JP2014034729A - Composite material, slide member made by using the same, and manufacturing methods of both - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite material capable not only of weight reduction but, based on the strength enhancing function of carbon prevailing as a matrix material therein, also of securing mechanical strengths.SOLUTION: The provided composite material 1 comprises an aluminum alloy and carbon; the composite material 1 includes at least a carbon foam 12 consisting of carbon in a state where multiple open pores 12a are formed thereon and an aluminum alloy material 13 consisting of an aluminum alloy impregnated into the open pores 12a of the carbon foam 12.

Description

  The present invention relates to a composite material composed of an aluminum alloy and carbon, a sliding member using the same, and a method for producing the same.

  Conventionally, aluminum alloys have been used for vehicle engines and the like for reasons of weight reduction and high heat transfer. In particular, when the members slide with each other at a high surface pressure, the oil film between the members easily breaks, and the plastic flow of the aluminum alloy on the surface of the member occurs, so this oxide film formed on the member surface is destroyed. The new surface was exposed and the aluminum alloy sometimes adhered to the sliding surface.

  In view of such a point, for example, a composite material composed of a green compact formed of 50 to 90% by volume of carbon powder (graphite powder) and an aluminum alloy material filled in the pores of the green compact is proposed. (For example, refer to Patent Document 1).

  According to such a composite material, the carbon particles constituting the carbon powder are bonded to each other to form a matrix and the volume ratio of aluminum is small, so that the aluminum alloy is maintained while maintaining high sliding characteristics and workability. Adhesion resistance can be improved.

JP 2010-036194 A

  However, in the composite material described in Patent Document 1, since the compacted body obtained by compacting carbon powder is a matrix, the bonding state of the carbon particles constituting the compacted body varies, and carbon Some particles are not sufficiently bonded together. Therefore, when such a composite material is used for a sliding member, for example, cracks may occur at the grain boundaries between the carbon particles constituting the green compact, and the carbon particles may fall off. As a result, the mechanical strength of the composite material decreases. Furthermore, when such a member is used as a sliding member, the occupation ratio of the aluminum alloy on the sliding surface increases and the aluminum alloy may adhere.

  The present invention has been made in view of the above points, and the object of the present invention is to reduce the weight and increase the strength of carbon as a matrix material, thereby ensuring the mechanical strength. It is possible to provide a composite material suitable for use as a sliding member and a method for producing the same.

  In view of the above problems, the inventors have intensively studied and, as a result, have focused on carbon foam as carbon used in the composite material. Specifically, the carbon foam was considered to be free from falling off of carbon particles because carbon was bonded at the molecular level, unlike the green compact formed from carbon powder.

  The present invention has been made in view of these points, and the composite material according to the present invention is a composite material made of an aluminum alloy and carbon, and the composite material has a plurality of openings made of the carbon. And a carbon foam having pores formed therein and an aluminum alloy material made of the aluminum alloy impregnated in the open pores of the carbon foam.

  According to the present invention, since it is a composite material of an aluminum alloy containing carbon, the weight can be reduced compared to a material made of only an aluminum alloy. Furthermore, as described above, since the carbon material is made of a carbon foam, carbon does not fall off as particles, and the mechanical strength of the composite material can be increased.

  As a more preferred embodiment, the open pore forming wall that forms the open pores impregnated with the aluminum alloy is not impregnated with the aluminum alloy, and further fine open pores are formed than the open pores.

  According to this aspect, since the fine open pores are formed in the open pore forming wall that forms the open pores impregnated with the aluminum alloy, the composite material can be further reduced in weight. Further, since the fine open pores are not impregnated with the aluminum alloy, the fine open pores can be impregnated with the lubricant by applying the lubricant to the surface. Thereby, the sliding characteristic of a composite material can be improved by improving the oil content of a composite material. Here, “fine open pores” in the present invention refers to open pores having a smaller pore diameter (pore cross-sectional area) than open pores impregnated with an aluminum alloy.

  The present application also discloses a sliding member provided with such a composite material. The sliding surface of the sliding member according to the present invention is a surface where the aluminum alloy and the carbon are exposed. According to the present invention, since the aluminum alloy and carbon are exposed on the sliding surface, the carbon acts as a solid lubricant during sliding, and the friction of the sliding member can be reduced.

  Furthermore, as a preferable aspect, lubricating oil is applied to the sliding surface, and the fine open pores are impregnated with the lubricating oil. According to this aspect, since the fine open pores are impregnated with lubricating oil, when the sliding member slides, the impregnated lubricating oil is supplied to the sliding surface. The oil film can be retained.

