Effect of Interpass Time and Cooling Rate on Apparent Activation Energy for Hot Working and Critical Recrystallization Temperature of Nb-microalloyed Steel

摘要

Two-stage In [sinh (ασ)]vs. 1/T relations indicative of double Q_(HW) behavior, are obtained from anisothermal multipass flow curves generated by testing Nb/Ti microalloyed steel in torsion (in the range 1250-800 deg C), except for the case of the high cooling rate-short interpass time tests, which gave rise to single-stage plots, indicative single Q_(HW) behavior. Above the T_(nr), the Q~U_(HW)(apparent activation energy for hot working corresponding to the upper temperature range) is little affected by test variables (interpass time and cooling rate) and type of deformation (isothermal continuous and anisothermal multipass deformation give virtually equivalent Q~U_(HW), values above the T_(nr). However, below the T_(nr), the Q~L_(HW), corresponding to the lower temperature range, becomes sensitive to test variables, and may show considerable deviation from Q~L_(HW) obtained in continuous tests.