GB/T 20887.3-2022Continuously hot rolled high strength steel sheet and strip for automobile—Part 3: Dual phase steel (English PDF)

1 Scope

This document specifies the terms and definitions, classification and designation representation method, dimension, shape, weight, technical requirements, test methods, inspection rules, package, mark and certification of continuously hot rolled high strength dual phase steel sheet and strip for automobile.

This document applies to continuously hot rolled dual phase steel strips with a thickness of not more than 6.0 mm, steel sheets cross-cut from them, and longitudinally-cut steel strips (hereinafter referred to as "steel sheets and strips").

2 Normative references

The contents of the following documents, through normative references in this text, constitute indispensable provisions of this document. Among them, for dated references, only the edition corresponding to that date applies to this document. For undated references, the latest edition (including all amendments) applies to this document.

GB/T 222 Permissible Tolerances for Chemical Composition of Steel Products

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 aluminium content - Chrome azurol S photometric method

GB/T 223.12 Methods for chemical analysis of iron, steel and alloy - The sodium carbonate separation-diphenyl carbazide photometric method for the determination of chromium content

GB/T 223.23 Iron, steel and alloy - Determination of nickel content - The dimethylglyoxime spectrophotometric method

GB/T 223.26 Iron, steel and alloy - Determination of molybdenum content - The thiocyanate spectrophotometric method

GB/T 223.40 Iron, Steel and Alloy - Determination of Niobium Content by the Sulphochlorophenol S Spectrophotometric Method

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 5028 Metallic materials - Sheet and strip - Determination of tensile strain hardening exponent

GB/T 6394 Metal - Methods for Estimating the Average Grain Size

GB/T 8170 Rules of Rounding off for Numerical Values and Expression and Judgement of Limiting Values

GB/T 10561 Steel - Determination of Content of Nonmetallic Inclusions - Micrographic Method Using Standards Diagrams

GB/T 13298 Inspection methods of microstructure for metals

GB/T 17505 Steel and Steel Products - General Technical Delivery Requirements

GB/T 18253-2018 Steel and steel products - Types of inspection documents

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 (BH)

GB/T 24524 Metallic materials - Sheet and strip - Hole expanding test

GB/T 38813 General requirements for hot-rolled pickled steel sheet and strip

3 Terms and definitions

The following term and definition applies to this document.

4 Classification and designation representation method

5 Order content

5.1 Contracts or orders placed according to this document shall include the following:

a) Product name (steel sheet or strip);

9 Inspection rules

9.1 The inspection and acceptance of steel sheets and strips shall be carried out by the quality inspection department of the supplier.

9.2 Steel sheets and strips shall be accepted in lots. Each lot shall consist of steel sheets or strips of the same designation, heat number, thickness and rolling system with a weight not greater than 60 t. Steel strips and continuously rolled sheets with a rolled coil weight greater than 30 t can be batched into two rolled coils.

9.3 The sampling quantity and sampling methods of steel sheets and strips shall comply with the provisions of Table 4.

9.4 The re-inspection and determination rules for steel sheets and strips shall comply with the provisions of GB/T 17505.

9.5 The test results of chemical composition and mechanical properties are rounded according to the rounding value comparison method. The rules of rounding off shall be in accordance with the provisions of GB/T 8170.

10 Package, mark and certification

The package, mark and certification of steel sheets and strips shall comply with the provisions of GB/T 247. The type of certification (inspection document) shall comply with the provisions in GB/T 18253-2018. When the inspection document type is not specified, it shall be in accordance with Type 3.1 of GB/T 18253-2018.