阅读说明：本技术 烧结摩擦材料 (Sintered friction material ) 是由 久保田学 水井直光 石本史雄 阿佐部和孝 神田修 中野晓 中野武 川崎一道 岛添功 于 2017-04-07 设计创作，主要内容包括：本发明提供一种烧结摩擦材料,其是将混合粉末在800℃以上加压烧结而形成的,所述混合粉末以质量％计含有Cu和/或Cu合金：40.0～80.0％、Ni：0％以上且低于5.0％、Sn：0～10.0％、Zn：0～10.0％、VC：0.5～5.0％、Fe和/或Fe合金：2.0～40.0％、润滑材料：5.0～30.0％、以及金属氧化物和/或金属氮化物：1.5～30.0％,剩余部分由杂质构成。(The present invention provides a sintered friction material which is formed by pressure sintering a mixed powder at 800 ℃ or higher, the mixed powder containing, in mass%, Cu and/or a Cu alloy: 40.0 to 80.0%, Ni: 0% or more and less than 5.0%, Sn: 0-10.0%, Zn: 0-10.0%, VC: 0.5-5.0%, Fe and/or Fe alloy: 2.0-40.0%, lubricating material: 5.0 to 30.0%, and a metal oxide and/or a metal nitride: 1.5-30.0%, the remainder being made up of impurities.)

1. A sintered friction material obtained by pressure sintering at 800 ℃ or higher a mixed powder containing, in mass%:

cu and/or Cu alloy: 40.0-80.0%,

Ni: more than 0% and less than 5.0%,

Sn：0～10.0％、

Zn：0～10.0％、

VC：0.5～5.0％、

Fe and/or Fe alloy: 2.0-40.0%,

Lubricating material: 5.0 to 30.0%, and

metal oxide and/or metal nitride: 1.5-30.0%, the remainder being made up of impurities.

2. The sintered friction material of claim 1,

the lubricating material comprises one or more selected from the group consisting of:

graphite: 5.0 to 15.0 percent,

Hexagonal boron nitride: less than 3.0 percent,

Molybdenum disulfide: less than 3.0 percent,

Mica: 3.0% or less, and

one or more selected from tungsten disulfide, iron sulfide, chromium sulfide, copper sulfide and matte: 10.0% or less.

3. The sintered friction material of claim 1 or 2,

the metal oxide and/or metal nitride includes one or more selected from the group consisting of magnesium oxide, zircon sand, silicon dioxide, zirconium oxide, mullite, and silicon nitride.

4. A sintered friction material as set forth in any one of claims 1 to 3,

the Fe alloy comprises more than one selected from ferrochrome, ferrotungsten, ferromolybdenum and stainless steel.

Technical Field

The present invention relates to a sintered friction material, and particularly to a sintered friction material for railways.

Background

Sintered friction materials formed by sintering metal powder particles and the like are used for brake linings and disc brake pads for railway vehicles. For these sintered friction materials, excellent friction characteristics and excellent wear resistance are required.

For example, patent documents 1 and 2 disclose sintered friction materials containing Cu, Sn, or Zn, graphite, a lubricant, and an abrasive. Patent documents 3 and 4 disclose techniques for obtaining a high friction coefficient by scratching the disk surface by containing a thermally extremely stable carbide of groups 4a, 5a, and 6a as hard particles. Patent document 5 discloses a technique for producing a sintered friction material having excellent fading resistance by finely dispersing WC to improve the high-temperature strength of a Cu base material.

Disclosure of Invention

Problems to be solved by the invention

High-speed rail vehicles such as Japan New mainline, Germany ICE (Intercity-Express), French TGV (Traina Grande vitesse) and the like have a low speed range of 0 to 70 km/h, a medium speed range of more than 70 and 170 km/h, a high speed range of more than 170 and 280 km/h, and an ultra high speed range of more than 280 km/h. Therefore, the sintered friction material for railways is required to exhibit excellent friction characteristics and wear resistance not only in the low-speed range to the medium-speed range but also in the high-speed range and the ultrahigh-speed range.

In a brake friction material for a railway, friction characteristics and wear resistance are a so-called trade-off relationship. That is, when the friction coefficient is to be increased in order to improve the friction characteristics, the amount of wear of the friction material during braking increases, the wear resistance deteriorates, and the life of the friction material shortens. As a result, the frequency of replacement of the friction material increases, and thus the economical efficiency is deteriorated.

On the other hand, when it is intended to improve the wear resistance, the friction coefficient is reduced, which is not preferable from the viewpoint of safety. Therefore, at present, a sintered friction material for railways, which has both excellent friction characteristics and wear resistance, has not yet been developed.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a sintered friction material for railways, which has excellent overall characteristics of both friction characteristics and wear resistance in a low speed range, a medium speed range, a high speed range, and an ultra high speed range of more than 280 km/hour.

