钛合金 VAR 过程中自感电磁场对流场与偏析行为的影响

A continuum model for alloy solidification was used to simulate the temperature evolution, solute distribution, liquid flow, and self-induced magnetic field during VAR process for titanium alloys. The work reveals the influence of self-induced magnetic force and/or buoyancy force on the melt flow and solute segregation by contrastively exerting the forces. When a small melting current of 0.3 kA is used, the melt flow is dominantly driven by the buoyancy force that the melt flows downward at the side of the melt pool and upward in the center of the melt pool. When a large melting current of 0.73 kA is used, the melt flow is dominantly driven by the self-induced magnetic force and the melt flows adversely, and the maximum velocity reaches 0.036 m/s. When a medium current of 0.45 kA is applied, both the two forces act evidently, forming two regions in the pool where the melt flow directions are opposite, and the maximum flow rate in the pool can reach a minimum value of 0.004 m/s due to their competition. With increasing the current, the total segregation of the ingot rises at begin, has a reduction stage after a peak, but then increase continuously again. The extreme values of the three stages are 0.54%, 0.39% and 0.57%, correspondingly. The minimum segregation can be obtained when the self-induced magnetic force and buoyancy force act equally.