JPH11335762A - Sliding member made of powdered aluminum alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sliding member made of powdered aluminum alloy, excellent in immunity to low temperature scuffing and free from deterioration in heat resistance, seizure resistance, wear resistance, and extrudability. SOLUTION: Graphite 12 grains and hard grains are dispersed in a powdered aluminum alloy 11, and the aluminum alloy contains at least one alloy component selected from the group consisting of iron, nickel, manganese, and silicon. The average grain size of the graphite grains is <10 μm and the content of the graphite grains based on the whole of the sliding member made of powdered aluminum alloy is >3 to <13 wt.%, and further, the total content of the alloy components and the hard grains based on the whole of the sliding member made of powdered aluminum alloy is >10 to 25 wt.% and the content of the hard grains based on the whole of the sliding member made of powdered aluminum alloy is 3 to 5 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder aluminum alloy sliding member, and more particularly to a powder aluminum alloy sliding member used as a cylinder liner.

[0002]

2. Description of the Related Art Conventionally, gray cast iron and the like, which are inexpensive and have excellent durability, have been used as cylinder liner materials for engines for automobiles and motorcycles.

In recent years, however, reduction in weight of each component has been studied in order to improve fuel efficiency. As part of this weight reduction, it has been considered to reduce the weight of the engine block and the cylinder liner of the engine. In order to reduce the weight of the cylinder liner, it is effective to use an aluminum alloy. For example, Japanese Patent Publication No. 6-21309 (Japanese Unexamined Patent Application Publication No. 2-120443) discloses that a powdered aluminum alloy, alumina and graphite powder are used. A cylinder liner comprising a sliding member made of a powdered aluminum alloy obtained by hot extrusion of the raw material is disclosed.

[0004]

However, in the cylinder liner described in the above publication, heat resistance, abrasion resistance, seizure resistance and extrudability (formability) are excellent.
When the cylinder liner and the piston ring are slid at low temperatures and in the absence of lubricating oil, the cylinder liner is easily damaged. That is, there is a problem that the low-temperature scuffing property is lower than that of a conventional iron alloy such as gray cast iron.

[0005] This low-temperature scuffing property is a characteristic particularly required for engines for automobiles used in cold regions.
Unless the low-temperature scuffing property is improved, the life of the engine is shorter than that of a conventional product when an aluminum alloy is used as a cylinder liner of an engine for a four-wheeled vehicle.

Accordingly, the present invention has been made to solve the above-described problems, and improves the low-temperature scuffing property without lowering the heat resistance, abrasion resistance, seizure resistance, and extrudability. It is an object of the present invention to provide a sliding member made of a powdered aluminum alloy that can be made to work.

[0007]

The present inventors conducted various experiments to improve the low-temperature scuffing property of a cylinder liner using a sliding member made of a powdered aluminum alloy, and found the following findings. Obtained.

First, if a large amount of graphite is added to a sliding member made of a powdered aluminum alloy, the low-temperature scuffing property is improved as compared with a conventional product. The graphite initially acts as a solid lubricant between the piston and the cylinder liner, and then the cylinder liner is used for a long time so that the liquid lubricant accumulates in the cavity where the graphite fell off. It is thought that it becomes.

Therefore, when the content of the graphite particles is made larger than that of the conventional product, the low-temperature scuffing property is improved at the time of starting the use of the engine because the graphite content is larger than that of the conventional product. Also, as the engine is used, a larger oil pool is formed on the cylinder liner wall than before,
Even when the engine is stopped, the liquid lubricant remains in the oil reservoir. Therefore, even when the engine is started next time, since the liquid lubricant is accumulated in the oil sump, the low-temperature scuffing property does not decrease even after the engine has been used for a long time.

However, when a large amount of graphite particles is contained, the moldability during hot extrusion deteriorates. The present inventors, as factors that determine the formability during hot extrusion,
It has been discovered that the amount of so-called additives other than aluminum, ie, the amount of graphite particles, alloy components (iron, nickel, silicon, etc.) and hard particles, determines the extrudability. Therefore, when the amount of the graphite particles increased, the extrudability was not reduced by reducing the amount of the additives other than the graphite particles.

