A powder metallurgy gate material, preparation method and gate.

Abstract

This application discloses a powder metallurgy brake pad material, its preparation method, and the brake pad itself. The powder metallurgy brake pad material is obtained by powder sintering and comprises the following raw materials in parts by weight: 67-70 parts electrolytic copper powder; 12-17 parts iron powder; 5-9 parts tungsten; 12-18 parts flake graphite; 7-9 parts molybdenum disulfide; 5-8 parts zirconium dioxide; 7-11 parts nano-silica; and 5-8 parts tantalum carbide. This improves the interfacial metallographic structure of the sintered body, enhances the bonding of the components within the powder metallurgy brake pad material, and provides the powder metallurgy material with resistance to deformation at high temperatures. This ensures that during high-speed train braking and rapid temperature rise of the brake pad, the components in the powder metallurgy brake pad material are tightly bonded and do not easily separate, inhibiting the thermal decay of the frictional performance of the powder metallurgy brake pad material. This guarantees excellent frictional performance and low wear of the brake pad under high-speed braking.

Description

Technical Field

[0001] This application relates to braking devices for rail transit trains, and in particular to a powder metallurgy brake pad material, a preparation method, and a brake pad. Background Technology

[0002] Brake pads are part of the braking system of rail transit trains. When the train brakes, the brake pads are attached to the brake discs of the wheels and reduce the rotation speed of the wheels through friction to achieve the braking effect.

[0003] Currently, copper-based powder metallurgy materials with high mechanical strength and good thermal conductivity are mostly used as brake pad materials. Furthermore, graphite, molybdenum disulfide, zirconium dioxide, and silicon dioxide are added to the copper powder to improve the friction coefficient and enhance friction performance. However, during the manufacturing process, the kinetic energy of the wheel is converted into internal energy, causing the brake pad temperature to rise rapidly. Under the high load and high temperature of the wheel, the copper matrix experiences thermal degradation. Simultaneously, the added components such as graphite, molybdenum disulfide, zirconium dioxide, and silicon dioxide have poor wettability and weak bonding with copper, making them prone to detachment. This leads to rapid degradation of friction performance under hot conditions, limiting the continuous manufacturing time. For the overload design requirements of high-speed train braking, it is necessary to further improve the heat degradation resistance of the brake pads to meet the future research and development needs of high-speed trains. Summary of the Invention

[0004] To better suit and meet the needs of high-speed braking, powder metallurgy brake pad materials, preparation methods, and brake pads are provided.

[0005] The first inventive objective of this invention is achieved through the following technical solution:

[0006] A powder metallurgy gate material, obtained by powder sintering, comprises the following raw materials in parts by weight:

[0007] 67-70 parts of electrolytic copper powder;

[0008] 12-17 parts iron powder;

[0009] 5-9 parts tungsten;

[0010] 12-18 parts of flake-like graphite;

[0011] 7-9 parts of molybdenum disulfide;

[0012] 5-8 parts of zirconium dioxide;

[0013] 7-11 parts of nano-silica;

[0014] 5-8 parts of tantalum carbide.

[0015] By adopting the above technical solution, the tantalum carbide added to the raw materials improves the interfacial metallographic structure during the high-temperature sintering process of the raw materials and the sintering process of the tantalum carbide with other metal alloys, enhances the bonding of each component in the powder metallurgy brake pad material, and provides the powder metallurgy material with high-temperature deformation resistance. This ensures that when the brake pad temperature rises rapidly during high-speed train braking, the components in the powder metallurgy brake pad material are tightly bonded and not easily separated, inhibiting the thermal decay of the friction performance of the powder metallurgy brake pad material, thereby ensuring the excellent friction performance and low wear of the brake pad under high-speed braking.

[0016] Optional: It also includes 5-8 parts of a fluxing agent, wherein the fluxing agent is micron-sized aluminum powder.

