Resin-based friction material with stable instantaneous friction coefficient and composite brake pad

Abstract

The invention discloses a resin-based friction material, particularly relates to a resin-based friction material with a stable instantaneous friction coefficient, and belongs to the technical field of friction braking. The material comprises the following components in percentage by weight: 5-20wt% of phenolic resin, 5-18wt% of rubber, 20-40wt% of steel wool fiber, 1-5% of aramid fiber, 5-10wt% of crystalline flake graphite, 5-20wt% of barite, 2-6% of stannous sulfide, 1-4% of white corundum, 6-10% of zirconium silicate, 2-8% of artificial graphite, 2-8% of potassium magnesium titanate and the balance of inevitable impurities. According to the method, a unique insight is provided for the film layer influencing the stability of the instantaneous friction coefficient, and the structure of the film layer on the friction surface is effectively controlled according to the principle. The brake pad has the advantages that the instantaneous friction coefficient in the braking process is stably controlled, too fast abrasion in the braking process is avoided, and noise generated by braking can be remarkably reduced.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of friction braking, in particular to a preparation method of resin-based friction material with stable instantaneous friction coefficient and a synthetic brake pad. BACKGROUND

[0002] The synthetic brake pad is an important product in the train braking unit, and the stability of the average friction coefficient during braking is conducive to the stable braking of the train. The stable average friction coefficient means stable braking distance and braking time, and stability is particularly important, especially in urban rail transit with a shield door. Unstable friction coefficient can cause the train door and the shield door to fail to connect, affecting passenger boarding and alighting and the time rhythm of line operation. In addition to the stable average friction coefficient, we find that the stability of the instantaneous friction coefficient under single braking is also crucial, especially when approaching the braking stop, the stability of the instantaneous friction coefficient has a significant impact on the braking noise of the station.

[0003] Through retrieval, it is found that CN112029227A discloses a resin-based friction body, a resin-based synthetic brake pad and a preparation method thereof. By adding 0.1-5wt% of graphene nanosheets in the resin-based friction material, the average braking friction coefficient stability under different pressures is obviously improved. Another invention patent CN113586637A discloses a synthetic brake pad for a power concentrated motor train unit vehicle and a preparation method thereof. By adding porous fiber balls in the formula, the synthetic brake pad obtains a stable friction coefficient. At present, the solution to stable braking mostly focuses on the stability of the average friction coefficient, and the stability of the instantaneous friction coefficient has not been concerned and there is no perfect scheme. SUMMARY

[0004] The purpose of the present application is to solve the defects in the prior art, and to provide a resin-based friction material with stable instantaneous friction coefficient and a synthetic brake pad. The finished product is a resin-based friction material with low instantaneous friction coefficient, excellent wear amount and small braking noise during braking.

[0005] The present application solves the technical problem by the following technical scheme: the present application first provides a resin-based friction material with stable instantaneous friction coefficient, which comprises the following components in mass percentage: phenolic resin 5-20wt%, rubber 5-18wt%, steel fiber 20-40wt%, aramid fiber 1-5%, flake graphite 5-10wt%, barite 5-20wt%, stannous sulfide 2-6%, white corundum 1-4%, zirconium silicate 6-10%, artificial graphite 2-8%, potassium magnesium titanate 2-8%, and the rest is composed of inevitable impurities.

[0006] The synthetic brake pad in the railway industry standard is usually composed of a binder, a reinforcing material and a friction component. The research on the brake is mostly focused on the stability of the average friction coefficient, and the stability of the instantaneous friction coefficient is not perfect. The invention controls the addition of scale graphite, potassium magnesium titanate and other abrasives within a reasonable range, so that the instantaneous friction coefficient during braking is stable.

[0007] The technical solution of the present application is that the inventor found in the research that the aramid fiber, steel fiber and other mixed materials are used as reinforcing materials, the phenolic resin, rubber and additives are dispersed in each mixed material sheet as a binder, and the potassium magnesium titanate and other abrasives are used as a friction component.

[0008] Stannous sulfide has a layered crystal structure, and the layers are combined by weak van der Waals force, which is easy to slide during friction, forming a transfer film, reducing the friction coefficient and reducing material wear. This characteristic has better oxidation stability at high temperature, which can form a lubricating film between the brake pad and the brake disc, effectively stabilize the friction coefficient of the material, and as the temperature rises, the stabilizing effect of stannous sulfide will be more obvious, and the present application preferably uses 2-6% stannous sulfide.

