JPH06145845A - Sintered friction material - Google Patents

Abstract

PURPOSE:To obtain a bronze-base dry sintered friction material to be used for the clutch, brake, etc., capable of stably securing a high friction coefficient, without attacking the counterpart, reduced in friction amt. and without causing seizure with the counterpart. CONSTITUTION:This sintered friction material consists of a Cu-Sn alloy and a solid lubricating component with a bronze-base sintered alloy as a mother alloy. The Cu-Sn alloy contains 3-20wt.% Sn and the balance Cu with inevitable impurities, and 3-20wt.% of hard particles having 1080mum average diameter are uniformly dispersed in the Cu alloy base. Further, the seizing resistance is improved by controlling the pore having <=30mum size to 1-30vol.%, a relatively high friction coefficient is stably secured, the counterpart attacking property is minimized, and hence the material can be applied to the dry friction material such as clutch and brake.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bronze-based dry-sintered friction material, which has excellent seizure resistance, can stably secure a relatively high coefficient of friction, and is superior to the counterpart material. Since it has extremely low aggressiveness, it can be applied to dry friction materials such as clutches and brakes.

[0002]

2. Description of the Related Art In recent years, bronze-based sintered alloys have been developed in place of asbestos-based friction materials as materials for dry friction type friction clutches and brakes.
In No. 8-157928 "Dry Sintered Friction Material", hard particles are added in order to obtain a high friction coefficient with a bronze-based sintered alloy.

However, in these sintered materials, there is no reaction layer between the hard particles dispersed in the alloy and the matrix, and a gap exists. Therefore, under high-speed, high-load sliding conditions, hard particles fall off from the base material during friction, making it impossible to secure a high coefficient of friction in a stable manner. Moreover, there is a problem that the fallen particles are caught and the opponent material is attacked.

[0004]

In order to overcome the above-mentioned problems, the present invention uniformly disperses hard particles added for the purpose of improving the coefficient of friction in a Cu-Sn alloy, and disperses hard particles. The problem is to prevent the hard particles from falling off from the substrate during sliding by forming a reaction layer at the interface between the particles and the substrate.

[0005]

Therefore, the present inventors have
As a result of various experiments and studies to solve the above problems, a high friction coefficient can be stably ensured under dry sliding friction conditions, so that the mating material is not attacked and the wear amount is small. Furthermore, we have developed a sintered friction material that does not cause seizure with the mating material.

According to the present invention, the specific alloy composition and the amount of vacancies are as follows.

The sintered friction material of the present invention is bronze.
In a sintered friction material containing a system sintered alloy as a master alloy, Sn: 3 to 20% by weight is contained, and the balance is substantially Cu.
And hard particles having an average particle size of 1 to 80 μm in the Cu alloy base having a composition of unavoidable impurities in a weight ratio of 3 to 20.
% A sintered friction material comprising a Cu—Sn alloy uniformly dispersed and a solid lubricating component.

The above hard particles are nitrides or F when Cu--Sn alloy powder is produced by the water atomizing method.
An oxide, a nitride, a carbide, a boride and an Fe-based metal when a commercially available powder composed of at least one or two or more e-type intermetallic compounds is produced by a mechanical alloying method, mechanical grounding method or granulation method It is composed of at least one or two or more of the intercalation compounds.

In the case of the water atomizing method, the Cu-Sn alloy has an average particle size of 100 μm or less and is hard alloy particles are uniformly dispersed by rapid solidification spraying to form an alloy. When powder is produced by a mechanical alloying method, a mechanical grounding method, a granulation method, or the like, the hard particles are mechanically alloyed with a Cu—Sn alloy powder or a mixed powder of Cu and Sn to form Cu particles. -Disperse uniformly in the Sn-based alloy substrate. Solid lubricant components are added to these powders. This solid lubricating component is graphite, MoS ₂ or CaF ₂
1 to 5% by weight of the whole consisting of at least one of
To configure. Cu-having such a composition
The Sn-based sintered alloy has 1 to 3 pores with a size of 30 μm or less.
0% by volume has a uniformly distributed structure.

Next, the reason why the alloy composition and the amount of holes are set as described above will be explained.

Sn Sn forms the base material of the present alloy together with Cu, has the effect of improving the high temperature strength and toughness of the alloy, and also has the effect of improving the seizure resistance with the mating material at high temperatures. If the addition amount is less than 3% by weight, these effects are not exerted, and if the addition amount exceeds 20% by weight, a hard and brittle phase precipitates, so that the strength and toughness are lowered. Therefore, the Sn content is 3 to 20.
Weight% was set.

