1、Designation: B 887 03 (Reapproved 2008)e1Standard Test Method forDetermination of Coercivity (Hcs) of Cemented Carbides1This standard is issued under the fixed designation B 887; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEThe units statement in subsection 1.2 was corrected editorially in April 2008.1. Scope1.1 This test method covers t
3、he 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 stand
4、ard 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 AS
5、TM Standards:2A 340 Terminology of Symbols and Definitions Relating toMagnetic TestingB 243 Terminology of Powder Metallurgy2.2 ISO Standard:3ISO 3326 Hardmetals - Determination of (the Magnetiza-tion) Coercivity3. Terminology3.1 Definitions:3.1.1 For definition of terms used in this procedure refer
6、 toTerminology A 340 and Terminology B 243.3.1.2 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 increasin
7、g 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
8、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
9、 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 volu
10、me. 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
11、 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 thedir
12、ection 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 resp
13、onsibility of Subcom-mittee B09.06 on Cemented Carbides.Current edition approved April 1, 2008. Published April 2008. Originallyapproved in 1998. Last previous edition approved in 2003 as B 88703.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at
14、 serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Bar
15、r Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.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. Procedure
16、8.1 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 M
17、agnetize 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 todemagnetize the test sample.8.6 Replicate measurement of the same test sample shall bemade, reversing the polarity
18、 of the saturation and demagnetiz-ing magnet fields, where possible.8.7 For asymmetric sample shapes, repeat measurementsshall be made by repositioning the specimen in the dc magneticfield of the instrumentation with consideration being given tothe shape, that is, symmetry of the test sample, and to
19、 its aspectratio, that is, length versus width.9. Report9.1 Report the following information:9.1.1 Test sample identification,9.1.2 Average Hcs coercivity (amp per metre (A/m) oroersteds), and9.1.3 Range of measured Hc values, especially for replicatemeasurements of asymmetric sample shapes.10. Prec
20、ision and Bias10.1 PrecisionMeasurement of coercive force is a relativecomparison against well characterized reference materials (seeSection 8). No statement about precision can be made due tothe effects of test specimen shape, variations in the bindercontent that are within material or product spec
21、ification, andthe presence of carbon deficiency.10.2 BiasMeasurement of coercive force is a relativecomparison against well characterized reference materials (seeSection 8). No statement about bias can be made due to theeffects of test specimen shape, variations in the binder contentthat are within
22、material or product specification, and thepresence of carbon deficiency.10.3 No certified cemented carbide standards are availablefor coercive force measurement. Most common practice is thedevelopment of (internal) reference materials representative ofthe product(s) being evaluated.11. Keywords11.1
23、cemented carbide; coercive force; coercivity;magnetizationASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such pate
24、nt rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited eith
25、er for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair h
26、earing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).B 887 03 (2008)e12
