A method for manufacturing automobile brake calipers based on selective laser melting additive manufacturing technology

Abstract

The present invention provides a method for manufacturing an automobile brake caliper based on a selective laser melting additive manufacturing technology. The method divides a three-dimensional digital model into structural areas, formulates an SLM process parameter strategy for the structural areas, and the SLM process parameter strategy includes adjusting laser power, scanning speed, scanning spacing, and powder layer thickness. According to the three-dimensional digital model of the brake caliper and the SLM process parameter strategy, additive powder is laid in a powder bed of an SLM device, a high-power density laser beam is used to scan the surface of the powder bed layer by layer, powder particles are selectively melted, laser energy density input is controlled, the thermophysical properties of the powder material are matched, microstructure evolution is controlled, and a gradient distribution of mechanical properties and thermal conductivity is obtained. After a layer is melted and solidified, the powder bed is lowered by a layer thickness, a new powder layer is spread, and the above process is repeated until the additive manufacturing of the brake caliper is completed. The method has the effects of lightweight, high structural strength, and good heat dissipation.

Description

Technical Field

[0001] The present invention belongs to the technical field of 3D printing, and in particular relates to a method for manufacturing an automobile brake caliper based on a selective laser melting additive manufacturing technology. Background Art

[0002] With the rapid development of the automobile industry, the performance and quality requirements of automobile parts are constantly increasing. As an important part of automobile safety, the design and manufacture of brake calipers directly affect the braking effect and safety of the vehicle. Traditional brake caliper manufacturing methods mostly use casting or forging processes. Although these processes are mature, they have certain limitations in meeting the requirements of complex shapes, lightweight designs, and the use of high-temperature resistant materials.

[0003] In recent years, additive manufacturing technology, especially selective laser melting (SLM) technology, has attracted widespread attention because it can directly manufacture complex structures based on three-dimensional digital models. SLM technology builds high-precision, complex-shaped parts by melting metal powder layer by layer, with the advantages of high design flexibility, high material utilization and short production cycle. In addition, SLM technology can also achieve in-situ composite of multiple materials, improve the mechanical properties and thermal conductivity of parts, and meet the diverse demands of the modern automotive industry for material properties.

[0004] In the manufacturing process of brake calipers, factors such as material selection, structural design, optimization of process parameters, and subsequent heat treatment and surface strengthening all have a significant impact on the performance of the final product. At present, although there have been some studies on additive manufacturing of brake calipers, there is still a lack of systematic and comprehensive methodology to achieve comprehensive optimization of their performance. Especially under the action of high-power density laser beams, how to accurately control the laser energy input to achieve microstructure optimization and gradient distribution of material properties is still a technical problem that needs to be solved urgently.

[0005] Therefore, developing a manufacturing method for automobile brake calipers based on SLM technology to achieve lightweight design, performance improvement and intelligent manufacturing process will be of great significance to improving the safety and reliability of automobile braking systems. Summary of the invention

[0006] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a method for manufacturing an automobile brake caliper based on selective laser melting additive manufacturing technology, which is mainly used to solve the shortcomings of automobile brake calipers manufactured by traditional manufacturing methods in terms of lightweight, high temperature resistance and other aspects.

[0007] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0008] The present invention provides a method for manufacturing an automobile brake caliper based on a selective laser melting additive manufacturing technology, comprising the following steps:

[0009] (1) dividing the three-dimensional digital model into structural regions and formulating a SLM process parameter strategy for the structural regions, wherein the SLM process parameter strategy includes adjusting laser power, scanning speed, scanning spacing, and powder layer thickness;

[0010] (2) According to the three-dimensional digital model of the brake caliper and the SLM process parameter strategy, the additive powder is laid in the powder bed of the SLM equipment, and the surface of the powder bed is scanned layer by layer using a high-power density laser beam to selectively melt the powder particles, control the laser energy density input, match the thermophysical properties of the powder material, control the evolution of the microstructure, and obtain a gradient distribution of mechanical properties and thermal conductivity. After a layer is melted and solidified, the powder bed is lowered by a layer thickness, and a new powder layer is spread. The above process is repeated until the additive manufacturing of the brake caliper is completed;

[0011] (3) During the forming process, the molten pool morphology and temperature field distribution are detected in real time, and the SLM process parameter strategy is dynamically optimized in combination with a machine learning algorithm;

[0012] (4) After forming, the brake caliper is heat treated and surface strengthened to release residual stress, refine grains, and prepare a gradient transition layer and a high-temperature resistant ceramic coating on the friction pair surface of the brake caliper.

[0013] In some embodiments, the additive powder includes Ti-6Al-4V titanium alloy powder, the powder particle size distribution is 2 to 50 nm, the particle morphology is spheroidized, and the loose density is not less than 50%. During the SLM forming process, the titanium alloy matrix is ​​promoted to refine the grains, introduce high-density dislocations, and induce α' martensitic phase transformation.

[0014] In some embodiments, when formulating the three-dimensional digital model of the brake caliper, the brake caliper is topologically optimized and bionic structurally designed to generate lightweight model data with complex hollow features and variable cross-sectional wall thickness, and high thermal conductivity material filling and surface heat dissipation structure are introduced as the three-dimensional solid model input for SLM molding.

[0015] In some embodiments, the topology optimization and bionic structure design include a lightweight design of a brake caliper, using a complex structure generative design method based on gradient materials and variable density topology optimization theory, dividing the structural area into a braking functional area and a non-critical functional area, generating a bionic structure model with a hollow cavity, variable cross-sectional wall thickness, and a honeycomb porous interior in the non-critical functional area, and optimizing the size and shape parameters of the topological boundary to reduce the overall weight of the brake caliper.

[0016] In some embodiments, the topology optimization and bionic structure design include the design of the heat dissipation structure of the brake caliper, which utilizes the shape freedom of the SLM technology to construct a three-dimensional cooling channel network in the braking functional area, and designs high specific surface area needle-rib and fin-shaped heat dissipation structure units on the surface of the cooling channel network, introduces graphene, carbon nanotubes or diamond particles with a thermal conductivity of not less than 400W / (m·K) at predetermined positions. High thermal conductivity materials, such as graphene, carbon nanotubes or diamond particles, construct directional heat conduction channels to accelerate heat conduction.

[0017] In some embodiments, during the molding process, the reinforcement area of ​​the brake caliper is analyzed and obtained in combination with the real-time detection data, and the reinforcement area is reinforced, and the reinforcement process includes:

[0018] The thin-walled area of ​​the brake caliper is structurally reinforced, with the wall thickness decreasing gradually from the outside to the inside, and grid-like reinforcement is used on the inner and outer surfaces to improve the deformation resistance of the thin-walled structure;

[0019] A scanning strategy is adopted for the inner cavity area of ​​the brake caliper, wherein the scanning strategy includes island area scanning or partition scanning, and the inner cavity area is divided into multiple sub-areas, each area is sequentially laser scanned and melted, and a cooling time is set between the sub-areas to reduce deformation and collapse of the inner cavity;

[0020] A multi-level tree-like support structure is used for the overhanging structure, the trunk diameter of the support structure is greater than 30% of the diameter of the overhanging structure, the branch diameter of the support structure is greater than 50% of the trunk diameter, and the support density decreases with the overhanging height.

