JPH1180854A - Copper-based sintered friction material and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper-based sintered friction material excellent in friction coefficient and wear resistance, and to produce the friction material easily in a manufacturing process without sacrificing economic efficiency. I will provide a. SOLUTION: The copper-based sintered friction material has a porosity of 35% by volume or more and 60% by volume or less. The above-mentioned copper-based sintered friction material is produced by compressing the mixed powder in a mold, heating the mixed powder, and then performing a heat treatment at 700 ° C or more and 1000 ° C or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper-based sintered friction material and a method for producing the same, and more particularly, to a lubricating oil such as a multi-plate clutch for an automatic transmission of an automobile and a synchronous ring for a manual transmission. The present invention relates to a copper-based sintered friction material effective in a mechanism used therein and a method for producing the same.

[0002]

2. Description of the Related Art As the above-mentioned application, an organic friction material using a thermosetting resin conventionally used can obtain a high friction coefficient in a lubricating oil, but under severe operating conditions of high temperature and high pressure. However, there is a disadvantage that the wear increases, which is insufficient for the requirement of durability.

[0003] On the other hand, the decrease in friction coefficient at high temperatures is small,
As a material having excellent durability which is less likely to cause problems such as image sticking and abrasion, copper alloy-based metal friction materials have been conventionally known, for example, JP-A-61-67737, JP-A-63-109131, It is disclosed in Japanese Patent No. 2605790 and the like.

In general, when a friction material is used in a lubricating oil, the lubricating oil is present at a contact interface between the friction material and a mating material, and the lubrication effect lowers the friction coefficient μ. As a countermeasure, it has been practiced to increase the porosity of the organic friction material to allow the lubricant at the contact interface to pass therethrough. The porosity of the organic friction material is about 50%.
However, since the conventional metal friction material has a lower porosity than the organic material, there is a problem that the friction coefficient is reduced due to the effect of the lubricating oil.

[0005] Further, since the metal friction material has higher rigidity than the organic friction material, local one-sided contact is likely to occur. That is, the substantial contact area at the interface between the friction material and the mating material is small, which causes a problem that the friction coefficient is reduced.

As a countermeasure against the above-mentioned problem, an attempt has been made to increase the porosity in an attempt to improve the friction coefficient of the metal friction material, which is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-3565. Have been. In this publication, in order to increase the porosity, molding at a low pressure and addition of a binder are performed, and the porosity of the sintered friction material is 20 to
30% by volume.

As a method for producing a porous metal material which is difficult to produce in a normal molding and sintering step, an electric current pressure sintering method is used.
No. 215909. According to this method, a metal fiber as a raw material is filled in a mold, and the material is pressurized and compressed, and is electrically heated to produce a sintered body having a desired porosity in a short time. An oil-impregnated bearing or a friction adjusting material can be added to produce a brake by adding a lubricant to a metal fiber and applying an electric pressure.

[0008]

In Japanese Patent Application Laid-Open No. 9-3565, the friction coefficient is improved by increasing the porosity in the friction material. Not enough. One of the inventors of the present invention has actually found that a friction material used in a lubricating oil expresses a high coefficient of friction due to porosity, and disclosed this in, for example, Japanese Patent Application Laid-Open No. 8-253826. I have. However, in order to further increase the coefficient of friction, it is required to improve the permeability of the lubricating oil film at the interface and to reduce the rigidity by further increasing the porosity.

[0009] However, in the powder molding and sintering process using a metal mold, which is a usual method of powder metallurgy, there is a limit to the porosity.
This is because in order to obtain a sintered body having a high porosity, it is necessary to increase the porosity of the compact. In order to produce a molded product having a high porosity, molding is performed under a pressure of 1 to ⁴ t / cm ² , but at this time, the contact area between the powders in the molded product is reduced, and the strength of the molded product is reduced. . Therefore, there is a problem of handling in the manufacturing process. As a countermeasure, an organic binder may be added to maintain the strength of the molded body. In this method, a material having a porosity of 30% or more and having a small density variation within the material is obtained. It is difficult.

