JPH0364576B2 - - Google Patents

Description

[Detailed description of the invention]

A. Purpose of the invention (1) Industrial field of application The present invention provides a fiber-reinforced part made of reinforcing fibers and an aluminum alloy matrix, and a single part made of the aluminum alloy that is integrated with the fiber-reinforced part. The present invention relates to a fiber-reinforced aluminum alloy member. (2) Prior Art Conventionally, an alloy having a hypereutectic composition has been used as the aluminum alloy (see Japanese Patent Publication No. 169154/1983). (3) Problems to be solved by the invention However, since the aluminum alloy with the hypereutectic composition has a large plate-like primary Si crystal and a eutectic (α+Si), the strength of the aluminum alloy matrix in the fiber reinforced part is improved. On the other hand, there is a problem in that the hardness of the single unit portion increases, resulting in poor machinability. In view of the above, an object of the present invention is to provide the above-mentioned member in which the strength of the aluminum alloy matrix in the fiber-reinforced part is improved and the machinability of the single part is improved. B. Structure of the Invention (1) Means for Solving the Problems The present invention provides a fiber-reinforced part made of reinforcing fibers and an aluminum alloy matrix, and a fiber-reinforced part that is integrated with the fiber-reinforced part and made of the aluminum alloy. In the fiber-reinforced aluminum alloy member having a single part, when the amount of primary Si in the aluminum alloy matrix is A weight %, and the amount of primary Si in the single part is B weight %, the ratio of A and B is A. /B is set to 1.1≦A/B≦4. (2) Effect In the aluminum alloy matrix of the fiber-reinforced part and the single part, the ratio of primary Si content A/
When B is specified as described above, the aluminum alloy matrix has a large amount of primary Si in the fiber-reinforced portion, so that the strength of the matrix is improved. Since the aluminum alloy matrix is subjected to the notch effect by the reinforcing fibers, it is required to have strength that can counteract the notch effect, and the aluminum alloy matrix with such a configuration satisfies the above requirements,
This contributes to improving the strength of the fiber reinforced portion. On the other hand, since the amount of primary crystal Si in the single part is small, the increase in hardness is suppressed and machinability is improved. In addition, when the ratio A/B of the amount of primary Si becomes less than 1.1,
If an aluminum alloy with a low Si content is used, sufficient improvement in the strength of the aluminum alloy matrix will not be achieved. On the other hand, the ratio A/B
If it exceeds 4, when an aluminum alloy with a low Si content is used, it causes a decrease in the strength of the single part. In addition, when using an aluminum alloy with a high Si content, if the ratio A/B is controlled to exceed 4, the temperature of the hot water during casting will decrease, resulting in poor filling properties of the aluminum alloy into the reinforcing fibers. produce defects. (3) Embodiment Figures 1 to 3 show a Siamese type cylinder block 1 as a fiber-reinforced aluminum alloy member, and each cylinder bore 2 of the cylinder block 1.
Surrounding the fiber-reinforced portion 1a is a fiber-reinforced portion 1a made of reinforcing fibers and an aluminum alloy matrix, and each fiber-reinforced portion 1a is integrated with a surrounding aluminum alloy single portion 1b. As reinforcing fibers, alumina fibers alone or a mixture of such fibers and carbon fibers are used.
Further, as the aluminum alloy, an aluminum alloy having a hypoeutectic composition containing 1.65 to 14.0% by weight of Si is used. In manufacturing the cylinder block 1, for example, using the mixed fibers, the fiber volume fraction (Vf) of the alumina fiber is 12% and that of the carbon fiber is 9%.
The process of producing a cylindrical molded body, the casting mold
A step of preheating to 200~300℃, the molded body is heated to 100~300℃.
The step of preheating the aluminum alloy to 400°C and placing it in the mold, the molten aluminum alloy is heated for a time t ₁ as shown in FIG.
The process includes a step of pouring the molten metal into the mold, a step of leaving the molten metal in the poured state for a period of ^time t ₂ shown in FIG. The steps of applying pressure p and filling the molded body with the pressure p are sequentially performed. As mentioned above, if the molten metal is left for a predetermined period of time before being pressurized, Si will form in the single part 1b during that time.
