JPH06346169A - Sintered friction material and its production - Google Patents

Abstract

PURPOSE:To obtain a sintered friction material excellent in initial fitness and seizing resistance and having a high coefficient of dynamic friction. CONSTITUTION:Graphite powder 1, inorganic material powder 2, copper alloy- constituting alloy elemental powder 3 and a part of copper powder 4 are stirred and mixed, which is added with an organic binder 5, and granulation is executed (a). It is successively mixed with the remaining copper powder 4 (b), and it is compacted and is thereafter sintered. After the sintering, the surrounding of the graphite grains 1 is formed into a high alloy area 6 in which the alloy elements are diffused (c). Since the high alloy area around the graphite grains is made hard by solid-solution strengthening and the inorganic material grains are largely distributed as well, the elongation of the matrix in a state in which the graphite grains are covered with the matrix can be prevented at the time of friction with the mating material. Among the matrix, a low alloy area in which the allay elements have not been diffused is soft and easy to execute plastic fluidity and is deformed at the time of friction with the mating material to solve local contact.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered friction material which is excellent in initial conformability and seizure resistance and has a high dynamic friction coefficient.

[0002]

2. Description of the Related Art There are two types of friction materials such as clutches and brakes, one for dry type and the other for wet type, and the wet type friction material is broadly divided into non-metal type (see, for example, JP-A-53-27755). ) And metal type. Among them, as a metal-based friction material, a sintered friction material containing a lubricant such as graphite and silica in a metal matrix and an abrasive is known,
Generally has higher heat resistance than non-metallic friction materials (probably due to superior heat conduction), but low friction coefficient (probably due to small true contact area) It has the characteristic that In addition, since the matrix of this sintered friction material is metallic, the modulus of elasticity is high, and the local contact is predominant at the initial stage of sliding, and the local contact promotes plastic flow of the metal part, which is in the low load range. Induces the phenomenon of image sticking.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described characteristics and phenomena of a metal-based sintered friction material, and an object thereof is to improve the seizure resistance of the sintered friction material and further improve its friction coefficient. And

[0004]

To achieve the above object, the present invention provides a sintered friction material containing graphite particles and inorganic material particles in a copper alloy matrix, wherein the alloying elements constituting the copper alloy are provided around the graphite particles. It is characterized by being distributed in large numbers. Further, the present invention relates to a method for producing the above-mentioned sintered friction material, wherein graphite powder, inorganic material powder, copper alloy constituent alloy element powder and a part of copper powder are stirred and mixed, and an organic binder is added thereto. The method is characterized in that granulation is performed, subsequently, this is mixed with the rest of the copper powder, the powder is compacted, and then sintered. further,
The above-mentioned sintered friction material is a mixture of graphite powder, inorganic material powder, copper alloy constituent alloy element powder, and a part of copper powder with stirring, powder compaction, sintering and crushing, and then this. It can also be manufactured by mixing with the rest of the copper powder, compacting and then sintering.

[0005]

In the sintered friction material of the present invention, a relatively high alloy region is formed around the graphite particles in the matrix. The high alloy region existing around the graphite particles, which is the lubricating phase, is hard and has high plastic flow resistance due to solid solution strengthening, and the matrix is prevented from expanding so as to cover the graphite particles at the time of friction with the counterpart material. Improves the seizure resistance of the binding friction material. When a matrix of uniform composition is used as in the past, the plastic flow resistance of the matrix as a whole increases, but since the surroundings of the graphite particles are not particularly reinforced, the graphite coating by the matrix is prevented. It's difficult to cut. Then, when the matrix covers the surface of the graphite particles, seizure is likely to occur, and the escape of oil to the pores formed between the graphite particles and the matrix is limited, thereby promoting fluid lubrication, It causes a decrease in the coefficient of friction.

Further, in the sintered friction material of the present invention, a matrix having a non-uniform composition in which a high alloy region and a low alloy region (including a non-alloyed region) are mixed in a macroscopic view is obtained, The soft low-alloy region causes plastic flow during initial contact with the mating material and deforms, eliminating local contact and consequently improving the contact state with the mating material. Therefore, the initial running-in property and the seizure resistance are improved, and the actual contact area is enlarged, thereby increasing the frictional resistance (friction coefficient).

The inorganic material in the sintered friction material of the present invention is, for example, silica, which is present in the matrix,
In addition to increasing the plastic flow resistance of the matrix to prevent deformation during friction, preventing the graphite particles from being covered by the matrix, the matrix material transferred to the mating material is removed by polishing to further promote transfer. In order to prevent the matrix from being abraded and worn away by the mating material because it is hard and is hard, it is desirable to distribute it intensively around the graphite particles from the viewpoint of preventing the coating of the graphite particles, but not necessarily. There is no need to do so, and it may be evenly distributed in the matrix.

