GB/T 2518-2019 PDF English
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Continuously hot-dip zinc and zinc alloy coated steel sheet and strip
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GB/T 2518-2019: PDF in English (GBT 2518-2019) GB/T 2518-2019
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.140.50
H 46
Replacing GB/T 2518-2008, GB/T 14978-2008
Continuously Hot-dip Zinc and Zinc Alloy Coated Steel
Sheet and Strip
ISSUED ON: DECEMBER 10, 2019
IMPLEMENTED ON: JULY 1, 2020
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 6
2 Normative References ... 6
3 Terms and Definitions ... 8
4 Designation Representation Methods, Classification and Codes... 10
5 Order Content ... 17
6 Dimensions, Shapes and Weights ... 17
7 Technical Requirements ... 18
8 Test Methods ... 36
9 Inspection Rules ... 37
10 Packaging, Marking and Quality Certificate ... 38
Appendix A (informative) A Comparison of Approximate Designations in This
Standard and Related Standards at Home and Abroad ... 39
Appendix B (informative) An Introduction and Selection Guide to Coating Type
... 42
Appendix C (normative) Weight Calculation Method in Theoretical Weighing 44
Appendix D (informative) Chemical Composition of Steel ... 46
Continuously Hot-dip Zinc and Zinc Alloy Coated Steel
Sheet and Strip
1 Scope
This Standard stipulates the terms, definitions, classification, codes, designation
representation methods, order content, dimensions, shapes, weights, technical
requirements, test methods, inspection rules, packaging, marking and quality
certificate of continuously hot-dip zinc, zinc-iron alloy, zinc-aluminum alloy and
aluminum-zinc alloy coated steel sheet and strip (hereinafter referred to as steel sheet
and strip).
This Standard is applicable to steel sheets and strips (with the thickness of 0.20 mm ~
6.0 mm) for the automotive, construction and household appliance industry, etc.
2 Normative References
The following documents are indispensable to the application of this document. 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 Steel and Iron - Determination of Aluminum 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 223.14 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 223.17 Methods for Chemical Analysis of Iron, Steel and Alloy - The
Diantipyrylmethane Photometric Method for the Determination of Titanium Content
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 223.59 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 Alloy - Determination of Manganese Content - Flame
Atomic Absorption Spectrometric Method
GB/T 223.78 Methods for Chemical Analysis of Iron, Steel and Alloy - Curcumin
Spectrophotometric Method for the Determination of Boron Content
GB/T 228.1-2010 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 1839-2008 Test Method for Gravimetric - Determination of the Mass per Unit
Area of Galvanized Coatings on Steel Products
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 5027 Metallic Materials - Sheet and Strip - Determination of Plastic Strain Ratio
GB/T 5028 Metallic Materials - Sheet and Strip - Determination of Tensile Strain
Hardening Exponent
GB/T 8170 Rules of Rounding off for Numerical Values & Expression and Judgement
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
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 25052-2010 Continuously Hot-dip Coated Steel Sheet and Strip - Tolerances on
Dimensions, Shape and Weight
ISO 6892-1:2016 Metallic Materials - Tensile Testing - Part 1: Method of Test at Room
Temperature
3 Terms and Definitions
The following terms and definitions are applicable to this document.
3.1 Hot-dip Zinc Coating
Hot-dip zinc coating refers to pure zinc coating obtained by immersing pretreated steel
strip in molten zinc solution on continuous hot-dip zinc production line.
NOTE: in the molten zinc solution, zinc content is not less than 99%.
3.2 Hot-dip Zinc-iron Alloy Coating
Hot-dip zinc-iron alloy coating refers to zinc-iron alloy coating obtained by immersing
pretreated steel strip in molten zinc solution on continuous hot-dip zinc production line.
NOTE: in the molten zinc solution, zinc content is not less than 99%. Through alloying
treatment process, form zinc-iron alloy layer on the entire coating, and iron content
in the alloy coating is generally: 8% ~ 15%.
3.3 Hot-dip Zinc-aluminum Alloy Coating
Hot-dip zinc-aluminum alloy coating refers to coating obtained by immersing pretreated
steel strip in molten zinc-aluminum alloy solution on continuous hot-dip zinc aluminum
production line.
NOTE: in the molten zinc aluminum alloy solution, the mass fraction of aluminum is
approximately 5%; contain a small amount of rare earth; the remaining ingredient
is zinc.
3.4 Hot-dip Aluminum-zinc Alloy Coating
be transformed into martensitic structure.
NOTE: it has a higher work hardening rate, uniform elongation rate and tensile strength. I
comparison with complex phase steel with equivalent tensile strength, it has a
higher elongation rate.
3.11 Complex Phase Steel
Complex phase steel refers to steel, whose microstructure is a small amount of
martensite, retained austenite or pearlite distributed on the ferrite or bainite matrix,
which is strengthened by fine crystals or precipitation of micro-alloy elements.
NOTE: in comparison with complex phase steel with equivalent tensile strength, it has a
higher yield strength and good bending property.
3.12 Dual Phase Steel with High Formability
Dual phase steel with high formability refers to steel, whose microstructure is mainly
ferrite, martensite, and a small amount of bainite or retained austenite.
NOTE: in comparison with complex phase steel with equivalent tensile strength, it has a
higher elongation rate after breaking and work hardening index. It is applicable to
the formation of parts with higher tensile demands.
3.13 Stretcher Strain Marks
Stretcher strain marks refers to defects that would impair the surface appearance (such
as: slip lines and orange peels) on the surface of steel sheets or strips due to aging
during the cold forming process.
3.14 Coating Mass
Coating mass refers to the sum of mass of double-sided coating.
NOTE: it shall be expressed in (g/m2).
4 Designation Representation Methods, Classification
and Codes
4.1 Designation Representation Methods
4.1.1 General
The designation of steel sheet and strip is constituted of five parts: product purpose
code, steel grade code (or serial number), steel type characteristic (if any), hot-dip
code (D) and coating type code. Specifically speaking, hot-dip code (D) and coating
h) G signifies that steel grade characteristic is not stipulated.
4.1.5 Hot-dip code
Hot-dip code is expressed in “D”.
4.1.6 Coating type code
Pure zinc coating is expressed in “Z”; zinc-iron alloy coating is expressed in “ZF”; zinc-
aluminum alloy coating is expressed in “ZA”; aluminum-zinc alloy coating is expressed
in “AZ”.
4.2 Examples of Designation
Example 1: DC57D+ZF
It signifies that product purpose is flat steel for cold forming; substrate is stipulated to
be cold-rolled substrate; steel grade serial number is 57; hot-dip zinc-iron alloy coated
product.
Example 2: S350GD+Z
It signifies that product purpose is for structural; the stipulated minimum yield strength
is 350 MPa; steel type characteristic is not stipulated; hot-dip pure zinc coated product.
Example 3: HX340LAD+ZF
It signifies that product purpose is high strength flat steel for cold forming; substrate
state is not stipulated; the stipulated minimum yield strength is 340 MPa; steel type is
low alloy steel; hot-dip zinc-iron alloy coated product.
Example 4: HC330/590DPD+Z
It signifies that product purpose is high strength flat steel for cold forming; substrate is
stipulated to be cold-rolled substrate; the stipulated minimum yield strength is 330 MPa;
the stipulated minimum tensile strength is 590 MPa; steel type is dual phase steel; hot-
dip pure zinc coated product.
4.3 Designations and Steel Type Characteristics
4.3.1 Designations and steel type characteristics of steel sheet and strip shall comply
with the stipulations in Table 1.
4.5.2 Please refer to Appendix B for an introduction and selection guide to the types of
coating.
5 Order Content
5.1 Contracts or orders which order products in accordance with this Standard shall
include the following content:
a) Product name (steel sheet or strip);
b) Serial No. of Standard;
c) Designation;
d) Coating type and coating mass code;
e) Dimensions and accuracy (including thickness, width, length, and internal
diameter of steel strip, etc.);
f) Unevenness accuracy;
g) Surface structure of coating;
h) Surface treatment;
i) Surface quality;
j) Weight;
k) Packaging mode;
l) Others (such as: finishing, surface orientation, etc.).
5.2 If order contract does not indicate specific requirements for dimensions,
unevenness accuracy, surface treatment type, surface quality, surface structure and
packaging mode, then, the supply-side shall supply in accordance with the common
accuracy of dimensions and unevenness; surface treatment: oiling (O); surface quality
level: common level of surface (FA) in GB/T 25052-2010, and the surface structure
and packaging mode appointed by the supply-side. If order contract does not indicate
the internal diameter of steel strip, then, it shall be selected by the supply-side.
6 Dimensions, Shapes and Weights
6.1 Dimensions
6.1.1 The range of nominal dimensions of steel sheet and strip shall comply with the
stipulations in Table 4. Through the negotiation between the demand-side and the
Appendix D as a reference. If the demand-side has requirements for chemical
composition, they shall be negotiated during the ordering.
7.2 Smelting Method
Steel should adopt oxygen converter or electric furnace for smelting. Unless it is
otherwise stipulated, the mode of smelting shall be selected by the supply-side.
7.3 Delivery State
Steel sheet and strip shall receive hot-dip or hot-dip and flattening (or finishing), then,
be delivered.
7.4 Mechanical Properties
7.4.1 The mechanical properties of steel sheet and strip shall respectively comply with
the stipulations in Table 5 ~ Table 13. Unless it is otherwise stipulated, tensile sample
is coated sample.
7.4.2 The warranty period of the mechanical properties of various designations of steel
sheet and strip shall comply with the stipulations in Table 14. The warranty period of
the mechanical properties shall be calculated since the date that manufacture is
completed.
NOTE 1: due to the effect of aging, the mechanical properties of steel sheet and strip will
deteriorate with the increase of storage time, such as: increase in yield strength
and tensile strength, decrease in elongation after break, and deterioration of
formality. Thus, it is recommended that users shall use it as soon as possible.
NOTE 2: generally speaking, the date of issue in the product inspection document is
specified as the date that manufacture is completed.
7.4.3 When steel sheet and strip are supplied in accordance with an appointed part,
the demand-side and the supply-side may agree on a range of mechanical properties
that meets the processing demands of the part as the criterion of acceptance
inspection. Under this circumstance, the mechanical properties specified in Table 5 ~
Table 13 will no longer be the basis for delivery.
7.5 Stretcher Strain Marks
7.5.1 The limitation period of stretcher strain marks of various designations of steel
sheet and strip shall comply with the stipulations in Table 14. The limitation period of
stretcher strain marks shall be calculated since the date that manufacture is completed.
Within the limitation period of stretcher strain marks, the supply-side shall guarantee
that stretcher strain marks will not emerge.
NOTE: with the increase of storage time, under the effect of aging, all designations of steel
might generate stretcher strain marks. Thus, it is recommended that users shall
B.3.1 Pure zinc coating (Z) is a most commonly used coating type in the manufacturing
industry and the construction industry. It is applicable to a series of applications where
steel requires coating’s sacrificial protective effect to extend the service life of the
product or the structure. The typical application includes: building and construction
components, for example: steel structures (purlins and girths); steel frame decorations;
painted rainwater fittings; automotive parts and body panels; pipes and profiles;
engineering components; household appliances (washing machine frames, cooker
boards, dryers and speaker stands, etc.); industrial products (oil pumps, fuel tanks,
heat exchangers, fan housings, trapezoidal profiles and cable tray systems);
electronics and agricultural machinery components.
B.3.2 Zinc-iron alloy coating (ZF) is applicable to most applications for subsequent
coating. The characteristic of this type of coating is that it has high hardness and
brittleness during the formation process; after coating, it has higher corrosion
resistance under film. It is mainly applied to exterior parts of automotive and household
appliances.
B.3.3 Zinc-aluminum alloy coating (ZA) has roughly the same sacrificial protective
effect as Z coating. In most environments, it has stronger corrosion resistance than
pure zinc coating. It is mainly applied to applications that demand better ductility (for
example, deep-drawing parts), and environments that demand moderate corrosion
resistance. Its typical application includes: building and construction components
(enclosure systems, roofs, partition walls, ceilings, doors, keels for residential buildings,
window frames, snowboards, nail plates and threaded ducts); automotive components
(motor housings, oil filters, shock absorber covers, alternator boards); household
appliances (washing machine frames and panels, cooker boards, industrial drying
drums and speaker brackets); industrial products (gasoline pumps, fuel tanks, heat
exchangers, fan housings, trapezoidal profiles and cable tray systems) and roadside
guardrails.
B.3.4 Aluminum-zinc alloy coating (AZ) has excellent effect in coating isolation
protection and electrochemical protection. In comparison with the above-mentioned
coatings, in most environments, it has higher corrosion resistance, and its long-term
durability has also been proved. It is applicable to environments that demand higher
corrosion resistance. In addition, this type of coating has better high temperature
resistance and heat reflection. This type of coated steel sheet has been extensively
applied to roofs and walls; it may be directly adopted, or, adopted as the substrate of
color-coated sheet. The other applications of this type of coated steel include: building
and construction components (enclosure systems; keels, roofs, walls, ceilings and
doors for residential buildings); rainwater fittings; furniture and outdoor cabinets;
unexposed automotive parts; appliances (ovens and heaters); pipes and computer
cases, etc.
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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