  Furthermore, in this application, the manufacturing method which can manufacture the composite material mentioned above suitably is also disclosed. A composite material according to the present invention is a method for producing a composite material made of an aluminum alloy and carbon, the step of disposing a carbon foam having a plurality of open pores made of carbon in a mold, and the carbon At least a step of impregnating the molten aluminum in the open pores of the carbon foam by introducing the molten aluminum made of the aluminum alloy into the mold in which the foam is disposed while applying pressure.

  According to the present invention, the molten aluminum made of an aluminum alloy is introduced into the carbon foam formed in the mold while being pressurized, so that the open pores of the carbon foam can be impregnated with the molten aluminum. As described above, since the carbon material includes the carbon foam as the matrix material, the composite material obtained in this way does not drop off carbon as particles, and can increase the mechanical strength of the composite material. .

  Further, as a more preferable aspect, in the step of impregnating the molten aluminum, the molten aluminum is used so that at least a part of the open pore forming wall that partitions adjacent open pores of the carbon foam is penetrated by the molten aluminum. Is introduced into the mold while being pressurized, so that the open pores finer than the open pores formed in the open pore forming wall are not impregnated with the molten aluminum.

  In this way, by pressurizing and introducing the molten aluminum into the mold, before the molten aluminum is impregnated into the fine open pores formed in the open pore-forming wall, the molten aluminum is formed between adjacent open pores. Since at least a part of the partitioned open pore forming wall is destroyed and penetrated, the fine open pores of the open pore forming wall having a large pressure loss are not impregnated with the molten aluminum. Since the fine open pores thus obtained are not impregnated with the aluminum alloy, the fine open pores can be impregnated with the lubricant by applying the lubricant to the surface. As a result, the sliding properties of the composite material can be enhanced by increasing the oil-impregnating property of the composite material.

  Furthermore, in the present application, a suitable manufacturing method of the sliding member including the above-described manufacturing method of the composite material is also disclosed. In the manufacturing method of the sliding member according to the present invention, in the step of impregnating the molten aluminum, the molten aluminum is impregnated so as to cast the carbon foam, and the surface containing the aluminum alloy and the carbon is used as a sliding surface. The portion in which the aluminum alloy is cast is removed so as to be exposed.

  According to the present invention, a plurality of open pores can be uniformly impregnated with an aluminum alloy by impregnating the molten aluminum so as to cast a carbon foam. And the sliding surface where the surface containing the said aluminum alloy and the said carbon was exposed can be obtained by removing the part by which the said aluminum alloy was cast in in this way. As a result, since the aluminum alloy and carbon are exposed on the sliding surface, the carbon acts as a solid lubricant during sliding, and the sliding member can be reduced in friction. Further, by applying lubricating oil to the sliding surface, the fine open pores described above are impregnated with lubricating oil, and when the sliding member slides, the impregnated lubricating oil is slid. The oil film on the sliding surface can be held by being supplied to the moving surface.

  According to the composite material according to the present invention, the mechanical strength can be ensured by reducing the weight and increasing the strength of carbon serving as the matrix material.

It is a figure for demonstrating the manufacturing method of the composite material which concerns on this embodiment, (a) is typical sectional drawing explaining the process of arrange | positioning a carbon foam, (b) is a molten aluminum. It is typical sectional drawing for demonstrating the process made to impregnate, (c) is typical sectional drawing which shows the composite material which concerns on this embodiment. The figure which showed the structure | tissue photograph of the surface of the test body which concerns on Examples 1, 2 and a comparative example. The figure which showed the measurement result of the surface hardness of the test body which concerns on Examples 1, 2 and a comparative example. The figure which showed the result of the friction test of the test body which concerns on Examples 1, 2 and a comparative example. It is the figure which showed the structure | tissue photograph of the surface of the test body which concerns on Example 1, 2 after a friction test, and a comparative example, (a) is the figure which showed the structure | tissue photograph concerning Example 1, (b) is an Example. The figure which showed the structure | tissue photograph which concerns on 2, The figure which showed the structure | tissue photograph which concerns on the comparative example.

An embodiment of the present invention will be described below with reference to FIG.
FIG. 1 is a view for explaining a method for producing a composite material according to the present embodiment, wherein (a) is a schematic cross-sectional view for explaining a step of arranging a carbon foam, and (b) FIG. 5 is a schematic cross-sectional view for explaining a step of impregnating a molten aluminum, and (c) is a schematic cross-sectional view showing a composite material according to the present embodiment.

