Powder metallurgy processes – Powder metallurgy processes with heating or sintering – Heat and pressure simultaneously to effect sintering
Reexamination Certificate
1999-06-24
2001-10-30
Jenkins, Daniel J. (Department: 1742)
Powder metallurgy processes
Powder metallurgy processes with heating or sintering
Heat and pressure simultaneously to effect sintering
C419S038000, C264S432000, C264S489000, C264S490000, C264S604000, C075S010130, C204S157430, C219S678000, C219S756000
Reexamination Certificate
active
06309594
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to the field of consolidating metallic bodies, and more particularly to rapid and efficient and heating and handling of granular media employed in such consolidation, as well as rapid and efficient heating and handling of pre-form powdered metal or metal and ceramic particulate material bodies to be consolidated.
The technique of employing carbonaceous particulate or grain at high temperature as pressure transmitting media for producing high density metallic objects is discussed at length in U.S. Pat. Nos. 4,140,711, 4,933,140 and 4,539,175, the disclosures of which are incorporated herein, by reference.
The present invention provides improvements in such techniques, and particularly improvements in heating of the granular media to be used to transmit pressure to the body and/or forged preform to be consolidated.
SUMMARY OF THE INVENTION
It is a major object of the invention to provide rapid and efficient microwave heating of carbonaceous and/or ceramic particles used as pressure transmitting media, and also transfer of heat generated in the particles to the work, i.e. the pre-form to be consolidated. Basic steps of the method of consolidating a metallic, metallic and ceramic, or ceramic body in any of initially powdered, sintered, fibrous, sponge, or other form capable of compaction, or densification (to reduce porosity) then include the steps:
a) providing flowable particles having carbonaceous and ceramic composition or compositions,
b) providing microwaves acting to heat said particles to elevated temperature,
c) locating said heated particles in a bed,
d) positioning said body at said bed, to receive pressure transmission,
e) effecting pressurization of said bed to cause pressure transmission via said particles to said body, thereby to compact the body into desired shape, increasing its density; and
f) the body to be consolidated consisting of one of the following:
i) metallic material
ii) ceramic material
iii) a mixture of metallic and ceramic material
iv) polymeric material, or polymeric composite material.
Typically, the pressure transmitting material (PTM), or particulate, is placed in a container to receive microwave energy from an external source, and for a time period, and at transmitted frequencies to achieve rapid and controllable heating of the PTM, to be subsequently transferred to a container wherein body consolidation is effected. Simultaneous, or near simultaneous heating of all particles is thereby achieved, for uniformity. Also, need for electrical resistance only heating by use of exclusively resistance elements in the PTM is thereby obviated. Microwave heating combined with some electrical resistance heating is contemplated.
A further object is to provide for flow of the PTM particles during such microwave heating, as by fluidization of a bed of such particles in the path of microwave transmission.
By the use of the methodology of the present invention, substantially improved structural articles of manufacture can be made having minimal distortion, as particularly enabled by the use of carbonaceous, or ceramic, or carbonaceous/ceramic particulate in flowable form.
An additional object include provision of a method for consolidating metal and/or ceramic powder, and/or composite material with or without polymeric powder, to form an object, that includes
a) pressing said powder into a preform, and preheating the preform to elevated temperature,
b) providing flowable pressure transmitting particles and transmitting microwaves into said particles to heat same, and providing a bed of said flowable and heated pressure transmitting particles,
c) positioning the preform in such relation to the bed that the particles substantially encompass the preform,
b) and pressurizing said bed to compress said articles and cause pressure transmission via the particles to the preform, thereby to consolidate the preform into a desired object shape, having final density.
The novel features which are believed to be characteristic of this invention, both as to its organization and method of operation, together with further objectives and advantages thereof, will be better understood from the following description considered in connection with the accompanying drawings in which a presently preferred embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawings are for the purposes of illustration and description only and are not intended as a definition of the limits of the invention.
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Lansing Lucile
Meeks, III Henry S.
Ceracon, Inc.
Haefliger William W.
Jenkins Daniel J.
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