Friction material for switch machine as well as preparation method and application of friction material

Abstract

The invention discloses a point switch friction material and a preparation method and application thereof, and belongs to the technical field of rail transit point switch friction materials, the preparation method comprises the following steps: adding resin, a functional filler, a lubricant, a stabilizer and rubber into a crushed fiber reinforcement, and stirring and mixing to obtain a mixture; carrying out hot-pressing curing to obtain a semi-formed material; and carrying out curing treatment to obtain the friction material of the switch machine. The fiber-reinforced resin-based composite friction material is prepared by optimizing the mass ratio of the resin, the fiber reinforcement body and other components and adopting specific hot-pressing curing and step-by-step heat preservation curing processes, and the dynamic friction coefficient of the fiber-reinforced resin-based composite friction material is 0.3-0.4; the problems that an existing switch machine copper-based friction material is large in abrasion, unstable in output torque, abnormal in sound and complex in speed reducer assembly process are effectively solved, and meanwhile the application field of the composite friction material is expanded. The friction material of the switch machine is promoted to be converted from copper-based powder metallurgy to fiber-reinforced resin-based composite, and the reliability development of a railway signal system is assisted.

Description

Technical Field

[0001] This invention belongs to the technical field of friction materials for rail transit switch machines, specifically relating to a friction material for switch machines, its preparation method, and its application. Background Technology

[0002] Switch machines are crucial basic equipment in railway signaling systems, installed at track switches. Their primary function is to drive the switch's point rail to the left or right, changing the switch's direction and thus determining whether a train enters the straight track or the siding. In actual operation, the fluctuation of frictional current is a significant factor affecting the normal operation of the track system. Research has found that the mechanical properties, coefficient of friction, friction coefficient stability, and wear rate of the friction material used in switch machines play a decisive role in the stability of the frictional current. Therefore, compared to structural design, the fabrication of friction material strips with stable performance and high reliability is even more important.

[0003] Chinese invention patent application CN119114946A discloses a method for manufacturing friction plates for switch machines, including the following steps: preparing and mixing materials required for the intermediate reinforcing substrate according to a set ratio; first loading a layer of friction material into a press, then loading a layer of intermediate reinforcing substrate mixture, and then loading another layer of friction material; pressing the three layers of materials together to form a compact; and then sintering the compact under pressure. This invention patent application presses the intermediate reinforcing substrate material and friction material together to form the friction plate, eliminating the need to prepare the substrate first and then the friction plate, thus simplifying the production process, improving production efficiency, and ensuring a lower defect rate. However, it does not fundamentally optimize the problems of high wear, unstable output torque, and abnormal noise in the reducer assembly process and existing copper-based friction materials. Chinese invention patent CN113275554B discloses a copper-based powder metallurgy clutch friction plate for switch machines and its manufacturing method. The friction layer comprises: electrolytic copper powder, iron powder, tin powder, manganese powder, mullite, molybdenum disulfide, silicon dioxide, flake graphite, and artificial graphite. The manufacturing method involves first weighing an appropriate amount of raw materials and mixing them in a mixer. The uniformly mixed powder is then placed on a pre-copper-plated steel core plate and cold-pressed into shape, followed by pressure sintering. After furnace cooling, the finished product is obtained. This invention patent studies the composition, manufacturing method, and performance of copper-based friction materials; however, the complex assembly process of the entire reducer and the problem of high wear still exist.

[0004] In the application of friction materials for switch machines, copper-based friction materials prepared by powder metallurgy are currently the norm, with no application of fiber-reinforced composite friction materials. The main problems with copper-based friction materials are high wear, unstable output torque, and abnormal noise, necessitating a new type of friction material to address these issues. Furthermore, the assembly process of switch machine reducers requires pre-run-in, cleaning, and secondary assembly of the copper-based friction materials, resulting in a lengthy overall assembly process. The novel fiber-reinforced resin-based composite friction material, however, can be directly assembled into the reducer and run-in tested in a testing device. Because of its low wear and absence of wear residue, it eliminates the need for disassembly, cleaning, and secondary assembly. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a switch machine friction material, its preparation method and application, so as to solve the technical problems of large wear, unstable output torque, abnormal noise and complex assembly process of existing copper-based friction materials.

