GB/T 6725-2017 English PDF (GBT6725-2017)

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GB/T 6725-2017: General requirements of cold forming steel sections
GB/T 6725-2017
General requirements of cold forming steel sections
ICS 77.140.70
H44
National Standards of People's Republic of China
Replacing GB/T 6725-2008
Cold-formed steel general technical requirements
2017-05-31 released
2017-12-01 Implementation
General Administration of Quality Supervision, Inspection and Quarantine of People's Republic of China
China National Standardization Administration released
Foreword
This standard was drafted in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 6725-2008 "cold-formed steel," compared with GB/T 6725-2008, the main changes are as follows.
--- Modify the standard name;
--- Modify the intensity level;
--- Modify the grade and composition requirements;
--- Modify the delivery status;
--- Modify the mechanical performance requirements;
--- Increased the coating requirements.
This standard is proposed by China Iron and Steel Association.
This standard by the National Standardization Technical Committee Steel (SAC/TC183) centralized.
This standard was drafted. Metallurgical Industry Information Standards Institute, Tianjin You Fa Steel Tube Co., Ltd., Wuhan Iron and Steel Jiangbei Group
Cold-formed steel Co., Ltd., Tangshan Jinghua Pipe Co., Ltd., Shanxi Dingrong cold-formed steel Co., Ltd., Taian Taixing metal structure with
Limited company.
The main drafters of this standard. Liu Baoshi, Chen Zilin, Zhu Shaowen, Wenchao Jiang, Yu Qingshui, Zhao Yong, Wang Yujie, Cao Jiyuan, Sheng Zhen sword, Liu Chunlei,
Song Yi, Li Jun, Yu Shubao, Song Yuguang.
This standard replaces the standards previously issued as follows.
--- GB/T 6725-1986, GB/T 6725-1992, GB/T 6725-2002, GB/T 6725-2008.
Cold-formed steel general technical requirements
1 Scope
This standard specifies the content of cold-formed steel order, classification and code, size, shape, weight and tolerance, technical requirements, test side
Law, Acceptance Rules, Packaging, Marking and Quality Certificates.
This standard applies to cold-working deformation of cold-rolled, hot-rolled or coated (coated) steel and strip in the continuous roll cold bending unit on the production of cold
Bending steel.
2 Normative references
The following documents for the application of this document is essential. For dated references, only the dated version applies to this article
Pieces. For undated references, the latest edition (including all amendments) applies to this document.
GB/T 222 steel finished chemical composition tolerance
GB/T 228.1 Tensile testing of metallic materials - Part 1. Room temperature test method
GB/T 229 Charpy pendulum impact test method for metallic materials
GB/T 699 high-quality carbon structural steel
GB/T 700 carbon structural steel
GB/T 714 bridge structural steel
GB/T 1591 low-alloy high-strength structural steel
GB/T 2101 steel acceptance, packaging, marking and quality certificate of the general provisions
GB/T 2518 continuous hot dip galvanized steel sheet and strip
GB/T 2650 welded joints impact test method
Tensile test method GB/T 2651 welded joints
GB/T 2975 steel and steel products mechanical properties test sampling location and sample preparation
GB/T 3280 stainless steel cold-rolled steel sheet and strip
GB/T 3524 carbon structural steel and low alloy structural steel hot-rolled strip
GB/T 4171 weathering structural steel
GB/T 6723 Universal cold-formed open section steel
GB/T 6726 automotive cold-formed hollow steel size, shape, weight and tolerances
GB/T 6728 Structural cold-formed hollow steel
GB/T 12754 color coated steel sheet and strip
GB/T 33162 cold-formed steel plate and strip
YB/T 081 Metallurgical Technical Standard for Value Approximation and Test Value Determination
3 order content
According to this standard contract or order should include the following.
a) standard number;
b) product specifications;
c) raw material grades and corresponding products yield strength grade;
d) delivery weight (or quantity) and delivery length;
e) type and thickness of coating (if any);
f) Other special requirements.
4 classification and code
4.1 Cold-formed steel by product cross-section shape classification and code
According to the product's cross-sectional shape, it usually adopts the first letter of Hanyu pinyin, which can represent the shape and shape of the product. Capital letters are usually used.
E.g.
Cold-formed circular hollow steel (can be referred to as the tube), code. Y (or φ).
