PURPOSE: To make it possible to manufacture clean steel of very low contents of phosphorus and sulfur surely, by refining molten steel with a combination of an AOD furnace with a converter or with an electric furnace.
CONSTITUTION: A low phosphorus steel contg. ≤0.005% P is melted and ingot cast using a converter or an electric furnace, and at least 50W60% the dephosphorizing slag is removed. The steel is subjected to secondary blowing thereby removing the slag nearly completely at tapping, then it is charged to an AOD furnace, where the molten steel is further subjected to refining such as decarburization, desulfurization, and deoxidation etc. Then the furnace is inclined so as to remove about 80% molten slag in the furnace, and the blowing is continued. The composition is adjusted by addition with alloy steel, and the slag is removed nearly completely. Finally, the molten steel is stirred sufficiently by blowing inert gas such as Ar etc., hereby very low sulfur steel contg. ≤0.001% S is obtained by said refining.
NASHIKAZU HAJIME
KISHIDA TATSU
IWAMI NORIMOTO
ADACHI TAKAHIKO
| JPH0995828A | 1997-04-08 |