Interstitial-free (IF) steels were rolled upto 98% of reduction in area at room temperature and even upto 97% at sub-zero temperatures of-50 to-90 C. Ultrafine-grained structure can be achieved with hardness double to that of coarse grained material by suitable flash annealing of deformed IF steel. Extent of refinement increases with lowering of rolling temperature and with increase in degree of deformation. At the initial stage of deformation, the microstructure contains bands. Their width decreases and dislocation density increases with amount of deformation. The band consists of cells/sub-grains. Cell sizes decrease with the decrease in rolling temperature as well as with the increase in amount of deformation. Below certain lower temperature ($\sim$-50 0 C), temperature has less pronounced effect on refinement. Flash annealing induces recrystallisation in cold rolled IF steel at 650 C but recrystallisation process could be advanced to 550 C due to higher defect density in cryorolled samples.