抄録
To make clear the ferrite grain refinement behavior of low carbon steels through accelerated cooling after controlled rolling, study was focussed on the transformation behavior and the ferrite nucleation behavior in continuous and isothermal transformation. Combination of strain imposed in unrecrystallization region and increase in supercooling by accelerated cooling caused remarkable increase of intragranular nucleation which resulted in ferrite grain refinement. Even small strain which could not produce deformation band and deformed annealing twin caused intragranular ferrite nucleation. The number of intragranular nuclei decreased as recovery and recrystallization progressed before transformation. It was suggested that intragranular nucleation sites were dislocation, cell structure, sub-grain boundary and inclusions which could not act as nucleation site under condition of controlled rolling. It was concluded that accelerated cooling brought about ferrite grain refinement by promotion of intragranular nucleation on the proper sites and suppression of grain growth.
