GB/T 41324-2022Fire-resistant weathering steels for structures (English PDF)

7.6 Ultrasonic testing

7.6.1 When there are requirements for through-thickness characteristics, the steel plate shall be ultrasonically tested in accordance with GB/T 2970, and the section steel shall be ultrasonically tested in accordance with YB/T 4811, where the qualification grade shall be indicated in the contract.

7.6.2 When it is required by the buyer, other steels can also be subjected to ultrasonic testing. The test method and qualification grade shall be negotiated by the supplier and the buyer, and shall be indicated in the contract.

7.7.1 Steel plate

7.7.1.1 There shall be no harmful defects such as air bubbles, scabs, folds, inclusions, and iron oxide scale pressing on the surface of the steel plate that affect the use, and the steel plate shall not have visible delamination.

7.7.1.2 The surface of steel plate is allowed to have a thin layer of iron oxide scale, rust, and inconspicuous roughness, reticulation, pitting, scratches and other local defects caused by pressing into the iron oxide scale and rollers that do not affect the use, but the depth shall not be greater than one-half of the thickness tolerance of the steel plate, and the allowable minimum thickness of the steel plate shall be guaranteed.

7.7.1.3 The surface defects of steel plate are allowed to be removed by grinding and other methods. The cleaning place shall be smooth without edges and corners; the cleaning depth shall not be greater than the lower deviation of the thickness of the steel plate; the minimum allowable thickness of the steel shall be guaranteed.

7.7.1.4 After it is negotiated between the supplier and the buyer, and indicated in the contract, the surface quality of the steel plate may also meet the requirements of GB/T 14977.

7.7.2 Steel strip and its sheared steel plate

7.7.2.1 The surface of steel strip shall not have any harmful defects such as scabs, cracks, folds, inclusions, air bubbles and indentation of iron oxide scales that affect the use; the steel strip shall not have visible delamination.

7.7.2.2 The surface of steel strip is allowed to have local defects such as thin iron oxide scale, rust, slight pitting, and scratches that do not affect the use, but the depth or height shall not exceed one-half of the thickness tolerance of the steel strip, and the minimum allowable thickness of the steel strip shall be guaranteed.

7.7.2.3 The steel strip is allowed to be delivered with local defects, but the part with defects shall not exceed 6% of the total length of each coil of steel strip.

7.7.2.4 After it is negotiated between the supplier and the buyer, and indicated in the contract, the surface quality of the steel strip can also meet the requirements of GB/T 14977.

7.7.3 Section steel

7.7.3.1 The surface quality of hot-rolled section steel shall comply with the provisions of GB/T 706; the surface quality of hot rolled H section steel shall comply with the provisions of GB/T 11263.

7.7.3.2 After it is negotiated between the supplier and the buyer, and indicated in the contract, the surface quality of section steel can also meet the requirements of YB/T 4427.

7.8 Special requirements. After it is negotiated between the supplier and the buyer, and indicated in the contract, other special technical requirements, such as the maximum force total elongation Agt and so on, can be put forward for the steel.

9.1 Batch rules

9.1.1 The steels shall be submitted for inspection and acceptance in batches, and each batch shall consist of steel plates, strips or section steels of the same designation, heat number, specification, rolling system, and delivery state.

9.1.2 In general, the weight of each batch shall not exceed 60 t. For different product types, batches can also be grouped according to the following regulations: -- Continuously rolled steel plates and strips with a rolled coil weight greater than 30 t can be batched into two rolled coils; -- For section steels, smelted in a converter, with a volume greater than 200 t, the weight of each batch shall not be greater than 80 t; -- The steel plate with through-thickness characteristics shall conform to the provisions of GB/T 5313.

9.1.3 The batch rules for high temperature tensile test shall be determined through negotiation between the supplier and the buyer, and shall be indicated in the contract.

9.2 Sampling quantity and sampling portion The sampling quantity and sampling portion of steel shall comply with the requirements in Table 10.

9.3 Re-inspection and determination rules The re-inspection and determination rules of steel inspection items shall comply with the provisions of GB/T 17505 or GB/T 2101.

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Note 3. 10. **Verification (USD

Notes and Explanations

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