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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; this 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 resistant 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 MPa
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
5.2High Strength Solution Strengthened and High Strength Low Alloy (HSLA) Hot-Rolled and Cold-
Reduced Sheet Steels and High Strength Recovery Annealed Cold-Reduced Sheet Steels—High strength, HSLA, and high strength recovery annealed categories include steel grades with minimum yield strengths in the range of 300 to 830 MPa. These sheet steels can be ordered and supplied as uncoated or coated.
Several different types of high strength steel based on chemistry can fall under this category. Solution strengthened high strength steels are those that contain additions of phosphorus, manganese, or silicon to conventional low carbon (e.g., 0.02 to 0.13% carbon) steels. HSLA steels have additions of carbide formers, such as, titanium, niobium (columbium), or vanadium made to conventional low carbon (0.02 to 0.13% carbon) steel. High strength recovery annealed steels have chemistries similar to the previous varieties of steels, but special annealing practices prevent recrystallization in the cold-rolled steel.
5.2.1T YPES AND M ECHANICAL P ROPERTY R EQUIREMENTS—Mechanical properties of these high strength sheet
steels shall be measured in longitudinal direction unless otherwise specified and shall conform to the requirements for the grades specified in Tables 4 and 5. Classification is based on the minimum yield strength: 300 to 830 MPa. Several categories at each strength level are defined as follows:
5.2.1.1Type S—High strength solution strengthened steels use carbon and manganese in combination with
phosphorus or silicon (as solution strengtheners) to meet the minimum strength requirements. Carbon
content is restricted to 0.13% maximum for improved formability and weldability. Phosphorus is restricted
to a maximum of 0.100%. Sulfur is restricted to a maximum of 0.020%.
5.2.1.2Type X—Typically referred to as HSLA steels, these high strength steels are alloyed with carbide and
nitride forming elements, commonly niobium (columbium), titanium, and vanadium either singularly or in
combination. These elements are used with carbon, manganese, phosphorus, and silicon to achieve the
specified minimum yield strength. Carbon content is restricted to 0.13% maximum for improved formability
and weldability. Phosphorus is restricted to a maximum of 0.060%. The specified minimum for niobium
(columbium), titanium, or vanadium is 0.005%. Sulfur is restricted to a maximum of 0.015%. A spread of
70 MPa is specified between the required minima of the yield and tensile strengths.
5.2.1.3Type Y—Same as Type X, except that a 100 MPa spread is specified between the required minima of the
yield and tensile strengths.
5.2.1.4Type R—High strength recovery annealed or stress-relief annealed steels achieve strengthening primarily
through the presence of cold work. Alloying elements mentioned under Types S and X may also be
added. Carbon is restricted to 0.13% maximum for improved formability and weldability. Phosphorus is
restricted to a maximum of 0.100%. Sulfur is restricted to a maximum of 0.015%. These steels are best
suited for bending and roll-forming applications since the mechanical properties are highly directional and
ductility and formability are limited.
5.2.2S UB T YPE F—Sub Type F may be specified to denote sulfide inclusion controlled. These steels are specified
for forming applications and are generally used in unexposed applications only. Special steel making practice is used to control the shape or the volume fraction of manganese sulfide inclusions to improve edge stretching or bending in some applications. It is recommended that the producer and purchaser consult to determine the specific forming requirements prior to specifying Sub Type F. Sub Type F steels may be specified by the “F” designator (e.g., SAE J2340 - 340XF).
5.2.3B ASE M ETAL—High strength steel furnished to this document shall be a 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.
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.
5.3
Ultra High Strength Cold-Rolled Steels; Dual Phase and Low Carbon Martensite—The Ultra High Strength Dual Phase and Low Carbon Martensite (LCM) categories include steel grades with minimum tensile strengths in the range of 500 to 1500 MPa. These sheet steels may be ordered and supplied as uncoated or coated.Contact your steel supplier to determine coating availability.
Special heat treating practices that involve quenching and tempering treatments are used to generate a martensite phase in the steel microstructure. The volume fraction and carbon content of the martensite phase determines the strength level. These steels are primarily alloyed with carbon and manganese. Boron may be added in some cases.
Specification of chemical limits for low carbon martensitic grades may be found in ASTM A 980.
TABLE 4—REQUIRED MECHANICAL PROPERTIES (1) OF HIGH STRENGTH AND HSLA HOT-ROLLED
AND COLD-REDUCED UNCOATED AND COATED SHEET STEEL (2)
1.The mechanical property requirements shall be determined in longitudinal direction unless otherwise specified and shall be performed
per Section 10.
2.Consultation between user and producer is recommended regarding the selection of specific steel grade and welding process optimiza-tion.
SAE J2340Grade Designation
and Type
Yield Strength (3)
MPa Minimum
3.Yield strength is 0.2% offset or, in the presence of yield point elongation, lower yield point.
Yield Strength (3)
MPa Maximum
Tensile Strength MPa Minimum
% Total Elongation
Min
Cold-Reduced
% Total Elongation
Min
Hot-Rolled (4)
4.For thickness less than 2.5 mm, minimum percent elongation is permitted to be 2% less than the value shown.
300 S 3004003902426300 X 3004003702428300 Y 3004004002125340 S 3404404402224340 X 3404404102225340 Y 3404404402024380 X 3804804502023380 Y 3804804801822420 X 4205204901822420 Y 4205205201619490 X 4905905601420490 Y 4905905901219550 X 5506806201218550 Y
550
680
650
12
18
TABLE 5—REQUIRED MECHANICAL PROPERTIES (1) OF HIGH STRENGTH RECOVERY ANNEALED
COLD-REDUCED SHEET STEEL (2)
1.The mechanical property requirements shall be determined in longitudinal direction unless otherwise specified and shall be per-formed per Section 10.
2.Consultation between user and producer is recommended regarding the selection of specific steel grade and welding process
optimization.
SAEJ2340
Grade Designation
and Type
Yield Strength (3)
MPa Minimum
3.Yield strength is 0.2% offset or, in the presence of yield point elongation, lower yield point.
Yield Strength (2)
MPa Maximum
Tensile Strength MPa Minimum
% Total Elongation Minimum
490 R 49059050013550 R 55065056010700 R 7008007108830 R
830
960
860
2
5.3.1
T YPES AND M ECHANICAL P ROPERTY R EQUIREMENTS —The mechanical property requirements of ultra high strength sheet steels are specified in Tables 6 and 7. Classification is based on the minimum tensile strength of the sheet steel: 500 to 1500 MPa. Typical mechanical properties of ultra high strength sheet steels are shown in Tables A2 and A3.
The formability and weldability characteristics of these ultra high strength steels shall be agreed upon between purchaser and supplier.
5.3.1.1
Type DH/DL—The ultra high strength dual phase steel microstructure is comprised of ferrite and martensite, (dual phase), with the volume fraction of low-carbon martensite primarily determining the strength level. Two types of dual phase steels are available; a) a high yield ratio (ratio of YS/TS) product designated as DH in Table 6; and b) a low yield ratio product designated as DL in Table 6. For the purpose of this specification, products with yield ratios of 0.7 or lower are designated as DL and products with yield ratios greater than 0.7 are designated as DH.
5.3.1.2
Type M—In these fully martensitic ultra high strength sheet steels, carbon content determines the strength level. These steels have limited ductility.
TABLE 6—REQUIRED MECHANICAL PROPERTIES (1) OF ULTRA HIGH STRENGTH DUAL PHASE
HOT-ROLLED AND COLD-REDUCED SHEET STEEL (2)
1.The mechanical property requirements shall be determined in longitudinal direction unless otherwise specified and shall be
performed per Section 10.
2.Consultation between user and producer is recommended regarding the selection of specific steel grade and welding pro-cess optimization.
SAE J2340
Grade Designation and Type
Yield Strength MPa
Minimum (3)
3.Minimum yield strength can be waived upon agreement between user and supplier.
Tensile Strength MPa Minimum
% Total Elongation in 50 mm Minimum
500 DL 30050022600 DH 50060014600 DL135060016600 DL228060020700 DH 55070012800 DL 5008008950 DL 55095081000 DL
700
1000
5
TABLE 7—REQUIRED MECHANICAL PROPERTIES (1) OF LOW CARBON MARTINSITE HOT-ROLLED AND COLD-REDUCED SHEET STEEL (2)(3)
1.The mechanical property requirements shall be determined in longitudinal direction
unless otherwise specified and shall be performed per Section 10.
2.Consultation between user and producer is recommended regarding the selection of
specific steel grade and welding process optimization.3.Minimum total elongation for all grades is 2%.
SAE J2340
Grade Designation and Type
Yield Strength MPa Minimum (4)
4.Minimum yield strength can be waived upon agreement between user and supplier.
Tensile Strength MPa Minimum
800M 600800900 M 7509001000 M 75010001100 M 90011001200 M 95012001300 M 105013001400 M 115014001500 M
1200
1500
5.3.2
B ASE M ETAL —High strength steel furnished to this document shall be a 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.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.
6.
Weldability—When the steel is used in welded applications, welding procedures shall be suitable for the steel chemistry and intended service. Unspecified chemical elements may be present. Limits on chemistry shall be as stated in Table 8. The sum Cu, Ni, Cr, and Mo shall not exceed 0.50% on heat analysis. When one or more of these elements are specified, the sum does not apply; in which case, only the individual limits on the remaining unspecified elements will apply.
6.1
High Strength Steel—In welding high strength steels it is important to consider several factors usually not considered in welding lower strength steels; for example, welding process, welding parameters and, of course,material combinations. Integration of these types of considerations can result in a successful system of welding for HSS. Various welding methods (arc welding, resistance welding, laser welding and high frequency welding) all have unique advantages in welding specific sheet steel combinations. Considerations for production rate, heat input, weld metal dilution, weld location access, etc., may make one system more weldable than another system. For instance, an HSS that is problematic for spot welding may not exhibit the same difficulty in arc or high frequency welding. In fact, a low heat input resistance seam welding method has been successfully employed for commercial production of bumper beams with a 1300M grade. Considerations with respect to material combinations are important for those welding processes that solidify from a molten pool, or that are constrained by thickness ratio. In general, caution should be exercised in spot welding an HSS to itself because of possible weld metal interfacial fracture tendencies, but even a problematic HSS can be spot welded to a low carbon mild steel.
