[0001]The present invention relates to a sintered friction material, particularly to railway sintered friction material.
[0002]The brake linings and disc brake pads for railway vehicles, sintered friction material formed by sintering a metal powder or granular material or the like is used. In these sintered friction material, together with the excellent frictional properties, it is required to have excellent wear resistance.
[0003]
　For example, Patent Documents 1 and 2, and Cu, and Sn, or Zn, and graphite, and lubricant, sintered friction material is disclosed containing a polishing material. Patent Documents 3 and 4, thermally very stable 4a, 5a, and 6a of group carbides contained as hard particles, a technique for obtaining a scratch high coefficient of friction disc surface is disclosed. Further, Patent Document 5, increase the high temperature strength of the Cu base material was finely dispersed WC, a technique for producing a sintered friction material having excellent fade resistance is disclosed.
CITATION
Patent Document
[0004]
Patent Document 1: JP 60-106932 Patent Publication
Patent Document 2: JP 63-109131 Patent Publication
Patent Document 3: JP-A 05-179232 JP
Patent Document 4: JP-A 09-222143 JP
Patent Document 5: JP 2007-107067 JP
Summary of the Invention
Problems that the Invention is to Solve
[0005]
　Japan's Shinkansen, the German ICE (Intercity-Express), the traveling speed of the high-speed rail vehicle, such as the French TGV (Train a Grande Vitesse) is, 0 ~ 70km / low-speed range of the time, 70 ultra ~ 170km / medium speed of time pass, 170 ultra ~ 280km / high speed range of time, reach up to ultra-high-speed range of 280km / h than. Therefore, the sintered friction material for railroad, not only the low speed range to medium speed range, the high speed range, exhibits excellent friction characteristics and wear resistance even at ultra high speed region is determined.
[0006]
　The brake friction material for railroad, the friction characteristics and wear resistance, in a so-called trade-off relationship. That is, if an attempt improve the coefficient of friction in order to improve the friction characteristics, wear amount of the friction material during braking is increased, the life of the friction material is reduced abrasion resistance is deteriorated. As a result, the frequency of replacement of the friction material increases, impairing the economy.
[0007]
　On the other hand, if an attempt improve the wear resistance, the friction coefficient is lowered, which is undesirable from the viewpoint of safety. Therefore, railway sintered friction material having both an excellent friction characteristics and wear resistance, at present, not been developed yet.
[0008]
　The present invention solves the above problems, the low-speed range, medium speed range, the high-speed range and 280 km / h ultra high speed region of the greater friction characteristics and combine the wear resistance, overall characteristics excellent for a railway and to provide a sintered friction material.
Means for Solving the Problems
[0009]
　The present invention has been made to solve the above problems, it is summarized as sintered friction material below.
[0010]
　(1) in
　mass%, Cu and / or Cu alloy: 40.0 ~
　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: from 2.0 to 40.0%,
　lubricant: 5.0 to 30.0%, and,
　metal oxides and / or metal nitride: 1.5 to 30.0%,
　containing the balance being a powder mixture consisting of impurities, is formed by pressure sintering at 800 ° C. or higher, sintered friction material.
[0011]
　(2) the lubricant is
　graphite: 5.0 to 15.0%,
　hexagonal boron nitride: 3.0% or less,
　molybdenum disulfide: 3.0% or less,
　mica: 3.0% or less, and,
　tungsten disulfide, iron sulfide, chromium sulfide, at least one species selected from copper sulfide and copper matte: 10.0% or less,
　including one or more selected from,
　sintered friction material according to (1) .
[0012]
　(3) the metal oxide and / or metal nitrides,
　magnesia, zircon sand, silica, zirconia, at least one selected from mullite and silicon nitride,
　baked according to the above (1) or (2) sintered friction material.
[0013]
　(4) the Fe alloy,
　ferrochrome, ferro tungsten, including one or more selected from the ferromolybdenum and stainless steel,
　sintered friction material according to any one of (1) to (3).
The invention's effect
[0014]
　According to the present invention, the low speed range, medium speed range, the high-speed range and 280 km / h greater than ultra-high-speed range, combine and excellent friction characteristics and wear resistance, sintered friction material for railroad is obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015]
[1] Figure 1 is a diagram for explaining the outline of the bench test machine used in the brake test.
