The welding process of straight seam steel pipe can be divided into resistance welded straight seam steel pipe and submerged arc welded straight seam steel pipe. During the manual hydraulic test machine, resistance welded straight seam steel pipe is divided into high frequency welded straight seam steel pipe, intermediate frequency welded straight seam steel pipe, and low frequency. Welding straight seam steel pipes, and submerged arc welding straight seam steel pipes are also known as double-sided submerged arc welding straight seam steel pipes or LSAW straight seam steel pipes, and the LSAW is (Longitudinally Submerged Arc Welding). Resistance welding straight seam steel pipe is also known as ERW straight seam steel pipe. The ERW between them is (Electric Resistance Weldin), which is abbreviated as ERW. High frequency welded straight seam steel pipe is also known as ERW straight seam steel pipe. ERW is a general term for resistance welded steel pipes. Straight seam high frequency resistance welded pipes (Electric Resistance Welding (ERW) for short) ERW is a letter corresponding to the English word list. Resistance welded steel pipe is divided into two methods: communication welded steel pipe and DC welded steel pipe. Communication welding is divided into low frequency welding, intermediate frequency welding, ultra intermediate frequency welding and high frequency welding according to the different frequencies.High-frequency welding is mainly used for the production of thin-walled steel pipes or thick-walled steel pipes. High-frequency welding is divided into touch welding and induction welding. DC welding is generally used for small diameter steel pipes.

Therefore, in general, high frequency welded pipe is included in ERW welded pipe, which is a kind of ERW welded pipe produced by high frequency welding process. ERW straight seam welded pipe is a kind of steel pipe with advanced functions, good quality and economy in the field of oil and gas storage and transportation. The probability of shortcomings is small, and it can conditionally transport wet acid natural gas. After the diameter expansion, the geometrical accuracy of the steel pipe is high. Welding is performed in a straight line at a horizontal position after the forming is completed. The diameter perimeter is well controlled and the welding quality is good.

Submerged arc welded straight seam steel pipe is also known as double-sided submerged arc welded straight seam steel pipe or LSAW straight seam steel pipe. LSAW steel pipe (Longitudinally Submerged Arc Welding) is a professional expression term for LSAW steel pipe. LSAW steel pipe is produced from a single medium-thick plate by pressing (rolling) the steel plate into a tube blank in a mold or a forming machine, using a double-sided submerged arc welding method and expanding the diameter. The finished product has a wide specification scale, good toughness, plasticity, uniformity and compactness of the weld, and has the advantages of large pipe diameter, pipe wall thickness, high pressure resistance, and low temperature and corrosion resistance. When constructing high-strength, high-quality long-distance oil and gas pipelines, most of the steel pipes required are large-caliber thick-walled straight seam submerged arc welded pipes. According to API rules and regulations, in large-scale oil and gas transportation pipelines, straight seam submerged arc welded pipes are the only applicable pipe types when they pass through Class 1 and Class 2 areas such as the alpine zone, the sea floor, and densely populated urban areas.