By the way, the above-mentioned matrix having a non-uniform composition cannot be obtained by the conventional powder metallurgical method. In other words, the conventional technology is mixing raw materials, compacting,
It is composed of a sintering process, and aims to uniformly mix the raw materials in the mixing process and obtain a matrix phase having a uniform composition in a macroscopic view after the sintering. However, from the viewpoint of conformability, it is not suitable when the composition of the matrix is uniform, and it is likely to cause local contact and seizure. Note that as a countermeasure that focuses only on the improvement of compatibility, there is a method of sintering at a low temperature at which alloying of the matrix does not proceed sufficiently. According to this method, alloying is suppressed, and thus the matrix is soft (elastic The ratio is low), the matrix undergoes plastic flow during friction with the mating material to increase the true contact area, improving the conformability, and as a result of sintering at a low temperature, a large amount of pores are formed inside the sintered material. Remains, and therefore the elastic modulus of the whole sintered material is lowered, so that the conformability is further improved, but on the other hand, in this method, there is a problem that the strength is lowered because the sintering temperature is low.

On the other hand, in the method for producing a sintered friction material of the present invention, two steps of mixing are carried out in the powder mixing step in order to obtain a non-uniform matrix of the sintered friction material of the present invention. Is. That is, FIG.
As schematically shown in (c), in the first step, the graphite particles 1,
The inorganic material particles 2, the copper alloy constituent alloy element powder 3 such as tin and zinc, the copper powder 4, and the organic binder component 5 are mixed and granulated, and the copper alloy constituent alloy element powder 3 is surrounded by the graphite particles 1.
Etc. are adhered (a), and subsequently, they are mixed so that the remaining copper powder 4 is covered by the second stage mixing (b), and this is molded and sintered. After sintering, the area around the graphite particles 1 becomes a diffusion region 6a of the copper alloy constituent alloy element, where it becomes a copper alloy having a relatively higher alloy than other parts, and the matrix 6 having a non-uniform composition is formed. (C).

The matrix of the present invention, which has an inhomogeneous composition, is prepared by preliminarily mixing graphite particles, inorganic material particles, copper alloy constituent alloy element powder, and copper powder, and pulverizing after preliminary sintering. It can also be obtained by mixing again with copper powder, compacting and sintering. This uses sintering and pulverization instead of adhering the copper alloy constituent alloy elements around the graphite particles with an organic binder, and there is no change in operation.

In the above-mentioned method of the present invention, the sintering temperature (second sintering in the latter method) is selected so that there is a region (low alloy region) in which sintering mediated by a liquid phase does not progress. Is preferred. In such a region, sintering by solid phase diffusion progresses, the pores introduced at the time of compacting are maintained as they are, and a sintered friction material having a high porosity is formed. As a result, the supply of oil as a cooling medium proceeds into the sintered body, cooling proceeds efficiently, and seizure resistance is improved.

[0012]

EXAMPLES Next, specific examples of the present invention will be described. First, graphite powder, copper powder (primary), tin powder, zinc powder, and silica powder were mixed in the weight ratio shown in Table 1, and a small amount of an organic binder was added for granulation. Furthermore, copper powder (secondary) is added to and mixed with this, and uniaxial compression molding is performed at a pressure of 3 ton / cm ² , followed by 60 kg at a temperature of 750 ° C. in a nitrogen atmosphere under a pressure of 20 kg / cm ^2. The sintered friction material of the present invention (Examples 2 to 2)
5) was obtained. In Comparative Example 1, the amount of the secondary powder mixture of copper powder was set to zero, and after granulation, compression molding and sintering were performed under the same conditions as in the above-described examples.

[0013]

[Table 1]

The obtained sintered friction materials of Comparative Example 1 and Examples 2 to 5 were processed into a disk shape, which was used as a test disk, and mating disks (S45C (tempered material), HRC30).
A friction test was conducted by a rubbing test with and the friction coefficient of each was measured, and the seizure condition was investigated by measuring the load at which the test disk material was transferred to the mating disk material. The test results are as shown in Table 1. Incidentally, adopted friction test conditions, the peripheral speed; 55m / sec, load; 2 kg / cm ² increments increase per rotation of 200 times starting from 6 kg / cm ^2, the oil temperature;
80 ° C, absorbed energy: 14 kg · m / cm ² , clutch frequency: 12 sec / cycle, oil amount: 8 cc / cm ² ·
min.

As a result, as shown in Table 1, when the sintered friction materials of Examples 2 to 5 were used, the friction coefficient was higher than that of Comparative Example 1, and seizure occurred even at a high surface pressure. It was confirmed that there was not.

[0016]

According to the present invention, it is possible to obtain a sintered friction material which is excellent in initial conformability and seizure resistance and has a high dynamic friction coefficient.

[Brief description of drawings]

FIG. 1 is a diagram schematically illustrating an example of a manufacturing process of a sintered friction material of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Graphite particles 2 Inorganic material particles 3 Copper alloy constituent alloy element powder 4 Copper powder 5 Organic binder 6 Sintered friction material matrix 6a Highly alloyed area of matrix

Claims (3)

[Claims] 1. A sintered friction material containing graphite particles and inorganic material particles in a copper alloy matrix, wherein a large amount of alloy elements constituting a copper alloy are distributed around the graphite particles. . 2. A graphite powder, an inorganic material powder, a copper alloy-constituting alloy element powder and a part of a copper powder are stirred and mixed, and an organic binder is added to the mixture to perform granulation. 1. A method for producing a sintered friction material, which comprises mixing with the copper powder of 1., compacting and sintering. 3. A graphite powder, an inorganic material powder, a copper alloy constituent alloy element powder and a part of a copper powder are stirred and mixed, compacted, compacted, sintered and then crushed. A method of manufacturing a sintered friction material, which comprises mixing with copper powder, compacting and sintering.