Manufacturing method of plug-in column for electric meter connector

Abstract

The invention relates to the technical field of electric meter connectors, in particular to a manufacturing method of a plug column for an electric meter connector, and aims to solve the problems that a pure copper or brass material generally adopted in the prior art has a good conductive characteristic, but the hardness of a base body is insufficient, surface plastic deformation and abrasion are extremely prone to occurring in the repeated plugging process, and the cost is low. The problems that the effective contact area is reduced, the contact resistance is continuously increased, the local overheating phenomenon is caused, and the metering accuracy and the electricity utilization safety of the electricity meter are seriously threatened are solved. Through the specific copper-based alloy component design, the precise heat treatment process and the gradient diffusion plating layer formation, the problem that in the prior art, the wear resistance and the conductivity of the insertion column are difficult to consider at the same time is effectively solved, and the insertion column has the advantages of being high in wear resistance, high in conductivity and long in service life.

Description

Technical Field

[0001] This application relates to the field of electricity meter connector technology, and more specifically, to a method for manufacturing a plug-in post for an electricity meter connector. Background Technology

[0002] As a core component in electricity metering equipment that ensures reliable circuit connections, the performance of the meter's connector pins directly determines its long-term stability and metering accuracy. In actual operating environments, the connector pins must simultaneously withstand the mechanical wear caused by frequent insertion and removal operations and the conductivity stability required for high-current transmission. This places stringent dual performance requirements on the materials. However, while the pure copper or brass materials commonly used in existing technologies possess good conductivity, their base hardness is insufficient. During repeated insertion and removal, they are prone to surface plastic deformation and wear, leading to a reduction in effective contact area, a continuous increase in contact resistance, and consequently, localized overheating. This seriously threatens the metering accuracy and electrical safety of the electricity meter.

[0003] To address the challenge of wear resistance, the industry typically uses surface electroplating with nickel or tin. However, the interfacial bonding strength between such plating and the copper substrate is low, and it is prone to peeling failure under long-term insertion and extraction stress. At the same time, the conductivity of the plating material is generally lower than that of the copper substrate, which further exacerbates the problem of increased overall contact resistance.

[0004] Another common strategy is to introduce reinforcing elements such as iron and manganese into the copper matrix for alloying to improve hardness. However, the addition of such elements will significantly weaken the conductivity of the material, making it impossible to maintain stable conductivity under high current conditions.

[0005] More notably, in the existing technological system, the alloying modification of the substrate material and the surface coating treatment have always been developed as isolated technical paths, lacking innovative ideas that organically combine the two. Implementing substrate strengthening alone can only improve the overall mechanical strength, but cannot effectively suppress surface wear and coating adhesion failure; while relying solely on surface treatment can enhance the surface hardness, the softening and deformation of the substrate itself will still accelerate the wear process and induce a chain of problems such as coating peeling and contact resistance fluctuations.

[0006] Therefore, current meter connector products on the market generally suffer from defects such as limited plug-in life and poor contact resistance stability. In high wear-resistant scenarios, they often fall into the predicament of insufficient conductivity or early failure of surface treatment layer, making it difficult to achieve the comprehensive performance goal of high wear resistance, high conductivity and long service life.

[0007] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention

[0008] (a) Technical problems to be solved The purpose of this application is to provide a method for manufacturing a plug-in post for an electric meter connector, which has the advantages of synergistically improving the wear resistance and conductivity of the plug-in post by optimizing the copper-based alloy composition, heat treatment process and gradient diffusion coating, thereby extending the service life and ensuring the stability of contact resistance.

