1988 Volume 74 Issue 2 Pages 294-301
The fundamental study has been made on the rate of nitrogen removal from molten steel to gas phase with reductive gas injection and flushing. A fluid flow on the surface of molten, steel is observed in hydrogen gas flushing. Hydrogen gas increases the rate of nitrogen removal. The apparent rate constant approaches to the chemical reaction rate constant. It is considered that the fluid flow on the surface of molten steel caused by Marangoni convection increases the liquid mass transfer, and thus, the nitrogen removal rate.
When CO is used as a reductive gas, partial pressure of CO, Pco, must be kept in a suitable range for each composition of molten steel, because silicon in molten steel is oxidized to silica by CO gas, and this oxide decreases the liquid-gas interface area for nitrogen removal from molten steel. The suitable CO partial pressure can be estimated by equilibrium calculation. The effects of gas flow rate on nitrogen removal with different gaseous materials in RH degassing equipment can be estimated from the results of the fundamental study.
