JP2003119531A - Aluminum alloy superior in abrasion resistance, heat resistance and thermal conductivity, and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy satisfactorily having characteristics such as abrasion resistance, high-temperature strength, and heat conductivity (a heat radiating property), which is preferably used for materials particularly for pistons of engines, and provide a manufacturing method therefor. SOLUTION: The aluminum alloy includes SiC particles and is made by means of molding rapidly solidified aluminum alloy powders, wherein the SiC particle is a β-type of the cubic system with a round form, has a content of 1-5%, and has a mean particle diameter of 2-10 μm, and the aluminum alloy comprises 2-6% Fe, 14% or more but less than 20% Si, 0.2-2% Mg, 0.5-3% Cu, 0.01-0.05% Ti, and the balance with unavoidable impurities. The method for manufacturing the aluminum alloy includes mixing the rapidly solidified powders having the above composition, with a β-type SiC particles, degassing the mixture powder, and solidifying it by adding plastic working.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy having excellent wear resistance, heat resistance and thermal conductivity, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, aluminum alloy castings have been used as materials for engine pistons because they are required to have various properties such as light weight, wear resistance, high strength at high temperature, and low coefficient of thermal expansion. However, the engine has a high output, and from the viewpoint of preventing air pollution, high thermal efficiency and high combustion efficiency are required in order to reduce incomplete combustibles. For example, JISAC8A (Si: 11 to 11) Thirteen
%, Cu: 0.8 to 1.3%, Mg: 0.7 to 1.3
%, Ni: 0.8 to 1.5%, balance Al) and other conventional aluminum alloy castings cannot withstand the load.

In order to solve this problem, a rapidly solidified aluminum alloy has been attracting attention, and a composite material in which a ceramics dispersion strengthening material is combined has also been studied. For example, Si: 14 to 25%, Fe: 3.5-6.5%, C
u: 0.4 to 1.2% and Mg: 0.2 to 0.7% are contained, and one or more of Zr, V and Mo are added in a total amount of 0.6.
SiC containing 2% to 2% and having an average particle size of 1 to 10 μm
A rapidly solidified aluminum alloy for pistons containing 0.5 to 10% of particles and the balance of Al and impurities has been proposed (Japanese Patent Application No. 10-20309 (Japanese Patent Application Laid-Open No. 11-199).
No. 959)) has a drawback of abrading the mating material when it is put into practical use (high mating material aggressiveness), and it has been confirmed that the material does not have sufficiently satisfactory properties as an engine material.

The inventors have found that Sera. In order to solve the above-mentioned problems in the rapidly solidified aluminum alloy materials that combine the dispersion-type strengthening materials of the x-type, the relationship between the properties of the dispersion-strengthening material and the aggressiveness of the mating material was tested and examined. Aggressiveness has been conventionally applied to SiC as a reinforcing material.
It was found that the form of

Conventionally, as SiC, a hexagonal α-type SiC whose manufacturing process is simple and temperature control during manufacturing is easy
Is used. In α-type SiC, the c-axis lattice constant changes due to the influence of crystal growth rate, temperature, impurities, etc.
Although there are 0 or more types of morphologies, it was confirmed that each of them had sharp corners and was likely to wear the mating material.

Cubic β-type SiC is also present in SiC, but β-type SiC uses special graphite or carbon, which is special in that it is reacted with vapor of molten silicon or silicon monoxide. It can be manufactured only by a simple manufacturing method, and when it reaches a temperature of 2200 ° C. or higher, it easily transforms to α-type SiC, so strict temperature control is required. Also, there is only one form. However, when β-type SiC is used as a dispersion-strengthening material for an aluminum alloy, its shape is rounded and does not have sharp corners, so the mating material is not aggressive and there is a stepped step on the surface. It was found from the experiments by the inventors that the contact area with the matrix was large and the matrix did not fall off.

[0007]

The present invention is based on the above findings, and in order to obtain an aluminum alloy material having particularly satisfactory properties as a material for an engine, a rapid cooling containing cubic β-type SiC. The solidified aluminum alloy has been made as a result of the examination, and its purpose is to provide an aluminum alloy having excellent wear resistance, heat resistance, and thermal conductivity, and having less aggressiveness to the mating material and its production. To provide a method. The aluminum alloy is preferably used for pistons of high power engines.

[0008]

The aluminum alloy excellent in wear resistance, heat resistance and thermal conductivity according to claim 1 of the present invention for achieving the above object contains SiC particles and is a rapidly solidified aluminum alloy. An aluminum alloy formed by molding powder, wherein the SiC particles are cubic β-type having a rounded shape, the content is 1 to 5%, the average particle size is 2 to 10 μm, and the aluminum is Alloy is F
e: 2 to 6%, Si: 14% or more and less than 20%, Mg:
0.2-2%, Cu: 0.5-3% and Ti: 0.01
.About.0.05% and the balance consists of unavoidable impurities.

