Brake pad and its preparation method and application

Abstract

This invention relates to a brake pad, its preparation method, and its application. The brake pad provided by this invention comprises the following raw material components: copper powder, 52-60 parts by weight; iron powder, 7-16 parts by weight; graphite powder, 6-18 parts by weight; ferrous sulfide, 2-6 parts by weight; cobalt-based alloy, 3-8 parts by weight; silicon dioxide, 4-6 parts by weight; and diamond powder, 7-12 parts by weight. The brake pad provided by this invention incorporates diamond and a cobalt-based alloy in its raw material components. Using diamond as an abrasive effectively improves and stabilizes the coefficient of friction. Simultaneously, the cobalt-based alloy forms a continuous oxide layer of 0.1-20 μm at high temperatures. The cobalt oxide softens at high temperatures, resulting in low shear strength. Furthermore, the in-situ regeneration and friction-reducing effect of the oxide prevents the development of the seizing process and reduces wear on the friction pair, thus providing excellent lubrication performance at high temperatures.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy technology, specifically to a brake pad, its preparation method, and its application. Background Technology

[0002] Currently, high-speed train brake pads are typically made from copper-based powder metallurgy materials, which include a metal matrix (e.g., copper and iron or iron alloys), friction components (e.g., oxides and ceramic materials), and lubrication components (e.g., graphite, molybdenum disulfide). These materials are suitable for braking at speeds up to 350 km / h. However, in extreme weather conditions (e.g., freezing weather), when the wheel-rail adhesion coefficient decreases, the train needs to brake in a shorter distance. When the braking power increases rapidly, the brake pad material needs to withstand extremely high thermal loads in a short time. Currently, brake pads made from materials disclosed in the market suffer from significant friction coefficient attenuation and high wear during high-speed braking. Summary of the Invention

[0003] This invention provides a material for brake pads, a brake pad for brake pads, a method for preparing brake pads and their applications, in order to solve the problems of significant friction coefficient attenuation and large wear of brake pads when used for high-speed braking of trains in the prior art.

[0004] In a first aspect, the present invention provides a material for brake pads, comprising the following raw material components:

[0005] Copper powder, 52-60 parts by weight; Iron powder, 7-16 parts by weight; Graphite powder, 6-18 parts by weight; Ferrous sulfide, 2-6 parts by weight; Cobalt-based alloy, 3-8 parts by weight; 4-6 parts by weight of silicon dioxide; Diamond powder, 7-12 parts by weight.

[0006] In one optional embodiment, the following raw material components are included: Copper powder, 52-56 parts by weight; Iron powder, 9-11 parts by weight; Graphite powder, 6-12 parts by weight; Ferrous sulfide, 3-6 parts by weight; Cobalt-based alloy, 4-6 parts by weight; 5-6 parts by weight of silicon dioxide; Diamond powder, 11-12 parts by weight.

[0007] In one alternative embodiment, the copper powder is one or more of electrolytic copper powder, reduced copper powder, or water-atomized copper powder.

[0008] In one alternative embodiment, the cobalt-based alloy is one or more of Co-Cr, Co-Cr-Ni, Co-Cr-8%Mo, Co-Cr-8%Mo-9%Ag, and Co-Re.

[0009] In one alternative embodiment, the diamond powder is prepared by grinding diamond. Preferably, the diamond includes one or more of natural diamond and synthetic diamond; Preferably, the diamond powder has a particle size of 78μm to 250μm.

[0010] Secondly, the present invention provides a brake pad, which is prepared using the brake pad material described above.

[0011] Thirdly, the present invention also provides a method for preparing the above-mentioned brake pads, comprising the following steps: S1. Weigh each raw material component according to the above weight proportions and mix them thoroughly to obtain a mixture; S2, press the mixture obtained in step S1 into a blank; S3, the blank obtained in step S2 is hot-pressed and sintered, and then cooled to obtain the brake pad.

[0012] In one alternative embodiment, the hot pressing sintering is carried out under a protective atmosphere, which includes one or more of an inert atmosphere or a reducing atmosphere. The mixture is thoroughly mixed, and the mixing time is 10-60 minutes.

[0013] The pressure for the pressing process is 500-900 MPa, and the pressing time is 10-20 seconds.

[0014] The hot pressing sintering includes: heating the billet to 900-1000℃ and holding it at that temperature for 2-3 hours; The pressure applied during hot pressing sintering is 0.5-7 MPa; In one alternative embodiment, the inert atmosphere includes a nitrogen atmosphere; The reducing atmosphere includes a hydrogen atmosphere.

[0015] Fourthly, the present invention provides an application of the brake pad described above or the brake pad prepared by the preparation method described above in train braking.

