Restricted: No
HIGH STRENGTH AND STRUCTURAL QUALITY STEELS - SHEET, STRIP, PLATE, FLAT BAR AND
WELDED MECHANICAL TUBING
1.0 GENERAL
CAUTION: Fasteners, springs or clips manufactured from this material that are surface treated to improve their cleanliness, appearance or corrosion resistance, may become hydrogen embrittled when exposed to the chemicals and coating methods used in processing. Consequently, if these parts are surface treated, it is required that they be hydrogen embrittlement relieved according to the procedures described in PS-9500.
1.1 Purpose of the Standard
This standard specifies the requirements for medium strength, high strength and ultra high strength cold rolled or hot rolled sheet, strip, plate and welded tubing. This standard follows much of the format and nomenclature of SAE-J1392 and SAE-J2340 but is different in several respects.
1.2 Purpose of the Material
High strength and structural quality steels are intended for use on parts which require specific minimum mechanical properties in order to meet applicable performance and safety standards. Typical applications include body panels, body structure components, bumpers, reinforcements, and chassis components.
1.3 Coverage of the Standard
High strength and structural quality steels are specified by strength level, type, and deoxidation practice. Available grades range from 25 ksi (172 MPa) to 120 ksi (827 MPa) minimum yield strength. Ultra-high strength, martensitic grades are specified by minimum tensile strength. Available grades range from 190 ksi (1300 MPa) to 220 ksi (1500 MPa). Formability of high strength materials can be more challenging than with low carbon mild steels because of greater springback concerns and reduced ductility. Advanced High Strength Steels (AHSS) include dual phase steels, partial martensitic steels, and TRIP steels, and are specified by minimum tensile strength. Available grades range from 490 MPa to 980 MPa minimum tensile strength materials.
Inclusion shape controlled grades as well as other chemistry requirements may be specified when special considerations apply, i.e., freedom from aging and stretcher strains or specific properties needed for dimensional control and forming. Most – if not all - automotive sheet steels are fully killed, and most of these are continuously cast.
High strength and structural quality steels achieve their properties through chemical composition and special thermo-mechanical processing and are generally not suitable for heat treatment by the part manufacturers. Subjecting these grades to heat treatment may lower the mechanical properties. Metallic Materials Engineering shall be consulted to specify the proper grade if annealing, normalizing, stress relief, or welding is to be performed.
This standard covers the mechanical properties, chemical composition, weldability, cleanability, and surface requirements for high strength steels.1.4 Correlation to Other Standards
Sheet and strip furnished under this standard shall conform to the applicable requirements designated by ASTM A-568(M), A-1008(M), A-1011(M), or A-749(M) as appropriate.
Tubing furnished under this standard shall be electric resistance welded and conform to the applicable requirements designated by ASTM A-513. The base sheet stock properties may be specified for certain part applications in addition to finished tube yield strengths.
2.0 MATERIAL CHARACTERISTICS
2.1 Mechanical Properties***
Material supplied under this standard shall meet the mechanical properties as designated by the type of steel (fourth character – see example under section 2.2) and strength level code (first three characters - see examples under section 2.3) specified in TABLE 1. Minimum tensile strength and elongation for selected structural (S) and HSLA (X) steels are listed in TABLES 2 and 3. Dual phase (D), Partial Martensitic (P), and TRIP (T) steels will be specified by minimum tensile strength, and required overall properties are presented in TABLE 4, 5, and 6. Ultra-high strength, martensitic (M) steel will be specified by minimum tensile strength, and guidelines for typical yield strength for a particular minimum tensile strength are shown in TABLE 7. As-received minimum yield strength, bake hardening index, and expected tensile strength for bake hardenable (HK) steel are listed in TABLE 8.
2.2 Code Designation
2.2.1 Strength Level (First, Second, & Third Character - Number Codes)
2.2.1.1 Strength - Sheet, Strip, Plate and Flat Bar
Sheet, strip, plate and flat bar strength shall be specified for steels in the incoming, unformed condition, with a standard sheet or bar-type test specimen, taken in the longitudinal/rolling direction, as described in ASTM A-370, unless otherwise indicated. Because of the unique properties of the dual phase steel, work hardening values should be reported for both 4 to 6% and 10 to 20% strains.