[0017] By adopting the above technical solution, aluminum powder is used as a fluxing agent. During the sintering process, aluminum melts first and is infiltrated into the billet. The surface tension of the molten aluminum causes adjacent raw material particles to move closer together and form a eutectic under the promotion of the molten aluminum, resulting in a denser powder sintering. On the other hand, the residual aluminum is oxidized under high-temperature friction to form alumina, which promotes the formation of a friction film on the brake pad, thereby increasing the friction coefficient of the brake pad material at high speeds and reducing wear.

[0018] Optional: The iron powder is foamed iron powder.

[0019] By adopting the above technical solution, foamed iron powder can improve the friction performance of powder metallurgy brake pad materials and reduce braking noise. The second objective of this invention is achieved through the following technical solution:

[0020] A method for preparing powder metallurgy gate material includes the following steps:

[0021] S1: Weigh the raw materials according to the usage ratio and mix them evenly to obtain the mixture;

[0022] S2: Add the mixture, media, and N-β-hydroxyethylethylenediaminetriacetic acid to a ball mill and ball mill.

[0023] S3: The slurry obtained from ball milling is spray-dried to obtain powder.

[0024] S4: The powder particles are filled into the pressing mold and pressed to form a blank;

[0025] S5: Powder metallurgy brake pad material is obtained by sintering the blank;

[0026] The medium is ethanol and polyethylene glycol, with the polyethylene glycol having a relative molecular weight distribution of 1000–1200.

[0027] The mass ratio of the mixture, ethanol, and polyethylene glycol is 100:(56-65):(15-20).

[0028] By adopting the above technical solution, N-β-hydroxyethylethylenediaminetriacetic acid dissolves in ethanol during ball milling, inhibiting and dissolving metal oxides generated by high temperature and extrusion stress during ball milling, especially iron oxides carried on the surface of iron powder or foamed iron powder. This avoids loose oxides affecting the composition of spray granulation and subsequent sintering eutectic, resulting in good strength of the eutectic after cooling and a tighter bond with unmelted solid powder particles, thus providing the powder metallurgy brake pad material with resistance to thermal degradation.

[0029] Optionally, the mass ratio of the mixture to N-β-hydroxyethyl ethylenediamine triacetic acid is 100:(0.3-0.5).

[0030] By adopting the above technical solution, it is preferable that the amount of N-β-hydroxyethyl ethylenediamine triacetic acid used in this application is 0.3-0.5 wt% of the mixture.

[0031] Optional: The particle size of S3 powder is 100-220 μm.

[0032] Optionally, the green body is obtained by blending powders with different particle sizes, and the particle size distribution is as follows: 46 wt% of particles with a particle size of 210±10 μm, 32 wt% of particles with a particle size of 150±10 μm, and 22 wt% of particles with a particle size of 110±10 μm.

[0033] By adopting the above technical solution, the preform of the powder metallurgy throttle material is obtained by mixing and pressing powders of three particle sizes before sintering. This mixed combination results in faster and higher densification during sintering, leading to better resistance to thermal degradation in the powder metallurgy throttle material. The third objective of this invention is achieved through the following technical solution:

[0034] The brake pads are made from the powder metallurgy brake pad material described above.

[0035] By adopting the above technical solution, the brake pad has heat fade resistance. Even when the brake pad heats up rapidly during high-speed braking, it still maintains an excellent coefficient of friction and low wear, making it better suited for and meeting the needs of high-speed braking.

[0036] In summary, this application has at least the following beneficial effects:

[0037] 1. The addition of tantalum carbide to the raw materials improves the interfacial metallographic structure of the sintered body, enhances the bonding of the components in the powder metallurgy brake pad material, and provides the powder metallurgy material with high-temperature deformation resistance. This ensures that when the brake pad temperature rises rapidly during high-speed train braking, the components in the powder metallurgy brake pad material are tightly bonded and not easily separated, inhibiting the thermal decay of the friction performance of the powder metallurgy brake pad material, thereby ensuring the excellent friction performance and low wear of the brake pad under high-speed braking.

