What is the difference between welded steel pipe and welded spiral steel pipe?
2022-05-07
Welded steel pipe refers to steel pipe with a welded seam, manufactured by bending steel strip or steel plate into circular, square, or other cross-sectional shapes and then welding them together. The raw material used for welded steel pipe is either steel plate or steel strip. Since the 1930s, driven by the rapid development of continuous strip‑rolling production and advances in welding and inspection technologies, weld quality has steadily improved, leading to an expanding range of grades and specifications. As a result, welded steel pipe has increasingly replaced seamless steel pipe in a growing number of applications. Compared with seamless steel pipe, welded steel pipe offers lower costs and higher production efficiency.
Welded steel pipe refers to steel pipe with a welded seam, manufactured by bending steel strip or steel plate into circular, square, or other cross-sectional shapes and then welding them together. The raw material used for welded steel pipe is either steel plate or steel strip. Since the 1930s, driven by the rapid development of continuous strip‑rolling production and advances in welding and inspection technologies, weld quality has steadily improved, leading to an expanding range of grades and specifications. As a result, welded steel pipe has increasingly replaced seamless steel pipe in a growing number of applications. Compared with seamless steel pipe, welded steel pipe offers lower costs and higher production efficiency.
Steel pipes are classified into seamless and welded types. Welded pipes are further divided into straight-seam steel pipes and spiral-welded steel pipes. Straight-seam welded pipes include ERW (electric resistance welded) and LSAW (longitudinal submerged-arc welded). The welding process for spiral-welded pipes is also submerged-arc welding; the key difference between SAW and LSAW lies in the weld seam configuration, while the distinction from ERW resides in the welding process itself. Submerged-arc welding requires consumables—such as welding wire and flux—whereas ERW does not; ERW relies on medium-frequency heating to achieve fusion. Steel pipes can be broadly categorized by manufacturing method into two main types: seamless steel pipes and welded steel pipes. Seamless steel pipes, according to their production processes, include hot-rolled seamless pipes, cold-drawn pipes, drawn‑down pipes, hot‑expanded pipes, cold‑spun pipes, and extruded pipes, among others. Seamless steel pipes are made from carbon steel or alloy steel and are available in hot‑rolled and cold‑rolled (cold‑drawn) forms.
The production process for straight-seam welded pipe is simple, with high productivity and low costs, leading to rapid development. Spiral-welded pipes generally have higher strength than straight-seam welded pipes; they can produce larger-diameter pipes from narrower blanks and can also manufacture pipes of different diameters using blanks of the same width. However, compared with straight-seam pipes of the same length, spiral-welded pipes have a weld seam that is 30% to 100% longer, and their production speed is lower. Consequently, smaller-diameter welded pipes are typically manufactured using the straight-seam process, while larger-diameter pipes are mostly produced by the spiral-welding method.
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