[0006] To achieve the above objectives, the present invention employs the following technical solution: This invention discloses a method for preparing a friction material for a switch machine, comprising the following steps: Resin, functional filler, lubricant, stabilizer and rubber are added to the pulverized fiber reinforcement, and after stirring and mixing, a mixture is obtained; after hot pressing and curing, a semi-molded material is obtained; after further curing, a switch machine friction material is obtained.

[0007] Preferably, the mass percentages of resin, functional filler, lubricant, stabilizer, rubber and fiber reinforcement are (15%-25%): (15%-25%): (5%-15%): (5%-15%): (5%-15%) (25%-35%); the resin is a thermosetting resin.

[0008] Preferably, the resin is at least one of cashew nut shell liquid modified phenolic resin and nitrile modified phenolic resin polyimide.

[0009] Preferably, the fiber reinforcement is at least one of pitch-based carbon fiber, wollastonite fiber, acrylic pulp and aramid fiber.

[0010] Preferably, the functional filler is at least one of silica, calcium hydroxide, calcium carbonate, diatomaceous earth, fluorite powder, alumina, barium sulfate, limonite, and carbon black.

[0011] Preferably, the lubricant is at least one selected from antimony sulfide, polytetrafluoroethylene, molybdenum disulfide, tungsten disulfide, hexagonal boron nitride, carbon nanotubes, graphite, and graphene.

[0012] Preferably, the hot-press curing temperature is 150-180℃, the pressure is 5-8MPa, and the time is 15-20min.

[0013] Preferably, the curing conditions include: holding the semi-molded material at 120°C for 30 minutes, at 160°C for 60 minutes, at 180°C for 120 minutes, and at 200°C for 90 minutes.

[0014] The present invention also discloses a switch machine friction material, which is prepared by the above-mentioned method for preparing switch machine friction material; the dynamic friction coefficient of the switch machine friction material is 0.3-0.4.

[0015] The present invention also discloses the application of the switch friction material prepared by the above-mentioned method in a speed reducer.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for preparing a friction material for a switch machine. By thoroughly mixing resin and other components with pulverized fiber reinforcement, and combining this with precisely controlled hot-press curing and staged curing processes, the method effectively solves the problems of uneven raw material dispersion and difficulty in precisely controlling the curing process. This ensures a dense internal structure and stable frictional performance, offering advantages such as uniform raw material dispersion, controllable curing process, dense internal structure, stable frictional performance, long service life, and simple process. Resin, functional fillers, lubricants, stabilizers, and rubber are added to the pulverized fiber reinforcement and mixed to form a homogeneous mixture. The pulverization process significantly increases the surface area and improves the surface roughness of the fiber reinforcement, effectively promoting the full adsorption and dispersion of each component during mixing. This avoids localized differences in frictional performance caused by uneven material distribution, laying a foundation for consistent structure in subsequent processes. After hot-press curing, a semi-formed material is obtained, promoting initial cross-linking of the resin and forming an intermediate with moderate strength and plasticity. This maintains the shape stability of the material and prevents deformation or cracking that may occur during subsequent processing. Through curing, the resin gradually completes deep cross-linking, internal stress is effectively released, and the molecular structure tends to stabilize, ultimately obtaining a switch machine friction material with balanced performance. This ensures the uniformity of the material's internal structure and the reliability of its overall performance, effectively suppresses fluctuations in the coefficient of friction, and significantly improves the stability of equipment operation.

[0017] Furthermore, by precisely controlling the mass percentage range of each component and the type of resin, the following measures are taken: When the resin proportion is too low, delamination due to insufficient bonding strength is avoided; when the proportion is too high, brittleness is prevented from affecting impact resistance. Functional fillers ensure the stability of the coefficient of friction when the proportion is too low, and prevent internal unevenness when the proportion is too high. Lubricants effectively reduce heat accumulation when the proportion is too low, and prevent slippage risk when the proportion is too high. Stabilizers inhibit high-temperature aging when the proportion is too low, and prevent the introduction of impurities when the proportion is too high. Rubber maintains elastic deformation capacity when the proportion is too low, and ensures the coefficient of friction when the proportion is too high. Fiber reinforcement provides mechanical support when the proportion is too low, and maintains processing fluidity when the proportion is too high. Thermosetting resins, compared to thermoplastic resins, better maintain dimensional stability and consistency of frictional performance, thus collectively solving the problems of dynamic friction coefficient fluctuations, insufficient mechanical strength, decreased thermal stability, and deterioration of wear resistance.