[0021] In some embodiments, when formulating the SLM process parameter strategy for the structural area, the thermal conductivity, specific heat capacity, melting point, viscosity thermophysical parameters of the powder material, as well as the mechanical properties, surface quality and production efficiency index requirements of different structural areas of the brake caliper are combined. Through orthogonal experimental design and numerical simulation, the optimal matching combination of laser power, scanning speed, scanning spacing and powder layer thickness parameters in different areas is obtained, and a regional parameter library is established to achieve real-time monitoring, intelligent analysis and closed-loop control of the SLM forming process.

[0022] In some embodiments, a solution aging treatment is used in the heat treatment, and the SLM-molded brake caliper is placed in a vacuum or protective atmosphere heat treatment furnace, kept at 820-850° C. for 1-5 hours, and air-cooled to room temperature to release residual stress;

[0023] Shot peening is used in the surface strengthening, the shot peening medium is ceramic or metal beads, the shot peening pressure is 0.3-0.6MPa, the coverage rate reaches more than 200%, and then vibration stress relief or low temperature tempering method is used to eliminate the surface residual stress introduced by shot peening.

[0024] In some embodiments, a gradient transition layer is prepared on the friction pair surface of the brake caliper by SLM process. The thickness of the transition layer is 0.5-2 mm. The material is high temperature alloy powder and solid lubricant MoS 2 A mixture of graphite and WS2, with a lubricant volume fraction of 5 to 20%, reduces friction factor and wear;

[0025] The high temperature resistant ceramic coating is prepared on the surface of the gradient transition layer by laser cladding or plasma spraying process. The coating material is 8YSZ, Cr 2 O 3 、Al 2 O 3 The coating thickness is 100-500 μm, which improves the high temperature wear resistance.

[0026] In some embodiments, a cooling structure is prepared inside the brake caliper using the SLM process, the cooling structure comprising a bionic tree-like fractal channel and a high thermal conductivity filling material, the diameter of the fractal channel increases from the inside to the outside, the diameter of the last tributary is not greater than 1 mm, and the ratio of adjacent stage diameters is not less than 1.5; the high thermal conductivity filling material is selected from Cu, Ag, and graphene, and the filling rate is 5 to 10%.

[0027] Compared with the prior art, the present invention has at least the following beneficial effects:

[0028] 1. Performance optimization and lightweighting: The use of titanium alloy or aluminum alloy powder and topology optimization design can significantly reduce the weight of the brake caliper while maintaining strength and rigidity. This lightweighting effectively improves the energy efficiency of the vehicle. In addition, optimizing the thermophysical properties of the material can effectively improve the thermal management of the brake system and reduce the risk of performance degradation at high temperatures, thereby ensuring reliability under extreme working conditions.

[0029] 2. Manufacturing capability of complex structures: The unique advantages of SLM technology enable brake calipers to realize complex internal cooling channels and diversified geometric structures, which help improve heat conduction efficiency and heat dissipation performance. Through the application of bionic structures, efficient heat dissipation structures are designed to further enhance the thermal management capabilities of brake calipers during operation. In addition, the hollow features and variable cross-section wall thickness designs can effectively reduce stress concentration and improve the deformation resistance of components under high load conditions, thereby improving the overall safety of the brake system.

[0030] 3. Improved production efficiency and reduced costs: Through real-time monitoring and intelligent optimization of SLM process parameters, combined with machine learning algorithms, manufacturing parameters can be dynamically adjusted during the production process to achieve precise control; this intelligent manufacturing process not only reduces the defective rate, but also shortens the production cycle and improves production efficiency; at the same time, it can quickly respond to changes in market demand and flexibly adjust design and manufacturing plans, further improving manufacturing flexibility and adaptability.

[0031] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention is further described using the accompanying drawings, but the embodiments in the accompanying drawings do not constitute any limitation to the present invention. A person skilled in the art can obtain other drawings based on the following drawings without creative work.

[0033] Figure 1 The present invention is a schematic flow chart of a method for manufacturing an automobile brake caliper based on the selective laser melting additive manufacturing technology under an embodiment.

[0034] Figure 2 This is a schematic diagram of the working principle of the SLM device.

[0035] Figure 3 The present invention is a schematic diagram of a process of topological optimization and bionic structure design of a brake caliper under an embodiment.

[0036] Figure 4 The present invention is a schematic diagram of a process for reinforcing a reinforcement area according to an embodiment. DETAILED DESCRIPTION

[0037] The applicant found that:

[0038] In the prior art of brake calipers, there are the following problems:

[0039] 1) Molten casting method: commonly used in cast iron brake calipers, generally adopting a floating structure design, which has problems such as heavy weight, troublesome after-sales maintenance, weak braking sensitivity, and weak heat dissipation;

[0040] 2) Aluminum molten casting method: A caliper with multiple pistons is cast in a specific mold after the aluminum is molten and cooled to form. It has problems such as weak structural strength, weak expansion resistance, easy cracking, weak heat dissipation, and weak high temperature resistance;

[0041] 3) Aluminum room temperature forging method, a caliper that is made by extruding the molten cast blank with a large-tonnage press and then machining it. It has problems such as difficult processing, weak high temperature resistance, difficult maintenance, and weak heat dissipation design;

[0042] 4) Aluminum hot forging method, which is a kind of caliper that is formed by controlling the temperature of the molten cast blank and repeatedly forging it with a large-tonnage press, and then machining it. It has problems such as complex molding, difficult processing, difficult maintenance, and weak heat dissipation design.

[0043] As the maximum speed of automobiles increases, the requirements for high temperature resistance of brake calipers are also increasing. The brake calipers prepared by the above ordinary preparation methods have poor heat dissipation design and weak heat dissipation effect. They cannot adapt to working environments such as ultra-high speeds of more than 300 kilometers per hour, have poor stability, and affect driving performance.

[0044] In view of this, refer to Figures 1 to 4 This embodiment provides a method for manufacturing an automobile brake caliper based on selective laser melting additive manufacturing technology, comprising the following steps:

[0045] (1) Divide the three-dimensional digital model into structural regions and formulate SLM process parameter strategies for the structural regions. The SLM process parameter strategies include adjusting the laser power, scanning speed, scanning spacing, and powder layer thickness. It should be noted that when modeling the brake caliper, the division has been made in combination with the functions of different regions. Because the brake caliper has an inner side that needs to directly contact the hub, while the other outer side does not need to contact the hub, the two sides face different heating environments. In addition, the stress conditions of different regions of the brake caliper are also different. Therefore, different structural regions have been divided during modeling. Different structural regions have corresponding SLM process parameter strategies to adapt to different functions, so that different regions obtain different microstructures and mechanical properties.

