: Roll operation in a 5-stand tandem mill.

Tandem cold rolling mills can be basically split into two groups; sheet mills if hot band is reduced to sheet gauge or tin mills if the incoming material is rolled to tinplate. Key advantages of the tandem rolling process include cost reduction and improved productivity, since multiple rolling processes are conducted in line.



Figure 11: Example of a cold mill (top) and a temper mill (bottom).

Cold rolling metals mills are of very large scale. Figure 11 gives an impression of the dimensions of metal rolling mills. The inline production of flat metal in tandem cold rolling mills is accordingly of large scale.

Reference values for a five stand tandem cold rolling steel mill are shown in Figure 12. However, those reference values vary according to the use of the flat metal and the campaign which is run. Still, the information provided gives an insight into the dimensions of the rolls used, the metal strips produced and the overall capacity of the mills.

Figure 12: Main data of a 5-stand (all 6 high) tandem cold rolling steel mill (WR= Work Roll; IMR= Intermediate Roll; BUR= Backup Roll) (Source: Lackinger et al., 2002).

Typical rolling reductions of 4 to 5 stand tandem mills are in the range of 50 to >80 % for sheet metal mills, and 80 to >90 % for tinplate cold rolling mills. To achieve such rolling reductions, motor power in each rolling mill stand typically ranges between 2 and 4 MW and even up to 6 MW in case of wide



strip rolling processes. The typical motor power of a single mill stand (4 MW) corresponds to 5365 horsepower. Roll forces are high and typically around 10 kN per mm strip width. Depending on the steel grade, strip width and desired rolling reduction, up to 20 kN per mm are not uncommon.

2.2.3. Categories of metal rolling mills

In the present AoA, the different metal rolling mills are subsumed under two main categories, namely cold rolling mills and temper mills. The subsumed metal mills encompass, but are not limited to:

- Tandem hot rolling mill (for aluminium strips only), - Reversing hot rolling mill, - Reversing cold rolling mill, - Tandem cold rolling mill, - Double Cold Reduction (DCR) mill - Batch (stand-alone) temper mill - Temper mill inline in a Continuous Annealing Process line (CAPL) - Temper mill inline in a galvanizing line

2.3. Purpose and benefits of chromium trioxide based chrome coatings of work rolls Using chromium trioxide has multifunctional positive effects, mainly based on the characteristics of the hexavalent chromium compound. The desirable properties of metallic chrome coatings produced from chromium trioxide have made this compound a state of the art substance for a wide range of applications for more than 50 years and crucial in many applications regarding work rolls of steel and aluminium cold rolling mills.

Chrome coated work rolls are used in several hot, cold and temper rolling processes. Importantly, not each work roll within the stands of the respective rolling mill is chrome coated. Some rolling mills do not depend on chrome coated work rolls while for others chrome coated work rolls cannot be replaced without major business impacts. The main driver behind this is variable, but it is mostly driven by customer demands.

The overall main driver, which makes chrome coated work rolls an essential part of the flat metal production for most sectors is the ever-growing customer demand in the high quality flat metal segment. Chrome plating enables the European steel industry to produce high quality products that are key to the continuity of the entire sector in Europe.

The functionalities of the metallic chrome coatings from chromium trioxide solutions on work rolls for steel and aluminium mills were evaluated during the consultation phase and the corresponding benefits are presented at a glance in Table 3.

Table 3: Functionalities and benefits of functional chrome plating of work rolls.

Functionality Benefit

High mechanical and wear resistance

Retention of the roughness of the work roll and less frequent work roll changes in long rolling campaigns.

Extreme hardness Avoiding pinch, indentation and granting for wear resistance.

Surface cleanliness

Avoiding fine iron dust on the strip surface. Reduced zinc pick-up from the rolled strip in galvanizing production lines due to anti-sticking properties. Lower Al-pick up from the strip in aluminium rolling mills, thus avoiding Al-related surface insufficiencies to be imprinted on the hot rolled and cold rolled flat metal product.



Functionality Benefit

Surface appearance

Brighter and more homogeneous strip product surface appearance during temper rolling and lower sensitivity to pick-up of zinc particles during temper rolling of galvanized steel strip. Same applies to pick-up of aluminium oxide build-up in hot rolling of aluminium.

Adhesion to the substrate Avoiding delamination and flake-off under high rolling forces.

Tribological advantages Stable coefficient of friction in the desired range.

Topography Reproduces the surface structure when applied in thin layers.

Layer thickness Adequate thin layer thickness possible for work rolls.

Coating of very large geometries Possibility to coat large work rolls in the plating bath.

Process conditions Eligible for surface treating heat sensitive work roll materials.

Surface morphology Micro-cracked structure Provides excellent functionality for lubricants.

Machinability Re-work and easy preparing of rolls by grinding and re-coating possible.

Treatment time Fast coating and corresponding high throughput rates in plating bath.

Altogether, chromium trioxide based functional chrome plating delivers important functionalities ensuring the process stability and product quality. Main threats impairing the rolling process are events of skipping and slipping due to deficient roughness retention of the surface, insufficient surface cleanliness leading to reduction in strip quality and banding effects leading to imprints on the strip during temper rolling and therefore to worsening of the surface appearance.

Functional chrome plated surfaces withstand the demanding conditions in metal mills and are compatible with the base materials used. It enables long and stable rolling campaigns while retaining good surface cleanliness and appearance. Lastly, functional chrome plating does not require highly specified equipment and therefore, the heavy work rolls (up to 8 tons per roll) do not have to be transported over long distances to specialist facilities. For a single steel cold rolling mill, the work roll fleet steadily comprises at least several dozens of rolls and work roll changes amount to hundreds to thousands changes per annum. Requirements in logistics and transport for work roll exchanges in large steel plants are accordingly high. The longer the process takes to restore the roll surface, the more rolls are needed in stock. Work roll changes vary depending on the steel quality.

Costs per roll depend on the roll size as well as grade and are typically above EUR 20,000. The functional chrome plating of work rolls thereby is compatible with efficient high-throughput roll shop operations. The average costs incurred for chrome plating work rolls of cold and temper rolling mills is 100 to 250 EUR.

Again, there are cold, temper and aluminium hot rolling mills operating without the use of functional chrome plated work rolls. However, as stated above, several rolling mills are reliant on chrome coated work rolls to deliver the required properties and quality demanded for. This mainly refers to requirements in strip cleanliness and roughness retention in cold rolling mills, roughness retention and surface appearance in temper mills and roughness retention in double cold reduction mills.

Identified benefits and functionalities of functional chrome coatings applied to work rolls of steel and aluminium mills are used as benchmark for the assessment of possible alternatives. Therefore, key functionalities, based on the functionalities and benefits presented above, are defined and further discussed in chapter 3.2. The functional chrome plating procedure is depicted in detail in chapter 3.1.



3. FUNCTIONAL CHROME PLATING

3.1. Functional chrome plating process Surface treatment of metals is a complex and stepwise process in many industry sectors. As illustrated in Figure 13, there are two steps within the surface treatment process of work rolls, which involve the use of chromium trioxide. These are divided into the pre-treatment process (for an adequate preparation of the substrate for the next process steps), and the respective subsequent process step (main process). There are no post-treatment processes for the functional chrome plating of metal mill work rolls, which involve chromium trioxide.

Figure 13: Simplified overview of different steps that may be involved in functional chrome plating using chromium trioxide.

It is of greatest importance that only the combination of adequate pre-treatment and the appropriate main process step leads to a well-prepared surface providing all of the necessary key requirements for the respective applications as described in detail in chapter 3.2. Chromium trioxide is a pre-requisite for the main treatment of functional chrome plating to ensure high quality of the product and to meet the requirements of the industry.

We therefore clearly state that for a thorough assessment of replacement technologies it is mandatory to include the whole process chain (including pre-treatments), taking into consideration that for all steps involved, chromium trioxide-free, SVHC-free respectively, solutions and processes must be developed, which in combination are technically equivalent to the current chromium trioxide containing treatments. As of today, complete SVHC and chromium trioxide free process chains are industrially available for some special applications only. For the majority of functional chrome plated products at least one process step, usually the main treatment, requires chromium trioxide and/or another SVHC to provide the required properties to the surfaces.

3.1.1. Pre-treatment

A number of pre-treatments, such as degreasing, electro-cleaning or reverse etching in the plating bath, are necessary to prepare the surface of the bare grinded and/or textured work rolls for the subsequent process steps. However, only one pre-treatment involves the use of chromium trioxide, which is etching, in turn applied as reverse etching in the plating bath. Adequate preparation of the base metal is a prerequisite: adhesion between the metallic chrome coating and the substrate depends on the force of attraction at a molecular level. Therefore, the surface of the metal must be absolutely free of contaminants, corrosion and other residuals until the plating process is finished.

Etching is defined as a surface activation step by removal of base material, from a metal surface. Etching affects metal surfaces in a more aggressive manner than the pickling process. For example, during an etching step of up to 2 minutes, a maximum of 0.3 µm metallic grinding debris is removed. The removal rates vary for different substrates. Etching is performed by immersing a metal substrate



in an acidic solution (bath application). The etching process creates a surface which is clean and free from defects, semi-loose metallic grinding debris or oxides, adequately preparing the metal surface for subsequent process steps and providing very good adhesion (RPA Report, 2005).

Mode of action: The purpose of etching is the removal of impurities (such as metal oxides) and a certain amount of semi-loose metallic grinding debris from the substrate and activating the surface of the substrate prior to the functional chrome plating process. Chromium trioxide is necessary for controlling a moderate etch rate and to avoid over-etching. Additionally, an aqueous solution of chromium trioxide fulfils the following major purposes for the pre-treatment:

An aqueous solution of chromium trioxide acts as strong oxidising agent of the base metal and an acidified solution of chromium trioxide is also used to remove oxides from the surface.

3.1.2. Main treatment

Functional chrome plating forms a coherent metal coating on the part to be plated (either the direct substrate or the substrate with already plated intermediate layers) by using the substrate as cathode and an inert anode (tin-lead anode) and inducing an electrical current. Currently, platinum-coated titanium anodes are being developed and tested for the coating of work rolls to further reduce the environmental footprint.

The work roll is immersed (Figure 14) in the electrolytic plating solution containing dissolved chromium trioxide and additives (electrolyte). During the electroplating process, the hexavalent chromium cations are reduced and build-up a metallic chrome coating layer (electrodeposition).

Figure 14: Roll hanging above the functional chrome plating tank (Source: HOCO-RST, 2014).



In the plating process, solutions of chromium trioxide, with a concentration between 200 g/l and 300 g/l are used. Catalysts, such as sulphate and fluoride, are added in concentrations of 1 to 5 g/l. The mixed catalysts bath has an efficiency of approximately 20%.

Proprietary (organic) catalysts provide higher cathodic efficiencies of up to 25% and have the advantage of not attacking the steel (unplated surface) in those areas of the cathodes where the current density is too low for chromium to be deposited, like the journals of the work rolls. The bath temperature usually lies between 50 and 60°C.

During the overall functional chrome plating process chain, extensive rinsing steps are carried out to prevent the drag-out of material from the cleaning step into the plating bath. Rinsing is conducted with high pressure rinsing rings above the cleaning bath. The temperature of the cleaning baths is 65 to 80 °C. The rinsing water evaporates due to the bath temperature (of up to 80˚C). The waste water is evaporated to minimize the disposal of water as chemical contaminated waste. The rinsing water from above the chrome bath is also evaporated in a special, separated, evaporator for the chromium. Most of the process water is handled in a closed-loop system minimizing wastewater streams by re-use of concentrated rinsing water in the process bath of the same type. Some water evaporates and must be replenished in order to keep the bath in balance.

3.1.3. Post-treatment

Post-treatments comprise rinsing and cleaning steps to remove potentially remaining process chemicals from the product, and a final drying of the product.

Subsequently to the plating process, rinsing is conducted above the chrome plating bath and the water is fed into the chrome plating tank again and is, in a separate step, evaporated After rinsing and drying, no further post-processing is needed. Since the thin chrome coating contours the roughness asperities of the substrate, the work rolls are directly ready for use in the rolling mill. Logistically and economically, this is a considerable advantage of chrome coatings over alternative coating methods, which often require a post-processing step to meet the roughness specifications from the mill.

3.2. Key functionalities of functional chrome plating An overview on the key functionalities of chromium trioxide in functional chrome plating of work rolls is provided in the following sections, subdivided into pre-treatment processes and the main coating process. Functional chrome plating can be applied on a variety of surfaces. In case of work rolls dedicated to the use in metal rolling mills, high-alloyed steels are mostly used as base material. During the consultation phase, the key functionalities for functional chrome plating were identified taking the whole surface treatment processes into account. Nevertheless, the most important key functionalities of the high-quality final product are related to the chromium trioxide based electroplating.

3.2.1. Key functionalities of chromium trioxide based surface pre-treatment

The pre-treatment process prepares the surfaces for the subsequent main process step. In Table 4, selected key functionalities and relevant advantages for the pre-treatment process are listed and discussed in more detail below. With its optimal behaviour chromium trioxide based pre-treatment ensures high quality products and is the decisive factor for the use of the chromium trioxide based pre-treatment solutions.



Table 4: Key functionalities of chromium trioxide based pre-treatment.

Process Key Process Functionality

Etching

Removal of grinding debris

Activation of the surface

Removal of residuals/oxides from the surface

Removal of metallic particles from the Electro Discharge Texturing process

Long-time bath stability if applied in a separate etch bath

Simple bath maintenance

Simple analytical method for process control

Etching The key functionality of etching is the adequate removal of oxide and debris from a metal surface. For etching, selective removal of certain amounts of base material is required for surface activation. This process is controlled by etch current and time. The careful control of this step influences the quality of the subsequent coating layer.

After the pre-treatment, the processed parts will be free of corrosion products, discoloration, uneven etching, increased surface roughness or other defects that would prohibit further chemical processing. The etching rate must be chosen according to the metal substrate used. Different types of steel require different etching rates. The longer and harder the etching, the greater the roughness of the surface.

Under-etching or over-etching should be avoided as not to affect the key functionalities of the subsequent coating (for example: poor adhesion resulting in cracks and blistering). The etch rate is controlled by controlling the tome and current during the etching process.

3.2.2. Key functionalities of metallic chrome coatings

Selected quantifiable and qualitative requirements of the key functionalities of the metallic chrome coating applied to work rolls, deposited by the chromium trioxide functional chrome plating process are listed in Table 5 to give a short overview. A more detailed description is given in the subsequent paragraphs. Different types of metal mills are in use as explained in chapter 2.2.1. However, cold rolling mills and temper mills cover the variety of rolling mills concerning the relevant key functionalities and are therefore representatively used in the following.

Table 5: Sector specific key functionalities of metallic chrome coatings.

Quantifiable key functionality Cold rolling mill Temper mill Aluminium hot rolling mill

Hardness 850-1000 HV 850-1,000 HV 700- 800 Hv30

Surface cleanliness (reflection tape method)

≥ 70 % - -

Topography (Ra, RPc, Wa0.8 after forming)

Ra: 0.2 to 13 µm, RPc: 20 to 160 cm-1, Wa0.8: <0.40 µm

Ra: 0.2 to 13 µm, RPc: 20 to 160 cm-1, Wa0.8: <0.40 µm

Ra: 1-3.5 µm

Adequate layer thickness 4-10 µm 4-10 µm 4-10 µm

Treatment time (deposition rate) 0.4 – 0.75 h 0.4 – 0.75 h 0.2 h



Quantifiable key functionality Cold rolling mill Temper mill Aluminium hot rolling mill

(0.3 to 0.8 µm/min) (0.3 to 0.8 µm/min) (0.5 µm/min)

Suitability for heat-sensitive substrates (max. coating process conditions)

<160 °C <120 °C <200°C

Resistance to rapid temperature changes

Repetitive ultrashort surface temperature flashes ≥200 °C

Repetitive ultrashort surface temperature flashes ≥200 °C

≥250 °C

Surface morphology (density of microcracks) 800 – 1100 cm-1 800 – 1100 cm-1

Plating of large geometries (overall length)

3 - 5 m 3 - 5 m 4 - 6 m

Surface appearance -

High, homogeneous appearance, Anti-sticking properties (low Zn pick-up in HDGL, low oxide build-up for Al)

Homogeneous appearance

Wear resistance Stable surface structure Stable surface structure Stable surface structure

Adhesion to the substrate High High High

Topography Reproducing Reproducing Reproducing

Machinability Good Good Good

Coefficient of friction Stable Stable Stable

Wear resistance

Rolls used in cold rolling and temper mills require a specific surface roughness for maintaining the rolling process stability. On the one hand, proper roughness avoids slipping or skidding, on the other hand the roughness profile is transferred to the strip, which is of special importance for temper mill rolling operations.

The average roughness (Ra), between 0.2 and 13 µm, and the peak count (RPc), 20 to 160 peaks per cm, need to stay stable for proper roughness transfer. In general, the requested Ra and RPc on the strip metal product depends on the customers' demand. Depending on the substrate, steel or aluminium, 30 to 70% of the roll roughness is transferred to the strip during rolling. When it comes to reproducible roughness transfer, roughness retention is of highest importance.

Therefore, one reason for functional chrome plating is the extension of roughness retention, which in turn is directly linked to wear resistance of the chrome coating. Reduced wear resistance entails more frequent roll changes.

Although often done, the roughness retention of a surface under mechanical strain cannot be adequately measured on the laboratory scale. The conditions in the roll bite of a cold rolling or temper mill are extraordinarily demanding so that no laboratory test is close enough to the relevant conditions to draw any meaningful conclusions. Meaningful testing needs to be conducted under relevant rolling conditions.



However, roughness retention is given as the stability of the Ra value along repetitive rotations in laboratory tests or rolled tonnage in relevant mill operation tests. Thereby, wear mainly refers to the abrasion of roll surface asperities and is in the micron range.

Hardness

Hardness is defined as the resistance of solid matter to various kinds of permanent shape changes when a force is applied. For work rolls the hardness of the chrome coating is one key functionality holding impact on its durability. The total hardness of the product is the combined result of the substrate hardness and coating hardness. Measuring Vickers hardness (HV) for metallic materials (ISO 6507-1) is the most common hardness test method. Chrome layers on work rolls reach approximately 1000 HV, improving the hardness of the base material. Hardness is linked to the wear resistance of the rolls.

In hot metal rolling, the surface hardness of the chrome plated work roll is of highest importance. While a high degree of hardness enables wear resistance for the sake of e.g. roughness retention in temper rolling applications, hardness in hot rolling applications makes the work roll less prone to incidents.

Surface cleanliness

Strip surface cleanliness is a critical product quality factor in several market sectors of cold and temper rolled metal, for example for drums and pressure vessels, for domestic appliances, and in the automotive market sector (segment uncoated steel strip). Furthermore, surface cleanliness is decisive in hot rolling of aluminium, including strips finished on hot mills without subsequent cold rolling processes.

In cold rolling, strip cleanliness is mainly impaired by the rolling procedure before annealing, due to the adverse effects of mainly iron fines and oil residues. Annealing improves the surface cleanliness of the strip. Thereby, batch annealing does not perform as good as continuous annealing does. In contrast to batch annealing, continuous annealing is applied to the uncoiled strip, therefore reducing transport limitations of the annealing gases. Those limitations are particularly severe regarding strip widths of more than 1600 mm.

In hot rolling processes, the strip surface cleanliness is mainly impaired by flakes and aluminium build-up related to the adhesion of aluminium on the work rolls. Chrome plated work rolls enable a lower aluminium pick-up from the strip in aluminium rolling mills, thus avoiding Al-related surface insufficiencies to be imprinted on the hot rolled and further cold rolled flat metal product.

Surface cleanliness specifications are assessed applying the reflection tape method. An adhesive tape is applied to the recently cold rolled metal strip and stuck on a blank white paper sheet after removal. The degree of strip cleanliness is measured by applying a light source to the paper and measuring the share of reflected light. In case 100% of the light is reflected, the tape is deemed transparent and the strip cleanliness is regarded the highest. In case of 0%, the tape is black, thus the cleanliness very low. Typical values are 40 to 80% (Jacobs et al., 2012).

In order to ensure an adequate strip surface cleanliness after annealing (and temper rolling) as required by the customer, internal strip surface cleanliness specifications are used for cold rolled strip before annealing, which differ between type of downstream annealing process and per steel coil type (Table 6).



Table 6: Surface cleanliness specifications of strip as-cold-rolled, before annealing (“Full Hard”)

Type of annealing process Strip width

Final product: customer specifies guaranteed cleanliness level

Minimum tape reflectivity

Maximum loss of tape reflectivity

Batch annealing > 1600 mm yes 70% 30%

Batch annealing > 1600 mm no 60% 40%

Batch annealing < 1600 mm yes 50% 50%

Batch annealing < 1600 mm no 45% 55% Continuous annealing in on-site hot dip galvanising lines

all widths Yes and No 45% 55%

Other destinations all widths Yes and No 50% 50%

Using chrome coated work rolls, the strip cleanliness can be assured. The mechanism this behind is not yet well understood. There are two hypotheses; one stating that chrome coatings decrease the ploughing impact of work rolls on the strip to be cold rolled by covering small scale structures on the surface, thus reducing the roughness. The other hypothesis considers functional chrome plating to deliver better adhesion properties concerning lubricant oil compared to uncoated steel surfaces. In fact, the occurrence of larger particles impairing the surface cleanliness does not decrease by using functional chrome coated work rolls. However, at higher process speed, chrome coated work rolls in cold mills – in contrast to non-coated materials – provide for increased plate-out of the lubricant thus improving the surface cleanliness (Jacobs et al., 2012).

Figure 15 depicts the mechanism of liquid application and plate-out in the rolling process for cooling and lubrication.

The strip surface cleanliness does not apply to temper rolling mills in the same way as to cold rolling mills. As mentioned above, in cold rolling mills it is related to generation of iron fines from the strip mixed with lubricant residues. In temper mills it is related to

Figure 15: Coolant/Lubricant application and plate-out in the rolling process.



- sensitivity to zinc pick-up when rolling galvanized strip (strip coating with zinc or a zinc alloy) and

- the general strip surface appearance, including gloss, absence of orange-peel look, homogeneity of colour and gloss over strip width and length as well as absence of local surface marks.

In hot rolling of aluminium, the sensitivity to pick-up of aluminium oxide build-up plays a similar role as the zinc pink-up in temper rolling. The latter is mainly important to temper mills, and therefore separately discussed in the following paragraph.

Surface appearance

In case of temper rolling mills, the surface appearance is of major importance. The surface appearance of the metal strip and the degree of gloss after temper rolling is dominated by the homogeneity of the surface structure. Chrome coated rolls ensure the brightness and homogeneous strip product surface appearance after temper rolling. The same is true for hot rolled aluminium.

In practice the quality of temper rolled flat steel is monitored by visual inspection and requires experienced personnel. However, the gloss of the surface can be measured applying a reflectometric device (glossmeter) according to ISO 2813:2014. Thereby, the ability of a surface to specularly reflect light serves as an indicator for its optical property. The Gloss Units (GU), as an expression of the degree of gloss, ranges from 0 (no gloss) to 100 (maximum gloss, full reflection). The samples are measured in as-painted condition.

The surface appearance is depending on the surface structure specifications of the rolled metal strip. In general, the surface is required to be homogeneous. The surface structure properties of flat metal products, such as the waviness or roughness, directly influences the appearance. For example, a high waviness leads to ‘orange peel’ look and blurry reflections, i.e. poor paint appearance. For further information on required surface structure specification related to surface appearance, refer to section 3.2.1.6.

Adhesion to the substrate

Work rolls of steel rolling mills operate under very high rolling loads, cyclic contact loads respectively. Those loads impacting the work roll requires high resistance to normal and shear stresses and rolling contact fatigue. For proper functioning the surface layer must not show any effects of flake-off or brittleness. Cr(VI) based chrome coatings delivers excellent adhesion to the substrate avoiding delamination even under highest rolling loads. A sufficient level of ductility is combined with high degrees in hardness. Functional chrome plating exhibits low internal stress within the coating and at the coating-substrate interface (Crahay et al., 2015). Furthermore, chrome coatings do not exhibit porosity. In the case of an alternative coating, it must fulfil the requirements in adhesion to the substrate, even under highest rolling forces in cold and temper rolling mills.

Coefficient of friction

Friction is the force resisting the relative motion of solid surfaces sliding against each other. In case of steel mills, the coefficient of friction of the tribological system in the respective rolling mill needs to be maintained in a suitable range enabling the rolling process without events of slipping and skidding. This is in particular important to cold rolling processes with high rolling reduction. Temper



rolling is less prone to slipping and skidding due to the lower degree of rolling reduction. Furthermore, the texture transfer in temper rolling is beneficial in terms of grip.

The coefficient of friction can be determined by tribological testing. It is a property of the entire tribological system, comprising the work roll surface in contact with the rolled metal strip, the lubricant and the type of process, which in turn includes a wide range of process parameters. Meaningful testing the coefficient of friction can only be conducted under real rolling conditions using industrial rolling mills.

Topography

Strip surface topography is a critical product quality factor in several market sectors. In those market sectors, customers specify at least a certain range for the most commonly used roughness parameter Ra. Surface specifications of work rolls differ according to the use, the type of mill, the position within the mill and the campaign which is run.

In the most critical markets, e.g. the automotive market sector, customers require that a range of surface parameters are met simultaneously:

- Roughness parameter Ra must be in a specific range - Density of roughness peaks, as defined by the 'peak count' parameter RPc, must be high,

above a specified minimum level - Waviness must be very low, below a specified maximum level

The average roughness (Ra) of work rolls in cold rolling and temper mills is between 0.2 and 13 µm, and the peak count (RPc) 20 to 160 peaks per cm. The Ra and RPc of metallic flat products is measured according to the European Standard EN 10049:2013.

Waviness is the result of regular or non-regular occurrence of macroscopic surface irregularities influencing the surface appearance of the flat metal product. Surface structure elements can be distributed stochastically or non-stochastically. The waviness of flat metal products is typically determined according to SEP 1941, expressed in Wsa (arithmetic mean of waviness), or often as Wa0.8 in case of sheet metal products.

In general, customers in the automotive industry require such sets of specifications to obtain an optimal balance of:

- Pressing behaviour in their production process; and - Excellent paint appearance

For the most critical applications, it is not sufficient for steel manufacturers to supply strips with e.g. low waviness as-delivered to the customer. The steel manufacturer has to guarantee a low waviness of the final product, even after the customer’s press shop. A CHL customer's branded grade for premium paint appearance – Serica® – a hot-dip galvanised surface finish for exposed automotive panels, is one example. Key surface parameters are:

Ra: 0.9 - 1.4 µm RPc: > 75 cm-1 Wa0.8 after forming: <0.40 µm

For the purpose of proper topographical properties, work rolls can be ground and sometimes subsequently textured during the pre-treatment to yield the desired topography. Being an important key functionality, the topography needs to be retained in case the roll is coated. Examples of reasons behind topographical requirements are:



- Prior to the coating process, work rolls for cold rolling mills and for double cold reduction mills are ground to specific roughness specifications, as required to ensure a stable rolling operation and a good strip surface quality.

- For the last stands of cold rolling mills, work rolls generally receive an additional surface texturing treatment between the grinding step and the coating process, in order to transfer a particular surface texture to strip as required by the next downstream strip product process (usually a batch annealing or continuous annealing process step).

- Work rolls for temper mills generally receive an additional surface texturing treatment between the grinding step and the coating process, in order to transfer a particular surface texture to the strip as required by the customers. The work roll coating process needs to preserve the texture on the strip to ensure a consistent transfer to the product. In several key markets, such as the automotive sector, the customers require a specific strip surface morphology, to comply with their manufacturing process whilst achieving excellent product surface quality.

Chromium trioxide based functional chrome plating provides the advantage of contouring instead of masking surface structures when deposited in thin layers (Figure 16), thus not impairing the established topographical properties to be transferred to the metal strip. Please note that the retention of the topography does only apply to coating processes and not to alternate roll manufacturing methods.

In the defined surface morphology, a certain amount of oil can be retained for lubrication in order to prevent tearing of sheets, e.g. in deep forming processes in the automotive industry.

Figure 16: Metallic chrome plated roughness (Ra= 2.6 µm) illustration and detailed view as photomicrographs from a scanning electron microscope showing clearly visible cracks (Source: Hoco-RST, 2014).

The surface finish of rolls in the steel industry has major influences on the rolled products and their properties. The formability of the products as well as the appearance of the coated surface are directly connected to the surface morphology of the rolls. Moiré- and orange peel effects can be avoided using a suitable surface structure.

Adequate layer thickness

The thickness of a functional chrome plating layer varies for each application and industrial sector. Functional chrome coatings easily may reach layer thickness up to 500 µm. As mentioned above, the replication of the topography of working rolls is a decisive feature for many rolling processes.



Therefore, the required layer thickness is rather thin and typically ranges between 4 and 10 µm. When applying an additional layer onto the substrate, possible alternatives need to be capable of depositing thin layers without impairing the surface roughness structure and at the same time, providing sufficient hardness and wear resistance. Determination of the layer thickness is conducted according to the coulometric method described in ISO 2177.

