JPS6215625B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an aluminum-based bearing material that has excellent seizure resistance, load resistance, and high oil temperature resistance. Conventionally, overlay plating type bearings and those without overlay plating have been put into practical use as aluminum-based bearings, but since overlay plating types have high plating costs, aluminum bearings for low to medium loads have been used. Generally, those without overlay plating are used. As aluminum bearing materials without overlay plating, materials in which low-melting point soft metals such as Pb, Sn, Bi, and Cd are added alone or in combination as lubricants are generally proposed; Soft metals mainly contain the elements Sn and Pb, either alone or mixed together. The amount added is
At least 15% by weight of Sn-based materials and at least 8% by weight of Pb-based materials are used due to the requirements for seizure resistance. However, the addition of such a large amount of low-melting-point soft metals leads to a decrease in the hardness and fatigue strength of the bearing material, which poses a problem when used in a high load range. Furthermore, bearing materials containing many low-melting-point soft metals have the disadvantage that when used as bearings, their hardness decreases significantly at high temperatures, resulting in a significant decrease in fatigue strength when the temperature of the lubricating oil increases. Ta. In order to improve these defects, Cr, Si, Cu,
Various attempts have been made to add Ni, etc., and to finely disperse low-melting soft metals, but still Sn, Pb, etc.
It is difficult to reduce the addition amount to less than the above-mentioned amount due to the requirements for anti-seizure properties, so the above-mentioned drawbacks have not been essentially eliminated. The present invention was discovered as a result of various studies aimed at improving the problems of conventional aluminum-based bearing materials as described above. That is, the present invention provides an aluminum-based bearing material that has excellent seizure resistance, load resistance, and high oil temperature resistance without overlay plating, and more specifically, provides an aluminum-based matrix-low melting point soft metal lubricant-based bearing material. It is something. In the aluminum-based matrix-low melting point soft metal lubricant-based bearing material of the present invention, fine alumina particles having a particle size of 3 μm or less in short diameter are contained in the aluminum matrix in a proportion of 0.5 to 6% by weight. and is uniformly dispersed,
It is characterized by 0.5 to 30% of one or more low melting point soft metals selected from Pb and Sn being dispersed. In the present invention, the aluminum-based matrix is composed of Si, which is known as an aluminum base strengthening element,
It can contain 0 to 5% of elements such as Cr, Cu, and Ni. In the present invention, as a low melting point soft metal lubricant, Pb and Sn are added alone or in combination at 0.5 to 30%.
It is dispersed in the aluminum matrix, preferably in an amount of 1 to 10%. That is, the key point of the present invention is to use an aluminum matrix in which alumina particles are finely and uniformly dispersed. Furthermore, if the amount of alumina is less than 0.5% by weight, little improvement in the frictional properties of the bearing material can be expected;
If the amount exceeds 0.5% by weight, the hardness of the aluminum matrix will increase and the friction characteristics of the bearing material will deteriorate rapidly, so it should be used in a range of 0.5 to 6% by weight. If the amount of low melting point soft metal is less than 0.5% by weight, even if the amount of alumina is adjusted, sufficient frictional properties will not be obtained as a bearing material, and if it is more than 30% by weight, the frictional properties will not improve any further, so there are no advantages. is not obtained, so it is used in a range of 0.5 to 30% by weight. The alumina particle size is set to 3 microns or less, since if the minor axis exceeds 3 microns, the frictional characteristics of the bearing material will deteriorate. Next, in order to use the bearing material of the present invention, the methods for uniformly dispersing fine alumina particles in an aluminum matrix include (1) Sintering method. (b) Sintering the powder, (b) Sintering the mixture of alumina particles and aluminum powder, (2) Thermal spraying method: (b) Spraying aluminum powder with an oxidized surface onto the back metal of the bearing material, (b) There are various methods such as thermal spraying a mixture of alumina powder and aluminum powder, and (c) thermal spraying in such a way that the aluminum powder is oxidized within the thermal spraying frame. Among the above methods,
2) In methods other than (c), alumina particles close to the alumina state of the raw material powder are found in the bearing material. In addition, in 2)-(c), the amount of alumina in the bearing material obtained after thermal spraying can be controlled by the thermal spraying distance, the amount of air, the air blowing angle, etc. To disperse low melting point soft metals such as Pb and Sn used as lubricants in bearing materials, the desired amount of powder of these metals is added to aluminum powder or a mixture of aluminum powder and alumina powder. Sintering or thermal spraying using the above methods. Note that since the bearing material coating obtained by the thermal spraying method generally contains several percent of pores, reduction-annealing can be performed to densify the pores. Appropriate conditions for this are a rolling reduction of 20 to 50% and an annealing temperature of 350 to 550°C. Next, the present invention will be explained in detail by giving examples. Example 1 A cold rolled steel material (JIS SPcc) with a thickness of 1.8 mm was degreased and pre-treated by blasting, and used as a backing metal, and aluminium-alumina-lead based material was applied to it by thermal spraying under the conditions described below. A sprayed layer was formed. The powder for thermal spraying is pure Al, Al-2.1%Pb, Al-
It has three compositions of 7.2%Pb, all of which are
Produced by the atomization method after melting at 850℃, -
Particle sizes of 100 mesh to +300 mesh were used. The thermal spraying equipment used was a 3M plasma spraying equipment manufactured by Metco, and conditions were set in advance so that the amount of alumina contained in the sprayed layer after thermal spraying was 0, 2, 3, 6, 8, and 10% by weight, respectively. I did it. The plasma gas for thermal spraying uses _N2 - _H2 gas,
The powder was sprayed to a thickness of 0.7 mm at a current of 500 A and a voltage of 75 V. The backing metal was preheated to a temperature of 250°C before thermal spraying. After thermal spraying, it is rolled down by about 35% to the thermal sprayed layer using rolling rollers, and then further heated in a hydrogen atmosphere at 450℃.
Annealing treatment was performed for 1.5 hours. Table 1 shows the chemical composition and hardness of the bearing material layer with backing metal thus obtained. The table shows that the cross-sectional hardness of the bearing material layer was strengthened by dispersing alumina particles in the matrix.

