| |voestalpine Böhler Weldingvoestalpine Böhler Weldingwww.voestalpine.com/welding

Welding of Duplex and Super Duplex Stainless Steels

Fronius Open DayWednesday 26th April 2017

| |voestalpine Böhler Welding

We are part of voestalpine AG

2

11,2 Billion EUR | 47,418 Employees

Metal Engineering Division

Metal Forming Division High-quality metal

processing solutions, precision steel strip &

special components

Special Steel Division

Tool steel & leading position for high-speed steel & special forged parts

Steel DivisionPremium steel strip, electricalsteel strip, heavy plate, cast products

Welding: 545 Mio EUR | 2,397 Employees

Turnouts, rails, processed wire,

seamless tubes & welding consumables

| |voestalpine Böhler Welding

More than 145 years of know-how

3

in the steel industrysince 1870

in the welding consumables business since 1926

mergers & acquisitionsof best-in-class welding companies: Thyssen, Böhler, UTP, Avesta Welding, Soudokay, Fontargen, Fileur, Maruti

a voestalpinecompanysince 2007

| |voestalpine Böhler Welding

Production sites in Europe

4

Kapfenberg | Austria27,000 tons annual capacity

Flux cored wire, stick electrodes, solid wireSeneffe | Belgium

7,500 tons annual capacity

Hardfacing flux cored wire formaintenance & repair, Welding fluxesfor maintenance & repair, Strips forstrip cladding process

Bad Krozingen | Germany3,000 tons annual capacity

Stick electrodes, Thermal spraying powders

Eisenberg | Germany400 tons annual capacity

Filler metals and fluxes forbrazing and soldering

Hamm | Germany55,000 tons annual capacity

Stick electrodes, solid wire, flux

Cittadella | Italy6,000 tons annual capacity

Seamless flux cored wire

Malmö | Sweden1,200 tons annual capacity

Filler metals and fluxes forbrazing and soldering

| |voestalpine Böhler Welding

Sales Customer Service Technical Support Product Distribution

Oldbury Nr Birmingham

voestalpine Bohler Welding UK Ltd

| |voestalpine Böhler Welding

3 Business Units - 3 Brands

6

| |voestalpine Böhler Welding

Comprehensive portfolio

7

Covered electrodes Solid wires/TIG rods Flux cored wires Sub arc wire and flux Strips for strip cladding Solders, pastes, fluxes Post-weld cleaning

chemicals and pickling pastes

Thermal spraying powders

Products Alloys / Grades Unalloyed and low

alloyed Aluminium Nickel-based alloys Special alloys

(nickel, copper, cobalt) Stainless steel High strength High / low temperature Corrosion resistant Heat resistant

| |voestalpine Böhler Welding

Certificates

8

| |voestalpine Böhler Welding

Why am I here doing this presentation?

9

- Austenitic stainless steels are increasingly being replaced by duplex grades that offer similar corrosion resistance with far higher strength

- Duplex steels require more attention during manufacture and welding

- You cannot take any shortcuts when welding them

- Taking shortcuts will result in a failure

- It costs companies thousands of pounds in retesting and potential lost business

- Training and reinforcement of basic guidelines will reduce failures

- New products and ideas

| |voestalpine Böhler Welding

10

STEEL: Iron-Carbon alloy with maximum Carbon content of 2% and other elements with specific effects

STAINLESS: Metallic alloy presenting Chromium content higher that 10/12% which promotes the formation of a passive film

DUPLEX: Type of stainless steel which has a biphasic microstructure formed by equal proportions of ferrite and austenite phases (50/50)

SUPERDUPLEX: Duplex stainless steel with improved corrosion resistance

Duplex and Super Duplex Stainless Steels

| |voestalpine Böhler Welding

11

Microstructure of DSS/SDSSDark phase: FERRITE

Bright phase: AUSTENITE

The Aim is 50/50

| |voestalpine Böhler Welding

FERRITE Body Centered Cubic

Ferrite Formers Include

Iron / Chromium

Molybdenum / Silicon

FERRITIC MATRIX PROVIDES

STRENGTH & RESISTANCE TO SCC

| |voestalpine Böhler Welding

AUSTENITE Face Centered Cubic

Austenite Formers Include

Nickel / Nitrogen / Carbon

Manganese / Copper

AUSTENITE ISLANDS CONTRIBUTE GOOD

DUCTILITY & RESISTANCE TO

CORROSION

| |voestalpine Böhler Welding

PREN vs. PREW

PITTING RESISTANCE EQUIVALENT (PRE) is a formula that gives an indication of the corrosion performance of a material

PRE(N) = %Cr + 3.3 × %Mo + 16 × %N (standard formula used)

PRE(W) = %Cr + 3.3 × %Mo + 0.5 + %W + 16 × %N

They are useful for ranking and comparing the different grades, but cannot be used to predict whether a particular grade will be suitable for a given application, where pitting corrosion may be a hazard.

