DoEIID/13734-l FERRITE MEASUREMENT IN AUSTENITIC AND DUPLEX STAINLESS STEEL CASTINGS FINAL REPORT C. D. Lundin W. Ruprecht G. Zhou August 1999 Work Performed Under Contract No. DE-FG07-991D13734 For U.S. Department of Energy Assistant Secretary for Energy Research Washington, DC By The University of Tennessee Knoxville, TN - .—. — .... ——
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DoEIID/13734-l
FERRITE MEASUREMENT IN AUSTENITIC ANDDUPLEX STAINLESS STEEL CASTINGS
FINAL REPORT
C. D. LundinW. RuprechtG. Zhou
August 1999
Work Performed Under Contract No. DE-FG07-991D13734
ForU.S. Department of EnergyAssistant Secretary forEnergy ResearchWashington, DC
ByThe University of TennesseeKnoxville, TN
- .—. —....——
DOEIID113734-1
FERRITE MEASUREMENT IN AUSTENITIC AND DUPLEXSTAINLESS STEEL CASTINGS
FINAL REPORT
C. D. LundinW. Ruprecht
G. Zhou
August 1999
Work Performed Under Contract No. DE-FG07-991D13734
Prepared for theU.S. Department of Energy
Assistant Secretary forEnergy ResearchWashington, DC
This report was prepared as an account of work sponsoredby an agency of the United States Government. Neither theUnited States Government nor any agency thereof, nor anyof their employees, make any warranty, express or implied,or assumes any legal liability or responsibility for theaccuracy, completeness, or usefulness of any information,apparatus, product, or process disclosed, o! represents thatits use would not infringe privately owned rights. Referenceherein to any specific commercia( product, process, orservice by trade name, trademark, manufacturer, orotherwise does .not necessarily constitute or imply itsendorsement, recommendation, or favoring by the UnitedStates Government or any agency thereof. The views andopinions of authors expressed herein do not necessarilystate or reflect those of the United States Government orany agency thereof.
DISCLAIMER
Portions of this document may be illegibIein electronic image products= Images areproduced from the best available originaldocument.
Aubrey, L.S., Wieser, P.F., Pollard, W.J. and Schoefer, E.A., “FerriteMeasurement and Control in Cast Duplex StainIess Steels”, Stainless SteelCastings, ASTM STP 756, V.G. Behal and A.S. Melilli, Eds., American Societyfor Testing and Materials, 1982, pp. 126-164
Bludleld, Dl, Clark, G.A. and Guha, P. 1981, “Welding Duplex Austenitic-Ferritic Stainless Steel”, Metal Construction (5): 269-273
Brantsma, L.H., and Nijhof, P., 1986, “Ferrite Measurements: An Evaluation ofmethods and experiences”, International Conference on Duplex Stainless Steel,Paper 45, Nederlands Instituut voor Lastechniek, The Hague
Bryhan, A.J. and Poznasky, A. 1984, “Evaluation of the Weldability of ES2205”,Report CP-280, AMAX Metals Group, Ann Arbor, Michigan
Bungart, K., Dietrich, H., and Amtz, H., “The Magnetic Determination of Ferritein Austenitic Materials, and Especially in Austenitic Welded Material”, DEW-Techn. Ber. 10, p. 298,1970
DeLong, W., Ostrom, G., and Szumachowski, E. 1956, “Measurement andCalculation of Ferrite in Stainless Steel Weld Metal”, Welding Journal 35(11),521-s to 528-s
DeLong, W.T., and Reid, Jr., H.F. 1957, “Properties of Austenitic Chromium inAustenitic Chromium-Manganese Stainless Steel Weld Metal”, Welding Journal,36(l), 41-s to 48-s
DeLong, W.T. 1974, “Ferrite in Austenitic Stainless Steel Weld Metal”, WeldingJournal 53(7): 273-s to 286-s
Dijkstra, F.H., and de Raad, J.A., “Non-destructive Testing of Duplex Welds”,Duplex Stairdess Steels 97 – 5ti World Conference Proceedings, Stainless SteelWorld, 01997 KCI Publishing
Elmer, J.W., and Eagar, T.W., 1990, “Measuring the residual ferrite content ofrapidly solidified stainless steeI alloys”, Welding Journal 69(4), pp. 141-s to 150-s
Espy, R.H. 1982, “Weldability of Nitrogen-Stren=@hened Stainless Steels”,Welding Journal 61(5), 149-s to 156-s
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Ginn, B.J., Gooch, T.G., Kotecki, D.J., Rabensteiner, G. and Merinov, P., “WeldMetal Ferrite Standards Handle Calibration of Magnetic Instruments”, WeldingJournal, pp. 59-64
Gunia, R.B., and Ratz, G.A., “The Measurement of Delta—Ferrite in AusteniticStainless Steels”, WRC Bulletin 132, New York, N.Y, August 1968.
Gunia, R.B., and Ratz, G.A., “How Accurate are Methods for MeasuringFerrite?”, Metals Progress, p. 76, Jan. 1969
Hull, F.C. 1973, “Delta Ferrite and Martensite Formation in Stainless Steels”,Welding Journal 52(5): 193-s to 203-s
International Standards Organization (1S0) Draft, “Standard Practice for theEstimation of Ferrite Content in Austenitic Stainless Steel Castings”, 1995
Kotecki, D.J. 1995, “HW Commission II Round Robin of FN Measurements –Calibration by Secondary Standards”, HW Document 11-C-043-95, InternationalInstitute of Welding
Kotecki, D.J. 1998, “FN Measurement Round Robin Using Shop and FieldInstruments After Calibration by Secondary Standards – Final Surnrnary Report”,IIW Document 11-C-1405-98, International Institute of Welding
Kotecki, D.J. 1990, “Ferrite Measurement and Control in Duplex Stainless SteelWelds”, Weldability of Materials – Proceedings of the Materials WeldabilitySymposium, October, ASM International, Materials Park, Ohio.
Kotecki, D.J. 1983, “Molybdenum Effect on Stainless SteeI Weld Metal Ferrite”,IIW Document 11-C-707-83 .
Kotecki, D.J. 1986, “Silicon Effect on Stainless Weld Metal Ferrite”, IIW. Dec.II-C-779-86, The American Council of the International Institute of Welding,Miami, F1.
Kotecki, D.J., 1995, “Standards and industrial methods for ferrite measurement”,Welding in the World 36, pp. 161-169
Kotecki, D.J. 1988, “Verification of the NBS-CSM Ferrite Diagram”,International Institute of Welding Document II-C-834-88
Kotecki, D.J. and Siewert, T.A., “WRC-1992 Constitution Diagram for StainlessSteel Weld Metals: A Modification of the WRC 1988 Diagram”, WeldingJournal, May 1992, Vol. 71, pp. 171-s –178-s
Lake, F.B. 1990, “Effect of Cu on Stainless Steel Weld Metal Ferrite Content”,Paper presented at AWS Annual Meeting
Leger, M.T., “Predicting and Evaluating Ferrite Content in Austenitic StainlessSteel Castings”, Stainless Steel Castings, ASTM STP 756, V.G. Behal and A.S.Melilli, Eds., American Society for Testing and Materials, 1982, pp. 105-125
Long, C.J. and DeLong, W.T. 1973, “The Ferrite Content of Austenitic StainlessSteel Weld Metal”, Welding Journal 52(7), 281-s to 297-s
Merinov, P., Entin, E., Beketov, B. and Runov, A. 1978, (February), “Themagnetic testing of the ferrite content of austenitic stainless steel weld metal”,NDT International, pp.9-14
McCowan, C.N. and Siewert, T.A. and Olson, D.L. 1989, “Stainless Steel WeldMetal: Prediction of Ferrite Content”, WRC Bulletin 342, Welding ResearchCouncil, New York, N.Y.
Olson, D.L. 1985, “Prediction of Austenitic Weld Metal Microstructure andProperties”, Welding Journal 64(10): 281s to 295s
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Pickering, E.W., Robitz, E.S. and Vandergriff, D.M., 1986, “Factors influencingthe measurement of ferrite content in austenitic stainless steel weld metal usingmagnetic instruments”, WRC Bulletin 318, Welding Research Council, NewYork, USA, pp. 1-22.
Potak, M. and Sagalevich, E.A. 1972, “Structural Diagram for Stainless Steels asApplied to Cast Metal and Metal Deposited during Welding”, Avt. Svarka (5): 10-13
Pryce, L. and Andrews, K.W. 1960, “Practical Estimation of compositionBalance and Ferrite Content in Stainless Steels”, Journal of Iron and SteelInstitute, 195:415,417
Rabensteiner, G., 1993, “Summary of 5fi Round Robin of FN Measurements”,IIW Document 11-C-902-92, International Institute of Welding.
