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 standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 2518-2008 Continuously hot-dip zinc-coated steel sheet and strip and GB/T 14978-2008 Continuously hot-dip aluminum-zinc alloy coated steel sheet and strip. GB/T 2518-2008 and GB/T 14978-2008 are integrated in this standard.
The following main technical changes have been made with respect to GB/T 2518-2008:
——The term and definition of coating mass have been added (see 3.14);
——The types and corresponding designations of hot-dip zinc-aluminum alloy coating and hot-dip aluminum-zinc alloy coating have been added (see 4.1.5 and Table 1);
——The designations of some dual phase steels, complex phase steels and dual phase steels with high formability have been added, and provisions on chemical component and mechanical property have been added in corresponding parts (see Table 1; Table 1 of GB/T 2518-2008);
——The default dimension and flatness precision grade when ordering have been added (see 5.2);
——The requirement that the tolerance of dimension and shape of steel sheets and strips comply with GB/T 25052-2010 is added (see 6.2);
——The requirements on yield strength and tensile strength have been modified (see Tables 5~13; Tables 5~12 of GB/T 2518-2008);
——The original chromium-free passivation has been divided into trivalent chromium passivation and chromium-free passivation (see 7.9; 7.9 of GB/T 2518-2008);
——The provisions on surface roughness and special requirements have been added (see 7.10.4);
——The requirements on position for thickness measurement have been deleted (see 8.3 of GB/T 2518-2008);
——The sampling position requirements for tensile test have been deleted (see 8.4 of GB/T 2518-2008);
——Annex A has been deleted (see Annex A of GB/T 2518-2008).
The following main technical changes have been made with respect to GB/T 14978-2008:
——The types and corresponding designations of hot-dip zinc coating, hot-dip zinc-iron alloy coating and hot-dip zinc-aluminum alloy coating have been added (see 4.1.5 and Table 1; 4.1.5 and Table 1 of GB/T 14978-2008);
——The designations of some high strength interstitial free steel, bake hardening steel and low alloy steel have been added, and provisions on chemical component and mechanical property have been added in corresponding parts (see Table 1 and Tables 7~9; Table 1 of GB/T 14978-2008);
——The requirements on yield strength and tensile strength have been modified (see Tables 5~6; Tables 5~6 of GB/T 14978-2008);
——The default dimension and flatness precision grade when ordering have been added (see 5.2);
——The requirement that the tolerance of dimension and shape of steel sheets and strips comply with GB/T 25052-2010 is added (see 6.2);
——The original chromium-free passivation has been divided into trivalent chromium passivation and chromium-free passivation (see 7.9; 7.9 of GB/T 14978-2008);
——The provisions on surface roughness and special requirements have been added (see 7.10.4);
——The requirements on position for thickness measurement have been deleted (see 8.3 of GB/T 14978-2008);
——Annex A has been deleted (see Annex A of GB/T 14978-2008).
This standard was proposed by the China Iron and Steel Association.
This standard is under the jurisdiction SAC/TC 183 the National Technical Committee on Iron and Steel of Standardization Administration of China.
The previous editions of this standard are as follows:
——GB/T 2518-1981, GB/T 2518-1988, GB/T 2518-2004 and GB/T 2518-2008.
——GB/T 14978-1994 and GB/T 14978-2008.
Continuously hot-dip zinc and zinc alloy coated steel sheet and strip
1 Scope
This standard specifies the terms and definitions; classification, code and expression method for designation; order contents; dimension, shape and weight; technical requirements; test methods; inspection rules; packaging, marking, and quality certificate in connection with continuously hot-dip zinc, zinc-iron alloy, zinc-aluminum alloy and aluminum-zinc alloy coated steel sheet and strip.
This standard is applicable to steel sheets and strips with a thickness of 0.20 mm ~ 6.0 mm used in automobile, construction, household appliances and other industries.
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 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 223.14 Methods for chemical analysis of iron, steel and alloy - The n-benzoyl-n-phenylhydroxylamine extraction photometric method for the determination of vanadium
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 alloyed - 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 (r-values)
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
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
For the purposes of this standard, the following terms and definitions apply.
