Metal treatment – Stock – Magnesium base
Reexamination Certificate
2000-12-04
2004-06-29
Ip, Sikyin (Department: 1742)
Metal treatment
Stock
Magnesium base
C148S272000, C420S409000
Reexamination Certificate
active
06755922
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel Mg based alloy and a novel Mg casting alloy capable of mass producing OA parts, car parts, electric appliance parts and so on through die casting, injection molding or the like, and relates to articles mold-cast using the alloy.
2. Description of the Prior Art
The casting Mg alloys practically used in present time are as follows:
(1) AZ, AM alloys (Mg—Al—(Zn)—Mn system, for example, ASTM: AZ91D);
(2) AS alloy (Mg—Al—Si—Mn system, for example, ASTM: AS41); and
(3) AE, QE, WE alloys (an alloy group containing one or more kinds of REM, Ag, Y).
The alloy (1) is most commonly used as the die casting and the injection molding Mg alloy, and particularly the AZ91D is good in die-castability and in corrosion resistance and widely applied to car parts and electric appliance parts. The alloys (2), (3) are alloys improving the mechanical properties such as the creep property and the high temperature strength. As the prior art in regard to these alloys, various kinds of alloys are disclosed in the following patent gazettes.
For example, Japanese Patent Application Laid-Open No.6-330216 discloses an Mg based alloy containing Ca, Si, Al, Zn and Mn, Japanese Patent Application Laid-Open No.9-104942 discloses an Mg based alloy containing 5 to 10 of Al, 0.2 to 1 of Si and 0.05 to 0.5 of Cu, and Japanese Patent Application Laid-Open No.10-147830 discloses an Mg based alloy containing 1 to 6 of Gd and 6 to 12 of Y.
With growing needs of thin thickness and high precision of parts in order to reduce in weight and size of potable devices, high fluidity alloys have been required. The alloy (1) of AZ91D described above is comparatively high in the fluidity, but the molding yield in injection molding is not always sufficiently high.
The alloy groups (2), (3) are prior to AZ91D in the mechanical properties such as creep property, strength at high temperature. However, because of the bad fluidity, the alloy groups (2), (3) are apt to cause casting cracks in the molding method of high speed cooling such as the injection molding method and are bad in castability.
The fluidity may be improved by raising the temperature of molten alloy. However, raising of the molten alloy temperature has problems in oxidation of the molten alloy and in shortening of durable lifetime of the production machines. Therefore, it is necessary to improve the fluidity by the other method.
It is known that the solidification structure of AZ91D becomes dendritic when it is cooled in a comparatively slow speed such as at ingot casting. As described above, the alloy is designed by placing special emphasis on the molten fluidity, and in regard to the properties after solidification, the alloy is designed so that the various kinds of properties such as the mechanical properties are optimized on the premise that the structure of AZ91D becomes dendritic.
However, in the cases of die casting and injection molding to which the alloy is widely applied, it is known that the structure after solidification becomes the cellular structure not the dendritic structure because the cooling rate is very fast. Therefore, it is required to change the designing method of the conventional alloying composition.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a high strength Mg based alloy and a Mg based casting alloy having a good fluidity and a good mechanical property, and a cast article using the alloy.
As a result of various kinds of studies in order to solve the problems described above, it is found that the melting point of the alloy is lowered and the fluidity is improved by adding appropriate amounts of Al, Sn and Zn to a magnesium alloy, and the present invention is established.
The present invention is characterized by a high strength Mg based alloy, which contains 2 to 20% of Al by weight; 0.1 to 10% of Zn; 0.1 to 15% of Sn; and 0.05 to 1.5% of Mn, or preferably the remainder which is consisting essentially of Mg.
The present invention is characterized by a high strength Mg based alloy, which contains 2 to 20% of Al by weight; 0.1 to 10% of Zn; 0.1 to 15% of Sn; and 0.05 to 1.5% of Mn, and has crystal size of 10 to 300 &mgr;m, or preferably the remainder which is consisting essentially of Mg.
The present invention is characterized by a high strength Mg based alloy, which contains 8 to 20% of Al by weight; 0.1 to 5% of Zn; 0.1 to 10% of Sn; and less than 1.5% of Mn, and has a tensile strength (x) at 20° C. larger than 240 MPa; and an elongation ratio (y) larger than 0.5% and at the same time larger than a value calculated by y=−0.295x+78, or preferably the remainder which is consisting essentially of Mg.
The present invention is characterized by a high strength Mg based alloy, which contains 12 to 15% of Al by weight; 0.1 to 5% of Zn; 1 to 10% of Sn; 0.1 to 0.5% of Mn, and the remainder contains Mg more than 75%, or preferably the remainder which is consisting essentially of Mg.
The present invention is characterized by a high strength Mg based alloy, which contains 12 to 15% of Al by weight; 0.1 to 5% of Zn; 1 to 10% of Sn; 0.1 to 0.5% of Mn; one kind or more than two kinds of elements selected from the group consisting of Ca, Si and rear-earth elements of which the total content is less than 5%; at least one kind of element selected from the group consisting of Sr and Sb of which the total content is less than 1%; or preferably the remainder which is consisting essentially of Mg.
The present invention is characterized by a Mg based casting alloy, which contains 2 to 20% of Al by weight; and 0.1 to 15% of Sn; or preferably the remainder which is consisting essentially of Mg.
The present invention is characterized by a Mg based casting alloy, which contains 2 to 20% of Al by weight; 0.1 to 10% of Sn; and less than 1.5% of Mn, or preferably the remainder which is consisting essentially of Mg.
The present invention is characterized by a Mg based casting alloy, which contains 10 to 15% of Al by weight; 0.5 to 3% of Zn; 1.5 to 4.5% of Sn; 0.05 to 0.5% of Mn, or the remainder which is consisting essentially of Mg.
The present invention is characterized by a Mg based casting alloy which is prepared by that the above-mentioned Mg based casting alloys are added with one kind or more than two kinds of elements selected from the group consisting of Ca, Si and rear-earth elements of which the total content is less than 5% by weight; and at least one kind of element selected from the group consisting of Sr and Sb of which the total content is less than 1%, or the remainder which is consisting essentially of Mg.
The present invention is characterized by a die cast article or injection molding article, which is casted using a molten metal of any one of the alloys described above.
The present invention is characterized by a thixotropic mold article, which is molded using a molten metal of a mixture of liquid phase and solid phase of any one of the alloys described above.
In detail, it is preferable that the magnesium based alloys described above are formed in desirable shapes through die casting by injection molding.
The magnesium alloys in accordance with the present invention are improved in the fluidity due to lowering of the melting point particularly by adding a small amount of Sn to the Mg based alloy containing Al, and accordingly members having less surface defects can be obtained. Further, since low temperature molding can be performed and accordingly the contraction at solidifying is small, members having a high dimensional accuracy can be obtained. Therefore, the molding yield can be largely improved.
Further, since the load to the machines, for example, the cylinder of an injection molding machine or the like is decreased, the durable lifetime of the heat resistant materials can be lengthened.
Furthermore, the magnesium alloys in accordance with the present invention are good in mechanical property and corrosion resistance because of the homogeneous and fine microstructure.
For the purpose of solid-solution harde
Abe Teruyoshi
Hirane Teruo
Nakamura Kiyomi
Uchida Toshio
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Ip Sikyin
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