In arc-melting zirconium metal with a tungsten electrode, tungsten appears in nonuniform anmunts throughout the ingot. To eliminate this, the use of consumable electrodes of zirconium sponge is proposed. All earl)" attempts to use sponge zirconium electrodes were unsuccessful due to instability of the are. This problem was solved by stabilizing the are with a small amount of magnesium metal added to the zirconium sponge used in making up the electrodes. A water-cooled copper sleeve was used as a melting section in the are-melting furnace. Melting was done under an inert atmosphere of argon or helium. Metallographic and radiographic studies show the finished ingots to be sound.
If vacuum metallurgy were the segment of the production of reactive metals with which one needed to be concerned, environmental aspects would be relatively simple to control. Air pollution could be handled by proper use of vapor and mist traps on mechanical pump exhausts and in the vicinity of oil reclaimers. Prevention of water pollution might prove to be more of a problem because of the difficulties in disposing of both mechanical pump and diffusion pump oils. An integrated plant for producing such a metal as zirconium uses relatively large quantities of chemicals which may be detrimental to the environment, if not carefully controlled. Chlorine, hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, ammonia, ammonium thiocyanate, and methyl isobutyl ketone are among those difficult to handle materials encountered in such an operation. Not only is disposal of waste products a potential evnironmental problem, containment of the reagents themselves present some unusual challenges. In many cases, a bootstrap approach is used wherein a reactive metal such as zirconium is found to possess the necessary corrosion resistant and noncontaminating properties highly desirable in equipment used for handling reagents or by-products encountered in its production.
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