Cold model study of slag entrainment into liquid steel in continuous slab caster

摘要

Slag entrainment in the mould is a common phenomenon during continuous casting of slabs, at high casting speed. However, very few cold model studies have been made in this direction. Sobolewski and Hurtuk1 used cork pieces in their water model to simulate slag entrainment. Tanaka et al~2. made water modelling studies using oils as the second phase. They studied the vortex depth formed at the oil/water interface. To simulate the slag phase over the liquid steel, the following equations must be satisfied where mu_i and rho_i are, respectively, the viscosity and density of the i th phase and subscripts 1 and 2 refer to the liquids used in the model to simulate the metal and slag phases, respectively. The viscosity and density of the slag phase depend on the composition of the casting powder and its temperature. At the slag/metal interface its temperature is expected to be close to that of liquid steel, but its top face which is exposed to the atmosphere will be at a much lower temperature. Besides, the temperature of the slag/metal interface also is not constant. Therefore, equation (1) can not be exactly satisfied by the cold model. However, if the average temperature of the flux is assumed to be 1300 deg C, the ratio of the viscosities of slag to metal is expected to lie between 15 and 120. The density ratio of slag to metal is only about 0.375. Unfortunately, no such liquid is available which satisfies the above criteria at room temperature. For this reason, studies were carried out to understand the two phase behaviour (i.e. the slag and liquid steel phase) using oils and a commercial grade zinc chloride solution in a wide range of viscosity and density.