ASTM_B_930_-_03_2017.pdf

Designation:B93003(Reapproved 2017)Standard Test Method forRating Grain Size and Frequency of Abnormally LargeGrains in Cemented Tungsten Carbides(Hardmetals)1This standard is issued under the fixed designation B930;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.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 describes a procedure for measuringabnormally large grains and the 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 applica-bility of regulatory limitations prior to use.1.3 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2B243 Terminology of Powder MetallurgyB406 Test Method for Transverse Rupture Strength of Ce-mented CarbidesB657 Guide for Metallographic Identification of Microstruc-ture in Cemented CarbidesB665 Guide for Metallographic Sample Preparation of Ce-mented Tungsten Carbides3.Terminology3.1 DefinitionsDefinitions of powder metallurgy termscan be found in Terminology B243.3.2 Definitions of Terms Specific to This Standard:3.2.1 E-Ratingthe number/cm2of grains larger than aspecified size 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 to the finer-grained background material,are identified.These grains arecategorized as:(1)The number of grains larger than aspecified size,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 materials 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 ofcemented 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 1500.6.2 Ordinary metallurgical laboratory equipment.6.3 Equipment for specimen preparation as outlined inGuide B665.7.Test Specimens7.1 Specimen SizeThe recommended specimen shall bethe standard transverse rupture specimen as specified in TestMethod B406;that is,ground to the following dimensions:5.00 6 0.25 mm(0.200 6 0.010 in)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: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 April 1,2017.Published April 2017.Originallyapproved in 2003.Last previous edition approved in 2012 as B930 03(2012).DOI:10.1520/B0930-03R17.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1 7.2.1 Polish the specimen/specimens according to the pro-cedure described in Guide B665,or other suitable metallo-graphic polishing procedure.If using the recommendedspecimen,polish the 6.25 by 19.0 mm side.7.2.2 Etch the specimen according to the procedure de-scribed in Test Method B657,or other suitable etching proce-dure that will reveal the tungsten carbide grain structure.8.Procedure8.1 Examine a fully-etched specimen at a minimum of 200magni