Electron beam additive manufacturing method for integrated copper-chromium contact-conducting rod assembly

Abstract

The invention discloses an electron beam additive manufacturing method for an integrated copper-chromium contact-conducting rod assembly, and belongs to the technical field of copper-chromium contact manufacturing. The electron beam additive manufacturing method comprises the steps that S1, a special powder system is designed and prepared, specifically, contact area powder and conducting rod area powder are prepared and subjected to drying treatment; s2, digital modeling and support design: establishing an integrated copper-chromium contact-conducting rod assembly model by using three-dimensional software and slicing; S3, fusing and integrally forming by using an electron beam powder bed: printing an integrated copper-chromium contact-conducting rod assembly in a vacuum chamber of the electron beam powder bed, and S4, a printing post-treatment process is carried out, specifically, returning treatment, hot isostatic pressing treatment and machining treatment are carried out on the integrated copper-chromium contact-conducting rod assembly printed piece. According to the printing post-treatment process, the residual stress of the integrated copper-chromium contact-conducting rod assembly can be effectively eliminated through the printing post-treatment process; and the problems of macroscopic cracks and part warping caused by high residual thermal stress can be effectively avoided.

Description

Technical Field

[0001] This invention relates to the field of copper-chromium contact manufacturing technology, specifically to an electron beam additive manufacturing method for an integrated copper-chromium contact-conductive rod assembly. Background Technology

[0002] This invention aims to solve three core technical challenges in the manufacturing and application of large-diameter (≥80mm) copper-chromium (CuCr50) contact and conductive rod assemblies in high-voltage vacuum circuit breakers: Interface reliability bottleneck: The interface formed between the contact and the conductive rod in the traditional brazing connection process is prone to becoming a weak point in mechanical and electrical performance or even a source of failure when subjected to huge electrodynamic forces (short circuit impact) and thermal cycles (arc erosion) for a long time. This is due to thermal stress concentration and metallurgical defects.

[0003] Direct molding of large-size CuCr50 materials is difficult: Due to the great difference in the thermophysical properties (thermal expansion coefficient, thermal conductivity) between copper and chromium, when using additive manufacturing technologies such as electron beam melting to directly mold large-size, fully dense CuCr50 components, macroscopic cracks and part warping caused by high residual thermal stress are very likely to occur.

[0004] System performance compromises and lengthy manufacturing processes: Selecting rods with suboptimal conductivity to match contact materials sacrifices system conductivity efficiency; at the same time, the separate manufacturing, processing, welding, and reprocessing processes for contacts and conductive rods result in long production cycles, high costs, and difficulties in consistency control. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides an electron beam additive manufacturing method for an integrated copper-chromium contact-conductive rod assembly, comprising the following steps: S1. Design and preparation of a dedicated powder system: Prepare two types of powder, namely contact area powder and conductive rod area powder. Place the two powders in a vacuum drying oven at 120-130℃ and dry them for 5-10 hours to obtain contact area powder and conductive rod area powder with a moisture content of less than 0.5%. S2. Digital Modeling and Supporting Design: Using 3D modeling software, an integrated copper-chromium contact-conductive rod assembly model is created and sliced. The integrated copper-chromium contact-conductive rod assembly model includes a contact area, a gradient transition area, and a conductive rod area. A support structure is added to the lower end face of the conductive rod area, and the contact area between the support structure and the molding substrate is 65-100% of the bottom area of ​​the conductive rod. S3, Electron Beam Powder Bed Melting Integrated Molding: The electron beam powder bed chamber was evacuated to a vacuum level of 3.0 × 10⁻⁶. -3 -5.0×10-3 Pa, in the chamber, powder is laid layer by layer from bottom to top according to the conductive rod area, gradient transition area and contact area, with a single layer thickness of 50μm. After each layer of powder is laid, it is first preheated by electron beam and then heated and solidified by electron beam. Then the worktable is lowered and the next layer of powder is laid. The next layer is preheated and heated and solidified by electron beam. This process is repeated until the entire integrated copper-chromium contact-conductive rod assembly is printed, and the integrated copper-chromium contact-conductive rod assembly is obtained. S4. Post-printing processing: The integrated copper-chromium contact-conductive rod assembly is printed and subjected to in-situ stress annealing in an electron beam powder bed chamber. Then, it is removed from the electron beam powder bed chamber and subjected to hot isostatic pressing. Finally, the integrated copper-chromium contact-conductive rod assembly is machined to obtain the finished integrated copper-chromium contact-conductive rod assembly.

[0006] Furthermore, in step S1, the contact area powder is made of copper-chromium alloy spherical powder, which is prepared by vacuum induction melting gas atomization (VIGA). The copper-chromium alloy spherical powder has a chromium content of 53 wt% and the balance is copper, and the particle size of the copper-chromium alloy spherical powder is 53-106 μm.

[0007] Note: The CuCr53 pre-alloyed spherical powder prepared by vacuum induction melting gas atomization (VIGA) has the following core advantages: First, pre-alloying ensures that chromium is atomically uniformly distributed within each individual powder particle, eliminating the problem of density differences (chromium 7.19 g / cm³) that can occur with traditional mechanical mixing methods. 3 Copper 8.96 g / cm³ 3 The macroscopic segregation caused by [unspecified factor] lays the foundation for the overall compositional uniformity of large-size components. Secondly, high sphericity and good flowability are beneficial for achieving uniform powder spreading of a thin layer (50μm) during EBM, which is a prerequisite for obtaining a high-density preform. Most importantly, the composition design, which increases the nominal chromium content to 53wt%, is a precise compensation strategy for the preferential volatilization of chromium caused by high-energy electron beam bombardment during EBM. Experimental verification shows that, within the set process window, this composition design can stably control the actual chromium content in the final formed contact area within the ideal range of 50±0.5wt%, solving the industry-wide problem of controlling the active metal composition in additive manufacturing.

[0008] Furthermore, in step S1, the powder in the conductive rod area is CuTe alloy powder with a tellurium content of 0.5wt% and the balance being copper, or CuCrZr alloy powder with a chromium content of 0.5wt%, a zirconium content of 0.1% and the balance being copper, and the particle size of the powder in the conductive rod area is consistent with that in the contact area.

