METHOD FOR DECARBONIZING MOLTEN STAINLESS STEEL

PURPOSE:To shorten time required for decarbonizing treatment by deciding oxygen blowing stopping timing and vacuum decarbonizing time from only a molten steel treating condition. CONSTITUTION:The decarbonization is executed by blowing oxygen into the molten steel from the side wall in a vessel under reduced pressure atmosphere. After stopping the oxygen blowing, by blowing inert gas from the side wall in the vessel under reduced pressure, vacuum decarbonization is executed. In the equation I, the decarbonizing oxygen efficiency is preset based on the relation between [Si]. Oxygen concn. increment during the decarbonization, is obtd. from difference between the oxygen concn. in the molten steel before the decarbonization and the oxygen concn. in equilibrium with the aimed [C] after the vacuum decarbonization to decide the oxygen blowing stopping timing. In the equation II, the oxygen concn. decrement after oxygen blowing is obtd. from difference between the oxygen concn. in the molten steel after oxygen blowing and the oxygen concn. in equilibrium with the aimed [C] after the decarbonization. The do/dt is found based on a decarbonizing speed dC/dt in correlation with (Si) before the treatment to decide the vacuum decarbonizing time (t). By this method, accuracy of the decarbonization can be improved.