JPH10287935A - Wear resistant metal matrix composite body and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a wear resistant metal matrix composite body excellent in wear resistance and seizure resistance by composing it of porous grain formed body consisting of a granular hard material and a metal matrix impregnated into the gaps of the inside and solidified and exposing the hard grain formed body from the metal matrix. SOLUTION: A hard grain formed body 1 by fly ash composed of a granular hard material is arranged in the cavities of a die, and, with molten metal of Al, Mg, Fe, Cu or the like as a matrix, die casting is executed. The molten metal of Al or the like is impregnated into the gap part of the hard grain formed body 1, which is cooled to form a metal matrix, by which a metal matrix composite body is produced. This metal matrix composite body is previously machined into a prescribed shape, and thereafter, the surface layer part of the metal matrix 2 is eluted to obtain a wear resistant metal matrix composite body 7 in which the hard grains 11 are exposed in three dimensions from the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a cylinder block for an internal combustion engine,
The present invention relates to a wear-resistant metal composite used for a member requiring wear resistance, such as a piston, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a wear-resistant metal composite has been used for a sliding portion of a cylinder block of an internal combustion engine. Conventionally, as such a wear-resistant metal composite, for example,
As disclosed in Japanese Patent Application Laid-Open No. 7-33089, there is a fiber-reinforced composite material comprising an inorganic fiber and a light alloy matrix in which the matrix is eluted to elute the inorganic fiber.

[0003] As disclosed in Japanese Patent Publication No. 6-84527, there is a composite material using alumina-silica fiber as a reinforcing fiber, in which a matrix is electrolytically etched. According to these conventional wear-resistant metal composites, it is said that abrasion resistance and seizure resistance can be further improved by positively exposing the reinforcing fibers from the matrix.

[0004]

In each of the above-mentioned conventional wear-resistant metal composites, a reinforcing fiber is contained in a matrix.
In addition, the reinforcing fibers are positively exposed from the matrix surface. Aggressive exposure of the reinforcing fibers can improve abrasion resistance and seizure resistance as compared with the case where the reinforcing fibers are not exposed. However, the effect of improving the wear resistance and the seizure resistance is not yet sufficient. In particular, for various sliding parts and the like in which the use environment becomes increasingly severe, further improvement in wear resistance and the like is desired.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional needs, and has as its object to provide a wear-resistant metal composite having better wear resistance and seizure resistance than the conventional one, and a method of manufacturing the same. .

[0006]

According to the first aspect of the present invention, there is provided a porous hard particle molded article formed by molding a hard particle having a predetermined shape into a predetermined shape, and a solidified solid body which is impregnated into voids inside the hard particle molded article. The hard particles are three-dimensionally exposed on the surface of the metal matrix.

What is most remarkable in the present invention is that the hard particles having the above particle shape are used, and the hard particles are positively protruded from the metal matrix to be three-dimensionally exposed.

As the hard particles, those having a particle shape which is higher in hardness than the metal matrix and excellent in wear resistance are used. Here, the particle shape has a small difference in width and length and is distinguished from fiber. Further, the particle size of the hard particles is preferably 1 to 100 μm. 1μ
If it is less than m, it may fall off when the metal matrix is three-dimensionally exposed. On the other hand, 100μ
If it exceeds m, the distance between the protruding particles becomes too wide, and it is difficult to form a uniform sliding surface.

The length of the hard particles protruding from the metal matrix is preferably 1 to 15 μm.
If it is less than 1 μm, there is a problem that the effect of improving wear resistance is small, while if it is more than 15 μm, there is a problem that hard particles having a small particle diameter fall off.

Next, the operation of the present invention will be described. In the wear-resistant metal composite of the present invention, the hard particles are positively protruded from the metal matrix and are three-dimensionally exposed. Here, the hard particles have a particle shape as described above. Therefore, the exposed state of the hard particles can be made to be a uniform exposed state as compared with the case where a fiber such as a conventional reinforcing fiber is used.

That is, in a conventional composite using reinforcing fibers, since the hardening material is a fiber, the exposed volume varies greatly depending on the direction in which it is contained. Specifically, when the tip of the fiber is exposed, the exposed volume is small, while when the side surface of the fiber is exposed over the entire length, the exposed volume is large. Therefore, the exposed state of the hardening material cannot be made very uniform.

On the other hand, since the hard particles are in the form of particles, the exposed volume hardly depends on the direction in which the hard particles are contained. Therefore, by using the hard particles as a hardening material, the hardening material (hard particles) can be more uniformly exposed than in the case of a fiber.

Therefore, when the wear-resistant metal composite of the present invention is used as a sliding part, only the hard particles can be uniformly contacted without contacting the metal matrix with the mating member. As a result, the wear-resistant metal composite of the present invention can improve the wear resistance due to the excellent properties of the hard particles and can surely prevent the wear and seizure of the metal matrix.

The surface of the wear-resistant metal composite is
The hard particles are formed into a uniform uneven shape by three-dimensional exposure. Therefore, the lubricating oil supplied during sliding is
It is easy to be held in the recess on the surface of the wear-resistant metal composite,
Lubrication characteristics can be greatly improved. Therefore, in the wear-resistant metal composite of the present invention, the wear resistance and the seizure resistance can be improved from the viewpoint of lubrication.

Further, the wear-resistant metal composite of the present invention comprises:
The hard particles are formed into a compact and impregnated with a metal matrix. Therefore, the overall strength can be improved as compared with the case where the hard particles are dispersed in the metal matrix in the unit of particles, and the characteristics as the wear-resistant metal composite can be further improved.

Next, it is preferable that the hard particles are fly ash. In this case, fly ash can be obtained at very low cost.
The cost of the wear-resistant metal composite can be significantly reduced. Here, fly ash means fine-grain ash generated by combustion, and includes coal ash. As fly ash, for example, blast furnaces of power companies, cast iron factories, etc.
There is dust and coal ash collected in the dust collecting furnace.

Also, fly ash is generally 0.1 μm.
m to several hundred μm particle size. Therefore, it is preferable to classify fly ash into an appropriate size before molding. Thereby, uniform characteristics of the wear-resistant metal composite can be obtained. For example, if the particle size of fly ash is 1
When the classification is performed in the range of 100 μm to 100 μm, a sliding surface with little aggregation of fly ash and little aggressiveness of the metal composite against a mating member can be obtained.

On the other hand, if the particle size of the fly ash is less than 1 μm, the fly ash tends to agglomerate in the fly ash compact, and the sliding surface may be uneven. If the particle size of the fly ash exceeds 100 μm, the aggressiveness of the metal composite on the mating member increases, and the abrasion of the mating member may increase.

Further, as in the invention of claim 3, the metal matrix is one or more selected from the group consisting of aluminum (Al), magnesium (Mg), iron (Fe) and copper (Cu). It is preferred that Since these metals are relatively inexpensive and have characteristics such as strength and weight, an optimal wear-resistant metal composite can be obtained by selecting them according to the application. In addition, the metal mentioned here is a concept including an alloy mainly composed of the metal. For example, aluminum is a general term for pure aluminum and aluminum alloy.

Next, there is the following invention as a method for producing the above-mentioned excellent wear-resistant metal composite. That is, claim 4
As described in the invention, the hard particles in the form of particles are formed into a predetermined shape to form a porous hard particle molded body, and then the metal is impregnated in the voids inside the hard particle molded body and solidified to form a metal. There is a method for producing a wear-resistant metal composite, which comprises forming a matrix and then eluting a surface layer of the metal matrix to three-dimensionally expose the hard particles on the surface.

The hard particles are formed by, for example, forming by a slurry method or compression forming. In this case, it is preferable to form the shape as close to the product shape as possible so that the post-processing is easy. Next, the impregnation of the metal into the hard particle molded body can be performed, for example, by placing the hard particle molded body in a casting mold, and then casting the metal by pressing the metal. Then, the metal matrix is obtained by solidifying the impregnated metal.

Next, the elution treatment of the metal matrix can be performed by, for example, a method of dipping the entire metal matrix in a bath of an etching solution, or a method of applying an etching solution to a desired surface of the metal matrix. The etching solution is selected according to the type of metal in the metal matrix. In this case, a material which is easier to etch metal than hard particles is selected. For example, when the metal is an aluminum alloy, hydrofluoric acid, sodium hydroxide, nitric hydrofluoric acid or the like is used. Then, by performing the above-mentioned elution treatment, the metal matrix is selectively etched, so that the hard particles are three-dimensionally exposed.

As described above, the hard particles can be easily three-dimensionally exposed by performing the above-mentioned elution treatment after molding the above-mentioned hard particle molded body. Therefore, according to the present manufacturing method, the above excellent wear-resistant metal composite can be easily manufactured.

Next, it is preferable that the hard particles are fly ash. In this case, the production cost can be reduced by using inexpensive fly ash.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment A wear-resistant metal composite and a method of manufacturing the same according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the wear-resistant metal composite 7 of the present embodiment has a porous hard particle molded body 1 formed by molding a hard particle 11 having a particle shape into a predetermined shape, and the inside of the hard particle molded body 1. It consists of a metal matrix 2 which has been impregnated into the voids and solidified.
The hard particles 11 are three-dimensionally exposed on the surface of the metal matrix 2.

In the wear-resistant metal composite 7 of this example, fly ash was used as the hard particles 11, and an aluminum die-cast alloy (JIS standard ADC12) was used as the metal for the metal matrix 2. In producing such a wear-resistant metal composite 7, a hard particle molded body 1 was first produced as shown in FIG. Specifically, fly ash was classified to a particle size of 1 to 40 μm, and a binder 13 was added thereto to form a mixture. Next, the mixture was formed into a disk shape by a slurry method to obtain a hard particle molded body 1.

Next, as shown in FIG. 3, the hard particle molded body 1 was placed in the cavity 30 of the mold 3. Next, the molten aluminum die-casting alloy 22 was injected into the cavity 30, and was pressed from above the cavity 30 by the upper die 31 at a pressure of 600 kg / cm ² . Thereby, the aluminum die-cast alloy 22 is impregnated into the voids of the hard particle molded body 1. Then, by cooling, the aluminum die-cast alloy 22 solidifies to become the metal matrix 2, and a metal composite in which the hard particle molded body 1 is 20% by volume and the metal matrix 2 is 80% by volume is obtained.

Next, the surface layer of the metal matrix 2 in the metal composite is eluted. However, in the present example, the elution treatment was performed after the metal composite was cut in advance and brought into a desired shape. As shown in FIG. 4, the elution treatment was performed by immersing the entire metal composite 79 in a bath 8 filled with an etching solution 81 maintained at about 55 ° C. for 60 seconds. Thereby, as shown in FIG. 1, the surface layer portion of the metal matrix 2 was eluted, and the hard particles 11 were three-dimensionally exposed from the surface, whereby the wear-resistant metal composite 7 was obtained.

In this example, in order to remove the smut adhered to the surface by the above-mentioned elution treatment, the wear-resistant metal composite 7 was further immersed in a smut removing liquid kept at about 55 ° C. for 30 seconds. Further, the etching solution 81 used in this example is Top Alsoft 108 manufactured by Okuno Pharmaceutical Co., Ltd.
(Trade name), Smut remover is Top AD manufactured by Okuno Pharmaceutical Co.
D320 (product name).

In the wear-resistant metal composite 7 obtained by such a series of manufacturing methods, as shown in FIG.
When the sliding surface 70 when used as a sliding part is hard particles 1
It is provided at one protruding tip position. Therefore, the mating member is supported by the hard particles 11, and direct contact between the mating member and the metal matrix 2 can be reliably prevented. Therefore, excellent wear resistance and seizure resistance of the wear-resistant metal composite 7 are ensured.

Further, the lubricating oil at the time of sliding tends to be held in the concave portion formed by the projection of the hard particles 11. Therefore, the wear-resistant metal composite 7 can always ensure a good supply state of the lubricating oil during sliding, and can also improve the wear resistance from the lubricated surface.

Embodiment 2 In this embodiment, the wear resistance of the wear-resistant metal composite 7 obtained in Embodiment 1 was quantitatively evaluated. In performing this evaluation, as shown in Table 1, three types of comparative products C1 to C3 were prepared in addition to the wear-resistant metal composite 7 of the first embodiment (product E1 of the present invention).

The comparative product C1 is a metal composite 79 prepared by the same method as that of the first embodiment without using a dissolution treatment. The comparative product C2 uses alumina-silica-based fibers in place of the hard particles 11, and the other components are the same as those in the first embodiment. Therefore,
In the comparative product C2, the alumina-silica fiber was three-dimensionally exposed on the surface of the metal matrix. Comparative product C3 uses the metal complex before elution treatment of comparative product C2 as it is.

The wear resistance was evaluated using a vertical reciprocating sliding wear tester 5 as shown in FIG. Specifically, first, lubricating oil was applied to the sliding surface 70 of the wear-resistant metal composite 7. Next, after wiping off excess lubricating oil, the wear-resistant metal composite 7 is fixed to the fixture 52 and the heater 5
1 to 100 ° C.

Next, the sliding surface 7 of the wear-resistant metal composite 7
0, the mating member 56 reciprocatingly moves the pressing load 20
N was added and slid. The mating member 56 was fixed by the holder 57 and slid at a sliding speed of 200 times / min. The mating member 56 is made of a material that assumes a piston ring formed by chrome plating SWOSC-V (JIS standard). At this time, the load applied to the fixture 52 from the wear-resistant metal composite 7 was detected by the load cell 53. From the detected load, the friction coefficient μ of the wear-resistant metal composite 7 was determined.

In this test, the wear-resistant metal composite 7
Was continued until burning occurred in principle, and the time until burning occurred was determined. The determination of the seizure time was made on the basis of the point at which the friction coefficient μ suddenly increased. Such a test was performed for each test product (E1, C1 to C3). Table 1 shows the results. In addition to these abrasion resistance tests, the surface roughness of each specimen before the sliding test was measured. Table 1 also shows the results of the surface roughness measurement.

[0037]

[Table 1]

As can be seen from Table 1, the product E1 of the present invention
Does not cause seizure even after 1116 minutes of test time,
It showed very good abrasion and seizure resistance. on the other hand,
The other comparative products C1 to C3 all caused seizure within 57 minutes. In addition, the coefficient of friction of the product E1 of the present invention using fly ash, which is a hard particle in particle shape, was higher than that of the comparative product C2 using fibers when comparing the metal matrix eluted (E1, C2). It showed a low value. Those that have not eluted the metal matrix (C
1, C3), the coefficient of friction of the comparative product C1 using fly ash was lower than that of the comparative product C3 using fiber.

From the above results, first, it is understood that the use of hard particles in the form of particles as the hardening material can significantly reduce the friction coefficient as compared with the case where fibers are used. Furthermore, since the product E1 of the present invention exhibited better wear resistance and seizure resistance than the comparative product C1, it was necessary to positively and three-dimensionally expose the hard particles from the metal matrix to obtain wear resistance and seizure resistance. It can be seen that this is extremely effective as a means for improving. It is considered that the reason for this is that the metal matrix can be reliably prevented from contacting the mating member, and that the lubrication characteristics can be improved by improving the lubricating oil holding power.

Therefore, according to the present embodiment, a hardened material of a particle-shaped hard particle (fly ash) is used as a hardening material, and the hard particle is positively exposed three-dimensionally, thereby providing abrasion resistance and seizure resistance. It has been clarified that a wear-resistant metal composite having extremely excellent properties can be obtained.

[0041]

As described above, according to the present invention, it is possible to provide an abrasion-resistant metal composite having better abrasion resistance and seizure resistance than before, and a method for producing the same.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a cross section of a wear-resistant metal composite according to a first embodiment.

FIG. 2 is an explanatory view showing a cross section of a hard particle molded body according to the first embodiment.

FIG. 3 is an explanatory view showing a method for casting a wear-resistant metal composite according to the first embodiment.

FIG. 4 is an explanatory view showing a method of elution treatment of a metal matrix surface layer in the first embodiment.

FIG. 5 is an explanatory view showing a vertical reciprocating sliding friction tester according to a second embodiment.

[Explanation of symbols]

 1. . . Hard particle molded body, 10. . . Voids, 11. . . 12. hard particles (fly ash); . . Binder, 2. . . 2. metal matrix; . . Mold, 7. . . 70. wear-resistant metal composite; . . Sliding surface,

Claims (5)

[Claims] 1. A molded article made of a porous hard particle formed by molding hard particles having a particle shape into a predetermined shape, and a metal matrix which is impregnated into voids inside the hard particle molded article and solidified. The wear-resistant metal composite, wherein the hard particles are three-dimensionally exposed on the surface of the metal matrix. 2. The wear-resistant metal composite according to claim 1, wherein said hard particles are fly ash. 3. The method according to claim 1, wherein the metal matrix comprises aluminum (Al), magnesium (M
g), one or more selected from the group consisting of iron (Fe) and copper (Cu). 4. Forming hard particles in the form of particles into a predetermined shape to form a porous hard particle molded body, and then impregnating and solidifying a metal in voids inside the hard particle molded body, and solidifying the metal matrix. And then elute the surface layer of the metal matrix to three-dimensionally expose the hard particles to the surface, thereby producing a wear-resistant metal composite. 5. The wear-resistant metal composite according to claim 4, wherein said hard particles are fly ash.