| |voestalpine Böhler Welding

Typical stainless steel composition, PRE and yield strength

| |voestalpine Böhler Welding

Phase Formation

| |voestalpine Böhler Welding

Formation of Secondary Phases

| |voestalpine Böhler Welding

SIGMA PhaseSigma is a hard, brittle intermetallic phase which is expected to contain iron, chromium and molybdenum. In duplex alloys, σ generally can be formed between about 600 and 950°C, with the most rapid formation occurring between 700 and 900°C.

| |voestalpine Böhler Welding

This is why you should NEVER weld duplex and super duplex without a welding consumable

| |voestalpine Böhler Welding

Heat Input – a measure of how much energy has been supplied to the workpiece to form a weld.

| |voestalpine Böhler Welding

The effect of Heat InputDue to the risk of these secondary phases forming at high temperature, maximum service temperature is reduced e.g. 250°C.

We must also limit the Heat Input

Too much energy = longer time spent in the sensitive temperature range

Heat input ranges

EN 1.4462 / UNS S31803 = 0.4 – 3.0kJ/mm (typical 0.6-1.5kJ/mm)

EN 1.4410 / UNS S32750 = 0.4 – 1.5kJ/mm (typical 0.6-1.2kJ/mm)

| |voestalpine Böhler Welding

The Root

To ensure good corrosion properties on 22%Cr duplex a super duplex filler wire is often used for the root run. This approach is recommended for G48-A tests at +25°C.

The most critical area of the joint weld, especially in pipework where the corrosive media will be in contact with the root bead

| |voestalpine Böhler Welding

Root Weld Beads

23

To avoid sigma phase formation in the root bead, avoid a high heat input for the cold (2nd) pass. As a rule of thumb, a thick bead should be used for the root pass but the maximum heat input must not be exceeded. The cold pass should then be welded at 70-80% of the heat input used in the root run.

| |voestalpine Böhler Welding

Weld Sequence Effects

TEMPERATURE

Time

Interpass Temperature Control

- Must be measured precisely on the weld metal and parent material

- Operate with controlled interpass to optimise results and achieve production

Interpass selection based on wall thickness

| |voestalpine Böhler Welding

| |voestalpine Böhler Welding

Small Bore, Thin walled Tubes

• When welding thin wall tube it is even more critical to use a carefully controlled weld procedure

• The tube can easily be overheated

• The maximum interpass temperature could even be reduced to 50°C

• Welds should be split into segments/quarters to prevent excessive heat build-up

| |voestalpine Böhler Welding

Lets talk about Gas

27

Torch

- Generally Pure Argon is used for GTAW (10-15lpm). Additions of Nitrogen up to 2% can be beneficial for tough requirements

- A 3 component gas is preferred for GMAW – Ar + 30% He + 2%CO2

Back-Purge

- A gas purge must be used for root runs deposited using the TIG process and should be maintained for the first three layers or approximately 10mm of deposit

- An effective purge system must be in place with a calibrated system to monitor oxygen content. Aim for <25ppm but you must achieve <50ppm in practise

- Purge flow rates are determined by the pipe size but it is important that following the removal of tacks, grinding etc. that the purge is allowed to stabilise again before welding. Typical value 8-15lpm

Nitrogen is very important for corrosion performance and in particular Austenite transformation

Nitrogen loss from the weld pool can lead to highly ferritic welds. This is particularly important in the case of single sided root pass welds with pure Argon as a backing gas. This can result in essentially ferritic welds at the surface of the duplex weld metal

| |voestalpine Böhler Welding

Backing Gas

28 4/26/2017 Corporate Presentation

Degassing of Nitrogen can be counteracted by the use of a nitrogen-based backing gas such as 100%N2 or 90%N2 + 10%H2

The effect of backing gas on austenite formation and pitting corrosion resistance was measured using a 1.5 mm thick lean duplex, EN 1.4162 / UNS S32101, manually welded from one side using Avesta LDX 2101 filler metal. The austenite content was measured using image analysis and the critical pitting temperature (CPT) of the root-side determined in 1 M NaCl (as per ASTM G150).

The use of Ar + 2%N2 as a backing gas was inferior

| |voestalpine Böhler Welding

Pitting Resistance measured as the CPT (ASTM G150) on the root side of a single sided GTAW sample (1mm and no root gap) in as welded condition and after pickling.

Nitrogen-based backing gas (90% N2 + 10% H2) significantly improved the pitting resistance of all grades in both the pickled and as-welded condition. When using Pure Argon as the backing gas, only the highest alloyed welds showed a measurable CPT in the as-welded condition. For this reason pickling is always recommended when using argon-based backing gas.

| |voestalpine Böhler Welding

Corrosion testing

30

For qualification / acceptance purposes, ASTM G48 or ASTM A923 can be performed at a single specified temperature.

