An aluminum matrix composite ventilated brake disc for automobiles and its preparation method

Abstract

The present invention relates to an aluminum matrix composite ventilated brake disc for automobiles. The brake disc is made of SiCp / A356 aluminum matrix composite by means of counter-gravity casting, and includes a first working disc (10), a second working disc (20), a connecting rib (30), a mounting portion (40) and an arc-shaped connecting portion (50). The first working disc and the second working disc are fixedly connected by the connecting rib. The inner braking surface (11) of the first working disc is arranged in parallel with the outer braking surface (21) of the second working disc. The mounting portion is fixedly connected to the second working disc through the arc-shaped connecting portion. The present invention also provides a preparation method for the aluminum matrix composite ventilated brake disc for automobiles. Compared with the brake disc made of gray cast iron, the brake disc of the present invention can achieve a weight reduction of more than 50%. At the same time, due to the high heat conduction capacity and heat storage capacity of this material, the friction temperature rise of the brake disc can be reduced, and the temperature distribution of the brake disc can be made uniform, avoiding the formation of large thermal stresses in the brake disc and preventing the initiation and propagation of cracks.

Description

Technical Field

[0001] The present invention belongs to the technical field related to automotive brake discs, and particularly relates to a lightweight and long-life ventilated brake disc for automobiles made of aluminum matrix composite material and a preparation method thereof. Background Art

[0002] The braking system of an automobile is very important for driving safety. The function of the braking system is to decelerate and stop a moving automobile. The working principle of the braking system is to convert the kinetic energy of the automobile into heat energy through friction.

[0003] The brakes of an automotive braking system mainly include drum brakes and disc brakes. Among them, the disc brake is an open type, and the heat generated during the braking process can be quickly dissipated, having good braking performance, and is now widely used in automobiles.

[0004] The brake disc of a disc brake is a disc-shaped component with an end plane as the friction working surface. The brake disc can be classified into a solid disc (single-piece disc) and a ventilated disc (double-piece disc) according to its structure. Among them, the ventilated disc is a brake disc with ventilation channels between two friction surfaces. When the automobile is running, air convection occurs at the air duct to achieve the purpose of heat dissipation, which can prevent the brake disc from overheating, reduce heat attenuation and extend the service life, and provide better braking performance. The channel design inside the ventilated disc includes straight channels, curved channels, and pillar-type channels, etc.

[0005] The reduction of the unsprung mass of an automobile makes the most significant contribution to vehicle lightweighting, energy conservation and emission reduction, and is also beneficial to improving the handling performance of the vehicle. The brake disc is one of the core components that can effectively reduce the vehicle weight. Therefore, it is necessary to develop lightweight brake discs for automobiles.

[0006] Currently, the mainstream material for automotive brake discs is gray cast iron, and a typical grade is HT250. However, the weight of steel materials is relatively large, which does not conform to the trend of automotive energy conservation, emission reduction and lightweighting.

[0007] Currently, there are mainly two types of materials that can be used as lightweight materials for brake discs: one is C / C composite material or C / C-SiC composite material; the other is particulate, whisker or fiber-reinforced metal matrix composite material. Both materials have good lightweight characteristics. However, the main problems of C / C-SiC materials are complex manufacturing processes and high costs, and further improvement is needed in terms of preparation and forming. The preparation methods of particulate-reinforced metal matrix composites include powder metallurgy method, stir casting method, etc. The SiC particulate-reinforced aluminum matrix composite material prepared by the powder metallurgy method has limitations in the structural complexity or flexibility of the parts, and the costs of material preparation and part forming are relatively high. In recent years, the stir casting method for preparing SiCp / A356 composites, that is, silicon carbide particulate-reinforced aluminum matrix composite material, has developed rapidly.

[0008] The SiCp / A356 aluminum matrix composite has the advantages of high specific strength and specific stiffness, good thermal conductivity, high heat capacity, and good wear resistance. Compared with the C / C-SiC composite material, its material preparation and forming process are relatively simple, and it has obvious cost advantages. Selecting the SiCp / A356 aluminum matrix composite reinforced with SiC particles as the material for the lightweight automotive brake disc is expected to reduce the weight of the brake disc by 30%-50%, and can also extend the service life, reduce the operation cost, improve the safety and reliability, and achieve noise-free green braking, which is especially suitable for the brake discs of new energy vehicles. Of course, compared with traditional steel materials, the SiCp / A356 aluminum matrix composite also has problems such as low melting point, large expansion coefficient, and poor liquid fluidity, which result in its inability to withstand high friction braking temperatures and large thermal stresses. In addition, when using casting forming, it is also necessary to consider designing a good sequential solidification process.

