1、AGMAINFORMATIONSHEET(This Information Sheet is NOT an AGMA Standard)AGMA939-A07AGMA 939-A07AMERICAN GEAR MANUFACTURERS ASSOCIATIONAustempered Ductile Iron for GearsiiAustempered Ductile Iron for GearsAGMA 939-A07CAUTION NOTICE: AGMA technical publications are subject to constant improvement,revision
2、 or withdrawal as dictated by experience. Any person who refers to any AGMAtechnicalpublicationshouldbesurethatthepublicationisthelatestavailablefromtheAs-sociation on the subject matter.Tablesorotherself-supportingsectionsmaybereferenced. Citationsshouldread: SeeAGMA 939-A07, Austempered Ductile Ir
3、on for Gears, published by the American GearManufacturers Association, 500 Montgomery Street, Suite 350, Alexandria, Virginia22314, http:/www.agma.org.Approved January 31, 2007ABSTRACTThis information sheet gives the background and basic guidelines to consider the feasibility of austemperedductileir
4、on(ADI)forgearapplications. Itcontainsexperimental,experientialandanecdotalinformationtoas-sist in the specification, purchase and manufacture of ADI components. The metallurgy of ADI, the relevantfactors in its production, allowable stress numbers, and stress cycle curves are reviewed. It also has
5、refer-ences, relevant standards, and evaluation methods used in the manufacture of ADI components.Published byAmerican Gear Manufacturers Association500 Montgomery Street, Suite 350, Alexandria, Virginia 22314Copyright 2007 by American Gear Manufacturers AssociationAll rights reserved.No part of thi
6、s publication may be reproduced in any form, in an electronicretrieval system or otherwise, without prior written permission of the publisher.Printed in the United States of AmericaISBN: 978-1-55589-901-1AmericanGearManufacturersAssociationAGMA 939-A07AMERICAN GEAR MANUFACTURERS ASSOCIATIONiii AGMA
7、2007 - All rights reservedContentsPageForeword iv.1 Scope 1.2 References 13 Definitions 2.4 Requirements for ductile iron blanks or castings that are austempered 2.5 Heat treatment process 46 Testing and process capability verification 57 Mechanical properties 5.8 Stress cycle factors 6.9 Other prop
8、erties of ADI 710 Typical applications of the SAE ADI grades 8.Bibliography 10.Tables1 Symbols 2.2 Five standard ductile iron grades defined by ASTM A536-04 3.3 Standard as-cast grades of spheroidal graphite (ductile) ironfrom ISO 1083:2004 3.4 Minimum property requirements for the various ADI stand
9、ards 5Figures1 Schematic of the austempering process 42 ADI allowable contact stress number 63 ADI allowable bending stress number (as austempered) for both asmachined and shot peened after austempering 6.4 ADI pitting resistance stress cycle factor, ZN75 ADI bending strength stress cycle factor, YN
10、8AGMA 939-A07 AMERICAN GEAR MANUFACTURERS ASSOCIATIONiv AGMA 2007 - All rights reservedForewordThe foreword, footnotes and annexes, if any, in this document are provided forinformational purposes only and are not to be construed as a part of AGMA 939-A07,Austempered Ductile Iron for Gears.Inearly200
11、4,membersoftheAGMAHelicalGearRatingCommitteerecognizedtheneedto gather process and rating data for the use of austempered ductile iron (ADI) in gearapplications. At that time, ADI was in use in a number of industries without standardizedguidance for its use in gearing. Concurrent activities were tak
12、ing place in the AGMA MillGearing Committee and in an ISO Technical Committee (TC 25/SC 2) for materials.The first draft of AGMA 939-A07 was made in December, 2005. It was approved by theAGMA Technical Division Executive Committee in January, 2007.Suggestionsforimprovementofthisstandardwillbewelcome
13、. TheyshouldbesenttotheAmericanGearManufacturersAssociation,500MontgomeryStreet,Suite350,Alexandria,Virginia 22314.AGMA 939-A07AMERICAN GEAR MANUFACTURERS ASSOCIATIONv AGMA 2007 - All rights reservedPERSONNEL of the AGMA Helical Gear Rating CommitteeChairman: John V. Lisiecki Rexnord Geared Products
14、.Vice Chairman: Michael B. Antosiewicz Rexnord Geared ProductsACTIVE MEMBERSK.E. Acheson Gear Works - Seattle, IncJ.B. Amendola MAAG Gear AGG. Elliott Lufkin Industries, Inc.G. Lian Amarillo Gear Company.L. Lloyd Lufkin Industries, Inc.J. Keough Applied Process, Inc.V. Kirov Merit Gear CorporationD.