  As shown in FIG. 1A, a carbon foam 12 is prepared. In the carbon foam 12, a plurality of open pores (first open pores) 12a, 12a,... Are formed. Each first open hole 12a is formed by an open hole forming wall 12b made of a carbon material, and adjacent first open holes 12a are partitioned by the open hole forming wall 12b. The open pore forming wall 12b further has an open pore (second open pore) smaller than the pore diameter (pore cross-sectional area) of the first open pore 12a, that is, finer than the first open pore 12a. Has been.

  Examples of such a carbon foam 12 include a carbon foam produced by adding a foaming agent to a thermosetting resin, and a carbon foam starting from coke such as bituminous coal. For example, as shown in JP 2012-011694 A and JP 2010-526017 A, it is a generally known carbon foam. For example, examples of commercially available carbon foams include CFOAM (carbon foam) manufactured by Touchstone Research Laboratory.

  Such a carbon foam 12 is different from a green compact in which carbon powder composed of carbon particles is pressure-molded, and carbon is bonded at a molecular level, so that the carbon particles are difficult to fall off. Furthermore, in the case of a compacted body, the surface layer of the compacted body is denser with carbon particles than the inside, and the porosity of the surface layer is lower than the internal porosity. The molten aluminum is hard to be impregnated. However, since the carbon foam 12 according to the present embodiment has almost no change in the density of carbon regardless of the surface layer and the inside thereof, the molten aluminum is easily impregnated as compared with the compacted body. As a result, a more homogeneous composite material in which aluminum and carbon are combined can be manufactured.

  Such a carbon foam 12 is fixedly arranged in a cavity 21 formed in a mold 20 as shown in FIG. Next, molten aluminum 13a made of an aluminum alloy is introduced into the mold 20 in which the carbon foam 12 is disposed while being pressurized. When the molten aluminum 13a is introduced, a known injection molding apparatus is used. At this time, it is preferable to perform the molding pressure at the time of injection molding in the range of 20 to 80 Ma.

  As the molten aluminum (aluminum alloy), Al-Cu aluminum alloy, Al-Cu-Mg aluminum alloy, Al-Cu-Mg-Ni aluminum alloy, Al-Si aluminum alloy, Al-Si-Mg aluminum An alloy, an Al—Si—Cu—Mg aluminum alloy, and the like can be given, and the alloy may further contain at least one element of Fe, Mn, Ti, Zi, and the like.

  Thus, in the step of impregnating the molten aluminum 13a, at least a part of the open pore forming wall 12b partitioning the adjacent first open pores 12a of the carbon foam 12 is penetrated by the molten aluminum 13a. The molten aluminum 13a can be introduced into the mold 20 while being pressurized within the range of the molding pressure described above.

  As a result, as shown in FIG. 1B, the molten aluminum 13 a flows, and the molten aluminum 13 a is impregnated with the plurality of first open pores 12 a and 12 a of the carbon foam 12 so as to cast the carbon foam 12. Can do.

  On the other hand, by pressurizing and introducing the molten aluminum 13a into the mold 20, before the molten aluminum 13a is impregnated into the fine second open pores formed in the open pore forming wall 12b, At least a part of the open pore forming wall 12b that divides the adjacent first open pores 12a and 12a is broken and penetrated, and the fine second open pores formed in the open pore forming wall 12b are: Since the pressure loss is large, the second open pores are not impregnated with the molten aluminum 13a.

  In general, the first and second open pores described above are formed in the carbon foam, and the condition that the molten aluminum is not impregnated in the second open pores is the temperature (viscosity) of the molten aluminum, It can be experimentally determined by the molding pressure, or even the porosity of the carbon foam and the shape of the pores. In particular, it has been found through experiments by the inventors that such a condition can be easily achieved by using the above-mentioned CFOAM (carbonfoam) for the carbon foam.

  As a result, as shown in FIG. 1C, the carbon foam 12 having a plurality of first open pores 12a made of carbon and the first open pores 12a of the carbon foam 12 are impregnated ( The composite material 1 including at least the aluminum alloy material 13A made of an aluminum alloy that is filled can be obtained. Since the aluminum alloy material 13A has a network-like structure that penetrates the open pore forming walls 12b that divide the adjacent first open pores 12a and 12a, the mechanical strength of the composite material 1 can be increased.

