RESEARCH PROJECT No. 17

SULFUR IN MOLDING SAND EFFECT ON FLAKE GRAPHITE AT THE CAST SURFACE

OF DUCTILE IRON CASTINGS

PROJECT DIRECTION - GEORGE DiSYLVESTRO PROJECT ASSISTANCE - AMERICAN COLLOID COMPANY

PROJECT SUMMARY - ROBERT J. CHRIST

SOCIETY

Issued by the Ductile Iron Society for the use of its Member Companies - Not for General Distribution

DUCTILE IRON SOCIETY 28938 Lorain Road

North Olmsted, Ohio 44070 216-734-8040

OCTOBER 1992

RESEARCH PROJECT No. 17

SULFUR IN MOLDING SAND EFFECT ON FLAKE GRAPHITE AT THE CAST SURFACE

OF DUCTILE IRON CASTINGS

PROJECT DIRECTION - GEORGE DiSYLVESTRO PROJECT ASSISTANCE - AMERICAN COLLOID COMPANY

PROJECT SUMMARY - ROBERT J. CHRIST

SOCIETY

Issued by the Ductile Iron Society for the use of its Member Companies - Not for General Distribution

DUCTILE IRON SOCIETY 28938 Lorain Road

North Olmsted, Ohio 44070 2 16-734-8040

OCTOBER 1992

Summary

Introduction

Investigational Procedure .

Responses to Questionnaire - Phase I

Reproducibility of Molding Sand Sulfur Analyses - Phase I1

Development of Standard Method - Phase I11

Recommendations

Acknowledgements

References

Figures and Tables

Appendices A 1 -A7

SULFUR IN MOLDING SAND EFFECT ON FLAKE GRAPHITE AT THE CAST SURFACE

OF DUCTILE IRON CASTINGS

Contents

Page

1

1

2

2

3

4 4 5

5

6-9

10

Figures and Tables

Figures and

Tables

Fig. I

Fig. 2

Table 1

Table 2

Table 3

Table 4

Table 5

Topic Page

Typical Example of Flake Graphite at Surface of Ductile 6 Iron Casting, Example 1

Typical Example of Flake Graphite at Surface of Ductile 6 Iron Casting, Example 2

Responses to Phase I Questionnaire 7

Responses to Phase I Questionnaire Continued 7

Core Binder Systems Providing a Potential Sulfur Source 8

Phase 11 - Sulfur in Molding Sand Round Robin 8

Phase III - Sulfur in Molding Sands Reported by 13 9 Foundries

SULFUR IN MOLDING SAND EFFECT ON FLAKE GRAPHITE AT THE CAST SURFACE

OF DUCTILE IRON CASTINGS

Ductile Iron Society Project PI7

A Research Project of the Committee on Structural Control

Project Direction - George Di Sylvestro Project Assistance - American Colloid Company

Project Summary - Robert J. Christ

SUMMARY not contribute sulfur. Periodic additions of new sand to the system are often required and

This project investigated the role of sulfur in a regular sulfur auditing program is desirable. molding sand on the formation of a layer of flake graphite just below the surface of ductile iron Repeatability andconsistency of sulfur in sand castings- Inf~nnation was compiled by analyses within an individual foundry is very questionnaire from 28 member fo~ndries On the good, although a lack of standardization prevalence of this condition and procedures results in only fair reproducibility between used to control sulfur in system molding sands. different laboratories. Six volunteers DarticiDated in round robin testing to dete&ine r6producibility of sulfur analyses methods. Eleven foundries then provided statistical data on system sand sulfur analyses from their own facilities using recommended practices identified in this study. A literature survey identified information on effects of sulfur and threshold levels.

The prevalence of flake graphite and the adverse effects was confirmed by 50% of producers, but. few foundries routinely monitor sulfur in sand. Those that do, generally use Leco type equipment, although no standards exist with regard to instrument models or procedures.

Unless the flake graphite is completely removed by machining, the surface hardness and bending fatigue properties of the casting will be reduced.

It is recommended that sulfur in system sand be controlled to <0.10%, and preferably <0.07%. Seacoals are universally required in green sand mixes to provide a reducing atmosphere under which ductile iron castings must solidify. Sulfur levels in sand can be reduced by using low sulfur varieties of seacoal and by selecting core processes, washes, coatings, mold releases, etc., that do

From a sampling of 13 foundries, four operate at sulfur levels exceeding 0.10%, and the balance maintain a range of 0.040-0.070%.

INTRODUCTION

This report culminates a three year study under the direction of George Di Sylvestro, formerly with the American Colloid Company, in which he served as the primary investigator.

The literature attributes the occurrence of flake graphite in ductile iron castings to a number of factors, the most important of which are inadequate magnesium treatment, base irons high in sulfur content and the presence of certain subversive elements. However, the formation of a layer of flake graphite at the cast surface, in an otherwise satisfactory ductile iron casting is due to other factors. Unless this surface skin is removed by machining or grinding, the casting will exhibit lower surface hardness and lower strength under bending loads in service. Flake graphitic skins have been reported by casting producers to reach depths of 114 inch (6.3 mm) or more. Figures 1 and 2 illustrate typical examples of flake graphite at the surface of ductile iron castings.

Numerous investigators1-"* have reported that the primary factor promoting degenerate graphite skins is a high sulfur content in the molding materials. As molten treated iron contacts the mold wall, and prior to formation of a solidification skin, the sulfur reacts with free magnesium that is not already in the form of sulfides or oxides. This depletes the residual magnesium in the iron below the level required for formation of nodular graphite. The result is flake or vermicular graphite. The slower the rate of formation of a solidification skin (i.e., in heavy section castings), the more extensive will be the degenerate graphite layer. Reduction of sulfur in the molding media and elimination of oxidation additives in the sand mix, such as iron oxide, are the most effective means for preventing this skin effect.