Redmond, J.D. and Davison, R.M., 1997, “Critical Review of Testing MethodsApplied to Duplex Stainless Steels”, Duplex Stainless Steels 97 – 5* WorldConference Proceedings, Stainless Steel World, 01997 KCI Publishing
Reid, Harry F. and DeLong, William T. “Making Sense out of FerriteRequirements in Welding Stainless Steels”, Metals Progress, June 1973, pp. 73-77
Schwartzendruber, L.J., Bennet, L.H., Schoefer, E.A., DeLong, W.T., andCampbell, H.C. 1974, “Mossbauer Effect Examination of Ferrite in StainlessSteel Welds and Castings”, Welding Journal 53(l), 1-s to 12-s
Szumachowski, E.R., and Kotecki, D.J. 1984, “Effect of manganese on StainlessSteel Weld Metal Ferrite”, Welding Journal 63(5), 156-s to 161-s *Could be64(5)
Siewert, T.A., McCowan, Cl?., and Olson, D.L. 1988, “Ferrite NumberPrediction to 100 FN in Stainless SteeI Weld Metal”, Welding Journal 67(12):289-s to 298-s
Simpkinson, T.V., “Ferrite in Austenitic Steels Estimated Accurately~’ Iron Age,170, pp. 166-169, 1952
86
51. Simpkinson, T.V., and Lavigne, M.J., “Detection of Ferrite by its Magnetism;’Metal Progress, Vol. 55, pp. 164-167,1949
52. Stalmasek, E., “Measurement of Ferrite Content in Austenitic StainIess SteelWeld Metal giving Internationally Reproducible Results”, Intemational Instituteof Welding Document II-C-595-79
53. Stalmasek, 1986,WRCBulIetin318, Welding Research Council, New York,USA, pp. 23-98
54. Thomas, Jr., R.D. 1949, “A Constitution Diagram Application to Stainless WeldMetal”, Schweizer Archiv fur Angewandte Wissenschaft und Techrik, No. 1,3-24
ANSI/AWS A4.2-91, “Standard Procedures for Calibrating Magnetic Instrumentsto measure the Delta Ferrite Content of Austenitic and DupIex Austenitic-FerriticStainless Steel Weld Metal, ISBN: 0-87171 -36-6 American Welding Society,Miami, Florida, 1991
ASTM A240-85, “Standard Specification for Heat-Resisting Chromium andChromium Nickel Stainless Steel Plate, Sheet and Strip for Pressure Vessels”,American Society for Testing Materials, Philadelphia, Pa
ASTM A799, “Standard Practice for Steel Castings, Stainless, InstrumentCalibration, for Estimating Ferrite Content”, ASTM International, WestConshohocken, Pennsylvania, USA, 1992
ASTM A800, “Standard Practice for Steel Casting, Austenitic Alloy, EstimatingFerrite Content Thereof”, ASTM International, West Conshohocken,Pennsylvania, USA, 1991
ASTM A890, “Standard Specification for Castings, Iron-Chromium-Nickel-Molybdenum Corrosion-Resistant, Duplex (Austenitic/Ferritic) for GeneralApplication”, ASTM International, West Conshohocken, Pennsylvania, USA,1991
ASTM E562, “Practice for Determining Volume Fraction by Systematic ManualPoint Count”, ASTM International, West Conshohocken, Pennsylvania, USA,1997
ASTM El301, “Standard Guide for Proficiency Testing by InterlaboratoryComparisons”, ASTM International, West Conshohocken, Pennsylvania, USA,1995
1S0 8249-85, “Welding – Determination of Ferrite Number in austenitic weldmetal deposited by covered Cr-Ni steel electrodes.”
Materials Joining Research GroupDepartment of Materials Science and Engineering
The University of Tennessee – Knoxville
in conjunction with
The Welding Research Council
and
The Steel Founders’ Society of America
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1.0 Introduction:
The UT Materials Joining Research Group is initiating a Ferrite MeasurementRound Robin study to examine the following issues:
● The reproducibility of ferrite measurement data, between laboratories, usingMagne Gage and Feritscope@ techniques
. The applicability of manufacturing cast secondary standards from static andcentrifugal castings
● A more defined correlation between ferrite measurement techniques will beestablished. These techniques include manual point counting and measurementby Magne Gage and Feritscope@.
2.0 Round Robin Timeline:
In an effort to minimize the work effort, the tirneline described in Table 1 hasbeen established. The primary goal is to send the round robin samples betweenthe Welding Research Council (WRC) committee members prior to the WRCHigh Alloys Committee meeting in May. The sample set will then proceed toSteel Founders’ Society of America (SFSA) participants before returning to UT.
Table 1: UT Ferrite Measurement Round Robin Schedule
Program Launch Date: February 24, 1999 -”Samples Arrive /D. Kotecki: March 1,1999D. Kotecki Evaluation Period: March 1-10, 1999Samples Shipped to Participant 2: March 11,1999Samples Arrive /F. Lake: March 15,1999F. Lake Evaluation Period: March 15-24,1999Samples Shipped to Participant 3: March 25,1999Samples Arrive /S. Jana March 29,1999S. Jana Evaluation Period: March 29, 1999 through April 7,1999Samples Shipped to Participant 4: April 8,1999Samples Arrive /T. Siewert: April 12, 1999T. Siewert Evaluation Period: April 12-21, 1999Samples Shipped to Participant 5: ApriI 22, 1999Samples Arrive /J. Feldstein: April 26, 1999J. Feldstein Evaluation Period: April 26, 1999 through May 5, 1999Samples Shipped to Participant 6: May 6,1999-\I/$..c ffjg’h AN oys Nhti’tlg: il&y 10 – 12, 1999
Table l(Continued~ UT Ferrite Measurement Round Robin ScheduleR. Bird Evaluation Period: May 10-19, 1999Samples Shipped to Participant 7: May 20,1999Samples Arrive /C. Richards: May 24,1999C. Richards Evaluation Period May 24,1999 through June 2, 1999Samples Shipped to UT: June 3,1999Publication of Results: June 30,1999
N-: This timetable establishes 9 business days for experimental evacuation and1 business day is provided to ship the samples to the next participant.Shipping will be provided. We anticipate that the WRC members willlikely require less analysis time, as they are adequately equipped tomeasure ferrite on a routine basis. Should the Round Robin progressahead of (or behind) schedule, each participant wilI be appropriatelynotified.
3.0 Requests of the Participants:
The Materials Joining Group is grateful for your participation in this study. Wevalue your time and seek to minimize your work effort. However, the followingrequests are made to project your success.
3.1 Adherence to the Timetable:
Should a participant, for any reason, be unable to adhere to the timetableoutlined in Table 1, please notify the Materials Joining Research Group. UTcontacts are listed as follows:
Dr. Carl D. Lundin William J. Ruprecht IIIDirector, Materials Joining Research Graduate Research AssistantPhone: (423) 974-5310 Phone: (423) 974-5299FAX: (423) 974-0880 FAX: (423) 974-0880E-Mail: lundin@,utk.edu E-Mail: [email protected]
In the event of such an occurrence, a quick scheduling response will facilitatethe implementation of this round robin.
3.2 (?uestions regarding the Work Request
If at any point in this investigation, there is a question with regard toexperimental techniques, calibration procedures, reporting of data orscheduling, feel free to contact our ofiice.
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3.3 Suwzestions from the Partici~ants:
If you have any suggestions to improve the implementation of furtherstudies, please submit them with your data package.
Immediate suggestions which would require a modification to yourindividual test procedure should be forwarded immediately.
Comments, are always appreciated.
4.0 Work Reauest:
5.1 Ferrite Measurement:
Participants are asked to measure ferrite @N) on the sample set provided.Acceptable methods of ferrite measurement incIude, but are not limited to,the following:
Magne Gage Feritscope@ MP3 (MJ?3-C)
Using the attached checklist and the provided forms, participants will beasked to calibrate (or report their current calibration) according to AWSA4.2 prior to taking measurements.
5.1 Reporting of Data:
Using the attached forms, participants are asked to record their ferritemeasurements and return them to the Materials Joining Group. A mailingenvelope is included for the return of the entire package.
A Federal Express mailer has been included so that you may forward thecast standards to the next participant. Please use a Federal Express Boxand utilize suitable packing material to prevent darnage during shipping.
The sample set provided contains 12 rectangular blocks which have beenfabricated from austenitic and duplex stainless steels. They are labeled onthe ends with a sample code. The following table correlates the samplecode with the alloy type.
* Indicates that the material was centrifugally cast, as opposed to astatic casting.
5.2 Condition of Samples:
Each sample has been prepared, on the measurement face, with a surfacefinish equal to a metallographic polish. This was done so that amicrostructural evaluation could be performed prior to initiating thero~d-robin. Note the presence of a scribed circle on the measurementface. No ferrite measurements are to be taken outside of this circle. Thisis done so that we may directly compare ferrite measurements withmetallographic point counting techniques.
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6.0 Ferrite Measurement Instruction Set:
6.1 Magne Gage:
Appendix 1 contains an operator checklist and instruction set forperforming ferrite measurements with a Magne Gage.
6.2 Feritsco~e@
Appendix 2 contains an operator checklist and instruction set forperforming ferrite measurements with a Feritscope@
6.3 Other:
Should a participant wish to utilize other methods of ferrite measurement,please contact the Materials Joining Group as indicated in Item 3.1 of thismanual.
7.0 Comdetion of your Work Effort:
7.1 Forwarding the Sam~Ie Set to the Next Participant:
A Federal Express invoice has been provided (pre-addressed / pre-paid).Please use a standard Federal Express Box to ship the sample set to thenext participant.
7.2 Returning vour Data to the University of Tennessee:
A return envelope (pre-addressed) has been provided. Please seal thismanual, containing your data, charts, graphs and comments in theenvelope and forward it to the University of Tennessee (c/o The MaterialsJoining Research Group).
8.0 Acknowledgements:
We would like to acknowledge the following individuals for their guidance and supportin performing this round robin study.
Dr. Damian Kotecki – Lincoln Electric Mr. Tom Siewert – N.I.S.T.Mr. Frank Lake – ESAB Mr. Ron Bird – Stainless FoundryMr. Sushil Jana – Hobart Brothers Co. Mr. Joel Feldstein – Foster Wheeler
ADPendix 1: Ferrite Measurement Using a Magne Gage
Please follow the checklist (below) to assure proper measurement and documentation offerrite content for each sample. You may check the boxes, located before each itemnumber, as you proceed through this study.
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1.
2.
3.
4.
Review AWS A4.2-91, Section 4, pp. 4-6, to familiarize yourselfwith the proper methods of calibrating a Magne Gage instrument. A COpyof AWS A4.2-91 has been included for your convenience and is located atthe end of this manual.
Calibrate your Magne Gage according to the specificationsoutlined in AWS A4.2-91 (Section 4).