Plating of large geometries

Chrome coated work rolls for steel mills in general are very large in size and weight. The typical mass ranges between 2 and 8 tonnes for a single work roll for cold and temper mills, and up to 16 tonnes for aluminium hot rolling mills. The barrel diameter lies between 350 and 650 mm at a barrel length of 1 to 2.5 meters resulting in a typical overall length of the rolls of 3 to 6 meters. Functional chrome plating is capable of handling such dimensions. Thereby, high degrees of homogeneity of the chrome coating are achieved. The homogeneity of the chrome coating is a pre-requisite for meeting process and product quality requirements, especially in temper mills.

Resistance to process conditions

Process conditions of the surface treatment process have to be well balanced with regard to requirements imposed by base material-related restrictions. Work rolls for cold and temper rolling mills are most commonly manufactured from 2-5% Cr forged steel alloys. For establishing the required barrel hardness, rolls are heat treated ("quench-and-temper" step) at rather low tempering temperatures of 100 to 200 °C, with temper mill work rolls more towards the lower end. Any surface treatment-related heating above the indicated temperatures impairs the mechanical strength, hardness and structural integrity, which needs to be avoided at any rate.

Functional chrome plating is conducted at moderate temperatures between 50 and 60 °C and therewith well below the tempering temperatures of work roll steel alloys. Since there is no heat-affected-zone (HAZ), functional chrome plating does not reduce the strength of the substrate and does not induce high internal stress.

It should be noted that besides material-related problems, excessive heat input may lead to (potential lethal) health safety issues resulting from explosive spalling of sharp metal pieces from the roll barrel due to high residual internal stress levels.

Resistance to rapid temperature changes

During the rolling process, the strip temperature in the roll bite can very rapidly increase to temperatures as high as 200 °C (only for milliseconds or less). Functional chrome coatings applied to the surface of work rolls in cold rolling and temper mills enable the resistance to such ultrashort flash temperatures. It is important to note that the heat flashes are so short that the heat has no time to penetrate into the roll and alter the microstructure and hardness of the substrate of currently used rolls. Any alternative needs to be resilient to very rapid temperature increases.

In hot rolling applications, temperatures are higher than for cold rolling. Therefore, the resistance to temperature is required to be ≥ 250 °C for aluminium hot rolling mills.

Surface morphology

Metallic chrome coatings on work rolls of steel and aluminium mills exhibit micro-cracks within the deposited layer being important for the maintenance of lubrication. At the same time, no macro-cracks



down to the substrate are evident and the coating does not show porosity. In general, the highest reachable count of cracks per cm is desirable. Depending on the use of catalysers in the plating baths, 800 to 1100 cracks per cm are achievable.

Machinability

During its lifetime, a chrome coated work roll used in steel and aluminium mills is re-worked many times. The number of work roll changes at a single steel cold rolling mill per year is in the range of hundreds to thousands. Worn rolls are re-worked in plating shops to be re-used. Thereby, 0.1 to 0.4 mm of the work roll is grinded, including 4 to 10 µm of metallic chrome coating. With a total thickness of 15 to 55 mm of the consumable outer, hardened part, a roll can be re-used at least 100 times before it must be entirely scrapped and replaced. The machinability is an important key functionality of applied coatings and manufactured rolls since the surface properties hold significant influence on the rolling process. A specific surface roughness needs to be achieved as well as a certain peak count of surface structures and waviness. Potential alternatives need to be capable of suitable machining, such as grinding and texturizing by e.g. electrical discharge texturizing. In summary, good machinability allows for lower treatment times, better handling of the work rolls in the roll shop and easy to establish surface structures.

Treatment time

The overall treatment time and therefore the deposition rate of functional chrome plating is decisive for the application to work rolls in steel mills. As mentioned above, turnover rates of rolls in steel mills are very high, typically in the range of thousands per annum. Worn rolls need to be re-built accordingly fast to maintain continuous production. Chromium trioxide based functional chrome plating in baths allows for high throughput, even in the case of large work rolls. The total process time for one ready-to-use work roll (including pre-treatment) is 30 to 45 minutes, at a chromium deposition rate between 0.3 to 0.8 µm per minute. Rolls are grinded to remove chrome remainders and other defects, and to re-shape prior to the plating process and not post-treated after the coating at all.

4. ANNUAL TONNAGE

4.1. Annual tonnage band of chromium trioxide The annual tonnage of chromium trioxide used in functional chrome plating of work rolls dedicated to the use in the steel and aluminium rolling industry is 40 tonnes per year.



5. GENERAL OVERVIEW OF THE ALTERNATIVE DEVELOPMENT AND APPROVAL PROCESS

The development of alternatives to chromium trioxide-based functional chrome plating poses various internal and external challenges. On the one hand, the production of flat metal products is conducted in metal mills individually attuned for certain campaigns and specifications. For the same flat metal product (e.g. sheet metal), depending on the specifications, chrome plated work rolls are essential for certain campaigns, while for others they can be dispensable. However, as for the high quality segment the European steel and aluminium industry are reliant on chrome coated work rolls are required to maintain guaranteed standards. As such, individual re-evaluation of respective product requirements would be necessary in case of a replacement to functional chrome plating to further guarantee constant product specifications. For potential alternatives it is mandatory to pass multiple development and evaluation steps on different scales. Only constant rolling results proven on the industrial mill scale and for a multitude of products allows for a final feasibility assessment of potential alternatives.

The actual process followed by Original Equipment Manufacturers (OEMs) in the steel processing industry more closely follows the framework for TRLs and MRLs originally developed by National Aeronautics and Space Administration (NASA) (Figure 17). OEMs usually adapt this TRL/MRL approach resulting in individual versions. A version for the steel processing industry is shown in Figure 17Error! Reference source not found. Error! Reference source not found.Error! Reference source not found.below. The OSD Manufacturing Technology Program (2011) offers best practices on MRLs and their connection to TRLs. According to the authors, TRL and MRL go hand in hand and for reaching various MRLs, corresponding TRLs should be reached. Most important, to reach demonstration of low (TRL 9) and full rate (TRL 10) of production respectively, the technology (alternative with regard to this AoA) should have matured to TRL 9. Therefore, it is important to note that only TRL and MRL in combination determine the overall readiness of a potential alternative, both, from the technological as well as from the manufacturing point of view. Some MRLs and TRLs may be accomplished concurrently, while others build on one another. Some potential alternatives may already have achieved MRLs advanced ahead of corresponding TRLs for some applications. This may be the case when for potential alternatives advanced manufacturing readiness levels are demonstrated, but technical suitability for the applications relevant within this AfA is still lagging behind, thus requiring further development

Please note that the economic feasibility of potential alternatives depends on the respective R&D stage. While first indications of the technical feasibility of a potential alternative can be given on the laboratory level, meaningful assessment of the economic feasibility can only be carried out for an alternative, which passed the laboratory scale and was tested on the relevant production scale.



Figure 17: Overview of and interconnections between individual TRL and MRL as well as estimated time for passing the respective stage.



Testing, evaluation and adaptation processes

The present AoA is part of the efforts of CHL in identifying a suitable alternative to chromium trioxide-based functional chrome plating.

R&D on potential alternatives has been and is currently ongoing, thereby being an iterative process. Some of the alternatives have already been internally trialled on the industrial mill scale (e.g. forged HSS, Ti-enhanced and cast (S)HSS work roll grades), but revealed technical insufficiencies. For the majority, meaningful up-scaled trials for cold and temper, as well as aluminium hot rolling mills do not exist (e.g. work rolls manufactured by means of PM HIP, ESR cladding or laser cladding as well as rolls alternatively coated by trivalent chrome plating, electroless plating, nickel and nickel alloy electroplating, nanocrystalline cobalt phosphorus alloy coating or high velocity thermal processes). Those alternatives would need to pass development and evaluation (TRL) steps as outlined in Figure 18, which gives an overview of steps to be taken in substituting chromium trioxide based functional chrome plating of work rolls in cold, temper and aluminium hot rolling work roll applications.

After identifying an alternative, extensive testing and evaluation needs to be carried out in the laboratory, pilot mill and at the industrial scale to ensure the feasibility of any alternative. At least 7 years of further evaluation and testing of alternatives are necessary for metallic chrome coatings for the work roll business in metal rolling mills. Further laboratory experiments and trials are required prior to moving into pilot mill trials and subsequently to industrial trials under real rolling conditions.

The scale up process requires significant financial investments as well as time for engineering, construction, testing and evaluation. Due to the large size of the rolls, of up to 6 meters with a diameter of 0.6 meter, make this last step extremely expensive. Furthermore, tests can only be conducted in full size mills under very heavy conditions of a cold mill in order to gain the necessary experience and test results. Smaller mills are not suitable as the maximum specific roll forces cannot be reached and simulated.

A minimum of 5 to 7 additional years are expected to be required in order to adapt the manufacturing processes accordingly. Time needed for approval of the products varies according to the application, while approval intervals for steel applications may take approximately 1 year, aluminium products dedicated to the aviation industry encompasses considerably longer approval and release periods. Acceptance processes take at least a few months but vary for each manufacturer. Certain functionalities are defined for each application, e.g. the surface roughness and roll texture. The customer technical support department of the manufacturer decides whether the requested specifications are met or not.

In summary, a minimum of 16 years is estimated to reach full technological maturity of an alternative for functional chrome plating in work rolls of cold, temper and hot rolling rolling mills, not regarding time required for achieving the subsequent full rate production in MRL 9 and 10 (Figure 17).



Figure 18: Schematic of relevant steps of the chromium trioxide substitution process in cold and temper rolling metal mills.



6. IDENTIFICATION OF POSSIBLE ALTERNATIVES

For almost 80 years hard chrome plated materials have been in production and use in several industrial sectors. The use of hard chrome plated rolls for production of cold rolled and coated steel strip started at the beginning of the 1980s. In the first place, the use of chrome coated rolls resulted in an increased service life including decreasing energy consumption and better resource efficiency.

In the 1990s, increasing steel product quality due to the use of hard chrome plated rolls resulted in changes and improvements in article production on the part of customers. The increased surface quality, which allowed for a decrease in lacquer consumption in car body shell production and the use of water-based paint is one example. Since then developments advanced by the steel industry, in cooperation with downstream users, have taken place in several branches of the industry. Those developments resulted in a constant flat steel product quality concerning surface roughness and peak count. Constant paint appearance, gloss level and colour tone are now available for large surfaces and needs to be disposable for a long production period.

New lacquer techniques implemented in the automotive industry are one example, such as the so-called Process 2010 of Volkswagen AG, which reduces lacquer consumption. This especially refers to the filler being completely removed thus reducing the production steps and plant components. The new process requires an excellent surface quality and yields a reduction of 20% in CO2 consumption in the varnishing process for the automotive industry.

Since the year 2000 the lightweight mode of construction using high strength steels is becoming increasingly important. In the automotive industry the increasing weight reduction and safety demands ask for innovative steel products plus the introduction of aluminium products. Those high strength steels are produced in cold roll mills using hard chrome plated rolls.

In the following years the improvements continued and the main customers of the high quality products are e.g. the automotive, enamelling, white goods and construction industry. Consistently good product quality is essential for the downstream user to ensure effective production e.g. at production lines with high number of pieces.

In conclusion, the use of chrome plated work rolls for high quality flat metal products proves to be essential up to the present day. However, extensive research was and currently is being conducted focussing on opportunities for the substitution of chromium trioxide based chrome plating in the steel industry. The efforts made, and corresponding R&D, is further presented in the following chapters.

6.1. Description of efforts made to identify possible alternatives CTAC is a consortium of 153 members from industry, started in 2012. The aim of CTAC was to efficiently gather and analyse all necessary information for the three pillars of the authorisation dossier (CSR, AoA, SEA). CHL is member of CTAC and in the context of this application, alternatives were extensively investigated, assessed and compared. The present AfA for the uses of chromium trioxide in functional chrome plating was prepared partially on the base of the CTAC (Chromium Trioxide Authorisation Consortium) dossier. Wherever appropriate information from these dossiers are included into the present AfA.

6.1.1. Research and development

As mentioned earlier in this document, much effort on alternatives for etching with chromium trioxide as well as for electroplating with chromium trioxide has been performed and is still ongoing. R&D is generally performed by specific companies by testing different plated products in feasibility studies.



The unique set of functionalities of chromium trioxide are explained in detail in chapter 3.2 and make chromium trioxide an ideal and not easily replaceable substance where high requirements with regard to hardness, wear resistance, adhesion or friction, and fatigue properties have to be fulfilled to ensure safe performance in a demanding environment. It is very difficult to find a single alternative which replaces the multi-functionality of chromium trioxide generated coatings simultaneously.

CrFreeRolls Tata Steel and ArcelorMittal were engaged in the European R&D project 'Substitution of chrome plating for rolls of skin-pass and temper mills' (Crahay et al., 2015). Working rolls in skin-pass or temper mills are chrome plated in favour of increased durability and proper surface roughness. Therefore, the project investigated alternatives to Cr(VI) based functional chrome plating that deliver comparable properties concerning wear resistance, surface hardness, layer thickness, micro-cracking and texture. In case of skin-pass or temper mills homogeneous metallic chrome layers are deposited with a layer thickness 5 to 15 µm and a hardness of up to 1200 HV. Those layers show no delamination under high rolling loads, micro-cracking for the retention of lubricants, high wear resistance and low friction. Potential alternatives are assessed with regard to the named functionalities.

Alternative coatings under investigation are; alternative electroplating, high velocity thermal spraying and coating by electrical discharges (EDC). Trivalent chromium is not considered for electroplating within the project since deposited layers are softer than Cr(VI) based ones. Nanostructured nickel, nickel-phosphorous and cobalt based coatings are found to be inferior to Cr(VI) based chrome coatings concerning hardness. For the assessment, a composite plating is used applying silicon carbide (SiC) and nickel in combination. The alternatives are experimentally evaluated at three stages, namely laboratory level, pilot line level and industrial level.

In summary, on the laboratory level, block-on-ring tests, flat sample tests and 2-discs & ring tests point at chrome layers from Cr(VI) based plating to be superior to the alternatives in wear resistance. Roughness retention tests under real rolling conditions at the pilot level reveal the very high standard of Cr(VI) based coatings in wear resistance. Only HVOF-WC shows similar retention of roughness among rolled strip length in the pilot testing, but the surface topography achieved with HVOF-coated pilot mill work rolls was far away from customer requirements. EDC showed higher wear rates but still good wear resistance. However, few tests on the industrial scale for the EDC technology reveals that the industrial application is feasible, roughness retention is better than for uncoated rolls, but not as good as for Cr(VI) chrome plated ones. However, the alternatives yield partially good results. EDC is promising in roughness, wear resistance and process efficiency but Cr(VI) based applications still remain unchallenged.

Alternative electrical discharge coating A CHL customer is involved in the 'Development of electrical discharge coating (EDC) as chrome-free alternative for increasing campaign length of temper mill work rolls' (Bröcking et al., 2015). The focus of the project is the evaluation of the application of EDC on temper mill work rolls as an alternative to hexavalent chromium based coatings with prior EDT (Electrical Discharge Texturing) texturing process.

To evaluate the potential of EDC, EDT treated rolls are compared to EDC surface treatments applying titanium carbide (TiC) and tungsten carbide (WC) phases to the work rolls. The roughness retention of the differently treated rolls are tested at the laboratory scale applying block-on-ring tests and 2-disc & ring wear tests. On a larger scale, rolls are tested in pilot mill roughness retention tests.



In summary, the laboratory scale study indicates that EDC-WC and EDC-TiC surface layers on temper mill work rolls exhibit roughness retention comparable to EDT textured ones rolls applying a functional chrome coating on top. However, on the larger pilot mill scale in roughness retention tests, possible alternatives are superior to uncoated EDT work rolls, but show lower roughness retention compared to functional chrome plated rolls. Macro-cracks increasingly occur at lower pulse currents and therefore at increased thickness of the recast layer cracks do not propagate at mechanical strain. The project indicates that EDC coating is a possible alternative to functional chrome plating (with EDT texturing), but further research needs to be conducted.

Hard chrome deposition from ionic liquid solutions project On behalf of HOCO RST – a joint venture of CHL and Tata Steel – TNO Science and Industry investigated hard chrome deposits from ionic liquid solutions as an alternative to hexavalent chromium based functional chrome plating.

In the study, Bressers and Gonzalez Rodriguez (2010) use Cr(III) for deposition from chromium trichloride contained in eutectic mixture with choline chloride. Establishment of chromium deposition form ionic liquids turns out to be possible. However, achieved layers are rough and inhomogeneous and show the build-up of large cauliflower-like shape grains. To date it is unclear whether those structures provide similar properties in cracking as Cr(VI)-based depositions. Advice is given to further investigate tribological properties regarding friction, wear and lubrication. Additionally, the tested ionic liquid is not found to fulfil requirements of hardness.

The study indicates that ionic liquids applying trivalent chromium are not ready for up-scaling. Before this method is applicable in industrial uses, further effort in fundamental research is needed.

Ecochrom The project Ecochrom on the “eco-efficient and high performance hard chromium process” is an Intelligent Manufacturing System-Growth project and has the objective to study and develop an environmentally and economically acceptable process allowing thick chromium coatings which are harder and more resistant to corrosion than traditional coatings, from a new and nontoxic electrolytic solution. Ecochrom is a consortium/working group of industrial platers, fundamental and applied researchers as well as end-users in Canada, USA, Japan and Korea, and is coordinated by TSM (Surface Treatment Mechanics), the main functional chrome plating specialist in France. The results of the Ecochrom project are still confidential.

The hard chrome alternatives team The Hard Chrome Alternatives Team (HCAT), is a US-Canadian collaboration of environmental working groups of the Departments of Defence of the two nations. They pursue the objective to demonstrate and validate that the alternative High Velocity Oxygen-Fuel (HVOF) is a superior alternative to functional chrome plating. Their efforts particularly focus on the aerospace industry and military use. Increasing time intervals between maintenance and reduced turnaround times for repair of components would lead to more sustainable performance. However, HCAT concluded that HVOF is not a generic alternative, neither technically (due to temperature and geometrical limitations) nor economically (high costs).

Advanced surface engineering technologies for a sustainable defense The Advanced Surface Engineering Technologies for a Sustainable Defense (ASETSDefense) is a US Department of Defense (DoD) initiative sponsored by the department’s two environmental research programs (Strategic Environmental Research and Development Program and Environmental Security Technology Certification Program (ESTCP)). Its objective is to facilitate the implementation

http://www.serdp-estcp.org/



of more environmentally friendly technologies for surface coatings and surface treatments. This initiative wishes to provide access to background information and technical data from research, development, test, and evaluation efforts as well as the status of approvals and implementations. ASETSDefense targets defence organizations and provides information to reduce environmental safety and occupational health impacts from coatings and treatment processes that utilize e.g. chromium plating from hexavalent solutions. The database providing information on the DoD´s data on authorization and implementation of alternatives is readily accessible to the public (http://www.asetsdefense.org as of August 6, 2014).

6.1.2. Data searches

For the CTAC AoA, extensive literature and test reports were provided by the technical experts of the Consortium members. Furthermore, searches for publically available documents were conducted to ensure that all potential alternate processes to chromium trioxide-containing applications were considered in the data analysis. The AoA at hand falls back on the CTAC data search and adds additional input from CHL experts.

In addition to databases for scientific literature, the following programmes were intensively consulted during the CTAC preparations: Toxics Use Reduction Institute, Massachusetts, US (www.turi.org/); and The Advanced Materials, Manufacturing, and Testing Information Analysis Center (AMMTIAC: http://ammtiac.alionscience.com/).

Searches for SDS for chromium trioxide-containing and chromium trioxide-free applications were conducted.

6.1.3. Consultations

Court Holdings Limited consultations For the purpose of the present AfA the extensive data collection from CTAC has been re-evaluated. All alternatives have been re-assessed for CHL applications with a focus on the application of chromium trioxide in the functional chrome plating of work rolls dedicated to the use in metal rolling mills.

In summary, the categorized table of alternatives listed in Section 5.3 below is the outcome of an extensive literature search, research conducted by CHL and its joint ventures respectively and consultations with technical experts in the field of surface treatment, including information derived from the CTAT consultations.

6.2. List of possible alternatives Regarding the substitution of chromium trioxide in the functional chrome plating of work rolls used in steel mills two general substitution concepts are identified.

1. The usage of work rolls with alternative properties without additional coating. 2. The application of alternative coating or surface treatment technology which is not based

on hexavalent chromium compounds.

For each of the two general concepts, possible alternatives are identified for replacing chromium trioxide against the backdrop of abovementioned key functionalities. Table 7 gives an overview of possible alternatives within the concepts 1 and 2 which are discussed in further detail in chapter 7.1 and 7.2.

http://www.asetsdefense.or/

http://www.turi.org/

http://ammtiac.alionscience.com/



Table 7: List of concepts and corresponding alternatives for replacing chromium trioxide.

Concept No. Alternative

1

1

Alternative forged steel work roll grades • Forged High-Speed Steel (HSS) rolls • Forged semi-HSS rolls • Forged Ti-enhanced rolls

2 Alternative cast steel work roll grades

• Cast High-Speed Steel (HSS) rolls • Cast semi-HSS rolls

3

Rolls with very fine microstructure produced by special roll manufacturing • Continuous pouring for cladding (CPC) • Powder Metallurgy-based Hot Isostatic Pressing (PM HIP) • Electro-Slag Remelting Cladding (ESR Cladding) • Laser Cladding

2

4 Chrome coating based on a Cr(VI)-free deposition process

5

Electro and electroless deposition processes • Electroless plating • Nickel and nickel alloy plating • Nano-crystalline cobalt phosphorous alloy coating • High velocity thermal process

6 Electro-Discharge Coating (EDC)



7. SUITABILITY AND AVAILABILITY OF POSSIBLE ALTERNATIVES

To assess the feasibility of the alternatives, colour-coded summary tables are included in the document. The colours are as follows:

The alternative assessments each comprise a non-exhaustive overview of substances used with the alternatives and alternative processes as well as the risk to human health and environment. These tables are provided in Appendix 2. Note that the list of substances provided for each alternative is extensive but not conclusive.

7.1. Concept 1: Work rolls with alternative properties Alternatives listed under Concept 1 encompass work roll materials with alternative metallurgic properties for replacing chromium trioxide based functional chrome coatings. Such alternative are forged and cast steel work roll grades as well as rolls equipped with very fine micro-structures established by special roll manufacturing. The technical assessment for these alternatives is illustrated in the following table. As of today, it can be clearly concluded that none of the replacement techniques can be seen as an alternative. For detailed assessment the reader is referred to section 7.1.

Table 8: Summary of technical assessment of Concept 1 alternatives (CR: Cold rolling; HR: Hot rolling; TR: Temper rolling).

Wea

r re

sist

ance

Har

dnes

s

Surf

ace

clea

nlin

ess

(CR

, HR

)

Surf

ace

appe

aran

ce (T

R)

Coe

ffic

ient

of f

rict

ion

Top

ogra

phy

Res

ista

nce

to r

apid

te

mpe

ratu

re c

hang

es

Surf

ace

mor

phol

ogy

Mac

hina

bilit

y

Tre

atm

ent t

ime

Forged (S)HSS

Forged Ti enhanced

Cast (S)HSS

CPC

PM HIP

ESR Cladding

Laser cladding

Colour Explanation

Not sufficient – the parameters/assessment criteria do not fulfil the requirements

The parameters/assessment criteria fulfilment not yet clear/ fulfil some requirements for some but not all applications

Sufficient – the parameters/assessment criteria do fulfil the requirements

No data available



7.1.1. Alternative 1: Alternative forged steel work roll grades

Alternative 1 encompasses alternative forged steel work roll grades, making use of extra carbide-forming alloying elements increasing the wear resistance and includes the following:

• Forged High-Speed Steel (HSS) rolls • Forged semi-HSS (SHSS) rolls • Forged Ti-enhanced rolls

Substance ID and properties

HSS is a loosely used term and there are no standards or definitions. HSS are multi-component alloys that contain tungsten, chromium, molybdenum, vanadium, as well as carbon (latter with >0.5 %wt). The alloys are transformed by an appropriate heat treatment process above 450 °C (Gaspard et al., 2002a) to HSS.

There is no clear demarcation between semi-HSS and HSS, but a general composition of both is given in Table 9.

Table 9: Shares of alloyed elements in semi-HSS and HSS (Source: Gaspard et al., 2002a).

Element Grade

Semi-HSS HSS

C 0.5 – 1.0 0.8 – 1.5

Cr 4.0 – 10.0 8.0 – 13.0

Mo 0.5 – 2.0 0.5 – 3.0

V 0.5 – 1.0 0.5 – 3.0

W < 1.0 < 2.0

HSS has been developed by the roll manufacturer Åkers A.B. (Sweden). At this manufacturer, focus of development has shifted since 2000 from SHSS to HSS. However, as mentioned above, there is no clear demarcation between semi-HSS and HSS. Several generations of HSS have been developed since then. Currently, Åkers offers forged High-Speed Steel for the use in cold rolling mills, partly under the tradename INVICTA. Available are ground or electrical discharge texturized forged HSS work rolls.

Titanium enhanced work rolls are another type of alternatively forged steel work grades seeking to increase wear resistance and hardness (Shimizu et al., 1992). Titanium is chosen to be added to standard 3 to 5% Cr forged work rolls, since the formed Titanium carbide exceeds hardness of 3000 HV, thus promising extended durability. Thereby, the Titanium content varies. Li et al. (2008a) indicate a 4% Cr steel enhance by 0.11% Ti. Ti-enhance work rolls are offered on the European market by Sheffield Forgemasters.

Technical feasibility

Wear resistance: Gaspard et al. (2015) (Åkers A.B., Sweden) report increased wear resistance of forged HSS in the form of percentage run length expressed as tonnes per campaign. Compared to the reference of standard 5% Cr forged steel, chrome plated standard steel exhibits approximately 200% while HSS forged steel shows 300 to 500% run length. This rather is related to the quality of the metal



strip rolled regarding issues like indentions or roughness retention. The percentage roll consumption per 1000 tonnes rolled metal strip for chrome coated work rolls is stated to be the same as for standard forged ones. In contrast, HSS forged work rolls reveal < 30% roll consumption. However, during the consultation phase it appeared that the results presented by Gaspard et.al. are by no means representative for all cold rolling and temper rolling mills, but only cherry-picked best results obtained in isolated cases under idealised circumstances. CHL’ customers have performed trials aimed at achieving similar results with forged HSS rolls with a disappointing outcome; in general no campaign length extension has been achieved, and sometimes premature unplanned roll changes were necessary. It is suspected that such disappointing field test results might be related to the poor machinability resulting in suboptimal as-ground roll surface topography.

Regarding the wear resistance of Ti-enhanced steel, only data from the laboratory scale is available. No results of tests under relevant cold or temper rolling conditions are available. However, forged (S)HSS work roll grades fulfil the requirements in hardness under real rolling conditions in cold, temper and hot rolling mills.

Hardness: The hardness of the matrix is reported to be up to 820 HV for semi-HSS and HSS forged steel work rolls (Gaspard et al., 2002b). Electrical discharge texturing of HSS forged steel temper mill work rolls, skin-pass work rolls respectively, thereby establishes hard eutectic carbides precipitations increasing the roughness retention. Although hardness of forged HSS allows for increased roughness retention it does not fulfil the requirements in hardness of up to 1000 HV, but may be sufficient for individual rolling campaigns.

According to the consultation, the roll manufacturer Sheffield Forgemasters indicates a hardness of more than 1000 HV for Ti-enhanced work rolls, which is sufficient for the application in cold and temper rolling metal mills.

Surface cleanliness: The surface cleanliness of the metal strip is of major importance in cold rolling of metal. Dirt remainders on the strip surface may impair subsequent treatment processes, such as galvanizing or annealing, especially batch annealing. Gaspard et al. (2002b) report the general absence of dirt and – therefore good strip cleanliness – for semi-HSS and low V-content HSS work rolls tested in tandem cold rolling mills. However, according to the consultations, the strip cleanliness of forged HSS work rolls turned out to not sufficiently fulfil the requirements. According to the consultations, results for strip cleanliness from the manufacturer Åkers A.B, publications from Gaspard et al. (2002b) on the topic respectively, is biased and data is not proven. Based on internal

Figure 19: Trials (T1-5) of forged HSS work rolls in the first two stands of a 5-stand cold rolling tandem mill (steel grades: H300LA and MBW 1500, HSS = forged High Speed Steel rolls, SSt (HV) = standard forged 3% Cr rolls (chrome plated), S = stand (1-5)).



trials, the surface cleanliness is even reported to be no better than the cleanliness of untreated standard work rolls. An internal trial in a 5-stand tandem cold mill with forged HSS rolls in stand number 1 showed a significant drop in strip surface cleanliness (about 10 percent points lower reflection value) as with Cr-plated rolls in the same stand (Figure 19). This drop in cleanliness is similar to the application of uncoated standard rolls. When removing the chrome coating from work rolls in up to 3 stands, the drop in surface cleanliness can even be up to 20 percent points lower reflection value).