[0009] After searching the existing technologies, Chinese Patent CN 209067715 U "An automotive brake disc" presents a duct design that spirally distributes along the circumference of the working part, which can improve the ventilation efficiency, reduce the temperature of the brake disc, and at the same time reduce the weight by reducing the thickness of the disc body to achieve lightweight. Several problems existing in this technical solution include: the weight reduction effect achieved by reducing the thickness of the disc body is limited, and it is not conducive to giving full play to the heat storage capacity of the material; the spiral heat dissipation duct design makes the air flow velocity and heat transfer coefficient vary greatly at different parts of the brake disc, resulting in large temperature differences and poor temperature uniformity at different parts of the brake disc, which is likely to form large thermal stresses and lead to thermal cracking; moreover, the dense spiral ducts are not easy to be cast and formed and are difficult to clean.

[0010] Chinese Patent CN 207034033 U "A ventilated automotive brake disc" discloses an automotive brake disc with a structural design of inner ring ventilation blocks, middle ring ventilation blocks, and outer ring ventilation blocks. The ventilation blocks are used to improve the heat dissipation effect and reduce the temperature of the brake disc. The ventilation block design of this technical solution is very distinctive, but it does not propose a lightweight solution.

[0011] Chinese Patent CN 210397521 U "A lightweight automotive brake disc" focuses on the cleaning component and the heat dissipation component. The cleaning component is used to clean the mud stains in real time to keep the brake disc always in normal heat dissipation, and the heat dissipation component is used to improve the heat dissipation effect of the brake disc. This technical solution involves many components and has a complex structure, which is not conducive to popularization and use.

[0012] Chinese Patent CN 105525153 A, "A silicon carbide particle-reinforced aluminum matrix composite brake disc", discloses a silicon carbide particle-reinforced aluminum matrix composite and its preparation method, and also provides a brake disc for rail transit vehicles manufactured based on the composite material. This technical solution does not involve brake discs for automobiles and cannot be directly used for automobile brake discs with small sizes and different braking conditions.

[0013] Chinese Patent CN 111442039 A, "A lightweight and wear-resistant aluminum matrix powder metallurgy composite automobile brake disc and its preparation method", discloses a brake disc composed of an aluminum matrix structural material disc body and a wear-resistant aluminum matrix composite friction surface, as well as the preparation method of the material. This material is prepared by the powder metallurgy principle, achieving the effects of wear resistance and weight reduction at the same time. However, relatively speaking, the powder metallurgy method has problems such as complex process methods and high manufacturing costs, is not suitable for large-scale industrial production, and is difficult to generate good economic benefits. In particular, this patent adds a certain amount of powder materials such as iron or copper in the preparation of the composite material to improve the performance of the powder metallurgy composite brake disc. Although this patent takes surface protection treatment measures, these substances are very likely to form primary batteries with aluminum powder or aluminum phase during service, generate electrochemical corrosion, reduce the service life of the brake disc, and affect service safety.

[0014] Based on this, the present invention is specifically proposed. Summary of the Invention

[0015] Under the conditions of meeting the structure and dimensions such as the interface of the automobile brake disc, design the structure of the aluminum matrix composite brake disc so that the heat capacity (braking temperature rise and thermal stress) of the brake disc under service conditions meets the service requirements.

[0016] The mechanical properties of the aluminum matrix composite are lower than those of traditional steel materials and the forming difficulty is greater. It is necessary to adopt more advanced forming methods and reasonable structure designs to improve the forming quality and mechanical properties of the aluminum matrix composite brake disc, reduce the braking temperature rise, and reduce the braking thermal stress.

