2003 Volume 43 Issue 5 Pages 663-670
Model experiments were carried out to understand the behavior of argon gas introduced into the immersion nozzle through the sliding gate. Water and air were modeled for molten steel and argon gas, respectively. A transparent straight pipe made of acrylic resin was used for a model of the immersion nozzle. Two kinds of repellents were coated on the inner wall of the pipe to change its wettability. The wettability was evaluated in terms of the contact angle. When the wettability was poor, air attached preferably to the wall. The attachment of air to the wall became more obvious as the contact angle increased. The flow pattern of a water-air two-phase flow was significantly dependent on the wettability of the pipe. In particular, when the contact angle reached 142°, liquid droplet flow and inverted annular flow were observed. The inverted annular flow is beneficial for the prevention of alumina particle adhesion to the immersion nozzle. An empirical equation was proposed for the boundary between the liquid droplet flow and inverted annular flow regimes.