ASTM_B_612_-_00.pdf

Designation:B 612 00Standard Specification forIron Bronze Sintered Bearings(Oil-Impregnated)1This standard is issued under the fixed designation B 612;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(e)indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1.Scope1.1 This specification covers iron-copper-tin-graphite sin-tered metal powder oil-impregnated bearings of one composi-tion commonly known as diluted bronze.1.2 The following safety hazards caveat pertains only to thetest method described in this specification:This standard doesnot purport to address all of the safety concerns,if any,associated with its use.It is the responsibility of the user of thisstandard to establish appropriate safety and health practicesand determine the applicability of regulatory limitations priorto use.2.Referenced Documents2.1 ASTM Standards:B 328 Test Method for Density,Oil Content,and Intercon-nected Porosity of Sintered Powder Metal Structural Partsand Oil-Impregnated Bearings2E 9 Test Methods of Compression Testing of Metallic Ma-terials at Room Temperature33.Ordering Information3.1 Orders for material under this specification shall includethe following information:3.1.1 Dimensions and3.1.2 Certification(12.1).4.Materials and Manufacture4.1 Bearings shall be made by briquetting and sinteringmetal powders with an addition of graphite so as to producefinished parts conforming to the requirements of this specifi-cation.5.Chemical Composition5.1 The material shall conform to the requirements as tochemical composition prescribed in Table 1.6.Physical Properties6.1 DensityThe density of bearings supplied fully impreg-nated with lubricant shall be 6.0 to 6.4 g/cm3.6.2 Oil ContentOil content of bearings shall not be lessthan 17%when determined in accordance with Test MethodB 328.6.3 Radial Crushing StrengthRadial crushing strengthdetermined as prescribed in 9.2 shall be not less than norgreater than the calculated value limits using the minimum andmaximum K values given below and using the followingequation:P 5 KLT2/D 2 T!(1)where:P=radial crushing strength(Note),lbs(or N);D=outside diameter of bearing,in.(or mm);T=wall thickness of bearing,in.(or mm);L=length thickness of bearing,in.(or mm);andK=strength constant with Kmin=22 000 psi(152 MPa)and Kmax=50 000 psi(345 MPa).NOTE1Strengths above the maximum value indicate high combinedcarbon,which has a deleterious effect on bearing performance.7.Workmanship,Finish,and Appearance7.1 Bearings shall be uniform in composition.When cut orfractured,the exposed surface shall be of uniform appearance.The parts shall be free of defects which would affect theirserviceability.Upon metallographic examination,the micro-structure of the material shall be iron dispersed through amatrix of substantially alpha bronze and containing no free tinvisible at 3003.To check for uniform permeability,the partshall be observed either while it is being heated or while theinside of the bearing is being subjected to air pressure.Oil shallexude uniformly from all critical surfaces.1This specification is under the jurisdiction of ASTM Committee B-9 on MetalPowders and Metal Powder Products and is the direct responsibility of Subcommit-tee B09.04 on Bearings.Current edition approved October 10,2000.Published December 2000.Origi-nally published as B 612 76.Last previous edition B 612 96.2Annual Book of ASTM Standards,Vol 02.05.3Annual Book of ASTM Standards,Vol 03.01.TABLE 1 Chemical RequirementsElementComposition,%Iron54.262.0Copper34.038.0Tin3.54.5Total carbon0.51.3Combined carbonA0.5 maxTotal other elements2.0 maxAOn basis of iron.1Copyright ASTM,100 Barr Harbor Drive,West Conshohocken,PA 19428-2959,United States.8.Sampling8.1 LotUnless otherwise specified,a lot shall consist ofparts of the same form and dimensions made from powders ofthe same composition,formed and sintered under the sameconditions,and submitted for inspection at one time.8.2 Sample for Chemical AnalysisAt least one sample forchemical analysis shall be taken from each lot.A sample shallconsist of not less than 2 oz(56 g)of chips obtained by millingor drilling from at least two pieces with clean dry tools withoutlubrication.To obtain oil-free chips,the parts selected for testshall be extracted in accordance with Test Method B 328,ifnecessary.8.3 Mechanical TestsThe manufacturer and purchasershall agree on a representative number of test pieces.9.Test Methods9.1 DensityTest Method B 328.9.2 Radial Crushing StrengthCompress the test speci-mens between two flat surfaces at a“no load”speed no greaterthan 0.2 in./min(5.0 mm/min),the direction of the load beingnormal to the longitudinal axis of the specimen.The point atwhich the load drops as a result of the first crack shall beconsid