CN113565907B

CN113565907B - Brake pad for motor car, friction material for brake pad and preparation method of friction material

Info

Publication number: CN113565907B
Application number: CN202110837880.8A
Authority: CN
Inventors: 李松; 王剑; 马兵; 黄福然; 张笑凡; 马永靖; 杨洋; 亢磊
Original assignee: Beijing Pulan Rail Transit Technology Co ltd; CRRC Changchun Railway Vehicles Co Ltd
Current assignee: Beijing Pulan Rail Transit Technology Co ltd; CRRC Changchun Railway Vehicles Co Ltd
Priority date: 2021-07-23
Filing date: 2021-07-23
Publication date: 2022-12-09
Anticipated expiration: 2041-07-23
Also published as: CN113565907A

Abstract

The invention relates to the technical field of brake pads of high-speed trains, and discloses a friction material for brake pads, which is used for solving the problems that the brake pads can only be used at the speed of 350km/h or less, and the strength of the brake pads is reduced, the friction coefficient is attenuated and the like at higher speed. The friction material for the brake pad comprises the following raw materials in parts by weight: 52-66 parts of a matrix component, 4-7 parts of a friction component, 15-28 parts of a reinforcing component and 19-32 parts of a lubricating component; the matrix component comprises copper-clad iron powder, the friction component comprises tungsten carbide, and the reinforcing component comprises transition metal alloy powder; the lubricating component comprises any one or more of graphene and silicon carbide whiskers. The invention effectively improves the heat resistance and the matrix strength of the friction material, reduces the heat attenuation and reduces the self wear rate. The invention also provides a preparation method of the friction material and a brake pad for a bullet train.

Description

Brake pad for motor car, friction material for brake pad and preparation method of friction material

Technical Field

The invention relates to the technical field of brake pads of high-speed trains, in particular to a brake pad for a bullet train, a friction material for the brake pad and a preparation method of the friction material.

Background

In the prior art, most of brake pads used by railway train vehicles are powder metallurgy brake pads, such as copper-based powder metallurgy brake pads. With the emergence of ultra-high speed motor train units, the maximum speed per hour can reach 450 kilometers, the continuous speed per hour is 400 kilometers, and various performance requirements, particularly braking performance, put forward more strict requirements. The maximum test speed of the brake pad used at home and abroad is 380km/h at present, and the braking energy of the ultra-high speed motor train unit is 1.4 times that of the existing brake pad in terms of the braking energy. The brake pad disclosed by the invention patents in the past is limited by strength, friction performance and heat resistance performance, so that the brake pad can be only used at the speed of 350km/h or less, and the defects of strength reduction, friction coefficient attenuation and the like of the brake pad are caused at higher speed.

Disclosure of Invention

In order to solve the problems that in the prior art, the brake pad can only be used at the speed of 350km/h or less, and the strength of the brake pad is reduced and the friction coefficient is attenuated at higher speed, the invention provides the brake pad for the motor train, the friction material for the brake pad and the preparation method thereof, so that the brake pad can be applied to the ultra-high speed motor train unit with the speed of 350km/h or even 400 km/h.

In a first aspect, the friction material for the brake pad provided by the invention comprises the following raw material components in parts by weight: 52-66 parts of a matrix component, 4-7 parts of a friction component, 15-28 parts of a reinforcing component and 19-32 parts of a lubricating component; the matrix component comprises copper-clad iron powder, the friction component comprises tungsten carbide, and the reinforcing component comprises transition metal alloy powder; the lubricating component comprises any one or more of graphene and silicon carbide whiskers.

Compared with the prior art, the friction material for the brake pad provided by the invention comprises a base component, a friction component, a reinforcing component and a lubricating component. The matrix component is copper-clad iron powder, and the copper-clad iron powder has good lubricity, so that when the copper-clad iron powder is used for the friction material, the copper-clad iron powder is matched with other components, the segregation phenomenon cannot be generated, the matrix strength of the friction material is increased, and the service life of the friction material is prolonged. In addition, the outer layer of the iron powder is plated with a compact pure copper layer, so that a heat transfer channel of the friction material can be improved, the heat conductivity of the friction material is improved, and the heat conductivity and the temperature conductivity of the friction material are improved. Furthermore, in the sintering process during the preparation of the friction body, the copper-clad iron powder and other metal powder can be alloyed, so that the alloying degree of the metal powder can be improved, and the mechanical property of the friction material is further improved. The lubricating component selects graphene and silicon carbide whiskers, the melting point of the silicon carbide whiskers is slightly higher, about 1400 ℃, the melting point of the graphene is 3000 ℃, the requirement of a higher temperature range can be met, and the lubricating component can be used for lubricating and protecting a friction surface at a high temperature. In addition, the chemical properties of the graphene and the silicon carbide whisker are more stable than those of a common reinforcing material, so that the graphene and silicon carbide whisker can play a role in reinforcing when used for a friction material. The graphene and the silicon carbide whiskers are matched with other components, so that the heat resistance and the matrix strength of the friction material are effectively improved, the heat attenuation is reduced, and the self wear rate is reduced. The friction coefficient has enough stability under various working conditions such as high temperature, high pressure, high cold, high sand wind and moist, especially has excellent heat resistance, and can ensure that the friction material has enough mechanical strength and friction resistance when heated to 800-900 ℃ for a long time and heated to 650-750 ℃ for a long time.

