Patent ID: 7247211
Filing Date: 2007-07-24
Classification: C21C,C22C

Abstract:
1. A method of manufacturing an ultra-low carbon steel sheet in which molten steel having a chemical composition including, in mass percent, C: at most 0.010%, Si: at most 0.5%, Mn: at most 1.5%, P: at most 0.12%, S: at most 0.030%, Al: at most 0.080%, N: at most 0.0080%, Ti: 0.002%˜0.10%, Nb: at most 0.05%, B: 0-0.0050%, V: 0-0.05%, and Ca: 0-0.0050% is subjected to refining in a converter, secondary refining after refining in the converter, continuous casting, hot rolling, and then coiling, wherein at the time of the secondary refining, the molten steel is tapped into a refining vessel, a vacuum immersion pipe having an interior that can be adjusted to a negative pressure is immersed in the molten steel in the refining vessel, and a stirring gas is blown into the molten steel wherein the amount of FeO+MnO in a slag in the refining vessel is at most 15 mass %, and the throughput at the time of casting is at most 5 tons per minute.