DESCRIPTION OF THE INVENTION
[0016]
　The present inventors have low speed region, middle speed range, not only the high-speed range, were investigated and discussed friction properties and wear resistance of ultra high-speed range of 280 km / h greater. Then, practically, since particularly important speed range is middle or high speed range ~ hypervelocity range, the frictional properties and wear resistance in 160 ~ 365km / hr, were comprehensive evaluation.
[0017]
　As a result, a matrix component as Cu mainly suitable amount of vanadium carbide (hereinafter VC hereinafter) sintered friction material formed by sintering a powder mixture containing a known pressure sintering method, the It found that combine excellent friction characteristics and wear resistance in the speed range.
[0018]
　Incidentally, the sintered friction material according to the present invention is a sintered material. Firing Yuizai is by sintering temperature during sintering under pressure, the structure of the sintered material (neck thickness, the bonding state of the powder particles to each other, the dispersion state of sintered material inside the pores, etc.) is determined . These structures, in the measurement techniques and analysis techniques of the present time, it is extremely difficult to identify the numerical limitation like. Therefore, the sintered friction material of the present invention, as described above, including the sintering temperature during sintering under pressure to the subject matter.
[0019]
　It will be described in detail below sintered friction material according to the present invention.
[0020]
　1. Chemical composition
　sintered friction material of the present invention, as described above, are utilized in the brake lining or disk brake pads for railway vehicles. Mixed powder as a raw material for sintered friction material contains the following composition (the matrix and the dispersing agent). The particle diameter of each particle of the mixed powder is not particularly limited, but is 1 ~ 1000 .mu.m as an example. Hereinafter, "%" relating to the composition of the mixed powder means mass%.
[0021]
　1-1. Matrix
　(substrate) Cu and / or Cu alloy: from 40.0 to 80.0%
　copper (Cu) serves as the matrix of the sintered friction material (base material). Cu has a high thermal conductivity. Therefore, when the brake can suppress an increase in the interface temperature between the braked in (Friction at) (brake disk) and sintered friction material inhibits excessive Seizure. Therefore, the wear resistance of the sintered friction material increases.
[0022]
　The total content of Cu and / or Cu alloy mixed powder is less than 40.0%, not the effect. On the other hand, if the total content of the exceeding 80.0%, the friction coefficient is excessively large. In this case, friction due to adhesion with respect to the sliding surface of the brake target (e.g. a brake disk) is excessively generated, the wear resistance of the sintered friction material is lowered.
[0023]
　Accordingly, the total content of Cu and / or Cu alloy, and 40.0 to 80.0%. The total content is preferably at 50.0% or more, more preferably 55.0% or more, even more preferably 60.0% or more. Also, preferably not more than 75.0%, more preferably not more than 70.0, more preferably not more than 67.0%.
[0024]
　Ni: 0% or more 5.0% less than
　nickel (Ni) is dissolved in the Cu base material, increase the melting point of the base material, since it has the effect of increasing the strength at high temperatures, it is contained if necessary it may be. However, when the Ni content is 5.0% or more, the sintering property is deteriorated. Therefore, Ni content is less than 5.0%. Ni content is preferably 3.0% or less. For obtaining the above effect, Ni content is preferably 0.5% or more.
[0025]
　Sn: 0 ~ 10.0%
　Sn, since melting point than Cu is lower metallic powder together by the appearance of melt phase in a heating step sintering attract by surface tension. As a result, the density of the sintered body is increased, also increases flexural strength. Therefore, it may be contained if necessary. However, when the Sn content is excessive, it degrades the heat resistance, easily fade occurs. Therefore, Sn content is at most 10.0%. Preferably the Sn content is 5.0% or less, and more preferably 3.0% or less. For obtaining the above effects is preferably Sn content is 0.3% or more, and more preferably 0.5% or more.
[0026]
　Zn: 0 ~ 10.0%
　Zn, since the melting point than Cu is lower metallic powder together by the appearance of melt phase in a heating step sintering attract by surface tension. As a result, the density of the sintered body is increased, also increases flexural strength. Therefore, it may be contained if necessary. However, if the Zn content is excessive, it degrades the heat resistance, easily fade occurs. Therefore, Zn content is at most 10.0%. Preferably the Sn content is 5.0% or less, and more preferably 3.0% or less. For obtaining the above effects is preferably Zn content is 0.3% or more, and more preferably 0.5% or more.
