Breakthrough in Molybdenum

To meet the demands of missile makers, U.S. scientists have worked for years on metals that can resist the high temperatures generated by supersonic speeds. One such metal is molybdenum, which melts at 4748DEG F., v. about 3000DEG F. in commonly used alloys. But making molybdenum castings was long impossible; its melting point is so high that it destroyed the crucible holding it. Last week the U.S. Bureau of Mines announced "a major metallurgical breakthrough"; it had succeeded in making molybdenum castings.

Metallurgists melted a 30-lb. piece of molybdenum with a high-density electric arc in a copper-lined, water-cooled crucible. The molten molybdenum was then poured through a series of troughs into a rotating graphite cylinder which forced the metal to cling to its walls while it hardened, produced a molybdenum cylinder 4 1/2 in. wide and 8 in. long.

If the development proves commercially successful, missile engineers will have greater flexibility in designing vital molybdenum parts for missiles. Molybdenum parts are now made by pressing or melting the powdered metal into ingots or billets, then forging, machining or extruding it. The new casting method may permit not only more intricate shapes but also lower costs, since the process may cut the number of steps necessary. But the major U.S. moly producer, American Metal Climax, Inc.. cautioned that it may be some time before the casting method becomes commercially feasible.

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