GB/T 6725-2017General requirements of cold forming steel sections (English PDF)

4.1 Classification and code of cold forming steel according to product

cross-section shape

4.2 Classification of cold forming steel according to yield strength

level It is usually divided into Q195, Q215, Q235, Q345, Q390, Q420, Q460, Q500, Q550, Q620, Q690, Q750, according to yield strength level.

6.1 Designation and chemical composition

6.1.1 The designation and chemical composition (smelting analysis) of cold forming steel shall comply with the requirements of 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.

6.1.2 Required by the purchaser and indicated in the contract, the cold forming steel of other designation shall be provided.

6.2 Delivery state

The cold forming steel is usually delivered in cold processing state. Agreed between both parties and indicated in the contract, it shall be delivered in heat treated, hot-dip galvanized, plastic coated states.

6.3 Mechanical properties

6.3.1 The yield strength, tensile strength, elongation after break of cold forming steel shall comply with Table 1. Other steel levels or special requirements shall be confirmed by the supplier and the purchaser.

6.3.3 For the cold forming steel of which the cross-section size is not greater than 60mm × 60mm (including the equal circumference round or rectangular cold forming steel) or of which the side (short side)-thickness ratio is not grater than 14 mm, the elongation after break of the flat part is allowed to reduce by 3% (absolute value) than the specified in the Table. The width of tensile specimen used is 12.5 mm.

6.4 Surface quality

6.4.1 Cracks, scars, folding, slag inclusions and end face delamination are not permitted on the surface of cold forming steel. Partial pitting, scratches and other minor defects of which the depth (height) does not exceed half of thickness tolerance are permitted but it shall ensure the minimum thickness of section steel defects.

6.5 Weld quality

6.5.1 Cold forming welded hollow steel joints must not have open welding, lap welding, burnt-through or dislocation that exceeds half of thickness deviation and crater.

6.5.2 The defects on the weld are allowed to repair, grind; but the welding repair shall meet the requirements of this Standard.

6.5.3 External burrs at the weld shall be removed. After the removal, the weld height is usually not more than 0.5mm. Usually, internal burrs at the weld are not removed.

8.1 Inspection and acceptance

The inspection and acceptance of cold forming steel shall be carried out by the supplier's quality inspection department. The purchaser has right to perform the inspection and the acceptance.

8.2 Batching rules

The cold forming steel shall be accepted in batches. Each batch shall consist of the products of same designation, of same raw material batch, of same specifications, of same process.

8.3 Re-inspection and determination

The re-inspection and determination rules for cold forming steel shall comply with GB/T 2101.

9.1 Packaging

9.1.1 Bundle packaging

9.1.2 Packing

9.1.2.1 Cold forming steel with high surface quality requirement shall use packing for packaging. The packing box shall strong. The wooden or steel packing box shall be used.

9.1.2.5 If packing is required, it shall be indicated in the contract by and between both parties.

9.1.3 Other

Cold forming steel with theoretical weight of more than 20 kg/m shall be delivered in bulk.

9.2 Marks

9.2.1 Whole package mark

Bundled or packed cold forming steel shall have more than two signs for each bundle (box). It shall use pasted label or other method that the sign is not easy to fall off.

9.2.2 Bulk sign

Each piece of cold forming steel delivered in bulk shall paste or print a mark on the surface close to the two ends. The mark shall be clear and not easy to fall off.

9.3 Quality certificate

The quality certificate shall comply with GB/T 2101. […]