Recent DIS Project #17 was initiated to answer a series of questions:

How prevalent is the problem of surface skin degenerate graphite among member foundries?

What levels of sulfur are found in molding sands and what are the methods being used to measure and control to acceptable concentrations?

How reproducible are these methods?

Based on the experience of member foundries, is there a recommended procedure for sulfur analyses that can be adopted as a standard? Participants were asked to contribute procedures used in their facilities.

INVESTIGATIONAL PROCEDURE

Phase I:

Survey DIS member participants and others to confirm occurrence of surface degenerate graphite and to provide information on sulfur analyses and control procedures used in their companies. A copy of the questionnaire is included in Appendix 1. Forty-three organizations were solicited. This included

foundries and independent consultants. Twenty-eight responded for a 65% return. The results are summarized in Tables 1 and 2.

Phase 11:

Supply six volunteer DIS members round robin samples consisting of high and low sulfur molding sands and ask each to analyze these for sulfur using their respective test equipment and procedures. Analyze results to determine reproducibility between laboratories. The results are tabulated in Table 4.

Phase 111:

Select the best procedure employed for sulfur in sand as submitted by participants in Phases I and 11.

Select research participants from members and other volunteers with available analytical equipment, to test their sand mixes and report the values and reproducibility of the procedures. The results are summarized in Table 5.

Results from the questionnaire and sample testing are coded to provide anonymity to participating organizations. All information has been developed for green sand molding media. However, some information gathered on sulfur sources in cured core sand materials is tabulated in Table 3.

RESPONSES TO QUESTIONNAIRE - PHASE I

The questionnaire as sent to 43 participants is included in the Appendix. Twenty-eight responses are summarized in Tables 1 and 2.

Sulfur that accumulates in sand from molds and cores can affect the surface graphite quality of ductile iron castings.

Fifty-four (54) percent of the respondents (15 foundries) claim to have experienced flake graphite skin problems at times, yet only one-half of these or eight foundries have related it to high sulfur in sand.

*Refers to references.

Although 10 foundries or 36% have sulfur in sand analytical capabilities available, only 5 foundries have established sulfur control testing practices and claim to have set target limits; yet 80% expressed interest in learning more about cause, effect and control of this condition.

The most widely used of several methods is the Leco method developed by the Dietert Company, although different models are used by the reporting foundries.

The role of sulfur in molding sand has been reported in BCIRA, AFS, and DIS literature1-12. The source is usually high sulfur seacoal and system sand buildup from recycled molding sand and sulfur containing core sand. The general recommended limit is 0.15%,',~*~.~ but preferably <0.12%~.'~. This would suggest a safe limit of 0.10% sulfur in sand. One automotive foundry targets a maximum of sulfur at 0.07% to be on the safe side. It must be remembered that other oxidants such as iron oxide in the mix or exothermic riser reactants can also have an accumulative effect of sulfur on microstructure. Adding all these factors

There is Or of further supports the recommended 0.07% procedures in use between the various maximum, as suggested earlier in this report. foundries.

A literature survey suggests sulfur in system sand should be held to ~0 .10% with some earlier references recommending a 0.15% maximum. However, experiences of several USA foundries suggests a limit of 0.07% is necessary to provide a margin of safety. A comparison of the questionnaire responses in Phase I, with the analyses reportedin Phase 111 for participating foundries, supports a recommendation of <0.07% sulfur in sand.

Information on test reproducibility brought sketchy and questionable data (see Table 2).

T h e literature and operating foundry experience indicates sources of sulfur include seacoal, certain core binders, and their catalysts, mold release agents, mold and core

Participants were asked to provide sulfur analyses procedures. From the limited responses, those using Leco equipment follow some semblance of using ASTM Method D4239. The written procedure from John Deere Foundry appears most complete. The Deere and ASTM methods are included respectively in Appendices 2 and 3. The George Fisher 3-Minute method is described in Appendix 4.

While the current study focused on green sand, from Table 3 it is clear sulfur can be sourced from core sands also. These do end up in the system sand and one foundry4 did report flake graphite skin effects on cold box molded core surfaces. Other sulfur sources are parting and mold release agents, requiring that these be selected with care.

coathgs containing sulfur, and riser sleeves or other feeding aids. REPRODUCIBILITY OF MOLDING

SAND SULFUR ANALYSES - PHASE n The data does not necessarily confirm that foundries not reporting as having experienced the flake skin problem do not in fact on occasion produce castings with this condition. The skin effect can only be confirmed by micro-examination of sections intersecting the surface. Unless customer complaints are received or cast parts are sectioned as an auditing procedure, this condition may not be detected. It is, however, equally important to remember that in many casting applications, either the surface is machined, or the function of the casting in service may not be adversely affected by the flake skin condition. Nevertheless, reduced casting surface hardness can be expected in regions of surface and subsurface flake or vermicular graphite.

Phase I1 utilized six volunteer foundries to conduct reproducibility tests on samples provided to each. Results of this round robin series are summarized in Table 4.

Each foundry used their own equipment; Leco type equipment predominated. The variation between foundries from the average or mean value ranged from 20%-34% for all samples except the one with an extremely low sulfur level. This variation can be classified as only fair, the differences between foundries being related to the capabilities of the specific model of equipment at each location, coupled with the lack of a standard procedure. At least three different models of Leco type equipment were used. One volunteer employed George Fisher

hardware. These data are insufficient to determine if one type or brand of sulfur analyses equipment should be preferred over another. It is interesting to note, that according to the Leco Corporation, accurate sulfur-in-sand analyses requires models designed for sand, coal and oil analyses, not analyzers that are intended primarily for carbon and sulfur analyses in irons. See Appendix 5.

