GB/T 14976-2025Seamless stainless steel pipes for fluid transport (English PDF)

4.1 Steel pipes are classified and coded according to their manufacturing method as

follows.

a) Cold-rolled (drawn) steel pipes, coded as W-C;

b) Hot-rolled (extruded, forged, expanded) steel pipes, coded as W-H.

4.2 Steel pipes are classified and coded according to dimensional accuracy as follows.

a) Ordinary grade, coded as PA;

b) High grade, coded as PC.

4.3 The following symbols apply to this document.

D. Outer diameter (unless otherwise specified, includes nominal outer diameter and/or calculated outer diameter, in millimeters).

Dc. Calculated outer diameter (outer diameter calculated from nominal inner diameter and nominal wall thickness, in millimeters).

d. Nominal inner diameter (in millimeters).

S. Wall thickness (unless otherwise specified, includes nominal wall thickness and/or average wall thickness, in millimeters).

Sc. Average wall thickness (the average of the maximum and minimum wall thickness values calculated from the minimum wall thickness and its allowable deviation, in millimeters).

Smin. Minimum wall thickness (in millimeters).

Sc. Average wall thickness (the average of the maximum and minimum wall thickness values calculated from the minimum wall thickness and its allowable deviation, in millimeters).

6.1 Steel smelting methods

Steel shall be smelted using an electric arc furnace with external refining, a converter with external refining, or an electroslag remelting method. Other smelting methods with higher requirements may be used upon negotiation between the supplier and the purchaser and as specified in the contract.

6.2 Steel pipe manufacturing method

Steel pipes shall be manufactured seamlessly by cold rolling (drawing) or hot rolling (extrusion, forging, expansion). If the purchaser specifies a particular manufacturing method, this shall be stated in the contract.

6.3 Delivery state

6.3.1 Steel pipes should be delivered in a heat-treated and pickled state. Steel pipes that have been through integral grinding, boring, or heat-treated in a protective atmosphere may be delivered without pickling. The recommended heat treatment schedule for steel pipes is shown in Table 1.

6.3.2 For hot-rolled (extruded) austenitic stainless steel pipes, if the steel pipes are

directly water-cooled or rapidly cooled by other means within the heat treatment temperature range specified in Table 1 after final thermal deformation, they shall be considered to meet the heat treatment requirements.

6.3.3 Upon request from the purchaser, after negotiation between the supplier and the

purchaser, and with this information specified in the contract, cold-rolled (drawn) austenitic stainless steel pipes may be delivered in the cold-worked state. Requirements for bendability, mechanical properties, and flattening tests shall be determined by negotiation between the supplier and the purchaser.

6.3.4 After negotiation between the supplier and the purchaser and with indication in

the contract, the steel pipe may adopt other heat treatment systems other than those listed in Table 1.

7.1 Steel designation and chemical composition

7.1.1 The steel designation and chemical composition (melting analysis) shall comply

with the provisions of Table 2.Based on the purchaser's requirements, after consultation between the supplier and the purchaser, and with indication in the contract, steel pipes with designations or chemical compositions other than those specified in Table 2 may be supplied.

7.1.2 If the purchaser requires analysis of finished products, this should be stated in the contract. The allowable deviation of the chemical composition of finished steel pipes should comply with the provisions of GB/T 222. Where, W - Theoretical weight per meter of steel pipe, in kilograms per meter (kg/m); pi - 3 1416;

rho - Density of steel, in kilograms per cubic decimeter (kg/dm3). Steel density is as specified in Table 1;

S - Nominal wall thickness or average wall thickness (when delivered at the minimum wall thickness) of the steel pipe, in millimeters (mm);

D - Nominal outer diameter or calculated outer diameter (when delivered at the nominal inner diameter) of the steel pipe, in millimeters (mm).

7.9.6.2 For steel pipes delivered according to minimum wall thickness, the theoretical

weight shall be calculated using the average wall thickness. For steel pipes delivered according to nominal inner diameter, the theoretical weight shall be calculated using the outer diameter.

7.9.6.3 When steel pipes are delivered according to theoretical weight, the supplier and

the purchaser may negotiate the allowable weight deviation and specify it in the contract.

8.1 Tensile test specimen

8.1.1 For steel pipes with a diameter of D < 219 mm, samples for the tensile test should be taken along the longitudinal direction of the steel pipe.

8.1.2 For steel pipes with a diameter of D >=219 mm, when the pipe size permits, a circular cross-section specimen with a diameter of 10 mm shall be cut from the transverse direction of the pipe for the tensile test. If the pipe size is insufficient to allow for a 10 mm specimen, a transverse circular cross-section specimen with a diameter of 8 mm or 5 mm, whichever is larger, shall be used. If the pipe size is insufficient to allow for a 5 mm circular cross-section specimen, the tensile test shall be conducted by sampling along the longitudinal direction of the pipe. Transverse circular cross-section specimens shall be taken from un-flattened sample blanks.

8.2 Impact test specimen

For impact test, specimens should preferably be cut transversely along the steel pipe. If transverse specimens are not possible, specimens should be cut longitudinally.

Regardless of whether the specimens are cut transversely or longitudinally, the impact specimens should be the larger of the standard sizes and thicknesses of 7.5 mm, 5 mm, ......