1、Designation: B 887 03Standard 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 year of last revisio
2、n. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 coer
3、cive force instrumentation. It is patternedafter ISO 3326.1.2 The values in either SI units or inch-pound units are tobe regarded separately as standard. The values stated in eachsystem may not be exact equivalents; therefore, each systemshall be used independently of the other. Combining valuesfrom
4、 the two systems may result in non-conformance with thestandard.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 appli
5、ca-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:A 340 Terminology of Symbols and Definitions Relating toMagnetic Testing2B 243 Terminology of Powder Metallurgy32.2 ISO Standard:ISO 3326 Hardmetals - Determination of (the Magnetiza-tion) Coercivity43. Termin
6、ology3.1 Definitions:3.1.1 For definition of terms used in this procedure refer toTerminology A 340 and Terminology B 243.3.1.2 dcdirect current4. Summary of Test Method4.1 A test sample is positioned in the dc magnetic field ofthe test apparatus and magnetized to technical saturation. Themagnetic f
7、ield 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
8、.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
9、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
10、 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 thema
11、gnetic 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
12、 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
13、Committee B09 on MetalPowders and Metal Powder Products and is the direct responsibility of Subcom-mittee B09.06 on Cemented Carbides.Current edition approved April 10, 2003. Published April 2003. Originallyapproved in 1998. Last previous edition approved in 1998 as B 88798.2Annual Book of ASTM Stan
14、dards, Vol 03.04.3Annual Book of ASTM Standards, Vol 02.05.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7. Apparatus7.1 Ins
15、trumentation 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 manufa
16、cturers 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 dem
17、agnetize 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 of the saturation and demagnetiz-ing magnet fields, where possible.8.7 For asymmetric sample sh
18、apes, repeat measurementsshall be made by repositioning the specimen in the d-cmagnetic field of the instrumentation with consideration beinggiven to the shape, that is, symmetry of the test sample, and toits aspect ratio, that is, length versus width.9. Report9.1 Report the following information:9.
19、1.1 Test sample identification,9.1.2 Average Hcs coercivity (amp per meter (A/m) oroersteds), and9.1.3 Range of measured Hc values, especially for replicatemeasurements of asymmetric sample shapes.10. Precision and Bias10.1 PrecisionMeasurement of coercive force is a relativecomparison against well
20、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 specification, andthe presence of carbon deficiency.10.2 BiasMeasurement of coercive force is a rel
21、ativecomparison 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 material or product specification, and thepresence of carbon deficiency.10.3 No certified cemen
22、ted 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 cemented carbide; coercive force; coercivity;magnetizationSUMMARY OF CHANGESCommittee B09 has i
23、dentified the location of selected changes to this standard since the last issue (B 887 98) that may impact the use of this standard.(1) Section 1.2 was added to the Scope to indicated the use ofSI units in the standard. Current Section 1.2 was renumbered to1.3.(2) The misspelling of asymmetrically
24、was corrected inSection 6.4.(3) Section 9.1.2 was removed because the reporting of masshas no bearing on the value obtained for coercivity testing.(4) Section 9.1.3 was renumbered to 9.1.2. The units werechanged to reflect SI units as the acceptable standard.(5) Section 9.1.4 was renumbered to 9.1.3
25、.ASTM 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 patent rights, and the riskof infringement of such rights, ar
26、e 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 either for revision of this standard or for additional standa
27、rdsand 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 hearing you shouldmake your views known to the ASTM Commit
28、tee 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).B887032
