ASTM B887-98

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Designation: B 887 – 98
Standard Test Method for
Determination of Coercivity (Hcs) of Cemented Carbides
This standard is issued under the fixed designation B 887; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 5. Significance and Use
1.1 This test method covers the determination of magneti- 5.1 Measurement of coercivity provides a relative compari-
zation coercivity (Hcs) of cemented carbide materials and son of carbide grain size, binder content, and possibly carbon
products using coercive force instrumentation. It is patterned deficiency for a given graded carbide material or product, and
after ISO 3326. may be employed as a non-destructive measurement indicating
1.2 This standard does not purport to address all of the deviation from a specified norm.
safety concerns, if any, associated with its use. It is the 5.2 This test method allows the non-destructive estimate of
responsibility of the user of this standard to establish appro- average carbide grain size in sintered cemented carbide hard-
priate safety and health practices and determine the applica- metals. It is appropriate for a wide range of compositions and
bility of regulatory limitations prior to use. tungsten carbide (WC) WC grain sizes, and can be used for
acceptance of material or product to specification.
2. Referenced Documents
6. Interferences
2.1 ASTM Standards:
A 340 Terminology of Symbols and Definitions Relating to 6.1 Hcs measurement is a non-destructive “bulk” measure-
Magnetic Testing ment that is averaged over the specimen volume. Bi-modal
B 243 Terminology of Powder Metallurgy grain size distributions will give approximately the same Hc
2.2 ISO Standard: value as would be obtained from a normal grain size distribu-
ISO 3326 Hardmetals - Determination of (the Magnetiza- tion about the same mean value.
tion) Coercivity 6.2 Large test specimens must be sized to fit within the
magnetic field coil spacing available for the apparatus em-
3. Terminology
ployed.
3.1 Definitions:
6.3 Small test specimens may be immeasurable if their size
3.1.1 For definition of terms used in this procedure refer to prohibits detection by the magnetic field coils for the apparatus
Terminology A 340 and Terminology B 243.
employed.
3.1.2 dc—direct current 6.4 Specimen shape, that is, symmetry and aspect ratio,
influence Hc measurement values and repeatability of results.
4. Summary of Test Method
Test specimens should be positioned with their long axis in the
4.1 A test sample is positioned in the dc magnetic field of
direction of the magnetic field. Asymetrically shaped test
the test apparatus and magnetized to technical saturation. The
specimens should be tested in several positions, the measure-
magnetic field polarity is then reversed and the test sample is
ment values recorded, and the average value reported.
demagnetized by increasing the energy of the reversed mag-
7. Apparatus
netic field until the test sample reaches zero magnetism. The
coercive force (Hc) is the magnetizing force required to return 7.1 Instrumentation capable of the dc magnetization of
the saturated magnetic induction to zero.
appropriately sized test samples to technical saturation and
accurate measurement of the energy required to restore the
magnetic induction to zero.
This test method is under the jurisdiction of ASTM Committee B-9 on Metal
Powders and Metal Powder Products and is the direct responsibility of Subcom-
8. Procedure
mittee B09.06 on Cemented Carbides.
Current edition approved May 10, 1998. Published November 1998. 8.1 For commercial instrumentation, refer to the equipment
Annual Book of ASTM Standards, Vol 03.04.
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