JPH116021A - Copper-based sintered friction material and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coppery sintered friction material in which coefficient of friction is stabilized in the early stage owing to fine, spherical, had grains and also fluctuations in the coefficient of friction are minimized. SOLUTION: This friction material consists of a coppery composite powder material prepared by mixing aluminum (Al)-containing hard grains with a coppery powder material consisting of copper (Cu) or a copper alloy composed essentially of copper (Cu) and free from aluminum (Al). The grain size of the hard grains dispersed in the metallic matrix of the coppery sintered friction material is regulated to <=8 μm, and aliuminum(Al) is contained by <=28% on a weight percentage basis to the metallic matrix. The coppery composite powder material is press-compacted into a green compact, and this green compact is sintered in a nonoxidizing atmosphere or reducing atmosphere at 700 at 1000 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard particle-dispersed copper-based sintered friction material useful as a brake pad material or a clutch material for an automobile or a motorcycle or a synchronous ring material for a transmission.

[0002]

2. Description of the Related Art A copper-based sintered friction material has been known as a metal-based sintered friction material having a high friction coefficient and hardly causing problems such as seizure. For example, Japanese Patent Application Laid-Open Nos. Sho 60-116751 and 61-67
No. 737, JP-A-63-109131 and the like. In these sintered friction materials, hard particles and a copper alloy powder material are simply mixed, molded and sintered to increase the coefficient of friction and improve wear resistance.

Since the hard particles and the copper alloy powder material are simply mixed, the hard particles are considered to be in the following situation from a microscopic viewpoint. That is, the hard particles do not form a diffusion reaction layer with the metal base of the copper-based sintered friction material even after sintering, and the grain boundaries of the metal base of the sintered friction material (the copper alloy powder before sintering) It is considered to correspond to the outer periphery of the powder of the material itself.) And exists with a partial gap from the grain boundary. As a result, at the time of friction sliding, the hard particles fall off from the grain boundaries of the metal base of the sintered friction material and become wear powder, attacking the mating material and the sintered friction material itself, and promoting the wear of the sintered friction material. Problems arise.

In order to solve this problem, Japanese Patent Laid-Open No. 8-253
As disclosed in Japanese Unexamined Patent Publication No. 826 and the like, in a process before forming a powder material, a mechanical treatment is performed by a mechanical alloying method (mechanical alloying method) or a mechanical pulverization method (mechanical grinding method). By dispersing the hard particles into a powder base of a copper-based powder material made of a copper alloy,
In addition, a composite powder material having a reaction layer formed at the interface between the powder base and the hard particles is produced, and such a composite powder material is molded and sintered.

[0005] The sintered friction material manufactured by the above-described method suppresses falling of hard particles and improves seizure resistance and abrasion resistance as compared with the sintered friction material obtained by simple mixing described above. That is, in the sintered friction material disclosed in Japanese Patent Application Laid-Open No. 8-253826, the hard particles have a diffusion reaction layer at the interface with the powder base of a copper-based powder material made of a copper alloy. The presence of the reaction layer is effective in suppressing the hard particles from falling off the sintered friction material.

[0006]

SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open No. 8-253
In the sintered friction material disclosed in Japanese Patent No. 826, hard particles dispersed in a powder base of a copper-based powder material composed of a copper alloy are fine, but do not exhibit spheroidization, so that the value of the friction coefficient There is a problem that it takes a long time to stabilize and that noise and vibration are generated due to a change in a value of a friction coefficient between the sintered friction material and a mating material at the beginning of friction sliding.

In the present invention, in order to solve such a problem, not only a diffusion reaction layer is formed at the interface between the hard particles and the powder base of the copper-based powder material made of a copper alloy, but also the hard particles are miniaturized. By spheroidizing, the friction coefficient is stabilized early, that is, the fluctuation of the friction coefficient at the initial stage of friction sliding is reduced, and the seizure between the sintered friction material and the mating material is reduced and the wear resistance is excellent. It is an object of the present invention to provide a sintered friction material.

[0008]

Means for Solving the Problems The present inventors have studied to achieve the above object. That is, in order to uniformly disperse the hard particles in the powder base of the copper-based powder material, by including Al in the hard particles, Al is formed at the interface between the hard particles and the powder base of the copper-based powder material during sintering. The diffusion reaction of Cu proceeds. As a result, in order to form a diffusion reaction layer, the chemical bond between the hard particles and the powder base of the copper-based powder material is improved, and the hard particles are prevented from falling off. The hard particles react with the metal substrate of the copper-based sintered friction material, and the hard particles become finer and spheroidized by the reaction, so that the friction coefficient reaches a steady value in a short time, and the fluctuation when the steady becomes stable is small. Become.

