METHOD FOR CONTROLLING CONTENT OF PHOSPHORUS IN MOLTEN STEEL

摘要

PURPOSE:To estimate the content of phosphorus at an end point with high accuracy and control said content in accordance with the estimated content by proposing the mathematical equations that make a dephosphorizing speed and the actually measured contents of phosphorus and carbon in steel correspondent and measuring the content of phosphorus and carbon in the steel and the temp. of the molten metal at the end period of blowing directly with a sub-line. CONSTITUTION:In the case of estimating the content of phosphorus in molten steel in the ending stage of blowing, first the temp. TS of the molten steel, the content Cs of C, and the content Ps of P are measured by using a sub-lance in a few minutes before the end of the blowing. These measured values as well as the target temp. and target content of C in the ending stage of blowing are given to the equations and the content of P in the molten steel in the ending stage of the blowing is estimated. In this case, a term for correcting time serial fluctuations in accordance with the actual records of the past ten-odd charges is added as a feedback term on the right side of the equations. Since the amt. W2CAO of lime is not usually charged, said amt. is made zero. Further, the amt. W2FEO of iron ore is determined separtely in accordance with heating models. The estimating accuracy of the content of P in the ending stage of blowing by said method is extremely high and the estimating accuracy as high as 97% in a + or -0.005% range is obtained.