Vacuum degassing apparatus and method for decarburizing molten steel using the same

摘要

PROBLEM TO BE SOLVED: To provide a decarbonization processing method capable of improving estimation accuracy of molten steel carbon concentration, and completing molten steel decarbonization processing at proper timing based on the estimation value of the molten steel carbon concentration.SOLUTION: Immersion pipes 3a, 3b of a vacuum tank 3 are immersed in molten steel 16 of a pod 2, and the molten steel is recycled between the pod and the vacuum tank via the immersion pipes under reduced pressure which is lower than air pressure for performing decarbonization processing of the molten steel. At the time, a recycle amount of the molten steel between the pod and the vacuum tank is calculated with consideration of inner diameter change of the immersion pipes according to the recycling of the molten steel. The calculated recycle amount of the molten steel, a material balance expression related to carbon in the molten steel in the decarbonization processing, decarbonization speed of the molten steel, and an in-tank reaction model expression indicating decarbonization reaction of the molten steel in the vacuum tank, are used for estimating the carbon concentration in the molten steel. When the estimated carbon concentration in the molten steel reaches the target value, the decarbonization processing of the molten steel is finished.