Ultra-fine grain size control and mixed grains elimination in industrial multi-pass rolling processing

Refinement of grain size is the most effective approach to obtain high toughness especially at low temperature with high strength level. Ultra-fine grain size can be achieved by dynamic recrystallization at large Z condition, by imparting large deformation at low temperature. Large Z condition is associated with a large critical strain for dynamic recrystallization. Large strain can be accumulated pass by pass in industrial multi-pass rolling processing to overcome large critical strain for dynamic recrystallization through optimization of composition and rolling schedule. The static recrystallization during passes should be suppressed completely in order to eliminate mixed grain size.