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

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.