Means for solving the problems

The present invention has been made to solve the above problems, and the gist of the present invention is the following sintered friction material.

(1) A sintered friction material obtained by pressure sintering at 800 ℃ or higher a mixed powder containing, in mass%:

cu and/or Cu alloy: 40.0-80.0%,

Ni: more than 0% and less than 5.0%,

Sn：0～10.0％、

Zn：0～10.0％、

VC：0.5～5.0％、

Fe and/or Fe alloy: 2.0-40.0%,

Lubricating material: 5.0 to 30.0%, and

metal oxide and/or metal nitride: 1.5-30.0%, the remainder being made up of impurities.

(2) The sintered friction material according to the above (1), wherein,

the lubricating material contains one or more selected from the following:

graphite: 5.0 to 15.0 percent,

Hexagonal boron nitride: less than 3.0 percent,

Molybdenum disulfide: less than 3.0 percent,

Mica: 3.0% or less, and

one or more selected from tungsten disulfide, iron sulfide, chromium sulfide, copper sulfide and matte: 10.0% or less.

(3) The sintered friction material according to the above (1) or (2), wherein,

the metal oxide and/or metal nitride contains one or more selected from the group consisting of magnesium oxide, zircon sand, silicon dioxide, zirconium oxide, mullite, and silicon nitride.

(4) The sintered friction material according to any one of the above (1) to (3),

the Fe alloy comprises more than one selected from ferrochrome, ferrotungsten, ferromolybdenum and stainless steel.

Effects of the invention

According to the present invention, a sintered friction material for railways, which has both excellent friction characteristics and wear resistance in a low speed range, a medium speed range, a high speed range, and an ultra high speed range of more than 280 km/hr, can be obtained.

Drawings

Fig. 1 is a diagram for explaining an outline of a bench tester used in a braking test.

Detailed Description

The present inventors investigated and studied the friction characteristics and wear resistance in a low speed range, a medium speed range, a high speed range, and an ultra high speed range of more than 280 km/hour. Further, since the speed range which is particularly important in practical use is the medium-high speed range to the ultra-high speed range, the frictional characteristics and the wear resistance at 160 to 365 km/hr were comprehensively evaluated.

As a result, it was found that a sintered friction material obtained by sintering a mixed powder containing a Cu-based base component and an appropriate amount of vanadium carbide (hereinafter referred to as VC) by a known pressure sintering method has both excellent friction characteristics and wear resistance in the above speed range.

The sintered friction material of the present invention is a sintered material. The structure of the sintered material (such as the thickness of the sintering neck, the bonding state of the powder particles, and the dispersion state of the pores in the sintered material) is determined by the sintering temperature at the time of pressure sintering. These structures are extremely difficult to specify by numerical limitations and the like under the current measurement techniques and analysis techniques. Therefore, the sintered friction material of the present invention includes the sintering temperature at the time of pressure sintering as described above in the specific matters of the invention.

The sintered friction material of the present invention will be described in detail below.

1. Chemical composition

As described above, the sintered friction material of the present invention is used for a brake lining or a disc brake pad for railway vehicles. The mixed powder serving as a raw material of the sintered friction material contains the following composition (base and dispersant). The particle diameter of each particle of the mixed powder is not particularly limited, and is, for example, 1 to 1000 μm. Hereinafter, "%" with respect to the composition of the mixed powder means mass%.

1-1. base (substrate)

Cu and/or Cu alloy: 40.0 to 80.0 percent

Copper (Cu) functions as a base (base material) of the sintered friction material. Cu has a high thermal conductivity. Therefore, it is possible to suppress an increase in the interface temperature between the sintered friction material and the braking target (brake disc or the like) during braking (during friction), and to suppress the occurrence of excessive seizure. Therefore, the wear resistance of the sintered friction material is improved.

When the total content of Cu and/or Cu alloy in the mixed powder is less than 40.0%, the above-described effects cannot be obtained. On the other hand, if the above-mentioned total content exceeds 80.0%, the friction coefficient excessively increases. In this case, friction due to adhesion to the sliding surface of the braking object (for example, a brake disc) excessively occurs, and the wear resistance of the sintered friction material is reduced.

Therefore, the total content of Cu and/or Cu alloy is 40.0-80.0%. The total content is preferably 50.0% or more, more preferably 55.0% or more, and still more preferably 60.0% or more. Further, it is preferably 75.0% or less, more preferably 70.0% or less, and further preferably 67.0% or less.

