Simulation Of Slag/Metal Two-phase Flow And Heat Transfer In Double-electrode And Three-electrode Electroslag Remelting Systems

Electroslag remelting(ESR)is a special metallurgical process in which the melting,refining and solidification of metals are completed in the same mold.The process of ESR contains many complicated physical and chemical phenomena,such as electromagnetic mutual inductance,coupling of flow and heat transfer,coexistence of melting and solidification crystallization.With the development of the high parameters and larger capacity equipment,the size and weight of large forgings are becoming larger.Due to the limitations of single electrode ESR equipment,multi-electrode ESR equipment are becoming more popular.It plays a significant role for the steel ingot quality in electromagnetic field,Joule heat field,temperature field and flow field.The multi-physical field and flow process of double-electrode and three-electrode ESR process are studied,which provide theoretical guidance for the production of high quality and large-scale ingots.The mathematical models of electromagnetic field,Joule heat field,temperature field and flow field are established in double electrode ESR system.In the process of double electrode ESR,most of the current through the slag layer,only a small part of the current enters the ingot.In the electrode,the current density mainly concentrates on the surface of the electrode.The center of the electrode hardly through the current.The current density in the slag pool is mainly concentrated in the upper part of the slag and on both sides of the two electrodes.The magnetic induction intensity mainly concentrates on the periphery of the electrode.The magnetic induction intensity inside the two electrodes is larger than that outside the two electrodes.The maximum value of the electromagnetic force is on the inside of the two electrodes.The maximum value of Joule heat density occurs at the junction of the bottom inside of the electrode and the slag.With the increase of electrode spacing,the current density in the central region of the slag pool decreases gradually.The maximum value of magnetic induction intensity in the center of slag pool increases gradually.The Joule heat of the central region of the slag pool decreases gradually.The Joule heat of the two sides of the slag pool near the mold wall increases gradually.When the droplets are dropping in the flow state,a part of current will diffuse to the bottom of slag pool and flow into the ingot.It makes the current density distribution more uniform in the remelting process.The Joule heat distribution in the slag pool is more uniform in the flow state than that in the non-flow state.When droplets fall through the slag pool,the movement of the slag is driven.A pair of swirls with opposite swirls are formed on both sides of the droplets.The swirls in opposite directions are formed on both sides of the slag pool near the mold wall and on both sides of the slag/metal interface.The mathematical models of electromagnetic field,Joule heat field,temperature field and flow field in three-electrode electroslag system are established.The current density in the slag pool is mainly concentrated in the region near the electrodes.The maximum current density is concentrated in the region near the inside of the three electrodes.The magnetic induction strength increases on the inside of the electrode and weakens on the other side.Joule heat is concentrated in the middle of the slag pool and in the slag pool area near both sides of the electrode terminal.With the increase of the electrode center distance,the maximum current density is gradually far away from the center of the slag pool.The current distribution is more uniform in the slag pool.The Joule heat density decreases on the left side of the slag pond and increases on the right side of the slag pool.The temperature in the slag pool is uniform,which is between 1700 K and 1980 K.The maximum value appears in the central region of the slag layer.The flow of molten slag caused by shear stress around the droplet is swirling.The velocity near the droplet is downward.There is a large temperature gradient in the slag pool near the mold wall in the radial direction.The floating lift force is greater than the Lorentz force.Therefore,the molten slag velocity wall is downward near the mold.