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Recrystallization process during the annealing of a 0,04%C Al-killed steel

Abstract:

The recrystallization process of a commercial 0.04%C Al-killed steel, cold rolled up to 80% subjected to a annealing heat treatment at variable heating rates was evaluated in the present study. For this purpose, samples were isothermally annealed at various heating rates (12°C/h, 20°C/h, 40°C/h and 650°C/min) and then soaked at 700°C for 15 hours. The microstructural evolution of the samples followed by optical microscopy, scanning and transmission electron microscopy, showed that the recrystallization process took place between 600 and 650°C for the samples heated at low rates (12°C/h, 20°C/h and 40°C/h), and the grain structure developed was the so called "pancake" type. The grain size for these samples showed an insignificant growth during the holding stage at 700°C. On the other hand, with the samples heated at 650°C/min, the recrystallizaction occurred on reaching 700°C, the grain structure was more equiaxial and the grain size changed appreciably during the holding stage. The spheroidization process of cementite occurred in significant amounts during the holding stage at 700°C. The precipitation and coarsening of AIN particles were also evaluated during the holding stage at 700°C.