Powder metallurgy processes – Powder metallurgy processes with heating or sintering – Making composite or hollow article
Patent
1995-04-07
1996-07-30
Walsh, Donald P.
Powder metallurgy processes
Powder metallurgy processes with heating or sintering
Making composite or hollow article
419 49, B22F 314
Patent
active
055408826
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns a method relating to powder metallurgical manufacturing of a body having a through hole, for example a hollowed tool blank or a thick-walled tube.
2. Discussion of Related Art
Hollowed tool blanks of high speed steels, hot or cold work steels, or advanced construction steels are used to a considerable extent for the production of various finished products. Examples of such products are cutting tools having a shaft, e.g. cutters, tool dies, linings in extrusion presses, gears and other machine elements. Among other technical fields may be mentioned the arms industry, where hollowed blanks can be used for the manufacturing of gun barrels.
The manufacturing of blanks by boring an urnhollowed working-piece is a costly task, particularly when it is the question of materials which are difficult to work by cutting operations, such as high speed steels and other tool steels, advanced construction materials, etc, whether the working-piece has been made powder metallurgically or by conventional production. Traditional powder metallurgical manufacturing by making a green body, which is subjected to subsequent sintering and working offers good opportunities of manufacturing hollowed blanks, while the manufacturing of hollowed blanks by hot isostatic compaction of metal powder implies substantially greater practical problems. It is true that it is possible to enclose the powder in a tube-shaped capsule, which is subjected to hot isostatic compaction, but the manufacturing and welding of such capsules is comparatively complicated and makes the manufacturing considerably more expensive.
It is also possible to provide a core in the capsule which is filled with metal powder and which is subjected to a subsequent hot isostatic compaction, whereafter the core can be removed after completed consolidation of the metal powder by hot isostatic compaction. The difficulty lies in the removal of the core, which integrates itself with the consolidated body which is formed of the metal powder at the hot isostatic compaction.
SUMMARY OF THE INVENTION
The overall object of the present invention is to solve this problem, which is possible by providing in an outer capsule a tube having substantially the same length as the capsule, so that the tube extends substantially through the entire length of the capsule, that in the tube there is provided a core which also extends through the capsule and the entire length of the tube, that the space between the tube and the inner side of the capsule is filled with a metal powder which shall form the desired body, that the space in the tube between the core and the inner side of the tube is filled with a non-metallic powder, that the capsule is closed hermetically, and that the closed capsule and its content is subjected to hot isostatic compaction at a temperature exceeding 1000.degree., so that the metal powder is compacted to complete (true) density. The invention herein resides on the principle to obtain a release agent from the non-metallic powder between the consolidated metal body and the core in spite of the fact that the non-metallic powder in the space between the core and the inner side of the tube is consolidated to a substantially dense material during the hot isostatic compaction, so that it can transfer the isostatic pressure, which is applied on the outer side of the capsule, to the core via the metal powder which is being compacted to true density. This, according to an aspect of the invention, can be achieved so that the hot isostatically compacted capsule with its content, possibly alter a subsequent hot treatment through forging and/or rolling, is cooled to room temperature or at least to a temperature at which the object can be practically handled, i.e. below 100.degree. C. wherein the substantially dense material which has been formed through the consolidation of the said non-metallic powder during the hot isostatic compaction is caused to deconsolidate, i.e. to be fragmented and/or return
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Bednarek Michael D.
Erasteel Kloster Aktiebolag
Jenkins Daniel J.
Walsh Donald P.
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