A general survey of contemporary work on the preparation of zirconium is presented. Experimental equipment for the production of rare metals in general is described and applied to zirconium by a detailed study of the reaction: ZrO~ + 2Ca = Zr + 2CaO. The relation of excess reducing agent and addition agents to residual impurities in the metal product is evaluated and the effect of these impurities on sintered and melted compacts is shown. By the control of variables referred to above, the preparation of relatively soft easily machinable zirconium compacts is described and some physical properties of the metal are determined and recorded. I NTRODU CTIONThe metallurgy of the metals of Group IV of the Periodic Table which includes titanium, zirconium, and thorium is not new, although it is only in the past twenty-five years that these metals have been produced in high purity and their properties evalulated. The oxides of the metals in this group are not reduced by hydrogen or carbon to the pure metallic state and, therefore, methods commonly used for iron, nickel or copper are excluded. Because of their high melting points and reaction with ordinary refractories, they are not easily melted or cast. ZIRCONIUM Review of Early WorkMethods of producing zirconium are, with few exceptions, very old, and modern methods are improvements resulting from purer starting materials and better technics. Old procedures and contemporary methods include: (1) reduction of zirconium halides with the alkali and alkaline earth metals; (2) reduction of oxides with calcium or magnesium; (3) alumino-thermic reductions; (4) thermal dissociation.Thermal dissociation of zirconium iodide on a heated filament, classically represented by the work of de Boer, Van Arkel and Fast x t Manuscript
Two methods for the determination of oxygen are reviewed and applied to the analysis of zirconium. The first is indirect and involves combustion of the metal and calculation of the oxygen content by difference. Corrections must be nmde for hafnium and other oxygen absorbing, inert, or volatile contamin,mts and the method is, therefore, useful only for contr()l purposes or where relatively large amounls of oxygen are present.The second procedure is a direct determination of the zirconium oxide content by w~porization ()f the met'd in chlorine gas. The micro-structures of heat; treated zirconium wires with and without added oxygen are shown. They indicate why, in some cases, hardness increased with heating alone. Microhardness measurements on a series of oxygen-doped wires have provided a correlation between oxygen content and hardness. The hardness of zirconium increases roughly 50 V.P.N. for each 0.1 per cent of added oxygen and metal containing more than about 0.2 per cent oxygen is probably not cold workable.
first attempt to prepare metallic uranium was made in 1842 by Peligot ( 14), who reduced uranium chloride by means of sodium in a glazed porcelain crucible. The sodium was covered with layers of dry potassium chloride and uranium chloride and the reaction was started by heating the crucible externally. Zimmerman's ( 16) method was similar except that sodium chloride was substituted for the potassium chloride in covering the mixture. According to Moissan (10) this method yields a powder which is contaminated with small amounts of sodium as well as combined nitrogen. Moissan used the more stable
Calculations were made to determine the heat of reaction of calcium with different oxides of vanadium. These calculations indicated better means of controlling the reaction. Ductile rod, wire, and sheet were fabricated from a powder produced by calcium reduction of V2O3 . Fabrication furnished some information on working and annealing while other studies yielded physical property, purity, and microstructure data.
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