In a second aspect, the present invention provides a method for preparing a friction material for brake pads, comprising:

weighing the raw material components according to the weight parts, and fully mixing to obtain a mixture;

adding a granulating agent into the mixture for granulation to obtain particles with the particle size of 1-3 mm;

carrying out die profiling on the particles to obtain a press blank;

and (3) carrying out pressure sintering on the pressing blank under the protection of a reducing atmosphere consisting of hydrogen and nitrogen, and then cooling to obtain the friction material for the brake pad.

The beneficial effects of the preparation method of the friction material for the brake pad provided by the invention are the same as those of the friction material for the brake pad in the technical scheme, and the detailed description is omitted here.

In a third aspect, the invention also provides a brake lining for a motor vehicle, comprising the friction material for a brake lining.

Compared with the prior art, the brake pad for the motor train unit improves the mechanical strength of the brake pad on the premise of providing enough stable friction coefficient, has no damage to the brake disc, can bear high temperature, thermal shock and the like caused by high braking load of the motor train unit at higher speed, and prolongs the service life of the brake pad and the brake disc.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.

At present, the brake pad for braking the high-speed train is mainly a copper-based powder metallurgy brake pad, which is because the copper-based brake pad has excellent friction performance, excellent braking effect and good heat-conducting performance. However, as the speed of a train increases, the braking load increases, and the heat energy and thermal shock generated during braking also increase greatly. The softening flow of the friction surface copper occurs at high extrusion pressures and high temperatures, resulting in large fluctuations in the coefficient of friction and significant heat decay during braking.

In order to solve the technical problems, embodiments of the present invention provide a friction material for brake pads, which solves the problems that the existing copper-based powder metallurgy brake pad has insufficient heat resistance, and is easy to cause unstable friction coefficient and heat fading at high temperature.

The embodiment of the invention provides a friction material for brake pads, which comprises the following raw material components: the material comprises the following raw materials in parts by weight: 52-66 parts of a matrix component, 4-7 parts of a friction component, 15-28 parts of a reinforcing component and 19-32 parts of a lubricating component; the matrix component comprises copper-clad iron powder, the friction component comprises tungsten carbide, and the reinforcing component comprises transition metal alloy powder; the lubricating component comprises any one or more of graphene and silicon carbide whiskers. By adopting the technical scheme, the copper-clad iron powder is used, and the copper-clad iron powder and the transition metal alloy powder contained in the reinforcing component can be alloyed in the high-temperature sintering process, so that the alloying degree between the metal powders is improved. And then adding lubricating components including graphene and silicon carbide whiskers. Due to the fact that the melting points of the graphene and the silicon carbide whisker are high, the graphene and the silicon carbide whisker can be used for lubricating and protecting a friction surface at high temperature, and the heat resistance of the friction material is greatly improved. In addition, the chemical properties of the graphene and the silicon carbide whisker are more stable than those of a common reinforcing material, so that the graphene and the silicon carbide whisker can play a role in reinforcing when used for a friction material. The components of the friction material are used cooperatively, so that the heat resistance and the matrix strength of the friction material are effectively improved, the heat decay is reduced, and the self wear rate is reduced.

Meanwhile, the matrix component also comprises transition metal powder; and/or the transition metal powder comprises one or more of superfine copper powder with the particle size of 1.0-3.0 microns and superfine iron powder with the particle size of 5-7 microns. The copper-clad iron powder is prepared from the matrix components, superfine copper powder and iron powder, wherein the matrix components comprise, by weight, 40-48 parts of the superfine copper powder, 8-12 parts of the superfine iron powder and the balance of the copper-clad iron powder. For example, the ultrafine copper powder may be 40 parts, 41 parts, 42 parts, 43 parts, 44 parts, 45 parts, 46 parts, 47 parts, 48 parts, etc., the ultrafine iron powder may be 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, etc., and the copper-clad iron powder may be 4 parts, 5 parts, 6 parts, etc., and is not particularly limited herein. The embodiment of the invention provides superfine copper powder and superfine iron powder which are matched with copper-clad iron powder for use. Because the copper-clad iron powder is formed by uniformly coating a layer of copper powder on the outer layer of the iron powder, when the copper-clad iron powder is mixed with superfine copper powder and/or superfine iron powder with a specific particle size range for use, the segregation phenomenon cannot be generated, and the matrix strength of the friction material is further increased.