A sintered friction material of a copper-based composite powder material in which hard particles containing an Al component are mixed with a copper-based powder material composed of a copper alloy containing Cu as a main component, The hard particles dispersed in the base material contain aluminum (Al) having an average particle size of 8 μm or less, a micro Vickers hardness (mH _V ) of 400 or more, and a weight% of 28% or less based on the metal base material.

The hard particles contain 30% or more and 70% or less by weight of Al, and contain Fe by weight to form hard particles.
Al-Fe based intermetallic compounds containing 30% or more and 70% or less. Elements other than Fe are also effective for forming hard particles. The copper-based sintered friction material contains 5-40% by weight of hard particles, and the balance consists of copper or a copper alloy, a lubricant and inevitable impurities. The copper alloy contains at least one metal element selected from Sn, Zn, and Ni. It contains at least 33% by volume of at least one solid lubricant selected from graphite, MoS ₂ , CaF ₂ and BN.

A copper-based powder material comprising copper (Cu) powder and at least one metal powder selected from tin (Sn), zinc (Zn) or nickel (Ni), or tin (Cu) (Sn),
At least selected from zinc (Zn) or nickel (Ni)
It is a copper-based powder material composed of at least one of copper-based powder materials composed of a copper alloy powder containing one kind of metal element.

In the step of preparing a copper-based composite powder material in which hard particles are dispersed in a powder base of a copper-based powder material, the copper-based powder material and the hard particles are mechanically alloyed (mechanical alloying method); Alternatively, the hard particles are uniformly dispersed in a powder base of a copper-based powder material by performing a mechanical treatment by a mechanical grinding method (mechanical grinding method).

In producing a sintered friction material, a copper-based composite powder material in which hard particles containing Fe and Al are dispersed in a powder base of a copper-based powder material made of a copper alloy or copper containing no Al is prepared. Forming a green compact by embossing the copper-based composite powder material; and 700 ° C. in a non-oxidizing atmosphere or a reducing atmosphere.
It comprises a step of sintering at a temperature of at least 1000 ° C.

In producing a sintered friction material, a step of preparing a copper-based composite powder material in which hard particles containing Fe and Al are dispersed in a powder base of a copper-based powder material made of a copper alloy containing no Al; In a non-oxidizing atmosphere or a reducing atmosphere,
A step of heat-treating at a temperature of 400 ° C. or more and 650 ° C. or less, followed by a step of forming a green compact by embossing the heat-treated copper-based composite powder; Sintering at 700 ° C. or more and 1000 ° C. or less in an atmosphere or a reducing atmosphere.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The most significant feature of the metal structure of the copper-based sintered friction material of the present invention is that the hard particles containing Al have a diffusion reaction layer at the interface of the metal base of the copper-based sintered friction material. And that the hard particles become fine and spherical during the sintering process.

When the copper-based sintered friction material frictionally slides with the mating material, the effect of preventing seizure with the mating material, the effect of reducing the wear of the copper-based sintered friction material and increasing the wear resistance, and Hard particles are added for the purpose of increasing the coefficient of friction by directly contacting the surface of the mating material. In order to exhibit such an effect, it is necessary that the hard particles do not fall off from the copper-based sintered friction material.

As the types of hard particles, ceramics such as Al ₂ O ₃ , SiO ₂ , ZrO ₂ , Si ₃ N ₄ , AlN, and SiC can be considered in addition to the iron-based intermetallic compound. However, these ceramic particles are inferior in machinability as compared with iron-based intermetallic compounds, and therefore have a problem in terms of economy because it is difficult to cut the friction material into an appropriate size. Therefore, iron-based intermetallic compounds are desirable as the hard particles.

The elements contained in the hard particles and the metal structure are considered as follows. In other words, by selecting hard particles containing Al, which is a metal element having high reactivity with the metal base of the copper-based sintered friction material, the Al component in the hard particles during the sintering is reduced to the copper-based sintered friction. Diffused into the metal base of the material,
A diffusion reaction layer is formed at the interface between the hard particles and the metal base.
By forming this diffusion reaction layer, the bond between the metal base and the hard particles of the copper-based sintered friction material is strengthened.

As a result, the hard particles are prevented from falling off due to shear stress when the sintered friction material is brought into contact with a mating material such as a metal and frictionally slid. And, by suppressing the falling off, abrasion powder generated at the interface between the sintered friction material and the mating material is reduced, and the wear resistance of the sintered friction material is improved.

Conversely, in the case of hard particles containing a metal element having low reactivity with the metal base or a metal element that does not react with the metal base, a diffusion reaction layer is hardly formed between the metal base and the hard particles, and the metal base and the hard base are hardly formed. The bonding strength of the particles is weakened.

As a result, the hard particles fall off during friction sliding, and the wear resistance of the sintered friction material decreases. Therefore, the hard particles in the copper-based sintered friction material preferably include Al, which is a metal element highly reactive with the metal base of the sintered friction material.