Additional internal trials in a 5-stand tandem cold rolling mill revealed superior strip surface cleanliness for chrome plated standard 3% Cr forged work rolls over forged SHSS work rolls (Figure 20). While trials with chrome plated standard work rolls (steel grade S320) show initial strip surface cleanliness of > 70% in reflectivity test, SHSS rolls reveal an initial value of 68% decreasing to < 50% after 75 coils rolled. In contrast, decrease in reflectivity is lower for chrome coated standard rolls with > 65% after 75 coils rolled. The S(HSS) rolls were applied in the first two stands of the tandem mill. Trials comparing HSS rolls to non-chrome plated standard rolls in stand 2 of a 5-stand tandem mill reveal similar results (Figure 20). The reflectivity value remains higher in case of campaigns run without HSS rolls in stand two among coils rolled thus indicating better resulting strip cleanliness than HSS work rolls.

However, Gaspard et al. (2002b) report problems with the cleanliness of the rolled strip when applying high vanadium content work rolls in cold rolling, which was sourced to the evolution of small dust particles resulting from the abrasive properties of vanadium carbides.

According to Sychterz (2015) reports limitations of SHSS II (2nd generation of semi-HSS) steel work roll grades concerning surface strip cleanliness for some applications. In cold steel reduction mills applying batch annealing severe strip cleanliness issues occurred. The author considers forged SHSS II work rolls to be currently applicable in mills with continuous annealing lines, additional cleaning devices, or in mills dedicated to tin plate production as well as aluminium rolling, where strip cleanliness is no issue. Sychterz (2015) refers to further improvements that have to be made before SHSS II work rolls may become an overall opportunity for cold rolling and temper mills. Therefore, forged (S)HSS work rolls are not a drop-in alternative to chrome coated work rolls in cold rolling mills.

Figure 20: Trials (T1-4) of forged Semi-HSS work rolls in the first two stands of a 5-stand cold rolling tandem mill (steel grades: T1 & T2: S320 and T3 & T4:; DC05, SHSS = forged Semi- High Speed Steel rolls, SSt (HV) = chrome plated standard forged 3% Cr rolls, S = stand (1-5)).



To date, there is limited data on the strip cleanliness of Ti-enhanced work rolls available. So far, a CHL customer has only trialled Ti-enhanced rolls in two temper mills. Preliminary results indicate surface quality issues in temper rolling with similar unfavourable prospects similar to cold rolling processes. Therefore, extensive trials under applied conditions in cold and temper rolling mills are needed to further assess the suitability of the alternative regarding the surface cleanliness after rolling, if ever to be sufficient.

According to the consultations, HSS, semi-HSS or Ti-enhanced rolls have not yet been trialled for galvanized strips, because such alternatives must first be qualified for less critical temper rolling applications. There are no records of successful testing of such new roll grades for temper rolling of galvanized strips. There are also no lab-scale results indicating that HSS, semi-HSS or Ti-enhanced rolls can challenge the excellent anti-sticking properties of the chrome plated work rolls.

However, in principle it is imaginable to improve the surface cleanliness by partial solutions in addition to the alternative forged steel work grades. Possible partial alternatives are strip or roll cleaning devices, tailored adjustments to the lubricant or alternative roll grinding processes to reduce the abrasive impact of the roll on the metal strip.

According to the consultations, the effectiveness of additional roll cleaning is variable and devices are often found to be insufficient for cold mills producing product mixes containing surface-critical products, such as tin plates or products for the automotive industry. Cleaning methods can be based on mechanical methods, such as brushing, high-pressure water sprays, possibly with additions of cleaning agents to the spray water.

Devices for cleaning the strip during rolling are separate strip cleaning lines, inline cleaning devices or interstand cleaning devices. Separate cleaning lines are technically feasible, but suffer from severe economic drawbacks. Estimated costs for additional e.g. electrolytic cleaning lines for flat steel are in the double-digit million EUR range (for detailed information, refer to the socio-economic analysis (SEA)). Furthermore, such cleaning lines are in need of extensive space at the production site, which is mostly not available. Figure 21 illustrates the dimensions of such cleaning line setups.

Figure 21: Electrolytic cleaning line for flat metal products as distributed by Cockerill Maintenance & Ingénierie (Source: CMI Group website, http://www.cmigroupe.com/en/p/electrolytic-cleaning-lines)

Inline cleaning sections are somewhat less costly (though still require investments of millions of Euro) and more compact but still require a large amount of space between mill hardware components. Such space is rarely available in existing cold rolling mills so that this option is only available in the design phase of new cold rolling mills.

http://www.cmigroupe.com/en/p/electrolytic-cleaning-lines



According to the consultations, although in principle feasible, the existing cold mills do not offer the spatial requirements. Methods of interstand cleaning in between the first stands of the rolling mill are theoretically possible. However, such devices are not commercially available. As they need to be extremely compact, highly effective and very robust to serve between industrial metal strip cold rolling mill stands, a dedicated development programme for novel interstand cleaning devices will be required, including design, construction, laboratory trialling and field trialling.

The tailored adjustment of the applied lubricant basically represents a theoretical opportunity for improving the strip surface cleanliness. However, in practice, recent research indicates that the composition and the concentration of the oil in the lubricant has little effect on the strip cleanliness (Jacobs et al., 2011). According to the consultations, research has been ongoing for decades without any robust effective results. Substantial effort in R&D has to be made to consider lubricant adjustments as being at least a partial solution.

Alternative roll grinding processes can theoretically improve the strip surface cleanliness by reducing the abrasive impact of the work roll on the rolled metal strip. However, as mentioned, the partial alternative is theoretical in nature and substantial R&D efforts have to be made since respective processes are to date unknown.

Adhesion to the substrate: In the case of forged HSS and Ti-enhanced work rolls no additional coating is applied to the rolls. Instead, the work rolls are manufactured from alternative forged steel grades. Regarding the electrical discharge texturized work rolls, the surface treatment is based on re-melting and solidification of the surface layer.

Surface appearance: Issues of surface appearance predominantly refers to temper mill operations. An internal trial in a standalone temper mill with Ti-enhanced work rolls showed a worsening of strip surface appearance, manifested by a rather inhomogeneous look in terms of broad duller and brighter bands. This worsening was not acceptable for the customer and even more severe than in a parallel trial with uncoated standard rolls.

Coefficient of friction: The coefficient of friction measured in pilot mill trials, simulation 4Hi TDM 5 stands mills dedicated to the production of automotive sheet metal indicates lower coefficients for grounded only forged HSS (µ=0.048) than for chrome plated work rolls (µ=0.060). Gaspard et al. (2015) refer to the lower rolling friction as potentially being the reason for improved roughness retention based on lower shear stresses in the gap between the work roll and the strip surface. Information on the application in work rolls of skin-pass mills rolls (temper mills) is – according to the authors – not yet sufficient. However, work roll applications in cold rolling mills is needed for stable tribological conditions. There is no indication that forged HSS may not fulfil friction-related requirements of cold rolling work roll surfaces.

Topography: The surface topography of forged (S)HSS and Ti enhanced rolls is dependent on the grinding process, which –according to Gaspard et al. (2002a) – can, in case of semi-HSS, be conducted with already established grinding equipment for conventional forged work rolls. For HSS, the grinding process needs to be adopted. However, grinding procedures for (S)HSS in practice is, according to the consultations, difficult (refer to 'Machinability').

Especially for temper rolling products dedicated to the automotive sector, domestic appliances or steel packaging, the surface specifications are highly demanding and therefore the exact adjustment of the surface roughness and waviness of the work roll surface is of major importance. According to the consultations, mill experience so far indicate that the most critical surface topography specifications can only be guaranteed when using chrome plated work rolls. Neither Ti-enhanced



rolls, nor HSS rolls have been trialled yet for those critical specifications since problems are already occurring in rolling operations with lower surface topography specifications.

Therefore, at the current state, alternate forged (S)HSS and Ti-enhanced work roll grades are not suitable alternatives to functional chrome plated ones.

Surface morphology: The surface morphology of HSS is characterized by a homogeneous distribution of secondary carbides of the alloyed elements (Gaspard et al., 2011). Figure 22 shows the difference in microstructure between standard and forged HSS work rolls.

Figure 22: Comparison of the microstructure of forged HSS and standard forged 1-6 % Cr work rolls (Source: Gaspard et al., 2011).

Resistance to rapid temperature changes: The tempering temperature of forged (S)HSS work rolls in the course of manufacturing can be up to 500 °C. Ultrashort surface temperature flashes in the roll bite are ≥200 °C and therefore, the alternative therefore matches the requirements in temperature resistance.

Machinability: According to the consultation, machinability of HSS work rolls is a major problem restricting the usability in cold, temper and hot rolling applications. For HSS work rolls, being of exceptional wear resistance, grinding wheel suppliers were found to be incapable of delivering tailored grinding wheels yielding sufficient results regarding the relevant mill specifications. The rolls need to be ground within the required Ra ranges, which differ per mill stand, without any grinding defects such as scratches, so-called commas, feedlines or facetting. Grinding appeared to be impossible with standard grinding wheels so that grinding wheel suppliers had to develop a tailored grinding wheel. The grinding result depends on a careful balance between roll properties, mill specifications for the grinding result, grinding wheel type, grinding machine characteristics and capabilities as well as process parameters for the multi-steps grinding process.

A CHL customer was engaged in trialling (S)HSS work roll grades for cold and temper mill applications. For one particular mill, the customer reported a long trial period (almost 2 years) to establish a suitable combination of the grinding wheel, the grinding machine characteristics and



capabilities as well as the process parameters for the multi-steps grinding process. Subsequently, the grinding wheel supplier went bankrupt so that the tailored grinding wheel could not be sourced anymore. It took another period of 2 years for grinding trials with various wheels. One wheel supplier failed, whereas more or less acceptable results were achieved with another supplier. To date, the grinding result is not optimal and further trialling is planned. The type of roughness obtained from grinding of HSS rolls appears to be different from, and less resilient, than the roughness on as-ground standard rolls. Therefore, HSS rolls are changed more frequently for "too smooth" or "skidding" than standard rolls.

Furthermore, a CHL customer has trialled an older type of forged semi-HSS rolls. Their machinability was clearly better compared to full HSS rolls, but these rolls were found to be soft and therefore not meeting the hardness specification. In addition, the rolls showed a relatively fast wear (loss of roughness asperities) when used in the non-chrome plated condition. The customer has not yet trialled the latest SHSS-II version (2nd generation), which exhibit higher degrees of hardness.

According to the consultations, Ti-enhanced work rolls have been found to provide for only poor machinability. In roll shop trials, grinding to the Ra specifications required for the target temper mill rolling campaigns appeared to be impossible. The achieved Ra level was consistently too low. In another roll shop trial, the Ti-enhanced rolls could be ground satisfactorily only because a low Ra value of the as-ground roll was acceptable for the respective application. After grinding, the required final Ra was applied by means of electrical discharge texturing, which is easily possible for Ti-enhanced work rolls.

During the consultation it was stated that relevant R&D of the grinding wheel suppliers for the niche application of grinding (S)HSS are lagging behind the roll suppliers. Even if a suitable grinding wheel and a corresponding programme is developed, the tailored wheel cannot be used for standard roll grinding processes. The roll shop capacity would be reduced each time the respective wheel would need to be changed.

Therefore, neither (S)HSS work roll grades, nor Ti-enhanced grades are suitable substitutes to chrome plated work rolls in terms of grindability.

Treatment time: Since no additional coating is applied in case of alternate manufacturing methods, the time needed for preparing the work rolls for the use in rolling mill operations is decisive. The treatment time is extended since grinding takes longer in case of higher alloyed grades. This is mainly due to increased wear resistance leading to longer grinding times and more grinding passes. For a modern grinding machine the grinding of standard rolls and (HS)HSS rolls differs by the factor of approximately 2. For older grinding machines, the factor may be higher, in case grinding of (S)HSS is even possible. Another aspect is that roll shops need to switch between the tailored grinding wheel for these higher-alloyed grades and the standard grinding wheel for the conventional rolls, which takes several hours each time to prepare the machine.

Summary of technical feasibility: The following chart gives an overview of the assessment of alternative forged (S)HSS and Ti-enhanced work grades as alternative to chrome coated work rolls in cold and temper rolling mills.



Economic feasibility

Against the background of significant technical failure of (S)HSS, no quantitative analysis of economic feasibility was conducted.

Despite the higher price of forged HSS work rolls, the forged HSS roll manufacturer Åkers A.B. refers to lower Total Cost of Ownership (TOC) compared to conventional chrome coated work rolls. The stated reduction in costs is reported to derived from lower mill downtime, smaller work roll stocks, the omission of the chrome coating and reduced grinding (Gaspard et al., 2015).

According to the consultations, quotations for forged HSS rolls consistently show prices that are at least 3 times, typically 4 times and occasionally even up to 7 times the price of a standard work roll of the same weight and dimensions. Especially claimed lower costs for grinding are challenged by the applicants based on internal R&D efforts (refer to the paragraph 'Machinability' above). The higher cost effectiveness of forged HSS rolls compared to chrome plated standard rolls, as claimed by Åkers, is based on a hypothetical situation, in which the mill campaign length can be increased by a large factor of at least 4. The higher mill productivity, the lower roll consumption rate and the saving of the chrome plating costs outweigh the higher purchasing costs of the roll, and the 4 times lower regrinding frequency outweighs the longer grinding time per redressing cycle.

However, according to the consultations, this hypothetical situation does not apply. By now, longer campaign lengths could not be achieved and technical issues with poor grindability and premature loss of roughness still persist. Semi-HSS and Ti-enhanced rolls are roughly 1.5 to 2.5 times more expensive than standard work rolls.

Therefore, from the economic point of view, alternative forged work roll grades are no suitable replacement for chrome coated work rolls in cold rolling and temper mills.

Reduction of overall risk due to transition to the alternative

As the alternative is not technically feasible, only classification and labelling information of substances and products reported during the consultation were reviewed for comparison of hazard profile, which is presented in the following. (Semi-) High Speed Steel is a loosely used term that defines alloys, containing iron, chromium, molybdenum, vanadium and tungsten. In case of Ti-enhanced work rolls, Ti is added to standard 3 to 5 % Cr forged work rolls. High Speed Steels are generally considered non-hazardous to human health and the environment. As a worst case scenario,

Wea

r re

sist

ance

Har

dnes

s

Surf

ace

clea

nlin

ess

Surf

ace

appe

aran

ce

Coe

ffic

ient

of f

rict

ion

Top

ogra

phy

Res

ista

nce

to r

apid

te

mpe

ratu

re c

hang

es

Surf

ace

mor

phol

ogy

Mac

hina

bilit

y

Tre

atm

ent t

ime

Assessment overview for forged Ti-enhanced work roll grades



tungsten is registered under REACH classified as Flam. Sol. 1 and Self.-heat. 2. However, transition from chromium trioxide, which is a non-threshold carcinogen, to forged (S)HSS or Ti-enhanced work roll grades would constitute a shift to a less hazardous substance.

Availability

According to the consultations, alternative forged steel work rolls were specifically developed for cold rolling and temper rolling mills. They are commercially available but not yet at large scale and not from many suppliers, and in most cases they are not yet fully optimized.

Until recently, the forged blanks for production of forged HSS rolls under Åkers’ brandname INVICTA were exclusively produced on Åkers’ manufacturing site in Thionville (France) and ESR-treated before forging on Åkers’ manufacturing site in Liège (Belgium). However, near the end of the consultation phase, all rollmaking activities on both Åkers production sites were shut down due to lack of economic viability and the sites were placed in receivership (which is also an indication that the INVICTA rolls did not bring the breakthrough technology hoped for by the metal rolling industry). Simultaneously, Ampco-Pittsburgh Corporation (USA), the corporate parent of roll manufacturer Union Electric Steel (UES) Corporation, has signed an agreement to acquire Åkers AB and certain of its affiliated companies, including Åkers’ rollmaking-related intellectual property (IP) but excluding Åkers’ sites in Liège (B), Thionville and Berlaimont (F). Consequently, there is currently no proven established manufacturing route anymore for INVICTA forged HSS rolls. The new owner Ampco-Pittsburgh Corporation intends to establish a new manufacturing route for INVICTA rolls via the production facilities of their subsidiary UES in the USA, but since the technical specifications of key equipments and the type of heat treatment technologies applied at UES are substantially different from those used in Thionville and Liège, ample time will be needed for development, fine-tuning, internal quality evaluation and external homologation (in customer trials) of this new INVICTA roll manufacturing route.

CHL's customers in the steel rolling industry have been engaged in field tests of forged HSS work rolls. Grinding turned out to be a major intricacy. The supplier of the tailored grinding wheels for grinding of HSS rolls went bankrupt during the trials at the customer. The grinding of work rolls is a niche application for grinding wheel suppliers, and grinding of HSS rolls to cold mill specifications is a niche within this niche application. Consequently, no grinding wheels were commercially available with similar HSS grinding behaviour, and the development of the HSS roll grinding process had to start all over again.

Trials were carried out but required functionalities have not yet been accomplished. Major issues to be solved are poor strip cleanliness and poor grindability. Grinding wheel suppliers need to develop tailored wheel grades and build up capacity. The only manufacturing site for large-size forged HSS roll blanks was shut down in December 2015 due to lack of economic viability. Therefore, new manufacturing capacity has to be developed and validated. The overall TRL/MRL assigned to forged HSS for cold rolling is 7.1/6 (chart below). For temper rolling, mill trials with forged HSS still need to be done and low hardness adds up to poor grindability leaving the TRL/MRL even lower with 6/6. TRL/MRL levels of forged HSS work rolls for aluminium hot rolling applications are 6/6 as well.



For SHSS work roll grades, mill trials for cold and temper rolling applications were carried out but required functionalities have not yet been achieved. Major issues to be solved are poor strip cleanliness and poor grindability. Grinding wheel suppliers need to develop tailored wheel grades and build up capacity. However, compared to HSS, the Manufacturing Readiness Level is higher. The overall TRL/MRL assigned to forged Semi-HSS for cold and temper rolling is 7.1/8 (chart below). TRL/MRL levels of forged Semi-HSS work rolls for aluminium hot rolling applications are equal to those of cold rolling.

Ti-enhanced work rolls were part of the portfolio of the Japanese roll manufacturer Hitachi and dedicated to the Japanese market only. According to the consultations, Hitachi never actively tried to sell the product outside of the domestic market. A customer of CHL approached Hitachi in the past for purchasing work rolls. Enquiries regarding a trial order by the customer were refused. Hitachi was not willing to quote for an export order to the European market. However, Ti-enhanced HSS work rolls are recently offered by the work roll manufacturer Sheffield Forgemasters and therefore are available. Trial rolls are manufactured for temper mills, but not yet as replacements for chrome plated rolls in cold mill operations. Major issues to be solved are poor strip cleanliness for cold rolling, poor surface appearance in temper rolling and grindability in both applications. Grinding wheel suppliers need to develop tailored wheel grades and build up capacity. The overall TRL/MRL assigned to Ti-enhance work rolls for cold rolling is 6/7 and for temper rolling 7.1/7 (chart below). TRL/MRL levels of Ti-enhanced work rolls for aluminium hot rolling applications are 5/6.



Despite the availability of HSS or Ti-enhance work rolls, it is not clear whether the capacities at the manufacturer suffice to cover the demand of the entire steel industry and how long it would take to provide for sufficient supply. According to the consultations, regular delivery times for work rolls are in the order of 5 months and can be expected to rise in case of shift to the alternative. Capacity building includes the adjustment of the work roll to the use in the respective mill and building up or extending the supply chain, potentially taking several years. This only refers to one supplier. Therefore, the availability of the alternative not only depends on the presence in the manufacturers' portfolio, but as well on the building up of supply capacities.

Overall, the alternative is due to insufficient capacities and too low TRL and MRL no suitable replacement for chrome plated work rolls, neither in cold nor in temper rolling mills.

Conclusion on suitability and availability for alternative HSS

In general, HSS work rolls bear the advantage of elevated wear resistance and corresponding roughness retention. However, the advantage turns into a disadvantage when it comes to machinability, which is of profound importance for cold, temper and hot rolling mill operations. Increased costs of purchase and long delivery times are further intricacies. Furthermore, the alternative requires a full redesign of the component because the process is completely different to functional chrome plating.

CHL’s customers in the steel rolling industry were engaged in field tests regarding forged HSS work rolls in cooperation with Åkers. According to the consultations, the possible alternative was not further followed because of

- very long and unreliable delivery times for follow-up trial orders, - grindability issues, - unsolved strip cleanliness issues, - and further gained experience in rolling difficult roll grades, reducing the mill incident

frequency while rolling such products, thus outweighing higher costs and grindability issues.

Forged semi-HSS and HSS work roll grades as alternative for functional chrome plating can, from a pure technical point of view, only cover some applications. The performance of several technical functionalities like wear resistance, coefficient of friction, and hardness were not sufficient. (Semi-)HSS rolls are not able to achieve a similar range of fundamental properties and benefits compared to a micro-cracked metallic chromium surface and thus are not a feasible alternative.



Forged Ti-enhanced work roll grades are recently available for temper mill applications, but not yet as replacement for chrome plated rolls in cold or hot mill operations. Data on the in-use performance in cold or temper rolling mills strip regarding functionalities like surface cleanliness and wear resistance is to date not present. Further testing would need to be carried out under real rolling conditions.

In summary, it is unlikely that (S)HSS or Ti-enhanced work roll grades will be a general replacement for chrome coated work rolls in cold, temper and hot rolling mills and it would take a minimum of 15 years to develop it as a general metallic chrome coating alternative, if ever possible.

7.1.2. Alternative 2: Alternative cast steel work roll grades

Alternative 2 encompasses alternative cast steel work roll grades, making use of extra carbide-forming alloying elements increasing the wear resistance and includes the following:

- Cast High-Speed Steel (HSS) rolls - Cast semi-HSS rolls


Cast HSS and Semi-HSS (SHSS) work rolls are bimetallic rolls with a relatively hard steel shell resulting from centrifugal casting, and a softer, lower alloyed core material. Table 10 provides the composition of cast Semi-HSS and HSS work rolls shells.

Table 10: Example chemical compositions of cast semi-HSS and HSS work rolls (Source: Tremea & Bellicini, 2010a).

Material %C %Cr %(Mo, W) %(V, Nb)

Semi-HSS 0.8 5 3 1

HSS 1.8 5 5 5

SHSS and HSS work roll grades are widely used in hot rolling mills for steel. However, they have not been specifically developed or adjusted for cold rolling and temper rolling mills, in which they are recently being trialled, nor for aluminium hot rolling mills. High degrees of hardness and wear resistance mainly derive from large amounts of alloying elements. Primary and secondary carbides as well as a martensitic structure are characteristics of cast High-Speed Steels. Thereby, SHSS differ from HSS in the presence of eutectic carbide networks (Tremea and Bellicini, 2010a) (Figure 23).



Figure 23: Microstructure of SHSS (M7C3 carbides 2-4%) left and HSS (M7C3 + MC carbides 8%) right (Source: Tremea and Bellicini, 2010a).


Wear resistance: The presence of primary and secondary carbides due extra carbide-forming alloying elements increasing the wear resistance, cast (S)HSS and HSS work rolls proved to be well wear resistant. Therefore, the alternative fulfils the requirements in wear resistance.

Hardness: Due to the lower mechanical strength of cast roll materials as compared to forged steel roll materials, cast steel rolls cannot be hardened up to the same hardness level as forged rolls. The maximum achievable hardness level of cast (S)HSS rolls is about 750 Vickers, which quite below the minimum hardness requirement for the current forged temper mill work rolls and also (but to a somewhat lesser extent) for cold mill work rolls. Hardness requirements for hot rolling is fulfilled.

Surface cleanliness: According to internal trials at a customer, the strip cleanliness of cast (S)HSS rolls in cold rolling operations is in the best case equal, but in average somewhat worse compared to uncoated standard rolls. However, the strip cleanliness is considerably worse than with chrome plated standard rolls. Cast (S)HSS rolls are even considered to be worse than forged (S)HSS rolls. Therefore, the alternative is not suitable to replace chromium trioxide based functional chrome plating of work rolls in cold and temper mill applications.

As for forged HSS work roll grades, additional roll cleaning devices for cleaning the strip, tailored adjustment of the applied lubricant or alternative roll grinding processes can theoretically improve the strip cleanliness. However, as discussed in chapter 7.1.1.2, none of those partial approaches to solve strip cleanliness issues of possible alternatives represents a ready-to-use solution.

Surface appearance: According to the consultations, cast (S)HSS rolls were not trialled in temper mills, because of insufficiency of cast roll types in terms of hardness specifications of work rolls for temper mills used at a CHL customer. Moreover, due to the coarseness of the microstructure a risk of an inferior surface appearance is anticipated. Therefore, cast (S)HSS does not fulfil the requirements in surface appearance after temper rolling operations

Topography: Like for forged (S)HSS and Ti enhanced rolls, the topography is dependent on the grinding and/or texturizing process. Especially for temper rolling products dedicated to the automotive sector, domestic appliances or steel packaging, the surface specifications are highly demanding and therefore the exact adjustment of the surface roughness and waviness of the work roll surface is of major importance. According to the consultations, mill experience so far indicate that the most critical surface topography specifications can only be guaranteed when using chrome plated work rolls.

Although establishing the required topography is generally possible, cast (S)HSS work rolls face the same problems regarding machinability like forged work roll grades (refer to chapter 7.1.1.2). Therefore, at the current state, the alternative is not suitable to replace functional chrome plating of work rolls.

Resistance to rapid temperature changes: Cast (S)HSS work roll grades differ regarding the alloy composition and are generally tempered at around 500 °C during roll manufacturing. Therefore, requirements in resistance to ultrashort temperature flashes of ≥200 °C and ≥250 °C in case of hot rolling are sufficiently fulfilled and there is no indication that the alternative may not be suitable in replacing chromium trioxide based functional chrome plating.



Machinability: As for forged (S)HSS work roll grades (refer to 'machinability' of alternative 1, section 7.1.1.2), cast ones bear the disadvantage of the grindability intricacy. For HSS work rolls, being of exceptional wear resistance, grinding wheel suppliers were found to be incapable of delivering tailored grinding wheels yielding sufficient results regarding the relevant mill specifications. Therefore, from the machinability point of view, cast (S)HSS work roll grades are by now no suitable alternative to chrome plated rolls.

Treatment time: Due to the poor machinability of cast (S)HSS work rolls, the treatment time needed to prepare the rolls for the use in cold rolling and temper mills, is expected to be significantly longer (refer to the paragraph 'treatment time' of alternative 1, section 7.1.1.2)

Summary of technical feasibility: The following chart gives an overview of alternative cast (S)HSS work roll grades as alternative to functional chrome coated rolls in metal mill applications.

Wea

r re

sist

ance

Har

dnes

s

Surf

ace

clea

nlin

ess

Surf

ace

appe

aran

ce

Top

ogra

phy

Res

ista

nce

to r

apid

te

mpe

ratu

re c

hang

es

Mac

hina

bilit

y

Tre

atm

ent t

ime

CR,TR


According to the consultations, for larger sized cold mill work rolls (>550 mm in diameter), prices are not significantly higher than for standard forged rolls. However, for the smaller sized cold mill work rolls, (<550 mm in diameter) and economic efficiency of manufacturer's operations (e.g. spun-casting, heat treatments) is expected to become inefficient, leading to an increase in the price difference to forged rolls. However, grinding problems are present for cast (S)HSS comparable to forged grades (refer to section 7.1.1.3), thus the alternative is expected to suffer from economic drawbacks as well. Therefore, from the economic point of view, alternative cast work roll grades so far are no suitable replacement for chrome coated work rolls in cold rolling and temper mills.


As the alternative is not technically feasible, only classification and labelling information of substances and products reported during the consultation were reviewed for comparison of hazard profile, which is presented in the following:

(Semi-) High Speed Steel is a loosely used term that defines alloys, containing iron, chromium, molybdenum, vanadium, tungsten and in some cases niobium. High Speed Steels are generally considered non-hazardous to human health and the environment. As a worst case scenario, tungsten is registered under REACH classified as Flam. Sol. 1 and Self.-heat. 2.

However, transition from chromium trioxide, which is a non-threshold carcinogen, to cast HSS would constitute a shift to a less hazardous substance.



Availability

The manufacturing capability for cast High-Speed Steel rolls is given for steel hot rolling mills only, since these rolls have not yet been adapted to cold rolling applications. SHSS work rolls are available, albeit from less suppliers than cast HSS. Mill trials were carried out, but required functionalities have not yet been achieved. Major issues to be solved are poor strip cleanliness, poor grindability and deficient hardness. Grinding wheel suppliers need to develop tailored wheel grades and build up capacity.

