METHOD FOR CONTROLLING END POINT CONCENTRATION OF NITROGEN IN TOP AND BOTTOM BLOWN CONVERTER

摘要

PURPOSE:To control exactly the content of N2 in a molten steel to a target value by calculating the gaseous N2 to be blown from the target content of N2 and the concn. of N2 prior to blowing of the gaseous N2 in accordance with the actual amt. of the gaseous N2 to be blown into the molten steel and the pick up amt. of the molten steel and blowing a required amt. of the gaseous N2 into the molten steel from a nozzle. CONSTITUTION:The content of N2 Nc in the molten iron which is the raw material is estimated from the concn. of Ti having a correlation therewith and the molten iron is charged into a converter where the molten iron is refined to a steel by oxygen top blown refining. The concn. DELTA(N) of N to pickup the difference between the target concn. (N)0 and (N)c of N2 in the steel of the final product is calculated. The weight R of the N2 to be picked up into the molten steel is calculated from such concn. of N and the amt. of the molten steel. The amt. of the gaseous N2 S to be blown into the molten steel upon lapse of the prescribed time t0 from the start of converter blowing is determined from the yield of the N2 blown. The time (t) for blowing N2 is determined from the amt. of the gaseous N2 passing through a lance for blowing gaseous N2 and the gaseous N2 is blown to the molten iron for the determined time, by which the molten steel having the intended concn. of N2 is produced.