JPS5846539B2 - Aluminum alloy for bearings and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aluminum alloy for bearings that has high strength, high fatigue strength, and excellent seizure resistance and wear resistance, and a method for producing the same.

Conventionally, sliding bearing materials include copper alloys such as brass, gunmetal, bronze, and lead bronze, tin-based white metals, lead-based white metals, and aluminum alloys (A 11-8n series,
AA-8i-Cd system, AlAl-8n-8i-Cu-N
i series, etc.) are used.

Copper alloys have been widely used due to their excellent seizure resistance and load resistance, but they suffer from high cost and high specific gravity.

In addition, white metal has excellent gripability and conformability, but it is too soft and cannot be used without a backing metal lining.In addition to the disadvantage of poor adhesion to the backing metal, it also has the disadvantages of high price and high specific gravity.

In view of these circumstances, it is desired to develop a low-cost, low-density aluminum alloy-based material that has bearing properties comparable to copper-based and white metal-based materials.

By the way, the properties generally required for bearing materials are mainly (1) load resistance, (2) wear resistance, and (3) seizure resistance.

Seizure resistance depends on conformability, and therefore a certain degree of softness,
It has brittleness, and even if the bearing surface is partially subjected to strong pressure or impact and undergoes plastic processing, it has little work hardening and is flexible enough to easily flow away or deform the shaft. Requires an adaptable nature.

In addition, it is necessary to have the ability to embed fine hard foreign matter that may become interposed between the shaft and the bearing during operation.

On the other hand, wear resistance is a property caused by a certain degree of hardness, and is a property that is difficult to coexist with seizure resistance.

Copper-based alloys and white metals cannot be said to have both of these contradictory properties, and while the contact surface with the shaft is easy to conform to, they have the disadvantage of being prone to "galling" and high wear under high loads. .

As a result, drawbacks have been pointed out, such as a decrease in bearing accuracy and a shortened bearing life due to the intrusion of working fluid into the bearing surface.

As mentioned above, conventional materials are unsatisfactory especially as bearing materials that are subjected to high loads.

In recent years, hydraulic pumps, etc., which are widely used in construction equipment, agricultural machinery, and various other industrial equipment, are small and
There is a trend toward higher performance, and high discharge pressures of 250 kg/loss or higher are required, but in such cases where the contact surface pressure between the shaft and bearing is high, conventional aluminum alloy bearing materials tend to wear unevenly. As soon as it is put away, it cracks due to fatigue, making it unusable.

Thus, there is a strong desire for an alloy for bearings that does not cause uneven wear under high loads and has high fatigue strength.

In view of these circumstances, the inventors of the present invention have conducted intensive research to develop aluminum for bearings that exhibits seizure resistance, wear resistance, high strength, and high fatigue strength under high loads, and has high precision, long life, and good corrosion resistance. This led to the development of an alloy material.

That is, the alloy of the first invention of the present application has a weight ratio of Si5.0 to 8.
．． 0%, Cu1.5-3.5%, Sn1.0-5.5%
The remainder consists of Al and impurities.

In addition to the above compositional elements, the alloy of the second invention of the present application has M
n0.2-1.5%, Mg0.5-1. ．． 5%, Ti0
．． 01-0.2%, Bo, 002-0.04% (the total amount of Ti and B is 0.2% or less), and the balance is A7 and impurities. aluminum alloy.

Further, the third invention of the present application has the composition of the first and second inventions above, has a crystal grain size of 2000 μm or less, a secondary dendrite arm spacing (hereinafter abbreviated as DAS) of 40 μm or less, and further comprises an intermetallic compound. This is an aluminum alloy for bearings, characterized by having a structure in which second phase particles are 30 μm or less.

The fourth invention of the present application has the composition and structure of the first, second, and third inventions, and further, the eutectic Si is spheroidized with a diameter of 15 μm or less, and the elemental Sn is formed in a network in the form of grains of 15 μm or less at the grain boundaries. This is an aluminum alloy for bearings characterized by having a structure arranged in a shape.

