Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This document is developed in accordance with the rules given in GB/T 1.1-2020 Directives for standardization—Part 1: Rules for the structure and drafting of standardizing documents.
This document is Part 3 of GB/T 20887 under the general title of Continuously hot rolled high strength steel sheet and strip for automobile. The following parts of GB/T 20887 have been published:
——Part 1: High yield strength steel for cold forming;
——Part 2: High hole expansion steel;
——Part 3: Dual phase steel;
——Part 4: Transformation induced plasticity steel;
——Part 5: Martensitic steel;
——Part 6: Complex phase steel;
——Part 7: Steels for hydraulic forming.
This document replaces GB/T 20887.3-2010 Continuously hot rolled high strength steel sheet and strip for automobile—Part 3: Dual phase steel. In addition to structural adjustments and editorial changes, the following main technical changes have been made with respect to GB/T 20887.3-2010:
a) “Terms and definitions" of dual phase steel is modified (see 3.1 hereof; 3.1 of Edition 2010);
b) The designations of HR300/540DP and HR380/680DP and their corresponding technical requirements are added (see Tables 1 and 2 hereof);
c) The requirements for chemical composition are added (see Table 1 hereof);
d) The requirements for guarantee time of mechanical properties are added (see 7.4 hereof);
e) The requirements for upper limit of tensile strength are added (see Table 2 hereof);
f) The upper limit of HR330/580DP yield strength is modified (see Table 2 hereof; Table 1 of Edition 2010);
g) The index for percentage elongation after fracture with a gauge length of 50 mm is added (see Table 2 hereof);
h) The requirements for tensile strain hardening exponent are modified (see 7.6 hereof; Table 1 of Edition 2010);
i) Special requirements for supplemental hole expansion rate, metallographic microstructure inspection and tensile strain hardening exponent (n-values) are added (see 7.6 hereof);
j) The batch weight is modified (see 9.2 hereof; 8.6 of Edition 2010);
k) The requirements for the inspection document type are added (see Clause 10 hereof).
Attention is drawn to the possibility that some of the parts of this document may be the subject of patent rights. The issuing body of this document shall not be held responsible for identifying any or all such patent rights.
This document was proposed by China Iron and Steel Association.
This document is under the jurisdiction of the National Technical Committee on Iron and Steel of Standardization Administration of China (SAC/TC 183).
This document was firstly issued in 2010, and this edition is the first revision.
Introduction
GB/T 20887 Continuously hot rolled high strength steel sheet and strip for automobile is one of the standards of steel sheet and strip for automobile developed by Subcommittee on Steel Sheet and Strip of National Technical Committee on Iron and Steel of Standardization Administration of China (hereinafter referred to as "Committee"). GB/T 20887, consisting of the following seven parts, is developed to standardize the classification and designation expression, order information, dimension, shape, weight, technical requirements, test methods, inspection rules, packaging, marking and quality certificate of continuously hot rolled high strength steel sheet and strip for automobile.
——Part 1: High yield strength steel for cold forming. To determine the technical requirements of continuously hot rolled steel strip with high yield strength for cold forming as well as the steel sheet and the slit wild strip respectively formed by cutting such steel strip horizontally and vertically.
——Part 2: High hole expansion steel. To determine the technical requirements of continuously hot rolled steel strip with thickness not greater than 6.0 mm and with high hole expansion performance as well as the steel sheet and the slit wild strip respectively formed by cutting such steel strip horizontally and vertically.
——Part 3: Dual phase steel. To determine the technical requirements of continuously hot rolled dual phase steel with thickness not greater than 6.0 mm as well as the steel sheet and the slit wild strip respectively formed by cutting such steel strip horizontally and vertically.
——Part 4: Transformation induced plasticity steel. To determine the technical requirements of continuously hot rolled transformation induced plasticity steel strip with thickness not greater than 6.0 mm as well as the steel sheet and the slit wild strip respectively formed by cutting such steel strip horizontally and vertically.
——Part 5: Martensitic steel. To determine the technical requirements of continuously hot rolled martensitic steel strip with thickness not greater than 6.0 mm as well as the steel sheet and the slit wild strip respectively formed by cutting such steel strip horizontally and vertically.