[0009] White corundum is a high-purity and high-hardness artificial abrasive (Mohs hardness 9.0), which is second only to diamond and silicon carbide, providing extremely strong anti-grit grinding ability, a melting point of up to 2050℃, and structural stability at high temperatures (>1000℃) with excellent heat decay resistance. It is resistant to acid and alkali corrosion and does not react with water, oil and other media, suitable for complex environments. It can improve the wear resistance of the friction material, so that the brake pad can still maintain good braking effect during long-term and high-intensity braking, effectively avoiding the problem of brake failure caused by high temperature, and the present application preferably uses 1-4% white corundum. Zirconium silicate has a Mohs hardness of about 7.5 and a melting point of up to 2550℃, and can maintain structural stability at high temperatures, resist corrosion and oxidation, and is suitable for complex working conditions (such as humid and salt spray environments). As a hard filler, it can increase the surface roughness, improve the compressive and shear strength of the matrix material through particle reinforcement effect, and effectively improve the thermal stability and wear resistance of the friction material, especially the stability of the friction coefficient under high temperature conditions, and the present application preferably uses 6-10% zirconium silicate.

[0010] Artificial graphite is made of petroleum coke / bitumen coke as raw material, which is graphitized at a high temperature of 2500-3000℃, and obtained through four steps of calcination, molding, roasting and graphitization. The order degree of the layered hexagonal crystal structure can reach more than 90%. The van der Waals force between the graphite layers is weak, and the shear strength is low (about 0.1 MPa), which can form a transfer film on the friction interface, reduce the dynamic friction coefficient, effectively reduce the friction coefficient, maintain the stability of the braking process, and has good thermal conductivity, which helps to dissipate heat during braking, reduces thermal decay, and improves the recovery performance, and the present application preferably uses 2-8% artificial graphite.

[0011] The flake graphite is a natural layered hexagonal crystal structure, and the interlayer shear strength is low (0.05-0.1 MPa), so that a continuous lubricating film can be formed on the friction interface, the dynamic friction coefficient fluctuation is reduced, the lubricating effect is achieved, and the energy consumption and surface wear of the friction material can be reduced under high temperature and high pressure conditions.

[0012] The potassium magnesium titanate has a Mohs hardness of 3.5-4, is a high-performance inorganic material, and has a layered structure that can be maintained above 1000 DEG C, has good high-temperature stability, a stable friction coefficient and reduced noise; the layered structure of the flake graphite is destroyed above 300 DEG C, so that the potassium magnesium titanate can maintain the structural stability of the friction film at high temperatures.

[0013] In a further limited technical scheme of the present application, the aforementioned resin-based friction material with stable instantaneous friction coefficient comprises: the rubber is styrene-butadiene rubber or nitrile rubber; the white corundum has a mesh number of 320-600, and the zirconium silicate has a mesh number of 325-600.

[0014] The aforementioned resin-based friction material with stable instantaneous friction coefficient comprises the following components in the following mass percentages: phenolic resin 8-10 wt%, rubber 8-15 wt%, steel wool fiber 25%-40%, aramid fiber 1-3%, flake graphite 5-9 wt%, barite 8-20 wt%, stannous sulfide 2-5%, white corundum 2-4%, zirconium silicate 6-9%, artificial graphite 3-7%, and potassium magnesium titanate 3-7%.

[0015] A preparation method of a resin-based friction material with stable instantaneous friction coefficient comprises the following steps: The raw materials are weighed and mixed according to the component ratio to obtain a uniformly mixed mixture; All the raw materials are put into a double-motion high-speed mixer at one time for mixing, the speed of the barrel is 25 r / min, the speed of the blade is 1450 r / min, the temperature of the barrel is kept at room temperature, the mixing time is 8-25 min, and a uniformly mixed mixture is obtained. The uniformly mixed mixture is sequentially subjected to mold pressing and heat treatment to obtain a resin-based synthetic brake pad with stable instantaneous friction coefficient. The purpose of heat treatment is to completely cure the binder in the friction material, so as to ensure the stability of the friction performance, especially the hot friction performance, of the product. The heating rate control and stage holding of heat treatment are because the resin-based friction material has slow heat conduction, and slow heating can prevent the product from being rapidly heated and causing blistering or deformation; the product is taken out after the furnace is cooled to below 50 DEG C, which also prevents the product from being deformed due to rapid cooling.

