电磁制动对FTSC结晶器内流场和钢渣界面的控制

Control of flow field and steel slag interface in FTSC mold under electromagnetic braking

针对高拉速时薄板坯连铸结晶器内流场及钢渣界面不稳定问题,以某钢厂FTSC(flexible thin slab caster)结晶器和多模式电磁制动MM-EMBr(multi-module electromagnetic braking)系统为研究对象,采用LES+VOF模型对不同电磁感应强度条件下的结晶器流场进行多物理场耦合计算,重点研究在水口浸入深度为190 mm、拉速为6 m/min条件下不同磁感应强度对结晶器内流场和钢-渣界面的影响。研究结果表明,无电磁制动时,结晶器内流场随着冲击深度的增加由最初的双环流逐渐转变成单环流模式,钢渣界面不稳定,起伏波动大,最大速度值超过0.65 m/s,最大波高值超过40 mm,出现卷渣甚至“渣眼”现象,部分上返流钢液的湍动能转化为势能,使钢-渣界面位置逐渐上升,液渣层减薄;开启多模式电磁制动系统后,当水口正下方位置C处磁感应强度不低于0.09 T时,可以有效控制主射流的速度和角度,使窄面冲击点在一定范围内上下波动,从而控制结晶器内流场;随着磁感应强度的增加,结晶器内湍动能总值逐渐减小,当AB、C、DE的磁感应强度增加到0.17、0.15、0.12 T时,能将钢渣界面的最大速度值控制在0.30 m/s以内,最大波高值控制在10 mm以内,钢渣界面位置平均高度控制在-2~2 mm,钢渣界面的湍动能控制在0.045 J/kg以内,此时电磁制动效果最理想,结晶器内流场和钢渣界面的稳定性最好;继续增大磁感应强度时,结晶器内和钢渣界面的湍动能反而增加,这说明磁感应强度并不是越大越好,需要各模块协同配合才能达到最佳制动效果。

Aiming to solve the problem of the instability of the flow field and steel slag surface in the thin slab continuous casting mold under high casting speed,the FTSC(flexible thin slab caster)mold and MM-EMBr(multi-module electromagnetic braking)system of a steel company were used as research objects,the LES and VOF model were used as numerical simulation to perform multi physics field coupling calculation on the flow field of mold under different electromagnetic induction intensity,the key is to study the effect of different magnetic induction intensities on the flow field inside the mold and the steel slag interface under the conditions of immersion depth of 190 mm and casting speed of 6 m/min.The results show that without electromagnetic braking,the flow field inside the mold gradually changes from the initial double circulation mode to a single circulation mode as the impact depth increases,the steel slag interface is unstable and fluctuates greatly,the maximum velocity of the steel slag interface exceeds 0.65 m/s,and the maximum wave height exceeds 40 mm,slag entrapment and slag holes appear at the steel slag interface,part of the turbulent kinetic energy of the upflow molten steel is converted into potential energy,which makes the position of the steel slag interface rise gradually and makes the liquid slag layer thinner;after the MM-EMBr system is turned on,when the magnetic induction intensity at position C directly below the SEN is not less than 0.09 T,the speed and angle of the main jet can be effectively controlled to make the impact point of the narrow wall fluctuate up and down within a certain range,so as to control the flow field in the mold;with the increase of magnetic induction intensity,the total turbulent kinetic energy in the mold gradually decreases,when the magnetic induction intensity of AB,C,DE increases to 0.17,0.15,0.12 T,the maximum velocity of steel slag interface can be controlled within 0.30 m/s,the maximum wave height can be controlled within 10 mm,the average height of steel slag interface position is controlled within-2-2 mm,and the turbulent kinetic energy of steel slag interface can be controlled within 0.045 J/kg,this electromagnetic braking intensity is the most effective,and the flow field in the mold and the steel slag interface are relatively stable;when the magnetic induction intensity continues to increase,the turbulent kinetic energy in the mold and at the steel slag interface increases instead,it shows that the stronger the magnetic induction intensity is,the more ineffective it is,the best braking effect can be achieved only by the cooperation of all modules.