GB/T 6728: Evolution and historical versions
| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivered in | Standard Title (Description) | Status | PDF |
| GB/T 6728-2025 | English | RFQ |
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Cold forming sectional steel for general structure
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GB/T 6728-2025
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| GB/T 6728-2017 | English | 145 |
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Cold forming hollow sectional steel for general structure
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GB/T 6728-2017
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| GB/T 6728-2002 | English | 70 |
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Cold formed steel hollow sections for general structure -- Dimensions, shapes, weight and permissible deviations
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GB/T 6728-2002
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| GB/T 6728-1986 | English | 399 |
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Cold forming sectional steel--Hollow sectional steel for general structure--Dimension, form, weight and permissible deviations
| Obsolete |
GB/T 6728-1986
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Basic data | Standard ID | GB/T 6728-2025 (GB/T6728-2025) | | Description (Translated English) | Cold forming sectional steel for general structure | | Sector / Industry | National Standard (Recommended) | | Date of Implementation | 2026-03-01 | | Older Standard (superseded by this standard) | GB/T 6728-2017, GB/T 6723-2017 | GB/T 6728-2017: Cold forming hollow sectional steel for general structure---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT6728-2017
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.140.70
H 44
Replacing GB/T 6728-2002
Cold forming hollow sectional steel for general structure
Issued on. JULY 12, 2017
Implemented on. APRIL 01, 2018
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine of the People's Republic of China;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword... 3
1 Scope... 4
2 Normative references... 4
3 Ordering content... 4
4 Classification, code... 5
5 Cross-section, dimension and permissible deviation... 5
6 Length and permissible deviation... 23
7 Shape... 24
8 Weight and permissible deviation... 25
9 Technical requirements... 25
10 Marking example... 26
Annex A (informative) Formulae for calculating cross-sectional characteristics
... 27
Bibliography... 29
Foreword
This Standard is drafted in accordance with the rules given in GB/T 1.1-2009.
This Standard replaces GB/T 6728-2002 “Cold formed steel hollow sections for
general structure - Dimensions, shapes, weight and permissible deviations”,
compared with GB/T 6728-2002, main changes are as follows.
- MODIFY the standard name;
- DELETE the relevant specifications for shaped tubes;
- ADD the specification of thin-walled sectional steel;
- ADD the relevant specifications for the side verticality;
- MODIFY the relevant specifications for the bending degree;
- ADD the relevant specifications for the technical requirements.
This Standard was proposed by China Iron and Steel Association.
This Standard shall be under the jurisdiction of National Technical Committee
on Steel of Standardization Administration of China (SAC/TC 183).
Drafting organizations of this Standard. China Metallurgical Information and
Standardization Institute, Tianjin Youfa Steel Pipe Group Co., Ltd., Handan
Zhengda Pipe Manufacturing Co., Ltd., Wuhan Iron and Steel Jiangbei Group
Cold-formed Sections Co., Ltd., Taian Tongtaixing Metal Structure
Manufacturing Co., Ltd., Shanxi Dingrong Cold-formed Sections Co., Ltd.,
Tangshan Jinghua Pipe Manufacturing Co., Ltd.
Main drafters of this Standard. Wang Yujie, Zhang Songming, Jiang Haidong,
Zhu Shaowen, Zhao Yong, Niu Yun, Wen Chaojiang, Liu Baoshi, Ding Xiuchen,
Li Yi, Sheng Zhenjian, Li Juncai, Song Yuguang, Liu Chunlei, Wang Yalin,
Zhang Sheng.
The previous released versions replaced by this Standard are as follows.
- GB/T 6728-1986, GB/T 6728-2002.
Cold forming hollow sectional steel for general structure
1 Scope
This Standard specifies the ordering content, classification, code, cross-section,
dimension and permissible deviation, length and permissible deviation, shape,
weight and permissible deviation, technical requirements and marking example
of cold forming hollow sectional steel for general structure.
This Standard is applicable to round, rectangular and square cold forming
hollow sectional steel (hereinafter referred to as sectional steel) made of cold-
rolled or hot-rolled steel plates, sheets and strips on continuous roll cold forming
units. It is also applicable to continuous hot-dip plated sectional steel. However,
it is not applicable to sectional steel made by drawing, stamping, bending, etc.,
and sectional steel made of galvanized steel plates, sheets and strips which
are cold-formed and welded.
