Powder metallurgy processes – Powder metallurgy processes with heating or sintering – Heat and pressure simultaneously to effect sintering
Patent
1998-01-14
1999-09-21
Jenkins, Daniel J.
Powder metallurgy processes
Powder metallurgy processes with heating or sintering
Heat and pressure simultaneously to effect sintering
419 26, 75228, 75246, 75247, 29DIG31, B22F 314
Patent
active
059565616
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to the production of dies and molds made directly from powdered metals. The dies, according to the invention, are made by placing a specially formed pattern, having the shape of the desired die cavity, into a canister and fixing it in an appropriate location inside of the canister. The spaces between the pattern and the canister are then filled with a selected powdered metal, evacuated and sealed. Hot Isostatic Pressing (HIP) is then used to consolidate the powdered metal to full density. Separation of the compact along an appropriate plane enables the pattern to be removed thereby revealing the desired die cavity formed in the consolidated powdered metal.
Present techniques for the production of dies involve casting ingots of the die material which must be reduced in size by rolling and/or forging. These steps result in significant yield loss of the material and create less than ideal mechanical properties due to the coarse nature of the microstructure. Following the rolling or forging, it is necessary to machine the cavity into the die. This is a very time consuming and labor intensive process which results in substantial expense and in additional wasted material.
SUMMARY OF THE INVENTION
The present invention is directed to a method of making dies and molds for subsequent use in the manufacture of shaped parts, such as by die casting, injection molding and the like. The method includes the steps of providing a pattern of a desired shape to define the finished mold or die cavity configuration; placing the pattern in a canister; filling the interior of the canister with a selected powdered metal to surround the pattern therein; hot isostatic pressing the canister and powdered metal by the application of heat and pressure to consolidate and densify the powdered metal surrounding the pattern; and sectioning the canister and densified metal along a plane to remove the pattern and thus provide a die or mold cavity of desired shape in the densified metal sections.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a cross section through the centerline of a canister showing the pattern with the space between the pattern and the canister filled with powder according to the present invention;
FIG. 2 is a view of the canister of FIG. 1 after hot isostatic pressing showing the sectioning lines;
FIG. 3 is a view showing the die with the pattern of FIGS. 1 and 2 removed; and
FIG. 4 is a perspective view of a compacted die, after separation, showing the pattern and parting plate used in the method of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A method of practicing this invention as shown in FIG. 1 involves the creation of a steel pattern 4 by classical machining techniques. This pattern is the size and shape of the desired cavity to be produced in the finished die. The pattern is affixed to the bottom of the canister 8 by tack welds 9. A coating of yttrium oxide 5 is applied to the surface of the pattern 4. In a separate operation, the fill/evacuation tube 1, top 2 and central portion of the canister 10 are welded together. This assembly is then welded to the bottom segment 8 of the canister.
Powder of the desired die material is then introduced into the canister via the opening 7 in the fill/evacuation tube 1. The powder 6 in this example is M4 tool steel and fills the space between the pattern and the internal surfaces of the canister. The air is evacuated from the canister through the fill/evacuation tube 1 which is then welded closed. The canister containing the pattern and the powder is then hot isostatic pressed at 2175.degree. F. for five hours at a pressure of 15,000 PSI. This process consolidates the powder creating a solid compact around the pattern.
In order to remove the pattern, the consolidated canister is bandsaw cut as shown in FIG. 2. Upon removal of the pattern halves from the compact, the desired die cavity is revealed, see FIG. 3.
A presently preferred embodiment of the invention is shown in
REFERENCES:
patent: Re31355 (1983-08-01), Rozmus
patent: 4233720 (1980-11-01), Rozmus
patent: 4492737 (1985-01-01), Conolly
patent: 5308556 (1994-05-01), Bagley
patent: 5435824 (1995-07-01), Dorsch et al.
Bugle Clifford M.
Lombard Carl A.
Dynamet Incorporated
Jenkins Daniel J.
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