Powder metallurgy processes – Powder metallurgy processes with heating or sintering – Making porous product
Patent
1997-03-21
1998-03-24
Jenkins, Daniel J.
Powder metallurgy processes
Powder metallurgy processes with heating or sintering
Making porous product
419 6, 419 7, 419 47, 419 57, B22F 310, B22F 704
Patent
active
057323232
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates to a method for fabricating dimensionally accurate pieces by sintering a material which, before the sintering, consists of a blend of at least three pulverous ingredients, the first ingredient being in the main an iron-group metal, the second ingredient being in the main copper and phosphorus, and the third ingredient being an alloy of copper and at least one other metal, this powder blend of ingredients containing the third ingredient in the largest amount and both the first ingredient and the second ingredient in lesser amounts.
2. Description of the Related Art
A powder blend of this type, from which it is possible, by sintering, to fabricate with dimensional accuracy metal pieces which do not substantially shrink or expand during the sintering, has been described, for example, in patent EP-0 420 962 B1 (corresponds to publication WO-90/11855). The method according to this patent uses conventional sintering in a furnace, which is a relatively slow process. During this slow process the particles of certain ingredients of the said specific metallic powder blend grow, other ingredients melt or dissolve and thereby shrink, and as a result of this particle growth and diffusion process the overall dimensions of the piece remain unchanged, as described in the publications. Thus the method according to this patent is suitable for use in the fabrication of products which are made in large series, in which case a large quantity of products can be sintered simultaneously if there is need for an economical price for the product. A large production quantity is required also for the reason that it enables investments to be made in furnaces in which the above-mentioned sintering of a large quantity of products simultaneously will be possible. There is also the disadvantage that the method requires a form mold or pattern of a refractory material. In addition, the method according to this patent produces, specifically because of the desired dimensional accuracy, porous pieces, as described in the publication. Since the method according to the patent is intended for the production of, for example, tools in which porosity in general is not of crucial significance, the porosity left in the piece has not been considered important in the patent; dimensional accuracy and surface quality have been regarded as the features of primary importance.
Publications EP-0 542 729, EP-0 538 244, U.S. Pat. No. 5,156,697 and article Manthiram, Bourell, Marcus: "Nanoface Materials in Solid Freeform Fabrication"; JOM, November 1993, pp. 66-70, describe a method in which individual parts are fabricated by sintering powder layers by means of heating produced by laser radiation. According to these publications, this selective laser sintering (SLS) is carried out in the following manner. The point of departure is a computer-designed model which is numerically sectioned into layers of predetermined thickness corresponding to the thickness of the powder layer deposited in connection with the sintering. The shapes corresponding to each calculated layer together make up the final desired shape of the part. The fabrication of the actual part is carried out by depositing on a base a powder layer of the above-mentioned thickness, the layer being made up of some conventional powder blend used in sintering. Thereafter the plane image of this powder layer in the computer memory is allowed to direct the laser beam aimed at the powder layer in such a manner that it scans the surface area corresponding to this cross-sectional surface of the part, sintering this area. Those areas of the powder layer which do not belong to the part will remain non-sintered, since they are not subjected to laser radiation. Thereafter, successive powder layers are introduced, layer by layer, and each of them is sintered in the manner described above, in accordance with the numerical plane image, i.e. the cross-sectional surface of the part, corresponding to the layer concerned, the sintered areas ultimately to
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Aktiebolaget Electrolux
Jenkins Daniel J.
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