[0038] 2. Using an appropriate amount of aluminum powder as a fluxing agent can improve the sintering density and promote the formation of the brake pad friction film, thereby increasing the friction coefficient of the brake pad material at high speeds and reducing wear.

[0039] 3. In the preparation of powder metallurgy thimble material, the raw materials, media, and N-β-hydroxyethylethylenediaminetriacetic acid are ball-milled together to inhibit and dissolve the metal oxides generated by high temperature and extrusion stress during ball milling. This prevents the loose oxides from affecting the composition of spray granulation and subsequent sintering eutectic, so that the eutectic has good strength after cooling and is more tightly bonded to the unmelted solid powder particles, thus providing the powder metallurgy thimble material with resistance to thermal degradation.

[0040] 4. The preform of the powder metallurgy throttle material is obtained by mixing and pressing powders of three different particle sizes before sintering. The mixing and combination of these powders results in faster and higher densification during sintering, which makes the powder metallurgy throttle material more resistant to thermal degradation. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the brake pad structure.

[0042] Figure 2 This is an exploded view of the brake pads.

[0043] Figure label:

[0044] 1. Steel back; 2. Friction body; 3. Fixed shaft; 4. Snap ring. Detailed Implementation

[0045] Example 1

[0046] A powder metallurgical gate material, the raw materials of which include electrolytic copper powder, iron powder, tungsten, flake graphite, molybdenum disulfide, zirconium dioxide, nano-silica, tantalum carbide, and fluxing agent.

[0047] The electrolytic copper powder has a particle size of 8 μm; the iron powder is foamed iron powder with a particle size of 5 μm; the tungsten powder has a particle size of 4 μm; the flake graphite has a particle size of 9 μm; the molybdenum disulfide has a particle size of 2 μm; the zirconium dioxide has a particle size of 2 μm; the nano-silica has a particle size of 90 nm; the tantalum carbide has a particle size of 1 μm; and the fluxing agent is aluminum powder with a particle size of 2 μm.

[0048] The preparation method of powder metallurgy gate pad material is as follows:

[0049] S1: Take 69kg of electrolytic copper powder, 16kg of iron powder, 8.3kg of tungsten, 16.5kg of flake graphite, 8.1kg of molybdenum disulfide, 7.4kg of zirconium dioxide, 10.3kg of nano-silica, 7.2kg of tantalum carbide, and 6.5kg of fluxing agent and mix them evenly to obtain a mixture.

[0050] S2: Add the mixture, media, and N-β-hydroxyethylethylenediaminetriacetic acid to a ball mill and ball mill until the solid particle size is 17.5±2.5μm.

[0051] S3: The slurry obtained from ball milling is divided into three parts, and each part is spray dried to produce powder with a particle size of 210±10μm, powder with a particle size of 150±10μm, and powder with a particle size of 110±10μm.

[0052] S4: Mix 46wt% of powder with a particle size of 210±10μm, 32wt% of powder with a particle size of 150±10μm, and 22wt% of powder with a particle size of 110±10μm, and then fill the mixture into a pressing mold to press and shape it into a blank.

[0053] S5: After sintering the billet, powder metallurgy brake pad material is obtained at a sintering temperature of 920℃.

[0054] The medium is ethanol and polyethylene glycol, with the polyethylene glycol having a relative molecular weight distribution of 1000–1200.

[0055] The mass ratio of the mixture, ethanol, polyethylene glycol, and N-β-hydroxyethylethylenediaminetriacetic acid is 100:61:17.5:0.42.

[0056] Example 2

[0057] A powder metallurgical gate material differs from Example 1 in that the raw materials do not contain a fluxing agent. That is, the mixture in S1 is composed of electrolytic copper powder, iron powder, tungsten, flake graphite, molybdenum disulfide, zirconium dioxide, nano-silica, and tantalum carbide.

[0058] Comparative Example 1

[0059] A powder metallurgical gate material differs from Example 1 in that it does not contain tantalum carbide in the raw materials. That is, the mixture in S1 is composed of electrolytic copper powder, iron powder, tungsten, flake graphite, molybdenum disulfide, zirconium dioxide, nano-silica, and a fluxing agent.

