Mechanism of Gas Evolution of Rimmed Steel

Abstract

During solidification of rimmed steel, solutes are rejected at solid-liquid interface, causing deoxidation reactions to form CO, MnO, FeO and SiO₂. Mechanism of the reactions is expressed by a mathematical formula, which could be applied to the C and Mn segregations in a rim zone and compositions of nonmetallic inclusions respectively.
The amount of gas generated during solidification and that of oxygen absorbed from air are calculated by mass balance of solutes in several ingots. The amount of oxygen absorbtion reaches to 0.02kg/t·min, which gives a strong effect on CO generation. Therefore gas generation from a capped steel is far less than that of a rimmed steel. The gas generation is considered to be caused by two different sources (the one from the inside of diffusion boundary layer and the other from the outside of it), and the ratio of the former to the latter would be 1: 2-2.
In a more accurate study on a mechanism of bubble growth during the solidification of rimmed steel, much more attention should be paid to the gas generation from the outside of the boundary layer rather than from the inside.