JPH0277547A - Al-sn-pb bearing alloy - Google Patents

Abstract

PURPOSE:To regulate the shape of hard Si grains dispersed and precipitated in the title alloy to the roundish one and to improve its fatigue resistance, seizure resistance and wear resistance in the range of high temp. by adding specific amounts of Sr to an Al-Sn-Pb bearing alloy contg. Si and matrix metal- strengthening elements. CONSTITUTION:To an Al-Sn-Pb bearing alloy contg., by weight, 3 to 35% Sn, >6 to 11% Si, 0.1 to 10% Pb, total 0.1 to 4% of Cu and Ti and the balance Al, 0.01 to 0.3% Sr is added. The shape of hard Si grains 2 dispersed and precipitated by the addition of Sr into an Al matrix 1 hardened and strengthened by Cu and Ti is converted into the spherical one, elliptic one or roundish one in the tip and Sn-Pb alloy grains 3 are furthermore precipitated adjacently to the Si grains 2 to drastically improve the lubricity, by which the Al-Sn-Pb bearing alloy having excellent fatigue resistance and other characteristics at a high temp. can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an Al-Sn-Pb bearing alloy, and more specifically, the present invention relates to an Al-Sn-Pb bearing alloy. Al is dispersed and precipitated, and has excellent fatigue resistance, seizure resistance, and wear resistance in high-temperature ranges, and is excellent during high-speed and high-load operation.
-Relating to Sn-Pb bearing alloy.

Conventional technology Recently, automobile engines have become smaller, more fuel efficient, and have higher output.As a result, the load on the bearings has increased, the temperature of the lubricating oil has increased, and the operating conditions for the bearings have increased. is becoming increasingly severe. Conventional multi-component systems and Al
Most of the type bearings have a Pb-Sn type surface (2) formed on the surface of the bearing base metal part by overlay plating or the like. However, bearings with this structure suffer from fatigue and seizure phenomena due to high temperatures on the lubricated surfaces, making them unable to withstand the above-mentioned severe operating conditions.

Therefore, recently there has been a demand for bearings in which surface areas are not formed by overlay plating or the like.

However, even with this type of bearing, the current situation is that stable performance cannot necessarily be achieved under the above-mentioned severe usage conditions.

That is, a bearing with an overlay plating on the surface has - JIS H5402, Al-1 (10%
sn, 0.75% C1l, 0.5% Ni, Aj! Ba
1), JIS H5402, Al-2 (6%Sn,
2.5%Cu, 1.0%N15AlBa/) etc., SAE 780 (6%sn, 2%Si, 1%Cu,
0.5%Ni, 0.1%Ni1, Aj! S of Bajri et al.
As shown in the AE standard, the bearing base metal part is made of a low n-1 alloy with relatively low Sn content.
A surface pedestal is further formed on the surface of these bearing alloy parts by overlay plating of a pb-sn alloy, and this surface pedestal constitutes a bearing surface. However, these bearings
In recent years, high-quality products have become unusable under high-temperature usage conditions, as the surface layer due to overlay plating on the surface deteriorates, leading to seizure. On the other hand, bearings that do not have a surface layer formed by overlay plating on the surface have SA
E 783 (20%Sn, 0.5%Si, 1.0%
Cu.

As shown in 0.1%T1 and AA'Bal1l, the bearing base metal part is made of a high 5n-A1 alloy containing a large amount of Sn. However, such an alloy containing as much as 20% Sn has low hardness and weakens the Al matrix, so it cannot withstand high loads.

In addition, regardless of the degree of SO content, bearing base metals made by adding PB to Al-Sn alloys to improve lubricity and provide seizure resistance have been developed, for example, by Takashi Mizuno - Hashi Nikkan in 1952. It is described in page 139 of r Bearing Base Metal J published by Kogyo Shimbunsha, and this bearing base metal is made of Al-Sn containing 10% Sn, 1.5% Cu, 0.5% S1 and adding 3% Ilb. −
It is a Pb-based alloy.

