Ferritic rolling of IF steels and the development of improved qualities

摘要

During the low temperature ferritic rolling, the requirements to achieve high r-value are: 1. To control the amount of solute carbon, 2. To perform the rolling schedule at a sufficiently low temperature in order to cumulate all deformations in the finishing mill, 3. To use very effective lubrication in all stands in order to avoid shear texture below the surface. At a laboratory scale, many experiments have allowed to define precisely the process windows, including the selection of the steel composition. 4. E.g., the correct balance of C, S and Ti contents in combination with an adequate low reheating temperature promotes the precipitation of the Ti_4C_2S_2 compound decreasing the soluble carbon during ferritic rolling and the subsequent recrystallisation. 5. The addition of Nb increases the non-recrystallisation temperature and consequently ensures a better straining control in the finishing mill.