As a method for producing a sintered body having a high porosity, an electric current pressure sintering method is used in Japanese Patent Application Laid-Open No. 1-215909. According to this manufacturing method, a sintered material in a state close to the packing density of the powder can be manufactured, and it is expected that this is effective in increasing the coefficient of friction from the viewpoint of lowering the rigidity. However, it has been confirmed that the strength decreases when the density of the sintered body decreases, and when applied as a friction material used under severe sliding conditions under high temperature and high pressure, high porosity In the case of a sintered body having a high rate, an increase in wear becomes a problem. As a measure against this,
Performing electric pressure sintering for a long time in order to advance the bonding reaction of the powder is that electric pressure sintering can only be batch processed due to its nature, and the number of products that can be produced in one process is small,
A problem arises during production from the viewpoint of productivity.

Therefore, one object of the present invention is to provide a copper-based sintered friction material having a high friction coefficient and excellent wear resistance.

Another object of the present invention is to provide a method for producing a copper-based sintered friction material having a high friction coefficient and excellent abrasion resistance without losing economy because of easy handling in the production process. It is to be.

[0013]

[Means for Solving the Problems]

(A) Copper-based sintered friction material of the present invention The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, by setting the porosity of the copper-based sintered friction material to a predetermined range, this friction has been improved. It has been found that a copper-based sintered friction material excellent in friction coefficient and abrasion resistance can be obtained by suppressing abrasion of a material base.

Therefore, the copper-based sintered friction material of the present invention is:
A copper-based sintered friction material obtained by solidifying a raw material powder containing copper as a main component has a porosity of 35% or more and 60% or less.

The reason why the porosity is set in the above range in the copper-based sintered friction material of the present invention will be described below.

The increase in the porosity is effective in increasing the friction coefficient in (a) the transmission of the lubricating oil present at the contact interface between the friction material and the mating material, and (b) the increase in the contact area due to the decrease in rigidity. is there.

(A) Permeation of Lubricating Oil When a friction material is used in a lubricating oil, the oil generally exists at the contact interface between the friction material and the mating material, and the lubrication effect lowers the friction coefficient. The oil film thickness of the lubricating oil changes depending on the frictional sliding conditions. The oil film thickness increases as the pressing pressure decreases and as the sliding speed increases, whereby the friction coefficient decreases. To increase the friction coefficient, it is effective to discharge the lubricating oil at the contact interface.

(B) Decrease in Rigidity The metallic friction material has a higher rigidity than the organic friction material, so that the substantial contact area at the interface between the friction material and the mating material is small. The problem of lowering occurs. In order to reduce the rigidity of the metal friction material and increase the friction coefficient by increasing the contact, it is effective to increase the porosity. Regarding the increase in the contact area due to the decrease in rigidity,
Similarly, when sliding friction occurs in the absence of lubricating oil,
It has the effect of increasing the coefficient of friction.

When the porosity is lower than 35% by volume, the permeation and rigidity of the lubricating oil are reduced, that is, the effect of increasing the friction coefficient is small. When the porosity is higher than 60% by volume, frictional sliding is performed. The wear resistance at the time decreases. A decrease in wear resistance is not preferable because it shortens the service life. Therefore, the porosity needs to be 35% by volume or more and 60% by volume or less, and preferably 40% by volume or more and 50% by volume or less.

(1) Hard Particles (a) Content Preferably, in the above aspect, the copper-based sintered friction material has hard particles and the balance of a copper alloy base material, and the hard particles are 5% by weight. The copper alloy base contains copper or a copper alloy, a lubricant, and unavoidable impurities.

When the amount of the hard particles is less than 5% by weight, the amount of the hard particles existing on the frictional sliding surface is reduced, so that the effect of increasing the friction coefficient and preventing seizure is small. Is inferior in the mechanical strength and thermal conductivity of the friction material. Therefore, the amount of the hard particles is preferably from 5% by weight to 40% by weight, more preferably from 15% by weight to 30% by weight.
% By weight or less is good.

(B) Kind Preferably, in the above aspect, the hard particles are iron-based intermetallic compound, oxide particles, nitride particles, carbide particles, Si particles.
It is composed of at least one selected from the group consisting of (silicon) particles and Mo (molybdenum) particles.

Hard particles have the effect of increasing the coefficient of friction.
Those having a micro Vickers hardness of 400 or more are desirable. For this purpose, iron-based intermetallic compounds, oxide particles, nitride particles, carbide particles, Si particles, and Mo particles can be used. Among them, the iron-based intermetallic compound is superior in machinability as compared with oxide particles, nitride particles, and carbide particles. Therefore, iron-based intermetallic compounds are more effective as hard particles.

