Interaction between Recrystallization and Precipitation during Multipass Rolling in a Low Carbon Niobium Microalloyed Steel.

Abstract

The interaction between recrystallization and precipitation processes during multipass deformation has been analysed in terms of the non recrystallization temperature ( Tnr). Multipass torsion tests performed at continuous cooling conditions have been used for thermomechanical simulation. The effect of the passstrain and the initial austenite microstructure on the Tnr value have been investigated. Conventionally reheated austenite ( Tsoak=1200–1250°C) and as-cast austenite, the latter simulated in the laboratory by reheating at very high temperatures (Tsoak=1400°C), have been considered. It was observed that at low pass-strains the retardation on recrystallization was mainly due to solute drag effects, while increasing the strain, precipitation induced by deformation was allowed to occur during the interpass interval leading to a drastic reduction of the softening reached between passes at temperatures below the Tnr. The increment of the reheating temperature led to higher Tnr values, being this effect related to higher austenite supersaturation levels prior to deformation.