METHOD FOR CONTROLLING DECARBURIZATION TO EXTRA-LOW CARBON STEEL

摘要

PROBLEM TO BE SOLVED: To control C concn. at the end point to a target value and to obtain an extra-low carbon steel by obtaining a decarburizing end point deciding timing from a relation between CO concn. and time at each reached C concn. when a coefficient of decarburizing rate varies in a vacuum refining and adjusting the decarburizing rate. ;SOLUTION: At the time of melting the extra-low carbon steel having 40-150ppm C concn. with the vacuum refining, the relation between the CO concn. and the time (t) at each reached C concn. when the coefficient Kc (1/min) of the decarburizing rate varies, is calculated by simultaneously satisfying the equations I, II, III and IV. The decarburizing end point deciding timing is decided based on this relation. At the same time, the treating vacuum degree is adjusted based on the relation between the reached carbon concn. and the reached vacuum degree pre-obtd. at each reached carbon concn. to adjust the decarburizing rate. The (x) in the equation III shows the treated molten steel quantity (ton) and the Y in the equation IV shows the quantity (kg/hr) of gas except CO introduced into the vacuum system per one hr. By this method, the decarburizing control into the range of 40-150ppm concn. is accurately and efficiently executed.;COPYRIGHT: (C)1998,JPO