背反射增效激光焊接熔池匙孔相变及流场分析

Analysis on keyhole phase change and flow field of back reflection induced synergistic laser weld

关键词:  激光焊接  背面羽辉  数值模拟  匙孔相变  流场

Key words:  laser welding  back plume  numerical simulation  keyhole phase change  flow field

摘要:

建立了背反射增效激光焊焊接熔池流动中气相区、液相区和固相区的统一模型，在模型中考虑了等离子体/蒸气云和小孔吸收机制，综合了表面张力、热浮力和重力的作用. 基于数值计算得到了熔池的三相匙孔相变以及流场，重点分析了表面张力对熔池流动和传热的影响. 此外，通过钛合金薄板的背反射增效激光焊接试验对模型进行了验证. 结果表明，匙孔引发等离子体/蒸气云与背面垫板诱发羽辉的耦合作用，是X形焊缝熔池形貌形成的主要原因；同时，表面张力是形成背反射增效激光焊接熔池内“椭圆回流环”的主要驱动力.

Abstract:

An unified model of gas phase area, liquid phase area and solid phase area during the molten pool flow process of back reflection induced synergistic laser welding was established. Plasma & vapor cloud and keyhole absorption were considered and effects of surface tension, thermal buoyancy and gravity were taken into account in the model. The three-phase keyhole phase change and flow field of molten pool were obtained by numerical calculation, surface tension effect on flow and heat transfer of molten pool was mainly discussed. Moreover, a validation experiment of back reflection induced synergistic laser welding was carried out by taking titanium alloy sheet as an example. Results show that the coupling effect of plasma & vapor cloud caused by keyhole and back plume induced by back sub-plate is the main reason for the formation of X-type weld, and surface tension is the main driving force of the “oval reflux ring” formation in the back reflection synergistic laser welding molten pool.