An aluminum-based composite solid brake disc for automobiles and its preparation method

Abstract

The present invention relates to an aluminum matrix composite solid brake disc for automobiles, which comprises a working part, a connecting part and a mounting part. The outer ring side of the connecting part is connected to the working part, and the inner ring side is connected to the mounting part. The brake disc is made of SiCp / A356 aluminum matrix composite by the counter-gravity casting method. Inner and outer brake surfaces are respectively arranged on the inner and outer sides of the working part. The connecting part adopts a structure with a gradually changing thickness, and the thickness gradually decreases from the working part to the mounting part. Inner or outer reinforcing ribs are arranged on the inner and outer sides of the connecting part. The present invention also provides a preparation method for the aluminum matrix composite solid 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 40%. At the same time, due to the high heat conduction and heat storage capacities of the 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 solid 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 automobile braking system mainly include two types: drum brakes and disc brakes. Among them, disc brakes are open-type, and the heat generated during the braking process can be quickly dissipated, having good braking performance, and are 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. Brake discs can be classified into solid discs (single-piece discs) and ventilated discs (double-piece discs) according to their structures. Among them, a solid disc is a brake disc without a ventilation duct between the two friction surfaces. A solid brake disc has a simple structure, is easy to manufacture, and has a low cost, but its heat dissipation performance is worse than that of a ventilated disc, and it is usually installed on the rear brakes.

[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] At present, the mainstream materials for automotive brake discs are mainly gray cast iron, and a typical grade is HT250. However, the weight of steel materials is relatively large, and the weight of a steel solid disc is even greater, which does not conform to the trend of automotive energy conservation, emission reduction and lightweighting.

[0007] At present, 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 particle, 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 particle reinforced metal matrix composites include powder metallurgy method, stir casting method, etc. The SiC particle reinforced aluminum matrix composite material prepared by the powder metallurgy method has limitations in the structural complexity or flexibility of the workpiece, and the costs of material preparation and workpiece forming are relatively high. In recent years, the stir casting method for preparing SiCp / A356 composites, that is, silicon carbide particle reinforced aluminum matrix composites, 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 the cost advantage is obvious. Selecting the SiCp / A356 aluminum matrix composite reinforced with SiC particles as the material for automotive lightweight brake discs is expected to reduce the weight of the brake discs by 30%-50%, and can also extend the service life, reduce the operating 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, the Chinese patent CN 210240379 U "A solid automotive brake disc" discloses a solid automotive brake disc, and the key point of its technical solution lies in the two-stage step structure design of the connecting wall area, which is used to reduce the vibration and noise of the brake disc and enhance the heat dissipation effect. In addition, the lightweight effect of this technical solution is not obvious.

[0010] The 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.

[0011] The Chinese patent CN 111442039 A "A lightweight wear-resistant aluminum matrix powder metallurgy composite automotive 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, and the effects of wear resistance and weight reduction are achieved simultaneously. However, relatively speaking, the powder metallurgy method has problems such as complex process method and high manufacturing cost, is not suitable for large-scale industrial production, and is difficult to generate good economic benefits. Especially in the preparation of the composite material in this patent, a certain amount of powder materials such as iron or copper is added to improve the performance of the powder metallurgy composite brake disc. Although this patent has taken surface protection treatment measures, these substances are very easy 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 the service safety.

[0012] Chinese Patent CN 109458417 A, "A Long-Life Automotive Brake Disc", discloses a long-life automotive brake disc. By setting dirt-retaining grooves on the friction surface, this brake disc solves the problem of reduced braking performance caused by wear debris. By adding heat dissipation holes at the edge of the friction body, it improves the poor heat dissipation effect. The key is to set a reciprocating point braking mechanism on one side of the brake disc to solve the problem of locking, and it does not involve technical means for lightweighting. Summary of the Invention

[0013] Under the conditions of meeting the structure and dimensions of the brake disc interface, etc., 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.

[0014] The mechanical properties of aluminum matrix composites 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.