[0046] (2) Combination Figure 2 According to the three-dimensional digital model of the brake caliper and the SLM process parameter strategy, high-strength and high-thermal-conductivity additive powder is laid in the powder bed of the SLM equipment. The surface of the powder bed is scanned layer by layer using a high-power density laser beam to selectively melt the powder particles, control the laser energy density input, match the thermophysical properties of the powder material, control the evolution of the microstructure, and obtain a gradient distribution of mechanical properties and thermal conductivity. After a layer is melted and solidified, the powder bed drops a layer thickness and a new powder layer is spread. The above process is repeated until the additive manufacturing of the brake caliper is completed.

[0047] (3) During the forming process, the molten pool morphology and temperature field distribution are detected in real time, and the SLM process parameter strategy is dynamically optimized in combination with a machine learning algorithm;

[0048] (4) After forming, the brake caliper is heat treated and surface strengthened to release residual stress, refine grains, and prepare a gradient transition layer and a high-temperature resistant ceramic coating on the friction pair surface of the brake caliper.

[0049] It should be noted that this method places high-strength and high-thermal-conductivity additive powders in the powder bed of the SLM equipment, and uses a high-power density laser beam to scan the selected area layer by layer to melt the powder particles, and then stack them layer by layer to form a dense entity. In this process, by optimizing the combination of SLM process parameters, matching the thermophysical properties of the additive powder materials, and controlling the laser energy density input, the powder is fully melted and metallurgically bonded, and an additive material with excellent mechanical properties and thermal conductivity is obtained. At the same time, computer-aided design software is used to perform topological optimization and bionic structural design on the brake caliper, generate a lightweight complex hollow structure model, and introduce high thermal conductivity material filling and surface heat dissipation structure to further improve the heat dissipation performance of the brake caliper. In addition, during the SLM molding process, customized process strategies are adopted for different structural areas of the brake caliper, supplemented by post-molding heat treatment and surface strengthening, to obtain an integrated brake caliper with excellent performance. Finally, online monitoring and feedback control technology is used to realize intelligent optimization of the molding process and improve the stability and consistency of the molding quality of the brake caliper. Through the above method, an automobile brake caliper with lightweight, high strength, high thermal conductivity, and high temperature wear resistance can be prepared to meet the requirements of harsh working conditions and improve braking performance and service life.

[0050] Additionally, combined Figure 2 , here is an explanation of the selective laser melting (SLM) forming technology:

[0051] The working principle of Selective Laser Melting (SLM) is similar to that of Selective Laser Sintering (SLS). The main difference is the way the powders are combined. SLS combines high-melting-point metal or non-metal powders by melting low-melting-point metals or binders, while SLM technology completely melts the metal powders, so it requires a much higher laser power density than SLS.

[0052] In order to achieve instant melting of metal powder, a high-power-density laser is required, and the spot is focused to tens of microns. SLM technology currently uses fiber lasers with laser powers ranging from 50W to 400W and power densities of 5×10 6 W / cm 2 above;

[0053] Forming principle: First, slice and layer the 3D model through the slicing software, discretize the model into 2D cross-sectional graphics, plan the scanning path, and then convert it into laser scanning information. Before scanning, the scraper evenly spreads the metal powder in the powder elevator to the laser processing area, and then the calculator controls the deflection of the scanning galvanometer according to the laser scanning information, selectively irradiates the laser beam to the processing area, and obtains the 2D entity of the current 2D cross section, and then the forming area drops a layer thickness, repeats the above process, and accumulates layer by layer to obtain the product prototype.

[0054] Furthermore, the additive powder is titanium alloy powder or aluminum alloy-ceramic composite powder, specifically:

[0055] As an implementation method, the additive powder is titanium alloy powder. In the SLM additive manufacturing process, Ti-6Al-4V titanium alloy powder (particle size distribution is 2 to 50 nm, particle morphology is spheroidized, and loose density is not less than 50%) is used as the material matrix. By accurately controlling the laser parameters and optimizing the scanning strategy, the grain refinement, dislocation strengthening and α' martensitic phase transformation mechanism of the titanium alloy are fully stimulated, thereby significantly improving the mechanical properties and fatigue properties of the molded parts, wherein:

[0056] 1. Grain refinement stimulation: By adjusting the laser power and scanning speed, the laser beam can melt the powder in a short time and cool it quickly. High energy density and fast cooling rate (up to 10 6 K / s) can promote the formation of a large number of non-equilibrium structures in the titanium alloy molten pool. During the rapid melting process, it can promote the rapid solidification of the liquid phase in the molten pool to form a fine grain structure. The refined grains can not only significantly improve the strength and hardness of the material, but also improve the toughness of the material and prevent the initiation and expansion of cracks;

[0057] 2. Excitation of dislocation strengthening: During the SLM molding process, the stress field introduced by high-speed cooling and laser scanning will produce high-density dislocations in the matrix material. The presence of dislocations can effectively hinder grain boundary slip and dislocation movement, thereby significantly improving the yield strength and hardness of the material. In order to maximize the dislocation strengthening effect, heat treatment can be performed after molding to partially restore and rearrange dislocations, form a sub-grain structure, and further improve the comprehensive mechanical properties of the material;

[0058] 3. Excitation of α' martensitic phase transformation: Under rapid cooling conditions, the β phase of Ti-6Al-4V alloy cannot be completely transformed into the stable α phase, but into the metastable α' martensitic phase. By optimizing the cooling rate and laser parameters, the high-strength and high-hardness α' martensitic phase is induced to form, which significantly enhances the strength and wear resistance of the material. Heat treatment after forming can transform part of the α' martensitic phase into the more stable α and β phases, further optimizing the material properties;

[0059] In order to achieve rapid cooling, the cooling rate of the molten pool can be effectively controlled by optimizing process parameters such as laser power, scanning speed, scanning spacing and powder layer thickness:

[0060] Laser power: Select a laser power of 200-400W to ensure that the powder is fully melted while avoiding excessive heat accumulation;

[0061] Scanning speed: Increasing the scanning speed to 800-1500mm / s can speed up the cooling rate of the molten pool;

[0062] Scanning spacing: Optimize the scanning spacing to 50-150μm to ensure uniform heating and rapid cooling;

[0063] Powder layer thickness: Choose a thinner powder layer thickness of 20-50μm to reduce the heat input per layer and speed up the cooling rate.

[0064] And it is configured with an optimized scanning strategy to evenly distribute heat, reduce local heat accumulation, and promote rapid cooling. Specifically, an island area scanning strategy is adopted to divide the entire molding area into several small island areas, and each island area is scanned in turn to reduce heat accumulation. In addition, the heat dissipation and cooling effect are improved by an efficient heat dissipation structure and a cooling structure, as shown in the following embodiments.

[0065] As another embodiment, the additive powder is an aluminum alloy-ceramic composite powder, and the aluminum alloy-ceramic composite powder includes an AlSi10Mg matrix and TiC, TiB with a volume fraction of 5 to 15%. 2 , SiC ceramic particle reinforcement phase, wherein the AlSi10Mg matrix gives the composite material good specific strength, thermal conductivity and casting formability; the ceramic particles are dispersed in the matrix, playing a role in dislocation pinning and grain boundary strengthening, significantly improving the mechanical properties of the material, especially high-temperature strength and wear resistance; by optimizing the volume fraction of the ceramic reinforcement phase (5-15%) and the powder particle size distribution (2-50nm), the ceramic particles are evenly dispersed to form a good interface bonding with the matrix; at the same time, the spheroidization of the powder particle morphology and the loose density (≥50%) are controlled to ensure good fluidity and spreadability of the powder while improving the laser absorption efficiency, thereby improving the density and mechanical properties of the SLM molded parts and obtaining a composite material with excellent mechanical properties and thermal conductivity; in the SLM molding process, the ceramic reinforcement phase and the matrix are promoted to be in-situ composited to complete the grain refinement, dislocation strengthening, and second phase dispersion strengthening reaction mechanism.

