A method for manufacturing a copper-based powder metallurgical composite brake pad

Abstract

The application discloses a preparation method of a copper-based powder metallurgy composite brake pad and belongs to the technical field of brake disc preparation.The polyethylene glycol, lithium functional group and organic copper complex component in the lithium-based dispersant can improve the surface energy of metal particles, so that the metal particles can be better dispersed in a liquid; this helps to ensure that the metal particles can be uniformly dispersed in the whole working environment and is favorable for adjusting the particle size of the material; the metal particles are stabilized, so that the metal particles are prevented from being gathered into large particles again and the processing and use performances are affected; the copper-based powder metallurgy composite brake pad prepared by the application has low abrasion and good comprehensive performance, and is widely applied in the fields of high-speed trains, airplanes and the like.

Description

Technical Field

[0001] This invention relates to the field of brake disc manufacturing technology, and in particular to a method for preparing copper-based powder metallurgy composite brake pads. Background Technology

[0002] The development of brake pad materials both domestically and internationally has progressed through stages, including cast iron materials, C / C composite materials, and powder metallurgy materials. Currently, powder metallurgy brake pad materials dominate the market for high-speed train brake pads due to their superior wear resistance and thermal conductivity. Powder metallurgy brake pads are typically prepared by adding reinforcing phases to metal powders, followed by mixing, pressing, and sintering.

[0003] Powder metallurgy friction materials are multi-component pseudo-alloys composed of metallic and non-metallic elements. They have stable friction coefficients, high mechanical strength, good wear resistance and high temperature resistance, and are an environmentally friendly and safe material.

[0004] Chinese Patent CN108916277B: A method for preparing copper-based brake pad friction material, comprising the following steps: 1. Raw material preparation; 2. Mixing and granulation; 3. Cold pressing; 4. Preparing the steel backing; 5. Cold assembly; 6. Placing and loading into the furnace; 7. Hot pressing and sintering; 8. Inspection upon exiting the furnace. This invention uses coarser flake graphite in the raw materials to prevent dust contamination; the addition of composite wear-resistant components improves the overall performance of the friction material; the addition of a certain proportion of glycerol mixed solution, followed by hand kneading and stirring for granulation, ensures the uniformity and stability of each component, good fluidity, uniform density distribution of the pressed blank, and high strength of the pressed blank; the high-temperature pressure sintering process parameters guarantee both the performance requirements of the friction material and the connection strength with the steel backing; the copper-based friction material prepared by this invention has a simple process, low cost, high production efficiency, no brake noise, low thermal fade, high bonding strength between the steel backing and the friction block, and good overall performance.

[0005] Chinese Patent CN110715005B belongs to the field of high-speed rail braking systems, specifically a method for preparing a high thermal conductivity copper-based brake pad with an oriented structure. This method uses copper as the matrix, iron and its alloys as matrix reinforcing components, graphite as a lubricating component, and alumina and silicon dioxide as friction components. First, a polymer solution is premixed with graphite powder to form a liquid. Then, fibers are prepared by spinning to disperse the graphite powder. The powder is oriented using the flow of the spinning liquid. The oriented structure is then fixed by a coagulation solution containing copper salts. Subsequently, the fibers formed from the graphite powder are mixed with the copper powder matrix material, and a double-pressing and double-firing technique is used to prepare a copper-based brake pad with a high-density, high-interfacial bonding strength, and high-oriented structure. This invention improves the thermal conductivity, enhances shear strength, increases wear resistance, and stabilizes the friction coefficient of the copper-based brake pad, thereby improving its performance.

[0006] Chinese Patent CN115233019B discloses a method for preparing copper-based brake pad materials, products, and applications, relating to the field of powder metallurgy materials technology. The method includes the following steps: Step 1, preparing copper and iron into copper-iron alloy powder, and preparing copper and tin into copper-tin alloy powder; Step 2, using the copper-iron alloy powder and copper-tin alloy powder as main components, mixing them with lubricating components, friction components, and auxiliary components to obtain a mixture; Step 3, pressing the mixture into a green blank; Step 4, subjecting the green blank to gas pressure sintering to obtain a sintered copper-based brake pad. This invention solves the technical problems of poor friction coefficient stability, low friction coefficient value (less than 0.5), and poor wear resistance in existing copper-based brake pad materials, and has the advantages of being pollution-free, having a simple process flow, and low cost.

[0007] The powder metallurgy brake pads prepared by the above patents and existing technologies are mainly composed of two major systems: iron-based and copper-based. Due to their poor thermal conductivity, iron-based brake pad materials heat up quickly under high-speed friction, which can easily cause metal adhesion at high temperatures and result in poor performance stability. Copper-based brake pads have low tensile strength and high wear.

[0008] Different metal powders, due to their different specific gravities and hardness, cannot be evenly dispersed during ball milling. The fine metal particles are prone to agglomeration, which affects the performance of powder metallurgy composite brake pads. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides a method for preparing copper-based powder metallurgy composite brake pads. The composite brake pads prepared by this method have low wear and good overall performance, and can be used in high-speed trains, aircraft and other fields.

[0010] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0011] A method for preparing copper-based powder metallurgy composite brake pads, comprising the following steps:

[0012] S1: Weigh 40-60 parts by weight of ultrafine copper powder, 5-10 parts of carbonyl iron powder, 10-20 parts of copper-plated graphite, 5-10 parts of fine chromium iron powder, 1-5 parts of additives, 0.7-2.2 parts of lithium-based dispersant, and 20-30 parts of polyethylene glycol, add them to a ball mill, and mix them by ball milling.

[0013] S2: The mixed powder is cold-pressed into shape using a hydraulic press;

[0014] S3: After cold pressing, it is sent into a sintering furnace, protected by nitrogen gas, and vacuum sintered to obtain a copper-based powder metallurgy composite brake pad.

[0015] Furthermore, the additives are silicon carbide, boron nitride, and aluminum oxide.

[0016] Furthermore, the ball milling time is 2-4 hours.

[0017] Furthermore, the cold pressing pressure is 400-600 MPa, and the pressure holding time is 10-15 seconds.

[0018] Furthermore, the vacuum sintering pressure is 1-2 × 10⁻⁶. -2 Pa, sintering temperature is 900-1000℃, holding time is 1-3h.

[0019] In another aspect, the present invention provides a method for preparing the lithium-based dispersant as follows:

[0020] A1: By weight, add 100-120 parts of methacrylic acid, 30-50 parts of 4-hydroxybutyl acrylate, 12-16 parts of acrylamide, 0.03-0.5 parts of copper acrylate, 2-4 parts of benzoyl peroxide, and 600-1000 parts of deionized water to a high-pressure reactor. Purge with nitrogen to replace the air, react at 70-80℃ for 5-10 hours, filter, and dry to obtain polymer A.

[0021] A2: By weight, mix 100-120 parts of polymer A1, 600-1000 parts of dichloroethane, 30-50 parts of α,Ω-diisocyanate-based polyethylene glycol, and 2-4 parts of stannous octoate; react at 70-80℃ for 50-100 min; then add 3-8 parts of dilithium mercaptosuccinate and 3-7 parts of triethylamine, and react at 70-80℃ for 30-60 min; filter and dry to obtain a lithium-based dispersant.

[0022] The preparation mechanism of the above-mentioned lithium-based dispersant is as follows:

[0023] S1: Copolymerization of methacrylic acid, 4-hydroxybutyl acrylate, acrylamide, and copper acrylate yields polymer A containing hydroxyl groups, amino groups, and organic copper.

[0024] S2: The hydroxyl groups of polymer A are subjected to a polycondensation reaction with the isocyanate of α,Ω-diisocyanate-based polyethylene glycol to graft polyethylene glycol functional groups onto the polymer surface.

[0025] S3: The amino group of polymer A is subjected to a Michael addition reaction with the mercapto group of dilithium mercaptosuccinate to graft the dilithium functional group onto the polymer surface.

[0026] Technical effects:

[0027] The present invention provides a method for preparing copper-based powder metallurgy composite brake pads, which, compared with the prior art, has the following significant advantages:

[0028] 1. The carbonyl iron added in this invention serves as a reinforcing matrix, which can promote oxidation and facilitate the formation of the friction film. The degree of oxidation of the friction film increases from the matrix to the surface, resulting in higher tensile strength of the brake pad.

[0029] 2. The copper-plated graphite added in this invention can provide the brake pads with the most stable coefficient of friction and good friction performance;

[0030] 3. The fine ferrochrome added in this invention can stabilize the friction coefficient of the brake pads;

[0031] 4. The copper-based powder metallurgy composite brake pads prepared by this invention have low wear and good comprehensive performance, and have been widely used in high-speed trains, aircraft and other fields.

[0032] 5. The polyethylene glycol, dilithium functional group, and organic copper complex components in the lithium-based dispersant of the present invention can improve the surface energy of metal particles, enabling them to be better dispersed in liquids. This helps to ensure that metal particles can be uniformly dispersed throughout the working environment and is beneficial for adjusting the particle size of materials. It stabilizes metal particles, thereby preventing them from re-aggregating into large particles and affecting processing and performance. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the embodiments, but the present invention is not limited to the following embodiments.

[0034] Example Test Method:

[0035] 1. Tensile strength testing was performed using a KGP-300kN electronic universal testing machine;

[0036] 2. Wear and friction coefficient tests were performed using a pin-disc friction and wear testing machine.

[0037] Example 1

[0038] A method for preparing copper-based powder metallurgy composite brake pads, comprising the following steps:

[0039] S1: Weigh 40g of ultrafine copper powder, 5g of carbonyl iron powder, 10g of copper-plated graphite, 5g of fine chromium iron powder, 1g of additive, 0.7g of lithium-based dispersant, and 20g of polyethylene glycol, add them to a ball mill, and mix them by ball milling.

[0040] S2: The mixed powder is cold-pressed into shape using a hydraulic press;

[0041] S3: After cold pressing, it is sent into a sintering furnace, protected by nitrogen gas, and vacuum sintered to obtain a copper-based powder metallurgy composite brake pad.

[0042] The additive mentioned is silicon carbide.

[0043] The ball milling time is 2 hours.

[0044] The cold pressing pressure is 400 MPa, and the pressure is held for 10 seconds.

[0045] The vacuum sintering pressure is 1×10⁻⁶. -2 Pa, sintering temperature is 900℃, holding time is 1h.

[0046] The preparation method of the lithium-based dispersant is as follows:

[0047] A1: 100g of methacrylic acid, 30g of 4-hydroxybutyl acrylate, 12g of acrylamide, 0.03g of copper acrylate, 2g of benzoyl peroxide, and 600g of deionized water were placed in a high-pressure reactor. Nitrogen gas was introduced to replace the air, and the reaction was carried out at 70°C for 5 hours. The mixture was then filtered and dried to obtain polymer A.

[0048] A2: Mix 100g of polymer A, 600g of dichloroethane, 30g of α,Ω-diisocyanate-based polyethylene glycol, and 2g of stannous octoate; react at 70℃ for 50min; then add 3g of dilithium mercaptosuccinate and 3g of triethylamine, and react at 70℃ for 30min; filter and dry to obtain a lithium-based dispersant.

[0049] Example 2

[0050] A method for preparing copper-based powder metallurgy composite brake pads, comprising the following steps:

[0051] S1: Weigh 45g of ultrafine copper powder, 6g of carbonyl iron powder, 14g of copper-plated graphite, 6g of fine chromium iron powder, 2g of additives, 1g of lithium-based dispersant, and 23g of polyethylene glycol, add them to a ball mill, and mix them by ball milling.

[0052] S2: The mixed powder is cold-pressed into shape using a hydraulic press;

[0053] S3: After cold pressing, it is sent into a sintering furnace, protected by nitrogen gas, and vacuum sintered to obtain a copper-based powder metallurgy composite brake pad.

[0054] The additive mentioned is boron nitride.

[0055] The ball milling time is 3 hours.

[0056] The cold pressing pressure is 450 MPa, and the pressure holding time is 12 seconds.

[0057] The vacuum sintering pressure is 1.5 × 10⁻⁶. -2 Pa, sintering temperature is 940℃, holding time is 2h.

[0058] The preparation method of the lithium-based dispersant is as follows:

[0059] A1: 105g of methacrylic acid, 35g of 4-hydroxybutyl acrylate, 13g of acrylamide, 0.2g of copper acrylate, 3g of benzoyl peroxide, and 700g of deionized water were placed in a high-pressure reactor. Nitrogen gas was introduced to replace the air, and the reaction was carried out at 75°C for 6 hours. The mixture was then filtered and dried to obtain polymer A.

[0060] A2: Mix 5g of polymer A10, 700g of dichloroethane, 35g of α,Ω-diisocyanate-based polyethylene glycol, and 3g of stannous octoate; react at 75°C for 60min; then add 4g of dilithium mercaptosuccinate and 4g of triethylamine, and react at 75°C for 40min; filter and dry to obtain a lithium-based dispersant.

[0061] Example 3

[0062] A method for preparing copper-based powder metallurgy composite brake pads, comprising the following steps:

[0063] S1: Weigh 55g of ultrafine copper powder, 9g of carbonyl iron powder, 18g of copper-plated graphite, 9g of fine chromium iron powder, 4g of additives, 2g of lithium-based dispersant, and 8g of polyethylene glycol, add them to a ball mill, and mix them by ball milling.

[0064] S2: The mixed powder is cold-pressed into shape using a hydraulic press;

[0065] S3: After cold pressing, it is sent into a sintering furnace, protected by nitrogen gas, and vacuum sintered to obtain a copper-based powder metallurgy composite brake pad.

[0066] The additive mentioned is boron nitride.

[0067] The ball milling time is 3 hours.

[0068] The cold pressing pressure is 550 MPa, and the pressure holding time is 14 seconds.

[0069] The vacuum sintering pressure is 1.5 × 10⁻⁶.-2 Pa, sintering temperature is 980℃, holding time is 2h.

[0070] The preparation method of the lithium-based dispersant is as follows:

[0071] A1: 115g of methacrylic acid, 45g of 4-hydroxybutyl acrylate, 15g of acrylamide, 0.4g of copper acrylate, 3g of benzoyl peroxide, and 900g of deionized water were placed in a high-pressure reactor. Nitrogen gas was introduced to replace the air, and the reaction was carried out at 75°C for 9 hours. The mixture was then filtered and dried to obtain polymer A.

[0072] A2: Mix 15g of polymer A1, 900g of dichloroethane, 45g of α,Ω-diisocyanate-based polyethylene glycol, and 3g of stannous octoate; react at 75℃ for 90min; then add 7g of dilithium mercaptosuccinate and 6g of triethylamine, and react at 75℃ for 50min; filter and dry to obtain a lithium-based dispersant.

[0073] Example 4

[0074] A method for preparing copper-based powder metallurgy composite brake pads, comprising the following steps:

[0075] S1: Weigh 60g of ultrafine copper powder, 10g of carbonyl iron powder, 20g of copper-plated graphite, 10g of fine chromium iron powder, 5g of additives, 2.2g of lithium-based dispersant, and 30g of polyethylene glycol, add them to a ball mill, and mix them by ball milling.

[0076] S2: The mixed powder is cold-pressed into shape using a hydraulic press;

[0077] S3: After cold pressing, it is sent into a sintering furnace, protected by nitrogen gas, and vacuum sintered to obtain a copper-based powder metallurgy composite brake pad.

[0078] The additive mentioned is aluminum oxide.

[0079] The ball milling time is 4 hours.

[0080] The cold pressing pressure is 600 MPa, and the pressure holding time is 15 seconds.

[0081] The vacuum sintering pressure is 1×10⁻⁶. -2 Pa, sintering temperature is 1000℃, holding time is 3h.

[0082] The preparation method of the lithium-based dispersant is as follows:

[0083] A1: 120g of methacrylic acid, 50g of 4-hydroxybutyl acrylate, 16g of acrylamide, 0.5g of copper acrylate, 4g of benzoyl peroxide, and 1000g of deionized water were placed in a high-pressure reactor. Nitrogen gas was introduced to replace the air, and the reaction was carried out at 80°C for 10 hours. The mixture was then filtered and dried to obtain polymer A.

[0084] A2: 20g of polymer A1, 1000g of dichloroethane, 50g of α,Ω-diisocyanate-based polyethylene glycol, and 4g of stannous octoate were reacted at 80℃ for 100min; then 8g of dilithium mercaptosuccinate and 7g of triethylamine were added, and the mixture was reacted at 80℃ for 60min; the mixture was filtered and dried to obtain a lithium-based dispersant.

[0085] Comparative Example 1

[0086] No lithium-based dispersant was added; otherwise, it was the same as in Example 1.

[0087] Comparative Example 2

[0088] Without the addition of 4-hydroxybutyl acrylate, otherwise the same as in Example 1.

[0089] Comparative Example 3

[0090] Without adding A,Ω-diisocyanate-based polyethylene glycol, otherwise the same as in Example 1.

[0091] Example test results:

[0092]

[0093] Based on the data analysis of the above embodiments and comparative examples, the copper-based powder metallurgy composite brake pads prepared by the present invention have high tensile strength, stable friction coefficient and good friction performance.

[0094] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A method for preparing a copper-based powder metallurgy composite brake pad, comprising the following steps: S1: Weigh 40-60 parts by weight of ultrafine copper powder, 5-10 parts of carbonyl iron powder, 10-20 parts of copper-plated graphite, 5-10 parts of fine chromium iron powder, 1-5 parts of additives, 0.7-2.2 parts of lithium-based dispersant, and 20-30 parts of polyethylene glycol, add them to a ball mill, and mix them by ball milling. S2: The mixed powder is cold-pressed into shape using a hydraulic press; S3: After cold pressing, it is sent into a sintering furnace, protected by nitrogen, and vacuum sintered to obtain a copper-based powder metallurgy composite brake pad. The preparation method of the lithium-based dispersant is as follows: A1: By weight, add 100-120 parts of methacrylic acid, 30-50 parts of 4-hydroxybutyl acrylate, 12-16 parts of acrylamide, 0.03-0.5 parts of copper acrylate, 2-4 parts of benzoyl peroxide, and 600-1000 parts of deionized water to a high-pressure reactor. Purge with nitrogen to replace the air, react at 70-80℃ for 5-10 hours, filter, and dry to obtain polymer A. A2: By weight, mix 100-120 parts of polymer A1, 600-1000 parts of dichloroethane, 30-50 parts of α,Ω-diisocyanate-based polyethylene glycol, and 2-4 parts of stannous octoate; react at 70-80℃ for 50-100 min; then add 3-8 parts of dilithium mercaptosuccinate and 3-7 parts of triethylamine, and react at 70-80℃ for 30-60 min; filter and dry to obtain a lithium-based dispersant.

2. The method for preparing a copper-based powder metallurgy composite brake pad according to claim 1, characterized in that: The additives are silicon carbide, boron nitride, and aluminum oxide.

3. The method for preparing a copper-based powder metallurgy composite brake pad according to claim 1, characterized in that: The ball milling time is 2-4 hours.

4. The method for preparing a copper-based powder metallurgy composite brake pad according to claim 1, characterized in that: The cold pressing pressure is 400-600 MPa, and the pressure holding time is 10-15 seconds.

5. The method for preparing a copper-based powder metallurgy composite brake pad according to claim 1, characterized in that: The vacuum sintering pressure is 1-2×10⁻⁶. -2 Pa, sintering temperature is 900-1000℃, holding time is 1-3h.

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