The overall TRL/MRL assigned to cast HSS and SHSS for cold rolling is 7.1/9 and 4/7 for temper mill rolling (chart below). TRL/MRL for cast (S)HSS in aluminium hot rolling applications are 6/6. The following chart gives on overview of the assigned TRL and MRL for cast (S)HSS work roll grades in cold and temper rolling applications.

Conclusion on suitability and availability for the alternative cast steel work roll grades

Spun-cast (Semi)HSS work rolls are not regarded as a potential drop-in solution for all operational mills. Provided substantial further development occurs, the alternative could become a partial solution for some cold rolling mill operations, but cast (S)HSS cannot meet the overall combination of technical specifications for cold and temper rolling as well as aluminium hot rolling mills in general. Major technical issues like poor strip surface cleanliness and grindability still need to be solved. Therefore, the potential alternative is not available as a technological mature, overall alternative to chrome plated work rolls for cold, temper and hot rolling mills.

7.1.3. Alternative 3: Fine micro-structured rolls

Alternative 3 comprises work rolls with specific fine microstructures which are achieved by special roll manufacturing methods, including:

- Continuous pouring for cladding (CPC). - Powder Metallurgy-based Hot Isostatic Pressing (PM HIP) - Electro-Slag Remelting Cladding (ESR Cladding) - Laser Cladding

According to the consultations, the conventional roll manufacturing methods (forging, spin casting, static casting) have limitations in terms of alloying freedom and achievable solidification rates, which are restrictive for development of novel roll grades with superior properties as desired for the work rolls of rolling mills.



With special alternative roll manufacturing methods, these limitations can potentially be circumvented, so that a high alloying level can be combined with a much finer microstructure than in conventionally produced forged or cast rolls. This could yield the desired combination of functionalities in the metal rolling mills, such as high wear resistance, roughness retention, high hardness and indentation resistance on the one hand, as well as high strip surface cleanliness and excellent strip surface appearance on the other hand.

However, according to the consultation, the manufacturing of work rolls for cold and, temper mills still needs to be proven. The same applies to work rolls for aluminium hot rolling mills. In the following, the availability and technical suitability of the possible alternatives CPC, PM HIP, ESR cladding and laser cladding are discussed in detail.

Continuous pouring for cladding (CPC)

7.1.3.1.1 Substance ID and properties

The continuous pouring for cladding (CPC) is based on the continuous cladding of a core steel part by applying a molten metal shell. The shell delivers fine cast structures due to hard carbide precipitations, as well as high hardness and wear resistance. During the cladding process molten metal is poured into the space between the core metal part and the surrounding water-cooled mould (Figure 24). Thereby, the core metal part is continuously withdrawn from the mould.

Figure 24: Schematic of the Continuous Pouring for Cladding (CPC) Process (Source: Hashimoto et al., 2002).

Subsequent heat-treatment at 200 °C is applied to increase the hardness (Hashimoto et al., 2002). Hashimoto et al. (2002) applied a medium-carbon HSS grade steel, containing 1 mass% C-Cr, Mo and V, for cladding the metal core. In general, various cladding materials may be used.

In contrast to ESR manufactured forged 'conventional' and HSS work roll grades, CPC cladded work rolls are characterized by hard eutectic M6C type carbides and fine grains, while forged HSS exhibits larger grains and a coarse eutectic carbide structure (Figure 25).



Figure 25: Comparison of the microstructure of CPC manufactured HSS and ESR casted forged 'conventional' as well as HSS work roll grades (Hashimoto et al., 2002).

7.1.3.1.2 Technical feasibility

Wear resistance: Wear resistance of work rolls used in cold rolling mills is a decisive point when it comes to durability and retention of the important feature of surface roughness. CPC manufactured work rolls with a HSS shell including chromium, vanadium and molybdenum is reported to show stable roughness retention under actual rolling operation conditions in a five-stand tandem cold mill over high rolling tonnage (Figure 26).

Hardness: The outer shell hardness of CPC manufactured HSS work rolls is reported to be around 800 HV, sharply decreasing at a distance to the surface of 50 mm (Figure 27). However, hardness up to 1000 HV, as required for current cold and temper rolling applications of chrome coated work rolls is not proven. Still, hardness may be sufficient for individual rolling campaigns. Hardness requirements for hot rolling are fulfilled.

Figure 26: Roughness retention of CPC, electro-slag re-melted (ESR) HSS and conventional 5 % Cr work rolls for tinplate rolling (Source: Hashimoto et al., 2002).



Figure 27: Hardness transect of a CPC treated High Speed Steel (HSS) work roll with a diameter of 580 mm (Source: Hashimoto et al., 2002).

Surface cleanliness: According to the consultations, no experiences on the performance of CPC manufactured work rolls in cold and temper rolling exist. The shell of a CPC roll has a similar alloy composition as the barrel shell of a spun-cast HSS work roll, but the microstructure is much finer due to the faster solidification rate. According to the consultations, one hypothesis states that the finer shell microstructure could have a positive effect on strip surface cleanliness during cold rolling but this hypothesis has not been validated yet. Costly and time-consuming preparation and execution of mill trials will be needed to examine the validity of the hypothesis. CPC rolls have not been trialled by the applicants, however, according to the consultations, there is no indication that CPC-HSS rolls could challenge the superior anti-sticking properties of chrome-plated standard rolls.

As for forged HSS work roll grades, additional roll cleaning devices for cleaning the strip, tailored adjustment of the applied lubricant or alternative roll grinding processes can theoretically improve potential drawbacks in strip cleanliness. However, as discussed in chapter 7.1.1.2, none of those partial approaches to solve strip cleanliness issues of possible alternatives represents a ready to use solution.

Surface appearance: According to the consultations, no experience with CPC work rolls exist and no data on trials for temper rolling is available in the public domain. There is no indication that CPC-HSS rolls could challenge the superior strip surface appearance achieved with chrome plated standard rolls.

Coefficient of friction: To ensure the appropriate rolling process quality as well as the quality of the rolled metal strip, the coefficient of friction needs to stay stable, even during long rolling campaigns. CPC manufactured and HSS cladded work rolls in five-stand tandem cold mills are reported to be stable in rolling above 2500 tonnes of tinplate (Hashimoto et al., 2002).

Topography: Although establishing the required topography by grinding and/or texturing is generally possible, CPC-HSS work rolls face problems regarding machinability (refer to paragraph 'machinability').

Resistance to rapid temperature changes: Hashimoto et al. (2002) report a tempering temperature for CPC cast work rolls of up to 500 °C (773 K). Therefore, the temperature resistance requirement of min. 200 °C, as present in the roll bite, is fulfilled.



Surface morphology: The micro-structure of CPC cast HSS work rolls is characterized by M6C, MC type carbides of 5 % (Hashimoto et al., 2002). The shell of the barrel (i.e. the working layer of the roll) of a CPC roll has a similar alloy composition like the barrel shell of a spun-cast HSS work roll with differences in the microstructure, which is much finer due to the faster solidification rate.

The shell is clad onto a forged core part, which has a higher mechanical strength than the nodular cast iron core of spun-cast HSS rolls making the CPC roll more suitable for mills with high total rolling forces, torques and bending forces. However, CPC rolls are relatively sensitive to cracks and failures in case of mechanical damages and therefore deemed not suitable for mills or mill stands where the risk of such damages is significant.

Machinability: The machinability of CPC manufactured rolls depends on the cladded material. In the case of CPC-HSS rolls, the finer microstructure is expected in theory to provide for better grindability compared to spun-cast HSS rolls and for equal to better grindability compared to forged HSS rolls. However grinding of CPC rolls is significantly more difficult than for standard rolls. In practice, grindability intricacies are expected. In case of CPC-HSS rolls, a time-consuming programme is needed for each cold mill to select the optimum tailor-made grinding wheel and to develop the multi-step grinding process parameters for each roughness/topography specification.

Treatment time: Due to the poor machinability of CPC-HSS work rolls, the treatment time needed to prepare the rolls for the use in cold, temper and hot rolling mills, is expected to be significantly longer (refer to the paragraph 'treatment time' of alternative 1, section 7.1.1.2)

Summary of technical feasibility: The following chart gives an overview of the assessment of CPC as alternative to functional chrome plating of work rolls in metal rolling mills.

Wea

r re

sist

ance

Har

dnes

s

Surf

ace

clea

nlin

ess

Surf

ace

appe

aran

ce

Coe

ffic

ient

of f

rict

ion

Top

ogra

phy

Res

ista

nce

to r

apid

te

mpe

ratu

re c

hang

e

Surf

ace

mor

phol

ogy

Mac

hina

bilit

y

Tre

atm

ent t

ime

7.1.3.1.3 Economic feasibility

CPC manufactured work rolls have been developed in Japan for steel hot rolling mills, as an alternative to spun-cast HSS rolls. Such rolls are considered as being high-end niche products, mainly used in Japanese steel hot rolling mills. The application of CPC rolls in steel hot rolling operations outside of Japan is very limited and CPC manufactured rolls are relatively expensive. However, nothing can be stated regarding the cost/price factor for the typical work roll dimensions of a cold rolling mill, since the expensive product has not been used yet for cold rolling outside Japan.



7.1.3.1.4 Reduction of overall risk due to transition to the alternative

As the alternative is not technically feasible, only classification and labelling information of substances and products reported during the consultation were reviewed for comparison of hazard profile, which is presented in the following.

For CPC, different alloys are used for cladding. However, HSS is used for the risk assessment. HSS is a loosely used term that defines alloys, containing iron, chromium, molybdenum, vanadium, tungsten and in some cases niobium. High Speed Steels are generally considered non-hazardous to human health and the environment. As a worst case scenario, tungsten is registered under REACH classified as Flam. Sol. 1 and Self.-heat. 2.

However, transition from chromium trioxide, which is a non-threshold carcinogen, to CPC would constitute a shift to a less hazardous substance.

7.1.3.1.5 Availability

According to the consultations, CPC work rolls are exclusively available from a few suppliers in Japan with limited production capacity. CPC rolls were primarily developed for steel hot rolling mills, although even in that segment they are high-end niche products, but are also used in some Japanese cold rolling mills, though not for the purpose of replacing chrome-plated rolls. In general, CPC work rolls are available thus exceeding the costs of functional chrome coated ones by far. To date there is no cold mill applying CPC-HSS rolls for the substitution of chrome plated rolls. Unknown factors are effects on strip cleanliness and grindability for critical cold rolling applications.

The overall TRL/MRL assigned to CPC work roll grades for cold and temper rolling is 4/8. The following chart gives on overview of the assigned TRL and MRL for cast (S)HSS work roll grades in cold and temper rolling applications.

Therefore, CPC work rolls are not considered to be a drop-in alternative to chrome plated work rolls in flat metal production.

7.1.3.1.6 Conclusion on suitability and availability for the alternative CPC

Applying High-Speed Steel grades as cladding material for CPC-manufacturing work rolls for the use in cold, temper and hot rolling mills would fulfil the requirements of wear and temperature resistance. However, reachable degrees of hardness are not sufficient and major deficiencies in the grindability and therefore in the topography of such rolls make the alternative technically unfeasible regarding the substitution of chromium trioxide-based functional chrome plating of rolls. Like spun-



cast HSS rolls, CPC-HSS rolls have not been specifically developed or adjusted for cold rolling and temper rolling mills. CPC-HSS rolls are already a niche product in case of steel hot mills but for cold rolling mills their use is even more limited. Recorded use for cold rolling operations is limited to a few Japanese cold mills. At present, there is no cold mill applying CPC-HSS rolls as substitution to chrome plated work rolls. Limited availability and high prices additionally dismiss the alternative from being a suitable replacement to Cr(VI)-based functional chrome plating.

Powder Metallurgy-based Hot Isostatic Pressing (PM HIP)


The Powder Metallurgy- based Hot Isostatic Pressing (PM HIP) is a procedure used for the manufacturing of steels and super-alloys from powdered base material and by densifying at high pressure and temperatures. The hot isostatic pressing is conducted for various powder alloys, including conventional steel compositions as well as alloys on the basis of nickel or cobalt.

The manufacturing of the metal powder is done by gas atomisation. Therefore, the metal is molten and atomized into small droplets applying inert gas jets. The yielded metal powder is subsequently used for HIP. Figure 28 exemplifies the atomization of molten metal and the general setup of a HIP furnace for metal powders.

Figure 28: Gas atomization of molten metal (left) and general scheme of a HIP furnace for metal powders (right) (Source: EPMA, 2013).

To produce the desired design of the metal part, vessels are produced within which the HIP process is conducted. After filling and evacuation, the vessel is heated to temperatures of 900 to 1250 °C in case of steels and super-alloys. The established argon gas pressure ranges within 100 to 200 MPa. After reaching and holding stable the maximum temperature and pressure plateau, cooling down is initiated.

After the main process, the final product can be heat treated, further surface treated or mechanically machined by e.g. grinding.



PM HIP of HSS allows for steels with high wear resistance, based on increased carbide content, as well as high fatigue strength and provides for a homogeneous surfaces exhibiting fine isotropic microstructure (European Powder Metallurgy Association (EPMA), 2013).


Wear resistance: PM HIP offers broad possibilities for alloying allow for high wear resistance of the hot isostatic pressed steel parts, such as work rolls, especially due to high carbide content. According to the consultations, small-sized PM HIP work rolls manufactured from High Speed Steel (HSS) alloy compositions, which are available for small cold rolling mills, are advertised to be superior to standard forged rolls regarding wear resistance. However, applying HSS alloy compositions, the wear resistance is likely to be comparable to spun-cast HSS rolls (chapter 7.1.2) and therefore the requirements may be fulfilled by PM HIP manufactured rolls.

Hardness: According to the consultations, PM HIP manufactured work rolls applying HSS alloy compositions are expected to be hardenable to fulfil the requirements in hardness for cold, temper and hot rolling mills.

Surface cleanliness: According to the consultations, no empirical evidence is yet available that proves PM HIP work rolls perform better than bare uncoated rolls in cold and temper rolling. PM HIP provides a high degree of freedom to select the alloy composition. A PM HIP roll manufactured from an HSS alloy could have a similar alloy composition as the barrel shell of a spun-cast HSS work roll, but the microstructure can be much finer due to the HIP process. According to the consultation, one hypothesis states that the finer shell microstructure could have a positive effect on the strip surface cleanliness during cold rolling, but the hypothesis has not been validated yet. Costly and time-consuming preparation and execution of mill trials will be needed to examine the validity of the hypothesis. By now, PM HIP manufactured HSS rolls have not been introduced for the purpose of substituting chrome plated rolls.


Surface appearance: Applying HSS alloy compositions, PM HIP manufactured rolls are, regarding the surface appearance, expected to be at least comparable to cast (S)HSS rolls, which were not trialled in temper mills, because of insufficiency of cast roll types in terms of hardness specifications of work rolls for temper mills used at a CHL customer. PM HIP manufactured rolls are not yet available in relevant sizes for industrial temper mills, and are still in too early TRL and MRL stages for such uses, in order to predict whether or not PM HIP rollscan fulfil the requirements in surface appearance after temper rolling operations

Topography: Like for forged (S)HSS and Ti enhanced rolls, the topography is dependent on the grinding and/or texturizing process. Especially for temper rolling products dedicated to the automotive sector, domestic appliances or steel packaging, the surface specifications are highly demanding and therefore the exact adjustment of the surface roughness and waviness of the work roll surface is of major importance. According to the consultations, mill experience so far indicate that the most critical surface topography specifications can only be guaranteed when using chrome plated work rolls.

Although establishing the required topography is generally possible, PM HIP work rolls manufactured from HSS alloy compositions face the same problems regarding machinability like



forged work roll grades (refer to chapter 7.1.1.2). Therefore, the alternative is not suitable to replace functional chrome plating of work rolls.

Plating of large geometries: No additional coating is applied and therefore, the plating of large geometries cannot be assessed. However, PM HIP furnaces are capable of producing geometries in dimensions of up to 2200 mm in diameter and more than 4000 mm in height (EPMA, 2013). The furnace is capable of up to 30 tonnes in weight. Work rolls reach diameters of 350 to 650 mm, total length of 3000 to 5000 mm and weights of 2 to 8 tonnes.

Resistance to rapid temperature changes: The resistance to temperature of the finished work roll is dependent on the final heat treatment. There is no indication that PM HIP manufactured HSS alloy grades do not fulfil the requirements regarding the resistance to occurring ultrashort surface temperature flashes of ≥ 200 °C, ≥ 250 °C respectively.

Machinability: The machinability of PM HIP manufactured work rolls depends on the PM material chosen. In case of PM HIP HSS rolls, the finer microstructure is – according to the consultations – theoretically expected to provide for better grindability than spun-cast HSS rolls (chapter 7.1.2) and equal to better grindability than forged HSS rolls. However grinding is significantly more difficult than it is for standard rolls. In practice, grindability complications are expected. Corresponding to HSS work rolls, for PM HIP rolls, a time-consuming programme would need to be established for each cold mill to select the optimum tailor-made grinding wheel and to develop the multi-step grinding process parameters for various roughness/topography specifications.

Treatment time: The treatment time of PM HIP mainly depends on the duration of the heat and gas pressure plateau, which in turn varies according to the materials used, and on the following cooling down period. Compared to conventional gradual cooling, uniform rapid cooling (URC) may reduce the cooling period significantly by up to 80 %. However, general treatment cycles for PM HIP are reported to be 8 to 24 hours (EPMA, 2013).

Summary of technical feasibility: The following chart gives an overview of the assessment of PM HIP as alternative to functional chrome plating of work rolls in metal rolling mills.

Wea

r re

sist

ance

Har

dnes

s

Surf

ace

clea

nlin

ess

Surf

ace

appe

aran

ce

Top

ogra

phy

Res

ista

nce

to r

apid

te

mpe

ratu

re c

hang

e

Mac

hina

bilit

y

Tre

atm

ent t

ime


PM HIP requires a special, complex and costly HIP installation. Additionally, the ultrafine pure starting alloy powders are very cost intensive. Already for small-sized rolls, the PM HIP roll price can roughly be estimated to be five times as high as for a standard forged roll. According the consultations, as of now only small scale rolls may be manufactured with PM HIP. Roll costs are expected to further increase for large rolls.



From the economic perspective, PM HIP manufactured work rolls are not an adequate replacement for chrome coated work rolls in cold rolling and temper mills.

7.1.3.2.4 Reduction of risk due to transition to the alternative


For PM HIP, various powder alloys, including conventional steel compositions as well as alloys on the basis of nickel or cobalt are applied. Nickel constitutes the worst case scenario as nickel powder is harmonized classified as Skin Sens. 1, Carc. 2, STOT RE 1 and Aquatic Chronic 3. Therefore, in accordance with CLP Regulation (EC) No 1272/2008, mixtures containing more than 1 % (w/w) nickel is classified as Carc. 2. Since the exact composition of a possible alternative powder mixture for PM HIP is not known, an assessment regarding the overall risk to human health and the environment is not possible.

However, transition from chromium trioxide, which is a non-threshold carcinogen, to PM HIP would constitute a shift to a less hazardous substance.


Rolls manufactured by means of Powder Metallurgy Hot Isostatic Pressing (PM HIP) of very fine steel alloy powders is already commercially available for rather small roll sizes of small cold mills (e.g. Sendzimir mills for cold rolling of stainless steel strips).

Such rolls are offered by a few roll manufacturers (e.g. Steinhoff GmbH & Cie. OHG, Germany) that also supply standard forged rolls, as an expensive high-end niche product for small metal mills.

PM HIP requires a special, complex and costly HIP installation. The characteristics and requirements of small mills differ from large mills for wide strips, which currently are dependent on chrome plated work rolls. Available HIP installations are few and small in size, so that only small-sized rolls for small rolling mills can be manufactured. Manufacturing capacity for large-sized rolls (diameter >350mm and length >2.5m) is lacking, requiring major investments by specialized suppliers. Technical complexity and investment costs of HIP installations increase progressively with size, so that the technical and economic feasibility of PM HIP for manufacturing large wide metal strip mill work rolls still is questionable.

Furthermore, PM-HIP rolls have not been tested in cold rolling mills with the aim to replace chrome-plated rolls and so their properties have not yet been adapted to such applications. Unknown factors are effects on strip cleanliness and grindability for critical cold rolling applications.

In general roll manufacturers do not have the financial resources to invest in a HIP installation. Outsourcing of the HIP part of the manufacturing process is the result. Several roll manufacturers have independently stated that inquiries to external providers concerning the HIP processing of a large work roll for any of the wide strip mills using chrome plated work rolls have been made. The inquiries have been answered negatively. Accordingly, there is currently no manufacturing route for large scale work rolls available. Therefore, from the availability point of view, PM HIP manufactured work rolls are no overall alternative to chrome plated ones.

The overall TRL/MRL assigned to PM-HIP manufactured work rolls for cold and temper rolling is 4/5. The following chart gives on overview of the assigned TRL and MRL for PM-HIP work roll grades in cold and temper rolling applications.



7.1.3.2.6 Conclusion on suitability and availability for the alternative PM HIP

Technical complexity and investment costs of HIP installations increase progressively with size, so that technical and economic feasibility of PM HIP for manufacturing large objects, such as wide metal strip mill work rolls, is still questionable. Overall, the suitability of PM HIP manufactured work rolls in replacing chrome coated work rolls is not given. Extensive progress in the development of the alternative would be needed, including:

- further development of PM HIP rolls metallurgy, tailored to the requirements of wide strip cold mill applications

- trial of PM-HIP rolls on laboratory cold mill scale - further development of the manufacturing route for production of large rolls - selection of tailored grinding wheel and development of a multi-step grinding programme (for

each cold mill and for each mill stand/roughness specification) - development of a robust Non-Destructive Testing (NDT) protocol (including

acceptance/rejection thresholds) for the new PM HIP roll type in the roll shop; - trials of full size PM HIP rolls in all mill stands down to scrap diameter, including monitoring

of the quality performance of rolled products in downstream processes and at the customer

For each of the development steps, at least 2 to 4 years are calculated. It is expected that at least 12 years will be needed to examine and validate the technical and economic feasibility of PM HIP rolls for wide strip cold mills, as well as temper and hot rolling applications. If it appears feasible, an additional period of 5 years will be needed to build up the manufacturing capacity to supply the metal rolling industry.

Electro-Slag Remelting Cladding (ESR Cladding)


ESR cladding of work rolls is based on the application of an outer metal shell to a metal axis resulting in a bimetallic composite roll. ESR cladding bases on the 'classical ESR'. Figure 29 shows the principle of 'classical' ESR and ESR cladding.



Figure 29: Principles of 'classical' ESR and ESR cladding (Source: Gaspard et al., 2002a; modified).

The core part, or 'axis', is brought into a copper mould, leaving a gap in between, which is filled with electro-conductive slag. The cladding material is filled into the slag, which in turn is heated by electric current. The cladding material is refined in the slag and at the same time protected from air. While continuously moving of the axis, the cladding material solidifies supported by the water cooled copper mold and thus establishes the outer shell. To avoid segregation and to enhance the homogeneity of the process, the slag is rotated during the cladding process. In addition to that, the surface of the metal core is cleaned by the slag thus providing improved metallurgic bonding properties (Gaspard et al., 2002a). The authors report the use of (S)HSS alloy compositions for ESR cladding instead of the 'conventional' forging of monoblock ingots.

ESR-cladded work rolls were initially designed as R&D concept by C. Gaspard (Åkers), as a potentially cost-efficient alternative to – on the one hand – the Japanese CPC rolls (chapter 7.1.3.1), and – on the other hand – the monoblock forged (S)HSS rolls (chapter 7.1.1). In contrast to the CPC rolls, the ESR-cladded roll developments were not dedicated to hot mill, but (also) to cold mill applications. Different from the CPC and forged (S)HSS rolls, the ESR-cladded work roll developments have never been further advanced by Åkers beyond the R&D stage to industrialisation, although a trial ESR-cladded roll pair has been produced for a narrow strip cold mill (closed down in 2006) but not with the aim to substitute the chrome plating of work rolls. Åkers has stopped the development so that ESR-cladded rolls are not available on the market.


Wear resistance: Work rolls manufactured by ESR cladding from HSS alloy compositions are expected to be comparable to alternative 1 forged HSS roll grades.

Hardness: The hardness of work rolls is an important feature since it feeds back into wear resistance and therewith influences the roughness retention during rolling campaigns. Gaspard et al. (2002a) refer to Vickers Hardness up to 800 of the shell surface layer after normalizing and final heat treatment. The final heat treatment is conducted applying progressive induction hardening. However, ESR cladding does not provide for hardness comparable to functional chrome coatings of work rolls in cold rolling mills, exhibiting approximately up to 1000 HV. However, in case of individual rolling



campaigns, achieved hardness may be sufficient. In case of hot rolling, hardness requirements are met.

Surface cleanliness: The strip surface cleanliness in the case of (S)HSS work rolls manufactured by ESR cladding is reported by the applicants to be comparable to forged (S)HSS work roll grades and therefore insufficient for replacing functional chrome plating.


Adhesion to the substrate: The ESR cladding process established a bonding zone without any events of segregation between the axis – in this case being the substrate – and the cladding (Gaspard et al., 2002a). ESR cladding represents an alternate work roll manufacturing process. Therefore, the adhesion of the cladded material, including HSS material, to the steel core is good.

Coefficient of friction: In accordance with alternative 1 forged HSS work roll grades, there is no indication that ESR clad HSS grades may not fulfil friction-related requirements of cold rolling and temper mill work roll surfaces.

Topography: Similar to forged (S)HSS and Ti enhanced rolls, the topography is dependent on the grinding and/or texturizing process. Especially for temper rolling products dedicated to the automotive sector, domestic appliances or steel packaging, the surface specifications are highly demanding and therefore the exact adjustment of the surface roughness and waviness of the work roll surface is of major importance. According to the consultations, mill experience so far indicates that the most critical surface topography specifications can only be guaranteed when using chrome plated work rolls.

Although establishing the required topography is generally possible, ESR clad work rolls manufactured from HSS alloy compositions, face the same problems regarding machinability like forged work roll grades (refer to chapter 7.1.1.2). Therefore, at the current state, the alternative is not suitable to replace functional chrome plating of work rolls.

Plating of large geometries: Since ESR cladding is an alternate manufacturing process the plating of large geometries cannot be assessed. However, in the course of research conducted by Gaspard et al. (2002a) composite work rolls of 585 mm in diameter and 3400 mm in total length were manufactured, especially for the application in cold rolling metal mills. Therefore, the manufacturing of large scale work rolls is possible.

Resistance to rapid temperature changes: Like forged (S)HSS, ESR clad manufactured rolls using HSS alloy compositions can be tempered up to 500 °C. Ultrashort temperatures flashes in the roll bite are ≥ 200 °C, ≥ 250 °C respectively, and therefore, the alternative matches the requirements in temperature resistance.

Machinability: Since (S)HSS grade material is used for the production of ESR-clad work rolls, machinability of such is accordingly difficult (refer to chapter 7.1.1.2).

Treatment time: Since no additional coating is applied in case of alternate manufacturing methods, the time needed for preparing the work rolls for the use in rolling mill operations is decisive. The treatment time is extended since grinding takes longer in case of higher alloyed grades. This is mainly due to increased wear resistance leading to longer grinding times and more grinding passes. Comparable to forged (S)HSS work roll grades, the grinding of standard rolls and ESR clad HSS rolls



differs by the factor of approximately 2. Accordingly, the additional time needed for surface treatment makes the alternative unsuitable in replacing the functional chrome plating of work rolls in cold, temper and hot rolling mills.

Summary of technical feasibility: The following chart gives an overview of the assessment of ESR cladding as alternative to functional chrome plating of work rolls in metal rolling mills.

Wea

r re

sist

ance

Har

dnes

s

Surf

ace

clea

nlin

ess

Surf

ace

appe

aran

ce

Adh

esio

n to

the

subs

trat

e

Coe

ffic

ient

of f

rict

ion

Top

ogra

phy

Res

ista

nce

to r

apid

te

mpe

ratu

re c

hang

es

Mac

hina

bilit

y

Tre

atm

ent t

ime


Since the alternative is not available on the market, nothing can be stated regarding the economic feasibility.

7.1.3.3.4 Reduction of risk due to transition to the alternative


High Speed Steel is a loosely used term that defines alloys, containing iron, chromium, molybdenum, vanadium and tungsten. High Speed Steels are generally considered non-hazardous to human health and the environment. As a worst case scenario, tungsten is registered under REACH classified as Flam. Sol. 1 and Self.-heat. 2.

However, transition from chromium trioxide, which is a non-threshold carcinogen, to HSS clad HSS work roll grades would constitute a shift to a less hazardous substance.


According to the consultations, ESR Cladding is not commercially available for work rolls of cold rolling steel mills. It was tested in the early 2000s with a set of relatively small rolls of a narrow strip mill, but not with the purpose to replace chrome plated rolls. No significant development progress has been reported since. The roll manufacturer Åkers stopped development and therefore ESR-cladded rolls are not available on the market.

The overall TRL/MRL assigned to ESR-cladding of work rolls used in cold and temper rolling is 3/4. The following chart gives on overview of the assigned TRL and MRL for ESR-cladding of work rolls used in cold and temper rolling applications.