15、R. McVittie Gear Engineers, IncA.G. Milburn Milburn Engineering, Inc.F. Pulley Caterpillar, Inc.J. Rinaldo Atlas Copco Comptec, Inc.F.C. Uherek Rexnord Geared Products.AGMA 939-A07 AMERICAN GEAR MANUFACTURERS ASSOCIATIONvi AGMA 2007 - All rights reserved(This page is intentionally blank)1 AGMA 2007
16、- All rights reservedAGMA 939-A07AMERICAN GEAR MANUFACTURERS ASSOCIATIONAmerican Gear ManufacturersAssociation -Austempered DuctileIron for Gears1 ScopeThis information sheet is designed to familiarize thegear designer with austempered ductile iron and, inparticular, its use in gears and power train
17、 compo-nents. It covers the areas of designing, purchasing,specifying and verifying the material for the applica-tion.1.1 IntroductionAustempered ductile iron (ADI) is produced by heattreating ductile iron (also known as nodular iron orspheroidalgraphite,SG,iron),usingtheaustemper-ingprocess,asdescr
18、ibedinclause5. Austemperingis a specialized, isothermal heat treatment. Whencomparedtoconventionalductileiron,ADIcanhaveover twice the strength for a given level of ductility.ADI can have fatigue strength comparable to that ofcastandforgedsteels.ADIsstrengthcanbegreatlyenhanced by subsequent grindin
19、g, fillet rolling orshot peening.Although the first commercial application of ADI didnotoccur until1972,thematerialhas foundapplica-tions in many industrial market segments. Its princi-pal attribute is its high strength-to-weight ratio,allowing it to replace steel forgings, castings andweldments at
20、equal, or lesser weight and reducedcost. ADI gears can be found in everything fromdiesel engines to wind turbines.The numeric values in this information sheet areintended to be used with ANSI/AGMA 2101-D04only. Use in other standards should be carefullyreviewed.1.2 AttributesADI components can be ma
21、chined in the as-castcondition(beforeaustempering);partiallymachined,austempered and then finish machined; or, in somecases,machinedcompleteafteraustempering. Theausferrite matrix in ADI (a matrix of acicular ferriteand carbon stabilized austenite) undergoes a straintransformation hardening when exp
22、osed to a highnormal force. This same strain transformationhardening is what gives ADI wear resistance betterthan its bulk hardness would indicate. The effectmakesmachiningofADIchallenging,butknowledgeofthiseffectallowsthemachinisttoadjustthefeeds,speeds, coolant and tool angles to adequatelycompens
23、ate.Other attributes of the material include good noisedampening, fracture toughness, low temperatureproperties,andreasonablestiffness. BecausemostADI gears are produced from engineered, castblanks, they can be nearer net shape than thoseproduced of bar stock and can have cast-in designfeatures.2 Re
24、ferencesThe following documents contain provisions which,throughreferenceinthistext,constituteprovisionsofthisinformationsheet. Atthetimeofpublication,theeditions were valid. All publications are subject torevision, and the users of this information sheet areencouragedtoinvestigatethepossibility ofa
25、pplyingthe most recent editions of the publications listed.ANSI/AGMA1012-G05,GearNomenclature,Defi-nition of Terms with SymbolsANSI/AGMA 2101-D04, Fundamental Rating Fac-tors and Calculation Methods forInvolute SpurandHelical Gear TeethANSI/AGMA 6114-A06, Gear Power Rating forCylindrical Shell and T
26、runnion Supported Equip-mentsASTMA247-06,StandardTestMethodforEvaluat-ing the Microstructure of Graphite in Iron CastingsASTM A536-04,Standard Specification for DuctileIron CastingsASTM A897/A897M:2006, Standard Specificationfor Austempered Ductile Iron CastingsASTM E562-02, Standard Test Method for
