GB/T 24187-2023Cold-drawn precision single welded steel tubes (English PDF)

4.1 Dimensional accuracy

Steel tubes are classified and coded according to dimensional accuracy as follows. […]

4.2 Mechanical properties

Steel tubes are classified and coded according to mechanical properties as follows. […]

4.3 Surface conditions

The classification and code of steel tubes according to surface conditions are shown in Table 1.

6.1 Outside diameter and wall thickness

6.1.1 The nominal outer diameter (D), nominal wall thickness (S) and theoretical weight of uncoated steel tubes shall comply with the requirements of Table 2. Steel tubes with dimensions other than those specified in Table 2 may be supplied upon request of the purchaser and after negotiation between the purchaser and the supplier.

6.1.2 The allowable deviation of the outer diameter of uncoated steel tubes shall comply with the provisions of Table 3.

6.2 Length

6.2.1 The usual length of steel tubes is 1.5 m~4000 m. Steel tubes with a length of no more than 8 m are delivered in strips. Steel tubes with a length of more than 8 m are delivered in coils.

6.4 Weight

6.4.1 Coiled steel tubes are delivered by actual weight. Strip-shaped steel tubes are delivered by actual weight, or by theoretical weight of number of pieces or without coating.

6.4.2 The theoretical weight of uncoated steel tubes shall comply with the requirements of Table 2 or be calculated according to formula (1).

6.4.3 For steel tubes delivered according to theoretical weight, the allowable deviation between the actual weight and the theoretical weight of each batch shall be ±7.5%.

6.5 Marking examples

The marking sequence of steel tubes is: (dimensional accuracy) - dimensional specifications - mechanical properties (category) - surface type and coating post-treatment - this document number.

7.1 Steel strip requirements

7.1.1 The steel strip used to manufacture steel tubes shall be cold-rolled low-carbon steel strip or cold-rolled ultra-low-carbon steel strip. The chemical composition (melting analysis) of the steel strip shall comply with the requirements of Table 6.

7.2 Manufacturing methods

Steel tubes shall be manufactured by forming steel strips, welding longitudinal seams, cold drawing and heat treatment. Steel tubes may be manufactured by other methods after consultation between the supplier and the purchaser and specified in the contract.

7.3 Mechanical properties

The room temperature longitudinal mechanical properties of the steel tube shall comply with the requirements of Table 7.

7.4 Process performance

7.4.1 Flattening

The steel tube shall be subjected to a flattening test. The length of the specimen is 50 mm~100 mm. During the test, the weld shall be located at 90° to the direction of force application. Use a pressure plate to flatten the specimen at a uniform speed until the inner wall fits. After the test, the specimen shall not have cracks, splits or weld cracks.

7.5 Hydraulic test

Automobile steel tubes shall be subjected to hydraulic pressure test. The test pressure is calculated according to formula (2). Under the test pressure, the pressure stabilization […]

7.6 Airtightness

The disc-shaped steel tube shall be subjected to underwater air tightness test or active gas air tightness test. For underwater air tightness test, the test pressure shall be not less than 1.8 MPa. The pressure stabilization time shall be not less than 3 min. The steel tube shall not have gas leakage. For active gas air tightness test, the active gas test pressure shall be not less than 0.5 MPa. The pressure stabilization time shall be not less than 10 min. The steel tube shall not have gas leakage.

7.9 Internal surface cleanliness

7.9.1 Steel tubes shall be inspected for internal surface cleanliness residues. The residues shall not exceed 160 mg/m².

7.9.2 Based on the purchaser's requirements, after consultation between the supplier and the purchaser and specified in the contract, the high cleanliness of the inner surface of high-cleanliness steel tubes for refrigeration shall comply with the provisions of Annex B.

7.10 Surface coating and cladding

7.10.1 The surface conditions of different types of steel tubes shall comply with the provisions of Table 1. According to the requirements of the purchaser, steel tubes with surface conditions other than those in Table 1 may be supplied after consultation between the purchaser and the supplier.

9.1 Inspection classification

The inspection of steel tubes is divided into exit-factory inspection and type inspection.

9.2 Exit-factory inspection

The exit-factory inspection and acceptance of steel tubes shall be carried out by the supplier's quality and technical supervision department. The exit-factory inspection items shall comply with the provisions of Table 9.

9.3 Type inspection

When any of the following situations occurs, type inspection shall be carried out. Type inspection items shall comply with the provisions of Table 9.

9.4 Batching rules

Steel tubes shall be inspected and accepted in batches. Each batch shall consist of steel tubes of the same steel strip category, the same mechanical property category, the same specification, and the same surface condition. The weight of each batch of steel tubes shall not exceed 10,000 kg.

9.5 Sampling quantity

The sampling quantity for each inspection of steel tubes shall comply with the provisions of Table 9.

9.6 Reinspection and judgment rules