热沉影响钛合金薄板焊接残余应力的试验分析

采用切条应力释放法测量了钛合金TC4薄板常规钨极氩弧焊(GTAW)和动态控制低应力无变形GTAW对接试件中的纵向残余应力和纵向残余塑性应变的分布。测量结果表明,钛合金常规GTAW缝中残余拉应力峰值小于其母材屈服强度,焊缝附近存在残余压缩塑性应变;动态控制低应力无变形GTAW焊技术中热沉的冷却作用使得热源与热沉之间的高温金属承受强烈的拉伸作用,产生拉伸塑性变形,部分抵消了焊接过程中已产生的缩短的塑性变形,使得试件中纵向残余塑性应变减小,焊接残余拉应力峰值降低,残余压应力水平降低。切条应力释放法是一种简便有效的薄板焊后残余应力测量方法,能够满足工程应用的精度要求。

Experimental study on effect of heat sink on welding residual stress of titanium alloy thin plate

The distributions of longitudinal residual stress and longitudinal residual plastic strain of titanium alloy Ti-6Al-4V thin plate welded by conventional GTAW and GTAW with a trailing heat sink(DC-LSND) were studied experimentally using "Slot-sectioning stress relaxation" method. The experimental results showed that the maximum residual tensile stress in the weld with conventional GTAW is 45% of the yield strength of the titanium alloy. Because of the extremely-high gradient cooling of the heat sink in DC-LSND GTAW, high tensile effect acts on the zone between the arc and the trailing heat sink, the tensile plastic strain is produced, which compensates some portion of the longitudinal incompatible strain cause by arc heat source. Therefore longitudinal residual plastic strain, the maximum residual tensile stress and residual compressive stress are reduced properly.