The Effects of MgO and Al[sub.2]O[sub.3] Content in Sinter on the Softening–Melting Properties of Mixed Ferrous Burden

The softening–melting properties of mixed ferrous burden made from high-basicity sinter with increased MgO and Al[sub.2]O[sub.3] content and acid pellets was investigated for optimization. The influences of MgO and Al[sub.2]O[sub.3] are discussed with the aid of phase analysis. The results showed that, with decreasing MgO mass%/Al[sub.2]O[sub.3] mass% in mixed burden, all the softening–melting characteristic temperatures decreased, which can be attributed to the low melting temperature and viscosity of the slag caused by MgO and Al[sub.2]O[sub.3]. The permeability of the melting zone deteriorated again when MgO mass%/Al[sub.2]O[sub.3] mass% decreased to a certain content. The softening interval widened slightly at first and then narrowed, while the melting interval first increased slightly and then increased greatly later. It can be deduced that the softening properties were improved, but the melting properties were worsened. Under comprehensive consideration of its softening–melting properties, permeability, iron ore reduction and the thermal state of the blast furnace hearth, the optimal softening–melting properties of a mixed ferrous burden with MgO mass%/Al[sub.2]O[sub.3] mass% of 0.82 is optimal.