The friction component further comprises alumina. Wherein, calculated by the weight portion of the friction component, the aluminum oxide accounts for 1 to 2 portions, and the rest is tungsten carbide. For example, the alumina may be 1 part by weight, 1.5 parts by weight, 2 parts by weight, etc., in which case the tungsten carbide may be 3 parts by weight, 4 parts by weight, 5 parts by weight, etc., and is not limited thereto. Here, it is to be noted that, when the mass ratio of tungsten carbide and alumina satisfies 4.

In the reinforced components, the transition metal alloy powder comprises any one or more of pre-alloyed copper-tin powder, high-carbon ferrochrome and high-carbon ferromanganese. Wherein, in the prealloyed copper-tin powder, the copper content is 89-91wt% and the tin content is 9-11wt%, and the grain diameter is 42-50 micrometers. Specifically, the copper content may be 89wt%, 90.2wt%, 91wt%, etc., and the tin content may be 9wt%, 9.8wt%, 11wt%, etc., without being particularly limited thereto. Here, it should be noted that it was confirmed through a lot of experiments that the friction material obtained was the most excellent in the friction property when the copper content was 90.2wt% and the tin content was 9.8 wt%.

And/or the high-carbon ferrochrome contains 68-73 wt% of chromium, 9-11wt% of carbon and the balance of iron, and the particle size of the high-carbon ferrochrome is 75-81 microns. Specifically, the high-carbon ferrochrome has a chromium content of 68wt%, 70.2wt%, 73wt%, etc., a carbon content of 9wt%, 10.3wt%, 11wt%, etc., and the balance being iron, and is not particularly limited herein. Here, it should be noted that when the chromium content of the high-carbon ferrochrome is 70.2wt%, the carbon content is 10.3wt%, and the balance is iron, the friction material prepared is the most excellent in friction performance.

And/or the high-carbon manganese iron powder contains 68-75 wt% of manganese, 9-11wt% of carbon and the balance of iron, and the particle size of the high-carbon manganese iron powder is 75-81 microns; specifically, the high-carbon manganese iron powder has a manganese content of 68wt%, 72.1wt%, 75wt%, etc., a carbon content of 9wt%, 9.8wt%, 11wt%, etc., and the balance being iron, and is not particularly limited herein. Here, it should be noted that when the high-carbon manganese iron powder contains 72.1wt% of manganese, 9.8wt% of carbon, and the balance of iron, the friction material obtained is the most excellent in friction performance.

The high-carbon ferrochrome and the high-carbon ferromanganese with the specific compositions are used as reinforcing components, and the high-carbon ferrochrome and the high-carbon ferromanganese are alloying agents with higher carbon content and act together with pre-alloyed copper-tin powder, so that the hardenability, ultimate strength, yield strength and strength of the friction material can be improved, and the wear resistance and hardness of the material are increased; the friction coefficient is improved, and the abrasion loss is reduced.

The reinforcing component may further include chromium powder. Wherein, the weight portion of the reinforcing component is 1 to 3 portions of the chromium powder, and the balance is the transition metal alloy powder. It is to be understood that the pre-alloyed copper tin powder, the high carbon chromium powder and the high carbon ferromanganese powder in the transition metal alloy powder may be mixed in any ratio, for example, 5 to 10 parts by weight of the pre-alloyed copper tin powder, 7 to 10 parts by weight of the high carbon ferrochrome powder and 2 to 5 parts by weight of the high carbon ferromanganese powder. By way of example, the chromium powder may be 1 part, 2 parts, 3 parts, etc., the pre-alloyed copper-tin powder may be 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, etc., the high-carbon ferrochrome may be 7 parts, 8 parts, 9 parts, 10 parts, etc., and the high-carbon ferromanganese powder may be 2 parts, 3 parts, 4 parts, 5 parts, etc., without being limited thereto. It should be noted here that, through a large number of experiments, it is determined that when the chromium powder is 2 parts, the pre-alloyed copper-tin powder is 8 parts, the high-carbon ferrochrome powder is 8 parts, and the high-carbon ferromanganese powder is 3 parts, the strength performance of the prepared friction material is the most excellent.

