Numerical simulation of inclusion transport behavior in vacuum induction melting process of nickel-based superalloy

Inclusions in nickel-based superalloys significantly influence their mechanical properties which limit the application and development. A two-dimensional axisymmetric model coupling electromagnetic flow, heat transfer, and inclusions transport was developed using the finite element method. The effects of current intensity and frequency on the transport behavior of inclusions and removal rate during vacuum induction melting were investigated using this model. To verify the accuracy of the mathematical model, experiments were conducted using the vacuum induction furnace model VIF200. A comparison of the experimental results with the simulation results reveals an excellent agreement. Four eddies exist in the central section of the molten pool, with any two eddies flowing in opposite directions. The drag force exerted by the eddies causes the inclusions converge toward the four corners of the cut surface. Due to buoyancy, an increase in the particle size of inclusions makes it easier for them to be adsorbed by the free surface, a phenomenon that is particularly noticeable for inclusions with a particle size of 400 μm. An increase in current intensity changes the adsorption interface of certain 400-μm inclusions from the free surface to the sidewall. Increasing both current intensity and frequency enhances the crucible removal rate of inclusions, with current intensity exerting a more significant effect, increasing the removal rate by approximately 1% for every 150 A. Upon completion of melting, the ingot is typically obtained by pouring or bottom pouring, and inclusions adsorbed to the free surface are difficult to separate. Therefore, higher current intensity and frequency should be employed during melting to enhance the crucible removal rate.