3.1
hot-dip zinc coating
zinc coating applied by immersing the pretreated steel strip in the molten zinc on a continuous hot-dip galvanizing line
Note: the molten zinc shall have a zinc content of at least 99%
3.2
hot-dip zinc-iron alloy coating
zinc-iron alloy coating applied by immersing the pretreated steel strip in the molten zinc on a continuous hot-dip galvanizing line
Note: the molten zinc shall have a zinc content of at least 99% A zinc-iron alloy coating is formed over the entire coating by alloying process, and the alloy coating usually has an iron content of 8% to 15%.
3.3
hot-dip zinc-aluminum alloy coating
coating applied by immersing the pretreated steel strip in the molten zinc-aluminum alloy on a continuous hot-dip zinc-aluminum alloy plating line
Note: the molten zinc-aluminum alloy contains a small amount of rare earth, about 5% of aluminum (by mass fraction), and zinc for the rest part.
3.4
hot-dip aluminum-zinc alloy coating
coating applied by immersing the pretreated steel strip in the molten aluminum-zinc alloy on a continuous hot-dip aluminum-zinc alloy plating line
Note: in the molten aluminum-zinc alloy, the mass fraction of aluminum is about 55%, the mass fraction of silicon is about 1.6%, and the rest is zinc.
3.5
interstitial free steel
steel produced by adding an appropriate amount of titanium or niobium to the ultra-low carbon steel so that the interstitial carbon and nitrogen atoms in the steel are completely fixed into carbide and nitride and no interstitial atoms exist in it
3.6
high strength interstitial free steel
interstitial free steel with high strength and good forming properties, which is produced by adding a certain amount of strengthening elements such as phosphorus, manganese and silicon
3.7
bake hardening steel
steel that retains a certain amount of solid solute carbon and nitrogen atoms, which can be strengthened by adding phosphorus, manganese and other strengthening elements, and further improved in terms of yield strength as a result of age-hardening after being processed and baked at a certain temperature
3.8
low alloy steel
steel produced by adding microalloy elements such as niobium, titanium and vanadium in a single or composite manner to low carbon steel to form carbon nitrides for precipitation strengthening, and at the same time, by grain refinement effect of microalloy elements for strength enhancement
3.9
dual phase steel
steel with the microstructure mainly composed of ferrite and martensite, and sometimes, certain bainite structure
Note: dual phase steels not only have a high tensile strength, but also have a low yield ratio and a high work hardening rate.
3.10
transformation induced plasticity steel
steel whose microstructure is composed of ferrite, bainite and residual austenite, and of which the residual austenite can be transformed into martensitic structure during forming
Note: it has a high work hardening rate, percentage uniform elongation and tensile strength. It has a higher elongation compared with dual phase steel of equal tensile strength.
3.11
complex phase steel
steel strengthened by refinement strengthening or precipitation strengthening of microalloy elements, with its microstructure composed of ferrite or bainite as the matrix on which a small amount of martensite, residual austenite or pearlite is distributed
Note: it has higher yield strength and better bending properties compared with dual phase steel of equal tensile strength.
3.12
dual phase steel with high formability
steel whose microstructure is mainly composed of ferrite, martensite and a small amount of bainite or residual austenite
Note: compared with dual phase steel of equal tensile strength, it has higher percentage elongation after fracture and work hardening exponent. It is suitable for forming parts with higher drawing requirements.
3.13
stretcher strain marks
defects such as slip lines and orange peels on the surface of the steel plate or strip due to aging during cold forming, which are detrimental to surface appearance
3.14
coating mass
total mass of the coating on both sides
Note: it is expressed in g/m2.
4 Expression method of designation, classification and code
4.1 Expression method of designation
4.1.1 General
The designation of steel sheet and strip consists of five parts: product use code, steel grade code (or serial number), steel characteristics (if any), hot dip code (D) and coating type code, in which, hot dip code (D) and coating type code are connected by "+".
