1、Designation: B887 12Standard 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.
2、 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 coerciv
3、e 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 therespon
4、sibility 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 Po
5、wder 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:3ISO 3326 Hardmetals - Determination of (the Magnetiza-tion) Coercivity3. Terminology3.1 Definition
6、s: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 the
7、n 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 co
8、ercivity 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
9、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 “
10、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 sp
11、acing 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 spe
12、cimens should be positioned with their long axis in thedirection of the magnetic field. Asymmetrically shaped test1This 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.
13、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 A
14、nnual 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 Barr Harbor Drive, PO Box
15、C700, West Conshohocken, PA 19428-2959, United States.specimens should be tested in several positions, the measure-ment values recorded, and the average value reported.7. Apparatus7.1 Instrumentation capable of the dc magnetization ofappropriately sized test samples to technical saturation andaccura
16、te 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 sh
17、ould 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 todemagnetize the test sa
18、mple.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 shapes, repeat measurementsshall be made by repositioning the specimen in the dc magneticfield of the instrumentati
19、on with consideration being given tothe shape, that is, symmetry of the test sample, and to 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 me
20、asured Hc values, especially for replicatemeasurements of asymmetric sample shapes.10. Precision and Bias10.1 The precision of this test method is based on aninterlaboratory study of ASTM B887- Standard Test Methodfor Determination of Coercivity (Hcs) of Cemented Carbides,conducted in 2010. Three la
21、boratories participated in thisstudy, recording the coercivity on three specimens each, of tendifferent materials. This procedure was performed three timeson each material in order to determine the precision of the testmethod. Every “test result” represents an individual observa-tion. Except for the
22、 limited number of participating laborato-ries, Practice E691 was followed for the design and analysis ofthe data.410.1.1 Repeatability limit (r)Two test results obtainedwithin one laboratory shall be judged not equivalent if theydiffer by more than the “r” value for that material; “r” is theinterva
23、l representing the critical difference between two testresults for the same material, obtained by the same operatorusing the same equipment on the same day in the samelaboratory.10.1.1.1 Repeatability limits are listed in Table 1 below.10.1.2 Reproducibility limit (R)Two test results shall bejudged
24、not equivalent if they differ by more than the “R” valuefor that material; “R” is the interval representing the criticaldifference between two test results for the same material,obtained by different operators using different equipment indifferent laboratories.10.1.2.1 Reproducibility limits are lis
25、ted in Table 1 below.10.1.3 The above terms (repeatability limit and reproduc-ibility limit) are used as specified in Practice E177.10.1.4 Any judgment in accordance with statement 9.1.1and 9.1.2 would normally have an approximate 95% probabil-ity of being correct, however the precision statistics o
26、btained inthis ILS must not be treated as exact mathematical quantitieswhich are applicable to all circumstances and uses. The limitednumber of laboratories reporting results guarantees that therewill be times when differences greater than predicted by theILS results will arise, sometimes with consi
27、derably greater orsmaller frequency than the 95% probability limit would imply.Consider the precision limits as general guides, and theassociated probability of 95% as only a rough indicator of whatcan be expected.10.2 BiasMeasurement of coercive force is a relativecomparison against well characteri
28、zed 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 The precision statement was determined through sta-tistic
29、al examination of 90 results, from three laboratories, onthe materials described in the table below.Material Description1 6.7%Ni, 0.12% VC, balance WC2 25%Co, 1.5%TaC, 1.5%NbC, balance WC3 8%Co, 0.32%VC, balance WC4 6.25%Co, 1.5%TaC, 1.5%NbC, balance WC5 8.5%Co,8%TiC, 6.8%TaC, 3%NbC, balance WC6 10%
30、Co, 0.25%VC, balance WC7 12.25%Co, balance WC8 25%Co, 0.3%VC, balance WC9 4.5%Co, 1%Ni, 0.5%VC, 0.4%Cr3C2, balance WC10 16%Co, balance WC10.4 No certified cemented carbide standards are availablefor coercive force measurement. Most common practice is thedevelopment of (internal) reference materials
31、representative ofthe product(s) being evaluated.4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:B09-1018.TABLE 1 Coercivity (Oe)MATERIAL AverageAsr sR r R10 56.0 0.0 0.0 0.0 0.05 78.0 0.0 0.0 0.0 0.02 128.6 0.5 0.5 1.3 1.57 154.
32、2 0.5 0.5 1.3 1.34 221.3 0.5 0.5 1.3 1.46 238.3 0.6 0.6 1.6 1.63 297.0 0.7 0.7 2.1 2.11 322.6 28.4 28.4 79.4 79.48 442.0 15.9 15.9 44.7 44.79 563.1 1.0 2.2 2.8 6.1AThe average of labortories calculated averagesB887 12211. Keywords11.1 cemented carbide; coercive force; coercivity;magnetizationASTM In
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36、tandards, 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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).B887 123