[0027]
　Incidentally, in the case of containing the above-described Sn, and Zn in a combined manner, it is preferable that the total content is less than 5.0%, preferably not more than 4.0%.
[0028]
　1-2. Dispersant
　VC: 0.5 ~ 5.0%
　of vanadium carbide (VC) is a hard particles are contained as particles in the matrix. The characteristic improvement by VC-containing, has both the effect of improving the wear resistance, the effect of improving the friction coefficient. This can be achieved by scratching the VC sliding surface of the braked (brake disks, etc.) as are hard particles, removing the oxide film generated on the sliding surface, as having an effect of stably generated cohesion at the same time, by functioning as a lubricant, because also has the effect of reducing the amount of wear of the friction material.
[0029]
　The unique features of such a VC, so that the two effects below can be obtained. That has the (a) high coefficient of friction, the addition of VC to the friction material relative wear resistance is poor, the effect is obtained remarkably improved wear characteristics. Although excellent in (b) wear resistance and relatively friction coefficient adding VC low friction material, the effect is obtained to enhance the friction coefficient. Therefore, the addition of VC, it is possible to improve the property balance of the friction material. As a result, it is possible to obtain a friction material having both conventional friction properties were related tradeoff and wear resistance.
[0030]
　However, if the content of VC is too high, sinterability of the sintered friction material is reduced, the wear resistance is lowered. Accordingly, VC content is 0.5 to 5.0%. VC content is preferably 0.6% or more, and more preferably 1.0% or more. Also, VC content is preferably 3.0% or less, and more preferably 2.5% or less.
[0031]
　Fe and / or Fe alloy: from 2.0 to 40.0%
　iron (Fe) and Fe alloy are contained as particles or aggregates in the matrix, the wear resistance of the sintered friction material by increasing the strength of the matrix to improve. Further, reacts with Fe in the disc, and caused the adhesive frictional called effect Ne Moga, increasing the friction coefficient. The total content of Fe and / or Fe alloy mixed powder is less than 2.0%, not the effect. On the other hand, if the total content of the exceeding 40.0%, not only the excessive adhesion is likely to occur, and lowers the sintering of the sintered friction material, wear resistance rather lowers.
[0032]
　Accordingly, the total content of Fe and / or Fe alloy, and 2.0 to 40.0%. The total content is preferably at 5.0% or more, more preferably 10.0% or more, even more preferably 12.0% or more. Also, preferably not more than 35.0%, more preferably at most 30.0%, more preferably not more than 25.0%.
[0033]
　Incidentally, if the Fe content is too high, excessively the adhesion is likely to occur, wear resistance of the sintered friction material rather decreases. Accordingly, the content of Fe itself is preferably at most 20.0%, more preferably from 15.0%, more preferably not more than 12.0 percent.
[0034]
　As the Fe alloy, for example, ferrochromium (FeCr), ferrotungsten (FeW), ferromolybdenum (FeMo) and stainless steel and the like, may contain one or more kinds selected from these. The total content of Fe alloy preferably not more than 20.0%, more preferably from more than 18.0%, more preferably not more than 16.0%.
[0035]
　In this specification, ferrochrome, high-carbon ferrochromium defined in JIS G 2303 (1998) (FCrH0 ~ FCrH5), medium carbon ferrochrome (FCrM3, FCrM4), and one or more low carbon ferrochrome (FCrL1 ~ FCrL4) including.
[0036]
　Furthermore, ferrotungsten is meant ferro tungsten (FW) having a chemical composition as defined in JIS G 2306 (1998). Furthermore, ferromolybdenum comprises one or more high-carbon ferromolybdenum defined in JIS G 2307 (1998) (FMoH) and low carbon ferro-molybdenum (fmol).
[0037]
　Then, in the present specification, stainless steel refers to steel alloys containing a greater than 50 wt% Fe and 10.5 percent chromium, more preferably, as specified in JIS G 4304 (2012) Stainless means steel. For example, it may be martensitic stainless steel such as typically SUS 403, SUS420 as defined above JIS standard, or a ferritic stainless steel represented by SUS430. SUS304, SUS316, or austenitic stainless steels typified by SUS316L. It may be a austenitic ferritic stainless steel, which is represented by SUS329J1. It may be precipitation hardened stainless steels as typified by SUS630.