[0015] One of the purposes of the present invention is to provide a solid aluminum matrix composite brake disc for automobiles. While meeting the interface dimensions, this brake disc realizes the lightweighting of the brake disc by adopting a new type of aluminum matrix composite and reasonable structure design. The second purpose of the present invention is to use 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.

[0016] The present invention includes two sets of technical solutions with similar inventive ideas. The first set of technical solutions is: a solid aluminum matrix composite brake disc for automobiles, including a working part, a connecting part, and a mounting part. The outer ring side of the connecting part is connected to the working part, and the inner ring side is connected to the mounting part. This brake disc is formed by the counter-gravity casting method using SiCp / A356 aluminum matrix composite. The inner and outer sides of the working part are respectively provided with an inner braking surface and an outer braking surface. The connecting part adopts a gradually transitioning thickness structure, with the thickness gradually decreasing from the working part to the mounting part, and inner strengthening ribs or outer strengthening ribs are provided on the inner and outer sides of the connecting part, or both inner strengthening ribs and outer strengthening ribs are provided on the inner and outer sides at the same time.

[0017] Furthermore, an outer circular heat dissipation groove is provided in the middle part of the outer circle of the working part.

[0018] Furthermore, there are multiple outer circular heat dissipation grooves.

[0019] Furthermore, wear limit marks are provided at the positions on both sides of the outer circle of the working part close to the inner braking surface and the outer braking surface, which are used to mark the wear state, and at the same time increase the surface area of this part and enhance the heat dissipation ability.

[0020] Furthermore, the inner reinforcing ribs and outer reinforcing ribs provided on both sides of the connecting portion are staggered in position to avoid casting hot spots and hole defects.

[0021] Furthermore, the installation portion is the installation structure of the brake disc, and fixing holes are provided thereon for fixing the brake disc on the axle or wheel hub of the vehicle.

[0022] The second set of technical solutions of the present invention is:

[0023] A preparation method of an aluminum matrix composite solid brake disc for vehicles, comprising 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 later use;

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

[0026] 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;

[0027] S4: Machine - process the casting blank obtained in step S3 to obtain an aluminum matrix composite solid brake disc for vehicles.

[0028] Optionally, in step S3, first pour the mixture of aluminum alloy and SiC obtained in step S2 into an ingot, cool it, and 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 a casting blank of the brake disc.

[0029] The beneficial effects of the present invention:

[0030] 1. The working portion of the brake disc of the present invention serves as the friction working surface of the brake disc and adopts a solid structure. On the premise of meeting the weight reduction requirements, it maximally increases the volume or weight of the brake disc, which can not only maximally ensure the stiffness of the brake disc, but also fully exert the heat storage capacity of the material, reduce the friction temperature rise of the brake disc, and ensure good braking performance.

[0031] 2. An outer - circle heat - dissipation groove is provided in the middle part of the outer circle of the working portion, which increases the heat - dissipation surface area of the disc body and reduces the temperature of the brake disc.

[0032] 3. Wear limit marks are provided on both sides of the outer circle of the working portion as required, and the wear limit marks can have various forms. The width of the wear limit marks is set according to the wear limit specified by the vehicle manufacturer to mark the wear condition of the brake disc, and at the same time increase the heat - dissipation surface area and improve the heat - dissipation capacity.

[0033] 4. The connecting part adopts a gradually changing thickness structure, with the thickness gradually decreasing from the working part to the installation part. Inner and outer reinforcing ribs can be respectively arranged on its inner and outer sides, or inner and outer reinforcing ribs can be arranged simultaneously. The reinforcing ribs are used to enhance the strength and stiffness of the connecting part, increase the heat dissipation surface area of the brake disc, improve the heat dissipation effect, reduce the temperature rise of the brake disc, improve the brake heat distribution, reduce the thermal stress, and at the same time improve the feeding effect of the brake disc blank and improve the forming quality.

[0034] 5. The inner and outer reinforcing ribs arranged on both sides of the connecting part are staggered in position to avoid casting hot spots and hole defects.

[0035] 6. The brake disc of the present invention is produced by using SiCp / A356 aluminum matrix composite material. Compared with the brake disc made of gray cast iron, it can achieve a weight reduction of more than 40%. At the same time, due to the high heat conduction capacity and heat storage capacity of this material, it can reduce the friction temperature rise of the brake disc, homogenize the temperature distribution of the brake disc, avoid the formation of large thermal stress in the brake disc, prevent crack initiation and propagation.

[0036] 7. The brake disc of the present invention is formed by an anti-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. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a longitudinal sectional view of the solid brake disc according to an embodiment of the present invention.

[0038] Figure 2 is a front view of the inner brake surface of the solid brake disc according to an embodiment of the present invention.

[0039] Figure 3 is a front view of the outer brake surface of the solid brake disc according to an embodiment of the present invention.

[0040] Figure 4 is a partial sectional schematic view of the structure of the wear limit mark of the solid brake disc according to an embodiment of the present invention.

[0041] Figure 5 is a partial sectional schematic view of the structure of the wear limit mark of the solid brake disc according to another embodiment of the present invention.

[0042] Figure 6 is a partial sectional schematic view of the structure of the wear limit mark of the solid brake disc according to another embodiment of the present invention.

[0043] Figure 7 is a partial sectional schematic view of the structure of the wear limit mark of the solid brake disc according to another embodiment of the present invention.

[0044] Figure 8It is a partial sectional view of the structure of the wear limit mark of the solid brake disc according to another embodiment of the present invention.

[0045] Figure 9 It is a counter-gravity casting process scheme according to an embodiment of the present invention.

[0046] Figure 10 Is Figure 9 The filling simulation result of the shown scheme.

[0047] Figure 11 Is Figure 9 The cooling curve simulation result of the shown scheme.

[0048] Wherein:

[0049] 1 - Working part, 11 - Inner braking surface, 12 - Outer braking surface, 13 - Outer circular heat dissipation groove, 14 - Wear limit mark, 2 - Connecting part, 21 - Inner reinforcing rib, 22 - Outer reinforcing rib, 3 - Mounting part, 31 - Fixing hole. Specific implementation mode

[0050] The following further describes the aluminum matrix composite solid brake disc for automobiles and its preparation method according to the present invention with reference to the accompanying drawings.

[0051] As Figures 1 - 3 Shown, the aluminum matrix composite solid brake disc for automobiles according to the present invention includes a working part 1, a connecting part 2 and a mounting part 3. The working part 1 is on the outermost side, the connecting part 2 is in the middle, and the mounting part 3 is on the innermost side. The outer ring side of the connecting part 2 is connected to the working part 1, and the inner ring side is connected to the mounting part 3. The brake disc is made of SiCp / A356 aluminum matrix composite material; the inner and outer sides of the working part 1 are respectively provided with an inner braking surface 11 and an outer braking surface 12; the connecting part 2 adopts a gradually changing thickness structure, and the thickness gradually decreases from the part connecting the working part 1 to the part connecting the mounting part 3; the inner and outer sides of the connecting part 2 are provided with inner reinforcing ribs 21 or outer reinforcing ribs 22, or both inner reinforcing ribs 21 and outer reinforcing ribs 22 are provided on the inner and outer sides at the same time.

[0052] The working part 1 is a solid structure without a ventilation duct design inside. The purpose of the solid brake disc is to maximize the volume or weight of the brake disc, ensure the stiffness of the brake disc, and fully utilize the heat storage capacity of the material to reduce the friction temperature rise of the brake disc.

[0053] As Figure 1 Shown, the inner and outer sides of the working part 1 are respectively the inner braking surface 11 and the outer braking surface 12, which serve as the friction working surfaces of the brake disc.

[0054] As Figure 1As shown, there is a circle of outer - circle cooling grooves 13 in the middle part of the outer circle of the working part 1. The purpose is to increase the heat - dissipation surface area of the disc body, improve the cooling effect, and reduce the temperature of the brake disc during operation. There can be multiple outer - circle cooling grooves 13, which can increase the heat - dissipation surface area of the disc body to a greater extent.

