激光深熔焊接运动熔池的动力学行为数值分析

Numerical analysis of moving molten pool dynamic behavior during laser deep-penetration welding

针对连续激光深熔焊接,考虑表面张力、气化压力、浮力和液固之间内部作用力,以及熔池内层流、辐射和气液界面传热传质等因素,建立连续激光深熔焊接激光热源随熔深变化的自适应模型和小孔填充模型,并对熔池的深度、温度分布、流场分布以及相同焊速、不同功率下小孔的动态演变过程进行分析.结果表明:运动熔池形成过程中,焊速为0.08m/s,功率分别为1 600、2 000、2 400W,焊接时间t<7.2ms时,小孔深度随时间成线性增长,当焊接时间t>7.2ms时,小孔深度值发生高频振荡,但深度平均值趋于稳定;随着激光光束的移动,熔池金属绕过小孔,从小孔前部熔池流向后部形成环流,凝固形成"鱼鳞状凝固线".

Aimed at the process of continuous laser deep-penetration welding and taking account of influ- encing factors such as surface tension, vaporization pressure, flotage, interaction force between liquid and solid, turbulence and radiation in molten pool, and heat-transfer and mass-transfer over gas-liquid inter- face, an adaptive model of continuous laser deep-penetration welding with laser heat-source varying with melt depth, and a keyhole filling model as well are established. The molten pool depth, temperature and velocity distribution, and keyhole dynamic evolution process with identical welding speed and different power are analyzed, also. It is shown by the result that when welding speed is 0.08 m/s and power is 1 600, 2 000, 2 400 W, respectively, and welding time t〈7. 2 ms, the depth of keyhole will growth line- arly with time. When welding time t〉7. 2 ms, its depth value will oscillate with high frequency, but its average will tend to be stable. With the moving of the laser beam, the metal in molten pool will go round the hole and form a circulation, solidifying into scalelike solidus.