A mathematical model for degassing process by rising bubbles is developed on the basis of material and heat balances in gas phase and material balance in liquid phase. From this model, the volume of inert gas which is necessary to degass hydrogen, oxygen and carbon in molten steel down to the required concentrations can be estimated.
The effects of the initial diameter of inert gas bubble, the depth of blowing point of inert gas, the pressure of gas at the surface of molten steel, the residence time of rising bubble and the concentration ratio of carbon to oxygen on the degassing rate and on the concentrations of CO and H₂ in rising bubble were determined by numerical calculations of the model with the aid of digital computer.