7.1.3.3.6 Conclusion on suitability and availability for the alternative ESR Cladding

Electro-slag remelting cladding (ESR) has been developed as an alternative manufacturing technology for High-Speed Steel work rolls for metal rolling mills. However, according to the consultation, the technology has not gained much attention and has never been commercialized and reveals major deficiencies in topography and machinability.

Laser cladding

7.1.3.4.1 Substance ID and properties / process description

During laser cladding, material, such as metals and alloys in form of powder, wire etc., is fused onto the substrate surfaces to form a coating (Legg, 2003a). Thereby, a high power laser beam is used to establish weld pools. Transported by an inert shielding gas, the metal powder is brought into the laser beam and subsequently into the weld pools. Figure 30 shows the laser cladding process.

Figure 30: Laser cladding process (Source: Lester et al., 2013).

Laser cladding bears the opportunity to apply composite structures to the substrate. A matrix, mostly a nickel based alloy, is applied first to give toughness, ductility and impact resistance. A subsequent



hard phase, mostly tungsten, titanium or chromium carbide, allows for additional hardness and wear resistance.

According to the consultations, laser cladding may be used to apply thick layers (>15 mm) onto a core metal substrate to manufacture work rolls for metal mills. Laser cladding as alternate roll manufacturing method needs to be differentiated from the deposition of rather thin layers (50 – 1000 µm) used for coating processes. In the course of the present AoA, only laser coating as alternate manufacturing process is considered. For thin laser cladding, see Appendix 1.

General information for the specifically chosen tungsten carbide cobalt coating and the risk to human health and the environment is provided in Appendix 2.1.10.


General assessment: Please note that, according to the consultations, laser cladding of thick layers on large surfaces is not available yet. Therefore, information on the technical feasibility of the potential alternative is very limited. Please refer to paragraph 7.1.3.4.5 for further information.

Wear resistance: Wear resistance of work rolls is an important key functionality, especially when it comes to roughness retention. Laser cladded coatings contain unmelted ceramic particles contributing to very high degrees of wear resistance (Lester et al., 2013).

Figure 31: Room temperature sliding wear tests of laser clad tungsten carbide and high carbon alloy cast steel (Lester, 2013, modified).

Figure 31 shows the results of room temperature sliding wear tests of laser clad tungsten carbide and high carbon alloy cast roll steel. After an initial increase, the wear rate stabilizes. However, regarding the wear resistance of an alternative laser cladded work roll, only wear tests under relevant rolling conditions are meaningful to assess suitability. According to the consultation, laser cladding was only tested on caster rolls so far, which are exposed to far lower mechanical strains than work rolls of cold and temper rolling mills.

Hardness: Due to the incorporation of carbides into the laser clad coatings, very high degrees of hardness and impact resistance is established (Lester et al., 2013). However, the hardness depends on the chosen material used and further development needs to be carried out.

Surface cleanliness: The strip surface cleanliness is dependent on the selection of the cladding material, the treatment settings, as well as the grinding methods, which are to be developed. Thus, nothing can be stated about the success of such development.



Surface appearance: The surface appearance is dependent on the selection of the cladding material, the treatment settings, as well as the grinding and texturing methods, which are to be developed. Thus, nothing can be stated about the success of such development.

Adhesion to the substrate: Since laser cladding is a welding technology, coatings derived from the alternative show excellent adhesion to the substrate (Legg, 2003a), deriving from the cladding material being alloyed onto the substrate (Lester et al., 2013). From that point of view, laser cladding can be considered as being a suitable alternative to functional chrome coating.

Topography: The topography of work rolls manufactured by laser cladding is dependent on grinding and texturing methods to be developed. Thus, nothing can be stated about the success of such development.

Adequate layer thickness: According to the consultations, laser cladding of a very thick shell layers above 15 mm on a new type of purpose-made forged core metals (so-called arbour), as alternative roll manufacturing method, is generally possible. However, since laser cladding is considered as an alternative manufacturing method, the adequate layer thickness is not assessed.

Plating of large geometries: Since laser cladding is considered as an alternative manufacturing method, the adequate layer thickness is not assessed. However, the manufacturing of large scale work rolls for cold rolling and temper mills is possible.

Surface morphology: The surface morphology of laser clad surfaces depends on the application and cladding materials used and depends on the manufacturing methods to be developed. Thus, nothing can be stated regarding the surface morphology.

Machinability: Cladding of more than >15 mm in thickness would allow for multiple re-grindings, potentially between 50-200 times, of the cladded layer as preparation for re-usage without the need for re-coating. Worn rolls can be cladded again, thus re-using the forged arbour and therefore enabling a second life time of the roll again with multiple re-grindings. The re-use of the forged arbour could be repeated up to 10 - 20 times. However, since laser cladding of thick layers on large surfaces is not available yet, nothing can be stated about machinability. Materials most commonly used for laser cladding on other types of metal substrates for various industry sectors are known to be rather difficult to machine, so for mill rolls new materials and associated deposition process practices have to be developed.

Summary of technical feasibility: The following chart gives an overview of the assessment of laser cladding as alternative to functional chrome coatings of work rolls in metal rolling mills.

Wea

r re

sist

ance

Har

dnes

s

Surf

ace

clea

nlin

ess

Surf

ace

appe

aran

ce

Top

ogra

phy

Surf

ace

mor

phol

ogy

Mac

hina

bilit

y




Against the background of non-availability of the potential alternative, no quantitative analysis of economic feasibility was conducted.

7.1.3.4.4 Reduction of overall risk due to transition to the alternative

Since the exact composition of a possible alternative powder mixtures for laser cladding of thick layers is not known, an assessment regarding the overall risk to human health and the environment is not possible.


Laser cladding is a commercially available process and used in production for niche applications (cladding of turbine blades) but is not available as standard equipment or as a standard workshop process (Legg K., 2003a). Developments so far were not aimed at cold rolling and temper rolling mill rolls, and are incompatible to the heat-sensitive work rolls and the mill conditions. Trials focussed on rather simple uses such as hot mill roller table rollers or continuous caster rollers. However, laser cladding of thin layers is (due to major deficiencies) only mentioned in Appendix 1.

According to the consultations, laser cladding of thick layers on large surfaces is not available yet. An entirely new roll system and a corresponding manufacturing method would be needed. Required steps would be the establishment of a suitable system at the laboratory scale fulfilling the required functionalities. This refers to the development of the core part to be cladded (the arbour), the cladding material(s) selection, a multi-layer cladding method, heat treatment as well as grinding and texturing methods. Upscaling to the pilot scale and subsequently to industrial mill sizes are additionally time consuming and cost intensive steps. The integrity and homogeneity need to be ensured, and testing and fine-tuning of the system at each scale, is necessary before a full industrial trial can even be considered. The development will take at least 10 years before starting full industrial trials, and additional 5 years for full roll life trialling for each relevant mill (stand) type. In total, at least 15 additional years are necessary to further develop laser cladding as an alternative to the functional chrome plating of work rolls in cold rolling and temper mills.

The overall TRL/MRL assigned to laser cladding of work rolls used in cold and temper rolling is 3/4. The following chart gives on overview of the assigned TRL and MRL for laser cladding of work rolls used in cold and temper rolling applications.



7.1.3.4.6 Conclusion on suitability and availability for alternative general laser and weld coating technology

Laser cladding is being developed as a versatile coating technique for a large variety of products and industry sectors, but mostly for fairly thin single or double layers. Laser cladding of thin layers on conventional work rolls is not possible due to major technical deficiencies as outlines in Appendix 1.

According to an expert of a CHL customer, laser cladding has not been tested so far on work rolls for cold rolling mills. Cold rolling of metal is regarded to be the most difficult application in terms of laser processing (local heating of a large, highly stressed forged rolls) and application performance (heavy deformations in cold rolling leading to extreme demands on coating and interface integrity). Based on financial analyses by one of CHL's customers, the development would currently not be feasible.

For these reasons, efforts so far have been limited to steel hot rolling mill rolls for long products rolling. However, even for this application, the alternative has not progressed beyond the laboratory stage due to circumspect performance and unattractive financial aspects. The focus on practical applications have rather been placed on caster rolls than on mill rolls.

Laser cladding has not been tested at the customer of CHL as a direct replacement for - and as such as yet has not been proven as a functionally and economically viable alternative to – functional chrome plating of work rolls for cold rolling and temper mills.

Laser cladding of thick layers for alternate manufacturing of work rolls is not yet available and at least 15 additional years are required to further development before the alternative could be considered as a potential replacement to chromium trioxide- based functional chrome plating of work rolls in cold rolling and temper mills.

7.2. Concept 2: Alternative coating or surface treatment technology Concept 2 comprises alternative coating procedures or surface treatment technologies for work rolls possibly replacing chromium trioxide based functional chrome plating. Alternatives listed under concept 2 are:

- Cr(VI)-free chrome deposition processes, - electro and electroless deposition processes, - and Electro Discharge Coating (EDC).

The technical assessment for these alternatives is illustrated in the following table. As of today, it can be clearly concluded that none of the replacement techniques can be seen as an alternative. The most important technical requirements such as wear resistance, hardness or topography cannot be fulfilled by the alternatives assessed. For detailed assessment the reader is referred to the following sections.



Table 11: Summary of technical assessment of Concept 2 alternatives (CR: Cold rolling; HR: Hot rolling; TR: Temper rolling).

Wea

r re

sist

ance

Har

dnes

s

Surf

ace

clea

nlin

ess

(CR

, HR

)

Surf

ace

appe

aran

ce (T

R)

Adh

esio

n to

the

subs

trat

e

Res

ista

nce

to r

apid

te

mpe

ratu

re c

hang

es

Suita

bilit

y fo

r he

at-

sens

itive

subs

trat

es

Surf

ace

mor

phol

ogy

Tre

atm

ent t

ime

Trivalent chrome plating

Electroless plating

Nickel and nickel alloy electroplating

Nanocrystalline cobalt phosphorus alloy coating

High velocity thermal process

EDC ™

7.2.1. Alternative 4: Trivalent chrome plating

Substance ID and properties / Process description

The trivalent chrome (Cr(III)) plating alternative relates to an electrodeposition process for producing a metallic chrome coating from a trivalent chromium electrolyte. The chromium in the electrolyte derives from chromium trichloride.

The temperature of a Cr(III) based electroplating bath is between 20 and 60°C whereas typical chromium trioxide functional chrome plating occurs between 50 and 60°C. The pH value of the Cr(III) based plating bath has to be between 2.1 and 2.3 to ensure reliable process conditions compared to the wider range of pH 1 to 3 for chromium trioxide.

A non-exhaustive overview of general information of substances used within trivalent chromium plating, as well as the overall risk to human health and the environment is provided in Appendix 2.3.


General assessment: The major advantage of Cr(III) plating is that it is close to a “drop-in” replacement for current chromium trioxide process technology as far as process type is concerned.

Results on R&D for Cr(III) metallic chrome coatings are mainly available from laboratory scale research. Almost no results are available on industrial application of Cr(III) based chrome plating applications, showing that Cr(III) as alternative for chromium trioxide is still under laboratory research.

Publicly available information from the ECOCHROM project stated that material loss for trivalent plated rapid steel is less than for chromium trioxide plated steel. However, chrome coatings from



trivalent chromium electrolytes have not been tested under relevant real rolling conditions. In accordance with Crahay et al. (2015), it is unlikely that coatings from Cr(III)-based electrolytes will be applicable within the next 15 years.

Investigations of TNO on behalf of HOCO RST indicate maximum hardness of 800 HV for chrome depositions from aqueous ionic liquid solutions (20 w% water) containing Cr(III) compounds. The addition of particles to the electrolyte to establish composite depositions, thermal or RF plasma post-treatment are identified as options for further increasing the hardness (Bressers and Gonzalez Rodriguez, 2010). However, feasibility on the industrial scale is not proven yet and further R&D needs to be carried out.

According to studies of Bressers and Gonzalez Rodriguez (2010) on behalf of HOCO RST, poor adhesion of the functional chrome depositions from trivalent chromium containing ionic liquids is assumed. Insufficient adhesion leads to flake-off during the rolling process due to the enormous rolling forces present in the bite.

In contrast to information provided by the 'CrFreeRolls' project, the desired layer thickness of 5 to 10 µm is generally possible. However, R&D is restricted to the laboratory scale and the application on an industrial scale is not proven yet. If possible, further research is needed.

Furthermore, Cr(III) baths are more sensitive to metallic impurities and the acidity of the bath than chromium trioxide baths. Small deviations in these process conditions can strongly influence the deposition success and the layer quality (Legg, 2003a). The process window for Cr(III) plating lies in a very narrow pH range from 2.1 to 2.3 (functional chrome plating: pH 1 to 3), which is difficult to maintain. Since bath temperatures range between 20 and 60°C, the process is suitable, like chromium trioxide plating, for heat sensitive work roll substrates.

Summary of technical feasibility: The following chart gives an overview of the assessment of chrome depositions from trivalent chromium electrolytes as alternative to chromium trioxide- based functional chrome plating of work rolls in cold and temper rolling mills.

Wea

r re

sist

ance

Har

dnes

s

Surf

ace

clea

nlin

ess

Surf

ace

appe

aran

ce

Adh

esio

n to

the

subs

trat

e

Ade

quat

e la

yer

thic

knes

s

Suita

bilit

y fo

r he

at-

sens

itive

subs

trat

es


Against the background of significant technical failure of trivalent chromium plating, no quantitative analysis of economic feasibility was conducted. However, the cost for trivalent chromium plating depends on numerous different factors and these are presented in a qualitative to semi-quantitative way below.



The electrodeposition of a metallic chrome coating with Cr(III) bath chemistry has not been implemented at a commercial scale yet. Based on laboratory testing, the costs for chemicals are estimated to be approximately equivalent to chromium trioxide plating.

The electricity costs are expected to be less, because the trivalent chromium process requires less current density. Accordingly less energy is needed compared to the chromium trioxide based processes. It should be noted that besides the inevitable costs of changing process and validation activity, production costs can be higher due to the need of sophisticated measuring technology in order to stabilize the more sensitive process and the need for ion exchange and filtration systems that are necessary to maintain requisite bath purity. Waste treatment and ventilation were reported to be less than those associated with chromium trioxide plating (TURI, 2006).

Taking material and process costs into account, costs for Cr(III) plating might be somewhat higher but are in a similar range as for chromium trioxide functional chrome plating.


As the alternative is not technically feasible, only classification and labelling information of substances reported during the consultation were reviewed for comparison of hazard profile (see Appendix 2.3).

Based on the available information on the substances used within this alternative (see Appendix 2.3), Cr(III) chloride would be the worst case with a classification as Skin Irrit. 2, Eye Irrit. 2, Acute Tox. In general, the trivalent electroplating processes are less toxic than chromium trioxide plating due to the oxidation state of the chromium. Cr(III) solutions do not pose serious air emission issues, but still pose the problems of disposal of stripping solutions (depending on the type of stripping solution) and exposure of staff to chrome dust during grinding.

In addition, there is a certain risk of Cr(VI) being generated during plating process. This is why appropriate security precaution and process management has to be adopted to prevent the formation of Cr(VI). The bath chemistry typically also comprises a high concentration of boric acid, which is a SVHC substance (toxic for reproduction) included on the candidate list and currently on the 6th recommendation for inclusion in Annex XIV. Despite these facts, the transition from chromium trioxide to trivalent chromium constitutes a shift to less hazardous substances.

Availability

The electroplating process based on Cr(III) bath chemistry as an alternative for chromium trioxide functional chrome plating is still in the early development stage. No up-scaled testing under real rolling conditions in metal mills has been conducted so far. Tests are ongoing but Cr(III) is neither technically ready nor qualified to replace chromium trioxide functional chrome plating applications. Therefore, it is not commercially available and has not gained market acceptance yet.

To date, there is no proof that Cr(III) performs equally to chromium trioxide based plating processes on the most important key functionalities, such as hardness, wear resistance or adhesion of the coating to the substrate. Thus, further R&D is necessary to ensure process conditions and to meet the requirements of the key functionalities first in laboratory scale and then in functional field tests. Certainly a further decade is required for R&D. (See Bressers and Gonzalez Rodriguez, 2010)

The overall TRL/MRL assigned to trivalent chrome plating of work rolls used in cold rolling is 3/7 and in tamper rolling even 3/3. The following chart gives on overview of the assigned TRL and MRL for trivalent chrome plating of work rolls used in cold and temper rolling applications.



Conclusion on suitability and availability for alternative trivalent chrome plating

The Cr(III) based electroplating systems do not perform as technically equivalent to chromium trioxide based products and are therefore not a general alternative at present. The development efforts have shown that the Cr(III) process require more careful control than the chromium trioxide process due to higher process sensitivity towards the presence of impurities. Today the instable process conditions still lead to unreliable reproducibility and unacceptable microstructure with cracks down to the substrate. This is a major issue that impairs the most important key functionalities concerning the Cr(III) layer properties.

To date there is no proof that Cr(III) performs equally compared to chromium trioxide on the most important key functionalities, such as hardness, wear resistance or adhesion of the coating to the substrate, which are essential key functionalities for cold, temper and hot rolling applications. Thus, further R&D is necessary to ensure process conditions and to meet the requirements of the key functionalities first in laboratory scale and then in functional field tests under relevant rolling conditions. Certainly a further decade is required for R&D.

To date, trivalent chromium plating is not an available and technical feasible alternative to replace chromium trioxide plating for work rolls in metal mill rolling applications.

7.2.2. Alternative 5: Electro and electroless deposition processes

Alternative 5 refers to electro and electroless deposition processes applying coatings by immersion of the work rolls into a plating bath. In the following, electroless plating, nickel and nickel alloy electroplating as well as nanocrystalline cobalt phosphorous alloy coating are discussed in detail.

Electroless plating

Substance ID and physicochemical properties of relevant substances

Electroless plating is a process in which metal ions in a dilute aqueous solution are deposited on a substrate by means of a heat induced reduction without the use of electric current. Heat induced reduction is a chemical reaction in which the substrate acts as a catalyst after being heated, causing ions to continuously deposit onto the substrate (NDCEE, 1995).

Nickel represents the most widely used base material for electroless plating. Electroless nickel deposits usually consist of nickel-phosphor (Ni-P) or nickel-boron (Ni-B) alloys. Typical bath solutions contain reducing agents, such as hypophosphite, aminoborane or borohydride and are used



to deposit Ni-P or rather Ni-B alloys. The primary goal behind the alloys is to enhance existing nickel layer properties.

A non-exhaustive overview of general information and properties of substances used in electroless plating as well as the overall risk to human health and environment caused by these substances, is provided within Appendix 2.4.


General assessment: As nickel phosphorous (Ni-P) deposits are the most promising alternatives amongst the electroless nickel coatings, these were used for the assessment. The figures in the following table which was provided in the consultation illustrate the effect of different phosphorous contents on the technical properties of the Ni-P alloy layers.

As-deposited alloys with low P-content show better wear resistance and have lower Taber wear index values compared to medium and high P-content alloys (e.g. 11 mg/1,000 cycles with low P-content and < 19 mg/1,000 cycles with high P-content). However, the wear resistance of a low P-content + heat treated Ni-P alloy is worse compared to chromium (as-deposited: 2 mg/1,000 cycles).

Electroless deposited Ni-P coatings achieve, depending on the phosphorous content, as maximum 700 HV in hardness in an as-deposited state. This performance is not sufficient regarding the minimal requirements of work rolls that range between 850 and 1,000 HV. Another possibility to improve hardness performance compared to the as-deposited state is heat treatment. However, heat treatment above 200 °C is not possible for heat sensitive work roll substrates.

The particles’ suspension and deposition uniformity in composite coatings are difficult to control. This makes it difficult to achieve homogeneous coating properties within nickel composite coatings containing particles (such as diamond, PTFE, etc.). Layer degradation and poor performance of the layer are possible consequences of uneven particle distribution (Legg , 2012).

The coefficient of friction is another important performance parameter. The tested alternative Ni-P coatings show values above 0.38. The steel sector however often requires values below 0.16 that can be achieved with chromium trioxide metallic chrome coatings. Thus, the minimum requirements on friction behaviour cannot be met by the alternative.

During the plating process, by-products/impurities are produced which cause e.g. tensile stress in the deposited Ni-containing layer, which can lead to spalling of the layer. Compared to functional chrome plating, electroless nickel deposition baths have a shorter life-time.

Heat treatment of electroless deposited nickel deposits is required to achieve better hardness and wear resistance performance due to precipitations (microstructural changes) compared to the as-deposited state. This post treatment is however an issue for the heat sensitive work roll substrates. As heat treatment is generally conducted at temperatures about 400°C for one up to eight hours, electroless nickel plating is unsuitable for work roll substrates that are tempered below 200 °C.

The deposition rate is low with 10 µm/h and a maximum of 25 µm/h are reported for acidic electroless baths (Daly and Barry, 2003). As a result process time is significantly longer compared to functional chrome plating.

Summary of technical feasibility: The following chart gives an overview of the assessment of electroless (nickel-) plating as an alternative to functional chrome plating of work rolls in metal mill applications.



Wea

r re

sist

ance

Har

dnes

s

Surf

ace

clea

nlin

ess

Surf

ace

appe

aran

ce

Adh

esio

n to

the

subs

trat

e

Coe

ffic

ient

of f

rict

ion

Ade

quat

e la

yer

thic

knes

s

Res

ista

nce

to r

apid

te

mpe

ratu

re c

hang

es

Suita

bilit

y fo

r he

at-

sens

itive

subs

trat

es

Tre

atm

ent t

ime

Heat treatment

for hardness


Against the background of significant technical failure of electroless nickel plating, no quantitative analysis of economic feasibility was conducted. However, the cost for electroless nickel plating depends on numerous different factors and these are presented in a qualitative to semi-quantitative way below.

Generally Ni is more expensive costs depend on many factors including part size, geometry, and post treatments. For other substrates than work rolls, post-heat-treatment (higher energy costs) must be taken into account if increased hardness is required for selected parts for which the significantly reduced corrosion resistance is still sufficient (Legg K., 2003a). However, for the heat-sensitive work rolls such post-heat treatments are technically unfeasible, as mentioned above, so that the required hardness cannot be achieved. The resulting bad performance will result in short lifetimes and hence lack of economic feasibility. Slow deposition rates require longer process times making the process also more expensive.

In contradiction to the above, a company from the steel sector stated that the costs for electricity during the main plating process is 10 times lower compared to functional chrome plating. Chromium trioxide baths require 500 € maintenance costs per year per m³ for recycling. However, the nickel bath maintenance costs are at least 7 times higher, since they are stable for hours only. In addition, the costs for nickel reactants are higher than for functional chrome plating.

Altogether, the per-part costs for electroless nickel process seem to be similar to functional chrome plating.


As the alternative is not technically feasible, only classification and labelling information of substances and products reported during the consultation were reviewed for comparison of the hazard profile. Based on the available information on the substances used within this alternative (refer to Appendix 2.4) nickel sulphate constitutes the toxicological worst case scenario and is classified as Skin Irrit. 2, Skin Sens. 1, Resp. Sens. 1, Muta. 2, Carc. 1A, Repr. 1B, STOT RE 1, Aquatic Acute 1, Aquatic Chronic 1. As such, transition from chromium trioxide – which is a non-threshold carcinogen – to the above mentioned alternative would clearly not constitute a shift to less hazardous substances. Based on the classification, soluble nickel compounds may meet the Substances of Very High Concern (SVHC) criteria under REACH.



In addition, the size of composites such as diamond, PTFE, etc. which might be added to the process, can range from nanometres up to several microns. Depending on their size-specific properties, nanoparticles may pose additional risks to human health, especially via inhalation, which need to be adequately evaluated and addressed for material handling and working exposure.

Aside from nickel, the bath chemistry can contain lead and cadmium as further hazardous substances. The legal limits related to RoHS (restriction of hazardous substances) in articles are Pb 0.1% (1,000 ppm) and Cd 0.01% (100 ppm).

Electroless nickel baths have a finite bath life and last approx. 10 metal turnovers, depending on how the bath chemistry is maintained and on the materials being processed. As nickel is plated onto the part, the nickel concentrations in the bath decrease over time. Nickel sulphate is periodically added to replenish these losses. When 100 percent of the original nickel content has been replaced, this is defined as one metal turnover. After 10 metal turnovers, the bath content must be dumped and disposed of as hazardous waste. Baths must also be dumped if they get contaminated with certain metals, e.g. chromium: for a low-P bath, 3 ppm of Cr3+ creates unacceptable deposits, while 0.2 ppm of Cr6+ stops deposition completely. Given that any existing component being internally plated will have chromium plated surfaces, the risk of contamination is high (National Center for Energy and Environment, NDCEE, 1995).

Availability

The electroless deposition of nickel is a well-defined process which has been in commercial use since the 1950s for certain products. Ni-P coating solutions are commercially more available than Ni-B and electroless nickel composite coating solutions (Legg K., 2003a). However, electroless nickel plating is suitable for some applications but they are not a like-for-like replacement for chromium trioxide functional chrome plating and failed to gain wide acceptance, especially in the aerospace industry, mostly due to the difficulty of maintaining a consistent plating.

There are a number of suppliers selling commercial plating equipment and bath solutions. NDCEE states that if electroless nickel is to be used very widely, methods will need to be developed and made commercially available to continuously monitor and control the bath chemistry, temperature, and performance as well as to control the heat treatment temperature and time. The use of composites would make such control methods even more important, since one must control bath chemistry more closely to prevent deposition onto bath particulates and one must control the particulates themselves. Methods must be found to maintain the filler powders in a uniform concentration and to obtain proper entrainment in the coating. This is clearly a concern for more difficult geometries.

In spite of the mature plating technology, electroless nickel coating systems do not offer comparable performance to functional chrome plating, in particular, the combination of wear resistance and hardness requirements cannot be met, and hardness in the unhardened state shows unacceptable performance compared to functional chrome plating, which makes electroless nickel plating unsuitable as a like-for-like technical alternative.

The overall TRL/MRL assigned to electroless plating of work rolls used in cold and temper rolling is 3/6. The following chart gives on overview of the assigned TRL and MRL for electroless plating of work rolls used in cold and temper rolling applications.



Electroless deposition of nickel is not considered a like-for-like alternative to functional chrome plating. More than 15 years would be needed to develop a general metallic chrome coating alternative, and it is questionable whether this alternative will be part of future investigation in the described sectors.

Conclusion on suitability and availability for alternative electroless plating

It is not possible for electroless deposited Ni layers to fulfil all requirements that are necessary to represent a technically suitable stand-alone alternative to metallic chrome coatings. Consequently, electroless deposited nickel layers are not an alternative for the majority of applications in metal rolling mills where metallic chrome coatings are used.

Electroless nickel shows significant technical (and therefore unacceptable) deficits regarding for example, wear resistance and hardness. The combination of hardness and resistance to wear are crucial key functionalities for the application in metal rolling mills. If electroless nickel coatings are heat treated in favour of increasing hardness, treatment temperatures exceed work roll tempering temperatures, which would jeopardize the roll’s mechanical strength and hardness.

In spite of the mature plating technology, electroless nickel coating systems do not offer comparable performance to functional chrome plating, in particular, the combination of wear resistance and hardness requirements cannot be met, and hardness in the unhardened state shows unacceptable performance compared to functional chrome plating, which makes electroless nickel plating unsuitable as a like-for-like technical alternative.

7.2.3. Alternative 6: Nickel and nickel alloy electroplating


Nickel and nickel alloy electroplating is generally based on a similar technology as functional chrome plating, but with important differences in the anode design, the bath chemistry and some operating parameters such as voltage. Besides the Watts-type composition, nickel sulphamate is also a frequently used salt in sulphamate nickel plating. Suitable electrolytes for nickel alloy coatings can contain: nickel-boron (Ni-B), nickel-cobalt (Ni-Co), nickel-phosphorus (Ni-P), nickel-tungsten (Ni-W), nickel-tungsten boron (Ni-W-B), nickel-zinc (Ni-Zn), nickel-tin (Ni-Sn) (NDCEE, 1995).

A non-exhaustive overview of general information on properties of relevant substances used within this alternative, as well as the overall risk to human health and the environment is provided within Appendix 2.5.




General assessment: The major advantage of nickel and nickel alloy electroplating is that it might be a close “drop-in” replacement for current chromium trioxide process technology. There is a basic fit of the necessary equipment for bath plating and depots but the anode design, bath chemistry and operation will need to be changed.

It was reported during the CATC consultation phase that wear resistance is significantly lower compared to metallic chrome coatings.

Crahay et al. (2015) report a hardness of approximately 700 HV for Ni-P coatings deposited at 1 A per dm² in Watt's type baths and containing ca. 4 % phosphorus. Even after heat treatment at up to 400 °C, the hardness does not exceed 890 HV, which would be acceptable for hot rolling. However, heat treatment in favour of hardness exceeds the tempering temperature of the applied substrates. Therefore, the alternative is no suitable substitution to functional chrome platings from the hardness perspective. Heat treatment of these substrate materials conducted at temperatures about 340–400°C for several hours is not suitable to achieve a better hardness performance.

