热输入量对换热器管板焊接接头缺陷及残余应力的影响

Effect of Heat-input on Defects and Residual Stress of Welded Joints of Heat Exchanger Tube-to-tubesheet

文章通过改变焊接的电流和电压,研究热输入量(2.16 kJ/mm,2.52 kJ/mm,2.88 kJ/mm)对换热器管板焊接接头缺陷的影响。基于有限元算法,研究热输入量对换热器管板焊接接头处残余应力的影响,进一步改进焊接工艺。结果表明,与热输入量为2.16 kJ/mm和2.88 kJ/mm相比,在热输入量为2.52 kJ/mm时,管板焊接接头的焊接质量最佳,具有焊缝成形好,无裂纹及少量可接受的焊接缺陷。通过对多管-板焊接接头的残余应力计算发现,中心换热管处热影响区残余应力较大。而且残余应力并不是随着热输入的增加而增加。与热输入量为2.16 kJ/mm和2.88 kJ/mm相比,当热输入量为2.52 kJ/mm时,管板接头处的残余应力分布最均匀且稳定,表明焊接质量最佳,这与实验结果一致。最后,通过增加焊间冷却时间和改变焊接顺序来改进焊接工艺,解决了局部残余应力分布集中的问题,改进了焊接接头质量。

In this study,the effects of heat-input(2.16 kJ/mm,2.52 kJ/mm,2.88 kJ/mm)on the defects of welded joints of heat exchanger tube-to-tubesheet were studied by changing the welding current and voltage.Based on the finite element(FE)algorithm,the effect of heat-input on the residual stress at the welded joints of the heat exchanger tube-to-tubesheet was studied,and the welding process was further optimized.The results show that compared with the heat input of 2.16 kJ/mm and 2.88 kJ/mm,when the heat input is 2.52 kJ/mm,the welding quality of the tube-to-tubesheet welded joints is the best,with good weld formation,no cracks,and a small number of acceptable welding defects.Through the calculation of the residual stress of the tube-to-tubesheet welded joints,it is found that the residual stress in the heat-affected-zone(HAZ)at the central tube is larger.And the residual stress does not increase with the increase of the heat-input.Compared with the heat input of 2.16 kJ/mm and 2.88 kJ/mm,when the heat input is 2.52 kJ/mm,the residual stress distribution at the tube-to-tubesheet joints is the most uniform and stable,indicating that the welding quality is the best,which is consistent with the experimental results.Finally,the welding process is optimized by increasing the cooling time between welds and changing the welding sequence,which solves the problem of local residual stress distribution concentration and optimizes the quality of welded joints.