Abstract
The effects of titanium, manganese and boron contents are studied on r-values and tensile properties of very low carbon sheet steel with extra deep drawability, for the purpose of producing cold-rolled sheet steel by a room-temperature coiling process after hot-rolling. The mean r-value (r) of the sheet produced by a process skipping coiling treatment after hot-rolling is better than that produced by a conventional coiling process at 700°C, if the soluble titanium/carbon atomic ratio is over 1.5 and the manganese content is less than 0.15%. This is probably due to the enhanced precipitation of Ti (C, N) during hot-rolling and cooling and the suppression of grain growth in hot-rolled sheets. The boron addition deteriorates the r-values of extra-low carbon titanium-killed sheet steels produced by both the conventional coiling and room-temperature coiling processes.