Further information on specific applications can be obtained from the equipment manufacturer. Leco type equipment appears to be the preferred choice of USA foundries and independent analytical laboratories. When using combustion methods for sulfur, users should observe recommended safety practices.

DEVELOPMENT OF A STANDARD METHOD - PHASE n 1

Thirteen foundries agreed to analyze and report results for their sand mixes using ASTM D4239 coupled with the John Deere Test Procedures. The results are tabulated in Table 5. Four of the foundries reported sand mixes exceeding 0.10% S, which was suggested as an upper limit to avoid flake graphite in an earlier section. The complete Phase 111 test results as reported by the individual foundries are included in Appendix 6. The questionnaire in Appendix 7 was also used in this phase to collect available information on participants' practices.

Using the John Deere Test Procedure, the following was concluded:

Two hundred tests were run on 15 molding sands and results reported statistically by the contributing foundries.

Very acceptable reproducibility was achieved within a given foundry (see Table 5) when using a recommended procedure.

Most of the foundries utilize analyzers incorporate the induction and infrareddetector apparatus for both carbon and sulfur typically used in the metals industry. These units are not recommended by the manufacturer for analyzing organic materials or molding sand.

The major error in the reproducibility is attributed to either free water or crystalline moisture contained in the materials used in the molding sand, making adequate pre-drying of the sand sample mandatory.

The 3-Minute Combustion-Iodometric Titration method for determining sulfur that has been used in the past, has been an old reliable procedure and can be the most economical equipment to use for those who will be auditing sulfur in a production quality control program.

The range of sulfur reported from all participating members included a low of 0.0260% and a high of 0.1290%.

A review of the literature produced no reports of standard methods for analyses of sulfur in molding sand, although several papers do report the incidence of flake graphite being related to excess sulfur in the mold media.

Those foundries making the largest new sand additions reported the lowest sulfur levels; whereas those making the highest seacoal additions also reported the highest sulfur readings.

RECOMMENDATIONS

Reduce or eliminate flake graphite skins at the cast surface of ductile iron castings by reducing sulfur and oxides content in system sand mixes, preferably to ~0 .07% as a margin of safety.

Select low sulfur seacoals, core mixes, mold and core washes, and parting compounds.

Monitor sulfur in sand levels regularly and set control limits.

Maintain system sand sulfur levels ~0 .07% if possible. Add new sand as required to reduce sulfur levels if flake graphic skins become an increasing concern.

The John Deere procedure coupled with Leco type equipment is an effective method for sulfur in sand determinations.

Select sulfur analyses equipment that is specifically designed for analyses of sands, coals, oils and other organics. Carbonlsulfur analyses equipment incorporating induction heating and infrared detection that has been designed for metal analyses is not recommended for sand analyses. Contact equipment manufacturers for selection of best types and models.

Oxidants in molding materials such as iron oxide additives and exothermic riser sleeves also remove surface magnesium from solidifying castings. These materials can compound the effect of sulfur in sand and must therefore also be considered.

ACKNOWLEDGEMENTS

Project 17 has been carried out primarily by the voluntary work of DIS members and their companies. All members are grateful for this effort and the results it produced. Particular recognition is due to George Di Sylvestro for his leadership in organizing and coordinating collection and analyses of experimental data.

REFERENCES

1. R. Barton, "A Note on Flake Graphite Structure at the Cast Forces of Nodular Iron Castings," BCIRA Journal, July 1967, Vol. 15, No. 4.

2. F. Martin, S.I. Karsay, "Localized Flake Graphite Structure as a Result of Reaction Between Molten Ductile Iron and Some Components of the Mold," Transactions m, Vol. 87, 1979, p. 221.

3. K.B. Palmer, "The Effect of Surface Structures and Casting Surface Imperfections on Rotating Bending Fatigue Properties of Pearlitic Ductile Iron," BCIRA Journd, March 1984, Vo1. 32, No. 2.

4. Internal Research Reports, Deere & Company, Moline, Illinois.

6. Carmeli, "Presentation of Graphite Deterioration in Ductile Iron," presented and videotaped at the 1986 DIS Annual Meeting.

7. G. Di Sylvestro, "Sulfur in Molding Sands and Cores," presented and videotaped at the 1989 DIS Annual Meeting.

8. V.S. LaFoy, S.L. Nelter, "The Value of Seacoal Supplements in Today's Foundry Industry," Transactions AFS, Vol. 95, 1987, p. 133.

9. R.E. Simmons, "Casting Defects Arising from Poor Sand Reclamation Practices and Tests for Control," BCIRA Journal, Vol. 37, Oct 1989, p. 371.

10. K.B. Palmer, "Summary of Present Knowledge of the Effect of Cast Surface Structures and Discontinuities on Rotating Bending Fatigue Properties of Ferrous Metals," BCIRA Research Cast Metals -,April 1990,Vol. 38,No. 2,p. 139.

11. G. Di Sylvestro, "Sulfur in Green Sands," presented and videotaped at the 1990 DIS Annual Meeting.

12. H. Moore, "Cold Dust in Green Sand-A New Look at Old Practice," BCIRA Technologv, May 1991.

13. G. Di Sylvestro, "Sulfur in Green Sands," presented and videotaped at the 1988 DIS Annual meeting.

14. BCIRA Broadsheet, "Bending Fatigue Properties Reduced by Surface Conditions," (restricted to BCIRA members).

5. J. Mullins, "Effect of Sulfur on Graphite at 15. Editorial, "Surface Flake Graphite Lowen the Skin of Ductile Iron Castings," Tensile Strength of Castings Produced in presented and videotaped at the 1986 DIS Green Sand," BCRA Technology, Annual Meeting. November 199 1.

Note: Videotapes and References 5, 6, 7,11 and 13 are available to DIS members by contacting the DIS ofice.