[0009] (II) Technical Solution This application provides a method for manufacturing a plug-in post for an electricity meter connector, the technical solution of which is as follows: Includes the following steps: S1. Prepare a copper-based alloy matrix, which consists of the following components by mass percentage: Cr 0.30%–0.35%, Zr 0.12%–0.18%, Ag 0.15%–0.20%, with the balance being Cu and unavoidable impurities, wherein the impurity content is ≤0.01%; S2. Heat treatment of the copper-based alloy matrix, including: S21. Heat the substrate to 950±10℃ and hold for 2 hours for solution treatment, then quench it in water to room temperature; S22. The solution-treated matrix is ​​kept at 450±10℃ for 4 hours for aging treatment, and then cooled in the furnace at a rate of 5℃ / min. S3. Pre-treat the surface of the substrate after heat treatment, including alkaline degreasing, pickling and activation treatment in sequence; S4. A composite diffusion coating layer is formed on the substrate surface using a gradient diffusion plating process, including: S41. A copper-tungsten transition layer is formed on the surface of the pretreated substrate by plasma diffusion plating process, and the thickness of the copper-tungsten transition layer is 5-8 μm. S42. A hard chrome wear-resistant layer is formed on the surface of the copper-tungsten transition layer by a low-temperature diffusion plating process. The thickness of the hard chrome wear-resistant layer is 3-5 μm.

[0010] Furthermore, this application also proposes that, in step S1, the preparation of the copper-based alloy matrix includes: The process involves melting electrolytic copper at 1180–1220℃ and a vacuum of ≤5Pa using a vacuum induction melting process. Chromium blocks, zirconium wires, and silver granules are then added sequentially, and the mixture is stirred at 50 r / min for 30 min. The molten alloy liquid is formed by low-pressure die casting. The mold preheating temperature is 250℃, the die casting pressure is 8~10MPa, the holding time is 15s, and after forming, it is water-cooled to room temperature to obtain the matrix blank. The density of the matrix blank is ≥99.5%.

[0011] Furthermore, this application also proposes that, in step S3, the preprocessing specifically includes: Alkaline degreasing: Use an alkaline degreasing agent containing 50 g / L NaOH and 30 g / L Na2CO3, and treat at 60℃ for 15 min; Pickling: Immerse in a 10% dilute sulfuric acid solution at 25°C for 3 minutes; Activation: Soak in 5% hydrochloric acid solution for 1 minute.

[0012] Furthermore, this application also proposes that the parameters of the plasma diffusion process in step S41 are as follows: using Cu-30%W target material, diffusion temperature 400℃, vacuum degree 10~20Pa, target current 2A, and diffusion time 90min.

[0013] Furthermore, this application also proposes that, in step S42, the parameters of the low-temperature diffusion plating process are as follows: a diffusion agent consisting of 80% chromium powder, 5% ammonium chloride and 15% alumina by mass percentage is used, the diffusion plating temperature is 550°C, and the holding time is 120 min.

[0014] Furthermore, this application also proposes that in step S1, the Ag element can be replaced with Au, and the mass percentage of Au is 0.10% to 0.15%.

[0015] Furthermore, this application also proposes that in step S41, the copper-tungsten transition layer can be replaced with a copper-molybdenum transition layer, wherein the mass percentage of Mo in the copper-molybdenum transition layer is 25% to 35% and the thickness is 5 to 8 μm.

[0016] Furthermore, this application also proposes that in step S42, the hard chrome wear-resistant layer can be replaced with a chromium nitride layer, the thickness of which is 3-6 μm and the hardness is ≥950HV.

[0017] Furthermore, this application also proposes a plug-in post for an electricity meter connector, which is manufactured using the above-described manufacturing method.

[0018] Furthermore, this application also proposes an electric meter connector, including the aforementioned plug, a conductive terminal electrically connected to the plug, and an insulating housing, wherein the plug is installed inside the insulating housing, and at least one end of the plug is connected to an external circuit through the conductive terminal.

[0019] (III) Beneficial Effects Compared with the prior art, the beneficial effects of the present invention are as follows: This invention effectively solves the problem of balancing wear resistance and conductivity of plug pins in the prior art through the design of specific copper-based alloy composition, precise heat treatment process and gradient diffusion coating, and has the advantages of high wear resistance, high conductivity and long service life. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the manufacturing process of the plug-in post; Figure 2 This is a step-by-step schematic diagram of step S2 in the manufacturing method of the plug-in post; Figure 3 This is a step-by-step diagram of step S4 in the manufacturing method of the plug-in post; Figure 4 This is a schematic diagram of the overall structure of the meter connector.

