Kinetics of Decarbonization in Molten Steel

Takehiko FUJII
1959 Tetsu-to-Hagané Abstracts  
Synopsis: To make the mechanism of decarbonization in molten steel clear, firstly many data of the refining of the 100 t basic open hearth furnace were examined, and secondly a high-frequency induction furnace was constructed in the laboratory, and many experiments were made under the constant conditions by using this furnace. The results of these experiments are as follows. As the absolute rate of the chemical reaction, Q+Q--'> CO i is extremely high at high temperature, the rate-determined
more » ... rate-determined step of Q-Q reaction in the open hearth furnace is the moving velocity of reaction substances and products through a boundary layer between slag and molten steel, and between gas phase and molten steel. In the high-frequency induction furnace where slag does not exist, the rate-determined step is the moving velocity of oxygen through the boundary layer at the · free surface of molten steel. This boundary layer is composed of Fe-a reaction phase right above the free surface and the thin layer just under the free surface where carbon does not dissolve. Then, if the arriving velocity of carbon in molten steel is higher than that of oxygen, the rate is determined by the arriving velocity of oxygen in gas phase, and this range is Q> 0.1596. On the contrary, if the arriving velocity of carbon is lower than that of oxygen, the rate is determined by the arriving velocity of carbon in molten steel, and this range is Q <0.15% . In an open hearth furnace where slag exists, the rate-determined step is the moving velocity of oxygen through the boundary layer between slag and molten steel, and the velocity of diffusion and escape of CO through the boundary layer between molten steel and gas phase of CO-bubbles or crevices of the hearth. And in the range of Q>0.30 %, as the arriving velocity of carbon in molten steel is higher than that of oxygen, the rate is determined by the arriving velocity of oxygen; and in the range of Q<0.3096 , as the arriving velocity of carbon is lower, the rate is determined by the arriving velocity of carbon, and the rate is decreased with decrease of carbon concentration. The difference of the limit values of this carbon in the open hearth furnace and in the high-frequency induction furnace is due to the difference of the capacity and the condition of stirring in both furnaces. Finally, this thesis is a concise abstract of five main theses.
doi:10.2355/isijabstracts.9.0_3 fatcat:ncvvu3af4be4zbkp26yz5psrvq