Production of titanium powder by metallothermic reduction of TiO₂ in cold pressed pellets

Abstract

In order to produce low-cost titanium (Ti) with high productivity, fundamental studies on producing metallic Ti from titanium dioxide (TiO₂) in the cold pressed pellets were conducted by metallothermic reduction with an indirect contact method. This paper focuses on discussing the mechanism of the reduction process and the relationships of R_M (a revised reduction index) with reduction temperature, reduction time, and mole ratio of TiO₂ to CaCl2 (${n_{{\rm{Ti}}{{\rm{O}}_2}}}/{n_{{\rm{CaC}}{{\rm{l}}_2}}}$) in the pellets. The results show that metallic Ti was obtained from the reduction of TiO₂ in the pellets by calcium (Ca) vapor; pellets were reduced homogenously and Ca vapor diffused into the porous pellets by Knudsen diffusion or the mixing diffusion of molecular diffusion and Knudsen diffusion at 1273 K; R_M increased with the increases of temperature and reduction time and was 96.34% when T_Redu=1273 K, t_Redu=6 h, and ${n_{{\rm{Ti}}{{\rm{O}}_2}}}/{n_{{\rm{CaC}}{{\rm{l}}_2}}} = 4$; the reasonable n_TiO2/n_CaCl2 value is 3–5 for the pellets with enough strength and high R_M.

摘要

为了高效生产低成本金属钛(Ti), 开展了基于非接触式二氧化钛(TiO₂)冷压块金属热还原法制备Ti 粉末的基础研究。 本论文重点考察了非接触式金属热还原法的还原机理和还原指数(R_M)与还原温度、 还原时间及TiO₂/CaCl₂ 摩尔比(${n_{{\rm{Ti}}{{\rm{O}}_2}}}/{n_{{\rm{CaC}}{{\rm{l}}_2}}}$)的关系。 研究结果显示, 钙(Ca)蒸气还原 TiO₂ 冷压块制备金属 Ti 粉末方法是可行的; 在1273 K 时, 冷压块可被均匀还原, Ca 蒸气在多孔冷压块内的扩散属于Knudsen 扩散或分子-Knudsen 混合扩散; R_M 随着温度的升高和时间的延长而增加; 在还原温度 1273 K、 还原时间 6 h、${n_{{\rm{Ti}}{{\rm{O}}_2}}}/{n_{{\rm{CaC}}{{\rm{l}}_2}}} = 4$ 的实验条件下, R_M 为 96.34%; 为了满足冷压块强度和高 R_M, 冷压块内 ${n_{{\rm{Ti}}{{\rm{O}}_2}}}/{n_{{\rm{CaC}}{{\rm{l}}_2}}}$ 控制在 3∼5 较为合理。