Estimation of Lubrication and Heat Transfer by Measurement of Friction Force in Mold

Abstract

In the continuous casting of steel, the state of the mold flux plays a significant role in the quality of the steel as well as the casting operation. In this study, the state of the mold flux was estimated by measuring the friction force of mold oscillation and establishing a lubrication model. The friction force was measured with a slab caster equipped with hydraulic oscillators, and the relationship between the friction force and continuous casting factors such as the mold oscillation conditions, mold flux properties and casting speed was investigated. The main results are summarized as follows.

(1) The friction force was proportional to the relative velocity of the slab to the mold. The lubrication condition became fluid lubrication when the value of the casting speed was higher than 1.4 m/min.

(2) The temperature dependence of viscosity was measured with a rotation viscometer. Employing the measured values, a new fluid lubrication model, which considers the temperature dependence of viscosity, was established. Using the model, the lubrication layer thickness was estimated as being approximately 50 μm.

(3) The heat transfer of the mold flux was also evaluated by using the developed lubrication model. The thermal resistance of the air gap and the solidified flux layer was successfully estimated by applying the model. As a result, the resistance of crystallized flux was larger than that of glassy flux.