[0017] One of the purposes of the present invention is to provide a ventilated aluminum matrix composite brake disc for automobiles. While meeting the interface dimensions, the brake disc realizes lightweight by adopting a new type of aluminum matrix composite material and reasonable structure design; the second purpose of the present invention is to adopt the counter-gravity forming method and reasonable forming process design to greatly improve the forming quality and mechanical properties of the brake disc compared with traditional gravity casting, and at the same time meet the requirements of service conditions.

[0018] The present invention includes two sets of technical solutions with similar inventive concepts. The first set of technical solutions is as follows: An aluminum matrix composite ventilated brake disc for an automobile, which is formed by counter-gravity casting using SiCp / A356 aluminum matrix composite, and includes a first working disc, a second working disc, a connecting rib, a mounting portion, and an arc-shaped connecting portion. The first working disc and the second working disc are fixedly connected by the connecting rib. The inner braking surface of the first working disc is arranged parallel to the outer braking surface of the second working disc. The mounting portion is fixedly connected to the second working disc through the arc-shaped connecting portion.

[0019] Further, the connecting rib has a structure of a plate shape, a column shape, or a combination of a plate and a column. Among them, the plate-shaped structure is in a straight or curved shape, and its cross-sectional plate thickness is not less than 6 mm; the column-shaped structure is in the shape of a cylinder, an elliptical cylinder, a prism, or a special-shaped structure, and its minimum diameter or inscribed circle diameter of the cross-section is not less than

[0020] Further, wear limit marks are provided at the positions near the braking surface of the outer circles of the first working disc and the second working disc to mark the wear state and enhance the heat dissipation capacity at the same time.

[0021] Further, the cylindrical connecting ribs are arranged along the tangential direction of the inner diameter circle of the friction working surface of the brake disc, serving as a strut-type ventilation duct structure of the brake disc. A total of 20 tangential directions are evenly divided in the whole brake disc, and 4 connecting ribs are arranged in each tangential direction. There are 80 connecting ribs in the whole brake disc.

[0022] Further, the mounting portion is the mounting structure of the brake disc, and fixing holes are provided thereon for fixing the brake disc on the axle or wheel hub of the automobile.

[0023] The second set of technical solutions of the present invention is as follows: A preparation method for an aluminum matrix composite ventilated brake disc for an automobile, which is characterized by including the following steps:

[0024] S1: Heat A356 aluminum alloy in a crucible to 680 - 750 °C, refine and degas it, then cool it down to 575 - 650 °C with the furnace, and keep it warm under the protection of nitrogen, argon, or vacuum for standby;

[0025] S2: Add 18 - 28 wt% of SiC to the A356 aluminum alloy melt obtained in step S1, and stir evenly;

[0026] S3: Heat the mixture of the aluminum alloy and SiC obtained in step S2 to 680 - 750 °C, and perform counter-gravity casting to obtain a casting blank of the brake disc;

[0027] S4: Machine the casting blank obtained in step S3 to obtain an aluminum matrix composite ventilated brake disc for an automobile.

[0028] Optionally, in step S3, the mixture of aluminum alloy and SiC obtained in step S2 is first poured into an ingot, and after cooling, it is used as the raw material for the aluminum matrix composite brake disc. When producing the brake disc, the ingot is heated to 680 - 750 °C under the protection of nitrogen, argon or vacuum, and then subjected to counter-gravity casting to obtain the rough casting of the brake disc.

[0029] Advantages of the present invention:

[0030] 1. The aluminum matrix composite ventilated brake disc of the present invention has excellent performance in terms of ventilation and heat dissipation capacity, temperature uniformity capacity, thermal load capacity, and structural strength, meeting the performance requirements under service conditions. Moreover, the casting quality is excellent. Compared with the typical ventilated brake disc made of HT250 gray cast iron of the same specification, the weight is reduced by more than 50%. Compared with other composite brake discs, it has an obvious cost advantage.

[0031] 2. The SiCp / A356 aluminum matrix composite ventilated brake disc of the present invention can be promoted as a lightweight brake disc for automobiles, and is expected to achieve the goal of reducing the weight of the brake disc by 30% - 50%. It can also extend the service life, reduce the operation cost, improve the safety and reliability, and achieve noise-free green braking, especially suitable for the brake discs of new energy vehicles.