The resistance spot weldability requirements for low strength steels evaluate the operational robustness of the candidate steel. This often embodies measurements of current range and electrode wear (for galvanized coatings). The resistance spot weldability requirements for HSS may be similar to those of low strength steels with the added requirement for mechanical performance. The evaluation of mechanical performance alone may also be sufficient to assess weldability. End use requirements will determine required spot weld performance. These requirements may limit the current range and/or electrode life based on individual company weld quality specifications. For instance, fast quenching of the weld may damage the weld metal integrity causing interfacial fracture, or excessive weld heat input may cause metallurgical changes that soften the heat affected zone. Both of these conditions could result in a loss of joint strength. Incorporation of appropriate weld and temper cycles or modification of weld chemistry through selective dilution of the joint can lead to acceptable weld strength and thus ensure the retention of advantages to using HSS for weight reduction in automotive components.
TABLE 8—CHEMICAL LIMITS ON UNSPECIFIED ELEMENTS
Element
Maximum Weight Percent Allowed Type A, B, and R
Maximum Weight Percent Allowed
Type S
Maximum Weight Percent Allowed Type X and Y
Maximum Weight Percent Allowed Type D and M
P 0.100(1)1.Maximum phosphorus shall be less than 0.050 on grades 180A and 180B.
0.1000.0600.020S 0.0150.0200.0150.015Cu 0.2000.2000.2000.200Ni 0.2000.2000.2000.200Cr 0.1500.1500.1500.150Mo
0.060
0.060
0.060
0.060
Weld Quality Test Method Manual (AZ-017-02 295 1.0C RI) or AWS/ANSI/SAE Standard D8.9-97, should be used as reference documents for further details. Note these standard test methods are intended for strength levels up to 420 MPa and modifications may be required for higher strength levels. Due to unique properties of HSS, selection of the weld process parameters should be determined in consultation with the steel supplier. It is recommended that product validation include production intent weld processes, preferably at the extremes of expected spot properties as determined by the laboratory studies.
Similar to resistance spot welding, the evaluation of other welding methods should take into account the appropriate operational robustness measures and the mechanical and/or fracture performance of the resulting weld quality. Weld performance, not absolute base material chemistry, is the important distinction between low and high strength steels. Since weldability requirements differ for different weld methods, it is difficult to summarize these requirements into a unified document. For example, ANSI/AWS/SAE Standard D8.8-97, may be used as a reference document for further details. Consultation is recommended between user and steel producer regarding the selection of specific steel grade as well as weld process optimization.
7.Cold Bending—High strength steels are frequently fabricated by cold bending. There are a multiplicity of
inter-related factors which affect the ability of a given piece of steel to form over any given radius in shop practice. These factors include thickness, strength level, degree of restraint in bending, relationship to rolling direction, chemical composition, and microstructure. Table A4 lists those ratios which should be used as minimums for 90 degree bends in actual shop practice. It recognizes that “hard way” bending (bend axis parallel to rolling direction) is common in production and presupposes that reasonably good forming practices will be employed. Where design permits, users are encouraged to employ large radii that are shown in Table A4 for improved performance. Where the bend axis can be designed across the width (“easy way”) of the sheet, or bends less than 90 degrees, slightly tighter radii can be employed. As the cold forming becomes progressively more difficult, that is, from a straight bend to a curved or offset bend to stretching or drawing, it is advisable that the producer and user consult to determine the special material, design, and tooling requirements of the application. The fabricator should be aware that steel may crack to some degree when bent on a sheared or burned edge. This is not to be considered to be the fault of the steel, but rather a function of the induced cold work or heat affected zone (HAZ).
8.Nomenclature and Suggested Ordering Practice
8.1Specifying sheet steel on the engineering drawing under this document should include the following
information to adequately describe the desired material:
https://www.doczj.com/doc/b615288407.html, of material being specified; such as electro-galvanized bake-hardenable steel.
b.SAE Recommended Practice number (SAE J2340).
c.Base metal type; hot rolled (HR) or cold reduced (CR).
d.Grade (four character identification which includes minimum yield strength and sheet steel product
type).
e.Coating type and coating weight, if any. Indicate hot-dip or electro-galvanized zinc coating and coating
weight. See SAE J1562 for detailed nomenclature.
f.Surface condition. Indicate exposed, E, unexposed, U; or semi exposed, Z, matte, or dull finish will be
supplied unless otherwise specified.
g.Part thickness plus the tolerance.
8.2Suggested ordering practice should include the specification from the engineering drawing plus the following
additional information.
a.Application (show part identification and description).
b.Dimensions (thickness, tolerance, width, and length for cut lengths).
c.Condition (specify pickled if required, specify oiled or not oiled as required, specify chemical treatment
for coated product if required).
d.Edges (must be specified for hot-rolled sheet and strip, that is, mill edge or cut edge).
e.Coil size and weight requirements (must include inside diameter, outside diameter, and maximum
weight).
f.Cut length weight restrictions, that is, maximum weight of individual bundle.
g.Heat or cast analysis and mechanical property report (if required).
8.3Typical specification and ordering descriptions are as follows:
a.Hot-dip galvanized dent resistant steel per SAE J2340 CR 180A HD70G70GZ, 1.00 mm min. +0.08
thick. Cold-reduced hot-dip galvanized dent resistant sheet for a semi-exposed application, cut edge,
1625 mm wide x coil.
b.Electro-galvanized bake-hardenable steel per SAE J2340 CR 250B EG70G70GE, 0.80 mm min. +
0.08 thick. Cold-reduced electro-galvanized bake-hardenable sheet for an exposed application, 1500
mm wide X 2540 mm.
c.High strength low alloy steel per SAE J2340 HR 340XU, 2.50 mm min +0.30 thick. Hot-rolled high
strength low alloy sheet steel, pickled and oiled, unexposed surface, 1400 mm wide X coil.
d.Ultra high strength sheet steel per SAE J2340 CR 1300M, 1.20 mm min + 0.10 thick. Cold-reduced
ultra high strength sheet steel, 1220 mm wide x coil.
9.Thickness Tolerances—Tolerances for dimensions are shown in SAE J1058.
10.Tensile Samples
10.1Method
10.1.1Samples should be flat and free of defects such as scores, wrinkles, die marks, etc.
10.1.2For standard testing, one longitudinal 0 degree coupon is needed.
10.1.3For r-Bar (r m) testing, one longitudinal 0 degree, one diagonal 45 degrees and one transverse 90 degrees
samples are required. r Bar (r m) is a calculated number from individual r value tests.
10.1.4Care should be taken to insure that the samples be cut exactly at 0 degree, 45 degrees, or 90 degrees to the
coil rolling direction.
10.1.5Tensile test shall be made with coating on.
10.2Preparation of Samples
10.2.1Method (ASTM E 8, E 517, E 646)
10.2.1.1Samples must have all oils, lubricants, or dry films removed prior to measurement.
10.2.1.2If base metal hardness is a desired value for correlation information, all coating must be removed from
samples prior to testing.
10.2.1.3Samples should be EDM (electrical discharge machining) cut if possible. If specimens are milled,
preparation must be such that minimal cold work is imparted to the edges of the reduced section.
10.2.2D IMENSIONS
10.2.2.1Gage Length—50 mm ± 0.10 mm.
10.2.2.2Width—12.50 mm ± 0.25 mm.
10.2.2.3Parallelism
a.Standard Testing—Reduced section must be parallel to ±0.025 mm.
b.r value Testing—Reduced section must be parallel to ±0.013 mm.
10.2.2.4Reduced section should be approximately 75 mm. 10.2.2.5Overall length should be approximately 200 mm.10.3Measurements 10.3.1E QUIPMENT
10.3.1.1Use a digital measuring device capable of resolving to at least 0.013 mm.
10.3.1.2Measuring device should be verified and documented with a test block or pin daily, before measurements
are made.10.3.1.3Measuring device should be zeroed after each set of tests. If it does not return to zero, reset the device
and re-measure the previous set of samples.10.3.2M EASUREMENT M ETHOD
10.3.2.1Standard Testing—Measure narrowest width and thickness within the 50 mm gage marks.
10.3.2.2r Value Testing—Measure at least three equally spaced width and thickness measurements across the
50mm gage length. Average these for the initial dimensions. End gage mark must be at least 25 mm from grips.10.4Testing
10.4.1T ENSILE M ACHINE O PERATING P ARAMETERS —See Table 9.
10.4.2Machine grips should cover at least 2/3 of the gripped section of the sample.10.4.3Stopping point for r value test measurement is 17% elongation.
10.4.4n-value determination range is 10% to 20% elongation, or 10% - ultimate load if uniform elongation is less
than 20%. Minimum 5 data pairs. Calculation per ASTM E 646 Part 10.10.4.5Tensile machine repeatability and reproducibility must be performed, and results documented as defined by
the quality control procedures of the testing laboratory.
TABLE 9—TENSILE MACHINE OPERATING PARAMETERS
Crosshead Speed
Strain Rate Ramp rate 1 (1)
1.Ramp rate 1 is prior to and through yield or YPE.
3.0 mm/min 1.5 mm/min Ramp rate 2(2) to determine r value 2.Ramp rate 2 is after yield or YPE (yield point elongation). Either crosshead speed control or strain rate control can
be used; the method must be noted in test report results. Speed of testing greatly affects stress values, making uni-formity critical.
12.5 mm/min 6.2 mm/min Ramp rate 2 for all standard tensile tests
25.0 mm/min
12.5 mm/min
10.5Calculation methods
10.5.1Elongation can be determined by either the piece-fit method or computer generated through the
extensometer. Whatever method is used must be stated in the lab report, because piece-fit elongation is generally higher than extensometer elongation. Elongation value is invalid if the specimen breaks within 6mm of, or outside the gage marks.
