JPH01180927A - Manufacture of piston - Google Patents

Abstract

PURPOSE:To increase the high temp. strength and wear resistance and to improve the workability and strength in a piston by compounding Al composite material having high compounding rate of ceramic to the top part of the piston and flute part of a piston ring. CONSTITUTION:The matrix consisting of Al alloy powder or fiber is prepd. Two kinds of mixed powder in which <10vf% ceramic powder and 10-25vf% ceramic powder are independently mixed to the matrix are prepd. The above each mixed powder in one layer is subjected to power molding into a two-layer body; it is than subjected to pressure heating to manufacture a preform. The preform as the starting material is then subjected to hot forging and the layer side having high compounding rate of ceramic powder is set on the top side of the piston. The layer side having low compounding rate of ceramic powder is furthermore set on the skirt part side to provide the piston with a shape.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a piston made of a composite material based on an aluminum alloy.

[Prior Art] Pistons for internal combustion engines such as automobiles are often manufactured by forging light alloy materials such as aluminum alloys for the purpose of weight reduction. However, pistons made of light alloy materials generally have low strength, and are often exposed to high temperatures and pressures, resulting in cracks and the like. Therefore, in recent years, attempts have been made to improve the strength by using metal composite materials such as fiber-reinforced metals, but since these materials have poor ductility, plastic working such as forging cannot be easily performed. For this reason, for example, JP-A-56-16636 discloses an alumina fiber-reinforced metal matrix composite material in which the matrix is a superplastic alloy, and JP-A-59-82156 discloses a light alloy material. A method of processing the semi-molten state is disclosed.

[Problem to be solved by the invention]

However, among the above-mentioned conventional techniques, the method of changing the matrix is unfavorable for the material properties of the target member, and the method of processing in a semi-molten state consumes the mold quickly, requires high thermal energy, and There are problems such as low productivity.

BACKGROUND ART Conventionally, in plastic working, it has been known to add a ductile metal around a preform (or edge) by welding or the like in order to prevent edge cracking due to rolling, for example. However, when this method is directly applied to a composite material such as a fiber-reinforced metal, the properties at the interface between the composite material and the ductile metal change significantly (this often leads to interfacial separation and cracking).

The present invention has been made in consideration of these problems, and its purpose is to provide a method for manufacturing a piston that improves moldability and has sufficient strength. It is to be.

[Means to solve the problem]

The piston manufacturing method of the present invention uses aluminum alloy powder or fiber as a base material, mixes ceramic powder with a blending ratio of less than 10 vf% and 10 to 25 vf%, and then forms a layer of each mixed powder into powder. A preform is manufactured by pressurizing and heating the molded two-layer body, and using the preform as a raw material, hot forging is performed so that the layer side with a higher blending ratio of the ceramic powder is the top side of the piston, and the blending ratio is It is characterized by being shaped with the lower side as the skirt portion side.

In this specification, ν is used in relation to ceramic powders.
f% indicates the ratio of the volume occupied by the powder to the volume of the base material.

Moreover, when the ceramic powder has an average particle size of more than 4μ,
It is preferable that the average grain size is 4 μm or less, because not only will cracks easily occur during forging, but the strength improvement effect will be lost.

Furthermore, this ceramic ↓ bundle is 81□O*, SiC
It is preferable to use one or more of the group consisting of SiO□ and SiO□, and SiC is particularly preferable because it has excellent bonding with the matrix.

In addition, in the method of the present invention, a preform consisting of two layers is first manufactured, but at this time, the blending ratio of ceramic powder in one layer is less than 10 νf%, because if it exceeds this, cracks will occur during forging. In order to further desirably reduce the difference in moldability with the other layer, it is preferable that the content is 3 vf% or more. Furthermore, the blending ratio of the ceramic powder in the other layer was set to 10 to 25 vf% because this part is molded and becomes the top side of the screwdriver, so in order to obtain strength and wear resistance, the blending ratio of the ceramic powder was set at 10 to 25 vf%. If it exceeds 25v, the difference in formability with one layer becomes significant.
f% or less.

[Effect]

The piston manufacturing method of the present invention has a preform with a two-layer structure, and the pressurized side of the preform has a ductile layer with a low blending ratio of ceramic powder. The occurrence of cracks can be prevented, and therefore workability can be improved.

