Maps of structural states for the optimization of hot-working regimes of steels

The structural-state maps (SSM) drawn in the "temperature-strain rate" coor dinates are proposed to outline the temperature-rate fields of the dynamic polygonization and recrystallization that occur upon hot working of steels and to quantitatively estimate the steel structure. The SSMs are constructe d for a certain degree of deformation and a certain initial grain size. The principal quantitative characteristics are the isolines of equal fractions of dynamically recrystallized volumes, equal sizes of dynamically recrysta llized grains, and equal subgrain sizes. The dynamic recrystallization temp erature increases with decreasing rate and degree of steady-stage deformati on, increasing initial grain size, increasing stacking-fault energy, decrea sing carbon content, and increasing degree of alloying. The SSMs were used to develop the thermomechanical treatment regimes providing the formation o f polygonized structure in low-carbon and medium-carbon tool steels; austen itic, ferritic, and austenitic-ferritic corrosion-resistant steels; acid el ectrical ferritic silicon steels. The polygonized structure of the high-tem perature phase not only increases the strength of these materials in the fi nal structural state, hut also improves the processing and service characte ristics of most steels.