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.TO PLACE A DOCUMENT ORDER: (724) 776-4970 FAX: (724) 776-0790SAE WEB ADDRESS http:/www.s
3、ae.orgCopyright 1999 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.A.SURFACEVEHICLE400 Commonwealth Drive, Warrendale, PA 15096-0001RECOMMENDEDPRACTICESubmitted for recognition as an American National StandardJ2340ISSUEDOCT1999Issued 1999-10Categorization and Properties of
4、 Dent Resistant, High Strength, and UltraHigh Strength Automotive Sheet SteelForewordThe primary reason higher strength steels are used is because their yield and tensile strengths arehigher than those of low-carbon sheet steel, which are described in SAE J2329. Higher strength steels aredesirable f
5、or dent resistance, increased load bearing capability, better crash energy management, or for part massreduction through a decrease in sheet metal thickness.An increase in strength generally leads to reduced ductility or formability. Care must be taken in designing parts,tooling, and fabrication pro
6、cesses to obtain the greatest benefit from the higher strength sheet steels.Consultation in grade selection between user and steel producer is recommended to insure compatibility of thestrength and forming characteristics.Strength in these steels is achieved through chemical composition (alloying) a
7、nd special processing. Specialprocessing includes mechanical rolling techniques, temperature control in hot rolling, and time/temperature controlin annealing of cold-reduced steel. Further or additional thermal treatment may modify the original mechanicalproperties.1. ScopeThis SAE Recommended Pract
8、ice defines and establishes mechanical property ranges for sevengrades of continuously cast high strength automotive sheet steels that can be formed, welded, assembled,and painted in automotive manufacturing processes. The grade of steel specified for an identified part shouldbe based on part requir
9、ements (configuration and strength) as well as formability. Material selection shouldalso take into consideration the amount of strain induced by forming and the impact strain has on the strengthachieved in the finished part. These steels can be specified as hot-rolled sheet, cold-reduced sheet,unco
10、ated, or coated by hot dipping, electroplating, or vapor deposition of zinc, aluminum, and organiccompounds normally applied by coil coating. The grades and strength levels are achieved through chemicalcomposition and special processing. Not all combinations of strength and coating types may be comm
11、erciallyavailable. Consult your steel supplier for details.Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-SAE J2340 Issued OCT1999-2-2. References2.1 Applicable PublicationsThe following publications
12、form a part of this specification to the extent specifiedherein. Unless otherwise indicated, the latest issue of SAE and ASTM publications shall apply.2.1.1 SAE PUBLICATIONSAvailable from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.SAE J1058Standard Sheet Thickness and TolerancesSAE J1562
13、Selection of Zinc and Zinc-Alloy (Hot Dipped and Electrodeposited) Coated Steel SheetSAE J2329Categorization and Properties of Low Carbon Automotive Sheet Steels2.1.2 ASTM PUBLICATIONSAvailable from ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959.ASTM A370Standard Test Methods and Defi
14、nitions for Mechanical Testing of Steel ProductsASTM A980Standard Specification for Steel Sheet, Carbon, Ultra High Strength Cold RolledASTM E8MStandard Test Methods of Tension of Metallic MaterialsASTM E517Standard Test Method for Plastic Strain Ratio r for Sheet MetalASTME646Standard Test Method f
15、or Tensile Strain-Hardening Exponents (n value) of Metallic SheetMaterials2.1.3 ANSI/AWS/SAE PUBLICATIONAvailable from ANSI, 11 West 42nd Street, New York, NY 10036-8002.ANSI/AWS/SAE D8.8-97A Specification for Automotive and Light Truck Component Weld Quality - ArcWelding2.1.4 OTHER PUBLICATIONAZ-01
16、7-02-295 1.0C RIWeld Quality Test Method Manual; Standardized Welding Test Method TaskForce, Auto/Steel Partnership (A/SP)2.2 Related PublicationsThe following publications are provided for information purposes only and are not arequired part of this document.2.2.1 SAE PUBLICATIONSAvailable from SAE
17、, 400 Commonwealth Drive, Warrendale, PA 15096-0001.SAE J416Tensile Test SpecimensSAE J810Classifications of Common Imperfections in Sheet SteelSAE J1392Steel, High Strength, Hot Rolled Sheet and Strip, Cold Rolled Sheet, and Coated SheetSAEJ2328Selection and Specification of Steel Sheet, Hot Rolled
18、, Cold Rolled, and Coated forAutomotive Applications2.2.2 ASTM PUBLICATIONSAvailable from ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959.ASTM A463Standard Specification for Cold Rolled Aluminum Coated Type 1 Iron and Steel Society Publication, January 19883. General InformationThis do
