Thermodynamic Analysis of Inclusions of Low Melting Point Area in Spring Steel

The activity data of each component of a CaO–SiO2–Al2O3 system were calculated by thermodynamic software Factsage. The composition of low melting point inclusions in a CaO–SiO2–Al2O3–MgO system was analyzed by thermodynamic calculation. The results show that the area of low melting point inclusions first increases then decreases with accumulating the alumina and magnesium oxide contents, respectively; the low melting area of CaO–SiO2–Al2O3–MgO inclusion is the biggest when the content of MgO and Al2O3 is 15%. To obtain low melting point inclusions, the alumina and magnesium contents should be approximately controlled to be 15%, and the CaO should be 40%.