[0032] 3. Due to the high thermal conductivity and heat storage capacity of the SiCp / A356 aluminum matrix composite, the brake disc of the present invention can reduce the friction temperature rise of the brake disc, and uniformize the temperature distribution of the brake disc, avoiding the formation of large thermal stresses in the brake disc and preventing the initiation and propagation of cracks.

[0033] 4. The brake disc of the present invention is formed by the counter-gravity casting method. The mold can be a hardened sand mold or a metal mold. The integral casting of the brake disc can ensure its overall stiffness. Description of the drawings

[0034] Figure 1 is a schematic structural diagram of the ventilated brake disc of an embodiment of the present invention, where Figure 1 (a) is the outer braking surface of the brake disc, Figure 1 (b) is the inner braking surface of the brake disc.

[0035] Figure 2 is a side view of the ventilated brake disc of an embodiment of the present invention.

[0036] Figure 3 is Figure 2 the longitudinal sectional view of.

[0037] Figure 4 is the half-sectional view of the ventilated brake disc of an embodiment of the present invention.

[0038] Figure 5It is a transverse sectional view of a ventilated brake disc according to an embodiment of the present invention, and the connecting ribs are of a cylindrical structure.

[0039] Figure 6 It is a transverse sectional view of a ventilated brake disc according to another embodiment of the present invention, and the connecting ribs are of a curved plate-like structure with a curved arc.

[0040] Figure 7 It is a transverse sectional view of a ventilated brake disc according to another embodiment of the present invention, and the connecting ribs are of a structure combining a linear plate shape and a cylindrical shape.

[0041] Figure 8 It is an enlarged schematic view of a partial structure of the wear limit mark of a solid brake disc according to an embodiment of the present invention.

[0042] Figure 9 It is an enlarged schematic view of a partial structure of the wear limit mark of a solid brake disc according to another embodiment of the present invention.

[0043] Figure 10 It is an enlarged schematic view of a partial structure of the wear limit mark of a solid brake disc according to another embodiment of the present invention.

[0044] Figure 11 It is an enlarged schematic view of a partial structure of the wear limit mark of a solid brake disc according to another embodiment of the present invention.

[0045] Figure 12 It is an enlarged schematic view of a partial structure of the wear limit mark of a solid brake disc according to another embodiment of the present invention.

[0046] Figure 13 It is an anti-gravity casting process scheme according to an embodiment of the present invention.

[0047] Figure 14 is Figure 13 The filling simulation result of the shown scheme.

[0048] Figure 15 is Figure 13 The cooling curve simulation result of the shown scheme.

[0049] Wherein:

[0050] 10 - The first working disc, 11 - The inner braking surface, 12 - The ventilation surface, 20 - The second working disc, 21 - The outer braking surface, 211 - The wear limit mark, 22 - The ventilation surface, 30 - The connecting ribs, 40 - The mounting part, 41 - The fixing hole, 50 - The arc-shaped connecting part. Detailed implementation manners

[0051] The following further describes the aluminum-based composite material ventilated brake disc for automobiles and its preparation method according to the present invention with reference to the accompanying drawings.

[0052] Such as Figures 1 - 3As shown in the figure, the aluminum matrix composite ventilation brake disc for automobiles of the present invention is made of SiCp / A356 aluminum matrix composite material, and includes a first working disc 10, a second working disc 20, a connecting rib 30, a mounting part 40 and an arc-shaped connecting part 50. The first working disc 10 includes two surfaces, one is the inner braking surface 11 and the other is the ventilation surface 12. The second working disc 20 also includes two surfaces, one of which is the outer braking surface 21 and the other is the ventilation surface 22. The first working disc 10 and the second working disc 20 are fixedly connected through the connecting rib 30. The inner braking surface 11 of the first working disc 10 is arranged parallel to the outer braking surface 21 of the second working disc 20. The mounting part 40 is fixedly connected to the second working disc 20 through the arc-shaped connecting part 50.

[0053] As Figure 2 and Figure 8 shown, wear limit marks 211 are provided at the positions of the outer circles of the first working disc 10 and the second working disc 20 close to the braking surfaces, and are distributed in a whole circle along the outer circle of the working disc. The width of the wear limit marks 211 is set according to the wear limit specified by the automobile manufacturer, so as to mark the wear condition of the brake disc, and further judge whether the brake disc needs to be replaced. At the same time, the heat dissipation surface area of the brake disc is increased, and the heat dissipation capacity is improved.

