焊接钢管高频感应加热的残余应力和组织演变

 随着中国钢铁、冶金与电磁等交叉学科的快速发展，焊接钢管产量及质量日益提升。高频感应加热是生产焊接钢管的核心工序，获取更加精确的焊管高频加热过程的应力分布和微观组织演化规律，是进一步提升焊管品质的关键要素和学者们关切的问题。综合考虑热传导和微观组织转变对应力的影响，针对高频焊管特有的沙漏形热源形貌，定量分析了焊接热影响区微观组织演变过程和残余应力的分布规律，获得了考虑热应力和组织应力的残余应力分布。发现该应力特点为在焊缝附近轴向残余应力较大，最大等效残余应力出现在距焊缝中心1/2壁厚处的热影响区，在壁厚方向管材内部的中间层的残余应力较大，且应力分布与反映高频焊接热源形貌特征的加热温度峰值和加热温度宽度相关。而在焊缝中心处，未考虑组织变化的等效残余应力值是考虑组织变化的1.3倍。掌握焊管高频焊接应力和组织演变的特点和规律，可为优化高频焊接工艺提供理论依据，对提升高频焊管质量具有重要意义。

Residual stress and microstructure evolution of high #br# frequency welding of longitudinal pipe

With the rapidly development of cross disciplines such as steel，metallurgy and electromagnetics in China，the output and quality of welded steel pipes are increasing day by day. The longitudinal pipe induction welding is the key process for producing high frequency welded pipes. Obtaining the more accurate residual stress distribution and microstructure evolution of welded pipes is the key factor to further improve the quality of welded pipes and the concerns of researchers. The effects of heat transfer and microstructure transformation on the stress are considered. For the unique hourglass welding temperature field of the high frequency longitudinal welded pipe，the evolution process and the residual stress distribution of microstructure in the heat affected zone are quantitatively analyzed. The residual stress distribution is obtained，considering the thermal stress and microstructural stress. The results show that the radial residual stress is smaller near the weld seam，and the axial residual stress is larger. The maximum equivalent residual stress appears in the heat affected zone about 1/2 of the wall thickness from the center of the weld，and the position is related to the shape of the hourglass shaped temperature distribution of the high frequency induction welding. At the center of the weld，the equivalent residual stress value without considering the change of the microstructure is 1.3 times that of the microstructure change. The distribution of residual stress at the peak of heating temperature and heating range is further quantitatively analyzed. Mastering the characteristics and laws of the high frequency welding stress and microstructure evolution of welded pipe can provide a theoretical basis for optimizing the design of high frequency welding process，which is great significance to improving the quality of high frequency welded pipe further.