19、cument defines seven grades of higher strength steel based on material typeand processing. These strength grades are shown in Table 1.4. ConditionSeveral conditions of hot-rolled and cold-reduced uncoated and coated sheet steels are used bythe automotive stamping and assembly operations. The conditi
20、ons of sheet steel are referred to by letter codethat follows the class designation.4.1 Cold-Reduced Uncoated and Metallic Coated Sheet SteelThree conditions of sheet steel surfacecharacteristics are produced.4.1.1 Exposed (E) is intended for the most critical exposed applications where painted surf
21、ace appearance is ofprimary importance. This surface condition of sheet steel will meet requirements for controlled surfacetexture, surface quality, and flatness.4.1.2 Unexposed (U) is intended for unexposed applications and may also have special use where improvedductility over a temper rolled prod
22、uct is desired. Unexposed can be produced without temper rolling; thissurface condition of sheet steel may be susceptible to exhibit coil breaks, fluting, and stretcher straining.Standard tolerances for flatness and surface texture are not applicable. In addition, surface imperfectionscan be more pr
23、evalent and severe than with exposed.4.1.3 Semi Exposed (Z) is intended for non-critical exposed applications. This is typically a hot-dip galvanizedtemper-rolled product, see SAE J1562 for full explanation. Acceptability of surface characteristics ordiscontinuities shall be negotiated between user
24、and supplier.4.2 Hot-Rolled Uncoated and Metallic Coated Sheet SteelFour conditions of hot-rolled sheet steel areavailable.4.2.1 Condition P is an as hot-rolled coiled product, typically known as hot roll black band, which has not beenpickled, oiled, temper rolled, side trimmed, rewound, or cut back
25、 to established thickness and widthtolerances.4.2.2 Condition W has been processed and is available in coils or cut lengths. This material may be susceptible tocoil breaks and aging. Yield strength range classes apply only to material that has been cut back toestablished thickness and width toleranc
26、es. Processed coils may receive any or all of the processing stepslisted in 4.2.1.4.2.3 Condition N has been processed and is available in coils or cut lengths. This material possesses mechanicalproperties that do not deteriorate at room temperature, however, condition N material is susceptible to c
27、oilbreaks.TABLE 1STEELS AND STRENGTH GRADESSteel Description Grade Type Available Strength Grade - MPaDent Resistant Non-Bake-Hardenable A 180, 210, 250, 280Dent Resistant Bake-Hardenable B 180, 210, 250, 280High Strength Solution Strengthened S 300, 340High Strength Low Alloy X non-bake-hardenable
28、and bake-hardenable. Both are available in grades with minimum yield strengths from 180 MPaand higher. Both are available uncoated or coated.Non-bake-hardenable, dent resistant steels achieve their final strength in the part through a combination oftheir initial yield strength and the work hardening
29、 imparted during forming. Bake-hardenable steels exhibit anadditional increase in strength due to age hardening after forming which is accelerated by subsequent paintbaking.Although dent-resistant steels are not specified by chemistry, the following is provided for information purposesonly. Both non
30、-bake-hardenable and bake-hardenable dent resistant steels can be based on conventional lowcarbon steel (0.02 to 0.08% C), steel vacuum-degassed to very low carbon levels (0.02% C), or interstitial-free (IF) steel. IF steel is vacuum degassed to ultra-low carbon levels (0.01% C) and then any carbonr
31、emaining in solution is removed by adding titanium, niobium (columbium), or vanadium to form carbideprecipitates. Solid solution strengthening elements such as phosphorous, manganese, or silicon may also beadded to increase the as-received strength while not significantly reducing the materials work
32、 hardenability. Amaterials bake hardenability depends upon the amount of carbon remaining in solution, which is controlledthrough the steel chemistry and thermomechanical processing.In this document, classification is based on minimum yield strength of the steel sheet and the strengtheningthat occur
33、s during forming and paint baking. Classification of dent resistant steel is not based on chemistry.5.1.1 TYPES AND MECHANICAL PROPERTY REQUIREMENTSMechanical property requirements of dent resistantcold-reduced uncoated and coated sheet steel grades are based on the minimum values of the following:
34、Asreceived yield strength (180, 210, 250, and 280 MPa), n value, tensile strength and the yield strength afterstrain (for non-bake-hardenable grades) or strain and bake (for bake-hardenable grades). These are theonly mechanical requirements of this document for dent resistant cold-reduced uncoated a
35、nd coated sheetsteel grades (see Table 3). Typical mechanical properties of dent resistant cold-reduced uncoated andcoated sheet steel grades are shown in Table A1 (“A” designates the Appendix).5.1.1.1 Type AThis is a non-bake-hardenable dent resistant steel in which increase in yield strength due t
36、o workhardening results from strain imparted during forming. For the purpose of this document, a non-bake-hardenable dent resistant steel shall gain at least 35 MPa in yield strength (longitudinal direction) after a2% tensile prestrain that represents the forming strain. This is considered the “stra
37、in hardening index”(SHI).TABLE 2PRODUCT CHARACTERISTICS OF HOT-ROLLED SAE J2340 STEELConditionFreedomFrom CoilBreaksNonAgingPickleand Oil(1)(2)1. a = available but not required2. n = not availableCutEdge(1)(2)SpecialSurface(1)(2)P No No n n nW No No a a nN No Yes a a nV Yes Yes a a aCopyright SAE In
38、ternational Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-SAE J2340 Issued OCT1999-5-5.1.1.2 Type BThis is a bake-hardenable dent resistant steel in which increase in yield strength due to workhardening results from strain impa
39、rted during forming and an additional strengthening increment thatoccurs during the paint-baking process. For the purposes of this document, bake-hardenable dentresistant steels are defined as those products which possess a “bake hardening index” (BHI) (as shown inFigure A1). This is an increase in
40、yield strength of at least 30 MPa in upper yield strength or 25 MPabased on lower yield point (longitudinal direction) after a 2% tensile strain and baking at 175 C for 30 min(representing the paint-baking process). The total hardening response is the sum of the SHI and the BHI.In order to help visu
41、alize the concept of the SHI and BHI, Figure A1 in the Appendix shows a portion of astress strain curve and how these two characteristics are determined.In practice, the magnitudes of the forming strain and the paint-baking temperature may be different thanthose designated for the purposes of this s
42、pecification. Figures A2 and A3 in the Appendix describe theirtypical effects on the strain hardening and bake hardening increments.5.1.2 SUB TYPE TSub Type T may be specified to denote an interstitial free dent resistant steel (Type A gradesonly). When interstitial free steel is used the tensile st
43、rength shall be 30 MPa higher than a non-interstitialfree steel. Sub Type T steels shall be specified by the “T” designator (e.g., SAE J2340 - 180AT).5.1.3 BASE METALDent resistant steel furnished to this document shall be cold-reduced low carbon deoxidizedsteel made by basic oxygen, electric furnac
44、e, or other process which will produce a material which satisfiesthe requirements for the specific grade. This steel shall be continuously cast. The chemical compositionshall be capable of achieving the desired mechanical and formability properties for the specified grade andtype. For grades 180 and
45、 210 using an interstitial free (IF) base metal having a carbon content less than0.010, an effective boron addition of 0.001% may be required to minimize secondary work embrittlement(SWE) and to control grain growth during welding. The steel supplier shall define the chemical compositionrange that w
46、ill be furnished on a production basis. The steel supplier shall not change the product/processwithout complying with the purchasers supplier quality assurance requirements.TABLE 3REQUIRED MINIMUM MECHANICAL PROPERTIES(1) OF DENT RESISTANT SHEET STEEL1. The mechanical property requirements shall be
47、determined in longitudinal direction unless otherwise specified and shall be per-formed per Section 10.SAE J2340Grade Designationand TypeAs ReceivedYield Strength(2)MPa2. Yield Strength is 0.2% offset or, in the presence of yield point elongation, lower yield point.As ReceivedTensile StrengthMPaAs R
48、eceivedn Value(3)3. n value shall be calculated, per ASTM E 646, from 10 to 20% strain or to the end of uniform elongation when uniform elongation is less than 20%.Yield StrengthAfter 2%Strain MPaYield StrengthAfter Strain andBake MPa(4)4. 2% tensile prestrain and baking at 175 C for 30 min at tempe
49、rature. The upper yield point is used for determination of yield strength. WIth lower yield point, requirement is 5 MPa lower.180 A 180 310 0.20 215180 B 180 300 0.19 245210 A 210 330 0.19 245210 B 210 320 0.17 275250 A 250 355 0.18 285250 B 250 345 0.16 315280 A 280 375 0.16 315280 B 280 365 0.15 345Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-SAE J2340 Issued OCT1999-6-5.2 High Strength Solution