10.5.2Uniform elongation is defined as the elongation value measured at peak stress.
10.5.30.2% offset yield strength will be used for all samples without YPE. For samples with YPE, the yield strength
at the lowest point of discontinuous yielding shall be reported, along with the percentage of YPE.
10.5.4r Bar (r m) Value = (r90° r0° + 2r45°)/4
10.5.5Earing Tendency (?r) = (r90° + r0° - 2r45° )/2
PREPARED BY THE SAE IRON AND STEEL TECHNICAL COMMITTEE
DIVISION 32—SHEET AND STRIP STEEL
APPENDIX A
DENT RESISTANT STEELS
DATA ARE SHOWN IN THE APPENDIX FOR INFORMATION ONLY.
A.1
Dent Resistant Steels—See Table A1.
A.1.1Determination of Strain-Hardening Index and Bake-Hardening Index—Bake-hardening steel strength
shall be determined in specimens that have been prestrained 2% and baked at 175 °C for 30 min. Standard test specimens will be taken from unstrained and unbaked material in the longitudinal (rolling) direction per ASTM A 370. Referring to Figure A1, both the bake-hardening index (BHI) and the strain-hardening index (SHI) of the material can be determined as follows in Equation 1:
(Eq. A1)
where:
B = Flow stress at 2% prestrain
C =Yield strength (either upper or lower yield strength) after baking at 175 °C for 30 min.
(Eq. A2)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 BHI (BHI U or BHI L ) + SHI.
TABLE A1—TYPICAL MECHANICAL PROPERTIES (1) OF DENT RESISTANT COLD-REDUCED SHEET STEEL
1.The mechanical property requirements shall be determined in longitudinal direction unless otherwise specified and shall be performed per
Section 10.
SAE J2340Grade and Type As Received Properties Yield Strength (2)
MPa
2.Yield Strength is 0.2% offset or, in the presence of yield point elongation, lower yield point.
As Received Properties Tensile Strength MPa
As Received Properties Total Elongation
%
As Received Properties 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%.
As Received Properties r m Value (4)
4.r value shall be calculated, per ASTM E 517, at 17% strain, r m calculation by (r 0 + r 90 + 2r 45)/4. The r m value can be up to 0.2 lower
for thickness greater than 1.4 mm and/or galvanneal products.
Yield Strength after 2%Strain MPa
Upper Yield Strength After 2% Strain and Bake MPa (5)
5.2% tensile prestrain and baking at 175 °C for 30 min at temperature.
180 A 200350400.22 1.7235
180 B 200330390.21 1.6265
210 A 230375380.21 1.7265
210 B 230350370.19 1.5295
250 A 270400360.20 1.5305
250 B 270370350.18 1.4335
280 A 300430360.18 1.4335
280 B
300
410
35
0.17
1.1
365BHI C B
–=SHI B A
–=
FIGURE A1—REPRESENTATION OF STRAIN-HARDENING AND BAKE-HARDENING INDEX
For the purpose of part design, it may be desirable to predict yield strength at various locations on the finished part. The yield strength for 180B, 210B, 250B, and 280B shown in Table 3 is attained by straining 2% during forming followed by a paint cycle of 30 min at 175 °C. Figure A2 approximates the changes from this yield
strength with varying amounts of prestrain.
FIGURE A2—TYPICAL CHANGES TO YIELD STRENGTH WITH VARYING AMOUNTS OF PRESTRAIN
The after strain and bake yield strengths given in Table 3 were initially developed with data derived from samples subjected to 2% strain followed by a 30-min bake at 175 °C. Figure A3 is presented to show the effect of lower paint bake temperatures following 2% strain on resulting typical yield strength values.
FIGURE A3—TYPICAL CHANGES TO YIELD STRENGTH WITH LOWER BAKE TEMPERATURES
A.2
Ultra High Strength Dual Phase Steels—See Table A2.
Forming limits studies are helpful in predicting the success of forming complex shapes. Roll forming processes are recommended. Stampings which require draws may be unsuccessful due to the limited flow of dual phase and martensitic microstructures. Spring back variation is much greater in dual phase and martensitic steel and should be considered in the part, tool, and weld fixture designs.
TABLE A2—TYPICAL MECHANICAL PROPERTIES (1) OF ULTRA HIGH STRENGTH DUAL PHASE
HOT-ROLLED AND COLD-REDUCED SHEET STEEL
1.The mechanical property requirements shall be determined in longitudinal direction unless otherwise specified and shall
be performed per Section 10.
SAE J2340
Grade Designation and
Type
Yield Strength MPa Yield after 2%Strain and Bake
MPa
Tensile Strength MPa % Total Elongation in 50 mm
Bend Radii (2)
r/t 2.90 degrees Bend test shall be conducted per ASTM A 370. Ratio of bend radius to thickness (T = transverse specimen
and L = longitudinal specimen).
500DL 34048055028.5 L & T 600DH 55069071020 2 L & T 600DL139056065022.5 L & T 600DL234049066027.5 L & T 700DH 60072076016 2 L & T 800DL 58080086014 1 L & T 950DL 6801030105012 4 L & T 1000DL
810
1070
1070
9
3 L & T
A.3
Ultra High Strength Martensitic Steels—See Table A3.
A.4High Strength Solution Strengthened and HSLA Steels—See Table A4.
TABLE A3—TYPICAL MECHANICAL PROPERTIES (1) OF ULTRA HIGH STRENGTH LOW CARBON
MARTENSITE COLD-REDUCED SHEET STEEL
1.The mechanical property requirements shall be determined in longitudinal direction unless otherwise specified and shall be
performed per Section 10.
SAE J2340Grade Designation
and Type
Yield Strength MPa Tensile Strength MPa % Total Elongation in 50 mm Bend Radii (2)
r/t 2.90 degrees Bend test shall be conducted per ASTM A 370. Ratio of bend radius to thickness (T = transverse specimen and
L = longitudinal specimen).
800M N. A.(3)3.N. A. - Information not available.
N. A.N. A.N. A.900M 90010255 4 L & T 1000M N. A.N. A.N. A.N. A.1100M 103011804 4 L & T 1200M 114013406 4 T & L 1300M 120014005 4 L & T 1400M 126014805 4 T & L 1500M
1350
1580
5
4 L & T
TABLE A4—TYPICAL INSIDE BEND RADII (1)(2)(3) HIGH STRENGTH AND HSLA,COLD-REDUCED AND HOT-ROLLED AND HIGH STRENGTH RECOVERY ANNEALED COLD-REDUCED UNCOATED AND COATED SHEET STEEL
1.90 degrees Bend test shall be conducted per ASTM A 370. Ratio of bend radius to thickness (T =
transverse specimen and L = longitudinal specimen).
2.The suggested minimum bending radius is based on the nominal rolled thickness, not the minimum
ordered thickness.
3.For thicknesses over
4.50 mm, add 1/2 t to the radius shown in the Table.SAE J2340Grade Designation
and Type Cold-Reduced Bend Radius/Thickness
Hot-Rolled Bend Radius/Thickness
300 S, X, & Y 1/2 T 1 T 340 S, X, & Y 1/2 T & L 1 T & L 380 X & Y 1 T & L 1 T & L 420 X & Y 1 T & L 1 T & L 490 X & Y 2 T & L 2 T & L 550 X & Y 2 T & L 2 T & L 490 R 3 T & L N. A.(4)4.N. A. - Information not available
550 R 3 T & L N. A.700 R 4 T & L N. A.830 R
6 T & L
N. A.
Rationale—This is a new SAE Recommended Practice. It combines content that is in SAE J1392 plus requirements for specifying additional high strength steels (180 MPa yield strength to 1500 MPa tensile strength.)
Relationship of SAE Standard to ISO Standard—CR HSLA grade levels equivalent to ISO 13887.
Application—This SAE Recommended Practice establishes a procedure for categorizing mechanical properties of dent resistant, high strength, and ultra high strength automotive sheet steels. These steels can be specified as hot-rolled or cold-rolled and uncoated or coated.
Reference Section
SAE J416—Tensile Test Specimens
SAE J810—Classifications of Common Imperfections in Sheet Steel
SAE J1058—Standard Sheet Thickness’ and Tolerances
SAE J1392—Steel, High Strength, Hot Rolled Sheet and Strip, Cold Rolled Sheet, and Coated Sheet
SAE J1562—Selection of Zinc and Zinc-Alloy (Hot Dipped and Electrodeposited) Coated Steel Sheet
SAE J2328—Selection and Specification of Steel Sheet, Hot Rolled, Cold Rolled, and Coated for Automotive Applications.
