管接头局部焊后热处理的加热带布置方案优化分析

Optimization Analysis of Heating Band Arrangement Schemes of Pipe Joint during Local Postweld Heat Treatment

对管接头进行局部焊后热处理时,一般通过限定焊缝局部温度梯度来控制热应力,这会导致过大的加热范围。通过对管接头局部加热时的轴向热应力产生机理和分布规律的分析,提出了利用第二加热带的反向弯矩来缓解热应力的方法,并通过实例计算表明:为了取得显著的应力缓解效果,环向管焊缝与第二加热带边缘的最佳距离为1.5√Rt;喷嘴接头第二加热带边缘与焊缝的轴向距离和环向距离分别为1.5√Rt和3.8√Rt。另外,为了避免产生新的应力集中,环向加热带边缘与几何不连续位置的距离应当大于2.5√Rt。

During the local postweld heat treatment of the pipe joint,thermal stress is generally controlled by limiting temperature gradient in practice,which always results in excessive heating zone.In this paper,an approach mitigating thermal stress by reverse moment of a secondary heating band was proposed by analyzing the generation mechanism and distribution rules of axial thermal stress of pipe joint during local heating.The calculation results through examples show that:in order to obtain significant stress mitigation effect,the best distance between girth weld of the pipe joint and edge of the secondary heating band was1.5√Rt;the axial and circumferential distance between the nozzle weld and the edge of the secondary heating band should be1.5√Rt and 3.8√Rt in axial and circumferential direction,respectively.In addition,in order to avoid new stress concentration,the distance between the edge of the circumferential heating band and location of geometrical discontinuity should be larger than2.5√Rt .