JPH01180929A - Manufacture of aluminum composite material having lubricative characteristics - Google Patents

Abstract

PURPOSE:To obtain a composite material having excellent wear resistance and compressive strength by interposing a lubricative material in the surface part of the preform body of ceramic short fiber and pouring Al alloy metallic molten metal to the preform body. CONSTITUTION:The short fiber integrated body made of alumina, silica, silicon nitride, silicon carbide, glass, carbon, etc., is prepd. The integrated body is subjected to pressure molding to form a preform body having 5-40vf% volume rate. A part of the surface on the preform body is coated with lubricative material and is dried. The preform body having the interposed lubricative material in its surface part is solidified to a mold. The Al metallic molten metal is then poured to the mold and is pressurized to impregnate the Al metal into voids of the preform body.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing an aluminum-based composite material having lubricity.

[Prior Art] Hiramic materials are used in cutting tools, etc., and have high rigidity and strength, but have poor lubricity and cause significant damage to mating members. In the case of a composite ion material such as a brake friction material, there is an example of using a material in which a hard ceramic phase and a relatively soft matrix metal such as an aluminum alloy are evenly blended to the core. In addition, there are still not many practical examples of aluminum matrix composite materials combined with lolamic substances, but silicon carbide (SIC), alumina (A120
By compounding ceramic particles or short fibers such as 3) into an aluminum alloy, a high-rigidity, high-strength aluminum structure can be obtained, and attempts are being made to apply it to engine parts, etc. In these engine parts, such as pistons, connecting rods, valve lifters, etc., high rigidity and high strength are required for the core portion, and wear resistance and self-lubricating properties are required for the outermost surface portion. Therefore, there are examples in which heat-resistant solid lubricants are uniformly dispersed in the matrix metal, but the lubricity of the surface portion is insufficient. In addition, attempts have been made to apply nickel-iron plating or thermal spraying of molybdenum to the surface of the aluminum composite material in order to impart wear resistance, lubricity, and damage resistance to the surface area, but sufficient lubricity has also been achieved. The current situation is that we are not able to obtain the desired results.

On the other hand, attempts have also been made to impart self-lubricating properties to aluminum-based composite materials containing reinforcing metals as reinforcing materials. For example, JP-A No. 61-104037 discloses that a three-dimensional metal structure mainly composed of Ni or Ni-Cr alloy is coated with or coated with a self-lubricating substance, and then molten aluminum alloy is cast. There is a disclosure of a wear-resistant member having an aluminum alloy as a matrix.

[Problems to be solved by the invention] Therefore, the core part has high rigidity, and the surface part has self-lubricating properties.
There is a desire for an aluminum-based composite material that has good wear resistance and less damage to mating members. Based on this background, we investigated various aluminum alloy a'ti with a hard reinforcing member in the core and a self-lubricating layer on the surface. An aluminum-based composite material obtained by applying a lubricating substance to the LC to form a preform body with LC voids, and then infiltrating the voids with aluminum-based metal by injecting and pressurizing the infiltration of aluminum-based metal. They found that it has excellent properties and high rigidity, and completed the manufacturing method of the present invention. The present invention provides an inexpensive method for manufacturing an aluminum-based composite material having lubricity, which has a ceramic reinforcement in its core and an aluminum-based metal layer containing a lubricating substance on its surface. The purpose is to

[Means for Solving the Problems 1] The method for manufacturing an aluminum-based composite material having lubricity according to the present invention includes a preform body in which a ceramic short fiber aggregate is pressure-molded to form a preform body having voids. body forming step, a coating step D in which a lubricating substance is applied to at least a portion of the surface of the preform body, dried, and the lubricating substance is interposed in the surface portion; a casting process of fixing the preform body in a mold, injecting and pressurizing aluminum-based metal infiltration to impregnate the voids of the preform body with aluminum-based metal to form an aluminum-based composite material; The present invention is characterized by obtaining an aluminum-based composite material having an aluminum-based metal containing a lubricant on its surface.

The preform body of the ceramic short fiber aggregate is:
Composed of glass, metal oxide, metal nitride, and metal carbide short fibers, among which are alumina fiber, silica fiber, glass fiber, silicon nitride fiber, and silicon carbide fiber, which have excellent rigidity and strength.
At least one type of short fiber of carbon-N fiber is used. In order to improve the strength of the aluminum-based composite material, the prene l-6 body preferably has a volume fraction of 5 to 40 vf%. If the volume fraction exceeds 40 vf%, the injection of molten aluminum metal will be insufficient, making it difficult to form an aluminum composite material, which is not preferable. Moreover, if the volume fraction is less than 5 vf%, the preform becomes a dense and dense material, and the resulting aluminum composite material lacks strength, which is not preferable.

In this preform body forming step, the ceramic short fibers are accumulated and a preform body having a desired shape is formed by ordinary pressure molding. Note that the volume ratio is expressed as a percentage of the fiber portion occupied in a preform body having a certain volume.

Lubricating substances include graphite, molybdenum disulfide, tungsten disulfide, tin, lead, cement (CaQ, AI
203, etc.) is formed by applying a mixture of one or more of gypsum, fluorite (CaF2), a binding resin, and a solvent and heating and drying the mixture.

In the coating step, the above-mentioned lubricating substance is made into a fluid with a viscosity that can be coated and is coated on the surface of the preform. This application can be applied by conventional brushing or spraying. Preferably, the coated preform is dried at a temperature below 1 o o'c.

Solvent additives and the like are scattered during this drying process. Further, a part of the binding resin is scattered during injection of the molten metal, and the remaining part forms a layer of a lubricating substance having voids. Aluminum metal is injected into this gap to form an aluminum layer with lubricating properties.

In the casting process, the preform body on which the lubricating material layer with voids is formed is fixed in a predetermined casting mold, and the molten aluminum or aluminum alloy that constitutes the matrix is injected and pressurized to fill the voids. This is a process of uniformly filling a preform in which a lubricant material layer with voids is formed on the surface portion that has lubrication. The filled molded body is machined into a predetermined shape if necessary. Since this molded body contains a lubricating substance and an aluminum-based metal matrix on the surface thereof, it becomes an aluminum-based composite material with sufficient lubricity without surface treatment.

Further, the aluminum-based metal portion formed on the lubricating material layer due to the draft of the casting mold during casting is removed by ordinary machining. Therefore, the sliding surface is an aluminum-based composite material having a surface portion in which a lubricating substance is mixed in an aluminum matrix. It is important that the aluminum matrix layer completely covers the preform of the reinforcing ceramic short fiber aggregate in order to impart wear resistance to the surface area having the lubricating substance. It is undesirable to have a highly rigid reinforcing material on the surface of the composite material because it may cause damage to the other material. Therefore, the coating film of the lubricating substance is preferably applied to a thickness that sufficiently covers the preform.

[Example code] The present invention will be explained below with reference to Examples.

An example of manufacturing a valve lifter, which is one of the components of an automobile engine, will be explained.

(Preform Body Molding Step) Silicon carbide fibers (manufactured by Tokai Carbon Co., Ltd.) having a diameter of 0.4 μm and a length of about 50 μm were gathered and pressed into the rough shape of a valve lifter shown in FIG. 1. The volume fraction of this preform body 1 was 15vf%. This preform body 1 was machined into a preform body 1 having the shape shown in FIG. 2.

(Coating process) Graphite: 2 parts by weight, Molybdenum disulfide: 2 parts by weight, Alumina cement 1 to 3 parts by weight, Phenol resin, 3 parts by weight
A mixed solution (slurry) of a lubricating substance prepared by adding 5 parts by weight of water to a mixture of 5 parts by weight was applied to the outer surface of the preform with a brush to a thickness of 5 mm. 120℃ in coating and drying oven
It was dried by heating for 1 hour. As shown in FIG. 2, a layer 2 of lubricant material having voids on the outer surface was formed.

(Casting process) After fixing the preform body 3 containing the lubricant trout with voids in the casting mold, J) 8707 was melted at 700°C.
After pouring the molten aluminum alloy from the top, 700 kg
The preform body 3 was uniformly filled with an aluminum alloy forming a thickness of 71 to 60 cm by pressurizing the aluminum alloy at a pressure of /cm2. Figure 3 shows the cast material obtained by solidification. This cast material is composed of a composite phase 4 of an aluminum alloy and prefun-6 bodies of ceramic short 4II fiber aggregates, a composite phase 5 of a lubricating substance and an aluminum alloy, and a phase 6 of only an aluminum alloy. Become. This phase 6 consisting only of aluminum alloy was formed due to the draft angle of the casting mold, and this portion was removed by machining. The obtained casting material was cut to a predetermined size to form a valve lifter 7 (shown in FIG. 4), and the following tests were conducted.

(Review) The fracture strength of a valve lifter made of an aluminum-based composite material and a conventional valve lifter made of steel was investigated through wear tests and compression tests. The results are shown in Table 1. The maximum wear depth after a 20-hour durability test (in the presence of lubricating oil) was 12 μm in the example and 8 μm in the steel comparative example, indicating that this aluminum-based composite material has almost the same wear resistance as steel. This shows that it has. In addition, the breaking load of the compression test in the strength test was 1900k (] in the example).

A comparative example made of steel weighs 1800 kg and has the same strength as steel.

Therefore, the aluminum-based composite material obtained by the manufacturing method of the present invention is a lightweight material that can be used as a steel substitute.

Moreover, this aluminum composite material can be applied with a lubricating substance only on the sliding surface to impart self-lubricating properties, and can be used as an ordinary aluminum composite material.

[Effects of the Invention] The method for producing an aluminum-based composite material having lubricity according to the present invention includes: forming a preform of ceramic short fibers; applying a lubricating substance to the culm and the surface of the preform to lubricate the surface portion; By implementing a coating process in which a lubricant is applied and a casting process in which molten aluminum alloy is poured into a preform coated with a lubricant to form a composite material, the wear resistance and compressive strength are compared to steel. You can get something comparable.

Therefore, by using the aluminum-based composite material produced by 1q in this manufacturing method d1, it is possible to produce parts that are significantly lighter in weight. For example, engine valve gear parts can be made lighter, friction loss in rotating bodies can be reduced, and engine performance can be improved. Furthermore, the weight reduction achieved by using aluminum for the valve lifter is expected to improve fuel efficiency by approximately 3 to 5%.

This composite material also contains a lubricating substance on its surface)) Due to the presence of the aluminum layer, the surface layer is relatively soft and has excellent machinability (this makes it easy to machine and allows the production of highly precise parts). .

This manufacturing method is an excellent manufacturing method in which a self-lubricating aluminum-based composite material can be obtained by simply applying a lubricating substance to a preform having voids and injecting molten metal.

[Brief explanation of the drawing]

Figures 1 to 4 are cross-sectional views showing the shape of the valve lifter of the example during the manufacturing process.
The figure shows a preform body coated with a lubricating substance after machining, FIG. 3 a cast body after casting, and FIG. 4 a sectional view of a valve lifter made of an aluminum-based composite material. 1... Preform body 2... Lubricating material layer 3 having voids,... Preform body 4 having a lubricating material layer having voids,... Composite phase 5 of aluminum alloy and preform body, ...Composite tag of aluminum alloy and lubricating substance 1
6. Aluminum alloy phase 7 Valve lifter patent applicant Toyota Motor Corporation representative
Patent Attorney Hiroshi Okawa Figure 1 Figure 2 Figure 1 Figure 3 Figure 4

Claims (4)

[Claims] (1) A preform body forming step in which a ceramic short fiber aggregate is pressure-molded to form a preform body having voids, a lubricating substance is applied to at least a part of the surface of the preform body, and the surface is dried. A coating step in which the lubricant substance is interposed in the preform body, the preform body coated with the lubricant substance and dried is fixed in a casting mold, and molten aluminum metal is injected and pressurized to fill the voids of the preform body with aluminum metal metal. A method for manufacturing an aluminum-based composite material having lubricating properties, the surface portion of which is coated with an aluminum-based metal containing a lubricating substance, the method comprising: a casting process of impregnating aluminum-based metal to form an aluminum-based composite material. (2) The preform body is composed of an aggregate of at least one type of short fibers selected from alumina fibers, silica fibers, silicon nitride fibers, silicon carbide fibers, glass fibers, and carbon fibers, and has a volume percentage of 5 to 40 vf%. A method for producing an aluminum-based composite material having lubricity according to claim 1, characterized in that: (3) The lubricating substance is a mixture of one or more of graphite, molybdenum disulfide, tungsten disulfide, tin, lead, alumina cement, gypsum, and fluorite, a binding resin, and a solvent, and heated to 1000°C after coating. The method for producing an aluminum-based composite material having lubricity according to claim 1, wherein the aluminum-based composite material is formed by drying at a temperature below. (4) The method for manufacturing an aluminum-based composite material having lubricity according to claim 1, wherein the aluminum-based metal is aluminum or an aluminum alloy.