GB735085A - Improvements in or relating to the purification of refractory metals and alloys thereof - Google Patents

Abstract

735,085. Refining metals and alloys; producing titanium ; crucibles. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Aug. 5, 1953 [Aug. 28, 1952], No. 21576/53. Classes 72 and 82 (1). [Also in Group XXII] Gaseous impurities, particularly oxygen and nitrogen, are removed from Ti, V, Ta, Cr, Mo or W or from alloys formed exclusively or predominantly of these metals by locating the metal, after it has been pressed in the powdered form to the desired shape, in molten cerium or in cerium vapour. The pressed metal powder may be sintered before treating it in the cerium, or the temperature of the cerium may be high enough to effect sintering during the treatment. In one form of apparatus described for carrying out the treatment, Fig. 1, the refractory metal compact 11 together with metallic cerium 14 is placed in a container 12 of molybdenum or iron lined with tantalum. The cerium may be in the form of mischmetal. The container 12 rests, via an insulator 15, on a water-cooled metal plate 16 and is covered by a bell-jar 17 filled with argon at reduced pressure. The container is heated, by a high-frequency coil 23, to 1000-1300‹ C. to melt the cerium and is kept at that temperature for some hours, e.g. 5 hours at about 1000‹ C. or 1 hour at about 1300‹ C. After cooling, the cerium is separated from the refractory metal by leaching with dilute hydrochloric or acetic acid. In another form of apparatus similar to that described above, the pressed refractory metal is supported in a cage which is first lowered into the molten cerium and then, after a suitable time, raised to allow treatment by the cerium vapour. A process for the production of purified Ti is also described in which a titanium compound, e.g. titanium oxide, is first partially reduced by a reducing material comprising mainly magnesium, e.g. a magnesium-rich alloy, and completing the reduction with a reducing material comprising mainly calcium, e.g. a calcium-rich alloy. The Ti produced is separated and pressed and the compact is treated in fluid cerium to remove the gaseous impurities. The reduction steps may take place in iron crucibles lined with magnesium oxide and calcium oxide respectively. The Specification also refers to the removal of oxygen from Ti, Zr, V and Hf by treatment in molten calcium or calcium vapour.