Furthermore, since pb in the 8l-Sn-Pb alloy hardly forms a solid solution with AI, an AI-Sn-Pb-Sb alloy with sb added is specially used to improve the pH dispersibility. It is described in Publication No. 52-12131, and Cr is added thereto to strengthen the Al matrix. −
Sn -Pt+ -Sb -Or system alloy was published in 1988-
No. 18985. However, these Al
The 1-Sn-pb alloy was developed for the purpose of improving rA lubricity during normal operation, but has the drawback of not exhibiting sufficient fatigue resistance under high-load operating conditions. The reason for this is that the lubrication mechanism between the shaft and bearing under high load operation is fundamentally different from that under normal operation.

From this point on, basic studies were conducted on the differences between the lubrication mechanism under high-load operation and that under normal operation, and one of the results of the study was the dispersion and precipitation of coarse Si in the Al-Sn alloy. A similar bearing has been proposed in Japanese Patent Application Laid-Open No. 58-64336.

This bearing has a cutting force made of hard Si precipitates, and because it has the cutting force, the unevenness on the surface of the mating shaft is shaved off and flattened, improving the bearing performance.

To explain in more detail, on the surface of the mating shaft made of graphite cast iron on which spherical or flaky graphite has been precipitated, a recess remains after the graphite particles that fell off during polishing, and around this recess there is hard work-hardened paris. Convex portions such as edges and edges are generated. Therefore, as mentioned above, Al-5n system, Al-Sn
- In a bearing base metal made of Pb or the like, abnormal wear is likely to occur during high-load operation due to these uneven portions. On the other hand, in the bearing base metal in which the coarse Si is dispersed and precipitated, the cutting force is applied by the hard Si precipitates, so the uneven parts of the mating shaft are mechanically cut and flattened. , therefore,
No abnormal wear or seizure occurs.

However, when the mating shaft is made of a material other than graphite cast iron, during high-load operation, the surface of the mating shaft is scratched irregularly by coarse Si precipitates, causing seizure and causing major problems.

Problems to be Solved by the Invention The present invention aims to solve the above-mentioned drawbacks, and specifically,
In the AX-S roll b series bearing alloy, we increase the content of gold such as Sn and PB to improve lubricity, and add elements such as Or, Sb, Mn, and N1 to strengthen the Al matrix. The hardness of the Al matrix is increased by these methods, but on the contrary, these methods actually increase the hardness of the Al matrix.
The alloy becomes brittle, and during high-load operation, it is difficult to operate at high temperatures (1
00 to 250°C).

However, in the present invention, Si having an oval, spherical, or rounded tip is placed in the Al matrix.
The solution by precipitating particles thus improves seizure resistance and wear resistance.

Means for solving the problem and its effect, that is, the bearing base metal according to the present invention has a ratio of 1% to 3 to 3%.
5% Sn, over 6% up to 11% S1 and 0.1 to 1
In an AI-Sn bearing alloy containing 0% Pb, the total content of Cu and metal is 0.1 to 4%, and the remainder is substantially AI, while 0.01 to 0.3% Sr is Add A
It is characterized by dispersing and precipitating 31 particles in a spherical, elliptical, or rounded tip shape in a matrix.

A more detailed explanation of the configuration of these means and their operation will be as follows.

First, the present invention was made to improve fatigue resistance under high temperature conditions.

In other words, in the conventional example, O, which is simply a high melting point element,
Addition of R, Go, Ni, etc. increases high-temperature strength, prevents sudden decrease in hardness at high temperatures, and improves wear resistance. However, in this way, Al-Sn-P
Increasing the fatigue resistance of B-series alloys at high temperatures cannot be achieved simply by adding high-melting-point elements to increase hardness; instead, the alloys become brittle, resulting in lower tensile strength, elongation, and impact resistance. value decreases.

Regarding this point, in the present invention, in order to provide a bearing base metal suitable for severe conditions under high temperature and high load, Sr is added as an essential component, and the sr of the mouth is made to act on 31 at the time of casting. Spheroidizing the crystal particles or partially spheroidizing the Si crystal particles, that is, rounding the tips of the Si crystal particles,
Furthermore, heat treatment under normal conditions enhances the spheroidization or roundness of the S1 crystal particles, thereby making the Al-Sn-
PB gold alloy increases tensile strength, elongation and impact strength.