SAE J2329—Categorization and Properties of Low Carbon Automotive Sheet Steels
ASTM A370—Standard Test Methods and Definitions for Mechanical Testing of Steel Products
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
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
ANSI/AWS/SAE D8.8-97—A Specification for Automotive and Light Truck Component Weld Quality -Arc Welding
AZ-017-02-295 1.0C RI—Weld Quality Test Method Manual; Standardized Welding Test Method Task Force, Auto/Steel Partnership (A/SP)
ISO 13887—Cold Reduced Steel Sheet of Higher Strength with Improved Formability
Steel Products Manual, Sheet Steel; Iron and Steel Society Publication, January 1988
QCC-JT---汽车钢板弹簧技术条件
————————————————————————————————作者：————————————————————————————————日期：
Q/CC x x汽车股份有限公司企业标准 Q/CC JT018—2008 代替Q/CC JT018—2006 汽车钢板弹簧技术条件 Technical Requirements of Leaf Spring Used on Vehicle 2008-09-06发布2008-12-01实施xx汽车股份有限公司发布
目次 前言................................................................................. II 1 范围 (1) 2 规范性引用文件 (1) 3 术语和定义 (1) 4 技术要求 (1) 5 检验和试验方法 (3) 6 检验规则 (3) 7 标志、包装、贮存 (4) 8 质量保证 (4) 附录A （规范性附录）汽车用钢板弹簧台架试验方法 (5)
前言 本标准是对Q/CC JT018—2006《汽车钢板弹簧技术条件》的修订。本标准在修订过程中主要参考了GB/T 19844-2005《钢板弹簧》。本标准与Q/CC JT018—2006相比，主要变化如下： ——增加了“3术语和定义”； ——增加了“附录A（规范性附录）”； ——增加了“4.4热处理”中洛氏硬度的数值要求； ——修订了“5 检验和试验方法”细化了具体方法； ——对相关条款进行调换和规范； ——删除了旧版中有关产品“断裂数据”方面的内容。 本标准自实施之日起代替Q/CC JT018—2006。 本标准由xx汽车股份有限公司技术研究院提出。 本标准由xx汽车股份有限公司技术研究院标准化科归口。 本标准由xx汽车股份有限公司技术研究院K-底盘部负责起草。 本标准主要起草人：纪国锋、宗召波。
各种许用应力与抗拉强度、屈服强度的关系 我们在设计的时候常取许用剪切应力，在不同的情况下安全系数不同，许用剪切应力就不一样。校核各种许用应力常常与许用拉应力有联系，而许用材料的屈服强度（刚度）与各种应力关系如下： <一> 许用（拉伸）应力 钢材的许用拉应力[δ]与抗拉强度极限、屈服强度极限的关系： 1.对于塑性材料[δ]= δs /n 2.对于脆性材料[δ]= δb /n δb ---抗拉强度极限 δs ---屈服强度极限 n---安全系数 轧、锻件n=1.2-2.2 起重机械n=1.7 人力钢丝绳n=4.5 土建工程n=1.5 载人用的钢丝n=9 螺纹连接n=1.2-1.7 铸件n=1.6-2.5 一般钢材n=1.6-2.5 注：脆性材料：如淬硬的工具钢、陶瓷等。 塑性材料：如低碳钢、非淬硬中炭钢、退火球墨铸铁、铜和铝等。 <二> 剪切 许用剪应力与许用拉应力的关系： 1.对于塑性材料[τ]=0.6-0.8[δ] 2.对于脆性材料[τ]=0.8-1.0[δ] <三> 挤压 许用挤压应力与许用拉应力的关系 1.对于塑性材料[δj]=1.5- 2.5[δ]
2.对于脆性材料[δj]=0.9-1.5[δ] 注：[δj]=1.7-2[δ]（部分教科书常用） <四> 扭转 许用扭转应力与许用拉应力的关系： 1.对于塑性材料[δn]=0.5-0.6[δ] 2.对于脆性材料[δn]=0.8-1.0[δ] 轴的扭转变形用每米长的扭转角来衡量。对于一般传动可取[φ]=0.5°--1°/m；对于精密件，可取[φ]=0.25°-0.5°/m；对于要求不严格的轴，可取[φ]大于1°/m计算。 <五> 弯曲 许用弯曲应力与许用拉应力的关系： 1.对于薄壁型钢一般采取用轴向拉伸应力的许用值 2.对于实心型钢可以略高一点，具体数值可参见有关规范。
车用钢板的知识普及 钢板, 知识 汽车车身外壳绝大部分是金属材料，主要用钢板。现代汽车的钢板用什么方式防锈？为什 么有些轿车声称车身防锈蚀年限达10年以上？ 镀锌薄钢板广泛应用在汽车上，这是因为它有良好的抗腐蚀能力。早年人们在试验中发现，将铁和锌放人盐水中，二者无任何导线联结时，铁和锌都会生锈，铁生红锈，锌生“白锈”；若在二者间用导线联结起来，则铁不会生锈而锌生“白锈”，这样锌就保护了铁，这种现象叫牺牲阳极保护。工程师正是将这种现象运用到实际生产中，生产了镀锌钢板。经研究，在镀锌量350克／平方米（单面）时，镀锌钢板在屋外的寿命（生红锈），田园地带约为15一18年，工业地带大约3一5年，这比普通钢板长几倍甚至十几倍。 从20世纪70年代开始轿车车身钢板采用镀锌薄钢板，装配时镀锌面置于汽车内侧，提高车身耐蚀性能，非镀锌面置于汽车外侧，喷涂油漆。随着汽车对耐腐蚀性能的要求不断提高，镀锌钢板不断增加镀锌层重量，还出现了双层镀锌钢板。但由于增加镀锌重量也会使电镀锌的电能消耗大幅增加，导致材料成本的上升，因此20世纪70年代末又出现一种采用热浸镀锌工艺生产的镀锌钢板，称为热镀锌钢板。这种镀锌钢板用连续热镀锌工艺：冷轧板（注*）→加热→冷却至镀锌温度→镀锌→冷却→矫直。为了满足汽车对镀锌钢板的各种要求，一些生产厂家在镀锌生产线上对镀锌钢板进行扩散退火等特殊处理，以使钢板表面形成一种“锌－铁”合金镀层，其特点是涂漆后的焊接性和耐腐蚀性比纯锌镀层板要好。以后还出现了诸如“锌－铝－硅”、“锌－铝－铼”等合金化热镀锌钢板，使得热镀锌钢板的耐腐蚀性成倍提高，与油漆间 的结合性能长期稳定。 目前轿车已经广泛使用镀锌钢板，采用的镀锌钢板厚度从0.5至3.0毫米，其中车身复盖件多用0.6至0.8毫米的镀锌钢板。德国奥迪轿车的车身部件绝大部分采用镀锌钢板（部分用铝合金板），美国别克轿车采用的钢板80%以上是双面热镀锌钢板，上海帕萨特车身的外复盖件采用电镀锌工艺，内复盖件内部采用热镀锌工艺，可以使车身防锈蚀保质期长达11年。 材料是影响汽车质量的重要因素。在现代汽车中，车身材料占全车材料的很大部分。为了提高汽车行驶的经济性，减轻汽车重量是世界各大车厂的目标，近年来汽车上越来越多使用了铝或塑料等非钢铁材料做车身部件，例如奥迪A2全铝制车身，日产SUV“奇骏”用塑料做前翼子板，更多的乘用车保险杠用塑料制成。在日益广泛使用非钢铁材料做车身部件的形势下，高度依赖汽车制造业的钢铁企业将面临直接的威胁。因此，研制和发展轻质、高强度的汽车钢板 成为多年来钢铁企业的一个热点。
35CrMo抗拉强度和35CrMo屈服强度 35CrMo抗拉强度和35CrMo屈服强度知识： 材料名称：合金结构钢 牌号：35CrMo 标准：GB/T 3077-1988 ●35CrMo特性及适用范围： 有很高的静力强度、冲击韧性及较高的疲劳极限，淬透性较40Cr高，高温下有高的蠕变强度与持久强度，长期工作温度可达500℃；冷变形时塑性中等，焊接性差。用作在高负荷下工作的重要结构件，如车辆和发动机的传动件；汽轮发电机的转子、主轴、重载荷的传动轴，大断面零件 ●35CrMo化学成份： 碳 C ：0.32～0.40 硅 Si：0.17～0.37 锰 Mn：0.40～0.70 硫 S ：允许残余含量≤0.035 磷 P ：允许残余含量≤0.035 铬 Cr：0.80～1.10 镍 Ni：允许残余含量≤0.030 铜 Cu：允许残余含量≤0.030 钼 Mo：0.15～0.25 ●35CrMo力学性能： 抗拉强度σb (MPa)：≥985(100) 屈服强度σs (MPa)：≥835(85) 伸长率δ5 (％)：≥12 断面收缩率ψ (％)：≥45 冲击功 Akv (J)：≥63 冲击韧性值αkv (J/cm2)：≥78(8) 硬度：≤229HB 试样尺寸：试样毛坯尺寸为25mm ●35CrMo热处理规范及金相组织： 热处理规范：淬火850℃,油冷;回火550℃,水冷、油冷。 ●35CrMo交货状态：以热处理（正火、退火或高温回火）或不热处理状态交货，交货状态应在合同中注明。