[0016] The technical solution of this invention has the following advantages: 1. The present invention provides a brake pad comprising the following raw material components: copper powder, 52-60 parts by weight; iron powder, 7-16 parts by weight; graphite powder, 6-18 parts by weight; ferrous sulfide, 2-6 parts by weight; cobalt-based alloy, 3-8 parts by weight; silicon dioxide, 4-6 parts by weight; and diamond powder, 7-12 parts by weight.

[0017] The brake pads provided by this invention contain diamond and cobalt-based alloys in their raw material composition. Using diamond as an abrasive can effectively improve and stabilize the coefficient of friction. At the same time, the cobalt-based alloy forms a continuous oxide layer of 0.1~20μm at high temperature. The cobalt oxides (CoO, Co2O3, Co3O4) soften at high temperature and have low shear strength. The in-situ regeneration and friction-reducing effect of the oxides can prevent the development of the seizing process and reduce the wear of the friction pair. Therefore, the brake pads still have good lubrication performance when the temperature rises sharply during high-speed braking of the train. Detailed Implementation

[0018] The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.

[0019] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0020] Example 1 - Brake Plate A This embodiment provides a brake pad and its preparation method. The brake pad includes the following raw material components: electrolytic copper powder, 56 parts by weight. Iron powder, 9 parts by weight; Graphite powder, 12 parts by weight; Ferrous sulfide, 5 parts by weight; Cobalt-based alloy, 5 parts by weight; 5 parts by weight of silicon dioxide; Diamond powder, 12 parts by weight; The diamond powder has a particle size of 250 μm; The cobalt-based alloy is 57%Co-25%Cr-8%Mo-9%Ag.

[0021] The brake pads are prepared by the following method: S1. Weigh each raw material component according to the above-mentioned weight parts and mix them thoroughly to obtain a mixture; The mixing process includes placing each raw material component in a V-type mixer and mixing thoroughly for 10 minutes to obtain a mixture; S2, press the mixture obtained in step S1 into a blank; The pressing process includes filling the mixture obtained in step S1 into a mold and holding it under a pressure of 700 MPa for 20 seconds to obtain a blank. S3, the blank obtained in step S2 is hot-pressed and sintered, and then cooled to obtain the brake pad; The hot pressing sintering process includes heating the blank to 1000°C in a mixed atmosphere of nitrogen and hydrogen using a hot press, applying a pressure of 5 MPa, holding it at that temperature for 2 hours, and then cooling it to obtain the brake pad, denoted as brake pad A.

[0022] Example 2 - Brake Plate B This embodiment provides a brake pad and its preparation method. The brake pad includes the following raw material components: reduced copper powder, 52 parts by weight. Iron powder, 7 parts by weight; Graphite powder, 12 parts by weight; Ferrous sulfide, 6 parts by weight; Cobalt-based alloy, 4 parts by weight; Silicon dioxide, 6 parts by weight; Diamond powder, 12 parts by weight; The diamond powder has a particle size of 78 μm; The cobalt-based alloy is 95% Co and 4% Re.

[0023] The brake pads are prepared by the following method: S1. Weigh each raw material component according to the above-mentioned weight parts and mix them thoroughly to obtain a mixture; The mixing process includes placing each raw material component in a V-type mixer and mixing thoroughly for 10 minutes to obtain a mixture; S2, press the mixture obtained in step S1 into a blank; The pressing process includes filling the mixture obtained in step S1 into a mold and holding it under pressure of 800 MPa for 20 seconds to obtain a blank. S3, the blank obtained in step S2 is hot-pressed and sintered, and then cooled to obtain the brake pad; The hot pressing sintering process includes heating the blank to 900°C in a mixed atmosphere of nitrogen and hydrogen using a hot press, applying a pressure of 0.5 MPa, holding it at that temperature for 3 hours, and then cooling it to obtain the brake pad, denoted as brake pad B.

[0024] Example 3 This embodiment provides a brake pad and its preparation method. The brake pad includes the following raw material components: water-atomized copper powder, 60 parts by weight. Iron powder, 12 parts by weight; Graphite powder, 6 parts by weight; Ferrous sulfide, 3 parts by weight; Cobalt-based alloy, 6 parts by weight; 5 parts by weight of silicon dioxide; Diamond powder, 12 parts by weight; The diamond powder has a particle size of 250 μm; The cobalt-based alloy is 65%Co-26%Cr-8%Mo.

[0025] The brake pads are prepared by the following method: S1. Weigh each raw material component according to the above-mentioned weight parts and mix them thoroughly to obtain a mixture; The mixing process includes placing each raw material component in a V-type mixer and mixing thoroughly for 10 minutes to obtain a mixture; S2, press the mixture obtained in step S1 into a blank; The pressing process includes filling the mixture obtained in step S1 into a mold and holding it under a pressure of 900 MPa for 20 seconds to obtain a blank. S3, the blank obtained in step S2 is hot-pressed and sintered, and then cooled to obtain the brake pad; The hot pressing sintering process includes heating the blank to 900°C and applying a pressure of 7 MPa in a mixed atmosphere of nitrogen and hydrogen using a hot press, holding it at that temperature for 2 hours, and then cooling it to obtain the brake pad.

