Stress on the High-frequency Straight Seam Resistance Welding Pipe Trench Corrosion

Roll-bending steel direct high-frequency resistance welding technology is a rapid production of pipeline technology, and it is widely used in many fields such as downhole casing and oil and gas gathering pipelines.


However, the area of such pipe welds is more active than that of the base metal and heat affected zone. Therefore, the weld zone determines the service life of the pipe. The channel corrosion is a special pipe joint. It is a crevice corrosion phenomenon. Grooves are formed in the weld zone. Under natural conditions, the groove tends to corrode the formation of corrosion media in a stagnant state, thereby reducing the oxygen concentration of joints gradually increasing the oxygen concentration of the battery and the outer weld to accelerate the corrosion of the metal weld.


High-frequency electric resistance welded steel pipe (ERW) as a whole, without heat treatment, achieves weld residual stress at 350mpa, near the yield strength of the steel pipe. When the weld is processed into a working electrode, the residual stress is reduced by about 100 MPa or less. The tensile stress in the hoop direction can reduce the weld, corrosion potential accelerates corrosion, and the corrosion sensitivity increases. After the heat treatment, the groove coefficient and the welded pipe have a small residual tensile stress of 10 to 100 MPa in the circumferential direction of the weld, after which the tensile stress is The change is a small process for the working electrode. This traditional measurement method cannot characterize the corrosion resistance of welded pipe products in practical applications, and cannot distinguish the corrosion resistance of actual or non-heat treated butt welded pipes.