(C) Size In the above aspect, preferably, the hard particles have an average particle size of 2
0 μm or less.

When the size of the hard particles is larger than 20 μm, since the hard particles partially contact the mating material on the sliding surface with the mating material, the fluctuation of the friction coefficient becomes large. Fluctuations in the coefficient of friction cause vibration and abnormal noise, and are not preferred. Therefore, the size of the hard particles is preferably 20 μm or less, more preferably 10 μm or less.

(2) Metal Base In the above aspect, preferably, the copper alloy base is made of Sn
One or more metal elements selected from the group consisting of (tin), Zn (zinc), and Ni (nickel) are included.

Sn, Zn, and Ni all have an effect of increasing the hardness and strength of the substrate by forming an alloy with copper. When the base material is formed only of copper, the hardness and the strength are reduced, so that the friction material has a low resistance to shear stress and the wear resistance is reduced. Therefore, the copper alloy base preferably contains one or more metal elements selected from the group consisting of Sn, Zn, and Ni.

(3) Lubricant In the above aspect, the lubricant is preferably composed of one or more solid lubricants selected from the group consisting of graphite, MoS ₂ , CaF ₂ , WS ₂ and BN, and is based on volume. At 25% or less.

The solid lubricant has an effect of forming a lubricating film on a sliding interface with a mating material to prevent a seizure phenomenon and to reduce a change in friction coefficient. Lubricant content is 2 by volume
If it exceeds 5%, the mechanical strength of the friction material is undesirably reduced. Therefore, the content of the lubricant is preferably 25% or less on a volume basis, and more preferably 15% or less.

(B) Method for Producing the Copper-Based Sintered Friction Material of the Present Invention As a result of intensive studies to achieve the above object, the present inventor has found that after the mixed powder is pressurized and compressed in a mold and energized and pressed. It has been found that by performing heat treatment at 700 ° C. or more and 1000 ° C. or less, a copper-based sintered friction material excellent in friction coefficient and abrasion resistance can be manufactured without easily losing economical efficiency in handling in a manufacturing process. .

Therefore, the method for producing a copper-based sintered friction material of the present invention includes the following steps. First, the raw powder is mixed into a predetermined composition to obtain a mixed powder. Then, the mixed powder is pressurized and compressed in a mold, and is electrically pressed to obtain a sintered body. Then, the sintered body is subjected to a heat treatment at 700 ° C. or more and 1000 ° C. or less.

(A) Electric Pressure Sintering In the step of compressing and compressing the mixed powder and heating the electric current, the sintering of the powder proceeds. As described above, since the forming and the sintering are performed in the same process, there is no problem of handling when the formed body is carried into the sintering furnace unlike the related art. In addition, since the bonding reaction at the contact portion between the powders can be advanced in a state close to the packing density of the powders, sintering proceeds while maintaining a high porosity. Therefore, a sintered body having excellent porosity and strength and abrasion resistance can be manufactured with the same porosity as compared with the conventional molding / sintering process.

By the electric heating, (i) dielectric breakdown of the surface oxide film of the metal powder, (ii) promotion of neck growth due to concentration of current and heat generation at the powder contact portion, and (iii)
Characteristic phenomena occur such as promotion of atom transfer due to a temperature difference between the powder contact portion and the powder center.

The reason for the above phenomenon will be described below. The surface of the raw metal powder is usually covered with an oxide film. During energization, a voltage is intensively applied to this insulating layer, and the interface between the powders becomes locally hot. Due to the high temperature of the contact interface,
Thermal diffusion is promoted, so that sintering proceeds in a short time.

Further, by applying a pulse waveform to the energization, the bonding reaction of the powder can be further advanced.
This is because, when a voltage is concentrated on the insulating layer on the metal surface, plasma is easily generated, so that the temperature of the powder interface becomes locally high and sintering proceeds in a short time.

(B) Heat Treatment Step By performing a heat treatment step after the current pressure sintering step, the sintering of the friction material can be promoted, and the strength and wear resistance of the sintered body can be improved. Performing a long-time current-pressure sintering for sintering causes a problem from the viewpoint of productivity. Therefore, it is difficult to perform continuous processing.
The processing time in the current-pressure sintering with a small number of products per process should be as short as possible, and this process can be performed continuously in the subsequent process, and the number of products produced per process in the batch process is large. Accordingly, a sintered friction material having excellent strength and wear resistance can be manufactured without impairing productivity. At the time of heat treatment, the structure of a sintered body using a composite powder in which hard particles are dispersed in a copper alloy base material can be controlled.

