METHOD FOR MELTING AND MANUFACTURING TITANIUM-ADDED ULTRA-LOW CARBON STEEL AND METHOD FOR PRODUCING TITANIUM-ADDED ULTRA-LOW CARBON STEEL CAST SLAB

摘要

PROBLEM TO BE SOLVED: To melt and manufacture a Ti-added ultra-low carbon steel with which a nozzle-clogging in continuous casting can be prevented and a cold-rolled steel sheet excellent in the surface characteristic and the internal quality can be obtained.;SOLUTION: In a vacuum-degassing facility, after decarbonizing a molten steel, the deoxidized molten steel satisfying [%Al]≤[%Ti]/10 is produced by adding Ti-containing alloy and deoxidizing, and the inclusion composition in the molten steel is adjusted to ≤90% Ti-oxide, 5-50% CaO and ≤70% Al₂O₃ by adding an alloy for inclusion adjusting composition containing Ca into the molten steel, and the concentrations in the ladle slag after deoxidizing is made to be ≤10 mass% T.Fe+MnO, ≥1 of (%CaO)/(SiO₂), ≥1 mass% TiO₂ and 10-50 mass% Al₂O₃. The nozzle-clogging caused by the inclusion can be prevented and the Ti-added ultra-low carbon steel, with which the cold-rolled steel sheet excellent in the surface characteristic and the internal quality can be obtained, can be melted and manufactured by optimizing the inclusion composition in the molten steel and reducing the inclusion quantity.;COPYRIGHT: (C)2010,JPO&INPIT