[0022] 10. Insulating housing; 20. Connecting post; 30. Conductive terminal. Detailed Implementation

[0023] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. The components of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0024] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0025] In the manufacturing process of traditional electricity meter connectors, the plug, as the core conductive component for power transmission, endures the dual effects of mechanical stress from repeated insertion and removal, and the thermal effects of high current flow. In existing technologies, there is an irreconcilable contradiction between the conductivity and wear resistance of the base material: when using pure copper or brass, insufficient base hardness leads to plastic deformation and surface wear during insertion and removal, resulting in a reduced contact area; while adding alloying elements to increase hardness or applying surface plating significantly degrades conductivity or weakens plating adhesion, causing a continuous increase in contact resistance and localized temperature rise, ultimately affecting the accuracy of power metering and the safety of system operation. Furthermore, the isolated application of base alloying and surface treatment technologies cannot achieve synergistic performance, making it difficult for the plug to maintain a stable conductive path and mechanical integrity under long-term operating conditions.

[0026] For example, in the field installation and periodic calibration of smart grid terminal meters, technicians need to frequently plug and unplug meters to replace equipment or adjust parameters. Under high temperature and humidity conditions, repeated friction causes micro-scratches on the plug surface and accelerates oxidation, forming a non-uniform conductive area at the contact point. This leads to fluctuations in the meter's operating status, requiring multiple service interruptions for contact surface cleaning or component replacement, increasing the uncontrollable factors in system maintenance and the risk of operational interruption. Furthermore, the combined effect of substrate plastic deformation and coating failure causes continuous deterioration of the contact interface, manifesting as intermittent anomalies in electrical signal transmission, directly affecting the real-time reliability of metering data.

[0027] If the above problems are not resolved, the performance degradation of the plug-in terminals will cause the electricity metering system to be in an unstable working state for a long time. The continuous increase in contact resistance may cause abnormal temperature rise and accumulate thermal stress, which may lead to accelerated aging of insulation materials and failure of electrical connections, thereby reducing the overall service life of the meter and threatening the safe operation of the power grid.

[0028] In this regard, refer to Figures 1-3 This application discloses a method for manufacturing a plug-in post for an electricity meter connector, comprising the following steps: S1. Prepare a copper-based alloy matrix, which consists of the following components by mass percentage: Cr 0.30%–0.35%, Zr 0.12%–0.18%, Ag 0.15%–0.20%, with the balance being Cu and unavoidable impurities, wherein the impurity content is ≤0.01%; S2. Heat treatment of the copper-based alloy matrix, including: S21. Heat the substrate to 950±10℃ and hold for 2 hours for solution treatment, then quench it in water to room temperature; S22. The solution-treated matrix is ​​kept at 450±10℃ for 4 hours for aging treatment, and then cooled in the furnace at a rate of 5℃ / min. S3. Pre-treat the surface of the substrate after heat treatment, including alkaline degreasing, pickling and activation treatment in sequence; S4. A composite diffusion coating layer is formed on the substrate surface using a gradient diffusion plating process, including: S41. A copper-tungsten transition layer is formed on the surface of the pretreated substrate by plasma diffusion plating process, and the thickness of the copper-tungsten transition layer is 5-8 μm. S42. A hard chrome wear-resistant layer is formed on the surface of the copper-tungsten transition layer by a low-temperature diffusion plating process. The thickness of the hard chrome wear-resistant layer is 3-5 μm.

[0029] For ease of understanding, the following explains some key terms in this embodiment: Copper-based alloy matrix: refers to a metallic material with copper as the main component and other alloying elements (such as chromium, zirconium, and silver) added. This matrix serves as the main structure of the connector, and its composition and microstructure directly affect the connector's conductivity, hardness, and mechanical strength.

[0030] Heat treatment refers to the process of heating, holding, and cooling metallic materials to alter their internal structure, thereby improving their mechanical properties (such as hardness, strength, and toughness) and physical properties (such as electrical conductivity). In this embodiment, heat treatment includes solution treatment and aging treatment.

[0031] Solution treatment: a heat treatment process in which an alloy is heated to a high temperature to allow the alloying elements to fully dissolve in the matrix to form a uniform solid solution, followed by rapid cooling to suppress the formation of precipitates, thereby obtaining a supersaturated solid solution.

[0032] Aging treatment: a heat treatment process in which, after solution treatment, the alloy is held at a low temperature for a period of time to promote the precipitation of solute atoms in the supersaturated solid solution to form fine and dispersed strengthening phases, thereby improving the hardness and strength of the alloy.

[0033] Pretreatment: refers to a series of cleaning and activation treatments performed on the substrate surface before surface coating or modification. Its purpose is to remove surface contaminants and oxide layers, and to improve surface activity, ensuring good adhesion between the subsequent coating and the substrate.

[0034] Gradient diffusion coating: a technique for forming a multilayer composite coating on a substrate surface, where the composition or structure of each layer varies in a gradient. This gradient structure helps to mitigate differences in the coefficients of thermal expansion and stress concentration between different materials, thereby improving the bonding strength and service life of the coating.

[0035] Plasma deposition process: a method for forming a coating on a material surface using plasma technology. By exciting a gas in a vacuum environment to form plasma, atoms or ions of the coating material are deposited onto the substrate surface, forming a dense coating.

[0036] Copper-tungsten transition layer: This refers to an intermediate coating composed of copper and tungsten formed between the substrate surface and the outermost wear-resistant layer. The main function of this layer is to act as a buffer, harmonizing the performance differences between the substrate and the wear-resistant layer, and providing good electrical conductivity.

[0037] Low-temperature diffusion plating: A process in which diffusion plating is performed at relatively low temperatures. Compared to high-temperature diffusion plating, low-temperature diffusion plating can reduce the impact on the properties of the substrate material (such as grain size and conductivity) and reduce energy consumption.

[0038] Hard chrome wear-resistant layer: refers to a chromium-based coating with high hardness and excellent wear resistance formed on the surface of the connector. This layer can effectively resist friction and wear during the insertion and removal process, extending the service life of the connector.

[0039] The main features of the above manufacturing method will be explained in more detail below: First, regarding the preparation of the copper-based alloy matrix. This step aims to provide a matrix material with specific properties to meet the conductivity and mechanical strength requirements of the plug-in terminals used in meter connectors. For example, the copper-based alloy matrix can be prepared using conventional melting and casting methods, where copper and the desired alloying elements are melted in a crucible and then directly cast. However, this method may result in uneven alloy composition distribution or the introduction of significant gaseous impurities during casting, thus affecting the density and subsequent properties of the matrix. Alternatively, the matrix can be obtained by mixing copper powder with alloying element powders and then pressing and sintering them using powder metallurgy. While this method allows for control of the composition, the sintered matrix may contain porosity, affecting its overall strength and conductivity.

[0040] Secondly, regarding the heat treatment of the copper-based alloy matrix. This step aims to optimize the internal microstructure of the matrix to further improve its mechanical properties and electrical conductivity. For example, the matrix can be subjected to a single high-temperature annealing treatment to eliminate internal stress and soften the material. However, a single annealing treatment may not fully utilize the strengthening effect of the alloying elements, resulting in limited improvement in matrix hardness. Alternatively, quenching can be used, where the matrix is ​​heated and then rapidly cooled to obtain higher hardness. However, without subsequent tempering or aging treatment, the quenched matrix may have significant internal stress, leading to increased brittleness and potentially affecting electrical conductivity.