The strip cleanliness was reported to be insufficient. Metallic chrome coatings do have the property to be anti-adhesive. Water, grease, oil, dirt, and dust can be easily wiped off. Nickel coatings in general do not have this anti-adhesive behaviour and contaminants firmly stick to the surface which heavily impairs the strip surface cleanliness during the rolling process.

A key functionality for functional chrome coatings applied to work rolls of metal rolling mills is a high degree of adhesion between the deposit and the substrate. Atoms of the electrodeposited metal align themselves in opposition to atoms of the substrate and are held to the surface by interatomic forces. Adhesion is maximised when the atomic bond strength is greater than the tensile strength of the weaker element.

The minimum requirement of the coefficient of friction is < 0.2. The coefficient of friction of a nickel layer on steel is higher than on metallic chrome coatings and does not fulfil the requirement.

The surface roughness of the steel substrate is not as perfectly followed as with metallic chrome coatings and the morphology does not fulfil the requirements for the steel industry, as reported by the CTAC steel sector.

Summary of technical feasibility: The following chart gives an overview of the assessment of nickel and nickel alloy electroplating as alternative to functional chrome plating of work rolls in metal rolling mills.

Wea

r re

sist

ance

Har

dnes

s

Surf

ace

clea

nlin

ess

Surf

ace

appe

aran

ce

Suita

bilit

y fo

r he

at-

sens

itive

subs

trat

es

Adh

esio

n to

the

subs

trat

e

Coe

ffic

ient

of f

rict

ion

Surf

ace

mor

phol

ogy

Heat treatment

for hardness




Against the background of significant technical failure of nickel electroplating, no quantitative analysis of economic feasibility was conducted. However, the cost for nickel electroplating depends on numerous different factors and these are presented in a qualitative to semi-quantitative way below.

It was stated in the CTAC consultation that the electricity costs during the plating process are four times lower compared to functional chrome plating. In contrast, the reactants for nickel electroplating are more expensive than the chromium reactants.

Including further related costs such as investment costs for process restructuring, different anode technology, installation of new baths, etc., maintenance and chemical costs, the electrodeposition of nickel coatings, for instance Ni-P, was evaluated to be 2-8 times more expensive than functional chrome plating.


As the alternative is not technically feasible, only classification and labelling information of substances and products reported during the consultation were reviewed for comparison of the hazard profile. Based on the available information on the substances used within this alternative (refer to Appendix 2.5) nickel sulphate constitutes the toxicological worst case scenario and is classified as Skin Irrit. 2, Skin Sens. 1, Resp. Sens. 1, Muta. 2, Carc. 1A, Repr. 1B, STOT RE 1, Aquatic Acute 1, Aquatic Chronic 1. As such, transition from chromium trioxide – which is a non-threshold carcinogen – to the above mentioned alternative would clearly not constitute a shift to less hazardous substances. Based on the classification, soluble nickel compounds may meet the SVHC criteria under REACH. As some of the alternate substances used are also under observation, the replacement has to be carefully evaluated on a case by case basis.

Amongst the composites used within this alternative, boric acid constitutes the toxicological worst case scenario and is classified as Repr. 1B. Furthermore, boric acid is a SVHC and was proposed for inclusion in REACH Annex XIV on September 1, 2014 due to its toxicity for reproduction. Therefore, the use of boric acid may become time limited by potentially transferring boric acid to the REACH authorization (Annex XIV).

In summary, electroplating based on nickel does not constitute a shift to significantly less hazardous substances.

Availability

Nickel electroplating is a commercially available process, similar to functional chrome plating but with different anode technology, bath composition and ingredients. Nickel electroplating is usually used as an undercoat for functional chrome plating and repair with metallic chrome coatings.

Currently, there are ongoing efforts of the electroplating industry, metal parts manufacturers, and suppliers to improve the wear and corrosion resistance of the Ni-P alloy coating and make it a potential metallic chrome coating replacement. However, the testing is time intensive and several years are scheduled for further research.

However, trials on the laboratory scale with nickel-based coatings were stopped and not further pursued due to failure in "adhesion tests" on EDT prepared rolls. As of today, further trails could be, if ever, an option for ground rolls only. Still, efforts never passed on to TRL 5. The poor coating adhesion, tested on EDT-textured rolls, does in particular eliminate the usability for temper rolling



mills, which are predominantly using textured work rolls to achieve the strip surface topography as required by the customer. Therefore, regarding temper rolling applications, the feasibility of the potential alternative would have to be evaluated on TRL 3.

The overall TRL/MRL assigned to nickel and nickel alloy electroplating of work rolls used in cold and temper rolling is 4/3 and 3/3, respectively. The following chart gives on overview of the assigned TRL and MRL for nickel and nickel alloy electroplating of work rolls used in cold and temper rolling applications.

In general, nickel electroplating is not considered a like-for-like alternative to functional chrome plating and more than 15 years would be needed to develop a general metallic chrome coating alternative.

Conclusion on suitability and availability for alternative nickel and nickel alloy electroplating

Nickel coatings are widely used as one component in multi-layer systems with a final metallic chrome coating. In these systems, the combination of different layers provides satisfactory performance regarding the key functionalities (hardness, friction, wear, adhesion). Systems consisting of a single nickel electroplated coating do not show satisfactory results during testing regarding the previously mentioned key functionalities. Hardness is a crucial functionality for work rolls in terms of roughness retention and electrodeposited nickel coatings do not meet the minimum requirements. Moreover, nickel coatings show insufficient surface cleanliness of the rolled metal strip which is another key parameter.

Although nickel electroplating is a commercially available process, it is not suitable as general alternative for functional chrome plating of work rolls due to technical failure of the electrodeposited nickel coating. Nickel alloy electroplating as an alternative to functional chrome plating is at early laboratory scale. Significant time, financial and R&D efforts are necessary to evaluate the potential future replacement of chromium trioxide. Also, the chemicals used for this alternative do not constitute a significant shift towards less hazardous substances according to their classification (Ni-compounds) or are a SVHC and already proposed for inclusion on REACH Annex XIV (boric acid).



7.2.4. Alternative 7: Nanocrystalline cobalt phosphorus alloy coating


Nanocrystalline cobalt-phosphorus alloy (nCoP) coatings are electrodeposited in an aqueous bath process that uses pulse plating technology. Pulse technology enables controlled deposition of nano grains (5-15 nm) resulting in an ultra-fine grain structure throughout the entire coating thickness from the substrate surface (Facchini et al. 2009; Legg K., 2003b). The steel industry also investigates Ni-W (nickel-tungsten) alloys with this electrodeposition method.

A non-exhaustive overview of general information of substances used within this alternative, and the risk to human health and the environment caused by this substances, is provided in Appendix 2.1.5


General assessment: Nano Co-P coating fails when applied on the work roll used in temper mill process where the loads are the lowest compared to other applications in the cold rolling process for producing steel. The surface is not uniform and pits are built and transferred from the work roll onto the produced material which is not acceptable.

At laboratory scale similar results were obtained compared to functional chrome plating for specific OEM or dimensional repair applications Ni-W alloys using Ni 60 wt% : W 40 wt% (refer to www.sifcoasc.com/wp-content/uploads/Nickel-Tungsten-5711.pdf & www.asetsdefense.org /documents/Workshops/ASETS2012/7/Clouser%20-%20For%20Web.pdf). Investigations indicated good corrosion and wear resistance.

The hardness of as-deposited nano Co-P alloys is in the range of 600-700 HV (Vickers Testing ISO 6507-1) and does therefore not fulfil the requirements of for cold, temper and hot rolling mill work rolls. In order to increase hardness, there are two possibilities: (a) Raising the phosphorous content for the as-deposited coating and (b) Heat treatment, also known as annealing. Annealing after electrodeposition at 300-400 °C leads to an increased hardness between 700-800 HV and 1,000-1,200 HV. However, heat treatment at the given temperatures would result in changes of the substrate microstructure and lead to degradation of the work roll substrate properties.

The Ni-W coating can be heat treated up to approx. 300°C; Tests showed an increase of Vickers microhardness to 950 HV after 6 hours of heat treatment at 190°C without causing microcracks for Ni-W depositions (http://www.myvirtualpaper.com/doc/nasf_aesf/pasf_may 10/2010052701/52.html#52 ). However, long heat treatments even at a temperature as low as 190°C will already lead to degradation of the work roll substrate properties.

Although some key requirements could be fulfilled at laboratory scale, the steel industry, according to the CTAC consultations, reports insufficient adhesion for their applications. Further investigations are reported to be ongoing.

The Ni-W deposition rate was determined to be between 0.4-1.6 µm/h in a bath chemistry consisting of NiSO4*6H2O & Na3C6H5O7 & Na2WO4*2H2O for tungsten concentrations varying between 5-25% (Alimadadi et al., 2009), which does not fulfil the requirements.

Summary of technical feasibility: The following chart gives an overview of the assessment of nanocrystalline cobalt phosphorous alloy coating as alternative to functional chrome plating of work rolls in metal rolling mills.

http://www.sifcoasc.com/wp-content/uploads/Nickel-Tungsten-5711.pdf

http://www.asetsdefense.org/documents/Workshops/ASETS2012/7/Clouser%20-%20For%20Web.pdf


http://www.myvirtualpaper.com/doc/nasf_aesf/pasf_may10/2010052701/52.html#52




Wea

r re

sist

ance

Har

dnes

s

Surf

ace

clea

nlin

ess

Surf

ace

appe

aran

ce

Adh

esio

n to

the

subs

trat

e

Ade

quat

e la

yer

thic

knes

s

Suita

bilit

y fo

r he

at-

sens

itive

subs

trat

es

Tre

atm

ent t

ime

Heat treatment

for hardness


Against the background of significant technical failure of nano Co-P alloy coating, no quantitative analysis of economic feasibility was conducted.

However, in one publication it was stated that compared to functional chrome plating, the energy consumption can be reduced while throughput is increased (due to high deposition rate up to 0.2 mm/h for nano Co-P and up to 0.04 mm/h for functional chrome plating). This results in higher plating efficiency (about 90 % for nano Co-P compared to less than 35 % for functional chrome plating). The relative process costs of nano Co-P plating with 1.3 are reported to be slightly higher compared to 1.0 with functional chrome plating (McCrea 2003).


As the alternative is not technically feasible, only classification and labelling information of substances and products reported during the consultation were reviewed for comparison of the hazard profile. Based on the available information on the substances used within this alternative (see Appendix 2.6), cobalt dichloride, as worst case scenario, is classified as Acute Tox. 4, Skin Sens. 1, Resp. Sens. 1, Muta. 2, Carc. 1B, Repr. 1B, Aquatic Acute 1, Aquatic Chronic 1. As well as other cobalt compounds, it is listed on the REACH candidate list for substances of very high concern. As such, transition from chromium trioxide – which is a non-threshold carcinogen – to one of these substances would not constitute a shift to significantly less hazardous substances.

Availability

According to the CTAC consultation, nano Co-P alloy coating is in early laboratory stages. The equipment and bath chemicals are commercially available.

Adhesion issues were solved, when the coating was used in a small trial mill. Issues still to solve are predictability are reproducibility, which are more process related challenges. In order to overcome these challenges, plans to build an appropriately designed and configured "pilot-plant" facility are in discussion. However, the development has not passed the laboratory scale yet and several years of R&D would be required.

The overall TRL/MRL assigned to nano Co-P alloy coating of work rolls used in cold rolling is 4/4 and 4/6 for temper rolling. The following chart gives on overview of the assigned TRL and MRL for nano Co-P alloy coating of work rolls used in cold and temper rolling applications.



However, nano Co-P alloy coating is no drop-in replacement for existing functional chrome plating equipment, and not a mature technology. Based on the technical deficiencies it is questionable whether nano Co-P coatings will be part of future investigation in the steel industry. At least 15 years would be needed to develop nano Co-P as a general metallic chrome coating alternative, if ever.

Conclusion on suitability and availability for alternative nanocrystalline cobalt phosphorus alloy coating

The nano Co-P plating was assessed with regard to the latest R&D results and their key parameters. Hardness is a very important performance parameter for the evaluation of metallic chrome coating alternatives dedicated to work rolls in metal rolling mills. Nanocrystalline Co-P coatings thereby cannot fulfil the required specifications. Heat treatment to improve the coating hardness is not an option, because the work roll substrate is heat-sensitive: heating above the tempering temperature (approximately 120 °C for temper mill rolls, about 160°C for cold mill rolls) will lead to microstructural changes and degradation of the roll quality. The alternative coating also fails in anti-stick behaviour and the requirement on uniformity of the surface. The electrodeposition of nano Co-P coatings does not produce technically equivalent and satisfying coatings compared to functional chrome plating and is therefore no suitable alternative. Ni-W is also not a feasible alternative to metallic chrome coatings applied to work rolls, as major technical functionalities including the adhesion to the substrate are not equivalent to chromium trioxide-based functional chrome coatings.

In summary, nano Co-P coatings are technically not feasible nor is the implementation of a Co-containing replacement technology desirable from a health perspective. Therefore, this process does not represent a suitable alternative to replace functional chrome plating of work rolls.

7.2.5. Alternative 8: High velocity thermal process


During the high velocity thermal spray process, coating powder is injected into a supersonic flame that accelerates the powder particles to high velocity (usually sub-sonic). The heat of the flame melts these high-speed powder particles, which hit the substrate and flatten in pancake-shaped “splats”. As they overlay each other, these splats form a very coherent and low porosity coating (Legg, 2003a).

In general, high velocity thermal spray processes offer a choice of possible starting powders, gases, types of equipment, coating materials and deposition conditions and are therefore very versatile concerning their application area.

Possible powder materials for high velocity processes include but are not limited to:



- pure metals (Cu, Al, Zn, Ni, Mo, W, …), - alloys (NiCr, NiAl, NiMoAl, NiCrSiB, CoCrMo, Inconel, Stellite, …), - carbides (WC-Co, WC-CoCr, WC, Co-Cr, Cr3C2-NiCr, …).

However, among possible substances used in high velocity thermal processes, tungsten carbide alloys like WC-Co, WC-CoCr and chromium carbide-nickel chromium (Cr3C2-NiCr), as well as CoCr-Mo showed promising results during R&D and/or are already applied for niche applications. Therefore the technical feasibility assessment presented in chapter 7.25.2 focuses on these substances.


General assessment: Crahay et al. (2015) report good results in roughness retention for HVOF treated skin-pass rolls in pilot test temper mills (Figure 32). The results indicate sufficient wear resistance of HVOF treated rolls in temper rolling operations.

According to Legg (2003a), hardness for HVOF coatings range from 1,100 to 1,400 HV. Crahay et al (2015) report a hardness of up to 1550 HV for composited adding CoCr to WC.

According to the consultations, regarding HVOF coatings, no approach or attempt has been made, proposed or is even under study to address the strip cleanliness requirement. When developing new ultrafine powder materials and corresponding HVOF processes, the strip surface cleanliness would have to be investigated under real rolling conditions.

According to the consultations, very thin HVOF layers are to date still 30 µm thick, which exceeds the adequate layer thickness to ensure the reproduction of the substrate’s surface topography. Much thinner HVOF layers (10 µm or less) would be needed whilst still ensuring a high and consistent coating quality. This calls for further development of new ultrafine powder materials and corresponding HVOF process.

A substrate surface being coated via HVOF is exposed to temperature rise due to the flame and particle temperature. This exposure to temperature can result in degradation of the substrate properties. The issue of process temperatures may be mitigated by applying simultaneous cooling by a strong forced (inert) gas flow, in order to minimize the depth and softening of the Heat Affected Zone. However, it is uncertain whether the effect can be strong enough to avoid significant overheating of the roll near-surface region above the rather low tempering temperatures of

Figure 32: Roughness retention of different work roll surface treatments under pilot test temper rolling conditions (Source: Crahay et al., 2015).



conventional forged steel work rolls (160°C for cold mill work rolls and 120°C for temper mill work rolls).

Heat during the coating process introduces stress in the work rolls and that can lead to roll spalling. Spalling of rolls is very dangerous because razor sharp pieces of the roll can explode off the roll, behaving like shrapnel and are therefore potentially lethal.

To date, the high process temperatures of HVOF makes the technology an unsuitable replacement for chromium trioxide-based functional chrome plating of work rolls for cold, temper and hot rolling mills.

Surfaces based on HVOF tend to be brittle and cannot be reproduced as required. Furthermore, they require post coating finishing.

The coating process is mostly conducted by a robot or other articulating arm equipped with the HVOF gun. The HVOF process is very fast with deposition rates of ca. 50 µm/min. The deposition of a 100 µm thick coating onto a cylinder (diameter 0.1 m, length 0.5 m) therefore generally takes less than 30 minutes. (Legg, 2012). Still, the current ready-to-use time for chrome plated work rolls, which are of much larger size, takes less than one hour. Therefore, the potential alternative is no suitable replacment.

Summary of technical feasibility: The following chart gives an overview of the assessment of high velocity thermal process as alternative to functional chrome plating of work rolls in metal rolling mills.

Wea

r re

sist

ance

Har

dnes

s

Surf

ace

clea

nlin

ess

Surf

ace

appe

aran

ce

Top

ogra

phy

Ade

quat

e la

yer

thic

knes

s

Suita

bilit

y fo

r he

at-

sens

itive

subs

trat

es

Surf

ace

mor

phol

ogy

Tre

atm

ent t

ime


Against the background of significant technical failure of HVOF, no quantitative analysis of economic feasibility was conducted. However, the cost for HVOF depends on numerous different factors and these are presented in a qualitative to semi-quantitative way below.

The technology for high velocity processes and functional chrome plating differ fundamentally in the equipment and peripherals. The implementation of high velocity processes requires complex machines and infrastructure equipment. The installation costs for completely new plant and machine lines comprise 75,000-200,000 € for equipment, 75,000 € for the robot and 200,000 € for the room, that is in total 350,000 to 475,000 € (Legg, 2003a).

Table 12 shows the comparison of process costs for HVOF compared to functional chrome plating, with data from HVOF equipment vendors and business information from a functional chrome plating company. The total production costs for the coating are based on several items such as material, energy, waste, repair, etc. to achieve the same production output.



Table 12: Comparison of production costs of the coating: HVOF & functional chrome plating.

Percentage of total direct production cost (functional chrome plating=100%)

HVOF Functional chrome plating Factor

Coating material 368 20 18.4

Labour 35 6 5.8

energy 51 39 1.3

Other costs 66 12 5.5

Depreciation 23 23 1

Production Cost total 543 100 5.4

The coating material costs are by far the biggest driver for increasing costs. In total, the costs to produce 1 m² of coated material are 5.4 times more expensive using HVOF instead of functional chrome plating.

Reduction of the overall risk

As the alternative is not technically feasible, only classification and labelling information of substances (see Appendix 2.7) and products reported during the consultation were reviewed for comparison of the hazard profile.

As mentioned above, various different powder materials are used for high velocity processes, for which some substances are confidential business information. As an example, the hazard profile from an often-used coating material is illustrated. According to suppliers’ SDS, the following hazard statements are given for WC-12Co: Skin Irrit. 2, Eye Irrit. 2, STOT SE 3, Carc. 2. As such, transition from chromium trioxide – which is a non-threshold carcinogen – to WC-12Co would constitute a shift to significantly less hazardous substances. However, some cobalt compounds are on the REACH candidate list for substances of very high concern so an assessment on the hazardous profile of these substances would have to be performed on a case by case basis.

Availability

In general, HVOF are fully developed commercial processes. Equipment and powders can be obtained commercially from a number of vendors.

However, to be applicable for the coating of work rolls for cold, hot and temper rolling mills, the alternative would need to be substantially modified. Solving the issues of too high process temperatures, adequate layer thickness, grindability and strip surface cleanliness will approx. take up to 10 years for further R&D. R&D may partly be conducted in parallel but many steps will have to be passed sequential and iteratively. If technically successful, the enhanced HVOF coatings will then require tests at pilot rolling mills, followed by extensive industrial trials at various mill types and in various roll shops with different types of grinding machines and grinding wheels. In total, 12 years of development are required, including full testing on industrial scale. This also includes the follow-up of the quality performance of steel strips rolled with the alternate coatings, up to the customers’ final products.



After the technical, economical and logistical feasibility have been convincingly demonstrated, further 3 to 5 years are needed to build up the capacity for all relevant European mills and to fully implement it across the industry. Therefore, the alternative is not available within the next 15 years.

The overall TRL/MRL assigned to High Velocity Thermal Processes for manufacturing work rolls used in cold and temper rolling is 3-4/6. The following chart gives on overview of the assigned TRL and MRL for High Velocity Thermal Processes in cold and temper rolling applications.

Conclusion on suitability and availability for alternative HVOF

At present, high velocity thermal process is technically not feasible and there are major shortcomings that need to be solved before the alternative could be considered for substituting chromium trioxide-based functional chrome plating. Apart from uncertainty of technical success, the economic and logistical feasibility is also still uncertain and will need to be evaluated during the industrial trialling period. After the technical, economical and logistical feasibility have been convincingly demonstrated, further 3 to 5 years are needed to build up the capacity for all relevant European mills and to fully implement it across the industry.

The economic assessment of this alternative showed that production costs of HVOF are at least 5 times higher compared to functional chrome plating.

In conclusion, these systems are technically not equivalent to chromium trioxide based products, have strong economic disadvantages and will not be available within the next 15 years. HVOF is therefore not considered to be a general alternative.

7.2.6. Alternative 6: Electrical Discharge Coating (EDC)


Electrical Discharge Coating (EDC) is based on the Electrical Discharge Texturing (EDT) and generally used for providing the substrate with a hard and wear resistant coating while establishing concurrently a textured topography.

While EDT is based on eroding part of the substrate surface thus forming micro-craters, EDC incorporates deposits of micro-particles into the surface layer. Thereby, EDC surface textures are similar to those obtained from EDT (Crahay et al., 2015).

The coating of the surface is conducted by electrical current ionising a dielectric located in the spark gap between the electrode and the substrate. Thus, temperatures of up to 8000 K cause events of local



melting and vaporisation at the electrode and the substrate surface. The diffusion of charged particles along the electrical field into the substrate surface establishes the so-called recast layer. (Bröcking et al., 2015).

In rolling operations of flat metal products, EDC is mostly used for texturizing work rolls of temper mills. In cold and hot rolling, mostly grinded, non-texturized rolls are applied. Therefore, EDC is only regarded as a partial alternative, if at all.


General assessment: According to Bröcking et al. (2015), the roughness retention of EDC rolls, as examined in a pilot trial temper mill, are superior to uncoated texturized ones but inferior to conventional work rolls being texturized and chrome coated (Figure 33).

Wear resistance is directly linked to roughness retention which is of major importance for ensuring stable rolling processes and quality of the rolled strip. From this point of view, EDC is not yet an adequate replacement for chromium trioxide based functional chrome plating of work rolls, and still needs further development and testing iterations to improve this key functionality.

The hardness of work roll surfaces in cold rolling of metal is an important key functionality regarding the resistance to mechanical strain and linked to the occurrence of pinch, indentation or banding impairing the process and strip quality. Electrical discharge coatings applied by using tungsten or titanium carbide (WC/TiC) electrodes improve the surface hardness by incorporating the carbides into the recast layer (Bröcking et al., 2015). Hardness levels are expected to be between 850 and 1000 HV, thus fulfilling the requirements.

EDC treated work rolls are mostly used in temper mills and not applied in cold rolling mills, However, according to the consultation, the strip cleanliness of rolled metal strips in temper mills is expected to be worse when applying EDC treated work rolls, especially when installed in early stands of the respective mill.

According to the consultation, initial trial results indicate varying results for the surface appearance of the rolled metal strip when using EDC treated rolls. In some cases, the metal strip appearance was observed to be comparable to flat metal rolled in mills applying chrome coated work rolls. In mills using EDC treated rolls, severe worsening, in the form of inhomogeneity of the strip, was observed.

Figure 33: Roughness retention of uncoated and chrome coated EDT work rolls as well as WC- and TiC- EDC work rolls in pilot trial mill testings (Source: Bröcking et al., 2015).



Therefore, presently, no stable strip surface quality can be guaranteed, which is essential for the production of high quality flat metal products. Further R&D is needed to overcome the deficiencies mentioned.

Currently, EDC is under investigation at a customer of CHL. So far, only one roll roughness range (Ra between 2.5 and 2.8 micron) has been targeted under real rolling conditions. The range still needs to be expanded down to 1 µm and up to 6 µm to cover the required Ra ranges for most of the campaign types for all relevant temper mills. This is not a trivial task, especially to achieve a good EDC layer thickness and performance at low Ra levels (for example for the packaging steel sector) is a challenge.

Therefore, the alternative is not suitable for replacing chromium trioxide based functional chrome coating of EDT textured work rolls of cold rolling mills. In case of temper mills, and at least 10 additional years are necessary to develop EDC as an alternative to chrome coated work rolls and only applicable for some mills.

The layer thickness of electrical discharge coated work rolls depends on the pulse current and treatment passes applied. Bröcking et al. (2015) established coatings using a tungsten carbide electrode of approximately 8 µm at a current of 4 A with 8 passes. Increased pulse current yields recast layers with lower layer thickness. WC-EDC fulfils the minimum requirement in layer thickness of 5 µm, but does not provide for a thickness up to 10 µm. However, the occurrence of macro-cracks is more likely for thicker layers.

Depending on the process parameters, EDC yields recast layers on the substrate exhibiting sufficient layer thickness. According to Bröcking et al. (2015), this is the case for EDC applying tungsten carbide electrodes at a pulse current of 4 A and eight passes. However, recast layers of adequate layer thickness show increased presence of cracks reaching down to the untreated substrate.

EDC, as an alternate surface treatment for rolls of temper mills, takes approximately twice as long as electrical discharge texturing (EDT), which is commonly used for texturizing. Accounting for the additional chrome plating of EDT work rolls, the overall time required for EDC can be expected to be equal. However, in case of a shift to the alternative, capacities would have to be doubled to balance the time short comings of EDC compared to EDT.

Summary of technical feasibility: The following chart gives an overview of the technical feasibility of Electrical Discharge Coating as potential alternative to functional chrome plating of work rolls in cold rolling steel mills.

Wea

r re

sist

ance

Har

dnes

s

Surf

ace

clea

nlin

ess

Surf

ace

appe

aran

ce

Adh

esio

n to

the

subs

trat

e

Top

ogra

phy

Ade

quat

e la

yer

thic

knes

s

Plat

ing

of la

rge

geom

etri

es

Surf

ace

mor

phol

ogy

Mac

hina

bilit

y

Tre

atm

ent t

ime

-




As mentioned above, R&D is currently being carried out to further develop EDC as an alternative to chrome coated work rolls in temper mills. Therefore, the economic feasibility depends on the outcomes of the ongoing development process and corresponding steps, which are outlined in the conclusion. Especially the demand for special electrodes and additional treatment capacity, compared to EDT, are main obstacles in terms of economic feasibility. The higher cost of the special electrodes and the costs of the extra EDT machine capacity requirement exceed the savings from the elimination of chrome plating. Moreover it is still uncertain if the functional chrome plating of work rolls can be eliminated without any loss of product quality or campaign length. This holds true for all mills, Ra levels and product types.

In conclusion, the economic feasibility of EDC treated work rolls in temper mills is uncertain and consider unlikely to be achieved before additional steps have been taken in further developing the alternative.


As the alternative is not technically feasible, only classification and labelling information of substances and products reported during the consultation were reviewed for comparison of the hazard profile. Based on the available information on the substances used within this alternative, neither tungsten carbide (WC) nor titanium carbide (TiC) is classified as hazardous substance.

As such, transition from chromium trioxide – which is a non-threshold carcinogen – to one of these substances would constitute a shift to significantly less hazardous substances.

Availability

The EDC technology is based on the EDT technology, which in turn is already applied for texturizing work rolls of cold rolling mills. Currently used EDT machinery can be modified for the utilization as EDC machine (Crahay et al., 2015). Therefore, the EDC technology in general is available. However, the alternative has only been applied on the industrial scale in a few short trials so far and needs to be further improved, tested more extensively and validated after up-scaling.

Initial temper mill trials were carried out with partly promising results, but still not comparable to chrome-plated work rolls in terms of roughness retention. More mill trials are required as well as further development of electrodes and EDC process parameters. The special electrodes used for EDC treatment are still produced at laboratory scale, so a supply chain for electrodes is still to be developed. Furthermore, the capacity to build EDT-machines with the capability of running the special EDC roll treatment process is still to be built up.

The overall TRL/MRL assigned to electrical discharge coating of work rolls used in temper rolling is 7.2/4. The following chart gives on overview of the assigned TRL and MRL for electrical discharge coating of work rolls used in temper rolling applications. No TRL/MRL is indicated for cold rolling or aluminium hot rolling applications, since EDC is dedicated to textured work roll surfaces only and therefore not suitable as general replacement of chrome plated work rolls in cold rolling or aluminium hot rolling mills. At best, EDC may become a partial replacement of chrome plated work rolls, in temper rolling mills.