27、 Deter-mining Volume Fraction by Systematic, ManualPoint CountAGMA 939-A07 AMERICAN GEAR MANUFACTURERS ASSOCIATION2 AGMA 2007 - All rights reservedSAE J434:2004, Automotive Ductile (Nodular) IronCastingsSAE J2477:2004, Automotive Austempered Duc-tile (Nodular) Iron Castings (ADI)ISO 1083:2004, Spher
28、oidal graphite cast irons -classificationISO 17804:2005, Ausferritic spheroidal graphitecast irons - classification3 DefinitionsThe terms used, wherever applicable, conform toANSI/AGMA 1012-G05. The symbols used in thisstandard are shown in table 1.NOTE: The symbols and terms contained in thisdocume
29、nt may vary from those used in other AGMAstandards. Usersofthisstandardshouldassurethem-selves that they are using these symbols and terms inthe manner indicated herein.4 Requirements for ductile iron blanks orcastings that are austemperedADI can be produced successfully from ductile ironcastings wi
30、th a wide range of chemistries andconfigurations. Ductile iron grades are specified byproperties,notbychemistryasinsteels,soatypicalgradeofductileironproducedinoneplacemayhavea different chemical analysis than the same gradecasting produced elsewhere. When specifyingductileironthatistobeaustempered,
31、thereareafewprincipal quality requirements that the purchasermust clearly specify.Theductileironblanksorcastingsshallbespecifiedto an as-cast grade as outlined in ISO 1083:2004,SAE J434:2004 or ASTM A536-04.ASTM A536-04 outlines five “as-cast” grades ofductile iron, specified by:- minimum tensile st
32、rength;- yield strength;- elongation.For process control, the Brinell hardness, HBW,ofthese as-cast grades can be approximated by thefollowing equation:HBW=0.4817 Rm0.000123 R2m55(1)whereRmis tensile strength, N/mm2;HBWis Brinell hardness, HBW.Tensile strengths, yield strengths and elongationsfor th
33、e ASTM standard as-cast grades are listed intable 2. Monotonic test properties for the standardISOgradesofas-castductileironareshownintable3.Hardenability. Hardenabilityistheabilityofagivenalloy to through harden. ADI assumes throughhardening of the component. The aforementionedas-cast grades of duc
34、tile iron may, for largercomponent sections, require additional alloying tothrough harden during austempering. To achievethecodifiedADImechanicalproperties,sectionsizefor unalloyed (e.g., %Mn + %Cu 0.5%) irongenerally shouldnotexceed16mm(0.63inches)toensure a uniform, through hardened structure.Sect
35、ion sizes above 16 mm may require additionalalloyingforthroughhardening. Typicalalloysaddedfor increased hardenability include Cu, Ni and Mo.WithNiandCuadditions,componentswithsectionsof 200 mm (7.9 inches) have been successfullyproduced,referenceANSI/AGMA2101-D04,annexF. The proper alloy configurat
36、ion should be deter-mined during the design phase by consultationbetween the designer, the casting source, and theheat treater.Table 1 - SymbolsSymbol Definition Units Where firstusedBWBrinell hardness HBW Eq 1N Number of cycles - 6RmTensile strength N/mm2Eq 1YNADI bending stress cycle factor - 6ZNA
37、DI pitting stress cycle factor - 6FPADI allowable bending stress number N/mm25HPADI allowable contact stress number N/mm25AGMA 939-A07AMERICAN GEAR MANUFACTURERS ASSOCIATION3 AGMA 2007 - All rights reservedTable 2 - Five standard ductile iron grades defined by ASTM A536-04Minimum requirementsPropert
38、y Grade60/40/18Grade65/45/12Grade80/55/06Grade100/70/03Grade120/90/02Tensile strength, psi 60 000 65 000 80 000 100 000 120 0000.2% offset Yield strength, psi 40 000 45 000 55 000 70 000 90 000Elongation in 2 inches, % 18 12 6.0 3.0 2.0Tensile strength, N/mm2414 448 552 689 8270.2% offset Yield stre