Examples of Flake Graphite Extending Below the Cast Surfaces of Ductile Iron Castings

Figure 1 Unetched lOOX Mag

Figure 2 Unetched 1 OOX Mag

6

Table 1 Responses to Questionnaire - Phase I

Yes and No Responses

Issue*

Surface graphite experienced (10)

Have related to sulfur in sand contamination (4)

Have sulfur in sand test equipment (1)

Have established threshold sulfur in sand limits (5)

Have written S test procedures (3)

If not now sulfur testing, interested in more information (7)

Foundries Responding, Number (%)

Yes No No Response

15 (54) 11 (39) 2 (7)

8 (29) 18 (64) 2 (7) 10 (36) 18 (64) -

5 (18) 20 (7 1) 3 (11)

7 (25) 20 (7 1) 1 (4)

22 (79) 4 (14) 2 (7)

*Number in parenthesis refers to question number. See Appendix for copy of questionnaire.

Table 2 Continuation of Responses to Questionnaire - Phase I

Specific Information Requested on Molding Sand Testing

Ouestion Number and Descri~tion

2.) Type of Sulfur Determination Used Frequency of Use

2 Leco Model SC 132 - No data 2 Leco Model CS 244 - No data 1 Leco Model CS 46 - No data 4 Leco - model not given - Varied from every 20 min to oncelday,

oncelmonth, each sand shipment 1 Geo Fisher Model 3 104 - No data 1 Leybold Heracus, Model CSA 302 - No data

*Test cycle times varied from 0.5 to 5.0 minutes with a 3 minute cycle most popular. *Note, 1 commercial lab analyses >10,000 samples per year.

6.) Normal reproducibility reported (all on Leco equipment). This question was misunderstood and did not produce viable data.

9.) Combustibles in molding sand.

5 reported 1200°F combustibles of 1.2-2.5%. 13 reported total loss on ignition range of 3.0-5.5%.

Type

Shell Hot box Hot box

Warm box No bake

No bake

No bake No bake No bake No bake Cold box

Cold box Cold box

Cold box Cold box Cold box

Table 3 Core Binder Systems Providing a Potential Sulfur Source

Binder System

Resinlcoated sand Phenolic Furan

Furan Furan:

- Phosphoric acid catalyst - Sulfonic acid catalyst

Phenolic: - Sulfonic acid catalyst

Phenolic ester Phenolic urethane Sodium silicate-ester

Alkyd urethane

Epoxy 1 SO, Furon / SO, Phenolic urethane

Phenolic ester Sodium silicate / CO, Free radical process

Sulfur Potential Sulfur Source

No No No

Yes

-

Catalyst

No Yes

Yes

No No No No

Yes Yes

No No No Yes

- Catalyst

Catalyst -

SO, gas SO, gas

-

SO, gas

Note: A major manufacturer of core sand mixes reports that many of these will result in 0.03-0.05% sulfur in the finished mold or core. Recycling therefore results in a gradual increase in sulfur levels in system sands unless a new sand replacement practice is in use.

Table 4 Sulfur in Molding Sand from Phase I1 Round Robin Tests

Percent Sulfur Reported - 3 Test Average

Avg Range, Partici~ant Code A B C D E F of All % ofAvg:

Pound Rob~n S&

1 - Low S mold sand

2 - High S mold sand

3 - Low S mold sand

4 - High S mold sand

Production sand

Production seacoal

Equipment

Model no.

Equipment age (yrs)

-

0.510

Leco

SC 132

1.5

0.0165

0.232

0.094

0.106

0.063

0.538

Leco

CS 46

12

Leco

SC 132

-

Leco

CS 244

6

0.0195 0.017 0.0175 * 0.322 0.330 0.288 34%

0.095 0.1 10 0.098 28%

0.126 0.130 0.122 20% - 0.063 -

- - 0.5 14 -

Geo Fisher Leco

3104 -

13 ?

"Extreme low and high values from participants A and F makes a calculation meaningless.

Table 5 Summary of Sulfur in Molding System Sands

Reported in Phase I11 by 13 Participating Foundries

Sulfur %

Foundry Code Average Range

3 0.123 0.118 - 0.129

7 0.06 1 0.51 - 0.073

17 0.07 1 0.062 - 0.082

22 0.055,0.095" 0.050 - 0.104*

24 0.050 0.039 - 0.067

3 5 0.049 0.040 - 0.056

3 6 0.070,O. 100" 0.061 - 0.1 13"

28 0.088 0.071 - 0.104

43 0.049,0.059* 0.037 - 0.063"

44 0.043 0.026 - 0.054

46 0.072 NR

E 0.056 0.049 - 0.060

F 0.1 15 0.098 - 0.131

"Multiple molding lines, separate sand systems. NR - Not reported.

Appendix 1

Copy of Questionnaire Sent to 43 DIS Members and Others as Part of

Phase I - Project 17

SULPHUR DETERMINATION IN MOLDING SAND

I. Do you have test equipment t o t e s t for sulphur in molding sand?

YES NO

2. If so, wha t equ ipmen t do you use?

Name of equipment: How o f t e n i s i t used: T i m e in minu te s t o run test:

3. Do you have wr i t t en procedure-s?

YES NO (Please a t t a c h a copy if you answer yes.)

What is i t s source:

4. Have you had problems tha t you c a n a s soc ia t e with sulphur contaminat ion in molding sand?

YES NO

T o wha t degree: -

5 . Have you es tabl i shed threshold l imi t s on sulphur in molding sand?

YES NO

What a r e they? -

6 . If you a r e tes t ing f o r sulphur i*olding sand, w h a t is t h e normal reproducibi l i ty of t h e t e s t you a r e using?

F rom % TO %

(See o the r side of shee t for o t h e r questions.)

