Hot Deformation and Recrystallization of 3 % Silicon Steel: Part 3: Effect of Hot Deformation Variables on Static Recrystallization

Abstract

The static recrystallization kinetics and the recrystallized grain size of 3% Si steel after hot rolling at temperatures of 900 to 1100°C to equivalent strains of 0.25 to 1.24 applied in a single pass or by two pass rolling have been investigated. When the annealing temperature was changed for a constant rolling temperature, an apparent activation energy of 230 kJ/mol, and a small increase in recrystallized grain size with increase in annealing temperature were found. Rolling at different temperatures had a surprisingly small effect. The growth rate of recrystallizing regions showed a rapid decrease with annealing time, being inversely proportional to time initially, but decreasing more rapidly at longer times. For conditions leading to long recrstallization times, growth rate fell to zero, resulting in plateaux in fraction recrystallized. Increase in equivalent strain accelerated recrystallization, but the effect after two pass rolling is complicated by a change in rolling direction between the passes. The majority of results can be interpreted by a simple model based on site saturated nucleation and negligible coarsening of recrystallized grains, but smaller strains in single pass rolling, or in the second pass of two pass rolling give large discrepancies with the model.