WELDED TUBE

1. Basic Definition

Welded steel pipe, shortened as welded pipe, is a hollow tubular steel product manufactured by curling steel strips or steel plates into cylindrical, rectangular or special-shaped profiles, then joining the adjacent edges through welding technology to form a continuous pipe body with a weld seam.Unlike seamless steel pipe without any welding joint, welded pipe features simpler production flow, higher output efficiency, richer specification diversity and lower overall manufacturing cost. With continuous upgrades in strip steel metallurgy, high-frequency welding and non-destructive inspection technologies, the mechanical performance and sealing reliability of weld seams have been greatly improved. Nowadays, welded pipes have replaced seamless pipes in most medium & low-pressure fluid transportation and structural engineering scenarios.

2. Main Classification by Welding Technology

Three mainstream industrial welded pipe types cover full diameter and pressure ranges:

2.1 ERW / HFW (Electric Resistance / High-Frequency Welded Straight Seam Pipe)

• Manufacturing Process: Continuous hot-rolled steel coils are uncoiled, leveled and cold-formed into a cylinder. High-frequency induction current rapidly heats the two strip edges to molten state, then squeeze rollers forge the edges together without welding filler metal. Internal burrs are removed online, and weld seams undergo annealing heat treatment to eliminate residual stress.

• Size Range: Outer diameter 19.05 mm ~ 200 mm , wall thickness ≤12.7 mm

• Core Advantages: Ultra-high dimensional precision, smooth inner & outer surface, stable straightness, low cost for small & medium diameters, mass production capacity

• Typical Applications: Municipal water & gas distribution pipelines, building scaffolding, mechanical structural tubes, low-pressure fluid conveyance, oil well casings