[0060] Comparative Example 2

[0061] A powder metallurgical gate material differs from Example 1 in that it does not contain tantalum carbide and fluxing agent in the raw materials. That is, the mixture in S1 is composed of electrolytic copper powder, iron powder, tungsten, flake graphite, molybdenum disulfide, zirconium dioxide and nano silica.

[0062] Example 3

[0063] A powder metallurgical brake pad material, which differs from Example 1 in that the iron powder in the raw material is ordinary iron powder.

[0064] Example 4

[0065] A powder metallurgical guillotine material, which differs from Example 1 in that in S2, the mixture and the medium are added together to a ball mill for ball milling, and the medium is ethanol and polyethylene glycol.

[0066] Example 5

[0067] A powder metallurgical brake pad material, which differs from Example 1 in that the mass ratio of the mixture and N-β-hydroxyethyl ethylenediamine triacetic acid in S2 is 100:0.1.

[0068] Example 6

[0069] A powder metallurgical gate material, which differs from Example 1 in that the mass ratio of the mixture and N-β-hydroxyethyl ethylenediamine triacetic acid in S2 is 100:0.3.

[0070] Example 7

[0071] A powder metallurgical thimble material, which differs from Example 1 in that the mass ratio of the mixture and N-β-hydroxyethyl ethylenediamine triacetic acid in S2 is 100:0.5.

[0072] Example 8

[0073] A powder metallurgical thimble material, which differs from Example 1 in that the mass ratio of the mixture and N-β-hydroxyethyl ethylenediamine triacetic acid in S2 is 100:0.8.

[0074] Example 9

[0075] A powder metallurgical guillotine material, which differs from Example 1 in that the particle size distribution of the powder in S4 is 110±10μm.

[0076] Example 10

[0077] A powder metallurgical guillotine material, which differs from Example 1 in that the particle size distribution of the powder in S4 is 210±10μm.

[0078] Example 11

[0079] A powder metallurgical gate material, which differs from Example 1 in that the mixture in S1 contains the following ingredients: 67 kg electrolytic copper powder, 12 kg iron powder, 5 kg tungsten, 12 kg flake graphite, 7 kg molybdenum disulfide, 8 kg zirconium dioxide, 7 kg nano silicon dioxide, 5 kg tantalum carbide, and 5 kg fluxing agent.

[0080] The mass ratio of the mixture, ethanol, polyethylene glycol, and N-β-hydroxyethyl ethylenediamine triacetic acid in S2 is 100:56:15:0.3.

[0081] Example 12

[0082] A powder metallurgical gate material, which differs from Example 1 in that the mixture in S1 contains the following ingredients: 70 kg electrolytic copper powder, 17 kg iron powder, 9 kg tungsten, 18 kg flake graphite, 9 kg molybdenum disulfide, 5 kg zirconium dioxide, 11 kg nano silicon dioxide, 8 kg tantalum carbide, and 8 kg fluxing agent.

[0083] In S2, the mass ratio of the mixture, ethanol, polyethylene glycol, and N-β-hydroxyethylethylenediaminetriacetic acid is 100:65:20:0.5. The average coefficient of friction and wear at braking speeds of 80–350 km / h were tested for Examples 1-11 and Comparative Examples 1-2 according to procedure C.6 of TJ / CL307-2019 "Provisional Technical Conditions for Brake Pads of EMU Trains". The test results are shown in Table 1 below.

[0084] Note: Wear amount is the wear amount compared with the wear amount before the start of the braking procedure, as specified in C.6 of TJ / CL307-2019 "Provisional Technical Conditions for Brake Pads of EMU".

