Reduction Reactions between Molten Slags Containing Titanium-Oxide and Pig Iron and the Behavior of Titanium-Oxide

Abstract

The author studied the reduction of titanium and silicon from the slags of the system CaO-SiO₂-TiO₂ (TiO₂ 15, 25, 35%; CaO/SiO₂ 0.5-1.3) into carbon-saturated iron in a graphite crucible at 1550°C. The duration of each study was 75 minutes during which metal and slag samples were taken at 10 or 15 minutes intervals. K_{Ti, Si}= { [ Ti] (Si) } / { (Ti) [ Si] } was determined from the analyses. It was found that a certain time had elapsed before the quasiequilibrium state was attained, when K_{Ti, Si} reached a constant value. This constant KTi, Si is termed the index number of the quasi-equilibrium state.
The influence of slag compositions upon the contents of titanium and silicon in the iron at the same time of reduction was somewhat complicated, except that the titanium was increased with the increase of titania in the slag and the silicon was decreased with increase of CaO/SiO₂. On the contrary, it was presumed that the relationship between the index number K_{Ti, Si} slag compositions was definitely established.
At the constant titania coatents the index number K_{Ti, Si} was increased with increase of CaO/SiO₂ and at the cunst, CaO/SiO₂ it was decreased as titania was increased. Then, (CaO) / { (SiO₂) +f_T (TiO₂) } or B_L, which the author had recently given as a new scale of basicity, was taken as the basicity of the slag, and K_{Ti, Si} was plotted against the basicity. It was shown by this plot that all the points representing slags of different titania contents lay along the same line, and KTi, Si was increased with increase of the basicity.
The contents of Ti₂O₃ in the slags was decreased with increase of CaO/SiO₂. It was establi shed as a rule that in the slags containing the oxide of a transition metal such as Fe, Cr or Ti the concentration of cations with higher valency was increased with increase of slag, basicity.
Furthermore, by studying the practical data of titaniferous iron sand smelting in an elec tric furnace, it was indicated that the reduction of each element was controlled by the common degree of reduction. It was found that K_{Ti, Si}=0.658 (σ=0.097) in the range of slag basicity B_L =0 - -1.0.