Microstructure and mechanical properties of as-cast and annealed high strength low alloy steel

This paper presents a study on the microstructure and mechanical properties of a microalloyed HSLA steel solidified by continuous casting process and annealed at 1100 °C for 1 hour. The techniques of confocal microscopy, scanning electron microscopy and hardness, tensile and Charpy mechanical tests were used. The results of this research showed that the microstructure of the sample in the as-received condition was mainly composed of acicular ferrite and aggregates of ferrite and carbides. Non-metallic inclusion characterization of as-cast steel showed that calcium content was not enough to modify the morphology of some aluminates. After thermal treatment, the initial microstructure was transformed into polygonal ferrite and pearlite. In both conditions, different types of precipitates were found, which were classified according to their distribution in the microstructure. The steel with solidification structure showed a higher tensile strength, but its application would be unlikely in components that require good impact strength.