为研究小孔的形成过程,在光纤激光平板扫描焊接低碳钢中,采用调制激光出光时间的方式进行实验。结果表明:小孔的形成过程极为迅速,完整的形成时间在ms量级。低速焊接时,小孔的形成过程包括急速增加、缓慢增加和基本稳定不变三个阶段。高速焊接时,小孔的形成过程仅有急速增加过程。进一步实验结果表明:小孔的形成时间不超过激光焊接特征时间,且激光焊接特征时间随焊接速度的增加而减小,这是高速焊接时小孔仅有快速形成过程的原因。

In order to study the formation process of keyhole, in the fiber laser plate scanning welding of low carbon steel, experiment was carried out by modulating laser light-out time. Experimental results show that the formation process of keyhole is extremely rapid, and the whole formation time of a keyhole is in ms level. In low-speed welding, the formation process of keyhole includes three stages: rapid increase, slow increase, and roughly stabilized stage. During high-speed welding, the formation process of keyhole only includes rapid formation stage. Further experiments show that the formation time of keyhole is not exceeding the characteristic time of laser welding and the characteristic time of laser welding decreases with the increase of welding speed, which together explain why keyhole formation only includes the rapid formation stage in high-speed welding.