[0055] As Figure 1 and Figure 4 shown, wear - limit marks 14 are set at the positions on both sides of the outer circle of the working part 1 close to the inner brake surface 11 and the outer brake surface 12, distributed along the entire outer circle of the working part 1. The width of the wear - limit marks 14 is set according to the wear limit specified by the automobile manufacturer, used to mark the wear condition of the brake disc, and then judge whether the brake disc needs to be replaced. At the same time, it increases the heat - dissipation surface area of the brake disc and improves the heat - dissipation ability.

[0056] Optionally, the wear - limit marks 14 can also be designed in the structural forms such as Figure 5 , Figure 6 , Figure 7 , Figure 8 .

[0057] As Figure 2 , 3 shown, inner strengthening ribs 21 are provided on the inner side of the brake - disc connection part 2, with multiple numbers, for example, 20, evenly distributed along the circumference; at the same time, outer strengthening ribs 22 are provided on the outer side, with multiple numbers, for example, 20, evenly distributed along the circumference. The strengthening ribs are used to enhance the strength and stiffness of the connection part 2, increase the heat - dissipation surface area of the brake disc, improve the heat - dissipation effect, reduce the temperature rise of the brake disc, improve the brake - heat distribution, reduce the thermal stress, and at the same time improve the feeding effect of the brake - disc blank and the forming quality.

[0058] In addition, the inner strengthening ribs 21 and the outer strengthening ribs 22 are evenly staggered from each other in position, so as to avoid the casting hot - spot effect and casting defects.

[0059] As Figure 2 shown, the installation part 3 is the installation structure of the brake disc, on which fixing holes 31 are opened, used to fix the brake disc on the axle or wheel hub of the automobile. The specific structure and size of the installation part 3 are designed according to the requirements of the automobile manufacturer.

[0060] In one embodiment, a preparation method of an aluminum - matrix composite material solid brake disc for automobiles provided by the present invention includes the following steps:

[0061] 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;

[0062] S2: Add 18 - 28 wt% of SiC into the A356 aluminum alloy melt obtained in step S1 and stir evenly.

[0063] S3: Heat the mixture of the 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 then perform counter - gravity casting to obtain the rough casting of the brake disc.

[0064] S4: Machine the rough casting obtained in step S3 to obtain the solid aluminum - matrix composite brake disc for automobiles.

[0065] In an alternative embodiment, in step S3 above, first pour the mixture of the aluminum alloy and SiC obtained in step S2 into an ingot. After cooling, it is used as the raw material for 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 then perform counter - gravity casting to obtain the rough casting of the brake disc.

[0066] In the present invention, the material of the solid 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 solid brake disc of the present invention can achieve a weight reduction of more than 40%. Moreover, this aluminum - matrix composite has relatively high thermal conductivity and heat storage capacity, which can reduce the friction temperature rise of the brake disc and homogenize the temperature distribution of the brake disc, avoiding the formation of large thermal stresses in the brake disc.

[0067] The brake disc of the present invention is formed by using a metal mold and counter - gravity casting method to form the rough brake disc. The forming quality and mechanical properties of the rough brake disc are significantly better than those of gravity casting with the same material. The tensile strength obtained by metal mold and counter - gravity casting of the brake disc can be increased by more than 60% compared with the gravity casting method, thus ensuring the performance requirements for the service of the aluminum - matrix composite brake disc.

[0068] After the brake disc is cast, it is further processed by machining to meet the specified technical conditions.

[0069] 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 for the friction braking performance of automobiles. The following are the results of analyzing, verifying and testing the solid aluminum - matrix composite brake disc for automobiles in the embodiments of the present invention by using simulation analysis and physical test methods.

[0070] 1. Fluid simulation analysis

[0071] The simulation calculation is carried out by using fluid simulation software. Taking the continuous braking condition from 100 kph to 20 kph as the simulation condition, the characteristics of ventilation, heat storage and temperature homogenization of the brake disc structure are analyzed. The results of the fluid simulation and analysis show that the aluminum matrix composite solid brake disc of the embodiment of the present invention is beneficial to reducing the air flow velocity on the surface of the brake disc and the difference in air flow velocity at different parts, and has a significant effect on reducing the heat transfer coefficient and the difference in heat transfer coefficient at different parts. This makes the aluminum matrix composite brake disc of the embodiment of the present invention have a good effect on homogenizing the temperature of the brake disc, is not easy to form large thermal stress, can avoid the occurrence of thermal cracking, can effectively prevent the initiation and propagation of cracks, and prolongs the service life of the brake disc.