The fifth to eighth inventions of the present application relate to a method for manufacturing the above-mentioned alloy.

That is, in the fifth and sixth inventions of the present application, the molten alloys having the compositions of the first and second inventions are solidified at a solidification rate of 5°C/se.
This is a method for producing an aluminum alloy, characterized in that the aluminum alloy is cast at a temperature of c or more, and thereby the alloy of the third invention of the present application is obtained.

In the seventh and eighth aspects of the present application, a molten alloy having the compositions of the first and second inventions is cast at a solidification rate of 5°C/sec or higher, and the resulting alloy ingot is subjected to plastic working at a working rate of 20% or higher. A method for producing an aluminum alloy for bearings, which is characterized in that the aluminum alloy for bearings is then subjected to solution heating and quenching at a temperature of 300 to 500°C, and then tempered at a temperature of 150 to 220°C, thereby achieving the fourth invention of the present application. An alloy of

The reasons for limiting the alloy composition in the present invention will be described.

First, regarding the basic constituents Si, Cu, and Sn, (1) Si: 5.0 to 5.8% by weight primary Si
All of them are finely dispersed as eutectics in the alloy matrix, giving the bearing material the necessary wear resistance and strength, and at the same time improving the fluidity of the molten metal during casting.

If it is less than 5.0% by weight, wear resistance will be insufficient, and if it is less than 8.0% by weight.
If it exceeds this, the toughness will decrease and the fatigue strength of the bearing material will deteriorate.

Moreover, the plastic workability of the alloy deteriorates.

(2) Cu: 1.5 to 3.5% by weight Cu dissolves solidly in the alloy matrix to increase strength and contribute to improving wear resistance, but if it is less than 1.5% by weight, the effect is insufficient. Yes, 3
．． If the amount exceeds 5% by weight, corrosion resistance will deteriorate and cause chemical wear.

(3) Sn: 1.0-5.5% by weight Sn is A
It hardly forms a solid solution in A, but is distributed alone along the grain boundaries, giving the alloy sliding properties and conformability, seizure resistance, and at the same time, the ability to embed foreign substances.

If it is less than 1.0% by weight, there is almost no effect, and 5.5
If the amount exceeds % by weight, the alloy becomes brittle, and particularly its plastic workability is impaired.

Next, Mn, M which is an additional selective component of the alloy of the present invention
The specific amounts of g, Ti, and B all strengthen the alloy matrix and improve its strength, and especially when the alloy is used as a bearing material, it provides excellent seizure resistance and wear resistance under high loads. Demonstrate.

Therefore, by adding one or more of the above-mentioned additional selective components, the properties of the alloy of the present invention can be made even more excellent.

The reasons for limiting each of the additional selected components will be described below.

If Mn exceeds 1.5% by weight, coarse intermetallic compounds will precipitate, significantly reducing strength and elongation.

Further, if it is less than 0.2% by weight, the effect is insufficient.

If the amount of Mg is less than 0.5% by weight, its effect will not be sufficiently exhibited, and if the amount exceeds 1.5% by weight, the elongation will decrease and the fatigue strength will decrease significantly.

Less than 0.01% by weight of TiO or 0.2% by weight of Bo has little effect, and 0.2% by weight of Ti or 4% by weight of Bo.
If the amount exceeds 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 crystals, it is preferable.

When T1 and B are used together, the total amount should be 0.2% by weight or less for the same reason.

The alloys having the compositions of the first and second inventions of the present application are themselves cast, shaped, and cut to exhibit the excellent bearing characteristics as described above as a so-called solid bearing with the cast structure.

Furthermore, even when the alloy is cast into a working ingot and subjected to plastic working such as rolling, extrusion, or forging, and used as a bimetal on a backing steel plate, bearing characteristics improved compared to conventional alloys can be obtained.