Conclusion on suitability and availability for alternative Electrical Discharge Coating (EDC)

EDC cannot be regarded as an overall alternative to functional chrome plating of work rolls in cold, temper and hot rolling mills. While in principle it is potentially applicable in temper rolling operations, EDC treated rolls are mostly not applied in cold or hot rolling of flat metal. Besides the issue of selectivity, EDC suffers from short comings regarding the treatment time and unreliable results concerning the surface appearance of the rolled strip.

According the consultations, extensive R&D is required including:

- further industrial temper mill trials with various types of strip products - further optimization of the EDC process due to mixed results from initial trails - further EDC development for expanding the roughness range - up-scaling of the production of the special EDC-electrodes, which are currently still produced

on laboratory scale. Commercially available WC-Ni electrodes appeared to exhibit an unstable sparking behaviour leading to bad surface defects on the roll.

- validation of the various EDC processes on pilot mill scale, which can only be performed after a comprehensive upgrade of the laboratory pilot rolling mill.

- extensive industrial mill trials, to validate and fine-tune the developed EDC processes for each mill and campaign type.

- capacity development to fully implement the EDC process in temper mills

The overall process is expected to take at least 10 years, without any guarantee that it will provide a solution for all temper mills.

7.3. Pre-treatment After several alternatives for the main surface treatment have been assessed in the former chapters, alternatives for pre-treatment using chromium trioxide in the functional chrome plating process are discussed in the following. The purpose of the pre-treatment is the removal of surface residues. As there is no clear demarcation, the term etching is used to cover both, etching and pickling as chromium trioxide pre-treatment in the following.



7.3.1. Mineral acids


Different mineral acids are currently under evaluation as alternatives to chromium trioxide in the surface pre-treatment process. Research is currently focused on using sulphuric acid composed with other acids, such as phosphoric acid and nitric acid, or with additives, such as peroxymonosulphate salts or peroxidisulphate salts.

An overview of general information on substances used within this alternative and the risk to human health and the environment is provided in Appendix 2.2.


General assessment: Pre-treatment is necessary to prepare the surface of the work rolls for the subsequent process steps. Adequate preparation of the base metal is a prerequisite: adhesion between the metallic chrome coating and the substrate depends on the force of attraction at a molecular level. The surface of the metal – which is mostly steel or hardened steel for functional chrome plating – must be absolutely free of contaminants, corrosion and other residuals until the plating process is finished.

For the chrome plating of work rolls, reverse etching in the chromium trioxide bath itself at the appropriate temperature or in a separate electro-cleaning at basic pH (ca. 12) is applied.

For Cr(VI)-based reverse etching, the same substance is used for pre-treatment and main treatment. Therefore, no additional rinsing working step involving water is required in between. Etching in the plating bath is especially advantageous for large parts, such as work rolls, which are immersed in large baths.

Many applications require the usage of chromium trioxide in the pre-treatment working step, especially when the etch rates need to be strictly controlled and over-etching must be avoided. For example, the steel industry requires that the coating does not affect the surface morphology of the substrate. The defined surface texture of the substrate is created during the pre-treatment and must be kept during the plating process. The desired surface roughness varies for different applications in the range of 0.2 µm to 13 µm. Pre-treatment with chromium trioxide provides surface roughness for metal mill work rolls in the application range as required.

Alternatives must have analogous key functionalities to chromium trioxide, most importantly excellent adhesion promotion. In addition, if another substance than chromium trioxide is used in the pre-treatment process, cross contamination with the plating bath must be prohibited. Minor contamination with sulphur or chlorides are sufficient to make the plating bath content unsuitable for functional chrome plating needs and require to dispose of and exchange the bath content. Cross contamination is especially critical for parts with complex geometry, where residues of the pre-treatment solutions may be trapped in holes, openings, excavations, inside tubes, etc.

Therefore, all parts must be thoroughly cleaned in additional working steps. If chromium trioxide is the only substance used for pre-treatment in manufacturing, no such cleaning installations are necessary. Furthermore, significant amounts of water are needed for the rinsing process which need to be adequately treated and discharged accordingly. Thus, appropriate water and waste water installations become mandatory. In summary, a diversity of additional equipment need to be implemented which fundamentally changes the existing facility design and require significantly more space.



In addition, the alternative pre-treatment should be compatible with all relevant substrates. If alternatives are substrate specific, a separate pre-treatment bath with appropriate installation would be required. The use of one substance for both, pre-treatment and main treatment ensures high quality and smooth process functionality.

The development of a pre-treatment alternative to chromium trioxide depends on the potential alternative for functional chrome plating and is no standalone process. While an alternative for functional chrome plating is investigated, adequate custom-tailored pre-treatments are evaluated in parallel or after the potential alternatives for the main process have been qualified.

Alternatives:

Sulphuric acid based solutions are assessed as a potential alternative for chromium trioxide based etching pre-treatments on work roll substrates. They are used at room temperature and the parts are not preheated. It is qualified for some applications and processes, but not as a general replacement for chromium trioxide pre-treatment.

Sulfuric acid anodic etching has been used successfully for some steels but smutting can be an issue.

Nickel strike solutions (usually NiCl2 / HCl) can be used as an alternative to back etching for many stainless steels, but nickel salts present very strong health and safety issues (CMR classification).

An etching solution of sulphuric acid with peroxymonosulphate (for example potassium peroxymonosulphate 2KHSO5·KHSO4·K2SO4) for different kinds of stainless steel was tested at ambient temperature at the laboratory scale. The etching process (removal of smut) showed rapid, suitable performance with regard to surface quality. Currently, this alternative is at a very early investigation state and would have to be tested under roll shop conditions. A detailed visual examination is mandatory to ensure that no end grain pitting occurs on stainless steel.

Conclusions: At the current stage, mineral acid based solutions are technically not feasible as a general alternative to chromium trioxide based etching of metals. Intensive R&D efforts are ongoing to improve their performance, as the surface is not adequately prepared for the subsequent process step and the applied layers do not adequately adhere to the substrate.


The economic feasibility of etching with mineral acid on metal substrates was not assessed, as the alternative is not technically feasible and already failed the requirements at early investigation stage.

Switching to a chromium trioxide-free etching alternative would generally necessitate the installation of additional bath equipment for rinsing processes. The larger the parts, the larger the separate pre-treatment baths and appropriate installations. For facilities producing large parts especially with complex geometry, changes of the facility design and need for space consuming and expensive additional equipment are significant.

However, based on the literature research and consultations there is no indication that the discussed alternative is not economically feasible.


As the alternatives are not technically feasible, only classification and labelling information of substances and products reported during the consultation were reviewed for comparison of the hazard profile. Based on the available information on the substances used within this alternative (see



Appendix 2.2.1), nitric acid would be the worst case with a classification as Ox. Liq. 3, Skin Corr. 1A, Met. Corr. 1, Skin Irrit. 2, Eye Dam. 1, STOT SE 3. As such, transition from chromium trioxide – which is a non-threshold carcinogen – to one of these substances would constitute a shift to less hazardous substances.

Availability

To date, the pre-treatment process on steel work roll substrates is conducted with chromium trioxide either in the plating bath itself.

For some applications and substrates, the use of sulphuric acid based solutions is qualified but not as a general replacement for the chromium trioxide pre-treatment. For example, an etching solution for aluminium and its alloys only based on sulfo nitro ferric acid is commercially available and qualified for some applications outside of the sectors analysed. The technical feasibility for etching of metals is not yet equivalent to the current chromium trioxide based process and further R&D is necessary.

The etching pre-treatment has to be adapted according to the subsequent chromium trioxide free electroplating alternative, which is also still under R&D. However, etching as a pre-treatment to adequately prepare the surface for the subsequent step is always performed in-line with the functional chrome plating step and it is not a stand-alone process.

As pre-treatment and main treatment using chromium trioxide are closely related, it will take a minimum of 10 – 15 years to develop a general alternative as pre-treatment which meets all requirements - analogous to the time frame expected for functional chrome plating alternatives.

Conclusion on suitability and availability for mineral acids

In summary, the use of chromium trioxide in pre-treatment processes is state of the art for metal mill work rolls to be chrome plated.

Using another substance than chromium trioxide for the pre-treatment process requires significant efforts to clean the parts after the pre-treatment by means of rinsing to avoid cross contamination of the plating bath. Already minor amounts of residues from the treatment solution such as sulphates or chlorides make the bath content unsuitable. If no water supply and water treatment facilities are already in place, this constitutes in combination with required additional bath equipment, a fundamental change of the facility design and demand large additional areas.

The development of a pre-treatment alternative to chromium trioxide depends on the potential alternative for functional chrome plating and is no standalone process. While an alternative for functional chrome plating is investigated, adequate custom-tailored pre-treatments are evaluated in parallel or after the potential alternatives for the main process have been qualified. Therefore, the time needed for R&D and industrial implementation of an alternative are identical for pre-treatment and main treatment, which is a minimum of 10 – 15 years.



8. OVERALL CONCLUSIONS ON SUITABILITY AND AVAILABILITY OF POSSIBLE ALTERNATIVES FOR FUNCTIONAL CHROME PLATING

In this AfA, a total of 27 potential alternatives have been identified as potential replacement for chromium trioxide-based functional chrome plating of work rolls used in cold, temper and hot rolling mills for flat steel and aluminium products. The pre-treatment using chromium trioxide has been assessed separately.

Chrome coated work rolls deliver high degrees of strip surface cleanliness during the cold rolling process and desired strip surface appearance in temper rolling operations. Furthermore, the zinc pick-up during rolling operations in hot dip galvanizing lines is lower for chrome coated rolls. Although in general not each work roll of a metal mill is chrome coated, several rolling operations are reliant on such rolls, especially in the high quality flat metal segment. The process is therefore specified for particular applications where this combination of performance characteristics is critical.

Functional chrome plating using chromium trioxide involves the immersion of the rolls in each of a series of treatment baths containing chemical solutions or rinses under specific operating conditions. Chromium trioxide is a pre-requisite for the main treatment of functional chrome plating to ensure the highest quality of the coating.

The analysis of alternatives shows that there are no technically feasible alternatives to chromium trioxide-based functional chrome plating of work rolls for cold, temper and hot rolling mills. Several potential alternatives are subject to ongoing R&D, but do currently not support the necessary combination of key functionalities and can therefore not be considered as technically feasible alternatives. Some alternatives (e.g. forged or cast (Semi-) High Speed Steel work roll grades ) are qualified for individual applications in metal mills with less critical performance requirements, mainly regarding strip surface cleanliness and surface appearance, but none delivers the combined key properties of functional chrome plating with chromium trioxide.

Functional chrome plated work rolls bear the advantage of very high lifetime. A switch to potential alternatives is linked to an increase in the replacement of worn rolls and therefore in the work roll stock and corresponding transport to the roll shop and back to the metal processing facilities, thus increasing costs tremendously. Some short comings of individual promising alternatives, such as the strip surface cleanliness, require major investments, for example in cleaning lines. Besides, those measurements would only be feasible in case spatial restrictions at the production facilities would be overcome.

Chromium trioxide is also used in the pre-treatment process 'etching' to prepare the substrate for the subsequent main treatment. To date, sulphuric acid based solutions are already qualified for some applications and substrates but not as a drop-in replacement for chromium trioxide in the pre-treatment of metal mill work rolls.

There are no post-treatment processes for functional chrome plating of work rolls, which involve chromium trioxide.

In summary, no ready-to-use alternative is identified, which fulfils the entirety of chromium trioxide-based functional chrome plating of work rolls used in cold, temper and hot rolling of flat steel and aluminium. Although some alternatives are qualified for individual applications, none of the alternatives is eligible to deliver the required key functionalities, especially needed in the high quality flat metal segment. Table 13 at the end of this section provides an overview of the technical deficiencies of all concept 1 and 2 alternatives assessed. For each sector and alternative, the major deficiencies are listed.


Use number:1 Copy right protected – No copying / use allowed. 101

Following the above mentioned, further development and testing needs to be carried out. In case technical feasibility is proven, additional time is required for adaptation of the manufacturing process, build-up of production capacities and approval. None of the assessed potential alternatives has passed Technology Readiness Level (TRL) 7 yet, thus proved to be adequate replacement for chromium trioxide-based functional chrome plating. Furthermore, none of the alternatives has reached Manufacturing Readiness Level (MRL) 10 yet, which indicates that full rate production capabilities have not been proven yet. It is important to note that only the combination of TRL and MRL determines the overall readiness of a potential alternative, both, from the technological as well as from the manufacturing point of view.

Review period Extensive evaluation of potential alternatives to chromium trioxide-based coating of work rolls in cold and temper steel rolling as well as hot aluminium rolling mills has been carried out in the present AoA. Furthermore, economic aspects, as well as aspects of approval and release in flat metal industry were assessed with regard to a future substitution of the substance. The following key points are relevant for deriving the review period:

• No ready-to-use alternative is identified. R&D to identify such an alternative is ongoing, but time and cost intensive due to the fact that the potential alternative's technical feasibility needs to be proven at the industrial mill scale. Process and quality stability are required to be shown in long rolling campaigns and for individual mill types.

• None of the assessed potential alternatives have passed Technology Readiness Level (TRL) 7 yet, and thus have not been proven to be an adequate replacement for chromium trioxide-based functional chrome plating. Furthermore, none of the alternatives have reached Manufacturing Readiness Level (MRL) 10 yet. Based on experience and with reference to the status of R&D programs, alternatives are not foreseen to be commercially available at sufficient capacities for key applications and pre-treatment before 12 years after the sunset date.

• Investment cycles for metal rolling mills are in the range of 30 to 40 years. Major investments in e.g. cleaning lines to uphold competitiveness in the high quality market segments impair calculated long-term returns on investment. The use of chrome plated work rolls is the only opportunity to keep existing, in-service metal rolling mills operating (refer to SEA).

• The socio-economic impacts of a non-granted authorisation, amounting to 95.3 million Euro related to foregone added value for the applicants themselves, 1.2 million Euro related to social impacts due to additional costs to society for unemployment, and 5.7 billion Euro per year for impacts on downstream users (rolling mills), outweigh by far the monetised residual risk to human health and the environment of a granted authorisation of 3.25 million Euro (refer to the SEA).

As a consequence of the above-mentioned key points, a review period of 12 years is selected because it coincides with best case estimates (by the applicants and their customers from the steel and aluminium industry) of the schedule required to industrialise alternatives to chromium trioxide in cold and temper steel as well as hot aluminium rolling mills, if ever possible.



Table 13: Technical deficiencies of potential alternatives.


7.1.1 Alternative forged steel work roll grades /(Semi-) High-Speed Steel /Ti-enhanced

1

- hardness - surface cleanliness - surface appearance - topography - machinability - treatment time - economically not feasible

7.1.2 Alternative cast steel work roll grades /(Semi-) High-Speed Steel

1

- hardness - surface cleanliness - surface appearance - topography - machinability - treatment time

7.1.3 Continuous Pouring for Cladding (CPC) 1

- hardness - topography - surface morphology - machinability - treatment time - economically not feasible - not available on the European market

7.1.3 Powder Metallurgy-based Hot Isostatic Pressing (PM HIP) 1

- surface appearance - topography - machinability - treatment time - economically not feasible - large rolls not available

7.1.3 Electro-Slag Remelting Cladding (ESR Cladding) 1

- hardness - surface cleanliness - topography - machinability - treatment time - not available

7.1.3 Laser Cladding 1 - laser cladding as alternate

manufacturing method not available - low technical readiness level

7.2.3.1 Trivalent Chrome Plating 2

- wear resistance - hardness - adhesion to the substrate - low technical readiness level

7.2.4.1 Electroless nickel plating 2

- wear resistance - hardness - adhesion to the substrate - resistance to process conditions - treatment time - low technical readiness level - soluble nickel compounds may meet the

SVHC criteria under REACH




7.4.1.2 Nickel & nickel alloy electroplating 2

- wear resistance - hardness - surface cleanliness - economically not feasible - soluble nickel compounds may meet the

SVHC criteria under REACH

7.2.4.3 (Nano) Co-P plating 2

- wear resistance - hardness - treatment time - cobalt compounds listed on the REACH

candidate list - low technical readiness level

7.2.4.4 High velocity thermal processes 2

- topography - adequate layer thickness - resistance to process conditions - surface morphology - treatment time - economically not feasible - low technical readiness level

7.2.5 Electrical Discharge Coating (EDC) 2

- surface appearance - topography - surface morphology - treatment time - not applicable to work rolls of cold

rolling mills



9. REFERENCE LIST

Bressers, P.M.M.C. and Gonzalez Rodriguez, F. (2010): TNO report – Hard chrome deposition from ionic liquid solutions. TNO Science and Industry, July 2010.

Bröcking, R., Meghwal, A., Melzer, S., Verdier, S., Evans, G., Lowbridge, T., Vanhumbeeck, F-F., Debrabandere, D., & Crahay, J. (2015): DEVELOPMENT OF ELECTRICAL DISCHARGE COATING (EDC) AS CHROME-FREE ALTERNATIVE FOR INCREASING CAMPAIGN LENGTH OF TEMPER MILL WORK ROLLS. Paper for the ROLLS 5 Conference 2015, 22 - 24 Apr., 2015, Birmingham (UK).

Crahay, J, Bertrandie, J.J., Bixquert, F., Bolt, P.H., Bröcking, R.G.J., Debrabandere, D., Doeding, Ch., Dietsch, H., Evans, G., Jansen, F., Lesenne, J-M., & Vanhumbeeck, J-F (2015): Substitution of hard chrome plating rolls of skin-pass and temper mills. Paper for the METEC and 2nd European Steel Technology and Application Days (ESTAD) conference, 15-19 June 2015, Düsseldorf.

Daly B.P. and F.J. Barry (2003): Electrochemical nickel-phosphorus alloy formation. IoM Communications Ltd and ASM International.

Department for Environment, Food and Rural Affairs (RPA) (2005): Environmental Risk reduction strategy and analysis of advantages and drawbacks for Hexavalent chromium.

European Powder Metallurgy Association (EPMA) (2013) Introduction to PM HIP Technology - A guide for Designers and Engineers, 2nd Edition, reprint 2013, retrieved from http://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCIQFjAAahUKEwjkw-ijgYvJAhXEDQ8KHd7HD4s&url=http%3A%2F%2Fwww.epma.com%2Fdoc_download%2F246-introduction-to-pm-hip-technology-hip-hot-isostatic-pressing&usg=AFQjCNHe2hrNrr-2j9vZPpLjXHBHDyr7Kw&bvm=bv.107406026,d.ZWU

Facchini et al. (2009): Electrodeposition of nanocrystalline cobald alloy coatings as a hard chrome alternative, Integran Technologies.

Gaspard, C. , Batazzi, D., Thonus, P., & Bataille, S. (2002a): Updated grades for work rolls dedicated to cold rolling and their evolution to HSS grades, Southern African Roll Users Conference (SARUC 2002), 2002, Vanderbijlpark (South Africa).

Gaspard, C, Bataille, S., Batazzi, D. & Thonus (2002b): Current trends for cold rolling applications with HSS rolls. 44th MWSP Conference Proceedings, Vol. XL, 2002, pp. 445-451.

Gaspard, C., Vergne, C., Batazzi, D., Nylen, T., Bolt, P. H., Mul, S., & Reuver, K. M. (2011): Implementation of in-service key parameters of HSS work roll grade dedicated to advanced cold rolling. Iron & Steel Technology, 8(8), 97-106.

Gaspard, C., Vergne, C. & Adams, T. (2015): Performance overview of forged HSS rolls for cold rolling in the steel industry. Rolls 5 Conference, 22-24 April 2015, Birmingham (UK).

Hashimoto, M., Tanaka, T., Inoue, T., Yamashita, M., Kurahashi, R., & Terakado, R. (2002): Development of Cold Rolling Mill Rolls of High Speed Steel Type by Using Continuous Pouring Process for Cladding. ISIJ international, 42(9), 982-989.

Jacobs, L., Vervaet, B., Hermann, H., Agostini, M., Kurzynski, J., Jonsson, N.-G., Perez, J., Reuver, K. & van Steden, H. (2011): Improving strip cleanliness after cold rolling, Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, Vol. 225, pp. 959-969.

Lackinger, C.V., Oemkes, H., & Nettelbeck, H.J. (2002). TAKO – The new PLTCM at Thyssen Krupp Stahl AG in Beeckerwerth works, Revue de Métallurgie, 99(7-8), pp. 661-669.

Legg, K. (2003a): Chrome Replacements for Internals and Small Parts, final report (http://www.asetsdefense.org/documents/DoD-Reports/Cr_Plating_Alts/Cr_Rplcmnt-IDs&Sm_Parts.PDF)

Legg, K. (2003b): Chromium and Cadmium Replacement Options for Advanced Aircraft, HCAT Program Review, KSC.

http://www.asetsdefense.org/documents/DoD-Reports/Cr_Plating_Alts/Cr_Rplcmnt-IDs&Sm_Parts.PDF



Legg, K. (2012): Choosing a Hard Chrome Alternative (http://www.rowantechnology.com/wp-content/uploads/2012/06/Hard-Chrome-Plating-Alternatives.pdf)

Lester, S., Longfield, N., Griffiths, J., Cocker, J., Staudenmaier, C., & Broadhead, G. (2013): New Systems for Laser Cladding – Laser surface modifications in steel industry. Laser Technik Journal (3), pp. 41-43.

Li, H., Jiang, Z., Tieu, A. K., & Sun, W. (2008). A microscopic examination on work roll wearing behaviour by disc-to-disc experiments. Steel research int. 79 (2) Special Edition Metal Forming Conference 2008

McCrea et al (2003): Electroformed nanocrystalline coatings: an advanced alternative to hard chromium electroplating, final report.

National Defense Center for Environmental Excellence (NDCEE) (1995): Regulatory Analysis of the Chromium Electroplating Industry and Technical Alternatives to Hexavalent Chromium Electroplating, USA, Environmental Information Analysis, final report.

OSD Manufacturing Technology Program and Joint Service/Industry MRL Working Group (May, 2011). Manufacturing Readiness Level (MRL) Deskbook – Version 2.0.

Shimizu, S., Aoki, K., Kobayashi, M., Saito, T., Yamada, Y., & Kosumi, F. (1992). A Ti-enhanced Cold Rolling Work Roll with Self-generating Optimal Roughness Characteristics. ISIJ international, 32(11), 1238-1243.

Sychterz, J. (2015) Improved roll performance and elimination of chrome plating using forged semi high speed steel roll materials in cold rolling application. Rolls 5 Conference, 22-24 April 2015, Birmingham (UK). Toxics Use Reduction Institute (TURI) (2006): Five chemicals alternative assessment study.

Toxic Use Reduction Institute (TURI) (2012): Trivalent Chromium Plating Conversion Case Study: Independent Plating, Worcester, Massachusetts.

Tremea, A., Bellicini, F., Fenandez, H., & Agazzani, D. (2010a).SEMI-HSS and SPUN CASTING ROLLS for A COLD MILL APPLICATIONS.

Internet sources:

- http://www.epa.gov

- Schulz website: http://www.schulz-metallveredelung.de/oberflaechenveredelung-metallveredelung/hartverchromen (pdf, accessed on 17.06.2014)

- Pfonline 2013: http://www.pfonline.com/articles/functional-trivalent-chromium-electroplating-of-internal-diameters (accessed on 17.06.2014)

- www.werkstoffoberflaeche.de

- http://sci.esa.int/

- http://www.topocrom.com/en_sites/principle_technology.php (accessed 18.06.2014)

- http://www.sulzer.com

- http://epp.eurostat.ec.europa.eu

- http://spray-molybdenum-wire.com

- http://www.roymech.co.uk

- http://echa.europa.eu

http://www.rowantechnology.com/wp-content/uploads/2012/06/Hard-Chrome-Plating-Alternatives.pdf

http://www.rowantechnology.com/wp-content/uploads/2012/06/Hard-Chrome-Plating-Alternatives.pdf

http://www.epa.gov/

http://www.schulz-metallveredelung.de/oberflaechenveredelung-metallveredelung/hartverchromen

http://www.schulz-metallveredelung.de/oberflaechenveredelung-metallveredelung/hartverchromen

http://www.pfonline.com/articles/functional-trivalent-chromium-electroplating-of-internal-diameters

http://www.pfonline.com/articles/functional-trivalent-chromium-electroplating-of-internal-diameters

http://www.werkstoffoberflaeche.de/front_content.php?idart=62

http://sci.esa.int/

http://www.topocrom.com/en_sites/principle_technology.php

http://www.sulzer.com/

http://spray-molybdenum-wire.com/

http://echa.europa.eu/documents/10162/3be377f2-cb05-455f-b620-af3cbe2d570b



- http://www.chemspider.com

- http://www.chemicalbook.com/

- http://pubchem.ncbi.nlm.nih.gov

- http://www.sigmaaldrich.com/

- www.partsfinishing.com/

- http://www.scbt.com

- http://www.chemblink.com/

- http://www.epa.gov/

- www.turi.org/

- http://ammtiac.alionscience.com/

- READE internet site: http://www.reade.com

- Chemie.de internet site: http://www.chemie.de/lexikon/Titannitrid.html

- Carl Roth SDS: http://www.carlroth.com

- MAK Collection for Occupational Health and Safety: http://onlinelibrary.wiley.com

- http://echa.europa.eu/documents/10162/13552/aviation_authorisation_final_en.pdf

- http://www.sifcoasc.com/wp-content/uploads/Nickel-Tungsten-5711.pdf

- http://www.asetsdefense.org/documents/Workshops/ASETS2012/7/Clouser%20-%20For%20Web.pdf

- http://www.myvirtualpaper.com/doc/nasf_aesf/pasf_may10/2010052701/52.html#52

http://www.chemspider.com/

http://www.chemicalbook.com/ChemicalProductProperty_EN_CB9454729.htm

http://pubchem.ncbi.nlm.nih.gov/

http://www.sigmaaldrich.com/catalog/product/aldrich/229555?lang=de&region=DE

http://www.partsfinishing.com/

http://www.scbt.com/

http://www.chemblink.com/MSDS/MSDSFiles/40372-72-3_Alfa%20Aesar.pdf

http://www.epa.gov/osw/hazard/wastetypes/wasteid/inorchem/docs/pot-dich.pdf

http://www.turi.org/

http://ammtiac.alionscience.com/

http://www.reade.com/

http://www.chemie.de/lexikon/Titannitrid.html

http://www.carlroth.com/

http://onlinelibrary.wiley.com/

http://echa.europa.eu/documents/10162/13552/aviation_authorisation_final_en.pdf

http://www.sifcoasc.com/wp-content/uploads/Nickel-Tungsten-5711.pdf





APPENDIX 1 – MASTERLIST OF ALTERNATIVES WITH CLASSIFICATION INTO CATEGORIES 1-3 AND SHORT SUMMARY OF THE REASON FOR CLASSIFICATION OF ALTERNATIVES INTO CATEGORY 3 (SELECTION PROCESS)

Section Alternative Substance/ Alternative Process Concept Screened out because

7.1.1

Alternative forged steel work roll grades /High Speed Steel (HSS) /Semi-High Speed Steel (SHSS) /Ti-enhanced work rolls

1 -

7.1.2 Alternative cast steel work roll grades /High Speed Steel (HSS) /Semi-High Speed Steel (SHSS)

1 -

7.1.3 Continuous Pouring for Cladding (CPC) 1 -

7.1.3 Powder Metallurgy-based Hot Isostatic Pressing (PM HIP) 1 -

7.1.3 Electro-Slag Remelting Cladding (ESR Cladding) 1 -

7.1.3 Laser Cladding 1 -

7.2.3.1 Trivalent Chrome Plating 2 -

7.2.4.1

Electroless nickel plating /nickel-tungsten, nickel-boron, nickel diamond composite, nickel-phosphorous, nickel-polytetrafluoretyhlene; Ni-SiC /NiP-PTFE

2 -

7.4.1.2

Nickel & nickel alloy electroplating /ickel-tungsten-boron, nickel-tungsten-silicon-carbide, tin-nickel, nickel-iron-cobalt, nickel-tungsten-cobalt, nickel tungsten, Fe-Ni-Cr /disperse nickel electroplating in bath containing a.o. NiSO4, MoO3 and SiC

2 -

7.2.4.3 (Nano) Co-P plating /cobalt electrolysis /(Nano) Co-P plating

2 -

7.2.4.4

High velocity thermal processes /HVOF CrC-NiCr, WC-Co, WC-Co-Cr, Co-Cr-Mo, Mo /HVAF /detonation spraying /CoCrMo commercially available product (by HVOF or plasma)

2 -

7.2.5 Electrical Discharge Coating (EDC) 2 -

- Case hardening (carburizing, , cyaniding, boronizing, nitriding)

-

Case hardening is no suitable alternative due to the excess of the maximum process temperature and time, difficult machinability and low technical readiness level concerning the issue of strip cleanliness in cold rolling.