[0054] Optionally, the wear limit marks 211 can also be designed into the structural forms such as Figure 9 , Figure 10 , Figure 11 , Figure 12 .

[0055] As Figures 4 - 7 shown, the connecting rib 30 can be a plate-shaped, columnar or plate-column combined structure. Among them, the plate-shaped structure is in a straight or curved shape (see Figure 6 ), and its cross-sectional plate thickness is not less than 6 mm; the columnar structure is in the shape of a cylinder, an elliptic cylinder, a prism or a special-shaped structure (see Figure 4 , Figure 5 ), and its minimum cross-sectional diameter or inscribed circle diameter is not less than As Figure 4 , Figure 5 shown, in a preferred embodiment, the cylindrical connecting ribs 30 are arranged along the tangent direction of the inner diameter circle of the friction working surface of the brake disc, serving as the strut-type ventilation duct structure of the brake disc. A total of 20 tangent directions are evenly divided on the entire brake disc, and 4 connecting ribs 30 are arranged in each tangent direction. There are a total of 80 connecting ribs 30 on the entire brake disc. The friction working surface of the brake disc here is the inner braking surface 11 and the outer braking surface 21.

[0056] As Figure 1 , Figures 4 - 7As shown, the installation part 40 is the installation structure of the brake disc, on which fixing holes 41 are provided. There are multiple fixing holes 41 for fixing the brake disc on the axle or wheel hub of the vehicle. The specific structure and dimensions of the installation part 40 are designed according to the requirements of the vehicle manufacturer.

[0057] In one embodiment, a preparation method of an aluminum matrix composite ventilated brake disc for vehicles provided by the present invention includes the following steps:

[0058] S1: Heat A356 aluminum alloy in a crucible to 680 - 750 °C. For example, 680 °C, 690 °C, 700 °C, 730 °C or 750 °C can be selected. After refining and degassing, cool it down to 650 °C with the furnace and keep it warm under the protection of nitrogen, argon or vacuum for later use;

[0059] S2: Add 18 - 28 wt% of SiC to the A356 aluminum alloy melt obtained in step S1 and stir evenly;

[0060] S3: Heat the mixture of aluminum alloy and SiC obtained in step S2 to 680 - 750 °C. For example, 680 °C, 690 °C, 700 °C, 730 °C or 750 °C can be selected, and perform counter - gravity casting to obtain the casting blank of the brake disc.

[0061] S4: Machine - process the casting blank obtained in step S3 to obtain a solid aluminum matrix composite brake disc for vehicles.

[0062] In an alternative embodiment, in step S3 above, first pour the mixture of aluminum alloy and SiC obtained in step S2 into an ingot. After cooling, use it as the raw material of the aluminum matrix composite brake disc. When producing the brake disc, heat the ingot to 680 - 750 °C under the protection of nitrogen, argon or vacuum and perform counter - gravity casting to obtain the casting blank of the brake disc.

[0063] In the present invention, the material of the ventilated brake disc is SiCp / A356 particle - reinforced aluminum matrix composite. The composite matrix uses A356 or 356Z.2 aluminum ingots, and the reinforcing phase uses SiC particles with a content of 18 - 28 wt%. Compared with the brake discs made of typical HT250 gray cast iron with the same specifications on the market, the SiCp / A356 aluminum matrix composite ventilated brake disc of the present invention can achieve a weight reduction of more than 50%. Moreover, this aluminum matrix composite has high thermal conductivity and heat storage capacity, which can reduce the friction temperature rise of the brake disc and make the temperature distribution of the brake disc uniform, avoiding the formation of large thermal stresses in the brake disc.

[0064] The present invention also provides the following embodiments.

[0065] Example 1:

[0066] The brake disc of the present invention is formed by using a metal mold and a counter-gravity casting method to form a brake disc blank. The forming quality and mechanical properties of the brake disc blank are significantly better than those of the same material formed by gravity casting. The tensile strength obtained by the counter-gravity casting of the brake disc with a metal mold can be increased by more than 60% compared with the gravity casting method, thus ensuring the performance requirements of the aluminum matrix composite brake disc during service.

