Steel with ultra-low carbon content and methods for controlling oxide discharges into ultra-low carbon steel

摘要

A method for controlling oxide discharges into steels with ultra-low carbon content. The process includes the following steps: 1) the converter melting process by ensuring that the molten steel meets the following conditions: [O] = 450 ~600 ppm, and [C] = 0,01-0,05%,when the blowing is over; during the steel stitch, the thickness of the slag is not more than 50 mm, 2,0-5,0 kg lime per tonne of steel are added at the early stage of the steel stitch and 0,5-2 kg of AI modifiers per tonne of steel are added at the final stage of the steel stitch to modify and de-oxidise the slag, so that the slag fulfils the following condition: [(weight-%Cao) + (weight-%MgO)]/(weight-%Al2O3) = 1,4~1,9 and the oxidised components fulfil the following condition: (weight-%FeO) + (weight-%MgO)*8; and 2) vacuum cooling treatment in an RH furnace; when vacuum cooling treatment is completed,AI is added to de-oxidise the molten steel with subsequent alloy, the duration of the circulation of the molten steel being more than six min, the rare metal CE is added and the circulation of the molten steel is carried out 2-10 min, and the vacuum treatment is completed. The verification procedure provided for in the disclosure reduces the damage caused by the steel inclusions remaining, improves the surface quality of a cold rolled finished product and also improves the defect rate of the cold rolled finished product.