/plasma diffusion: plasma nitriding, nitrocarburizing, low pressure nitiriding /explosive hardening

- Nitrocarburizing -

Rolls, which currently are chrome plated, are incompatible with the process temperatures present during nitrocarburising. The machinability of nitrocarburized work rolls might be poor due to potential irreversible alternations of the substrate thus making a post-treatment grinding step necessary, thus removing material from the substrate as high as the overall nitriding layer.The treatment time required for current nitrocarburizing is multiple times higher compared to functional chrome plating. Therefore, the work roll stock would have to be significantly enlarged, which is linked to an increase in operational costs.

-

Chemical Vapour Deposition (CVD) /Chemical Vapour Deposition (CVD): TiN, WC, ZrN /Plasma enhanced Chemical Vapour Deposition Coating (PECVD)

-

CVD (CVD and PECVD) is no suitable alternative due to the excess of the maximum process temperature, the unsuitability to plate large geometries, very high treatment times, difficult machinability and low technical readiness level concerning the issue of strip cleanliness in cold rolling.

-

PVD /Physical Vapour Deposition (PVD) techniques: Cr, CrC, CrN, MoS2, SiC, TiAlN, TiN, WC-C:H, ZrN, Zr oxides, organic zirconates /DLC (PVD technique)

-

PVD-based coatings that meet hardness and adequate process temperatures cannot withstand the high mechanical stresses during metal rolling due to issues of brittleness and high internal stress within the layer. Furthermore, PVD is no suitable alternative due to very high treatment times, difficult machinability and low technical readiness level concerning the issue of strip cleanliness in cold rolling.

- Plasma spraying -

Plasma spraying is no suitable alternative due to the excess of the maximum process temperature, poor layer quality (porosity, brittleness and/or high internal stress), deficiencies in reproducing the topography, difficult machinability and low technical readiness level concerning the issue of strip cleanliness in cold rolling.

-

General laser and weld coating processes weld coatings /electro spark alloying (tungsten carbids, Co-based alloys) /explosive bonding /plasma powder welding torch laser alloying and laser cladding (NiC)

-

General laser and weld processes are no suitable alternatives due to the excess of the maximum process temperature, poor layer quality (porosity, brittleness and/or high internal stress), deficiencies in reproducing the topography, difficult machinability and low technical readiness level concerning the issue of strip cleanliness in cold rolling.

- Stainless steel-based work roll grades - Stainless steel-based work roll grades are no suitable alternative due to major technical deficiencies in hardness, mechanical strength and machinability. Furthermore, the alternative




is not economically feasible because of high cost for alloying elements (e.g. nickel) and high machining costs.

-

Thermal spray processes /arc Spraying /cold gas spraying /flame spray coating -wire flame spraying -powder flame spraying /molybdenum thermal sprayed coatings

-

Thermal spray processes are no suitable alternatives due to the excess of the maximum process temperature, poor layer quality (porosity, brittleness and/or high internal stress), deficiencies in reproducing the topography, difficult machinability and low technical readiness level concerning the issue of strip cleanliness in cold rolling.

- Superalloy-based work roll grades /Stellite alloys

-

Superalloy-based work roll grades are no suitable alternatives due to insufficient hardness and mechanical strength, high costs of alloying elements (e.g. cobalt) and limited availability of cobalt to supply the European metal rolling industry.

- Ion Implantation -

Ion implantation is not working as stand-alone replacement for functional chrome plating as no additional layer is applied and the surface is not rebuilt to its original layer thickness and rebuilding parts can thus not be reworked. In addition, the process has to be conducted under vacuum conditions which is not feasible for large parts.

- Iron-phosphor coating - Salt spray tests for iron phosphor coatings showed decomposition of the layer leading to severe substrate corrosion.

- Plastic coating -

Plastic coating was mentioned as alternative to copper coating with functional chrome plating in gravure printing. Early R&D coating tests showed insufficient performance for hardness. This significantly reduces the maximum amount of copies to 200,000. Furthermore, plastic coatings cannot be engraved with the traditional method using diamonds and existing alternative engraving methods are not compatible. Plastic coatings do not withstand shape cutting as the material is too brittle.

- Chromium III ionic liquids - R&D ongoing regarding alternative for decorative applications but not for functional chrome plating.

- Cobalt-tin plating - Cobalt-tin plating is mainly used for decorative applications and not for functional chrome plating.

-

Zinc-based materials (zinc, zinc-tin, zinc-aluminium, zinc-nickel based passivation, non-electrolytic zinc plating)

-

Zinc is a “soft” metallic material with hardness values below 450 HV and therefore not a metallic chrome coating alternative. Zinc-based coating materials show insufficient performance in corrosion and wear resistance, and the coefficient of friction.



APPENDIX 2 – INFORMATION ON SUBSTANCES USED IN ALTERNATIVES

APPENDIX 2.1: (SEMI-) HIGH SPEED STEEL ((S)HSS)

(Semi-) High Speed Steel is a loosely used term that defines alloys, containing iron, chromium, molybdenum, vanadium and tungsten. In case of Ti-enhanced work rolls, Ti is added to standard 3 to 5 % Cr forged work rolls. High Speed Steels are generally considered non-hazardous to human health and the environment. As a worst case scenario, tungsten is registered under REACH classified as Flam. Sol. 1 and Self.-heat. 2.

APPENDIX 2.2: LASER CLADDING

Table 1: Substance ID and properties for an exemplary tungsten carbide-cobalt coating.

Parameter Value Physicochemical properties Value

Chemical name and composition

WC-12Co Commercially available product

Physical state at 20°C and 101.3 kPa Solid (grey, odourless)

EC number Multiple components Melting point 3,410°C

CAS number Multiple components Density -

IUPAC Name Multiple components Vapour Pressure -

Molecular Formula Multiple components Water solubility Insoluble in Water

Molecular weight Multiple components Flammability Flash Point

- -

Table 2: Hazard classification and labelling overview.

Substance Name Hazard Class and Category Code(s)

Hazard Statement Code(s) (labelling)

Number of Notifiers

Additional classification and labelling comments

Regulatory and CLP status

WC-12Co (commercially available product; Multiple component System)

Skin Irrit. 2, Eye Irrit. 2, STOT SE 3, Carc. 2

-

According to suppliers’ SDS, the following hazard statements are given: May cause eye and skin irritation. Contains Material that may cause target organ damage (based on animal data) Possible cancer hazard-contains material which may cause cancer (based on animal data).

Substance is not REACH registered. Hazard information from suppliers’ SDS.



APPENDIX 2.3: TRIVALENT CHROME PLATING

Table 1: Substance ID and physicochemical properties



Chromium trichloride hexahydrate

Physical state at 20°C and 101.3 kPa Solid (green)

EC number - Melting point 80-83°C

CAS number 10060-12-5 Density -

IUPAC name Chromium(III) chloride hexahydrate Vapour pressure -

Molecular formula CrCl3 · 6H2O Water solubility 590 g/L (at 20°C)

Molecular weight 266.45 g/mol Flammability Flash point

Non flammable -



Boric acid (mono constituent substance)

Physical state at 20°C and 101.3 kPa Solid (crystalline, odourless)

EC number 233-139-2 Melting point No melting point detected below 1,000°C

CAS number 10043-35-3 Density 1.49 g/cm3

IUPAC name Boric acid Vapour pressure 9.90 . 10-8 kPa (25 °C)

Molecular formula B(OH)3 Water solubility 48.40 g/L (20°C, pH = 3.6)


Non flammable -



Chromium potassium bi(sulphate)

Physical state at 20°C and 101.3 kPa Solid (purple red)

EC number - Melting point 89.0°C


IUPAC name Chromium(3+) potassium sulfate hydrate (1:1:2:12) Vapour pressure -

Molecular formula CrKS2O8 .12 H2O Water solubility 250 g/L

Molecular weight 499.4 g/mol Flammability Flash Point

Non flammable -



Formic acid (mono constituent substance)

Physical state at 20°C and 101.3 kPa Liquid

EC number 200-579-1 Melting point 4.0°C

CAS number 64-18-6 Density 1.22 g/cm3 (at 20°C)

IUPAC name Formic acid Vapour pressure 42.71 hPa (20°C)

Molecular formula CH2O2 Water solubility Miscible in any ratio


Flammable 49.5°C (at 1,013 hPa)




Chemical name and composition Ammonium sulfamidate Physical state at 20°C and

101.3 kPa Solid (colourless)

EC number 231-871-7 Melting point 131-135°C


IUPAC name Ammonium sulphamate Vapour pressure -

Molecular formula H6N2O3S Water solubility 1,666 g/L


Non flammable -


Chemical name and composition Ammonium chloride Physical state at 20°C and

101.3 kPa Solid (crystalline)

EC number 235-186-4 Melting point 340°C (sublimation)

CAS number 12125-02-9 Density 1.53 g/cm3 (at 20°C)

IUPAC name Ammonium chloride Vapour pressure -

Molecular formula NH4Cl Water solubility 283 g/L (25°C)


Non flammable -

Table 2: Classification and labelling of relevant substances.



Number of Notifiers



Chromium trichloride hexahydrate (CAS 10060-12-5)

Skin Irrit. 2 Eye Irrit. 2 STOT SE 3

H 315 (causes skin irritation) H 319 (causes serious eye irritation) H 335 (may cause respiratory irritation)

30

Substance is not REACH registered. Not included in the CLP Regulation, Annex VI; Included in C&L inventory

Acute Tox.TOX 4

H 302 (ha rmful if swallowed)

24

Chromium potassium bi(sulphate) dodecahydrate (CAS 7788-99-0)

Skin Irrit. 2 Eye Irrit. 2

H 315 (causes skin irritation) H 319 (causes serious eye irritation)

5

Pre-registered substance Not included in the CLP Regulation, Annex VI; Included in C&L inventory

Formic acid (CAS 64-18-6 (EC 200-579-1)

Skin Corr 1A H 314 (causes severe skin burns and eye damage)

Skin Corr. 1A; H314: C ≥ 90% Skin Corr. 1B; H314: 10% ≤ C < 90% Skin Irrit. 2; H315: 2% ≤ C < 10% Eye Irrit. 2; H319: 2% ≤ C < 10%

Harmonised classification- Annex VI of Regulation (EC) No 1272/2008 Included in CLP Regulation, Annex VI (index number 607-001-00-0);

Ammonium sulphamidate Acute Tox. 4 H302 (harmful if

swallowed) 49 Pre-registered Substance





Number of Notifiers



(CAS 7773-06-0) (EC 231-871-7)

Not classified - 46 Not included in the CLP Regulation, Annex VI; Included in C&L inventory Acute Tox. 4

Aquatic Acute 1

H 302 (harmful if swallowed) H 400 (very toxic to aquatic life)

23

Ammonium chloride (CAS 12125-02-9) (EC 235-186-4)

Acute Tox 4 Eye Irrit. 2

H 302 (harmful if swallowed) H 319 (causes serious eye irritation)

Harmonised classification- Annex VI of Regulation (EC) No 1272/2008 Included in CLP Regulation, Annex VI (index number 017-014-00-8);

APPENDIX 2.4: ELECTROLESS PLATING

Table 1: Substance IDs and properties.



Nickel sulfate (mono constituent substance) Physical state at 20 °C and 101.3 kPa Solid (greenish-yellow,

anhydrous form)

EC Number 232-104-9 Melting point ≥ 840°C (anhydrous form decomposes at 848°C)

CAS Number 7786-81-4 Density 3.68 g/cm3

IUPAC name nickel(2+) sulfate Vapour pressure -

Molecular formula NiSO4 Water solubility ≥ 625 g/L

Molecular weight 154.8 g/mol Flammability Flashpoint

- -


Chemical name and composition Sodium phosphinate Physical state at 20 °C and 101.3 kPa Solid (white)

EC Number 231-669-9 Melting point Substance decomposes at T≥ 238°C.

CAS Number 7681-53-0 Density 1.77 g/cm3

IUPAC name Sodium phosphinate Vapour pressure -

Molecular formula NaPH2O2 Water solubility 909 g/L (at 30°C, pH 5.8-5.9)


Non flammable -



Sodium borhydride (mono constituent substance)

Physical state at 20 °C and 101.3 kPa Solid (white, granular)

EC Number 241-004-4 Melting point > 360°C

CAS Number 16940-66-2 Density 1.080 g/cm³ (at 20°C)

IUPAC name Sodium tetrahydroborote Vapour pressure < 5.4 x 10-5 Pa (at 25°C)




Molecular formula NaBH4 Water solubility -


Not highly flammable -

Table 2: Hazard classification and labelling.



Substance Name

Hazard Class and Category Code(s)


Number of Notifiers



Nickel sulphate (CAS 7786-81-4) (EC 232-104-9)

Acute Tox. 4 Skin Irrit. 2 Skin Sens. 1 Acute Tox. 4 Resp. Sens. 1 Muta. 2 Carc. 1A Repr. 1B STOT RE 1 Aquatic Acute 1 Aquatic Chronic 1

H 302 (harmful if swallowed) H 315 (Causes skin irritation) H 317 (may cause allergic skin reaction) H 332 (harmful if inhaled) H 334 (may cause allergy or asthma symptoms or breathing difficulties) H 341 (suspected of causing genetic defects) H 350 I (may cause cancer by inhalation) H 360D (may damage the unborn child) H 372 (causes damage to organs) H 400 (very toxic to aquatic life) H 410 (very toxic to aquatic life with long lasting effects)

Skin Sens. 1; H317: C ≥ 0,01% STOT RE 1; H372: C ≥ 1% Skin Irrit. 2; H315: C ≥ 20% M=1 STOT RE 1; H373: C ≥ 1% STOT RE 2; H373: 0,1% ≤ C < 1%

REACH registered. Harmonised Classification- Annex VI of Regulation (EC) No 1272/2008 (CLP Regulation). Index Number: 028-009-00-5

Sodium hypophosphite (CAS 7681-53-0) (EC 231-669-9)

Not classified 326

REACH registered; Not included in the CLP Regulation, Annex VI; Included in C&L inventory

Eye Irrit. 2 H 319 (causes serious eye irritations 56

Skin Irrit. 2 H 315 (causes skin irritation) 23

Substance Name



Number of Notifiers



Sodium borhydride (CAS 16940-66-2) (EC 241-004-4)

Water react. 1 Acute Tox. 3 Acute Tox. 3 Skin Corr. 1B

H 260 (In contact with water releases flammable gases which may ignite spontaneously) H 301 (toxic if swallowed) H 311 (toxic in contact with skin) H 314 (causes severe skin burns and eye damage)

105

REACH registered; Not included in the CLP Regulation, Annex VI; Included in C&L inventory Water react. 1

Acute Tox. 3 Acute Tox. 3 Skin Corr. 1B Eye Dam. 1

H 260 (In contact with water releases flammable gases which may ignite spontaneously) H 301 (toxic if swallowed) H 311 (toxic in contact with skin) H 314 (causes severe skin burns and eye damage) H 318 (causes serious eye damage)

93



APPENDIX 2.5: NICKEL AND NICKEL ALLOY ELECTROPLATING

Table 1: Substance IDs and properties for relevant substances in nickel and nickel alloy electroplating.



Boric acid (mono constituent substance)

Physical state at 20°C and 101.3 kPa Solid (crystalline, odourless)

EC number 233-139-2 Melting point No melting point detected below 1,000°C


IUPAC name Boric acid Vapour pressure 9.90 . 10-8 kPa (25 °C)

Molecular formula B(OH)3 Water solubility 48.40 g/L (20°C, pH = 3.6)

Molecular weight 61.83 g/mol Flammability Flash Point:

Non flammable -


Nickel sulphate (mono constituent substance)

Physical state at 20°C and 101.3 kPa

Solid (greenish-yellow, anhydrous form)

EC number 232-104-9 Melting point ≥ 840°C (anhydrous form decomposes at 848°C)


IUPAC name nickel(2+) sulfate Vapour pressure -

Molecular formula NiSO4 Water solubility ≥ 625 g/L


- -



Nickel dichloride (mono constituent substance)

Physical state at 20°C and 101.3 kPa Solid

EC number 231-743-0 Melting point 1,001°C


IUPAC name nickel(2+) dichloride Vapour pressure -

Molecular formula NiCl2 Water solubility -


Non flammable -

Table 2: Hazard classification and labelling.



Number of Notifiers



Boric acid (CAS 10043-35-3) (EC 233-139-2)

Repr. 1B

H360FD (May damage fertility. May damage the unborn child)

n/a -

REACH registered; Harmonised classification- Annex VI of regulation (EC) No 1272/2008 (CLP





Number of Notifiers



Regulation); index number: 005-007-00-2. Included according to Annex XVI on the candidate list (SVHC substance)

Nickel sulphate (CAS 7786-81-4) (EC 232-104-9)


H 302 (harmful if swallowed) H 315 (Causes skin irritation) H 317 (may cause allergic skin reaction) H 332 (harmful if inhaled) H 334 (may cause allergy or asthma symptoms or breathing difficulties) H 341 (suspected of causing genetic defects) H 350 I (may cause cancer by inhalation) H 360D (may damage the unborn child) H 372 (causes damage to organs) H 400 (very toxic to aquatic life) H 410 (very toxic to aquatic life with long lasting effects)

kin Sens. 1; H317: C ≥ 0,01% STOT RE 1; H372: C ≥ 1% Skin Irrit. 2; H315: C ≥ 20% M=1 STOT RE 1; H373: C ≥ 1% STOT RE 2; H373: 0,1% ≤ C < 1%

REACH registered; Harmonised classification- Annex VI of regulation (EC) No 1272/2008 (CLP Regulation); Index number: 028-009-00-5.

Nickel dichloride (CAS 7718-54-9) (EC 231-743-0)


H 301 (toxic if swallowed) H 315 (causes skin irritation) H 317 (may cause an allergic skin reaction) H 331 (Toxic if inhaled) H 334 (may cause an allergy or asthma symptoms or breathing difficulties if inhaled) H 334 (suspected of causing genetic defects) H 350i (may cause cancer by inhalation) H 360D (may damage the unborn child) H 372 (causes damage of organs) H 400 (very toxic to aquatic life)

Skin Irrit. 2; H315: C ≥ 20% Skin Sens. 1; H317: C ≥ 0,01% STOT RE 2; H373: 0,1% < C < 1% M=1 STOT RE 1; H373: C ≥ 1% STOT RE 1; H372: C ≥ 1%

Harmonised Classification- Annex VI of Regulation (EC) No 1272/2008 (CLP Regulation). Index Number: 028-011-00-6.





Number of Notifiers



H 410 (very toxic to aquatic life with long lasting effects)

APPENDIX 2.6: NANOCRYSTALLINE COBALT PHOSPHORUS ALLOY COATING

Table 1: Substance IDs and physicochemical properties.


Chemical name and composition Orthophosphoric acid Physical state at 20°C and

101.3 kPa Liquid, colourless, viscous

EC number 231-633-2 Melting point 41.10 °C (101 kPa)

CAS number 7664-38-2 Density 1.87 g/cm³ (20 °C)

IUPAC name Phosphoric acid Vapour pressure 4 Pa (20 °C)

Molecular formula H3PO4 Water solubility 5,480 g/L (cold water, pH = 0.5)


- -


Chemical name and composition Cobalt dichloride Physical state at 20°C and

101.3 kPa Solid, crystalline

EC number 231-589-4 Melting point 737 °C

CAS number 7646-79-9 Density 3.37 g/cm³ (25 °C)

IUPAC name Cobalt(II)dichloride Vapour pressure 100 hPa (at 818 °C)

Molecular formula CoCl2 Water solubility 585.90 g/L (20 °C, pH = 7)


- -

Table 2: Hazard classification and labelling

Substance Name



Number of Notifiers



Orthophosphoric acid (EC 231-633-2) (CAS 7664-38-2)

Skin Corr. 1B, 1C Eye Dam. 1 Acute Tox. 4 STOT SE 3

H314 (Causes severe skin burns and eye damage) H318 (Causes serious eye damage) H312 (Harmful in contact with skin) H335 (May cause respiratory irritation) H302 (Harmful if swallowed)

52 -

REACH registered. Harmonised Classification- Annex VI of Regulation (EC) No 1272/2008 (CLP Regulation). Index Number: 015-011-00-6

Cobalt(II) dichloride

Acute Tox. 4 Skin Sens. 1

H302 (Harmful if swallowed) 26 -

REACH registered. Harmonised Classification-



Substance Name



Number of Notifiers



(EC 231-589-4) (CAS 7646-79-9)

Resp. Sens. 1 Muta. 2 Carc. 1B Repr. 1B Aquatic Acute 1 Aquatic Chronic 1

H317 (May cause an allergic skin reaction) H334 (May cause allergy or asthma symptoms or breathing difficulties if inhaled) H341 (Suspected of causing genetic defects) H350i (May cause cancer by inhalation) H360F (May damage fertility) H400 (Very toxic to aquatic life) H410 (Very toxic to aquatic life with long lasting effects)

Annex VI of Regulation (EC) No 1272/2008 (CLP Regulation). Index Number: 027-004-00-5

APPENDIX 2.7: HIGH VELOCITY THERMAL PROCESS

Table 1: Substance ID and properties for an exemplary tungsten carbide-cobalt coating.


Chemical name and composition WC-12Co Physical state at 20°C and

101.3 kPa Solid (grey, odourless)

EC number Multiple components Melting point 3,410°C

CAS number Multiple components Density -

IUPAC Name Multiple components Vapour Pressure -

Molecular Formula Multiple components Water solubility Insoluble in water

Molecular weight Multiple components Flammability Flash Point

- -

Table 2: Hazard classification and labelling overview.



Number of Notifiers



WC-12Co (commercially available product; Multiple component System)

Skin Irrit. 2, Eye Irrit. 2, STOT SE 3, Carc. 2

-

According to suppliers’ SDS, the following hazard statements are given: May cause eye and skin irritation. Contains Material that may cause target organ

Substance is not REACH registered. Hazard information from suppliers’ SDS.



damage (based on animal data) Possible cancer hazard-contains material which may cause cancer (based on animal data).

APPENDIX 2.8 - PRE-TREATMENTS: MINERAL ACIDS

Table 1: Substance IDs and physicochemical properties are presented (not exhaustive):

Parameter Value Physico-chemical properties Value


Sulphuric acid (mono constituent substance)

Physical state at 20°C and 101.3 kPa Liquid (odourless)

EC number 231-639-5 Melting point 10.4-10.5°C (pure sulfuric acid)

CAS number 7664-93-9 Density 1.83 g/cm3 (20°C, pure sulphuric acid)

IUPAC name Sulfuric acid Vapour pressure 0.49 hPa (20°C)

Molecular formula H2SO4 Water solubility Miscible with water


Non flammable -



Orthophosphoric acid (mono constituent substance)

Physical state at 20°C and 101.3 kPa

Solid (crystalline, if no water attached)

EC number 231-633-2 Melting/freezing point 41.1 °C (101 kPa)

CAS number 7664-38-2 Density 1.84 g/cm3 (38°C)

IUPAC name Phosphoric acid Vapour pressure 80 Pa (25°C, extrapolated)

Molecular formula H3PO4 Water solubility 5,480g/ L (cold water, pH= 0.5)


Non flammable -



Nitric acid (mono constituent substance)

Physical state at 20°C and 101.3 kPa Liquid (fumes in moist air)

EC number 231-714-2 Melting/freezing point - 41.60 °C

CAS number 7697-37-2 Density 1.51 g/cm3 (20°C)

IUPAC name Nitric acid Vapor pressure 9.00 kPa (25°C)

Molecular formula HNO3 Surface Tension -

Molecular weight 63.01 g/mol Water solubility > 1,000g /L (20°C, pH= -1)

Molecular structure Flammability Flash point

Non flammable -





Chemical name and composition Chromium(III) sulphate Physical state at 20°C and

101.3 kPa Solid

EC number 233-253-2 Melting point 90 °C

CAS number 10101-53-8 Density 3.10 g/cm³ (anhydrous)

IUPAC name Chromium(III) sulphate Vapour pressure -

Molecular formula Cr2(SO4)3 Water solubility Insoluble (anhydrous). Soluble as hydrate.


Non-flammable -


Chemical name and composition Iron(II)-sulphate Physical state at 20°C and

101.3 kPa Solid

EC number 231-753-5 Melting point > 300°C (decomposes)

CAS number 7720-78-7 Density 3.65 g/cm³

IUPAC name Iron(2+) sulfate Vapour pressure -

Molecular formula FeSO4 Water solubility Very soluble (>10,000 mg/L)


Non flammable -

Table 2: Hazard classification and labelling overview



Number of Notifiers



Sulphuric acid (CAS 7664-93-9) (EC 231-639-5)

Skin Corr. 1A Met. Corr. 1

H314 (Causes severe skin burns and eye damage) H290 (may be corrosive to metals)

n/a

Specific Concentration limits: Skin Corr. 1A: C ≥ 15%, H314 Skin Irrit. 2: 5% ≤ C < 15%, H315 Eye Irrit. 2: 5% ≤ C < 15%; H319

REACH registered; Included in CLP Regulation, Annex VI (index number 016-020-00-8);

Phosphoric acid (CAS 7664-38-2) (EC 231-633-2)

Skin Corr. 1B H314 (Causes severe skin burns and eye damage)

n/a Legal classification. REACH registered; Included in CLP Regulation, Annex VI (index number 015-011-00-6); Met. Corr. 1 H290 (May be

corrosive to metals) n/a Additional self-classification according to REACH registration;

Nitric acid (CAS 7697-37-2) (EC 231-714-2)

Ox. Liq. 3 H272 (May intensify fire; oxidizer)

n/a

REACH registered; Included in CLP Regulation, Annex VI (index number 007-004-00-1)

Skin Corr. 1A H314 (Causes severe skin burns and eye damage)

Met. Corr. 1 H290 (May be corrosive to metals)

Additional classification according to REACH registration.





Number of Notifiers



Not classified - 257 Classification notified to the C&L inventory.

Skin Irrit. 2 H315 (Causes skin irritation)

271

Classification notified to the C&L inventory. Further 163 notifiers classified the substance as Eye Dam. 1 only.

Eye Dam. 1 H318 (Causes serious eye damage)

STOT SE 3 H335 (May cause respiratory irritation)

Chromium sulphate (CAS 10101-53-8) (EC 233-253-2)

Not classified - 1103 1103 notifiers did not classify the substance.

Currently not REACH registered; Not included in the CLP Regulation, Annex VI; Included in C&L inventory

Iron(II) sulphate (CAS 7720-78-7) (EC 231-753-5)

Acute Tox. 4 Skin Irrit. 2 Eye Irrit. 2

H302 (harmful if swallowed) H315 (causes skin irritation) H319 (causes serious eye irritation)

-

Reach registered substance; Harmonised classification- Annex VI of Regulation (EC) No 1272/2008 (CLP Regulation). (Index number: 026-003-00-7)



APPENDIX 3 – SOURCES OF INFORMATION

Information on substance identities, physicochemical properties, hazard classification and labelling are based on online data searches. All online sources were accessed between June and September 2014. The main sources are:

1. European Chemicals Agency: http://echa.europa.eu/de/

2. ChemSpider internet site: http://www.chemspider.com

3. Merck SDS: www.merckgroup.com

4. Sigma Aldrich SDS: http://www.sigmaaldrich.com

5. READE internet site: http://www.reade.com

6. Chemie.de internet site: http://www.chemie.de

7. Alfa Aesar SDS: http://www.alfa.com/content/msds/German/14510.pdf

8. Carl Roth SDS: http://www.carlroth.com

9. MAK Collection for Occupational Health and Safety: http://onlinelibrary.wiley.com

10. Chemical Book internet site: http://www.chemicalbook.com

11. Merck SDS: http://www.merck-performance-materials.com

12. Analytyka SDS: http://www.analytyka.com

13. Airgas.com internet site: http://www.airgas.com/msds/001069.pdf

14. Air Liquide internet site: http://encyclopedia.airliquide.com

15. Air Liquide SDS: http://www.airliquide.de

17. Sciencelab internet site: www.sciencelab.com

http://echa.europa.eu/de/

http://www.chemspider.com/

http://www.merckgroup.com/

http://www.sigmaaldrich.com/

http://www.reade.com/

http://www.chemie.de/

http://www.alfa.com/content/msds/German/14510.pdf

http://www.carlroth.com/

http://onlinelibrary.wiley.com/

http://www.chemicalbook.com/

http://www.merck-performance-materials.com/merck-ppf/detailRequest?unit=CHEM&owner=MDA&productNo=102487&language=DE&country=DE&docType=MSD&source=GDS&docId=/mda/chemicals/msds/de-DE/102487_SDS_DE_DE.PDF

http://www.analytyka.com/

http://www.airgas.com/msds/001069.pdf%204

http://www.airgas.com/msds/001069.pdf%204

http://encyclopedia.airliquide.com/

http://www.airliquide.de/

http://www.sciencelab.com/

ANALYSIS OF ALTERNATIVES non-confidential report · ANALYSIS OF ALTERNATIVES . ANALYSIS OF...

Documents

Transcript of ANALYSIS OF ALTERNATIVES non-confidential report · ANALYSIS OF ALTERNATIVES . ANALYSIS OF...