AGMA 942-A12-2012 Metallurgical Specifications for Powder Metallurgy PM Steel Gearing.pdf

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1、AGMA 942-A12AGMA Information SheetMetallurgical Specifications forPowder Metallurgy, PM, SteelGearingAGMA942-A12iiMetallurgical Specifications for Powder Metallurgy, PM, Steel GearingAGMA 942-A12CAUTION NOTICE: AGMA technical publications are subject to constant improvement,revision, or withdrawal a

2、s dictated by experience. Any person who refers to any AGMAtechnical publication should be sure that the publication is the latest available from theAssociation on the subject matter.Tablesorotherself-supportingsections maybereferenced. Citationsshouldread: SeeAGMA 942-A12, Metallurgical Specificati

3、ons for Powder Metallurgy, PM, Steel Gearing,publishedbytheAmericanGearManufacturersAssociation,1001N.FairfaxStreet,Suite500, Alexandria, Virginia 22314, http:/www.agma.org.Approved August 16, 2012ABSTRACTThis information sheet provides the metallurgical requirements for powder metallurgy (PM) geari

4、ng. Fourdifferent powder metallurgy processes are identified: as-sintered, through hardened or sinter hardened, car-burizedcasehardened,andinductionhardened. Inaddition,therequirementsarecodedbyprocessandclassnumber, the latter based on the density of the PM gear teeth. Product requirements are tabu

5、lated in four datatables by process and class.Published byAmerican Gear Manufacturers Association1001 N. Fairfax Street, Suite 500Alexandria, Virginia 22314Copyright 2012 by American Gear Manufacturers AssociationAll rights reserved.Nopartofthispublicationmaybereproducedinanyform,inanelectronicretri

6、evalsystemorotherwise,withoutpriorwrittenpermission of the publisher.Printed in the United States of AmericaISBN: 978-1-61481-031-5AmericanGearManufacturersAssociationAGMA 942-A12AMERICAN GEAR MANUFACTURERS ASSOCIATIONiii AGMA 2012 All rights reservedContentsForeword iv1 Scope 12 Normative reference

7、s 12.1 Gear related specifications 12.2 Steel related specifications 12.3 Powder metallurgy related specifications 23 Definitions 24 Procedures 9.4.1 Carbon and surface carbon 10.4.2 Chemical composition 104.3 Decarburization 10.4.4 Density 10.4.5 Effective case depth 10.4.6 Hardness 10.4.6.1 Appare

8、nt hardness 104.6.2 Case hardness 104.6.3 Core hardness 11.4.7 Intergranular oxidation 114.8 Mechanical testing 114.9 Metallography and microstructure analysis 11.4.10 Surface finger oxides 114.11 Non-destructive testing 11.4.12 Tooth crush testing 115 Metallurgical requirements 11.5.1 As-sintered g

9、earing 135.2 Through hardened including sinter hardened gearing 13.5.3 Carburized case hardened gearing 14.5.4 Induction hardened gearing 14.5.5 Guidance in using grade specifications 16.5.5.1 Priority of conflicting standards 16Bibliography 17Figures1 Gear tooth pin crush samples 3.2 Intergranular

10、oxidation in a powder metallurgy gear 43 Non-martensitic transformation products (NMTP) in a carburized steel gear 5.4 Non-martensitic transformation products associated with Ni-rich regions (circled) of PM hybridsteel FLN2-4405 at 7.3 g/cm3density (nital etch) 55 Photomicrograph of PM steel with 7.

