Prevention of Air Suction from the Contact-part between Sliding Gate and Immersion Nozzle

抄録

With increasing requirement of steel quality in continuous casting, it is extremely important to regulate reasonably flow rate of molten steel without either biased flow or reoxidation by the suction of air from around the contact-part between sliding gate (SG) and immersion nozzle (SEN). In this study, a novel/method to prevent the suction of air from all around the contact-part between the SG and SEN during controlling the flow rate of molten steel, has been developed by giving a step to the SEN. The effects of the step in the SEN on the prevention of air suction from all around the contact-part can be summarized as follows:
(1) The flow squeezed passing through the SG is turned abruptly just before the step in the SEN and, as a reverse flow, passes towards the contact-part between the SG and SEN, where its kinetic energy is converted into the pressure energy as a kind of impinging-flow-action, resulting in a positive pressure on the contact-part.
(2) With increasing amount of sliding-gate-opening, the distance downstream from the gate to the step, that is necessary for the contact-pressure to be positive on the contact-part, becomes wider. Over some opening amount, the contact pressure is always positive under the condition that a dimensionless step width (ratio of step-width to inner-diameter of nozzle) is over 0.15.
From the above-mentioned issues, it is found possible to prevent the air suction from all around the contact-part between the SG and SEN using the SEN with the step beneath the sliding gate.