Please include all graphs and tables used to calibrate your Magne Gageand report whether you are calibrating to Primary Thickness Standards orSecondary Weld Metal Standards. Calibration to Primary ThicknessStandards is preferred. Examples of suitable calibration curves are locatedin the AWS specification on Page 6 and are illustrated by Figure 1.
The data recording sheet is presented on Page 3 of this appendix. Pleaseprovide the Instrument Type / Serial Number, Operator Name and Date,as indicated.
Utilize the samples submitted and reference the characteristics of eachblock, as described in Item 5 of this manual. Petiorm 5 “sets” ofdeterminations as described below. Each “set” must contain 6 separatedeterminations. Only the highest FN measured will be reported for each“set” of determinations.
Lower the plastic “magnet guard” until it is in contact with the sample andis wholly contained within the scribed circle. Perform 6 successivedeterminations without moving the plastic “magnet guard”. This willconstitute a single “set” of determinations. Ferrite determinations takenoutside the scribed circle must be considered invalid.
Record only the highest FN, achieved fi-omeach of the 6 determinations,in the space provided. After each “set” of 6 determinations, raise theplastic “magnet guard” and lower it again, within the scribed circle, priorto performing the next “set” of determinations. The highest determinedFN should be recorded for each individual “set” of determinations.
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Review the data for each sample. For each sample, your data sheetshould reflective FN determinations, which are the highest FN’sobserved in each of the measurement ‘%etsJJ. (Each ‘(set” should be..composed of 6 individual measurements, obtained at one location withinthe scribed circle, with the plastic “magnet guard” in contact with thesample.)
5. Upon completion of the successive ferrite determinations, return the—samples to their plastic cases and proceed to Appendix 2, Ferrite
Appendix 2: Ferrite Measurement Using a Feritscope@Please follow the checklist (below) to assure proper measurement and documentation offerrite content for each sample. You may check the boxes, located before each itemnumber, as you proceed through this study. .
1. Review AWS A4.2-91, Section 5, p.7, to familiarize yourself withthe proper methods of calibrating a Feritscope@ instrument. A copyof AWS A4.2-91 has been included for your convenience and islocated at the end of this manual.
2. Calibrate your Feritscope@ according to the specifications outlinedin AWS A4.2-91 (Section 5). Calibration to secondary caststandards will be the accepted method for this study. Standardizedforms have been provided to assist you in recording yourcalibration and are located on the following pages.
Table 1 is a sample Feritscope@ calibration form, provided courtesy ofIIS/IIW-1405-98. A blank calibration form is provided, in the form ofTable 2 of this appendix. Highlight the measurements which exceedaccepted tolerances, as demonstrated (Blue Underlined) in Table 1, onyour calibration sheet (Table 2).
If you wish to provide data for multiple Feritscopes@ audlor operators,additional copies of calibration forms maybe made from this packet.
-3. Locate the data recording sheet (Data Sheet 2) on Pages 4-5 of thisappendix. Please provide the Instrument Type / Serial Number,Operator Name and Date, as indicated. If you wish to record datafor multiple operators and/or Feritscopes@, additional copies of thedata recording sheet should be made, as needed. Pleasedifferentiate between Feritscope@ model numbers and operators inthe “background information”.
-4. Utilize the Sample Set and reference the characteristics of eachblock, as described in Item 5.0 of this manual.
By lowering the probe perpendicular to the sample, petiorrn 10 successivemeasurements within the scribed circle. Ferrite measurements takenoutside the scribed circle must be considered invalid.
Record each measurement on the attached data sheets and report theaverage FN value observed for each sample.
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-5. Upon completion of the ferrite measurements, return the samplesto their plastic cases and review your paperwork to ensure that all data hasbeen included. This concludes ferrite measurement by the Feritscope@technique.
and The Welding*Research Council Subcommitteeon Welding Stainless Steels
Under the Direction ofAWS Technical Activities Committee
Abstract
Calibration procedures are specified for a number of commercial instruments that can then provide reproduciblemeasurements of the ferrite content of austenitic stainless steel weld metals. Certain of these instrum~nts can be furthercalibrated for memrernents of the ferrite content of duplex austenitic-ferritic stainless steel weld metals. Calibrationwith primw stmd=ds (non-ma=~etic coating thickness standards from the U. S. National Institute of Standards andTechnology) is the preferred method for appropriate instruments. Alternatively, theseand other instrumentscanbecalibratedwithweldmetalsecondarystandxds.
!:””AII standards (codes, specifications, recommended practices, methods, classifications, and guides) of the Amencm ‘<.Welding Society are voluntary consensus standards that have been developed in accordance with the rules of theAmerican National Standards Institute. When AWS standards are either incorporated in, or made part of, docuentsthat are included in federal or state laws and regulations, or the regulations of other governmental bodies, theirprovisions carry the full legal authority of the statute. In suchcases,anychangesin thoseAWSstandardsmustbeapprovedby the governmental bodyhavingstatutoryjurisdictionbeforetheycan becomea part of thoselawsandregulations.In ~ C=es,thesestandardscarrythefulllegalauthorityoftheContractorotherdocumentthat invokestheAWSstandards.where this contractualrelationshipexists,chmgesin or deviationsfromrequirementsof an AWSstandardmustbe W agreementbetweenthecontractingparties.
@ 1991 by American Welding Society. All rights reserved
~’Printed in the United States of America ~: ,
Note: The primary purpose of AWS is to serve and benefit its members. To this end, AWS provides a forum for theexchange, consideration, and discussion of ideas and proposals that are relevant to the weldimg indutry and theconsensus of which forms the basis for these standards. By providing such a forum AWS does not assume my duties towhich a user of these stand~ds maybe required to adhere. By publishing this standard, the American Welding Societydoes not insure anyone using the information it contains against any liability arising from that use. Publication of astandard by the American Welding Society does not carry with it any right to make, use, or sell any patented items.Users of the information in this standard should make an independent investigation of the validity of that informationfor their particular use and the patent status of any item referred to herein.
With regard to technical inquiries made concerning AWS standards, oral opinions on AWS standards may berendered. However, such opinions represent only the personal opinions of the particular individu~ giving them. Theseindividuals do not speak on behalf of AWS, nor do these oral opinions constitute official or unoffici~ opinions orinterpretations of AWS. In addition, oral opinions are informal and should not be used as a substitute for an officialinterpretation.
This standard k subject to revision at anytime by the AWS Ffler Metal Committee. It must be reviewed every five ye~and if not revised, it must be either reapproved or withdrawn. Comments (recommendations, additions, or deletions)ad my pertinent data that maybe of use in impro~g thisstandardare requested and should be addressed to AWSHeadquarters. Such comments will receive ~ef~ consideration by the AWS Fiier Met~ co~ttee ad the authorof the comments will be informed of the Committee’s response to the comments. Guests are invited m attend allmeetings of the AWS Ffler Metal Committee to express their comments verbally. Procedures for appe~ of an adversedecision concerning all such comments are provided in the Rules of Operation of the Technic~ Acti~& Committee.A copy of these Rules can be obtained from the &nerican Welding Society, 550 N.W. LeJeune Road, P.O. Box 351040,Miami, Florida 33135.
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Personnel
AWSCommitteeon Ftier Metal
D. J. Kotecki, Chairman
R. A. LaFave, 1st Vice ChairmanJ. P. Hunt, 2nd Vice Chairman
H. F. Reid, Secretary
D. R Amos
B. E. Anderson
K. E. Banks
R S. Brown
J. Caprarola, Jr.
L J. Christensen*R J. Chrirtofel
D.A. DelSignore
H. K Ebert
S. E. Ferree
D.A. FinkG. Halktrom, Jr.
R L Harris’
R W. HeidD. C. HeltonW. S. Howes
R W JudR. B. Kadiyala
P. A. Kammer*J. E. Kelly
G. A. Kur&ky
N. E. tirson
A. S. Lin.ueruon
G. H. MacShane
D. 1?Manning
M. Z MerloS. .X Mem-ck
G. E. Metzger
J. W. Mortimer
C. L h%~i
Y. Ogata*1 Payne
R L Peaslee
E. W. Rckering, Jr.M. A. Quintana
S. D. Reynokls, Jr.*
L E RobertsD. Rozet
*Advisor
The Lincoln Electric CompanyElliott CompanyINCO Alloys InternationalAmerican Welding SocietyWestinghouse Turbine PiantAlcotecTeledyne McKayCarpenter Technology CorporationAlloy Rods CorporationconsultantconsultantWestinghouse EIectric CompanyExxon Researciiad Engi.neetig Company –Alloy Rods CorporationThe Lincoln Electric CompanyUSNILC-RIIR. L. Harris AssociatesNewport News ShipbuildingConsuh.ntNational Electrical Manufacturers AssociationChrysler MotorsTech-alloyMaryland,IncorporatedEutecticCorporationEutecticCorporationMarylandSpecial~WueUnionCarbide,IndustrialGasDivisionconsultantMACAssociatesHobart BrothersCompanyTri-hlark,IncorporatedTeledyneMcKayconsultantconsultantNavalSea+SystemsCommandKobeSteel,LimitedSchneiderServicesInternationalWallCoimonoyCorporationconsultantGeneralDynarnicsCorporationWestinghouseElectricPGBUCanadianWeldingBureauconsultant
