Metal founding – With product severing or trimming means
Reexamination Certificate
1999-10-06
2001-02-20
Lin, Kuang Y. (Department: 1722)
Metal founding
With product severing or trimming means
C164S312000
Reexamination Certificate
active
06189600
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and apparatus for the production of an amorphous alloy article formed by metal mold casting under pressure.
2. Description of the Prior Art
The single roll method, twin roll method, gas atomizing method, etc. are adopted for the production of amorphous alloy because this production generally necessitates a high cooling rate falling in the approximate range of 10
4
-10
6
K/s. The products obtained by such methods are limited in shape to ribbons of foil, fine wires, and particles. This fact constitutes itself a factor for rigidly limiting the field of applications found for amorphous alloy.
Feasibility studies are under way, therefore, regarding a method of producing a formed article of amorphous alloy with a large thickness by shaping an amorphous alloy prepared in the form of powder by some means such as extrusion or impact compression at a temperature not exceeding the crystallization temperature of the alloy. The production by this method, however, requires complicated steps such as sieving the powder, degasing the prepared powder, and preforming the powder prior to the main forming and calls for expensive facilities as well. This method, therefore, is at a disadvantage in inevitably furnishing only expensive products.
As a means for producing a formed article of amorphous alloy by a simple process unlike such powder molding process, published Japanese Patent Application, KOKAI (Early Publication) No. 8-199,318 discloses a method for the production of a rod or tube of a Zr-based amorphous alloy by disposing a forced cooling casting mold having a molding cavity fitted with a molten metal transfer tool on the bottom of a hearth opened on the top side, melting a zirconium alloy containing an element capable of conferring amorphousness on the alloy in the hearth, then extracting the molten metal transfer tool downwardly thereby transferring the melt of the zirconium alloy into the forced cooling casting mold, and rapidly cooling and solidifying the melt of zirconium alloy in the forced cooling casting mold thereby conferring amorphousness on the zirconium alloy.
According to the method described above, however, the cast products have their shapes limited to rods or tubes because their shapes are restricted by the shape of the molten metal transfer tool and the method of extraction of this tool. Further, this method is incapable of substantially pressing the molten alloy because the transfer of the molten alloy is induced simply by the extraction of the molten metal transfer tool. The method, therefore, incurs difficulty in yielding formed articles which are delicate or complicate in shape and the products thereof have room for improvement in terms of denseness and mechanical properties.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a method which, owing to the combination of a technique based on the conventional metal mold casting process with the quality of an amorphous alloy exhibiting a glass transition region, allows a formed article of amorphous alloy satisfying a stated shape, dimensional accuracy, and surface quality despite complexity or delicateness of shape to be mass-produced with high efficiency by a simple process and, therefore, enables the production of even a precision machined article to omit or diminish markedly such machining steps as grinding and consequently provide an inexpensive formed article of amorphous alloy excelling in durability, strength, and resistance to impact.
It is another object of the present invention to provide an apparatus of relatively simple construction which fits the production of such formed article of amorphous alloy as mentioned above.
To accomplish the objects described above, according to the first aspect of the present invention, there is provided a method for the production of a formed article of amorphous alloy, which method is characterized by comprising melting an alloying material capable of yielding an amorphous alloy in a melting vessel, forcibly transferring the resultant molten alloy into a forced cooling casting mold provided with at least one molding cavity and meanwhile exerting pressure on the molten alloy, and rapidly cooling and solidifying the molten alloy in the forced cooling casting mold to confer amorphousness on the alloy thereby obtaining a formed article of an alloy containing an amorphous phase.
In a preferred embodiment, the steps mentioned above are carried out in a vacuum or under an atmosphere of inert gas. In another preferred embodiment, the formed article of an alloy containing an amorphous phase is obtained by melting an alloying material capable of yielding an amorphous alloy in a melting vessel having an upper open end, forcibly transferring the resultant molten alloy into the forced cooling casting mold provided with at least one molding cavity via a sprue thereof and meanwhile exerting pressure on the molten alloy, rapidly cooling and solidifying the molten alloy in the forced cooling casting mold thereby conferring amorphousness on the alloy and meanwhile gradually cooling and solidifying the molten alloy in the part of the sprue of the forced cooling casting mold thereby crystallizing the alloy in that part, cutting the part which has been embrittled by the crystallization, and thereafter separating the melting vessel from the forced cooling casting mold.
The forced transfer of the molten alloy into the forced cooling casting mold can be preferably effected by a method which comprises disposing movably in the melting vessel a molten metal transferring member adapted to effect forced transfer of the molten alloy and forcibly transferring the molten alloy held in the melting vessel into the forced cooling casting mold and meanwhile exerting pressure on the molten alloy now filling the molding cavity of the forced cooling casting mold by means of the molten metal transferring member.
Another method available for this purpose comprises disposing preparatorily the molten metal transferring member movably in the forced cooling casting mold and moving the molten metal transferring member so as to generate negative pressure inside the molding cavity and consequently induce forced transfer of the molten alloy into the molding cavity. In one preferred embodiment of this method, the molten metal transferring member to be used is furnished with a cross section conforming to that of the molding cavity of the forced cooling casting mold and slidably disposed in the molding cavity. The exertion of pressure on the molten alloy filling the molding cavity is attained by applying a pressurized gas to the molten alloy via the sprue.
In any of the methods described above, as the alloying material mentioned above, an alloy which possesses a composition represented by the following general formula and which is capable of yielding an amorphous alloy having a glass transition region of a temperature width of not less than 30K is advantageously used.
X
a
M
b
Al
c
wherein X represents either or both of the two elements, Zr and Hf, M represents at least one element selected from the group consisting of Mn, Fe, Co, Ni, and Cu, and a, b, and c represent such atomic percentages as respectively satisfy 25≦a23 85, 5≦b≦70, and 0<c≦35. This amorphous alloy contains an amorphous phase in a volumetric ratio of at least 50%.
In accordance with the second aspect of the present invention, there is provided an apparatus which can be suitably used for producing such formed article of amorphous alloy as mentioned above.
The first embodiment of the apparatus of the present invention for the production of the formed article of amorphous alloy is characterized by comprising a forced cooling casting mold which is provided in the lower part thereof with a sprue and in the inner part thereof with at least one molding cavity communicating with the sprue through the medium of a runner and further provided with a cutting member disposed in the casting mold movably in the direction of the sprue;
Nagahora Junichi
Taniguchi Takeshi
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Lin Kuang Y.
YKK Corporation
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