[0066] It should be noted that after the brake caliper model is divided into different structural areas, ceramic particle reinforcement can be filled in specific areas, and by optimizing the SLM process parameters, during the SLM molding process, the high-energy density laser beam irradiates the powder layer, the matrix phase melts rapidly, the ceramic particles are evenly dispersed therein, and the in-situ composite of the ceramic reinforcement phase and the aluminum matrix is ​​realized during the solidification process. On the one hand, the in-situ generated ceramic phase plays a role in grain refinement and dislocation strengthening, thereby improving the strength of the matrix; on the other hand, the ceramic particles have good interface compatibility with the matrix, and metallurgical bonding is formed during the laser melting process, the movement of grain boundaries and dislocations is hindered, the dislocation density is increased, and a dislocation strengthening effect is produced; on the other hand, the ceramic particles themselves have excellent high-temperature mechanical properties, and are dispersed in the matrix as the second phase. The presence of the second phase particles causes the matrix to form non-uniform deformation, produces additional geometric dislocations, improves the strength and hardness of the material, further strengthens the material, and at the same time hinders the movement of dislocations, thereby improving the high-temperature creep resistance of the automotive caliper. At the same time, ceramic particles themselves have the characteristics of high hardness, high modulus, high thermal conductivity, etc., and their dispersed distribution can significantly improve the wear resistance and thermal conductivity of composite materials. This laser-induced in-situ reaction strengthening mechanism utilizes the characteristics of instantaneous high temperature in the additive manufacturing process, which is difficult to achieve with ordinary post-composite processes.

[0067] As an implementation method, in order to improve the formability of the powder during the SLM molding process, the wettability of the liquid metal must be improved. During the molding process, if the liquid metal forms a ball, it means that the wettability of the liquid metal is poor, which seriously affects the formability; therefore, in this implementation method, a self-lubricating phase such as graphite, molybdenum disulfide, etc. is also added to the Ti-6Al-4V titanium alloy or AlSi10Mg matrix to form a multi-component composite material system. Under the action of the laser, the self-lubricating phase melts and is evenly dispersed in the matrix to form a lubricating film, which can further reduce the friction coefficient (reduced by 20-40%), improve the interface lubrication performance, and improve the wear resistance.

[0068] Reference Figure 3 As an implementation method, compared with the traditional manufacturing method, when using the selective laser melting (SLM) technology to manufacture automobile calipers, significant breakthroughs can be achieved in both lightweight and heat dissipation performance. In detail, when formulating the three-dimensional digital model of the brake caliper, the brake caliper is topologically optimized and bionic structure designed, and lightweight model data with complex hollow features and variable cross-sectional wall thickness is generated. High thermal conductivity material filling and surface heat dissipation structure are introduced as the three-dimensional solid model input of SLM molding.

[0069] Specifically, the topology optimization and bionic structure design include lightweight design of brake calipers, and adopt a complex structure generative design method based on gradient materials and variable density topology optimization theory. First, a three-dimensional digital model of the brake caliper is established, and mechanical performance constraints (such as strength, stiffness, etc.) and objective functions (such as minimizing weight) are defined, and the structural area is divided into a braking functional area and a non-critical functional area. Then, the model is iteratively solved using an optimization algorithm, and redundant materials in non-critical functional areas are removed under the premise of satisfying mechanical performance constraints through the evolution of material distribution and structural morphology to obtain the optimal material distribution and structural layout. This generative model can generate a complex bionic structure model with a hollow cavity, variable cross-sectional wall thickness, and honeycomb porous interior in non-critical functional areas to achieve the integrated functional and structural design of the brake caliper. Further, a bionic optimization strategy based on biological structures is adopted to adjust the morphology and size of the topology optimization results, such as setting a dendritic branch structure in the stress concentration area and setting a honeycomb porous structure in the light load area, so as to minimize the overall weight of the brake caliper while taking into account the strength and stiffness requirements of the local area. Through the above method, the functionalization and lightweight design of the brake caliper structure can be achieved without affecting the performance, thereby effectively reducing the weight of the brake caliper.

[0070] Specifically, the topology optimization and bionic structure design include the design of the heat dissipation structure of the brake caliper, making full use of the shape freedom of SLM additive manufacturing technology and breaking through the design limitations of traditional manufacturing processes. In the braking function area of ​​the brake caliper, a three-dimensional cooling channel network is constructed. Specifically, inside the brake caliper, three-dimensional cooling channels such as serpentine, spiral, and tree branches are designed to increase the heat transfer area, strengthen heat exchange, and accelerate heat conduction; in addition, high-specific surface area heat dissipation structural units such as needle ribs, fins, and multi-level branches are designed on the surface to increase the heat transfer area and enhance heat exchange and accelerate heat conduction by increasing the heat transfer area and turbulence. At the same time, powder filling and multi-material gradient deposition technology are used to introduce graphene, carbon nanotubes or diamond particles with a thermal conductivity coefficient of not less than 400W / (m·K) at the predetermined positions of the cooling channel and the heat dissipation structure to construct a directional heat conduction channel, fully utilizing the anisotropic thermal conductivity of the material, and realizing the rapid conduction of heat flow in the specified direction, accelerating heat conduction, and improving local heat dissipation efficiency. Furthermore, powder filling and laser cladding processes can be used to deposit a layer of high thermal conductivity material with a thickness gradient on the surface, such as diamond, silicon carbide, boron nitride, etc. The local thermal conductivity can reach 400-2000W / (m·K), forming a directional heat transfer channel pointing to the heat sink.

[0071] In this embodiment, the internal cooling channel takes away the heat, the surface heat dissipation structure accelerates the heat conduction convection, and the high thermal conductivity material provides a fast channel for heat conduction. The three work together to significantly improve the heat dissipation efficiency of the brake caliper. The above heat dissipation structure design is used to improve the heat dissipation and cooling effect during the processing process, and to improve the heat dissipation effect during the braking process of the finished product. Compared with the conventional casting process, the above heat dissipation structure design method can break through the manufacturing constraints, realize the three-dimensional layout of the heat transfer channel and the complex topological configuration of the surface heat dissipation structure, and at the same time introduce high thermal conductivity materials to form a directional heat conduction path, and the heat dissipation efficiency is increased by more than 20%, thereby significantly improving the heat dissipation performance of the brake caliper, reducing the heat accumulation during the braking process, and ensuring the stability and reliability of the braking performance.

[0072] Reference Figure 4 As an implementation method, when using SLM to form a brake caliper, defects such as thin-wall deformation, inner cavity collapse and overhang structure deformation are prone to occur. Therefore, during the forming process, this embodiment combines real-time detection data to analyze and obtain the reinforcement area of ​​the brake caliper, and reinforces the reinforcement area to perform corresponding structural reinforcement and process optimization measures.

[0073] The reinforcement area of ​​the brake caliper is analyzed and obtained by combining the real-time detection data, including: real-time acquisition of multi-source heterogeneous data of the forming process, including melt pool morphology, temperature field distribution, powder spreading state, etc.;

[0074] Reinforcement area identification based on molten pool morphology: Use a high-speed CCD camera or infrared camera to collect molten pool images in real time and extract characteristic parameters such as molten pool size, shape, and melting trajectory. When the molten pool shows unstable flow, sudden size change, abnormal shape, etc., it indicates that there may be molding defects in the area and reinforcement treatment is required. Use image processing algorithms to identify and locate abnormal areas and generate a distribution map of reinforcement areas;

[0075] Reinforcement area identification based on temperature field distribution: Use infrared thermal imagers to monitor the temperature field distribution of the forming process in real time and extract parameters such as temperature gradient and cooling rate. When a certain area has a sudden temperature rise / drop, excessive temperature gradient, abnormal cooling rate, etc., it indicates that the area may have stress concentration or thermal crack tendency and needs reinforcement. Use thermal imaging data to build a three-dimensional temperature field model, locate the abnormal area, and generate a distribution map of the reinforcement area.

[0076] Wherein, the reinforcement treatment includes:

[0077] The thin-walled area of ​​the brake caliper is structurally reinforced. A variable cross-section design is adopted in the thin-walled area. The wall thickness decreases gradually from the outside to the inside, and a taper angle is set to improve the support strength and heat dissipation speed during the molding process, and inhibit deformation and cracking tendencies. At the same time, grid reinforcement is used on the inner and outer surfaces to improve the bending stiffness and anti-buckling ability of the thin-walled structure, effectively inhibiting deformation and cracking tendencies during the SLM molding process.

[0078] A scanning strategy is adopted for the inner cavity area of ​​the brake caliper, and the scanning strategy includes island area scanning or partition scanning, which divides the inner cavity area into multiple sub-areas, and each area is laser scanned and melted in turn, and a cooling time is set between the sub-areas to reduce deformation and collapse of the inner cavity and avoid deformation and collapse caused by heat accumulation;

[0079] A multi-level tree-like support structure is adopted for the overhang structure, and a graded support from coarse to fine is constructed below the overhang surface. The trunk diameter of the support structure is greater than 30% of the diameter of the overhang structure, and the branch diameter of the support structure is greater than 50% of the trunk diameter. The support density decreases with the overhang height. While meeting the support strength, the impact on the surface quality of the molded part is reduced, which is convenient for subsequent removal.

[0080] In addition, the laser process parameters are optimized, and the laser power, scanning speed and scanning spacing are reasonably controlled to reduce the single-pass energy input, residual stress and deformation while ensuring sufficient melting.

[0081] The structural reinforcement and process optimization strategies involved in the above-mentioned reinforcement treatment can effectively improve the various defects that are prone to occur in the SLM molding of the brake caliper, improve the molding quality and surface accuracy, and ensure the assembly accuracy and performance of the brake caliper.

[0082] In some embodiments, when formulating the SLM process parameter strategy for the structural area, the thermal conductivity, specific heat capacity, melting point, viscosity thermophysical parameters of the powder material and the index requirements for mechanical properties, surface quality and production efficiency of different structural areas of the brake caliper are combined.

[0083] As an implementation method, for braking functional areas that are subject to greater stress and high operating temperature (such as the friction pair surface in contact with the brake disc), higher laser power and lower scanning speed will be used to provide higher energy density, ensure that the material is fully melted and densified, and improve the mechanical properties of the components.

[0084] As an implementation method, for non-critical functional areas or lightweight structures (such as internal honeycomb porous structures), lower laser power and higher scanning speed can be used to reduce energy input, form a certain porosity, and achieve the lightweight goal.

[0085] As an implementation method, for areas requiring high precision and surface quality, a smaller scanning pitch and powder layer thickness are used to improve the molding accuracy and surface finish.

[0086] As an implementation method, for internal structures or non-critical areas, the scanning interval and powder layer thickness can be appropriately increased to improve the molding efficiency.

[0087] As an implementation method, for thin-walled structures, an island scanning or partition scanning strategy can be adopted to divide the area into multiple sub-areas and scan them in sequence to reduce thermal stress accumulation and deformation.

[0088] As an implementation method, for large solid areas, a checkerboard scanning strategy can be used to alternately scan different areas to evenly distribute heat.

[0089] Through the adaptive optimization of the SLM process parameter strategy under different implementation modes, the performance requirements of different regions can be met, local optimization of performance can be achieved, thermal stress accumulation can be reduced, and the risk of deformation and cracking can be reduced; and through the continuous change of parameters, a gradient transition of material properties can be achieved, such as the gradient distribution of mechanical properties or thermal conductivity; by adjusting the parameters to control the porosity, the lightweight structure can be achieved while ensuring the performance; through reasonable regional process design, the gradient distribution of mechanical properties and thermal conductivity can be finally obtained inside the brake caliper, achieving lightweight while meeting the use requirements.

[0090] Furthermore, through orthogonal experimental design and numerical simulation, the best matching combination of laser power, scanning speed, scanning spacing and powder layer thickness parameters in different regions is obtained, and a regional parameter library is established to achieve real-time monitoring, intelligent analysis and closed-loop control of the SLM forming process. Using the above method, through orthogonal experiments and numerical simulations, the optimal parameter combination library for different regions is established, the molten pool morphology and temperature field are monitored in real time during the forming process, and the process parameters are dynamically optimized by combining machine learning algorithms to achieve real-time monitoring and closed-loop control. In addition, combined with macro-micro multi-scale simulation, the microstructure evolution and macro performance under different parameters are predicted, and the optimal scanning path and parameter distribution are automatically generated according to the structural characteristics and performance requirements.

[0091] As another implementation method, in the SLM process parameter optimization, multi-field coupling numerical simulation and process tests are carried out for different structural areas of the brake caliper, and a multi-objective optimization design system and performance evaluation system covering the entire process chain are established. In terms of numerical simulation, factors such as material properties, heat source characteristics, and powder spreading state are comprehensively considered to establish a multi-physical field coupling model of the SLM forming process, simulate the dynamic process of temperature field, stress field, and organizational evolution under different process parameters, predict forming defects, deformation, residual stress, etc., and optimize the process window. In terms of process experiments, through a systematic study of "process parameters-organization performance-service performance", the intrinsic relationship between parameters such as laser power, scanning speed, and powder layer thickness and microstructure, mechanical properties, surface quality, and production efficiency is revealed, and the best matching combination of process parameters is obtained. On this basis, a multi-objective optimization model is established, with the mechanical properties, heat dissipation performance, and lightweight indicators of the brake caliper as optimization targets, and process parameters as optimization variables. The global optimal solution is solved under the constraints to form a brake caliper SLM forming process parameter library. The parameter optimization method combining the above-mentioned multi-field coupling simulation and process experiment can achieve accurate correspondence between process parameters and brake caliper performance, maximize the performance potential of SLM technology and additive materials, and prepare high-performance and lightweight brake calipers.