  Further, the open pore forming wall 12b that forms the first open pore 12a impregnated with the aluminum alloy is not impregnated with the aluminum alloy, and a second open pore finer than the first open pore 12a is further formed. Therefore, as will be described later, if the open pore forming wall 12b can be exposed, an oil-impregnating function can be imparted to the composite material 1.

  In this embodiment, when manufacturing a sliding member from the composite material 1, a portion in which the aluminum alloy is cast in the composite material 1 so that the surface containing the aluminum alloy and carbon is exposed as a sliding surface. At least a part of 13B is removed by machining such as cutting or grinding.

  As a result, the aluminum alloy of the aluminum alloy material 13A and the carbon of the carbon foam 12 (the open pore forming wall 12b) are exposed on the sliding surface, so that the carbon acts as a solid lubricant during sliding. Thereby, the adhesion of the aluminum alloy can be suppressed and the friction of the sliding member can be reduced.

  Further, since the second open pores formed in the open pore forming wall 12b are also exposed on the sliding surface, the lubricating oil is applied to the second open pores by applying lubricating oil to the sliding surface. Is impregnated. As a result, when the sliding member slides, the impregnated lubricating oil is supplied to the sliding surface, the oil film on the sliding surface can be retained, and the sliding characteristics of the sliding member are improved. Can do.

The following examples of the present invention will be described.
Example 1
Five test bodies (sliding members) according to Example 1 were manufactured by the following manufacturing method. Specifically, first, a carbon foam CFOAM20 (manufactured by Touchstone Research Laboratory) having dimensions of 30 mm × 15 mm × 5 mm and a porosity of 57% by volume was prepared. This carbon foam is placed in a mold, and a molten A1-Si-Cu aluminum alloy (JIS standard: ADC12) heated to 680 ° C. is introduced into the mold, and the molten aluminum is added to the carbon foam at a molding pressure of 50 MPa. Was cast and impregnated to prepare a composite material. Next, the surface layer made of only the aluminum alloy of this composite material was ground to prepare a test body in which the surface of the carbon foam impregnated with the aluminum alloy was exposed to the sliding surface.

(Example 2)
In the same manner as in Example 1, five test specimens were produced. The difference from Example 1 is that the carbon foam used was CFOAM30 having a porosity of 35% by volume (manufactured by Touchstone Research Laboratory).

(Comparative example)
In the same manner as in Example 1, five test specimens were produced. A difference from Example 1 is that a casting made of only an aluminum alloy (JIS standard: ADC12) was used as a test body without using a carbon foam.

<Microscope observation>
The surface of the carbon foam before impregnation with the aluminum alloy according to Examples 1 and 2 and the sliding surface (surface) of the comparative example were observed with a microscope. The result is shown in FIG.

[Result 1]
As shown in FIG. 2, it was confirmed that the sliding surfaces of the sliding members of Example 1 and Example 2 were impregnated with an aluminum alloy in the open pores of the carbon foam. Further, the open pore forming wall that forms the open pores impregnated with the aluminum alloy is not impregnated with the aluminum alloy, and the open pores that are finer than the open pores impregnated with the aluminum alloy are further formed. confirmed.

<Hardness test>
The surface hardness of the test bodies according to Examples 1 and 2 and the comparative example was measured using a micro Vickers hardness meter with a measurement load of 0.1 kgf. The result is shown in FIG. N shown in FIG. 3 and below is the number of the specimen.

[Result 2]
As shown in FIG. 3, the surface hardness of the test bodies according to Examples 1 and 2 was substantially the same or lower than that of the comparative example. From this result, it is considered that Al ₄ C ₃ is not generated in the test bodies according to Examples 1 and 2 when the open pores of the carbon foam are impregnated with molten aluminum.

<Density measurement test>
The density of the test body which concerns on Examples 1, 2 and a comparative example was measured. Since the open pores are formed on the surface (sliding surface) of the specimens according to Examples 1 and 2, the volume is calculated from the dimensions of the specimen without performing volume measurement using the Archimedes principle. The specific gravity (density) was measured. The results are shown in Table 1.

[Result 3]
As shown in Table 1, the density (specific gravity) of the specimens according to Examples 1 and 2 is smaller than that of the comparative example, and the specimens of Examples 1 and 2 include a carbon foam as compared with the comparative example. It can be said that the weight has been reduced.