When the molten metal is pressurized after alpha primary crystals with a low content are precipitated, the molded body will be filled with the molten metal with a relatively high Si content. Then the first crystal
The Si amount A (wt%) is larger than the primary Si amount B (wt%) in the single part 1b, and the ratio A/B of the primary Si amount in both parts 1a and 1b is 1.1≦A/B≦4. (preferably 1.2 to 2.0). Figure 5 is a micrograph (200x) showing the metal structure of the fiber-reinforced part 1a and the single part 1b.
indicates alumina fiber, C indicates carbon fiber, and S indicates primary crystal.
Si represents an aluminum alloy, and M represents an aluminum alloy. As is clear from FIG. 5, the fiber-reinforced portion 1a has a large amount of primary Si, and the amount A is 12% by weight in the aluminum alloy matrix excluding alumina fibers and carbon fibers, while the single portion 1b
In this case, the amount of primary Si is small, and the amount B is 8.5% by weight in the single part 1b. Therefore, the primary Si
The quantity ratio A/B is A/B=1.4. In this way, the amount of primary Si in the aluminum alloy matrix of the fiber-reinforced part 1a increases, which increases the strength of the matrix and improves the sliding properties.On the other hand, the amount of primary Si in the single part 1b decreases. , the increase in hardness is suppressed and machinability is improved. The table below compares the primary Si content, strength, etc. of the fiber-reinforced portion 1a and the single portion 1b in various cylinder blocks. Cylinder block No.2~
No. 4 corresponds to the present invention, cylinder block No. 1,
No. 5 is a comparative example. In addition, cylinder block No.
3 corresponds to the example in FIG. In the table, the strength of the fiber-reinforced portion is lower than that of the aluminum alloy matrix because the matrix is subjected to a notch effect by the reinforcing fibers.

[Table] The average grain size of primary Si in the aluminum alloy matrix of the fiber-reinforced portion 1a is set to be less than or equal to the average diameter of the alumina fibers. Such control is
This is accomplished simply by adjusting the preheating temperature of the compact to control the solidification rate and time of the molten metal in and around the compact. When the average grain size of primary Si is specified as above,
The primary Si crystals are made finer, thereby improving the strength of the aluminum alloy matrix in the fiber-reinforced portion 1a, and suppressing the dropping of the primary Si crystals as much as possible to improve the sliding properties. When the average particle size of the primary crystal Si exceeds the above-mentioned average diameter, the amount of primary crystal Si falling off increases, and the falling primary crystal Si accelerates the wear of the piston, which is the mating material. The casting method produces primary crystals in both parts 1a and 1b.
In order to control Si, an aluminum alloy having a hypoeutectic composition containing 1.65 to 14.0% by weight of Si as described above is optimal. In this case, if the Si content is less than 1.65% by weight, primary Si crystals will form in the fiber reinforced part 1a.
On the other hand, if the Si content exceeds 14.0% by weight, the single part 1b tends to have a hypereutectic composition, and coarse primary Si crystals tend to crystallize. This causes a decrease in strength and also deteriorates the machinability of the single part 1b. Alumina fibers inevitably contain unfiberized particulate matter, that is, shot, due to their manufacturing process, and the strength and sliding resistance of the fiber reinforced portion 1a depend on the particle size and content of the shot. Dynamic characteristics etc. are affected. As a result of various studies, the inventors found that the particle size
Not only shot of 150μm or more, but also particle size of 150μm
The following shot investigates the influence of the fiber-reinforced portion 1a on the strength and the relationship between the average particle diameter of the shot and the average fiber diameter, which influence the strength. FIG. 6 shows the seizure limit characteristics under non-lubricated conditions of the fiber-reinforced portion 1a in which the average particle diameter of shots is set to 150 μm or less in alumina fibers having an average diameter of 3.0 μm. Line a corresponds to the case where the above-mentioned mixed fiber is used, and line b corresponds to the case where alumina fiber with a fiber volume ratio of 12% is used alone. As shown by lines a and b, if the content of shots with an average particle diameter of 150 μm or less relative to the alumina fiber (containing shots) is 4.0% by weight or less, the seizure limit surface pressure is high and the material is sufficiently practical as a sliding member. has. Furthermore, in the case of line a, it is clear that the seizure limit characteristics are improved as compared to line b due to the combined use of carbon fibers having lubricating ability. In addition, regarding the relationship between the average particle diameter of the shot and the average diameter of the alumina fibers, the strength of the fiber reinforced portion 1a depends on the content of shots whose average particle diameter is 50 times or more the average diameter. In this case as well, the same sliding characteristics as described above can be obtained by setting the shot content to 4.0% by weight or less. Figure 7 shows the relationship between the total shot content in the alumina fibers and the tensile strength of the fiber reinforced portion 1a, where the total shot content is 10.0% by weight with respect to the alumina fibers (shot content). When it exceeds
