HIGH SPEED DECARBURIZATION METHOD FOR HIGH PURITY STAINLESS STEEL

摘要

The present invention relates to a new, high-speed decarburization method simultaneously using lower side blowing and upper top blowing to additionally inject a mixed gas of gaseous oxygen and argon or nitrogen by actively using a lance for top blowing rather than relying only on lower side blowing injection unlike conventional blowing operations for decarburizing high-purity stainless steels to have carbon concentration less than 0.03% in a refining furnace. In order to perform decarburization of austenitic stainless steels having target carbon concentration less than 0.03% using an AOD refining furnace, the present invention provides a high-speed decarburization method for austenitic stainless steels to perform decarburization by injecting a lower side-blown mixed gas containing oxygen into a molten steel using a tuyere in the lower part of the AOD refining furnace; injecting oxygen into the upper part of the refining furnace at this time through a top-blown lance in an early stage of decarburization; and injecting top-blown mixed gas additionally containing oxygen simultaneously with the lower side-blown mixed gas until completion of a decarburization process. According to the present invention, time required for decarburization operation for molten steels in a refining furnace can be shortened by increasing decarburization speeds of molten steels compared with time required for conventional operation through increasing a total amount of oxygen injected in a molten steel for a unit time based on introduction of a combined blowing method of side blowing and top blowing in active utilization of a top-blown lance in the upper part of AOD. [Reference numerals] (AA) Time for 2-5 steps; (BB) Comparative example; (CC) Example