The wear resistance according to claim 2 of the present invention,
A method for producing an aluminum alloy having excellent heat resistance and thermal conductivity comprises mixing a rapidly solidified powder of the aluminum alloy according to claim 1 with the SiC particles according to claim 1, and degassing the mixed powder at 300 ° C. or higher. It is characterized by solidifying after treatment.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The significance of the β-type SiC particles and alloy components contained in the aluminum alloy of the present invention and the reasons for limitation thereof will be explained. Β-type SiC particles are similar to conventional α-type SiC particles in aluminum alloy. With the function of dispersing and improving the wear resistance at room temperature and high temperature,
It has the function of reducing the aggressiveness of the opponent material. The preferred content range for the aluminum alloy is 1 to 5%. If it is less than 1%, the effect of wear resistance cannot be sufficiently exerted, and if it exceeds 5%, the workability is deteriorated and the effect of improving wear resistance is saturated. Therefore, the inclusion of more than that is not economical. In addition, SiC
The preferred average particle size of the particles is in the range of 2-10 μm,
If it is less than 2 μm, the effect is not sufficient, and if it exceeds 10 μm, the workability is deteriorated.

Fe improves heat resistance and high temperature strength,
Further, it has the functions of improving the elastic coefficient and lowering the thermal expansion coefficient. The preferable content range of Fe is 2 to 6%
If it is less than 2%, sufficient high temperature strength cannot be obtained.
If it exceeds, the ductility and toughness decrease. A more preferable content range of Fe is 4 to 5%.

Si has the functions of improving wear resistance, elastic coefficient and thermal expansion coefficient, and further decreasing density. S
The preferable content range of i is 14 to less than 20%,
If it is less than%, a sufficient effect cannot be obtained, and if it is 20% or more, it becomes brittle. The more preferable content range of Si is 16-18.
%.

Mg has the function of forming a solid solution in the matrix and improving the strength at normal and high temperatures. The preferable content range of Mg is 0.2% to 2%, and if it is less than 0.2%, a sufficient effect cannot be obtained, and if it exceeds 2%, the toughness at room temperature decreases. A more preferable content range of Mg is 0.8
˜2%, more preferably 0.8 to 1.5%.

Cu improves the strength at medium and high temperatures,
In particular, it has a function of improving high temperature strength around 150 ° C. The preferable content range of Cu is 0.5% to 3%,
If it is less than 0.5%, a sufficient effect cannot be obtained, and if it exceeds 3%, ductility and toughness deteriorate. The more preferable content range of Cu is 1-2%.

Ti has the function of improving the strength at high temperatures even with a trace amount. The preferable content range of Ti is 0.01% to
If it is less than 0.01%, a sufficient effect cannot be obtained, and if it exceeds 0.05%, the thermal conductivity is remarkably reduced. Further, when Ti is added, it is necessary to raise the temperature of the molten metal during powder preparation, but if the content is 0.05% or less, atomization can be performed at a temperature of 830 ° C to 890 ° C. It is possible to reduce the cost and extend the life of refractory materials.

A preferred embodiment for producing the aluminum alloy of the present invention will be described. An aluminum alloy having the above composition is melted and, for example, an aluminum alloy powder is produced by an air atomizing method. in this case,
In order to make the primary crystal Si and the Al-Fe compound fine, it is desirable that the cooling rate at the time of producing the aluminum alloy powder by the air atomization method is 100 ° C / sec or more. When the primary crystal Si is refined, the brittleness of the material is suppressed and the fine S
The dispersion of i particles improves the high temperature strength. Furthermore, the high temperature strength is remarkably improved by the dispersion of the finely divided Al-Fe compound particles.

A predetermined amount of β-type SiC particles is mixed with an aluminum alloy powder produced by the rapid solidification powder metallurgy method, the mixed powder is filled in a can, and sufficient degassing is performed by a vacuum pump or the like at 300 ° C or higher. After the treatment, the can is sealed and subjected to plastic working such as hot pressing, extrusion and forging.

[0018]

EXAMPLES Examples for confirming the effects of the present invention will be described below, including a preliminary test for selecting preferable ceramics as a dispersion strengthening material. These examples show one embodiment of the present invention,
The present invention is not limited to these.

