Study On The Structure Optimization Of Mold Electromagnetic Stirrer For Continuous Casting Bloom

Mold electromagnetic stirring can greatly improve the casting defects in the mold area and product quality.Therefore,the research on electromagnetic stirrer of mold can play a more important role in continuous casting production.In this paper,a 360 mm × 300 mm CC bloom 20 CrNiMo low carbon steel is taken as the research object.The structure of the conventional mold electromagnetic stirrer is improved,and two new stirrers are proposed.The influence of different electromagnetic parameters(current intensity and current frequency)and the structure of stirrer(layered rotation angle and core deflection angle)on the distribution of magnetic field in continuous casting mold was studied by establishing three-dimensional electromagnetic field model and numerical simulation.Then,the electromagnetic force is coupled to the flow field and temperature field model,and the distribution of the flow field and temperature field in the mold is obtained under different electromagnetic parameters and stirrer body structure.In order to explain the micro mechanism of the effect of electromagnetic stirring on the initial solidification of molten steel more clearly,the solidification structure of the bloom was simulated.The results show that when the electromagnetic parameters are changed only,the electromagnetic force produced by the electromagnetic stirrers increases with the increase of current intensity and current frequency,and the magnetic induction intensity increases with the increase of current intensity,but decreases with the increase of current frequency,which conforms to the skin effect.The temperature and velocity of the meniscus of three kinds of stirrers increase with the increase of current intensity and current frequency.Among them,the temperature of the meniscus of the inclined pole stirrer is the highest and the fluctuation is the largest,and the temperature of the layered stirrer is the lowest and the fluctuation is the smallest.The velocity of molten steel increases with the increase of current intensity and current frequency under three kinds of stirrers,among which there are many reflux areas in the mold under the layered stirrer,and the flow is the most complex.When only the structure of electromagnetic stirrer is changed,the electromagnetic force and magnetic induction intensity in the mold do not change obviously at first,and then decrease sharply with the increase of layered rotation angle and core deflection angle.The conventional electromagnetic stirrer and the inclined pole electromagnetic stirrer can meet the stirring intensity under the lower electromagnetic parameter(1Hz / 350A).With the increase of layered rotation angle,the range of hot zone of molten steel did not change obviously at first,then the range of hot zone expanded and the temperature increased;for the layered electromagnetic stirrers with layered rotation of 0 ° and 15 °,the flow rate of molten steel in the mold was significantly higher than that of layered electromagnetic stirrers with layered rotation of 30 °.With the increase of core deflection angle,the range of hot zone of molten steel first decreases,then the range of hot zone expands,and the temperature increases;the flow velocity in the mold of inclined pole electromagnetic stirrer with core deflection of 30 ° decreases obviously.To sum up,the stirring capacity of the inclined pole mold electromagnetic stirrer is the strongest.When the electromagnetic parameter is 1Hz / 350 A,the effect of the stirrer with the core deflection of 15 ° is the best.The growth trend of the bloom in the mold is that the area of fine grains on the outer surface of the bloom develops into coarse columnar crystals,and the center of the bloom is equiaxed crystal region.With the increase of superheat degree,the range of equiaxed crystal area in the center is decreasing,and the grain size is increasing.It can refine the grain by low temperature pouring near liquidus temperature for the molten steel in the mold;with the increase of the number of body nucleation,the number of grains is increasing,and equiaxed crystal is more refined,which is beneficial to improve the quality of slab.