车架用方钢T型接头焊接残余应力评估及焊接路径优化

Evaluation of Welding Residual Stress and Welding Path Optimization of Square Steel T-type Joint for Frame

焊接残余应力直接影响着车架的承载能力和疲劳寿命。通过数值模拟4种焊接顺序下车架用方钢T型焊接接头的温度场和应力场,对比了固态相变与不同焊接顺序下的焊后残余应力分布,并对最优焊接顺序下的焊件进行疲劳寿命分析。结果表明:考虑固态相变后计算出来的焊接残余应力比不考虑固态相变的偏小,固态相变对Q345钢焊接残余应力影响不可忽略;在不同焊接方案下,温度随时间变化的曲线出现明显差异;在垂直于焊缝方向的路径上,改变焊接顺序可降低横向残余应力;沿焊缝方向的路径,焊缝端部的纵向残余应力因二次循环加热的情况不同而差异明显;采用退焊顺序能有效控制焊接残余应力。将焊接残余应力考虑在内,得出车架的最小疲劳安全系数为0.5,危险区域在焊缝附近。

The welding residual stress directly affects the load-bearing capacity and fatigue life of the frame. The temperature field and stress field of T-type welded joint of square steel for frame under four welding sequences were simulated, and the distribution of residual stress under solid phase transformation and different welding sequence was compared. And the fatigue life of weldments under the optimal welding sequence was analyzed. The results show that the welding residual stress considering the solid phase transformation is smaller than that without considering the solid phase transformation, and the influence of the solid phase transformation on the welding residual stress of Q345 steel cannot be ignored;under different welding schemes, the curves of temperature changing with time are obviously different. Along the path vertical to the weld direction, changing the welding sequence can reduce the transverse residual stress;along the path of the weld direction, the longitudinal residual stress at the end of the weld is obviously different due to different condition of secondary cycle heating. Adopting the backstep welding sequence can effectively control the welding residual stress. Taking the welding residual stress of the frame into account, the minimum fatigue safety factor is 0.5, and the dangerous area is near the weld.