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激光焊接过程中较快的冷却速度可能会加剧凝固热裂纹的发生。目前对于激光焊接过程中凝固热裂纹敏感性的系统研究还较少,如何准确测量焊接凝固热裂纹发生的临界应变和温度是获得热裂纹敏感性数据的关键。利用基于高速高倍在线摄像的U型热裂纹实验,捕捉到激光焊接过程中凝固热裂纹发生的瞬间,并通过跟踪测量热裂纹尖端附近两点的位移变化获得凝固热裂纹发生的临界应变;同时,在焊接过程中采用在线观察热电偶投入法对焊接熔池后端的温度变化进行了测量。通过改变U型热裂纹实验的拉伸载荷,获得不同温度下热裂纹发生时的临界应变,从而构建表征凝固热裂纹敏感性的韧性曲线。
The faster cooling rate during laser welding may exacerbate the occurrence of solidified hot cracks. At present, there are few systematic researches on the susceptibility to hot cracking in laser welding. How to accurately measure the critical strain and temperature of hot cracking in welding and solidification is the key to obtain the data of hot cracking susceptibility. The U-type hot-cracking experiment based on high-speed and high-power on-line photography was used to capture the instantaneous occurrence of the hot cracking in the laser welding process. The critical strain of the solidified hot crack was obtained by tracking the displacement change at two points near the hot crack tip. During the welding process, the thermocouple input method was used to measure the temperature change at the back of the weld pool. By changing the tensile load of the U-shaped hot crack experiment, the critical strain at the occurrence of the hot crack at different temperatures is obtained, and a toughness curve characterizing the susceptibility to the hot cracking of the solidification is constructed.