JPH0873972A - Composite material excellent in strength, wear resistance, and thermal conductivity and its production - Google Patents

Abstract

PURPOSE: To produce a composite material excellent in strength, wear resistance, and thermal conductivity by incorporating specific amounts of silicon carbide into an aluminum alloy and specifying its thermal conductivity and coefficient of thermal expansion, respectively. CONSTITUTION: Silicon carbide is incorporated by 35-45wt.% into an aluminum alloy, and the aluminum-ceramics composite material in which thermal conductivity and thermal expansion coefficient are regulated to >=150W/(m.k) and 10×10<-6> / deg.C to 12×10<-6> / deg.C, respectively, is produced. At this time, an aluminum alloy for casting, containing 8-11wt.% Si and 4-8wt.% Mg as essential components and having the balance essentially Al, is used as the aluminum alloy, and the average grain size of the silicon carbide in the aluminum alloy is regulated to 12 to 18μm. By this method, the composite material, suitable for use as a material for engine parts, etc., and excellent in strength, wear resistance, and thermal consuctivity, can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to strength, wear resistance and heat conductivity suitable for use as a material for engine parts and the like, which are required to have excellent strength, wear resistance and heat conductivity. The present invention relates to an aluminum / ceramic composite material excellent in heat resistance and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a valve seat, which is a valve seat of an engine valve, is required to have excellent wear resistance, and therefore various countermeasures such as those shown below have been considered.

(1) Ceramics (silicon nitride, silicon carbide, sialon, etc.) are used for the tapered portion that contacts the valve.
And a structure in which a metal ring is provided on the outer peripheral side of the ceramic ring that forms the tapered portion (Japanese Patent Laid-Open No. 62-191607 and Japanese Patent Laid-Open No. 62-107216).
Japanese Patent Laid-Open No. 62-23512).

(2) Without using a valve seat ring, the valve seat portion is reinforced with ceramic fibers and the surface of the fiber reinforced metal portion with ceramic fibers is coated with a metal coating layer to improve the wear resistance of the valve seat portion. A structure having such a structure (JP-A-61-76742, JP-A-61-76744, JP-A-61-87947, JP-A-61-87948).

(3) Electroless Ni on hard ceramic particles
A structure of a valve seat in which plated composite particles are dispersed in an iron-based sintered material (JP-A-64-56850).

(4) A structure of a valve seat in which fine aluminum oxide hard phases are dispersed in a base material of an Fe-based sintered alloy (Japanese Patent Laid-Open No. 4-128348).

[0007]

However, in these conventional valve seat structures, the purpose is to improve the wear resistance of the seat portion, and since ceramics having poor thermal conductivity is used, the heat insulating effect is large. Since there is a problem that the temperature inside the engine cylinder rises and the engine output decreases, there is a problem to solve such a problem.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and by combining ceramics and metal, the wear resistance required for engine valve seats, engine cylinder liners, etc. By providing a material that has both strength and strength and also has excellent thermal conductivity, it is possible to prevent the above-mentioned conventional problems from occurring and improve the performance of engines, etc. Strength and wear resistance The purpose is to provide a composite material with excellent thermal conductivity.

[0009]

The composite material excellent in strength, wear resistance and heat conductivity according to the present invention is, as described in claim 1, 35% by weight or more and 45% by weight or more in an aluminum alloy. Containing less than or equal to wt% silicon carbide, thermal conductivity is 1
50 W / (m · K) or more, thermal expansion coefficient of 10 × 10 ⁻⁶ /
It is characterized in that it has a configuration of not less than 12 ° C. and not more than 12 × 10 ⁻⁶ / ° C.

