The Influence of Swirl Nozzle on the Flow Field in the Bloom Mould and the Interface Behavior of Steel Slag

In order to improve the quality of vertical continuous casting 40Mn2 square bloom ， a four-quarter tangential swirl nozzle was proposed， using a Particle image velocimetry technique， the molten steel flow and slag interface behavior at different casting speeds and nozzle immersion depths were studied in a steel plant's bloom mold with 410 mm × 560 mm vertical continuous casting section. The results show that the fluidity of the mold powder at the interface of steel slag is poor when the depth of the nozzle is 90 mm and the casting speed is 0.25 m/min， and the slag entrapment occurs when the casting speed is 0.35 m/min and 0.45 m/min，When the immersion depth of the nozzle is 100 mm， the fluidity of the mold powder at the interface of steel slag is poor while the casting speed is 0.25 m/min， and at 0.35 m/min casting speed ， the inclusion will float upwards. The interface of steel slag is active and there is no slag entrapment， and slag entrapment will occur at 0.45 m/min casting speed . When the immersion depth of the nozzle is 110 mm， the fluidity of the mold powder at the interface of steel slag is poor while the casting speed is 0.25 m/min. When the casting speed is 0.45 m/min， the slag entrapment will occur. When the casting speed is 0.35 m/min， no slag entrapment will occur， compared with the same casting speed and 100 mm immersion depth of nozzle， it is unfavorable to the floating of inclusions. Combined with the actual production practice， the optimum operating parameters of the vertical continuous casting bloom mold are the depth of nozzle immersion 100 mm and casting speed 0.35 m/min.