[0041] Furthermore, regarding the pretreatment of the substrate surface after heat treatment, this step aims to provide a clean and activated surface for subsequent diffusion plating processes, ensuring good adhesion between the composite diffusion plating layer and the substrate. For example, simple mechanical grinding or brushing can be used to remove the oxide layer and dirt from the substrate surface. However, mechanical treatment may not completely remove microscopic contaminants and may leave scratches on the surface, affecting the uniformity of the subsequent plating. Alternatively, a single pickling or alkaline degreasing agent can be used. However, a single treatment method may not be able to comprehensively remove different types of surface contaminants. For example, alkaline degreasing agents are effective for oil stains but not for oxide layers; pickling is effective for oxide layers but has limited ability to remove oil stains.

[0042] Finally, regarding the formation of a composite diffusion coating layer on the substrate surface using a gradient diffusion plating process. This step aims to achieve a synergistic effect of high wear resistance and good conductivity on the plug surface through a multi-layer structure. For example, a hard chromium layer can be directly formed on the pretreated substrate surface using a single electroplating or electroless plating process. However, this directly formed hard chromium layer may have a large difference in the coefficient of thermal expansion between itself and the copper substrate, which can easily generate interfacial stress during temperature changes or long-term use, leading to cracking or peeling of the coating. Alternatively, a wear-resistant material can be directly deposited on the substrate surface using methods such as physical vapor deposition (PVD) or chemical vapor deposition (CVD). However, these methods may require higher deposition temperatures, which can adversely affect the performance of the substrate material, and the bonding strength between the deposited layer and the substrate may not be as strong as the metallurgical bond formed by the diffusion plating process.

[0043] The following example will provide a more detailed explanation of the above technical solution: First, in step S1, a copper-based alloy matrix is ​​prepared. Specifically, by precisely controlling the alloy composition, elements such as Cr, Zr, and Ag are added to copper in specific mass percentages, while strictly controlling the impurity content. This alloy matrix not only possesses excellent electrical conductivity but also significantly improves the hardness and resistance to plastic deformation through the strengthening effect of the alloying elements. For example, during the smelting process, high-purity raw materials can be used, and smelting can be carried out under an inert atmosphere to minimize the introduction of impurities and ensure the purity of the matrix.

[0044] Subsequently, in step S2, the prepared copper-based alloy matrix is ​​heat-treated. This heat treatment includes solution treatment and aging treatment. In the solution treatment, the matrix is ​​heated to 950±10℃ and held for 2 hours to allow the alloying elements to fully dissolve in the copper matrix, forming a homogeneous solid solution. It is then rapidly cooled to room temperature by water quenching to retain the supersaturated solid solution state. Next, aging treatment is performed, where the solution-treated matrix is ​​held at 450±10℃ for 4 hours to promote the uniform precipitation of fine strengthening phases, further improving the hardness and strength of the matrix. It is then cooled in the furnace at a rate of 5℃ / min to avoid generating excessive internal stress. Through this customized heat treatment process, the grain structure of the matrix is ​​optimized, internal stress is released, and the precipitation of strengthening phases allows the matrix to achieve higher hardness and strength while maintaining high conductivity, thus effectively resisting plastic deformation during insertion and extraction.

[0045] Next, in step S3, the surface of the heat-treated substrate is pretreated. This pretreatment includes sequential alkaline degreasing, pickling, and activation treatment.

[0046] First, alkaline degreasing removes oil and organic matter from the substrate surface. Then, acid pickling removes the oxide layer and rust. Finally, activation treatment brings the substrate surface to a highly active state, providing an ideal bonding interface for subsequent diffusion coating. For example, ultrasonic cleaning can be used after alkaline degreasing to ensure surface cleanliness. This multi-step pretreatment ensures a highly clean and activated substrate surface, laying the foundation for a strong bond in the subsequent composite diffusion coating and preventing coating peeling due to surface uncleanliness.

