| 摘要 |
PURPOSE:To increase considerably the r-value of a steel sheet and to improve the drawability by annealing the sheet having a regulated C content by heating to a temp. between the Ac1 and Ac3 transformation points and slow cooling at a cooling rate corresponding to the C content. CONSTITUTION:A cold or hot rolled steel sheet contg. <=0.15wt% C is annealed by heating or soaking to a temp. between the Ac1 and Ac3 transformation points and controlled cooling to 600 deg.C under conditions satisfying an equation C.V<=0.2 [where C is the carbon content (wt%) of the steel sheet, and V is the average cooling rate ( deg.C/sec)]. The r-value of the sheet is considerably increased, and superior drawability can be obtd. |