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P. K. Salvesen
H. S. Sayre*
O. W. Seth
R. W Straitord
R D. Sutton
R. A. Swain
J. W. Tackett
R. D. Z$omas, Jr.
R. iTmerman*
R Z Webster
A. E Wiehe*W. A. Wzehe
W L Wilcox
E J. Wmor*
K G. Woid
T J. Wonder
American Bureau of ShippingconsultantChicago Bridge and Iron CompanyBechtel Group, IncorporatedL-Tee Welding and Cutting SystemsWelders SupplyHaynes International IncorporatedR. D. Thomas and CompanyCONARCO, S. A.Teledyne Wah ChangConsultantArcos AIloysconsultantconsultantAqua Chem IncorporatedVSE Corporation
AWS Subcommittee on Stainless Steel FflIer Metals
D. A. DeKignore, Chairman
H. E Reid, Secretary
E S. BabishKE. Bartla
R. S. Brown
R A. Bushey
R. J. ChristoffelD. D. Crocket~
E A. FlynnA. L Gombach*
B. Herbert*
J. 1? HuntR B. ~adiyala
P. A. Kamme#’
G. A. Kurirkyw z LQyo*
G. H. MacShane
A. H. MilleF
Z Ogala*
M. P. ParekhE. W. picketing, Jr.
L J. Privoznik
C. E Ridenour
H. S. Sayre’R W Straiton
R. A. Swain
J. G. Tack
R Tihnerrnan’
W A. W~he*
K L Wilcox
D. W Yonker, Jr.
●Advisor
Westinghouse Electric CorporationAmerican Welding SocietySandvik, IncorporatedTeledyne McKayCarpenter Technology CorporationAlloy Rods CorporationconsultantThe Lincoln Electric CompanySun R&MChampion Welding ProductsUnited Technologies-ElliottInto Alloys InternationalTechalloy Maryland, IncorporatedEutectic CorporationMaryland Specialty WueSandvik Steel CompanyMAC AssociatesDISCKobe Steel, LimitedHobart Brothers CompanyconsultantconsultantTri-Mark, IncorporatedconsultantBechtel Group, IncorporatedWelders SupplyArmco, IncorporatedCONARCO, S. A.Arcos AlloysconsultantNational Standards Company
Lincoln Electric CompanyWestinghouse Electric Corporation
Clarkson CoUegeConsuhl’ltAllegheny Ludlum SteelOak Ridge National LaboratonesTeledyne McKayU.S. Nuclear Regulatory CommissionUniversity of Illinois at ChicagoGeneral AssociatesAlloy RodsGML PublicationsEdison Welding InstituteNiobium Products CompanyUniversity of TennesseeINCO Alloys InternationalConsultantCCM 2CIU0Preciion Components CorporationWeld MoldconsultantNational Institute of Standards and TechnologyLehigh UniversityWelders SupplyR. D. Thomas and CompanyOntario HydroJ. A. Jones Applied ResearchWestinghouse Electric Corporation
Foreword
(This Foreword is not a part of A.NSIIAWS A4.2-91, Standard Procedures for Calibrating Magnetic Instruments to
Measure the Delta Ferrite Content of Austenitic and Duplex Austenitic-Ferritic Stainless Steel Weld Metal, but isincluded for information purposes only.)
This document is a revision of the Standard Froceduresfor Calibrating Magnetic Instruments to Measure the Delta
Ferrite Content of Amtenitic Stainless Steel Weld Metal, fmt published in 1974 and revised in 1986. This revision wasby the Subcommittee on Welding Stainless Steel of the Welding Research Council and by the AWS Ffler MetalCommittee. The current revision expands the range of calibration and measurement to include, for the fWt time,duplex austenitic-ferntic stainless steel weld metals.
A certain minimum ferrite content in most austenitic stainless steel weld metals is useful in assuring freedom frommicrofissures and hot cracks. Upper limits on ferrite content in austenitic stainless steel weld metals can be imposed tolimit corrosion in certain media or to limit embrittlement due to transformation of ferrite to sigma phase during heattreatment or elevated temperature service. Upper limits on ferrite content in duplex austenitic-ferritic stainless steelweld metals can be imposed to help assure ductility, toughness, and corrosion resistance in the as-welded condition.
Reproducible quantitative ferrite measurements in stainless steel weld metals are therefore of interest to ftier metalproducers, fabricators of weldments, weldment end users, regulatory authorities, and insurance companies.
Comments and suggestions for improvement are welcome. They should be sent in writing to Secretary, Filler MetalCommittee, American Welding Society, 55o N.W. LeJeune Road, P.O. Box 351040, Miami, FL 33135.
L Scope molten state upon freezing. Much of the original ferrite
1.1 This standard prescribes procedures for the calibra-that formed upon freezing transforms to austenite dur-
tion and maintenance of calibration of instruments foring cooling.
measuring, by magnetic attraction or permeability, thedelta ferrite content of an austenitic or duplex austenitic- 2.2 Draw Ffig. A weld pad surface preparation tech-
ferntic stainless steel weld metal in terms of its Ferrite nique suitable for subsequent ferrite measurements only
Number (EN). _ up to about 20 FIJ. (See 8.2.) A sharp clean 14-inch mill
1.2 A thorough review of the Append= is recom-mended before any instrument is calibrated or used. TheAppendix presents background information which isessential to understanding the many problems and pit-falls in determining and specifying the ferrite content ofweld metals.
1.3 Calibration can be accomplished with the use of theNational Institute of Standards and Technology (N’IST,formerly National Bureau of Standards) primary stan-dards or weld metal secondary standards. At the presenttime, only three instruments ~agne-Gage (iicluding atorsion balance using essentially a Magne-Gage Number3 magnet, hereinafter referred to as a MaO~e-Gage type
instrument), Feritscope(also sometimesidentiled asFen-itescope), and InspectorGage]canbecalibratedbythe use of NIST pri.mw standards, and the range ofpossiblecalibrationdependsupon theparticularinstru-ment(seeTables1,2,and3).Thisisnot anendorsementof anyparticularinstrument.(See3.1.)
— —
2. Definitions*
2.1 Delta Ferrite. Tle ferrite which remains at roomtemperature from that which was formed from the
1. For AWSterms and definitions, refer to the latestedition ofANS1/AWS A3.0, Stmhd Terms and Definitions. Pleasenote that some of the terms and deffitions used in this publi-cation are not included in AWS A3.O.They are either newterms defined after the latest revision of A3.Oor they are usedspecillc to this publication
bastard fde which has not been contaminated by ferro-magnetic materials, held parallel to the base metal andperpendicular to the long axis of the weld metal sample,is stroked smoothly with a fm downward pressure,forward and backward along the weld length. No crossffig ~ done. The f~hed surface k flat with at least
a 1/8-in. (3.2 mm) width where all weld ripples areremoved.
23 Ferrite Number (FN). An arbitrary, standardizedvalue designating the ferrite content of austenitic andduplex austenitic-ferntic stainless steel weld metal (seeAppendix A2).
2.4 Primary Standards. Specimens with accurate thick-ness of non-magnetic materird on carbon steel base platecontaining 0.25 percent carbon maximum. Each primarystandard is assigned an ~ of an equivalent magneticweld metal, this assigned value being speci.ilc to a par-ticular mike (and model, if applicable) of measuringinstrument (i.e., Magne-Gage, Feritscope, or InspectorGage). (See Appendix A3.L)
The primary standards upon which the standardprocedures are based are the NIST’S sets of coatingthickness standards, consisting of a very uniform layerof electroplated copper covered with a chromium flashover a carbon steel base. (See AppendLX A4.1.)
~.~ Weld Met~ Secondav S~dm& Small weld
metal pads certified for FN in a manner traceable tothese standard procedures. (See Append~ A4.2.)
3.1 Primary Standards. Since each type of ferritemeasuring instrument responds differently to the pri-mary standards, it is not possible to specify a genericcalibration procedurq rather, it is necessary to tailor acalibration procedure to a particular instrument. As ofthe previous revision of this standard, three types ofinstruments had been subjected to extensive testing, and
detailed procedures and appropriate tables and valueswere contained in that standard to provide for theircalibration to primary standards. These instrumentsare the Magne-Gage-type instruments, Feritscope, andInspector Gage. At the time of publication of AiYSI/AWS A4.2-86, however, the probe of the Feritscope waschanged so that the Feritscope calibration table does notapply to newer instruments. This situation continues.Since that time, the range of calibration by primary
stand~ds of Magne-Gage-type instruments has beenexpanded to include l?Ns appropriate to duplex austen-itic-ferritic stainless steel weld metals.
3.2 Secondary Standards
3.2.1 Calibration by means of primary standards isthe preferred method of maintaining calibration ofappropriate instruments. But the need for frequent in-process checks is recognized along with the fact thatprimary standards are not necessarily “durable” for fre-quent use outside of a laboratory environment. There-,fore, it is recommended that a set of secondary standardsbe used for frequent in-process checks. (See AppendixA4.~.)
3.2.2 When secondary standards are used, the aver-age reading on each standard shall be within the ma.xi-
mum allowable deviation from the calibration curve asspecified in Table 4. If a maximum allowable deviationis exceeded, the instrument cannot be considered cali-brated. Calibration with primary standards or instru-ment repair is then necessary.
3.23 Instruments for which~here is not a detailedcalibration procedure in this standard utilizing primvstandards can only be calibrated using secondruy st=-dards. Refer to Section 7 for proper calibration ins~c-tions.
33 For all calibration methods and instruments, therage of c~bration is dermed by the ~tervd of ~S
between and includin~ the lowest FN standard and thehi~est ~ st~d~d wed ~ deVelop@the calibration
according to the correspondm~ procedure.
I
4
Table 3Ferrite Numbers (FN) for Primary Standards for Inspector Gage Calibration* .6.
4.1 Calibration by Means of Primary standards. AllMagne-Gage-type instruments carI be calibrated by thefollowing procedure. Torsion balances other than aMagne-Gage may not require use of counterweighs, sothat statements regarding ranges of calibration may notapply. However, the requirements for the number ofstandards for calibration over a specific FN range sh~
2.Trademark of Magne-Gage Sales & Service.(See Appen-dix A6.1.)
---- ---—-=-..—.=..__.
apply to all Magne-Gage-type instruments. (See Appen-dix A6.1.)
