This study aims at investigating the microstructural modification in hot rolled formable steels in order to monitor the amount and shape of grain boundary carbides. The steels were deoxidized with aluminum and aluminum-silicon addition, hot rolled, and coiled at the temperature range between 600℃ and 650℃. Detailed microstructural analyses of the hot rolled steels showed that film- or bulk-type grain boundary carbides, together with banded pearlite structures, were observed and that the morphology of these carbides were varied with processing variables, e.g., killing procedure and coiling temperature. In the Al killed steels, the carbide shape had a trend of changing from film-type to bulk-type, which might be beneficial to the improvement of elongation and consequently deep drawability. In addition, as the coiling temperature was increased, the amount of band structure and bulk-type carbides tended to increase. These findings suggest that deep drawability can be improved by modifying the carbide morphology in the microstructures.