PRODUCTION
Mallory's new powder metallurgy process gives dense structural parts. Here, flanged bushings made of powdered iron alloy a r e unloaded from sintering furnace
High Density Boosts Strength Mallory's Steelmet process uses special powders to make powder metallurgy parts with higher density STEELMET-a new powder metallurgy Powder metallurgy makes it possible process developed by P. R. Mallory & to produce precision metal parts withCo.—promises a wider range of powder out expensive machining. But a big metallurgy products in the future. drawback of powder metallurgy products in the past has been the difficulty High density is the secret. Products of the Steelmet process have of making them dense enough. Manuproperties comparable to those of ma- facturers have long considered high density the key to powder metallurgy chine-wrought parts. Previously, this parts with high strength and other imwas impossible by conventional powder proved properties. metallurgy techniques, Mallory's F. R. Steelmet products have this high Hensel told the American Association density. Iron powder metallurgy parts for the Advancement of Science, meet- m a d e by this process can now be ing in Indianapolis. used in highly stressed structures, HenMallory is operating a pilot plant in sel says. Indianapolis to produce test quantities Steelmet components can serve as of Steelmet parts. Products from the gears, cams, levers, ratchets, and other pilot plant will be offered for sale early precision parts now produced by more this year. Mallory may build a multi- costly machining. One Steelmet commillion-dollar commercial Steelmet ponent being tested by an outside complant. But the company won't decide pany costs less than one quarter the on this until early 1959. price of an ordinary wrought part.
• Process Differs. In the past, t h e density of powder metallurgy parts has been increased by repeated pressing and sintering. Another way h a s been to infiltrate the sintered material with copper or brass to fill t h e voids. A more recent technique involves subjection of hot sintered parts to very high pressure. T h e Mallory process is different. It was developed primarily b y modifying the chemical and physical properties of the starting materials, rather than by changing the later processing of t h e powders. Metallic elements i n Steelmet powders diffuse at a high rate. They also show good flow properties and high particle strength which permit fast, automatic pressing, Mallory says. Furthermore, the size a n d size distribution of the particles are closely controlled. As its basic starting material, the Steelmet process uses relatively cheap grades of commercial iron p o w d e r s . Later, in a single pressing and sintering operation, these powders can be converted to a wide range of iron alloy compositions that contain only 5 % voids. Tensile strength of these alloys ranges from 42,000 to 200,000 p.s.i. They can b e elongated as m u c h as 36%. Conventional or special h e a t treating cycles can improve the properties of the alloys. For the present, Mallory is highlighting four alloys: • S t e e l m e t 100—a 1% -manganese, 1%-nickel, 98%-iron alloy; a generalpurpose material with good tensile strength and very good ductility. • S t e e l m e t 1 0 1 - a 9%-nickel, 1 % manganese, 90%-iron alloy with high tensile strength and good ductility. • Steelmet 302 — equivalent to wrought 302 stainless steel in analysis a n d having sintered tensile strengths of 75,000 to 90,000 p.s.i. • Steelmet 600—a 2%-copper, 0.25