4.1.2 Use code
Use codes are as follows:
a) DX: The first letter D represents flat steel for cold forming; if the second letter is X, it indicates that the as-rolled state of the substrate is not specified; if the second letter is C, it indicates that the substrate is a cold-rolled substrate; if the second letter is D, it indicates that the substrate is a hot-rolled substrate.
b) S: It represents structural steel.
c) HX: The first letter H represents high-strength flat steel for cold forming; if the second letter is X, it indicates that the as-rolled state of the substrate is not specified; if the second letter is C, it indicates that the substrate is a cold-rolled substrate; if the second letter is D, it indicates that the substrate is a hot-rolled substrate.
4.1.3 Steel grade code (or serial number)
Steel grade codes are as follows:
a) 51 ~ 57: 2 digits, which represent steel grade serial number;
b) 180 ~ 1,180: 3 ~ 4 digits, which represent the steel grade code; as per different naming method of designation, it is generally the specified minimum yield strength or minimum yield strength and minimum tensile strength, expressed in MPa.
4.1.4 Steel characteristics
The steel characteristics are usually expressed by 1-2 letters, with the characteristic codes as follows:
a) Y represents high strength interstitial free steel;
b) LA represents low alloy steel;
c) B represents bake hardening steel;
d) DP represents dual phase steel;
e) TR represents transformation induced plasticity steel;
f) CP represents complex phase steel;
g) DH represents dual phase steel with high formability;
h) G indicates that the steel characteristics are not specified.
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Expression method of designation, classification and code
5 Order contents
6 Dimensions, shape and weight
7 Technical requirements
8 Test methods
9 Inspection rules
10 Packaging, marking and quality certificate
Annex A (informative) Comparison between similar designations in this standard and relevant standard at home and abroad
Annex B (Informative) Introduction and selection guide of coating types
Annex C (Normative) Mass calculation method for theoretical weighing
Annex D (Informative) Chemical composition of steel
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 standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 2518-2008 Continuously hot-dip zinc-coated steel sheet and strip and GB/T 14978-2008 Continuously hot-dip aluminum-zinc alloy coated steel sheet and strip. GB/T 2518-2008 and GB/T 14978-2008 are integrated in this standard.
The following main technical changes have been made with respect to GB/T 2518-2008:
——The term and definition of coating mass have been added (see 3.14);
——The types and corresponding designations of hot-dip zinc-aluminum alloy coating and hot-dip aluminum-zinc alloy coating have been added (see 4.1.5 and Table 1);
——The designations of some dual phase steels, complex phase steels and dual phase steels with high formability have been added, and provisions on chemical component and mechanical property have been added in corresponding parts (see Table 1; Table 1 of GB/T 2518-2008);
——The default dimension and flatness precision grade when ordering have been added (see 5.2);
——The requirement that the tolerance of dimension and shape of steel sheets and strips comply with GB/T 25052-2010 is added (see 6.2);
——The requirements on yield strength and tensile strength have been modified (see Tables 5~13; Tables 5~12 of GB/T 2518-2008);
——The original chromium-free passivation has been divided into trivalent chromium passivation and chromium-free passivation (see 7.9; 7.9 of GB/T 2518-2008);
——The provisions on surface roughness and special requirements have been added (see 7.10.4);
——The requirements on position for thickness measurement have been deleted (see 8.3 of GB/T 2518-2008);
——The sampling position requirements for tensile test have been deleted (see 8.4 of GB/T 2518-2008);
——Annex A has been deleted (see Annex A of GB/T 2518-2008).
