熔池表面Marangoni力诱导的表面速度奇异现象

通过对焊接熔池流体流动与传热过程控制方程组、合金元素气化方程、Ｍａｒａｎｇｏｎｉ力方程以及其他辅助方程的耦合求解，定量计算了ＦｅＣｒＮｉＳ合金系中具有不同Ｓ含量时焊接熔池的表面温度分布和浮力、电磁力、Ｍａｒａｎｇｏｎｉ力共同作用下的表面速度分布．结果表明，在微量的Ｓ含量条件下，熔池表面上的Ｍａｒａｎｇｏｎｉ力会出现一个最大值．随Ｓ含量增大，Ｍａｒａｎｇｏｎｉ力减小，Ｍａｒａｎｇｏｎｉ力的最大值对应的温度增大．在Ｍａｒａｎｇｏｎｉ力诱导下，熔池内会形成两个方向相反的涡流环路，它们具有不同的温度，并在熔池表面上逆向而流，相遇处产生很大的温度梯度，从而在该部位引发表面速度奇异峰值．当Ｓ含量较小时，表面速度奇异峰值发生在液相线前沿，当ｗ（Ｓ）大于０．０３％时，速度奇异性消失．

Analysis of Weld-Pool Surface Velocity Singularity Induced byMarangoni Force

Numerical calculations are made for coupled equations of heat and fluid flow involving vapo rization, Marangoni force and other effects concerned with the welding of FeCrNiS alloys. Assessed quantitatively are the effects of sulfur content on the surface temperature and velocity distributions. Two cells driven by Marangoni force are identified. They collide with each other on the welding pool surface and give rise to a surface velocity singularity where a large temperature gradient presents with a peak of the Marangoni force. As the sulfur content increases, the location of peak surface velocity approaches the pool center. Maximum peak of surface velocity initially increases and then decreases before it tends to zero.