Some Aspects of Powder Metallurgy 



By EARLE E. SCHUMACHER and ALEXANDER G, SOUDEN 



Introduction 



THIS correlated review is an attempt to present some of the more 

 common aspects of the powder metallurgy process in order to acquaint 

 telephone engineers with an increasingly important production method, 

 and to provide an outline of topic references that could otherwise be obtained 

 only from many different sources. 



Basically, the art of powder metallurgy deals with the preparation of 

 metal powders and their utiUzation. This is a general description, however, 

 and covers not only the metallurgical field, but also the paint and pigment 

 and other more strictly chemical industries. As a more pertinent definition, 

 the following has been suggested: "Powder metallurgy is the art of pro- 

 ducing metal powders and shaped objects from individual, mixed, or alloyed 

 metal powders, with or without the inclusion of non-metalUc constituents, 

 by pressing or forming objects which are simultaneously or subsequently 

 heated to produce a coalesced, sintered, alloyed, brazed, or welded mass, 

 characterized by the absence of fusion, or the fusion of a minor component 

 only"i. 



In the past few years, powder metallurgy has received considerable atten- 

 tion, not only in technical publications, but also in the newspapers and 

 popular periodicals, the general imphcation of the latter being that a com- 

 pletely new and revolutionary field of metallurgical endeavor has been 

 uncovered. Actually, however, instead of something new, .we are dealing 

 with an art that had its inception at the time man first started using metals; 

 numerous examples exist today of the early attempts to produce solid articles 

 from metal powders. It is not surprising that early investigators and 

 workers dealt with powders rather than massive structures of metals. 

 With the exception of a few low melting metals such as tin and lead, most 

 of the metals available melted at temperatures above those which could 

 be attained at the time with crude furnace equipment. It was possible, 

 however, to prepare powders of many metals by rather simple means without 

 extensive furnace equipment, and a number of such powders were produced. 

 Iron, for example, was reduced from its ores and worked to solid form at 

 least 5,000 years ago, long before furnaces were devised which could even 

 approach the melting point of the metal. The resulting reduced product 

 was not, of course, massive iron, but was a sponge powder material which 



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