1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro
2、m, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.QUESTIONS REGARDING THIS DOCUMENT: (412) 772-8512 FAX: (412) 776-0243TO PLACE A DOCUMENT
3、 ORDER; (412) 776-4970 FAX: (412) 776-0790SAE WEB ADDRESS http:/www.sae.orgCopyright 1995 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.A.SURFACEVEHICLE400 Commonwealth Drive, Warrendale, PA 15096-0001INFORMATIONREPORTSubmitted for recognition as an American National Stand
4、ardJ412REV.OCT95Issued 1912-01Revised 1995-10Superseding J412 JUN89GENERAL CHARACTERISTICS AND HEAT TREATMENTS OF STEELSForewordThis Document has not changed other than to put it into the new SAE Technical Standards BoardFormat.1. ScopeThe information and data contained in this SAE Information Repor
5、t are intended as a guide in theselection of steel types and grades for various purposes. Consideration of the individual types of steel ispreceded by a discussion of the factors affecting steel properties and characteristics.SAE steels are generally purchased on the basis of chemical composition re
6、quirements (SAE J403, J404, andJ405). High-strength, low alloy (HSLA) steels (SAE J1392 and J1442) are generally purchased on the basis ofmechanical properties; different chemical compositions are used to achieve the specified mechanicalproperties. Because these steels are characterized by their spe
7、cial mechanical properties obtained in the as-rolled condition, they are not intended for any heat treatment by the purchaser either before, during, or afterfabrication.In many instances, as in the case of steels listed in SAE J1268 and J1868, hardenability is also a specificationrequirement. This i
8、nformation report can be used as a reference for determining the general characteristicsand applications of commonly used SAE steels. The use of the typical heat treatments listed in Tables 1through 7 is recommended. These and other heat treatments commonly used on steel are briefly described atthe
9、end of this section.2. References2.1 Applicable PublicationsThe following publications form a part of this specification to the extent specifiedherein. The latest issue of SAE publications shall apply.All of the heat treatments briefly described in this article are discussed in detail in Metals Hand
10、bookNinthEditionVolume 4Heat Treating, published by ASM International.2.1.1 SAE PUBLICATIONSAvailable from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.SAE J403Chemical Compositions of SAE Carbon SteelsSAE J404Chemical Compositions of SAE Alloy SteelsSAE J405Chemical Compositions of SAE Wr
11、ought Stainless SteelsSAE J406Methods of Determining Hardenability of SteelsSAE J411Carbon and Alloy SteelsSAE J1868Restricted Hardenability Bands for Selected Alloy SteelsSAE J412 Revised OCT95-2-3. Factors Affecting Properties and Characteristics of Steel3.1 HardenabilityHardenability, or response
12、 to heat treatment, is one of the most important characteristics ofheat-treated steels. Hardenability is the property of steels that determines the depth and distribution ofhardness induced by quenching the steel from above the transformation temperature. Hardenability is usuallymeasured by the end
13、quench test described in SAE J406. Specified hardenability bands for standard carbonand alloy steels are shown in SAE J1268 and J1868.The chemical composition and grain size of the steel completely determine its hardenability with almost all ofthe elements making varying degrees of contribution. Man
14、y elements are discussed in SAE J411; however,carbon, boron, manganese, chromium, and molybdenum have the strongest effect. Boron is a particularlypotent hardenability agent. Typical additions in the range of 0.0005 to 0.003% will have a major effect onhardenability. Boron is most effective in lower
15、 carbon steels; it becomes less effective as carbon contentincreases. Carbon-manganese-boron steels generally fill a gap between plain carbon and alloy steels in termsof hardenability. Empirical relationships can be used to calculate or predict the hardenability for a givenchemistry of steel. Actual
16、 depth and distribution of hardness will depend on quench severity.Hardenability should not be confused with hardness per se or with maximum hardness. The maximumhardness obtainable with any steel quenched at the critical cooling rate depends only on the carbon content.That is to say, the maximum ma
17、rtensitic hardness obtainable on hardened steels is governed by the carboncontent at the surface. It has been established that, under the conditions of scale-free heating, completesolution and achievement of critical cooling rate, maximum hardness is attained at about 0.60% carbon. If thematerial is
18、 decarburized, scaled, or overheated, or if it is quenched at less than the critical cooling rate, fullhardness will not be achieved.The term hardening implies that the hardness of the material is increased by suitable treatment, usuallyinvolving heating to a suitable austenitizing temperature follo