40Cr的屈服强度、化学成分、力学性能 【40cr化学成分】 根据标准GB/T 3077-1999： 【40cr力学性能】 试样毛坯尺寸（mm）：25 热处理： 第一次淬火加热温度（℃）：850；冷却剂：油 第二次淬火加热温度（℃）：- 回火加热温度（℃）：520；冷却剂：水、油 抗拉强度（σb/MPa）：≥980 屈服点（σs/MPa）：≥785 断后伸长率（δ5/%）：≥9 断面收缩率（ψ/%）：≥45 冲击吸收功（Aku2/J）：≥47 布氏硬度（HBS100/3000）（退火或高温回火状态）：≤207 【40cr参考对应钢号】 我国GB的标准钢号是40Cr、德国DIN标准材料编号1.17035/1.7045、德国DIN标准钢号41Cr4/42Gr4、英国EN标准钢号18、英国BS标准钢号41Cr4、法国AFNOR标准钢号42C4、法国NF标准钢号38Cr4/41Cr4、意大利UNI标准钢号41Cr4、比利时NBN标准钢号42Cr4、瑞典SS标准钢号2245、美国AISI/SAE/ASTM 标准钢号5140、日本JIS标准钢号SCr440(H)/SCr440、美国AISI/SAE/ASTM标准钢号5140、国际标准化组织ISO标准钢号41Cr4。 【40cr临界点温度】 （近似值） Acm=780℃ 【40cr正火规范】
钢筋抗拉强度标准值和屈服强度的标准值有什么区别 普通钢筋的抗拉强度设计值?y是普通钢筋强度标准值（屈服强度标准值）除以材料分项系数γs。钢筋的强度标准值应具有不小于95％的保证率。钢筋屈服强度特征值是在无限多次检验中，与某一规定概率所对应的分位值。屈服强度的标准值?yk相当于钢筋标准中的屈服强度特征值ReL。 如表4.2.3-1中抗拉强度设计值?y及抗压强度设计值?ˊy是由表4.2.2-1中屈服强度标准值?yk除以材料分项系数γs所得： HPB300的270（N/mm2），是300÷1.10＝272.7＝270（N/mm2）； HRB335的300（N/mm2），是335÷1.10＝304.5＝300（N/mm2）； HRB400的360（N/mm2），是400÷1.10＝363.6＝360（N/mm2）； HRB500的435（N/mm2），是500÷1.15＝434.7＝435（N/mm2）。 设计是根据钢产品标准的修改，不再限制钢筋材料的化学成分和制作工艺，而按性能确定钢筋的牌号和强度级别，并以相应的符号表达。普通钢筋采用屈服强度标志。增列了钢筋极限强度（即钢筋拉断前相于最大拉力下的强度）的标准值?stk，相当于钢筋标准中的抗拉强度特征值Rm。 钢筋的强度设计值为其强度标准值除以材料分项系数γs的数值。延性较好的热轧钢筋γs取1.10。但对新列入的高强度500MPa级钢筋适当提高安全储备，取为1.15。 向左转|向右转 向左转|向右转
参考资料：《混凝土结构设计规范》GB50010-2010和《钢筋混凝土用钢第1部 分热轧光圆钢筋》GB1499.1-2008和《钢筋混凝土用钢第2部分热轧带肋钢筋》 GB1499.2-2007 钢筋抗拉强度、抗拉强度标准值、设计值区别，帮解释下 以HRB335为例，抗拉强度为455，标准值为355，设计值为300，为什么抗拉强度标准值和抗拉强度怎么不一样，还有，为什么屈服强度等于抗拉强度标准值？ 答：钢筋在受到外力作用下会产生变形，变形过程分为弹性阶段、屈服阶段、强化阶段和颈缩阶段。在屈服阶段之前，如果卸去外力，还可以恢复到以前状态（物理变化），标准值说的就是下屈服值（例：HRB335钢筋屈服点为335Mpa。抗拉强度为最大力强度，即为455Mpa.）一般设计时都采用屈服强度为设计值，所以设计值远远小于抗拉强度，就是考虑到钢筋在收到外力作用下的变形，（即：在达到屈服强度还可以回复原来状态）。
１ 车用钢板弹簧概述 车用钢板弹簧又称为叶片弹簧，它是汽车悬架中应用广泛的一种弹性元件。它由若干片长度不等、曲率半径不同、厚度相等或不等的弹簧钢片叠合在一起，组成一根近似等强度的弹性梁。钢板弹簧的断面形状除采用对称断面外，还有采用上下对称的特殊断面。这样可改善弹簧的受力状况，不仅提高了其疲劳强度，还节约了金属材料。 钢板弹簧在载荷作用下变形，各片之间因相对滑动而产生摩擦，可使车架的振动衰减。各片之间处于干摩擦，同时还要将车轮所受冲击力传递给车架，因此增大了各片的磨损。所以在装合时，各片之间要涂上较稠的石墨润滑脂进行润滑，并应定期维护。钢板弹簧本身还起导向装置的作用，可不必单设导向装置，使结构简化。有些高级轿车的后悬架也采用钢板弹簧作弹性元件。目前一些汽车上采用变厚度的单片或２～３片的钢板弹簧，可以减小片与片之间的干摩擦，同时减轻了重量。 ２ 钢板弹簧的功能结构 在采用传统弹簧的吸震式悬架设计上，弹簧起支持车身以及吸收不平路面和其他施力对轮胎所造成的冲击的作用，而这里所谓的其他施力包含加速、减速、制动、转弯等对弹簧造成的施力。更重要的是在消除振动的过程中要保持轮胎与路面的持续接触，维持车辆的循迹性。如果弹簧很软，则很容易出现“坐底”的情况，即将悬架的行程用尽。假如在转弯时发生坐底情况，则 可视为弹簧的弹力系数变成无限大 （已无压缩的空间），车身会立即产 生质量转移，使循迹性丧失。如果 这辆车有着很长的避振行程，那么 或许可以避免“坐底”，但相对的车 身也会变得很高，而很高的车身意 味着很高的车身重心，车身重心的 高低对操控表现有决定性的影响， 所以，太软的弹簧会导致操控上的 障碍。 如果路面的崎岖度较大，那就 需要比较软的弹簧才能确保轮胎与 路面接触，同时弹簧的行程也必须 增加。弹簧的硬度选择要由路面的 崎岖程度来决定，越崎岖要越软的 弹簧，但要多软则是个关键的问题， 通常这需要经验的累积。一般来说， 软的弹簧可以提供较佳的舒适性以 及行经较崎岖的路面时可保持比较 好的循迹性；但是，在行经一般路 面时，却会造成悬架系统较大的上 下摆动，影响操控。而在配备有良 好空气动力学组件的车辆上，软的 弹簧在速度提高时会使车高发生变 化，造成低速和高速时不同的操控 特性。一般载货汽车均采用钢板弹 簧作为弹性元件的非独立悬架，因 钢板弹簧既有缓冲、减振的功能，又 起传力和导向的作用，使得悬架结 构大为简化。 为了充分利用材料，钢板弹簧 做成接近于应力粱的形式，分为２种 类型：一种是等厚度，宽度呈现两 端狭，中间宽，即多片钢板弹簧，传 统的钢板弹簧就是这一类型。这种 钢板弹簧由多片长度不等、宽度一 样的钢片迭成，现在多数大客车、货 车都使用这种钢板弹簧。另一种是 等宽度、两端薄、中间厚的。常见 的少片钢板弹簧就是这一类型，多 用于轻中型汽车。 多片钢板弹簧的各片钢板叠加 成倒三角形状，钢板的片数与支承 汽车的质量和减振效果相关，钢板 越多越厚越短，弹簧刚性就越大；但 是，当钢板弹簧挠曲时，各片之间 就会互相滑动摩擦产生噪声，摩擦 还会引起弹簧变形，造成行驶不平 顺，因此，在承载量不是很大的汽 车上，就出现了少片钢板弹簧，以 消除多片钢板弹簧的缺陷。少片钢 板弹簧的钢板截面变化大，从中间 到两端的截面是逐渐不同，因此轧 制工艺比较复杂。为了减轻质量和 轧制工艺难度，目前出现了一种纤 维增强塑料（ＦＲＰ）代替钢板，质量 可减少１／２以上。 钢板弹簧的中部一般固定在车 桥上。主片卷耳受力严重、是薄弱 处，为改善主片卷耳的受力情况，常 将第二片末端也弯成卷耳，包在主 片卷耳的外面（亦称包耳）。为了使 得在弹簧变形时各片有相对滑动的 可能，在主片卷耳与第二片包耳之 间留有较大的空隙。有些悬架中的 钢板弹簧两端不做成卷耳，而采用 其他的支承连接方式（如非独立悬 架）。中心螺栓用来连接各种弹簧 片，并保证各片装配时的相对位置。 中心螺栓到两端卷耳中心的距离可 以相等，也可不相等者。 钢板弹簧端部有三种结构型 式：端部为矩形的钢板，其制造简 单，广泛应用在载货汽车上；端部 为梯形的钢板，其质量小、节省钢 材，较多的用在载货汽车上；端部 为椭圆形的钢板，这种结构改善了 汽车钢板弹簧的应用及其发展趋势 肖 军
