Numerical Simulation Study On Solidification Process And Thermal Stress Of Electroslag Remelted Hollow Ingot

The electroslag remelting technology is a production process for smelting metal castings with high added value,and the products have the characteristics of pure components and compact components.Hollow ingots are heterogeneous castings in the field of casting,and they play an important role in important national industries such as aerospace,nuclear power and energy transportation.There are two types of castings for hollow castings,such as rotary casting and stamping forging.The controllability of the rotary casting process is poor,the automatic control system has high complexity,and the forging stamping method is easy to cause the hollow ingot to be produced.Cracks,deformations,etc.,and external force extrusion will change the stress distribution of the ingot,resulting in poor metal properties.Due to the increasing demand for hollow ingots and the increasing requirements for casting quality,it is necessary to introduce electroslag remelting technology into the casting process of hollow ingots.In the process of electroslag remelting to prepare hollow ingots,the problem of consumable electrode selection is faced.Generally,there are two options:annular consumable electrode and multi-electrode cluster consumable electrode,and annular consumable electrode due to preparation process The complexity is relatively costly,so multi-electrode clustered consumable electrodes are generally used.The research content of this paper mainly includes:(1)Based on the Ukrainian Y578 electroslag furnace,the physical model is established,and the physical model is meshed.The meshing is all based on a hexahedral mesh.The electromagnetic field and temperature field are calculated using an integrated electroslag furnace model containing electrodes.In the calculation,the calculation of the stress field uses a physical model that excludes the electrodes for calculation.(2)The Maxwell equations are solved based on the finite element method to obtain the current density and Joule heat distribution of the electroslag remelting process of the hollow ingot.During the smelting process of the annular ingot,the current distribution in the electrode cluster is concentrated near the outer surface of the electrode cluster,and the focus ear heat distribution is affected.The Joule heat distribution on the outer side of the electrode is slightly higher than the inner Joule heat distribution.(3)Based on the finite element method,the temperature field,heat flux distribution and shape of the molten pool are calculated.Under the same height,the temperature inside the casting is higher than the temperature on the near wall side,and the temperature on the inner wall side is higher than the temperature on the outer wall side.The rise is faster and the temperature is higher.In the height direction,the shape of the molten pool gradually deepens as the height increases.The heat flux is distributed during the smelting process.As the height position increases,the influence of the bottom tank gradually decreases,and the heat flux gradually decreases.At the same height,the internal heat flux is smaller than the outside.(4)The stress distribution is solved based on the finite element method,and the von-mises stress distribution,residual stress distribution and shear stress distribution are calculated respectively.At the same time,the von-mises stress is mainly concentrated in the lower part of the ingot and the bottom of the ingot,and the maximum stress on the inner wall side is larger than the outer wall side is larger than the bottom.Over time,the initial stage of the cooling process is the maximum stress generation phase.For the residual stress,at the end of the cooling process,the residual stress on the outer wall side is greater than the residual stress on the inner wall side.For the shear stress distribution,the possible position of shear yield is judged based on the fourth strength theory based on the equivalent stress algorithm,and the distribution of the maximum shear stress and the twisting trend are analyzed by the more stringent third strength theory.(5)Change the cooling boundary conditions,input current density,ingot size and other factors,calculate and analyze the equivalent stress distribution,shear stress distribution and residual stress distribution,and according to the calculation results,the internal and external temperature difference is the main factor that determines the yield.The conclusion of the factor.The convective heat transfer coefficient of the bottom water tank has little effect on the stress distribution of the inner and outer walls,but has a great influence on the bottom stress distribution.The convective heat transfer coefficient of the side wall increases,and the reduction of the ingot size and the decrease of the current density lead to the reduction of the maximum stress.,reduction of residual stress and reduction of shear stress.