——Part 6: Complex phase steel. To determine the technical requirements of steel strip with thickness not greater than 8 mm that are used for making automobile structures and reinforcers as well as the steel sheet and the slit wild strip respectively formed by cutting such steel strip horizontally and vertically.
——Part 7: Steels for hydraulic forming. To determine the technical requirements of steel strip with thickness not greater than 6 mm that are used for manufacturing structural components such as automobile subframe and instrument panel support as well as the steel sheet and the slit wild strip respectively formed by cutting such steel strip horizontally and vertically.
For the comprehension ambiguities and the resulting consequences caused by the publicizing or interpretation of this standard by other organizations without written entitlement or approval of the Committee, the Committee will not undertake any responsibility.
Continuously hot rolled high strength steel sheet and strip for automobile—
Part 3: Dual phase steel
1 Scope
This document 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 continuously hot rolled high strength dual phase steel sheet and strip for automobile.
This document is applicable to the continuously hot rolled dual phase steel strip with thickness not greater than 6.0 mm, as well as the steel sheet by transverse-cutting and steel strip by longitudinal-cutting (hereinafter referred to as steel sheet and strip).
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 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 223.53 Methods for chemical analysis of iron, steel and alloy—The flame atomic absorption spectrophotometric method for the determination of copper content
GB/T 223.54 Iron, steel and alloy—Determination of nickel content—Flame atomic absorption spectrometric 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 223.60 Methods for chemical analysis of iron, steel and alloy—The perchloric acid dehydration gravimetric method for the determination of silicon content
GB/T 223.63 Methods for chemical analysis of iron, steel and alloy—The sodium (potassium) periodate photometric method for the determination of manganese content
GB/T 223.64 Iron steel and alloyed—Determination of manganese content—Flame atomic absorption spectrometric method
GB/T 223.76 Methods for chemical analysis of iron, steel and alloy—The flame atomic absorption spectrometric method for the determination of vanadium content
GB/T 223.78 Methods for chemical analysis of iron, steel and alloy—Curcumin spectrophotometric method for the determination of boron content
GB/T 223.84 Steel and alloy—Determination of titanium content—Diantipyrylmethane spectrophotometric method
GB/T 223.85 Steel and iron—Determination of sulfur content—Infrared absorption method after combustion in an induction furnace
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 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 709 Dimension, shape, weight and tolerance for hot-rolled steel strip, plate and sheet
GB/T 2975 Steel and steel products—Location and preparation of samples and 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 (n-values)
GB/T 6394 Determination of estimating the average grain size of metal
GB/T 8170 Rules of rounding off for numerical values & expression and judgment 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 (BH2)
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
For the purposes of this standard, the following terms and definitions apply.
3.1
dual phase steel; DP
steel with its microstructure mainly composed of ferritic and martensite, and a small amount of bainite and other structures
Note: dual phase steels not only have a high tensile strength, but also have a low yield ratio and a high work hardening rate.
4 Classification and designation expression
4.1 Classification
4.1.1 The steel sheet and strip shall be classified by surface condition into:
a) hot rolled surface;
b) hot rolled pickled surface, which is indicated by the code “P”.
4.1.2 The steel sheet and strip shall be classified by surface quality into:
a) ordinary grade surface (FA);
b) superior grade surface (FB).
4.2 Designation expression
The designation of steel sheet and strip consists of three parts: the initial capital letters of “Hot Rolled”, i.e., “HR”, the specified minimum yield strength/specified minimum tensile strength, and the initial capital letters of “Dual Phase”, i.e., “DP”.
Example: HR450/780DP
HR——the initial capital letter of “Hot Rolled”;
450/780——450: the specified minimum yield strength; 780: the specified minimum tensile strength, Mpa;
DP——the initial capital letter of "Dual Phase".
Foreword i
Introduction iii
1 Scope
2 Normative references
3 Terms and definitions
4 Classification and designation expression
5 Order information
6 Dimension, shape and weight
7 Technical requirements
8 Test methods
9 Inspection rules
10 Packaging, marking and quality certificate
Annex A (Informative) Comparison of similar designations of standards both in China and abroad
Bibliography