Cold-formed square hollow steel (can be referred to as square tube), code. F.
Cold-formed rectangular hollow steel (can be referred to as rectangular tube), code. J.
Cold deformed shaped steel, (can be referred to as shaped tube), code. YI.
Cold-formed open section steel (which may be abbreviated as open section steel), according to the cross-sectional shape codes are. JD (equilateral angle), JB (unequal angle)
CD (equilateral channel), CB (unequal channel), CN (inner coil channel), CW (outer coil channel), Z (Z shape), ZJ (hemmed Z shape) ,
YX (Cold Bending Profiled Steel).
4.2 Cold-formed steel according to yield strength classification
Classification by yield strength is usually divided into. Q195, Q215, Q235, Q345, Q390, Q420, Q460, Q500, Q550, Q620,
Q690, Q750.
5 size, shape, weight and tolerance
Cold-formed steel size, shape, weight and tolerances should be consistent with GB/T 6723, GB/T 6726, GB/T 6728 and other corresponding product standard
Quasi provisions.
6 technical requirements
6.1 grade and chemical composition
6.1.1 Cold-formed steel grades and chemical composition (melting analysis) should be consistent with GB/T 699, GB/T 700, GB/T 714, GB/T 1591,
GB/T 2518, GB/T 3280, GB/T 3524, GB/T 4171, GB/T 12754, GB/T 33162 and other standards.
6.1.2 According to the requirements of the buyer and specified in the contract, other grades of cold-formed steel may also be provided.
6.1.3 Cold-formed steel chemical composition of the finished product tolerance should be consistent with the provisions of GB/T 222.
6.2 Delivery Status
Cold-formed steel is usually delivered in cold working condition. Negotiated by both supply and demand, and stated in the contract, but also heat treatment, hot-dip galvanized, Tu
Plastic state delivery.
6.3 Mechanical Properties
6.3.1 Cold-formed steel products yield strength, tensile strength, elongation after breakage shall comply with the provisions of Table 1, other steel grade or special requirements by the supply and demand
The two sides negotiated.
Table 1 Mechanical Properties
Product yield
power level
Wall thickness t
mm
Lower yield strength aReL
MPa
Tensile strength Rm
MPa
Elongation at break A
195 - ≥195 315 ~ 490 30
215 - ≥ 215 335 ~ 510 28
≤19
≥235 370 ~ 560 ≥24
≥345 470 ~ 680 ≥20
≥ 390 490 ~ 700 ≥ 17
≥ 420 520 ~ 730 protocol
≥ 460 550 ~ 770 agreement
≥500 610 ~ 820 protocol
≥550 670 ~ 880 agreement
≥620 710 ~ 940 agreement
≥690 770 ~ 1000 agreement
≥ 750 750 ~ 1010 protocol
a Rp0.2 can be measured when the yield is not obvious.
6.3.2 Upon consultation between the buyer and the buyer and specified in the contract, the impact test may be carried out on cold-formed sections of not less than 6 mm in thickness. Impact test
Results and reinspection should be consistent with the relevant provisions of GB/T 699, GB/T 700, GB/T 714, GB/T 1591, GB/T 4171 and other related standards.
6.3.3 For cold-formed steel products with a cross-sectional area not larger than 60mm × 60mm (including round and rectangular cold-formed sections of equal circumference)
Or the edge (short edge) thickness ratio of not more than 14mm cold-formed steel products, the elongation of the flat part of the allowable percentage reduction than the table specified in 3% (absolute
Value), using a tensile specimen width of 12.5mm.
6.4 surface quality
6.4.1 cold-formed steel surface without cracks, scarring, folding, slag and the end face delamination, allowing depth (height) does not exceed the thickness tolerance
Half of the local pitting, scratches and other minor defects, but should ensure that the minimum thickness of steel defects.
6.4.2 Cold-formed steel surface defects allowed to clean up with the grinding method, but the thickness of the cold-formed steel after cleaning is not less than the minimum allowable thickness.
6.4.3 When the demand side has special requirements on the surface quality, it shall be negotiated by the supply and demand parties and shall be indicated in the contract.
6.5 weld quality
6.5.1 Cold Bending Welded hollow steel welds shall be free from open welds, lapped welds, burnt-through and over half of the thickness deviations and craters.