[0085] Table 1. Average friction coefficient and wear amount results for Examples 1-12 and Comparative Examples 1-2

[0086]

[0087]

[0088] Referring to Table 1, Examples 1-2 and Comparative Examples 1-2, Example 1 added tantalum carbide to the raw materials compared to Comparative Example 1, and Example 2 added tantalum carbide to the raw materials compared to Comparative Example 2. During the high-temperature sintering process of the raw materials, tantalum carbide improved the interfacial metallographic structure during the sintering process with other metal alloys, enhanced the bonding of the components in the powder metallurgy brake pad material, and provided the powder metallurgy material with high-temperature deformation resistance. This ensured that when the brake pad temperature rises rapidly during high-speed train braking, the components in the powder metallurgy brake pad material are tightly bonded and not easily separated, inhibiting the thermal decay of the friction performance of the powder metallurgy brake pad material. This ensured the excellent friction performance and low wear of the brake pad under high-speed braking. Therefore, Example 1 not only has a higher coefficient of friction than Comparative Example 1 at low speeds of 80-160 km / h and at high speeds of 300-350 km / h, but also has a lower wear than Comparative Example 1.

[0089] Similarly, Example 2 also showed a significant advantage over Comparative Example 2 in the test results.

[0090] In a further comparison of Example 1 and Example 2, Example 1 added aluminum powder as a fluxing agent compared to Example 2. During the sintering process, aluminum melts first and wets the billet. The surface tension of the molten aluminum causes adjacent raw material particles to move closer together and form a eutectic under the promotion of the molten aluminum, resulting in a denser powder sintering. On the other hand, the residual aluminum oxidizes under high-temperature friction to form alumina, which promotes the formation of a friction film on the brake pad, thereby increasing the friction coefficient of the brake pad material at high speeds and reducing wear. Therefore, the average friction coefficient of Example 1 is greater than that of Example 2 in both low-speed and high-speed stages, and the wear is less than that of Example 2.

[0091] As can be seen from Examples 1 and 3, the difference between Examples 1 and 3 is that the iron powder used in Example 1 is foamed iron powder. The average friction coefficient of the powder metallurgy brake pad material obtained in Example 1 is significantly improved compared with that in Example 3, while the wear amount is only slightly reduced. Therefore, the use of foamed iron powder in this application can improve the friction performance of the powder metallurgy brake pad material.

[0092] In Example 1, ethanol was added as a diluent and polyethylene glycol as a binder during the ball milling process of the mixed raw materials, along with N-β-hydroxyethylethylenediaminetriacetic acid (N-β-hydroxyethylethylenediaminetriacetic acid). N-β-hydroxyethylethylenediaminetriacetic acid is soluble in ethanol and inhibits and dissolves metal oxides generated during ball milling due to high temperature and extrusion stress, especially iron oxides carried on the surface of iron powder or in foamed iron powder. This prevents loose oxides from affecting the composition of the spray granulation and subsequent sintering eutectic, resulting in a eutectic with good strength after cooling and a tighter bond with unmelted solid particles, thus improving the heat fading resistance of the powder metallurgy brake pad material. A comparison of Examples 1 and 4 verifies that the average friction coefficient of Example 1 under high-speed braking is significantly better than that of Example 4, and the wear is lower than that of Example 4.

[0093] On the other hand, the addition of N-β-hydroxyethyl ethylenediamine triacetic acid (N-β-hydroxyethyl ethylenediamine triacetic acid) has a correlated effect on the accelerator and other raw material components. The amount of N-β-hydroxyethyl ethylenediamine triacetic acid affects the overall benefit of the powder metallurgy gate material, whether positive or negative. Referring to Examples 5-8, the amount of N-β-hydroxyethyl ethylenediamine triacetic acid continuously increases in Examples 5-8. Example 6 shows an increase in the average friction coefficient and a decrease in wear compared to Example 5; Example 7 shows an increase in the average friction coefficient and a decrease in wear compared to Example 6; while Example 8 shows a slight decrease in the average friction coefficient and a considerable increase in wear compared to Example 7. Therefore, in this application, the amount of N-β-hydroxyethyl ethylenediamine triacetic acid is preferably 0.3-0.5 wt% of the mixture.

