1、Designation:A799/A799M10(Reapproved 2015)Standard Practice forSteel Castings,Stainless,Instrument Calibration,forEstimating Ferrite Content1This standard is issued under the fixed designation A799/A799M;the number immediately following the designation indicates the yearof original adoption or,in the
2、 case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope*1.1 This practice covers the procedure for calibration ofinstruments to be used for estimating
3、the ferrite content of themicrostructure of cast stainless steels by magnetic response ormeasurement of permeability.This procedure covers bothprimary and secondary instruments.1.1.1 A primary instrument is one that has been calibratedusing National Institute of Standards and Technology-StandardRefe
4、rence Material(NIST-SRM)thickness coating standards.It is a laboratory tool to be used with test specimens.Someprimary instruments may be used to directly measure the ferritecontent of castings.1.1.2 Asecondary instrument is one that has been calibratedby the use of secondary standards that have bee
5、n measured bya calibrated primary instrument.Secondary instruments are tobe used to directly measure the ferrite content of castings.1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard.The values stated ineach system may not be exact equivalents;ther
6、efore,eachsystem shall be used independently of the other.Combiningvalues from the two systems may result in non-conformancewith the standard.1.2.1 Within the text,the SI units are shown in brackets.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its us
7、e.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2A941 Terminology Relating to Steel,Stainless Steel,RelatedAlloys,and Ferroall
8、oysB499 Test Method for Measurement of Coating Thicknessesby the Magnetic Method:Nonmagnetic Coatings onMagnetic Basis MetalsE562 Test Method for Determining Volume Fraction bySystematic Manual Point Count2.2 NIST Standard:NIST-SRM Coating Thickness StandardsNOTE1The specific coating thickness stand
9、ards previously refer-enced in this practice are no longer available.Similar ones are nowavailable from NIST.3.Terminology3.1 DefinitionsThe definitions in Terminology A941 areapplicable to this standard.3.2 Definitions of Terms Specific to This Standard:3.2.1 ferrite,nthe body-centered cubic microc
10、onstituentin stainless steel.3.2.2 ferrite percentage,na value designating the ferritecontent of stainless steels.3.2.2.1 DiscussionThe Steel Founders Society ofAmerica(SFSA)has assigned ferrite percentages to the seriesof NIST coating thickness standards3.This assignment wasbased on the magnetic at
11、traction for a standard magnet by thecoating standards when compared with the magnetic attractionof the same magnet by a series of cast stainless steels whoseferrite content had been determined by an accurate metallo-graphic point count.A similar assignment based on magneticpermeability was also est
12、ablished.Algebraic equations havenow been derived from a plot of the thickness of thesestandards and the assigned ferrite percentages.By the use ofthese equations,any primary instrument will have its calibra-tion traceable to the SFSAs instruments or any other calibratedinstrument and thus afford co
13、mparable reproducible ferritepercentages.It also allows traceability to NIST.3.2.3 secondary standards,na piece of cast stainless steelwhose ferrite percentage has been determined by a calibratedprimary instrument.1This practice is under the jurisdiction of ASTM Committee A01 on Steel,Stainless Stee
14、l and Related Alloys and is the direct responsibility of SubcommitteeA01.18 on Castings.Current edition approved Nov.1,2015.Published November 2015.Originallyapproved in 1982.Last previous edition approved in 2010as A799/A799M 10.DOI:10.1520/A0799_A0799M-10R152For referenced ASTM standards,visit the
15、 ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.DOI:10.1520/A0799_A0799M-04R09.3Aubrey,L.S.,Weiser,P.F.,Pollard,W.J.,and Schoefer,E.A.,“FerriteMeasurement
16、 and Control in Cast Duplex Stainless Steels,”Stainless Steel Castings,ASTM STP 756,ASTM,1982,p 126.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.2.3.1 DiscussionSecondary statements are used to cali-brate secondary instruments(see Calibration of SecondaryInstruments).4.Significance and Use4.1 The amount of ferrite present in an austenitic stainlesssteel has been sho