[0009] Note: High-conductivity copper alloy powders such as CuTe or CuCrZr are selected to optimize the performance of the conductive rod section. The addition of trace amounts of Te to the CuTe alloy significantly increases the recrystallization temperature of copper, ensuring high strength and resistance to softening during subsequent heat treatment and service, while having minimal impact on its electrical conductivity (≥90% IACS). The CuCrZr alloy, through the precipitation strengthening effect of Cr and Zr, achieves superior mechanical strength while maintaining high conductivity. Controlling the powder particle size in the conductive rod area to be consistent with that in the contact area not only ensures uniform powder distribution but also guarantees similar melting and solidification behavior of the two powder systems under the same preheating and solidification parameters. This reduces interlayer stress caused by differences in powder properties and is crucial for achieving a high-quality gradient transition.

[0010] Furthermore, in step S3, the preheating is performed by scanning and preheating the currently laid powder layer with an electron beam in defocus mode. The preheating temperature is set according to the area where the powder layer is located: the preheating temperature of the contact area is 900±20℃, the preheating temperature of the gradient transition area is 850±20℃, and the preheating temperature of the conductive rod area is 750±20℃. The beam spot diameter of the electron beam in defocus mode is 2-5mm.

[0011] Note: This regional ultra-high temperature preheating is the most critical means of suppressing thermal stress in this scheme. It makes the powder in each region melt at a temperature close to its solidus temperature, which greatly reduces the temperature difference between the molten pool and the surrounding materials.

[0012] Furthermore, in step S3, the heating and melting process uses an electron beam in focused mode to melt and scan the currently laid powder layer according to a "checkerboard" partitioning strategy. The current a1 of the electron beam in the contact area is 20-25mA, the scanning speed b1 is 900-1300mm / s, and the line spacing of the electron beam is 0.12-0.25mm. The current a2 of the electron beam in the conductive rod area is 15-20mA, the scanning speed b2 is 1100-1500mm / s, and the line spacing of the electron beam is 0.10-0.25mm. Theoretically, the gradient transition region requires N layers, but the actual number of layers in the gradient transition region is N-1. The formula for calculating N is: N = H / (h / 1000) + 1 (1) Where H is the thickness of the gradient transition zone in mm, and h is the thickness of a single layer of powder in μm; Beam I in each layer of the gradient transition region m The calculation formula is: I m =I m-1 +(a1-a2) / N (2) Among them, I mLet I0 be the beam current of the m-th layer in the gradient transition region, where m = 1 ~ (N-1), I0 = a2, a1 is the beam current of the electron beam in the contact region (in mA), and a2 is the beam current of the electron beam in the conductive rod region (in mA). Electron beam scanning speed v of each layer in the gradient transition region m The calculation method is as follows: v m =v m-1 +(b1-b2) / N (3) Among them, v m Let m be the scanning speed of the electron beam in the m-th layer of the gradient transition region, where m = 1 ~ (N-1), v0 = b2, b1 is the scanning speed of the electron beam in the contact region (mm / s), and b2 is the scanning speed of the electron beam in the conductive rod region (mm / s).

[0013] Note: The above-mentioned partitioned variable parameter melting and solidification strategy is the optimal energy input combination verified by thermodynamic simulation and experiments.

[0014] For the contact area (CuCr53): a higher volumetric energy density is used (determined by a higher beam current, moderate velocity and larger line spacing) because chromium has a high melting point (1860℃) and the alloy melt has a high viscosity, requiring sufficient energy to ensure complete melting and good spreading, and to avoid incomplete fusion defects.

[0015] For the conductive rod region (high-conductivity copper alloy): Copper alloy has a low melting point and excellent thermal conductivity. By using a lower volumetric energy density and a smaller line spacing, it is possible to prevent the molten pool from becoming too wide, the grains from becoming coarse, or even the copper from evaporating excessively due to excessive heat input. This allows for the maximum preservation of the high conductivity of the copper alloy while obtaining a fully dense structure.

[0016] Linear interpolation in the gradient transition zone ensures a smooth transition of heat input from the contact area to the conductive rod area, realizing continuous changes in the thermal history of the molten pool. This is a crucial process guarantee for obtaining a seamless transition in composition, microstructure, and properties.

[0017] Furthermore, in step S3, when spreading powder in the gradient transition zone, a mixed powder is formed by mixing the powder from the contact area and the powder from the conductive rod area. The mass ratio of the powder from the contact area in each layer of mixed powder in the gradient transition zone is increased layer by layer. The formula for calculating the incremental amount of powder in the contact area of ​​each layer of mixed powder in the gradient transition zone is as follows: C=100% / N (4) Where C is the incremental mass percentage of the contact area powder in each layer of mixed powder in the gradient transition zone, and N is the theoretical number of layers required to divide the gradient transition zone; the actual number of layers in the gradient transition zone is N-1. The formula for calculating the mass percentage of the contact area powder in each layer of mixed powder is as follows: W m =W m-1 +C (5) Among them, W m W1 represents the mass percentage of the contact area powder in the m-th layer of mixed powder in the gradient transition zone, where m = 1 ~ (N-1). The mass percentage W1 of the contact area powder in the first layer of mixed powder is also C.

[0018] Explanation: The gradient transition zone involves mixing powders from the contact area and the conductive rod area layer by layer according to a specific function (e.g., linear). Its core function is to achieve a continuous gradient in material composition and thermophysical properties (e.g., coefficient of thermal expansion). Taking an increase of approximately 1.23% in powder content per layer in the contact area as an example, this microscopic compositional design allows the transition from pure conductive rod material to pure contact material to be completed within 80 layers (4 mm). This design effectively smooths out the significant difference in thermal expansion coefficients between copper and chromium (Cu: 17 × 10⁻⁶). -6 / K,Cr:6×10 -6 The interfacial thermal stress induced by / K avoids stress concentration and interfacial cracking caused by abrupt performance changes in traditional brazing or direct connection. At the same time, in the subsequent hot isostatic pressing process, this gradient structure provides an ideal path for interdiffusion of elements, ultimately forming a metallurgical bonding transition zone with continuously changing chemical composition and crystal structure, whose bonding strength can be higher than that of the weaker base material itself.

[0019] Furthermore, during the melting and solidification process in step S3, an infrared thermal imager integrated in the chamber is used to monitor the temperature distribution of the molten pool and its heat-affected zone in real time. When the system detects that the temperature of a certain area deviates from the set value by more than ±25℃, the beam current is automatically fine-tuned by ±1.5mA when scanning the adjacent grids of that area based on the temperature feedback from the infrared thermal imager. The deviation of the area temperature from the set value is negatively correlated with the beam current fine-tuning, so as to achieve dynamic balance of heat input and ensure dimensional accuracy and tissue stability.