Preliminary test 1 Si: 17%, Fe: 4%, Mg: 1%, Cu: 1%,
Ti: 0.01% is contained, and an aluminum alloy having a composition consisting of balance Al and impurities is melted, and a rapidly solidified aluminum alloy powder is produced by an air atomizing method (atomizing temperature: 830 to 890 ° C.), and is reduced to 297 μm or less. Classified To this aluminum alloy powder, α-type SiC, β-type SiC, Al ₂ O ₃ , Al having an average particle size of 5 μm
5% each of ₄ N ₃ and Si ₃ N ₄ was added and mixed, and these mixed powders were filled in an aluminum can, and the temperature was 380 ° C to 4 ° C.
Vacuum degassing was performed at 95 ° C. Then, the aluminum can was sealed to form a billet for extrusion, hot extrusion was performed at an extrusion ratio of 20 at 380 ° C to 400 ° C, and a round bar having a diameter of 20 mm was extruded.

The round bar thus obtained was machined and the wear amount of the bite was measured. As a result, the wear amount of the SiC-containing material was 10
If 0, the Al ₂ O ₃ -containing material is 180, the Al ₄ N ₃ -containing material is 170, and the Si ₃ N ₄ -containing material is 170.
It has been proved that the C-containing material has less wear of the cutting tool and is superior in workability than the materials containing other ceramics.

Preliminary Test 2 Next, in order to compare the characteristics of the aluminum alloy containing hexagonal α-type SiC and the aluminum alloy containing cubic β-type SiC, an aluminum alloy having the same composition as in Preliminary Test 1 A powder was prepared in the same manner as in Preliminary test 1, and the obtained aluminum alloy powder was classified to have an average particle size of 5 μm.
5% each of α-type SiC and β-type SiC of m,
By mixing and using these mixed powders, a round bar having a diameter of 60 mm was prepared in the same manner as in the preliminary test 1, and processed into a disk material having a diameter of 60 mm and a thickness of 5 mm. For comparison, Si
A round bar material having a diameter of 60 mm to which C was not added was also prepared, and used as a disk material.

A pin disk wear test was carried out using a pin-on wear tester shown in FIG. 1 by combining these three types of disk materials and a pin material made of a sintered metal material.
As a test condition, 490N (2MP
It was pressed against the disc material under the load of a), the disc material was rotated at a friction speed of 2 m / sec for 2 hours, and a friction distance of 14400 m and three pin materials were run on the disc material.

As a result, as shown in FIG. 2, in the material containing β-type SiC, both the wear amount of the disc material and the wear amount of the pin material are small, and the wear resistance and the attacking property of the mating material are excellent. Was confirmed.

Example 1 Test material No. 1 in Table 1 An aluminum alloy having a component composition of 1 to 11 was blended and melted, and in the same manner as in the preliminary test 1,
An aluminum alloy powder was prepared at an atomizing temperature of 830 to 890 ° C., and after classification, cubic β-type SiC was added and mixed as shown in Table 1. Using these mixed powders, in the same step as in the preliminary test 1, A round bar material having a diameter of 60 mm was produced.

The obtained round bar material was heat-treated under the conditions of 490 ° C. × 4 hours → water cooling → 210 ° C. × 4 hours → air cooling, and then (1) wear resistance and mating material attacking property were measured according to the following method.
(2) Heat resistance and (3) Thermal conductivity (electrical conductivity) are measured and evaluated.

(1) Abrasion resistance and mating material aggressiveness A disk material having a diameter of 60 mm and a thickness of 5 mm was prepared from a round bar material after heat treatment, and a preliminary test 2 was conducted by a pin-on abrasion tester shown in FIG. Under the same conditions as above, a pin disk wear test is performed to evaluate the amount of wear of the disk material and the aggression of the mating material due to the wear of the pin material. The evaluation criteria are as follows. Abrasion resistance: ○ when the wear amount of the disc material is less than 10 μm, Δ when the wear amount is 10 μm to 20 μm, × when the wear amount exceeds 20 μm Opponent aggression: The wear amount of the pin material is 0.8 mm If the wear amount is less than ◯, the wear amount is 0.8 mm to 1.5 mm, the wear amount is Δ, and if the wear amount exceeds 1.5 mm, is the X mark.

(2) Heat resistance After heat treatment, a tensile test piece is sampled from a bar and subjected to a tensile test at 200 ° C. and 300 ° C. for evaluation. The evaluation criteria are as follows. If the yield strength in a high temperature tensile test at 200 ° C is less than 140 MPa, x, 140MP
A is a or more and less than 160 MPa, and Δ is 160 MPa or more. (3) Thermal conductivity (conductivity) Since the thermal conductivity is proportional to the conductivity, the conductivity was measured for ease of measurement. The evaluation criteria are as follows.
Conductivity is less than 20, x is more than 20 and less than 25, and is 25 or more.

The results are shown in Table 1. As can be seen from Table 1, it is recognized that Examples 1 to 11 according to the present invention are all excellent in wear resistance, opponent attack, heat resistance, and thermal conductivity (electrical conductivity).