Next, regarding the hardness, the hardness of the hard particles existing in the sintered friction material is 400 micro Vickers hardness.
If it is smaller, the effect of increasing the coefficient of friction by the hard particles and the effect of improving the wear resistance are small. for that reason,
It is desirable to use hard particles that have a hardness of 400 or more in the sintered friction material.

Next, regarding the size of the hard particles in the sintered friction material, when the size is larger than 8 μm, one part of the hard particles comes into contact with the mating material on the sliding surface with the mating material. Therefore, the fluctuation of the friction coefficient becomes large. Therefore, the size of the hard particles is desirably 8 μm or less.

Further, regarding the composition of the hard particles, Al
In the case of producing a sintered friction material by mixing hard particles with less than 30% and less than 70% Fe, diffusion of the copper-based sintered friction material with the hard particles at the interface of the metal substrate during sintering Since the number of reaction layers is reduced, the bonding strength between the hard particles and the metal base is reduced, and the hard particles fall off during friction sliding, thereby increasing the wear of the sintered friction material.

On the other hand, in the case where a sintered friction material is manufactured by mixing hard particles containing more than 70% Al and less than 30% Fe, the hardness of the hard particles becomes smaller than 400 in micro Vickers hardness. The effect of increasing the coefficient of friction and the effect of improving the wear resistance are small. Therefore, the composition of the hard particles contains 30% or more and 70% or less by weight of Al and 30% by weight of Fe.
It is desirable that the content be at least 70%.

When the content of the hard particles is less than 5% by weight, the number of the hard particles existing on the frictional sliding surface decreases, so that the effect of increasing the friction coefficient and preventing the seizure is small. If it is more than 40%, the mechanical strength and heat conductivity of the sintered friction material are inferior. Therefore, the content of the hard particles is preferably 5% or more and 40% or less.

The maximum diffusion amount of Al into the metal base of the sintered friction material is 28% corresponding to all of the hard particles having a maximum content of 40% (maximum content of 70% in the hard particles). It is.
Al of hard particles with a minimum content of 5% (minimum 30
1.5%, which corresponds to all of the above (% content), is not the minimum diffusion amount of Al into the metal substrate of the sintered friction material. In some cases, only a part of Al of hard particles having a minimum content of 5% (minimum content of 30% in hard particles) is diffused into the metal base, and the diffusion is confirmed by elemental analysis.

When the metal element of the copper-based sintered friction material contains an alloy element, it contains at least one selected from Sn, Zn and Ni. The content is 5% or more and 40% or less by weight. In the following Example 4, an example of 9% or more and 15% or less is shown, but the same can be applied to 5% or more and 40% or less.

Each of Sn, Zn, and Ni has an effect of increasing the hardness and strength of the metal base by forming an alloy with copper. When a metal base is formed only with copper, the hardness and strength are reduced, so that the resistance of the sintered friction material to shear stress is reduced, and the seizure resistance is reduced. For this reason, the metal base preferably contains at least one metal element selected from Sn, Zn, and Ni.

The solid lubricant is present at the sliding interface with the mating material, has the effect of preventing seizure and reducing the variation in the coefficient of friction. In the sintered friction material of the present invention, when the content of the lubricant is more than 33% by volume, the mechanical strength of the friction material is undesirably reduced. In addition, at least 5% by volume is necessary to maintain the lubricity of the sintered sliding component.

Therefore, the content of the lubricant is 5% by volume.
% To 33%, preferably 10% to 33%.
In addition, molybdenum disulfide, calcium fluoride, and boron nitride are useful as lubricants.
The content of 5% or more and 33% or less is a content that does not reduce the bending strength of the sintered friction material.

Next, specific conditions relating to the method for producing a copper-based sintered friction material in the present invention will be described. That is,

(1) The production of a copper-based composite powder material is carried out using a copper-based powder material (copper (Cu) powder and at least one metal powder selected from tin (Sn), zinc (Zn) or nickel (Ni)). Or a copper-based powder material comprising a copper alloy powder containing at least one metal element selected from tin (Sn), zinc (Zn) or nickel (Ni) in copper (Cu) Any of the copper-based powder materials, or the copper-based powder material composed of both) and hard particles, if necessary, by mechanical alloying (mechanical alloying) or mechanical mixing (mechanical grinding) Mechanical processing of a copper-based powder material and hard particles as represented by For the treatment, a ball mill such as a rotary ball mill, a vibration ball mill, a planetary ball mill, or an attritor ball mill is used.

According to the above manufacturing method, the hard particles can be finely pulverized, and the finely pulverized hard particles and the powder of the copper-based powder material can be uniformly dispersed. The size of the hard particles in the copper-based composite powder material can be controlled by the time of mechanical treatment or the ratio of the powder to the ball of the ball mill.

(2) A lubricant is mixed with the composite powder material in which hard particles are dispersed in a powder base of a copper-based powder material in a ratio suitable for forming a green compact by embossing. The hard particles are uniformly dispersed using a mixer, kneader, ball mill or the like.