[0020] Description: An integrated infrared thermal imager, with a deviation threshold of ±25℃ and a beam current fine-tuning of ±1.5mA, constitutes a real-time feedback-feedforward composite control system. When printing large-size components using EBM, localized overheating or insufficient heat is highly likely due to the long scanning path and significant heat accumulation effect. This system can capture such temperature field fluctuations in real time and perform "local smoothing" by fine-tuning the energy input of subsequent adjacent grids. This not only controls the temperature fluctuations throughout the forming process within a precise range (e.g., reducing melt pool temperature fluctuations from over ±100℃ in traditional open-loop control to within ±30℃), ensuring that each micro-region experiences a nearly uniform thermal history, thus obtaining a highly uniform microstructure (e.g., reducing the standard deviation of chromium phase size distribution by more than 50%), but also significantly improves the overall dimensional accuracy (tolerance controllable within ±0.1%) and shape fidelity of the component, effectively suppressing warping deformation.

[0021] Furthermore, in step S4, the in-situ stress annealing process involves first heating the integrated copper-chromium contact-conductive rod assembly printed part to 890-910°C in an electron beam powder bed chamber and holding it for 55-65 minutes. Then, the integrated copper-chromium contact-conductive rod assembly printed part is cooled to 150°C at a cooling rate of 5-10°C / min. Finally, the cooling system is turned off and the part is allowed to cool naturally to room temperature.

[0022] Note: Immediately after printing, in-situ annealing is performed within the forming chamber, a form of "online" stress relaxation. Its advantage lies in keeping the part at a high temperature, avoiding the additional thermal cycle caused by reheating after cooling to room temperature. Holding at this temperature allows for the annihilation of a large number of crystal defects such as dislocations and vacancies formed during printing, stabilizing the metastable structure and eliminating over 70% of the residual stress in the printed state. Subsequent controlled slow cooling further prevents the generation of new thermal stress due to excessively rapid cooling. This step is a crucial safeguard against stress cracking or deformation in large, complex parts during subsequent processing or use.

[0023] Furthermore, in step S4, the hot isostatic pressing process involves placing the integrated copper-chromium contact-conductive rod assembly printed part, which has undergone in-situ stress annealing, into a hot isostatic pressing apparatus. The heating temperature of the hot isostatic pressing apparatus is 915-925℃, and the process is carried out in an argon atmosphere of 140-150MPa for 120-360 minutes.

[0024] Explanation: Hot isostatic pressing (HIP) combines high temperature and high pressure, serving three main purposes: First, densification: High-pressure argon gas isotropically pressurizes the parts, effectively closing isolated spherical pores (below micrometers) that may remain from the EBM process. This increases the density from 99.0%-99.5% in the printed state to nearly 100% of the theoretical density, significantly improving the material's dynamic load-bearing capacity and electrical performance stability. Second, promoting diffusion: Applying high pressure at high temperature greatly accelerates the interdiffusion rate of copper and chromium atoms across the original powder interface in the gradient transition zone, transforming the transition zone from "mechanical mixing" to true "metallurgical alloying," resulting in a significant increase in interfacial bonding strength. Third, optimizing microstructure: The high-temperature, high-pressure environment helps refine grains and dissolve brittle phases, making the overall material properties more uniform and stable.

[0025] Furthermore, in step S4, the machining process involves removing the molded substrate and support structure using wire cutting, grinding the contact working surface of the integrated copper-chromium contact-conductive rod assembly printed part using a CNC machine tool to ensure that the flatness of the contact working surface is ≤0.01mm and the surface roughness Ra is ≤0.4μm, and then turning the conductive rod connection part of the integrated copper-chromium contact-conductive rod assembly printed part according to the assembly dimension requirements.

[0026] Note: The precision machining described is not a typical post-processing step, but a customized process designed for the extreme operating conditions of vacuum circuit breaker contacts. Ultra-high flatness ensures surface contact during contact mating, minimizing contact resistance and guaranteeing uniform arc distribution on the working surface, preventing localized overheating and ablation. Ultra-low surface roughness directly reduces microscopic field strength concentration points, contributing to improved pressure resistance of the vacuum gap. Furthermore, precision turning of the conductive rod connection ensures high coaxiality and tight fit between the component and other parts of the circuit breaker, guaranteeing mechanical stability and electrical contact reliability during dynamic opening and closing.

[0027] The beneficial effects of this invention are: (1) The dual powder system and gradient transition design of the present invention can form a continuously changing powder ratio layer through pre-physical mixing, and construct a technical solution for an interface-free gradient transition zone. Through one-step molding technology, an integrated component with a continuous gradual change in composition and full metallurgical bonding between the contact and the conductive rod is manufactured, thus eliminating interface failure from the root.

[0028] (2) The present invention uses electron beam powder bed melting and integral molding. According to the powder type of the area to be melted, different ultra-high preheating temperatures are dynamically and independently set and maintained. At the same time, according to the parameters of energy input in the material area, a scanning strategy that strongly correlates and binds specific electron beam process parameters with characteristic material areas, as well as the continuous transition rules of parameters in the gradient area, can effectively avoid the occurrence of large-size CuCr50 cracking problem and achieve a smooth transition of performance in the gradient transition area.

[0029] (3) The present invention can effectively eliminate the residual stress of the integrated copper-chromium contact-conductive rod assembly through the printing post-processing process, and can effectively avoid macroscopic cracks and part warping caused by high residual thermal stress.

[0030] (4) The conductive rod of the present invention has high conductivity and meets the requirements of wear resistance of the contact part and conductivity of the conductive rod. It avoids the complicated process of manufacturing independent contacts and conductive rods, simplifies the production process of copper-chromium contact-conductive rod assembly, and can not only improve the production efficiency of copper-chromium contact-conductive rod assembly, but also ensure the consistency of the quality of the produced copper-chromium contact-conductive rod assembly. Attached Figure Description

[0031] Figure 1 This is a metallographic diagram of the present invention. Detailed Implementation