In other words, 1l14 fatigue strength is caused by the material's tensile strength, elongation, impact strength, organizational structure, etc., and cannot be solved simply by adding bearing components. However, in the present invention, 31
The aim is to make the crystal grains spheroidal, and this spheroidization is further enhanced by Sr during heat treatment.

In addition, in the present invention, by adding Sr, R'4! Since it is possible to prevent the deterioration of i-characteristics, even if high-melting-point elements are added to the AI-Sn-Pb alloy as mentioned above, the deterioration of i-characteristics at high temperatures can be prevented from rapidly decreasing. There is no. These features of the present invention can be supported by the fact that fatigue strength was improved as a result of fatigue tests conducted at high temperatures and under high loads.

Next, when Si particles having a spherical shape or a rounded tip are precipitated in the Al matrix as described above, a bearing surface that is suitable for high temperature and high load conditions and has significantly improved surface performance can be obtained.

- It is said that it is difficult to understand the phenomenon of seizure in the shell because the process of reaching it is complex and many conditions interact synergistically. However, Pb on the surface
In a bearing made of a Cu--Pb alloy that has a surface layer formed by oval plating of a -Sn alloy, the surface layer of this plating wears away under high load operation, leading to burning f=j. On the other hand, S
Consisting of an At-Sn-Pb alloy containing l, Cu,
Seizing does not occur in bearings that do not have a surface layer formed by overlay plating on the surface.

The present inventors paid attention to this point and conducted a structural comparative study of both bearings. That is, FIG. 3 is an enlarged sectional view of a part of a bearing having a surface layer formed by overlay plating (hereinafter simply referred to as an overlay plating base) on the surface, and FIG.
The figure is an enlarged cross-sectional view of a part of a bearing made of an AI-Sn-Pb alloy, which does not have an overlay plating layer on its surface (but also contains Sl, Cu, etc.).
This bearing consists of an overlay plating layer 4 on the surface, an alloy layer 5 and a backing metal 6.
The axial load is supported by the entire surface of the On the other hand, as shown in Fig. 4, in the Al-Sn-Pb alloy, Si, C
The bearing including u, etc. consists of an alloy layer 5 and a back metal 6, and 31 rod-shaped or flake-shaped particles 2 are precipitated in the matrix of this alloy layer 5.

Therefore, in this bearing, the load of the mating shaft is supported by the hard Si particles 2, and moreover, the Si particles have a cutting force as described above.

In short, the difference between the two is surface contact and point contact, and this difference makes a decisive difference in lubrication and temperature rise of the friction surface. In other words, in surface contact, as in the bearing shown in Figure 3, the temperature of the friction surface rises rapidly under high speed and high load conditions, whereas in point contact, as in the bearing shown in Figure 4, the temperature of the friction surface increases rapidly under high speed and high load conditions. A gap is formed between the surface of layer 5 and the surface of the mating shaft, and since no large load is applied to the oil film in this gap, sufficient lubrication is maintained and temperature rise on the friction surface is suppressed.

Proceeding further, the present inventors based on the basic viewpoint that supporting shaft loads through point contact as shown in Fig. 4 is extremely effective for lubrication under high loads, and in order to make the most of the effect. Through research on the composition and structure of the bearing base metal according to the present invention, they completed research on the composition and structure of the bearing base metal.

Specifically, the present inventors have discovered that S in a bearing base metal containing an AI-Sn-Pb alloy such as 5ifICu
Focusing on the precipitation form of l, we conducted research on the effect of this form on the lubricating surface. First, we found that Si is a stable substance with a melting point of 1f, and has strong nonmetallic properties, making it difficult for the mating shaft to 200℃~ for main component Fe
The point support means for the axial load is Sl
was found to be extremely suitable.

