GB/T 13296-2023Seamless stainless steel tubes for boilers and heat exchangers (English PDF)

6.1 Outer Diameter and Wall Thickness

6.1.1 Unless otherwise specified in the contract, the steel tubes shall be delivered in accordance with the nominal outer diameter (D) and minimum wall thickness (Smin). In accordance with the requirements of the demand-side, through negotiation between the supply-side and the demand- side, the steel tubes can be delivered in accordance with the nominal outer diameter and nominal wall thickness (S).

6.1.2 The dimensions and specifications of the steel tubes shall comply with the stipulations of GB/T 17395.In accordance with the requirements of the demand-side, through negotiation between the supply-side and the demand-side, steel tubes of other dimensions other than those specified in GB/T 17395 can be supplied.

6.1.3 When the steel tubes are delivered in accordance with the nominal outer diameter and minimum wall thickness, the allowable deviations of the nominal outer diameter and minimum wall thickness shall comply with the stipulations of Table 1

6.1.4 In accordance with the requirements of the demand-side, through negotiation between the supply-side and the demand-side, and statement in the contract, steel tubes with allowable deviations in dimensions other than those specified in Table 1 and Table 2 can be supplied.

6.2 Length

6.2.1 General length The general length of the steel tubes is 2,000 mm ~ 12,000 mm. In accordance with the requirements of the demand-side, through negotiation between the supply-side and the demand- side, and statement in the contract, steel tubes with a length exceeding 12,000 mm can be supplied.

6.3 Curvature The curvature per meter of hot rolled (extruded) steel tubes shall not be greater than

2.0 mm. The curvature per meter of cold drawn (rolled) steel tubes shall not be greater than

1.5 mm. The curvature of the entire length of the steel tubes shall not be greater than 0.15% of the length of the steel tubes.

6.4 Out-of-roundness and Uneven Wall Thickness The out-of-roundness and uneven wall thickness of the steel tubes shall respectively not exceed 80% of the tolerances of outer diameter and wall thickness.

6.5 End Shape The end faces of both ends of the steel tubes shall be perpendicular to the axis of the steel tubes, and the burrs on the cut shall be removed.

6.6 Weight

6.6.1 The steel tubes shall be delivered in accordance with the actual weight. In accordance with the requirements of the demand-side, through negotiation between the supply-side and the demand-side, the steel tubes can also be delivered in accordance with the theoretical weight.

6.6.2 When delivered in the theoretical weight per meter of the steel tubes is calculated in accordance with Formula (1).

6.6.3 When delivered in accordance with the minimum wall thickness, the average wall thickness (Sc) shall be used for the calculation of the theoretical weight per meter of the steel tubes.

7.1 Designation and Chemical Composition of Steel

7.1.1 The designation and chemical composition (smelting analysis) of steel shall comply with the stipulations of Table 3.

7.1.2 The allowable deviation of the chemical composition of finished steel tubes shall comply with the stipulations of GB/T 222.

7.2 Manufacturing Method

7.2.1 Smelting method of steel Steel shall be smelted by electric arc furnace plus external refining or converter plus external refining, or electroslag remelting method. Through negotiation between the supply-side and the demand-side, and statement in the contract, other methods of smelting can also be used.

7.2.2 Manufacturing method of steel tubes The steel tubes shall be manufactured using hot rolled (extruded) or cold drawn (rolled) seamless method.

7.3 Delivery State

7.3.1 The steel tubes shall be heat treated and acid-pickled for delivery. The heat treatment system of the steel tubes shall comply with the stipulations of Table

4.Steel tubes that have been integrally ground, bored or heat treated in a protective atmosphere can be delivered without acid-pickling.

7.4 Mechanical Properties

7.4.1 The room-temperature longitudinal tensile properties of heat-treated steel tubes shall comply with the stipulations of Table 4.

7.4.2 In accordance with the requirements of the demand-side, through negotiation between the supply-side and the demand-side, and statement in the contract, steel tubes with a wall thickness of not less than

1.7 mm can be tested for Brinell hardness, Rockwell hardness or Vickers hardness, and the value shall comply with the stipulations of Table 5.

7.5 Hydraulic Test

7.5.1 The steel tubes shall be subjected to hydraulic test one by one, and the test pressure is calculated in accordance with Formula (2). The maximum test pressure shall not exceed 20 MPa, and the pressure stabilization time shall not be less than 10 seconds. Under the test pressure, the steel tubes shall not leak.

7.5.2 The supply-side may use eddy current test to replace hydraulic test. During eddy current test, the acceptance level shall comply with the stipulations of Level-E3H in GB/T 7735-2016.

7.6 Process Performance

7.6.1 Flattening Steel tubes with a wall thickness not greater than 10 mm shall undergo a flattening test. During the test, press the specimen, until the distance between the two flat plates is H. After the test, there shall be no cracks or cracking. H is calculated in accordance with Formula (3).

7.7 Corrosion

7.7.1 Steel tubes with designations 07Cr19Ni10, 16Cr23Ni13, 20Cr25Ni20, 07Cr17Ni12Mo2, 07Cr19Ni11Ti and 07Cr18Ni11Nb do not need to undergo intergranular corrosion test, and other austenitic steel tubes shall undergo intergranular corrosion test. The intergranular corrosion test is performed in accordance with Method E in GB/T 4334-2020.After the test, the specimen shall not manifest a tendency of intergranular corrosion.

7.7.2 Through negotiation between the supply-side and the demand-side, and statement in the contract, the demand-side may specify other test methods for corrosion.

7.8 Grain Size The grain size level of steel tubes 07Cr19Ni10, 07Cr17Ni12Mo2, 07Cr19Ni11Ti and 07Cr18Ni11Nb shall be Level-4 ~ Level-7.

7.9 Non-destructive Testing

7.9.1 The steel tubes shall be subjected to ultrasonic testing one by one in accordance with the stipulations of GB/T 5777-2019, and the acceptance level shall be U2.

7.9.2 In accordance with the requirements of the demand-side, through negotiation between the supply-side and the demand-side, and statement in the contract, other non-destructive testing methods and acceptance levels can be used.