%.’:,) 4.1.1 The FNs shall be assigned from Table 1to each
.“ of the available primary standards (coating thicknessstandards) as defined in 2.3. For thicknesses betweenthose given in the table, the FNs shall be interpolated asclosely as possible. Alternatively, FN maybe calculateddirectly from one of the two following formulas:
For thickness (T) in roils:ln(FN) s 4.5891-0.50495 In(T) -0.08918 [ln(T)]2
+ 0.01917 [1n(T)]3 -0.00371 [1n(T)]4
For thickness (T) in mm.ln(FN) = 1.8059-1.11886 in(T) -0.17740 [ln(T)]2
-0.03502 [1n(T)]3 -0.00367 [ln(T)]4
See Section 9 for information on the precision of themeasurements.
4.1.2 MaWe-Gage-type instruments are sensitive topremature magnet detachment from a standard or froma sample due to very small vibrations. The Magne-Gageminimizes, but does not eliminate, this effect, as com-paxed to other torsion balances. Repetitive measure-ments at a given point will yield a range of FN values dueto this effect, and the range increases with increasingFN. With a Magne-Gage, above 20 FN, it is necessaryto make several measurements at any given point of a
F-, standard or sample, and to accept only the highest FN., as the correct value for that point. Whh other Magne-
Q-”< Gage.t~e instruments (torsion balances) th~ practice iS
necessary for all levels of FN.
4.1.3 A Magne-Gage can be used for measurementsover a range of about 30 FN with a single calibration.The exact range to be used at any given time is deter-mined by the choice of a counterweight (if any) added tothe balance beam of the instrument at a hole providedfor this purpose. The hole is located about 1.5 inches(38 mm) from the fulcrum opposite from the point ofsuspension of the magnet (see Figure Al). Care shouldbe taken that the counterweight, if used, is free to swingwithout touching any other part of the instrument whenthe magnet is in contact with specimen or standards.Without a counterweight, a Magne-Gage wiiI coverfrom Oto about 30 ~. With a counterweight of about7.5 grams, a Ma@e-Gage wiu cover from about 30 tO60 ~ with a counterweight of about 15 g, the mea-surement range will be about 60 to 90 I?N. Exact rangeswill depend upon the precise weight of the counter-weight and upon the strength of the magnet in use. Aseparate calibration is required for each counterweight,and recalibration is required whenever the magnet ischanged.
c)“, 4.1.4 Wkhout a counterweight, eight or more pri-.1 mary standards shaU be used, with nominal thicknesses
that provide corresponding Ferrite Numbers well dis-
tributed over the range of O to 28 FN. With the No. 3magnet in place, the zero point (the whhe dial reading atwhich the magnet lifts free from a completely nonmag-netic material) shall be determined. U a counterweight isused, five or more primary standards, similarly welldistributed, shall be used, but no zero point can bedetermined. In either case, the white dird reading foreach ofthe available primary standards covering the FNrange of interest shall then be determined. (See Appen-dix A4.1).
4.1.5 The white dial readings shall be plotted on Car-tesian coordinate paper versus the FNs as illustrated inFigure 1. If no counterweight is used, the zero pointreading (white dial reading when the ma~et just barelylifts from a nonmagnetic material) on the dial of the gagecan be included as O FN.
4.1.6 A “best fit”straight line shall be drawn throughthe points plotted in accordance with 4.1.5. Altern-atively,a linear regression equation shall be fit to the datacollected as described in 4.1.4. Magne-Gages tested todate have produced a straight lineup to at least 10 FN.Most yield a straight line through all points, but somehave shown a slight bend. An example of each is shownin F@re 1. For acceptable calibration, ail points mustfall within the maximum allowable deviations shown inTable 5. If any of the calibration points faUoutside of theallowed variations, the data shall be restudied, or themanufacturer of the instrument shall be consulted, orboth.
4.1.7 Two common sources of discrepant readingsduring calibration (as well as during measurement) aremechanical vibrations and dirt (usually ma=metic par-ticles) clinging to the magnet. Either factor tends toproduce premature detachment of the magnet from thesample, with a correspondingly low FN determination(high white dial reading). A vibration-free environmentis essential to accurate FN determination, especiallyabove 15 FN. Wiping of the ma=wet end with a clean,
Table 5Tolerance on the Position of
Calibration Points Using Primary Standards—.
Ferrite Nu%ber Rmtge Maximum Allowable De~iation
0[05 * 0.40over 5 to IO k 0.50cwer 10to 15 * 0.70over 15 to 20 * 0.90over 20 to 30 21.00over 30 to 90 =5% of assigned FN
Note The maximumvti,ations in the positionof the edibcuionpointsfromthe curve(exampleis shownin l?ig.i) ocertrwhentheprimarythicknessstandardsare acthe maximumfivepe~nt V~~-tionfromthecertifkdthicknesses.
Figure 1—Examdes of ~alibration Curves for Two Ma~ne-Ga2e Instruments,Eac~with a No. 3 Magnet for Measuring
lint-free cloth is suggested when dirt is encountered. Incase of doubt, examination of the maagnetend under amicroscope is appropriate.
4.1.8 The graph plotted as in 4.1.6, or a regressionequation fit to it, may now be used to determine the FNsof stainless steel weld metals from the white dial readingsof the instrument obtained on those weld metals with thesame No. 3 magnet and counterweight (if used).
the Delta Ferrite-Conte& of Weld Me&Is
4.2 Calibration by Means of Weld Metal SecondaryStandards
4.2.1 Calibration by primary standards is the recom-mended method, as previously mentioned, but caiibm-tion utiliing secondary standards is acceptable: Five dr
3. Weld metal second~ standards have been commerciallysold by The Welding Institute, Abington Hall, Abington,Cambridge, CB1 SAL, United Kingdom.
3,:...:.<)
-. --—. . - —..s-—~z ———— .— ..—-— — ——. .——
more such standards are required for calibration curves
forO to 15 FN; eight or more are required for calibrationN curves for Oto 30 FN; and five or more are required for..,1’. any range of 30 FN above 15FN. ln all cases, the Ferrite
Numbers of the standards shall be well distributed overthe range of interest. (Seealso Append~ A4.2).
4.2.2 It should be recognized that weld metal second-
ary standards are unlikely to provide readings frompoint to point that areas uniform as those from primarystandards. Care must therefore be exercised to takereadings on secondav standards in precisely those loca-tions used in assigning the original l?Ns to the standards.In case of doubt, the producer of the secondary stan-dards should be consulted.
4.2.3 Other than the departures noted in 4.2.1 and4,2.z, the remtinder of the calibration procedure with
secondary standards shall be the same as that used withprimary standards as given in 4.1.2 through 4.1.8.
5. Calibration of Feritscopes(“~erritescopes”)
5.1 Calibration by Means of Primary Standards
5.1.1 This instrument is calibrated to the FN scaleby the manufacturer, but ca.Iibration should be vefilecl
->. by the user. The only Fentscope4 (Ferritescope) which
dcan be calibrated with primary standards according toTable 2 is the pre-1980 Model FE8-KF with ardogreadout and duakontact (“normalized~ probe. Notables for calibration with primary standards are avail-able for post-1980 instmments (those with digital read-outs or single-pole probes). Other Feritscopes may becalibrated by weld metal secondary standards as de-scribed in Section 7.
4. Trademark of l%cher Technology. (See Appendix A6.2.)
5.1.2 The manufacturer’s instructions with regard tothe use of the instrument and the adjustments of thescale shall be folIowed.
5.1.3 The ~s shall be reigned from Table 2 to eachof the avaiIable prinmty thickness standards as definedin 2.3. For thicknesses between those given in the table,the FNs shall be interpolated as.closely as possible. Eightor more thickness standards shall be used, with nominalthickness corresponding to Ferrite Numbers well dis-tributed in the range O to 25 FIN (see Appendix A4. 1).The instrument reading for each of the available primarystandards shall then be determined.
5.1.4 The instrument readings shall be plotted onCartesian coordinate paper versus the FINassigned fromTable 2 for each primary standard, A“best fit”lineshallbe drawn through the data. Alternatively, a regressionequation shall be fit to the data collected as described in5.1.3.
5.1.5 For approved calibration, all readings shall fallwithin the maximum allowable deviations from the“best fit” line shown in Table 6. If any of the calibrationreadings fall outside of these allowed variations, the datashall be restudied, or the manufacturer of the instrumentshall be consulted, or both.
5.1.6 The graph plotted as in 5.1.4, or a regressionequation fit to it, may now be used to determine the FMof stainless steel weld metals from the instrumentreading.
5.2 Calibration by Means of Weld Metal Secondary
Standards
5.2.1 As previously mentioned, calibration to pri-mary standmds is the preferred method for suitableinstruments, but calibration to weld metal second~standards is acceptable. Calibration to weld metalsecondmy standards is necessary for other Feritscopes.
k....
Table 6Maximum Allowable Deviation of the
—Periodic Ferrite Number fFN) Check for Feritscopes (Ferritescopes)
Maximum AIIowableDeviation of the Periodic Ferrite Number Check
From the Ferrite Number From the Ferrite Number From the Ferrite NumberValue Assigned to the ValueAssignedto the Value Fii .Assignedto the
Primary Standard Secondary Stmdard Seeondary Stan&d
Ferrite Number R~ge in Table 2 by the Seller by tbe User
5.2.2 Refer to 7.2 for instructions to calibrate theFeritscOpe to weld metal secondary standards.
6. Calibration of inspector Gages5
6.1 Calibration By Means of Primary Standards ‘
6.1.1 This instrument is the Inspector Gage ModelNumber 111 with either a 6F (“% ferrite? Or a7F (~scale. The latter is preferable because it has smallerdivisions. (see also Appendix A6.3).