[Table] As a representative example of the cross-sectional structure of the bearing material layer (sprayed layer), the structure of A-2-2 material is shown in FIG. Amimina is distributed in the form of dots or rods, and the major axis is less than 30 μm, and the short axis is less than 3 μm. In addition, in the case of the other bearing materials of this example, the shape and size were almost the same as those shown in FIG. 1, although the amount of alumina was more or less. Next, a mechanical testing laboratory type friction and wear test was conducted using this bearing material as a flat plate test piece. The test conditions are as follows. Mating material: S45C (Hardness Hv213) Rotation speed: 1000rpm (Sliding speed 119.3
cm/sec) Oil used: SAE 30 Oil temperature: 35 to 45°C As a result, bearings made of A-0-0 bearing material seized at a load of 350 kg (surface pressure 175 kg/cm ² ), but Although it was not possible to measure the coefficient of friction at a load of 500 kg, all bearings made of other bearing materials did not seize up to a load of 500 kg (surface pressure of 250 kg/cm ² ). The friction coefficient at a load of 500 kg is as shown in column 7 of Table 1. When the obtained friction coefficient is illustrated using the amount of alumina as a parameter, the second
As shown in the figure, it can be seen that the friction coefficient decreases within the range of the present invention, where the amount of alumina is 0.5 to 6%, which is preferable. Among these bearing materials, the high-temperature hardness of the bearing material layer (sprayed layer) obtained for material A-2-2 was measured. The equipment used was Nippon Kogaku's Nikon QM high-temperature hardness measurement equipment, which was used at room temperature (RT), 50℃, 100℃, and 150℃.
Measurements were made at each temperature of ℃, 200℃, and 250℃. The measurement results are shown in the fifth column along with the results for the bearing material of the comparative example described below.
As shown in the figure. This shows that the bearing material of the present invention provides a bearing material layer having good high-temperature hardness. Example 2 A bearing material layer (sprayed layer) was prepared in the same manner as in Example 1, except that the thermal spraying powder was changed and the thermal spraying conditions were only 0 alumina production.
formed. Table 2 shows the thermal spray powder used and the components and hardness of the bearing material layer formed. Also,
The cross-sectional microscopic structure of the bearing material layer is shown in FIGS. 3 and 4, respectively. In the case of B-2-0 material, dot or slightly thread-like alumina particles are uniformly dispersed (particle size is 3 μm or less in short axis). On the other hand, in the case of C-2-0 material, the alumina particles are coarse and have a short diameter of 3 to 1.5 μm.
It was hot. Friction and wear tests were conducted on the bearing material layers thus obtained using the same machine and under the same conditions as in Example 1, and both bearing material layers were subjected to a load of 500 kg.
No seizure occurred up to a surface pressure of 250 kg/cm ² . The friction coefficient at a load of 500 kg was also good. The results are shown in the fifth and sixth columns of Table 2.