[0032] Example 1: An electron beam additive manufacturing method for an integrated copper-chromium contact-conductive rod assembly includes the following steps: S1. Design and preparation of a dedicated powder system: Two types of powder were prepared, including contact area powder and conductive rod area powder, respectively. Both powders were dried in a vacuum drying oven at 120℃ for 5 hours to obtain contact area powder and conductive rod area powder with a moisture content of less than 0.5%. The contact area powder was made of copper-chromium alloy spherical powder, prepared by vacuum induction melting gas atomization (VIGA). The chromium content in the copper-chromium alloy spherical powder was 53wt%, with the balance being copper, and the particle size was 53-58μm. The CuCr53 pre-alloyed spherical powder prepared by vacuum induction melting gas atomization (VIGA) has the following core advantages: First, pre-alloying ensures that chromium is atomically uniformly distributed within each powder particle, eliminating the problem caused by density differences (chromium 7.19g / cm³) in traditional mechanical mixing methods. 3 Copper 8.96 g / cm³ 3The macroscopic segregation caused by the high tellurium content lays the foundation for the overall compositional uniformity of large-size components. Secondly, high sphericity and good flowability are conducive to achieving thin-layer (50μm) uniform powder spreading during EBM, which is a prerequisite for obtaining a high-density preform. The most critical aspect is the composition design, which increases the nominal chromium content to 53wt%, a precise compensation strategy for the preferential volatilization of chromium caused by high-energy electron beam bombardment during EBM. Experimental verification shows that, under the set process window, this composition design can stably control the actual chromium content in the final formed contact area within the ideal range of 50±0.5wt%, solving the industry problem of controlling the active metal composition in additive manufacturing. The powder in the conductive rod area uses high-conductivity copper alloy powder, specifically CuTe alloy powder with a tellurium content of 0.5wt% and the balance being copper, or CuTe alloy powder with a chromium content of 0.5wt%, a zirconium content of 0.1%, and the balance being copper. The powder in the conductive rod region and the powder in the contact region are of the same particle size as CuCrZr alloy powder. High-conductivity copper alloy powders such as CuTe or CuCrZr are selected to optimize the performance of the conductive rod section. The addition of trace amounts of Te to the CuTe alloy significantly increases the recrystallization temperature of copper, ensuring high strength and resistance to softening during subsequent heat treatment and service, while having minimal impact on its electrical conductivity (≥90% IACS). The CuCrZr alloy, through the precipitation strengthening effect of Cr and Zr, achieves superior mechanical strength while maintaining high conductivity. Controlling the particle size of the powder in the conductive rod region to be consistent with that in the contact region not only ensures uniform powder distribution but also ensures that the two powder systems have similar melting and solidification behaviors under the same preheating and solidification parameters, reducing interlayer stress caused by differences in powder properties, which is key to achieving a high-quality gradient transition. S2. Digital Modeling and Supporting Design: Using 3D modeling software, an integrated copper-chromium contact-conductive rod assembly model was created and sliced. The integrated copper-chromium contact-conductive rod assembly model includes a contact area, a gradient transition area, and a conductive rod area. The gradient transition area is designed to be 4mm thick. A support structure is added to the lower end face of the conductive rod area. The contact area between the support structure and the molding substrate is 65% of the bottom area of ​​the conductive rod. S3, Electron Beam Powder Bed Melting Integrated Molding: The electron beam powder bed chamber was evacuated to a vacuum level of 3.0 × 10⁻⁶. -3 Pa, in the chamber, powder is laid layer by layer from bottom to top according to the conductive rod area, gradient transition area and contact area, with a single layer thickness of 50μm. After each layer of powder is laid, it is first preheated by electron beam and then heated and solidified by electron beam. Then the worktable is lowered and the next layer of powder is laid. The next layer is preheated and heated and solidified by electron beam. This process is repeated until the entire integrated copper-chromium contact-conductive rod assembly is printed, and the integrated copper-chromium contact-conductive rod assembly is obtained. Preheating involves scanning and preheating the currently deposited powder layer with an electron beam in defocus mode. The preheating temperature is set according to the region where the powder layer is located: 880℃ for the contact area, 830℃ for the gradient transition area, and 730℃ for the conductive rod area. The beam spot diameter of the electron beam in defocus mode is 2mm. This regional ultra-high temperature preheating is the most critical means of suppressing thermal stress in this scheme. It allows the powder in each region to melt at a temperature close to its solidus temperature, greatly reducing the temperature difference between the molten pool and the surrounding material. Heating and melting are performed by scanning the currently laid powder layer in a "checkerboard" partitioning strategy using an electron beam in focusing mode. The electron beam current a1 in the contact area is 20mA, the electron beam scanning speed b1 is 900mm / s, and the electron beam line spacing is 0.12mm. The electron beam current a2 in the conductive rod area is 15mA, the electron beam scanning speed b2 is 1100mm / s, and the electron beam line spacing is 0.10mm. Theoretically, the gradient transition region requires N layers, but the actual number of layers in the gradient transition region is N-1. The formula for calculating N is: N = H / (h / 1000) + 1 (1) Where H is the thickness of the gradient transition zone in mm, and h is the thickness of a single layer of powder in μm; Beam I in each layer of the gradient transition region m The calculation formula is: I m =I m-1 +(a1-a2) / N (2) Among them, I m Let I0 be the beam current of the m-th layer in the gradient transition region, where m = 1 ~ (N-1), I0 = a2, a1 is the beam current of the electron beam in the contact region (in mA), and a2 is the beam current of the electron beam in the conductive rod region (in mA). Electron beam scanning speed v of each layer in the gradient transition region m The calculation method is as follows: v m =v m-1 +(b1-b2) / N (3) Among them, v m Let m be the scanning speed of the electron beam in the m-th layer of the gradient transition region, where m = 1 ~ (N-1), v0 = b2, b1 is the scanning speed of the electron beam in the contact region (mm / s), and b2 is the scanning speed of the electron beam in the conductive rod region (mm / s).

[0033] Based on a gradient transition zone thickness of 4mm, the theoretical number of layers required is N = 4 / (50 / 1000) + 1 = 81 layers; That is, the gradient transition zone is designed to be 4mm thick, the single-layer powder thickness is 50μm, the actual number of powder layers in the gradient transition zone is 80, the electron beam current during the first layer printing is 15 + 0.06 = 15.06mA, and so on, with the electron beam current increasing by 0.06mA for each layer. The scanning speed of the electron beam during the first layer printing is 1100 - 2.47 = 1097.53mm / s, and so on, with the scanning speed of the electron beam decreasing by 2.47mm / s for each layer.

