Kinetics of Decarburization Reaction of Molten Steel with CO Bubble Evolution in Pressure Decreasing Stage

The dominant factors of the carbon removal reaction from a molten steel with an Ar injection stirring under the pressure decreasing stage have been studied using a vacuum tank degassing furnace containing 7 ton melt.1) The decarburization rate constant, kc', increased with the increase in the pressure decreasing rate and with the increase in an oxygen content.2) The vigorous CO bubble evolution in the molten steel was observed in the pressure decreasing stage. So, the CO bubble evolution rate constant, kCh and the super-saturation pressure, Pco*, for the CO bubble evolution were taken into consideration in a decarburization reaction model. The decarburization behaviors were simulated successfully by the reaction model.3) The value of kCh increased with the increase in the Ar injection flow rate, and the value of Pco* was estimated to be 22.525.0 mmHg.4) In the pressure decreasing stage, the decarburization reaction was divided into three types, namely, a) an evacuating control, b) a stirring control and c) a mixed control of evacuating and stirring. In order to increase the decarburization rate, it is essential to keep a high oxygen content, to evacuate fast and to supply enough stirring to a molten steel according to the evacuating rate.