Swirling Flow Effect in Immersion Nozzle on Flow in Slab Continuous Casting Mold.

With increasing requirement of steel productivity and quality in continuous casting in the conventional casting system using an immersion nozzle with side pouring holes, it is very difficult to establish a reasonable molten flow pattern. In order to overcome this difficulty, we propose a new method imparting a swirling motion to the flow in the immersion nozzle and to control the flow pattern in the mold. Obtained results are as follows:1) High amplitudes of oscillation with a period of 10 to 15 sec are observed in the outlet flow of the immersion nozzle and meniscus flow in the conventional casting system, while these phenomena are remarkably suppressed using swirling motion in the immersion nozzle, which leads to very calm and uniform flow pattern at the outlets of the immersion nozzle, in the mold and on the meniscus in the mold.2) The steady outlet flow softly impinges on the side wide face, and then turns around as a reverse flow along the other wide face describing a S-shaped curve in the cross section and clock-wise rotational flow in the vertical section. This outlet flow exerts a shearing-effect on the inner wall of the mold, leads to the considerable energy consumption and exerts a braking effect in the flow which results in suppression of self-excitation-vibration in the bulk mold flow and biased flow on the meniscus. In other words, imparting a swirling motion to the flow in the immersion nozzle, remarkably reasonable bulk mold flow can be obtained.