| In the process of casting solidification,the electromagnetic oscillation has the advantages of refining the billet grain,promoting the overheated dissipation of molten steel,expanding the solidification equiaxed crystal area and reducing the central shrinkage cavity,so as to improve the casting quality.Therefore,in view of the continuous casting process of 140mm×35mm thin slab,considering the influence of electromagnetic oscillation,this paper systematically studied the molten steel flow,temperature distribution,solidification process and inclusion distribution in the mold.Firstly,the coupled mathematical model of flow field temperature field inclusion in small slab is established,and the influence of flow temperature and inclusion distribution in mold is analyzed in detail.The results of numerical simulation show that the molten steel enters the mold and shoots at the narrow surface of the mold,which is divided into upper and lower flow streams,forming the upper and lower flow zones respectively;the turbulence intensity at the narrow surface of the molten steel impact is the highest,and the closer it is to the outlet of the mold,the molten steel becomes a horizontal movement,the turbulence intensity gradually weakens,and the turbulence intensity of the mold wall is the lowest due to the cooling effect of the molten steel solidification.The distribution of temperature field in the mold is largely affected by the flow field.The temperature of molten steel in the center is the highest,and the temperature in the narrow wall is the lowest.The farther away from the meniscus,the greater the thickness of solidified shell,and the phenomenon of zero growth of shell appears at the entrance of the mold.The volume fraction and quantity density distribution of inclusions are consistent with that of molten steel in the mold.The volume fraction and quantity density of inclusions are higher in the flow direction of molten steel,lower in the liquid phase and lowest in the free liquid surface.Secondly,the coupling model of circuit and magnetic field is built based on ANSYS software platform.When the working current is 60 A,the frequency is 50 Hz,and the magnetic induction intensity of permanent magnet is 1.35 T,the electromagneticforce of reciprocating oscillation of 1.2×10-4N/m3 can be produced in the slab.The distribution and magnitude of the oscillating electromagnetic force and Joule heat produced in the slab at any time are obtained by using the transient solution method.The influence of the electromagnetic parameters of the oscillating electromagnetic field on the electromagnetic oscillating force and Joule heat produced in the slab is also studied.The results show that when there is alternating current in the slab,the current distribution in the slab is not uniform.The closer it is to the surface of the slab,the more current density it is.The current inside the slab is smaller.The magnetic induction intensity is fan-shaped distribution in the slab and concentrated on the narrow surface of the slab.The distribution of oscillating electromagnetic force is similar to the distribution of magnetic induction intensity.The reciprocating electromagnetic force in the metal slab will affect the overall flow trend of the molten steel in the mold on the one hand,and on the other hand,it will also affect the regional turbulence intensity of the molten steel.Finally,a three-dimensional coupled mathematical model of electromagnetic flow,heat transfer solidification and inclusion distribution in small slab is established,and the differences of liquid steel flow,temperature,solidification and inclusion distribution in the mold with or without electromagnetic oscillation are analyzed.The simulation results show that: after the electromagnetic oscillation,the movement track of the molten steel in the mold changes,forming multiple return areas,the speed of the vortex center in the upper return area increases by 678%,and the speed of the molten steel impacting the narrow surface decreases by 73%;because of the newly formed return area in the mold,the residence time of the molten steel in the mold increases,the heat exchange increases,the solidified shell thickens,and the range of the solid-liquid two-phase area increases.Under the action of the oscillating electromagnetic force,the inclusions are not agglomerated and grow up,but dispersed uniformly and finely in the molten steel.The distribution of inclusions in the mold is uniform,and the maximum characteristic radius is reduced from R~*=7.1?m to R~*=6.4?m. |
PDF Full Text Request