GB/T 20564.5-2022Continuously cold rolled high strength steel sheet and strip for automobile—Part 5: Isotropic steel (English PDF)

Foreword

This document was drafted in accordance with the rules in GB/T 1.1-2020 Directives for Standardization - Part 1: Rules for the Structure and Drafting of Standardizing Documents.

This document is Part 5 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 Steels;

---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 serves as a replacement of GB/T 20564.5-2010 Continuously Cold Rolled High Strength Steel Sheet and Strip for Automobile - Part 5: Isotropic Steel. In comparison with GB/T 20564.5-2010, apart from structural adjustments and editorial modifications, the main technical changes are as follows:

---Some normative references are modified (see Chapter 2; Chapter 2 of Version 2010);

---The definition of isotropic steel is modified (see Chapter 3; Chapter 3 of Version 2010);

---The tensile strength of each designation is modified; the upper limit is uniformly lowered by 20 MPa (see Table 4; Table 4 of Version 2010);

---The description and expression of the test methods for plastic strain ratio (value r) and tensile strain hardening exponent (value n) are modified (see 8.3; 8.3 of Version 2010);

---The stipulations of the type of inspection documents are added (see Chapter 10);

---The reference value of Mn content (melting analysis) is modified (see Appendix A; Appendix A of Version 2010).

Please be noted that certain content of this document may involve patents. The institution issuing this document does not undertake the responsibility of identifying these patents.

1 Scope

This document specifies the classification and designation expression method, order contents, dimensions, shapes, weights, technical requirements, test methods, inspection rules, packaging, marking and quality certificate of continuously cold rolled isotropic high strength steel sheet and strip for automobile.

This document is applicable to continuously cold rolled isotropic high strength steel sheet and strip (with a thickness not greater than 2.5 mm) mainly used to fabricate outer covers of automobile (hereinafter referred to as "the steel sheet and strip").

2 Normative References

The contents of the following documents constitute indispensable clauses of this document through the normative references in this text. In terms of references with a specified date, only versions with a specified date are applicable to this document. In terms of references without a specified date, the latest version (including all the modifications) is applicable 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 Aluminum Content - Chrome Azurol S Photometric Method

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 223.63 Iron, Steel and Alloy - Determination of Manganese Content - Sodium (potassium) Periodate Spectrophotometric Method

3 Terms and Definitions

What is defined in GB/T 5027, and the following terms and definitions are applicable to this document.

4 Classification and Designation Expression Method

5 Order Content

5.1 Contracts or orders placed in accordance with this document shall include the following contents:

5.2 If the dimensions, unevenness accuracy, surface quality level, surface structure type, edge state and packaging are not specified in the order contract, then, […]

6 Dimensions, Shapes and Weights

The dimensions, shapes, weights and allowable deviations of the steel sheet and strip shall comply with the stipulations of GB/T 708.

7 Technical Requirements

8 Test Methods

8.1 Generally speaking, the test of the chemical composition of steel shall be carried out in accordance with GB/T 4336, GB/T 20123, GB/T 20125 and GB/T 20126, or commonly used chemical analysis methods.

8.2 The inspection items and test methods of the steel sheet and strip shall comply with the stipulations of Table 7.

8.3 The value r is obtained through the calculation with 15% plastic strain. When the maximum force-plastic elongation is less than 15%, perform the calculation in accordance with the plastic strain value at the end of the maximum force-plastic elongation.

9 Inspection Rules

9.1 The inspection and acceptance inspection of the steel sheet and strip shall be carried out by the inspection department of the supply-side.

9.4 The re-inspection and determination rules of the steel sheet and strip shall comply with the stipulations of GB/T 17505.

9.5 The inspection results of chemical composition and mechanical properties shall be rounded off in accordance with the rounding-off value comparison method; the rounding-off rules shall comply with the stipulations of GB/T 8170.

10 Packaging, Marking and Quality Certificate

The packaging, marking and quality certificate of the steel sheet and strip shall comply with the stipulations of GB/T 247.

11 Comparison of Similar Designations in China and Foreign Countries

The comparison of similar designations of this document and international standards is shown in Appendix B. […]