[0047] Finally, in step S4, a composite diffusion layer is formed on the substrate surface using a gradient diffusion plating process. This process includes two sub-steps: First, a copper-tungsten transition layer with a thickness of 5–8 μm is formed on the pretreated substrate surface using a plasma diffusion plating process. This copper-tungsten transition layer has good compatibility with the copper substrate, while possessing both the conductivity of copper and the hardness of tungsten. Serving as a buffer layer between the substrate and the outer wear-resistant layer, it effectively mitigates the difference in thermal expansion coefficients between different materials and reduces interfacial stress. For example, during the plasma diffusion plating process, plasma parameters can be precisely controlled to ensure uniform deposition of the copper-tungsten alloy.

[0048] Subsequently, a hard chrome wear-resistant layer with a thickness of 3–5 μm is formed on the surface of the copper-tungsten transition layer using a low-temperature diffusion plating process. This hard chrome layer possesses extremely high hardness and excellent wear resistance, effectively resisting wear caused by repeated insertion and removal. For example, low-temperature diffusion plating can be performed at relatively low temperatures, avoiding the negative impact of high temperatures on the substrate performance. Through this gradient composite diffusion plating structure, a wear-resistant layer with high conductivity, high hardness, and high adhesion is formed on the surface of the connector, ensuring that the connector can stably conduct large currents and resist wear from repeated insertion and removal during long-term use, and that the plating layer is not easily peeled off.

[0049] In summary, this manufacturing method, through precise control of the matrix composition, customized heat treatment, and the synergistic effect of gradient composite plating process, enables the plug-in posts of the meter connectors to significantly improve their wear resistance and service life while meeting the requirements for high current conduction.

[0050] Based on the above examples, the overall technical concept of this application demonstrates a significant technical contribution. Traditionally, when pursuing high conductivity, the plugs of electricity meter connectors often struggle to simultaneously achieve high wear resistance, and vice versa. For example, in the prior art, although pure copper or brass substrates have excellent conductivity, they are easily worn and deformed under repeated insertion and removal, leading to increased contact resistance. Adding a large amount of alloying elements to the copper substrate to improve wear resistance would severely sacrifice conductivity.

[0051] This application achieves improved matrix hardness while maintaining or even slightly improving conductivity by preparing a copper-based alloy matrix with synergistic reinforcement of trace amounts of Cr, Zr, and Ag in step S1. This is in stark contrast to the existing understanding that "adding alloying elements inevitably reduces conductivity".

[0052] Furthermore, in existing technologies, surface plating treatments often suffer from weak adhesion between the plating layer and the substrate, as well as mismatches in thermal expansion coefficients, leading to plating layers that are prone to peeling or cracking after prolonged insertion and removal. For example, conventional electroplated nickel / tin layers may peel off after hundreds of insertions and removals. In step S4 of this application, a gradient diffusion plating process is employed. First, a copper-tungsten transition layer is formed. This transition layer acts as a bridge between the substrate and the hard chromium layer, with a thermal expansion coefficient between the two, effectively alleviating interfacial stress and fundamentally solving the problem of plating peeling. The subsequent low-temperature diffusion plating of the hard chromium layer ensures high hardness and wear resistance while avoiding the negative impact of high temperatures on the substrate performance. This gradient structure design allows the composite diffusion plating layer to remain intact after thousands of insertions and removals, exhibiting an extremely low contact resistance change rate, far exceeding the performance of existing products.

[0053] Furthermore, the heat treatment process (step S2) of this application is precisely matched with the base alloy composition and subsequent diffusion plating process. The parameters of the solution treatment and aging treatment are carefully designed to maximize the strengthening effect of trace alloying elements while ensuring the orderliness of the base lattice, thereby achieving a balance between "high hardness" and "high conductivity". This customized heat treatment provides a stable and high-performance substrate for subsequent gradient diffusion plating, avoiding overall failure due to insufficient base performance. Compared with the single or mismatched heat treatment schemes in the prior art, the synergistic optimization strategy of this application enables the plug-in post to achieve a qualitative leap in overall performance, completely solving the core technical problem that has long plagued the meter connector industry of the difficulty in simultaneously achieving high conductivity, high wear resistance, and long service life.

