Specialized metallurgical processes – compositions for use therei – Compositions – Consolidated metal powder compositions
Patent
1986-11-03
1987-10-13
Lechert, Jr., Stephen J.
Specialized metallurgical processes, compositions for use therei
Compositions
Consolidated metal powder compositions
72272, 75246, 419 23, 419 28, 419 31, 419 38, 419 48, 419 53, 419 66, 419 67, B22F 100
Patent
active
046996575
ABSTRACT:
Very fine grain metal billets are produced by loading alloy metal powder of desired composition into a metal extrusion container in successive layers of two or four inches deep. Each layer after loading is compacted by a high energy rate forming ram so as to introduce energy on the order of 3.times.10.sup.6 psi per layer and at least 18.times.10.sup.6 psi total. An inner plate is then loosely placed on the compacted powder. On top of the inner plate is placed a cover plate which is welded to the container. The filled container is then heated in a furnace to an extrusion temperature below the melting point of the alloy and is extruded in an extrusion press having a ratio of about 3:1 with a force of about 3,000 tons. The inner plate does not move at the same rate as the container and in effect is partially extruded against the powder so as to raise the density of the extruded billet to substantially 100% of its theoretical density.
The energy stored in the compacted powder is released by the heating and the extrusion causing multiple dislocations of the grain within a given particle and resulting in a very fine grain size, as small as 25 on the Snyder-Graff intercept scale.
If desired the powder may be compacted around a solid metal core. The inner cover plate is then provided with a clearance hole; the outer plate also has clearance but is welded to the core. The resulting extruded billet then has a very fine grain circumferential region.
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Lechert Jr. Stephen J.
Worl-Tech Limited
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