GB/T 34201-2017Seamless hot-rolled square and rectangular steel tubes for structure (English PDF)

4.1 Dimension and shape

The shape of square and rectangular steel tubes shall conform to the requirements of Figure 1 and Figure 2, respectively.

4.2 Permissible tolerances for dimensions

4.2.1 The permissible tolerances for dimensions of steel tubes shall comply with the provisions of Table 1. When the demander does not specify the permissible tolerance level for dimensions of steel tubes in the contract, the permissible tolerances for dimensions of steel tubes shall comply with the provisions of the dimensional accuracy of the ordinary grade.

4.3 Side convex-concave degree

The side convex-concave degree of the square steel tube shall not exceed 1%A.

The side convex-concave degree for long and short sides of the rectangular steel tube shall not be greater than 1%A and 1%B, respectively.

4.4 Round radius

The round radius (R) of the end face of the steel tube shall not be greater than 3 times the nominal wall thickness (S).

4.6 Torsion value

Steel tubes must not be significantly reversed. The torsion value of the full length of the steel tube shall not be greater than (2 + 0.5 × L/1000) mm.

4.7 Side perpendicularity

The perpendicularity of two adjacent sides of the steel tube shall be 90° ± 1°.

4.8 Length

4.8.1 Normal length

The typical length of the steel tube is 2,000mm to 12,000mm. According to the requirements of the demander, both the supplier and the demander shall negotiate with each other and indicate in the contract that it is allowed to supply steel tubes of other than the specified length.

4.9 End profile

The end face of both ends of the steel tube shall be perpendicular to the axis of the steel tube. The burrs at the incisions shall be removed.

4.10 Weight

4.10.1 Delivery weight

The steel tube shall be delivered according to the actual weight. The contract states that it can also be delivered in terms of theoretical weight (steel density is taken as 7.85kg/dm³).

5.1 Designation and chemical composition of steel

5.1.2 The designations of carbon structural steels are Q195, Q215, and Q235.

The chemical compositions (smelting analysis) thereof shall comply with the provisions of GB/T 700.

5.1.3 The designations and chemical compositions (smelting analysis) of low-

alloy high-strength structural steels shall meet the requirements of Table 2.

5.1.4 The designation of alloy structural steel is 20Mn2.The chemical composition (smelting analysis) thereof shall comply with the provisions of GB/T 3077.

5.2 Manufacturing method

5.2.1 Steel smelting method

Steel shall be smelted using the method of electric arc furnace plus external refining or oxygen converter plus external refining.

5.2.3 Steel tube manufacturing method

Steel tubes shall be manufactured using the method of hot rolling (expanding) for making seamless tube. When the demander specifies a certain manufacturing method, it shall be specified in the contract.

5.3 Delivery status

Steel tubes shall be delivered under hot rolling (expanding) or heat treatment.

5.4 Mechanical properties

5.5 Macroscopic examination

Steel tubes directly rolled with continuous casting billets or steel ingots shall be conducted with macroscopic examination.

5.6 Non-metallic inclusions

Steel tubes directly rolled with continuous casting billets or steel ingots shall be tested for non-metallic inclusions. The non-metallic inclusions of steel tubes are rated according to the method A in GB/T 10561-2005.A, B, C and D types of inclusions (coarse and fine) shall not exceed Grade 2.5. The total number of fine and coarse grades of A, B, C and D types of inclusions shall not be greater than 6.5, respectively. DS type of inclusions shall not exceed Grade 2.5.

7.1 Inspection and acceptance

The inspection and acceptance of steel tubes shall be carried out by the quality and technical supervision department of the supplier.

7.2 Rules for group batch

7.3 Sample size

The sample size for the inspection items of steel tubes shall comply with the provisions of Table 5.

7.4 Rules for retesting and determination

The rules for retesting and determination of steel tubes shall comply with the provisions of GB/T 2102.