[0067] After the brake disc is cast, it is further processed by machining to meet the specified technical conditions.

[0068] The mechanical properties, thermophysical properties, and friction and wear properties of the SiCp / A356 aluminum matrix composite in the embodiments of the present invention can meet the requirements of automotive friction braking performance. The following are the results of analyzing, verifying, and testing the ventilated brake disc of the SiCp / A356 aluminum matrix composite for automobiles in the embodiments of the present invention by using simulation analysis and physical test methods.

[0069] 1. Fluid simulation analysis

[0070] Using fluid simulation software to carry out simulation calculations, taking the working condition of continuous braking from 100 kph to 20 kph as the simulation working condition, and analyzing the characteristics of ventilation, heat storage, and temperature homogenization of the brake disc structure. The results of the fluid simulation analysis show that the ventilation duct structure design of the ventilated brake disc of the aluminum matrix composite in the embodiments of the present invention significantly reduces the air flow velocity and the difference in flow velocity at different parts, and the heat transfer coefficient and the difference in heat transfer coefficient at different parts are small. This enables the brake disc of the aluminum matrix composite in the embodiments of the present invention to have good ventilation and heat dissipation capabilities, a good temperature homogenization effect, and is not easy to form large thermal stresses, which can avoid the occurrence of thermal cracks, effectively prevent the initiation and propagation of cracks, and extend the service life of the brake disc.

[0071] 2. Heat capacity simulation analysis

[0072] Using finite element software to carry out heat capacity simulation calculations, setting the heat capacity simulation calculation working conditions according to the relevant requirements of automotive brake disc tests, and analyzing and checking the temperature and structural strength of the ventilated brake disc of the SiCp / A356 aluminum matrix composite. The simulation calculation results are summarized in Table 1 and Table 2. The results of the finite element heat capacity simulation analysis show that under the set working conditions, the ventilated brake disc of the aluminum matrix composite in the embodiments of the present invention has good heat dissipation and heat storage capabilities, the temperature distribution is relatively uniform, the stress is small, and the structural design of the brake disc can meet the allowable temperature requirements and strength requirements under the given working conditions.

[0073] Table 1 Summary table of the weight of the brake disc design in the embodiments of the present invention and the highest temperature of the simulation working conditions

[0074]

[0075] Table 2 Summary Table of Stress Simulation Calculation for Brake Discs in Embodiments of the Present Invention

[0076]

[0077] 3. Simulation Analysis of Forming Process

[0078] The solidification simulation software is used to simulate the counter-gravity casting process of the metal mold and resin sand core of the aluminum matrix composite ventilated brake disc in the embodiments of the present invention, and analyze and evaluate the pouring, solidification process and the quality of the brake disc casting. Figure 13 For the optimized forming process plan, where point A1 is the position of the upper disc surface of the casting, point A2 is the position of the lower disc surface of the casting, point A3 is the position of the ingate, point A4 is the position of the runner, and point A5 is the position of the riser tube. The simulation analysis results carried out by the Procast solidification simulation software in the present invention show that by using Figure 13 the counter-gravity casting process shown, a Figure 14 stable filling effect shown can be obtained, and the risk of defects such as porosity and slag inclusion generated during the filling process can be effectively reduced; Figure 15 is the solidification cooling curve of each point from A1 to A5. According to the principle of sequential solidification, the reasonable solidification sequence should be A1 - A2 - A3 - A4 - A5, that is, point A1 solidifies first, followed by point A2, point A3, point A4, and finally point A5 solidifies. Figure 15 The cooling curve shows that the counter-gravity casting process designed in the present invention can achieve a good sequential solidification mode, that is, during the solidification process, the cooling time from the riser tube A5 to the runner A4 and then to the ingate A3 gradually becomes shorter in sequence, and the solidification sequence is reasonable, which can establish a good feeding channel, and can implement solidification feeding for the lower disc body part A2 and the upper disc body part A1, and obtain a sound brake disc casting blank without shrinkage holes.

[0079] Through the designed casting process, the filling process of the aluminum matrix composite ventilated brake disc in the embodiments of the present invention is stable, a good sequential solidification mode can be established, the porosity and slag inclusion defects can be effectively reduced, and a good feeding effect can be achieved, and a SiCp / A356 aluminum matrix composite ventilated brake disc with excellent forming quality can be obtained.