It is clear that the tensile strength of the fiber reinforced portion 1a decreases rapidly. Therefore, the total shot content is 10.0% by weight
The following are preferred. Alumina fibers such as alumina fibers and alumina-silica fibers contain silica to facilitate their formation into fibers. In this case, if the silica content is too high, the wettability between the alumina fibers and the aluminum alloy will deteriorate, and improvement in the strength of the member will be hindered, while if the silica content is too low, the effect of silica content will not be obtained. Also, if the alumina gelatinization rate is too high, the alumina fibers will
The increased hardness of the fibers makes them brittle, resulting in poor formability when forming a compact using the fibers, further increasing the scratch hardness and accelerating the wear of the mating material, and furthermore, the alumina from the aluminum alloy matrix deteriorates. The amount of fibers that fall off tends to increase, and the fallen fibers also promote wear on the mating material. on the other hand,
If the alpha conversion rate is too low, wear resistance will deteriorate. Therefore, in order to achieve sufficient fiber reinforcement of the member, it is necessary to specify the range of the silica content and gelatinization rate. From this point of view, the silica content should be 2% by weight or more and 25% by weight or less based on the alumina fiber.
It is preferably 2 to 5% by weight, and the gelatinization rate of alumina is set to 2% or more and 60% or less, preferably 45% or less. Figure 8 shows the relationship between silica content and tensile strength in aluminum alloy members reinforced using only alumina fibers, and line c is α of alumina.
When the gelatinization rate is 5%, line d indicates that the gelatinization rate of alumina is 50.
%, line e corresponds to the case where the gelatinization rate of alumina is 85%. As shown in lines c and d, if the silica content is 25% by weight or less and the alumina gelatinization rate is 60% or less, a member with sufficient strength for practical use can be provided. Figure 9 shows the relationship between the gelatinization rate of alumina and the tensile strength in the aluminum alloy member with a silica content of 5% by weight, and the gelatinization rate of alumina is 60%.
If it is below, a member having practically sufficient strength can be provided. By specifying the silica content and the alumina gelatinization rate as described above, the strength of the member can be improved by 8 to 20% at a fiber volume fraction of 12% compared to conventional ones. Figure 10 shows fiber-reinforced aluminum alloys in which the fiber volume fraction of alumina fibers with various diameters is set to 10.0% and the mating material spheroidal graphite cast iron (JIS
The results of the chip-on-disk sliding test with FCD75) are shown. Line f corresponds to the seizure limit characteristic, and line g corresponds to the scratch limit characteristic. The alloy corresponds to the constituent material of the fiber-reinforced portion 1a, and the chip is formed from this material. Further, the cast iron corresponds to a material constituting a compression ring attached to a piston (not shown), and a disk is formed from this material. The sliding surfaces of these chips and disks are polished so that they have various surface roughnesses of 1.0 μm or more. In this case, the surface roughness is 1.0μ
The reason why the surface roughness is set to be greater than m is that obtaining a surface roughness lower than that by polishing requires a lot of effort. The test method was to rotate the disk at a speed of 9.5 m/sec, and press the sliding surface of the chip against the sliding surface of the disk with a predetermined pressing force without lubrication. The relationship between this and the surface pressure acting on the chip at the scratch limit was determined. As is clear from Fig. 10, if the surface roughness of the chip is in the range of 1.0 to 3.0 μm, the surface pressure at the scratch limit is about 25 to about 35 kg/ ^cm2 , and the surface pressure at the seizure limit is 66 to 35 kg/cm2. It has a high sliding characteristic of 82Kg/cm ² , which is sufficient for practical use. In such sliding tests between fiber-reinforced aluminum alloy chips and cast iron disks, the scratching and seizure phenomena are promoted by alumina fibers that are shed from the aluminum alloy matrix of the chips during the sliding tests. Therefore, it is necessary to firmly hold the alumina fibers in the matrix, and to satisfy this requirement, the surface roughness of the chip must be set to less than half the average diameter of the alumina fibers. is good. With this setting, approximately half of the alumina fibers dispersed on the sliding surface of the chip with their axes arranged approximately parallel to the sliding surface are embedded in the matrix and held by the matrix. This suppresses the falling off of the alumina fibers. On the other hand, since the alumina fibers, which are arranged and dispersed with their axes substantially perpendicular to the sliding surface, are embedded in a large amount in the matrix, their relationship with the surface roughness is small. Considering the above points, when the average diameter of the alumina fibers is set to 2.0 to 6.0 μm, the surface roughness of the chip is set to 1.0 to 3.0 μm. In order to obtain the best sliding properties, the average diameter of the alumina fibers is set to 2.0 to 4.0 μm, and the surface roughness of the sliding surface is set accordingly. Figure 11 shows fiber-reinforced aluminum alloys with various fiber volume fractions of alumina fibers with an average diameter of 3 μm and the mating material, spheroidal graphite cast iron (JIS