[0092] As an implementation method, in order to further improve the fatigue performance and service life of the SLM molded brake caliper, heat treatment and surface strengthening are performed after molding. In the heat treatment, a solid solution aging treatment is used, and the SLM molded brake caliper is placed in a vacuum or protective atmosphere heat treatment furnace, kept at a set heat treatment temperature for a set time, and cooled to room temperature;

[0093] In some embodiments, when Ti-6Al-4V titanium alloy powder is used as a molding material, a solution treatment is performed in the α+β phase region to partially dissolve the β phase and form an α+β dual-phase structure. This structure has good strength, toughness and fatigue properties. Specifically, the temperature is selected between 820 and 850°C, kept warm for 1.5 hours, and air-cooled to room temperature. This temperature can obtain the best comprehensive mechanical properties in the α+β phase region;

[0094] It should be noted that during the SLM forming process of Ti-6Al-4V titanium alloy, the α' martensite phase is induced to form, and then it is transformed into more stable α phase and β phase through heat treatment. The main purpose of this is to obtain high strength and high hardness while taking into account the toughness and fatigue performance of the material, so as to achieve a balance and optimization of performance; specifically, the α' martensite phase formed under rapid cooling conditions has the characteristics of high strength and high hardness, which can significantly improve the tensile strength and wear resistance of the material. The formation of the α' martensite phase is accompanied by volume expansion, which can introduce compressive stress inside the material and improve fatigue strength and fracture toughness. The needle-like morphology and high-density dislocations of the α' martensite phase are conducive to hindering crack propagation and improving the fracture toughness of the material; however, the α' martensite phase has high strength and high hardness, but its metastable characteristics may lead to a decrease in the toughness and fatigue performance of the material. , there is a risk of brittle fracture. Therefore, by performing appropriate heat treatment after SLM forming, part of the α' martensite phase can be transformed into more stable α phase and β phase to form an α+β two-phase structure. The α+β two-phase structure has both the high strength of the α phase and the high toughness of the β phase. It can improve the fracture toughness and fatigue properties of the material while maintaining high strength, and achieve a balance of strength and toughness. Heat treatment can also eliminate residual stress, refine grains, optimize microstructure, and further improve the comprehensive mechanical properties of the material; therefore, in the SLM forming process of Ti-6Al-4V titanium alloy, the α' martensite phase is first induced to form, and then it is transformed into an α+β two-phase structure through heat treatment. This is a balanced strategy that takes into account high strength, high hardness, high toughness and high fatigue performance, which can meet the performance requirements of different areas of the brake caliper and improve the reliability and durability of the braking system.

[0095] In other embodiments, when aluminum alloy-ceramic composite powder is used as a molding material, the solution treatment temperature is higher than the solution temperature of the aluminum alloy precipitation phase, but lower than the eutectic temperature, to ensure that the matrix is ​​fully dissolved and the precipitation phase is completely dissolved; specifically, the temperature is kept at 540-580°C for 2-8 hours, and the furnace is cooled to room temperature. The holding time is sufficient to achieve the diffusion of alloy elements and the release of residual stress, but should not be too long to avoid grain coarsening. During the heat treatment process, the alloy elements diffuse and precipitate in the matrix, and solution strengthening and precipitation strengthening occur inside the material to form a dispersed nanoscale precipitation phase, which produces a precipitation strengthening effect, improves material strength, refines grains, and improves matrix strength. At the same time, the grains grow at high temperatures, the residual stress is fully released, and the plasticity and toughness of the material are improved.

[0096] On this basis, shot peening is used in the surface strengthening, and ceramic or metal beads are used to impact the surface of the workpiece with high-speed jet (50-80m / s), so as to introduce residual compressive stress in the surface layer, improve the surface hardness and wear resistance, and inhibit the initiation and expansion of fatigue cracks; by optimizing the shot peening process parameters, the shot peening medium is ceramic or metal beads, the shot peening pressure is 0.3-0.6MPa, and the coverage rate reaches more than 200%, so as to obtain a uniform and dense surface compressive stress layer, significantly improve the fatigue strength and service life of the brake caliper, and then use vibration stress relief or low-temperature tempering method to eliminate the surface residual stress introduced by shot peening, which can significantly improve the surface hardness and wear resistance and delay fatigue failure.

[0097] By combining the above-mentioned heat treatment with surface strengthening, the comprehensive mechanical properties of the SLM-molded brake caliper can be improved from the two levels of internal organization and surface performance, and the microstructure and residual stress distribution of the SLM-molded brake caliper can be regulated to maximize the strengthening potential of the material, thereby ensuring the service safety and reliability of the brake caliper under harsh working conditions such as high stress, high temperature, and vibration, especially improving fatigue strength and wear life to meet the long life and high reliability requirements of the brake caliper.

[0098] As an implementation method, in order to further improve the friction and wear performance of the SLM-molded brake caliper at high temperatures, a gradient transition layer and a high-temperature resistant ceramic coating are prepared on the friction pair surface of the brake caliper. Specifically, the gradient transition layer is prepared on the friction pair surface of the brake caliper by the SLM process. The thickness of the transition layer is 0.5 to 2 mm, and the material is a high-temperature alloy powder and a solid lubricant MoS 2 A mixture of graphite and WS2, with a lubricant volume fraction of 5-20%. Under the action of laser, the high-temperature alloy matrix melts and fully fuses with the lubricant particles to form a composite coating with self-lubricating properties, reducing the friction factor by 10-20% and the wear rate by 1-2 orders of magnitude, thereby reducing the friction factor and wear rate and improving the resistance to high-temperature oxidation;

[0099] The high temperature resistant ceramic coating is prepared on the surface of the gradient transition layer by laser cladding or plasma spraying process. The coating material is 8YSZ, Cr 2 O 3 、Al 2 O 3 The coating thickness is 100-500μm. The ceramic coating has excellent high-temperature oxidation resistance and thermal insulation properties. The working temperature can reach 1000-1400℃, which can effectively prevent the high-temperature oxidation wear of the friction pair. At the same time, it reduces the heat load of the braking process, avoids the generation of hot spots and thermal cracks, and further improves the surface's high-temperature oxidation resistance, thermal insulation, flame retardancy and wear resistance.

[0100] The composite design of the above-mentioned gradient transition layer and ceramic coating enhances the high-temperature friction and wear performance of the friction pair surface of the SLM-molded brake caliper from both the material and structural levels. While reducing the friction coefficient and delaying wear, it significantly improves the high-temperature oxidation resistance of the friction pair surface of the brake caliper, reduces the wear rate, extends the service life, and ensures the stability of the braking performance.

[0101] Furthermore, the composite coating system of gradient transition layer + high temperature resistant coating can improve the high temperature friction and wear performance, but under some extreme working conditions, the bonding strength and coating stability need to be improved. In this embodiment, nano metal particles (such as Ag, Cu) are added to the ceramic coating to form a metal-ceramic composite coating. The nano metal particles can play the following roles: on the one hand, they fill the microscopic holes and defects of the ceramic coating and improve the density of the coating; on the other hand, the nano particles melt at high temperature to form a lubricating film, reduce the friction factor, and at the same time improve the fracture toughness of the coating (increase by 30-50%) and improve the anti-stripping performance of the coating.

