何林基 张天雷 徐刚 马春伟

摘 要： 考虑激光深熔焊过程中存在对流、辐射、热传导等传热过程以及蒸汽反冲作用力，表面张力，热浮力等力学过程，采用移动旋转高斯体热源来简化焊接的热过程，使用VOF方法跟踪自由界面，通过焓孔隙法实现焊接过程的凝固熔化，同时采用连续表面张力模型将蒸汽反冲作用力转化为在一定厚度上连续的作用力。建立数学模型，获得了奥氏体不锈钢深熔焊接过程中动态熔池的溫度场以及流场分布。结果表明小孔存在周期性的震荡，小孔壁面在蒸汽反冲作用力、表面张力、流体静压力下形成凸台。凸台再随着小孔周期性的震荡则会形成气孔，产生缺陷。焊接试验的焊缝横截面熔合线同模型计算结果相吻合，验证了模型的可靠性。

关键词： 激光深熔焊;熔池流场;小孔行为;熔池震荡

文章编号： 2095-2163（2021）03-0124-07 中图分类号：TG402 文献标志码：A

【Abstract】Considering the heat transfer process such as convection， radiation， heat conduction and steam recoil force， surface tension， thermal buoyancy and other mechanical processes in the laser deep penetration welding process， a moving and rotating Gaussian heat source is used to simplify the thermal process of welding， and the VOF method is used to is track the free interface， the solidification and melting of the welding process is realized by the enthalpy pore method， and the continuous surface tension model is used to convert the steam recoil force into a continuous force on a certain thickness. A mathematical model is established to obtain the temperature field and flow field distribution of the dynamic molten pool during the deep penetration welding of austenitic stainless steel. The results show that the small holes have periodic oscillations， and the walls of the holes form bosses under the steam recoil force， surface tension， and hydrostatic pressure. When the boss oscillates with the keyholes， pores will be formed， resulting in defects. The weld cross-section fusion line of the welding test is consistent with the calculation result of the model， which proves the accuracy of the model.

【Key words】 laser deep penetration welding; molten pool flow field; keyhole behavior; molten pool oscillation

0 引 言

作为易于实现自动化控制且具有广阔发展前景的先进焊接技术，激光焊接是一种重要的现代材料加工技术[1]，具有大的焊缝深宽比，焊接速度快，工件变形小，热影响的区域小，同时也有着较高的组装精度，较低的焊接杂质含量，良好的焊接接头机械性能等特点[2] 。从上世纪70年代开始，国内外学者即已使用数值模拟方法对激光深熔焊的熔池和熔池小孔的动态行为进行了深入的研究[3]。Ki等人[4-5]考虑到激光焊接过程中材料对于激光的菲涅尔吸收，以及材料蒸发引起的均匀沸腾，建立了三维激光焊接小孔模型。……