[0080] 4. Mechanical Properties

[0081] After heat treatment, the mechanical properties such as strength and hardness of the SiCp / A356 aluminum matrix composite specimens formed by the metal mold and counter-gravity casting method are tested, and the test results are shown in the following table. It can be seen from Table 3 that the tensile strength of the aluminum matrix composite formed by the metal mold and counter-gravity casting method is increased by about 60% compared with the ordinary gravity casting method.

[0082] Table 3 Properties of Aluminum Matrix Composites in Embodiments of the Present Invention

[0083] Forming method Normal temperature tensile strength / MPa Hardness / HBS Gravity casting Approximately 170 Approximately 80 Metal mold, counter - gravity ≥280 ≥110

[0084] 5. Physical and friction wear properties

[0085] The test results show that the specific heat capacity of the aluminum matrix composite material in this embodiment at room temperature is ≥856 J / (kg·K), and the thermal conductivity at room temperature is ≥143 W / (m·K).

[0086] The friction test results of the aluminum matrix composite ventilated brake disc and the synthetic brake pad show that in the dry and wet states, the repeatability and stability of the static friction coefficient are good, and the average static friction coefficient is 0.42 - 0.48. The average friction coefficient under dry friction conditions is higher than 0.35. The instantaneous friction coefficient curve is smooth, and under the same braking conditions, the instantaneous friction coefficient has good repeatability and stability.

[0087] In addition, the nominal weight of the aluminum matrix composite ventilated brake disc in the embodiment of the present invention is 4.46 kg. Compared with the typical HT250 gray cast iron brake disc of the same specification in the current market, the weight of the brake disc of the present invention is reduced by more than 50%, and the lightweight effect is significant.

[0088] Embodiment 2:

[0089] Embodiment 2 is a ventilated brake disc with curved plate-shaped connecting ribs.

[0090] As Figure 6 shown, in this embodiment, the connecting rib 30 is a curved plate-shaped structure with a bending arc. One end of the plate-shaped structure connecting rib 30 extends inward to the installation part 40 and is connected to the installation part 40, and the other end extends outward to near the maximum outer diameter of the brake disc. A total of 30 plate-shaped structure connecting ribs 30 are evenly distributed along the circumference of the entire brake disc.

[0091] The simulation analysis shows that the connecting rib 30 of this embodiment has excellent air pumping ability, a large air flow velocity in the ventilation duct, a significant heat dissipation and cooling effect, and can effectively reduce the friction temperature rise.

[0092] The remaining structural features of the ventilated brake disc in Embodiment 2 are the same as those in Embodiment 1 and will not be elaborated here.

[0093] Embodiment 3:

[0094] Embodiment 3 is a ventilated brake disc combining straight plate-shaped connecting ribs and cylindrical connecting ribs.

[0095] As Figure 7As shown in the figure, in this embodiment, the connecting rib 30 is composed of three loops. The inner loop is a linear plate-like structure. One end of the plate-like structure connecting rib 30 extends inwards to the mounting portion 40 and is connected to the mounting portion 40, and the other end extends outwards to a position near the middle diameter of the brake disc body. A total of 30 plate-like structure connecting ribs 30 are evenly distributed along the circumference of the entire brake disc; the middle loop is a cylindrical structure connecting rib 30, and 30 are evenly distributed on the same circumference of the brake disc, and are staggered with the inner loop plate-like connecting ribs 30 in position; the outer loop is a cylindrical structure connecting rib 30, and 30 are evenly distributed on the same circumference of the brake disc, and are staggered with the middle loop cylindrical connecting ribs 30 in position.

[0096] The simulation analysis shows that the connecting rib 30 of this embodiment combines the advantages of Embodiment 1 and Embodiment 2 in terms of ventilation and heat dissipation effect. It has both good ventilation and heat dissipation ability to reduce the temperature of the brake disc and good ability to equalize the temperature of each part of the brake disc.

[0097] The remaining structural features of the ventilated brake disc of Embodiment 3 are the same as those of Embodiment 1 and will not be elaborated here.