Hard Particles Hard particles are uniformly dispersed in the base material of the present sintered alloy and suppress the occurrence of adhesion with the mating material at normal temperature and high temperature under dry friction conditions to improve seizure resistance and to prevent mating. It has the effect of increasing the friction coefficient by directly contacting the surface of the material and improving the wear resistance.

The influence of the size and the addition amount is as follows. If the average particle size is less than 1 μm and the content is less than 3% by weight, the effect is not obtained. If the average particle size exceeds 80 μm or the content exceeds 20% by weight, the hard particles are apt to be a starting point of cracking, As a result, the strength and toughness of the alloy are lowered, and also from the viewpoint of opponent attacking property, addition of a nitride in such a range causes severe abrasion of the opponent material, which is not preferable.

Therefore, the hard particles in the alloy have an average particle size of 1 to
It is appropriate that the total content is 80 μm and the total content is 3 to 20% by weight. The oxides, nitrides, carbides, borides and F that are hard particles that are uniformly dispersed in the alloy base of the present invention.
The specific components of the e-based intermetallic compound are as follows.

Oxide: Al ₂ O ₃ , MgO, ZrO ₂ ,
SiO ₂ nitride; Si ₃ N ₄ , TiN, CrN, AlN, WN carbide; SiC, TiC, CrC, ZrC, WC boride; TiB, ZrB, CrB Fe-based intermetallic compound; Fe-Mo, Fe-Cr, Fe-
W, Fe-Ti

However, in the case of spray quench solidification by water atomization, the hard particle component is selected from nitrides and Fe-based intermetallic compounds that can form a reaction layer at the interface between the molten Cu--Sn base material and the hard particles. When these hard particles fall off the base material during sliding, seizure occurs due to transfer and adhesion with the mating material starting from the falling part, and the mating of the fallen particles into the mating material causes the mating material to wear.・ Damage. Therefore, in order to suppress such a phenomenon and ensure a stable high friction coefficient, it is necessary to uniformly disperse the hard particles in the matrix and suppress the falling of these particles.

Therefore, the above-mentioned hard particles are uniformly dispersed in a molten Cu-Sn alloy, and a Cu-Sn mother alloy having a reaction layer formed at the interface with the Cu-Sn alloy is water-atomized or hard atomized. By mechanically alloying the particles with a Cu-Sn alloy powder or a mixed powder of Cu and Sn, the hard particles can be uniformly dispersed in the Cu-Sn alloy base, and the Cu-Sn alloy of the base can be dispersed. By forming a reaction layer at the interface between the hard particles and the hard particles, the hard particles can be firmly fixed in the matrix.

In the case of water atomized alloy powder, when the average particle size exceeds 100 μm, the cooling rate from the molten metal is 10 ³ ° C.
Since it is smaller than / sec, Sn segregates around the outer periphery of the α phase in the base material when the atomized powder solidifies, and as a result, the seizure resistance and strength / toughness of the alloy after sintering deteriorate. Therefore, it should be 100 μm or less.

In the case of the mechanical alloying method, concretely, the mechanical alloying method, the mechanical grounding method, and further the mechanical alloying method such as the granulation method are applied to make the hard particles uniform in the matrix. A Cu—Sn alloy powder that is dispersed and does not fall off during sliding is obtained.

Solid Lubrication Component The solid lubrication component has the effects of improving the aggressiveness to the mating material under dry friction conditions and stabilizing the friction coefficient at high temperatures, thereby improving the lubricity between sliding surfaces. It is also possible to suppress the generation of squeal when sliding.

Solid lubricant components having these effects in the Cu--Sn system sintered alloy are graphite, MoS ₂ and CaF.
_{Is 2} . These are easily mixed as powders and have no economical problem. On the other hand, for other lubricating components, for example, Pb is used.
Is used in a Cu-Sn alloy bearing, but since it exists as fine particles between α-phase dendrites without forming a compound with the base material, it may fall off during sliding when applied to a friction material.

Therefore, graphite, MoS ₂ and CaF ₂ were selected as the solid lubricating components. Its content is graphite, MoS
₂ or at least one of CaF ₂ and 1 to 5
Weight percent is a suitable amount. If the content is less than 1% by weight, the above effect is not obtained, and if it is added in excess of 5% by weight, the effect is not improved and, conversely, the strength and toughness of the sintered body are deteriorated, which is not preferable.