If the amount of these additives is excessively reduced, the heat resistance and abrasion resistance are reduced as compared with conventional products.
The lower limits were set for the amounts of these additives.

The sliding member made of a powdered aluminum alloy of the present invention based on these findings has graphite particles and hard particles dispersed in a powdered aluminum alloy. The powdered aluminum alloy contains an alloy component containing at least one selected from the group consisting of iron, nickel, manganese, and silicon. The total content of the alloy component and the hard particles in the entire sliding member made of the powdered aluminum alloy is 1
More than 0% by weight and 25% by weight or less. The content of the graphite particles in the entire sliding member made of the powdered aluminum alloy is more than 3% by weight and less than 13% by weight. The average particle size of the graphite particles is less than 10 μm. The content of the hard particles in the entire sliding member made of the powdered aluminum alloy is 3% by weight or more and 5% by weight or less.

[0013] Iron, nickel,
The alloy component containing at least one selected from the group consisting of manganese and silicon is included for the purpose of improving heat resistance, seizure resistance, and wear resistance. In addition,
Copper or magnesium may be included in the powdered aluminum alloy as an alloy component. The inclusion of the hard particles is for improving the abrasion resistance.

When the total content of the alloy component and the hard particles is 1
More than 0% by weight and 25% by weight or less is 10% by weight.
This is because the heat resistance, seizure resistance and abrasion resistance are reduced below, and if it exceeds 25% by weight, the extrudability deteriorates. The content of the hard particles in the entire sliding member made of powdered aluminum alloy is set to 3% by weight or more and 5% by weight or less.
If the amount is less than 3% by weight, the abrasion resistance decreases, and if it exceeds 5% by weight, the toughness and machinability deteriorate.

The content of graphite particles in the entire sliding member made of a powdered aluminum alloy is set to be more than 3% by weight and less than 13% by weight, as long as the content is 3% by weight or less, the low-temperature scuffing property is reduced and 13% by weight or more. This is because extrudability decreases. The reason why the average particle size of the graphite particles is less than 10 μm is that if the average particle size is 10 μm or more, the extrudability decreases.

The alloy component preferably contains at least one of iron and nickel. In this case, heat resistance is further improved.

It is preferable that a powdered aluminum alloy formed by rapid solidification is hot-extruded with a mixed powder obtained by adding graphite particles and hard particles to form a sliding member made of a powdered aluminum alloy. In this case, since the powder aluminum alloy is formed by rapid solidification, the alloy components are finely dispersed in the aluminum alloy. Therefore, the heat resistance, wear resistance, and seizure resistance of the powdered aluminum alloy are improved without deteriorating toughness and machinability. In addition, the powder aluminum alloy sinters during the hot extrusion, and the shape of the product can be formed. Further, as described above, alloy components,
Because there is an upper limit on the content of hard particles and graphite,
Extrusion does not deteriorate even if it is formed by such hot extrusion.

If the total content of the alloy component and the hard particles in the sliding member made of powdered aluminum alloy is 15% by weight or more and 20% by weight or less, heat resistance, wear resistance, seizure resistance,
It is preferable because the extrudability is further improved.

It is preferable that the content of the graphite particles in the sliding member made of the powdered aluminum alloy is 4% by weight or more and 6% by weight or less, because the low-temperature scuffing property and the extrudability are further improved.

It is preferable that the diameter of the graphite particles is 2 μm or more and 4 μm or less, because the low-temperature scuffing property and the extrudability are further improved.

When these powdered aluminum alloy sliding members are used as cylinder liners, they have excellent low-temperature scuffing properties, and have heat resistance, abrasion resistance, seizure resistance and extrudability equal to or higher than those of conventional ones. , It has a long life,
Further, it is possible to provide a lightweight engine for a four-wheeled vehicle.

[0022]

EXAMPLES (Example 1) In order to improve the low-temperature scuffing property, it was considered that graphite particles having an average particle size of 3 μm were added in a large amount to an aluminum alloy formed by rapid solidification.
This aims at increasing the oil retention of the sliding surface of the cylinder liner at a low temperature at a portion where the added graphite particles form an oil reservoir. This is because in order to improve the low-temperature scuffing property, it is important to increase the oil retaining property of the sliding surface.

