Simulation Of Flow And Solidification Behavior In Continuous Casting Of Billet With EMS

Electromagnetic stirring is widely used in continuous casting process,and the quality of billet can be significantly improved with mold electromagnetic stirring and final electromagnetic stirring.However,only with appropriate parameters,the electromagnetic stirring could better promote the improvement of billet quality.The current research on electromagnetic stirring still stay on the stage of regularity,and it is difficult to make the most appropriate theoretical guidance for special production.In this paper,for the continuous casting of 160mm x 160mm billet of 65 steel,the mathematical model of electromagnetic field and the coupled model of flow and solidification are developed to describe the induction electromagnetic field of rotating electromagnetic stirrer and the flow and solidification process of billet.Moreover,the effects of casting speed,superheat degree and specific water flowrate in secondary cooling zone on flow and solidification of billet has been investigated.The main conclusions are as follows:The distribution of magnetic induction intensity is uniform,and the distribution of magnetic force is basically similar to that of magnetic induction,which increase first and then decrease along the axis,and reach maximum at the central cross section of stirrer.Along the radial direction,it is relatively lower in central region and gets bigger close to the edge of billet.Above distribution rule will remain unchanged with the change of current parameters,however,when the current intensity and frequency increases within a certain range,the magnetic induction intensity and electromagnetic force also increases accordingly.Upper and lower circulation regions are formed in the longitudinal cross section,and the liquid steel rotates on the cross section with electromagnetic stirring.Rotational flow of molten steel in the mold cause the fluctuation of solidification shell thickness,however,it is basically stable at the exit of mold.The solidification speeds and the length of liquid core reduce with electromagnetic stirring.As the current of mold electromagnetic stirrer is 640A and 4Hz,the solidified shell at the exit of mold changes significantly and gets more uniform relative to the current of 320 A and 4Hz.The solidification process is accelerated after improving the current intensity,and the current intensity of mold electromagnetic stirrer is recommended to be 640A.With the increment of superheat degree to 27 ?,the surface temperature and central temperature at the final secondary cooling zone increase.Meanwhile,the liquid fraction increases while the mush zone decreases,and the liquid core extends after promoting the degree of superheat.The superheat degree is recommended to be 27?.With the casting speed increasing from 1.75m/s to 1.9m/s,the mush zone decreases and moves down,solidification rate decreases,and the length of liquid core increases by 0.72 m.Taken together,setting ceiling and improving casting speed is suggested.With the improving of specific water flowrate,the solidification speeds up,which shorten the length of liquid core,besides,the mush zone narrows down and moves up.The surface temperature of billet decreases from 900? to 700?850 ?,when the water ratio increases from 0.68L/kg to 1.27L/kg and 1.68L/kg,which brings about the generation and enlargement of the crack.Therefore,the specific water flowrate remains 0.68L/kg is suggested.Simulation results show that the final electromagnetic stirrer has no obvious effect on the solidification of billet at the practical position.Only when final electromagnetic stirrer moves up 2.6m,where the liquid fraction in the central billet is not less than 0.997,the stirrer can force the liquid steel to rotate.