(I) Acceleration of sintering reaction As described in the above item (a), the bonding reaction of the powder proceeds in a short time by the current pressure sintering. However, in order to further improve the strength and wear resistance, Sintering can be advanced by subjecting the sintered body after the pressure sintering to a heat treatment.
In a compact formed by a normal molding process, the strength decreases at a high porosity, causing a handling problem in the manufacturing process.
On the other hand, in the current pressure sintering, since the strength of the porous body can be increased, it is possible to perform sintering by a heat treatment in a later step without a handling problem.

The heat treatment temperature needs to be 700 ° C. or more and 1000 ° C. or less. In the copper-based sintered friction material of the present invention,
In order to completely advance sintering at a temperature lower than 700 ° C., the sintering time becomes long, which causes an economic problem. Therefore, the sintering temperature must be 700 ° C. or higher in order to advance sintering without impairing the economic efficiency.
On the other hand, when the sintering temperature exceeds 1000 ° C., a liquid phase is generated in the powder compact, and the sintered compact shrinks. as a result,
There is a problem that dimensional accuracy is reduced. Therefore, the sintering temperature must be 1000 ° C. or less.

The copper-based sintered friction material of the present invention is desirably heat-treated in a non-oxidizing atmosphere or a reducing atmosphere. The reason is that when the heat treatment atmosphere is not a non-oxidizing atmosphere or a reducing atmosphere, an oxide film is formed on the surface of the copper powder, and the sinterability is significantly impaired, resulting in the strength and wear resistance of the sintered body. This is because a decrease in sex occurs.

(Ii) Microstructure Control After conducting electric heating sintering, heat treatment is performed at 700 ° C. or more and 1000 ° C. or less in a non-oxidizing or reducing atmosphere to obtain a composite powder in which hard particles are dispersed in a copper base material. Can control the structure of the sintered material using the raw material.
By the heat treatment, the reaction between the hard particles in the composite powder and the copper alloy base proceeds, and the hard particles are refined. The reaction strengthens the bond between the hard particles and the element, so that the hard particles are prevented from falling off during frictional sliding and the wear resistance is improved. Further, by making the hard particles finer, the contact with the counterpart material becomes uniform, and the fluctuation of the friction coefficient decreases. As an effect, abnormal noise and vibration are suppressed.

As described in the above item (a), in the electric pressure sintering, since the interface between the powders locally becomes high in temperature, the sintering in a short time promotes the bonding reaction of the powders. The temperature inside is small and the reaction is not easily promoted. For this reason, it is possible to promote the reaction inside the powder by performing heat treatment after current pressure sintering.

The temperature of the heat treatment must be 700 ° C. or more in order to allow this reaction to proceed completely within a range in which there is no problem in economy.

As described above, the present invention by the steps of powder mixing, current pressure sintering, and heat treatment has been described. However, the structure control is not limited to the heat treatment of the present invention, and a heating step may be inserted before current pressure sintering. But it is possible. The heating temperature at this time is 50
The temperature is preferably from 0 ° C to 650 ° C. If the temperature is lower than 500 ° C., the heating time becomes longer, which causes a problem of economy. Also 650
If the temperature is higher than 0 ° C., the powder is sintered and bonded, so that it is difficult to uniformly fill the powder in the mold in the current pressure sintering step, which is not preferable.

By adding this heating step, the effect of shortening the heat treatment time can be obtained.

(C) Mixing Hard particles and a lubricant are mixed with the copper-based metal powder as required at a predetermined ratio, and the mixed powder obtained by mixing and stirring uniformly is used as a starting material. For mixing and stirring, a mixer such as a V-type mixer, a kneader, and a ball mill can be used.

(1) Diffusion Bonding of Metal Plate and Sintered Body In the above aspect, preferably, in the step of pressing and compressing the mixed powder and energizing and heating, the mixed powder is sintered to obtain a sintered body. At the same time, the metal plate and the sintered body are diffusion-bonded.

Thus, a sintered body can be obtained in one step and the metal plate and the sintered body can be bonded by diffusion.

(2) Type and Production Method of Composite Powder In the above aspect, preferably, a copper alloy powder in which hard particles are homogeneously dispersed in a copper alloy base is used as a raw material powder.

