| 摘要 |
PURPOSE:To produce the titled steel sheet having high Lankford value with a simple process in the production of steel sheet including a continuous annealing stage by controlling the annealing stage by specifying the relation between the carbon content of steel sheet and the rate of transformation to austenite. CONSTITUTION:An annealing stage is controlld so as to satisfy the formula, wherein Xc is wt% of carbon content of the steel sheet and Ygamma(%) is the rate of max. transformation rate of austenite when the steel sheet is heated to above the Ac1 transformation point and then cooled to Ar1 transformation point. By the formula, preferred relation between Xc(%) and Lankford value is obtd. Accordingly, in the continuous annealing of a steel sheet having a constant value for Xc(%), the control is to be performed so as to let the value Yalpha to satisfy the formula. By this method, the control is performed more easily because the variable to be controlled is only Yalpha, therefore, the control is executed easily and accuracy of the control is high. |
