Effects of MnO on slag viscosity and wetting behaviour between slag and refractory

As more and more Mn bearing iron ores are used to decrease steel cost and deal with the problem of hearth deposition, slag regime change and hearth refractory erosion in blast furnace become more often. To address these problems, it is urgent to clarify the effects of MnO upon the ironmaking production. Herein, the viscosities of slags with different MnO contents were measured for the first time, and the influence mechanism of MnO was analysed by infrared spectrum. The wetting behaviours between slags with different MnO contents and alumina–carbon refractory were investigated. The results showed that meltability temperature and viscosity decrease simultaneously with the increasing MnO content from 0 to 2.0 wt-%. Infrared spectrum analysis also proved that the existence of Mn⁺, Ca²⁺ and Mg²⁺ makes the Si–O bonds peak moving towards high frequency and the asymmetry of Si–O bond increasing, leading to the decrease in viscosity decreasing. In addition, the characteristic temperatures for wetting reaction increased by ∼40°C with the increasing MnO content from 0 to 3 wt-% (basicity = 1.18). The characteristic temperatures decreased by nearly 50°C with the basicity of slag increasing from 1.0 to 1.3 (MnO = 1 wt-%). Therefore, the increasing MnO content in slag accelerates the erosion rate of BF hearth lining and then decreases the campaign life of blast furnace.