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2.References
2.1Applicable 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.
2.1.1SAE P UBLICATIONS—Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.
SAE J1058—Standard Sheet Thickness’ and Tolerances
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
2.1.2ASTM P UBLICATIONS—Available from ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959.
ASTM A370—Standard Test Methods and Definitions for Mechanical Testing of Steel Products
ASTM A980—Standard Specification for Steel Sheet, Carbon, Ultra High Strength Cold Rolled
ASTM E8M—Standard Test Methods of Tension of Metallic Materials
ASTM E517—Standard Test Method for Plastic Strain Ratio r for Sheet Metal
ASTM E646—Standard Test Method for Tensile Strain-Hardening Exponents (n value) of Metallic Sheet Materials
2.1.3ANSI/AWS/SAE P UBLICATION—Available from ANSI, 11 West 42nd Street, New York, NY 10036-8002.
ANSI/AWS/SAE D8.8-97—A Specification for Automotive and Light Truck Component Weld Quality - Arc Welding
2.1.4O THER P UBLICATION
AZ-017-02-295 1.0C RI—Weld Quality Test Method Manual; Standardized Welding Test Method Task Force, Auto/Steel Partnership (A/SP)
2.2Related Publications—The following publications are provided for information purposes only and are not a
required part of this document.
2.2.1SAE P UBLICATIONS—Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.
SAE J416—Tensile Test Specimens
SAE J810—Classifications of Common Imperfections in Sheet Steel
SAE J1392—Steel, High Strength, Hot Rolled Sheet and Strip, Cold Rolled Sheet, and Coated Sheet
SAE J2328—Selection and Specification of Steel Sheet, Hot Rolled, Cold Rolled, and Coated for Automotive Applications
2.2.2ASTM P UBLICATIONS—Available from ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959.
ASTM A463—Standard Specification for Cold Rolled Aluminum Coated Type 1 & Type 2 Steel Sheet
ASTM A568—General Requirements for Carbon and High Strength, Low Alloy Steel Sheet
ASTM A653—Steel Sheet, Zinc Coated (Galvanized) or Zinc-Iron Alloy Coated (Galvanneal) by the Hot-Dip Process
ASTM A751—Standard Test Methods for Determining Chemical Composition of Steel Products
ASTM A924—General Requirements for Steel Sheet Metallic Coated by the Hot Dip Process
2.2.3ISO P UBLICATION—Available from ANSI, 11 West 42nd Street, New York, NY 10036-8002.
ISO 13887—Cold Reduced Steel Sheet of Higher Strength with Improved Formability
2.2.4O THER P UBLICATION
Steel Products Manual, Sheet Steel; Iron and Steel Society Publication, January  1988
3.General Information—This document defines seven grades of higher strength steel based on material type
and processing.  These strength grades are shown in Table 1.
TABLE 1—STEELS AND STRENGTH GRADES
Steel Description Grade Type Available Strength Grade - MPa
Dent Resistant Non-Bake-Hardenable A180, 210, 250, 280
Dent Resistant Bake-Hardenable B180, 210, 250, 280
High Strength Solution Strengthened S300, 340
High Strength Low Alloy X & Y300, 340, 380, 420, 490, 550
High Strength Recovery Annealed R490, 550, 700, 830
Ultra High Strength Dual Phase DH & DL500, 600, 700, 800, 950, 1000
Ultra High Strength Low Carbon Martensite M800, 900, 1000, 1100, 1200, 1300, 1400, 1500
4.Condition—Several conditions of hot-rolled and cold-reduced uncoated and coated sheet steels are used by
the automotive stamping and assembly operations.  The conditions of sheet steel are referred to by letter code that follows the class designation.
4.1Cold-Reduced Uncoated and Metallic Coated Sheet Steel—Three conditions of sheet steel surface
characteristics are produced.
4.1.1Exposed (E) is intended for the most critical exposed applications where painted surface appearance is of
primary importance.  This surface condition of sheet steel will meet requirements for controlled surface texture, surface quality, and flatness.
4.1.2Unexposed (U) is intended for unexposed applications and may also have special use where improved
ductility over a temper rolled product is desired.  Unexposed can be produced without temper rolling; t
his surface 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 imperfections can be more prevalent and severe than with exposed.
4.1.3Semi Exposed (Z) is intended for non-critical exposed applications.  This is typically a hot-dip galvanized
temper-rolled product, see SAE J1562 for full explanation.  Acceptability of surface characteristics or discontinuities shall be negotiated between user and supplier.
4.2Hot-Rolled Uncoated and Metallic Coated Sheet Steel—Four conditions of hot-rolled sheet steel are
available.
4.2.1Condition P is an as hot-rolled coiled product, typically known as hot roll black band, which has not been
pickled, oiled, temper rolled, side trimmed, rewound, or cut back to established thickness and width tolerances.
4.2.2Condition W has been processed and is available in coils or cut lengths.  This material may be susceptible to
coil breaks and aging.  Yield strength range classes apply only to material that has been cut back to established thickness and width tolerances.  Processed coils may receive any or all of the processing steps listed in 4.2.1.
4.2.3Condition N has been processed and is available in coils or cut lengths.  This material possesses mechanical
properties that do not deteriorate at room temperature, however, condition N material is susceptible to coil breaks.