[0102] As an implementation method, in order to further improve the heat dissipation performance of the SLM molded brake caliper, a cooling structure is prepared inside the brake caliper using the SLM process. The cooling structure includes a bionic tree-like fractal channel and a high thermal conductivity filling material to accelerate heat conduction inside the device.

[0103] First, referring to the vascular network and leaf vein system in animals and plants in nature, a three-dimensional cooling channel network inside the brake caliper is designed. The bionic tree-like fractal channel branches out from the main pipe step by step to form multi-level tributaries from coarse to fine. The diameter of the fractal channel increases from the inside to the outside. The diameter of the last tributary is no more than 1mm, and the ratio of adjacent diameters is no less than 1.5, so as to achieve efficient flow and heat transfer of cooling medium in a small space.

[0104] Then, the fractal channel is filled with a material with high thermal conductivity. The high thermal conductivity filling material is selected from Cu, Ag, and graphene. The filling rate is 5-10%. The high thermal conductivity filling material is mixed with AlSi10Mg powder in a certain proportion and placed in the powder cabin of the SLM equipment as a raw material to construct a local high thermal conductivity network. The high thermal conductivity of the filling material is used to accelerate the heat conduction inside the device and reduce the temperature gradient.

[0105] During the molding process, the laser beam melts the powder in a selected area, and the high thermal conductivity particles are evenly dispersed in the matrix of the additive powder and form an enriched layer on the wall of the cooling channel. The thermal conductivity can reach 300-400W / (m·K), which is 3-4 times that of the original additive powder material. When the coolant flows in the channel, it fully exchanges heat with the high thermal conductivity wall surface and takes away the heat generated by the braking process. Since the fractal channel structure increases the contact area and reduces the heat transfer distance, the heat transfer efficiency is greatly improved. At the same time, the high thermal conductivity filler provides a fast channel for heat conduction, accelerates the conduction of internal heat to the outside, reduces the temperature gradient, and improves the thermal deformation of the brake disc.

[0106] Compared with conventional straight channels or serpentine channels, bionic tree-like fractal channels have the advantages of large specific surface area, high heat transfer efficiency, and low pressure drop. Combined with high thermal conductivity fillers, the heat dissipation efficiency can be increased by 50-200%, thereby significantly improving the heat dissipation performance of the brake caliper, reducing the surface temperature of the brake disc, and improving braking efficiency and reliability.

[0107] As an implementation method, in order to realize the online monitoring and intelligent optimization of the quality of SLM molded brake calipers, a multi-sensor integrated process monitoring system is built. High-speed digital image sensors, infrared thermal imagers, etc. are used to collect multi-source heterogeneous data such as molten pool morphology, temperature field distribution, powder spreading state, and plume splash in the molding process in real time, and obtain multi-source heterogeneous data of the SLM molding process. Using algorithms such as image processing and signal analysis, key process parameters such as molten pool size, peak temperature, temperature gradient, cooling rate, powder layer thickness, and stacking density are extracted. Combined with machine learning algorithms, intelligent identification of defects and adaptive optimization of process parameters are realized, and the stability and consistency of molding quality are improved through real-time closed-loop control. A high-speed digital image sensor (sampling frequency 1-5kHz) is installed inside the SLM equipment to record the morphological characteristics of the molten pool in the molding process in real time, and extract parameters such as molten pool size, melting depth, and melting trajectory. At the same time, an infrared thermal imager (resolution 0.1-0.2mm, sensitivity 0.1-0.2K) is used to image the temperature field of the molding process in real time to obtain parameters such as instantaneous temperature distribution, maximum temperature, and cooling rate. The above parameters are associated with the microstructure, mechanical properties, residual stress, defect type and other data obtained by offline characterization to build a multi-parameter, multi-scale process-structure-performance database;

[0108] Based on massive monitoring data, combined with machine learning algorithms (such as support vector machines, convolutional neural networks, decision trees, etc.), intelligent defect recognition models and process parameter optimization models are established; the defect recognition model can realize real-time detection and positioning of defects such as unstable molten pool, cracks, pores, etc. during the molding process, with an accuracy rate of more than 90%; the process optimization model can adaptively adjust parameters such as laser power, scanning speed, and powder layer thickness according to defect type and molding quality feedback, to achieve online intelligent identification of defects and adaptive optimization control of key parameters. Through real-time closed-loop feedback driven by monitoring data, process parameters such as laser power, scanning speed, and spot diameter are dynamically adjusted to suppress defects, improve the stability and consistency of the quality of molded parts, and ultimately ensure the stable and reliable performance of SLM molded brake calipers.

[0109] The above-mentioned online monitoring and intelligent control methods are key measures to achieve visualization of the SLM forming process, traceability of quality, and optimization of process parameters. They are of great significance for improving the quality level and production efficiency of SLM-formed brake calipers.

[0110] In summary, compared with the prior art, the above embodiment provides a method for manufacturing an automobile brake caliper based on the selective laser melting additive manufacturing technology. The automobile brake caliper prepared by the SLM additive manufacturing technology achieves a significant improvement in the comprehensive performance of the brake caliper while meeting the performance requirements, compared with the traditional casting process, through system optimization and integrated innovation in materials, structure, process, surface treatment, etc.

[0111] In terms of materials, when using high-strength, high-toughness, and high-thermal conductivity Ti-6Al-4V titanium alloy powder as the molding material, the SLM process can be used to obtain a dense and uniform microstructure with low density and high specific strength. At the same time, α' martensite phase transformation and dislocation strengthening are induced during the molding process to further improve the strength and toughness of the material, so that the brake caliper has better deformation resistance and fatigue resistance in high stress areas, the tensile strength is increased by more than 30%, and the fracture toughness is increased by more than 55%.

[0112] By using high-strength, high-toughness, and high-thermal conductivity aluminum alloy-ceramic composite powder as the molding material, the SLM process is used to achieve in-situ composite of the ceramic reinforcement phase and the aluminum alloy matrix at the microscale. Through multiple strengthening mechanisms such as grain refinement, dislocation strengthening, and second phase dispersion strengthening, a composite material with greatly improved mechanical properties is obtained, with the tensile strength increased by more than 20% and the fracture toughness increased by more than 50%.

[0113] In terms of structural design, topology optimization and bionic design methods are used to design lightweight brake calipers with complex structures. Redundant materials in non-load-bearing areas are removed through variable density optimization algorithms, and lightweight structural designs such as hollow, honeycomb, and tree-like structures are adopted to reduce the overall weight of the brake calipers by more than 30% while ensuring strength and rigidity. In terms of surface strengthening, a self-lubricating gradient transition layer and a high-temperature resistant ceramic coating are prepared on the surface of the brake caliper to reduce the friction factor by 10-30%, improve the surface hardness and wear resistance, and delay the initiation of fatigue cracks. Combined with the design of the internal cooling channel, the heat dissipation efficiency is increased by more than 20%, significantly extending the service life of the brake caliper (more than 1 times). In addition, thanks to the precise molding parameter control and optimization during the SLM process, the internal structure of the molded part is dense and uniform, and the residual stress and defect content are low, which further guarantees the fatigue performance and reliability of the brake caliper.