The present inventors conducted research on the alloys having the compositions of the first and second inventions in order to further improve the bearing characteristics, and found that the structure of the alloy, together with the composition of the alloy, has a strong influence on the characteristics. Focusing on this, the third invention and the fourth invention of the present application are made based on this.
invention has been achieved.

As mentioned above, the third invention has a crystal grain size of 200 μm and a DAS
It is necessary to have a fine and homogeneous cast structure with upper limits of 40 μm and 30 μm of second phase particles.

In this case, the second phase particles include primary crystals, Al-, C
u, Al-8i, MgSi, A7Mn
Fe, Al-Fe-8i, Al-Cu-M
Refers to intermetallic compounds such as g.

The alloy of the present invention having a defined structure as described above is
It has been found that by using the cast material as it is or by cutting it into bearings, it has further improved strength and fatigue strength, as well as further improved wear resistance and seizure resistance.

Such excellent properties cannot be obtained with tissues outside the above-mentioned limits.

As described above, the fourth invention requires the structural characteristics of eutectic Si and Sn, and such a structure has a remarkable effect of improving seizure resistance, conformability, and galling property, and also has cutting workability. The smoothness and dimensional accuracy of the cut surface are also improved.

As mentioned above, the methods for producing the alloy of the present invention all require that the molten alloy be cast at a solidification rate of 5° C./sec or more.

Such high solidification rates are generally achieved by DC casting (vertical or horizontal direct cooling continuous casting) or die casting with forced cooling by a suitable cooling medium.

Note that the solidification rate herein means the rate of temperature drop at the solid phase-liquid phase interface during solidification of an ingot or casting.

It is more desirable to obtain a finer and more homogeneous structure through high-speed solidification, such as a solidification rate of 20°C/sec or more, but in order to efficiently achieve this state, it is necessary to use a DC casting method to form a finer and more homogeneous structure. Consolidated casting into a billet is the most preferred embodiment.

The structure of the ingot obtained by casting the molten alloy having the composition of the present invention under the solidification rate conditions described above satisfies the structure requirements of the alloy of the third invention.

Such solidification rate conditions are also essential for the refinement of eutectic Si in the alloy.

In other words, the decrease in the width of the Si crystal in the eutectic structure is controlled by the solidification rate of the alloy during the production of the ingot, and thin needle-shaped eutectic Si, which is obtained at a sufficiently high solidification rate, is precipitated and the ingot is By plastic working beyond a certain limit, the eutectic Si is finely divided to form spherical eutectic Si particles.

In this way, the solidification rate is a prerequisite for the fourth invention.

The fourth invention also specifies the state of existence of Sn.

The aforementioned Sn does not form a solid solution in A7, but precipitates in the form of a network at the grain boundaries of αAA crystals.

If the α-AA crystals are fine grains of <200 μm or less as in the third invention, the Sn precipitation width is also small.

When the precipitated Sn is divided into grains by plastic working and heat treatment, the strip-like Sn is arranged in a network at the grain boundaries of α-Al crystals, as shown in the micrograph in Figure 3 (magnification x 440). I come to do it.

If both Si and Sn form a structure like the fourth invention,
The alloy has been found to have improved conformability, galling and embedding properties without sacrificing strength or wear resistance, and ultimately exhibits excellent seizure resistance.

Such an alloy structure can only be obtained by performing a specific heat treatment subsequent to the requirements of the seventh and eighth inventions, that is, production of an alloy ingot and plastic working.

Note that the heat treatment time is adjusted within a range of 1 to 10 hours at a predetermined temperature range for both solution treatment and tempering treatment.
Considering the solid solution hardening of elements such as , Mg, etc., a solution temperature of 450 to 500°C is recommended.

The present invention will be explained below based on experiments.

(Experiment Example 1) Weight ratio: Si6.5%, Cu2.9%, Sn4.8%,
Mn0.1%, Mg1.1%, Ti0.15% balance Al
A molten alloy consisting of unavoidable impurities is solidified at a rate of 10℃/
Vertical semi-continuous casting was performed by holding at 100 sec.

The structure of the obtained alloy ingot is shown in the micrograph in Figure 1 (magnification:
120).