In the above aspect, preferably, in the step of producing the copper alloy powder, a mechanical mixing method or a mechanical grinding method is used to mechanically mix and grind the mixed powder of the copper-based metal powder and the hard particles. Is applied, the hard particles are uniformly dispersed in the copper-based metal base.

After mixing the copper or copper alloy powder and the hard particles constituting the base of the composite copper-based powder at a predetermined ratio,
Before adding and mixing the lubricant, mechanical mixing, pulverization and alloying of the powder, as required by mechanical alloying (mechanical alloying) and mechanical mixing (mechanical grinding), as necessary It is also effective to perform processing. At this time, equipment such as a rotary ball mill, a vibration ball mill, a planetary ball mill, or an attritor ball mill is used. According to this method, the hard particles can be pulverized more finely, and the finely pulverized hard particles can be uniformly dispersed in the base material of the copper-based powder. By dispersing hard particles without gaps in the copper powder base,
The bond between the copper base and the hard particles becomes stronger as compared with the sintered friction material obtained by the conventional mixing method without performing the compounding, and the hard particles are prevented from falling off during friction sliding. Further, the variation in the coefficient of friction is reduced due to the finer hard particles, and abnormal noise and vibration are suppressed. The size of the hard particles in the composite powder can be controlled by operating conditions of mechanical mixing, pulverization, and alloying treatment (for example, treatment time and the ratio of powder to ball).

[0051]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

Example 1 FIG. 1 is a process chart showing a method for producing a copper-based sintered friction material in Example 1 of the present invention.

Referring to FIG. 1, Cu: Sn = 9 by weight ratio.
1: 9 powder and hard particles FeAl in a weight ratio of 80: 2
0, and mechanically alloyed by a vibrating ball mill to obtain a hard particle-dispersed composite copper alloy powder (Step 1: S1). The composite powder was filled into a carbon mold having an inner diameter of 30 mm so as to have a porosity shown in Table 1 below. The porosity was adjusted by the volume of the carbon mold and the amount of powder. At this time, the metal plate was inserted into the mold together with the powder. The mixed powder was pressure-compressed at a surface pressure of 300 kgf / cm ² and heated by heating at 700 ° C. for 2 minutes in a nitrogen atmosphere (Step 2: S2). The obtained sintered body was heat-treated at 800 ° C. for 1 hour in a nitrogen atmosphere (Step 3: S
3). Then, the friction sliding characteristics of the sintered body were evaluated.

The friction test was performed by the following method. Using a chip-on-disk friction tester, AT
F, using S35C mild steel as the mating material, pressure force 30kgf /
cm ² , the peripheral speed was changed in the order of 100, 80, 60, and 40 cm / s, and the evaluation was carried out by holding at each speed for 15 minutes.

Table 1 shows the friction sliding characteristics of the obtained sintered body. In addition, in Table 1, the present invention example is a sample No. 1 to 6; 7 and 8.

[0056]

[Table 1]

From the above results, it was found that in the examples of the present invention having a porosity of 35% by volume or more and 60% by volume or less, good frictional sliding properties and mechanical properties were obtained. The size of each hard particle was 10 μm or less on average. Further, sintering of the metal plate and the sintered material progressed, and diffusion bonding was possible. On the other hand, the following problems occurred in the comparative example.

Sample No. In 7, the porosity is low,
The effect of lubricating oil permeation and low rigidity was small, and the coefficient of friction was reduced. Because the thickness of the lubricating oil film increases, especially at high speeds,
Great effect of lowering the friction coefficient.

Sample No. In No. 8, the amount of wear of the material increased due to the high porosity. Example 2 Powder having composition of Cu: Sn = 91: 9 and hard particles FeAl
Were subjected to mechanical alloying treatment by a vibration type ball mill to obtain hard particle-dispersed copper alloy powder. The composite powder was filled into a carbon mold having an inner diameter of 30 mm so as to have a porosity of 50% by volume. Surface pressure of 300kgf mixed powder
/ Cm ² under pressure and 400 in a nitrogen atmosphere.
C. for 2 minutes. Table 2 below shows the obtained sintered body.
The heat treatment was carried out under the conditions shown in FIG. Then, the friction sliding characteristics of the sintered body were evaluated.

