高频直缝焊管中频热处理参数分析

 为减小热影响区域残余应力集中,提高焊缝质量,高频直缝焊管需进行中频热处理。但在中频感应加热后,焊缝上下表面存在一定的温差,受传热顺序的影响,厚壁管材的下表面不易达到热处理温度,严重时会影响成品钢管质量。根据焊管中频电磁加热特点,分析了两组线圈轴向间距、线圈翻转角度和主、副线圈间距对感应加热效果的影响规律。焊缝上下表面温差和加热后H点温度随着两组线圈轴向间距的增大呈现减小趋势。当线圈角度为正值时,H点温度和温差随着角度的增大而增大,角度为50°时出现最小值;当角度为负值时,温差和H点温度在一定范围内波动,此时H点温度较高,温差较小。当单组主、副线圈间距为30 mm时,温差最小。利用专业焊接软件SYSWELD进行组织场模拟,对比分析了热处理后焊缝上表面的组织分布,并发现经过中频热处理后,铁素体体积分数增加到了25%左右,珠光体体积分数减少到75%。最终通过Gleeble热模拟试验和金相试验,间接验证了温度模型的正确性。为进一步优化直缝焊管热处理加热工艺参数提供理论参考,对企业的生产改进具有一定的指导意义。

Analysis of intermediate frequency heat treatment parameterson high frequency straight welded pipe

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.