Production of Titanium Powders by the Calciothermic Reduction of TiO₂

Abstract

According to the measurements of equilibrium oxygen concentration in Ti under Ca-CaO co-existence, the deoxidation limit is 500 ppm at 1273 K. On the basis of these data, preparation of Ti powders have been carried out by reduction of TiO₂ using saturated Ca vapors, liquid Ca and CaH₂ powders at 1273 K and subsequent rinsing of CaO in the aqueous solution of HCl, CH₃COOH or NH₄Cl.
The oxygen and calcium levels in the Ti powders reduced by the saturated Ca vapors and the liquid Ca were not below 2000 and 1000 ppm, respectively. This was attributed to the CaO which were confined inside the sintered Ti particles and could not be exposed to the rinsing solution.
Reduction of the TiO₂-CaO mixtures has led to the residual oxygen with the range of 1000-2000 ppm, thus the presence of CaO in the starting oxide was effective to control the sintering between reduced Ti powders. The particle size of the reduced Ti was 1-10μm.
Reduction of TiO₂ by mixing with excess amount of CaH₂ powders could eliminate oxygen below 700 ppm which is close to the deoxidation limit for Ti by Ca of activity of unity.