1、 SURFACE VEHICLE RECOMMENDED PRACTICE J2745 APR2015 Issued 2007-07 Reaffirmed 2015-04 Superseding J2745 JUL2007 Categorization and Properties of Advanced High Strength Automotive Sheet Steels RATIONALE J2745 has been reaffirmed to comply with the SAE five-year review policy. _ SAE Technical Standard
2、s 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 entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole respon
3、sibility of the user.” SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2015 SAE International All rights reserved. No part of this publication may be reprod
4、uced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-4970 (outside USA) Fax: 724
5、-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/J2745_201504 FOREWORD The grades described in this specification are distinguished by their higher yield
6、strengths, tensile strengths, and formability than those of conventional low-carbon sheet steel, which are described in SAE J2329. Dual Phase and Martensitic grades along with TRIP grades are being incorporated in this specification. Higher strength steels are desirable for dent resistance, increase
7、d load bearing capability, better crash energy management, better intrusion control performance, or part mass reduction 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 fabric
8、ation processes 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 the strength, forming, and joining characteristics. Strength in these steels is achieved through chemical co
9、mposition (alloying) and thermo-mechanical processing. Thermo-mechanical processing includes mechanical rolling techniques, temperature control in hot rolling, and time/temperature control in annealing of cold-reduced steel. Steel users should be aware that further thermal treatment may modify the a
10、s-produced mechanical properties. 1. SCOPE This SAE Recommended Practice defines various grades of continuously cast high-strength sheet steels and establishes mechanical property ranges. These sheet steels can be formed, welded, assembled and painted in automotive manufacturing processes. They can
11、be specified as hot-rolled or cold-rolled sheet. Furthermore, they can be coated (hot-dipped galvanized, hot-dipped galvannealed, and electrogalvanized) or uncoated. Not all combinations of strength, dimensions and coatings may be commercially available; consult your steel supplier for details. 2. R
12、EFERENCES 2.1 Applicable Publications The following publications form a part of this specification to the extent specified herein. Unless otherwise indicated, the latest issue of SAE and ASTM publications shall apply. 2.1.1 SAE Publications Available from SAE, 400 Commonwealth Drive, Warrendale, PA
13、15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org. SAE J1562 Selection of Zinc and Zinc-Alloy (Hot Dipped and Electrodeposited) Coated Steel Sheet SAE J2329 Categorization and Properties of Low Carbon Automotive Sheet Steels SAE J2340 Categorization and
14、 Properties of Dent Resistant, High Strength, and Ultra High Strength Automotive Sheet Steel 2.1.2 ASTM Publications Available from ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, Tel: (610) 832-9585, www.astm.org. ASTM A 370 Standard Test Methods and Definitions for Mechanical Testin
15、g of Steel Products ASTM A 980 Standard Specification for Steel Sheet, Carbon, Ultra High Strength Cold Rolled ASTM E 8/E 8M Standard Test Methods of Tension of Metallic Materials ASTM E 517 Standard Test Method for Plastic Strain Ratio r for Sheet Metal ASTM E 646 Standard Test Method for Tensile S
16、train-Hardening Exponents (n value) of Metallic Sheet Materials ASTM A 568/A 568M General Requirements Specification for Steel, Sheet, Carbon, Structural, and High-Strength, Low-Alloy, Hot-Rolled and Cold-Rolled ASTM A 635/A 635M Standard Specification for Steel, Sheet and Strip, Heavy-Thickness Coi
17、ls, Hot-Rolled Carbon, Structural, High Strength Low-Alloy with Improved Formability ASTM A 924/A 924M General Requirements for Steel Sheet Metallic Coated by the Hot Dip Process 2.1.3 ISO Publications Available from ANSI, 25 West 43rd Street, New York, NY 10036-8002, Tel: 212-642-4900, www.ansi.org
18、. ISO 377-1 Selection of preparation of samples and test pieces of wrought steel ISO 6892 Metallic materialsTensile testing at ambient temperature ISO 7438 Metallic materialsBend test ISO 7500 Metallic materialsVerification of static uniaxial testing machines ISO 9513 Metallic materialsCalibration o
19、f extensometers used in uniaxial testing ISO 10113 Metallic materialsSheet and stripDetermination of plastic strain ratio ISO 10275 Metallic materialsSheet and stripDetermination of tensile strain hardening exponent ISO TS 16630 Hole expansion testing _ SAE INTERNATIONAL J2745 Reaffirmed APR2015 2 o
20、f 122.1.4 JIS Publications Available from Japanese Standards Association, 4-1-24, Akasaka Minato-ku, Tokyo 107-8440, Japan; Phone: +81-3-3583-8005, Fax: +81-3-3586-2014, www.jsa.or.jp/. JIS Z 2201 Test Pieces for Tensile Test for Metallic Materials JIS Z 2204 Bend Test Pieces for Metallic Materials
21、2.1.5 EN Publications Available from CEN Management Centre, 36 rue de Stassart, B-1050 Brussels, Belgium, Tel: +32-2-550-08-11, www.cenorm.be. EN 10 051 Hot Rolled Flat Strips and Sheets without Coating Unalloyed and Alloyed EN 10 131 Cold Rolled Flat Strips without Coating with Low and Higher YS EN
22、 10 143 Continuously Hot Dipped Coated Steel Sheet and StripTolerances on Dimensions and Shape 2.1.6 ANSI/AWS/SAE Publications Available from ANSI, 25 West 43rd Street, New York, NY 10036-8002, Tel: 212-642-4900, www.ansi.org. ANSI/AWS/SAE D8.7M-05 Recommended Practices for Automotive Weld QualityRe
23、sistance Spot Welding ANSI/AWS/SAE D8.8-97 A Specification for Automotive and Light Truck Component Weld QualityArc Welding 2.1.7 Other Publication Available from Auto/Steel Partnership (A/SP), 2000 Town Center, Suite 320, Southfield, MI 48075, www.A-SP.org. AZ-017-02-295 1.0C RI Weld Quality Test M
24、ethod Manual; Standardized Welding Test Method Task Force, Auto/Steel Partnership (A/SP) 2.2 Related Publications The following publications are provided for information purposes only and are not a required part of this document. 2.2.1 SAE Publication Available from SAE, 400 Commonwealth Drive, Warr
25、endale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org. SAE J810 Classifications of Common Imperfections in Sheet Steel _ SAE INTERNATIONAL J2745 Reaffirmed APR2015 3 of 122.2.2 ASTM Publications Available from ASTM, 100 Barr Harbor Drive, West Co
26、nshohocken, PA 19428-2959, Tel: (610) 832-9585, www.astm.org. ASTM A 463 Standard Specification for Cold Rolled Aluminum Coated Type 1 Iron and Steel Society Publication, latest revision 3. GENERAL INFORMATION This document defines various grades of advanced higher strength steel based on material t
27、ype. These strength grades with cold-rolled substrate are shown in Table 1 and with hot-rolled substrate are shown in Table 2. Collectively, DP, TRIP, HHE, and MS grades are referred to as “Advanced High Strength Steels” (AHSS) to reflect their enhanced properties over what has traditionally been us
28、ed for automotive applications. The chemical composition in this specification is not mandated but is for reference only, with the exception of the elements listed below. TABLE 1 - ADVANCED HIGH STRENGTH STEEL GRADES - COLD ROLLED Steel Description Grade Designator Available Strength Levels - MPa (m
29、in. Tensile Strength/min. Yield Strength)Dual Phase DP 440T/250Y, 490T/290Y, 590T/340Y, 690T/550Y, 780T/420Y, 980T/550Y Transformation Induced Plasticity TRIP 590T/380Y, 690T/400Y, 780T/420Y Ultra High Strength Low Carbon Martensitic MS 900T/700Y, 1100T/860Y, 1300T/1030Y, 1500T/1200Y TABLE 2 - ADVAN
30、CED HIGH STRENGTH STEEL GRADES - HOT ROLLED Steel Description Grade Designator Available Strength Grade - Mpa (min. Tensile Strength/min. Yield Strength)Dual Phase DP 590T/300Y, 780T/380Y High Hole Expansion HHE 440T/310Y, 590T/440Y, 780T/600Y Transformation Induced Plasticity TRIP 590T/400Y, 780T/4
31、50Y _ SAE INTERNATIONAL J2745 Reaffirmed APR2015 4 of 12TABLE 3 - CHEMICAL LIMITS Element Maximum Weight Percent Allowed S 0.015 Cu 0.20 4. GRADE DESCRIPTIONS 4.1 Dual Phase (DP) Grades The microstructure of these steels typically consists of martensite in a ferritic matrix, with the volume fraction
32、 of martensite influencing the strength level. The C and Mn content are generally higher than in HSLA steels (e.g. 0.15%C, 2%Mn). Additions of Mo, Cr, B or other elements may be made, their levels depending on the subsequent processing. Nb, Ti and V additions may be made for precipitation strengthen
33、ing. DP steels exhibit excellent energy-absorption behavior. Accordingly, they are advantageously used in “crash sensitive“ structural applications. 4.2 High Hole-Expansion (HHE) Grades The microstructure of these steels typically consists of a high proportion of bainite. Excellent edge stretching b
