GB833767A - Continuous electrolytic production of titanium - Google Patents

Abstract

833,767. Producing titanium by electrolysis. TIMAX CORPORATION. Oct. 19, 1956, No. 31952/56. Class 41. A process for continuously producing ductile titanium in crystalline form comprises electrolysing a molten electrolyte 31 consisting of at least one oxide of titanium, e.g. TiO or TiO 2 , and a fused salt whose cations are more electropositive than titanium, e.g. halides, oxides, sulphates, phosphates, borates or fluorides of alkali or alkaline earth metals or mixtures thereof, e.g. calcium halides with or without strontium halides, in one compartment having a dependent, insoluble anode 36, e.g. graphite, and a liquid alloy electrode 15 as cathode, the alloy containing titanium metal as solute in a solvent having at least one metal more electronegative than titanium, e.g. Cu, Ag, Sn, Sb, Zn, Pb, Bi, Fe, Ni, Cd, Si, Co or mixtures thereof, whereby oxygen comes off at the anode and Ti is deposited and dissolved in the electrode 15, and simultaneously electrolysing between the electrode 15 as anode and a dependent cathode 44, e.g. having a titanium or molybdenum tip 48, a molten electrolyte 32 containing at least one lower halide of Ti, e.g. up to 43% by weight, and as solvent at least one fused salt from the group consisting of the alkali and alkaline earth metal halides, whereby Ti is deposited as crystals on the cathode tip 48. The cell 10 comprises an iron shell 11 lined with silica 12 and fired magnesia bricks 13, electrical connection to a graphite layer 16 under the alloy 15 being through screwed-in leads 19, 20 and a carbon block 18. An iron baffle 30 sheathed in graphite 33 and fired magnesia 34 depends from a cover 28 and separates the electrolytes 31, 32. One or more anodes 36 depend in the cell and are progressively lowered by means 39, each anode passing through a water-cooled alumina sheath 38. A gas vent leads to a manifold 42, and material is fed to the compartment 31 through a worm-feeder 43 which has means for delivering an inert gas, e.g. argon, to the compartment. In the other compartment 32 are one or more cathodes 44 progressively withdrawn by means 45 and passing through an air-tight waterjacketed cooling chamber 46 separated by a manually-operated gate valve 50 from the compartment 32. The valve 50 includes argonsupply and withdrawal means. The shell 11 and cover 28 may be water-cooled, and the compartment 32 and chamber 46 are flooded with argon. The cell is operated as follows:-A low voltage arc is struck across 36, 16 and the cathodes 44 lowered (the tip 48 replaced by graphite) until an arc is struck, and electrolyte 32, e.g. CaCl 2 or a eutectic mixture of CaCl 2 - NaCl, CaCl 2 -SrCl 2 or NaCl-KCl, added. Argon is then passed through the cell to remove air and the temperature allowed to rise to a value above the melting-point of the alloy 15, when the alloy metal is added at 43, preferably as small lumps, until the level of 15 rises above the bottom of the baffle 30. The alloy 15 must not touch the magnesia 34, 35. The electrodes 36, 44 are slowly withdrawn to their operating positions, and the electrolyte level 32 made up and the solvent for electrolyte 31 added. Specific solvents are MgF 2 -NaF-KF, BaF 2 -MgF 2 -CaCl 2 , BaF 2 -BaCl 2 -CaF 2 , CaF 2 -LiF, CaCl 2 -SrCl 2 , CaCl 2 , CaCl 2 -CaO, CaF 2 -BaCl 2 , CaF 2 -SrCl 2 , CaF 2 - CaCl 2 , and CaO-CaCl 2 -CaF 2 . Finally, the oxide solute is added to the electrolyte 31 and the halide solute, preferably the chloride, is added to the electrolyte 32, the A.C. voltage cut off and the D.C. voltages applied, after replacing the tip 48. Thermocouples actuate relays to increase the D.C. current or superimpose an A.C. current across the electrodes of the compartments 31, 32 if the temperature falls. From then on, rate of supply of oxide feed material and the'rates of lowering and raising the electrodes 36, 44, respectively, are synchronized, and argon is circulated through the compartments. The alloy 15 may be purified in situ by applying low voltage A.C. across electrodes 36, 16. Operating conditions are as follows:-In compartment 31, anode current density may be up to 85 amps per square inch, oxide concentration up to 5% by weight and titanium fluorotitanate may be added to improve the solubility. The cathode current density may be up to 265 amps. per square inch. A bath temperature of 1100‹ C. to 1250‹ C. is mentioned. In compartment 32, the anode current density is up to 10 amps. per square inch, and for the cathode 44 up to 1000 amps. per square inch. Two examples are described in detail.