Composition control of CaO-MgO-Al2O3-SiO2 inclusions in tire cord steel a thermodynamic analysis

The effect of oxide component content on the low melting point zone (LMP) in the CaO-MgO-Al2O3-SiO2 system has been analysed using FactSage software. The contents of dissolved elements [Sil, [Mg], [O] and [AI] in liquid steel in equilibrium with the LMP inclusions in the CaO-MgO-Al2O3-SiO2 system have been calculated. The results show that the CaO-MgO-Al2O3-SiO2 system has the largest LMP zone (below 1400 degrees C) when the Al2O3 content is 20% or the MgO content is 10%. The LMP zone becomes wide with the increase in CaO content (within the range of 0-30 mass%) and the decrease in SiO2 (from 25 to 5 mass%). To obtain the LMP (below 1400 degrees C) inclusions, the [Mg], [Al] and [O] contents must be controlled within the range of 0.2 similar to 2 ppm, 1.0 similar to 2.0 ppm and 60 similar to 100 ppm, respectively.