Influence of initial swirling flow position on flow field in continuous casting round billet mould

Flow characteristics in a continuous casting round billet mould affected by different initial positions of swirling flow in the nozzle was investigated by water model experiment under conditions including no stirring, stirring propeller, swirling rotors and multi-port nozzles. Results show that swirling flow initial position affects impact depth, liquid level fluctuation, and flow uniformity. With a double helix rotor in the middle of nozzle, impact depth at the 2nd second decreased to 275 mm, and liquid level fluctuation reached within ±0.2 mm. When swirling flow generated at the nozzle outlet, the optimised four-port nozzle reduced impact depth to 205 mm and the fluctuation to less than ±0.1 mm. Thus, with the swirling flow from the middle of nozzle, stable outward flow formed by increasing swirling intensity alleviates macro-segregation. When using a multi-port nozzle, the flow out of the ports should be dispersed to weaken the turbulence, keeping the mainstream away from the free surface.