Bake hardenable and dual phase steels shall have yield strength increases due to work hardening from strain imparted during forming and an additional strengthening increment that occurs during the paint-baking process. The “bake hardening index” (BHI) as shown in Figure 1 is an increase in yield strength after 2 percent pre-strain and baking at 350 degrees F (177 degrees C) for 30 minutes.
Standard test specimens will be taken from unstrained/unbaked material in the longitudinal rolling direction per ASTM A-370. Referring to the Figure 1 below, both the bake hardening index (BHI) and the strain hardening index (SHI) of the material can be determined as follows:
BHI = C - B
Where: B = Flow stress at 2% pre-strain
C = 0.2% yield strength or lower yield point after baking @ 350 degrees F (177 degrees C) for
30 minutes
SHI = B - A
Where: A = Initial 0.2% offset yield strength
B = Flow stress at 2% prestrain
The original specimen area is used in calculation of all engineering strengths in this test (A, B and C). The total increase in strength from the test is reported as SHI + BHI.
FIGURE 1: BAKE HARDENING INDEX
2.2.1.2 Strength - Welded Mechanical Tubing
Tubing strength is defined, as the yield strength required in the finished tube. As defined in ASTM A-370, tubing strength shall be determined with a full size tubular section or longitudinal strip cut from the tube or pipe, depending on the limits of the test equipment. In instances where the base yield strength of the incoming flat stock to be used to form the tube is critical, it may be specified on the drawing instead of the yield strength required in the finished part.
Welded tubing covered by this standard shall have weld flash removed from the outside diameter. Inside diameter weld flash shall not exceed the limits called out in the applicable ASTM Standard, in the engineering drawing, or on the purchase requisition. Tube welds are expected to be functional for the intended use and, where necessary, shall meet the appropriate weld tests as detailed in ASTM A-513 or A-512 Supplementary Requirements.
2.2.2 General Steel Types
The general type of steel is designated by the following 6 categories, each representing a compositional/microstructural system or special characteristic as noted below:
Code S: Plain Carbon Structural Steel
Code X: High Strength, Low Alloy (HSLA) Steel
Code H: Bake Hardenable Steel
Code D: Dual Phase Steel
Code P: Partial Martensitic Steel
Code T: TRIP (Transformation Induced Plasticity) Steel
Code M: Martensitic Steel
2.2.3 Deoxidation Practice
Deoxidation Practice and Sulfide Inclusion Control are specified by one of two letter codes as follows:
Code K: Killed steel made to a fine grain practice. This code is used when freedom from aging, increased formability and/or reduced variation in material properties are required by Engineering or the manufacturing plant for fabrication and/or quality requirements.
Code F: Killed steel made to a fine grain practice with sulfide inclusion control. Special steel making practice is used to control the shape or the volume fraction of manganese sulfide inclusions to improve edge stretching or edge bending in some applications.
2.2.4 Tensile Strength Designation
Code T - This code is used with dual-phase, partial martensitic, TRIP, and martensitic steels when a minimum tensile strength is required.
2.3 Examples
- MS-2 -050XK: 50 ksi minimum yield strength, HSLA, killed steel.
- MS-2 -035SK: 35 ksi minimum yield strength, plain carbon structural killed steel.
- MS-2 E-30HK: Exposed quality, 30 ksi minimum yield strength as received, bake hardenable steel
- MS-2 -590DT: 590 MPa minimum tensile strength dual phase steel with a yield strength range of 340 to 440 MPa.
- MS-2 590PT: 590 MPa minimum tensile strength Partial Martensitic steel with a yield strength of 440 to 620 MPa.
- MS-2 690TT: 690 MPa minimum tensile strength TRIP steel with a yield strength of 410 to 550 MPa.
The Safety Shield, , needs to be added for the CATIA standard release Q-checker (qualifier).
FIGURE 2: FIGURE SHOWING THE ORDER IN WHICH THE VARIOUS CODES AND QUALIFIERS ARE ARRENGED TO SPECIFY ENGINEERING REQUIREMENTS
3.0 CHEMICAL COMPOSITION
Chemical composition of a specific steel may vary from one producer to another. Since different compositions may produce equivalent results, it is not practical to list all combinations of compositions and processes available to produce a steel of a given strength level. Each approved source shall file their chemical composition limits with the Metallic Materials Engineering Department, Vehicle Engineering, Chrysler Group LLC.
For welding consideration (See Section 4.2) the maximum carbon content for structural (SK), Bake Hardenable (BH), and HSLA (XK/XF) steels (not applicable to Dual Phase, partial martensitic grades, TRIP, and martensitic steels) is 0.13% maximum and shall be met by all suppliers unless a deviation is given by the Metallic Materials Engineering Department, Vehicle Engineering, Chrysler Group LLC.
Steel and parts to be subsequently welded must meet the additional requirements detailed in Section 4.2 - Weldability and Welding.
TRIP steel base metal composition analysis shall conform to the requirements listed in Table 10 below. Additional demands and restrictions may be imposed, depending on the application.
4.0 PERFORMANCE REQUIREMENTS OF THE MATERIAL
4.1 Paintability
The criteria for acceptable performance shall be defined in “Paint Performance Requirements” of Chrysler standard CS-PAINT. Test panels, prepared with the candidate material according to Chrysler Laboratory Procedure LP-463PC-01-01 or production parts processed according to Process Standard PS-962 or PS-5990 shall meet or exceed the minimum requirements included in CS-PAINT.4.2 Weldability and Welding***
When welding is performed on a particular part made from MS-2, it is the responsibility of the steel supplier, the part manufacturer, and the welder of the parts (assembly) to control both the chemical composition of the steel used and the welding process to ensure continuing compatibility with the appropriate welding process employed. Basic material chemistry, steel thickness, and welding processes and parameters used are major factors affecting weldability. Engineering standards cannot cover all possible variables and circumstances for every application. Additional restrictions and controls in manufacturing may be necessary by any or all parties concerned to produce satisfactory parts and welds. All applications of MS-2 that are subsequently welded must be approved by the Metallic Materials Engineering Department, Vehicle Engineering, Chrysler Group LLC.
4.2.1 Resistance Spot Welding
The MS-2 sheet steel shall be capable of meeting the requirements detailed in Chrysler's Process Standard PS-10947 "Resistance Spot Welding Automotive Components and Assemblies Including Advanced High Strength Steels" and Laboratory Procedure LP-461K-170.
Resistance spot welded structural (SK), Bake Hardenable (BH), and HSLA (XK/XF) sheet steels should have a maximum carbon equivalent (C.E.) of 0.30% (not applicable to dual phase, partial martensitic grades, TRIP, and martensitic steels) as determined by the following formula. Any exception should be submitted to the Metallic Materials Engineering department, Vehicle Engineering, Chrysler Group LLC.
NOTE: MS-2 sheet steel grades under structural (SK), Bake Hardenable (BH), and HSLA (XK/XF) classification are not generally considered weldable to themselves using the standard Automotive practices if the carbon content exceeds 0.13% (not applicable to dual phase, partial martensitic
grades, TRIP, and martensitic steels).
The percent phosphorus shall not exceed 0.06%.
4.2.2 Arc Welding
The MS-2 sheet steel shall be capable of meeting the requirements detailed in Chrysler's Process standard PS-9472 "Arc Welding Automotive Components".
The % phosphorus shall not exceed 0.06%. The sulfur content shall not exceed 0.05%; however it is desirable to maintain the sulfur level below 0.035%.
4.2.3 Other Welding Processes
Other welding processes such as high frequency electric resistance welding, inertia, electron beam, laser, and resistance projection welding may require other restrictions or conditions not mentioned in this standard. In all instances, the requirements of the appropriate welding material and process standards prevail.
4.3 Cleanability - Body-In-White Parts
To assure clean metal surfaces for satisfactory phosphatability, parts shall be formed using only metal forming lubricants defined by Chrysler MS-9680. This requirement is intended only for stampings that become part of the body-in-white prior to cleaning, phosphating, and painting. A list of approved lubricants is in MS-9680. Use of any other metal forming lubricants must have prior approval from the Materials Engineering and Manufacturing Department of Chrysler Group LLC.4.4 Surface Texture and Finish
4.4.1 Surface Condition - Code "E" (Exposed Quality)
When Code “E” is specified, the surface quality shall be suitable for critically exposed (Class 1) surfaces and shall be free from any surface imperfection or discontinuity which will detract from the final appearance of the part. The substrate steel shall not exhibit yield point elongation (Lüders bands or stretcher strain). The steel sheet shall meet the surface texture requirements for critical exposed applications as shown in Figures 3 and 4.
4.4.2 Surface Condition - Code “F” (Semi-Exposed Quality)
When Code F is specified the surface quality shall be suitable for non-critical or semi-exposed applications. Acceptability of surface defects or discontinuities shall be negotiated between the user and the supplier. The substrate steel shall not exhibit yield point elongation (Lüders bands or stretcher strain). The steel sheet shall meet the surface texture requirements for non-critical exposed applications as shown in Figures 3 and 4.
4.4.3 Surface Condition – Code "U" (Unexposed Quality)
Steel sheet, purchased for the manufacture of unexposed parts such as hood inners and floor pans designated as "U" (Class 2 - not temper rolled), shall have no specific surface requirements.
4.4.4 Surface Roughness Measurement
Surface roughness and peak count shall be measured in accordance with Chrysler Process Standard PS-9, with a 0.8 mm (0.030 inch) cut-off and a 25.4 mm (1 inch) stroke. Peak count measurements are to be made with a 12.5x10-4mm (50x10-6 in) threshold.
FIGURE 3: SURFACE ROUGHNESS REQUIREMENTS (ENGLISH UNITS)
FIGURE 4: SURFACE ROUGHNESS REQUIREMENTS (METRIC UNITS)
5.0 QUALITY
Refer to CS-9801 for general quality requirements.
This steel shall be purchased only from those sources, which are marked as approved on the Engineering Approved Source List included as an addendum to this standard. Prior to supplying material to this standard, steel producers must have their product approved by the Metallic Materials Engineering Department, Vehicle Engineering, Chrysler Group LLC. All material subsequently supplied to this standard shall be equivalent in all respects to the material originally approved by the Metallic Materials Engineering Department. Changes in property and composition ranges are not permitted without prior Metallic Materials Engineering approval.
Steel orders must include the appropriate Chrysler Group LLC Material Standard (MS-2 XXXY1Y2) number, the part number, and the part application(s). Heat or ladle chemistry and residuals along with the heat number and mechanical properties are to be certified by the producer to the user.
Steel shipped direct to Chrysler Group LLC plants shall be inspected in accordance with the instructions in Process Standard PS-5570. The steel shall meet any additional requirements detailed on the Stamping Metal Parts Specification Sheet and/or the additional manufacturing requirements specified by outside part manufacturers.
The material shall be formulated to eliminate, as far as possible, constituents that would be classified as hazardous under the Resource Conservation and Recovery Act (40CFR 260-265, as amended) and any applicable federal, state, or local statute regulating the composition of liquid or solid wastes, as administered by the EPA or any authorized state or local governmental unit.
Materials submitted for laboratory approval, if containing hazardous materials, or if determined to generate hazardous waste products during their normal plant usage, must be accompanied by the appropriate
RCRA analysis document(s) for the virgin material and/or the generated waste.6.0 DEFINITIONS/ABBREVIATIONS/ACRONYMS
6.1 Definition of Steel Types
Structural Quality Steel: This term describes steels which use primarily carbon and manganese as the main strengthening elements. Nitrogen and/or phosphorus may be added at the producer's option. These steel types include structural quality mild steel, recovery annealed steel, cold rolled full hard steel, and martensitic steel.
High Strength, Low Alloy (HSLA) Steel: This type of steel achieves higher strength through alloy additions of Cb, Ti, V, Zr, etc., either singly or in combination. These steels usually have better formability than structural quality grades at comparable strength levels.
Dual Phase Steel: This type of steel has a microstructure consisting of martensite/bainite in a ferrite matrix. These steels have high ductility for any given tensile strength level combined with a high work hardening capacity when compared to HSLA grades. Because of the high work hardening capacity, dual phase steels are often produced to minimum tensile strengths rather than minimum yield strengths. Partial Martensitic Steel: Partial Martensitic steels have a multiphase microstructure containing a substantial amount of bainite. Consequently, they have higher yield/tensile strength ratios and a lower initial n-value than dual phase steels. Nevertheless, Partial Martensitic steels are more bendable and have higher edge stretchabilty because of their refined and homogeneous microstructures. These steels can be found under several names including Stretch Flange, High Hole Expansion, and Complex Martensitic.