6.1.2 The manufacturer’s instructions with regard tothe use of the instrument and adjustments of the scaleshall be followed.
6.13 The FM shall be assignedfrom Table 3 to eachof the availab[eprimary thickness standards as definedin 2.3, For thicknessesbetween those givenin the table,the FNs shall be interpolated ascloselyaspossible.Eightor more thicknessstandards shall beused, with nominalthicknessescorresponding to Ferrite Numbers welldis-tributed in the range Oto 30 FN (see Appendix A4.1).The instrument readingfor each of the availableprimarystandards shall then be determined.
6.1.4 The instrument readings shall be plotted onCartesian coordinate paper versus the FN assignedfromTable 3 for each primary standard. A “bestfit”line shallbe drawn through the data. Alternatively, a re~essionequation shall befit to the data collectedas describedin6.1.3.
6.1.5 For approved calibration, all readingsshalIfallwithin the maximum allowable deviations from the“best fit” line shown in Table 7. If any of the cfllbrationreadingsfall outsideof these allowedvariations, the datashallbe restudied, or the manufacturer of the instrumentshall be consulted, or both.
5. Trademark of Elcometer Instruments Ltd. (See AppendixA6.3.)
6.1.6 The graph plotted aa in 6.1.4, or a regressionequation fit to it, may now be used to determine the .
FNs of stainless steel weld metals from the instrument ~ ‘l.>.reading. .. II
6.2 Calibration by Means of Weld Metal SecondaryStandards -- ---
6.2.1 As previously mentioned, calibration to pri-mary standards is the preferred method, but calibrationto weld metal secondary standards is acceptable.
6.2.2 Refer to 7.2 for instructions to calibrate theInspector Gage to weld metal secondary standards.
.—
7. Calibration of Other Instruments
7.1 Calibration by Means of Primary Standards. Asofthis revision of this standard (see3.1)only Ma5ne-Gagetype instruments, Feritscopes with normalized probes,and Inspector Gagescan be calibrated to this standardby means of primary standards. All other instrumentsmust be cahbrated by means of weld metal secondarystandards (see also Appendix A6.4).
7.2 Calibration by Means of Weld Metal SecondaryStandards
7.2.1 Other instruments can be calibrated by weldmetal secondary standards to produce a satisfactorycorrelation between the instrument readout and weldmetal I?N. While it may be desirable that the instrumentreadout be precisely the calibrated value of FN, this isnot essential, so long as a unique correlation betweenreadout and FN can be determined. Such instrumentsmay be used.if they have been calibrated using second-ary weld metal standards to which H% were assigned byan instrument with primary standard calibration.
7.2.2 Five or more such secondary standards arerequired for calibration curves covering O to 15 ~,eight or more such secondary standards are required for
Table 7Maximum Allowable Deviation of the
Periodic Ferrite Number (FN) Check for Inspector Gages
From the FerriteNumber FromtheFerriteNumber From the FerriteNumberValueAssignedto the ValueAssignedto the ValueFii ksi:ned to the
Primary Standard Secondary Standard Secondq Stantid
Ferrite Number Range in Table 3 by the Seller by the USIX
oto5 * 0.40 * 0.40 &o.~()
over 5 to 10 * 0.40 * 0.4’0 * 0.20
over 10to 15 * 0.70 ~ ().70 * ().~()
over 15 * 1.0 * 1.0 * 0.30
‘~>
3~..,
3‘e”.. ,./
calibration from O to 28 ~, and five or more suchsecondary standards are required for calibration of any
\ 30 FN intend above 15 FN. In all cases, the Ferrite.,;1 Numbers of the secondary standards shall be well dis-
tributed over the range of interest.
7.2.3 Instrument readings shall be determined foreach of the available secondary standards and, if possi- .ble, for a zero point. When taking readings on secondarystandards, the same precaution noted in 4.2.2 should betaken.
7.2.4 Instrument readings shall be plotted againstassigned secondary standard FN values on Cartesiancoordinate paper, and the zero point can be included ifapplicable.
7.2.5 A“best fit’’smooth line shall be drawn throughthe points plotted in 7.2.4. For acceptable calibration,no data point may vary from the curve any more thanthe allowable deviations shown in Table 4. If any pointfalls outside of the appropriate allowed deviation, thedata shall be restudied, or the manufacturer of theinstrument shall be consulted, or both.
7.2.6 The graph plotted as in 7.2.4, or a regressionequation fit to it, may now be used to determine the FNsof stainless steel weldmetals over the calibration range.
7.2.7 It is the responsibility of the user to ensure thatP, the instrument isproperly calibrated-i.e., such that the
dresults obtained with weld metal secondary standards inthe FN range(s) of use are within the expected range ofvariations shown in Table 4.
8. Use of Calibrated Instruments
8.1 Maintaining Calibration. Instruments Rust bechecked penodic~y on a regular basis against primary
or secondary standards to ensure and verify the mainte-nance of the original calibration. Records of such checksshali be maintained. It is the responsibility of the user tocheck at a frequency which is adequate to maintaincalibration. For frequently used instruments, a weeklycalibration check is recommended. For seldondy usedinstruments, a calibration check before each use isrecommended. Two”standards, one ne& each extremeof the calibration range being checked, shall be used foreach of the ranges shown in Tables 4 and 6 through 8, asappropriate, for which the instrument is used. When theinstrument no longer produces values within the maxi-mum deviation spechled in the relevant table, it shall beremoved from service and the manufacturer shall beconsulted. (see Appendix A3.2).
8.2 Variations in Measurements. Based upon roundrobin tests within the Welding Research Council Sub-committee on Weldlng Stainless Steels, the FNs deter-mined by these instruments are expected to fdl withinthe limits shown in Table 9, IO,or 1I as compared to theoverall average FN values of stainless steel weld metalschecked on other instruments of the same type cali-brated to this standard. When measurements are madewith a variety of calibrated instrument types, somewhatlarger variation in measurements than those indicated inTable 9,10, or 11 might be expected, but the magnitudeof the variation has not been determined. Weld ripplesand other surface perturbations must be removedbecause surface finish affects measurement accuracy.Up to about 20 FN, the practice known as “draw ftig”produces acceptable accuracy (see 2.2). For accurateand reproducible ferrite measurements, above 20 FN, aMagne-Gage No. 3 magnet or equivalent requires a flatsurface at least 1/8-in. (3.2 mm) in diameter finished nocoarser than with a 600 grit abrasive [about 8 microinches(0.2 microns) RMS]. Rougher surfaces or convex sur-
Table 8
Maximum Allowable Deviation of the IPeriodic Ferrite Number (FN) Check for Magne-Gage-Type Instruments
Maximum Allowable Deviation of the Periodic Ferrite Number Check—
—
From the Ferrite Number From the Ferrite Number From the Ferrite Number
Value Assignedto the Value ksio~ed to the Value l?ii Assignedto the
Primary Standard Second~ Stmdmd Secondary Stand~d
Ferrite Number Range in Table 1 by the Seller by the User
oto5 20.50 * 0.50 * 0.20
over 5 to 10 * 0.50 ~ 0.50 & 0.20i 0.60 & 0.30
over 10 [0 15 &0.60over 15 to 25 &0.80 k 0.80 * 0.40 I
over 25 [0 90 &5% of assigned = 5V0 of assigned & 3% of assigned
in Measurements with CalibratedMagne-Gage-Type Instruments’
Ferrite Nttntber 67%of the 95%of theRange ktruments Instruments
o to 10 * 0.30m * 0.60~over 10to 18 * 0.35 m * 0.70 mover 18to 25 * 0.45 m * 0.90 mover 25 to 90 t 5?Z0of mean 3 10’%of mean
FN value FN value
*Basedupon WRC round robh tests.
Table 10Expected Range of Variation
in Measurements with CalibratedFeritscopes (Ferritescopes)”
Fem”te Number 67%of the 95%of theRange Instruments Irqtruments
o to 10 * 0.20 m * 0.40 mover 10 to 18 * 0.40m &0.80 FNover 18to 25 * 0.50 m * l-()I=Jqover 25 to 80 * 5’%0 of mean * 107oof mean
FN value FN value
● Based upon WRC round robin tests.
faces will result in artificially low FN values and shall beavoided. Other instruments may respond differently to
rough, convex, or narrow surfaces and should be ex~-ined fully before use. At all ferrite levels, surface prepa-ration must be accomplished without contamination byferromagnetic materials.
Table 11Expected Range of Variation
in Measurements with CalibratedInspector Gages*
Ferrite Number 67%of the -= 95%of theRange Instruments Instruments
o to 10 20.20 FN * 0.40 mover 10 to 18 + 0.40 m = 0.80 lWover 18to 30 * 0.50 FN * 1.0 m
“BaseduponWRC round robin tests.
9.
9.1
.—
Sigtilcant Figures in lleportingMeasurement Results
Calibration Data. For purposes of developingcal-ibration data or demonstrating compliance of aninstrument with calibration requirements, the numberof signitlcant figures shown in the relevant Table hereinshall be used.
9.2 Measurement Data. For purposes of reportingmeasurement data on weld metal test samples or demon-strating compliance with the requirements of a speei.flca-
3
tion other than this specification, the precision implied Fby the number of signflcant figures in the Tables herein
:.,
is generally inappropriate. For ferrite measurements of25 FN or higher, rounding off to the nearest wholenumber conveys appropriate precision. For ferritemeasurement of 5 to 25 FN, rounding off to the nearest0.5 FN conveys appropriate prectilon. For ferrite mea-surements less than 5 FN, rounding off~o the nearest0.1 FN conveys appropriate precision.
—
I
●“-)
,?
~.,
I
\,.,.;l
Appendix
((..
(This Appendix is not a part of ANSI/ AWS A4.2-91, St~rzdardProcedures for Calibrating Magnetic Instruments to
Measure the Delta Ferrite Content of Austenitic and Duplex Austenitic-Ferritic Stainless Steel Weld Metal, but isincluded for information purposes onIy.)
