EFFECT OF LARGE PARTICLES AND FINE PRECIPITATES ON RECRYSTALLIZATION AND TRANSFORMATION BEHAVIOR OF TI TREATED LOW-CARBON TIO STEEL

Austenite recrystallization and ferrite transformation behaviour of a Ti treated low carbon TiO steel was studied by uniaxial hot compressio n in a temperature range of 780 to 1300 degrees C. The results have be en compared to that of a conventional TiN steel. It was found that lar ge oxide particles present in TiO steel have shown ability to stimulat e recrystallization nucleation and transformation during deformation b ut failed to accelerate recrystallization of bulk material because of an insufficient volume fraction of these large particles in the steel. The influence of Ti:N ratio in TiO steel is critical to TiN precipita tion behaviour which affects microstructural development during thermo mechanical processing. TiN precipitates in TiO steel are coarser in co mparison to conventional Ti microalloyed steel thus reducing grain bou ndary pinning effects. It was also found that recrystallization of fer rite in cold worked TiO and TiN steels was not affected significantly by large particles and fine precipitates but controlled by pearlite si ze and distribution.