The mechanism of improving r-value of continuously annealed steel sheets by high temperature hot-coiling in Cu-bearing ultra low C interstitial-free (IF) steel has been investigated, by using the hot-bands heat-treated at different temperatures from 500 to 800°C in order to change the morphology of pre-precipitates in hot-bands. By the ODF analysis of recrystallization texture, it was clarified that the γ-fiber texture (<111>//ND) extremely developed by the heat-treatment at the temperature ranging from 720 to 760°C. TEM observations also revealed that the complex-precipitates composed of Ti-carbosulfide and Cu were observed only in the same range of heat-treating temperature. Improvement of r-value by high temperature hot-coiling is caused by the precipitation of Cu combined with coarse Ti-carbosulfides which avoids the detrimental influence of fine pre-precipitation of Cu in matrix.
