高拉速板坯连铸结晶器浸入式水口的水模型研究

Water modeling study on submerged entry nozzles in continuous slab casting molds for high speed casting

利用染料示踪法，采用波高传感器和旋桨式流速仪在全比例水模型中研究了四种浸入式水口（A型：凹型，15°（上角度）-15°（下角度）；B型：凸型，15°-15°；C型：凹型，40°-15°，D型：凸型，40°-15°）下板坯连铸结晶器内的流场和液面特征．发现采用凹型水口时结晶器液面的波动与表面流速均小于凸型水口．凹型水口F的表面流速变化的功率（频率为0．03～0．1Hz）比凸型水口小约50％，所以凹型水口更有利于减少结晶器内卷渣的发生．在高拉速条件下（拉速为1．8m·min^-1，较大的水口出口上角度有利于抑制水口出口流股的漩涡流，进而减少剪切卷渣的发生．四种水口中C型水口条件下结晶器液面的表面流速最小，约为0．27m·s^-1，为提高拉速留有较大余地，所以适合高拉速连铸的最佳浸入式水口为C型．

The flow field and surface characteristics in a continuous slab casting mold with four kinds of submerged entry nozzles （Type A： well-shaped bottom, 15° （upper port angle）-15° （lower port angle）; Type B： mountain-shaped bottom, 15°-15°; Type C： well-shaped bottom, 40°-15°; Type D： mountain-shaped bottom, 40°-15°） were studied by using the dye tracer injection technique, a wave sensor and a propeller velocimeter within a full scale water model. It is found that the level fluctuation and surface velocity in the mold using a well-shaped bottom nozzle are less than those using a mountain-shaped bottom nozzle. The power of surface velocity fluctuations （frequencies ranging from 0.03 Hz to 0.1 Hz） using a well-shaped bottom nozzle is 50% less than that using a mountain-shaped bottom nozzle, so the molten slag entrapment may be reduced when using a well-shaped bottom nozzle in the mold. At a high casting speed of 1.8 m.min-1, a larger upper port angle of the nozzle outlet is in favor of depressing the swirling flow and vortexes at the nozzle outlet, and then the molten slag entrapment decreases. The surface velocity in the mold fed by a Type C nozzle is the lowest and its value is about 0.27 m.s 1 among the four investigated nozzles, so a Type C nozzle provides much allowance for increasing the casting speed. As a result, the optimal design for high speed casting is Type C nozzles.