11、3 g/cm3density illustrating porosity, as shown by arrow(unetched) 66 Photomicrograph of surface densification on the (a) tooth flank and the (b) tooth root (unetched) 6.7 Photomicrograph of surface densification in a spur gear (unetched) 78 Photomicrograph of PM steel illustrating porosity morpholog

12、y, as shown by arrow (etched) 79 Retained austenite in FX-1008 steel (estimated at 5%, 1% nital, 4% picral etch) 8.10 Retained austenite in FX-1008 steel (estimated at 20%, 1% nital, 4% picral etch) 811 Surface finger oxide in a powder forged steel part (unetched) 9.Tables1 AGMA PM grade classificat

13、ion system 12.2 Metallurgical characteristics for as-sintered gearing 133 Metallurgical characteristics for through hardened or sinter hardened gearing 14.4 Metallurgical characteristics for carburized case hardened gearing 15.5 Metallurgical characteristics for induction hardened gearing 16.AGMA 94

14、2-A12 AMERICAN GEAR MANUFACTURERS ASSOCIATIONiv AGMA 2012 All rights reservedForewordTheforeword,footnotesandannexes,ifany,inthisdocumentareprovidedforinformationalpurposesonlyandarenottobeconstruedasapartofAGMAInformationSheet,942-A12,MetallurgicalSpecificationsforPowderMetallurgy, PM, Steel Gearin

15、g.This document provides the critical metallurgical characteristics of powder metallurgy, PM, gears that willensure the metallurgical quality of the teeth. The format of the document has been modeled on AGMA923-B05, Metallurgical Specifications for Steel Gearing, and may be considered a companion do

16、cument forgeardesignersseekingthesametypeofmetallurgicalfeaturesinPMsteelgearsasfoundinwroughtgears. Byusing AGMA923-B05asa guidethegeardesignercaneasilyevaluatea PMmaterial-processsystembasedon the familiar features of wrought steel gears.This information sheet is dedicated to Howard Sanderow. His

17、participation and inspiration led to thedevelopment of this information sheet. His thoroughness and enthusiasm for the powder metallurgy industry,alongwithhis contributions, aswellasthe contributionsofhisfellowcommittee members broughtout the bestfrom the committee as a whole.The first draft of AGMA

18、 942-A12 was made in May, 2007. It was approved by the AGMA membership inAugust 16, 2012.Suggestions for improvement of this standard will be welcome. They should be sent to the American GearManufacturers Association, 1001 N. Fairfax Street, Suite 500, Alexandria, Virginia 22314.AGMA 942-A12AMERICAN

19、 GEAR MANUFACTURERS ASSOCIATIONv AGMA 2012 All rights reservedPERSONNEL of the AGMA Powder Metallurgy Gearing CommitteeChairman: Paul A. Crawford MTD Products, IncVice Chairman: Ernie Reiter Web Gear Services LtdACTIVE MEMBERSJ.R. Hamilton Cloyes Gear Method2. Combustion,perASTME1019-11. Forsurfacec

20、arbonthecombustionmethodutilizeschipscutfrom0.02-0.10mm(0.001-0.004inch)inthicknessfromthegearoracarboncontrolspecimen. Thechipsfrom this cut are collected and analyzed by combustion for carbon content. The specimen should be ma-chineddrywithhigh speedcuttingtoolsandatleastone gramofcleanchips,freeo

21、fcontamination,shouldbe used for the analysis.4.2 Chemical compositionChemical composition can be determined by any of the following test methods: ASTM A751-11,ASTM E415-08 or ASTM E1184-10.4.3 DecarburizationIn order to evaluate the extent of decarburization, a metallographic specimen is prepared p

22、er ASTM E3-11,etched per ASTM E407-07 and evaluated per ASTM E1077-01.4.4 DensityDensity is determined by MPIF Std 42(04) for porous materials or MPIF Std 43(05) for impermeable materials(powder forged steel). Density values shown in Table 2 through Table 5 refer to the tooth section only. Lowerdens

23、ities may be allowable in the body of the part.4.5 Effective case depthEffective case depth is determined by MPIF Std 52(05). For carburized and hardened gearing, unlessotherwisespecified,theeffectivecasedepthisdeterminedatalocationmidwaybetweentherootandthetipofthetooth. Forinductionhardenedgearing

24、,unlessotherwisespecified,theeffectivecasedepthisdeterminedata location of 1/4 of the tooth height above the root.4.6 HardnessSurface hardness is measured by the apparent hardness method. Case and core hardness are typicallymeasured by the particle hardness method.4.6.1 Apparent hardnessAnapparentha

25、rdnesstestmeasuressurfacehardnessusingstandardindentationmethodswhichincludethematrix hardness plus the effects of porosity.For carburized and hardened parts, the Vickers testing method is preferred according to ASTM E92-04 orISO 4498:2010. For as-sintered, through hardened, sintered hardened and in

26、duction hardened parts, eithertheVickerstestingmethodorRockwelltesting,perASTME18-11,ISO4498:2010orMPIFStd43(05),canbeused.TheRockwelltestisnotused forcase hardenedpartssincethe resultswould beinaccurate duetocrushingofthe case.4.6.2 Case hardnessCase hardness is measured using a particle hardness t

27、est, which is conducted using microindentationhardnesstestingmethodsfoundinASTMB933-09,ASTM E384-11,ISO4498:2010orMPIFStd51(05). Caremust be taken to follow the guidelines given in MPIF Std 51(05) to assure that this test does not include theeffects of porosity.AGMA 942-A12AMERICAN GEAR MANUFACTURER

28、S ASSOCIATION11 AGMA 2012 All rights reservedThis test is typically performed on carburized case hardened or induction hardened powder metallurgy gears.4.6.3 Core hardnessCore hardness is measured using a particle hardness test in the center of the part, which is conducted usingmicroindentation hard

29、ness testing methods found in ASTM B933-09, ASTM E384-11, ISO 4498:2010 orMPIF Std 51(05). This test does not include the effects of porosity.This test is typically performed on carburized case hardened or induction hardened powder metallurgy gears.4.7 Intergranular oxidationSee 4.9 metallography an

30、d microstructure analysis.4.8 Mechanical testingMechanicaltestingisdeterminedbyASTME8-11orMPIFStd10(00)fortensiletestingandMPIFStd40(00)forimpact testing. Bending fatigue is determined at 107cycles at 90% survival per MPIF Std 56(01). Rollingcontact fatigue is determined using the Caterpillar style

31、contact fatigue tester with -43% sliding at 107cyclesand50%survival1. TheZFstylecontactfatiguetesterhasbeenshowntogivesimilarresultsat -24%sliding2.4.9 Metallography and microstructure analysisMetallography is performed at a magnification of 400-600X. Metallographic samples shall be prepared perASTM

32、 E3-01 and etched per ASTM E407-07, except for intergranular oxidation and surface finger oxideswhich shall be evaluated in the unetched condition, see Figure 2.4.10 Surface finger oxidesSurface finger oxides are determined by ASTM B797-93 for powder forged gears, examined in the unetchedcondition p

33、er 4.9, see Figure 11.4.11 Non-destructive testingNon-destructive testing techniques such as visual examination, eddy current, ultrasonic, x-ray and resonantacoustical frequency may be considered either as development techniques or ongoing inspection for criticalapplications.4.12 Tooth crush testing

34、In order to verify powder metal process consistency, heat treat response, surface hardness, case hardness,case depth or microstructure, test gears may be subjected to a tooth crush test. One possible arrangement isshowninFigure1.Statistical analysis of the test results are recommended in order to de

35、velop a meaningful specification.Acceptancecriteriaandtestmethodsshouldbebaseduponanagreementbetweenthecustomerandsupplier.5 Metallurgical requirementsThe metallurgical characteristics identified in the tables of this clause are intended to be used for all powdermetallurgy steel gearing. These chara

36、cteristics are intended to assure the quality of the gear teeth.The PM grade classification code consists of a process identification number and a density class number asillustrated in Table 1.Classification code: AGMA PMX-YwhereX is process identification number (1, 2, 3 or 4);Y is density class nu

37、mber (1, 2, 3 or 4), see Table 2 through Table 5 for an explanation of the densityclasses.AGMA 942-A12 AMERICAN GEAR MANUFACTURERS ASSOCIATION12 AGMA 2012 All rights reservedTable 1 - AGMA PM grade classification systemProcessPM gradeclassificationMinimumdensity in geartooth, g/cm3TablereferenceComp

38、actionmethod(s)SinteringprocessHeat treatmentResultingmicrostructureof tooth core1)Resultingmicrostructureof tooth case1)Shot peeningAs-sinteredgearingAGMA PM1-1 6.7See Table 2Single press ConventionalNone - noquench aftersinteringNot applicable Not applicable Not applicableAGMA PM1-2 7.0AGMA PM1-3

39、7.3Single press,warmcompaction ordouble pressdouble sinteredConventionalor hightemperaturesinteringThroughhardened,includingsinterhardenedgearingAGMA PM2-1 6.7See Table 3Single press ConventionalSinter harden, orquench andtemper at 175 CminimumNot applicableNot applicableShot peeningmay be used toin

40、creasesurfaceresidualcompressivestress. AGMA938-A05should bereviewed todetermine if thebenefits ofsurfaceresidualcompressivestress achievedby shotpeening maybe beneficial tothe particularapplication andto ensure nodetrimentaleffects arecaused to thegearing.AGMA PM2-2 7.0Temperedmartensite with10% ma

41、xnon-martensitictransformationproducts and30% maxretainedausteniteAGMA PM2-3 7.3Single press,warmcompaction ordouble pressdouble sinteredConventionalor hightemperaturesinteringCarburizedcasehardenedgearingAGMA PM3-2 7.0See Table 4Single press ConventionalCase carburize,quench andtemper at 175 Cminim

42、umNot applicable Not applicableAGMA PM3-3 7.3Single press,warmcompaction ordouble pressdouble sinteredConventionalor hightemperaturesinteringPredominantlytemperedmartensite andfree of ferriteand perliteevaluated at adepth of twicethe minimumcase depth.Below thisdepth, primarilytemperedmartensite wit

43、hsome acicularferrite andbainitepermissible.Temperedmartensite with5% maxnon-martensitictransformationproducts and30% maxretainedaustenite.Continuous orsemi-continuouscarbide networknot allowedAGMA PM3-4 7.8, see Table 4Single press,warmcompaction ordouble pressdouble sinteredfollowed bypowder forge

44、or surfacedensificationprocessTemperedmartensite withonly tracenon-martensitictransformationproducts and30% maxretainedaustenite. Onlyfine dispersedcarbidesacceptable.InductionhardenedgearingAGMA PM4-1 6.7See Table 5Single press ConventionalInductionharden, quenchand temper at175 CminimumNot applica

45、blePrimarily fine,aciculartemperedmartensite withless than 10%non- martensitictransformationproducts and30% maxretainedausteniteAGMA PM4-2 7.0Temperedmartensite with10% maxnon-martensitictransformationproducts and30% maxretainedausteniteAGMA PM4-3 7.3Single press,warmcompaction ordouble pressdouble

46、sinteredConventionalor hightemperaturesinteringNOTE1)Sample is evaluated at a location midway between the root and the tip of the tooth.Users of this document must be aware that the Grade PM1, PM2, PM3 and PM4 gearing are produced fromdifferentmaterials,manufacturedatdifferentdensities,and,insomecas

47、es,bydifferentprocesses. Inadditionthesegrades,whenprocessedbydifferentheattreatmentswillhavedifferentmechanicalproperties,especiallybendingfatigueandcontactfatigue. Ingeneralbothbendingfatigueandcontactfatigueresponsewillimproveas density increases and grade level increases.Individualcustomersandma

48、nufacturersmayhavespecificmodificationstothedensitygraderequirementsorspecial material and processing conditions that are not covered in these tables. These modifications andspecial conditions are permissible by mutual agreement.AGMA 942-A12AMERICAN GEAR MANUFACTURERS ASSOCIATION13 AGMA 2012 All rig

49、hts reservedThe various characteristics are listed in the order in which that characteristic is typically evaluated during themanufacturingsequence. EachindividualcharacteristichasthesameitemnumberinTable 2throughTable 5,regardless of which table it appears. Some characteristics are only applicable to certain grades, for exampleheattreatmethods,andarenotusedinsomematerialgrades.Characteristicsmarked“Required”aretypicallyrequired for part conformance. All other characteristics are opt