METHOD OF VACUUM DECARBURIZATION/REFINING OF MOLTEN STEEL AND APPARATUS THEREFOR

摘要

In a straight barrel type vacuum refining apparatus, use is made of a combination of: a decarburization method wherein the flow rate of oxygen fed into a vacuum tank and the flow rate of an inert gas fed into the vacuum tank are regulated and, at the same time, the flow rate of oxygen gas blown is reduced at a rate of 0.5 to 12.5 Nm<3>/h/t/min in a low carbon concentration region having a carbon concentration of not more than the critical carbon concentration; a refining method wherein, in an aluminum temperature elevation period, the atmosphere in the vacuum tank is regulated to a value of not more than -20 in terms of G value determined by the equation (1), and, in a decarburization refining period, decarburization is carried out while regulating the atmosphere in a high carbon concentration region having a carbon concentration of not less than the critical carbon concentration to a G value of -35 to -20; and regulation of slag, conditions for blowing of an inert gas from the low portion of a ladle in an oxygen blowing decarburization period/degassing period and a reduction period by addition of aluminum, or a vacuum refining apparatus provided with dust accumulation preventing means: <MATH> wherein <MATH> P < 760 wherein T represents a molten steel temperature, K, and P represents the degree of vacuum in the tank, Torr. <IMAGE>