GB/T 3091-2025Welded steel pipes for low pressure fluid delivery (English PDF)

5.1 Outside diameter, wall thickness and allowable deviation

5.1.1 Steel pipes are delivered according to nominal outside diameter (D) and nominal

wall thickness (t). For steel pipes with a nominal outside diameter not exceeding 219.1 mm (excluding steel pipes with threaded or grooved ends), their nominal outside diameter, nominal wall thickness and allowable deviation shall comply with the provisions of Table 1.

5.1.2 For steel pipes with a nominal outside diameter greater than 219.1 mm, their nominal outside diameter and nominal wall thickness shall comply with the provisions of GB/T 17395, and the allowable deviations of the nominal outside diameter and nominal wall thickness shall comply with the provisions of Table 2.

5.1.3 For steel pipes with threaded or grooved ends, the nominal outside diameter and nominal wall thickness are given in Appendix A. The allowable deviations of the outside diameter and wall thickness shall comply with the requirements of Table 1.

5.2 Length

5.2.1 Random length

The random length of steel pipes shall be 3 000 mm ~ 12 000 mm.

5.2.2 Specific length

The specific length of steel pipes shall be within the random length range. The allowable deviation of the specific length of straight-seam high-frequency electric welded steel pipes is +15 0 mm; the allowable deviation of the specific length of submerged-arc welded steel pipes is +50 0 mm.

5.3 Shape

5.3.1 Curvature

5.3.2 Out-of-roundness

The out-of-roundness of steel pipes (the difference between the maximum and minimum outside diameters of the same transverse plane) shall comply with the requirements of Table 3.

5.3.3 End shape

5.3.3.1 The two ends of the steel pipe shall be cut flat; the end face bevel shall not be greater than 3 mm; the cut burrs shall be removed.

5.3.3.2 As required by the buyer, negotiated between the supplier and the buyer, and indicated in the contract, the pipe ends may be threaded in accordance with the provisions of GB/T 7306.2.

5.3.4 Other shapes

As required by the buyer, negotiated between the supplier and the buyer, and indicated in the contract, steel pipes of other shape requirements can be supplied.

5.4 Weight

5.4.1 Steel pipes are delivered according to actual weight. After negotiation between

the supplier and the buyer, steel pipes can also be delivered according to the theoretical weight.

5.4.2 The theoretical weight of steel pipes is calculated according to Formula (1) (the density of steel is 7.85 kg/dm3).

6.1 Steel designation and chemical composition

6.1.1 The steel designation and chemical composition (melting analysis) shall conform

to the requirements for Q195, Q215A, Q215B, Q235A, Q235B, Q275A, and Q275B in GB/T 700, as well as Q355B in GB/T 1591, respectively. As required by the buyer, and negotiated between the supplier and the buyer, steel pipes of other designations can also be supplied.

6.2 Raw material requirements

The steel strips and steel plates used to manufacture steel pipes shall comply with the requirements of GB/T 709, GB/T 3274 and GB/T 3524 respectively; zinc ingots shall comply with the requirements of GB/T 470.As required by the buyer, negotiated between the supplier and the buyer, and indicated in the contract, raw materials of other requirements may also be used.

6.3 Manufacturing methods of steel pipes

Steel pipes shall be manufactured by straight-seam high-frequency electric welding, straight-seam submerged-arc welding or spiral-seam submerged-arc welding.

6.4 Delivery state

6.4.1 Steel pipes are delivered in welded or hot-dip galvanized state.

6.5 Mechanical properties

6.5.1 Base material stretching

6.6 Process performance

6.6.1 Bending

Straight-seam high-frequency electric welded steel pipes with a nominal outside diameter not exceeding 60.3 mm shall be subjected to a bending test. During the test, the sample shall not have fillers; the bending radius shall be 6 times the nominal outside diameter of the steel pipe; the bending angle shall be 90°; the weld shall be located at a position 90° to the bending plane (i.e., the neutral line of the bending). After the test, no cracks or breaks are allowed on the samples.

6.7 Hydraulic

6.8 Surface quality

6.8.1 Weld seam

6.8.1.1 Flash height of straight-seam high-frequency electric welded steel pipe

The external burrs of the steel pipe weld shall be removed and the remaining height shall not exceed 0.5 mm. As required by the buyer, negotiated between the supplier and the buyer, and indicated in the contract, the internal burrs of the steel pipe weld can be removed. After internal burrs of the weld seam are removed, the remaining height shall not be greater than 1.5 mm, and the groove depth shall meet the following requirements.

7.1 The sampling for chemical composition analysis of steel pipes shall comply with

the rules of GB/T 20066.Chemical composition analysis shall generally comply with the provisions of GB/T 4336, GB/T 20123, GB/T 20124, GB/T 20125 or other general methods. During arbitration, the provisions of GB/T 223.9, GB/T 223.12, GB/T 223.14, GB/T 223.23, GB/T 223.26, GB/T 223.37, GB/T 223.40, GB/T 223.53, GB/T 223.59, GB/T 223.60, GB/T 223.63, GB/T 223.84, GB/T 223.85, GB/T 223.86 and GB/T 20125 shall be followed.

7.2 The dimensions and shape of steel pipes, the burr height of electric welded steel pipes and the weld bead height of submerged-arc welded steel pipes shall be measured using measuring tools or instruments that meet the accuracy requirements.

7.3 The surface quality of steel pipes shall be visually inspected pipe by pipe under adequate lighting conditions.

7.4 The sampling quantity, sampling method and test method of other inspection items

of steel pipes shall comply with the provisions of Table 8.

8.1 Inspection and acceptance

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

8.2 Batch rules

Steel pipes shall be inspected and accepted in batches. Each batch shall consist of steel pipes of the same designation, same furnace number, same specification, same welding process, same heat treatment system (if applicable) and same zinc coating (if applicable) requirements. The quantity of each batch of steel pipes shall not exceed the following provisions.

8.3 Sampling quantity

The sampling quantity for each inspection of steel pipes shall comply with the provisions of Table 8.

8.4 Re-inspection and determination rules

8.4.1 The judgment rule for the test result of the zinc coating weight of galvanized steel pipes shall comply with the following.

8.4.2 The re-inspection and determination rules for other inspection items of steel pipes

shall comply with the provisions of GB/T 2102.

9.1 Packaging

The packaging of steel pipes shall comply with the provisions of GB/T 2102.

9.2 Marking

9.2.1 In addition to the labels affixed to each bundle, each galvanized steel pipe shall be marked on the surface of at least. the manufacturer's name or trademark, this document number, steel designation, dimensions and traceability identification number (or code).

9.2.2 Other requirements for steel pipe marking shall comply with the provisions of GB/T 2102.

9.3 Storage

Steel pipes shall be stored away from contact with corrosive media, and the storage environment shall avoid being damp, dark, and airtight.

9.4 Quality certification

The quality certification of steel pipes shall comply with the provisions of GB/T 2102. ......