Optimum To The Electrolyte Composition Of New Titanium Smelting Method And Its Application To Titanium Alloy Materials

Titanium and its alloys have the advantages of less density, high strength, corrosion resistance and high temperature resistance, and have been used from transitional aeronautics and astronautics industry to civil industries of metallurgy, energy source, transportation, chemic industry, biology and pharmacy. Because of complex manufacturing process and non-continuous production of the existing Kroll process, production cost of titanium is high, limiting greatly its application. FFC process proposed by the University of Cambridge is a new technology for producing metals and their alloys and is of advantages of short manufacturing process, low cost and no pollution, and has been the potentials to take the place of the Kroll process.In present work, the electrolyte compostion of the new smelting method of titanium has been optimized from the thermodyanmics. The solubility and activity coefficient of CaO in molten salt CaCl2-x(x=0, NaCl, KCl, SrCl2, BaCl2 and LiCl) and have been studied by chemical analysis method and the activity coefficient of CaO in the molten salts has been calculated. With increasing temperature the solubility of CaO in the molten salts increases and the activity coefficient decreases. The solubility of CaO in equimolar mixed molten salt is lower than that in CaCl2. The activity coefficient of CaO in CaCl2-NaCl is higher than that in CaCl2, which shows that the attractive forces between CaO and CaCl2-NaCl is stronger than that between CaO and CaCl2. The excess Gibbs free energy and enthalpy as well as entropy for the dissolution of CaO in the molten salts have been calculated from its activity coefficients. The excess entropy of CaCl2-CaO is as low as 5.07J/mol, showing that the behavior of the mixed salt is close to the regular solution.Titanium materials need to be cleaned and shaped by corundum sand of high hardness because of the surface oxidation during processing. The process is of complex and difficult in operation and high cost. In present work, the FFC process has been used to treat titanium mterials to clean and shape titanium material. Oxides and nitrides on the surface of titanium material have been removed by electrolysis directly in molten salt. Titanium material was as cathode electrode and graphite crucible was as anode. After 4h'electrolysis at voltage of 3.0V, the content of impurity C, N and O has been decreased and meets the requirement of GB(国家标准) Titanium(ZTA15).