高速列车6005A-T6铝合金焊接接头软化分析

测试了6005A-T6铝合金双丝MIG焊和激光-双丝MIG复合焊的焊接热循环曲线,并利用热处理方法进行了焊接软化的热模拟试验,探讨了6005A-T6铝合金焊接接头的软化问题.结果表明,焊接热循环峰值温度超过260℃时热影响区开始软化,当峰值温度达到350℃左右时软化最为严重,晶内的非稳态强化相β"相及β'相转变为平衡态的β相(Mg₂Si)并聚集长大是造成软化的根本原因;受热温度在260~500℃的热影响区,焊后经简单的时效处理后,硬度无法恢复至原始状态;复合焊的焊接热循环曲线在260℃以上的高温停留时间相对较短,这是造成复合焊接头软化程度低于常规MIG焊的直接原因.

Study on the softening of 6005A-T6 aluminum alloy welding joints for high-speed train

Welding thermal cycle curves of 6005A-T6 aluminum alloy by using tandem MIG welding and laser-tandem MIG hybrid welding was tested individually. The softening of the welding joints was studied through welding thermal simulation with heat treatment method. The test results demonstrated that the notable softening in HAZ began as long as the peak temperature of welding thermal cycle curve exceeded 260℃, and the most serious softening in HAZ occurred while the peak temperature of welding thermal cycle curve was up to 350℃. The unstable phase of β" and β', the main strengthening phase of 6005AT6 aluminum alloy, transformed to β(Mg₂Si) which aggregated and grew to block was the main reason why the softening happened. The hardness of the joints in HAZ, where the peak temperature of welding thermal cycle curve was between 260-500℃, could not recover totally through ageing treatment. The detention time beyond 260℃ on the thermal cycle curve of lasertandem MIG hybrid welding joints was much shorter than that of tandem MIG welding joints, so that the softening of laser-tandem MIG hybrid welding joints was little slighter than that of tandem MIG welding joints.