Ni: more than 0% and less than 5.0%

Nickel (Ni) is dissolved in Cu of the base material, and has an effect of increasing the melting point of the base material and increasing the strength at high temperature, and therefore may be contained as needed. However, if the Ni content is 5.0% or more, the sinterability may be reduced. Therefore, the Ni content is set to less than 5.0%. The Ni content is preferably 3.0% or less. In order to obtain the above-described effects, the Ni content is preferably 0.5% or more.

Sn：0～10.0％

Since Sn (tin) is a metal having a lower melting point than Cu, a molten phase appears in the heating step of sintering, and the powders attract each other due to surface tension. As a result, the density of the sintered body is increased and the bending strength is also improved. Therefore, it may be contained as necessary. However, when the Sn content is excessive, the heat resistance is deteriorated and the deterioration is liable to occur. Therefore, the Sn content is 10.0% or less. The Sn content is preferably 5.0% or less, more preferably 3.0% or less. In the case where the above-described effects are to be obtained, the Sn content is preferably 0.3% or more, and more preferably 0.5% or more.

Zn：0～10.0％

Since Zn (zinc) is a metal having a melting point lower than that of Cu, a molten phase appears in the heating step of sintering, and the powders attract each other by surface tension. As a result, the density of the sintered body is increased and the bending strength is also improved. Therefore, it may be contained as necessary. However, when the Zn content is excessive, the heat resistance is deteriorated and deterioration is likely to occur. Therefore, the Zn content is 10.0% or less. The Zn content is preferably 5.0% or less, more preferably 3.0% or less. In the case where the above-described effects are to be obtained, the Zn content is preferably 0.3% or more, and more preferably 0.5% or more.

When Sn and Zn are contained in combination, the total content is preferably less than 5.0%, and more preferably 4.0% or less.

1-2 dispersing agent

VC：0.5～5.0％

Vanadium Carbides (VC) are hard particles, contained in the matrix in the form of particles. The improvement in properties by the inclusion of VC has both the effect of improving abrasion resistance and the effect of improving friction coefficient. This is because VC has an effect of removing an oxide film formed on a sliding surface of a braking target (a brake disc or the like) by scraping the sliding surface as hard particles, thereby stably generating adhesion, and also has an effect of reducing the amount of wear of a friction material by functioning as a lubricant.

According to such a special function of VC, the following two effects can be obtained. That is, (a) when VC is added to a friction material having a high friction coefficient but relatively poor wear resistance characteristics, the effect of significantly improving the wear resistance characteristics can be obtained. In addition, (b) when VC is added to a friction material having a relatively low friction coefficient although excellent in wear resistance, the effect of increasing the friction coefficient can be obtained. Therefore, by the addition of VC, the balance of characteristics of the friction material can be improved. As a result, a friction material having both friction characteristics and wear resistance, which are currently trade-offs, can be obtained.

However, if the content of VC is too high, the sinterability of the sintered friction material is lowered, and the wear resistance is lowered. Therefore, the VC content is set to 0.5 to 5.0%. The VC content is preferably 0.6% or more, more preferably 1.0% or more. The VC content is preferably 3.0% or less, and more preferably 2.5% or less.

Fe and/or Fe alloy: 2.0 to 40.0 percent

Iron (Fe) and Fe alloys are contained in the matrix in the form of particles or aggregates, and the strength of the matrix is increased to improve the wear resistance of the sintered friction material. Further, the reaction with Fe in the disk generates the so-called homoalloy (と も "" ね) effect of the adhesion friction, thereby increasing the friction coefficient. When the total content of Fe and/or Fe alloy in the mixed powder is less than 2.0%, the above-described effects cannot be obtained. On the other hand, if the total content exceeds 40.0%, not only excessive adhesion is likely to occur, but also sinterability of the sintered friction material is lowered, and wear resistance is rather lowered.

Therefore, the total content of Fe and/or Fe alloy is set to 2.0-40.0%. The total content is preferably 5.0% or more, more preferably 10.0% or more, and further preferably 12.0% or more. Further, it is preferably 35.0% or less, more preferably 30.0% or less, and further preferably 25.0% or less.

If the Fe content is too high, excessive adhesion tends to occur, and the wear resistance of the sintered friction material is rather lowered. Therefore, the content of the Fe monomer is preferably 20.0% or less, more preferably 15.0%, and further preferably 12.0% or less.

Further, examples of the Fe alloy include: the chromium iron (FeCr), the ferrotungsten (FeW), the ferromolybdenum (FeMo), and the stainless steel may contain one or more selected from these. The total content of the Fe alloy is preferably 20.0% or less, more preferably 18.0% or less, and further preferably 16.0% or less.

