Structural and microstructural characterization of 1045 steel SAE submitted to thermal treatment

Abstract

As the object of investigation for the present study, SAE 1045 steel was used, as it is a steel with medium carbon content, having wide use, however it has limited mechanical properties for severe applications. This study is justified by the need to improve material properties, expanding the applications range. The aim of this research is to understand the effect of austenitizing time and temperature as well as the cooling method and its implications on the SAE 1045 steel hardness. In view of this, quenching and tempering were used as thermal treatments. For the experimental development, the cooling medium used for quenching were water and brine, and the temperatures determined were 850ºC, 875ºC and 900ºC, with the objective of obtaining martensitic structure and the maximum steel hardness. In tempering, the cooling medium was outdoors at ambient temperature, and the heating temperatures determined were 250°C, 325°C and 400°C, in order to reduce the excessive hardness of the martensite and make the steel more tenacious and ductile. The hardness test confirmed the presence of martensite as well as optical microscopy and scanning electron microscopy in the tempered samples. In the tempered samples, microconstituents appeared, which improve toughness and ductility such as bainitic ferrite and retained austenite. The analysis of variance did not have a significance level of 5% in the first phase of experiments, but in the second phase it was observed. In the microstructure investigation was applied optical microscopy and scanning electron microscopy, which showed improvement in the microstructure of the material. The traction test was carried out on samples, however it was unsuccessful.