Cementite spheroidization during conventional soft annealing treatment, usually applied to medium carbon steels prior to cold forming, has been studied. Initial ferrite-pearlite microstructural features and conditioning of such microstructures by deformation assisted techniques allow a wide range of spheroidized microstructures and mechanical properties after annealing. The application of low deformations (8=0.3) at warm temperatures on undercooled austenite or pearlite results in a higher cementite spheroidization and ferrite grain size refinement, improving consequently cold formability. This can be achieved without a considerable increase in hardness which is interesting for extending cold forming tool life. The improvement of spheroidization kinetics is related to the activation of cementite lamellae breakup mechanisms and the enhancement of the solute diffusion through both grain (sub)boundaries and ferrite matrix. The austenite warm deformation induces ferrite and pearlite dynamic transformation. And if the deformation is applied on pearlite, the refinement is achieved by continuous recrystallization as the cementite spheroidization proceeds.
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