Bake Hardenable Steel: Bake hardenable steels are chiefly used in applications requiring good dent resistance. The strength increase due to work hardening during forming is supplemented by an additional strengthening increment that occurs during paint baking.
Martensitic Steel: This type of steel has a microstructure consisting primarily of martensite. The structure is formed typically by fast quenching a low-carbon alloy-free steel. Because the yield strength of this material is difficult to define, martensitic steels are produced to minimum tensile strengths.
TRIP Steel: Transformation Induced Plasticity (TRIP) steels have a ferrite based microstructure with embedded retained austenite. During deformation retained austenite can transform to martensite (TRIP effect). These steels show strong work hardening, high uniform elongation, and high tensile strength, resulting in ability to absorb crash energy at much higher rate during crash.
6.2 Definition of Standard Number
6.2.1 Structural Quality Steel, High Strength Low Alloy (HSLA) Steel, and Bake Hardenable Steels (MS-2 XXXY1Y2)
The minimum yield strength of the material shall be specified in ksi by a three-digit numerical (XXX) code succeeding the standard number "MS-2". Following the strength level designation, two letter codes (Y1Y2) shall be used to further define the type and quality of the steel. The first letter code shall define the type of steel and the general chemical composition. The second letter code shall define the deoxidation practice and inclusion shape control. Details of the codes are listed under the Requirements section of this standard.
6.2.2 Dual Phase Steel (MS-2 XXXDT)
The minimum tensile strength of the material shall be specified in MPa by a three digit numerical (XXX) code succeeding the standard number "MS-2". Foll owing the strength level designation, the “D” designates dual phase, and the “T” indicates that the strength code refers to the ultimate tensile strength.
6.2.3 Martensitic Steel (MS-2 XXXMT)
The minimum tensile strength of the material shall be specified in ksi by a three digit numerical (XXX) code succeeding the standard number "MS-2". Following the strength level designation, the “M” designates martensitic and the “T” indicates that the strength code refers to the ultimate tensile strength..
6.2.4 Partial Martensitic Steel (MS-2 XXXPT)
The minimum tensile strength of the material shall be specified in MPa by a three digit numerical (XXX) code succeeding the standard number "MS-2". Following the strength level designation, the “P” designates partial martensitic, and the “T” indicates that the strength code refers to the ultimate tensile strength.
6.2.5 Transformation Induced Plasticity (TRIP) Steel (MS-2 XXXTT)
The minimum tensile strength of the material shall be specified in MPa by a three digit numerical (XXX) code succeeding the standard number "MS-2". Following the strength level designation, the first “T” designates TRIP, and the second “T” indicates that the strength code refers to the ultimate tensile strength.
7.0 GENERAL INFORMATION
Three asterisks “***” after the section/paragraph header denotes single or multiple technical changes to the section/paragraph. Specific technical changes within a section, subsection, table, or figure may be highlighted in yellow.
Certain important information relative to this standard has been included in separate standards. To assure the processes submitted meet all of Chrysler requirements, it is mandatory that the requirements in the following standards be met.
CS-9800 - Application of this standard, the subscription service, and approved sources
CS-9003 - Regulated substances and recyclability
Within Engineering Standards, the Regulatory (Government-mandated) requirements are designated by For specific information on this document, please refer to the contact person shown in the "Publication Information" Section of this document. For general information on obtaining Engineering Standards and Laboratory Procedures, see CS-9800 or contact the Engineering Standards Department at engstds@chrysler.com. 8.0 REFERENCES Previous standards for high strength steel correspond to this standard in the manner designated by TABLE 11. 9.0 ENGINEERING APPROVED SOURCE LIST*** 10.0 PUBLICATION INFORMATION Contact/Phone Number: Jugraj Singh, 248-512-0029 Alternate Contact/Phone Number: Ajit Desai, 248-576-7455 Department Name & Department Number/Tech Club/Organization: Metallic Materials Engineering, Dept. 5810 Date Standard Originally Published: 1935-10-21 Date Published: 2010-06-09 Change Notice: Description of Change: - Section 2.1: Revised TABLE 6 - Section 4.0: Revised section on weldability and welding. - Section 9:0: Updated EASL TABLE 13 # # # # #下载本文
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