The lubricating component also comprises one or more of molybdenum disulfide and graphite. Wherein, calculated by the weight portion of the lubricating component, the molybdenum disulfide is 1 to 4 weight portions; 16-24 parts of graphite; the graphene is 1-2 parts by weight, and the silicon carbide whisker is 1-2 parts by weight. For example, the molybdenum disulfide may be 1 part, 2 parts, 3 parts, 4 parts, etc.; the graphite can be 16 parts, 18 parts, 20 parts, 22 parts, 24 parts and the like; the graphene may be 1 part, 2 parts, etc., and the silicon carbide whisker is 1 part, 2 parts, etc., and is not particularly limited herein. It should be noted here that, through a lot of experiments, it is determined that when the molybdenum disulfide is 3 parts; 18 parts of graphite; when the graphene accounts for 2 parts by weight and the silicon carbide whiskers account for 2 parts by weight, the prepared friction material has the most excellent heat resistance and strength.

The embodiment of the invention provides a preparation method of a friction material for brake pads, which is used for the friction material for the brake pads. The preparation method of the friction material for the brake pad provided by the embodiment of the invention can be used for directly preparing the friction material for the brake pad, so that the production process is simplified, and the production efficiency is improved. Specifically, the preparation method of the friction material for the brake pad comprises the following steps:

and S10, weighing the raw material components according to the weight parts, and fully mixing to obtain a mixture.

And S11, adding a granulating agent into the mixture for granulation to obtain particles with the particle size of 1-3 mm. The granulating agent may be selected to be a hydrogenated styrene-isoprene-butadiene copolymer. It is to be understood that the mixing step of step S10 and the granulating step of step S11 can be realized by a mixing granulator in the prior art. Or can be realized by a mixer and a granulating agent in the prior art respectively. The grain size of the obtained mixture may be 1mm, 1.5m, 2mm, 2.6mm, 3mm, etc., and is not particularly limited herein.

S12, carrying out die profiling on the particles to obtain a press blank; the molding press for molding the mold is a powder molding hydraulic press. The pressure of the die pressing is 15-20Mpa, and the time for die pressing is 10-20s. It is to be understood that the pressure at which the die pressing is performed may be 15Mpa, 16.2Mpa, 17.5Mpa, 18Mpa, 18.6Mpa, 19Mpa, 19.5Mpa, 20Mpa, etc., and the time at which the die pressing is performed is 10s, 14s, 16s, 18s, 20s, etc., without being particularly limited thereto.

And S13, carrying out pressure sintering on the pressing blank under the protection of a mixed gas of hydrogen and nitrogen, and then cooling to obtain the friction material for the brake pad. The protective atmosphere is selected to be a mixed gas of hydrogen and nitrogen, wherein in the mixed gas, the volume ratio of the hydrogen to the nitrogen can be 1: (5-7). In the high-temperature sintering process, in order to prevent the metal powder from being inevitably oxidized by oxygen, a small amount of hydrogen is used in the mixed gas, so that the oxidized powder can be subjected to a reduction reaction, and the influence of the oxidized powder on the performance of the friction material is avoided. The pressure sintering is carried out at the temperature of 1000-1100 ℃ for 1-2h and under the pressure of 4-6Mpa; the cooling is carried out for 4-6h. Specifically, the pressure sintering temperature may be selected from 1000 ℃, 1020 ℃, 1050 ℃, 1100 ℃ and the like for 1 hour, 1.2 hours, 1.5 hours, 2 hours and the like, and the pressure is 4Mpa,4.3Mpa, 5Mpa, 5.6Mpa, 6Mpa and the like, without being particularly limited.

Compared with the prior art, when the friction material for the brake pad is prepared by adopting the preparation method, the components of the material are uniformly distributed by mixing and granulating in a proper mode. And then pressing at a specified pressure and time, wherein the components are matched with each other in the pressing process and are not easy to segregate. And then the friction material has enough mechanical strength through compact blank pressing and pressure sintering. When the friction material is used for the brake pad, stable braking force can be provided all the time in the braking process. The strength requirements in temporary technical conditions of brake pads of motor train units (TJ/CL 307-2019) issued by the state iron group are met, namely the shear strength of a friction body (6 MPa) and the shear strength of an adhesive surface (7 MPa) are more than 3 times.

The embodiment of the invention also provides a brake pad for a bullet train, which comprises the friction material. When the friction material is used for the brake pad, because the components of the friction material are mutually matched, the heat resistance and the matrix strength of the friction material are effectively improved, the heat attenuation is reduced, the self wear rate is reduced, the friction coefficient has enough stability under various working conditions such as high temperature, high pressure, high cold, high wind sand and humidity, the heat resistance ensures that the friction material is heated to 800-900 ℃ for a long time and heated to 650-750 ℃ for a long time, the heat damage and abnormal wear such as hot spots, cracks and the like can not be generated on the brake disc, the working surface of the friction pair can not be bonded, and the peeling, scratching, welding and other destructive damages can not be formed on the working surface in the friction process. Therefore, the brake pad for the motor train unit is particularly suitable for being listed at a super high speed, improves the mechanical strength of the brake pad on the premise of providing a stable enough friction coefficient, has no damage to the brake disc, can bear high temperature, thermal shock and the like caused by high braking load of a motor train unit at a higher speed, and prolongs the service life of the brake pad and the brake disc.