The following main technical changes have been made with respect to GB/T 14978-2008:
——The types and corresponding designations of hot-dip zinc coating, hot-dip zinc-iron alloy coating and hot-dip zinc-aluminum alloy coating have been added (see 4.1.5 and Table 1; 4.1.5 and Table 1 of GB/T 14978-2008);
——The designations of some high strength interstitial free steel, bake hardening steel and low alloy steel have been added, and provisions on chemical component and mechanical property have been added in corresponding parts (see Table 1 and Tables 7~9; Table 1 of GB/T 14978-2008);
——The requirements on yield strength and tensile strength have been modified (see Tables 5~6; Tables 5~6 of GB/T 14978-2008);
——The default dimension and flatness precision grade when ordering have been added (see 5.2);
——The requirement that the tolerance of dimension and shape of steel sheets and strips comply with GB/T 25052-2010 is added (see 6.2);
——The original chromium-free passivation has been divided into trivalent chromium passivation and chromium-free passivation (see 7.9; 7.9 of GB/T 14978-2008);
——The provisions on surface roughness and special requirements have been added (see 7.10.4);
——The requirements on position for thickness measurement have been deleted (see 8.3 of GB/T 14978-2008);
——Annex A has been deleted (see Annex A of GB/T 14978-2008).
This standard was proposed by the China Iron and Steel Association.
This standard is under the jurisdiction SAC/TC 183 the National Technical Committee on Iron and Steel of Standardization Administration of China.
The previous editions of this standard are as follows:
——GB/T 2518-1981, GB/T 2518-1988, GB/T 2518-2004 and GB/T 2518-2008.
——GB/T 14978-1994 and GB/T 14978-2008.
Continuously hot-dip zinc and zinc alloy coated steel sheet and strip
1 Scope
This standard specifies the terms and definitions; classification, code and expression method for designation; order contents; dimension, shape and weight; technical requirements; test methods; inspection rules; packaging, marking, and quality certificate in connection with continuously hot-dip zinc, zinc-iron alloy, zinc-aluminum alloy and aluminum-zinc alloy coated steel sheet and strip.
This standard is applicable to steel sheets and strips with a thickness of 0.20 mm ~ 6.0 mm used in automobile, construction, household appliances and other industries.
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 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 223.14 Methods for chemical analysis of iron, steel and alloy - The n-benzoyl-n-phenylhydroxylamine extraction photometric method for the determination of vanadium
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 alloyed - 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 (r-values)
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
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
For the purposes of this standard, the following terms and definitions apply.
3.1
hot-dip zinc coating
zinc coating applied by immersing the pretreated steel strip in the molten zinc on a continuous hot-dip galvanizing line
Note: the molten zinc shall have a zinc content of at least 99%
3.2
hot-dip zinc-iron alloy coating
zinc-iron alloy coating applied by immersing the pretreated steel strip in the molten zinc on a continuous hot-dip galvanizing line
Note: the molten zinc shall have a zinc content of at least 99% A zinc-iron alloy coating is formed over the entire coating by alloying process, and the alloy coating usually has an iron content of 8% to 15%.
3.3
hot-dip zinc-aluminum alloy coating
coating applied by immersing the pretreated steel strip in the molten zinc-aluminum alloy on a continuous hot-dip zinc-aluminum alloy plating line
Note: the molten zinc-aluminum alloy contains a small amount of rare earth, about 5% of aluminum (by mass fraction), and zinc for the rest part.
3.4
hot-dip aluminum-zinc alloy coating
coating applied by immersing the pretreated steel strip in the molten aluminum-zinc alloy on a continuous hot-dip aluminum-zinc alloy plating line
Note: in the molten aluminum-zinc alloy, the mass fraction of aluminum is about 55%, the mass fraction of silicon is about 1.6%, and the rest is zinc.
3.5
interstitial free steel
steel produced by adding an appropriate amount of titanium or niobium to the ultra-low carbon steel so that the interstitial carbon and nitrogen atoms in the steel are completely fixed into carbide and nitride and no interstitial atoms exist in it
3.6
high strength interstitial free steel
interstitial free steel with high strength and good forming properties, which is produced by adding a certain amount of strengthening elements such as phosphorus, manganese and silicon
3.7
bake hardening steel
steel that retains a certain amount of solid solute carbon and nitrogen atoms, which can be strengthened by adding phosphorus, manganese and other strengthening elements, and further improved in terms of yield strength as a result of age-hardening after being processed and baked at a certain temperature
3.8
low alloy steel
steel produced by adding microalloy elements such as niobium, titanium and vanadium in a single or composite manner to low carbon steel to form carbon nitrides for precipitation strengthening, and at the same time, by grain refinement effect of microalloy elements for strength enhancement
3.9
dual phase steel
steel with the microstructure mainly composed of ferrite and martensite, and sometimes, certain bainite structure
Note: dual phase steels not only have a high tensile strength, but also have a low yield ratio and a high work hardening rate.