Al. Acknowledgment
These standard procedures are based upon the studiesand recommendations made by the Subcommittee onWeldlng Stainless Steel of the High AIIoys Committeeof the Welding Research Council (WRC)$ The docu-ment on which most of this standard is based is the
- Calibration Procedure for Instruments to Measure the
Delta Ferrite Content of Austenitic StainlessSteel WeldMetal, published by the WRC on July 1, 1972.
Expansion of the measurement system beyond 28 FNis based upon Ektension of the WRC Ferrite Number
System, D. J. Kotecki, Welding Journal, November,1982 and International Institute of Welding Documents11-C-730-84, II-C-821-88, H-C-835-88 and II-C-836-88.
A2. Ways of Expressing Ferrite Content
A2.1 The methods of determining ferrite content instainless steel weld metals have evolved over an extendedtime period. The interested reader is referred to WRCBulletin 318 (September, 1986). Only a few of the perti-nent conclusions of that Bulletin are summarized brieflyin the following paragraphs.
A2.2 Measured Percent Ferrite. The percent ferrite inaustenitic stainless steel weld metals in the past has toooften been regarded as a firm fried value. Extensiveround robins have been run onsets o~weld metaI speci-mens, cOnt&ning up tO a nominal 25 percent ferrite, inthe U.S. under the sponsorship of the WRC and onsimilar sets in Europe by the International Institute ofWelding (IISV). These round robins showed that mostlaboratories used somewhat different calibration ewesas well as a variety of instruments. At nominal levels ofup to 10 percent ferrite, which is often the most useful
6. Welding Research Council, 345 East 47th St., New York,NY 10017.
and pertinent range, the values obtained by participat-ing laboratories ranged from (3+6to 1-6 times the nomi-
nal value. The instrument calibration procedure definedin this standard is designed to overcome this problem.
A similar problem existed with metallographic deter-minations due to the extreme freeness of the ferrite inweld metals, variations in the etching media and thedegree of etch, and to the Quantitative Television Micro-scope (QTM) settings, if a QTM was used. Similarprobleins, though perhaps to a lesser degree, have beenencountered with magnetic saturation, x-ray diffraction,Mossbauerstudies, and with other methods of determin-ing the ferrite content of weld met~. ThUS a “percent
ferrite” figure in past literature k very dependent uponthe source, and should be defined in relation to theinstrument, the laboratory using iq and the calibrationsource, or to the diagram if derived from a constitutiondiagram. In the opinion of the WRC Subcommittee, ithas been irnpossible, to date, to determine accurately thetrue absolute ferrite content of stainless steel weld metals.
A23 Ferrite Number. Because on a given specimen,laboratory A might rate the percent ferrite at as low as3 percent, laboratory B at 5 percen~ and laboratory C atas high as 8 percent, the WRC Subcommittee decided touse the new term Ferrite Number (~ to define theferrite quantity as measured by instruments calibratedwith its recommended procedure. Thus, FN is an arbi-trary, standardized value related to the ferrite content ofan equivalently magnetic weld metal. It is not necesstiythe true absolute ferrite percentage of the weld. l%
below 10 do represent an excellent average of the “per-cent ferritem as determined by U.S. and world methodsof me~uring delta ferrite, based upon the previouslydiscussed round robins conducted by the WRC Sub-committee and the IIW Subcom.mission II-C. FNsabove 10 clearly exceed the true volume percent. hfa&netic saturation measurements on castings of knownpercent ferrite have shown that the magnetic response ofa given percent ferrite depends upon its composition. So
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any relation between percent ferrite and FN will beitiuenced somewhat by composition of the ferrite. For
common duplex austenic-ferntic weld metals, it is notunreasonable to estimate that the percent ferrite is on theorder of 0.7 times the FN x measured herein, but thisshould not be considered as exact.
A2.4 Ferrite Content Calculated From ConstitutionDiagrams. The several committees that have investi-gated and reviewed this subject recommend for mostapplications the use of measured ferrite as opposed totheuse of ferrite calculatedfrom the weldmetalanalysis.The basic reason for this is that the variablesinvolvedindetermining the chemicalcomposition, and other varia-bles involved in the diagrams themselves,are verylikelyto have substantially greater effects than those asso-ciated with the direct determination of ferrite contentusing instruments calibrated in accordance with thisstandard, Nevertheless, constitution diagrams are veryuseful tools, even though they are less exact, becausethey permit anticipati~n or prediction of ferritecontentfor a variety of situations. By taking into account dilu-tion effects,such diagrams can also be useful for antici-pating or predicting the ferrite content of weld overlaysand d~sirn.ilar metal joints.
The Schaeffler diagrmn, developed in the late 1940s,presents its values as percent ferrite, but these are said tobe directly equivalent to FNs. The DeLong diagram,January 1973 version, was the fmt diagram presented interms of FN. Espy, in 1982, proposed a rnodiflcation ofthe SchaeffIer Diagram to take into account high nitro-gen, high manganese stainless steel weld metals. Themore recent diagram of Siewefi, McCowan, and Olson,prepared under WRC sponsorship in 1988, is, at thetime of this writing, the best estimation tool available formost austenitic and duplex austenitic-ferntic stainlesssteel weid metals. See Weldz%gJournal,December, 1988,pp. 289s-298s, or WRC Bulletin 342, April, 1989. Toassist in Ferrite Number estimation, a Personal Com-puter “software package, FERRITEPREDICTOR, isavailable from the American Welding Society, although,at the time of this writing, only the Schaeffler andDeLong Diagrams are included.
A3. Cautions on the Use of Ferrite151umber
A3.1 Instrument Calibration
A3.1.l Various thicknessesof nonmagnetic materialovercarbon steelrepresent a veryconvenientmethod ofcalibrating instruments for the measurement offerrite instainless steal weld metals. Useful general informationon the subject can be obtained from the latest editionof The American Society for Testing and Materials(ASTM) B499, Standard Method for Measurement of
Coating Zhicknessesby Magnetic Method Nonmagnetic
Coatings on Magnetic BaseMetals? The response of theinstrument when a nonmagnetic “skin” is between the
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measuring probe and the plate, versus its response to ‘.
ferrite in stainless steel weld metal at several ievels, canbe plotted and the relationship between them estab-lished. A change in the magnet size or strength, or in theprobe characteristics, changes the relationship. Thus, acalibration cume or table for FN versus nonmagneticcoating thickness for a Magne-Gage-type instrument
(Figure Al) will be ddferent for each of the magnets(Nos. 1,2,3 and 4) becausethe strengths of the magnetsare dtiferent.
A3.1.2 Whh Magne-Gage-type instruments, onlycalibration using a No. 3 magnet is considered in thisstandard. A weaker magnet Q?o. I or No. 2), ifused withthe calibration points of Table 1, will on weld metal yieldfalsely high FN values. Conversely, a stronger magnet(No. 4), if used with the calibration points of Table 1,will on weld metal yield falsely low FNvalues. IftheNo.3 magnet of a Magne-Gage is damaged, such as byrough handling or exposure to an ac field which weak-ens it, it will also yield false readings. Work within theWRC Subcommittee on Welding Stainless Steel, onbehalf of the International Institute of Welding, Sub-commission II-C, has demonstrated that accurate read-ings on weld metal are obtained via calibration from
1Table 1when the magnet strength is such that it provides < .’~a tearing-off force as a function of FN of 5 FN/grarn “ .‘+0.5 FN/gTa.m. Wkh a torsion balance other than aMagne-Gage, compliance with this requirement is deter-mined directly from the slope of the calibration line.With a Magne-Gage, this can be evaluated simply bysuspending a 5 gram iron weight from the No. 3 magnet.When the white dial of the Magne-Gage is turned to justbarely lift the weight past the balance point of theinstrument, the reading shouid correspond to 25 FN*2.5 FN using the cahbration line of white dial readingsversus FTJ.
A3S3 It is strongly recommended that referenceweld metal secondary standards be used along with thecalibration curves obtained from primary standardswhen using a Feritscope to check for compliance withTable 6, when using an Inspector Gage to check forcompliance with Table 7, or when using a Magne-Gagetype instrument to check for compliance WithTable 8. Ifcompliance cannot be obtained as required by theappropriate table, the instrument is in need of recalibra-tion or semicing by the manufacturer, or it is not suitablefor calibration with primary standards.
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J7. ASTM standards can be obtained from the Americm ~::Society for Testingand hdaterials,1916Race .3reI%Pbilticl- :/”pbi~ PA 19103.
A3.2 Instrument Malfunction. Recalibration or re-checking of each instrument at periodic and sometimti
i frequent intervals is necessary to ensure that the instru-.,‘1
/;’ ment is operating properly (see 8. 1).Permanent magnetsmay be partially demagnetized by exposure to any sig-nificant ac field such as that generated by a strongalternating current in a wire or by a weaker alternatingcurrent in a coil. The tips of such permanent magnets, or
of the probes which are used to establish a magnetic fieldin the specimen, may become worn and the response ofthe system may change for this reason. Bearings maybecome fouled with dirt and thus fail to operate freely.
A4. Standards for InstrumentCalibration
A4.1 Primary Standards. NIST8 coating thicknessstandards were developed many years ago to crdibrateinstruments for the determination of coating thickness.The standards useful for the determination of deltaferrite consist of varying thicknesses of copper electro-plated on a carbon steel base and protected with achromium flash. NESTcertfles the thicknessof the totalcoating to within &5% of the stated thickness, but themajority will be within* 270or even A l~o.The use of thetwo sets listed below is recommended for calibration up
These 8 thicknesses corresp~d nominally to 0.26,0.39,0.50,0.64,0.80, 1.00, 1.53, and 1.94~ respec-tively.
