JPS5844139B2 - Sintered alloy friction material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a friction material made of a sintered alloy, and particularly to a sintered alloy friction material for high loads.

Sintered alloy friction materials usually have a base metal matrix of copper alloy or iron alloy, a lubricating substance such as lead or black pencil to provide smooth operating characteristics, and hard particles such as alumina or silica to maintain and improve frictional resistance. and friction-increasing substances to improve wear resistance.

These sintered alloy friction materials have traditionally been used in the linings of clutches and brakes for various construction machinery, railway vehicles, and general vehicles, but in recent years, as high-class machinery and vehicles have become faster and heavier, they have become increasingly harsh. There is currently a demand for the development of friction materials that have characteristics that can withstand usage conditions.

Alumina and silica, which are friction-increasing substances in sintered alloy friction materials, greatly affect the coefficient of friction and wear resistance, but in order to exert their effects, the hard particles of alumina and silica dispersed on the friction surface must be in a metal matrix. However, since hard oxide particles such as silica and alumina are themselves fragile, they easily fall off, and under harsh usage conditions of high speed and high load, they do not necessarily have sufficient frictional properties. The hard particles that fall off due to the abrasive abrasive action significantly increase the wear of the friction material itself, and also have a large effect on the wear of the mating friction surface.

The falling off of alumina and silica is largely influenced by the hardness of the hard particles, and in general, powders with coarse consistency have a large wear on the mating surface, while fine powders and hard particles have a good dispersion state, but It tends to fall off easily.

The object of the present invention is to improve such drawbacks and provide a sintered alloy friction material that has a stable friction coefficient from low speeds to high speeds and has excellent wear resistance.

In order to achieve this objective, the present invention has a comparatively coarse-grained powder of alumina, silica, and other oxide friction-enhancing substances having a hardness of 2 to 15 wt% and an equivalent or higher hardness, and a mechanical and thermal impact strength. Relatively fine powder of silicon nitride with a large amount of 0.5
By containing ~4.0 wt%, the shedding and dispersion of these friction-enhancing hard particles are improved, and the material of the present invention has a stable friction coefficient with little fluctuation due to speed changes and excellent wear resistance. However, it has friction characteristics that cause less wear on the mating friction surface.

The reasons for selecting the composition range etc. will be explained below.

Oxide friction-enhancing substances such as alumina and silica are 2 to 15
wt% is appropriate.

When the amount added is less than 2%, the effect is not sufficiently exhibited, and hardly any improvement in the friction coefficient or wear resistance is observed.

If the amount added is 15% or more, the strength of the sintered material itself will be weakened, the wear resistance will actually decrease, and the wear on the mating friction surface will increase.

The particle size of these oxide friction-enhancing substances is optimally in the range of 160 mesh to +250 mesh.

If the number of meshes exceeds 60, the mating friction surface will be excessively hit and friction will be generated, which will wear out the mating friction surface and cause hard particles to easily fall off.

Moreover, if the mesh size is less than 250, it becomes a factor that inhibits sintering, and the strength decreases and the wear resistance also deteriorates.

This tendency is more pronounced as the amount added is larger.

The amount of silicon nitride added must be determined depending on the amount of the oxide friction-enhancing substance added, and is 0.5 to 4.0.
wt% is appropriate.

The addition of relatively fine powder silicon nitride, which has better mechanical and thermal impact strength than step 1 and is difficult to fall off from the metal base,
The main purpose is to homogenize the dispersion state of hard particles, which are friction-enhancing substances, on the friction surface, and the addition ratio of oxide friction-enhancing substances and silicon nitride is 3% by weight. If the silicon ratio is 2 or less, the amount of silicon nitride, which is a relatively fine powder, becomes excessive, and although the dispersion state of the hard particles is good, the wear resistance is rather deteriorated, which is unsuitable.

Furthermore, if the oxide friction-enhancing substance/silicon nitride ratio is 4 or more, the dispersion state of the hard particles is not sufficiently homogenized, and the effect of improving friction properties** is reduced.

This effect of adding silicon nitride is also effective when the oxide friction-enhancing substance contains one or more of alumina, silica, chromium oxide, zirconia, magnesia, and the like.

If the consistency of silicon nitride powder is 100 mesh or more,
Although a certain degree of improvement in wear resistance is recognized, there are drawbacks such as no improvement in the dispersion state of the hard particle size and increased wear on the mating friction surface. 50wt of powder with a suitable, broad particle size distribution, preferably 250 mesh or less
% or more is optimal.

Next, an example will be described.

Example 1 Copper powder of -100 mesh 73%, tin powder of -200 mesh 7%, lead powder of -80 mesh 11%, -10
Table 1.
The oxide friction-enhancing substance and silicon nitride shown in are added and mixed, and both were molded at a molding pressure of 3t/ci.
740℃ x 29 minutes in a two-gas atmosphere, pressure 8kg/c
The product of the present invention was manufactured by performing pressure sintering in step a.

Note that comparative products shown in Table 1 were manufactured under the same conditions.

Regarding the samples obtained in the examples, the mating disk material, cast iron FC-25 material, speed 7 m/s, 14 m/s, 2
Table 3 shows the results of a friction test conducted under test conditions of 1 m/s and a load of 10 kg/crA.

As is clear from the friction test results, the product of the present invention has a high coefficient of friction, has little variation in the coefficient of friction due to changes in speed, and exhibits excellent properties in terms of wear resistance and wear of the mating material.

Example 2 70% of iron powder of 1100 meshes, 15% of copper powder of 100 meshes, 5% of lead powder of -80 meshes, -100% by weight
Oxide friction-enhancing substances and silicon nitride shown in Table 2 were added to and mixed with 10% mesh graphite powder**, and both were molded at a molding pressure of 5t/c4. The product of the present invention was manufactured by pressure sintering at a pressure of 10 to 9/crA for 30 minutes at ℃.

Note that comparative products shown in Table 2 were manufactured under the same conditions.

The samples obtained in Examples were subjected to a friction test under the same test conditions as in Example 1, and the results are shown in Table 4.

As is clear from the friction test results, the product of the present invention has excellent friction properties.

Claims (1)

[Claims] 1. In sintered friction materials based on copper alloy or iron alloy, silicon nitride 0.5 in a weight percent of 100 mesh or less
~4.0%, -60 mesh + 250 mesh alumina, silica oxide friction increasing substance added 2-15%,
A sintered alloy friction material characterized in that the weight ratio of silicon nitride to oxide friction-enhancing substance is 2 to 40 to 1 part silicon nitride.