Characterization and 3D Reconstruction of the Crushing Behavior of SiO2–CaO–Al2O3–MgO Complex Inclusions in Spring Steel with High Basicity Slag Treatment

Abstract

This article mainly studies the element content, phase composition, and fragmentation mechanism of SiO₂–CaO–Al₂O₃–MgO composite inclusions that cause fatigue fracture of spring steel. The study found that the SiO₂–CaO–Al₂O₃–MgO composite inclusions in the wire rod are not a homogeneous phase. According to the electron microscopy energy spectrum analysis results, although the SiO₂–CaO–Al₂O₃–MgO composite inclusion is in the low-melting-point area of the phase diagram according to the component content ratio. However, field-emission transmission electron microscopy analysis reveals that this type of composite inclusions includes MgAl₂O₄, CaAl₂Si₂O₈, CaSiO₃, MgSiO₃, and a small amount of CaS. The Zeiss Crossbeam 550 electron microscope is used to conduct a three-dimensional reconstruction analysis of this type of composite inclusions, which once again verified that the composition of this type of inclusions includes calcium silicate, MgAl₂O₄, MgO, and other phases. It is also found that there is a certain gap between the inclusions and the matrix, and the gap between the inclusions with high-melting-points such as MgAl₂O₄ and MgO and the matrix is more obvious. During the rolling process of SiO₂–CaO–Al₂O₃–MgO composite inclusions, due to differences in hardness and deformation rate between different phases, the rolling process is deformed and fragmented for extended periods.