Al.l

Page 2 - Questiomire - Sulphur Determination in Molding Sand

7. If you a r e not, a r e you interested in this information?

YES NO

8. Would you be interested t o part icipate in a production round roubin test t o compare with t h e other ducti le iron membefs?

YES NO

9. Please advise the combustible content of your present ducti le iron molding sand.

at 900°F for one hour % at 1,2000 for one hour % at to ta l loss of ignition %

10. Have you experienced any casting surfaces with unacceptable graphite shape?

YES NO

Appendix 2

I. DEFINITION: Analyze system sand for sulfur content using Leco equipment.

John Deere Foundry

Process and Materials Technology Manual

L

11. EQUIPMENT

Section:

Subject:

- Leco CS244 Carbon-Sulfur Determinator or Equivalent (CS344 01 CS444)

- Crucibles. Leco - Accelerator; Lecocel, Leco - Carbon Sulfur Standards (CRM8s) - Drying Oven

111. PROCEDURE

1. Obtain samp1.e of system sand.

2. DryOa 50gosample for one hour using drying oven set at 225 F + 5 F to remove all moisture.

3. Standardize CS244 using known standards.

4 . Weigh a .250 gram sample of system sand, enter weight.

- Add half scoop of accelerator. - Start test and record results. - Repeat test and average results.

5. Check carbon-sulfur machine with known standard in range of averaged result.

- If known standard runs within its certified values (ex. .008 2 .002), clean combustion tube and rerun test.

- Clean combustion tube after each system sand sample is complete.

6. Additional samples, unknown.

- Follow above procedure. As sulfur content changes, recheck averaged results with a known standard to check machine for drift and repeatability.

7 . Testing of system sands completed.

- Clean combustion tube. - Change wire screen filter. - Restandardize CS244 for iron samples.

Appendix 3

Designation: D 4239 - 85

AMERICAN SOCICTV FOR TESTING A N 0 MATERIALS 1916 R a St., Pktl&r(ohir.?8. 19103

Rcorinted trom the Annud 800k 01 ASTM S t a d u d ~ . Coovr~qht ASTM If not l~strd In the cwrmt mbnd indrr . will aooerr In the next edit~on.

Standard Test Method for SULFUR IN THE ANALYSIS SAMPLE OF COAL AND CCKE USING HIGH TEMPERATURE TUBE FURNACE COMBUSTION METHODS1

This arrrdvd is issued undrr the tkcd daigrrtion D 4239: the number immcdiudy following the -don indiata rhe y u r of o n ~ & g u o o o r . ~ n t h e ~ o f ~ a r b e ~ d ~ ~ ~ A n u m b a i n ~ t b a e r i n d i c u a t h e ~ o f ~ r ~ A ~ g c & n ( O indicusm e d i t o r i r l ~ n a a t h e L a m k i o n a r a p ~ r o n l

1. Scope and derennine the applicability of regulatory limi- 1.1 These test mcthods cover t h m alternative tations prior lo use-

padm using high-tem~nturr Nbe - 2. Appliable Docnmenrr combustion methods for the rapid determination of sulfur in samples of coal and coke. 2.1 ASTM S l h d r :

N m I-It is imporrant to note the high tan- D 346 Method of CoUcction and Preparation

tun combustion methods do not dacrmrne told &, of Coke Sampies far Laboratory ~nalysis ' only total wmbwlble sulfur. The diffcrcna between D 1193 specification for Rtagcnt w a d to& and combustible sulfur is minimal except what dealing with high-lsh, high-& coJ,

1.2 The proaurcs appear in the following order

Secriols ,Uethod A-High Temperam Comb*

tion Method with Acid h e Titration Derecnoa Rocedurrr . . . . . . . . . . . . . . 6 to 9

, U d d &High Temperature C o m b tion Method with Iodimeaic Titration Detection Rocedurcs . . . . . . . . . . . . . . 10 to 13

,h'orhcd C-High Tempemure Combus tioa Method witb Infrared Absorption Detaxion Rocedura . . . . . . . . . . . . . . 14 to 16

D 201 3 Method for ~ n p a n n ~ Coal Sample for ~nalydsZ

D 236 1 Test Method for Chlorine in Coal2 D 3 173 Test Method for Moisture in the Anal-

ysis Sample of Coal and Cokc' D 3 176 Methods for Ultimate Analysis of Coal

and Cokcf D 3 180 Methods for Calculating Coal and

Cokc Analyses h m &Determined to Dif- fmnt B d

D4208 Test Method for Total Chiorine in Coal by the Oxygen Bomb Cornbustion/Ion Selective Electrode Method2

1.2.1 When automated equipment is used to d o r m any of the three methods of this test 3- of Methods method, the procedures can be ci;.Lstified as in- suumenul

Please see current issue of ASTM standards nrnn that offer to the coal indusuy, equipment with instrumental analysis capabilities for the for balance of Co~J'writed procedure. determination of the sub content of coal and coke samples.

1.3 This standard may involve hazardous ma- 'Tb ir~mcrbod~Wthejur id in iooof&YlMCom- t e n d , operations, and equipment. This standard ,, on core lar aua nambhv

ha not purpon to address'dl of the safety pro&- Subcomminrt m5.a oa ~ c t h o b /ems associated with its use. It is the responsibil- ity of whoever rues [his standard to consult and z Ad 4- vol 05.05. establish appropriate safety and healrh practices ' . - i d Bodr of.dSI;USlcMdOrdl, V d I 1.01.