The strength, wear resistance, and
In an embodiment of the composite material having excellent thermal conductivity, the particle size of silicon carbide contained in the aluminum alloy is 12 μm or more and 18 μm on average as described in claim 2.
The aluminum alloy may be a casting aluminum alloy, as described in claim 3, and the aluminum alloy may be aluminum as described in claim 4. The alloy contains Si: 8 to 11% by weight and Mg: 4 to 8% by weight as a basic component (others such as Cu: 5.0% by weight or less, Ni: 2.3% by weight or less), and the balance substantially. It is possible to use an aluminum alloy for casting that consists essentially of Al, and as described in claim 5, it can be used as a material for an engine valve seat, and is described in claim 6. As such, it can be used as a material for engine cylinder liners.

The method for producing a composite material excellent in strength, wear resistance and thermal conductivity according to the present invention is, as described in claim 7, an aluminum alloy containing 55% by weight or more and 65% by weight or less. It is characterized in that the molten metal and 35% by weight or more and 45% by weight or less of silicon carbide powder are mixed and then cast and molded.

The composite material excellent in strength, wear resistance, and thermal conductivity and the method for producing the same according to the present invention have the above-mentioned constitution. As an aluminum alloy, JI
Aluminum alloys for die casting established in SH 5302 (ADC 1, ADC 3, ADC 5, ADC
6, ADC 10, ADC 10Z, ADC 12, A
DC 12Z, ADC 14 etc. are used, and as described in claim 3, aluminum alloys for casting (AC 1A, 1B, AC established in JIS H 5202).
2A, 2B, AC 3A, AC 4A, 4B, 4C,
4CH, 4D, AC 5A, AC 7A, 7B, AC
8A, 8B, 8C, AC 9A, 9B, etc.) are used.

When the application is an engine valve seat as described in claim 5 or an engine cylinder liner as described in claim 6, Si: 8 to 11 as described in claim 4. It is desirable to use an aluminum alloy for casting which contains wt% and Mg: 4 to 8 wt% as basic components and the balance substantially consists of Al.

In this case, if the Si content is less than 8% by weight, the wettability of the surface of the silicon carbide particles is lowered and the structure tends to have an air layer remaining around the silicon carbide particles. If it exceeds the limit, Si element will precipitate during cooling of the alloy and the hardness will increase, tending to cause damage to valves and piston rings, so Si content in aluminum alloy when used as a material for engine valve seats and engine cylinder liners The amount is preferably in the range of 8 to 11% by weight.

If the Mg content is less than 4% by weight, the alloy cannot penetrate into the fine pores of the silicon carbide particle compact and the structure tends to have fine pores (pores) remaining around the agglomerates. If it exceeds 8% by weight, intermetallic compounds tend to be precipitated and become brittle when the alloy is cooled, so the Mg content in the aluminum alloy when used as a material for engine valve seats and engine cylinder liners is 4-8% by weight. It is desirable to set the range to.

The content of silicon carbide (SiC) contained in such an aluminum alloy is 35% by weight or more and 4
5% by weight or less. In this case, when the silicon carbide content is less than 35% by weight, the ratio of the aluminum alloy relatively increases, so that the strength and toughness of the composite material are improved and the thermal conductivity is increased. Is large, but the thermal expansion coefficient is large, and the hardness is lowered, so that the wear resistance is deteriorated.
When it is more than 5% by weight, the proportion of aluminum alloy decreases relatively, so that the hardness of the composite material increases and the wear resistance improves, but the strength and toughness decrease and the thermal conductivity also decreases. And the coefficient of thermal expansion becomes small, which is not preferable.

By setting the silicon carbide content in the aluminum alloy to 35% by weight or more and 45% by weight or less, the coefficient of thermal expansion is 10 × 10 ⁻⁶ / ° C. or more and 12 × 10.
^-6 / ° C or less and thermal conductivity of 150W /
(M · K) or more, and the strength can be high.

FIG. 1 is a sectional view showing a silidan head portion of an engine, and FIG. 2 is a sectional view showing a valve seat provided in the cylinder head portion. The cylinder head 1 of the engine is made of an aluminum alloy. A cooling water passage 2 and a cylinder upper space 3 are formed therein, a valve seat 4 is provided in the valve seat portion, and a valve face portion of the valve 5 is brought into contact therewith. ing. Further, the valve 5 reciprocates while being guided by the valve guide 6, and the cylinder upper space 3 and the port 7 are opened and closed.

