| 摘要 |
PURPOSE:To develop a lance having excellent treating power by using specifically constructed inside pipe and outside pipe to constitute the lance to be used for preliminary refining of a molten iron, mixing oxygen and treating agent in a nozzle part and blowing the mixture into the molten iron. CONSTITUTION:The molten iron is subjected to preliminary refining such as desiliconization, dephosphorization and desulfurization prior to refining of the molten iron to a steel. Powder of Na2CO3, CaO, etc., as the treating agent for preliminary refining and gaseous O2 for oxidizing impurities are blown by a lance into the molten iron. The lance to be used in this case is constituted of a double pipe system in which the inside pipe 4 is freely attachably and detachably inserted into the outside pipe 3 coated with refractories 2. A right- angled conduit part 5 and a convergent type nozzle 6 are formed to the top end of the outside pipe 3 and the top end 4A of the inside pipe 4 is bent toward the nozzle 6 and is provided in the part inner than the outlet of the outside pipe 3 in such a manner that the center lines 6C coincide with each other. The gaseous O2 is ejected from the outside pipe 3 and the treating agent 7 for preliminary refining from the inside pipe 4 into the molten iron.
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