[0018] Furthermore, the cashew nutshell liquid-modified phenolic resin releases a uniform lubricating effect during the hot-press curing stage, reducing fluctuations in the coefficient of friction. Simultaneously, the elastic segments of the nitrile-modified phenolic resin enhance the interfacial bonding with the fiber reinforcement during curing, effectively inhibiting microcrack propagation. In addition, the rigid molecular structure of polyimide remains stable during the stepped-temperature curing process, preventing thermal degradation. These specific resin selections collectively optimize the hot-press curing reaction kinetics, enabling the final friction material to exhibit stable performance output in dynamic friction behavior, thereby reliably maintaining the coefficient of dynamic friction within the target range.

[0019] Furthermore, by specifying the exact type of fiber reinforcement, pitch-based carbon fibers can efficiently conduct heat during the hot-pressing stage, preventing fluctuations in the coefficient of dynamic friction caused by localized overheating. The needle-like structure of wollastonite fibers constructs a three-dimensional support network in the mixture, enhancing the overall compressive strength of the material and reducing wear inconsistencies. The flexible fiber bundles of acrylic pulp improve the interfacial compatibility between the resin and filler, ensuring uniform dispersion of components during mixing. Aramid fibers maintain structural stability during high-temperature curing and subsequent applications, synergistically ensuring the stability of the coefficient of dynamic friction over a wide temperature range. The combined application of these fibers forms a complementary functional system, effectively solving the performance fluctuation problem caused by unclear fiber types.

[0020] Furthermore, functional fillers are used to regulate the dynamic friction coefficient and thermal stability of friction materials. However, in the process of implementation, the selection of functional filler types lacks specificity, which can easily lead to fluctuations in the friction coefficient exceeding the ideal range, local degradation of the material or accelerated wear during the hot-pressing curing stage, thereby affecting the reliability and lifespan of the switch machine. Through the specific selection of functional fillers, during the mixing stage, the high specific surface area of ​​silica promotes the uniform bonding of each component, avoiding friction coefficient fluctuations caused by local aggregation; the acidic byproducts generated in the alkaline neutralization reaction of calcium hydroxide prevent chemical degradation of the material during hot-pressing curing; calcium carbonate adjusts the hardness and density of the material, inhibiting excessive wear; the porous structure of diatomaceous earth provides thermal insulation, reducing the heat accumulation effect; the low friction characteristics of fluorite powder help stabilize the dynamic friction coefficient in the range of 0.3-0.4; alumina and barium sulfate together improve the durability and wear resistance of the material; limonite optimizes the microstructure of the friction interface, ensuring consistent friction behavior; and carbon black improves conductivity and dispersibility. These functional fillers play a complementary role in the mixture, ensuring a stable structure during hot pressing and subsequent curing processes, thereby avoiding the problem of frictional performance imbalance caused by filler mismatch.

[0021] Furthermore, lubricants are used to reduce friction and provide stability. However, in their implementation, improper selection of lubricant type can lead to fluctuations in the coefficient of friction, increased material wear, or insufficient high-temperature performance, thus affecting the reliability and service life of the switch machine during operation. By introducing the aforementioned specific lubricants into the mixture, these lubricants form a stable lubrication layer at the friction interface and synergistically regulate friction behavior during hot pressing and subsequent curing processes. Antimony sulfide forms a dense film under thermal action to prevent high-temperature adhesion; polytetrafluoroethylene reduces surface energy to reduce molecular-level adhesion during dynamic friction; the layered structure of molybdenum disulfide and tungsten disulfide undergoes interlayer slippage under pressure to maintain lubrication continuity under load changes; hexagonal boron nitride maintains crystal structure stability in high-temperature environments to ensure that lubrication performance does not degrade; carbon nanotubes and graphene uniformly disperse interfacial heat through high thermal conductivity to avoid performance degradation caused by local overheating; and graphite provides a reliable basis for friction control. Together, they maintain the dynamic coefficient of friction within the ideal range of 0.3-0.4 under dynamic operating conditions.

[0022] Furthermore, through precise coordinated control of temperature, pressure, and time parameters, the hot-press curing temperature is 150-180℃ to ensure that the resin achieves full cross-linking and avoids thermal decomposition during the hot-pressing process, the pressure is 5-8MPa to provide appropriate compressive force to promote the tight bonding of fibers and fillers, and the time is 15-20min to ensure that the reaction is completed. This optimizes the controllability of the curing process and effectively prevents the generation of internal structural defects in the material.

