To study the kinetics of decarbonization in molten steel precisely, a high-frequency induction furnace in which atmosphere could be controlled during experiments was made in a laboratory, and the effect of carbon in molten steel and gaseous oxygen on the rate of decarbonization in molten steel was studied. In this experiments, 1.4kg of electrolytic iron was melted in a pure MgO crucible under flow of 100% argon gas, and after adding appropriate amount of carbon to molten iron, the concentration of gaseous oxygen in flowing argon gas was appropriately controlled constantly at 0, 2, 5, 6, 8, 10, 13, 16 and 20%. Then the rate of decarbonization between 0-0.80% C was measured by sampling from molten steel every 15 minutes at 1600°C under flow of gas, oxygen concentration of which was constant. The following results were obtained.
(1) The constant rate of decarbonization was recognized, also when atmosphere was 100% argon. This reaction of decarbonization caused by reaction of the C in molten steel with the crucible wall (MgO).
(2) C>0.15%; when the concentration of gaseous oxygen was constant, the rate of decarbonization (this rate was a difference between the total rate of decarbonization which was measured and the rate of decarbonization by the crucible wall (MgO). The following rates were the same.) was constant in spite of the concentration of carbon in molten steel.
(3) C<0.15%; the rate of decarbonizaton dropped rapidely and apProached zero. This tendency was similar to the case of open hearth furnaces.(4) When the concentration of gaseous oxygen increased from 0% to 10%, the rate of decarbonization increased gradually. But since it was more than 10%, the rate became approximately constant, and the oxide-film was recognized on free surface of molten steel when concentration of C became under 0.15%.
(5) In this experiments, C-O relation was under the Vacher & Hamilton's curve, and concentration of O increased rapidly when the concentration of C became under 0.15%.