Do you know what the production process of spiral welded steel pipe is?

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2022-06-14

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Spiral welded steel pipe is manufactured by using coiled strip steel as the raw material, forming it under ambient temperature through extrusion, and welding it with an automated double-wire, double-sided submerged-arc welding process. In the production of spiral welded steel pipe, the strip steel is fed into the pipe‑welding unit, where it undergoes multi‑roll rolling, gradually curling to form a circular tube blank with an open seam. By adjusting the downward pressure of the extrusion rolls, the weld gap is maintained within 1–3 mm, ensuring that both ends of the joint are flush.

　　 Spiral steel pipe It is a spiral‑seam steel pipe manufactured from coiled strip steel as the raw material, formed by cold extrusion and welded using an automated double‑wire, double‑sided submerged‑arc welding process. In the production of spiral steel pipes, the strip steel is fed into the pipe‑welding unit; through multi‑roll rolling, the strip gradually coils to form a circular tube blank with an open seam. By adjusting the downward pressure of the extrusion rolls, the weld gap is maintained within 1–3 mm, and the ends of the joint are kept flush.

　　Spiral steel pipe production process:

　　(1) The raw materials consist of coil stock, welding wire, and flux. Prior to use, they must undergo rigorous physical and chemical testing.

　　(2) The end-to-end joint of the steel strip shall be welded using single-wire or double-wire submerged arc welding, and after coiling into a steel pipe, automatic submerged arc welding shall be employed for repair welding.

　　(3) Prior to forming, the strip steel is leveled, trimmed, planed, surface-cleaned, conveyed, and pre-bent.

　　(4) The spiral steel pipe electrical contact pressure gauge is used to regulate the pressure of the lowering cylinders on both sides of the conveyor, ensuring smooth strip steel conveyance.

　　(5) Employ either external or internal roller pressing for forming.

　　(6) A weld gap control device is employed to ensure that the weld gap meets welding requirements, with strict control over pipe diameter, misalignment, and weld gap.

　　(7) Both internal and external welds are performed using Lincoln electric welding machines with either single‑wire or dual‑wire submerged arc welding to ensure consistent weld quality.

　　(8) All weld seams are inspected using an online, continuous ultrasonic automatic flaw detector, ensuring 100% coverage of nondestructive testing for spiral welds. If any defects are detected, the system automatically triggers an alarm and applies a marking, enabling production personnel to adjust process parameters at any time and promptly eliminate the defects.

　　(9) Use an air plasma cutter to cut the steel pipe into individual pieces.

　　(10) After each batch of steel pipes is cut into individual lengths, a rigorous first‑article inspection is conducted to verify the pipe’s mechanical properties, chemical composition, weld quality, surface finish, and nondestructive testing results. Production may proceed only upon confirmation that the manufacturing process meets all specified requirements.

　　(11) After manual ultrasonic and X-ray re-inspection, if defects are detected in welds marked by continuous ultrasonic testing, the affected areas shall be repaired and subjected to nondestructive testing again until it is confirmed that the defects have been eliminated.

　　(12) Both the butt welds of strip steel and the T-joints where they intersect with spiral welds shall be inspected by X-ray fluoroscopy or radiographic film.

　　(13) Each spiral steel pipe undergoes a hydrostatic pressure test with radial sealing. The pipe’s hydrostatic pressure testing system, operated by a microcomputer, precisely controls the test pressure and duration. Test parameters are automatically printed and recorded.

　　(14) Machine the pipe ends to precisely control end-face perpendicularity, bevel angle, and edge chamfer.

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