6.5.2 Weld defects at the weld repair, grinding, but welding repair should meet the requirements of this standard.
6.5.3 The outer burr at the weld should be removed and the remaining weld height after removal should not exceed 0.5mm. Welds at the internal burr generally not
Clear, if there are special requirements, negotiated by the supply and demand sides.
6.5.4 Upon consultation between the supplier and the buyer and specified in the contract, the mechanical and technological properties of the weld can be checked and the non-destructive testing conducted.
7 test method
Each batch of cold-formed steel test items, the number of samples, sampling methods and test methods shall comply with the provisions of Table 2.
Table 2 cold-formed steel test items, the number of samples, sampling methods and test methods
Number of test items Sampling methods Sampling methods Test methods
1 chemical composition per furnace 1 according to the relevant product standards
2 Tensile test a, b 1
GB/T 2975
Longitudinal sample
GB/T 228.1
3 impact test a, b 1
GB/T 2975
Longitudinal sample
GB/T 229
4 Welds 6.5.4 6.5.4 GB/T 2650, GB/T 2651
5 NDT 6.5.4
6 by the root size - measuring tools, templates
7 Surface by root - visual
a When there is no relevant regulation in GB/T 2975, the longitudinal direction should be taken in the flat part of the product. Flat parts should not include welds and corners.
b For rectangular steel pipes, the sampling location should be on a wide face (excluding welds).
8 Acceptance rules
8.1 inspection and acceptance
Cold-formed steel inspection and acceptance by the supplier quality inspection departments. Demand-side has the right to inspect and acceptance.
8.2 group rules
Cold-formed steel batch acceptance, each batch by the same brand, the same batch of raw materials, the same size specifications, the same composition of the product. Peripheral
Products not exceeding 400mm in length shall not exceed 60t weight per batch and products each having an outer circumference longer than 400mm shall not exceed 100t weight in each batch.
8.3 reinspection and determination
Cold-formed steel reinspection and decision rules should be consistent with the provisions of GB/T 2101.
8.4 Numerical repair
The value of the test results rounding and determination should be consistent with the provisions of YB/T 081.
9 packaging, marking and quality certificate
9.1 Packaging
9.1.1 bundled packaging
9.1.1.1 Cold-formed steel is usually delivered in bundles. One end of the bundled cold-formed steel should be neatly placed. Each bundle should be the same lot number
Of cold-formed steel, the maximum weight per bundle shall comply with the provisions of Table 3.
Table 3 binding weight regulations
Theoretical weight
(kg/m)
The maximum weight per bundle
< 1 1
1 ~ < 10 3
10 ~ < 20 5
≥20 10
9.1.1.2 cold-formed steel application package with steel bands or tie tie strong binding. Cold-formed steel length of not more than 7m bundled 3, 7m to 10m
4 strapping, more than 10m strapping 5, both ends of the strapping position from the end of not more than 1m.
9.1.2 Packing
9.1.2.1 Cold formed steel with higher surface quality shall be packed in crates. The crates shall be strong and be of wood or steel type.
9.1.2.2 Each box should be composed of the same batch of cold-formed steel. If different batch number and box, each batch number should be bundled separately and then loaded into the box.
9.1.2.3 The weight of cold-formed sections per box shall not exceed 4t.
9.1.2.4 The external packaging of the package is fastened with steel tape or by other means.
9.1.2.5 both packing and packing should be indicated in the contract when packaging.
9.1.3 Other
For the theoretical weight of more than 20kg/m of cold-formed steel can be delivered in bulk.
9.2 mark
9.2.1 package mark
Bending or boxing of cold-formed steel beam (bundle) should be hung with more than two signs, but also can be used to paste labels or other easy to fall off signs
Methods. The label or label should indicate the supplier's name and trademark, product specifications, raw material grade, production batch number, product standard number, weight, set
Length of the ruler, date of manufacture and imprint of the supplier's QC department.
9.2.2 bulk logo
Each cold-formed steel in bulk delivery shall have a label or print mark affixed to the surface near both ends and be marked clearly and easily
drop. Marks should indicate the supplier name and trademark, product specifications, raw material grades, production lot numbers, product standards, weight, length fixed length, manufacturing
Date and the quality inspection department for the supplier mark.
9.3 Quality Certificate
Quality certificate should be consistent with the relevant provisions of GB/T 2101.