GB/T 20564.12-2019 English PDF (GBT20564.12-2019)

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GB/T 20564.12-2019: Continuously cold rolled high strength steel sheet and strip for automobile - Part 12: Dual phase steel with high formability
GB/T 20564.12-2019
Continuously cold rolled high strength steel sheet and strip for automobile - Part 12. Dual phase steel with high formability
ICS 77.140.50
H46
National Standards of People's Republic of China
High-strength cold continuous rolling steel sheet and strip for automobile
Part 12. Reinforced formability duplex steel
automobile-Part 12. Dualphasesteelwithhighformability
Published on.2019-03-25
2020-02-01 implementation
State market supervision and administration
China National Standardization Administration issued
Foreword
GB/T 20564 "High-strength cold-rolled steel sheet and strip for automobiles" is divided into 12 parts.
---Part 1. Bake hardened steel;
--- Part 2. Dual phase steel;
--- Part 3. High-strength gap-free atomic steel;
---Part 4. Low alloy high strength steel;
--- Part 5. Isotropic steel;
---Part 6. Phase change induced plastic steel;
---Part 7. Martensitic steel;
---Part 8. Duplex steel;
---Part 9. Quenching and distribution steel;
---Part 10. Twinned induced plastic steel;
---Part 11. Carbon-manganese steel;
--- Part 12. Reinforced formability duplex steel.
This part is the 12th part of GB/T 20564.
This part is drafted in accordance with the rules given in GB/T 1.1-2009.
This part was proposed by the China Iron and Steel Association.
This part is under the jurisdiction of the National Steel Standardization Technical Committee (SAC/TC183).
This section drafted by. Shougang Group Co., Ltd., Metallurgical Industry Information Standards Institute, Anshan Iron and Steel Co., Ltd., Beijing Science and Technology
the University.
The main drafters of this section. Tang Mu, Han Wei, Zhang Weixu, Su Shi, Zhao Zhengzhi, Shi Li, Li Qian, Wang Keqiang, Teng Huaxiang, Xie Chungan,
Liu Huasai, Jiang Yinghua.
High-strength cold continuous rolling steel sheet and strip for automobile
Part 12. Reinforced formability duplex steel
1 Scope
This part of GB/T 20564 specifies the terms and definitions, classification and grades of cold rolled reinforced formability duplex high strength steel sheets and strips.
Representation method, order content, size, shape, weight, technical requirements, test methods, inspection rules, packaging, marking and quality certificate.
This part is applicable to the manufacture of complex structural automotive structural parts, steel plates and steel strips with thicknesses of 0.50mm~3.00mm.
Hereinafter referred to as "steel and steel strip").
2 Normative references
The following documents are indispensable for the application of this document. For dated references, only dated versions apply to this article.
Pieces. For undated references, the latest edition (including all amendments) applies to this document.
GB/T 223.4 Determination of manganese content in steel and alloys - Potentiometric titration or visual titration
GB/T 223.9 Determination of aluminium content in steels and alloys - chrome azure S spectrophotometric method
GB/T 223.11 Determination of chromium content in steels and alloys - either titration or potentiometric titration
GB/T 223.12 Methods for chemical analysis of steels and alloys - Sodium carbonate separation - Diphenylcarbonyl hydrazide photometric method
GB/T 223.17 Methods for chemical analysis of steels and alloys - Determination of titanium content by diantipyrylmethane photometric method
GB/T 223.26 Determination of molybdenum content of steels and alloys - thiocyanate spectrophotometric method
GB/T 223.40 Determination of bismuth content of steels and alloys - chlorosulfonol S spectrophotometric method
GB/T 223.58 Methods for chemical analysis of steels and alloys - Determination of manganese content by sodium arsenite - sodium nitrite titration
GB/T 223.59 Determination of phosphorus content of steels and alloys - phosphine molybdenum blue spectrophotometric method and bismuth phosphomolybdenum blue spectrophotometric method
GB/T 223.60 Steel and alloys - Determination of silicon content by perchloric acid dehydration gravimetric method
GB/T 223.67 Determination of sulphur content of steels and alloys
GB/T 223.69 Determination of carbon content of steel and alloys
GB/T 223.72 Determination of sulfur content of steel and alloys - Gravimetric method
GB/T 223.78 Determination of boron content by direct photometric method of curcumin
GB/T 223.86 Determination of total carbon content of steels and alloys - Infrared absorption method after induction furnace combustion
GB/T 228.1-2010 tensile testing of metallic materials - Part 1
General provisions for GB/T 247 steel and steel strip packaging, marking and quality certificates
GB/T 708 cold rolled steel sheet and strip size, shape, weight and tolerance
GB/T 2523 Cold rolled sheet metal (belt) surface roughness and peak number measurement method
GB/T 2975 steel and steel products mechanical properties test sampling position and sample preparation
GB/T 4336 Determination of multi-element content of carbon steel and medium-low alloy steels by spark discharge atomic emission spectrometry (conventional method)
GB/T 5028 Determination of tensile strain hardening index (n value) of thin sheets and strips of metallic materials
GB/T 8170 Numerical Rounding Rules and Representation and Determination of Limit Values
General technical requirements for the delivery of GB/T 17505 steel and steel products
GB/T 20066 Sampling and sample preparation method for samples for determination of chemical composition of steel and iron
GB/T 20123 Determination of total carbon and sulfur content of steels - Infrared absorption method after high-frequency induction furnace combustion (conventional method)
GB/T 20125 Determination of multi-element content of low alloy steels by inductively coupled plasma atomic emission spectrometry
GB/T 20126 Determination of low carbon content of non-alloy steels - Part 2. Infrared absorption method after combustion in induction furnaces (preheated)
GB/T 24174 steel bake hardening value (BH2) determination method
3 Terms and definitions
The following terms and definitions apply to this document.
3.1
Enhanced formability duplex steel dualphasesteelwithhighformability; DH
The microstructure is mainly ferrite, martensite and a small amount of retained austenite or bainitic steel.
Note. Compared with duplex steel of the same tensile strength, it has higher elongation after fracture and work hardening index. Suitable for parts with high drawing requirements
Forming.
4 classification and brand representation
4.1 Classification
4.1.1 Steel plates and steel strips are classified according to surface quality as shown in Table 1.
Table 1 Surface quality classification
Level code
Higher level surface FB
Advanced surface FC
4.1.2 Steel plates and steel strips are classified according to surface structure as shown in Table 2.
Table 2 Surface structure classification
Surface structure code
Pockmark D
Glossy B
4.2 Brand representation
The steel plate and steel strip are graded from the cold-rolled English "ColdRoled" initial "CR", the specified minimum yield strength value/minimum specified
Tensile strength value, enhanced formability dual phase steel English "Dualphasesteelwithhighformability" feature letter "DH" three parts
composition.
Example. CR440/780DH.
CR --- cold rolled English "ColdRoled" initials;
440/780 --- specified minimum yield strength value of 440, the specified minimum tensile strength value of 780, the unit is megapascals (MPa);
DH --- Enhanced Formability Dual Phase Steel English "Dualphasesteelwithhighformability" feature letter.
5 Ordering content
5.1 The contract or order ordered in accordance with this section shall include the following.
a) product name (steel or steel strip);
b) the implementation of the standard number;
c) the brand number;
d) specifications and dimensions, unevenness accuracy;
e) surface quality level;
f) surface structure;
g) edge state;
h) packaging method;
i) weight;
j) use;
k) Other special requirements.
5.2 If the size and unevenness accuracy, surface quality level, surface structure type, edge state and packaging information are not indicated in the order contract,
The supplier shall supply the normal size and unevenness accuracy, the higher surface and the surface structure for the pitting, trimming, and according to the package provided by the supplier.
Packing method.
6 size, shape, weight
The dimensions, shape, weight and tolerance of steel plates and strips shall comply with the provisions of GB/T 708.
7 Technical requirements
7.1 Chemical composition
Refer to Appendix A for reference values for chemical composition (melting analysis) of steel. If the manufacturer has requirements for chemical composition, it should be negotiated at the time of ordering. domestic
See Appendix B for an approximate comparison of external standard grades.
7.2 Smelting method
The steel used for steel plates and steel strips is smelted in an oxygen converter or an electric furnace. Unless otherwise specified, the smelting method is selected by the supplier.
7.3 Delivery status
7.3.1 Steel plates and strips are delivered in an annealed and flat condition.
7.3.2 Steel plates and steel strips are usually supplied with oil. The oil film to be coated should be removed with an alkaline aqueous solution or a usual solution, in the usual packaging, transportation,
Under the conditions of loading and unloading and storage, the supplier shall ensure that the surface of the steel plate and the steel strip does not rust within 6 months from the date of completion of the manufacture. If you need not to apply
Oil supply should be negotiated at the time of order.
Note. For non-oiled products required by the purchaser, rust may occur, and the surface may be slightly scratched during transportation, handling, storage and use.
7.4 Mechanical properties
The supplier shall ensure that the mechanical properties of the steel plate and the steel strip meet the requirements of Table 3 within 6 months from the date of completion of the manufacture.
Note. Due to the influence of aging, the mechanical properties of steel plates and steel strips will change with the storage time, such as the increase of yield strength and tensile strength, after the break
The elongation is lowered, the forming property is deteriorated, tensile strain marks appear, etc., and the supplier may be advised to use the product as soon as possible.
Table 3 Mechanical properties
Brand
Lower yield strength
ReLa/MPa
tensile strength
Rm/MPa
Elongation after break
A80mmb/%
Bake hardening value
(BH2)c/MPa
not less than
CR330/590DH 330~430 590 26 0.16 30
CR440/780DH 440~550 780 18 0.13 30
CR550/980DH 550~700 980 15 - 30
CR700/980DH 700~900 980 13 - 30
The sample is a P6 sample (L0=80 mm, b0=20 mm) in GB/T 228.1-2010, and the sample direction is longitudinal.
a When the yielding phenomenon is not obvious, the specified plastic elongation strength Rp0.2 may be used instead.
b When the thickness is not more than 0.7 mm, the minimum elongation after break can be reduced by 2% (absolute value).
c If the supplier can guarantee, it can be omitted.
7.5 Welding
The buyer should determine the appropriate welding process based on the chemical composition and strength level, and consult the supplier if necessary.
7.6 Surface quality
7.6.1 The surface of steel plates and steel strips shall be free of defects such as crusting, cracks and inclusions, and the steel plates and steel strips shall not be delaminated.
7.6.2 The surface quality of steel plates and steel strips shall comply with the requirements of Table 4.
Table 4 Surface quality levels and characteristics
Level code feature
Higher level surface FB
The surface is allowed to have a small amount of defects that do not affect the formability and coating and plating adhesion, such as slight scratches, indentations, and hemp.
Point, roll and oxidation color, etc.
Advanced surface FC
The better side of the steel plate and the steel strip has no obvious visible defects, and the other side should at least reach FB.
Requirements
7.6.3 For steel strips, defective delivery is allowed due to the lack of opportunity to remove defective parts, but the defective part should not exceed the total volume of each roll.
6% of the length.
7.7 Surface structure
The surface structure of steel plates and steel strips shall comply with the requirements of Table 5. If the side has special requirements for roughness, it should be negotiated when ordering.
Table 5 Surface structure
Surface structure code average roughness target value Ra/μm
Pockmark D >0.6~1.9
Smooth surface B ≤0.9
8 test methods
8.1 The chemical composition test of steel is generally based on GB/T 4336, GB/T 20123, GB/T 20125, GB/T 20126 or general chemical points.
Analytical method, according to GB/T 223.4, GB/T 223.9, GB/T 223.11, GB/T 223.12, GB/T 223.17,
GB/T 223.26, GB/T 223.40, GB/T 223.58, GB/T 223.59, GB/T 223.60, GB/T 223.67, GB/T 223.69,
GB/T 223.72, GB/T 223.78, GB/T 223.86 and GB/T 20125 are carried out.
8.2 The inspection items and test methods for steel plates and strips shall comply with the requirements of Table 6.
8.3 The tensile test is carried out in accordance with Method B specified in GB/T 228.1-2010. In order to improve the reproducibility of measurement results, beam position should be used.
The shift control method measures the yield strength rate as a parallel length of 5% of the sample per minute (the parallel length of the sample is expressed by Lc).
8.4 The value of n is calculated from 10% to 20% strain range. Calculated strain when the uniform elongation is less than 20% and not less than 12%
The range is from 10% to the end of uniform extension; when the uniform elongation is less than 12%, the strain hardening index should be calculated according to the end point of uniform elongation
True strain value report (n uniform extension = ε uniform extension).
Table 6 Inspection items, sampling quantities, sampling methods and test methods for steel plates and strips
Serial number test item sampling quantity sampling method test method
1 Chemical analysis 1/furnace GB/T 20066 See 8.1
Stretching test <...