汽车车身钢板的规格及选用 汽车车身外壳绝大部分是金属材料，主要用钢板。现代汽车的钢板用什么方式防锈？为什么有些轿车声称车身防锈蚀年限达10年以上？ 镀锌薄钢板广泛应用在汽车上，这是因为它有良好的抗腐蚀能力。早年人们在试验中发现，将铁和锌放人盐水中，二者无任何导线联结时，铁和锌都会生锈，铁生红锈，锌生“白锈”；若在二者间用导线联结起来，则铁不会生锈而锌生“白锈”，这样锌就保护了铁，这种现象叫牺牲阳极保护。工程师正是将这种现象运用到实际生产中，生产了镀锌钢板。经研究，在镀锌量350克／平方米（单面）时，镀锌钢板在屋外的寿命（生红锈），田园地带约为15一18年，工业地带大约3一5年，这比普通钢板长几倍甚至十几倍。 从20世纪70年代开始轿车车身钢板采用镀锌薄钢板，装配时镀锌面置于汽车内侧，提高车身耐蚀性能，非镀锌面置于汽车外侧，喷涂油漆。随着汽车对耐腐蚀性能的要求不断提高，镀锌钢板不断增加镀锌层重量，还出现了双层镀锌钢板。但由于增加镀锌重量也会使电镀锌的电能消耗大幅增加，导致材料成本的上升，因此20世纪70年代末又出现一种采用热浸镀锌工艺生产的镀锌钢板，称为热镀锌钢板。这种镀锌钢板用连续热镀锌工艺：冷轧板（注*）→加热→冷却至镀锌温度→镀锌→冷却→矫直。为了满足汽车对镀锌钢板的各种要求，一些生产厂家在镀锌生产线上对镀锌钢板进行扩散退火等特殊处理，以使钢板表面形成一种“锌－铁”合金镀层，其特点是涂漆后的焊接性和耐腐蚀性比纯锌镀层板要好。以后还出现了诸如“锌－铝－硅”、“锌－铝－铼”等合金化热镀锌钢板，使得热镀锌钢板的耐腐蚀性成倍提高，与油漆间的结合性能长期稳定。 目前轿车已经广泛使用镀锌钢板，采用的镀锌钢板厚度从0.5至3.0毫米，其中车身复盖件多用0.6至0.8毫米的镀锌钢板。德国奥迪轿车的车身部件绝大部分采用镀锌钢板（部分用铝合金板），美国别克轿车采用的钢板80%以上是双面热镀锌钢板，上海帕萨特车身的外复盖件采用电镀锌工艺，内复盖件内部采用热镀锌工艺，可以使车身防锈蚀保质期长达11年。 材料是影响汽车质量的重要因素。在现代汽车中，车身材料占全车材料的很大部分。为了提高汽车行驶的经济性，减轻汽车重量是世界各大车厂的目标，近年来汽车上越来越多使用了铝或塑料等非钢铁材料做车身部件，例如奥迪A2全铝制车身，日产SUV“奇骏”用塑料做前翼子板，更多的乘用车保险杠用塑料制成。在日益广泛使用非钢铁材料做车身部件的形势下，高度依赖汽车制造业的钢铁企业将面临直接的威胁。因此，研制和发展轻质、高强度的汽车钢板成为多年来钢铁企业的一个热点。 目前汽车生产中，使用得最多的是普通低碳钢板。低碳钢板具有很好的塑性加工性能，强度和刚度也能满足汽车车身的要求，同时能满足车身拼焊的要求，因此在汽车车身上应用很广。为了满足汽车制造业追求轻量化的要求，钢铁企业推出高强度汽车钢材系列钢板。这种高强度钢板是在低碳钢板的基础上采用强化方法得到的，抗拉强度得到大幅增强。利用高强度特性，可以在厚度减薄的情况下依然保持汽车车身的机械性能要求，从而减轻了汽车重量。例如BH钢板是在低强度的条件下，经过冲压成形之后，进行烤漆加工热处理，以提高其抗拉强度。对比之下，以往生产的强度在440MPa的钢板，在采用这种加工技术以后强度可增加到500MPa。原来用厚度1毫米钢板做侧面板，用高强度钢板只需厚度0.8毫米。采用高强度钢板还可以有效地提高汽车车身的抗冲击性能，防止在行驶中由于路面的砂石飞溅碰撞产生凹痕，延长了汽车的使用寿命。
中国汽车用钢材深度分析报告 新闻出处：中国矿业联合会发布时间： 2006-10-19 09:00 汽车用钢品种构成 汽车用钢品种主要包括钢板、优质钢、型钢、带钢、钢管、金属制品等。汽车工业的发展，对钢铁材料提出了更高的要求。汽车用钢中的板材（包括热轧钢板、冷轧钢板和镀层板）是生产汽车的最主要原材料，发达国家板材产量的50%以上是供应给汽车制造厂的。目前，全球汽车制造业在全球所消费的钢材已超过了1亿吨，加上生产汽车部件所消费的钢材，全球每年仅汽车行业消费的钢材就超过1.5亿吨。用于制造汽车的钢板简称汽车板，制造一辆轿车约需使用薄钢板600～800kg。根据汽车板的使用部位是否暴露在外，又可将它分为汽车外板和汽车内板。其中，汽车外板是汽车板中生产难度最大的产品，通常采用德国标准称之为“O5”板，它要求表面无缺陷，同时还要具有一般汽车板所要求的优良冲压成型性、焊接性及耐蚀性。为解决腐蚀问题，新型的镀层钢板应运而生。目前，汽车制造业规定的汽车车体表面涂层耐蚀为5年、车体穿孔耐蚀为10年。为了保证人员的乘车安全，要检验汽车的安全性，作为主要手段之一的实车正面碰撞破坏性实验是国际上的通用做法，这也检验了汽车板的性能，对汽车板的质量提出了更加严格的要求。虽然新材料将取代部分汽车用钢，但钢铁在相当长的时间内仍是汽车最主要的原材料，并长期稳定在60～70％的比例。钢铁是汽车安全、长寿及低成本的关键。当前全球汽车工业正积极寻求减轻汽车自重的方法和途径。汽车工业用来减轻汽车自重的先进的高强度钢材主要用于汽车外壳和结构件，并和轻金属进行竞争。同时，夹层钢板也是改善刚度减轻汽车自重的另一种材料选择。据预测，未来几年内，高强度钢在汽车中的应用将迅速增长，，年增长率达到5%。有人预计，到2010年，在通用汽车公司车身所用的材料中，双相钢可能占约45%，中强度钢约33%，低碳钢和马氏体钢各占约10%。 中国汽车板生产企业情况 自2002年起，宝钢已实现向南京菲亚特、上海通用、上海大众、一汽大众、神龙汽车、广州本田、风神汽车、东南汽车、长安汽车、四川丰田及国内各
问题：什么是抗拉强度，延伸率，屈服强度？ 球铁管是一种即有高强度和高弹性的输水管道，球铁管优秀的力学性能是它在种类繁多的输水管材中立于不败之地的保证，因而我们有必要对描述球铁管的各种力学性能做一番介绍： 1． 延伸率 延伸率主要衡量球墨铸铁塑性性能-即发生永久变形而不至于断裂的性能。 δ= (L-L 0)/L 0*100% δ---伸长率 L 0----试样原长度 L----试样受拉伸断裂后的长度 2． 强度 强度是金属材料在外力作用下抵抗永久变形和断裂的能力。工程上常用来表示金属材料强度的指标有屈服强度和抗拉强度。 a. 屈服强度是金属材料发生屈服现象时的屈服极限，亦即抵抗微量塑性变形的应力。 δS =Fs/A O Fs----试样产生屈服现象时所承受的最大外力（N ） A O ----试样原来的截面积（mm 2） δS ---屈服强度(Mpa) b. 抗拉强度是指金属材料在拉断前所能承受的最大应力，用δb =F O /A O F O ----试样在断裂前的最大外力（N ） A O ----试样原来的截面积（mm 2） δb ---抗拉强度（Mpa ） Table:三种不同材料之间的机械性能对比 对于球墨铸铁管而言，其试样实际就是取自插口处试样加工过后的试棒；对球墨铸铁管件而言，其试样通常是取自与管件同批的铁水铸出的Y 型试块加工成的试棒。 管材和管件的抗拉强度实验，就是用试棒拉断前的最大持续力除以试棒面积计算得出的抗拉强度。把试棒断裂的两部分拼在一起测量伸长的标距，用伸长标距与初始标距之比求得伸长率。 不同的管材之间因为力学性能实验方法有别，所以某些管材宣传他们的力学性能甚至优于铸铁管是毫无根据的。 退火球墨铸铁 铸态球墨铸铁管 灰口铁管 屈服强度 ≥300MPa 未定义 未定义 抗拉强度 ≥420MPa ≤300MPa ≥200 MPa 延伸率 ≥10% ≥3% ≤3% 断裂形式 塑性变形 突然断裂 突然断裂
板材分类及牌号常识 上海鲁亿实业公司主营汽车高强钢，提供加工配送一条龙服务，纵剪宽度最小能达到3MM，公差保持0.05-0.1MM 之间，可以根据客户尺寸加工，加工精确度高 一、钢板（包括带钢）的分类： 1、按厚度分类：（1）薄板（2）中板（3）厚板（4）特厚板 2、按生产方法分类：（1）热轧钢板（2）冷轧钢板 3、按表面特征分类：（1）镀锌板（热镀锌板、电镀锌板）（2）镀锡板（3）复合钢板（4）彩色涂层钢板 4、按用途分类：（1）桥梁钢板（2）锅炉钢板（3）造船钢板（4）装甲钢板（5）汽车钢板（6）屋面钢板 （7）结构钢板（8）电工钢板（硅钢片）（9）弹簧钢板（10）其他 二、普通及机械结构用钢板中常见的日本牌号 1、日本钢材(JIS系列)的牌号中普通结构钢主要由三部分组成第一部分表示材质。 如：S（Steel）表示钢，F（Ferrum）表示铁；第二部分表示不同的形状、种类、用途，如P(Plate)表示板，T （Tube）表示管，K(Kogu)表示工具；第三部分表示特征数字，一般为最低抗拉强度。如：SS400--第一个S表示钢(Steel)，第二个S表示"结构"（Structure），400为下限抗拉强度400MPa，整体表示抗拉强度为400 MPa的普通结构钢。 2、SPHC--首位S为钢Steel的缩写，P为板Plate的缩写，H为热Heat的缩写，C商业Commercial的缩写，整体表示一般用热轧钢板及钢带。 3、SPHD--表示冲压用热轧钢板及钢带。 4、SPHE--表示深冲用热轧钢板及钢带。 5、SPCC--表示一般用冷轧碳素钢薄板及钢带，相当于中国Q195-215A牌号。其中第三个字母C为冷Cold的缩写。需保证抗拉试验时，在牌号末尾加T为SPCCT。 6、SPCD--表示冲压用冷轧碳素钢薄板及钢带，相当于中国08AL（13237）优质碳素结构钢。 7、SPCE--表示深冲用冷轧碳素钢薄板及钢带，相当于中国08AL（5213）深冲钢。需保证非时效性时，在牌号末尾加N为SPCEN。冷轧碳素钢薄板及钢带调质代号：退火状态为A，标准调质为S，1/8硬为8，1/4硬为4，1/2硬为2，硬为1。表面加工代号：无光泽精轧为D，光亮精轧为B。如SPCC-SD表示标准调质、无光泽精轧的一般用冷轧碳素薄板。