The friction test was performed by the following method. Using a chip-on-disk friction tester, peripheral speed 40 cm
/ Sec, pressure 30 kgf / cm ² , lubricating oil ATF,
Evaluation was performed for one hour continuously using S35C mild steel as a mating material. Table 1 shows the friction sliding characteristics of the obtained sintered body. Table 1
In the sample of the present invention, the sample No. 1 to 5; 6-9.

[0061]

[Table 2]

From the above results, it was found that in the present invention example in which the sintering temperature was 700 ° C. or more and less than 1000 ° C. and the heat treatment step was performed in a non-oxidizing or reducing atmosphere, good friction characteristics were obtained. . On the other hand, the following problems occurred in the comparative example.

Sample No. In No. 6, abrasion increased because no heat treatment was performed. Sample No. In No. 7, since the heat treatment temperature was low, the sintering reaction did not proceed and wear increased.

Sample No. In No. 8, since the sintering temperature was high, the shrinkage was large, and the dimensional accuracy was deteriorated.

Sample No. In No. 9, since sintering was performed in the air, oxidation proceeded and the sintering reaction was significantly inhibited.

Example 3 A powder having a composition of Cu: Sn = 91: 9 and a composition having a composition of Fe: Al
= 50: 50 hard particles were blended after sintering so as to have a weight ratio shown in Table 3 below, and mechanically alloyed by a vibration type ball mill to obtain hard particle-dispersed copper alloy powder. The composite powder was filled into a carbon mold having an inner diameter of 30 mm so as to have a porosity of 50% by volume. The mixed powder was pressed and compressed at a surface pressure of 300 kgf / cm ² and heated by heating at 700 ° C. for 2 minutes in a nitrogen atmosphere. The obtained sintered body was heat-treated at 800 ° C. in a nitrogen atmosphere.

The frictional sliding characteristics of the obtained sintered body were evaluated. Table 3 shows the evaluation results. Note that, in Table 3, the present invention examples correspond to the sample Nos. 1 to 5;
6 and 7.

[0068]

[Table 3]

From the above results, it was found that in the examples of the present invention containing hard particles in an amount of 5% by weight or more and 40% by weight or less, good frictional sliding characteristics were obtained. On the other hand, the following problems occurred in the comparative example.

Sample No. In No. 6, wear resistance deteriorated because the amount of the copper base was small and bonding of the bases was insufficient.

Sample No. In No. 7, the amount of the hard particles was small, the effect of increasing the friction coefficient by the hard particles, and the effect of suppressing wear were small. Therefore, the friction coefficient of the sintered body was small and the wear resistance was poor.

Example 4 A powder having the composition shown in Table 4 below and hard particles FeAl were blended and subjected to mechanical alloying treatment by a vibration type ball mill to obtain hard particle-dispersed copper alloy powder. The composite powder was filled into a carbon mold having an inner diameter of 30 mm so as to have a porosity of 35% by volume. Surface pressure of 300kgf / cm
^2. Press and compress at 2
It was heated by energizing for minutes. The obtained sintered body is placed in a nitrogen atmosphere for 8 hours.
Heat treatment was performed at 00 ° C.

The frictional sliding characteristics of the obtained sintered body and the micro Vickers hardness of the metal base were evaluated. The hardness was evaluated with a load of 10 g. Table 4 shows the evaluation results. In Table 4, the examples of the present invention correspond to the sample No. 1-4,
The comparative example is a sample No. 5

[0074]

[Table 4]

From the above results, it was found that Cu was the main component and S
It was found that good frictional sliding characteristics were obtained in the examples of the present invention containing any of n, Zn, and Ni.

On the other hand, in the comparative example (Sample No. 5), there was a problem that wear was increased during frictional sliding because the hardness of the sintered body was low.

Example 5 Powder composed of Cu: Sn = 91: 9 and hard particles FeAl
Were subjected to mechanical alloying treatment by a vibration type ball mill to obtain hard particle-dispersed copper alloy powder. The composite copper alloy powder and graphite as a lubricant are blended in the sintered body after sintering so as to have a volume ratio shown in Table 5 below, and the mixed powder has an inner diameter such that the porosity is 35% by volume. 3
It was filled into a 0 mm carbon mold. Surface pressure of mixed powder is 30
It was pressurized and compressed at 0 kgf / cm ² and heated by heating at 700 ° C. for 2 minutes in a nitrogen atmosphere. The obtained sintered body was heat-treated at 800 ° C. in a nitrogen atmosphere.

