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GB/T 41747-2022 (GB/T41747-2022)

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GB/T 41747-2022: PDF in English (GBT 41747-2022)

GB/T 41747-2022
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.140.50
CCS H 46
Continuous hot-dip zinc-coated twin-roll cast steel sheet
and strip of structural quality and high strength steel
(ISO 15211:2012, Continuous hot-dip zinc-coated twin-roll cast steel sheet of
structural quality and high strength steel, MOD)
ISSUED ON: OCTOBER 12, 2022
IMPLEMENTED ON: OCTOBER 12, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 6
4 Dimensions, shape, mass ... 7
5 Technical requirements ... 8
6 Test methods ... 12
7 Inspection rules ... 12
8 Classification and code ... 13
9 Packaging, marking and quality certificate ... 15
10 Order contents ... 15
Appendix A (informative) Structural changes of this document compared with ISO
15211:2012 ... 17
Appendix B (informative) Technical differences between this document and ISO
15211:2012 and their reasons ... 19
Appendix C (informative) Approximate designations comparison table ... 22
Continuous hot-dip zinc-coated twin-roll cast steel sheet
and strip of structural quality and high strength steel
1 Scope
This document specifies the dimensions, shape, mass, technical requirements, test
methods, inspection rules, classification and code, packaging, marking, quality
certificate and order contents of continuous hot-dip zinc-coated steel sheets and strips
of structural quality and high strength steel produced by twin-roll casting process.
The products corresponding to this document are applied to inner and outer covering
parts and structural parts that require corrosion resistance. This document applies to
continuous hot-dip zinc-coated twin-roll cast steel sheets and strips of structural quality
and high strength steel with a thickness not greater than 2.0 mm (hereinafter referred to
as “steel sheets and strips”).
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 223.12 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 223.14 Methods for chemical analysis of iron, steel and alloy - The N-benzoy-
N-phenylhydroxylamine extraction photometric method for the determination of
vanadium content
GB/T 223.18 Methods for chemical analysis of iron, steel and alloy - The sodium
thiosulfate separation iodimetric method for the determination of copper 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 20123 Steel and iron - Determination of total carbon and sulfur content -
Infrared absorption method after combustion in an induction furnace (routine
method)
GB/T 20124 Steel and iron - Determination of nitrogen content - Thermal
conductimetric method after fusion in a current of inert gas (routine method)
GB/T 20125 Low-alloy steel - Determination of multi-element contents - Inductively
coupled plasma atomic emission spectrometric method
GB/T 25052 Continuously hot-dip coated steel sheet and strip - Tolerances on
dimensions, shape and mass
3 Terms and definitions
For the purpose of this document, the following terms and definitions apply.
3.1
twin-roll cast steel sheet and strip
Steel sheet and strip produced by the twin-roll casting process to cast into a cast strip
with a thickness near the final thickness directly from the liquid metal, and subsequently
hot-rolled with a small reduction.
3.2
continuous hot-dip zinc-coated steel sheet and strip
Product obtained by hot-dip coating of descaled twin-roll cast steel sheets and strips
(3.1) or subsequent cold-rolled steel sheets and strips on a continuous zinc-coating line.
3.3
normal spangle coating
Coating with obvious spangle morphology, formed as a result of unrestricted growth of
zinc grains during normal solidification process of zinc layer.
NOTE: Normal spangles have metallic luster and are widely used. It may be supplied as coating
condition S or N (see 8.5); however, its appearance may be variable, and it is not suitable for
decorative coating.
3.4
minimized spangle coating
Fine spangle coating that is formed by artificially restricting the zinc grains formed
during solidification process of zinc layer.
NOTE: The surface appearance of this product may have some unevenness in the coating on a single
coil or from coil to coil.
3.5
zero spangle coating
Fine spangle coating that is invisible to the naked eye, obtained through a special
control method.
3.6
differential coating
Coating having different specified zinc layer masses on the two surfaces of zinc-coated
steel sheet.
3.7
skin pass
Process of light cold rolling of zinc-coated steel sheet.
NOTE: The purpose of skin pass is to make the surface smoother to improve the surface appearance.
Skin pass also temporarily reduces the occurrence of stretcher strain (Lüders lines) on the surface
during fabrication of finished parts. The skin pass also controls and improves roughness. The skin
pass results in an increase in hardness and a decrease in ductility.
4 Dimensions, shape, mass
4.1 The thickness of steel sheets and strips shall not exceed 2.0 mm, and width shall not
exceed 1800 mm.
4.2 Zinc-coated steel sheets with a width of less than 900 mm may be cut from wide
sheets.
4.3 The thickness of steel sheets and strips is the sum of the thickness of substrate and
coating.
4.4 The dimensions, shape, mass and allowable deviation of steel sheets and strips shall
comply with the provisions of GB/T 25052.
7.2 Steel sheets and strips shall be checked and accepted in batches, and each batch
shall consist of steel products of the same designation, same furnace number, same
specification and same delivery status.
7.3 The re-inspection and determination rules for steel sheets and strips shall comply
with the provisions of GB/T 17505.
7.4 The measured values of various inspections and checks of steel sheets and strips
shall be rounded off according to the rounding off value comparison method, and the
rounding off rules shall comply with the provisions of GB/T 8170.
8 Classification and code
8.1 Designation naming method
8.1.1 General
The designation of steel sheets and strips are composed of steel use or characteristic
code, steel grade code, steel characteristics, hot-dip code (D) and coating type code,
where the hot-dip code (D) and coating type code are connected by “+”.
8.1.2 Steel type use code
SU: Indicates that it is structural quality steel.
HU: Indicates that it is high strength steel.
8.1.3 Steel grade code
280 ~ 650: 3 digits, used to represent the steel grade code, generally specified as the
minimum yield strength, in megapascal (MPa).
8.1.4 Steel type characteristics code
G: Indicates that the steel type is uncertain.
LA: Indicates that the steel type is low alloy steel.
8.1.5 Hot-dip code
The hot-dip code is D.
8.1.6 Coating type code
The zinc-coated coating is denoted as Z.
8.2 Examples of designation naming
- Normal spangle, N;
- Normal spangle (skin pass), S;
- Minimized spangle, M;
- Minimized spangle (skin pass), E;
- Zero spangle, F.
8.6 Classification and code of surface treatment
The classification and code of surface treatment are as follows:
- Chromium-free passivation, CN;
- Chromic acid passivation, C;
- Phosphating, P;
- Oiling, O;
- Passivation oiling CO.
9 Packaging, marking and quality certificate
The packaging, marking and quality certificate of steel sheets and strips shall comply
with the provisions of GB/T 247. If the purchaser has special requirements on
packaging, it can be negotiated when ordering.
10 Order contents
When ordering, the purchaser shall provide the following information and indicate them
in the contract:
a) the serial number of this document;
b) the product name;
c) the designation;
d) the coating type and coating mass code;
e) the dimensions and their precision (including thickness, width, length, inner
diameter of steel strips, etc.);
f) the surface treatment;
......
 
(Above excerpt was released on 2022-12-28, modified on 2022-12-28, translated/reviewed by: Wayne Zheng et al.)
Source: https://www.chinesestandard.net/PDF.aspx/GBT41747-2022