The results of the chip-on-disk sliding test with FCD75) are shown. Line h corresponds to the seizure limit characteristic, and line i corresponds to the scratch limit characteristic. The alloy corresponds to the constituent material of the fiber-reinforced portion 1a, and the chip is formed from this material. Further, the cast iron corresponds to the constituent material of the compression ring, and this material forms the disk. The surface roughness of the chip and disk is set to 1 μm. The test method was to rotate the disk at a speed of 9.5 m/sec, press the sliding surface of the chip against the sliding surface of the disk with a predetermined pressing force without lubrication, and then The relationship between the volume fraction and the surface pressure acting on the chip at the seizure limit and scratch limit was determined. As is clear from Fig. 11, when the fiber volume fraction of alumina fiber is set to 8.0% to 20.0%, the line i
The surface pressure at the scratch limit on the chip is approximately
30 to about 95 Kg/cm ² , and the surface pressure at the seizure limit is as high as about 70 to about 170 Kg/cm ² as shown by line h. Furthermore, the chips are sufficiently reinforced with fibers, have excellent wear resistance, and can also reduce the amount of wear on the mating material. However, if the fiber volume percentage is less than 8.0%,
Fiber reinforcement ability is small, and wear resistance and seizure resistance are reduced. On the other hand, if the fiber volume fraction exceeds 20.0%, the filling properties of the aluminum alloy matrix will deteriorate, making it impossible to achieve sufficient fiber reinforcement, and the hardness of the sliding parts will increase, reducing the amount of wear on the mating material. Moreover, the thermal conductivity also decreases. In FIG. 11, lines j and k correspond to the seizure limit characteristics and scratch limit characteristics, respectively, of a hybrid fiber-reinforced aluminum alloy chip using mixed fibers of alumina fibers and carbon fibers. In this case, the fiber volume fraction of carbon fiber is set to 0.3%. As described above, it is clear that in the hybrid type chip, its seizure limit characteristics and scratch limit characteristics are improved compared to the cases of lines h and i. However, if the fiber volume fraction of carbon fiber is less than 0.3%, the above-mentioned effect based on the lubricating ability of carbon fiber cannot be obtained, and on the other hand, if the fiber volume fraction exceeds 20.0%, the overall The fiber volume fraction becomes high, and when a molded article is obtained using the mixed fibers, moldability deteriorates. Therefore, it is appropriate for carbon fiber to have a fiber volume fraction of 0.3 to 20.0%, preferably 15% or less. Furthermore, since carbon fiber has a lubricating ability, even if it falls off from the matrix, the scratch limit characteristics etc. will not be impaired. In addition, in the mixed fiber, carbon fiber has the effect of improving wear resistance, seizure resistance, etc., so the fiber volume fraction of alumina fiber can be lowered compared to when the alumina fiber is used alone. If the fiber volume fraction is less than 5.0%, the properties of alumina fibers will not be exhibited, while if it exceeds 50.0%, the total fiber volume fraction will increase in relation to the amount of carbon fiber, and the filling properties of the matrix will deteriorate. Therefore, the fiber volume fraction of the alumina fiber is 5.0 to 50.0%, preferably 10.0 to 50.0%. Figure 12 shows fiber-reinforced aluminum alloys with various fiber volume fractions of alumina fibers with an average diameter of 3 μm and the mating material, spheroidal graphite cast iron (JIS
The results of the chip-on-disc wear test with FCD75) are shown. The line m corresponds to the wear amount of the alloy, and the line n
corresponds to the amount of wear of the cast iron. The alloy corresponds to the constituent material of the fiber-reinforced portion 1a, and the chip is formed from this material. Further, the cast iron corresponds to the constituent material of the compression ring, and this material forms the disk. The surface roughness of the chip and disk is set to 1 μm. The test method was to rotate the disk at a speed of 2.5 m/sec, and press the sliding surface of the chip against the sliding surface of the disk with a pressing force of 20 kg under lubrication until the sliding distance reached 2000 m. It was maintained. The amount of lubricating oil supplied is 2 to 3 ml/min. As is clear from Fig. 12, when the fiber volume percentage of alumina fiber is set to 8.0 to 20.0%, the wear amount of the chip is approximately 0.5 to 0.85 μm as shown by line m.