First, an aluminum alloy powder formed by rapid solidification of a predetermined composition having a particle size of 42 mesh or less by an air atomizing method was prepared. Predetermined hard particles (alumina particles) and graphite particles were added to this aluminum alloy powder and mixed uniformly with a rotary blade mixer. Using this mixed powder, a billet having a diameter of 170 mm and a length of 300 mm was formed in a cold isostatic press.

The billet was heated in an electric furnace, and immediately after the billet temperature reached 400 ° C., the billet was formed into a round bar extruded material having a diameter of 65 mm by an indirect extruder. At this time, a disk made of A5052 (JIS) having a predetermined size was set in front of the billet in order to ensure extrudability. Thereby, samples 1 to 7 in Table 1 were obtained.
Was manufactured. These samples were subjected to a friction test with a piston ring material as a mating material of a cylinder liner in oil under a constant load. It can be said that the lower the frictional force, the higher the low-temperature scuffing property.

Further, the surface condition of each sample after the test was observed. Table 1 shows the results.

[0026]

[Table 1] From Table 1, it was found that when graphite particles having an average particle diameter of 3 μm were added in an amount of 4% by weight or more, the frictional force (friction coefficient) was suppressed, and the low-temperature scuffing property was improved. On the other hand, when the amount of the graphite particles is 13% by weight or more, the metal bond between the rapidly solidified aluminum alloy powders during hot extrusion is hindered, the surface of the extruded material is peeled, and the moldability (extrudability) is increased. Was found to undermine.

(Example 2) In terms of the graphite content (4% by weight, 6% by weight, and 10% by weight) having good low-temperature scuffing property and the graphite content impairing formability (13% by weight), Hot extrusion was performed by changing the amount, and improvement in moldability (extrudability) was examined. Hot extrusion was performed in the same manner as in Example 1 to obtain Samples 8 to 31 in Table 2. The surface of the extruded material was observed for each sample. Table 2 shows the results.

[0028]

[Table 2] From Table 2, if the sum of the contents of the alloy component and alumina (hard particles) is 15% by weight or less, the graphite content is 4% by weight,
It was found that molding was possible at 6% by weight and 10% by weight.

On the other hand, when the graphite content is 13% by weight, the formability cannot be improved within the above-mentioned range of the alloy component amount, so that further addition of graphite particles cannot be expected.

Since the formability depends on the graphite content, the total content of the alloy components and alumina can be increased by reducing the graphite content. Here, the graphite content is 4
Weight%, the total content of the alloy components and alumina is 2
It was confirmed that the moldability was not impaired even if it was increased to 5% by weight.

A sample was formed by hot extrusion using graphite particles having an average particle size of 5 μm or 10 μm in the same manner as in Example 1. For this sample, the surface of the extruded material was observed to evaluate the moldability. Table 3 shows the results.
And Table 4.

[0032]

[Table 3]

[0033]

[Table 4] From Tables 3 and 4, it was found that molding was possible if the average particle size of the graphite particles was 5 μm or less. Even if the average particle size of the graphite particles was 10 μm, the sample 50 could be molded, but the abrasion resistance was deteriorated. On the other hand, if the total content of the alloy component and alumina is too small, not only the HRB hardness (Rockwell hardness of B scale), which is an alternative property of wear resistance and seizure resistance, cannot be maintained, but also the low-temperature scuff property is impaired. I understood.

(Example 3) The HRB hardness (B-scale Rockwell hardness) of the samples extruded in Examples 1 and 2 was measured. As a result, the total content of the alloy components and alumina was 20% by weight. If it is above, it turned out that HRB hardness which is an alternative characteristic of heat resistance and seizure resistance can be maintained. However, if the graphite content is set to 6% by weight or less, even if the total content of the alloy component and alumina is 15% by weight, H
It was found that the RB hardness could be maintained.

(Example 4) The effective particle diameters of graphite particles and alumina used for producing the samples so far were examined by a laser method. As a result, it was found that the graphite particles having an average particle diameter of 3 μm were effectively distributed between 2 and 4 μm. Therefore, the average particle size of the graphite particles is 2 μm to 4 μm.
μm is preferred. It was also found that the particle diameter of alumina having an average particle diameter of 3 μm was effectively distributed between 2 μm and 4 μm.

Example 5 The surface of Sample 18 was observed in detail. Referring to FIG. 1, a portion of the optical microscope photograph of sample 18 that looks like a black vertical streak is a graphite particle. When the area ratio of this portion was analyzed by an image processing analyzer, it was 9.3 area%. As shown in the scanning electron micrograph of Sample 18 shown in Table 2, this portion has a concave portion, and serves as an oil reservoir. The direction of the vertical streaks is the extrusion direction, and it is desirable that the surface on which the vertical streak-like graphite particles are dispersed be a sliding surface. This state is schematically shown in FIG. 3 and FIG. 4, in which the concave portion 13 is formed in the powdered aluminum alloy 11, and the graphite 12 is present in the concave portion 13.

(Example 6) The methods for evaluating extrudability in Tables 1 to 4 will be described in detail. Samples 4, 5, and 6 indicated by “○”, “△”, and “×” in the column of extrudability in Tables 1 to 4
5 to 7 are shown in FIGS. 5 corresponds to “○”, FIG. 6 corresponds to “Δ”, and FIG. 7 corresponds to “×”. “O” and “Δ” were evaluated as good.

(Example 7) A friction test performed on the sample formed by extrusion in Examples 1 and 2 and an evaluation method thereof will be described in detail. First, the test piece was processed into a rectangular parallelepiped test piece in which the surface on which the graphite particles were distributed in the extrusion direction became the test surface. The test surface was finished to about the inner diameter surface of a general cylinder liner. This test surface was observed with an optical microscope. Using a general piston ring material machined into a disk shape as a mating material of this test piece, a friction test in general engine oil was performed using a chip-on-disk type friction tester as shown in FIG. .

Referring to FIG. 8, engine oil 23 was put in container 22. A rotating member 27 was provided in engine oil, and a mating member 26 made of a piston ring material was fixed to the rotating member 27. The test piece 29 is fixed to the fixing member 24, and the test piece 2
The test surface of No. 9 was brought into contact with the mating member 26.

A load was applied to the fixing member 24 from the direction indicated by the arrow 21 while the counter member 26 was rotated at a peripheral speed of 2.5 m / sec in the direction indicated by the arrow R. When the pressure at the contact surface between the test piece 29 and the mating member 26 reached 16.2 MPa, the load was kept constant and a friction test was performed for 3 hours.

During this time, the oil was circulated so that the oil temperature did not rise more than necessary. The load in the rotating direction was read by a load cell by the fixing member 24 holding the test piece 29, and the average value of the frictional force generated during the test was measured using the load as a frictional force. Further, the test surface after the test and the surface of the mating member 26 that was in contact with the test surface were observed with an optical microscope. The results are shown in FIGS.

Referring to FIGS. 9 to 11, in sample 3, the test surface of the test piece as the cylinder liner material is substantially unchanged before and after the test. Also, almost no scuff (scratch) has occurred on the surface of the mating material. Therefore, such a state was marked with “「 ”in the low temperature scuffing and wear resistance columns in Tables 1 to 4.

Referring to FIGS. 12 to 14, in sample 8, the test surface of the test piece as the cylinder liner material is worn after the test from the state before the test. Therefore, for such a sample, the column of abrasion resistance in Tables 1 to 4 was marked with "x". In addition, some scuffs are generated on the surface of the partner material. Therefore, for such a sample, the column of low-temperature scuffing property in Tables 1 to 4 is indicated by “△”.
And

Referring to FIGS. 15 to 17, since the test surface of the test piece as the cylinder liner material does not substantially change before and after the test, such a sample is described in Tables 1 to 4. Of the abrasion resistance column was marked with “○”. In addition, scuffing has clearly occurred in the partner material. for that reason,
The column of low-temperature scuffing property in Tables 1 to 4 is indicated by "x".

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[Brief description of the drawings]

FIG. 1 is an optical micrograph of the surface of Sample 18.

FIG. 2 is a scanning electron micrograph of the surface of Sample 18.

FIG. 3 is an elevational view of a sliding member made of a powdered aluminum alloy according to the present invention.

FIG. 4 is a diagram showing a cross section viewed along line IV-IV in FIG. 3;

FIG. 5 is a photograph of a metal structure on the surface of an extruded material of Sample 4.

FIG. 6 is a photograph of a metal structure on the surface of an extruded material of Sample 5.

FIG. 7 is a photograph of a metal structure on the surface of an extruded material of Sample 6.

FIG. 8 is a schematic view of a chip-on-disk friction tester.

FIG. 9 is an optical micrograph of a test surface of Sample 3 before a chip-on-disk friction test.

FIG. 10 shows a sample 3 after a chip-on-disk friction test.
3 is an optical microscope photograph of the test surface of FIG.

FIG. 11 shows a sample 3 after a chip-on-disk friction test.
5 is an optical micrograph of the surface of a mating material with respect to FIG.

FIG. 12 shows a sample 8 before a chip-on-disk friction test.
3 is an optical microscope photograph of the test surface of FIG.

FIG. 13: Sample 8 after the chip-on-disk friction test
3 is an optical microscope photograph of the test surface of FIG.

FIG. 14: Sample 8 after chip-on-disk friction test
5 is an optical micrograph of the surface of a mating material with respect to FIG.

FIG. 15 shows a sample 1 before a chip-on-disk friction test.
3 is an optical microscope photograph of the test surface of FIG.

FIG. 16 shows a sample 1 after a chip-on-disk friction test.
3 is an optical microscope photograph of the test surface of FIG.

FIG. 17 shows a sample 1 after a chip-on-disk friction test.
5 is an optical micrograph of the surface of a mating material with respect to FIG.

[Explanation of symbols]

 11 powdered aluminum alloy 12 graphite

Claims (10)

[Claims] 1. A sliding member made of a powdered aluminum alloy in which graphite particles and hard particles are dispersed in a powdered aluminum alloy, wherein the powdered aluminum alloy is selected from the group consisting of iron, nickel, manganese, and silicon. An alloy component containing at least one kind, wherein the average particle size of the graphite particles is less than 10 μm, and the content of the graphite particles is more than 3% by weight and less than 13% by weight with respect to the entire sliding member made of the powdered aluminum alloy. The total content of the alloy component and the hard particles with respect to the entire sliding member made of the powdered aluminum alloy is 10% by weight.
, And the content of the hard particles with respect to the entirety of the powdered aluminum alloy sliding member is 3% by weight or more and 5% by weight or less. 2. The sliding member made of a powdered aluminum alloy according to claim 1, wherein the alloy component contains at least one of iron and nickel. 3. The powdered aluminum according to claim 1, wherein a mixed powder obtained by adding the graphite particles and the hard particles to the powdered aluminum alloy formed by rapid solidification is formed by hot extrusion. Alloy sliding member. 4. The total content of the alloy component and the hard particles in the entire sliding member made of the powdered aluminum alloy is 13% by weight or more and 25% by weight or less.
4. The sliding member made of a powdered aluminum alloy according to any one of the above items 3. 5. The powder aluminum alloy product according to claim 4, wherein the total content of the alloy component and the hard particles with respect to the entire powder aluminum alloy sliding member is 15% by weight or more and 20% by weight or less. Sliding member. 6. The powder aluminum alloy product according to claim 1, wherein the content of said graphite particles in the whole powder aluminum alloy sliding member is 4% by weight or more and 10% by weight or less. Sliding member. 7. The sliding member made of a powdered aluminum alloy according to claim 6, wherein the content of the graphite particles in the whole sliding member made of the powdered aluminum alloy is 4% by weight or more and 6% by weight or less. 8. The graphite particles have an average particle size of 2 μm or more and 6 μm or more.
The sliding member made of a powdered aluminum alloy according to any one of claims 1 to 7, which is not more than μm. 9. An average particle size of the graphite particles is 2 μm or more.
The sliding member made of a powdered aluminum alloy according to claim 8, which is not more than μm. 10. The sliding member made of a powdered aluminum alloy according to claim 1, wherein the sliding member made of a powdered aluminum alloy is a cylinder liner.