[0016] The preparation method of the aforementioned stable instantaneous friction coefficient resin-based friction material, the compression molding process is to put the uniformly mixed material into the compression molding mold, and the compression process is: temperature ≤ 40℃, pressure 4000N / cm 2 ~6500N / cm 2 , holding time 60-120s, to obtain a compression blank.

[0017] The preparation method of the aforementioned stable instantaneous friction coefficient resin-based friction material, the heat treatment process is to use a segmented temperature rising heat treatment on the blank obtained by the compression molding process, the first heat treatment temperature is room temperature~80℃, the temperature rising rate is 1.3℃ / min, the holding time is 12min; the second temperature is 80~110℃, the temperature rising rate is 0.4℃ / min, the holding time is 76min; the third temperature is 110~130℃, the temperature rising rate is 0.16℃ / min, the holding time is 76min; the fourth temperature is 130~150℃, the temperature rising rate is 0.16℃ / min, the holding time is 76min; the fifth temperature is 150~170℃, the temperature rising rate is 0.16℃ / min, the holding time is 76min; the sixth temperature is 170~200℃, the temperature rising rate is 0.16℃ / min, the holding time is 720min to obtain the resin-based synthetic brake pad.

[0018] A synthetic brake pad with stable instantaneous friction coefficient resin-based friction material, comprising a steel back and a resin-based friction body made of stable instantaneous friction coefficient resin-based friction material, the resin-based friction body is fixed on the steel back to form a resin-based synthetic brake pad.

[0019] Compared with the prior art, the film layer which affects the stability of the instantaneous friction coefficient is proposed, and the structure of the film layer on the friction surface is effectively controlled according to this principle. The instantaneous friction coefficient of the brake process is stably controlled, the wear is avoided during the brake process, and the noise generated during braking is significantly reduced. The wear-resistant component of the present application is composed of stannous sulfide, white corundum, zirconium silicate, artificial graphite and potassium magnesium titanate. The multi-component coordination makes the instantaneous friction coefficient stability of the friction body better. Tests show that the resin-based synthetic brake pad of the present application has stable instantaneous friction coefficient under different initial braking speeds (120km / h, 100km / h, 80km / h, 60km / h, 40km / h, etc.), and the synthetic brake pad can solve the problem of unstable instantaneous friction coefficient of ordinary brake pads. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The instantaneous friction coefficient curve of the former 120km / h A-type vehicle is improved.

[0021] Figure 2 The instantaneous friction coefficient curve of the former 120km / h B-type vehicle is improved.

[0022] Figure 3 Instantaneous friction coefficient plot for Example 1 composition brake pad for 120 km / h A car.

[0023] Figure 4 Instantaneous friction coefficient plot for Example 1 composition brake pad for 120 km / h B car.

[0024] Figure 5 Instantaneous friction coefficient plot for Example 2 composition brake pad for 120 km / h A car.

[0025] Figure 6 Instantaneous friction coefficient plot for Example 2 composition brake pad for 120 km / h B car.

[0026] Figure 7 Comparison of brake noise for the improved and Example 1, Example 2.

[0027] Figure 8 Friction surface topography for the improved.

[0028] Figure 9 Friction surface topography for Example 1. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0030] The resin-based friction material with stable instantaneous friction coefficient in the embodiment comprises phenolic resin, butadiene-acrylonitrile rubber, steel fiber, aramid fiber, flaky graphite, barite, and functional mixture.

[0031] The resin-based synthetic brake pad disclosed in the embodiment comprises a steel back and a resin-based friction body with stable instantaneous friction coefficient, and the friction body is fixed on the steel back. The material and specific shape of the steel back can be determined according to actual use requirements, and the connection relationship between the steel back and the friction body is fixedly connected by using a bonding means. The steel back is manufactured by using a steel plate with a nominal thickness not less than 1.5 mm; the yield strength of the steel plate is not less than 235 MPa, and the tensile strength is not less than 370 MPa.