Second, when supporting the mating material at a point via an oil film, the 31 particles are so hard that their Vickers hardness reaches 599, and the 81 particles are not a compound, so they are not brittle, have high elasticity, and can withstand rapid fluctuations in load. It was found that it can withstand

However, despite having the above-mentioned properties, Si has strong crystallinity (even in the form of eutectic precipitation with Al,
It has a plate-like or rod-like shape, and its shape changes only slightly even after subsequent rolling and heat treatment. For this reason,
If the precipitation form of Si particles is not controlled from the time of casting, as shown in FIG.
The 81 particles 2 precipitated together with the i-Pb alloy particles become plate-shaped or rod-shaped, while the 81 particles 2 separated from these Si particles 2 form 5
n-Pb alloy particles 3 will be present. In this state, the edges of the hard Si particles 2 cannot scrape the mating shaft and are likely to attach, and on the contrary, the lubricity is reduced and seizure occurs.

From this point of view, in the present invention, in order to dramatically improve the lubricity, the cutting force is removed from the 31 particles, and the edges are controlled to have a rounded shape, such as spherical shape.

That is, FIG. 1 is an enlarged sectional view of a part of a bearing base metal according to one embodiment of the present invention, and as shown in FIG.
1 particles 2 are spherical, and the spherical 81 particles 2 bring the ideal point contact closer to the ideal point contact, further increasing lubricity and wear resistance. Furthermore, even if a high load is suddenly applied at high speed, the mating shaft will not be damaged. Also, Sl
Since it is spherical, there is no notch effect in the matrix, making it possible to create a 1q matrix that is stable in terms of strength and has excellent wear resistance.

This spheroidization of 81 particles can be achieved by improving the properties of the A1 alloy liquid phase at the eutectic point where 81 precipitates by adding Sr, and furthermore, even if the conditions are normal in the subsequent heat treatment, The spheroidization is enhanced by S.

Furthermore, the addition of Sr changes the precipitation form of the 5n-Pb alloy particles 3, and as shown in FIG.
The 5n-Pb alloy 3 is present more closely adjacent to the 5n-Pb alloy 3. This structure dramatically improves the lubrication performance compared to the conventional structure (see, for example, FIG. 5).

In addition to solving the surface performance structurally as described above,
AI is highly sensitive to heat (if it exceeds 150℃,
)lv 10 or less and loses its strength,
There is a need for g+ to strengthen the matrix at high temperatures, and Cu and i are added from this point.

That is, among these additive elements, Cu forms a solid solution with Al and hardens the Al matrix.

When these are in the range of 0.1 to 4%, part of them dissolves in solid solution and the rest precipitates, and the balance strengthens the Al matrix. In particular, adding 0.1 to 4% of Cu alone is appropriate. It is.

Further, (1) is a precipitation hardening type matrix reinforcing element, and when the strength at high temperatures is improved by this 11-strengthening element, the appropriate amount of (1) to be added is 0.1 to 4%.

In this way, the precipitation hardening type reinforcing element 1 is added, and the strength is improved by solid solution of these elements.

There is no particular control on the addition ratio of CU and Ti, but Cu is
In order to form a solid solution in X, it is preferable to add a large amount compared to (1).

For example, if the remaining Cl is 13% or less, preferably 2% or less, T
Let it be i.

As described above, in the present invention, in addition to simply adding base-strengthening elements as in the past, S'' is added together with these reinforcing elements to improve not only the hardness (but also the tensile strength and durability). The purpose is to increase fatigue resistance and improve bearing performance under high load operation.The mechanism and composition of each component are explained as follows.

In the bearing with the configuration shown in FIG. 1, the lubricating surface that supports the shaft load is the tip of the Si particles 2 protruding from the surface of the matrix 1, and there is 'all' between the Si particles and the mating shaft.
l intervenes to maintain fluid lubrication. However, this oil film ruptures under severe fluctuating loads and locally reaches boundary lubrication, and if a 5n-Pb alloy film is interposed on the upper surface of the Si particles 2 at this time, seizure can be prevented. , the oil i can be normally regenerated and the state of fluid lubrication can be quickly restored. Also at this time, if the structure shown in FIG. 1 is used, sn-11b alloy particles 3 are located near the Si particles 2
exists, and this alloy has an affinity for lubricated surfaces even in the molten state, so it does not cause oil depletion. ,
Heat is absorbed by the heat of fusion of 5i-Pb, making it difficult for the adjacent matrix Al alloy to seize with the mating shaft.

