Carbon Steel Straight Seam Welded Pipe (Carbon Steel Longitudinal Welded Pipe)

This is a type of welded steel pipe made from carbon steel strips/plates, with a longitudinal weld parallel to the pipe's axis, mainly divided into ERW (Electric Resistance Welded) for medium-small diameters and LSAW (Longitudinal Submerged Arc Welded) for large diameters and thick walls. It is widely used in construction, energy, municipal engineering, and other fields due to its high production efficiency, low cost, and stable quality.

What are its core production processes?

ERW Process (most common for small and medium sizes, e.g., OD 21.3–630 mm): Uncoiling → leveling → edge trimming → forming → high-frequency resistance heating (100–500 kHz) to melt the edges → extrusion welding → deburring (internal and external) → sizing → cutting → non-destructive testing (ultrasonic/eddy current) → hydrostatic pressure testing. No filler metal, narrow heat-affected zone, fast speed.

LSAW Process (for large diameters and thick walls, e.g., OD 406–1422 mm): Plate cutting → JCOE/UO forming (step-by-step bending into a circle) → pre-welding → multi-wire submerged arc welding (SAW) → mechanical expanding (to uniform stress and improve dimensional accuracy) → X-ray inspection → end processing. Suitable for high-pressure pipelines, with deep weld penetration and high joint strength.

What materials and standards apply?

Common Grades: Q235B, Q355 (Chinese standards); API 5L Grade B, X42, X52, X65; ASTM A53, A106, A252. Low-carbon steel (C ≤ 0.25%) is the main material, which is easy to weld and has good ductility.

Key Standards: API 5L (oil and gas pipelines), ASTM A53 (black and hot-dipped galvanized steel pipe), GB/T 3091 (low-pressure fluid transportation), GB/T 9711 (oil and gas pipeline steel pipe), EN 10217.

What are the main characteristics and advantages?

Advantages: Low production cost, high output, short weld (lower defect probability than spiral pipes), easy non-destructive testing, high dimensional accuracy, and convenient on-site connection.

Limitations: The length is limited by the raw material (strip/steel plate); the circumferential stress distribution is slightly different from seamless pipes, and the resistance to external pressure is not as good as spiral welded pipes of the same specification.