Combination of welding can significantly improve the welding speed. Preheat combination of high frequency welded stainless steel pipe, welded pipe weld quality with conventional welding, plasma welding seam quality considerable. Combination of high-frequency welding preheat simple, easy to automate the entire welding system, this combination easily with existing high-frequency welding equipment interface, the investment cost-effective good. 3 by a continuous heat treatment furnace protective gas bright heat treatment of stainless steel, widely used abroad, with no oxidation protective gas to the middle of a continuous heat treatment furnace and heat treatment products, steel can be obtained without the surface oxidation of light, thus eliminating the conventional pickling process . The heat treatment used to improve both the quality of steel, but also to avoid the acid emissions on the environment.