Also, at this time, as shown in FIG. 2, at least a portion of the Sn--Pb alloy particles 3 adjacent to the 81 particles 2 are in a liquid phase, and this liquid phase 3a is supplied to the protruding surfaces of the S+ particles 2. . As the temperature increases, this supply port increases by 5% to 31
Since the 5n-Pb liquid phase 3a is always present on the lubricated surface of the particles 2, overheating can be prevented. In short, the Si particles 2 are spheroidized, and the 5n-Pb alloy particles 3 are spheroidized.
The structure in which the two are adjacent to each other is very effective in the boundary lubrication state (the bolt R is broken), and even in the normal fluid lubrication state, the hard Si particles 2 suitably fit into the mating shaft, and the soft 5n-pbl This acts as a shock absorber.

The reasons for limiting each element as described above are as follows.

First, C is an element that forms a strong Al matrix.
The reason for setting the total amount of addition of u and precipitation hardening type strengthening element 1 to 0.1 to 4% is that if CU exceeds 4% in 7A addition, the amount of precipitation will increase, which will cause In addition, if the amount added in (1) is 0.1 to 4%, fatigue resistance can be imparted to the bearing, but if it is added in excess of 4%, the compound becomes coarse and its toughness deteriorates. Therefore, 0.1 to 4% of CU and Ti are added to fully express the effects of CU and Ti.

Furthermore, a continuous lubricating surface can be formed when the sn content is in the range of 3 to 35% and the pb content is in the range of 0.1 to 10%. In addition, Sl has seizure resistance,
Effective for improving wear resistance, adding more than 6% to 11% is sufficient! il structure can be maintained.

In addition, Sr controls the shape of Sl to be spherical, and furthermore, 5n-
It causes Pb particles to precipitate near the S1 particles, and is an extremely effective element. However, if the Sr content is 0.01% or less, there is no such addition effect, and if the Sr content is 0.3% or more, cavities are more likely to occur during casting, causing problems.

Example Next, examples of the present invention will be described.

Example 1 First, an AI-Sn bearing alloy having the composition shown in Fig. 1 was cast as a plate material with a thickness of 20 mm by continuous casting, and the upper and lower surfaces of each cast billet were milled by 1.0 + n + a, and then cooled. It was rolled down to a thickness of 2 mm by inter-rolling.

In this state, heat treatment is performed at 300 to 350°C to remove strain, and then a thin pure aluminum plate is crimped onto a steel backing plate to a thickness of 1. A soml bearing was obtained.

Among these bearings, test materials N6.1 to N6.5 are conventional test materials that do not contain Sr, and N16 to N10 are test materials according to the present invention.

Each of these test materials was used as a bearing at normal temperature and
To examine the mechanical properties at 00°C, tensile strength, elongation and hardness tests were conducted and are shown in Table 2. In addition, the backing metal of each sample material was removed by machining and At
-Only the Sn alloy part, the shape of the test piece is JIS z
22 old No. 5.

From these results, the test materials Na6-10 show less strength loss at high temperatures (200°C) than conventional materials (Cu,
The effect of adding Ti can be seen. In other words, it is considered that the spheroidization of Si and the reinforcement of the matrix were phase-opened and the strength and elongation were improved. It can be said that the mechanical properties at High; B were improved.

Next, in order to find out the seizure resistance and abrasion resistance of the sample materials, a test was conducted using a Suzuki type friction and wear tester, and the test conditions were as follows.

Massage speed 4m/sec, mating material 345G, hardness HFIC=55 surface roughness 0.8
~1. O3 Oil used: SAE, 20w-40 Oil temperature: 150±5℃ Seizure load: 100klJ/Im2 to 10kg/Cl1
In 2Siep, the surface pressure is increased every 15 minutes until seizure occurs, and the surface pressure that causes seizure is defined as the seizure vJ weight.

Abrasion resistance On the other hand, to check the abrasion resistance, 100klJ/
The test was conducted for 6 hours at a constant Ii, and the change in weight was observed thereafter.