4.2.4
Condition V has been processed and is available in coils or cut lengths.  This material is free from coil breaks and its mechanical properties do not deteriorate at room temperature.
Some of the product characteristics available for each type of hot-rolled steel are listed in Table 2.
5.Steels and Strength Grades
5.1
Dent Resistant Cold-Reduced Sheet Steels—There are two types of dent-resistant steel; non-bake-hardenable and bake-hardenable.  Both are available in grades with minimum yield strengths from 180 MPa and higher.  Both are available uncoated or coated.
Non-bake-hardenable, dent resistant steels achieve their final strength in the part through a combination of their initial yield strength and the work hardening imparted during forming.  Bake-hardenable steels exhibit an additional increase in strength due to age hardening after forming which is accelerated by subsequent paint baking.
Although dent-resistant steels are not specified by chemistry, the following is provided for information purposes only.  Both non-bake-hardenable and bake-hardenable dent resistant steels can be based on conventional low carbon 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 carbon remaining in solution is removed by adding titanium, niobium (columbium), or vanadium to form carbide precipitates.  Solid solution strengthening elements such as phosphorous, manganese, or silicon may also be added to increase the as-received strength while not significantly reducing the material's work hardenability.  A material's bake hardenability depends upon the amount of carbon remaining in solution, which is controlled through the steel chemistry and thermomechanical processing.
In this document, classification is based on minimum yield strength of the steel sheet and the strengthening that occurs during forming and paint baking.  Classification of dent resistant steel is not based on chemistry.
5.1.1
T YPES  AND  M ECHANICAL  P ROPERTY  R EQUIREMENTS —Mechanical property requirements of dent resistant cold-reduced uncoated and coated sheet steel grades are based on the minimum values of the following:  As received yield strength (180, 210, 250, and 280 MPa), n value, tensile strength and the yield strength after strain (for non-bake-hardenable grades) or strain and bake (for bake-hardenable grades).  These are the only mechanical requirements of this document for dent resis
tant cold-reduced uncoated and coated sheet steel grades (see Table 3).  Typical mechanical properties of dent resistant cold-reduced uncoated and coated sheet steel grades are shown in Table A1 (“A” designates the Appendix).
5.1.1.1
Type A—This is a non-bake-hardenable dent resistant steel in which increase in yield strength due to work hardening 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 a 2% tensile prestrain that represents the forming strain.  This is considered the “strain hardening index”(SHI).
TABLE 2—PRODUCT CHARACTERISTICS OF HOT-ROLLED SAE J2340 STEEL
Condition
Freedom From Coil Breaks
Non Aging Pickle and Oil (1)(2)
1.  a = available but not required
2.n = not available
Cut Edge (1)(2)
Special Surface (1)(2)
P No No n n n W No No a a n N No Yes a a n V
Yes
Yes
a
a
a
5.1.1.2
Type B—This is a bake-hardenable dent resistant steel in which increase in yield strength due to work
hardening results from strain imparted during forming and an additional strengthening increment that occurs during the paint-baking process.  For the purposes of this document, bake-hardenable dent resistant steels are defined as those products which possess a “bake hardening index” (BHI) (as shown in Figure A1).  This is an increase in yield strength of at least 30 MPa in upper yield strength or 25 MPa based 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 visualize the concept of the SHI and BHI, Figure A1 in the Appendix shows a portion of a stress 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 than those designated for the purposes of this specification.  Figures A2 and A3 in the Appendix describe their typical effects on the strain hardening and bake hardening increments.
5.1.2
S UB  T YPE  T—Sub Type T may be specified to denote an interstitial free dent resistant steel (Type A grades only).  When interstitial free steel is used the tensile strength shall be 30 MPa higher than a non-interstitial free steel.  Sub Type T steels shall be specified by the “T” designator (e.g., SAE J2340 - 180AT).
5.1.3
B ASE  M ETAL —Dent resistant steel furnished to this document shall be cold-reduced low carbon deoxidized steel made by basic oxygen, electric furnace, or other process which will produce a material which satisfies the requirements for the specific grade.  This steel shall be continuously cast.  The chemical composition shall be capable of achieving the desired mechanical and formability properties for the specified grade and type.  For grades 180 and 210 using an interstitial free (IF) base metal having a carbon content less than 0.010, 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 composition range that will be furnished on a production basis.  The steel supplier shall not change the product/process without complying with the purchaser’s supplier quality assurance requirements.
TABLE 3—REQUIRED MINIMUM MECHANICAL PROPERTIES (1) OF DENT RESISTANT SHEET STEEL
1.The mechanical property requirements shall be determined in longitudinal direction unless otherwise specified and shall be per-formed per Section 10.
SAE J2340Grade Designation
and Type
As Received Yield Strength (2)
MPa
2.Yield Strength is 0.2% offset or, in the presence of yield point elongation, lower yield point.
As Received Tensile Strength
MPa
As Received n 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 Strength After 2%Strain MPaxposed
Yield Strength After Strain and Bake MPa (4)
4.2% tensile prestrain and baking at 175 °C for 30 min at temperature.  The upper yield point is used for determination of yield
strength.  WIth lower yield point, requirement is 5 MPa lower.
180 A 1803100.20215
180 B 1803000.19245210 A 2103300.19245
210 B 2103200.17275
250 A 2503550.18285
250 B 2503450.16315
280 A 2803750.16315
280 B
280
365
0.15
345

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