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GB/T 20564 Continuously Cold Rolled High Strength Steel Sheet and Strip for Automobile consists of the following 11 parts under the general title:
——Part 1: Bake Hardening Steel;
——Part 2: Dual Phase Steel;
——Part 3: High Strength Interstitial Free Steel;
——Part 4: High Strength Low Alloy Steel;
——Part 5: Isotropic Steel;
——Part 6: Transformation Induced Plasticity Steel;
——Part 7: Martensitic Steels;
——Part 8: Complex Phase Steel;
——Part 9: Quenching and Partitioning Steel;
——Part 10: Twinning Induced Plasticity Steel;
——Part 11: Carbon Manganese Steel.
This is Part 3 of GB/T 20564.
This part is developed in accordance with the rules given in GB/T 1.1-2009.
This part replaces GB/T 20564.3-2007 Continuously Cold Rolled High Strength Steel Sheet and Strip for Automobile - Part 3: High Strength Interstitial Free Steel in whole. The following technical changes have been made with respect to GB/T 20564.3-2007:
——the range of nominal thickness is modified (see Chapter 1; Chapter 1 in 2007 edition);
——risk warning of unoiled product and the requirements of production completion date are added (see 7.3.2);
——description of mechanical performance guarantee period is added (see 7.4.1);
——the requirements of mechanical performance where supplied as designated parts are added (see 7.4.2);
——requirements for stretcher strain marks are added (see 7.5);
——the requirements of tensile test method are added (see 8.3);
——the reference values for chemical compositions of various designations in Annex A are modified (see Annex A; Annex A in 2007 edition).
This part was proposed by China Iron and Steel Association.
This part is under the jurisdiction of National Technical Committee on Iron and Steel of Standardization Administration of China (SAC/TC 183).
The previous edition of the standard replaced by this part is as follows:
—GB/T 20564.3-2007.
Continuously Cold Rolled High Strength Steel Sheet and Strip for Automobile - Part 3: High Strength Interstitial Free Steel
1 Scope
This part of GB/T 20564 specifies the terms and definitions, classification and designation expression method, ordering information, dimension, shape, weight, technical requirements, test methods, inspection rules, packaging, marking and quality certificate of continuously cold rolled high strength interstitial free steel.
This part is applicable to steel sheets and strips with thickness of 0.50~3.00mm and used for manufacturing of outer panel, inner panel, partial structural parts, etc. of automobile (hereinafter referred to as "steel sheets and strips").
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 223.5 Steel and Iron - Determination of Acid-soluble Silicon and Total Silicon Content - Reduced Molybdosilicate Spectrophotometric Method
GB/T 223.9 Iron Steel and Alloy - Determination of Aluminum Content - Chrom Azurol S Photometric Method
GB/T 223.14 Methods for Chemical Analysis of Iron, Steel and Alloy - The N-benzoy-N-phenylhydroxylamine Extraction Photometric Method for the Determination of Vanadium Content
GB/T 223.16 Methods for Chemical Analysis of Iron, Steel and Alloy - The Chromotropic Acid Photometric Method for the Determination of Titanium Content
GB/T 223.40 Iron Steel and Alloy - Determination of Niobium Content by the Sulphochlorophenol S Spectrophotometric Method
GB/T 223.59 Iron Steel and Alloy - Determination of Phosphorus Content - Bismuth Phosphomolybdate Blue Spectrophotometric Method and Antimony Phosphomolybdate Blue Spectrophotometric Method
GB/T 223.64 Iron Steel and Alloy - Determination of Manganese Content - Flame Atomic Absorption Spectrometric Method
GB/T 223.78 Methods for Chemical Analysis of Iron, Steel and Alloy - Curcumin Spectrophotometric Method for the Determination of Boron Content
GB/T 223.86 Steel and Iron - Determination of Total Carbon Content - Infrared Absorption Method After Combustion in An Induction Furnace
GB/T 228.1-2010 Metallic Materials - Tensile Testing - Part 1: Method of Test at Room Temperature
GB/T 247 General Rule of Package Mark and Certification for Steel Plates (Sheets) and Strips
GB/T 708 Dimension Shape Weight and Tolerance for Cold-rolled Steel Plates and Sheets
GB/T 2523 Measuring Method of Surface Roughness and Peak Count for Cold-rolled Metal Sheet (Strip)
GB/T 2975 Steel and Steel Products - Location and Preparation of Test Pieces for Mechanical Testing
GB/T 4336 Carbon and Low-alloy Steel - Determination of Multi-element Contents - Spark Discharge atomic Emission Spectrometric Method (Routine Method)
GB/T 5027 Metallic Materials - Sheet and Strip - Determination of Plastic Strain Ratio
GB/T 5028 Metallic Materials - Sheet and Strip - Determination of Tensile Strain Hardening Exponent
GB/T 8170 Rules of Rounding Off for Numerical Values & Expression and Judgment of Limiting Values
GB/T 17505 Steel and Steel Products - General Technical Delivery Requirements
GB/T 20066 Steel and Iron - Sampling and Preparation of Samples for the Determination of Chemical Composition
GB/T 20123 Steel and Iron - Determination of Total Carbon and Sulfur Content Infrared Absorption Method after Combustion in An Induction Furnace (Routine Method)
GB/T 20125 Low-alloy Steel - Determination of Multi-element Contents - Inductively Coupled Plasma Atomic Emission Spectrometric Method
GB/T 20126 Unalloyed Steel - Determination of Low Carbon Content - Part 2: Infrared Absorption Method after Combustion in an Induction Furnace (with Preheating)
3 Terms and Definitions
For the purposes of this document, the following term and definition apply.