[0026] Example 4 This embodiment provides a brake pad and its preparation method. The brake pad includes the following raw material components: electrolytic copper powder, 58 parts by weight. Iron powder, 10 parts by weight; Graphite powder, 12 parts by weight; Ferrous sulfide, 6 parts by weight; Cobalt-based alloy, 6 parts by weight; Silicon dioxide, 6 parts by weight; Diamond powder, 10 parts by weight; The diamond powder has a particle size of 250 μm; The cobalt-based alloy is 71% Co and 28% Cr.

[0027] The brake pads are prepared by the following method: S1. Weigh each raw material component according to the above-mentioned weight parts and mix them thoroughly to obtain a mixture; The mixing process includes placing each raw material component in a V-type mixer and mixing thoroughly for 10 minutes to obtain a mixture; S2, press the mixture obtained in step S1 into a blank; The pressing process includes filling the mixture obtained in step S1 into a mold and holding it under a pressure of 500 MPa for 20 seconds to obtain a blank. S3, the blank obtained in step S2 is hot-pressed and sintered, and then cooled to obtain the brake pad; The hot pressing sintering process includes heating the blank to 1000°C and applying a pressure of 5 MPa in a mixed atmosphere of nitrogen and hydrogen using a hot press, holding it at that temperature for 3 hours, and then cooling it to obtain the brake pad.

[0028] Comparative Example 1 - Brake Plate C This comparative example provides a brake pad and its preparation method, wherein the brake pad comprises the following raw material components: electrolytic copper powder, 56 parts by weight; Iron powder, 9 parts by weight; Graphite powder, 12 parts by weight; Ferrous sulfide, 5 parts by weight; Cobalt-based alloy, 5 parts by weight; 5 parts by weight of silicon dioxide; Silicon carbide, 12 parts by weight; The particle size of the silicon carbide powder is 250 μm; The cobalt-based alloy is 57%Co-25%Cr-8%Mo-9%Ag.

[0029] The brake pads are prepared by the following method: S1. Weigh each raw material component according to the above-mentioned weight parts and mix them thoroughly to obtain a mixture; The mixing process includes placing each raw material component in a V-type mixer and mixing thoroughly for 10 minutes to obtain a mixture; S2, press the mixture obtained in step S1 into a blank; The pressing process includes filling the mixture obtained in step S1 into a mold and holding it under a pressure of 700 MPa for 20 seconds to obtain a blank. S3, the blank obtained in step S2 is hot-pressed and sintered, and then cooled to obtain the brake pad; The hot pressing sintering process includes heating the blank to 1000°C in a mixed atmosphere of nitrogen and hydrogen using a hot press, applying a pressure of 5 MPa, holding the temperature for 2 hours, and then cooling it to obtain the brake pad, denoted as brake pad C.

[0030] Comparative Example 2 - Brake Plate D This comparative example provides a brake pad and its preparation method, wherein the brake pad comprises the following raw material components: electrolytic copper powder, 56 parts by weight; Iron powder, 9 parts by weight; Graphite powder, 12 parts by weight; Ferrous sulfide, 5 parts by weight; Molybdenum disulfide, 5 parts by weight; 5 parts by weight of silicon dioxide; Diamond powder, 12 parts by weight.

[0031] The diamond powder has a particle size of 250 μm; The brake pads are prepared by the following method: S1. Weigh each raw material component according to the above-mentioned weight parts and mix them thoroughly to obtain a mixture; The mixing process includes placing each raw material component in a V-type mixer and mixing thoroughly for 10 minutes to obtain a mixture; S2, press the mixture obtained in step S1 into a blank; The pressing process includes filling the mixture obtained in step S1 into a mold and holding it under a pressure of 700 MPa for 20 seconds to obtain a blank. S3, the blank obtained in step S2 is hot-pressed and sintered, and then cooled to obtain the brake pad; The hot pressing sintering process includes heating the blank to 1000°C and applying a pressure of 5MPa in a mixed atmosphere of nitrogen and hydrogen using a hot press, holding it at that temperature for 2 hours, and then cooling it to obtain the brake pad, denoted as brake pad D.

[0032] Experimental Example 1 An emergency braking test was conducted on a 1:1 braking test bench with an 8.5t wheel disc at an initial speed of 350 km / h. The specific experimental parameters are shown in Table 1 below, and the friction coefficient and wear amount are shown in Table 2 below. Table 1 Experimental parameters of the simulated braking experiment

[0033] In the simulated braking experiment of the present invention, the brake pads are first braked at an initial speed of 120 km / h, and the process is repeated x times until the contact area of ​​the brake pads exceeds 85% during braking. After completing one braking experiment, the brake pads are allowed to cool to 100°C before the braking experiment is repeated. The brake pads are weighed and their mass is recorded. The brake pads were then subjected to 10 braking tests at an initial speed of 350 km / h. After each braking test, the brake pads were allowed to cool to 60°C before being tested again. The friction performance test results of the brake pads during the braking process were recorded and calculated.

[0034] The wear of the brake pads is calculated using the following formula:

[0035] In the formula: Brake pad wear per unit braking energy, expressed in cubic centimeters per megajoule (cm³). 3 / MJ); The weight of the brake pad is the result of the i-th weighing, in grams (g). This is the weight result of the brake pad in the (i+n)th weighing, in grams (g). The braking energy generated during the entire braking experiment from the i-th brake pad weighing to the (i+n)-th brake pad weighing is expressed in megajoules (MJ). The density of the brake pad friction material is expressed in grams per cubic centimeter (g / cm³). 3 ).

[0036] Table 2 Test results of friction performance of brake pad AD

[0037] As shown in Table 2, the average friction coefficient of brake pad AB during braking at 350 km / h is consistently higher than 0.310 and remains stable. The average wear during the entire 350 km / h braking process is less than 0.45 cm. 3 / MJ, by optimizing the content of each component, can further improve the friction coefficient and reduce wear. A comparison with brake pad C shows that using non-diamond abrasive significantly reduces friction performance, resulting in a braking distance greater than 6500 meters. A comparison with brake pad D shows that using molybdenum disulfide as the lubricant significantly increases wear.

[0038] This fully demonstrates that the brake pads of the present invention not only have a high coefficient of friction, but also exhibit small fluctuations in the coefficient of friction and low wear during high-speed braking, resulting in very stable friction performance that can meet the braking requirements of high-speed trains.

[0039] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A material for brake pads, characterized in that, It includes the following raw material components: Copper powder, 52-60 parts by weight; Iron powder, 7-16 parts by weight; Graphite powder, 6-18 parts by weight; Ferrous sulfide, 2-6 parts by weight; Cobalt-based alloy, 3-8 parts by weight; 4-6 parts by weight of silicon dioxide; Diamond powder, 7-12 parts by weight.

2. The material of the brake pad according to claim 1, characterized in that, Includes the following raw material components: Copper powder, 52-56 parts by weight; Iron powder, 9-11 parts by weight; Graphite powder, 6-12 parts by weight; Ferrous sulfide, 3-6 parts by weight; Cobalt-based alloy, 4-6 parts by weight; 5-6 parts by weight of silicon dioxide; Diamond powder, 11-12 parts by weight.

3. The material of the brake pad according to claim 1 or 2, characterized in that, The copper powder is one or more of electrolytic copper powder, reduced copper powder, or water-atomized copper powder.

4. The material of the brake pad according to any one of claims 1-3, characterized in that, The cobalt-based alloy is one or more of Co-Cr, Co-Cr-Ni, Co-Cr-8%Mo, Co-Cr-8%Mo-9%Ag, and Co-Re.

5. The material of the brake pad according to any one of claims 1-4, characterized in that, The diamond powder is obtained by grinding diamond; Preferably, the diamond includes one or more of natural diamond and synthetic diamond; Preferably, the diamond powder has a particle size of 78μm to 250μm.

6. A brake pad, characterized in that, It is prepared using the material of the brake pads described in any one of claims 1-5.

7. A method for preparing a brake pad according to claim 6, characterized in that, Includes the following steps: S1. Weigh each raw material component according to the above weight proportions and mix them thoroughly to obtain a mixture; S2, press the mixture obtained in step S1 into a blank; S3, the blank obtained in step S2 is hot-pressed and sintered, and then cooled to obtain the brake pad.

8. The preparation method according to claim 7, characterized in that, The hot pressing sintering is carried out under a protective atmosphere, which includes one or more of an inert atmosphere or a reducing atmosphere; And / or, the hot pressing sintering includes: heating the billet to 900-1000℃ and holding it at that temperature for 2-3 hours; And / or, the pressure applied during hot pressing sintering is 0.5-7 MPa; And / or, the pressure of the compression molding is 500-900MPa, and the pressing time is 10-20s; And / or, the thorough mixing time is 10-60 min.

9. The preparation method according to claim 8, characterized in that, The inert atmosphere includes a nitrogen atmosphere; And / or, the reducing atmosphere includes a hydrogen atmosphere.

10. The application of a brake pad as described in claim 6 or a brake pad prepared by any one of claims 7-9 in train braking.

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