In addition, the preform is made into a two-layered body during powder molding, and each layer has a matrix with a common composition.
No peeling occurs at the interface.

Furthermore, the method of the present invention uses an aluminum composite material with a high blending ratio of ceramic powder for the top of the piston, which requires high-temperature strength, and the screw I ring groove, which requires wear resistance, and a composite material with a low blending ratio of ceramic powder for other parts. Pistons can be manufactured by arranging. Therefore, sufficient strength required for the piston can be provided.

[Example] Next, the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

Example 1 Aluminum alloy fibers with a diameter of 60 μm and a length of 3 mm were obtained by chatter cutting from a forged material consisting of 7% by weight Si (hereinafter referred to as %), 1% Cu, 5% Mg, and the balance aluminum.

This fiber was used as a base material, and SiC powder with an average particle size of 2μ was mixed with a vibrating mill at 200 rpm and an amplitude of 9 mm.
Mix and grind for 0 min, 5vf%SiC and 15vf%S
Each iC mixed powder was manufactured.

Next, these mixed powders were preheated to 200°C in the atmosphere, and then put into a φ93 mold 7 that had been preheated to 200°C, as shown in FIG. At this time, add 5vf% SiC mixed powder (No. 11) 1, smooth the surface with the weight of pressure punch 8, and then add 15vf% SiC mixed powder (second layer) 2 to the first layer. were added so that the content ratio was 1:1, and then pressurized at 3 ton/cm2 for 10 seconds.

Furthermore, this preload body was preheated to 550°C, and using a φ93 mold 7 preheated to 500°C, it was heated to 1 at 3 ton/cm2.
Main pressure was applied for 0 seconds to obtain a preform 3 consisting of two layers of φ93×42.

Next, after preheating this preform 3 to 450'C, a mold 9 preheated to 300C is used as shown in FIG.
Then, it was forged into a piston shape using a pressure punch 10 at about 8 ton/cm2. At this time, the second layer 2 having a higher blending ratio of the ceramic powder was placed on the piston top 4 side, and the first layer 1 having a lower blending ratio was placed on the skirt portion 5 side.

In the piston 6 manufactured in this way, cracking at the end and peeling at the interface between the two layers did not occur.

Example 2 Aluminum alloy powder was used as powder of 100μ or less by air atomizing method, and 5vf%81□03
A piston was manufactured in the same manner as in Example 1, except that the content ratio of mixed powder (first layer) and 15 vf% AlO3 mixed powder (second layer) was 1:2. Even in this case, cracking at the edges and peeling at the interface between the two layers did not occur.

Comparative Example 1 A piston was manufactured using only the 5vf% SiC mixture and performing the same operations as in Example 1, but cracks occurred at the ends.

〔Effect of the invention〕

As explained above, the piston manufacturing method of the present invention includes:
The piston is manufactured by placing an aluminum composite material with a high blending ratio of ceramic powder in the top of the piston, which requires high-temperature strength, and in the piston ring groove, which requires wear resistance, and by placing a composite material with a lower blending ratio in other parts. This made it possible. Therefore, a high-strength and lightweight piston can be provided without cracking during hot forging.

Further, since the powder is formed into a two-layered product during powder molding, and each layer has a matrix having a common composition, peeling or the like does not occur at the interface.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the production of a preform in an embodiment of the piston production method of the present invention. FIG. 2 is an explanatory diagram showing the provision of a shape to a piston in an embodiment of the piston production method of the present invention. It is a diagram. In the figure, 1... First layer 2... Second layer 3... Preform 4... Piston top 5... Skirt part 6... Piston -136=

Claims (1)

[Claims] Aluminum alloy powder or fiber is used as a base material, ceramic powder is mixed with this at a blending ratio of less than 10 vf% and 10 to 25 vf%, and then each mixed powder is formed as one layer and a two-layer body is powder-molded and heated under pressure. A preform is manufactured by using the preform as a raw material, and the layer side with a higher blending ratio of the ceramic powder is formed as the top side of the piston, and the layer side with a higher blending ratio of the ceramic powder is shaped as the skirt side by hot forging. A method for manufacturing a piston, characterized by: