Composition Control of CaO‐MgO‐Al 2 O 3 ‐SiO 2 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‐Al 2 O 3 ‐SiO 2 system has been analysed using FactSage software. The contents of dissolved elements [Si], [Mg], [O] and [Al] in liquid steel in equilibrium with the LMP inclusions in the CaO‐MgO‐Al 2 O 3 ‐SiO 2 system have been calculated. The results show that the CaO‐MgO‐Al 2 O 3 ‐SiO 2 system has the largest LMP zone (below 1400°C) when the Al 2 O 3 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 SiO 2 (from 25 to 5 mass%). To obtain the LMP (below 1400°C) inclusions, the [Mg], [Al] and [O] contents must be controlled within the range of 0.2~2 ppm, 1.0~2.0 ppm and 60~100 ppm, respectively.