Welded pipe is the common pipe material in gas pipeline, greater than 426 mm in diameter (508 mm) or the welded pipe is generally referred to as the large diameter welded pipe, according to the welding as a way for tube, can be divided into spiral welded pipe and straight seam welded pipe.

Spiral welded pipe is the low carbon carbon structural steel and low alloy structural steel strip according to certain helix Angle (also called the molding Angle) rolled into a tube billet, then pipe seam welding made up, it can use a narrow strip in the production of large diameter steel pipe. Spiral welded pipe is mainly spiral submerged arc welding (SSAW), widely used in all kinds of gas pipeline construction in our country, its specification in diameter * wall thickness. Spiral welded pipe with one-side welding and double welding, tube welding shall ensure that the water pressure test, the tensile strength and cold bending properties of the weld in accordance with regulations.

Straight seam welded pipe is the hot rolled plate volume after molding machine molding, the deformation of steel coil to smooth cylinder, using high frequency current skin effect and proximity effect or flux layer burning under the arc welding, the tube billet is heated to melt, and fusion under certain extrusion effect, after the final cooling forming. Edge of tube billet by using high frequency current melting is known as the high frequency straight seam welded pipe (ERW), using arc melting is known as the straight seam submerged arc welding pipe (LSAW).

Straight seam welded pipe main raw material is low carbon steel hot-rolled coil, hot rolled band, in petroleum, metallurgy, construction, coal mine, port, machinery and other industries are widely used in oil and gas transportation, low pressure water gas, mine fluid conveyor, belt conveyor roller, auto transmission shaft, etc.