34、ehavior is typically achieved in these grades through a combination of special chemistry and/or thermo-mechanical processing. The edge stretching behavior is quantified by a hole-expansion test described in ISO TS 16630. 4.3 Transformation-Induced Plasticity (TRIP) Grades The microstructure of these
35、 steels typically consists of bainite and retained austenite in a ferritic matrix. During deformation (forming), the retained austenite transforms to martensite, resulting in excellent formability. Achieving this microstructure may require the addition of Si (e.g. 1.5%Si) and/or Al (e.g. 1.7%Al), al
36、ong with an addition of Mn (e.g. 1.5%Mn). The carbon levels may be higher than in the dual phase grades (e.g. 0.25%C). Compared to DP steels, TRIP steels exhibit superior formability and similar energy-absorption behavior. 4.4 Martensitic (MS) Grades Ultra-high strengths are achieved typically with
37、a fully martensitic microstructure. The carbon content (e.g. 0.25% C) and manganese content (e.g. 1.25% Mn) influence the strength level. Martensitic steel grades exhibit extremely high yield and tensile strengths and are typically used for anti-intrusion and/or load bearing applications. 5. COLD-RO
38、LLED, UNCOATED OR COATED, STEEL GRADES Cold-Rolled steel grades, and their required tensile properties, are listed in Table 4. Both uncoated and coated (electrogalvanized, hot-dip galvanized or galvannealed) steels are included. Applications can be exposed or unexposed. _ SAE INTERNATIONAL J2745 Rea
39、ffirmed APR2015 5 of 12TABLE 4 - ADVANCED HIGH STRENGTH, COLD ROLLED (COATED AND UNCOATED) SHEET STEELS MECHANICAL PROPERTY REQUIREMENTS* Yield Strength (MPa) Tensile Strength (MPa) Total Elongation, Min Grade Min Max Min 50mm (ISO I or ASTM A 370)50mm(JIS #5)80mm(ISO II) n value (10-20%)Min. n valu
40、e (4-6%) Min. BHI2 (MPa)Min. Applicable Notes DP 440T/250Y 250 330 440 28 30 27 0.16 30 1, 2, 3, 4, 5, 6 DP 490T/290Y 290 390 490 25 27 24 0.15 0.19 30 1, 2, 3, 4, 5, 6 DP 590T/340Y 340 440 590 21 22 20 0.14 0.18 30 1, 2, 3, 4, 5, 6 DP 690T/550Y 550 660 690 13 15 12 0.06 0.08 30 1, 2, 3, 4, 5, 6, 7D
41、P 780T/420Y 420 550 780 15 17 14 0.11 0.15 30 1, 2, 3, 4, 5, 6, 7DP 980T/550Y 550 730 980 8 10 7 n/a 0.08 30 1, 2, 3, 4, 5, 6, 7TRIP 590T/380Y 380 480 590 27 29 26 0.19 30 1, 2, 3, 4, 6, 8 TRIP 690T/400Y 400 520 690 25 27 24 0.19 30 1, 2, 3, 4, 6, 8 TRIP 780T/420Y 420 560 780 21 23 20 0.15 30 1, 2,
42、3, 4, 6, 7, 8MS 900T/700Y 700 1000 900 3 3 2 1, 2, 6 MS 1100T/860Y 860 1100 1100 3 3 2 1, 2, 6 MS 1300T/1030Y 1030 1300 1300 2 3 2 1, 2, 6 MS 1500T/1200Y 1200 1500 1500 2 3 2 1, 2, 6 NOTE 1: Test direction shall be either longitudinal or transverse, but not both, as agreed upon between customer and
43、supplier. In the absence of an agreement, the longitudinal direction shall be used. NOTE 2: The yield stress values shall be measured as the 0.2% proof stress, Rp 0.2. If yield point elongation is present, the lower yield stress, Rel, shall be used. NOTE 3: If maximum uniform elongation is less than
44、 20%, then n-value shall be measured from 10% to end of uniform elongation. NOTE 4: When the specified nominal thickness is less than 0.7 mm and greater than 0.5 mm the minimum value for elongation is reduced by 2 units. For thickness less than or equal to 0.5 mm the minimum value is reduced by 4 un
45、its. NOTE 5: For ZnNi and Galvanneal coated steels, elongation shall be reduced by 1 unit and n-value shall be reduced by 0.01. NOTE 6: Test using one of the following methods, as agreed upon between user and supplier: ISO I, ISO II, ASTM A 370, or JIS method. NOTE 7: If maximum uniform elongation i
46、s less than 10%, then n-value shall be measured from 6% to end of uniform elongation. NOTE 8: For Galvanneal coated TRIP steels, elongation and n-value shall be reduced by an amount agreed upon between the customer and supplier. _ SAE INTERNATIONAL J2745 Reaffirmed APR2015 6 of 126. HOT-ROLLED, UNCO
47、ATED OR COATED, STEEL GRADES Hot-Rolled Steel grades, and their required tensile properties, are listed in Table 5. Both uncoated and coated (hot-dip galvanized or galvannealed) steels are included. TABLE 5 - ADVANCED HIGH STRENGTH, HOT ROLLED (COATED AND UNCOATED), SHEET STEELS MECHANICAL PROPERTY REQUIREMENTS* Yield Strength (MPa) Tensile Strength (MPa) Total Elongation, Min Grade Min Max Min 50mm (ISO I or ASTM A 370) 50mm(JIS #5)80mm(ISO II) n value (10-20%)Min. n value(4-6%) Min. BHI2 (MPa) Min. Hole ExpansionRatio (%) Applicable
