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GB/T 20887 consists of the following seven parts under the general title Continuously hot rolled high strength steel sheet and strip for automobile:
——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 is Part 7 of GB/T 20887.
This part is developed in accordance with the rules given in GB/T 1.1-2009.
This part was proposed by China Iron and Steel Association.
This part is under the jurisdiction of the National Technical Committee on Iron and Steel of Standardization Administration of China (SAC/TC 183).
Continuously hot rolled high strength steel sheet and strip for automobile - Part 7: Steels for hydraulic forming
1 Scope
This part of GB/T 20887 specifies the terms and definitions, classification and designation representation methods, order information, dimensions, shape, weight, technical requirements, test methods, inspection rules, packaging, marking and quality certificate of the continuously hot rolled high strength steel sheet and strip for hydraulic forming.
This part is applicable to the steel strip with thickness not greater than 6mm that are used for manufacturing structural components such as automobile subframe and instrument panel support, as well as the steel sheet and the slit wide strip respectively formed by cutting such steel strip horizontally and vertically (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 223.16 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 223.62 Methods for chemical analysis of iron, steel and alloy - The butyl acetate extraction photometric method for the determination of phosphorus 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 223.79 Iron and Steel - Determination of multi-element contents - X-ray fluorescence spectrometry (routine 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 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
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
hydraulic forming
plastic processing technology that is used for forming the workpiece by using liquid as a force transmission medium or mould
3.2
steels for hydraulic forming
steel sheet and strip used for hydraulic forming, characterized by pure material, uniform performance and high elongation and n value
4 Classification and designation representation methods
4.1 Classification
4.1.1 The surface conditions of steel sheet and strip are classified as hot rolled and hot rolled pickled, and the latter is indicated with “P”.
4.1.2 The surfaces of steel sheet and strip are classified as ordinary (FA) and superior (FB) in accordance with surface quality.
4.2 Designation representation method
The designation of steel sheet and strip is composed of three parts: the initial capital letters of “Hot Rolled”, i.e. “HR”, the specified minimum yield strength, and the initial capital letters of “Hydraulic Forming”, i.e. “HF”.
Example: HR440HF
HR——the initial capital letter of “Hot Rolled”;
440——the specified minimum yield strength, in MPa;
HF——the initial capital letters of “Hydraulic Forming”.
5 Ordering information
5.1 Contracts or orders made based on this part shall cover the following information:
a) product name (steel sheet or strip);
b) number of this part;
c) designation;
d) specification, dimension and unevenness precision;
e) surface quality grade;
f) surface condition (pickled surface is indicated by code "P");
g) edge condition;
h) oiling condition (oiled or unoiled);
i) pipe making methods (electric resistance welding, laser beam welding, etc.);
j) weight;
k) other special requirements.
5.2 If the information such as thickness precision, surface quality grade, edge condition and oiling condition is not indicated in the order contract, the products of this part shall be delivered as ordinary thickness precision, ordinary surface (FA), trimmed and oiled condition.
6 Dimension, shape and weight
The dimension, shape, weight and tolerance of steel sheet and strip shall meet the requirements of GB/T 709.
7 Technical requirements
7.1 Designation and chemical composition
7.1.1 The designation and chemical composition (smelting analysis) of steel shall meet the requirements of Table 1.
7.1.2 The tolerance of the chemical composition of the finished steel sheet and strip shall meet the requirements of GB/T 222.
Table 1 Designation and chemical composition
Designation Chemical composition (mass fraction)a, b, c/%
C Si Mn P S Als
≤ ≥
HR270HF 0.10 0.35 0.50 0.020 0.015 0.015
HR370HF 0.12 0.50 1.20 0.020 0.015 0.015
HR400HF 0.18 0.60 1.50 0.020 0.015 0.015
HR440HF 0.21 0.60 1.50 0.020 0.015 0.015
a In order to improve the properties of the steel, refined grain elements such as Nb, V and Ti may be added into the steel and indicated in the quality certificate.
b If the steel is used for making steel pipes with ERW method, the carbon content of the steel shall not be less than 0.01%.
c The aluminum total (Alt) may be used to replace acid-soluble aluminum (Als), in this case, its content shall not be less than 0.020%.
7.2 Smelting method
The steel used for steel sheet and strip shall be smelted in oxygen converter, and then be subjected to refining processing outside the converter. Unless otherwise specified, the smelting method shall be selected by the supplier.
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Classification and designation representation methods
5 Ordering information
6 Dimension, shape and weight
7 Technical requirements
8 Test methods
9 Inspection rules
10 Packaging, marking and quality certificate
