Numerical simulation and experimental study of vacuum arc remelting (VAR) process for large-size GH4742 superalloy

Numerical modeling and industrial experiment were used to study the entire vacuum arc remelting (VAR) process of 660 mm GH4742 superalloy. In order to calculate the electromagnetic field, flow field, temperature field, and melt pool shape change throughout the entire VAR process, a 2D axisymmetric model with coupled multi-physical fields matching industry trials was constructed. The microstructure and elemental distribution conditions in the large-size GH4742 ingot were analyzed in combination with the industrial ingot dissection experiment, and the most likely locations of freckle defects were predicted. According to the research, the melt pool has two clockwise flow fields that are affected by buoyancy and Lorentz forces. The melt pool depth deepens gradually as melting proceeds, with a maximum melt pool depth of 0.32 m and a paste zone width of 0.16 m. Although the ingot's elemental distribution is largely consistent, there is microsegregation between the dendrites. Where the freckle is most likely to appear, at (0.322, 0.075), the Rayleigh has a great value of 1.1. For melt pool form and dendritic spacing throughout the entire melting process, the results of the industrial ingot dissection experiment and the simulation results show good agreement, proving the accuracy of the thermal history and solidification microstructure calculation for the entire melting process. Furthermore, the prospect of combining numerical simulation with a special material database for accurate defect prediction is proposed.