A METHOD FOR MANUFACTURING HIGH GRADE BILLETS CONTAINING LOW CARBON AND HAVING A BIG CROSS SECTION

摘要

A method for manufacturing a soft steel billet having a large cross section is provided to prevent nozzle from closing or surface quality defect like a pinhole by steadily controlling C and Si in a refining process of steel including C and Si. A method for manufacturing a soft steel billet having a large cross section comprises: a step(S10) blowing molten steel in a converter; a step(S20) controlling the carbon content of the blown molten steel over 04 weight%; a step(S30) degasifying the molten steel; and a step(S40) of refining the carbon content of the degasified molten steel below 0.07 weight% and the oxygen content of the degasified molten steel below 0.007 weight%. The step of blowing the molten steel in the converter comprises a step of blowing the carbon content of the molten steel below 0.07 weight%.