processo para produzir placa, tira ou chapa de aço de ultrabaixa carbono

摘要

Process producing ultra low carbon steel strip or sheet including producing a vacuum-degassed steel melt in a steelmaking step including a ladle treatment containing, by weight, at most 0.008% carbon; at most 0.008% nitrogen; at most 0.20% phosphorus; at most 0.020% sulphur; balance iron and inevitable impurities. Melt target oxygen content at end of ladle treatment of the melt is obtained by measuring the melt actual oxygen content followed by adding a suitable amount of aluminium in a suitable form to the melt to bind oxygen. Melt target oxygen content at the end of the ladle treatment is at most 80 ppm. Casting steel thus produced in a continuous casting process to form slab or strip. The process provides slab, strip or sheet of ultra low carbon steel containing at most 0.002% of acid soluble aluminium and at most 0.003% silicon and total oxygen content at most 100 ppm.