Abstract：In order to reduce the residual stress concentration in the heat-affected area and improve the weld quality performance,the high-frequency straight seam welded pipe must undergo intermediate frequency heat treatment. However,after intermediate frequency induction heating,there is a certain temperature difference between the upper and lower surfaces of the welding seam. Affected by the heat transfer sequence,the lower surface of the thick-walled pipe is not easy to reach the heat treatment temperature,which will seriously affect the quality of the finished steel pipe. According to the characteristics of intermediate frequency electromagnetic heating of welded pipe,the effects of the axial distance of two sets of coils,the turning angle of coils,and the distance between main and secondary coils on the induction heating effect are analyzed. The temperature difference between the upper and lower surfaces of the weld and the temperature at point H after heating presented a decreasing trend with the increase of the axial distance between the two coils. When the coil angle is positive,the temperature and temperature difference at point H increase with the increase of the angle,and the minimum value occurs when the angle is 50°. When the angle is negative,the temperature difference and the temperature at point H fluctuate within a certain range. In this case,the temperature at point H is higher and the temperature difference is smaller. When the distance between the primary and secondary coils of a single set is 30 mm,the temperature difference is the smallest. Professional welding software SYSWELD was used to conduct tissue field simulation,and the tissue distribution on the upper surface of the weld after heat treatment was compared and analyzed. It was found that after intermediate frequency heat treatment,the volume percent of ferrite increased to about 25% and the volume percent of pearlite decreased to 75%. Finally,the Gleeble thermal simulation experiment and metallographic experiment were conducted to indirectly verify the correctness of the temperature model. It provides a theoretical reference for further optimizing heat treatment process parameters of straight seam welded pipe and has certain guiding significance for the production improvement of enterprises.
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2021, Vol. 56 