再如SPCCT-SB表示标准调质、光亮加工，要求保证机械性能的冷轧碳素薄板。 8、JIS机械结构用钢牌号表示方法为： S+含碳量+字母代号（C、CK），其中含碳量用中间值×100表示，字母C：表示碳 K：表示渗碳用钢。如碳结卷板S20C其含碳量为0.18-0.23%。 三、我国及日本硅钢片牌号表示方法 1、中国牌号表示方法： （1）冷轧无取向硅钢带（片）。表示方法：DW+铁损值（在频率为50HZ，波形为正弦的磁感峰值为1.5T的单位重量铁损值。）的100倍+厚度值的100倍。如DW470-50 表示铁损值为4.7w/kg，厚度为0.5mm的冷轧无取向硅钢，现新型号表示为50W470。 （2）冷轧取向硅钢带（片）。表示方法：DQ+铁损值（在频率为50HZ，波形为正弦的磁感峰值为1.7T的单位重量铁损值。）的100倍+厚度值的100倍。有时铁损值后加G表示高磁感。如DQ133-30表示铁损值为1.33，厚度为0.3mm的冷轧取向硅钢带（片），现新型号表示为30Q133。 （3）热轧硅钢板。热轧硅钢板用DR表示，按硅含量的多少分成低硅钢（含硅量≤2.8%）、高硅钢（含硅量＞2.8%）。表示方法：DR+铁损值（用50HZ反复磁化和按正弦形变化的磁感应强度最大值为1.5T时的单位重量铁损值）的100倍+厚度值的100倍。如DR510-50表示铁损值为5.1，厚度为0.5mm的热轧硅钢板。家用电器用热轧硅钢薄板的牌号用JDR+铁损值+厚度值来表示，如JDR540-50。 2、日本牌号表示方法： （1）冷轧无取向硅钢带。由公称厚度（扩大100倍的值）+代号A+铁损保证值（将频率50HZ，最大磁通密度
钢板是汽车的主要用材，按生产工艺分为热轧板和冷轧板，热轧板的厚度多在3mm以上，冷轧板在3mm以下。目前，汽车车身生产中，特别是冲压生产中，使用得最多的是普通低碳钢板。低碳钢板具有很好的塑性加工性能，其强度和钢度也能完全满足汽车车身的强度和钢度要求，同时能满足车身拼焊的焊接要求。随着汽车向安全环保节能目标发展的要求，冶金企业和汽车生产厂还开发出高强度钢板、深冲钢板、镀层钢板等新型汽车用钢。 (1)低合金钢强度热轧钢板 随着汽车向轻量化和节能方向发展，用高强度钢板生产汽车零件已成为发展趋势。热轧高强度钢板在载货汽车上用量很大，约占载重车用热轧钢板总量的60-70％。主要用于汽车车架纵梁、横粱，车厢的纵、横梁以及刹车盘等受力结构件和安全件。经过多年的开发和应用研究，我国已形成锰钢或锰稀土系列，硅—钒钢、含钛钢系列和含钒钢系列。 含钛系热轧钢板含钛热轧钢板在汽车上的用量很大。由于含钛钢板强度高，实际冲压性能好，不仅可大幅度降低汽车自重，同时，汽车使用寿命成倍提高。钢中加入钛，既提高钢板的强度，又改变钢中硫化物夹杂的形态和分布。含钛钢板的冲击韧度很高。但热轧含钛钢也存在一些问题，一是钛对温度很敏感，当终轧后冷却速座控制不当，会导致含钛钢板的头、中、尾的强度波动大，形成强度分布的盆形曲线。 热轧含铌钢系列为节约合金元素，降低钢的生产成本，目前，国内外大量应用热轧含铌钢板。铌的强化能力大于钛，由于钛优先与氮化合并与硫形成钛硫化合物，直接增加了钛在钢中的含量。铌只是强化元素，要获得同级强度的钢板，钢中含铌量仅为含钛量的1/ 3左右，显示了含铌的优越性。 双相钢板其主要添加元素为Si、Mn、(Nb)、Cr。已形成了Si-Mn系、Si-Mn-Cr 系和Si-Mn-Mo系，有540MPa、590MPa和640MPa三种强度级别材料，强度和延伸率都很高、延伸率好、屈服强度较低，更易变形，具有良好的冷成形性，其重要特性是具有优良的翻边性能，很适合冲压翻边性能良好的部件。 TRIP钢TRIP钢是含有残余奥氏体的低碳、低合金高强度钢，主要化学成分为C-Si-Mn元素，强度级别为500 MPa-700MPa，强度和塑性配合良好，用于生产汽车的零部件。浦项钢铁公司现在正开发1000MPa级TRIP钢并己商业化。在
钢筋的屈服强度和抗拉强度 HPB235钢筋，屈服点强度为235MPa，（延伸率为17%）； HRB335钢筋，屈服点强度为335MPa，（延伸率为16%)； HRB400钢筋，屈服点强度为400MPa，（延伸率为15%）。 根据规定，直径28－40的钢筋，断后延伸率可降低1%，40以上的钢筋可降低2%。 以上要求是交货检验的最小保证值 实验钢筋的拉伸试验 简单的说就是钢筋伸长段与钢筋原长的比。 ①钢筋强度的计算 试件的屈服强度按下式计算： 式中ps——屈服点荷载，n； a0——试件横截面积，cm2。 试件的抗拉强度按下式计算： 式中p0——屈服点荷载，n； a0——试件横截面积，cm2。 ②伸长率的测定 a. 将已拉断试件的两段在断裂处对齐，尽量使其轴线位于一条
直线上。如拉断处由于各种原因形成缝隙，则此缝隙应计入试件拉断后的标距部分长度内。 b. 如拉断处到邻近标距端点的距离大于(1／3)l0时，可用卡尺直接量出已被拉的标距长度l1（mm)。 c. 如拉断处到邻近的标距端点的距离小于或等于(1/3)l0时，可按移位法计算。 d. 伸长率按下式计算（精确至1％）： 式中δ——伸长率，％，精确至1％； l0——原标距长度，mm； l1——试件拉断后直接量出或按移位法确定的标距部分的长度，mm（测量精确 mm）。 e. 如试件在标距端点上或标距外断裂，则试验结果无效，应重作试验。 将测试、计算所得到的结果δ10、δ5（δ10、δ5分别表示l0＝10a和l0＝5a时的断后伸长率），对照国家规范对钢筋性能的技术要求，如达到标准要求则合格，如未达到，可取双倍试验重做，如仍未达到标准者，则钢筋的伸长率不合格。 联系电话： 企业网址：山东金业机械有限公司
（汽车行业）汽车车身新材料的应用及发展方向
汽车车身新材料的应用及发展趋势 现代汽车车身除满足强度和使用寿命的要求外，仍应满足性能、外观、安全、价格、环保、节能等方面的需要。在上世纪八十年代，轿车的整车质量中，钢铁占80％，铝占3％，树脂为4％。自1978年世界爆发石油危机以来，作为轻量化材料的高强度钢板、表面处理钢板逐年上升，有色金属材料总体有所增加，其中，铝的增加明显；非金属材料也逐步增长，近年来开发的高性能工程塑料，不仅替代了普通塑料，而且品种繁多，在汽车上的应用范围广泛。本文着重介绍国内外在新型材料应用方面的情况及发展趋势。 高强度钢板 从前的高强度钢板，拉延强度虽高于低碳钢板，但延伸率只有后者的50％，故只适用于形状简单、延伸深度不大的零件。当下的高强度钢板是在低碳钢内加入适当的微量元素，经各种处理轧制而成，其抗拉强度高达420N/mm2，是普通低碳钢板的2～3倍，深拉延性能极好，可轧制成很薄的钢板，是车身轻量化的重要材料。到2000年，其用量已上升到50%左右。中国奇瑞汽车X公司和宝钢合作，2001年在试制样车上使用的高强度钢用量为262kg，占车身钢板用量的46%，对减重和改进车身性能起到了良好的作用。低合金高强度钢板的品种主要有含磷冷轧钢板、烘烤硬化冷轧钢板、冷轧双相钢板和高强度1F冷轧钢板等，车身设计师可根据板制零件受力情况和形状复杂程度来选择钢板品种。含磷高强度冷轧钢板：含磷高强度冷轧钢板主要用于轿车外板、车门、顶盖和行李箱盖升板，也可用于载货汽车驾驶室的冲压件。主要特点为：具有较高强度，比普通冷轧钢板高15％～25％；良好的强度和塑性平衡，即随着强度的增加，伸长率和应变硬化指数下降甚微；具有良好的耐腐蚀性，比普通冷轧钢板提高20％；具有良好的点焊性能；烘烤硬化冷轧钢板：经过冲压、拉延变形及烤漆高温时效处理，屈服强度得以提高。这种简称为BH钢板的烘烤硬化钢板既薄又有足够的强度，是车身外板轻量化设计首选材料之壹；冷轧双向钢板：具有连续屈服、屈强比低和加工硬化高、兼备高强度及高塑性的特点，如经烤漆后其强度可进壹步提高。适用于形状复杂且要求强度高的车身零件。主要用于要求拉伸性能好的承力零部件，如车门加强板、保险杠等；超低碳高强度冷轧钢板：在超低碳钢（C≤0.005％）中加入适量的钛或铌，以保证钢板的深冲性能，再添加适量的磷以提高钢板的强度。实现了深冲性和高强度的结合，特别适用于壹些形状复杂而强度要求高的冲压零件。 轻量化迭层钢板 迭层钢板是在俩层超薄钢板之间压入塑料的复合材料，表层钢板厚度为0.2～0.3mm，塑料层的厚度占总厚度的25％～65％。和具有同样刚度的单层钢板相比，质量只有57％。隔热防振性能良好，主要用于发动机罩、行李箱盖、车身底板等部件。铝合金 和汽车钢板相比，铝合金具有密度小（2.7g/cm3）、比强度高、耐锈蚀、热稳定性好、易成形、可回收再生等优点，技术成熟。德国大众X公司的新型奥迪A2型轿车，由于采用了全铝车身骨架和外板结构，使其总质量减少了135kg，比传统钢材料车身减轻了43％，使平均油耗降至每百公里3升的水平。全新奥迪A8通过使用性能更好的大型铝铸件和液压成型部件，车身零件数量从50个减至29个，车身框架完全闭合。这种结构不仅使车身的扭转刚度提高了60%，仍比同类车型的钢制车身车重减少50%。由于所有的铝合金都能够回收再生利用，深受环保人士的欢迎。根据车身结构设计的需要，采用激光束压合成型工艺，将不同厚度的铝板或者用铝板和钢板复合成型，再在表面涂覆防具有良好的耐腐蚀性。 镁合金 镁的密度为1.8g/cm3，仅为钢材密度的35％，铝材密度的66％。此外它的比强度、比刚度高，阻尼性、导热性好，电磁屏蔽能力强，尺寸稳定性好，因此在航空工业和汽车工业中得到了广泛的应用。镁的储藏量十分丰富，镁可从石棉、白云石、滑石中提取，特别是海水的