[0032] The preparation method of the resin-based synthetic brake pad in the embodiment is as follows: S1, the raw materials are weighed and mixed according to the component ratio to obtain a uniformly mixed mixture; specifically, all raw materials are put into a double-movement high-speed mixer at one time for mixing, the barrel rotation speed is 25 r / min, the blade rotation speed is 1450 r / min, the barrel temperature is kept at room temperature, the mixing time is 8-25 min, and a uniformly mixed mixture is obtained.

[0033] S2, the mixture is sequentially subjected to molding and heat treatment to obtain a resin-based synthetic brake pad.

[0034] Step S2 specifically includes: S21, pressing The steel back and the mixture are added to the mold cavity for molding to obtain a pressed blank; wherein the pressing pressure is 4000 N / cm 2 ~6500 N / cm 2 , the molding temperature is 50±10℃, the holding time is 60-120s, and the pressed blank is obtained.

[0035] S22, heat treatment The heat treatment process adopts a stepwise heating heat treatment in an electric heating air drying oven to ensure that the surface and the inside of the brake pad can be fully and uniformly cured; the specific control parameters of the heat treatment process are: the first heat treatment temperature is room temperature~80℃, the heating rate is 1.2℃ / min, the holding time is 20min; the second temperature is 80~110℃, the heating rate is 1.2℃ / min, the holding time is 25min; the third temperature is 110~130℃, the heating rate is 1.2℃ / min, the holding time is 20min; the fourth temperature is 130~150℃, the heating rate is 0.8℃ / min, the holding time is 30min; the fifth temperature is 150~170℃, the heating rate is 0.8℃ / min, the holding time is 30min; the sixth temperature is 170~200℃, the heating rate is 0.6℃ / min, the holding time is 720min to obtain a resin-based synthetic brake pad.

[0036] The improved and unimproved formulations are shown in Table 1, with barite as the formulation ratio adjustment material, and each component is calculated in mass percentage.

[0037] Table 1

[0038] According to the "T / CAMET04004.9-2018 Urban Rail Transit Vehicle Braking System Part 9: Synthetic Brake Pad Technical Specification", the braking friction performance test is carried out, and the unimproved formula is tested for 120km / h A-type vehicle (axle load 16t) and 120km / h B-type vehicle (axle load 14t), and the instantaneous friction coefficient curve is as follows Figure 1 Figure 2It can be seen that the braking instantaneous friction coefficient stability is poor before the formula is improved, and obvious "V" shaped fluctuation is presented. The formula of the improved embodiment 1 is tested by the 120km / h A type vehicle (axle load 16t) and the 120km / h B type vehicle (axle load 14t), and the instantaneous friction coefficient curve is as shown in Figure 3 Figure 4 It can be seen that the braking instantaneous friction coefficient stability is good, and the friction coefficient almost presents a straight line state from the initial braking speed to the braking stop. The formula of the improved embodiment 2 is tested by the 120km / h A type vehicle (axle load 16t) and the 120km / h B type vehicle (axle load 14t), and the instantaneous friction coefficient curve is as shown in Figure 5 Figure 6 It can be seen that the braking instantaneous friction coefficient stability is good. The blue curve in the figure is the dry working condition, and the red curve is the wet working condition. According to the "T / CAMET04004.9-2018 Urban Rail Transit Vehicle Braking System Part 9: Technical Specification of Synthetic Brake Pad", only the stability of the instantaneous friction coefficient in the dry working condition is examined.

[0039] The parking brake noise of the whole braking process of the improved sample and the samples of the embodiment 1 and the embodiment 2 is collected in the 23-33 braking sequence, the braking conditions of 23-33 are as shown in Table 2, and the noise data comparison is as shown in Figure 7 It can be seen that the noise of the embodiment is obviously reduced compared with that before the improvement.

[0040] Table 2

[0041] The whole process wear amount of the improved sample and the samples of the embodiment 1 and the embodiment 2 is calculated, and the wear amount test result is as shown in Table 3. It can be seen that the wear amount of the embodiment is obviously reduced compared with that before the improvement.

[0042] Table 3

[0043] The surface morphology of the improved sample and the sample of the embodiment 1 is observed under the scanning electron microscope. The improved sample is as shown in Figure 8 , and the embodiment 1 is as shown in Figure 9 It can be found that the friction film before the improvement is less and unstable, and the embodiment 1 has a larger area of stable friction film.