[0038]
　Lubricant: 5.0 to 30.0%
　sintered friction material of the present invention contains a lubricant. The content of lubricant is less than 5.0%, may be insufficient to stabilize the coefficient of friction, while when it exceeds 30.0%, the sintering property is deteriorated, sufficient sintered body strength obtained Never not only there is sometimes deteriorated wear resistance. Therefore, the content of lubricant is between 5.0 to 30.0%.
[0039]
　The lubricant, graphite, hexagonal boron nitride, molybdenum disulfide, mica, tungsten disulfide, iron sulfide, chromium sulfide, may include one or more selected from copper sulfide and copper matte preferred. In particular, it is preferred to include in the range shown graphite below as lubricant. The reason will be described.
[0040]
　Graphite: from 5.0 to 15.0%
　graphite referred to herein includes a natural graphite and artificial graphite. In sintered friction material after pressure sintering, graphite is contained in the matrix as particles. Graphite serves as a lubricant, the friction coefficient stabilizes and reduces the amount of wear of the sintered friction material. When the graphite content is less than 5.0%, the above effect is not obtained. On the other hand, when the graphite content exceeds 15.0%, the mixed powder during pressure sintering is not sufficiently sintered, so that the wear resistance of the sintered friction material may be lowered. Accordingly, the graphite content is preferably 5.0 to 15.0%. It is preferably graphite content is 8.0% or more, more preferably 9.0% or more. Further, it is preferable graphite content is less 13.0%, and more preferably not more than 12.0 percent.
[0041]
　Further, as the lubricant may contain one or more selected from the group consisting of the following (a) ~ (d).
　(A) hexagonal boron nitride: 3.0% or less
　(b) molybdenum disulfide: 3.0% or less
　(c) Mica: 3.0% or less
　(d) tungsten disulfide, iron sulfide, chromium sulfide, copper sulfide and one or more selected from copper matte: 10.0% or less
[0042]
　Hexagonal boron nitride (h-BN), molybdenum disulfide (MoS 2 ), mica and, tungsten disulfide (WS 2 ), iron sulfide (FeS), chromium sulfide (CrS), copper sulfide (Cu 2 S ) and both copper least one selected from the mat acts as a lubricant. These lubricant, like graphite, the friction coefficient of the sintered friction material stabilized, resulting excellent friction characteristics.
[0043]
　However, if the content of each of these lubricant is excessive, sinterability of the sintered friction material is reduced, 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 the mica is not more than 3.0%, tungsten disulfide, iron sulfide, chromium sulfide, the total content of one or more selected from copper sulfide and copper matte or less 10.0%.
[0044]
　Copper matte are those listed in copper products term number 5400 of JIS H 0500 (1998), mainly consisting of iron sulfide and copper sulfide. Iron sulfide, which acts as a lubricant, respectively copper sulfide alone. It may also be used in the mixture of iron sulfide and copper sulfide. Copper matte described above can be used in a mixture with copper sulfide and iron sulfide, and is advantageous in economical point of view because it is inexpensive.
[0045]
　Metal oxides and / or metal nitrides: 1.5 to 30.0%
　metal oxides and / or metal nitrides are both function as the hard particles. In sintered friction material after pressure sintering, it is contained in the matrix as particles. Any metal oxide and / or metal nitride, by scratching the sliding surface of the braked (brake disks, etc.), to remove an oxide film generated on the sliding surface, stable generating cohesion make. This can suppress the reduction of the friction coefficient for braking target sintered friction material (brake disks, etc.), obtained excellent friction characteristics.
[0046]
　In less than 1.5% total content of metal oxides and / or metal nitride, it can not be obtained excellent friction characteristics. On the other hand, if the total content of these exceeds 30.0%, sinterability of the sintered friction material is lowered. In this case, the wear resistance of the sintered friction material is lowered. Accordingly, the total content of metal oxides and / or metal nitride and 1.5 to 30.0%. Is preferably the total content of the above is 2.0% or more, more preferably 4.0% or more. The total content is preferably at most 25.0%, more preferably at most 20.0%, more preferably not more than 15.0%.
[0047]
　Further, as the metal oxide and / or metal nitride, for example, magnesia (MgO), zircon sand (ZrSiO 4 ), silica (SiO 2 ), zirconia (ZrO 2 ), mullite (3Al 2 O 3 · 2SiO 2 ~ 2Al 2 O 3 · SiO 2 ) and silicon nitride (Si 3 N 4 ) can be mentioned, it may contain one or more kinds selected from these.