(3) In the sintering step, the following two points are important regarding the reaction between the hard particles and the metal base of the copper-based sintered friction material. (a) The Al component of the hard particles diffuses into the metal base of the copper-based sintered friction material, that is, the powder base of the copper-based powder material, using thermal energy as a driving force, and the interface between the powder itself of the copper-based powder material and the hard particles. To form a diffusion reaction layer. (b) Due to the formation of the diffusion reaction layer, the Al component of the hard particles is reduced, and the hard particles have an increased proportion of the Fe component, and at the same time, the particle size of the hard particles is reduced.

As the effect of the above (a), the formation of the diffusion reaction layer strengthens the bond between the hard particles and the copper-based sintered friction material, and prevents the hard particles from falling off during friction sliding. the above
The effect of (b) is that the size of the projections of the hard particles having high hardness is reduced due to the miniaturization of the hard particles, so that the projections from the surface of the sintered friction material are reduced. When frictionally sliding, the contact with the counterpart material becomes uniform, and the fluctuation of the friction coefficient becomes small.

In order for the above diffusion reaction to proceed in the sintering process, the hard particles and the metal base of the sintered friction material need to be in contact with each other without any gap. When the hard particles and the copper-based powder material are simply mixed, a gap exists between the hard particles and the powder of the copper-based powder material itself in the green compact after molding, and the diffusion reaction hardly proceeds during sintering. . The hard particles were present at the grain boundaries of the metal body of the sintered friction material (considered to correspond to the outer periphery of the powder of the copper alloy powder material before sintering), and had partial gaps with the grain boundaries. Exist in shape. Therefore, because the diffusion reaction proceeds during the sintering process,
After preparing a composite powder material in which hard particles are dispersed in a powder base of a copper-based powder material, the composite powder material is molded and sintered.

Regarding the sintering temperature, when the copper-based composite powder material of the present invention is used, in order to completely advance sintering at a temperature lower than 700 ° C., the sintering time is longer than ordinary sintering. It becomes longer and causes economic problems. Therefore, in order to advance sintering without impairing economic efficiency, the sintering temperature is set to 700 ° C. or higher.

On the other hand, when the sintering temperature exceeds 1000 ° C., a liquid phase is partially formed in the copper-based composite powder material during sintering, and the copper-based sintered friction material shrinks. As a result, there is a problem that the dimensional accuracy is reduced. Therefore, the sintering temperature is 10
It should be below 00 ° C.

Regarding the sintering atmosphere, the friction material of the present invention needs to be sintered in a non-oxidizing atmosphere or a reducing atmosphere. If the atmosphere is not the above, an oxide film is formed on the surface of the powder of the copper-based powder material, and the sinterability is significantly impaired. As a result, the strength and wear resistance of the sintered friction material are reduced.

(4) The heat treatment of the copper-based composite powder material is as follows. That is, in the manufacturing method according to the above (3), it has been described that the diffusion reaction between Al in the hard particles and the powder base of the copper-based powder material proceeds during the sintering process.
On the other hand, a diffusion reaction layer can be generated at the interface between the hard particles and the powder body of the copper-based powder material by heat-treating the composite powder material in a step before molding (ie, before sintering) the copper-based composite powder material.

That is, the copper-based composite powder material is heated at 400 ° C.
By performing the heat treatment at a temperature of 50 ° C. or less, the above diffusion reaction can be advanced. If the temperature is lower than 400 ° C., the diffusion reaction between copper and Al does not proceed, so the heat treatment temperature needs to be 400 ° C. or higher.

On the other hand, if the above heat treatment temperature exceeds 650 ° C., the sintering reaction proceeds, so that the filling property of the copper-based composite powder material into the compact at the time of molding in the next step is reduced. Therefore, the heat treatment temperature needs to be 650 ° C. or less. From the above,
The heat treatment temperature for promoting the diffusion reaction between the Al component of the hard particles in the copper-based composite powder material and the powder base of the copper-based powder material, which is also the powder base of the composite powder material, is 400 ° C. or more and 650 ° C.
C or lower is good.

Regarding the heat treatment atmosphere, it is necessary to perform sintering in a non-oxidizing atmosphere or a reducing atmosphere as in the above item (3). When the sintering atmosphere is not a non-oxidizing atmosphere or a reducing atmosphere, an oxide film is formed on the powder surface of the copper-based composite powder material. Therefore, the sinterability is significantly impaired, and as a result, the strength and wear resistance of the sintered friction material decrease.

Regarding the sintering conditions, as in the above item (3),
Non-oxidizing atmosphere or reducing atmosphere, 700 ° C or higher, 100
It is necessary to sinter below 0 ° C. If the sintering atmosphere is not a non-oxidizing atmosphere or a reducing atmosphere, an oxide film is formed on the powder surface of the composite powder material, and the sinterability is significantly impaired. As a result, the strength of the sintered friction material is reduced. And a decrease in wear resistance. Further, in order to completely advance the sintering at a temperature lower than 700 ° C., the sintering time becomes long, which causes an economic problem.