[0023] Furthermore, through the coordinated control of staged gradient heating and precise holding time, the moisture and low-boiling-point components in the material are slowly released during the 120℃ holding stage, preventing excessive temperature from causing bubbles or cracks, thus laying a dense structural foundation for subsequent reactions. Secondly, the resin cross-linking reaction acceleration zone is precisely matched during the 160℃ holding stage, ensuring that the molecular chains are fully entangled to form a stable framework, preventing low cross-linking degree from weakening the material's strength. Subsequently, the deep curing process is thoroughly completed during the 180℃ holding stage, effectively eliminating internal stress concentration and improving thermal stability. Finally, the physicochemical changes are driven to conclude the process during the 200℃ holding stage, ensuring complete homogenization of the material's interior and avoiding performance degradation due to sudden temperature increases or insufficient time, thereby achieving precise control and long-term stability of the friction coefficient.

[0024] This invention discloses a friction material for a switch machine. By uniformly mixing resin, functional filler, lubricant, stabilizer, and rubber with pulverized fiber reinforcement, combined with hot-press curing and staged curing processes, the internal structure of the material is ensured to be uniform and dense, avoiding abrupt changes in friction performance caused by uneven component distribution. The dynamic friction coefficient is in the range of 0.3-0.4, which is the result of optimized matching between material composition and processing technology. This prevents the risk of slippage caused by excessively low friction coefficients and avoids abnormal wear caused by excessively high friction coefficients, thereby achieving reliable power transmission and braking control under the dynamic operating conditions of the switch machine.

[0025] This invention discloses the application of a switch machine friction material in a speed reducer, effectively avoiding the unreliability problem in the deceleration process caused by fluctuations in the friction coefficient, thus improving the smoothness of the speed reducer's operation and the reliability of the equipment. This switch machine friction material is based on a precise ratio of a thermosetting resin system with functional fillers, lubricants, and other components, and is generated through a specific hot-press curing and segmented curing process. Its internal structure is uniformly distributed, and its frictional performance is stable, ensuring a continuous and consistent frictional force under the speed reducer's operating environment, avoiding slippage or jamming caused by deviations in the material's own properties. By applying a switch machine friction material with precisely controlled dynamic friction coefficient to the speed reducer, and utilizing its frictional stability characteristics, reliable torque transmission is achieved, significantly reducing the risk of equipment failure, and thereby improving the overall operating efficiency of the speed reducer. Attached Figure Description

[0026] Figure 1 Wear rate diagrams of the switch machine friction material CFRP-1 prepared in Example 1, the switch machine friction material CFRP-2 prepared in Example 2, and the copper-based friction material prepared in the comparative example. Figure 2 The friction coefficient diagrams are for the switch machine friction material CFRP-1 prepared in Example 1, the switch machine friction material CFRP-2 prepared in Example 2, and the copper-based friction material prepared in the comparative example. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0029] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0030] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0031] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0032] In this invention, unless otherwise specified, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" indicates that all real numbers between "6~22" have been listed in this document, and "6~22" is simply a shortened representation of these numerical combinations.

[0033] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0034] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0035] In this invention, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.

[0036] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0037] The present invention provides a friction material for a switch machine, comprising, by mass fraction, 15%-25% resin, 25%-35% fiber reinforcement, 15%-25% functional filler, 5%-15% lubricant, 5%-15% stabilizer and 5%-15% rubber.

[0038] The resin is a thermosetting resin.

[0039] Preferably, the resin is one or more of cashew nut shell liquid modified phenolic resin and nitrile modified phenolic resin polyimide.

[0040] The fiber reinforcement is one or any combination of pitch-based carbon fiber, wollastonite fiber, acrylic pulp and aramid fiber.

[0041] The functional filler is one or any combination of several of the following: silica, calcium hydroxide, calcium carbonate, diatomaceous earth, fluorite powder, alumina, barium sulfate, limonite, and carbon black.

[0042] The lubricant is one or any combination of antimony sulfide, polytetrafluoroethylene, molybdenum disulfide, tungsten disulfide, hexagonal boron nitride, carbon nanotubes, graphite and graphene.

[0043] The coefficient of dynamic friction of the friction material of the switch machine is 0.3-0.4.