Rubbrr Tubing Connac~lonr F l ~ r r lo Sor

To I

Push Schrd. Mark11 - kSomp40 Boot Qu4h.r

-Flow Motor

Vocuum 125rnl 1 (10s Abrorplbon Rogulolor 80lI las wrlh

fflll.4 OLDh8

FIG. I Apparatus lor the U c t c r P l u l b . rJsrYvr Uda# Acld-haa W t 8 h

I

- I

OETECTOR EXnAUST I

Appendix 4

George Fischer Foundry Systems, Inc. 407 Hadley Street, P.O. Box 40, Holly, Michigan 48442 U.Sk

BY: MARY BETH MIZZI

Three Minute Determination of Sulfur in Moldina Sand Combustion - Iodo~stric Titration Method

The apparatus for the method described consists of four solution bottles, a buret, a titration vessel and a support column with a base.

The 20 ml. buret is graduated to read directly in percent sulfur from 0 to 0.20 % sulfur for a one-gr'am sample.

The titration vessel is specially designed with a drain cock at the bottom, two stopcocks on the upper right and left, and two lines to indicate proper solution volumes.

The bottles are mounted on four shelves above the titration vessel and are idantified as upper and lower, right and left. The bottles have hose connections at the bottom to gravimetrically feed the stopcocks to which they are attached.

Other equipment required includes: a combustion furnace with an oxygen inlet and control valve, analytical balance, oxygen regulator, oxygen purifying'train, high temperature sulfur free combustion boats ( 9 5 x 13 x 11 nun), fitted boat shields, and'a restricted end combustion tube with a filter. The combustion tube should be : 27 mm. ID, 33.3 mm. OD, 686mm length (restricted section 3.2 ~un. ID, 254 mm. length) . The restricted end combustion tube is recommended because it can be fitted with a filter which is desirable for samples which create a considerable amount of dust in combustion.

Description of the Apparatus

The sulfur determinator should be set on a work bench approximately 36" high, close to the rear of the furnace. For best artificial lighting, provide an overhead fluorescent light in front of the determinator.

The buret is mounted so that the tip extends into the titration vessel.

A rinsing stopcock assembly is positioned with a wash tip extending into the titration vessel.

The oxygen should be connected so that it passes through a flowmeter and oxygen purifying train after the regulator.

Open the valvo on the furnace and the valve on the flowmetor. Adjust tho valve on the oxygen regulator to produce a maximum o-upgen flow of 1 1/2 liters per minute, then close tho valve at the front of the furnace. Do not change the position of the valve on the purifying train unless a lower oxygen flow is to be used. Use the valve on the furnace for "stop and go" oxygen control.

The front end of the combustion tube should extend approximately 3 1/2" beyond the clamp of the furnace. In this position, the filter material in tho tube will bo in a temperature zone from 1900 to 2000 dog. F. - the desired range.

If the filter material is not already in tho tube, place a perforated porcelain disc against the restricted portion of the tube.

With the furnace at operating temperature, place approximately ten to fifteen grams of filter materiai in the combustion tubs. This is approximately four combustion boats full of the filter material. The filter may bo easily placed in the tube by placing the material in a boat and turning the boat upside down in the cold end of tho tube. Quickly push the filter material through the hot zona and against the perforated disc so that the top of the disc is covered with as much of the filter material as possible. Use a filter disc ramrod for this operation.

A bubbler tube is attached to a 12" length of tubing, followed by a tube connector and a short piece of 3 /8" tubing. The short piece of tubing should be fitted over the restricted end of the combustion tube. For best accuracy, it is desirable to keep the connection between the combustion tube and bubbler as short as possible.

Solution Pre~aration

Distilled Water

The upper left hand bottle should be filled with distilled water for rinsing the titration vessel.

Starch Solution

Weigh out 2.4 grams of Lintner's starch and add 7 ml. of distilled water to make a smooth paste by stirring. Add this paste slowly to 500 ml. of boiling water, stirring rapidly. Cool, add four grams of potassium iodide and bring volme to 2000 al. This solution should be placed in the lower right hand bottle.

Hydrochloric Acid Solution

Mix 40 ml. of concentrated hydrochloric acid and 1960 ml. of distilled water. This solution is used in the lower left hand bottle.

Potassium Iodate

Dissolve 0.2069 grams potassium iodate in about 300 ml. of distilled water and dilute exactly to one liter. This is the titrating solution and should be placed in the upper right hand bottle which serves the buret.

Collect all tubing neatly behind the column, using clips.

Test Procedure

For solutions as specified in these instructions, each ml. of titration solution is equivalent to 0.0001 gram of sulfur or 0.01 3 S when a one gram sample is used. The buret should dispense 20 ml. of solution for a reading of 0.20 percent sulfur on a 1 gram sample, or 0.40 percent on a 0.50 gram sample. For higher sulfur content3 make up a stronger iodate solution.

Close the drain cock below the titration vessel and open the left hand hydrochloric acid solution stopcock. Fill the titration vessel to the lower left hand mark, and then add starch-potassium iodide solution from the right hand stopcock until the solution reaches the upper right hand line of the titration vessel.

Turn on the oxygen at a rate of 1 1/2 liters par minute. Slowly add three drops of titration solution from the center buret to give the solution in the titration vessel a light blue color. This is the blank titration operation. Turn the stopcock of the buret to refix1 to zero, which cancels out any blank calculation. Stop the oxygen flow.

Weigh out a dried one-gram sample of molding sand and place it in a combustion boat without any bedding. The sample should be spread out in a continuous row at least one inch long with no isolated particles. Place a dualaccelerator strip on the sample and cover with a boat shield. Then, place the sample in the hot zone of the combustion tube and start the oxygen flow. Note: The dualaccelerator strip has a tin coating which insures complete combustion and a copper core which helps keep down dusting. The boat shield also helps to reduce dusting as well as protecting the combustion tube.

Titrate to maintain a light blue color in the upper two-thirds of the solution. Never allow the solution in the titration vessel to become clear during the combustion period. When the bubbles no longer bleach the solution, the test is complete. Add sufficient titration solution to produce the same blue color as in the blank titration at the beginning of the test. Record buret reading as percentage sulfur and refill.

