Powder metallurgy processes – Powder metallurgy processes with heating or sintering – Powder pretreatment
Reexamination Certificate
2000-09-18
2001-12-04
Mai, Ngoclan (Department: 1742)
Powder metallurgy processes
Powder metallurgy processes with heating or sintering
Powder pretreatment
C419S039000
Reexamination Certificate
active
06325964
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of manufacturing a titanium alloy article, and particularly to a method of manufacturing a titanium alloy article by means of a powder metallurgy sintering method.
2. Description of the Prior Art
Titanium is a material of high strength, lightweight, and highly anticorrosive. In the prior art, a titanium alloy article can be manufactured by methods such as casting, powder metallurgy (P/M) sintering, and sheet pressing. The casting method results in an alloy article of high strength but with an unstable quality, a bad throughput, and a high cost. The conventional powder metallurgy sintering method has disadvantages such as a low density, an insufficient tensile strength and extensibility. The sheet pressing method has disadvantages such as a high mold-wearing rate, a poor changeability in shape, and a poor accuracy, due to the high hardness of the titanium alloy. By means of the sheet pressing method, right-angle portions of an article are not as good as expected.
As far as the conventional powder metallurgy sintering method is concerned, in addition to a conventional powder-compression-molding method, a powder-inject-molding method has been proposed to overcome the disadvantage of insufficient strength. The conventional powder-compression-molding method needs a large amount of lubricant, serving as a disengaging agent, to easily release an unbaked article from a die and to prevent the die from becoming jammed. However, since the lubricant cannot be completely expelled from the titanium alloy article in the conventional powder metallurgy sintering method, the density of the sintered titanium alloy article is relatively low. The powder-inject-molding method uses titanium powder of smaller diameter as well as a large amount of lubricant much more than in the powder-compression-molding method. To expel the lubricant, a chemical method incorporated with particular equipment has ever been proposed. However, such a chemical method is costly and requires a long processing time. In addition, the titanium alloy article produced by such a sintering and chemical method can only have a density of no more than 95% of theoretical density and a strength inferior to that of the casting method.
On the other hand, with various superior properties, titanium alloy has been applied to various articles such as the frame for glasses and the hitting face of a golf club. In the case of the hitting face, a titanium hitting face manufactured by the casting and cutting method is very expensive. As for the use of the pressing method to alternatively manufacture the hitting face, it has a problem to obtain a well-defined shape. This is one of the reasons that a stepped edge is necessary for a hitting face and the stepped angle for the stepped edge should be very precise so that the hitting face can be fit into a head of a club. Moreover, in case a hitting face is manufactured by the conventional powder metallurgy sintering method, the hitting face is of insufficient strength. Thus, the conventional sintering method is not appropriate to produce a high-quality hitting face. In view of the above, the existing manufacturing methods cannot produce a titanium alloy article having high stability, a more precise pattern, high strength, and high density at a low cost, especially for a hitting face of a club.
SUMMARY OF THE INVENTION
An object of this invention is to provide a method of manufacturing a titanium alloy article having a precise pattern and a high strength at a low cost.
To achieve the above object, the present invention discloses a method of manufacturing a high-density titanium alloy article, comprising:
a mixing and granulating step for mixing titanium powder with other metal powder and granulating the mixed powder into titanium-based grain;
a high-pressure molding step for compressing the granulated titanium-based grain into a particular pattern of unbaked article; and
a high-temperature sintering step for heating the unbaked article at a high temperature so as to form a titanium alloy article.
By means of the above method, since the titanium powder and the other metal powder are mixed and granulated first and then compressed into an unbaked article at a high pressure, the problem of the die jamming can be avoided and a high-density sintered titanium alloy article could be obtained in light of the fact that the binder agent and the lubricant mixed into the unbaked article are completely removed. Moreover, the diameter of the titanium-based grain is preferably larger than 150 mesh, the compressing pressure is preferably higher than 2.8 Ton/cm
2
, and the temperature for sintering is preferably higher than 1200° C. In view of the above conditions, a titanium alloy article having a density near 99% of theoretical density is obtainable.
The advantages and features of this invention can be easily comprehended by persons skilled in the art through the drawings and detailed explanations.
REFERENCES:
patent: 4478790 (1984-10-01), Huther et al.
patent: 5773099 (1998-06-01), Tanaka et al.
patent: 5977033 (1999-10-01), Lefebvre et al.
patent: 6106412 (2000-08-01), Kosugi et al.
Chan Jean
Cheng Chin-Liang
LaRiviere Grubman & Payne, LLP
Mai Ngoclan
New Century Technology Co., Ltd.
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