[0048]
　The rest of the mixed powder for sintered friction material is an impurity. Here, the impurities, in preparing the mixed powder industrially, there is to be mixed, such as from a raw material or manufacturing environment, those allowed in a range that does not adversely affect the sintered friction material of the present invention means.
[0049]
　2. For sintered friction material
　sintered friction material according to the present invention is formed by pressure sintering a mixed powder described above at 800 ° C. or higher. Sintered friction material according to the present invention, the matrix composed mainly of Cu, in particular by containing VC, combine and excellent friction characteristics and wear resistance.
[0050]
　3. Manufacturing method
　of an example of a manufacturing method of the sintered friction material of the present invention will be described. An example of a method of manufacturing sintered friction material of the present invention comprises a mixed powder preparation step, a molding step, a pressure sintering process. The above manufacturing method may further comprise coining process and / or machining process. Hereinafter, the respective steps will be described.
[0051]
　3-1. Mixed powder production process
　described above for the matrix and preparing a granular material for the dispersing agent. The prepared granular material was mixed using a known mixer or mixing, to produce a mixed powder. Known mixer, for example, a ball mill or a V-type mixer.
[0052]
　3-2. Molding process
　the produced powder mixture is molded into a predetermined shape to produce a green compact. In the molding of the mixed powder may be applied to a known molding method. For example, by press molding, to produce the green compact. Specifically, to prepare a mold for molding a predetermined shape (die). Filling the mixed powder into a mold. Been granule filling the mold is pressurized in a well known pressure by the press, it is formed into a green compact. The pressure in the press machine, for example, 196 N / mm 2 at least. Molding may be carried out in the atmosphere.
[0053]
　3-3. Pressure sintering process
　was performed a known pressure sintering respect manufactured green compact to produce a sintered friction material. For example, placing the green compact on a graphite plate of the pressure in the sintering device. Thereafter, the inner peripheral surface to the high-frequency heating coil is arranged a box-shaped frame, and stores the graphite plate which compact is disposed in stacking. Then, while pressing the green compact by applying pressure to the top of the graphite plate and sintered at a predetermined sintering temperature in the sintering atmosphere.
[0054]
　Pressure sintering may be performed at conditions well known. Sintering temperature during sintering under pressure is directed to 800 ° C. or higher. However, the melting point of copper is 1083 ° C.. Therefore, the sintering temperature during sintering under pressure is required to be less than 1083 ° C.. Preferred sintering temperature is 800 ~ 1000 ° C.. Pressure applied to the green compact during sintering under pressure, for example, 0.2 ~ 2.0 N / mm 2 is. Holding time at the sintering temperature during sintering under pressure, for example, 60 to 120 minutes. Atmosphere during pressure sintering, for example, AX gas (ammonia decomposition gas, N 2 : H 2 = 1: 3), AX gas and N 2 gas mixture (5-20% of H the gas 2 and the gas, N 2 mixed gas of gas), or Ar gas.
[0055]
　By the pressure sintering, the neck is formed in the contact portion of the green compact of the granular material, sintered friction material described above is manufactured.
[0056]
　3-4. Coining process
　coining step may be carried out after the pressure sintering process. The coining step, the sintered friction material after the pressure sintering step pressurized with cold, adjust the shape of the sintered friction material.
[0057]
　3-5. Cutting step
　cutting process, it may be carried out after the pressure sintering process or after the coining process. The cutting step, by cutting the sintered friction material to a desired shape.
[0058]
　Sintered friction material according to the present invention is manufactured by the above manufacturing process. If the sintered friction material is a brake line training, one or more sintered friction material to the mounting plate member is fixed, it is attached to the railway vehicle.
[0059]
　The following examples illustrate the present invention more specifically, the present invention is not limited to these examples.
Example 1
[0060]
　A mixed powder having the composition shown in Table 1 were prepared. In the present embodiment, it is set to the composition design emphasis on friction properties.
[0061]
[Table 1]

[0062]
　Specifically, raw material, was charged into a V type mixer, mixes 20-100 minutes at a rotation speed 20 ~ 40 rpm, the mixed powder was produced. Then, using each of the mixed powders were produced green compact by molding. In molding, after filling the mixed powder into a mold made of hard metal, about 343N / mm 2 and pressurized with, were molded green compact.