39、ngth, N/mm2276 310 379 483 621Elongation in 50.8 mm, % 18 12 6.0 3.0 2.0Table 3 - Standard as-cast grades of spheroidal graphite (ductile) iron from ISO 1083:2004PropertyMinimum requirements by Graderoper350 400 450 500 550 600 700Tensile strength, N/mm2350 400 450 500 550 600 7000.2% Proof stress,
40、N/mm2220 240 310 320 350 370 420Elongation, % L0=5d 22 18 10 7 5 3 2Nodule count is a measure of the distribution ofgraphite nodules in the metal matrix. In general, ahighernodulecountmitigatesmicrosegregationandincreases the tensile strength, elongation, andimpact properties of the casting. Larger
41、sectionstendtohavelower nodulecounts.Thenodulecountin the controlling sections of the casting shouldexceed 100 nodules per square millimeter asmeasuredby thetechniqueinASTMA247-06 or bycomparison to the Ductile Iron Society wall chart forrating ductile iron, see 1.Nodularityis the sphericity of the
42、graphite nodules.Near perfectly spherical nodules improve the prop-ertiesoftheiron. Nodularityinthecriticalsectionsofthecastingshouldexceed90%,asdefinedinASTMA247-06.Prior microstructure. As-cast, ferritize annealedand normalized ductile iron castings have a metallicmatrix that consists of pearlite
43、and ferrite. For agiven austempering cycle a variation in the pearliteto ferrite ratio in the castings prior to austemperingwill give a variable dimensional response. Aconsistent pearlite to ferrite ratio in the ductile ironblank will yield the most consistent dimensionalresults. The pearlite to fer
44、rite ratio should becontrolled to a tolerance of15% (i.e., 15%pearlite-85% ferrite can be: 0% pearlite-100%ferriteto30%pearlite-70%ferrite),as measuredbythe technique outlined in ASTM E562-02, or vali-dated image analysis, or by comparison to theDuctileIronSocietycharttoindicatepearlitetoferriterati
45、os, see 2.Metal castings exhibit microscopic defects that canbe controlled or mitigated by control of the castingprocess. The combined area fraction of micro-shrinkage and carbides should be less than 1%, asmeasured by the technique outlined in ASTME562-02,orvalidatedimageanalysis,orbycompar-ison to
46、 the Ductile Iron Society wall chart for ratingductile iron, see 1.Chemical analysis. As with any engineeringmaterial, a consistent chemical analysis is requiredfor consistent results. Different suppliers of ductileiron castings utilize differing techniques and rawmaterialsupplies tomeetthepropertyr
47、equirementsof the purchaser. Many combinations of chemistrycan achieve similar results. However, once asupplier and a material composition is chosen itshould be controlled to the chemistry ranges:Carbon0.20%Silicon0.20%Manganese0.05%Copper0.05%Ductile iron, similar to steel, will only be as good ast
48、he specification requirements. Ductile iron is notnormally specified by chemical analysis, but byAGMA 939-A07 AMERICAN GEAR MANUFACTURERS ASSOCIATION4 AGMA 2007 - All rights reservedphysical properties of the as-cast material. So it isimportant for the supplier of the ductile iron materialto specify
49、 the chemistry to which they will producethe gear blanks and to consistently produce thatsame material, so that the heat treater can consis-tently meet the requirements.The designer should beaware thatthe coefficientofthermal expansion for ADI can be 5 to 20% greaterthan that of steel or ductile iron depending on thegrade of ADI selected. This increased thermalexpansion must be addressed in close tolerancedesignsthatwillseesignificanttemperaturefluctua-tions in service