[0034] The aforementioned partitioned variable parameter melting and solidification strategy is the optimal energy input combination verified through thermodynamic simulation and experiments; For the contact area (CuCr53): a higher volumetric energy density is used (determined by a higher beam current, moderate velocity and larger line spacing) because chromium has a high melting point (1860℃) and the alloy melt has a high viscosity. Sufficient energy is needed to ensure complete melting and good spreading, and to avoid incomplete fusion defects. For the conductive rod region (high-conductivity copper alloy): Copper alloy has a low melting point and excellent thermal conductivity. By using a lower volumetric energy density and a smaller line spacing, it is possible to prevent the molten pool from becoming too wide, the grains from becoming coarse, or even the copper element from evaporating excessively due to excessive heat input. This allows the high conductivity of the copper alloy to be preserved to the maximum extent while obtaining a fully dense structure. Linear interpolation in the gradient transition zone ensures a smooth transition of heat input from the contact area to the conductive rod area, realizing continuous changes in the thermal history of the molten pool. This is a crucial process guarantee for obtaining a seamless transition in composition, microstructure, and properties. When spreading powder in the gradient transition zone, a mixed powder is formed by mixing the powder from the contact area and the powder from the conductive rod area. The mass ratio of the powder from the contact area in each layer of mixed powder in the gradient transition zone is increased layer by layer. The formula for calculating the incremental amount of powder in the contact area of ​​each layer of mixed powder in the gradient transition zone is as follows: C=100% / N (4) Where C is the incremental mass percentage of the contact area powder in each layer of mixed powder in the gradient transition zone, and N is the theoretical number of layers required to divide the gradient transition zone; the actual number of layers in the gradient transition zone is N-1. The formula for calculating the mass percentage of the contact area powder in each layer of mixed powder is as follows: W m =W m-1 +C (5) Among them, W m W1 represents the mass percentage of the contact area powder in the m-th layer of mixed powder in the gradient transition zone, where m = 1 ~ (N-1). The mass percentage W1 of the contact area powder in the first layer of mixed powder is also C. The gradient transition zone is designed with a thickness of 4 mm. The incremental amount of powder in the contact area increases layer by layer, C = 100% / 81 = 1.23%. That is, the thickness of a single layer of powder in the gradient transition zone is 50 μm, and the total number of powder layers in the gradient transition zone is 80. The first layer of powder in the contact area accounts for 1.23% of the total mass of the mixed powder. And so on, the proportion of powder in the contact area increases by 1.23% in each layer of mixed powder.

[0035] The gradient transition zone employs a layer-by-layer mixing of powders from the contact area and the conductive rod area according to a specific function (such as linearity). Its core function is to achieve a continuous gradient in material composition and thermophysical properties (such as the coefficient of thermal expansion). Taking an increase of approximately 1.23% in powder content per layer in the contact area as an example, this microscopic compositional design allows the transition from pure conductive rod material to pure contact material to be completed within 80 layers (4 mm). This design effectively smooths out the significant difference in thermal expansion coefficients between copper and chromium (Cu: 17 × 10⁻⁶). -6 / K,Cr:6×10 -6 The interfacial thermal stress caused by / K avoids stress concentration and interfacial cracking caused by abrupt performance changes in traditional brazing or direct connection; at the same time, in the subsequent hot isostatic pressing process, this gradient structure provides an ideal path for interdiffusion of elements, and finally forms a metallurgical bonding transition zone with continuous changes in chemical composition and crystal structure, whose bonding strength can be higher than that of the weaker base material itself. S4. Post-printing processing: The integrated copper-chromium contact-conducting rod assembly is printed in an electron beam powder bed chamber and then subjected to in-situ stress annealing. It is then removed from the electron beam powder bed chamber and subjected to hot isostatic pressing. Finally, the integrated copper-chromium contact-conducting rod assembly is printed and machined to obtain the finished integrated copper-chromium contact-conducting rod assembly. In-situ stress annealing involves heating the integrated copper-chromium contact-conductive rod assembly to 890°C in an electron beam powder bed chamber and holding it for 55 minutes. Then, the assembly is cooled to 150°C at a rate of 5°C / min, and the cooling system is shut off for natural cooling to room temperature. Immediately after printing, in-situ annealing is performed in the forming chamber, a form of "online" stress relaxation. Its advantage lies in maintaining the part at a high temperature, avoiding the additional thermal cycle caused by reheating after cooling to room temperature. Holding at the above temperature allows for the annihilation of many crystal defects such as dislocations and vacancies formed during printing, stabilizing the metastable structure and eliminating over 70% of residual stress in the printed state. Subsequent controlled slow cooling further prevents the generation of new thermal stress due to rapid cooling. This step is a crucial safeguard against stress cracking or deformation in large-sized, complex structural parts during subsequent processing or use. Hot isostatic pressing (HIP) involves placing the integrated copper-chromium contact-conductive rod assembly printed part, which has undergone in-situ stress annealing, into a hot isostatic pressing (HIP) apparatus. The HIP apparatus is heated to 915℃ and treated for 120 minutes in an argon atmosphere at 140MPa. Hot isostatic pressing (HIP) combines high temperature and high pressure, serving three main purposes: First, densification: High-pressure argon gas isotropically pressurizes the parts, effectively closing isolated spherical pores (smaller than micrometers) that may remain during EBM, increasing the density from 99.0%-99.5% in the printed state to nearly 100% of the theoretical density, significantly improving the material's dynamic load-bearing capacity and electrical performance stability. Second, promoting diffusion: Applying high pressure at high temperature greatly accelerates the interdiffusion rate of copper and chromium atoms across the original powder interface in the gradient transition zone, transforming the transition zone from "mechanical mixing" to "metallurgical alloying," resulting in a significant increase in interfacial bonding strength. Third, optimizing microstructure: The high-temperature, high-pressure environment helps refine grains and dissolve brittle phases, making the overall material properties more uniform and stable. Machining involves removing the molded substrate and support structure using wire cutting, grinding the contact working surface of the integrated copper-chromium contact-conductive rod assembly printed part using a CNC machine tool to ensure that the flatness of the contact working surface is ≤0.01mm and the surface roughness Ra is ≤0.4μm, and then turning the conductive rod connection part of the integrated copper-chromium contact-conductive rod assembly printed part according to the assembly dimension requirements. The precision machining described is not a typical post-processing step, but a customized process designed for the extreme operating conditions of vacuum circuit breaker contacts. The ultra-high flatness ensures surface contact during contact engagement, minimizing contact resistance and ensuring uniform arc distribution on the working surface to prevent localized overheating and erosion. The ultra-low surface roughness directly reduces microscopic field strength concentration points, which helps improve the withstand voltage of the vacuum gap. In addition, the precision turning of the conductive rod connection ensures high coaxiality and tight fit between the components and other parts of the circuit breaker, guaranteeing mechanical stability and electrical contact reliability during dynamic opening and closing.