[0063]
　The green compact was pressure-sintered by pressure sintering to form a sintered friction material. Specifically, placing the green compact on the graphite plate. Thereafter, the inner peripheral surface to the high-frequency heating coil is arranged a box-shaped frame, and stores the staked a graphite plate which compact is placed. It was heated for 60 minutes at 950 ° C., the green compact 1.0 N / mm 2 the green compact is sintered under pressure at, to produce a sintered friction material. Atmosphere in the frame in the pressure sintering, AX gas and N 2 gas mixture of gas (5% H 2 : gas, balance N 2 was mixed gas of the gas). With the above-described manufacturing process, to produce a sintered friction material.
[0064]
　[Brake Test]
　using a sintered friction material produced was carried out brake tests. The brake test was used bench tester shown in FIG. Bench testing machine includes a brake disc, a flywheel, a motor, and a caliper. Brake disk via a shaft, is coupled with the flywheel and motor. The material of the brake disc is SCM440 steel by quenching and tempering, it is obtained by the tensile strength 1000 MPa. Incidentally, the brake disc is about 1/2 the size of the brake disk used in the Shinkansen, diameter 400 mm, thickness was 20 mm.
[0065]
　Four sintered friction material (liner) attached to the mounting plate. Then, the mounting plate 4 of the sintered friction material is attached to two sets prepared was attached to the right and left of the inner surface of each caliper the mounting plate. Each sintered friction material is a rectangular parallelepiped, a width 38mm, length 55 mm, a height of 15 mm. Four sintered friction material, on a virtual circle of radius 170mm from the center of the brake disc, are arranged in a line shifted by 25 ° around the center axis of the brake disc.
[0066]
　[Friction coefficient measurements in the brake test]
　was then carried out brake tests. Specifically, with respect to the rotating brake disc, the sintered friction material which is attached to the left and right inner surfaces of the caliper, against the two sides of the brake disc at a constant pressure 2.24KN (braked), torque measured to determine the coefficient of friction. Speed (braking initial speed) of the disc brake when the start braking, 160,240,300,325,365Km / sometimes in each braking initial speed calculated coefficient of friction. Calculated friction coefficient by multiplying the three brake in each braking initial speed, the average of three friction coefficient was defined as the average friction coefficient in the braking initial speed. The higher the value of the average coefficient of friction, so that the friction properties excellent.
[0067]
　[Amount of wear of the brake Test
　before and after the brake test at each braking initial speed described above, obtains a mass difference of the sintered friction material, from the resulting mass difference, one side of the brake disc of a single brake test average abrasion loss of the sintered friction material per a (g / one side) was determined. Specifically, to measure the total mass before the test in a state of sintered friction material is attached to the mounting plate, three measured total mass after braking in the same state, the mass difference one set I was determined. Then, after total mass difference between the right and left two sets, divided by 3 brakes times, further divided by the second set number, was defined as the average amount of wear at the brake rate (g / one side-times) . As the value of the average wear amount is low, so that the wear resistance is excellent.
[0068]
　[Test Results]
　The test results of the mark D1 ~ D3 in Table 2. Further, 160 ~ 365km / for conducting a comprehensive evaluation of friction characteristics and wear resistance in time, Table 2, a value obtained by calculating an average value of respective measurement values when 160,240,300,325,365Km / the combined and shows.
[0069]
[Table 2]

[0070]
　Incidentally, the friction coefficient and wear amount of the sintered friction material is dependent largely on the components and production conditions, in a relative difference between the reference and made material, it is necessary to evaluate the effects of the present invention. In the evaluation of the friction characteristics, as compared with the comparative example as a reference, when the average coefficient of friction was increased 0.01 or more, it was to determine the improved effect is observed. Further, even if the increase in the average friction coefficient is small or reduced, it was decided to determine that the value is equal to 0.30 or more in all the braking speed, no practical problem.
[0071]
　Further, in the evaluation of wear resistance, as compared with the comparative example as a reference, the average wear amount was possible to determine that when you are reduced 1.0 g / or more one-sided-times, is observed improvement. Further, in the case since prone to relatively variation in the measurement results of the average wear amount, even if reduced even when the average wear amount increases, the amount of change is less than 1.0 g / one side-times, because it is within the range of error, it was decided to determine that no change.
[0072]
　Referring to Table 2, with respect to D1 of Comparative Example Average wear amount is 8.568 (g / one side-times), D2 and D3 were added VC are both large average wear amount of the friction material reduced, the wear resistance is greatly improved. The average coefficient of friction was slightly decreased by the addition of VC, and greatly exceeds 0.30 at all braking rate was determined that no practical problem. Thus, it was possible to impart excellent comprehensive property by VC added.
Example 2
[0073]
　Further investigated in order to systematically assess the impact of the content of the VC. A mixed powder having the composition shown in Table 3 were prepared. Also in this embodiment, it is a component designed with an emphasis on similar friction characteristics as in Example 1.
[0074]
[table 3]

[0075]
　Production conditions of the sintered friction material, evaluation methods and evaluation criteria for the friction characteristics and wear resistance are the same as in Example 1. Table 4 shows the test results of the mark E1 ~ E4.
[0076]
[Table 4]

[0077]
　Table 4 See, against E1 in Comparative Example Average wear amount is 3.750 (g / one side-times), E2 ~ E4 with added VC are all clear the average wear amount of the friction material It decreased, the wear resistance is improved. The average coefficient of friction but also those slightly reduced by the addition of VC, and greatly exceeds 0.30 at all braking rate was determined that no practical problem. Thus, it was possible to impart excellent comprehensive property by VC added.
Example 3
[0078]
　A mixed powder having the composition shown in Table 5 were prepared. In the present embodiment, it is a component designed with an emphasis on abrasion resistance.
[0079]
[table 5]

[0080]
　Production conditions of the sintered friction material, evaluation methods and evaluation criteria for the friction characteristics and wear resistance are the same as in Example 1. Table 6 shows the test results of the mark F1 ~ F4.
[0081]
[Table 6]

[0082]
　Referring to Table 6, F4 added with VC respect F3 of added F2, and Comparative Examples a VC against F1 of the comparative example, both the average coefficient of friction is increased, frictional properties were improved . On the other hand, change in the average wear amount is small, wear resistance was originally good did not change. Thus, it was possible to impart excellent comprehensive property by VC added.
Example 4
[0083]
　Further investigated in order to systematically assess the impact of the content of the VC. A mixed powder having the composition shown in Table 7 were prepared. Also in this embodiment, it is a component designed with an emphasis on abrasion resistance in the same manner as in Example 3.
[0084]
[Table 7]

[0085]
　Production conditions of the sintered friction material, evaluation methods and evaluation criteria for the friction characteristics and wear resistance are the same as in Example 1. Table 8 shows the test results of the marks G1 ~ G6.
[0086]
[Table 8]

[0087]
　Referring to Table 8, G2 ~ G6 addition of VC against G1 of the comparative examples are all increased by an average coefficient of friction, frictional properties were improved. On the other hand, the average wear amount of change is small, wear resistance originally average abrasion loss was as good as 2.880 (g / one side-times) did not change. Thus, it was possible to impart excellent comprehensive property by VC added.
Industrial Applicability
[0088]
　According to the present invention, the low speed range, medium speed range, the high-speed range and 280 km / h greater than ultra-high-speed range, combine and excellent friction characteristics and wear resistance, sintered friction material for railroad is obtained.

WE CLAIM

[Requested item 1]
　By
　mass%, Cu and / or Cu alloy: 40.0 ~
　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: from 2.0 to 40.0%,
　lubricant: 5.0 to 30.0%, and,
　metal oxides and / or metal nitrides: 1.5 to 30.0 percent,
　containing the balance being a powder mixture consisting of impurities, is formed by pressure sintering at 800 ° C. or higher, sintered friction material.
[Requested item 2]
　The lubricant is
　graphite: 5.0 to 15.0%,
　hexagonal boron nitride: 3.0% or less,
　molybdenum disulfide: 3.0% or less,
　mica: 3.0% or less, and,
　tungsten disulfide , iron sulfide, chromium sulfide, at least one species selected from copper sulfide and copper matte: 10.0% or less,
　including one or more selected from,
　sintered friction material according to claim 1.
[Requested item 3]
　It said metal oxide and / or metal nitrides,
　magnesia, zircon sand, silica, zirconia, contains at least one element selected from mullite and silicon nitride,
　claim 1 or sintered friction material according to claim 2.
[Requested item 4]
　The Fe alloy,
　ferrochrome, ferro tungsten, including one or more selected from the ferromolybdenum and stainless steel,
　sintered friction material according to any one of claims 1 to 3.