19、wed by cooling at a certain minimum rate whichdepends upon the alloy content. If quenching is complete, the resulting structure is untempered martensite. Ifthe quenching conditions produce a minimum of 90% martensite, followed by proper tempering, it may bereasonably expected that the surface hardne
20、ss and the cross-sectional hardness will have achieved thecommercial possibilities for that material and section size. Smaller percentages of martensite will result in acorresponding reduction in mechanical properties.3.2 Grain SizeWhen used in reference to heat-treated steels, the term grain size i
21、mplies austenitic grain size. Itis an important parameter governing mechanical properties. A fine austenitic grain size will improvetoughness, ductility, and fatigue strength, but will reduce hardenability. The inherent austenitic grain size isdetermined by the choice of deoxidizer or grain refiner
22、used in the steel-making process. With few exceptions,steels to be heat-treated should have a fine austenitic grain size.Ferritic grain size is a parameter that is important to nonheat-treated steels as it will affect formability,toughness, and ductility. Fine grain steels are stronger but will have
23、 less formability and ductility.3.3 MicrostructureMicrostructure means the quantity, size, shape, and distribution of various phases in steel. Itdepends totally on the chemistry, hardenability, heat treatment, and cooling rates employed. Ferrite, the purestform of iron in steel, is the softest and l
24、owest strength constituent with highest ductility. Martensite,supersaturated solution of carbon in iron, is the hardest. Controlled diffusion of carbon from martensiteachieved by controlling the heat treatment (tempering time and temperature) softens the steel and improvesductility. Slow cooling fro
25、m high temperatures causes the carbon to precipitate out as iron carbide or cementitewhich is a hard phase. A mixture of ferrite and lamellar or plate-like cementite is called pearlite.Austenite is a term applied to the solid solution of carbon in gamma iron (or face centered cubic) and is presentin
26、 carbon steels when they are heated above the A3 transformation temperature. Retained austenite isaustenite that remains in the microstructure after a part is quenched from its austenitizing temperature. It is asofter microstructure constituent.SAE J412 Revised OCT95-3-3.4 CleanlinessCleanliness is
27、a measure of nonmetallic oxides, sulfides, coarse-nitrides, silicates, and othersuch inclusions developed during the steel-making process. Depending on their size, shape, population, anddistribution, nonmetallic inclusions may adversely affect toughness, ductility, and fatigue properties.Cleanliness
28、 is of utmost importance in critical components under high stresses, impact, cyclic loading, or lowtemperatures.3.5 Surface QualitySurface quality, a measure of the surface condition of steel, is important in cyclic loading,contact fatigue, and wear resistance applications. It is also very important
29、 in applications requiring surfacecoating, plating, painting, or aesthetics in exposed parts. Surface conditioning or scarfing of ingots, slabs,blooms, and billets may be utilized to improve surface quality.3.6 HomogeneityChemical and microstructural homogeneity and soundness (absence of voids, pinh
30、oles, andporosity) are important in predicting the consistency of product performance and integrity. Proper deoxidationand stirring of molten steel alleviate some of these problems.4. Characteristics of Plain Carbon Steels4.1 Group I (SAE 1005, 1006, 1008, 1010, 1012, 1013)These steels are the lowes
31、t carbon steels of the plaincarbon type and are selected when cold formability or drawability is the primary requisite. These steels haverelatively low tensile values. Within the carbon range of the group, strength and hardness will increase withincrease in carbon and with cold work. Such increases
32、in strength are at the sacrifice of ductility or the abilityto withstand cold deformation.When under 0.15% carbon, the steels are susceptible to grain growth and consequent brittleness if they arecold worked and subsequently heated to temperatures between 595 C (1100 F) and the lower transformationt
33、emperature. If coarse grains develop, they can be refined by heating above the A3 transformation temperatureand then cooling.Cold-rolled sheets are made from the lower carbon steels in the group. They have excellent surfaceappearance and are used in automobile panels, appliances, and so forth. The m
34、achinability of bar, rod, andwire products in this group is improved by cold drawing. In general, these steels are considered suitable forwelding or brazing but may suffer strength reductions either locally in the heat affected zone or overall,depending upon process details.4.2 Group II (SAE 1015, 1