As shown in FIG. 2, the valve seat 4 made of the composite material according to the present invention has a ring shape formed by dispersing silicon carbide 4b in the form of particles in the aluminum alloy 4a. Has become.

As described above, the composite material according to the present invention contains the silicon carbide ceramics (eg, 1000) in the aluminum alloy (eg, Al--Si--Mg alloy).
No. powder) containing 35% by weight or more and 45% by weight or less. As a manufacturing process of such a composite material, for example, silicon carbide powder is mixed with the powder of aluminum alloy component or agglomerate and melted. Can be obtained by doing.
In this case, for example, the preferable melt impregnation temperature is in the range of 670 ° C. to 750 ° C., which can be the same as the usual melting method for aluminum alloys.

When forming a valve seat, an aluminum alloy containing silicon carbide particles is poured from the gate into a casting mold made of iron or foundry sand having a casting space corresponding to the valve seat shape and a gate continuous with the casting space. To do. Then, the ring-shaped valve seat made of this composite material is fixed at a position corresponding to the valve seat in the engine head casting process to manufacture the engine cylinder head by casting.

[0022]

According to the silicon carbide-aluminum alloy composite material of the present invention, as described in claim 1, the aluminum alloy contains 35% by weight or more and 45% by weight or less of silicon carbide. Since the alloy phase constitutes a continuous body, the thermal conductivity is 1
50 W / (m · K) or more and base material (for example, AC 2A)
Is very close to the characteristic value of, and the coefficient of thermal expansion is also 10 × 1.
0 ^-6 / ° C. or higher 12 × ^{10 -6} / ℃ less a by a value close to 13.5 × ^{10 -6} / ℃ of aluminum alloy.

Therefore, the thermal expansion difference makes it difficult for the cylinder head to separate from the aluminum alloy phase, and since the thermal conductivity is 150 W / (m · K) or more, the heat inside the cylinder head is transferred to the cooling water side. It is possible to escape to.

When the composite material according to the present invention is applied to a valve seat, it is conventionally necessary to mechanically connect the cylinder head and the valve seat, so that a metal ring is provided on the outer peripheral portion or the outer peripheral portion is provided. Although the parts were unevenly processed, such a structure or processing is unnecessary by using the composite material of the present invention.

Further, as described in claim 2, the average particle size of silicon carbide is 12 μm or more and 18 μm or less, so that the silicon carbide ceramics in the aluminum alloy are not dense but bear load. Therefore, the aluminum-ceramics composite material has the highest level of strength of 450 to 500 MPa. Further, since the residual metal prevents the crack development at the time of fracture, the fracture toughness value also shows a high value of 11 to 13 MPa√m.

When the composite material according to the present invention is applied to an engine valve seat, not only the mechanical characteristics but also the wear characteristics with a valve necessary for use as a cylinder head of an engine are evaluated by a wear test by the impact of the valve. As a result of measuring the amount of wear, it was found to be extremely good. In this abrasion test, the valve was Stellite (STL) # 32. The test conditions were heating with a burner, the valve seat temperature was 150 ° C, and the valve temperature was 550 ° C. The durability condition was a cam rotation speed of 2000 rpm for 5 hours. This is a test for measuring the amount of wear of the valve seat.

The reason why the wear resistance is good is that the surface is made of aluminum alloy as well as ceramics, so that the coefficient of friction of the surface is remarkably lowered, and the hardness (Vickers) is usually This is because it is several GPa lower than the ceramics. The reason for this is that the silicon carbide is in a particulate state and thus it is easy to move, and the residual aluminum is easily deformed.

