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川崎製鉄技報
KAWASAKI STEEL GIHO
Vol.25 (1993) No.4
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RH真空脱ガス装置における脱炭反応の解析と極低炭素鋼製造
Analysis of decarburization Reaction and Its Application to Ultra-low Carbon Steel Production in RH Degasser

加藤 嘉英(Yoshiei Kato) 桐原  理(Tadasu Kirihara) 藤井 徹也(Tetsuya Fujii)
要旨 :
RHの脱炭反応特性におよぼす溶鋼流道および反応サイトの影響を反応工学的な解析と実験で明らかにし、迅速脱炭に必要な装置条件を提示した。処理中の取鍋内炭素濃度の不均一性は最大約2倍しかなく、脱炭を阻害するデッドゾーンはRH内に存在しない。RHの反応サイトに関して、耐火物−溶鋼界面の脱炭反応への寄与は3%以下と小さく、極低炭素濃度域では浴表面の寄与が、それ以外では溶鋼内部の寄与が最も大きい。浸漬管径を0.6→1.0m、下部槽断面積を3.5→5.1m2としたRHで脱炭速度が大幅に増加し、到達炭素濃度値も6〜12ppmを安定して得た。目標到達炭素濃度を得るための一般的なRH装置条件の決定方法を新たに示した。
Synopsis :
Theoretical and experimental studies were carried out to quantitatively understand the effects of the fluid flow, reaction sites and geometry of the vacuum vessel on decarburization properties of the RH degasser. Distribution of carbon concentration in the ladle was calculated throughout the treatment. Its maximum value found near the bottom of the ladle was two times lager than the minimum one. This difference was proved to have no effect on the decarburization rate. The ratio of the decarburization rate at the bath suface to the overall one in RH was the largest in the ultra-low carbon content region, whereas that at the molten steel-refractory interface was the smallest. The maximum decarburization rate and minimum final carbon content between 6 and 12 ppm were attained with the largest vacuum vessel (cross-sectional area, 5.1m2 ; inner diameter of snorkel, 1.0m). On the basis of the theoretical and experimental analyses, the procedure for determining the geometry of the RH vacuum vessel required was established to obtain specified aimed carbon content.
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