Abstract
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.
Highlights
Nowadays, the need of using materials in increasingly hostile environments, such as the exploration of oil in the pre-salt layer, boost the research about microalloyed HSLA steels in order to meet higher safety standards
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
Non-metallic inclusion characterization of as-cast steel showed that calcium content was not enough to modify the morphology of some aluminates
Summary
The need of using materials in increasingly hostile environments, such as the exploration of oil in the pre-salt layer, boost the research about microalloyed HSLA (high strength low alloy) steels in order to meet higher safety standards. These materials have microalloyed elements that form carbides, nitrides and carbonitrides (V, Nb and Ti), which act principally to increase the strength through grain refining and can lead to bimodal grain size distribution, depending on the precipitates distribution. Calcium treatment is performed, which functions are to increase melting, minimizing nozzle blockage through the formation of a compound with lower melting point, to improve the machining of the steel and to extend the useful life of the cutting tool (Basanta et al, 2011; Cicutti et al, 1997; Holappa et al, 2003; Turkdogan, 1996; Xu et al, 2018; Wu, 2009)
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