Therefore, a sintering temperature of 700 ° C. or more is desirable in order to promote sintering without impairing economy. On the other hand, when the sintering temperature exceeds 1000 ° C., a liquid phase is partially generated in the metal base of the copper-based sintered friction material and the sintered friction material shrinks. As a result, there is a problem that the dimensional accuracy of the sintered friction material is reduced. Therefore, the sintering temperature is 10
It is desirable that the temperature is not higher than 00 ° C. Hereinafter, an example which specifically shows how to carry out the present invention will be described.

[0048]

【Example】

(Example 1) A copper-based powder material made of a copper alloy having a weight ratio of Cu to Sn of 91: 9 and hard particles (((Comparative Example 1 is shown together with Example 1)) having a composition shown in Table 1 (( (Co., Ltd., manufactured by Nakako Co., Ltd., the same applies hereinafter) at a weight ratio of 80:20, mechanically alloyed by a vibratory ball mill, and hard particles dispersed in a powder base of copper powder material. I got The weight ratio of the copper-based composite powder material to graphite is 93
The powder was compounded in a ratio of 7 and cold compacted at a surface pressure of 8 t / cm ² to obtain a green compact.

[0049]

[Table 1]

The sintering temperature of the obtained green compact in a nitrogen atmosphere
Sintered and solidified at 800 ° C. EPMA (Electron Pro) was used to check the diffusion of metal particles and hard particles in the sintered friction material.
Elemental analysis was performed using beX-ray Micro Analyzer).

The metal structures of the green compact (before sintering) and the sintered friction material were observed with an optical microscope. In addition, frictional sliding characteristics (friction coefficient μ, fluctuation rate of friction coefficient (%) and abrasion amount (μm)), bending strength (5 mm long, 5 mm wide, 30 mm long rectangular sintered friction body) The test length was 20 mm.) The hardness (micro Vickers hardness under a load of 10 g) and the size of the hard particles were evaluated using the sintered friction material.

The rate of change of the coefficient of friction (μ) was defined by the following equation. Fluctuation rate (%) = Δμ / μ _AV × 100 where Δμ = μ _{n + 1} -μ _n where Δμ is the time variation of the friction coefficient, μ _AV is the average value of the friction coefficient, and μ _n is the time n minutes. The coefficient of friction.

The friction test was performed by the following method. That is, using a chip-on-disc type friction tester (the situation is shown in FIG. 4), a test condition of a peripheral speed of 1.2 m / sec, a pressing force (w) of 10 kgf / cm ² , and a continuous 1 hour in the atmosphere. The evaluation was performed using SCM420 carburized steel as the partner material 2. That is, the mating member 2 is a disk having a diameter of 60 mm and a thickness of 5 mm, and is rotated by the shaft 3 as shown by an arrow in FIG. (Test piece 1 is fixed.)

FIG. 1 shows the results of elemental analysis of the sintered body of Example 1. The whitish part in FIG. 1 (a) is Cu, FIG. 1 (b) is Fe, and FIG. 1 (c)
Is Al. It was observed that Al was present in the metal base, and it was confirmed that the diffusion reaction had progressed. That is, the whitish portion of FIG. 1 (c), which is Al, and the whitish portion of FIG. 1 (a), which is the metal base, Cu, overlap each other.

On the other hand, in the sintered body of Comparative Example 1 in which FeMo was used for the hard particles, Fe and Mo did not exist in the metal base, and no diffusion of the element of the hard particles into the metal base was observed. (A photograph of the result of the elemental analysis is not attached.) When producing a copper-based sintered friction material in which hard particles are dispersed,
Is selected, the copper-based sintered friction material after sintering has a diffusion reaction layer formed by heat treatment of the metal base and the hard particles.

FIG. 2 shows a photograph of the metal structure observation of the unsintered green compact and the sintered friction material. In Example 1 (FIG. 2 (a)), Al in the hard particles diffused into copper of the metal base due to the heat treatment, so that the particles became finer and spherical. That is, the above facts are found out when the hard particles of the green compact become the hard particles of the sintered friction material. The average particle size of the hard particles in the green compact before sintering was 10 μm, and the average particle size of the hard particles in the sintered friction material was 5 μm.

In Comparative Example 1 (FIG. 2B), the particle size of the hard particles in the unsintered green compact was the same as the particle size of the hard particles in the sintered friction material, and a change was recognized. And both have an average particle size of 10μ
m. That is to say, the above facts become clear when the hard particles in the green compact of FIG. 2B become hard particles in the sintered friction material. The shape of the hard particles in the sintered friction material is similar to that of the unsintered green compact and has a square shape.