[0036] Example 2: The difference between this embodiment and Embodiment 1 is that in step S1 of this embodiment, the two powders are placed in a vacuum drying oven at 125°C and dried for 8 hours; the particle size of the copper-chromium alloy spherical powder is 58-75μm. In step S2, the contact area between the support structure and the molded substrate is 80% of the bottom area of ​​the conductive rod. In step S3, the electron beam powder bed chamber is evacuated to a vacuum level of 4.0 × 10⁻⁶. -3Pa; the preheating temperature of the contact area is 900℃, the preheating temperature of the gradient transition area is 850℃, the preheating temperature of the conductive rod area is 750℃, and the beam spot diameter of the electron beam in defocusing mode is 3mm. Heating and melting are performed by scanning the currently laid powder layer in a "checkerboard" partitioning strategy using an electron beam in focusing mode. The electron beam current a1 in the contact area is 23mA, the electron beam scanning speed b1 is 1200mm / s, and the electron beam line spacing is 0.20mm. The electron beam current a2 in the conductive rod area is 18mA, the electron beam scanning speed b2 is 1300mm / s, and the electron beam line spacing is 0.20mm. Theoretically, the gradient transition region requires N layers, but the actual number of layers in the gradient transition region is N-1. The formula for calculating N is: N = H / (h / 1000) + 1 (1) Where H is the thickness of the gradient transition zone in mm, and h is the thickness of a single layer of powder in μm; Beam I in each layer of the gradient transition region m The calculation formula is: I m =I m-1 +(a1-a2) / N (2) Among them, I m Let I0 be the beam current of the m-th layer in the gradient transition region, where m = 1 ~ (N-1), I0 = a2, a1 is the beam current of the electron beam in the contact region (in mA), and a2 is the beam current of the electron beam in the conductive rod region (in mA). Electron beam scanning speed v of each layer in the gradient transition region m The calculation method is as follows: v m =v m-1 +(b1-b2) / N (3) Among them, v m Let m be the scanning speed of the electron beam in the m-th layer of the gradient transition region, where m = 1 ~ (N-1), v0 = b2, b1 is the scanning speed of the electron beam in the contact region (mm / s), and b2 is the scanning speed of the electron beam in the conductive rod region (mm / s).

[0037] Based on a gradient transition zone thickness of 4mm, the theoretical number of layers required is N = 4 / (50 / 1000) + 1 = 81 layers; That is, the gradient transition zone is designed to be 4mm thick, the single-layer powder thickness is 50μm, the actual number of powder layers in the gradient transition zone is 80, the electron beam current during the first layer printing is 18 + 0.06 = 18.06mA, and so on, with the electron beam current increasing by 0.06mA for each layer. The scanning speed of the electron beam during the first layer printing is 1300 - 1.23 = 1298.77mm / s, and so on, with the scanning speed of the electron beam decreasing by 1.23mm / s for each layer.

[0038] In step S4, the in-situ stress annealing process involves first heating the integrated copper-chromium contact-conductive rod assembly printed part to 900°C in an electron beam powder bed chamber and holding it for 60 minutes, then cooling the integrated copper-chromium contact-conductive rod assembly printed part to 150°C at a cooling rate of 8°C / min; the hot isostatic pressing equipment is heated to 920°C and treated in an argon atmosphere of 145MPa for 200 minutes. Example 3: The difference between this embodiment and Embodiment 1 is that in step S1 of this embodiment, the two powders are placed in a vacuum drying oven at 130°C and dried for 10 hours; the particle size of the copper-chromium alloy spherical powder is 75-106 μm. In step S2, the contact area between the support structure and the molded substrate is 100% of the bottom area of ​​the conductive rod. In step S3, the electron beam powder bed chamber is evacuated to a vacuum level of 5.0 × 10⁻⁶. -3 Pa; the preheating temperature of the contact area is 920℃, the preheating temperature of the gradient transition area is 870℃, the preheating temperature of the conductive rod area is 790℃, and the beam spot diameter of the electron beam in defocusing mode is 5mm. Heating and melting are performed by scanning the currently laid powder layer in a "checkerboard" partitioning strategy using an electron beam in focused mode. The electron beam current a1 in the contact area is 25mA, the electron beam scanning speed b1 is 1300mm / s, and the electron beam line spacing is 0.25mm. The electron beam current a2 in the conductive rod area is 20mA, the electron beam scanning speed b2 is 1500mm / s, and the electron beam line spacing is 0.25mm. Theoretically, the gradient transition region requires N layers, but the actual number of layers in the gradient transition region is N-1. The formula for calculating N is: N = H / (h / 1000) + 1 (1) Where H is the thickness of the gradient transition zone in mm, and h is the thickness of a single layer of powder in μm; Beam I in each layer of the gradient transition region m The calculation formula is: I m =I m-1 +(a1-a2) / N (2) Among them, I m Let I0 be the beam current of the m-th layer in the gradient transition region, where m = 1 ~ (N-1), I0 = a2, a1 is the beam current of the electron beam in the contact region (in mA), and a2 is the beam current of the electron beam in the conductive rod region (in mA). Electron beam scanning speed v of each layer in the gradient transition region m The calculation method is as follows: v m =vm-1 +(b1-b2) / N (3) Among them, v m Let m be the scanning speed of the electron beam in the m-th layer of the gradient transition region, where m = 1 ~ (N-1), v0 = b2, b1 is the scanning speed of the electron beam in the contact region (mm / s), and b2 is the scanning speed of the electron beam in the conductive rod region (mm / s).

[0039] Based on a gradient transition zone thickness of 4mm, the theoretical number of layers required is N = 4 / (50 / 1000) + 1 = 81 layers; That is, the gradient transition zone is designed to be 4mm thick, the single-layer powder thickness is 50μm, the actual number of powder layers in the gradient transition zone is 80, the electron beam current during the first layer printing is 20 + 0.06 = 20.06mA, and so on, with the electron beam current increasing by 0.06mA for each layer. The scanning speed of the electron beam during the first layer printing is 1500 - 2.47 = 1497.53mm / s, and so on, with the scanning speed of the electron beam decreasing by 2.47mm / s for each layer.

