MODELING THE EVOLUTION OF MICROSTRUCTURE DURING HOT TORSION OF NIOBIUM MICROALLOYED STEELS

By considering the competition between recrystallization, precipitatio n, and interpass time during multi-pass deformation, a microstructural model is developed to simulate the microstructural evolution during m ulti-pass rolling based on the current isothermal equations for recrys tallization, grain growth, and precipitation, in which the condition ' 't0.05PS < t0.95RX and t0.05PS < interpass time'' is suggested to repl ace ''t0.05PS < t0.95RX'' especially at short interpass time in modell ing the T(nr) temperature for multi-pass deformation. The agreement be tween the austenite grain size obtained by hot torsion test and by cal culation is satisfactory using this microstructural model for multi-pa ss deformation.