LSAW steel pipe is a cylindrical shape in which a hot rolled coil is formed by a forming machine and deforms the coil into a smooth shape, and is welded by using a skin effect and a proximity effect of a high-frequency current or an arc burning under a layer of the solder. The edge is heated and melted, and it is fused under a certain squeezing force and finally cooled to form. The edge of the tube, which is melted by a high-frequency current, is called a high-frequency straight welded tube (
ERW), and the arc melting is called a longitudinal welded pipe (LSAW).
There are two types of lsaw steel pipe welding: one is a double-sided submerged arc welding and the other is high-frequency welding. However, the diameter of the steel pipe that can be made between these two types is very different. High-frequency welding of the general wall thickness of the welded pipe does not exceed 12mm, this situation is caused by the high-frequency welding performance, too thick the welder can not melt the steel plate will be able to weld the anger. The double-sided submerged arc welding is different from it. It is not limited by the size of the steel pipe to be processed, and the diameter and thickness far exceed the size of the high-frequency welding. Therefore, double-sided submerged arc welded pipe is divided into butt welded pipe (also known as circular seam welded pipe) and a seam welded pipe, invisible welded pipe. The so-called butt welded pipe is produced by the roll winder (because it is affected by the degree of coiling machine, the general length is between 1.5 m and 2.5 m) and the shorter welded pipe is then welded together in a section so that to achieve the required length, this is called a butt welded pipe. A slotted welded pipe is formed by pressing a medium plate through a large hydraulic forming machine at a time (the length can be up to 14 meters depending on the length of the plate), and then welding and rounding. The invisible welded pipe is generally made of 402 or less in diameter and 12 mm in wall thickness and is made of high-frequency welding. After expanding the hole diameter through the expanding machine, the required size is achieved. Large-diameter straight submerged arc welding steel pipes are formed by U-shaped hydraulics.
