1、Designation: B 930 03Standard Test Method forRating Grain Size and Frequency of Abnormally LargeGrains in Cemented Tungsten Carbides (Hardmetals)1This standard is issued under the fixed designation B 930; the number immediately following the designation indicates the year oforiginal adoption or, in
2、the case of revision, the 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.1. Scope1.1 This test method describes a procedure for measuringabnormally large grains and the
3、 frequency of those grains incemented tungsten carbides (hardmetals).1.2 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
4、applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:B 243 Terminology of Powder Metallurgy2B 406 Test Method for Transverse Rupture Strength ofCemented Carbides2B 657 Test Method for Metallographic Determination ofMicrostructure in Cemented Tungsten Carbid
5、es2B 665 Guide for Metallographic Sample Preparation ofCemented Tungsten Carbides23. Terminology3.1 DefinitionsDefinitions of powder metallurgy termscan be found in Terminology B 243.3.2 Definitions of Terms Specific to This Standard:3.2.1 E-Ratingthe number/cm2of grains larger than aspecified size
6、in a fully-etched specimen.3.2.2 L-Ratingthe size, in m, of the largest grain ob-served in a fully-etched specimen.4. Summary of Test Method4.1 A polished and fully etched specimen/specimens havinga minimum observable area of 0.5 cm2is examined using ametallograph. Abnormally large grains, compared
7、to the finer-grained background material, are identified. These grains arecategorized as: (1) The number of grains larger than a specifiedsize, or (2) The largest grain observed, or both.5. Significance and Use5.1 The microstructure and grain growth of cemented tung-sten carbides affect the material
8、s mechanical and physicalproperties. The grain size and distribution will affect thematerials wear resistance and fracture toughness. Abnormallylarge grains as compared to the background may introduce anarea of weakness in a sintered part.5.2 This test method may be used in acceptance testing ofceme
9、nted tungsten carbide materials or the tungsten carbidepowder used in their manufacture. The specified grain size usedfor the E-Rating is to be agreed upon between purchaser andsupplier.6. Apparatus6.1 Metallographic Microscope, capable of magnificationsof up to 15003.6.2 Ordinary metallurgical labo
10、ratory equipment.6.3 Equipment for specimen preparation as outlined inGuide B 665.7. Test Specimens7.1 Specimen SizeThe recommended specimen shall bethe standard transverse rupture specimen as specified in TestMethod B 406; that is, ground to the following dimensions:5.00 6 0.25 mm (0.200 6 0.010 in
11、) thick by 6.25 6 0.25 mm(0.250 6 0.010 in) wide by 19.0 mm (0.750 6 in) long.Alternatively, the specimen shall be a size to provide aminimum 0.5 cm2surface area of examination, or it mayconsist of several samples that provide this minimum area.7.2 Specimen Preparation:7.2.1 Polish the specimen/spec
12、imens according to the pro-cedure described in Guide B 665, or other suitable metallo-graphic polishing procedure. If using the recommended speci-men, polish the 6.25 by 19.0 mm side.7.2.2 Etch the specimen according to the procedure de-scribed in Test Method B 657, or other suitable etchingprocedur
13、e that will reveal the tungsten carbide grain structure.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 Oct. 1, 2003. Published October 2
14、003.2Annual Book of ASTM Standards, Vol 02.05.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.8. Procedure8.1 Examine a fully-etched specimen at a minimum of2003 magnification.8.1.1 For E-ratingCount the number of grains larger thant
15、he specified size observed in the full cross-section of thepolished and etched specimen/specimens. Divide this numberby the total area examined (1.2 cm2for the recommendedtransverse rupture specimen) to obtain a number of grains/cm2.8.1.2 For L-RatingMeasure the largest dimension of thelargest grain
16、 observed in the polished and etched specimen/specimens.9. Report9.1 The report shall include the following:9.1.1 Reference to this test method,9.1.2 Complete identification of the test specimen,9.1.3 Details of any occurrence that may have affected theresults,9.1.4 The total area examined, in cm2,9
17、.1.5 The E-Rating as grains/cm2, rounded to the nearestwhole integer, and9.1.6 The L-Rating in m, rounded to the nearest wholeinteger.10. Precision and Bias10.1 No statement regarding precision and bias of this testmethod can be made at this time. Plans for an interlaboratorystudy are being formulat
18、ed.11. Keywords11.1 abnormally large grains; cemented carbides; cementedtungsten carbide; E-rating; hardmetals; L-rating;microstructureASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this stand
19、ard are expressly advised that determination of the validity of any such patent 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 andi
20、f not revised, either reapproved or withdrawn. Your comments are invited either 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, wh
21、ich you may attend. If you feel that your comments have not received a fair hearing 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).B930032