The test temperatures given in the ASTM G48 standard are only recommendations, and the required test temperature will be given in the relevant application code or standard.

The G48 test is designed to assess materials for pitting corrosion resistance in chloride media (stress is not relevant). The test solution is actually quite aggressive, certainly more so than the materials would be subjected to in normal service. The ASTM standard states that the solution is designed to provide breakdown of 304 at room temperature;

22%Cr testing temperature is normally +22°C or +25°C

25%Cr testing temperature is normally +35°C or +40°C.

Unwelded base material (or solution annealed welds) will pass the test at higher temperatures.

NORSOK M-601 and M-630 (oil and gas industry standards) incorporate a maximum weight loss requirement of 4g/m2. The acceptance temperatures are 50°C for 25Cr super duplex base material (M-630) and 40°C for welds (M-601).

| |voestalpine Böhler Welding

Corrosion testing (Continued)

31

All ferric chloride immersion tests include any saw-cut faces. Weld cross-sections will be exposed to the test solution and thus are also evaluated

Sub-surface regions seldom exposed to the corrosive medium in an actual application can influence the test outcome if weight loss criteria are used

All saw-cut surfaces should be polished. The “grit” will normally be specified in the appropriate specification/code

Pickling of welds prior to testing is also recommended

NORSOK M-601 states that the whole specimen shall be pickled before being weighed and tested. Pickling may be performed for 5 min at 60°C in a solution of 20 % HNO3 (Nitric Acid) + 5% HF (Hydrofluoric acid)

Ferric chloride immersion methods are very aggressive. Consequently, the most common standard austenitic grades cannot be tested

Ensure you use a competent test house

| |voestalpine Böhler Welding

Which Welding Process?

32

Process Advantages DisadvantagesGTAW Gives the cleanest weld metal, offering a superior weld bead finish providing the highest

corrosion resistance, fatigue performance and impact toughness.Can be automated

The least productiveRequires high skill level

GMAW Semi-Automated - Higher productivity compared to GTAWClean weld metal offering high impact toughness

Lower arc stability and weld pool fluidity compared to standard austenitic grades (hence He containing gases)

More prone to spatter than standard austenitic grades

Best results obtained with synergic pulsed equipmentProne to Porosity especially with higher Nitrogen contents (25%Cr). Avoid Narrow gaps, small joint

angles and large land (reduce dilution)

SMAW The most flexible processMid-range impact toughness

Low productivityAutomation not possible

Does not offer optimum corrosion propertiesSAW Highest productivity

Mid-range impact toughness (subject to careful selection of wire and a basic flux)Welding of thicker materials (10mm+)

Restricted to PA welding positionHI restrictions e.g. <1.5Kj/mm for optimum impact

toughness restricts the productivityPenetration is lower than with other standard

austenitic grades making joint preparation criticalBe careful with harsh corrosion requirements

(22%Cr ok but 25%Cr difficult)FCAW High productivity

All positional Reduced risk of lack of fusion compared to GMAW

Less risk of spatter and PorosityUses a standard Ar+20%CO2 shielding gas

Impact toughness from a Rutile slag system

| |voestalpine Böhler Welding

Please take a flyer

Thermanit 25/09 CuT super duplex MIG and TIG welding wires by voestalpine Böhler welding are designed to achieve the highest corrosion resistance in demanding welding operations.

Excellent cleanliness resulting in less “scum” on weld pool – Ask welders who have tested this product!!

This new HRW allows welding by GMAW process with lowest levels of porosity

Product manufactured 100% in house from billet to final product. Controlled chemical composition resulting in excellent corrosion resistance with increased G48 success rate with many references @ +40C

Thermanit 2509CuT

Super duplex welds with PREN>42

| |voestalpine Böhler Welding

New Super Duplex FCW’s

| |voestalpine Böhler Welding

Tensile and impact toughness test results for a V-joint (free shrinkage) welded in 15 mm UNS S32750 using Avesta FCW 2507/P100-PW NOR against a ceramic backing in the PF position

35

Oil treater and degasser

subject to NORSOK

requirements – all fillet welds were made using

Avesta FCW

2507/ P100-PW NOR

Superduplex Seawater Pump

| |voestalpine Böhler Welding

Conclusion

36

• Suitable Preheat & Interpass temperatures must be selected for your base material

• Control the Heat Input according to the base material

• Filler material must be added at all times (Nickel addition)

• Over alloying of filler material is required (Nickel addition)

• Correct procedure for Root run and subsequent passes)

• Minimise weld oxide by adequate gas protection (shield & backing)

• Positive effect of Nitrogen in gases

• Remove weld oxides by post weld cleaning (acid pickling most efficient)

| |voestalpine Böhler Welding

Questions?

Thank You For Your Attention