The sectional steel specified in this Standard mainly adopts high-frequency
resistance welding method. It may also adopt argon arc welding or other
welding methods.
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 6725 General requirements of cold forming steel sections
3 Ordering content
Contracts or orders ordered in accordance with this Standard shall include the
following.
a) Standard number;
b) Product name;
c) Grade;
d) Delivery weight;
e) Dimension and shape;
f) Special requirements.
4 Classification, code
The sectional steel is divided into square, rectangular and round sectional steel
according to the shape. The code name is.
5 Cross-section, dimension and permissible deviation
5.1 The cross-sectional view of square sectional steel is shown in Figure 1.The
cross-sectional dimension, permissible deviation, cross-sectional area,
theoretical weight and cross-sectional characteristics shall comply with the
specifications of Table 1.
5.2 The cross-sectional view of rectangular sectional steel is shown in Figure 2.
5.3 The cross-sectional view of circular sectional steel is shown in Figure 3.
5.4 The cross-sectional dimension, cross-sectional area, permissible deviation,
theoretical weight and cross-sectional characteristics of thin-walled sectional
steel may be in accordance with the relevant specifications of GB 50018.
5.5 According to the requirements of the demand party, sectional steel other
than those listed in Table 1, Table 2 and Table 3 may be provided. The
dimension permissible deviation shall be in accordance with the deviation of
the adjacent small dimensions in the table. The cross-sectional characteristics
may be calculated in accordance with Annex A.
5.7 The deviation of the bending angle θ of sectional steel shall not exceed
±1.5°. The measurement method is shown in Figure 6.
5.8 The outer arc radius R (or C1, C2) value of the corner of sectional steel shall
comply with the specifications of Table 4.The measurement method for the R
(or C1, C2) value is as specified in Figure 4 or measured with a fillet gauge.
5.9 The plane convexity and concavity X1 and X2 of the section of sectional
steel shall not exceed 0.6 % of the side length, but the minimum value is 0.4
mm.
5.10 The dimension of sectional steel shall be measured at a distance of not
less than 100 mm from the end.
6 Length and permissible deviation
6.1 The general delivery length of sectional steel is 4000 mm ~ 12000 mm.
Agreed upon between the supply and demand parties, sectional steel of other
lengths may be supplied.
6.3 The sectional steel is allowed to be delivered in short and non-specific
length of not less than 2000 mm, or in the form of interface tube, but the demand
party shall cut off the interface tube during use. The weight of short and non-
specific length tube shall not exceed 5 % of total delivery, and shall not exceed
10 % of total delivery for sectional steel with theoretical weight greater than 20 kg/m.
7 Shape
7.1 The curvature of sectional steel shall not exceed 2 mm per meter, and the
total curvature shall not exceed 0.15 % of the total length. The measurement
method is shown in Figure 7.
7.2 Agreed upon between the supply and demand parties and indicated in the
contract, the torsion of cold forming sectional steel may be measured. The
measurement shall be carried out on the platform. The measurement method
is shown in Figure 8.The measured value shall be less than the V value and
calculated according to the formula (1).
7.3 The end of the sectional steel shall be straight and the non-perpendicularity
shall not be greater than that specified in Table 6.Small deformations and burrs
caused by the cutting method are allowed to exist.
8 Weight and permissible deviation
The sectional steel is usually delivered in actual weight. When delivered in
theoretical weight,
9 Technical requirements
9.1 The grade and chemical composition (smelting analysis), mechanical
properties, surface quality, weld quality, etc. of sectional steel shall comply with
the specifications of GB/T 6725.
9.2 For galvanized steel, the total weight per unit area of the galvanized layer
on the inner and outer surfaces of the galvanized layer shall not be less than
200 g/m2.
10 Marking example
The cold forming rectangular hollow sectional steel of 150 mm × 100 mm × 6
mm made of carbon structural steel Q235 specified in GB/T 700 is marked as.
Annex A
(informative)
Formulae for calculating cross-sectional characteristics
Table 1, Table 2 and Table 3 in Clause 5 give the nominal cross-sectional
characteristics within the standard dimension range of cold forming square,
rectangular and round hollow sectional steel. The nominal cross-sectional
characteristics of cold forming round, square and rectangular hollow sectional
steel of other dimensions and thicknesses for general structure may be
calculated according to the formulae in Table A.1 and Table A.2.
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