The evaluation results of the coefficient of friction, the rate of change of the coefficient of friction, the amount of wear, the bending strength, and the hardness and size of the hard particles are also shown in the table.
Shown in 1. As described above, in Example 1, since the diffusion reaction layer was formed at the interface between the hard particles and the metal base material of the copper-based sintered friction material, the bonding was strengthened and the amount of wear was reduced.

FIG. 3 shows the applied force and friction torque during the friction test (one scale of the vertical axis of the friction torque is 1 kgf, one scale of the vertical axis of the applied force is 100 kgf. The horizontal axis is time in minutes. ). Example 1 (FIG. 3A) is the same as Comparative Example 1 (FIG.
Compared with (b)), the time until the friction torque reaches the steady value is short, and the fluctuation of the friction torque after reaching the steady value is small. For this reason, the variation rate of the coefficient of friction in Example 1 is reduced. This is because the contact between the friction material and the mating material was made uniform due to the miniaturization and spheroidization of the hard particles in the sintering process.

The following problems occurred in Comparative Example 1. A diffusion reaction layer is not formed at the interface between the hard particles and the metal base, and the amount of wear increases because the bonding between the metal base and the hard particles is weak.
Further, the hard particles are not refined or spheroidized, so that it takes a long time for the initial familiarization between the sintered friction material and the mating material, and the fluctuation rate of the friction coefficient increases.

(Examples 2 to 9) The weight ratio of Cu to Sn was 91: 9.
The weight ratio of the copper-based powder material composed of a copper alloy and the Al-Fe-based hard particles shown in Table 2 was mixed at a ratio of 80:20, and a mechanical alloying process was performed using a vibration-type ball mill to disperse the hard particles. A copper-based composite powder material was obtained. Graphite was blended with this copper-based composite powder material in a weight ratio of 93: 7, and a green compact was obtained by cold molding with a surface pressure of 8 t / cm ² .

The green compact was sintered at a sintering temperature of 80 in a nitrogen atmosphere.
Sintered at 0 ° C. The frictional sliding characteristics, strength, and hardness and size of the hard particles of the obtained copper-based sintered friction body were evaluated. Table 2 shows the evaluation results.

[0063]

[Table 2]

Examples 2 to 4 of the present invention (Example 3 is the same sintered friction material as in Example 1) and Comparative Examples 2 and 3 are shown. In Examples 2 to 4, good frictional sliding characteristics and good mechanical characteristics were obtained as in Example 1.

The following problems occurred in the comparative example. In Comparative Example 2, since the Al component in the hard particles is small, the bond between the metal base of the copper-based sintered friction body and the hard particles is weak, and the amount of wear increases. Further, the hard particles are not refined, and the variation in the coefficient of friction is increased. In Comparative Example 3, since the Fe component in the hard particles is small, the hardness of the hard particles is small, and the effect of the hard particles to increase the friction coefficient is small.

(Examples 5 to 9) The weight ratio of Cu to Sn was 91: 9.
Copper-based powder material consisting of a copper alloy and the weight ratio of Fe to Al is 50
Hard particles having a ratio of 50 were mixed and subjected to mechanical alloying treatment with a vibration ball mill to obtain a copper-based composite powder material in which the hard particles were dispersed. This composite powder was mixed with graphite as a lubricant, and a green compact was obtained by cold compacting at a surface pressure of 8 t / cm ² .

[0067]

[Table 3]

The solidified green compact was sintered at a sintering temperature of 800 ° C. in a nitrogen atmosphere. Table 3 shows the weight percent of the base metal, hard particles and lubricant from the copper-based powder material of the sintered friction material in the sintered friction material. (Since it is considered that the escape of the components to the outside or the inclusion of unavoidable impurities can hardly occur, it is sufficient to assume that the weight% of the green compact is the same as the weight% of the sintered friction material.) The friction sliding properties and bending strength of the copper-based sintered friction body were evaluated. Table 3 shows the evaluation results.
Shown in Examples 5 to 9 of the present invention (Example 7 is
This is the same sintered friction material as 1 and 3. ) And Comparative Examples 4 and 5 are shown. In Examples 5 to 9, good frictional sliding characteristics and good bending strength were obtained as in Examples 1 and 3.

The following problems occurred in the comparative example. In Comparative Example 4, the effect of increasing the coefficient of friction and the effect of suppressing wear were small due to the small amount of hard particles. Therefore, the coefficient of friction of the sintered friction material is small and the wear resistance is poor. Comparative Example 5 is inferior in mechanical strength because the amount of copper base is small and bonding of bases is insufficient.

(Examples 10 to 13) A copper-based powder material having the composition shown in Table 4 and hard particles (weight ratio of Fe to Al: 50:50) were mixed at a weight ratio of 80:20, and vibrated. Mechanical alloying was performed by a ball mill to obtain a copper-based composite powder material in which hard particles were dispersed. The copper-based composite powder and graphite as a lubricant were blended so that the weight ratio was 93: 7, and a green compact was obtained by cold compacting with a surface pressure of 8 t / cm ² .