[0044] A method for preparing a friction material for a switch machine includes the following steps: S1. Weigh the resin, fiber reinforcement, functional filler and lubricant according to the set mass. S2, the fiber reinforcement is stirred and pulverized in a high-speed pulverizer to obtain pulverized fiber reinforcement; S3, resin, functional filler and lubricant are added to fiber reinforcement, and after stirring and mixing, a mixture is obtained; S4, the mixture is placed in a mold, and after hot pressing and curing, a semi-molded material is obtained; S5 is a fiber-reinforced wet friction material with an ultra-low coefficient of friction obtained by curing the semi-formed material.

[0045] In S4, the hot-press curing temperature is 150-180℃, the pressure is 5-8MPa, and the time is 15-20min.

[0046] In S5, the curing process involves placing the semi-molded material in a high-temperature electric heating drying oven and holding it at 120°C for 30 minutes, at 160°C for 60 minutes, at 180°C for 120 minutes, and at 200°C for 90 minutes.

[0047] This invention discloses a friction material for switch machines, which is a composite of a resin matrix, fiber reinforcement, functional filler, stabilizer, rubber, and lubricant. Its composition by mass percentage is: resin 15-25%, fiber reinforcement 25%-35%, functional filler 15%-25%, lubricant 5%-15%, stabilizer 5%-15%, and rubber 5%-15%. By systematically optimizing the proportions of each component, a novel friction material for switch machines that meets customer needs is prepared. The fiber-reinforced friction material prepared based on the above proportions effectively solves the problems of high wear, unstable torque, abnormal noise, and complex assembly processes associated with existing copper-based friction materials for switch machines. This expands the application fields of fiber-reinforced resin composite friction materials.

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0049] Example 1 A method for preparing a friction material for a switch machine includes the following steps: Step 1: Weigh the total weight of 500g according to the mass fraction. The ingredients are: cashew nut shell oil modified phenolic resin 20%, carbon fiber 12%, aramid fiber 10%, wollastonite fiber 8%, silica 3%, calcium hydroxide 2%, calcium carbonate 8%, diatomaceous earth 5%, fluorite powder 4%, antimony sulfide 2%, polytetrafluoroethylene 3%, molybdenum disulfide 8%, zinc stearate 5%, and rubber 10%. The second step is to mix and grind the carbon fiber, aramid fiber and wollastonite fiber in a high-speed pulverizer for 10 seconds, then pause for 3 minutes, and then mix for another 10 seconds. Open the lid and add all the powder, and repeat the mixing operation twice to mix all the powder evenly. The third step is to place the mixture in a mold and hot press it at 150°C and 5 MPa for 17 minutes to obtain a semi-molded material. The fourth step involves placing the semi-formed material in a high-temperature electric heating drying oven and holding it at 120℃ for 30 minutes, 160℃ for 60 minutes, 180℃ for 120 minutes, and 200℃ for 90 minutes to obtain the switch machine friction material. The dynamic friction coefficient of the obtained switch machine friction material is 0.4.

[0050] Example 2 A method for preparing a friction material for a switch machine includes the following steps: Total mass: 500g, weighed according to mass fraction.

[0051] Nitrile-modified phenolic resin polyimide (15%), pitch-based carbon fiber (30%), barium sulfate (20%), tungsten disulfide (5%), calcium stearate (15%), and rubber (15%).

[0052] Step 1: Weigh each substance according to the mass fractions mentioned above.

[0053] Step 2: Pulverize the pitch-based carbon fiber in a high-speed pulverizer for 10 seconds, pause for 3 minutes, then pulverize for another 10 seconds. Open the lid and add the other powders. Repeat the pulverizing process twice more to mix all the powders evenly.

[0054] Step 3: Place the mixture in a mold, heat at 180℃ and pressure at 8MPa for 20 minutes.

[0055] Step 4: Place the semi-formed material in a high-temperature electric heating drying oven and maintain the temperature at 120℃ for 30 minutes, 160℃ for 60 minutes, 180℃ for 120 minutes, and 200℃ for 90 minutes to obtain the switch machine friction material. The dynamic friction coefficient of the obtained switch machine friction material is 0.33.

[0056] Example 3 A method for preparing a friction material for a switch machine includes the following steps: Total mass: 500g, weighed according to mass fraction.

[0057] Cashew shell oil modified phenolic resin: nitrile modified phenolic resin polyimide = 1:1 (20%), acrylic pulp (30%), limonite (20%), hexagonal boron nitride (10%), calcium stearate (10%), rubber (10%).

[0058] Step 1: Weigh each substance according to the mass fractions mentioned above.

[0059] Step 2: Grind the acrylic fiber pulp in a high-speed grinder for 10 seconds, pause for 3 minutes, then grind for another 10 seconds. Open the lid and add the other powders. Repeat the grinding process twice more to mix all the powders evenly.

[0060] Step 3: Place the mixture in a mold, heat at 165℃, pressure at 6.5MPa, and hot press for 17.5min.

[0061] Step 4: Place the semi-formed material in a high-temperature electric heating drying oven and maintain the temperature at 120℃ for 30 minutes, 160℃ for 60 minutes, 180℃ for 120 minutes, and 200℃ for 90 minutes to obtain the switch machine friction material. The dynamic friction coefficient of the obtained switch machine friction material is 0.3.

[0062] Example 4 A method for preparing a friction material for a switch machine includes the following steps: Total mass: 500g, weighed according to mass fraction.

[0063] Cashew shell oil modified phenolic resin (25%), wollastonite fiber (25%), carbon black (20%), graphene (10%), calcium stearate (5%), and rubber (15%).

[0064] Step 1: Weigh each substance according to the mass fractions mentioned above.

[0065] Step 2: Pulverize the wollastonite fiber in a high-speed pulverizer for 10 seconds, pause for 3 minutes, then pulverize for another 10 seconds. Open the lid and add the other powders, then repeat the pulverizing process twice more to mix all the powders evenly.

[0066] Step 3: Place the mixture in a mold, heat at 150℃ and pressure at 5MPa for 15 minutes.

[0067] Step 4: Place the semi-formed material in a high-temperature electric heating drying oven and maintain the temperature at 120℃ for 30 minutes, 160℃ for 60 minutes, 180℃ for 120 minutes, and 200℃ for 90 minutes to obtain the switch machine friction material. The dynamic friction coefficient of the obtained switch machine friction material is 0.37.

[0068] Example 5 A method for preparing a friction material for a switch machine includes the following steps: Total mass: 500g, weighed according to mass fraction.

[0069] Nitrile-modified phenolic resin polyimide (20%), pitch-based carbon fiber (15%), acrylic pulp (15%), silica (5%), calcium carbonate (5%), limonite (10%), alumina (5%), carbon nanotubes (5%), graphite (5%), magnesium stearate (10%), and rubber (5%).

[0070] Step 1: Weigh each substance according to the mass fractions mentioned above.

[0071] Step 2: Mix and grind the pitch-based carbon fiber and acrylic pulp in a high-speed pulverizer for 10 seconds, pause for 3 minutes, then mix for another 10 seconds. Open the lid and add the other powders, and repeat the mixing operation twice more to mix all the powders evenly.

[0072] Step 3: Place the mixture in a mold, heat at 170℃ and 7MPa for 15 minutes.

[0073] Step 4: Place the semi-formed material in a high-temperature electric heating drying oven and maintain the temperature at 120℃ for 30 minutes, 160℃ for 60 minutes, 180℃ for 120 minutes, and 200℃ for 90 minutes to obtain the switch machine friction material. The dynamic friction coefficient of the obtained switch machine friction material is 0.35.

[0074] Comparative Example A method for preparing a copper-based friction material includes the following steps: The composition is as follows: 58% electrolytic copper powder, 14% iron powder, 0.5% tin powder, 4.5% manganese powder, 4% mullite, 5% molybdenum disulfide, 3% silicon dioxide, 8% flake graphite, and 3% artificial graphite.

[0075] Weigh the finished raw materials according to the mass fractions of each component, and add 0.5-1.5% of the total mass of the raw materials as machine oil. Place them in a mixer and mix them at the same time. Set the speed to 30 r / min and the mixing time to 180 min. First, the steel core board is sandblasted until its surface is bright. Then, the bonding surface of the steel core board is cleaned with anhydrous ethanol to ensure that it is free of water, oil, and rust. Next, the surface of the steel core board is copper plated.

[0076] The uniformly mixed powder is evenly placed on a steel core plate and then placed into a mold for cold pressing; the pressing pressure is 350MPa and the holding time is 10-15s.

[0077] The cold-pressed blank is placed in a mold and then placed in a bell-type sintering furnace. Under the protection of nitrogen atmosphere, it is sintered under pressure. After sintering, it is cooled with the furnace to obtain the copper-based powder metallurgy clutch friction plate of the switch machine. The sintering temperature is 920℃ and the sintering pressure is 3.5MPa.

