Numerical Simulation Of Semi-continuous Casting Of Large-Scale Magnesium Alloy Slab

The large-scale slab rooling is base on the large-scale magnesium alloy flat ingot,but the magnesium alloy ingot has a tendency with coarse microstructure,solute segregation and hot cracking in Solidification Process Especially Non axisymmetric large volume ingot.In recent years,although semi-continuous casting has progress fast,the large-scale magnesium alloy sheets have a higher requirements with low cost and high quality.This study is a part of the projects,"The liquid forming of large-scale magnesium alloy slabs with low cost and high quality" in National Key Fundamental Research Program(973).Based on the results of the effects of ultrasonic field and electromagnetic field on the fluid flow,heat transfer and solidification behavior of magnesium alloy,and study of ultrasonic-electromagnetic compound field and the shunt in semi-continuous casting of Large-Scale Magnesium Alloy Slab,and give some parameters and data for industrial production.In this paper,the finite element software ANSYS/Fluent is used to establish a coupled mathematical model to describle the process of semi-continuous casting of large-scale slab of 400mmx 1450mm magnesium alloy,which is applied to both sigle external field(ultrasonic field(UC)or electromagnetic field(LFEC))and multi-physical fields casting processes.The conclusions obtained from this paper are as follows:(1)In the processes of ultrasonic-electromagnetic compound field casting,a accurate-coupled mathematical model which considers the interaction of ultrasonic field,electromagnetic field,fluid field,temperature field and solidification is established.UDS technology is used to solve the equation of Helmholtz,and as momentum source the effect of ultrasonic is added to semi-continuous casting of magnesium alloys.(2)In the UC process,the resulted into two strong "fountain" whirlpools near the emitter.With the increasing of the casting speed,the velocity of the melt flow and the depth of the liquid are increase.The cavitation effect region is an ellipsoid(3)In the LFEC process,low frequency electromagnetic field influenced both flow field and temperature field.A vigorous forced convection of the melt,and it entirely changed direction of melt flow and increase velocity of melt flow.A large "fountain" whirlpool region generates in melt alloy,the depth of liquid decrease close to the surface of ingot.(4)In the US+LFEC process,as the speed of casting increase,isotherm surface and the depth of the fluid move down.The flow velocities near the surface of ingot have the same distribution.On the contrary,the flow velocities increase as the speed of casting increase in the center of ingot;As the water distribution ratio decrease,the depth of fluid and isotherm surface move up,and the flow velocities decrease in the center of ingot;Ultrasonic influenced both flow field and temperature field significantly near the emitter;The effect of electromagnetic field on fluid flow and heat transfer is significantly,and generate a strong"fountain" whirlpool in fluid.The vast majority of the melt outflow through the first hole of shunt,the depth of solidified shell decrease near the small face of ingot casting,but increase slightly in the center of ingot casting.(5)In the US+LFEC process,the tapping hole should design far from the center of bedding face for flat ingot.