The friction material for brake pads, the preparation method thereof and the brake pads for motor vehicles provided by the present invention are further described below with reference to the following examples, which are merely illustrative of the present invention and are not intended to be limiting. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without inventive step, are within the scope of the present invention. The test methods used in the following examples are all conventional methods unless otherwise specified; the raw materials used in the following embodiments are commercially available ones unless otherwise specified, and the physical properties of the raw materials may be selected as follows:

the purity of the superfine copper powder is more than or equal to 99.5wt%, and the particle size is 1.0-3.0 microns;

pre-alloyed copper-tin powder, wherein the copper content is 89-91wt% and the tin content is 9-11wt%, and the particle size is 42-50 microns;

the content of the superfine iron powder is more than or equal to 99wt% of Fe, and the particle size is 5-7 microns;

the grain size of the copper-clad iron powder is 42-50 microns;

high-carbon ferrochrome, wherein the chromium content is 68-73 wt%, the carbon content is 9-11wt%, and the balance is iron, and the particle size is 75-81 microns;

the content of the chromium powder is that Cr is more than or equal to 99wt%, and the grain diameter is 42-50 microns;

high-carbon manganese iron powder, wherein the manganese content is 68-75 wt%, the carbon content is 9-11wt%, and the balance is iron, and the particle size is 75-81 micrometers;

the content grain diameter of tungsten carbide is 75-81 microns;

the content of molybdenum disulfide is more than or equal to 98wt%, and the molybdenum disulfide is 42-50 microns;

the graphite content is more than or equal to 99wt%, and is 42-50 microns;

the content of alumina is more than or equal to 99wt%, and the alumina is 65-70 micrometers;

the content of the silicon carbide whisker is more than or equal to 99wt percent and is 65-70 microns.

The selection of the raw materials is only for illustration, and is not a limitation on the performance of the raw materials, and the raw materials meeting the performance requirements may be selected according to actual needs.

Example one

The friction material for the brake pad selected in the embodiment comprises the following components: 520g of copper-clad iron powder; 40g of tungsten carbide; the pre-alloyed copper tin powder is 47g; 62g of high-carbon ferrochrome; 41g of high-carbon manganese iron powder; 101g of graphene; the silicon carbide whisker was 89g. The volume ratio of hydrogen to nitrogen in the selected protective gas in this example is 1.

Example two

The friction material for the brake pad selected in the embodiment comprises the following components: 615g of copper-clad iron powder; 50g of tungsten carbide; 79g of prealloyed copper-tin powder; the content of the high-carbon ferrochrome is 83g; 60g of high-carbon manganese iron powder; 145g of graphene; the silicon carbide whisker was 111g. The volume ratio of hydrogen to nitrogen in the selected protective gas in this example was 1.

EXAMPLE III

The friction material for the brake pad selected in the embodiment comprises the following components: 660g of copper-clad iron powder; 70g of tungsten carbide; the pre-alloyed copper tin powder is 93g; 108g of high-carbon ferrochrome; 79g of high-carbon manganese iron powder; 163g of graphene; the silicon carbide whisker was 157g. The volume ratio of the selected protective gas to the selected nitrogen gas in the embodiment is 1.

Example four

The friction material for the brake pad selected in the embodiment comprises the following components: 127g of copper-clad iron powder; 411g of superfine copper powder with the particle size of 1.0-3.0 microns; 70g of tungsten carbide; the pre-alloyed copper tin powder is 93g; 108g of high-carbon ferrochrome; 79g of high-carbon manganese iron powder; 163g of graphene; the silicon carbide whisker was 157g. The volume ratio of hydrogen to nitrogen in the selected protective gas in this example was 1.

The friction material of the embodiment 1 to the embodiment 4 is adopted to be made into the brake pad by adopting the following process, and the process comprises the following steps:

respectively weighing the raw material components and uniformly mixing to form a mixture; adding the mixture into a granulating agent to prepare granules with the diameter of 1-3mm in a granulator; placing the particles in a mould, pressing for 10s under the pressure of 15MPa to obtain a friction particle pressing blank, and then placing the pressing blank in a sintering furnace at 1020 ℃ for sintering for 2h under the sintering pressure of 6MPa, wherein the protective gas is ammonia decomposition gas; cooling for 4h to room temperature after sintering to prepare friction particles; and mounting the friction particles on a floating structure to form the brake pad.

EXAMPLE five

The friction material for the brake pad selected in the embodiment comprises the following components: the weight of copper-clad iron powder is 421g; 93g of superfine iron powder with the particle size of 2000 meshes; the alumina is 18; 43g of tungsten carbide; 198g of pre-alloyed copper-tin powder, wherein the copper content in the pre-alloyed copper-tin powder is 90.1wt% and 9.9wt% of tin, and the particle size is 325 meshes; 224g of graphite; 13g of graphene; the silicon carbide whisker was 11g. The volume ratio of the selected protective gas to the selected nitrogen gas in the embodiment is 1.

EXAMPLE six

The friction material for the brake pad selected in the embodiment comprises the following components: 440g of superfine copper powder with the particle size of 3.0 microns; 80g of superfine iron powder with the particle size of 2000 meshes; 50g of copper-clad iron powder; the pre-alloyed copper-tin powder is 80g, wherein the copper content in the pre-alloyed copper-tin powder is 89wt% and the tin content is 11wt%, and the particle size is 325 meshes; 80g of high-carbon ferrochrome, wherein the high-carbon ferrochrome contains 70wt% of chromium, 9wt% of carbon and the balance of iron, and the particle size of the high-carbon ferrochrome is 200 meshes; the grain size of the high-carbon manganese iron powder is 40g, wherein the high-carbon manganese iron powder contains 70wt% of manganese, 9wt% of carbon and the balance of iron, and the grain size of the high-carbon manganese iron powder is 200 meshes; 20g of chromium powder; 40g of tungsten carbide; 20g of molybdenum disulfide; 200g of graphite; 10g of graphene; 15g of alumina; the silicon carbide whisker was 10g. The volume ratio of hydrogen to nitrogen in the selected protective gas in this example is 1.

EXAMPLE seven

Comprises the following material components: 420g of superfine copper powder with the particle size of 1.0-1.1 microns; 120g of superfine iron powder with the particle size of 2000 meshes; 60g of copper-clad iron powder; the pre-alloyed copper tin powder is 80g, wherein the pre-alloyed copper tin powder contains 89.6wt% of copper, 10.4wt% of tin and 325 meshes of particle size; 80g of high-carbon ferrochrome, wherein the high-carbon ferrochrome contains 70wt% of chromium, 10.3wt% of carbon and the balance of iron, and the particle size of the high-carbon ferrochrome is 200 meshes; 20g of chromium powder; the high-carbon manganese iron powder is 30g, wherein the manganese content in the high-carbon manganese iron powder is 70wt%, the carbon content is 10.2wt%, and the balance is iron, and the particle size of the high-carbon manganese iron powder is 200 meshes; 50g of tungsten carbide; 15g of alumina; 30g of molybdenum disulfide; 180g of graphite; 20g of graphene; the silicon carbide whisker was 20g.

Example eight

Comprises the following material components: 460g of superfine copper powder with the particle size of 1.5-2.0 microns; 100g of superfine iron powder with the particle size of 2000 meshes; 50g of copper-clad iron powder; 60g of pre-alloyed copper-tin powder, wherein the copper content is that 91wt% of tin content is 9wt% and the particle size is 42-50 microns (325 meshes); 100g of high-carbon ferrochrome, wherein the high-carbon ferrochrome contains 70wt% of chromium, 10.3wt% of carbon and the balance of iron, and the particle size of the high-carbon ferrochrome is 200 meshes; 20g of chromium powder; the high-carbon ferromanganese powder is 40g, wherein the manganese content in the high-carbon ferromanganese powder is 70wt%, the carbon content is 10.2wt%, and the balance is iron, and the particle size of the high-carbon ferromanganese powder is 200 meshes; 40g of tungsten carbide; 15g of alumina; 20g of molybdenum disulfide; 200g of graphite; 15g of graphene; the silicon carbide whisker was 15g.

The friction material of the embodiment 5 to the embodiment 8 is made into the brake pad by adopting the following process, which comprises the following steps:

respectively weighing the raw material components and uniformly mixing to form a mixture; adding granulating agent into the mixture, and granulating in a granulator to obtain granules of 1-3 mm; placing the particles in a mould, pressing for 20s under the pressure of 18MPa to obtain a friction particle pressing blank, and then placing the pressing blank in a sintering furnace at 1050 ℃ for sintering for 1.5h under the sintering pressure of 5MPa, wherein the protective gas is ammonia decomposition gas; cooling for 5h to room temperature after sintering to prepare friction particles; and mounting the friction particles on a floating structure to form the brake pad.

Example nine

420g of superfine copper powder with the particle size of 2.0 to 2.5 microns; 90g of superfine iron powder with the particle size of 2000 meshes; 60g of copper-clad iron powder; the pre-alloyed copper-tin powder is 80g, wherein, the copper content is that 91wt% of tin content is 9wt%, the grain diameter is 42-50 micron (325 mesh); 80g of high-carbon ferrochrome, wherein the high-carbon ferrochrome contains 70wt% of chromium, 11wt% of carbon and the balance of iron, and the particle size of the high-carbon ferrochrome is 200 meshes; 20g of chromium powder; the high-carbon ferromanganese powder is 40g, wherein the manganese content in the high-carbon ferromanganese powder is 70wt%, the carbon content is 10.2wt%, and the balance is iron, and the particle size of the high-carbon ferromanganese powder is 200 meshes; 50g of tungsten carbide; 30g of molybdenum disulfide; 180g of graphite; 20g of graphene; 15g of alumina; the silicon carbide whisker was 20g.

Example ten

450g of superfine copper powder; the pre-alloyed copper-tin powder is 80g, wherein the copper content is 90.7wt% and the tin content is 10.3wt%, and the particle size is 42-50 microns (325 meshes); 100g of superfine iron powder; 40g of copper-clad iron powder; 80g of high-carbon ferrochrome, wherein the high-carbon ferrochrome contains 70wt% of chromium, 11wt% of carbon and the balance of iron, and the particle size of the high-carbon ferrochrome is 200 meshes; 20g of chromium powder; the high-carbon ferromanganese powder is 40g, wherein the manganese content in the high-carbon ferromanganese powder is 70wt%, the carbon content is 11wt%, the balance is iron, and the particle size of the high-carbon ferromanganese powder is 200 meshes; 40g of tungsten carbide; 20g of molybdenum disulfide; 180g of graphite; 10g of graphene; 15g of alumina; the silicon carbide whisker was 20g.

EXAMPLE eleven

450 parts of superfine copper powder; 120g of superfine iron powder; 40g of copper-clad iron powder; the pre-alloyed copper-tin powder is 80g, wherein the copper content is 90.7wt% and the tin content is 10.3wt%, and the particle size is 42-50 microns (325 meshes); 100g of high-carbon ferrochrome, wherein the high-carbon ferrochrome contains 70wt% of chromium, 11wt% of carbon and the balance of iron, and the particle size of the high-carbon ferrochrome is 200 meshes; 20g of chromium powder; the high-carbon ferromanganese powder is 40g, wherein the manganese content in the high-carbon ferromanganese powder is 70wt%, the carbon content is 11wt%, the balance is iron, and the particle size of the high-carbon ferromanganese powder is 200 meshes; 20g of alumina; 40g of tungsten carbide; 30g of molybdenum disulfide; 180g of graphite; 20g of graphene; the silicon carbide whisker was 10g.

The friction material of the embodiment 9 to the embodiment 11 is adopted to be made into the brake pad by the following process, and the process comprises the following steps:

respectively weighing the raw material components and uniformly mixing to form a mixture; adding granulating agent into the mixture, and granulating in a granulator to obtain granules of 1-3 mm; placing the particles in a mould, pressing for 15s under the pressure of 20MPa to obtain a friction particle pressing blank, and then placing the pressing blank in a sintering furnace at 1100 ℃ for sintering for 1h under the sintering pressure of 4MPa, wherein the protective gas is ammonia decomposition gas; cooling for 6h to room temperature after sintering to prepare friction particles; and mounting the friction particles on a floating structure to form the brake pad.

Comparative example 1 the high carbon ferrochrome in example 3 was replaced with chromium powder in equal amount and the other components were unchanged.

Comparative example 2 the high carbon manganese iron powder in example 3 was replaced with manganese powder in equal amounts, and the other components were unchanged.

Comparative example 3 the pre-alloyed cuprum-stannum powder in example 3 was replaced with nickel powder in equal amount, and the other components were unchanged.

Comparative example 4 in example 3, chromium powder was substituted with equal amount of high-carbon ferrochrome powder, manganese powder was substituted with equal amount of high-carbon ferromanganese powder, nickel powder was substituted with equal amount of pre-alloyed copper-tin powder, and other components were unchanged.

Comparative example 5 in example 7, the pre-alloyed copper-tin powder and the high carbon chromium powder were replaced with copper powder in equal amounts, the high carbon ferromanganese powder was replaced with atomized iron powder in equal amounts, and the other components were unchanged.

Comparative example 6 both the graphene and silicon carbide whiskers of example 7 were replaced equally with graphite, the other components being unchanged.

The brake pads prepared in the above examples 1 to 11 and comparative examples 1 to 6 were subjected to a frictional wear test in a frictional wear testing machine under the following test conditions: the diameter of a brake disc arranged on a cast steel wheel is 750mm, the friction radius is 305mm, the disc load is 8.5t, the wheel diameter is 920mm, the bilateral braking pressure is 36kN, and the initial temperature is 50-60 ℃. The results are shown in table 1 (3 runs per speed, averaged):

TABLE 1 brake pad Friction wear test results

According to test results, the friction material still has good friction stability at high speed, and both the friction performance and the wear rate meet the provisional technical conditions of the TJ/CL307-2019 motor train unit issued by the national iron group, and meet the application requirements of the motor train unit at ultrahigh speed of 450 km/h.

