GB/T 6728-2025 Cold forming sectional steel for general structure
1 Scope
This document specifies the order information, classification, code, technical requirements, inspection rules, packaging, marking, transportation, storage and quality certificates of cold forming sectional steel for general structure (hereinafter referred to as “sectional steel”), and it also describes the test methods for sectional steels.
This document is applicable to general cold forming open sectional steels (hereinafter referred to as “open sectional steels”), as well as round, rectangular and square cold forming closed sectional steels (hereinafter referred to as “closed sectional steels”) produced by cold-rolled or hot-rolled steel sheets and steel strips on a continuous cold roll forming machine, and also applicable to continuous hot-dip galvanized sectional steels (hereinafter referred to as galvanized sectional steels).
This document does not apply to steel sections made of galvanized steel sheets and strips that are cold formed and welded.
2 Normative References
The following documents contain provisions which, through reference in this text, constitute provisions 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 222 Steels and alloys - Permissible deviations of product analyzed chemical composition
GB/T 228.1 Metallic materials - Tensile testing - Part 1: Method of test at room temperature
GB/T 229 Metallic materials - Charpy pendulum impact test method
GB/T 470-2008 Zinc ingots
GB/T 699 Quality carbon structure steels
GB/T 700 Carbon structural steels
GB/T 709 Dimension, shape, weight and tolerance for hot-rolled steel strip, plate and sheet
GB/T 714 Structural steel for bridge
GB/T 1591 High strength low alloy structural steels
GB/T 2101 General requirement of acceptance, packaging, marking and certification for sectional steel
GB/T 2102 Acceptance, packaging, marking and quality certification for steel tubular products
GB/T 2975 Steel and steel products - Location and preparation of samples and test pieces for mechanical testing
GB/T 3280 Cold rolled stainless steel plate, sheet and strip
GB/T 4171 atmospheric corrosion resisting structural steel
GB/T 8170 Rules of rounding off for numerical values & expression and judgment of limiting values
GB/T 20066 Steel and iron - Sampling and preparation of samples for the determination of chemical composition
GB/T 20878 Stainless steels - Designation and chemical composition
GB/T 33162 Continuously hot-rolled steel sheet and strip for cold-forming steel sections
3 Terms and Definitions
For the purposes of this document, the following terms and definitions apply.
3.1
free edge
edge having an arc angle (R angle) only at one end in an open sectional steel
3.2
non-free edge
edge having arc angles (R angle) at both ends in an open sectional steel
4 Order information
Contracts or orders made based on this document shall cover the following information:
a) Code of this standard;
b) Name of the product;
c) Grade of the steel;
d) Delivery weight;
e) Dimensions and shape;
f) Special requirements.
5 Classification and codes
5.1 Closed sectional steels, divided into square, rectangular and round ones by shapes, are coded according to the following rules:
a) Square sectional steel (also referred to as square tube): F;
b) Rectangular sectional steel (also referred to as rectangular tube): J;
c) Round sectional steel (also referred to as round tube): Y (or ϕ);
5.2 Open sectional steels, divided into 9 types by cross-section shape, are coded according to the following rules:
a) Cold-forming equilateral angle steel: JD;
b) Cold-forming unequilateral angle steel: JB;
c) Cold-forming equilateral channel steel: CD;
d) Cold-forming unequilateral channel steel: CB;
e) Cold-forming inward crimped channel steel: CN;
f) Cold-forming outward crimped channel steel: CW;
Contents
Foreword i
1 Scope
2 Normative References
3 Terms and Definitions
4 Order information
5 Classification and codes
6 Technical requirements
6.1 Cross sections, dimensions and permissible deviations
6.2 Length and allowable deviation
6.3 Shape
6.4 Weight and permissible deviation
6.5 Grade and chemical composition
6.6 Raw material
6.7 Manufacturing process
6.8 Mechanical properties
6.9 Surface quality
6.10 Weld quality
6.11 Zinc coating
7 Test method
8 Inspection rules
8.1 Inspection and acceptance
8.2 Batching rules
8.3 Reinspection and judgment rules
8.4 Rounding off of numerical values
9 Packaging, marking, transportation, storage and quality certificate
9.1 Packaging
9.2 Marking
9.3 Transportation
9.4 Storage
9.5 Quality certificate
Annex A (Informative) Formula for calculating cross-section characteristics
Annex B (Normative) Allowable deviation of wall thickness of sectional steels
Annex C (Normative) Determination of weight of zinc coating - antimony chloride method
Annex D (Normative) Uniformity test of zinc coating - Impregnation method with cupric sulfate