[0040] In step S4, the in-situ stress annealing process involves first heating the integrated copper-chromium contact-conductive rod assembly printed part to 910°C in an electron beam powder bed chamber and holding it for 65 minutes, then cooling the integrated copper-chromium contact-conductive rod assembly printed part to 150°C at a cooling rate of 10°C / min; the hot isostatic pressing equipment is heated to 925°C and treated in an argon atmosphere of 150MPa for 360 minutes. Compared with Examples 1-3, the integrated copper-chromium contact-conductive rod assembly prepared in Example 2 showed the best performance in terms of overall density, average size of Cr phase in the contact area, room temperature tensile strength in the gradient region, thermal resistance at the interface between the contact and the rod, uniformity of cross-sectional hardness, conductivity of the conductive rod, overall circuit resistance, arc erosion resistance, and performance degradation after thermal cycling. Therefore, Example 2 is the best example. Example 4: The difference between this embodiment and Embodiment 2 is that, in this embodiment, during the melting and solidification process in step S3, an infrared thermal imager integrated within the chamber is used to monitor the temperature distribution of the molten pool and its heat-affected zone in real time. When the system detects that the temperature of a certain area deviates from the set value by more than ±25°C, the beam current is automatically fine-tuned by ±1.5mA when scanning adjacent grids of that area based on the temperature feedback from the infrared thermal imager. The deviation of the area temperature from the set value and the beam current fine-tuning are negatively correlated to achieve dynamic balance of heat input, ensuring dimensional accuracy and microstructure stability. For example, when the system detects that the temperature of a certain area deviates from the set value by more than +25°C, the beam current is automatically fine-tuned by -1.5mA when scanning adjacent grids of that area based on the temperature feedback from the infrared thermal imager; conversely, when the system detects that the temperature of a certain area deviates from the set value by more than -25°C, the beam current is automatically fine-tuned by +1.5mA when scanning adjacent grids of that area based on the temperature feedback from the infrared thermal imager.

[0041] Compared to Example 2, this embodiment integrates an infrared thermal imager and sets a deviation threshold of ±25℃ and a beam current fine-tuning amount of ±1.5mA to form a real-time feedback-feedforward composite control system. When printing large-size components using EBM, due to the long scanning path and significant heat accumulation effect, local overheating or insufficient heat is prone to occur. This system can capture such temperature field fluctuations in real time and perform "local smoothing" by fine-tuning the energy input of subsequent adjacent grids. This not only controls the temperature fluctuations throughout the forming process within a precise range (e.g., reducing melt pool temperature fluctuations from over ±100℃ in traditional open-loop control to within ±30℃), ensuring that each micro-region experiences a nearly uniform thermal history, thereby obtaining a highly uniform microstructure (e.g., the standard deviation of chromium phase size distribution can be reduced by more than 50%), but also significantly improves the overall dimensional accuracy of the component (tolerance can be controlled within ±0.1%) and shape fidelity, effectively suppressing warping deformation.

[0042] Therefore, in actual production, the products produced in Example 4 have higher consistency.

[0043] Experimental example: This invention group (Example 4): An integrated copper-chromium contact-conductive rod assembly was prepared strictly according to the electron beam additive manufacturing method of the integrated copper-chromium contact-conductive rod assembly described in Example 4 of this invention. The metallographic structure is as follows: Figure 1 As shown, the contact diameter is Φ110mm, and CuCr53 pre-alloy powder and CuTe0.5 alloy powder are used to implement zoned preheating and closed-loop control processes.

[0044] Comparative Example A (Existing Integrated Sintered Component): A traditional powder metallurgy process of mixing, molding, and sintering was employed. Cu and Cr powders of the same composition were mechanically mixed, then layered with CuTe powder and filled into a mold. The mixture was sintered in a vacuum sintering furnace at 1050°C for 2 hours to produce an integrated component of the same size. This method represents an existing technology characterized by "no interface but with abrupt compositional changes."

[0045] Comparative Example B (Conventional Brazed Assembly): Utilizing mainstream industry processes, CuCr50 contacts were fabricated using vacuum infiltration, and CuTe0.5 conductive rods were fabricated using forging. These were then brazed together in a vacuum furnace using a high-temperature silver-based brazing filler metal (BAg-8). This method represents existing technology that offers "high performance but with a mechanical interface."

[0046] Table 1 compares the performance of the integrated copper-chromium contact-conductive rod assembly prepared in Example 4 of this invention with that of Comparative Examples A and B: Table 1: Performance Comparison Table of the Invention Group, Comparative Example A, and Comparative Example B

[0047] In conclusion, comparing the performance of the present invention group with that of Comparative Examples A and B, it can be seen that the integrated copper-chromium contact-conductive rod assembly prepared by the present invention group is superior to the prior art in terms of microstructure, basic mechanical and physical properties, key electrical properties, and simulated working condition testing.

Claims

1. An electron beam additive manufacturing method for an integrated copper-chromium contact-conductive rod assembly, characterized in that, Includes the following steps: S1. Design and preparation of a dedicated powder system: Prepare two types of powder, namely contact area powder and conductive rod area powder. Place the two powders in a vacuum drying oven at 120-130℃ and dry them for 5-10 hours to obtain contact area powder and conductive rod area powder with a moisture content of less than 0.5%. S2. Digital Modeling and Supporting Design: Using 3D modeling software, an integrated copper-chromium contact-conductive rod assembly model is created and sliced. The integrated copper-chromium contact-conductive rod assembly model includes a contact area, a gradient transition area, and a conductive rod area. A support structure is added to the lower end face of the conductive rod area, and the contact area between the support structure and the molding substrate is 65-100% of the bottom area of ​​the conductive rod. S3, Electron Beam Powder Bed Melting Integrated Molding: The electron beam powder bed chamber was evacuated to a vacuum level of 3.0 × 10⁻⁶. -3 -5.0×10 -3 Pa, in the chamber, powder is laid layer by layer from bottom to top according to the conductive rod area, gradient transition area and contact area, with a single layer thickness of 50μm. After each layer of powder is laid, it is first preheated by electron beam and then heated and solidified by electron beam. Then the worktable is lowered and the next layer of powder is laid. The next layer is preheated and heated and solidified by electron beam. This process is repeated until the entire integrated copper-chromium contact-conductive rod assembly is printed, and the integrated copper-chromium contact-conductive rod assembly is obtained. S4. Post-printing processing: The integrated copper-chromium contact-conductive rod assembly is printed and subjected to in-situ stress annealing in an electron beam powder bed chamber. Then, it is removed from the electron beam powder bed chamber and subjected to hot isostatic pressing. Finally, the integrated copper-chromium contact-conductive rod assembly is machined to obtain the finished integrated copper-chromium contact-conductive rod assembly.

