Preliminary treatment of straight seam steel pipes: nondestructive testing inside welds. Since the pipe is a super-large steel pipe in the water supply project, especially the steel pipe with a thickness of t=30mm is used as a pipe bridge. It must withstand both the internal water pressure and the bending moment formed by the deadweight of the steel pipe and the water body, so the welding requirements are particularly high. For large-diameter steel pipes with a thickness of t=30mm used in pipe bridges, the longitudinal seams and circumferential seams are both Class I welds, requiring 100% X-ray film inspection and 100% wave flaw detection inspection; while for buried steel pipes with a thickness of t=24mm, the longitudinal seams belong to Class I welding, and 20% X-ray film inspection and 50% wave flaw detection inspection are carried out.

Uses of straight seam welded pipes: There are many types of straight seam welded pipes, according to the use: general welded pipes, oxygen-blown welded pipes, galvanized welded pipes, wire casings, roller pipes, metric welded pipes, automobile pipes, deep well pump pipes, transformer pipes, electric welded special-shaped pipes, and electric welded thin-walled pipes.

General welded pipes: General welded pipes are used to transport low-pressure fluids. Made of Q235A, L245, and Q235B steel.
Galvanized steel pipes: It is to coat the surface of the black pipe with zinc. It is divided into hot and cold. The hot zinc layer is thick, and the cold price is cheap.
Oxygen-blown welded pipes: Generally, they are small-diameter welded steel pipes, which are often used for steelmaking oxygen blowing.
Wire casings: They are pipes for distribution structures, which are ordinary electric welded carbon steel pipes.
Electric welded thin-walled pipes: They are small-diameter pipes used for furniture and lamps.
Roller pipes: The electric welded steel pipes on the belt conveyor have required ovality.
Transformer pipes: They are ordinary carbon steel pipes. Used to manufacture transformer cooling tubes and other heat exchangers.