In order to improve the service life of high-frequency welding 316L large-diameter stainless steel welded pipe, foreign countries have been vigorously developing metal plating and non-metallic coating technologies on the inner and outer surfaces of large-diameter stainless steel welded pipe. The economic effect of the steel pipe surface coating is obvious.

The quality of high-frequency welded large-diameter stainless steel welded pipes depends to a large extent on the development of non-destructive testing technology and is guaranteed. Using non-destructive testing, on the one hand, the weld defects of the pipe can be checked to ensure the reliability of the welded pipe; on the other hand, the quality feedback of the production process of the 316L large-diameter stainless steel welded pipe can be controlled through the information feedback system of the detection result. Therefore, the development of non-destructive testing is an important technical measure to improve the quality and production level of welded pipes.

In order to achieve the above goals, all countries attach great importance to the experimental research on new production process and new technology of 316L large diameter stainless steel welded pipe. For example, the United States has recently researched and developed a new technology of square wave welding for the production of large-diameter stainless steel welded pipes with a diameter of 200-1200 mm. Since the square wave welding has no influence of the peak current, the edges are heated uniformly and the weld quality is good. The roll forming technology for producing thin-walled and ultra-thin-wall stainless steel welded pipes is now used in many countries.

The large-diameter stainless steel welded pipe cooperates with cold drawing and cold rolling to achieve continuous production, and has also achieved good results. The United States is also equipped with a cold expander in a 406 mm stainless steel straight seam welded pipe unit to improve the strength of the finished pipe (about 25%), while improving the shape and dimensional accuracy of the pipe section.