GB/T 6725-1992 Cold-bent steel technical conditions
This general technical conditions for cold-bent steel GB/T 6725-1992 stipulates the order and technical requirements for the cold-bent of steel plates and narrow strips.
This code is applicable to cold-bent steel plates with thickness of ≤1.5mm and steel strips ≤4.5mm, which are used for manufacturing such as beams, columns, columns and braces for large-span structure.
1. Terms and definitions
In the general technical conditions for cold-bent steel GB/T 6725-1992, the following terms and definitions are applicable.
1.1 Cold-bending
Cold-bending: refers to the shape-forming process of the steel plate and narrow strip using the method of cold-bending to obtain the required mechanical or shape-forming performance.
1.2 Cold-bends
Cold-bend: refers to the part that is added to the cold-bend steel plate or strip during cold-bending process. Its shape is basically the same as the shape obtained by cold-bending.
1.3 Cold-bend force
Cold-bend force: refers to the external force applied to the cold-bend section of the steel plate or narrow strip during the cold-bend process.
1.4 Cold-bend radius
Cold-bend radius: refers to the radius of the arc-shaped cross section obtained by cold-bend steel plate or strip.
1.5 Torsional strength
Torsional strength: refers to the maximum internal torsional force per unit width of the steel plate or strip, which can be borne by the cold-bend section during cold-bending.
2. Technical requirements
2.1 Cold-bend properties
2.1.1 Cold-bend properties of steel plates and steel strips should meet the relevant requirements of Table 1.
2.1.2 The angle of the cold-bend section should meet the requirements in Table 2.
Table 1 Cold-bend properties of steel plates and narrow strips
Material Intensity Yield strength Bending angle(α) Cold-bend radius(Rc)
General grade ≥ 250MPa ≥ 16MPa 90°±2° ≥12mm
High-strength ≥ 360MPa ≥ 27MPa 90°±2° ≥20mm
Table 2 Angle of the cold-bend section
α ≧ 120°
α＞90°
2.2 Cold-bend force
The cold-bend force should meet the requirements of Table 3.
Table 3 Cold-bend force requirements
Material Intensity Bending angle(α) Cold-bend force (Rc)
General grade ≥ 250MPa 90° ≤165KN/m
High-strength ≥ 360MPa 90° ≤360KN/m
2.3 Torsional strength
The torsional strength of steel plates and steel strips should meet the requirements of Table 4.
Table 4 Torsional strength requirements
Material Intensity Thickness(t) Torsional strength(τp)
General grade ≥ 250MPa ≥1.6mm,≤2.0mm ≥65MPa·m
High-strength ≥ 360MPa ≥1.6mm,≤2.0mm ≥90MPa·m
3. Inspection rules
3.1 The test block should sample the same raw material and process production batch as the sample steel plate or narrow strip.
3.2 The test cold-bend force should be applied to the test block without fracture.
3.3 The bending angle of the cold-bent section should be measured by means of protractor or instrument.
3.4 Measure torsional strength by metal torsion testing machine.
4. Marking
4.1 For steel plates, apart from the GB/T 6725-1992 cold-bend steel general technical conditions that must be marked on the product identification number, the following information should also be marked:
a) The steel grade;
b) The cold-bend angle of the plate;
c) Cold-bend force;
d) Cold-bend radius (if applicable).
4.2 For narrow strips, apart from the GB/T 6725-1992 cold-bend steel general technical conditions that must be marked on the product identification number, the following information should also be marked:
a) The steel grade;
b) The cold-bend angle of the strip;
c) Cold-bend force;
d) Torsional strength.
5. Inspection
Relevant departments should decide the inspection method and acceptance criteria according to GB/T 6725-1992 cold-bend steel general technical conditions.
This code takes effect from April 1st, 1992. The original GB/T 6725-1991 cold-bend steel general technical conditions are abolished from this day.