[0072] 2. Thermal capacity simulation analysis

[0073] The thermal capacity simulation calculation is carried out by using finite element software. According to the relevant requirements of the automotive brake disc test, the thermal capacity simulation calculation conditions are set, and the temperature and structural strength of the SiCp / A356 aluminum matrix composite solid brake disc are analyzed and checked. The simulation calculation results are summarized in Table 1 and Table 2. The results of the finite element thermal capacity simulation analysis show that under the set conditions, the aluminum matrix composite solid brake disc of the embodiment 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 conditions.

[0074] Table 1 Summary of the weight and the highest temperature of the simulation conditions of the brake disc design of the embodiment of the present invention

[0075]

[0076] Table 2 Summary of the stress simulation calculation of the brake disc of the embodiment of the present invention

[0077]

[0078] 3. Forming process simulation analysis

[0079] The simulation of the counter-gravity casting process of the metal mold and resin sand core of the aluminum matrix composite solid brake disc of the embodiment of the present invention is carried out by using solidification simulation software, and the filling, solidification process and casting quality are analyzed and evaluated. Figure 9 For the optimized forming process plan, where point A1 is the outer edge part of the brake disc, point A2 is the inner edge part of the brake disc, point A3 is the ingate part, point A4 is the runner part, and point A5 is the riser pipe part. The results of the forming process simulation analysis carried out by the present invention using Procast solidification simulation software show that by using Figure 9 the counter-gravity casting process shown can obtain Figure 10 the stable filling effect shown, and can effectively reduce the risk of defects such as porosity and slag inclusion generated during the filling process; Figure 11The solidification cooling curves of each part from A1 to A5. According to the principle of progressive 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 11 The cooling curves of Figure 11 show that the designed counter - gravity casting process can achieve a good progressive solidification mode. That is, during the cooling and solidification process, the cooling time from the riser A5 to the runner A4 and then to the ingate A3 gradually shortens in sequence, and the solidification sequence is reasonable. A good feeding channel can be established, which can implement solidification feeding for the inner and outer edges of the brake disc, and obtain a sound brake disc casting blank without shrinkage holes.

[0080] Through the designed casting process, the filling process of the aluminum - matrix composite solid brake disc in the embodiment of the present invention is stable, a good progressive solidification mode can be established, which can effectively reduce porosity and slag inclusion defects and achieve a good feeding effect, and a SiCp / A356 aluminum - matrix composite solid brake disc with excellent forming quality can be obtained.

[0081] 4. Mechanical properties

[0082] After heat treatment, the mechanical properties such as strength and hardness of the SiCp / A356 aluminum - matrix composite specimens formed by permanent - mold and counter - gravity casting method are tested. 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 permanent - mold and counter - gravity casting method is increased by about 60% compared with the ordinary gravity casting method.

[0083] Table 3 Properties of the aluminum - matrix composite in the embodiment of the present invention

[0084] Forming method Tensile strength at normal temperature / MPa Hardness / HBS Gravity casting Approximately 170 Approximately 80 Metal mold, counter - gravity ≥280 ≥110

[0085] 5. Physical and friction - wear properties

[0086] The test results show that the specific heat capacity of the aluminum - matrix composite in this embodiment at room temperature ≥ 856 J / (kg·K), and the thermal conductivity at room temperature ≥ 143 W / (m·K).

[0087] The friction test results between the aluminum - matrix composite ventilated brake disc and the synthetic brake pad show that under dry and wet conditions, the repeatability and stability of the static friction coefficient are good, and the average static friction coefficient is 0.42 - 0.48. Under dry friction conditions, the average friction coefficient 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.