On the other hand, a molten alloy having the same composition as above was solidified at a solidification rate of 1'C/
Sand casting was carried out at Sec, and the structure of the cross section of the ingot is shown in the micrograph (magnification XI 20 ) of FIG.

In the ingot shown in Figure 1, the particle size of the intermetallic compound is 3.
It was observed that the DAS was 40 μm or less in the ingot shown in Figure 2.
In addition, the second phase particles are also considerably coarse and are observed to be approximately 60 μm or more.

(Experiment Example 2) Weight ratio: Si7.0%, Cu3.1%, Sn5.4%,
Mn1.1%, Mg1.0%, Ti0.11%, BO,
A molten alloy consisting of 0.05% balance Al and unavoidable impurities was vertically semi-continuously cast into a billet with a diameter of 50 mm, the solidification rate being maintained at a specific value of 1-b.

FIG. 4 shows the relationship between the solidification rate and the DAS size in the structure of the obtained billet.

As is clear from the figure, the solidification rate corresponding to the DAS limit value of 40 μm found by the present inventors is 5'C/SeC.

Next, the present invention will be explained based on examples.

(Example 1) Table 1 shows the composition of the alloy used in this example.

Among them, A1-, %15 is the invention alloy, and AI6~A
No. 17 is a typical comparative alloy that has been used in conventional bearings.

These molten alloys were mold cast into rod-shaped ingots with a diameter of 40 mm.

The solidification rate is 6°C/sec for the alloy of the present invention and 1-2°C/sec for the comparative alloy.

716.1~/162 are as-cast, but A
3 to 4, the ingots were subjected to T5 treatment (heated at 200°C for 6 hours), and A5 to 15 were ingots subjected to T6 treatment (500°C
Solution heating for 6 hours → water quenching → tempering heating at 170° C. for 6 hours) was performed.

Ingots of comparative alloys 416 to A17 were subjected to T5 treatment (200℃
X6hr heating) was applied.

Ingots heat-treated as described above at room temperature and high temperature (100,2
The mechanical properties were measured at 00°C.

Abrasion resistance was measured using an Okoshi type abrasion tester.

Table 2 shows the mechanical property values at room temperature, Table 3 shows the mechanical property values at high temperature, and FIG. 5 shows the friction test results.

As is clear from the values in these tables and figures, the alloy of the present invention has superior strength, yield strength, and hardness at room temperature compared to conventional alloys (comparative alloys), regardless of whether heat treatment is performed, making it suitable as a high-load bearing material. It is recognized that

Furthermore, as shown in Table 3, both the strength and elongation at high temperatures are excellent, and it is recognized that the alloy of the present invention is a bearing material that can withstand high speed and high loads.

In particular, it is recognized that the T6 treatment of the alloy of the present invention exhibits excellent properties that are significantly different from conventional alloy materials.

The results in Figure 5 show a friction distance of 60 when the mating material is FC-30.
0 m, the final load was 18.8 kg, and turbine oil was used as the lubricant.

The waste in the figure corresponds to the waste in Table 1. Invention alloy 41
, scraps 5, 9, and 12 are all conventional alloys A16AI.
It is recognized that the abrasion resistance is particularly excellent compared to No. 7.

(Example 2) Table 4 shows the composition of the alloy used in this example.

Of these, /1618, 19, 20, and 21 are alloys of the present invention, and 22.423 is a typical comparison alloy that has been used in conventional bearings.

These molten alloys were mold cast into rod-shaped ingots with a diameter of 40 mm.

The ingot of the alloy of the present invention/1618 was treated with T6 (500℃
hr solution heating → water quenching → tempering heating at 160° C. for 6 hr).

The ingot of the invention alloy 419, /16.20, 21 is 50
After homogenization heat treatment at 0°C x 4 hours, air cooling, swage processing at room temperature with a processing rate of 30%, and then T6 treatment (
Solution heating at 500°C for 2 hours → water quenching at 1160°C for 6 hours
hr tempering heating) was applied.

