考虑自由表面的定点A-TIG焊数值分析

Numerical analysis of fixed point A-TIG welding with free surface

根据流体力学基本原理,并用VOF方法追踪自由表面,建立了更接近实际情况的三维定点A-TIG焊熔池数学模型,综合考虑了熔池液态金属所受的浮力、电磁力、电弧压力和表面张力,同时考虑了熔池内液态金属的对流、辐射和热传导,运用FLOW-3D软件求解得到了定点A-TIG焊熔池自由表面、温度场及流场,并重点分析了有、无活性剂时熔池自由表面的变化情况.结果表明,不使用活性剂时,熔池自由表面呈中心下凹、两边凸起的形状;使用活性剂时,表面张力温度系数由负变正,使熔池自由表面呈中心凸起、两边下凹的形状;在焊接电流I≤150 A的条件下,有、无活性剂时考虑自由表面变形情况下温度场、流场及熔池形貌的数值模拟结果与试验结果和不考虑自由表面变形时现有的数值模拟结果基本一致.

According to the basic principles of fluid mechanics,tracking the free surface by using VOF method,a three dimensional mathematical model for fixed-point A-TIG welding was established. Considering the buoyancy, electromagnetic force,arc pressure and surface tension of liquid metal in the molten pool,as well as the convection,radiation and heat transfer,the FLOW-3D software was used to simulate the fixed-point A-TIG welding molten pools' free surfaces,temperature fields and flow fields,in particularly,the free surfaces of the molten pools with or without active flux was analyzed. The results show that in case of the process without active flux addition,the free surfaces' centers are concave surrounded by convex surface,while in case of the process with active flux,surface tension temperature coefficient changed from negative to positive,thus free surfaces' centers are convex, and the periphery is concave.When the welding current is 150 A or less,the simulated result of the molten pools' temperature fields,flow fields and shapes with the consideration of free surface are consistent with the experimental results,as well as the simulated process without considering free surface.