Composited cast member, iron-based porous substance for composited cast members, and pressure casing processes for producing the same, constituent member of compressors provided with composited cast members and the compressors

Abstract

A pressure casing includes a composited cast member. The composited cast member includes an iron-based porous substance whose major component is Fe and which has a large number of pores, and a cast-wrapping member whose major component is a light metal and which cast-wraps a part of the iron-based porous substance at least. The iron-based porous substance includes a connector disposed adjacent to a boundary between the iron-based porous substance and the cast-wrapping member and exhibiting a larger porosity, and a high-strength reinforcer disposed in the iron-based porous substance free from the connector and exhibiting a smaller porosity. The connector is impregnated with the cast-wrapping member, and solidifies therewith, thereby firmly bonding the iron-based porous substance and the cast-wrapping member in the composited cast member. The pressure casing secures strength with the reinforcer, and secures adhesiveness with the connector.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a composited cast member in which an iron-based porous substance is wrapped with a light alloy, an iron-based porous substance used in the composited cast member, a pressure casing provided with the composited cast member, processes for producing the same, a constituent member of compressors, an example of the composited cast member or pressure casing, and the compressors. [0003] 2. Description of the Related Art [0004] In view of weight saving, outputting higher power and recycling, raw materials for various component parts are changing from iron-based materials, such as iron, steels and cast steels, to light metallic materials, such as aluminum alloys and magnesium alloys. However, when such light alloy materials substitute for the entire component members, it is difficult to secure strength, rigidity, slidability, wear resistance and durability. Accordingly, composited cast produc...

AI Technical Summary

Benefits of technology

[0021] Secondly, the iron-based porous substance according to the present invention comprises the reinforcer in addition to the connector. The reinforcer exhibits high strength, because it exhibits a smaller porosity and higher density, that is, because the Vf of the reinforcer is high. Therefore, the iron-based porous substance comprising the reinforcer can fully reinforce the cast-wrapping material of relatively low strength. Note that the reinforcer is disposed in the iron-based porous substance free from the connector, but all of the iron-based porous substance free from the connector cannot necessarily be turned into the reinforcer. As far as the strength required for composited cast members is secured depending on their applications, the position or proportion of the reinforcer do not matter. For example, when the entire surface of the iron-based porous substance is cast-wrapped by the cast-wrapping member completely, the connector can be disposed on the entire outer peripheral surface of the iron-based porous substance, and the reinforcer can be disposed at the center or in the middle of the iron-based porous substance. When only one of the opposite surfaces of the iron-based porous substance is cast-wrapped by the cast-wrapping member, the connector can be disposed on the opposite surface of the iron-based porous substance, and the reinforcer can be disposed on the other one of the opposite surfaces of the iron-based porous substance.

[0022] Thus, the present composited cast member fully secures the adhesiveness between the iron-based porous substance and the cast-wrapping member. Simultaneously therewith, the iron-based porous substance demonstrates the reinforcement effect stably and securely, because the iron-based porous substance comprises the high-strength reinforcer. (Process for Producing Composited Cast Member)

[0034] In the present production process, the powder compacts whose porosities differ with each other are formed independently of each other. Accordingly, the degree of freedom enlarges in controlling the porosities, or in selecting raw materials to be used. As a result, the porosities or strengths can be controlled with ease depending on the parts of the resulting iron-based porous sintered substance, and consequently it is easy to produce the iron-based porous sintered substance whose porosity or strength is optimized. Note that the laminated powder compact produced after the laminating step and the iron-based porous sintered substance comprise two layers at least, but can naturally comprise three layers or more.

[0038] In the present production process, the pore-making material is mixed abundantly in the portion (i.e., the first powdery portion) which is turned into the connector in the powder compact so that the portion is adapted to the connector whose porosity is larger after sintering. In the present production process, it is possible to readily control the porosity of the iron-based porous sintered substance produced after sintering by changing the mixing proportion of the pore-making material. Moreover, not only it is easy to control the porosity of the iron-based porous sintered substance, but also it is easy to control the strength of the iron-based porous sintered substance at parts thereof. In addition, the present production process is very efficient, because the forming step can be finished at once in the following manner. Specifically, the ferrous powder and pore-making material whose mixing proportions are changed at the parts of the resulting iron-based porous sintered substance are formed by simply pressing them immediately after filling them into the cavity of forming molds.

[0046] The present pressure casing fully secures the adhesiveness between the iron-based porous substance and the cast-wrapping member in the same manner as the above-described composited cast member. Simultaneously therewith, the iron-based porous substance demonstrates the reinforcement effect stably and securely, because the iron-based porous substance comprises the high-strength reinforcer. Thus, the present pressure casing effects not only the advantages of weight saving but also sufficient strength.

Problems solved by technology

However, when such light alloy materials substitute for the entire component members, it is difficult to secure strength, rigidity, slidability, wear resistance and durability.

However, it cannot necessarily be said that the weight saving of cylinder blocks is fully achieved when sleeves made of cast steels are cast-wrapped by light metallic materials.

Moreover, in this instance, the adhesiveness is poor at the interface between cast-steel sleeves and cast-wrapping members composed of light metallic material, such as aluminum alloys, for example, and consequently the cast-steel sleeves and cast-wrapping members might be separated at the interface during the service as cylinder blocks.

When the porosity of iron-based porous substances is large, that is, when the volume fraction of iron (Vf) is less, such iron-based porous substances cannot demonstrate a sufficient reinforcement effect naturally.

Accordingly, the adhesiveness between iron-based porous substances and cast-wrapping members are likely to degrade.

Consequently, it is hardly possible to expect to strengthen composited cast members as a whole.

However, it is not preferable to add harmful Be.

As a result, although the resulting composited cast members can secure wear resistance as cylinder liners, it is hardly expected for the porous substances to produce the reinforcement effect as expected from composited cast members as a whole.

The use of composite materials is not suitable for mass-produced products which are required to be produced at low cost, because ceramic fibers, the reinforcement members, are expensive.

Moreover, component parts using composite materials exhibit poor processability, because ceramic fibers are very hard.

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