3.1
high strength interstitial free steel; IF
the interstitial free steel added with a specific amount of strengthening elements, e.g. phosphorus, manganese and silicon, so as to make the steel have relatively high strength and maintain favorable forming performance
4 Classification and Designation Expression Method
4.1 Classification
4.1.1 See Table 1 for the classification of steel sheets and strips according to purpose.
Table 1 Classification According to Purpose
Designation Recommended purpose
CR180IF Punching or deep punching
CR220IF General purpose or punching
CR260IF Structuring or general purpose
4.1.2 See Table 2 for the classification of steel sheets and strips according to surface quality.
Table 2 Classification According to Surface Quality
Grade Code
Relatively high grade surface FB
High grade surface FC
Superior grade surface FD
4.1.3 See Table 3 for the classification of steel sheets and strips according to surface texture.
Table 3 Classification According to Surface Texture
Surface texture Code
Pitted surface D
Smooth surface B
4.2 Designation expression method
The designations of steel sheets and strips consist of three parts: the initials "CR" of "Cold Rolled", the specified minimum yield strength, and the initials "IF" of "Interstitial Free".
Example: CR180IF
CR——the initials of "Cold Rolled";
180——the specified minimum yield strength, MPa;
IF——the initials of "Interstitial Free".
5 Ordering Information
5.1 The contract or order made according to this part shall include the following contents:
a) Product name (steel sheet or steel strip);
b) Serial number of this part;
c) Designation;
d) Specification, dimension and roughness precision;
e) Surface quality grade;
f) Surface texture;
g) Edge condition;
h) Packaging mode;
i) Weight;
j) Purpose;
k) Oiled unless otherwise required.
5.2 If information, e.g. dimension and roughness precision, surface quality grade , surface texture type, edge condition and packaging, are not specified in the order contract, the products of this part shall be supplied as trimmed pitted-surface products with ordinary dimension and roughness precision and relatively high-grade surface, and shall be packaged in mode provided by the supplier.
6 Dimension, Shape and Weight
The dimension, shape, weight and permissible deviation of steel sheets and strips shall comply with the requirements of GB/T 708.
7 Technical Requirements
7.1 Chemical composition
See Annex A for reference value of steel chemical composition (melting analysis). Any chemical composition requirement proposed by the demander shall be negotiated upon ordering. See Annex B for approximate comparison of designations in national and foreign standard.
7.2 Smelting method
The steels for steel sheets and strips are smelted with oxygen converter or electric furnace; unless otherwise specified, the smelting method shall be selected by the supplier.
7.3 Delivery state
7.3.1 Steel sheets and strips shall be delivered after being annealed and then flattened.
7.3.2 Generally, steel sheets and strips are supplied as oiled. The oil film shall be removed with aqueous alkali or common solvent. In common conditions of packaging, transportation, handling and storage, the supplier shall ensure that the surfaces of steel sheets and strips are free of rust within 6 months from the completion date of manufacturing. If the demander requires to supply as unoiled, it shall be negotiated upon ordering.
Note: for unoiled products required by the demander, rust may be possible and the surface is subject to slight scratch during transportation, handling, storage and use.
7.4 Mechanical performance
7.4.1 The supplier shall ensure that the mechanical performance of steel sheets and strips meet those specified in Table 4 within 6 months from the completion date of manufacturing.
Notes:
1 due to the aging effect, the mechanical performance of steel sheets and strips will vary with time, e.g. the yield strength and tensile strength increase, the percentage elongation after fracture declines, the forming performance deteriorates and stretcher strain marks appear; the user is suggested to use steel sheets and strips as soon as possible.
2 Since secondary processing embrittlement may occur to interstitial free steel, so it shall be avoided during use.
7.4.2 Where steel sheets and strips are supplied as designated parts, the supplier and the demander may determine a range of mechanical performance complying with the processing demand of such parts through negotiation as acceptance criterion, and the mechanical performance specified in Table 4 will not serve as the delivery basis.
Foreword i
1 Scope
2 Normative References
3 Terms and Definitions
4 Classification and Designation Expression Method
5 Ordering Information
6 Dimension, Shape and Weight
7 Technical Requirements
8 Test Methods
9 Inspection Rules
10 Packaging, Marking and Quality Certificate
Annex A (Informative) Steel Chemical Composition
Annex B (Informative) Approximate Comparison of Domestic and Foreign Designations
