Decarburization of pretreated hot metal with less slag was studied by use of a 10 t ladle type travelling furnace based on a new idea. The characteristics of refining and the mechanism of post combustion of off gas were discussed.
(1) In spite of deep bath (L0/D= 1.0) in the furnace, molten steel was not overoxidized in the case that the flow rate of argon blown from the bottom was more than 0.05 Nm3/min·t with super soft oxygen top blowing (L≅100 mm).
(2) In this method, the post combustion ratio (CO2/(CO+CO2)) was very high, so the high temperature rising, almost 200°C/%C, was obtained.This decarburization furnace had large flexibility for heat balance.
(3) On post combustion, the parameter K (=(ΣiSi+αΣjSj')×3600/(FO2+ FO2')) was proposed and the mechanism could be explained by this parameter K on this ladle type furnace and the conventional top and bottom blowing converter.
