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局部焊后热处理通常用来改善焊接接头的性能和消除焊接残余应力。影响局部焊后热处理的因素很多 ,其中加热宽度是最重要的一个控制参数。然而对于加热宽度的确定 ,各国标准规定就很不一致。本文采用粘弹塑性有限元分析 ,提出一个基于残余应力消除效果的局部焊后热处理的直接评定方法。该方法可清楚地显示整个热处理过程中的应力变化并可找到临界的加热宽度。对存在原始焊接残余应力的管接头在不同的热处理条件下进行分析。研究表明 ,局部热处理后的最大残余应力随加热宽度的增加而降低 ,当加热宽度达到一定值时 ,残余应力变化十分缓慢 ,可找到一临界加热宽度 ,其残余应力值与均匀热处理时十分接近。采用此方法可评价各种因素对局部焊后热处理的影响 ,并寻求最佳加热条件。通过系列的分析计算表明 ,5rq的加热宽度准则是合理的。
Local post-weld heat treatment is usually used to improve the performance of welded joints and eliminate welding residual stress. There are many factors affecting the local post-weld heat treatment, of which the heating width is the most important control parameter. However, the determination of heating width, the national standard is very inconsistent. In this paper, we use viscoelasto-plastic finite element analysis to propose a direct evaluation method of local post-weld heat treatment based on residual stress elimination. This method clearly shows the stress changes throughout the heat treatment and can find critical heating widths. Pipe joints with residual stress in the original weld were analyzed under different heat treatment conditions. The results show that the maximum residual stress after local heat treatment decreases with the increase of heating width. When the heating width reaches a certain value, the residual stress changes slowly and a critical heating width can be found. The residual stress is close to that of the uniform heat treatment. This method can evaluate the impact of various factors on the local post-weld heat treatment, and seek the best heating conditions. Through a series of analysis and calculation shows that the heating width of 5rq criteria is reasonable.