[0071]

[Table 4]

The green compact was sintered at a sintering temperature of 80 in a nitrogen atmosphere.
Sintered at 0 ° C. Copper-based sintered friction material (Since it is considered that the escape of components to the outside or the inevitable mixing of impurities is unlikely to occur, it is assumed that the weight percent of the green compact and the weight percent of the sintered friction material are the same. Table 4 shows the results of the evaluation of the presence or absence of seizure after the friction test and the Rockwell hardness based on the F standard among the friction sliding characteristics of the above. Embodiment of the present invention
Examples 10 to 13 (Example 10 is the same sintered friction material as Examples 1, 3, and 7) and Comparative Example 6.

In Examples 10 to 13, good frictional sliding characteristics similar to those of Examples 1, 3, and 7 and a state without seizure after the friction test were obtained. The Rockwell hardness of the sintered friction material shows a similar value. In Comparative Example 6, there was a problem that the Rockwell hardness of the sintered friction material was low and seizure occurred during friction sliding.

(Examples 14 to 17) The weight ratio of Cu to Sn was 91: 9.
Copper-based powder material consisting of a copper alloy and the weight ratio of Fe to Al is 50
The hard particles were mixed with 50 hard particles and mechanically alloyed by a vibration ball mill to obtain a copper-based composite powder material in which the hard particles were dispersed.

After the sintering, the copper-based composite powder material and graphite as a lubricant were blended so as to have a weight ratio shown in Table 5, and cold compacted at a surface pressure of 8 t / cm ² to obtain a green compact. The obtained green compact was sintered at a sintering temperature of 800 ° C. in a nitrogen atmosphere.

[0076]

[Table 5]

The frictional sliding characteristics (friction coefficient μ and abrasion amount (μm)) and bending strength of the copper-based sintered friction material were evaluated. Table 5 also shows the evaluation results. Examples 14 to 17 of the present invention (Example 1
Reference numeral 6 denotes a sintered friction material which is essentially the same as in the first, third, seventh and tenth embodiments. In the case of), the same favorable frictional sliding characteristics and sufficient transverse rupture strength as those in Examples 1, 3, and 7 were obtained. In Comparative Example 7, there was a problem that the transverse rupture strength was inferior.

(Examples 18 to 22) The weight ratio of Cu to Sn was 91:
9 copper-based powder material consisting of copper alloy and hard particles (Fe and Al
The weight ratio is 50:50) and the weight ratio is 80:20, and mechanical alloying treatment is performed by a vibration ball mill.
A copper-based composite powder in which hard particles were dispersed was obtained.

This copper-based composite powder material and graphite as a lubricant were blended in a weight ratio of 93: 7, and the surface pressure was 8 t / cm ^2.
To obtain a green compact. The obtained green compact was sintered under the conditions shown in Table 6.

[0080]

[Table 6]

Table 6 also shows the state of the copper-based sintered friction material. Examples 18 to 22 of the present invention (Example 19 is
1, 3, 7, 10 and 16 are essentially the same sintered friction material. )
As in Examples 1, 3, 7, 10, and 16, a copper-based sintered friction material having good friction sliding characteristics and bending strength and good appearance was obtained.

The following problems occurred in the comparative example. In Comparative Example 8, the sintering reaction did not proceed because the heat treatment temperature was low. In Comparative Example 9, since the sintering temperature was high, the shrinkage was large, and the dimensional accuracy was deteriorated. In Comparative Example 10, sintering was performed in the air, so oxidation proceeded, and the sintering reaction was significantly inhibited.

(Examples 23 to 26) The weight ratio of Cu to Sn was 91:
9 copper-based powder material consisting of copper alloy and hard particles (Fe and Al
The weight ratio is 50:50) and the weight ratio is 80:20, and mechanical alloying treatment is performed by a vibration ball mill.
A copper-based composite powder material in which hard particles were dispersed was obtained. The obtained copper-based composite powder material was heat-treated under the conditions shown in Table 7. Table 7 also shows the state of the diffusion reaction layer at the interface between the powder base of the heat-treated copper-based composite powder material and the hard particles.

[0084]

[Table 7]

In Examples 23 to 26 of the present invention, a copper-based composite powder material having a diffusion reaction layer formed between the hard particles and the powder base of the copper-based powder material was obtained.

The following problems occurred in the comparative example. In Comparative Example 11, the heat treatment was performed at a low temperature,
The diffusion reaction between the Al component and the powder base of the copper-based powder material did not proceed. In Comparative Example 12, the heat treatment temperature was high, and the powder particles of the copper-based powder material sintered and agglomerated during the heat treatment. This agglomeration is not preferable because it lowers the packing density of the copper-based powder material and the hard particles during molding and generates coarse pores in the copper-based sintered friction material.

