PROCESS FOR PRODUCING AN ULTRA-LOW-CARBON STEEL SLAB, STRIP OR SHEET

摘要

This invention relates to a process for producing ultra-low-carbon steel strip or sheet, said process comprising: - producing a vacuum-degassed steel melt in a steelmaking step comprising a ladle treatment comprising, by weight, o at most 0.003% carbon, o at most 0.004% nitrogen, o at most 0.20% phosphorus, o at most 0.020% sulphur, o and balance iron and inevitable impurities, - wherein a target oxygen content of the melt at the end of the ladle treatment of the melt is obtained by measuring the actual oxygen content of the melt followed by adding a suitable amount of aluminium in a suitable form to the melt to bind oxygen wherein the target oxygen activity or dissolved oxygen content of the melt at the end of the ladle treatment is at most 80 ppm; - casting the steel thus produced in a continuous casting process to form a slab or strip; - wherein said process provides a slab, strip or sheet of ultra-low-carbon steel comprising at most 0.002% of acid soluble aluminium and at most 0.004% silicon and a total oxygen content of at most 120 ppm.