Metal founding – Process – Shaping liquid metal against a forming surface
Reexamination Certificate
1999-12-29
2003-05-20
Elve, M. Alexandra (Department: 1725)
Metal founding
Process
Shaping liquid metal against a forming surface
C164S900000
Reexamination Certificate
active
06564854
ABSTRACT:
BACKGROUND OF THE INVENTION
Present invention relates to parts formed by injection molding with semi-solid particulate metal or alloy and manufacturing method thereof. More particularly, when semi-solid particulate metal is injected into a mold to form parts in a desired shape, it is arranged such that a liquid phase of the semi-solid particulate metal is distributed to a surface portion of the parts and a solid phase of the semi-solid particulate metal is distributed to an internal portion of the parts, so that each of the physical properties of the material, attributed to each chemical composition of the liquid phase portion and solid phase portion, can be utilized as a function of the parts.
Generally, parts manufactured by die casting or gravity casting (casting by slowly pouring molten raw material into a cast) with aluminum and magnesium alloy as raw materials have virtually homogeneous chemical composition on the surface and inside, and the material characteristic rarely changes. Therefore, characteristics such as wear resistance and corrosion resistance required on a surface of molded parts are usually different from high flexibility or the like required for an internal portion of the parts, and it is considered difficult to attain both characteristics simultaneously.
In contrast, a technique has been proposed to partially provide wear resistance to molded parts, where a rigid porous material such as ceramic fiber or the like is located at a predetermined position inside a mold and a molten alloy is poured into the mold and pressed inside the mold to compound the porous material with the molded parts.
Moreover, it is a well-known technique which enables SiC (silicon carbide) particles to be concentrated at a particular portion with high density by setting a filter at a predetermined position inside a mold, pouring a molten alloy into the mold and pressing the molten alloy inside the mold, where large particles such as non-metal material or the like are scattered, to be molded (Japanese Patent Application Laid-Open No. 3-5063).
Furthermore, a method has been suggested where magnesium alloy material is half molten to have a solid phase rate of 60% or less, injected to a mold to form a cast product, and then a plasticizing process is performed thereon to form a molded product (Japanese Patent Application Laid-Open No. 6-297127).
In the foregoing injection molding with semi-solid particulate metal (hereinafter referred to as semi-solid injection molding), semi-solid alloy includes both a solid phase portion and a liquid phase portion, each of which has different chemical compositions and has the following characteristics. That is:
{circle around (1)} In aluminum-magnesium (hereinafter referred to as Al—Mg) magnesium alloys, the solid phase portion has a small amount of aluminum (hereinafter referred to as Al) component, and the liquid phase portion has a large amount of Al component;
{circle around (2)} In aluminum-silicon (hereinafter referred to as Al—Si) aluminum alloys, the solid phase portion has a small amount of silicon (hereinafter referred to as Si) component, and the liquid phase portion has a large amount of Si component.
In the above described technique for partially providing wear resistance to molded parts, since the porous material needs to be preliminarily heated or to be maintained at more than a predetermined temperature in order be located in a mold, such processing causes a reduction in production efficiency.
Further, in the semi-solid injection molding, compositions of the material one different in the solid phase portion and the liquid phase portion. It is possible to change characteristics of the material on the surface and inside portion of molded parts by varying the arrangement of the solid phase portion and liquid phase portion. However, there has been no art suggested to positively achieve the above.
For instance, when the semi-solid injection molding is applied to Al—Mg magnesium alloys, a liquid phase portion which has relatively large amount of Al component tends to exist in the surface of molded parts. Although this characteristic can be utilized to provide corrosion resistance to the surface, there has been no art suggested to constructively arrange Al component included in the liquid phase portion to a portion where high corrosion resistance is required. Therefore, corrosion of parts could not be further prevented.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above situation, and has as its object to provide parts formed by injection molding with semi-solid material and manufacturing method thereof for constructively arranging a liquid phase portion to those portions that require high corrosion resistance such as a surface of parts formed by semi-solid injection molding, in order to enhance corrosion resistance and wear resistance, and to readily obtain molded parts having different material characteristics between a surface portion and an internal portion.
In order to solve the above problem and attain the foregoing objective, the present invention provides a manufacturing method of parts molded by injecting half-molten alloy material including a solid phase portion and a liquid phase portion into a mold, characterized in that a layer comprising the liquid phase portion is partially formed in a predetermined portion of the parts.
Further, parts molded by semi-solid injection molding according to the present invention have the following characteristic. That is, the parts are molded by injecting semi-solid alloy material including a solid phase portion and a liquid phase portion into a mold, and characterized in that a layer comprising of the liquid phase portion is partially formed in a predetermined portion of the parts.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.
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Partial English translation of JPA 8-120390, paragraphs 13 through 15.
Hirabara Shoji
Sakamoto Kazuo
Sakate Nobuo
Yamamoto Yukio
Elve M. Alexandra
Mazda Motor Corporation
Tran Len
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