宝钢高强度汽车钢板 宝钢新开发的高强度汽车用钢有4个强度级别（屈服强度），与欧洲标准一致。 1. 技术标准 表1 宝钢高强度汽车钢板的技术指标（欧洲标准） 注：厚度大于8mm屈服强度可降低20MPa。 注：Nb+ V+ Ti≤0.22% 2．实物水平
2.2 650MPa级冷弯照片 8mm钢板 3mm钢板 3mm和8mm钢板2.3 700MPa级冷弯照片 8mm钢板 8mm钢板 4mm钢板 3. 可供规格 4.焊接 宝钢汽车用热轧高强钢通过低碳低合金设计降低钢的碳当量和焊接裂纹敏感系数，具有良好的可焊接性能，不需预热就可直接进行焊接。 Ceq=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15 Pcm=C+(Mn+Cr+Cu)/20+V/10+Mo/15+Si/30+Ni/60+5B 焊接方法 宝钢汽车用热轧高强钢可使用气体保护焊（MAG）和手工电弧焊（SMAW）、埋弧焊（SAW）进
行焊接，推荐使用气体保护焊（MAG ）。 焊接热输入 焊接时使用推荐的热输入，可使热影响区具有良好的机械性能。并且热输入范围越宽说明该钢种的焊接性能越好。 焊接热输入由下列公式计算： 60 1000 k U I Q v ???= ? 下图为按钢板厚度推荐的最佳焊接热输入范围： 在厚度一定的条件下宝钢汽车用热轧高强钢的许用焊接热输入范围很宽，具有优良的焊接性能。 坡口形式 宝钢汽车用热轧高强钢适用于多种接头型式的焊接，常用的接头型式有：I 型坡口、V 型坡口 焊接材料 在焊接接头力学性能满足构件要求的情况下，为避免接头处的应力集中、降低焊缝的内应力，应尽可能选择强度不超过推荐值的焊材。
抗拉强度与屈服强度的区别及实例 首先自我介绍一下，本人现在某检测机构任职，我任职的这家机构主要是对金属材料进行理化检验，有CMA认证（中国计量认证）、CNAS 认证（国家认可委认证），属国家级实验室。检测结果全球100多个国家互认。本人任金属物理检测室副主任，物理检测技术组组长。应当算得上是专业人士。 什么是的屈服强度和抗拉强度。 要说这两个概念，先从材料是如何被破坏的说起。任何材料在受到不断增大或者持续恒定或者持续交变的外力作用下，最终会超过某个极限而被破坏。对材料造成破坏的外力种类很多，比如拉力、压力、剪切力、扭力等。 屈服强度和抗拉强度这两个强度，仅仅是针对拉力而言。这两个强度是通过拉伸试验得出的，是通过拉力试验机（一般是万能试验机，可以进行各种拉和压以及弯曲的试验），用规定的恒定的加荷速率(就是单位时间内拉力的增加量)，对材料进行持续拉伸，直到断裂或达到规定的破坏程度（比如有些对接焊缝强度试验可以不拉断），这个造成材料最终破坏的力，就是该材料的抗拉极限载荷。 抗拉极限载荷是一个力的表述，单位为牛顿（N），因为牛顿是一个很小的单位，所以，大部分情况下用千牛（KN）的比较多。因为各种材料大小不一，所以抗拉极限载荷很难评判材料的强度。所以，用抗拉极限载荷除以实验材料的截面积，就得到单位面积的抗拉极限载荷。单位面积上受的力，这是一个强度的表述，单位是帕斯卡（Pa），同
样，帕斯卡是一个极小的单位，一般都用兆帕（MPa）来表述。所以，抗拉极限载荷与实验材料的截面积之比，就是抗拉强度。抗拉强度是材料单位面积上所能承受外力作用的极限。超过这个极限，材料将被解离性破坏。 那什么是屈服强度呢？屈服强度仅针对具有弹性材料而言，无弹性的材料没有屈服强度。比如各类金属材料、塑料、橡胶等等，都有弹性，都有屈服强度。而玻璃、陶瓷、砖石等等，一般没有弹性，这类材料就算有弹性，也微乎其微，所以，没有屈服强度一说。 弹性材料在受到恒定持续增大的外力作用下，直到断裂。究竟发生了怎样的变化呢？首先，材料在外力作用下，发生弹性形变，遵循胡克定律。什么叫弹性形变呢？就是外力消除，材料会恢复原来的尺寸和形状。当外力继续增大，到一定的数值之后，材料会进入塑性形变期。材料一旦进入塑性形变，当外力，材料的原尺寸和形状不可恢复！而这个造成两种形变的的临界点的强度，就是材料的屈服强度！对应施加的拉力而言，这个临界点的拉力值，叫屈服点。从晶体角度来说，只有拉力超过屈服点，材料的晶体结合才开始被破坏！材料的破坏，是从屈服点就已经开始，而不是从断裂的时候开始的！弄清楚这两个强度怎么来的了，所以说，屈服强度高的材料，能承受的破坏力就
抗拉强度和屈服强度 抗拉强度 抗拉强度（tensile strength） 抗拉强度（бb）指材料在拉断前承受最大应力值。 当钢材屈服到一定程度后，由于内部晶粒重新排列，其抵抗变形能力又重新提高，此时变形虽然发展很快，但却只能随着应力的提高而提高，直至应力达最大值。此后，钢材抵抗变形的能力明显降低，并在最薄弱处发生较大的塑性变形，此处试件截面迅速缩小，出现颈缩现象，直至断裂破坏。钢材受拉断裂前的最大应力值称为强度极限或抗拉强度。 单位:kn/mm２（单位面积承受的公斤力） 抗拉强度：extensional rigidity. 抗拉强度=Eh，其中E为杨氏模量，h为材料厚度 目前国内测量抗拉强度比较普遍的方法是采用万能材料试验机等来进行材料抗拉/压强度的测定! 拉伸强度 拉伸强度（tensile strength）是指材料产生最大均匀塑性变形的应力。 （1）在拉伸试验中，试样直至断裂为止所受的最大拉伸应力即为拉伸强度，其结果以MPa 表示。有些错误的称之为抗张强度、抗拉强度等。 （2）用仪器测试样拉伸强度时，可以一并获得拉伸断裂应力、拉伸屈服应力、断裂伸长率等数据。 （3）拉伸强度的计算： σt = p /（b×d） 式中，σt为拉伸强度（MPa）；p为最大负荷（N）；b为试样宽度（mm）；d为试样厚度（mm）。 注意：计算时采用的面积是断裂处试样的原始截面积，而不是断裂后端口截面积。 屈服强度 材料拉伸的应力-应变曲线 yield strength 是材料屈服的临界应力值。 （1）对于屈服现象明显的材料，屈服强度就是在屈服点在应力（屈服值）；（2）对于屈服现象不明显的材料，与应力-应变的直线关系的极限偏差达到规定值（通常为0.2%的永久形变）时的应力。通常用作固体材料力学机械性能的评价指标，是材料的实际使用极限。因为材料屈服后产生颈缩，应变增大，使材料失去了原有功能。 当应力超过弹性极限后，变形增加较快，此时除了产生弹性变形外，还产生部分塑性变形。当应力达到B点后，塑性应变急剧增加，曲线出现一个波动的小平台，这种现象称为屈服。这
什么是屈服强度和抗拉强度 要说这两个概念，先从材料是如何被破坏的说起。任何材料在受到不断增大或者持续恒定或者持续交变的外力作用下，最终会超过某个极限而被破坏。对材料造成破坏的外力种类很多，比如拉力、压力、剪切力、扭力等。屈服强度和抗拉强度这两个强度，仅仅是针对拉力而言。这两个强度是通过拉伸试验得出的，是通过拉力试验机（一般是万能试验机，可以进行各种拉和压以及弯曲的试验），用规定的恒定的加荷速率(就是单位时间内拉力的增加量)，对材料进行持续拉伸，直到断裂或达到规定的破坏程度（比如有些对接焊缝强度试验可以不拉断），这个造成材料最终破坏的力，就是该材料的抗拉极限载荷。抗拉极限载荷是一个力的表述，单位为牛顿（N），因为牛顿是一个很小的单位，所以，大部分情况下用千牛（KN）的比较多。因为各种材料大小不一，所以抗拉极限载荷很难评判材料的强度。所以，用抗拉极限载荷除以实验材料的截面积，就得到单位面积的抗拉极限载荷。单位面积上受的力，这是一个强度的表述，单位是帕斯卡（Pa），同样，帕斯卡是一个极小的单位，一般都用兆帕（MPa）来表述。 所以，抗拉极限载荷与实验材料的截面积之比，就是抗拉强度。抗拉强度是材料单位面积上所能承受外力作用的极限。超过这个极限，材料将被解离性破坏。 那什么是屈服强度呢？屈服强度仅针对具有弹性材料而言，无弹性的材料没有屈服强度。比如各类金属材料、塑料、橡胶等等，都有弹性，都有屈服强度。而玻璃、陶瓷、砖石等等，一般没有弹性，这类材料就算有弹性，也微乎其微，所以，没有屈服强度一说。 弹性材料在受到恒定持续增大的外力作用下，直到断裂。究竟发生了怎样的变化呢？ 首先，材料在外力作用下，发生弹性形变，遵循胡克定律。什么叫弹性形变呢？就是外力消除，材料会恢复原来的尺寸和形状。当外力继续增大，到一定的数值之后，材料会进入塑性形变期。材料一旦进入塑性形变，当外力，材料的原尺寸和形状不可恢复！而这个造成两种形变的的临界点的强度，就是材料的屈服强度！对应施加的拉力而言，这个临界点的拉力值，叫屈服点。从晶体角度来说，只有拉力超过屈服点，材料的晶体结合才开始被破坏！材料的破坏，是从屈服点就已经开始，而不是从断裂的时候开始的！ 弄清楚这两个强度怎么来的了，所以说，屈服强度高的材料，能承受的破坏力就大，这是正确的。