[0087]

According to the present invention, Al in the hard particles dissolves in the metal base of the copper-based sintered friction material during heat treatment such as sintering, and forms a diffusion reaction layer at the interface between the hard particles and the metal base. Particle dropout is reduced, and the wear resistance of the copper-based sintered friction material is improved. As a result, the service life of the copper-based sintered friction material is prolonged. In addition, due to the fineness and spheroidization of the hard particles, the fluctuation of the friction coefficient is reduced, and abnormal noise and vibration during sliding are reduced.

[Brief description of the drawings]

FIG. 1 shows the results of elemental analysis of a copper-based sintered friction material by EPMA.

FIG. 2 is a structural photograph of a green compact and a sintered friction material. (1000x magnification)

FIG. 3 shows measurement data of a pressing load and a friction torque of a sintered friction material.

FIG. 4 is a diagram for explaining a friction test.

[Explanation of symbols]

 1: Copper-based sintered friction material 2: Partner material 3: Shaft S: Sliding surface W: Pressure load

────────────────────────────────────────────────── ─── front page continued (51) Int.Cl. ⁶ identifications FI C22F 1/08 C22F 1/00 627 // C22F 1/00 627 628 628 630E 630 630C 631A 631 687 687 691B 691 B22F 3/10 F

Claims (8)

[Claims] 1. A copper-based sintered material comprising a copper-based composite powder material obtained by mixing a copper-based powder material containing copper (Cu) as a main component and not containing aluminum (Al) with hard particles containing aluminum (Al). A friction material, wherein the hard particles dispersed in the metal base of the copper-based sintered friction material have a micro Vickers hardness (mH _V ) of 400 or more, an average particle size of 8 μm or less, and a weight% with respect to the metal base. A copper-based sintered friction material characterized in that it contains 28% or less of aluminum (Al). 2. Hard particles mixed with a copper-based powder material whose main component is copper (Cu) and does not contain aluminum (Al) are iron (Fe).
And the balance is 30% or more and 70% or less by weight of aluminum (Al)
The copper-based sintered friction material according to claim 1, which is an iron-based intermetallic compound consisting of: 3. The hard particles have a weight percentage of 5% or more and 40% or less,
The copper-based sintered friction material according to claim 1, wherein the balance is a copper alloy, a lubricant, and unavoidable impurities. 4. A copper-based powder material whose main component is copper (Cu) and does not contain aluminum (Al) includes copper (Cu) powder, tin (Sn) and zinc.
(Zn) or nickel (Ni) is a copper-based powder material composed of at least one metal powder selected from copper (Cu) or tin (S
n), zinc (Zn) or nickel (Ni) is a copper-based powder material composed of at least one of a copper-based powder material comprising a copper alloy powder containing at least one metal element selected from the group consisting of: It is characterized in that copper (Cu) as a main component contains at least one metal element selected from tin (Sn), zinc (Zn) or nickel (Ni) in a weight percentage of 5% or more and 40% or less. The copper-based sintered friction material according to claim 1. 5. A graphite, molybdenum disulfide (Mo)
_{2. The method according} to claim 1, wherein at least one solid lubricant selected from S ₂ ), calcium fluoride (CaF ₂ ) and boron nitride (BN) is blended in an amount of 5% to 33% by volume. Copper-based sintered friction material. 6. A copper-based powder material whose main component is copper (Cu) and does not contain aluminum (Al) is mixed with hard particles containing aluminum (Al), and the hard particles are mixed with a powder base of the copper-based powder material. It is characterized in that a solid lubricant is blended with a copper-based composite powder material dispersed in, and the pressed green compact is sintered at 700 ° C or higher and 1000 ° C or lower in a non-oxidizing atmosphere or a reducing atmosphere. The method for producing a copper-based sintered friction material according to claim 1. 7. A copper-based powder material whose main component is copper (Cu) and does not contain aluminum (Al) is mixed with hard particles containing aluminum (Al), and the hard particles are mixed with a powder base of the copper-based powder material. The copper-based composite powder material dispersed in a non-oxidizing atmosphere or a reducing atmosphere is heat-treated at 400 ° C. or more and 650 ° C. or less, and a solid lubricant is blended with the heat-treated copper-based composite powder material, and embossed. 2. The method for producing a copper-based sintered friction material according to claim 1, wherein the molded green compact is sintered in a non-oxidizing atmosphere or a reducing atmosphere at a temperature of 700 ° C. or more and 1000 ° C. or less. 8. A copper-based powder material whose main component is copper (Cu) and does not contain aluminum (Al), and hard particles containing aluminum (Al) are mixed by a mechanical alloying method or a mechanical grinding method. 8. The method for producing a copper-based sintered friction material according to claim 6, wherein a copper-based composite powder material in which hard particles are dispersed in a powder base of a copper-based powder material is used.