[0044] It will be apparent to those skilled in the art that the application is not limited to the details of the above-exemplified embodiments and that the present application can be implemented in other particular forms without departing from the spirit or essential characteristics of the present application. The embodiments should therefore be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the above description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. No limitation is intended to the scope of the claims based on any statement herein that contains the term comprise and / or other variations such as includes, has, contains, etc.

Claims

1. A stable instantaneous coefficient of friction resin-based friction material, characterized by: The resin-based friction material comprises the following components by mass percentage: phenolic resin 5-20 wt%, rubber 5-18 wt%, steel fiber 20-40 wt%, aramid fiber 1-5%, flake graphite 5-10 wt%, barite 5-20 wt%, stannous sulfide 2-6%, white corundum 1~4%, zirconium silicate 6~10%, artificial graphite 2~8%, potassium magnesium titanate 2~8%, and the rest is combined by inevitable impurities.

2. The stable, transient friction coefficient, resin-based friction material of claim 1, wherein: The rubber is styrene-butadiene rubber or nitrile-butadiene rubber.

3. The stable instantaneous coefficient of friction, resin-based friction material according to claim 1, characterized in that: The white corundum has a mesh number of 320 mesh~600 mesh, and the zirconium silicate has a mesh number of 325 mesh~600 mesh.

4. The stable, transient friction coefficient, resin-based friction material of claim 1, wherein: The resin-based friction material comprises the following components by mass percentage: phenolic resin 8-10 wt%, rubber 8-15 wt%, steel wool fiber 25%-40%, aramid fiber 1-3%, flake graphite 5-9 wt%, barite 8-20 wt%, stannous sulfide 2-5%, white corundum 2~4%, zirconium silicate 6~9%, artificial graphite 3~7%, and potassium magnesium titanate 3~7%.

5. The stable, transient friction coefficient, resin-based friction material of claim 1, wherein: The resin-based friction material comprises the following components by mass percentage: phenolic resin 8 wt%, rubber 14 wt%, steel wool fiber 36%, aramid fiber 2%, flake graphite 5 wt%, barite 8 wt%, stannous sulfide 5%, white corundum 34%, zirconium silicate 8%, artificial graphite 6%, and potassium magnesium titanate 5%.

6. The stable, transient friction coefficient, resin-based friction material of claim 1, wherein: All raw materials are put into a double-motion high-speed mixer at one time for mixing, the barrel rotation speed is 25 r / min, the blade rotation speed is 1450 r / min, the barrel temperature is kept at room temperature, and the mixing time is 8-25 min to obtain a uniformly mixed material.

7. A method of making a stable instantaneous coefficient of friction resin based friction material characterized by The method comprises the following steps: The raw materials are weighed and mixed according to the component ratio to obtain a uniformly mixed material; The uniformly mixed material is sequentially subjected to die pressing and heat treatment to obtain a resin-based synthetic brake pad with stable instantaneous friction coefficient.

8. The method of claim 7, wherein the resin-based friction material is a stable transient friction coefficient resin-based friction material. The compression molding process is to put the uniform mixture into the press mold, and the compression process is: temperature ≤ 40℃, pressure 4000N / cm 2 6500N / cm 2 , holding time 60-120s, to obtain the compression blank.

9. The method of claim 7, wherein the resin-based friction material is a stable transient friction coefficient resin-based friction material. The heat treatment process is a segmented heating heat treatment of the blank prepared by the die pressing process, the first heat treatment temperature is room temperature~80℃, the heating rate is 1.3℃ / min, the holding time is 12 min; the second temperature is 80~110℃, the heating rate is 0.4℃ / min, the holding time is 76 min; the third temperature is 110~130℃, the heating rate is 0.16℃ / min, the holding time is 76 min; the fourth temperature is 130~150℃, the heating rate is 0.16℃ / min, the holding time is 76 min; the fifth temperature is 150~170℃, the heating rate is 0.16℃ / min, the holding time is 76 min; and the sixth temperature is 170~200℃, the heating rate is 0.16℃ / min, the holding time is 720 min to obtain the resin-based synthetic brake pad.

10. A resin-based friction material synthetic brake pad having a stable instantaneous coefficient of friction, characterized by: The resin-based synthetic brake pad comprises a steel back and a resin-based friction body made of the resin-based friction material with stable instantaneous friction coefficient, and the resin-based friction body is fixed on the steel back to form the resin-based synthetic brake pad.

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