[0028]

EXAMPLES Examples 1 and 2, Comparative Examples 1 and 2, 50% by weight, 45% by weight, 35% by weight and 30% by weight corresponding to the component column of Table 1 were added to crucibles for melting metal.
Silicon carbide powder (having an average particle diameter of 15 μm) and the following aluminum alloys of 50% by weight, 55% by weight, 65% by weight and 70% by weight are weighed, heated and melted, and sufficiently stirred, and then produced by casting sand The valve seat material was manufactured by casting in the above mold and then finished into a valve seat shape.
The aluminum alloy used here is a JIS-AC8A material (Cu: 0.8 to 1.3% by weight, Si: 11 to 13% by weight, Mg: 0.7 to 1.3% by weight, Ni: 0.8). ~
1.5% by weight, balance Al and Zn, Fe, Mn, Cr
Alloy produced by dissolving 5% by weight of magnesium at 700 ° C. (Si content in aluminum alloy is 10% by weight, Mg content is 4.5% by weight, the balance is aluminum and trace components, and Aluminum alloy as impurities). The shape of the test piece at this time was a specified shape according to each test method shown in Table 1, and the thermal conductivity, thermal expansion coefficient, bending strength, fracture toughness value, and hardness (Vickers) of the composite material were measured. These results are also shown in Table 1.
Shown in

[0029]

[Table 1]

Next, a durability test was carried out by a unit evaluation test (valve seat test) machine when the four types of composite materials shown in Table 1 were used as valve seats. The results are shown in Table 2.
Shown in In this case, the valve seat was processed from the above composite material into a valve seat shape having an inner diameter of 30 mm, an outer diameter of 37 mm, and a thickness of 14 mm, and the seat wear amount and the valve attachment amount were evaluated. The valve seat tester is a device that simulates the hitting state between the engine valve and the valve seat, and heats the valve temperature to 760 ° C with a burner, keeps the seat temperature at 300 ° C, and rotates it. A durability test (5 hours) was carried out by giving a knocking equivalent to several 2000 revolutions.
At this time, the valve seat material is Stellite (STL) #
32 was used.

[0031]

[Table 2]

As is clear from the results shown in Table 2, the amount of wear of the valve seat increased and the amount of adhesion to the valve also increased as the proportion of aluminum alloy increased. And in the aluminum-silicon carbide composite material of the present invention, compared with the reference value of the copper alloy valve seat material shown in the reference column of Table 2, when the aluminum alloy is 55% by weight or more and 65% by weight or less, that is, silicon carbide is 35% by weight. When the content is not less than 45% by weight, it is possible to satisfy this standard value, reduce the amount of adhesion to the valve, reduce the amount of wear of the valve seat, and lower the temperature of the cooling water around the cylinder head. It was

Examples 1, 3, 4 and Comparative Examples 3 to 5 In the 45 wt% silicon carbide-55 wt% aluminum alloy composite material used in Example 1, the composite material when the particle size of the silicon carbide raw material powder was changed When the durability evaluation test of No. 2 was conducted in the same manner as described above, the results shown in Table 3 were obtained. In this case, as shown in Table 3, silicon carbide used was a powder having an average particle diameter of 10 μm to 35 μm.
Also, the variation of each particle size is 20% above and below the average diameter.
It is something that has a spread of.

[0034]

[Table 3]

As is clear from the results shown in Table 3, the amount of wear of the valve seat increases as the particle size of silicon carbide increases, and when the particle size of silicon carbide decreases, the amount adhered to the valve increases. It was found that the sliding property of the valve was deteriorated due to the increase of the particle size, and that the particle size was limited, and that it was desirable that the average particle size of silicon carbide be 12 μm or more and 18 μm or less.

As is clear from the results of such implementation,
The composite material according to the present invention uses a ceramic-metal composite material made of a silicon carbide-aluminum alloy, rather than a ceramic material obtained by sintering, to significantly reduce wear loss. (Manufacturing by press-fitting the valve seat and casting encapsulation)
It is possible to create a valve head integrated cylinder head that has sufficient strength and toughness to withstand, and when applied to a cylinder liner, it is possible to prevent the seizure of the piston ring due to heat. Is brought about.

