SOME ASPECTS OF POWDER METALLURGY 423 



could be compacted, heated, sintered, and forged in much the same manner 

 that metal powders are treated today. An outstanding example of the 

 massive pieces produced by such methods is the 6| ton Delhi pillar made 

 about 1,600 years ago-. 



History of Development 



The ancient Egyptians and probably other early civilizations discovered 

 how to make powders of gold, silver, copper, bronze, iron, lead, and to a 

 limited extent, tin, antimony, and platinum^, but it was necessity rather 

 than desire which led these early workers to produce their massive metal 

 tools, ornaments, and weapons by powder methods. It is interesting to 

 note that as furnaces were devised to obtain higher temperatures, the list 

 of metals prepared from powders decreased. The lower melting metals, 

 of course, were the first to be prepared by melting and casting methods, 

 and as higher temperatures were attained, only the more highly refractory 

 metals remained on the powder preparation list. 



Although iron had been known in prehistoric days, it remained a scarce, 

 precious metal for several thousand years, and did not come into general 

 use until introduced by the Hittites around 1300 B.C. The Hittites presum- 

 ably mined iron ore in the iron region along the Black Sea in Asia Minor 

 and worked the material to metal form*. By 100 B.C., the use of iron had 

 spread westward to include many of the countries bordering the Aegean 

 and the Mediterranean. The primitive methods of iron working probably 

 consisted in heating the iron ore in a charcoal fire fanned by an air blast 

 from a bellows until reduction of the oxide was attained. The spongy 

 mass was then pressed, heated, and forged to the desired shape. 



That this was the general practice followed in many countries in the 

 production of metal objects has been observed from articles unearthed 

 from earlier civilizations. Somewhat similar methods of working other 

 metals have been observed, and where difficulty was experienced in ob- 

 taining sintering, other metal powders were added that were lower melting 

 themselves, or that formed lower melting alloys which wet and welded 

 together the particles of metal being worked to form a lump that could 

 be shaped. The Incas in South America used such a method in fabricating 

 many small articles of platinum^. The grains of native platinum were 

 mLxed with some gold and silver, and, by means of a blow-pipe, were fritted 

 together by the lower melting alloy of gold and silver. The resulting mass 

 could then be forged to the desired shape. 



During the eighteenth century there was a fair amount of activity in 

 the production of metal powders, and in studies of the fabrication of metal 

 parts from the powders. Platinum was introduced into England in 1741 

 and attempts were made to produce the metal in compact usable form^. 



