以聚酰胺(PA)和不锈钢(1Cr18Ni9Ti)搭接接头为研究对象,计算了焊接过程中界面处的热过程,并分析了其对塑料热分解行为影响,获得了优化的焊接热输入;然后通过试验验证,获得了稳定连接的PA-1Cr18Ni9Ti接头,并对PA-1Cr18Ni9Ti界面的连接机制进行研究。结果表明:焊接过程中聚酰胺的热分解与时间、升温速率有关;当激光焊接热输入为77.8 J·mm -1(激光功率700 W,焊接速度9 mm·s -1,离焦量70 mm)时,可保证PA-1Cr18Ni9Ti界面处的聚酰胺在充分熔化、铺展的同时,减少热分解,同时可避免聚酰胺的烧蚀和碳化;PA-1Cr18Ni9Ti界面能够形成Cr—O—C化学键,有利于提高两者的结合强度。

PA-1Cr18Ni9Ti joints were welded by fiber laser. The thermal process at the interface during the welding process was calculated to analyze its effect on the plastic pyrolysis. Thus the welding heat input was optimized. The calculated results were verified by experiments, in which a stable welded joint of PA-1Cr18Ni9Ti was obtained. In addition, the interfacial connection mechanism was also studied. The results show that the pyrolysis of the PA plastic during the welding process is related to temperature and rate of temperature increase. When the heat input of laser welding is 77.8 J·mm -1 (laser power is 700 W, welding speed is 9 mm·s -1 and defocus amount is 70 mm), the PA plastic can be fully melted and spread at the interface while reducing the pyrolysis, ablation and carbonization. Chemical bond of Cr—O—C can be formed at the PA-1Cr18Ni9Ti interface, which is benefit for joint strength.