As an example of the structure of the alloy of the present invention thus produced, a micrograph of alloy A19 is shown in FIG. 3 (magnification: X440).

Comparative alloys A22 and /1623 were both subjected to tempering treatment in accordance with normal usage.

The processing conditions are as follows: The waste 22 is heated at 250℃
Heating for 5 hours, A23 is 'l'5 (heating at 200°C for 6 hours) treatment.

The alloy prepared as described above was machine-formed and assembled into a gear pump bearing, and a durability test was conducted.

The gear pump specifications are as shown in Table 5, with a maximum pressure of 15
It is 0 kg/-.

The pump was connected to a diesel engine with a rotational speed of 250 Or.pm via a reduction gear, and an 80-hour durability test was conducted with a load and no-load kettle for 1 second and a cycle of 2 seconds.

The test results are shown in Table 6. The alloy of the present invention had a small amount of wear, the contact surface with the shaft was beautiful, and there was no deterioration in performance before and after the durability test, and good results were obtained.

Claims (1)

[Claims] 1 Si5. O~8.0%, Cu1.5~3.
5% Sn, 1.0 to 5.5% Sn, and the balance Al and impurities. 2 Si 5.0-8.0%, Cu 1.5~ by weight ratio
3.5%, S n 1. C) -5,5%, and Mn0
．． 2-1.5%, Mg0.5-1.5%, TiO,01
-0.2%, BO, 002-0.04% (the total amount of Ti and B is 0.2% or less), and the balance is Al and impurities. . 3. Claims 1 or 2, characterized by having a structure in which the crystal grain size is 200 μm or less, the secondary dendrite arm spacing is 40 μm or less, and the second phase particles made of an intermetallic compound are 30 μm or less. Aluminum alloy for bearings listed. 4. Claim No. 4 characterized by having a structure in which eutectic Si is spheroidized and dispersed with a size of 5 μm or less, and elemental Sn exists in grain boundaries arranged in a network in the form of grains of 15 μm or less The aluminum alloy for bearings according to item 1, item 2, or item 3. 5 Si5. O~8.0%, Cu1.5~3.
5%, Sn1. 1. A method for producing an aluminum alloy for bearings, which comprises casting a molten alloy having a composition of O~5.5% and the balance AA and impurities at a solidification rate of 5° C./sec or more. 6 Si 5.0-8.0% by weight, Cu 1.5~
3.5%, Sn1.0-5.5%, and Mn0.2~
1.5%, Mg0.5-1.5%, Ti0.01-0.
2%, BO, 002 to 0.04, (total amount of Ti and B is 0.2% or less), and solidify a molten alloy having a composition of A7 and impurities. speed 5
A method for manufacturing an aluminum alloy for bearings, characterized by casting at a temperature of ℃/sec or higher. 7 Si 5.0-8.0%, Cu 1.5-8.0% by weight
3.5%, Sn1. A molten alloy having a composition of O~5.5% and the balance Al and impurities is cast at a solidification rate of 5°C/see or higher, and the resulting alloy ingot is subjected to plastic working at a processing rate of 20% or higher, A method for manufacturing an aluminum alloy for bearings, which comprises: followed by solution heating and quenching in a temperature range of 300 to 500°C, and then tempering in a temperature range of 150 to 220°C. 8 S i by weight ratio 5. O~8.0%, Cu1.5~
3.5%, S n 1.0-5.5%, and Mn 0.
2-1.5%, Mg0.5-1.5%, Ti0.01-
0.2%, BO, 002~0°04% (Tazoshi Ti and B
containing one or more types (with a total amount of 0.2% or less),
A molten alloy having a composition consisting of the remainder A [and impurities] was heated at 5°C/
The alloy ingot obtained by casting at a solidification rate of 300 to 500 m
Quenched after solution heating in the temperature range of 0℃, then 150℃
A method for producing an aluminum alloy for bearings, which comprises tempering in a temperature range of ~220°C.