[0098] Optionally, for the aluminum matrix composite brake disc for automobiles involved in the present invention, its casting mold can also adopt a hardened sand mold, such as a resin sand mold.

[0099] The ventilation and heat dissipation ability, temperature equalization ability, thermal load ability, and structural strength of the aluminum matrix composite ventilated brake disc of the present invention all have good performances, meeting the performance requirements under the use conditions, and having excellent casting quality. Compared with the typical ventilated brake disc made of HT250 gray cast iron with the same specifications, it realizes a weight reduction of more than 50%. Compared with other composite material brake discs, it has an obvious cost advantage. The SiCp / A356 aluminum matrix composite ventilated brake disc of the present invention can be promoted as an automotive lightweight brake disc, and is expected to achieve the goal of a 30% - 50% weight reduction of the brake disc. It can also extend the service life, reduce the operation cost, improve the safety and reliability, and achieve noise-free green braking, and is especially suitable for the brake discs of new energy vehicles.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A preparation method of an aluminum-based composite ventilation brake disc for an automobile, the brake disc comprising a first working disc (10), a second working disc (20), a connecting rib (30), a mounting portion (40) and an arc-shaped connecting portion (50), wherein the first working disc (10) and the second working disc (20) are fixedly connected through the connecting rib (30), the inner braking surface (11) of the first working disc (10) is arranged parallel to the outer braking surface (21) of the second working disc (20), and the mounting portion (40) is fixedly connected to the second working disc (20) through the arc-shaped connecting portion (50); characterized in that, It includes the following steps: S1: Heat the A356 aluminum alloy in a crucible to 680 - 750 °C, after refining and degassing, cool it in the furnace to 575 - 650 °C, and keep it for use under the protection of nitrogen, argon or vacuum; S2: Add 18 - 28 wt% of SiC into the A356 aluminum alloy melt obtained in step S1, and stir evenly; S3: Heat the mixture of aluminum alloy and SiC obtained in step S2 to 680 - 750 °C, and perform counter-gravity casting to obtain a casting blank of the brake disc; S4: Machine the casting blank obtained in step S3 to obtain an aluminum matrix composite ventilated brake disc for automobiles.

2. The preparation method of the aluminum matrix composite ventilation brake disc for automobiles according to claim 1, characterized in that, The connecting rib (30) is in a plate-shaped, columnar or combined plate-column structure. Among them, the plate-shaped structure is in a straight or curved shape, and its cross-sectional plate thickness is not less than 6 mm; the columnar structure is in a cylindrical, elliptical cylindrical, polygonal prism or special-shaped structure shape, and its minimum cross-sectional diameter or inscribed circle diameter is not less than φ8 mm.

3. The preparation method of the aluminum matrix composite ventilation brake disc for automobiles according to claim 1, characterized in that, Wear limit marks (211) are provided at the outer circle of the first working disc (10) and the second working disc (20) near the braking surface, which are used to mark the wear state and enhance the heat dissipation capacity at the same time.

4. The preparation method of the aluminum matrix composite ventilation brake disc for automobiles according to any one of claims 1-3, characterized in that, The cylindrical connecting ribs (30) are arranged along the tangent direction of the inner diameter circle of the friction working surface of the brake disc, serving as a pillar-type ventilation duct structure of the brake disc. There are a total of 20 tangent directions evenly divided in the whole brake disc, and 4 connecting ribs (30) are arranged in each tangent direction. There are a total of 80 connecting ribs (30) in the whole brake disc.

5. The preparation method of the aluminum matrix composite ventilation brake disc for automobiles according to any one of claims 1-3, characterized in that, The installation part (40) is the installation structure of the brake disc, and fixing holes (41) are opened thereon for fixing the brake disc on the axle or wheel hub of the automobile.

6. The preparation method of the aluminum matrix composite ventilation brake disc for automobiles according to claim 1, characterized in that, In step S3, first pour the mixture of aluminum alloy and SiC obtained in step S2 into an ingot, and use it as the raw material of the aluminum matrix composite brake disc after cooling. When producing the brake disc, heat the ingot to 680 - 750 °C under the protection of nitrogen, argon or vacuum, and perform counter-gravity casting to obtain a casting blank of the brake disc.

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