This part of GB/T 20564 specifies the terms and definitions, classification and designation expression method, dimension, shape, weight, technical requirements, test methods, inspection rules, packaging, marking and quality certificate of cold rolled bake hardening high strength steel sheets and strips.
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 223.16 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 223.86 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)
GB/T 24174 Steel - Determination of Bake-Hardening-Index (BH2)
3 Terms and Definitions
For the purposes of this document, the following terms and definitions apply.
3.1
bake hardening steel; BH
the steel reserved with a specific amount of solid solute carbon and nitrogen atoms, of which, the strength may be improved through adding strengthening elements such as phosphorus and manganese, and the yield strength may be further improved due to age hardening after baking at certain temperature after forming
3.2
stretcher strain mark
the phenomena such as slip line and orange peel on steel sheet surface caused by aging during forming
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.
GB/T 20564.1-2017 The following standards are cited：