[0088] In addition, the nominal weight of the aluminum - matrix composite solid brake disc in the embodiment of the present invention is 5.59 kg. Compared with the typical HT250 gray 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 40%, and the lightweight effect is significant.

[0089] Optionally, for the aluminum matrix composite brake disc for automobiles involved in the present invention, the casting mold can also adopt a hardened sand mold, such as a resin sand mold.

[0090] The ventilation and heat dissipation capacity, temperature homogenization capacity, thermal load capacity, and structural strength of the solid brake disc made of aluminum matrix composite for automobiles of the present invention all have good performances, meeting the performance requirements under the service conditions, and the casting quality is excellent. Compared with the typical ventilated brake disc made of HT250 gray cast iron with the same specifications, the weight is reduced by more than 40%. Compared with other composite brake discs, it has an obvious cost advantage. The solid brake disc made of SiCp / A356 aluminum matrix composite of the present invention can be popularized 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, and is especially suitable for the brake discs of new energy vehicles.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not 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 by the scope of the claims of the present invention.

Claims

1. A solid brake disc made of aluminum matrix composite material for automobiles, comprising a working part (1), a connecting part (2) and a mounting part (3), wherein the outer ring side of the connecting part (2) is connected to the working part (1), and the inner ring side is connected to the mounting part (3); characterized in that: The brake disc is formed by the counter-gravity casting method using SiCp / A356 aluminum matrix composite material; the inner and outer sides of the working part (1) are respectively provided with an inner braking surface (11) and an outer braking surface (12); the connecting part (2) adopts a gradually changing thickness structure, and the thickness gradually decreases from the working part (1) to the mounting part (3), and the inner and outer sides of the connecting part (2) are simultaneously provided with an inner reinforcing rib (21) and an outer reinforcing rib (22); There is an annular groove formed by the outer surface of the connecting part (2) between the outer braking surface (12) and the mounting part (3), and the outer reinforcing rib (22) is arranged in the annular groove; The inner reinforcing rib (21) and the outer reinforcing rib (22) arranged on both sides of the connecting part (2) are staggered in position to avoid forming casting hot spots and hole defects.

2. The solid brake disc made of aluminum matrix composite material for automobiles according to claim 1, characterized in that: An outer circular heat dissipation groove (13) is arranged in the middle of the outer circle of the working part (1).

3. The solid brake disc made of aluminum matrix composite material for automobiles according to claim 2, characterized in that: There are multiple outer circular heat dissipation grooves (13).

4. The solid brake disc made of aluminum matrix composite material for automobiles according to claim 1, characterized in that: Wear limit marks (14) are arranged at the positions on both sides of the outer circle of the working part (1) close to the inner braking surface (11) and the outer braking surface (12), which are used to mark the wear state, and at the same time increase the surface area of this part and enhance the heat dissipation capacity.

5. The solid brake disc made of aluminum matrix composite material for automobiles according to claim 1, characterized in that: The mounting part (3) is the mounting structure of the brake disc, and fixing holes (31) are opened thereon for fixing the brake disc on the axle or wheel hub of the vehicle.

6. A preparation method of the solid brake disc made of aluminum matrix composite material for automobiles according to any one of claims 1-5, characterized in that: It includes the following steps: S1: Heat the A356 aluminum alloy in a crucible to 680 - 750 °C, refine and degas it, then cool it in the furnace to 575 - 650 °C, and keep it warm under the protection of nitrogen or argon or vacuum for standby; S2: Add 18 - 28 wt% of SiC to 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 the casting blank of the brake disc; S4: Machine the casting blank obtained in step S3 to obtain a solid brake disc made of aluminum matrix composite material for automobiles.

7. The preparation method of the solid brake disc made of aluminum matrix composite material for automobiles according to claim 6, characterized in that: In step S3, the mixture of aluminum alloy and SiC obtained in step S2 is first cast into an ingot, and after cooling, it is used as the raw material of the aluminum matrix composite brake disc. When producing the brake disc, the ingot is heated to 680 - 750 °C under the protection of nitrogen or argon or vacuum, and counter-gravity casting is performed to obtain the casting blank of the brake disc.

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