[0094] Comparing Examples 1 and 9-10, it can be seen that the powder metallurgy brake pad material in Example 1 was obtained by mixing and pressing powders of three different particle sizes before sintering. Under this mixed combination, the sintering densification was faster and the degree of densification was higher, which made the powder metallurgy brake pad material more resistant to heat decay. The average friction coefficient of Example 1 during high-speed braking was greater than that of Examples 9-10, and the wear amount at the end of the process was less than that of Examples 9-10.

[0095] As can be seen from Examples 1 and 11-12, the powder metallurgy brake pad material of this application, when the raw material ratio is electrolytic copper powder, iron powder, tungsten, flake graphite, molybdenum disulfide, zirconium dioxide, nano-silica, tantalum carbide, and fluxing agent = (67-70):(12-17):(5-9):(12-18):(7-9):(5-8):(7-11):(5-8):(5-8), can achieve good heat fading resistance and is well suitable for high-speed braking requirements.

[0096] Example 13

[0097] As attached Figure 1 As shown, a brake pad includes a steel back 1 and a friction body 2 fixed to one side of the steel back 1.

[0098] The shape of friction element 2 can be determined according to the actual design specifications, and is generally hexagonal prism. The number and layout of friction elements 2 are determined according to the requirements of different train models in the actual design specifications.

[0099] As attached Figure 2 As shown, a fixed shaft 3 is fixed to the back of the friction body 2. The fixed shaft 3 passes through the steel back 1 and is engaged with a snap ring 4 to fix the friction body 2 to the steel back 1.

[0100] Friction body 2 is prepared from the powder metallurgy brake pad material in Examples 1 to 12.

[0101] The brake pads exhibit heat-resistant friction properties, maintaining an excellent coefficient of friction and low wear even when the brake pads heat up rapidly during high-speed braking, thus better meeting the demands of high-speed braking.

[0102] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of protection claimed by the present invention, they are protected by patent law.

Claims

1. A powder metallurgy gate material, characterized in that: Obtained by powder sintering, it comprises the following raw materials in parts by mass: 67-70 parts of electrolytic copper powder; 12-17 parts iron powder; 5-9 parts tungsten; 12-18 parts of flake-like graphite; 7-9 parts of molybdenum disulfide; 5-8 parts of zirconium dioxide; 7-11 parts of nano-silica; 5-8 parts of tantalum carbide; 5-8 parts of melt accelerator; The fluxing agent is micron-sized aluminum powder, and the iron powder is foamed iron powder.

2. The method for preparing powder metallurgy gate material according to claim 1, characterized in that: Includes the following steps, S1: Weigh the raw materials according to the usage ratio and mix them evenly to obtain the mixture; S2: Add the mixture, media, and N-β-hydroxyethylethylenediaminetriacetic acid to a ball mill and ball mill. S3: The slurry obtained from ball milling is spray-dried to obtain powder. S4: The powder particles are filled into the pressing mold and pressed to form a blank; S5: Powder metallurgy brake pad material is obtained by sintering the blank; The medium is ethanol and polyethylene glycol, with the polyethylene glycol having a relative molecular weight distribution of 1000~1200. The mass ratio of the mixture, ethanol, and polyethylene glycol is 100:(56~65):(15~20).

3. The method for preparing powder metallurgy gate material according to claim 2, characterized in that, The mass ratio of the mixture to N-β-hydroxyethyl ethylenediamine triacetic acid is 100:(0.3~0.5).

4. The method for preparing powder metallurgy gate material according to claim 2, characterized in that: The particle size of S3 powder is 100~220μm.

5. The method for preparing powder metallurgy gate material according to claim 2, characterized in that: The green body is obtained by blending powders with different particle sizes, and the particle size distribution is as follows: 46 wt% of particles with a particle size of 210±10 μm, 32 wt% of particles with a particle size of 150±10 μm, and 22 wt% of particles with a particle size of 110±10 μm.

6. A brake pad, characterized in that: It includes a friction body (2), which is made of the powder metallurgy brake pad material as described in claim 1.

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