ERW( Electric Resistance Welding Pipes) pipes have two kinds of welding, induction welding and contact welding. The ERW pipe applied wide hot rolling steel profile as raw material, and went through pre-bending, continuous forming, welding, straightening, cutting and other processes. The pipe has short weld joints, high dimensional accuracy, uniform thickness, and excellent surface and can bear high pressure. However, it also has shortcomings, such small diameter and thin wall, and the weld joints are easy to be eroded. Currently, ERW pipes are mainly used to transport gas as well as oil to city residents.