Microstructural and mechanical properties evolution during an isothermal annealing of a 0.04% C al-killed steel

The effect of heating rate and annealing time on the microstructure and mechanical properties of a commercial 0.04% C Al-killed steel, cold rolled up to 80% is evaluated in the present study. For this purpose samples were isothermally annealed at various heating rates (12, 20, 40 and 650 degree centigree/min) and then soaked at 700 degree centigree for 15 h. The microstructural evolution of the samples during the heating process and holding temperature was evaluated by optical microscopy, scanning and transmission and transmission electron microscopy. Tensile mechanical properties and hardness measurements were also correlated with the microstructural features. Results showed that with soaking time greater than 6 h, the mechanical properties specified for the material are reached, even through, appropriate plastic anisotropy values were only obtained in samples heated at low rates, where a pancake type of structure is also formed. (Author) 38 refs