In order to understand the air oxidization of molten steel during teeming, model experiments on the gas entrainment of pouring stream were carried out by using water, ethanol, glycerin aqueous solution and liquid tin.
The breakup length of pouring stream depends on the shape of nozzle, the pouring rate of liquid and the flow of liquid in the tank. In the present experimental range, the amplitude of disturbance at the nozzle exit ε₀ decreases with decreases of nozzle length and pouring rate as indicated by the following equation ;
In(a₀/ε₀) =44.3(l₀/ D₀)^-0.75 (Re) ^-0.1
where a₀ : radius of liquid stream at the nozzle exit, l₀ : nozzle length, D₀ : diameter of nozzle and Re : Reynolds number. The rates of gas entrainment by the pouring stream increase with increasing the height of teeming and the rate of teeming.
The rate of gas entrainment is represented by a model postulating that the pure cylindrical stream entrains no gas and that the gas entrainment occurs by the cavity produced by the collision between the bath surface and the stream surface protuberances. Consequently, taking the cavity radius Rc into account, the rates of gas entrainment are described for all kinds of liquid stream as follows ;
V _g/V_l= 0.02 {(Rc-a) / a₀}³
where V_g : gas entrainment rate, V₁ : volumetric flow rate of stream and a : radius of liquid stream at the teeming height z.