35、016, 1017, 1018, 1019, 1020, 1021, 1022, 1023, 1025, 1026, 1029, 1513, 1522, 1524,1526, 1527)Steels in this group have increased strength and hardness and reduced cold formabilitycompared to the lowest carbon group. For heat treating purposes, they are commonly known as carburizing orcase hardening
36、grades.Selection of one of these steels for carburizing applications depends on the nature of the part, the propertiesdesired, and the processing practices preferred. Increase in carbon content of the base steel results in greatercore hardness with a given quench. Increase in manganese improves the
37、hardenability of both the core andthe case.In this group, the intermediate manganese grades (0.60 to 1.00) machine better than the lower manganesegrades. For carburizing applications, SAE 1016, 1018, and 1019 are widely used for water quenched parts.SAE 1022 and the 1500 series in this group are use
38、d for heavier sections or with thin sections where oilquenching is desired.In cold-formed or cold-heated parts, the lowest manganese grades offer the best formability at a given carbonlevel. The next higher manganese types (SAE 1018, 1021, and 1026) provide increased strength.SAE J412 Revised OCT95-
39、4-These steels are used for numerous forged parts. In general, these steels are suitable for welding or brazingprior to carburizing. If welding is to be performed after carburizing, the area to be welded must be protectedfrom the carburizing media during the process. An alternative to protection is
40、to machine away the area to bewelded after carburizing, but before hardening.A typical application for carburized plain carbon steel is for parts requiring a hard wear-resistant surface, butwith little need for increased mechanical properties in the core; e.g., small shafts, plungers, and lightly lo
41、adedgearing.4.3 Group III (SAE 1030, 1035, 1037, 1038, 1039, 1040, 1042, 1043, 1044, 1045, 1046, 1049, 1050, 1053, 1536,1541, 1548, 1551, 1552)Steels of the medium carbon type are selected for uses where higher mechanicalproperties are needed. They are frequently further hardened and strengthened by
42、 heat treatment or by coldwork. Steels in this group are suitable for a wide variety of automotive applications. Selection of the particularcarbon and manganese level is governed by a number of factors. Increase in mechanical properties required,section thickness, or depth of hardening ordinarily ne
43、cessitate either higher carbon, higher manganese, orboth. The heat treating practice used, especially the quenching medium, also has a great effect on the steelsselected. In general, any of the grades over 0.30% carbon may be induction or flame hardened.The lower carbon and manganese steels in this
44、group find wide usage for certain types of cold-formed parts.In nearly all cases, the parts cold formed from these steels are annealed, normalized, or quenched andtempered prior to use. Stampings are usually limited to flat parts or simple bends. The higher carbon gradesare frequently cold drawn to
45、specified mechanical properties for use without heat treatment for someapplications.All of these steels can be used for forgings, the selection being governed by the section size and themechanical properties desired after heat treatment. Thus, SAE 1030 and 1035 are used for many smallforgings where
46、moderate properties are desired. SAE 1536 is used for more critical parts where a higherstrength level and better uniformity is essential. The SAE 1038, 1052, 1053, and 1500 groups are used forlarger forgings. They are also used for small forgings where high hardness after oil quenching is desired.S
47、uitable heat treatment is necessary on forgings from this group to provide machinability.These steels are also widely used for parts machined from bar stock. They are used both with and withoutheat treatment, depending upon the application and the level of properties needed. As a class, they arecons
48、idered good for normal machining operations. It is possible to weld these steels by most commercialmethods, but precautions should be taken to avoid cracking from rapid heating or cooling.4.4 Group IV (SAE 1055, 1059, 1060, 1065, 1069, 1070, 1074, 1075, 1078, 1080, 1085, 1086, 1090, 1095, 1561,1566)
49、Steels in this group are of the high carbon type which are used for applications where the highercarbon is needed to improve wear characteristics and where strength levels required are higher than thoseattainable with the lower carbon groups.In general, cold-forming methods are not practical with this group of steels as they are limited to flat stampingsand springs coiled from small-diameter wire. Practically all parts from these steels are heat-treated before use.Variations in heat-treating methods are required to obtain optimum properties for particular composition