Amount of Voids The size of the voids is 30 μm or less, and by being evenly distributed on the sliding friction surface of the sintered alloy, the voids are deformed during sliding and seizure resistance and the mating material. It has the effect of improving the compatibility with. If the size of the pores exceeds 30 μm, this becomes the starting point of crack generation, and the strength and toughness of the sintered body are significantly reduced. Further, if the amount is less than 1% by volume, the above effect is small, and if it exceeds 30% by volume, the strength and toughness of the sintered alloy deteriorate. Further, if the pores are unevenly distributed, the conformability with the mating material during sliding is locally reduced, so that a stable friction coefficient cannot be obtained. Therefore, in the present sintered friction material, it is appropriate that the pores have a size of 30 μm or less and that the pores are uniformly distributed in the friction material in an amount of 1 to 30% by volume.

The sintered friction material having the alloy composition and the porosity as described above has sufficient strength / toughness, wear resistance and self-lubricity. Further, under dry friction-sliding conditions, a normal Cu-Sn alloy has a friction coefficient of about 0.2 to 0.3 at the initial stage of sliding, and the friction coefficient increases and fluctuates as the friction progresses, and finally Causes seizure with the mating material, whereas this sintered friction material can stably maintain a relatively high coefficient of friction of about 0.5 to 0.7, and the same material or iron / copper alloy is used. Even when it is used as a mating material, it does not attack them and does not cause seizure with the mating material.

[0025]

Example 1 Table 1 shows alloy compositions of the sintered friction material of the present invention (when hard particles are nitrides) and a comparative material.
Incidentally, (1) to (9) are friction materials of the present invention, and (10) to
(20) is a comparative material (all are expressed in weight% except for the amount of voids). Table 2 shows the mechanical characteristics of the sintered friction material and the friction test results (friction coefficient, wear amount of friction material and mating material S10C material). The friction test was carried out by the dry friction tester shown in FIG.

[0026]

[Table 1]

[0027]

[Table 2]

Materials (1) to (9) are the alloys of the present invention and have good mechanical properties and friction test results.
On the other hand, the test results for the comparative material are as follows.

(10) Since the Sn content is as small as 1%, the friction material wears due to insufficient strength of the base material, and the μ value increases. (11) Since the Sn content is as large as 25%, the base material significantly hardens and attacks the mating material, increasing the μ value. (12) Since the average grain size of the nitride is as large as 90 μm, it lacks toughness and attacks the partner material. (13) Sufficient μ because the added amount of nitride is as small as 2%.
I can't get the value. (14) Since the amount of nitride added is as large as 30%, the toughness is insufficient and the opponent material is attacked. (15) Since the total amount of nitride added is as large as 30%, the toughness is insufficient and the other material is attacked. (16) Since no solid lubricant is contained, poor lubrication occurs and seizure occurs with the mating material. (17) Since the amount of pores is 0%, seizure resistance is reduced and seizure occurs with the mating material. (18) Since the porosity is as large as 35%, the strength and toughness are insufficient and the friction material is worn. (19) Since the size of the pores is as large as 45 μm on average, the strength and toughness are insufficient and the friction material wears. (20) When the nitride slides, it falls off from the base material and seizes with the mating material.

Example 2 Table 3 shows the alloy compositions of the sintered friction material of the present invention (when the hard particles are Fe-based compounds) and the comparative material. In addition, (1) to (9) are friction materials of the present invention, and (10) to (20) are comparative materials (all are shown by weight% except for the amount of pores). Mechanical properties and friction test results of the sintered friction material (friction coefficient, friction material and mating material S
Table 4 shows the amount of wear of the 10C material). The friction test is shown in Fig. 1.
The dry friction tester shown in FIG.

[0031]

[Table 3]

[0032]

[Table 4]

Materials (1) to (9) are the alloys of the present invention and have good mechanical properties and friction test results.
On the other hand, the test results for the comparative material are as follows.

(10) Since the Sn content is as small as 1%, the friction material wears due to insufficient strength of the base material and the μ value increases. (11) Since the Sn content is as large as 25%, the base material significantly hardens and attacks the mating material, increasing the μ value. (12) Since the hard particles have a large average particle size of 90 μm, they lack in toughness and attack the mating material. (13) A sufficient μ value cannot be obtained because the amount of hard particles added is as small as 2%. (14) Since the amount of hard particles added is as large as 30%, the toughness is insufficient and the partner material is attacked. (15) Since the total amount of hard particles added is as large as 30%, the toughness is insufficient and the mating material is attacked. (16) Since no solid lubricant is contained, poor lubrication occurs and seizure occurs with the mating material. (17) Since the amount of pores is 0%, seizure resistance is reduced and seizure occurs with the mating material. (18) Since the porosity is as large as 25%, the strength and toughness are insufficient and the friction material is worn. (19) Since the size of the pores is as large as 45 μm on average, the strength and toughness are insufficient and the friction material wears. (20) When the nitride slides, it falls off from the base material and seizes with the mating material.