Another sample may be weighed out during the last half minute of the combustion period,

At the end of the combustion period, with the oxygen still flowing, open the drain stopcock and allow the titration solution to drain. Use the wash tip to rinse off the bubbler and to wash down the sides of the titration vessel. Shut off the oxygen flow. Close the drain cock acd repeat test procedure as above for the next sample.

The purpose of the ceramic filter is to keep any iron oxide dust in the hot zone where it cannot influence the ratio of sulfur dioxide to sulfur trioxide formed in the combustion. The filter material may cake up with dust in time and slow down the oxygen flow. This will cause pressure to build up in the combustion tube which always results in incomplete combustion. Break up the filter material occasionally with the ramrod to prevent caking. Let oxygen flow about five minutes through the hot combustion tube after loosening the filter and before the next sample.

If, after breaking up the ceramic filter, a back pressure still exists, it indicates that the porcelain disc has clogged. To replace the disc, cool the furnace and remove the loose filter material. Clean the end of the tube with a small wire brush before inserting a new disc and repacking.

Any iron oxide which gets past the ceramic filter and lodges in the cold end of the combustion tube or bubbler connections should be removed daily. Use a wire brush to clean the combustion tube, being careful not to dislodge the filter disc.

If the bubbler should happen to clog with dust, it can be cleaned by allowing it to stand in 1:l hydrochloric acid. It should be rinsed and dried before using. The rubber and glass connecting tubes should be kept clean and dry to prevent the absorption of sulfur gases.

Appendix 5

Phone: (61 6) 983-5531 Telex: 21 1605 Facsimile: (61 6) 983-3850

September 07, 1990

Mr. George DiSylvelrtro American Colloid Company Park Ridge Satellite Office 717 Florence Drive Park Ridge, Illinois 60068-2103

Dear Mr. DiSylvestro:

I have just received a copy of your fax to Bill Stockwell regarding Sulfur in molding sand and an associated problem with one of your members regarding analysis of molding sands on the LECO CS244 system.

I would like to make a few comments regarding Sulfur analysis uaing LECO determinators. Hopefully, t h ~ s will help you better understand the analytical process and problems that can occur.

The LECO combustion analyzers utilized in your test procedure incorporate an Induction Furnace and Infrared Detector for both Carbon and Sulfur. These units are typically used in the metals industry. Many other of our customers use these type of analyzers for other inorganic sampie materials. Leco does not recommended that organic materials and/or samples containing significant amounts of organic materials be analyzed on these instruments, for a variety of reasons.

LECO manufactures a complete line of Sulfur analyzers uslng a Resistance Furnace and IR Detection for organic materials as well as samples containing significant amounts of organic material. In addition, inorganic materials which have significant amounts of moisture present cannot be analyzed successfully on the Induction Furnace units and must be analyzed on the Resistance Furnace units.

It must be noted that some materials contain both "free" moisture and crystalline moisture (hydrated). Drying a sample at 105' C for a period of time will normally remove the free moisture, but not the crystalline moisture. Many crystalline moisture bonds requlre temperatures in excess of 600. C for decomposition and removal; unfortunately this may also result in loss of Sulfur.

Moisture is the key element in Sulfur analysis. If moisture is allowed to condense in the delivery system, significant amounts of Sulfur Dioxide from the sample combustion will be trapped prior to detection. Small traces of moisture which may be present are not a problem, however, large amounts of moisture either being released from the sample upon heating, and/or produced by the combustion of organic materials (C-H bonds combusting to Cae and HE81 will cause Sulfur recovery problems.

Analyzing a dry clean sand can be accomplished on the Induction Furnace units such as the LECO CS244, however, sand with organic binders and additives cannot be successfully analyzed on these systems.

The LECO model SC132/432 systems are designed to analyze samples such as coals, oils, cokes and soils as well as many other materials, however, they are not designed to analyze metals. Since the foundry people are in need of Carbon and Sulfur analysis in Cast Irons, they purchase LECO Induction Furnace Carbon and Sulfur simultaneous systems such as the CS244, however, when trying to apply these systems to a variety of molding sands, they are not the instruments of choice.

I would suggest that you submit some of your "typical" sand samples to LECO's application lab for analysis. We will analyze them for Sulfur and can recommend the appropriate equipment to you.

If I can be of further assistance regarding this matter, please contact me at (616) 982-2277.

Sincerely,

Dennis Lawrenz Manager of Applications Laboratories

nlv

cc: L. O'Brien L. Essig B. Stockwell B. Ball

Appendix 6

DUCTILE IRON SOCIETY RIPSEARCH REPORT

Phase I11 - Test Results

From Member Coded l&:

Results on four tests, same sand, using Leco XCS344 analyzer.

0.120 % 0.129 % 0.125 % --------- 0.123 % Average

From Member Coded X7:

Results on one sample divided into ten parts using Leybold Hereaus CSA3 analyzer, carbon and sulphur were tested on same sample.

Carbon

Average---3.334%

From Member Coded #17:

1 retest

2 retest

3 retest

4 retest

5 retest

Sulphur

Results on five sand samples, same molding line, using LECO CS46 analyzer.

Test 1 -- Test 2 -- Averaqe

From Member Coded X24:

Results on three sand samples, tested in triplicate, using Leco analyzer.

Test 1 -- -- Test 2 -- Test 3 Aver aqe 1 .0472 % -0462 % .0395 % .0443 %

standard .0350 f .0001 -- actual .0344 %

2 .0615 % .0606 % .0665 % .0628 % standard .0350 f .001 -- actual .0348 %

3 .0394 % -0520 % .0386 % .0430 % standard .0350 f .001 -- actual .0346 %

SOCIETY

From Member Coded #36:

Results of three samples, from three different molding lines, tested three times, using Leco CS125 Analyzer.