The determination methods of the technical indexes of the invention are all standard methods used in the field, and specific reference can be made to the latest national standard unless otherwise stated.

When the friction material is applied to the brake pad, thermal damage such as hot spots and cracks and abnormal abrasion can not be generated on the brake disc, the working surface of the friction pair can not be bonded, and the working surface can not be peeled off, scratched, welded and damaged by other destructiveness in the friction process. The transition metal alloy powder is used as an alloy agent with higher carbon content, so that the hardenability of the friction material is improved, the wear resistance and hardness of the material are increased, the friction coefficient is improved, and the abrasion loss is reduced.

The friction block prepared by the invention not only improves the shearing strength of the friction body per se, reduces abrasion, prolongs the abrasion to the limited time, but also greatly improves the connection strength of the friction body and the back plate, reduces the risk of brake runaway caused by falling off of the friction body, simultaneously prolongs the whole service life of the brake pad, improves the service speed of the brake pad, and provides a high-performance and high-reliability friction block manufacturing method for the high-speed brake pad.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention and do not limit the spirit and scope of the present invention. Various modifications and improvements of the technical solutions of the present invention may be made by those skilled in the art without departing from the design concept of the present invention, and the technical contents of the present invention are all described in the claims.

Claims

1. The friction material for the brake pad is characterized by comprising the following raw material components in parts by weight: 52-66 parts of a matrix component, 4-7 parts of a friction component, 15-28 parts of a reinforcing component and 19-32 parts of a lubricating component; wherein the content of the first and second substances,

the matrix component comprises copper-clad iron powder;

the friction component comprises tungsten carbide and aluminum oxide, wherein the aluminum oxide accounts for 1 to 2 parts by weight of the friction component, and the balance is tungsten carbide;

the reinforced component comprises transition metal alloy powder, wherein the transition metal alloy powder comprises prealloyed copper-tin powder, high-carbon ferrochrome, high-carbon ferromanganese and chromium powder, and the prealloyed copper-tin powder accounts for 5-10 parts by weight, the high-carbon ferrochrome accounts for 7-10 parts by weight, the chromium powder accounts for 1-3 parts by weight, and the high-carbon ferromanganese accounts for 2-5 parts by weight;

the lubricating component comprises graphene, silicon carbide whiskers, molybdenum disulfide and graphite, and the weight part of the molybdenum disulfide is 1-4; 16-24 parts of graphite; the graphene is 1-2 parts by weight, and the silicon carbide whisker is 1-2 parts by weight.

2. The friction material for brake lining of claim 1 wherein said matrix component further comprises a transition metal powder.

3. The friction material for the brake lining as claimed in claim 2, wherein the transition metal powder comprises one or more of ultrafine copper powder with a particle size of 1.0-3.0 microns and ultrafine iron powder with a particle size of 5-7 microns.

4. The friction material for brake lining as claimed in claim 3, wherein said copper-coated iron powder comprises 40-48 weight parts of said copper-coated iron powder, 8-12 weight parts of said iron powder, and the balance of said copper-coated iron powder.

5. The friction material for the brake pad as claimed in claim 1, wherein the pre-alloyed copper-tin powder comprises 89-91wt% of copper and 9-11wt% of tin, and the particle size of the pre-alloyed copper-tin powder is 42-50 microns;

and/or the high-carbon ferrochrome contains 68 to 73wt% of chromium, 9 to 11wt% of carbon and the balance of iron, and the particle size of the high-carbon ferrochrome is 75 to 81 micrometers;

and/or the high-carbon ferromanganese has 68 to 75wt% of manganese, 9 to 11wt% of carbon and the balance of iron, and the particle size of the high-carbon ferromanganese is 75 to 81 micrometers.

6. A preparation method of a friction material for brake pads, which is used for the friction material for brake pads as defined in any one of claims 1 to 5, is characterized by comprising the following steps:

carrying out die compression on the particles to obtain a compression blank;

and (3) carrying out pressure sintering on the pressing blank under the protection of a mixed gas of hydrogen and nitrogen, and then cooling to obtain the friction material for the brake pad.

7. The method for preparing a friction material for a brake lining as claimed in claim 6, wherein the granulating agent is a hydrogenated styrene-isoprene-butadiene copolymer; the pressure for die pressing is 15-20Mpa, and the time is 10-20s; the pressure sintering is carried out at the temperature of 1000-1100 ℃ for 1-2h and under the pressure of 4-6Mpa; the cooling is carried out for 4-6h.

8. A brake pad for a motor vehicle, comprising the friction material for a brake pad according to any one of claims 1 to 5.