3.10
transformation induced plasticity steel
steel whose microstructure is composed of ferrite, bainite and residual austenite, and of which the residual austenite can be transformed into martensitic structure during forming
Note: it has a high work hardening rate, percentage uniform elongation and tensile strength. It has a higher elongation compared with dual phase steel of equal tensile strength.
3.11
complex phase steel
steel strengthened by refinement strengthening or precipitation strengthening of microalloy elements, with its microstructure composed of ferrite or bainite as the matrix on which a small amount of martensite, residual austenite or pearlite is distributed
Note: it has higher yield strength and better bending properties compared with dual phase steel of equal tensile strength.
3.12
dual phase steel with high formability
steel whose microstructure is mainly composed of ferrite, martensite and a small amount of bainite or residual austenite
Note: compared with dual phase steel of equal tensile strength, it has higher percentage elongation after fracture and work hardening exponent. It is suitable for forming parts with higher drawing requirements.
3.13
stretcher strain marks
defects such as slip lines and orange peels on the surface of the steel plate or strip due to aging during cold forming, which are detrimental to surface appearance
3.14
coating mass
total mass of the coating on both sides
Note: it is expressed in g/m2.
4 Expression method of designation, classification and code
4.1 Expression method of designation
4.1.1 General
The designation of steel sheet and strip consists of five parts: product use code, steel grade code (or serial number), steel characteristics (if any), hot dip code (D) and coating type code, in which, hot dip code (D) and coating type code are connected by "+".
4.1.2 Use code
Use codes are as follows:
a) DX: The first letter D represents flat steel for cold forming; if the second letter is X, it indicates that the as-rolled state of the substrate is not specified; if the second letter is C, it indicates that the substrate is a cold-rolled substrate; if the second letter is D, it indicates that the substrate is a hot-rolled substrate.
b) S: It represents structural steel.
c) HX: The first letter H represents high-strength flat steel for cold forming; if the second letter is X, it indicates that the as-rolled state of the substrate is not specified; if the second letter is C, it indicates that the substrate is a cold-rolled substrate; if the second letter is D, it indicates that the substrate is a hot-rolled substrate.
4.1.3 Steel grade code (or serial number)
Steel grade codes are as follows:
a) 51 ~ 57: 2 digits, which represent steel grade serial number;
b) 180 ~ 1,180: 3 ~ 4 digits, which represent the steel grade code; as per different naming method of designation, it is generally the specified minimum yield strength or minimum yield strength and minimum tensile strength, expressed in MPa.
4.1.4 Steel characteristics
The steel characteristics are usually expressed by 1-2 letters, with the characteristic codes as follows:
a) Y represents high strength interstitial free steel;
b) LA represents low alloy steel;
c) B represents bake hardening steel;
d) DP represents dual phase steel;
e) TR represents transformation induced plasticity steel;
f) CP represents complex phase steel;
g) DH represents dual phase steel with high formability;
h) G indicates that the steel characteristics are not specified.
Contents of GB/T 2518-2019
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Expression method of designation, classification and code
5 Order contents
6 Dimensions, shape and weight
7 Technical requirements
8 Test methods
9 Inspection rules
10 Packaging, marking and quality certificate
Annex A (informative) Comparison between similar designations in this standard and relevant standard at home and abroad
Annex B (Informative) Introduction and selection guide of coating types
Annex C (Normative) Mass calculation method for theoretical weighing
Annex D (Informative) Chemical composition of steel