[Table] Example 3 A bearing material layer (sprayed layer) was formed in the same manner as in Example 2 except that the thermal sprayed powder was changed. Components of the thermal spraying powder used and the bearing material layer formed,
The hardness is shown in Table 3. Note that Cu and Si are base-strengthening components of the aluminum-based matrix. Friction and wear tests were conducted on the bearing material layer thus obtained using the same machine and under the same conditions as in Example 1. Both bearings made of both bearing materials had a load of 500 kg (surface pressure of 250 kg/cm ^{2 ).} ) No burn-in occurred. The friction coefficient at a load of 500 kg was also good. The results are shown in columns 7 and 8 of Table 3.

【table】

[Table] Comparative example 1 Two types of commercially available aluminum-tin bearing materials,
Obtain Al-6.2Sn-1.31Si-0.91Cu bearing material (comparative bearing material A) and Al-20.5Sn-0.86Cu bearing material (comparative bearing material B), and use the same machine as in Example 1. Friction and wear tests and room temperature and high temperature hardness tests were conducted under the same conditions. The bearing made of comparative bearing material A has a load of 425 kg, and the bearing made of comparative bearing material B has a load of 425 kg.
Seizing occurred at 475 kg and was clearly inferior to that of the bearing material of the present invention. The compositions of comparative bearing materials A and B and the results of the hardness test at room temperature are shown in Table 4, and the results of the high temperature hardness test are shown in FIG. It is clear from these results that both comparative bearing materials A and B are better than the bearing material of the present invention, except that the hardness of the bearing obtained from comparative bearing material A at room temperature is comparable to that of the bearing obtained from the bearing material of the present invention. was inferior to

