| 摘要 |
PURPOSE:To exactly control the carbon content of a molten steel in a vacuum refining furnace by quantitatively determining the carbon contents of the molten steel in a vacuum oxygen decarburization period and vacuum degassing period as a function of operating conditions and determining the adequate end of the vacuum oxygen decarburization and vacuum degassing. CONSTITUTION:Oxygen blowing is stopped (vacuum oxygen decarburization period) and the decarburization reaction is progressed by further increasing the degree of vacuum (vacuum degassing period) and stirring the molten steel with the Ar alone when the Ar is supplied to the vacuum refining furnace, then the evacuation is started and the oxygen blowing is started and when the decarburization progresses by a prescribed rate. The carbon contents of the molten steel in the respective stages of the vacuum oxygen decarburization period and the vacuum degassing period are preliminarily quantitatively determined as the function of the operating conditions such as the molten steel temp. of the molten steel components Cr, Ni, and Co prior to the refining treatment and the flow rate of the Ar, etc., during the treatment in the above-mentioned operation. The required oxygen quantity of the vacuum oxygen decarburization and the required treatment time of the vacuum degassing period are calculated by the quantitatively determined relation in such a manner that the carbon content at the end of the refining attains the target value. The carbon content of the molten steel is controlled in accordance with the respective calculated value.
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