ASTM_B_887_-_12.pdf

Designation:B88712Standard Test Method forDetermination of Coercivity(Hcs)of Cemented Carbides1This standard is issued under the fixed designation B887;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of magneti-zation coercivity(Hcs)of cemented carbide materials andproducts using coercive force instrumentation.It is patternedafter ISO 3326.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.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:2A340 Terminology of Symbols and Definitions Relating toMagnetic TestingB243 Terminology of Powder MetallurgyE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standard:Available from American National Stan-dards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY10036,http:/www.ansi.org.ISO 3326 Hardmetals-Determination of(the Magnetiza-tion)Coercivity3.Terminology3.1 Definitions:3.1.1 For definition of terms used in this procedure refer toTerminology A340 and Terminology B243.3.1.2 dcdirect current.4.Summary of Test Method4.1 A test sample is positioned in the dc magnetic field ofthe test apparatus and magnetized to technical saturation.Themagnetic field polarity is then reversed and the test sample isdemagnetized by increasing the energy of the reversed mag-netic field until the test sample reaches zero magnetism.Thecoercive force(Hc)is the magnetizing force required to returnthe saturated magnetic induction to zero.5.Significance and Use5.1 Measurement of coercivity provides a relative compari-son of carbide grain size,binder content,and possibly carbondeficiency for a given graded carbide material or product,andmay be employed as a non-destructive measurement indicatingdeviation from a specified norm.5.2 This test method allows the non-destructive estimate ofaverage carbide grain size in sintered cemented carbide hard-metals.It is appropriate for a wide range of compositions andtungsten carbide(WC)WC grain sizes,and can be used foracceptance of material or product to specification.6.Interferences6.1 Hcs measurement is a non-destructive“bulk”measure-ment that is averaged over the specimen volume.Bi-modalgrain size distributions will give approximately the same Hcvalue as would be obtained from a normal grain size distribu-tion about the same mean value.6.2 Large test specimens must be sized to fit within themagnetic field coil spacing available for the apparatus em-ployed.6.3 Small test specimens may be immeasurable if their sizeprohibits detection by the magnetic field coils for the apparatusemployed.6.4 Specimen shape,that is,symmetry and aspect ratio,influence Hc measurement values and repeatability of results.Test specimens should be positioned with their long axis in thedirection of the magnetic field.Asymmetrically shaped testspecimens should be tested in several positions,the measure-ment values recorded,and the average value reported.1This test method is under the jurisdiction of ASTM Committee B09 on MetalPowders and Metal Powder Products and is the direct responsibility of Subcom-mittee B09.06 on Cemented Carbides.Current edition approved May 15,2012.Published September 2012.Originallyapproved in 1998.Last previous edition approved in 2008 as B88703(2008)E01.DOI:10.1520/B0887-12.2For referenced ASTM standards,visit the 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 7.Apparatus7.1 Instrumentation capable of the dc magnetization ofappropriately sized test samples to technical saturation andaccurate measurement of the energy required to restore themagnetic induction to zero.8.Procedure8.1 For commercial instrumentation,refer to the equipmentoperators manual and follow the manufacturers operatinginstructions.8.2 Position the test sample in the center of the magneticfield.The test sample should be positioned with its long axis inthe direction of the magnetic field(see 6.4).8.3 Magnetize the test sample to technical saturation.8.4 Reverse the magnetic field polarity and demagnetize thetest sample to zero.8.5 Record the Hc measurement,that is,energy required to