[0029]

[Table 1]

Comparative Example 1 Test material No. An aluminum alloy having a composition of 12 to 19 was blended and melted, an aluminum alloy powder was prepared in the same manner as in the example, and after classification, hexagonal α-type SiC
Alternatively, cubic β-type SiC was added and mixed as shown in Table 1, and the mixed powders were used to produce a round bar material having a diameter of 60 mm in the same process as in the preliminary test 1. The test material N
o. No. 12 was atomized at a temperature of 950 ° C to 1000 ° C.

The obtained round bar was heat-treated under the conditions of 490 ° C. × 4 hours → water cooling → 210 ° C. × 4 hours → air cooling, and then (1) wear resistance and mating material attack ,
(2) Heat resistance and (3) Thermal conductivity (electrical conductivity) are measured and evaluated. The results are shown in Table 2.

[0032]

[Table 2] << Table Note >> Test material No. 19 is AC8A alloy casting

Test material Nos. 12-
No. 19 is inferior in at least one characteristic. That is, the test material No. In No. 12, since Ti is 2.0%, which is higher than the upper limit value, the electrical conductivity (thermal conductivity) is insufficient. Test material No. No. 13 has poor heat resistance because it does not contain Ti, and the test material No. In No. 14, wear resistance was insufficient due to a small amount of Si, and since the mating material was aggressive because SiC was α type, heat resistance was insufficient because Ti was not contained.

Test material No. In No. 15, since the SiC was α type, the mating material had a high attack property, and since Ti was not contained, the heat resistance was insufficient. Test material No. No. 16 has a low Fe content and thus lacks heat resistance. Further, since the SiC is α-type, the mating material is highly attackable. Test material No. 17 and 18 are
Since the amount of Si is large, the electrical conductivity is insufficient, that is, the thermal conductivity is insufficient, the heat dissipation is poor, and the temperature tends to be high, which may cause melting loss. Further, since Ti is not contained, the heat resistance is insufficient. Test material No. No. 19 is a JIS AC8A aluminum alloy casting, and since it does not contain SiC, its wear resistance is poor.

Example 2 Test material No. 1 of Example 1 An aluminum alloy having the composition of No. 2 was produced by the same method as in Example 1 and was formed into a piston shape by forging, and the piston was subjected to a durability test according to the following method to measure the wear condition of the ring groove of the piston. Then, the durability was evaluated.

Durability test: A piston processed into a product is incorporated into an engine, and an engine durability test is performed at 13000 rpm for 100 hours. After the durability test of the engine, the wear condition of the ring groove of the piston (the wear condition measuring portion is shown in FIG. 3). ) Is measured. Table 2 shows the wear condition of the ring groove evaluated by the angle γ of the lower surface of the ring groove. The angle γ before the durability test is 0.00 to 0.01 °.

[0037]

[Table 3]

As shown in Table 3, almost no wear was observed in the ring groove of the piston, and it was confirmed that the piston ring exhibits excellent wear resistance in practical use.

[0039]

As described above, according to the present invention, there are provided an aluminum alloy having various characteristics such as wear resistance, high temperature strength, and high thermal conductivity (heat dissipation), and a method for producing the same.
The aluminum alloy can be preferably used especially as a material for engine pistons.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a pin-on wear tester.

FIG. 2 is a diagram showing wear amounts of a disc material and a pin material by a pin-on wear tester.

FIG. 3 is a diagram showing wear measurement positions of a ring groove of a piston made of the aluminum alloy of the present invention.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masahiro Takahashi             300, Takatsuka-cho, Hamamatsu City, Shizuoka Prefecture Suzuki shares             In the company (72) Inventor Akio Kikuchi             Sumitomo Light Gold 5-11-3 Shimbashi, Minato-ku, Tokyo             Inside the industry (72) Inventor Yoshimasa Okubo             Sumitomo Light Gold 5-11-3 Shimbashi, Minato-ku, Tokyo             Inside the industry F-term (reference) 4K018 AA16 AB04 AC01 BA20 BB01                       BB06 BC10 KA08

Claims (2)

[Claims] 1. An aluminum alloy containing SiC particles and formed by molding a rapidly solidified aluminum alloy powder, comprising:
The SiC particles are cubic β type having a rounded shape, the content is 1 to 5% (mass%, the same hereinafter), the average particle size is 2 to 10 μm, and the aluminum alloy is F
e: 2 to 6%, Si: 14% or more and less than 20%, Mg:
0.2-2%, Cu: 0.5-3% and Ti: 0.01
An aluminum alloy having excellent wear resistance, heat resistance and thermal conductivity, characterized in that it contains ˜0.05% and the balance is unavoidable impurities. 2. The rapidly solidified powder of the aluminum alloy according to claim 1 is mixed with the SiC particles according to claim 1, the mixed powder is degassed at 300 ° C. or higher, and then solidified. A method for producing an aluminum alloy having excellent wear resistance, heat resistance and thermal conductivity.