[0078] The copper-based powder metallurgy clutch friction plate blank after sintering is processed to ensure that the thickness tolerance, flatness and oil groove size of the friction plate meet the product technical specifications, and then the copper-based friction material can be obtained.

[0079] Figure 1The figures show the wear rates of the switch machine friction material CFRP-1 prepared in Example 1, the switch machine friction material CFRP-2 prepared in Example 2, and the copper-based friction material prepared in the comparative example. It can be clearly seen from the figures that the wear rates of the copper-based friction materials CFRP-1 and CFRP-2 are reduced by 98% and 93% respectively compared with those of the copper-based friction materials.

[0080] Figure 2 The graphs show the friction coefficients of the CFRP-1 switch machine friction material prepared in Example 1, the CFRP-2 switch machine friction material prepared in Example 2, and the copper-based friction material prepared in the comparative example. As can be seen from the graphs, the friction coefficient stability of the fiber-reinforced composite friction material is superior to that of the copper-based friction material.

[0081] In summary, this invention provides a friction material for a switch machine, its preparation method, and its application. It employs a multi-component synergistic formulation of resin (15-25%), fiber reinforcement (25-35%), functional filler (15-25%), lubricant (5-15%), stabilizer (5-15%), and rubber (5-15%). The process involves high-speed fiber pulverization, multi-component mixing, and application at 150-180℃ and 5-8 MPa. An optimized process involving hot-press curing and step-by-step heat preservation curing at 120-200℃ was used to prepare fiber-reinforced resin-based composite friction materials with a stable dynamic friction coefficient of 0.3-0.4. This not only breaks through the technical limitations of existing copper-based powder metallurgy materials for switch machines in terms of material system, effectively solving the core pain points of traditional materials such as high wear, unstable output torque, and abnormal noise during operation, but also simplifies the reducer assembly process. It eliminates the need for pre-run-in, cleaning, and secondary assembly, and can be directly assembled and run-in completed through testing equipment. This significantly shortens the assembly cycle and reduces maintenance costs, providing a high-performance, high-reliability, and low-maintenance new friction material solution for railway signaling systems, and helping railway signaling systems upgrade towards high efficiency, stability, and low cost.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a friction material for a switch machine, characterized in that, Includes the following steps: Resin, functional fillers, lubricants, stabilizers, and rubber are added to the pulverized fiber reinforcement, and the mixture is stirred to obtain a compound; after hot pressing and curing, a semi-molded material is obtained. After further curing, the friction material for the switch machine is obtained.

2. The method for preparing the friction material of a switch machine according to claim 1, characterized in that, The mass percentages of the resin, functional filler, lubricant, stabilizer, rubber, and fiber reinforcement are (15%-25%): (15%-25%): (5%-15%): (5%-15%): (5%-15%) (25%-35%); the resin is a thermosetting resin.

3. The method for preparing the friction material of a switch machine according to claim 1, characterized in that, The resin is at least one of cashew nut shell liquid modified phenolic resin and nitrile modified phenolic resin polyimide.

4. The method for preparing the friction material of a switch machine according to claim 1, characterized in that, The fiber reinforcement is at least one of pitch-based carbon fiber, wollastonite fiber, acrylic pulp and aramid fiber.

5. The method for preparing the friction material of a switch machine according to claim 1, characterized in that, The functional filler is at least one of the following: silica, calcium hydroxide, calcium carbonate, diatomaceous earth, fluorite powder, alumina, barium sulfate, limonite, and carbon black.

6. The method for preparing the friction material of a switch machine according to claim 1, characterized in that, The lubricant is at least one of antimony sulfide, polytetrafluoroethylene, molybdenum disulfide, tungsten disulfide, hexagonal boron nitride, carbon nanotubes, graphite, and graphene.

7. The method for preparing the friction material of a switch machine according to claim 1, characterized in that, The hot-press curing temperature is 150-180℃, the pressure is 5-8MPa, and the time is 15-20min.

8. The method for preparing the friction material of a switch machine according to claim 1, characterized in that, The curing conditions include: holding the semi-molded material at 120°C for 30 minutes, at 160°C for 60 minutes, at 180°C for 120 minutes, and at 200°C for 90 minutes.

9. A friction material for a switch machine, characterized in that, The friction material of the switch machine is prepared by the method described in any one of claims 1-8; the coefficient of dynamic friction of the friction material of the switch machine is 0.3-0.

4.

10. The application of the switch friction material prepared by the method of any one of claims 1-8 in a speed reducer.

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