[Table] In Example 1 above, the bearing material component was 0%.
Regarding Pb, about 1.5% Pb, about 5% Pb,
We measured and investigated the friction coefficient when the amount of Al ₂ O ₃ was almost 0% and when it was finely and uniformly distributed at approximately 2%, 3%, 6%, 8%, and 10% depending on the thermal spraying conditions. It is shown in Figure 2. The following is clear from this result. 1. Too little or too much Al ₂ O ₃ is not preferable because the coefficient of friction increases. If the amount of Al ₂ O ₃ is too small, the coefficient of friction increases, which is thought to be due to adhesion between the material and the other material, and if the amount of Al ₂ O ₃ is too large, the bearing This is thought to be due to the hardness of the material becoming too high. Therefore, it is thought that there are some bearing materials with a good friction coefficient when the amount of Al ₂ O ₃ is in the intermediate range. In other words, the friction characteristics can be improved by controlling the amount of Al ₂ O ₃ . 2 The greater the amount of Pb, the lower the friction coefficient, but when the amount of Al ₂ O ₃ is about 2 to 3%, even about 1.5% Pb material has almost the same value as about 5% Pb material. As has long been known, Pb improves friction characteristics with any amount of Al ₂ O ₃ due to its excellent lubricating effect, but as mentioned above, when the amount of Al ₂ O ₃ is
~3%, even with a Pb content of about 1.5%, 5%Pb
It is noteworthy that it has a friction coefficient equivalent to that of steel. This is because it has conventionally been said that in aluminum-lead bearing materials, the amount of Pb is required to be 5% or more, preferably 8% or more. Next, the bearing material of the present invention will be further explained while comparing the above examples and comparative examples. First, comparing in terms of seizure resistance, comparative bearing materials A and B shown in the comparative example are widely used as aluminum-based bearing materials for automobiles, but in a friction test, both of them seize at a weight of 500 kg or less.
Therefore, as far as the seizure resistance is concerned, the bearing material of Example 1 is the comparative material A, except for the A-0-0 material.
Better than B. However, when manufactured into an actual bearing, the behavior of the friction coefficient before seizure occurs is also important, but even if this condition is taken into consideration, the A-2-2 material and the A-2 material, which are within the scope of the present invention, -2-3 material, A-
It can be seen that material 7-2, material A-7-3, and material A-7-6 have better friction characteristics than comparative materials A and B. Next, from the results of the high temperature hardness test shown in Figure 5,
Including the comparison with comparative materials A and B, the following can be seen. In other words, the bearing material of the present invention exhibits less decrease in hardness at high temperatures than Comparative Materials A and B. Compared to Comparative Material A, which is said to be extremely superior among aluminum-based bearing materials in terms of fatigue strength, the hardness decreases less at high temperatures, so it has high load resistance, especially under high oil temperature conditions. Provides fatigue resistance. This characteristic is considered to be due to the presence of Al ₂ O ₃ in the bearing material of the present invention, based on a comparison of the chemical components of the bearing material layer. Next, in Example 2, a bearing material manufactured by mixing Al ₂ O ₃ powder into powder and thermal spraying, rolling and annealing is explained. As is clear from this example, in the bearing material (B-2-0) of the present invention in which the Al ₂ O ₃ powder to be mixed is fine in size, the Al ₂ O ₃ distributed in the bearing material layer (sprayed layer) is also fine. , bearing material with the same amount of Pb oxidized by thermal spraying in Example 2 (A-2-
2 and A-2-3). On the other hand, when the Al ₂ O ₃ powder size to be mixed is coarse (C-2-0), the bearing material layer (sprayed layer) is also coarse and the friction coefficient is as large as 0.073. It is clear from the material comparison of the two materials that this difference is due to the difference in particle size of Al ₂ O _3. Direct contact between the coarse Al ₂ O ₃
This is thought to be due to a decrease in compatibility with the mating material. Example 3 is the result of investigating a case where Sn was used as the low melting point soft metal lubricant, whereas Examples 1 and 2 used Pb as the low melting point soft metal lubricant. Sn in this case
The amount corresponds to the amount of Sn in Comparative Materials A and B of Comparative Example 1, but when comparing the friction test results, it was found that even when the low melting point soft metal was Sn, it was distributed as finely and uniformly as when Pb was used. It can be seen that the friction properties are greatly improved by the action of Al ₂ O ₃ . From this, it can be easily inferred that similar effects will be obtained with other commonly used low melting point soft metal lubricants such as Cd and Bi. As explained above, conventionally, when manufacturing aluminum bearings without overlay plating, it was necessary to add a low melting point soft metal as a lubricant, but if a sufficient amount of low melting point soft metal is used as a lubricant, However, there was a contradiction in that the hardness of the bearing decreased and the fatigue strength decreased. The bearing material of the present invention completely solves the above problems by using an aluminum-based matrix in which alumina particles are finely and uniformly dispersed. Compared to conventional aluminum-low-melting-point soft-metal lubricant-based bearing materials, 1. Good frictional properties can be obtained with a small amount of low-melting-point soft metal lubricant, which improves both cost and fatigue resistance. It has advantages over conventional materials. 2. It can be used under high oil temperature conditions because it has little hardness loss at high temperatures. 3. It has much better seizure resistance than conventional materials, so it can be used under high loads ( It has various advantages such as being able to be used under high surface pressure.

[Brief explanation of the drawing]

Figures 1, 3, and 4 are photographs of the cross-sectional structure of the bearing material layer, and Figure 2 is a graph showing the relationship between the amount of lead and alumina in the bearing material and the coefficient of friction (load 500 kg) in the friction and wear test. FIG. 5 shows a graph showing the measurement results of high-temperature hardness of bearing materials.

Claims (1)

[Claims] 1 Short diameter 3μ in aluminum matrix
Alumina particles having the following particle sizes are finely and uniformly dispersed at a weight ratio of 0.5 to 6%, and one or more low melting point soft metals selected from Pb and Sn are dispersed at 0.5 to 30%. An aluminum-based bearing material characterized by: