Coupled Multiphysics Behavior During GH984G Electroslag Remelting And Vacuum Arc Remelting Process

GH984G nickel-based superalloy has become a high-performance new heat-resistant alloy candidate material for advanced ultra-supercritical power stations due to its good thermal stability and corrosion resistance.The melting process of nickel-based superalloys usually chooses VIM+ESR or VIM+VAR double melting.Electroslag remelting and vacuum consumable remelting will cause freckle segregation during the melting process,which seriously affects the mechanical properties of the material.Therefore,the choice of process and smelting parameters becomes even more important.In recent decades,with the rapid development of computer technology,numerical simulation technology has become more and more mature,and has become an important support point in actual production.In this paper,numerical simulations of GH984G alloy electroslag remelting process and vacuum consumable remelting process are established.Based on Maxwell's equations,N-S equations,energy conservation equations,and heat transfer equations,slag pools and steel ingots are used as research objects.Two solutions are obtained.The distribution of electromagnetic field,temperature field and velocity field under the process reveals the distribution and internal relations of the multi-physics field under the two processes.At the same time,combined with the Rayleigh number black spot criterion,the formation trend of black spot segregation in the steel ingot is predicted,which provides a theoretical basis for the industrial preparation of GH984G nickel-based superalloy.On the electroslag remelting process,a mathematical model with a diameter of ?155 mm,melting parameters of 2.3 kA and 35 V,and a steel type of GH984G was established.The simulation results were compared with the experimentally measured ingot molten pool shape and depth to verify the Model accuracy.Then,in the simulation,the magnitude of the current and the depth of the slag pool were changed,and the influence of the current and the depth of the slag pool on the multiphysics was investigated.In the process of vacuum self-consumption,a mathematical model with a diameter of ?160 mm,melting parameters of 2.3 kA and 25 V,and a steel type of GH984G was established to compare and analyze the distribution laws of multiple physical fields of vacuum consumable and electroslag remelting.Secondly,the smelting current was changed,and the influence of the current on the vacuum consumable multiphysics was investigated.In the laboratory,an electroslag remelted steel ingot was prepared by the VIM+ESR duplex process at a melting parameter of 2.3 kA and 35 V.Through the analysis of the macrostructure,chemical composition and microstructure of the steel ingot,it was found that the macrostructure is uniform and fine,the grains are small,and there are no obvious defects such as looseness and shrinkage.The monitoring and analysis of various chemical elements in the steel can show that nitrogen and oxygen content is well controlled,the element loss rate is low,and the element content is stable.Statistics on the dendrite distances show that under the smelting conditions,the ingot solidifies well.According to the simulation results,the dendrite spacing in the model is calculated by using the dendrite spacing calculation formula.The experimental measured values are compared with the simulated values.The results show that the simulated values and the measured values have the same radial distribution trend.it is good.Secondly,the calculated value of dendrite spacing and the Rayleigh number freckle criterion were used to obtain the Rayleigh number distributed in the radial direction under different process parameters.The results show that the VIM+VAR process has parameters of 2.3 kA,35 V the freckle formation tendency is small.