Comparison of Ferrite Refinement Mechanisms by Different Processing Schedules in 08 and 20Mn Steels

The influence of deforming temperature on ferrite refinement was analyzed by comparing the microstructures obtained by deformation at above A_r3, in two-phase region of (α + γ) and at below A₁ in clean 08 and 20Mn steels. The results indicate that ferrite refinement through strain induced transformation by deformation at above A_r3 is more effective than that by deformation simply through ferrite dynamic recrystallization. The main problem of ferrite refinement by deformation at below A_r3 is the inhomogeneity of microstructure which is controlled by the orientations and sizes of ferrite grains and the distribution of second phases. Ferrite dynamic recrystallization after strain induced transformation can further effectively refine ferrite.