[0114] In summary, the SLM-molded automobile brake caliper of the present invention optimizes the additive material system, lightweight structure design, surface strengthening treatment and other aspects, and makes full use of the advantages of additive manufacturing technology such as material flexibility, structural freedom, and functional integration to achieve the comprehensive performance improvement of the brake caliper, which is "lightweight, high strength, high thermal conductivity, and wear resistance". Compared with the traditional casting process, while reducing the weight by more than 30%, the strength is increased by more than 20%, the toughness is increased by more than 50%, the service life is extended by more than 1 times, the heat dissipation efficiency is increased by more than 20%, and the friction coefficient is reduced by 10-30%, thereby significantly improving the working performance and reliability of the brake caliper, and having broad engineering application prospects.

[0115] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A method for manufacturing an automobile brake caliper based on selective laser melting additive manufacturing technology, characterized in that: The following steps are involved: (1) dividing the three-dimensional digital model into structural regions and formulating a SLM process parameter strategy for the structural regions, wherein the SLM process parameter strategy includes adjusting laser power, scanning speed, scanning spacing, and powder layer thickness; (2) According to the three-dimensional digital model of the brake caliper and the SLM process parameter strategy, the additive powder is laid in the powder bed of the SLM equipment, and the surface of the powder bed is scanned layer by layer using a high-power density laser beam to selectively melt the powder particles, control the laser energy density input, match the thermophysical properties of the powder material, control the evolution of the microstructure, and obtain a gradient distribution of mechanical properties and thermal conductivity. After a layer is melted and solidified, the powder bed is lowered by a layer thickness, and a new powder layer is spread. The above process is repeated until the additive manufacturing of the brake caliper is completed; (3) During the forming process, the molten pool morphology and temperature field distribution are detected in real time, and the SLM process parameter strategy is dynamically optimized in combination with a machine learning algorithm; (4) After forming, the brake caliper is heat treated and surface strengthened to release residual stress, refine grains, and prepare a gradient transition layer and a high-temperature resistant ceramic coating on the friction pair surface of the brake caliper; The additive powder includes Ti-6Al-4V titanium alloy powder, the powder particle size distribution is 2 to 50 nm, the particle morphology is spheroidized, and the bulk density is not less than 50%. During the SLM forming process, the titanium alloy matrix is ​​promoted to refine the grains, introduce high-density dislocations, and induce α' martensitic phase transformation; When formulating the three-dimensional digital model of the brake caliper, topology optimization and bionic structure design are performed on the brake caliper to generate lightweight model data with complex hollow features and variable cross-sectional wall thickness, and high thermal conductivity material filling and surface heat dissipation structure are introduced as the three-dimensional solid model input for SLM molding; The topology optimization and bionic structure design include lightweight design of the brake caliper, using a complex structure generative design method based on gradient materials and variable density topology optimization theory, dividing the structural area into a braking functional area and a non-critical functional area, generating a bionic structure model with a hollow cavity, variable cross-sectional wall thickness, and a honeycomb porous interior in the non-critical functional area, and optimizing the size and shape parameters of the topological boundary to reduce the overall weight of the brake caliper; The topology optimization and bionic structure design include the design of the heat dissipation structure of the brake caliper, which utilizes the shape freedom of the SLM technology, constructs a three-dimensional cooling channel network in the braking functional area, designs high specific surface area needle-rib and fin-shaped heat dissipation structure units on the surface of the cooling channel network, introduces graphene, carbon nanotubes or diamond particles with a thermal conductivity of not less than 400W / (m·K) at a predetermined position, constructs a directional heat conduction channel, and accelerates heat conduction; A cooling structure is prepared inside the brake caliper using the SLM process. The cooling structure includes a bionic tree-like fractal channel and a high thermal conductivity filling material. The diameter of the fractal channel increases from the inside to the outside, the diameter of the last tributary is not greater than 1 mm, and the ratio of adjacent stage diameters is not less than 1.

5. The high thermal conductivity filling material is selected from Cu, Ag, and graphene, and the filling rate is 5 to 10%.

2. The method according to claim 1, characterized in that During the forming process, the reinforcement area of ​​the brake caliper is analyzed and obtained in combination with the real-time detection data, and the reinforcement area is reinforced. The reinforcement process includes: The thin-walled area of ​​the brake caliper is structurally reinforced, with the wall thickness decreasing gradually from the outside to the inside, and grid-like reinforcement is used on the inner and outer surfaces to improve the deformation resistance of the thin-walled structure; A scanning strategy is adopted for the inner cavity area of ​​the brake caliper, wherein the scanning strategy includes island area scanning or partition scanning, and the inner cavity area is divided into multiple sub-areas, each area is sequentially laser scanned and melted, and a cooling time is set between the sub-areas to reduce deformation and collapse of the inner cavity; A multi-level tree-like support structure is used for the overhanging structure, the trunk diameter of the support structure is greater than 30% of the diameter of the overhanging structure, the branch diameter of the support structure is greater than 50% of the trunk diameter, and the support density decreases with the overhanging height.

3. The method according to any one of claims 1 to 2, characterized in that: When formulating the SLM process parameter strategy for the structural area, the thermal conductivity, specific heat capacity, melting point, viscosity thermophysical parameters of the powder material, as well as the index requirements for mechanical properties, surface quality and production efficiency in different structural areas of the brake caliper are combined. Through orthogonal experimental design and numerical simulation, the optimal matching combination of laser power, scanning speed, scanning spacing and powder layer thickness parameters in different areas is obtained, and a regional parameter library is established to achieve real-time monitoring, intelligent analysis and closed-loop control of the SLM forming process.

4. The method according to claim 3, characterized in that: In the heat treatment, a solution aging treatment is adopted, and the SLM-molded brake caliper is placed in a vacuum or protective atmosphere heat treatment furnace, kept at 820-850° C. for 1-5 hours, and air-cooled to room temperature to release residual stress; Shot peening is used in the surface strengthening, the shot peening medium is ceramic or metal beads, the shot peening pressure is 0.3-0.6MPa, the coverage rate reaches more than 200%, and then vibration stress relief or low temperature tempering method is used to eliminate the surface residual stress introduced by shot peening.

5. The method according to claim 4, characterized in that The gradient transition layer is prepared on the friction pair surface of the brake caliper by SLM process. The thickness of the transition layer is 0.5-2mm. The material is a mixture of high-temperature alloy powder and solid lubricants MoS2, graphite, and WS2. The volume fraction of the lubricant is 5-20%, which reduces the friction coefficient and wear. A high temperature resistant ceramic coating is prepared on the surface of the gradient transition layer by laser cladding or plasma spraying process. The coating material is 8YSZ, Cr2O3, Al2O3, and the coating thickness is 100-500 μm, which improves the high temperature wear resistance.

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