In this specification, the ferrochrome includes one or more of high carbon ferrochrome (FCrH 0-FCrH 5), medium carbon ferrochrome (FCrM3, FCrM4) and low carbon ferrochrome (FCrL 1-FCrL 4) prescribed in JIS G2303 (1998).

Further, ferrotungsten is Ferrotungsten (FW) having a chemical composition defined in JIS G2306 (1998). The ferromolybdenum includes at least one of high-carbon ferromolybdenum (FMoH) and low-carbon ferromolybdenum (FMoL) defined in JIS G2307 (1998).

In the present specification, the stainless steel refers to an alloy steel containing 50 mass% or more of Fe and 10.5 mass% or more of chromium, and more preferably refers to a stainless steel defined in JIS G4304 (2012). For example, martensitic stainless steel represented by SUS403 and SUS420 specified in the JIS standard, ferritic stainless steel represented by SUS430, austenitic stainless steel represented by SUS304, SUS316, and SUS316L, austenitic/ferritic stainless steel represented by SUS329J1, and precipitation hardening stainless steel represented by SUS630 may be used.

Lubricating material: 5.0 to 30.0 percent

The sintered friction material of the present invention contains a lubricating material. If the content of the lubricant is less than 5.0%, the stability of the friction coefficient may be insufficient, while if it exceeds 30.0%, the sinterability may be deteriorated, and not only a sufficient sintered body strength may not be obtained, but also the wear resistance may be deteriorated. Therefore, the content of the lubricant is 5.0 to 30.0%.

The lubricant preferably contains at least one member selected from the group consisting of graphite, hexagonal boron nitride, molybdenum disulfide, mica, tungsten disulfide, iron sulfide, chromium sulfide, copper sulfide, and matte. As the lubricant, graphite is particularly preferably contained in the range shown below. The reason for this will be explained.

Graphite: 5.0 to 15.0 percent

The graphite referred to in this specification includes natural graphite and artificial graphite. In the sintered friction material after pressure sintering, graphite is contained in the form of particles in a matrix. Graphite functions as a lubricating material, stabilizes the friction coefficient, and reduces the amount of wear of the sintered friction material. When the graphite content is less than 5.0%, the above-described effects may not be obtained. On the other hand, if the graphite content exceeds 15.0%, the mixed powder cannot be sufficiently sintered at the time of pressure sintering, and as a result, there is a concern that the wear resistance of the sintered friction material may be reduced. Therefore, the graphite content is preferably 5.0 to 15.0%. The graphite content is preferably 8.0% or more, and more preferably 9.0% or more. The graphite content is preferably 13.0% or less, and more preferably 12.0% or less.

The lubricant may contain one or more selected from the following (a) to (d).

(a) Hexagonal boron nitride: 3.0% or less

(b) Molybdenum disulfide: 3.0% or less

(c) Mica: 3.0% or less

(d) One or more selected from tungsten disulfide, iron sulfide, chromium sulfide, copper sulfide and matte: 10.0% or less

Selected from hexagonal boron nitride (h-BN), molybdenum disulfide (MoS)₂) Mica (mica), and tungsten disulfide (WS)₂) Iron sulfide (FeS), chromium sulfide (CrS), copper sulfide (Cu)₂S) and/or matte function as a lubricant. These lubricating materials, like graphite, stabilize the friction coefficient of the sintered friction material and can obtain excellent friction characteristics.

However, if the content of each of these lubricating materials is excessive, the sinterability of the sintered friction material is lowered, and the wear resistance is lowered. Accordingly, the content of hexagonal boron nitride is 3.0% or less, the content of molybdenum disulfide is 3.0% or less, the content of mica is 3.0% or less, and the total content of one or more selected from tungsten disulfide, iron sulfide, chromium sulfide, copper sulfide, and matte is 10.0% or less.

Matte is described in JIS H0500 (1998) under the nomenclature 5400 for a copper rolled product, and is mainly composed of iron sulfide and copper sulfide. Iron sulfide and copper sulfide each function independently as a lubricant. Alternatively, iron sulfide and copper sulfide may be used as a mixture. The above-mentioned matte can be used in the form of a mixture of iron sulfide and copper sulfide, and is inexpensive, and therefore is advantageous from the viewpoint of economy.

Metal oxide and/or metal nitride: 1.5 to 30.0 percent

The metal oxide and/or the metal nitride each function as hard particles. In the sintered friction material after pressure sintering, they are contained in the form of particles in the matrix. The metal oxide and/or the metal nitride are each scraped off the sliding surface of the braking object (brake disc or the like) to remove the oxide film formed on the sliding surface, thereby stably generating adhesion. This can suppress a decrease in the friction coefficient of the sintered friction material with respect to the braking target (brake disc, etc.), and can obtain excellent friction characteristics.

