GB/T 20564.7-2022Continuously cold rolled high strength steel sheet and strip for automobile—Part 7: Martensitic steel (English PDF)

Foreword

This document is drafted in accordance with GB/T 1.1-2020 "Directives for standardization - Part 1: Rules for the structure and drafting of standardizing documents".

This document is Part 7 of GB/T 20564 "Continuously cold rolled high strength steel sheet and strip for automobile". GB/T 20564 has issued the following parts.

- 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 steel;

- Part 8: Complex phase steel;

- Part 9: Quenching and partitioning steel;

- Part 10: Twinning induced plasticity steel;

- Part 11: Carbon manganese steel;

- Part 12: Dual phase steel with high formability.

This document replaces GB/T 20564.7-2010 "Continuously cold rolled high strength steel sheet and strip for automobile - Part 7: Martensitic steels". Compared with GB/T 20564.7-2010, in addition to structural adjustments and editorial changes, the main technical changes are as follows.

- Change the description of term of martensitic steel (see 3.1; 3.1 of the 2010 edition);

- Add CR1350/1700MS designation and performance technical indicators; delete CR500/780MS designation (see Table 1; Table 1 of the 2010 edition);

- Change the upper limit of yield strength of CR700/900MS designation (see Table 4; Table 4 of the 2010 edition);

- Change the indicator of elongation after fracture (see Table 4; Table 4 of the 2010 edition);

- Add provisions for inspection document type (see Clause 10).

1 Scope

This document specifies the classification and designation representation method, order content, dimension, shape, weight, technical requirements, test methods, inspection rules, package, mark and certification of continuously cold rolled high strength martensitic steel sheet and strip.

This document applies to the continuously cold rolled high strength martensitic steel sheet and strip (hereinafter referred to as "steel sheet and strip") with a thickness of 0.50 mm~2.1 mm, which are mainly used for manufacturing automobile structures, reinforcements, and anti-collision parts.

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 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

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.

5.2 If the information, such as dimension and roughness accuracy, surface quality level, surface structure type, edge state and package, is not specified in the order contract;

6 Dimension, shape, weight

The dimension, shape, weight and tolerance of steel sheets and strips shall comply with the provisions of GB/T 708.

7 Technical requirements

8 Test methods

8.1 The chemical composition tests of steel are generally carried out according to GB/T 4336, GB/T 20123, GB/T 20125, GB/T 20126 or general chemical analysis methods.

8.2 The inspection items and test methods of steel sheets and strips shall comply with the provisions of Table 7.

9 Inspection rules

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

9.2 Steel sheets and strips shall be inspected in lots. Each inspection lot shall be composed of steel sheets or strips of the same designation, specification, and processing state. The weight of each lot shall be no more than 30 t.

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.

Appendix A (Informative)

Chemical composition of steel sheets and strips The reference values of chemical composition (heat analysis) of steel sheets and strips are shown in Table A.1.

Appendix B (Informative)

Comparison of similar designations at home and abroad See Table B.1 for the comparison between the designations in this document and the foreign similar standard designations.