Optimization Basis and Control of the Vacuum Induction Melting Process for Monel K-500 Alloy

During the vacuum induction melting (VIM) casting process of Monel K-500 alloy, a large number of shrinkage defects are likely to occur in the upper part of the ingot, resulting in low yield and poor quality. To address this issue, this study investigates the thermal and physical properties and solidification process of Monel K-500 alloy through thermodynamic calculations using Jmat-Pro. The experimental results show that the solidification range of Monel K-500 alloy is between 1250 and 1350 °C. The solidification path is: L→L+γ→L+γ+MC→γ+MC+M7C3→γ′+γ+MC+M7C3. During the solidification process, as the mass fraction of the residual liquid phase decreases, Ni exhibits negative segregation, while Cu exhibits positive segregation. Combining the thermodynamic calculation results with a finite element model (FEM), a simulation of the industrial VIM casting process for Monel K-500 alloy of 6 t was conducted. The simulated results were compared with the actual shape and size of the shrinkage defects in the upper part of the induction ingot to verify the reliability of the casting model. In addition, this study explores the effects of different pouring parameters on shrinkage defects in VIM ingot based on the model. The results show that the addition of a riser has the most significant improvement on the shrinkage defects in VIM ingot. As the riser volume ratio increases, the volume of shrinkage defects in the ingot decreases significantly, with no shrinkage defects present in the ingot at a riser volume ratio of 20%. When the pouring speed is in the range of 2.5–17.5 kg/s, the volume of shrinkage defects in the VIM ingot decreases as the pouring speed decreases. However, when the poring speed is below 7.5 kg/s, the shrinkage defects move inward within the ingot.