The frictional sliding characteristics of the obtained sintered body were evaluated. Table 5 shows the evaluation results. Note that, in Table 5, the present invention examples correspond to Sample No. 1 to 4, and the comparative example is sample No. 5
It is.

[0079]

[Table 5]

From the above results, it was found that in the examples of the present invention in which the content of the lubricant is small, good frictional sliding characteristics can be obtained.

On the other hand, in the comparative example (sample No. 5), there was a problem that the abrasion resistance was poor because the ratio of the metal base was reduced.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0083]

According to the copper-based sintered friction material of the present invention, since the porosity is 35% by volume or more and 60% by volume or less, a lubricating oil film existing at the contact interface between the friction material and the mating material can be eliminated. Further, since the rigidity of the friction material can be reduced, the coefficient of friction is improved.

In the method for producing a copper-based sintered friction material of the present invention, the bonding reaction between the powders proceeds by the current-pressing sintering step and the heat treatment step. A porous sintered friction material having a volume percentage of 60% by volume or more and 60% by volume or less can be produced. Further, since the forming and sintering are performed simultaneously in the current-pressing sintering step, there is no problem of handling when transferring the formed body to the sintering furnace unlike the conventional example. In addition, since the strength of the porous body can be increased by current pressure sintering, there is no problem in handling after current pressure sintering.

Further, it is difficult to perform continuous processing, and the processing time in the current-pressing sintering step, in which the number of products produced per processing during batch processing is small, is as short as possible. By providing a heat treatment step with a large number of products per process in this case, a sintered friction material excellent in strength and wear resistance can be manufactured without impairing productivity. In addition, the reaction between the hard particles in the powder and the copper alloy base proceeds by the heat treatment step, and the hard particles are refined, so that the bonding between the hard particles and the base is strengthened and the hard particles fall off during friction sliding. It is suppressed and the wear resistance is improved.

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for producing a copper-based sintered friction material in Example 1 of the present invention.

Claims (12)

[Claims] 1. A copper-based sintered friction material obtained by solidifying a raw material powder containing copper as a main component and having a porosity of at least 35% by volume
A copper-based sintered friction material, which is not more than% by volume. 2. The copper-based sintered friction material according to claim 1, which is used in a lubricating oil. 3. The copper-based sintered friction material has hard particles and a balance of a copper alloy base, and the hard particles are contained in an amount of 5% or more and 40% or less on a weight basis. The copper-based sintered friction material according to claim 1, wherein the copper alloy body has copper or a copper alloy, a lubricant, and unavoidable impurities. 4. The hard particles include iron-based intermetallic compounds, oxide particles, nitride particles, carbide particles, Si particles and M particles.
The copper-based sintered friction material according to claim 3, comprising one or more members selected from the group consisting of o particles. 5. The copper-based sintered friction material according to claim 3, wherein the hard particles have an average particle diameter of 20 μm or less. 6. The copper alloy body contains Sn, Zn and N
The copper-based sintered friction material according to claim 3, wherein the copper-based sintered friction material contains at least one metal element selected from the group consisting of i. 7. The lubricant is made of graphite, MoS
₂ , one or more solid lubricants selected from the group consisting of CaF ₂ , WS ₂ and BN, and 25% by volume.
% Of the copper-based sintered friction material according to claim 3. 8. A step of mixing a raw material powder into a predetermined composition to obtain a mixed powder, a step of compressing and pressing the mixed powder in a mold, and applying a current to heat to obtain a sintered body; Performing a heat treatment at a temperature of 700 ° C. or more and 1000 ° C. or less. 9. The method according to claim 8, wherein the step of performing the heat treatment on the sintered body is performed in a non-oxidizing or reducing atmosphere. 10. In the step of compressing and compressing the mixed powder and energizing and heating, the mixed powder is sintered together to obtain the sintered body, and at the same time, the metal plate and the sintered body are diffusion-bonded. The method for producing a copper-based sintered friction material according to claim 8, characterized in that: 11. The method for producing a copper-based sintered friction material according to claim 8, wherein a copper alloy powder in which hard particles are homogeneously dispersed in a copper alloy base material is used as the raw material powder. 12. In the step of preparing the copper alloy powder, the mixed powder of the copper-based metal powder and the hard particles is subjected to mechanical mixing and pulverization by a mechanical alloying method or a mechanical pulverization method. The method for producing a copper-based sintered friction material according to claim 11, wherein the hard particles are uniformly dispersed in the copper-based metal body.