Production process of carbon steel welded pipe

Carbon steel welded pipes are primarily produced using three processes: electric resistance welding (ERW), spiral submerged arc welding (SSAW), and straight seam submerged arc welding (LSAW). Each process has distinct characteristics, making them suitable for different applications based on raw materials, forming processes, caliber sizes, and quality.

1. Straight Seam Electric Resistance Welded Pipe (ERW)

Electric resistance welded (ERW) pipe is the earliest and most widely used type of steel pipe in China. With over 2,000 production units, ERW pipes account for about 80% of the total welded pipe production. These pipes are available in diameters ranging from Ф20 to 610mm. Since the 1980s, China has imported approximately 30 sets of ERW219-610mm units, significantly advancing equipment technology and product quality. The low investment cost, rapid production turnaround, and broad application range have fueled the rapid development of ERW pipes. The advent of the CSP plate production process has provided low-cost, reliable raw materials, facilitating further advancements. ERW pipes, initially used for fluid transportation and structural applications, have now expanded into oil well pipes and line pipes, traditionally the domain of seamless pipes.

2. Spiral Submerged Arc Welded Pipe (SSAW)

Spiral submerged arc welded (SSAW) pipes require less equipment investment and utilize low-cost narrow strip (plate) coils for continuous welding to produce large-diameter pipes (Ф1016~3200mm). The production process is simple, and operational costs are low, making SSAW pipes economically advantageous. In China, oil and gas transmission pipelines primarily use SSAW pipes manufactured by steel pipe factories affiliated with the petroleum system. Advanced technologies such as low residual stress forming and pipe end mechanical expansion ensure that the quality of SSAW pipes, which undergo stringent quality control, is comparable to that of straight seam welded pipes. SSAW pipes are the primary choice for long-distance oil and gas pipeline projects in China, meeting domestic demands and being exported in large quantities.

3. Straight Seam Submerged Arc Welded Pipe (LSAW)

Longitudinal submerged arc welding (LSAW) is a relatively advanced pipe-making technology in China. Initially dominated by UOE technology, the industry has seen the gradual adoption of JCOE technology as a new mainstream method. LSAW pipes are known for their reliable quality and are widely used in high-pressure oil and gas transportation trunk lines. However, the production of LSAW pipes involves significant investment, using single wide and thick plates as raw materials, which are costly. The complex production process, lower efficiency, and higher product costs also contribute to the higher overall investment in LSAW pipe production units.

Each type of carbon steel welded pipe offers specific advantages and is chosen based on the requirements of the application, balancing factors like cost, production efficiency, and quality.