<Friction test>
Abrasion test was performed on the specimens according to Examples 1 and 2 and the comparative example using a ball-on-disk test apparatus. Specifically, Toyota motor oil as a lubricating oil is applied to the sliding surfaces of the test bodies of Examples 1 and 2 and the comparative example, and a high carbon chrome bearing steel (JIS standard: SUJ2) with a diameter of 3/16 inch is applied. The sample was pressed at 3000 g and slid against the specimen at a reciprocating width of 5 mm and a reciprocating speed of 60 cpm, and the friction coefficient was measured. The result is shown in FIG. Further, the sliding surfaces of the test bodies of Examples 1 and 2 and the comparative example after sliding were observed with a microscope. The result is shown in FIG. 5 is a diagram showing a structure photograph of the surface of the specimens according to Examples 1 and 2 and the comparative example after the friction test, (a) is a diagram showing a structure photograph according to Example 1, (B) is the figure which showed the structure | tissue photograph which concerns on Example 2, (c) is the figure which showed the structure | tissue photograph which concerns on a comparative example.

[Result 4]
As shown in Table 4, compared with the comparative example, the friction coefficient of the test bodies according to Examples 1 and 2 was a low value regardless of the passage of time. The open pores not impregnated with the aluminum alloy of the specimens according to Examples 1 and 2 were impregnated with the lubricating oil applied to the sliding surface. As a result, the lubricating oil was supplied to the sliding surface during sliding, and the sliding surface This is probably because the oil film on the moving surface could be retained. Further, as shown in FIGS. 5A to 5C, the wear state of the sliding surfaces of the test bodies of Examples 1 and 2 is substantially the same as that of the comparative example, and compared with Example 1. It was found that the specimen of Example 2 was not worn.

  As mentioned above, although it explained in full detail using embodiment of this invention, a concrete structure is not limited to this embodiment and an Example, There exists a design change in the range which does not deviate from the summary of this invention. They are also included in the present invention.

  For example, in the present embodiment, the sliding member is manufactured by removing the portion in which the aluminum alloy is cast so that the surface containing the aluminum alloy and carbon is exposed as a sliding surface. You may use a foam as a core at the time of casting. In this case, the portion of the carbon foam that is not impregnated with the aluminum alloy can be easily removed after casting. Further, the surface of the removed portion is exposed to a portion in which the aluminum alloy is impregnated in a part of the carbon foam, and thus oil repellency can be imparted to this portion.

1: composite material, 12: carbon foam, 12a open pores, 12b: open pore forming wall, 20: mold, 21: cavity, 13a: molten aluminum, 13A: aluminum alloy material, 13B: aluminum alloy was cast portion

Claims (8)

A composite material composed of an aluminum alloy and carbon,
The composite material includes at least a carbon foam in which a plurality of open pores made of carbon are formed, and an aluminum alloy material made of the aluminum alloy impregnated in the open pores of the carbon foam. Characteristic composite material.   The open pore forming wall that forms the open pores impregnated with the aluminum alloy is not impregnated with the aluminum alloy, and further has fine pores that are finer than the open pores. The composite material according to 1. A sliding member comprising the composite material according to claim 2,
The sliding member is characterized in that the sliding surface of the sliding member is a surface where the aluminum alloy and the carbon are exposed.   The sliding member according to claim 3, wherein lubricating oil is applied to the sliding surface, and the fine open pores are impregnated with the lubricating oil. A method for producing a composite material comprising an aluminum alloy and carbon,
Placing a carbon foam having a plurality of open pores in a mold; and
At least a step of impregnating the molten aluminum in the open pores of the carbon foam by introducing the aluminum molten metal made of the aluminum alloy into the mold in which the carbon foam is disposed while applying pressure. A method for producing a composite material.   In the step of impregnating the molten aluminum, the molten aluminum is pressed into the mold while pressurizing the molten aluminum so that at least a part of the open pore forming wall that partitions adjacent open pores of the carbon foam is penetrated by the molten aluminum. 6. The method for producing a composite material according to claim 5, wherein the molten aluminum is not impregnated into the open pores formed on the open pore-forming wall and finer than the open pores. A method for manufacturing a sliding member including the method for manufacturing a composite material according to claim 6,
In the step of impregnating the molten aluminum, the molten aluminum is impregnated so as to cast the carbon foam,
A method for producing a sliding member, comprising: removing a portion where the aluminum alloy is cast so that a surface containing the aluminum alloy and the carbon is exposed as a sliding surface.   The method for manufacturing a sliding member according to claim 7, wherein the fine open pores are impregnated with the lubricating oil by applying a lubricating oil to the sliding surface.

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