Also, as shown by line n, the amount of wear on the disk is approximately
It becomes smaller at 2.85 to about 5 μm. In order to minimize the amount of wear on the chips and disks, it is preferable to set their surface roughness to 1 μm or less and to set the fiber volume fraction of the alumina fibers to 12.0 to 14.0%. The present invention relates to a connecting rod with fiber reinforced around the crank pin hole, a rocker arm with fiber reinforced slipper surface and its vicinity, a cylinder head with fiber reinforced valve seat, a camshaft with fiber reinforced journal, and various bearing materials as sliding members. Applies to etc. C. Effects of the Invention According to the present invention, by specifying the relationship between the amount of primary Si in the aluminum alloy matrix in the fiber-reinforced portion and the amount of primary Si in the single portion as described above, the notch effect due to the reinforcing fibers can be obtained. It is possible to provide the aluminum alloy member in which the strength of the aluminum alloy matrix and, by extension, the strength of the fiber-reinforced portion are improved, and the machinability of the single unit portion is improved.

[Brief explanation of drawings]

Figures 1 to 3 show the cylinder block;
Figure 2 is a perspective view, Figure 2 is a plan view, Figure 3 is a sectional view taken along the line shown in Figure 2, Figure 4 is a graph showing the relationship between the pressure applied to the molten metal and time in the casting method, and Figure 5 is fiber reinforcement. Figure 6 is a graph showing the relationship between the content of shot with an average grain size of 150 μm or less and the seizure limit surface pressure.
Figure 7 is a graph showing the relationship between total shot content and tensile strength, Figure 8 is a graph showing the relationship between silica content and tensile strength, and Figure 9 is a graph showing the relationship between silica content and tensile strength.
Figure 10 is a graph showing the relationship between the surface roughness of the chip and disk and the surface pressure acting on the chip. Figure 11 is the graph showing the relationship between the fiber volume fraction of alumina fiber and the chip. FIG. 12 is a graph showing the relationship between the fiber volume fraction of alumina fibers and the wear amount of chips and disks. A...Alumina fiber, C...Carbon fiber, M...
...Aluminum alloy, S...Primary Si, 1a,...
Fiber reinforced part, 1b...Single part.

Claims (1)

[Scope of Claims] 1. A fiber-reinforced aluminum alloy member comprising a fiber-reinforced portion made of reinforcing fibers and an aluminum alloy matrix, and a unitary portion integrated with the fiber-reinforced portion and made of the aluminum alloy. , the amount of primary Si in the aluminum alloy matrix is A weight %, and the primary crystal in the single part is
When the amount of Si is B weight %, the ratio of A and B is A/B
A fiber-reinforced aluminum alloy member, characterized in that: 1.1≦A/B≦4. 2. The fiber-reinforced aluminum alloy member according to claim 1, wherein the average grain size of primary crystal Si in the aluminum alloy matrix is set to be equal to or smaller than the average diameter of the reinforcing fibers. 3. The fiber-reinforced aluminum alloy member according to claim 1 or 2, wherein the aluminum alloy contains 1.65 to 14.0% by weight of Si.