MANUFACTURE OF SUPER-LOW CARBON STEEL

PROBLEM TO BE SOLVED: To provide a method for manufacturing a super-low carbon steel having a carbon concentration close to the target value. SOLUTION: An arithmetic unit 15 in which an analysis value of an exhaust gas analyzer 9 and a measured value of an exhaust gas flow meter 10 are inputted operates the estimated value of the carbon concentration in a molten steel from these values, considering the delay time of each measured value. The sampling of the molten steel is performed by a molten steel sampling device 11, and the carbon content in the molten steel is analyzed by a carbon concentration in molten steel analyzer 13. The arithmetic unit 15 corrects the estimated value of the carbon concentration in the molten steel considering the time when the molten steel sampling device 11 performs the sampling. The arithmetic unit 15 corrects the estimated value of the carbon concentration of the molten steel, and then, determines the coefficients of the regression formula from these corrected values by substituting the carbon concentration in the molten steel in the regression formula expressed by the time function. The estimated carbon concentration in the molten steel considering the delay time due to the analysis is calculated from the obtained regression formula, and the decarburizing is completed when the carbon concentration reaches the final target.