Specialized metallurgical processes – compositions for use therei – Compositions – Consolidated metal powder compositions
Reexamination Certificate
2000-08-04
2001-10-23
Mai, Ngoclan (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Compositions
Consolidated metal powder compositions
C075S236000, C075S243000, C428S547000, C449S014000, C449S029000
Reexamination Certificate
active
06306196
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a sintered Ti-based material product derived from injection molding of a powder material and a producing method thereof, in which the product can be provided with a mirror surface without any cloud by a finish machining of mirror-polishing.
Conventionally, a Ti-based alloy material required to have a mirror appearance has been used for exterior components of clocks or watches, for example. These components have been provided primarily by hot forging and machining of a material derived from the melting and casting process. But, those produced by the conventional method are inferior in the degree of freedom when designing since the forging is unsuitable for producing a product having a complicated form, and also be inferior in anti-scratch property since they must be provided with a limited low hardness for ensuring easy machining. Further, because they need a finishing allowance, the machining cost is expensive.
On the other hand, there has been known the metal powder injection molding (usually called “MIM”) which is a method of producing a sintered body. The method comprises the steps of deforming feedstock by an injection molding machine, the feedstock consisting of a kneaded mixture of a metal powder and an organic binder; preparing a debinded body (brown body) by eliminating the binder from the molded body (green body) by means of an organic solvent or heating (herein below, this step is referred to as “a debinding process”); and heating the debinded body at a high temperature to obtain a sintered body.
The MIM is an excellent mass-production method of a three dimensional complicated form body made of a tough working material such as a Ti-based alloy. There is proposed in JP-A-7-90318 to produce a sintered Ti-based material product.
However, it has been impossible to provide excellent mirror surface to the conventional sintered Ti-based sintered MIM material because a white cloud can not be avoided even after finish mirror-polishing. While there are exterior components of watches as well as a watch frame, which are included in an item that is strictly required to have a mirror surface, until now there has not appeared the exterior components of watches made of the sintered Ti-based sintered MIM material in the market as an alternative of forged products.
BRIEF SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a sintered Ti-based material product derived from injection molding of a powder material which can have a satisfactorily good mirror appearance to users and a producing method thereof, and a producing method thereof.
The present inventors found from examinations that one of causes, which degrade the mirror appearance of a sintered Ti-based material product derived from injection molding of a powder material, is a Ti-based carbide generated from carbon that is inevitably comprised as an impurity. In addition, as a result of further examinations, the inventors found a sintered Ti-based material product derived from injection molding of a powder material with a novel structure, which is prevented from degradation of mirror appearance due to the Ti-based carbide and suitable for mass production.
Thus, according to the present invention, there is provided a sintered Ti-based material product derived from injection molding of a powder material, wherein the outer layer region of the product comprises a lower amount of carbon than the inner layer region.
In the sintered Ti-based material product, preferably the inner layer region comprises a Ti-based carbide having an average grain size of not less than 1 &mgr;m and being dispersed in the inner structure at an area fraction of 0.1% to 20%, whereas the outer layer region comprises a relatively lower amount of the Ti-based carbide than the inner layer region.
Desirably, the present invention is applied to a sintered Ti-based material product derived from injection molding of a powder material which has a carbon amount of 0.2 mass % to 1.0 mass %.
Also desirably, in the invention product, a Ti-based carbide observed on the surface having an average grain size of not less than 1 &mgr;m is present at an area fraction of less than 0.1%.
More preferably, the outer layer region having a lower amount of Ti-based carbide than the inner layer region has a thickness of not less than 0.05 mm.
According to the invention, the surface hardness can be higher than the inner layer region by 15% or more.
The sintered Ti-based material product can be obtained by the producing method according to the invention which comprises any one of the following steps for decomposing a Ti-based carbide residing at the surface of the Ti-based material:
a) the Ti-based material is sintered at a temperature of not lower than 1350° C., and
b) the Ti-based material is subjected to a heat treatment at a temperature of not lower than 1350° C. after sintering.
REFERENCES:
patent: 3802939 (1974-04-01), Ohtani et al.
patent: 3841848 (1974-10-01), Kasai
patent: 4606767 (1986-08-01), Nagato
patent: 5403374 (1995-04-01), Kitagawa et al.
patent: 5403411 (1995-04-01), Smith et al.
patent: 5441695 (1995-08-01), Gladden
patent: 5545248 (1996-08-01), Tokumoto et al.
patent: 6027686 (2000-02-01), Takahashi et al.
patent: 7-62466 (1995-03-01), None
patent: 7-90318 (1995-04-01), None
patent: 9-13153 (1997-01-01), None
Patent Abstract of Japan 07062466 Mar. 7, 1995.
Patent Abstract of Japan 09013153 Jan. 14, 1997.
Patent Abstract of Japan 07090318 Apr. 4, 1995.
Date Kenji
Kubo Yutaka
Morimoto Yoshifumi
Hitachi Metals Ltd.
Mai Ngoclan
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
Sintered Ti-system material product derived from injection... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Sintered Ti-system material product derived from injection..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Sintered Ti-system material product derived from injection... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2587394