Sets SRM 1368 (8 to 20 rnils), SRM 1369 (25 to60 roils) and individual standards are no longer avai.l-able. The-8 rnil thickness is now available in set SRM1362A.
For Ferrite Numbers from about 30 to about 85, theuse of the three sets listed below is recommended forcalibration
SRM 1323, Nominal Thicknesses-3.7, 4.4,5.3, and6.6 rnils (.094,.112, .135, and .167 mm, respectively).
The sets can be ordered from NIST. Other thicknesssets are also available, but do not, of themselves, offerclose enough spacing of corresponding Ferrite Numbersfor adequate cdlbration.
A4.2 Secondary Standards
A4.2.1 WeldMetal SecondaryStandards. Magneticinstruments may also be calibrated by using weldmetalsecondary standards prepared from weld metals ratedby 2 or more instruments carefully calibrated throughthe use of these standard procedures. Each such stan-dard should be provided with FN values at specitlcpoints on its test surface.Thesesecondarystandards canbeused for the czdibrationof a suitable instrument or formaintaining calibration. They can also be used to estab-lish the relationship between other instruments andMagne-Gage-typeinstruments.
A4.2.2 Other Types of Secondary Standards. Theuse of cast specimens or powder compacts is riskybecausethe size,shape, and orientation of the ma=~eticparticles may influence the response of the magnetic orother type probes to varying degrees. However, castspecimens or powder compacts calibrated with oneinstrument traceable to this procedure can be used forcalibrating instruments of the same type and manufac-ture or for day-to-day veri.ticationof such instruments.
A5. Effect of Ferrite Size, Shape, andOrientation
It has been established that the ferrite size, shape, andorientation can influence the relative response of the lowfield strength maagnetsand proba tied with the me~ur-@ ~t~ments. For this reason, a measuting instm-
ment may respond differently to a given volume percentferrite in a stainless steel weld metal as compared to thesame volume percent ferrite in a cast stainless steel, oreven in a solution heat treated stainless steel weld metal.The ferrite in as-welded weld metal up to about 15 FNis very fme and in the form of lacy, dendritic stringengenerally perpendicular to the fikon line, and oftenextensively intercorme~ed at ferrite contents over 3 or4 FN. Above about 15 FN in as-weided weld metal, theferrite and austenite generrdly form laths which are alSOvery free. The ferrite in castings is usually much largerand tends to be more spheroidrd and much less inter-connected except perhaps at very high ferrite contents.The ferrite in wrought steels and in solution heat-treatedweld metals tends to be lesser in volume and morespheroidized than in an as-welded weld metal of thesame composition because heat treatment tends to
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transform some ferrite to austenite and spheroidize thebalance. Since the volume percent of ferrite in castings isin c[ose agreement when measured by either magneticresponse or by metal.lographic point count, the ferritecontent of castings k expressed as a percentage and notby the arbitrary FN, as noted in ASTM Practice A800.
A6. Instruments
A6.1N12gne-GageandMagne-Gag&TypeInstruments
A6.1.1TheMwne-Gageg(FigureAl)isusabIeonlyin the flat positionon relatively small specimens.Theprobe is a long, thin magnethung on a spiral spring.Thespring is wound by means of turning a knob with acorresponding reading on a dial. When the magnet ispulled free of a specimen,the white dial reading used inconjunction with the calibration curve establishes theFN of the specimen.
A6.1.2 Returning the Magne-Gage periodically tothe factory for maintenanceisdesirabie.With heavyuse,1year is a reasonable time; with light use, 2 years.
A6.1.3 A Magne-GageNumber 3 Magnet or equiv-alent can be used with a variety of torsion balances toobtain the same results as are obtained with a Magne-Gage. A complete example of such a Magne-Gage-type,instrument is given in “Extension of the WRC FerriteNumber System” referencedin Section Al. Numerousother conf@rations could also be conceived. This isoutside the scope of this Standard.
A6.2 Fentscope 1°(Ferritescope). This instrument, con-sisting of a probe connected by a cable to an electronicspackage (Figure A2), is usable in any position. Severalmodels and a variety of probes are available. Only onemodel and probe has been shown to be able to becalibrated with primary standards as given in Table 2(see5.1.1).All others must be cdlbrated withweldmetalsecondary standards. Models are availablein either bat-tery powered or accurrent versions. At least one modelcan be calibrated withsecondary standards up to 80 FN.
A6.3 Inspector Gage.’1This instrument (Figure A3), isusable in any position. It is a hand held magneticinstrument with thumb actuated spMgs tension. Theinstrument gives direct readings in FN if it is a newmodel designed to do so. Older models can be rebuilt bythe manufacturer to give acceptable readings on weld
9. Manufactured by Magne-Gage Sales & Service, 14376Dorsey MN Road, G1enwood,MD 21738.10. Manufactured by F~cher Technology, 75o MarshallPhelps Road, Windsor, CT 06095.1I. Manufactured by E!cometer Instruments Ltd., 1180EastBig Beaver,Troy, MI 48083.
metal in terms of FN. As of 1989, the ability of InspectorGages to determine ferrite above 30 FN is unknown.
A6.4 Other Instruments
A6.4.1 The following instruments at the time of thewriting of this revision are not capable of being cali-brated to primary standards. They can, however, becalibrated to weld metal secondary standards and pro-duce acceptable consistent results. A@n, it is theresponsibility of the user to ensure that instrument cali-bration is maintained and to have the instrumentrepaired by the manufacturer if consistent readings onthe weldmetal secondarystandards cannot be obtained.As of 1989,the ability of these instruments to determineferrite above 30 FN is unknown.
A6.4.L1 Ferrite Indicator (more commonlycalleda Severn Gage).12This instrument (Figure A4) isusablein any position. It is a go-, no-go-type gage which deter-mines whether the ferrite content is above or below eachof a number of inserts of various magnetic strengthswhich come with the instrument. At least one unthreaded-test insert must be available for use in conjunction withone of the threaded inserts with specified FN values. Thepurpose of the unthreaded inserts is to assure that themagnet has not lost strength. Details may be obtainedfrom the manufacturer for conversion of percent ferritevalues on earlier model Sevcm gagesto FN. Severegages calibrated directly in terms of FN are now avail-able. Older model gages can be converted to the FNscale by the manufacturer.
A6.4.1.2 Foerster Ferrite Content Meter.13 This isa ligh~ portable, battery-operated instrument (FigureA5) usable in any position. It’ closely resembles theFeritscope in its operation except that it has a singlecontact point probe which allows ferrite determinationin very localized regions. On older models, the meteroutput indicates ferrite content as a percentage, whichcan be effectively converted to FN values by the use ofsuitable weld metal secondary standards to produce asatisfactory Calibration cume. Newer models are nowavailable on which the meter reads directly in FN values.—
A6.4.2 Anumber ofother magneticmeasuringinstru-ments are available for various purposes. Many areregarded as not suitable in their present form becauseoflimitations such as range, problems in calibration, orvarying response due to the position of use or to theirrelation to the north-to-south magnetic field lines of the
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12. Manufactured by Severe Engineering Co., Inc., 98 Edge- .. .wood Stre% Annapolis, MD 21401.
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13. Marketed by Foerster Instrument Inc., 202 Rosemont ‘“>’Dr., Coraopolii, PA 15108.
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(A) STANDARD MAGNE-GAGE
Il.
(B) MAGNE-GAGE FROM REAR. COUNTERWEIGHTADDED TO LE17 SIDE OF BAIANCE BEAM
earth. One that seems promising is the FerntectorGageJ4 Instruments which are suitable in other respectsmust still be calibrated to the 17N scale in a mannertraceable to this standard. This can be accomplished bythe use of a set of 5 or more weld metal secondarystandards if the calibration is extended up to 15 FN, or8 or more if it is Up to 25 FN. The establishment of anadequate correlation is the responsibility of the user.
A7. Use of Calibrated Instruments
A7.1Distancefor FerromagneticMaterial. The FNvalues of sta.idess steel weld deposits on ferromagneticbase metal may be increasedby varyingdegxeeson eachinstrument depending on the distance of the magnet orprobe from the basemetal, on the ferritecontent, and onthe permeabilhy of the base metal. Hence, to limit theincrease in FN values to 0.2 FN maximum due to theeffect of a ferromagnetic carbon steel base metal, thecarbon steel base plate should be approximately 0.3 in.(8 mm) or more away from a Magne-Gage magnet orInspector Gage magnet, LOin. (25 mm) from a Ferrite
14. Manufactured by Elcometer Instruments Ltd., 1180 EastBig Beaver, Troy, MI 48083.
Indicator (Severe Gage), and 0.2 in. (5 mm) from aFeritscope or Foerster Ferrite Content Meter probe.For other instruments, a safe distance can be obtainedby experimentation or by contacting the instrumentmanufacturer. If it is not possible to obtain the aboveminimum distances from ferromagnetic materkd in aproduction situation, FN measurements can still bemeaningful if the effect of the proximity of the ferro-magnetic can be taken into account. One way to dothis is by comparing FN measured with ferromagneticmaterial in place to FN measured with ferromagneticmaterial removed using laboratory samples.
A7.2 Wrought Staixdes.sSteels. It is not intended thatthe determination of FN be extended to wrought stairl-less steels. Wrought steels are beyond the scope of thisstandard.
A73 Cast StaixdeSSSteels. The I?Ns are not used forcast stainless steels. The same measurement scales usedfor weld metals cannot be used for cast steels (see A5 foran explanation). To calibrate instruments for measuringthe ferrite content of cast stainless steels, obtain ASTMA799, Standard Praclice for Calibration Iitstrumentsfor Ertirnazing Ferrite Content of Cast Stainless Steek.
Equally useful will be ASTM A800, Standard Practicefor Estimating Ferrite Content in Atitenitic A11oY