2. The electron beam additive manufacturing method for an integrated copper-chromium contact-conductive rod assembly as described in claim 1, characterized in that, In step S1, the contact area powder is made of copper-chromium alloy spherical powder, which is prepared by vacuum induction melting gas atomization (VIGA). The copper-chromium alloy spherical powder has a chromium content of 53 wt% and the balance is copper, and the particle size of the copper-chromium alloy spherical powder is 53-106 μm.

3. The electron beam additive manufacturing method for an integrated copper-chromium contact-conductive rod assembly as described in claim 1, characterized in that, In step S1, the powder in the conductive rod area is CuTe alloy powder with a tellurium content of 0.5 wt% and the balance being copper, or CuCrZr alloy powder with a chromium content of 0.5 wt%, a zirconium content of 0.1% and the balance being copper. The particle size of the powder in the conductive rod area is consistent with that in the contact area.

4. The electron beam additive manufacturing method for an integrated copper-chromium contact-conductive rod assembly as described in claim 1, characterized in that, In step S3, preheating is performed by scanning and preheating the currently deposited powder layer with an electron beam in defocus mode. The preheating temperature is set according to the area where the powder layer is located: the preheating temperature of the contact area is 900±20℃, the preheating temperature of the gradient transition area is 850±20℃, and the preheating temperature of the conductive rod area is 750±20℃. The beam spot diameter of the electron beam in defocus mode is 2-5mm.

5. The electron beam additive manufacturing method for an integrated copper-chromium contact-conductive rod assembly as described in claim 1, characterized in that, In step S3, the heating and melting process uses an electron beam in focused mode to melt and scan the currently laid powder layer according to a "checkerboard" partitioning strategy. The current a1 of the electron beam in the contact area is 20-25mA, the scanning speed b1 is 900-1300mm / s, and the line spacing of the electron beam is 0.12-0.25mm. The current a2 of the electron beam in the conductive rod area is 15-20mA, the scanning speed b2 is 1100-1500mm / s, and the line spacing of the electron beam is 0.10-0.25mm. Theoretically, the gradient transition region requires N layers, but the actual number of layers in the gradient transition region is N-1. The formula for calculating N is: N = H / (h / 1000) + 1 (1) Where H is the thickness of the gradient transition zone in mm, and h is the thickness of a single layer of powder in μm; Beam I in each layer of the gradient transition region m The calculation formula is: I m =I m-1 +(a1-a2) / N (2) Among them, I m Let I0 be the beam current of the m-th layer in the gradient transition region, where m = 1 ~ (N-1), I0 = a2, a1 is the beam current of the electron beam in the contact region (in mA), and a2 is the beam current of the electron beam in the conductive rod region (in mA). Electron beam scanning speed v of each layer in the gradient transition region m The calculation method is as follows: in m =v m-1 +(b1-b2) / N (3) Among them, v m Let m be the scanning speed of the electron beam in the m-th layer of the gradient transition region, where m = 1 ~ (N-1), v0 = b2, b1 is the scanning speed of the electron beam in the contact region (mm / s), and b2 is the scanning speed of the electron beam in the conductive rod region (mm / s).

6. The electron beam additive manufacturing method for an integrated copper-chromium contact-conductive rod assembly as described in claim 5, characterized in that, In step S3, when spreading powder in the gradient transition zone, a mixed powder is formed by mixing the powder from the contact area and the powder from the conductive rod area. The mass ratio of the powder from the contact area in each layer of mixed powder in the gradient transition zone is increased layer by layer. The formula for calculating the incremental amount of powder in the contact area of ​​each layer of mixed powder in the gradient transition zone is as follows: C=100% / N (4) Where C is the incremental mass percentage of the contact area powder in each layer of mixed powder in the gradient transition zone, and N is the theoretical number of layers required to divide the gradient transition zone; the actual number of layers in the gradient transition zone is N-1. The formula for calculating the mass percentage of the contact area powder in each layer of mixed powder is as follows: W m =W m-1 +C (5) Among them, W m The mass percentage of the contact area powder in the m-th layer of mixed powder in the gradient transition zone is given by m = 1 ~ (N-1). The mass percentage of the contact area powder in the first layer of mixed powder, W1, is also C.

7. The electron beam additive manufacturing method for an integrated copper-chromium contact-conductive rod assembly as described in claim 1, characterized in that, During the melting and solidification process in step S3, an infrared thermal imager integrated in the chamber is used to monitor the temperature distribution of the molten pool and its heat-affected zone in real time. When the system detects that the temperature of a certain area deviates from the set value by more than ±25℃, the beam current is automatically adjusted by ±1.5mA when scanning the adjacent grids of that area based on the temperature fed back by the infrared thermal imager. The deviation of the area temperature from the set value is negatively correlated with the beam current adjustment.

8. The electron beam additive manufacturing method for an integrated copper-chromium contact-conductive rod assembly as described in claim 1, characterized in that, In step S4, the in-situ stress annealing process involves first heating the integrated copper-chromium contact-conductive rod assembly printed part to 890-910℃ in an electron beam powder bed chamber and holding it for 55-65 minutes. Then, the integrated copper-chromium contact-conductive rod assembly printed part is cooled to 150℃ at a cooling rate of 0-10℃ / min. Finally, the cooling system is turned off and the part is allowed to cool naturally to room temperature.

9. The electron beam additive manufacturing method for an integrated copper-chromium contact-conductive rod assembly as described in claim 1, characterized in that, In step S4, the hot isostatic pressing process involves placing the integrated copper-chromium contact-conductive rod assembly printed part, which has undergone in-situ stress annealing, into a hot isostatic pressing apparatus. The heating temperature of the hot isostatic pressing apparatus is 915-925℃, and the process is carried out in an argon atmosphere of 140-150MPa for 120-360 minutes.

10. The electron beam additive manufacturing method for an integrated copper-chromium contact-conductive rod assembly as described in claim 1, characterized in that, In step S4, machining is performed by removing the molded substrate and support structure using wire cutting, grinding the contact working surface of the integrated copper-chromium contact-conductive rod assembly printed part using a CNC machine tool to ensure that the flatness of the contact working surface is ≤0.01mm and the surface roughness Ra is ≤0.4μm, and then turning the conductive rod connection part of the integrated copper-chromium contact-conductive rod assembly printed part according to the assembly dimension requirements.

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