Dissolution of Al2TiO5 inclusions in CaO-SiO2-Al2O3 slags at 1823 K

Abstract

Al-Ti-O inclusions always clog submerged nozzles in Ti-bearing Al-killed steel. A typical synthesized Al2TiO5 inclusion was immersed in a CaO-SiO2-Al2O3 molten slag for different durations at 1823 K. The Al2TiO5 dissolution paths and mechanism were revealed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Decreased amounts of Ti and Al and increased amounts of Si and Ca at the dissolution boundary prove that inclusion dissolution and slag penetration simultaneously occur. SiO2 diffuses or penetrates the inclusion more quickly than CaO, as indicated by the w(CaO)/w(SiO2) value in the reaction region. A liquid product (containing 0.7–1.2 w(CaO)/w(SiO2), 15wt%–20wt% Al2O3, and 5wt%–15wt% TiO2) forms on the inclusion surface when Al2TiO5 is dissolved in the slag. Al2TiO5 initially dissolves faster than the diffusion rate of the liquid product toward the bulk slag. With increasing reaction time, the boundary reaches its largest distance, the Al2TiO5 dissolution rate equals the liquid product diffusion rate, and the dissolution process remains stable until the inclusion is completely dissolved.