The results are shown in Table 2.

According to this, all of sample materials No. 6 to 10 show better seizure resistance and wear resistance than conventional materials, and it can be seen that the surface performance is also improved by adding Sr and matrix-strengthening elements. . This shows that the alloy according to the present invention has an excellent lubrication radius.

Next, each sample material was actually processed into a bearing shape, and R
When we conducted a fatigue test on the bearing, the second
The results shown in the table were obtained. This test was conducted under the following conditions, with the bearing fixed to the connecting rod and an eccentric load applied to the shaft, almost the same as in an actual engine, and the performance was maintained without seizure or damage. Criticize based on the length of time (this is a song test).

Surface pressure 600kgr/cf rotation
Number 400Or, p, m Compatible material FCD 70,
Oil used for roughness 0.8-1.5S SAE 201
-40 Oil temperature 150℃±5℃ The upper limit of this test time is 300 hours, N=5
The average values are shown in Table 2. As a result, all of the alloys exhibited longer durability than the conventional materials of comparative examples, and the alloys according to the present invention exhibited excellent fatigue resistance.

On the other hand, in order to investigate the morphology of Sl in the case where 0.03% Sr was added to the alloy of conventional example N. When deeply etched and examined using an electron microscope, it was found that the addition of Sr made the Si spheroidal.

Example 2 In order to confirm whether the bearing base metal according to the present invention has the effect of improving the brittleness of the alloy by adding a high melting point metal etc. as a reinforcing agent to the AI matrix, impact value was measured as a substitute property. was measured, and the improvement effect due to the addition of Sr was determined through experiments.

A comparative experiment was carried out using the conventional materials No. 5, which do not contain S, shown in Table 1 of Example 1, and the specimen material &6 according to the present invention, as test materials.

The experiment was conducted using No. 3 test pieces (n=5) prepared according to JIS z 2242 and the Charpy impact test method.

The average value of the Yuto conventional material in the experiment was [0.84 klJ・ri/al
However, the average value of the one according to the present invention was 2,90 klJ.
・Ill/I]2, and it was clear that the bearing base metal according to the present invention had an improvement effect due to the addition of SrJ.

<Effects of the Invention> As explained in detail above, the present invention has an effect of 3 to 3% by weight.
5% Sn, more than 6% and less than 11% S1 and 0.1 to 10
Contains %Pb, 0.01-0.3%Sr and Cu
and 11, with the remainder essentially consisting of AI, and Si particles are precipitated in this matrix in the shape of a sphere, an ellipse, or a shape with a rounded tip.

The bearing alloy of the present invention with this configuration has extremely excellent lubricity,
In addition, the bearing base metal has extremely good mechanical properties at high temperatures of 100 to 250°C, and can sufficiently withstand severe usage conditions due to high-load operation.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of a part of a bearing base metal according to one embodiment of the present invention, FIG. 2 is an explanatory diagram of the lubrication mechanism of the bearing base metal shown in FIG. 1, and FIGS. 3 and 4. 5 is an enlarged sectional view of a part of the conventional bearing, and FIG. 5 is an enlarged sectional view of a part of the bearing base metal of FIG. 4. Code 1...Matrix 2...Si
Particle 3...Sr+-Pb alloy particle 3a--5n-Pbi phase 4...Overlay plating layer 5...Bearing alloy layer 6...・Secret money special 3
'F Applicant Agent: KoNDC Co., Ltd.
Patent Attorney Yoshikatsu Matsushita Attorney Dl Shima
Text Yu 1st Figure 3 sn-pb Tsukuda 1 ÷ Figure 2

Claims (1)

[Claims] 1) In weight%, 3 to 35% Sn, more than 6% to 11% Si
In addition to containing 0.1 to 10% Pb, an Al-Sn bearing alloy containing Cu and Ti in a total of 0.1 to 4%, with the remainder substantially consisting of Al. 3%
containing Sr and dispersing Si particles in a spherical, oval, or rounded tip shape in an Al matrix,
An Al-Sn-Pb bearing alloy characterized by precipitation.