Direct high frequency resistance welding of rolled section steel is a fast production pipeline technology. At present, it has been widely used in many fields, such as downhole casing, oil and gas gathering and transportation pipeline.


However, the welded area of the pipeline has higher activity than the base metal and heat affected area, so the service life of the pipeline groove etching is determined by the welded area, which is a special pipe joint for crevice corrosion. Usually, it will form grooves in the groove. Welding zone. Under natural conditions, the formation of grooves can easily make the corrosive medium stagnate in the corrosive state, resulting in the reduction of oxygen concentration in the joints, gradually forming oxygen concentration battery and external seam, accelerating the corrosion of metal seams.


High frequency resistance welded (ERW) pipe does not need heat treatment as a whole, and can achieve the residual stress of circumferential weld about 350 MPa, which is close to the yield strength of the pipe. When welded into working electrodes, the residual stress is reduced to 100 MPa or less. The circumferential tensile stress can reduce the corrosion potential of the weld, accelerate corrosion, increase the groove coefficient and the welded pipe after heat treatment. The circumferential tensile residual stress of the weld is less than 10-100 MPa, and the circumferential tensile stress changes little after the working electrode is processed. This conventional measurement method can not characterize the corrosion resistance in the practical application of welded pipe products, and can not distinguish the corrosion resistance of welded pipe between real and non-real heat treatment.