TEST 1 -- Test 2 -- Test 3 -- Aver aqe Ajax -068 % -067 % .073% . 069%

-071 % -073 % .076 % .073% .074 % .074 % .076 % .075%

Average of all nine samples = .072% Car .065 % .061 % .064 % .063%

.068 % -068 % -067 % -068%

.066 % .065 % -068 % .066%

Average of all nine samples = Loop .095 % -091 %

.096 % N A

.099 % .099 % -113 % .097 % -104 % .lo9 %

Average of all nine samples = .099%

From Member Coded #28 -- Resuits of ductile iron green sand system using 0.350 gram sample on three different days consecutively.

High Value Low Value Average of Tests

4/18/90 4/19/90 4/20/90 0.093 % 0.099 % 0.104 % 0.077 % 0.071 % 0.087 %

0.0827% 0.0881% 0.0924% (10 tests) (9 tests) (10 tests)

Data on Sand Additions -- 1% new sand added (washed and dried silica 75 AFS) 2.8% core sand added (washed and dried silica 54 AFS) Carbon addition is seacoal (-9-1.0 sulfur) Combustible range 6.0%-6.5%

From Member Code #22

Results of two tests on two molding lines

Test No.

1 2

Average

Line 1. Line 2.

FROM MEMBER CODE #35

Two tests were run on one day. Then five more tests on same sample second day.

1st Dav

Sample # Test 1st Buq Test 2nd Bum Aver=

2nd Dav

Range of individual test 0.0399 to 0.0562 spread of 0.0163%.

Range of averages of each to readings 0.0443 to 0.0515 or 0.0072% spread.

From Member Code #43

Five sampels taken from 2 molding lines. Check twice from two days production of Dutile Iron Castings.

Moldinq Line 1. Std.

Sample No. 1st Read 2nd Read Aver. Check

Moldinq Line 2.

)q DUCTILE IRON

From Member Code #44 A

TRIAL TRIAL 0

TRIAL TRIAL SAMPLE 1 2 3 4

-

STD. (.072) .0704

STD. (.072) .0704 STD. ( .013)

STD. ( . 054) .0534 STD. (.072)

AVERAGE : .0403 .0426 .0472 .0416 RANGE : .0280 .0119 .0168 .0148

@ NOTE: "TRIAL 3" HAD APPROXIMATE SAMPLE WEIGHTS OF .500gm. INSTEAD OF THE RECOMMENDED WEIGHT OF .250gm.

DUCTILE IRON SOCIETY

From Member Code "En

Two weeks continual test were received from Ductile Iron Foundry of supplier associate member. This project was to audit the variation in two molding lines in a 2 week production period using LECO Model SC132

DATE SYSTEM 1 DATE SYSTEM 2

10/16/89 .0588% 10/19/89 .0596% 10/22/89 .0561 10/25/89 .0489% 10/27/89 .0603 10/30/89 .0603% Average .0584 Average ,8562

2 week 2 week Variation .0561 to .0603 Variation .0489 to ,0603

From Member Code "F1I using secondary standard test procedures

The Sulfur tests were performed using a Dietert No. 3104 Sulfur Determinator, equipped with a No. 3420 Varitemp Combustion Furnace and No. 3004 Oxygen Purifying Train. The tests were performed using a sample weight of 1.0000 gram.

3 Minute Test Sample Identification Sulfer Content, %

Molding Sands, Foundry Code #28 6-24-90, 7:30* 6-25-90, 7:25* 6-26-90, 7:25* 6-26-90, 16:33* 6-27-90, 7:50* 6-27-90, 19: 00 6-28-90, 7:25* 6-29-90, 7:25* 6-29-90, 18 : lo** 6-30-90, 7:25 7-05-90, 7:30 7-06,90, 7:15

0.1312 0.1170 0.1200 0.1135 0.1197 0.1085 Ave: 0.1147 0.1262 0.0967 0.1129 0.0982 0.1158 0.1170

Molding Sand Foundry Code $46 Ave: 0.0715

*Samples were extremely small ** These samples opened during shipment and may have been contaminated.

SOCIETY

Appendix 7

DIS Sulphur Tksting Research - P m 111 F-p- Requ-t survey

1. 'lhe percent new unbonded silica tha t is being ackied to t!! green sand systan is apLnoximately:

Lirre No. % LJne No. - % Line No. - % -- 2. The percent core sand being returned to the systan is a~proximately:

LJne No. - % Line M. - % Line No. - %

3 . 'mel core prcce?3s used is: A. 1. 2 . 3.

-te pezcent of each is: 8. 1. 2. 3.

4 . Give the type of b o d and additives being used for rebonding the sand systan? G i v e percent of each additive here:

Western Bentonite % CeUulose % southem Bentanite % Corn flour cereal % Seacoal % Other organic % -w- % Pdditive 'b (-1 (-1

5 . Tb total loss on ignitionm&itah& in the man - give range: fIIln % to % mt %

6 . Are -l.ling the sulphur in t h mlding sand m? Y e s No

7 . If so, what is your maximrm limit? Spec max. % We take action at %.

8.If so h w do you mcbtx sulphur in the systen?

9. Can you recammd a test casting design that could be considered for lMking p-on tests for confbning sulphur limits that cause graphitization in casting ductile iron (Phase IV)? We recamend: (Please pmvide &mmg or sketch i f available for r e f a m e on b t t a n of page. )

10. Do you wish to continue participating in this very valuable and cost effective research for ywur IXlctile Iron Society and its mmbrs? Yes No

This survey 'to improve the quality of ductUe iron was canpleted by: Nam: Date: T i t l e :