The cylinder liner using the composite material according to the present invention has not only wear resistance but also the advantage of not damaging the mating material and the like, which is sufficient not only for the cylinder liner of the engine but also for other hydraulic cylinders and the like. It can be applied. Furthermore, the specific gravity is about 2.85 g / cm.
^3, which is significantly lighter than that of a liner made of cast iron (7.8 g / cm ³ ).

[0038]

As described in claim 1, the composite material according to the present invention contains 35% by weight or more and 45% by weight or less of silicon carbide in an aluminum alloy and has a thermal conductivity of 150 W / (M · K) or more, coefficient of thermal expansion 10 × 10
^Since it is configured to be not less than ⁻⁶ / ° C. and not more than 12 × 10 ⁻⁶ / ° C., it has excellent strength, wear resistance, and thermal conductivity.
For example, it has the strength and wear resistance required for engine valve seats, cylinder liners, etc.,
In addition, it is also a material that is excellent in thermal conductivity, not only has good wear resistance of the part itself that uses the composite material, but also reduces the amount of wear of the mating material. There is a remarkably excellent effect.

The strength, wear resistance, and
In an embodiment of the composite material having excellent thermal conductivity, the particle size of silicon carbide contained in the aluminum alloy is 12 μm or more and 18 μm on average as described in claim 2.
The following effects bring about an effect that the wear resistance of the self can be further improved and the wear to the mating material can be made small, and as described in claim 3, The manufacturability of the aluminum alloy can be improved by making it an aluminum alloy for casting. Particularly, as described in claim 4, the aluminum alloy contains Si: 8 to 11% by weight and Mg: 4 to 8% by weight. % As a basic component, and the balance is made of an aluminum alloy for casting which substantially consists of Al, which has good castability, good strength and wear resistance, and low aggression against the mating material. As described in claim 5, when used as a material for an engine valve seat, a ball having excellent heat conductivity and excellent durability can be obtained. It is possible to provide a seat, and as described in claim 6, it is possible to provide a cylinder liner having excellent durability and excellent heat conductivity by using it as a material of an engine cylinder liner. There is a remarkably excellent effect.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view showing a cylinder head portion of an engine.

FIG. 2 is a cross-sectional explanatory view of a valve seat provided in a cylinder head portion of an engine.

[Explanation of symbols]

 4 Valve seat (composite material) 4a Aluminum alloy 4b Silicon carbide

Claims (7)

[Claims] 1. An aluminum alloy containing 35% by weight or more and 45% by weight or less of silicon carbide and having a thermal conductivity of 15%.
0 W / (m · K) or more, thermal expansion coefficient of 10 × 10 ⁻⁶ / ° C.
A composite material excellent in strength, wear resistance, and thermal conductivity, which is not less than 12 × 10 ⁻⁶ / ° C. 2. The composite material excellent in strength, wear resistance and thermal conductivity according to claim 1, wherein the silicon carbide contained in the aluminum alloy has an average particle size of 12 μm or more and 18 μm or less. 3. The strength, wear resistance, and wear resistance according to claim 1, wherein the aluminum alloy is a casting aluminum alloy.
Composite material with excellent thermal conductivity. 4. The casting aluminum alloy according to claim 3, wherein the aluminum alloy contains Si: 8 to 11% by weight and Mg: 4 to 8% by weight as a basic component, and the balance substantially consists of Al. A composite material with excellent strength, wear resistance, and thermal conductivity. 5. The composite material excellent in strength, wear resistance and thermal conductivity according to claim 1, which is a material for an engine valve seat. 6. The strength and wear resistance according to claim 1, which is a material for an engine cylinder liner.
Composite material with excellent thermal conductivity. 7. Strength, wear resistance and heat, characterized by mixing 55% by weight or more and 65% by weight or less of an aluminum alloy melt and 35% by weight or more and 45% by weight or less of silicon carbide powder and then casting. A method for manufacturing a composite material having excellent conductivity.