Aluminum Volatilization and Inclusion Removal in the Electron Beam Cold Hearth Melting of Ti Alloys

The electron beam cold hearth melting (EBCHM) process has emerged as either an alternative or a complement to vacuum arc remelting, since it is capable of enhancing the elimination of hard-alpha inclusions by dissolution or sedimentation. The present article describes the use of a mathematical model to simulate the electron beam melting of titanium in a cold hearth. The mathematical model is based on the numerical solution of the coupled momentum, solute, and heat transport equations in a transient regime for a three dimension geometry. The model calculates the velocity, turbulence intensity, temperature, and alloy composition in the liquid and the solid phases. The calculation provides the overall heat balance and the volatilization of metallic elements such as aluminum. A postprocessor numerical tool simulates also the behavior of a hard-alpha inclusion during melting (trajectory and kinetics of dissolution). In order to demonstrate the usefulness of this model, the authors examine the influence of the casting rate and of the beam scanning frequency on the volatilization of aluminum and on the capacity of the process to remove hard-alpha defects.