When the total content of the metal oxide and/or the metal nitride is less than 1.5%, excellent friction characteristics cannot be obtained. On the other hand, if their total content exceeds 30.0%, the sinterability of the sintered friction material is reduced. In this case, the wear resistance of the sintered friction material is reduced. Therefore, the total content of the metal oxide and/or the metal nitride is set to 1.5 to 30.0%. The total content is preferably 2.0% or more, more preferably 4.0% or more. The total content is preferably 25.0% or less, more preferably 20.0% or less, and still more preferably 15.0% or less.

Examples of the metal oxide and/or the metal nitride include: magnesium oxide (MgO) and zircon sand (ZrSiO)₄) Silicon dioxide (SiO)₂) Zirconium oxide (ZrO)₂) Mullite (3 Al)₂O₃·2SiO₂～2Al₂O₃·SiO₂) And silicon nitride (Si)₃N₄) May contain one or more selected from them.

The remainder of the mixed powder for sintering the friction material is impurities. Here, the impurities are substances mixed from raw materials, production environments, and the like in the industrial production of the mixed powder, and are substances that are allowable within a range that does not adversely affect the sintered friction material of the present invention.

2. Sintered friction material

The sintered friction material of the present invention is obtained by pressure sintering the above mixed powder at 800 ℃ or higher. The sintered friction material of the present invention has both excellent friction characteristics and wear resistance by containing VC in particular in a matrix mainly composed of Cu.

3. Manufacturing method

An example of the method for producing the sintered friction material of the present invention will be described. One example of the method for producing a sintered friction material according to the present invention includes a mixed powder production step, a molding step, and a pressure sintering step. The manufacturing method may further include an embossing process and/or a cutting process. Hereinafter, each step will be explained.

3-1. Mixed powder production Process

The above-mentioned base material and the powder for the dispersant were prepared. The prepared powder particles were mixed (mixing) using a known mixer to produce a mixed powder. Known mixers are for example ball mills or V-mixers.

3-2. Forming Process

The produced mixed powder was molded into a predetermined shape to produce a green compact. In the molding of the mixed powder, a known molding method can be applied. The powder compacts are produced, for example, by a press molding method. Specifically, a mold (die) for molding a given shape is prepared. And filling the mixed powder into a mold. The powder or granule filled in the mold is pressurized by a press at a known pressure to be molded into a green compact. The pressure of the press is, for example, 196N/mm²The above. The shaping can be carried out in the atmosphere.

3-3, pressure sintering process

The sintered friction material is produced by applying a known pressure sintering method to the produced green compact. For example, a green compact is disposed on a graphite plate in a pressure sintering apparatus. Then, a graphite plate with a compressed powder is stacked and placed in a frame of a frame body shape having an inner peripheral surface on which a high-frequency heating coil is placed. Then, the pressure is applied to the uppermost graphite sheet to pressurize the green compact, and sintering is performed at a given sintering temperature in a sintering gas atmosphere.

The pressure sintering may be performed under known conditions. The sintering temperature during pressure sintering is set to 800 ℃ or higher. However, the melting point of copper is 1083 ℃. Therefore, the sintering temperature at the time of pressure sintering needs to be set to be lower than 1083 ℃. The preferable sintering temperature is 800-1000 ℃. The pressure applied to the green compact during pressure sintering is, for example, 0.2 to 2.0N/mm². The holding time at the sintering temperature in the pressure sintering is, for example, 60 to 120 minutes. The atmosphere at the time of pressure sintering is, for example, AX gas (ammonia decomposition gas, N)₂∶H₂1: 3), AX gas and N₂Mixed gas of gases (5-20% of H)₂Gas, N₂Mixed gas of gases), Ar gas, or the like.

The sintered friction material is produced by forming a sintering neck at the contact portion of the powder particles in the green compact by the pressure sintering.

3-4. embossing process

The imprinting step may be performed after the pressure sintering step. In the imprinting step, the sintered friction material after the pressure sintering step is pressurized under cold conditions to adjust the shape of the sintered friction material.

3-5. cutting procedure

The cutting step may be performed after the pressure sintering step or after the imprinting step. In the cutting step, the sintered friction material is cut into a desired shape.

The sintered friction material of the present invention can be produced by the above-described production steps. In the case where the sintered friction material is a brake lining, one or more sintered friction materials are fixed to the mounting plate member and mounted on the railway vehicle.

The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples.