A super wear-resistant automobile brake disc / plate prepared from a graphene-based composite new material

Abstract

The application relates to a super-wear-resistant automobile brake disc / plate prepared from a graphene-based composite new material and belongs to the technical field of automobile new materials. Most automobile disc brake devices are combined with gray cast iron brake discs (brake discs) and non-asbestos organic material brake pads (brake disc friction blocks), and the brake pads need to be replaced after 40,000-80,000 kilometers of driving. The graphene-based composite new material super-wear-resistant automobile brake disc / plate product with a surface hardness roughly equivalent to that of steel is prepared by using the unique performance of graphene, taking graphene powder and steel powder as main raw materials, through special processes such as powder mixing, wax mixing granulation, pressing forming, dewaxing, hot isostatic pressing and sintering. If the design and preparation are reasonable, the service life of the brake disc / plate can be almost synchronized with the service life of the vehicle, and the performance can be improved by orders of magnitude.

Description

I. Technical Field

[0001] The present invention, “A method for preparing super wear-resistant automotive brake discs / pads using graphene-based composite materials,” belongs to the field of automotive new materials technology. II. Background Technology

[0002] The braking system is a crucial component of a vehicle's structure. There are generally two types of automotive braking systems: disc brakes and drum brakes. Disc brakes work by hydraulically actuating brake pads (also known as brake disc friction blocks) to press against the brake disc (also known as the brake disc), creating friction between the brake pads and the brake disc. This friction causes the vehicle to decelerate and brake.

[0003] Currently, the materials used for brake discs and brake pads in automotive disc brake systems vary. Brake discs are mostly made of gray cast iron. To improve wear resistance or prevent squeaking, nickel or chromium is sometimes added, or high-temperature carbonization is applied. Brake pad friction materials include asbestos friction materials and non-asbestos friction materials (including organic friction materials). Early on, fibrous asbestos (3MgO·2SiO2·2H2O) was used as a friction material. However, Europe was the first to stop using fibrous asbestos friction materials after the 1980s. Non-asbestos friction materials are currently the main brake pad friction materials used, and there is no significant difference between them and semi-metallic friction materials. Non-asbestos friction materials are composed of metal fibers other than steel fibers, processed from non-ferrous metals such as copper, brass, and aluminum into fibers through cutting, vibration, or shearing methods. Most non-asbestos friction materials are organic friction materials. These consist of an organic filler material such as phenolic powder or rubber powder outside the fiber matrix. Inorganic fillers such as barium sulfate and calcium carbonate, metal powders such as copper, brass, and aluminum, and solid lubricants such as graphite and molybdenum disulfide are appropriately proportioned to form composite materials according to performance requirements. Furthermore, for lightweight and wear-resistant applications, carbon fiber reinforced materials (carbon / carbon composite materials) are used in vehicles and aircraft as composite materials and related matching materials. The matrix consists of carbon fibers and carbon graphite, impregnated with phenolic resin as a binder.

[0004] Currently, the friction materials used in automotive disc brake systems typically require replacement after 40,000 to 80,000 kilometers due to wear and tear. With the development of the automotive industry, reducing vehicle weight and ensuring the durability of wear-resistant components are key ways to enhance automotive competitiveness. III. Summary of the Invention

[0005] The purpose of this invention is to overcome the bottleneck that the combination of gray cast iron brake discs and asbestos-free materials (organic friction materials) in automotive disc brake devices is not lightweight and wear-resistant enough, in order to meet the needs of the rapid development of automotive technology and provide an automotive disc brake material that is super wear-resistant and has a long service life, so as to achieve safe, durable and economical effects.

[0006] To achieve this goal, this invention creatively develops a novel graphene-based composite material for manufacturing lightweight, super-wear-resistant automotive disc brake discs and pads. The invention's content and mechanism are as follows:

[0007] Modern science has confirmed that graphene (C) 60 Graphene (C) possesses excellent mechanical, thermal, and other physicochemical properties. Combined with its two-dimensional planar morphological structure and relatively low manufacturing cost, it offers significant advantages over gray cast iron brake discs and asbestos-free (organic friction material) brake pads in automotive disc brake systems in terms of mechanical performance, functionality, and cost control. 60 Carbon nanomaterial (C₂) is a two-dimensional layered nanomaterial composed of carbon atoms. It is also the most spherical solid carbon molecule discovered in nature to date, possessing a unique spherical shape. Its molecule consists of 60 carbon atoms, and its structure is a hollow 32-sided polyhedron composed of 12 pentagons and 20 hexagons. Each carbon atom occupies one of the 60 vertices and lies within a radius of... On the surface of a sphere (angstrom). Graphene (C 60 The molecules are held together primarily by van der Waals forces. At room temperature, they form a face-centered cubic structure.

[0008] This structure of graphene endows it with extremely high strength, toughness, wear resistance, hardness, lubricity, and thermal conductivity. Graphene is an ultralight material; its areal density is estimated to be only 0.77 mg / m³. 2 Graphene is the strongest and hardest known material. Its elastic modulus is as high as 1 TPa, and its tensile strength is 130 Pa. Graphene is 100 times stronger than steel. Its thermal conductivity is 1.5 times higher than that of diamond (2200 W / (m·K)), the highest known thermal conductivity among natural materials, more than 10 times that of copper (401 W / (m·K)), approximately 5000 W / (m·K), and 5 times higher than that of graphite (carbon) (1000 W / (m·K)). Currently, graphene materials are widely used in superconducting materials, lubricants, abrasives, and other applications.

[0009] Science and practice have proven that the quality of friction materials in automotive disc brake systems, specifically brake discs and brake pads, primarily depends on their mechanical and physical properties, such as hardness, strength, wear rate, thermal conductivity, thermal expansion, and lightweight. Higher hardness results in stronger wear resistance and a lower wear rate. Higher strength leads to greater resistance to fatigue and shear stress, and a longer service life.

[0010] This invention utilizes the performance characteristics of graphene (C60) as a material for brake discs (brake discs) and brake pads (brake disc friction blocks) in automotive disc braking systems for application research.

[0011] This invention utilizes graphene (C 60 ) has a special spherical shape and the same oily, lubricating, and soft properties as graphite. This is because in the structure where graphene molecules are condensed together, two graphene molecules (C1, C2, ...) form a single, round bead. 60 The distance between the centers of the molecular spheres is approximately It has a volume of approximately (angstrom) and relatively large pores. However, when compressed to less than 70% of its original volume, it becomes harder than diamond.

[0012] Based on this verified experimental evidence, this invention creatively uses cold isostatic pressing / hot isostatic pressing (or other pressure equipment) to press and form graphene molecules in a powder particle aggregated state, reducing the distance between the centers of the spheres from... Compress to After high-temperature (or high-temperature and high-pressure) sintering, automotive disc brake discs and brake pads with surface hardness roughly equivalent to that of steel, and which are lightweight and extremely wear-resistant are obtained.

[0013] Because graphene has significantly superior strength, hardness, and thermal conductivity compared to gray cast iron and asbestos-free (organic materials), and also possesses excellent friction and wear resistance, self-lubricating properties, and lightweight yet high-temperature and high-pressure resistance, if designed and manufactured properly, it is estimated that the weight of the brake disc and brake pad combination in automotive disc brake systems made of graphene-based composite materials will be 30-50 kg lighter than the current combination of gray cast iron brake discs and asbestos-free (organic friction materials) brake pads. Furthermore, the service life of graphene-based composite brake pads will almost be synchronized with the service life of the vehicle, resulting in an order-of-magnitude improvement in performance.

[0014] This invention uses graphene powder and steel (or aluminum / other metal) powder as the main raw materials for brake discs (brake discs) and brake pads (brake disc friction blocks) of automotive disc brake devices. Graphene is the matrix, and steel (or aluminum / other metals) is the binder (other trace elements may be added according to performance requirements). The composition ratio is: graphene powder ≥85%, steel (or aluminum / other metals) ≤15%.

[0015] Through wet milling and mixing, graphene powder particles are refined, as are steel (or aluminum / other metal) powder particles, resulting in rounded grains. At high temperatures, these particles undergo solid-liquid sintering. The steel (or aluminum / other metal) coats the surface of the graphene particles (crystals), acting as a binder phase, bonding the graphene particles (crystals) together into a spherical shape. These spherical graphene particles (crystals) and steel (or aluminum / other metal) grains exhibit superior wear resistance. Because the distance between the graphene molecules' centers is compressed, and they are densely sintered and interconnected with the steel (or aluminum / other metal), they possess extremely high hardness, strength, and wear resistance, demonstrating exceptional wear resistance under high temperature and pressure, and ensuring long-term use.

[0016] This invention creatively uses graphene (C 60 Graphene (C) powder and steel (or aluminum / other metal) powder are used as the main raw materials for brake discs and brake pads in automotive disc brake systems. Through wet milling, mixing, wax addition, spray granulation, and cold / hot isostatic pressing (or other pressure equipment) molding, graphene (C) powder is formed. 60 The distance between the centers of the molecular spheres is determined by (E) was compressed to (Å) Through special processes such as high-temperature (or high-temperature and high-pressure) sintering at around 1000-1500℃, a lightweight and super wear-resistant automotive brake disc / pad product with a surface hardness roughly equivalent to that of steel is prepared. IV. Detailed Implementation

[0017] The specific implementation method of the present invention, "A method for preparing super wear-resistant automotive brake discs / pads using graphene-based composite materials," is as follows:

[0018] (Since the equipment used to prepare graphene-based composite materials for automotive disc brake devices varies, the optimal / expected material performance indicators can be achieved by adjusting the specific preparation process parameters.)

[0019] 1. Mix and dry.

[0020] Graphene (C 60 Graphene powder and steel (or aluminum / other metal) powder are used as the main raw materials for brake discs and brake pads in automotive disc brake systems (other trace elements may be added according to performance requirements). The composition ratio is: graphene powder ≥ 85%, steel (or aluminum / other metal) powder ≤ 15%. These two powders are placed in a drum ball mill and wet-milled for 8-12 hours using steel balls and a steel-lined inner plate. The wet-milling liquid medium is industrial alcohol. Then, the mixture is vibrated and dried at approximately 100°C, the alcohol is recovered, and the mixture is sieved through a 300-mesh sieve to obtain a powder mixture of 30-40 micrometer-sized graphene powder and steel (or aluminum / other metal) powder particles.

[0021] The main purpose of this process is to uniformly mix graphene powder and steel (or aluminum / other metal) powder, and grind the powder particles of both into a uniform size and finer particles, so that the steel (or aluminum / other metal) grains are ground into round grains.

[0022] (Note: The raw materials used in this invention, such as graphene (C 60 The powders, steel (or aluminum / other metal) powders, alcohol, and paraffin wax are all supplied by other manufacturers and are not within the scope of this invention.

[0023] 2. Granulation with wax addition.

[0024] The well-mixed and dried graphene powder and steel (or aluminum / other metal) powder mixture is placed in a spiral mixer, and about 5-8% liquid paraffin is added as a molding agent. After mixing evenly, the mixture is dried by spray dryer to form spherical powder particles of about 0.2-0.5 mm.

[0025] The purpose of wax addition in this process is primarily to give the pressed automotive brake disc and brake pad semi-finished products, after the powder mixture has been molded, a certain strength so that they will not crumble during subsequent processes (such as processing or handling of the semi-finished products). The purpose of granulation is primarily to give the powder mixture a certain degree of fluidity, facilitating filling of the mold cavity and pressing.

[0026] 3. Pressing and molding.

[0027] First, based on the shape, specifications, and size of the brake disc / brake pad of the automotive disc brake system, design and manufacture the mold for pressing and molding. This should take into account the relationship between the loosely packed volume space of the powder particle mixture, including graphene powder and steel (or aluminum / other metal) powder, and the sintering shrinkage ratio.

[0028] (Note: The molds used for pressing powder mixtures are usually designed and manufactured by specialized mold designers and process departments. The scope of this invention does not cover the design and manufacture of molds for pressing.)

[0029] A mixture of wax-doped spray-granulated graphene powder and steel (or aluminum / other metal) powder is placed in a molding die and pressed into shape using a cold isostatic press (or other pressure equipment) with a capacity of approximately 50-100 tons, resulting in a semi-finished automotive brake disc / brake pad preform. During the pressing process, the powder particles undergo a certain degree of deformation, and the graphene powder particles and steel (or aluminum / other metal) powder particles are densified and compressed together.

[0030] 4. Dewaxing.

[0031] The pre-formed automotive brake disc / pad blank, which has been cold isostatically pressed (or formed by other pressure equipment), is placed in a bell-type dewaxing furnace and kept at a temperature of about 100-200℃ (the temperature before the paraffin melts and flows out but has not yet decomposed) for 4-8 hours to dewax (recover the paraffin). After cooling, the dewaxed automotive brake disc / pad blank is obtained.

[0032] 5. Hot isostatic pressing (sintering).

[0033] The dewaxed automotive brake disc / pad semi-finished blanks are placed in a 100-500 ton (or even thousands of ton) hot isostatic press (or other hot pressing equipment) and held at a high temperature of approximately 1000-1500℃ for 1-2 hours for high-temperature and high-pressure sintering. Under high temperature and pressure, the distance between the centers of the graphene molecules in the aggregated state of the powder particles is reduced from... (E) was compressed to (Å) , connections occur between particles / crystals, and graphene particles (crystals) and steel (or aluminum / other metal) grains are sintered together through a solid-liquid phase. After cooling, a new graphene-based composite material for automotive brake discs / pads is obtained, with a surface hardness roughly equivalent to that of steel (or aluminum / other metals), and is lightweight and extremely wear-resistant.

[0034] Sintering (or hot isostatic pressing sintering) is a key step in the process, primarily aimed at controlling the microstructure and properties of the product. During sintering, powder aggregates transform into crystalline aggregates, resulting in automotive brake discs / pads with specific mechanical and physical properties. Generally, under certain conditions, increasing the sintering temperature and extending the holding time (including increasing the hot isostatic pressing pressure) will increase the product's density, thereby improving its strength, hardness, and wear resistance.

[0035] 6. Finishing.

[0036] Lightweight and super wear-resistant automotive brake discs and pads made from graphene-based composite materials obtained by hot isostatic pressing (or other hot pressing equipment) can be precision-machined (milled or ground) according to the size, shape and precision requirements required for the installation (assembly) of automotive disc brake devices to obtain finished products of lightweight and super wear-resistant automotive brake discs / pads made from graphene-based composite materials.

[0037] The specific operational parameters required for the preparation processes, such as wet milling and mixing, vibration drying, wax addition, spray granulation, cold isostatic pressing (or other pressure equipment) molding, dewaxing, hot isostatic pressing (or other hot pressing equipment) sintering, etc., vary slightly depending on the equipment used (including newly introduced process equipment).

Claims

1. Using graphene powder and steel (or aluminum / other metal) powder as the main raw materials (other trace elements may be added as needed), a method of pressing and molding is used to compress the distance between the centers of graphene molecules in a powder particle aggregate state to [a specific value]. (Angle), after high temperature (or high temperature and high pressure) sintering, to obtain automotive disc brake disc and brake pad products with a hardness roughly equivalent to that of steel, and which are lightweight and super wear-resistant, as well as automotive drum brake friction pad products.