Example 3 Tables 5 and 6 show alloy compositions of the sintered friction material of the present invention and the comparative material. In addition, 1 in Table 5
Nos. 17 to 17 are friction materials of the present invention, and Nos. 18 to 28 in Table 6 are comparative materials (all are expressed by weight% except for the amount of pores). Mechanical properties of the sintered friction material and friction test results (friction coefficient,
Table 7 shows the wear amounts of the friction material and the mating material S10C. The friction test was carried out by the dry friction tester shown in FIG.

[0036]

[Table 5]

[0037]

[Table 6]

[0038]

[Table 7]

Materials 1 to 17 are the alloys according to the invention and have good mechanical properties and friction test results. On the other hand, the test results for the comparative material are as follows.

18: Since the Sn content was as small as 1%, the friction material was abraded due to insufficient strength of the base material, and the μ value increased. 19: Since the Sn content is as large as 30%, the base material is significantly hardened and attacks the mating material to increase the μ value. 20: Since the hard particles have a large average particle size of 100 μm, the toughness is insufficient and the mating material is attacked. 21: A sufficient μ value cannot be obtained because no hard particles are contained. 22 ・ 23: Due to a large amount of hard particles of 35%, the toughness is insufficient and the opponent material is attacked. 24: Since solid lubricant is not included, poor lubrication occurs and seizure occurs with the mating material. 25: Since the amount of voids is 0%, seizure resistance is lowered and seizure occurs with the mating material. 26: Since the porosity is as large as 35%, the strength and toughness are insufficient and the friction material is worn. 27: Since the size of the pores is as large as 45 μm on average, the strength and toughness are insufficient and the friction material wears. 28: No mechanical alloying method was performed, only the powders each having a predetermined component were simply mixed, and then sintered, so that a reaction layer between the hard particles and the base material was not formed, and the hard particles did not form a base material during sliding. Will fall off and cause seizure with the mating material.

[0041]

The bronze-based sintered friction material of the present invention can stably maintain a relatively high coefficient of friction of about 0.5 to 0.7 under dry friction sliding conditions, and the same material or iron / copper can be used. Even when an alloy or the like is used as a mating material, it does not attack them and seizure with the mating material does not occur. It also has sufficient strength and toughness. Therefore, it can be used as a clutch material for compressors and a brake friction material for automobiles and motorcycles.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a dry friction tester for carrying out a friction test of the present invention.

Claims (7)

[Claims] 1. A sintered friction material comprising a bronze-based sintered alloy as a master alloy, wherein Sn: 3 to 20 in weight ratio.
%, With the balance substantially consisting of Cu and unavoidable impurities in a Cu alloy matrix having an average particle size of 1 to 80 μm.
Hard particles of 3 to 20% by weight in a uniform dispersion of C
A sintered friction material comprising a u-Sn alloy and a solid lubricating component. 2. The sintered friction material according to claim 1, wherein Cu-Sn alloy powder having an average particle diameter of 100 μm or less and which is rapidly solidified and alloyed by a water atomizing method is used as a raw material powder. 3. The hard particles are Si nitride, Ti nitride, C
The sintered friction material according to claim 2, wherein the sintered friction material comprises at least one kind or two or more kinds of r nitride, W nitride, Al nitride, and Fe-based intermetallic compound. 4. The Cu—Sn alloy is made of Cu—Sn alloy powder or Cu and Sn which are hard particles formed by a mechanical alloying method, a mechanical grounding method, or a granulation method.
The sintered friction material according to claim 1, wherein the hard particles are uniformly dispersed in the Cu-Sn alloy base material by mechanically alloying with the mixed powder of. 5. The sintered friction material according to claim 4, wherein the hard particles are made of at least one kind or two or more kinds of oxides, nitrides, carbides, borides and Fe-based intermetallic compounds. 6. The solid lubricating component is graphite, MoS ₂ or C
The sintered friction material according to claim 1, which contains 1 to 5% by weight of at least one of aF ₂ . 7. The sintered friction material according to claim 1, wherein the Cu—Sn based sintered alloy has a structure in which pores having a size of 30 μm or less are uniformly distributed in an amount of 1 to 30% by volume.