[0054] In some of the above-mentioned solutions of this application, a copper-based alloy matrix is ​​prepared to provide a substrate with high conductivity and wear resistance. However, in this process, if the preparation process is improper, it may lead to excessive impurity content and insufficient density, thereby affecting the conductivity and mechanical properties of the matrix. In this regard, this application further proposes that in step S1, the preparation of the copper-based alloy matrix includes: using a vacuum induction melting process, electrolytic copper is melted at 1180-1220℃ and a vacuum degree ≤5Pa, and chromium blocks, zirconium wire and silver granules are added sequentially, and stirred at a stirring speed of 50r / min for 30min; the molten alloy liquid is then formed by low-pressure die casting, with the mold preheating temperature at 250℃, the die casting pressure at 8-10MPa, and the holding time at 15s. After forming, the matrix blank is water-cooled to room temperature to obtain a matrix blank with a density ≥99.5%.

[0055] Vacuum induction melting is a method of melting metallic materials in a vacuum environment using the principle of induction heating. Its main function is to isolate the metal from oxygen and nitrogen in the air, preventing oxidation and nitriding reactions during high-temperature melting, thereby effectively controlling the purity of the alloy and reducing the introduction of gaseous impurities and non-metallic inclusions. Besides using high-frequency induction coils to heat the metal in the crucible and using a vacuum pump to evacuate to the required vacuum level, medium-frequency induction melting equipment can also be used, adjusting the induction frequency and power to adapt to the melting requirements of different metals; or a combination of electron beam melting and induction melting can be used to further improve the purity of the melt.

[0056] Electrolytic copper is melted at 1180–1220℃ under a vacuum of ≤5Pa to ensure the purity of the molten copper and prevent oxidation and the introduction of impurities. The temperature range of 1180–1220℃ ensures complete melting and good fluidity of the copper, while avoiding excessively high temperatures that could lead to the volatilization of alloying elements or contamination of the crucible material. A vacuum of ≤5Pa minimizes the presence of oxygen and nitrogen, creating an oxygen-free environment for the subsequent addition of alloying elements. In addition to real-time monitoring of the melt temperature via thermocouples and precise adjustment of the induction heating power by a PID controller, non-contact temperature measurement using an infrared thermometer can be combined with an automatic temperature control system for precise temperature control. Vacuum control can be achieved using a combination of mechanical and diffusion pumps, or more advanced vacuum equipment such as turbomolecular pumps to reach even lower vacuum levels, further enhancing the purity of the melting environment.

[0057] The sequential addition of chromium blocks, zirconium wire, and silver granules is to ensure the uniform integration of these trace alloying elements into the copper matrix. Chromium and zirconium serve as reinforcing elements, while silver enhances conductivity; the order and form of their addition can affect their dissolution rate and uniformity in the melt. Besides manually or via a robotic arm to add pre-weighed alloying elements to the melt, an automated feeding system can be used to precisely and stably add the alloying elements to the melt using a vibrating feeder or screw feeder; alternatively, the alloying elements can be pre-formed into a master alloy to improve their dissolution efficiency and uniformity in the molten copper.

[0058] Stirring at 50 rpm for 30 minutes promotes the complete dissolution and uniform distribution of the added alloying elements in the molten copper, preventing component segregation. Besides electromagnetic stirring via induction coils, mechanical stirrers can be used to physically stir the melt using rotating blades or paddles; alternatively, inert gases (such as argon) can be used to purge the melt, achieving a stirring effect through the rising movement of air bubbles. Low-pressure die casting is a method that uses relatively low pressure to force molten metal into a mold cavity and solidify it. Its advantages include stable filling, reduced air entrapment and oxide inclusions, and improved density and mechanical properties of the casting.

[0059] In addition to using traditional low-pressure die casting machines, which press molten metal into the mold via pneumatic or hydraulic systems, vacuum-assisted low-pressure die casting can also be employed. This involves evacuating the mold cavity before filling to further reduce porosity defects within the casting. Alternatively, gravity casting combined with localized pressurization can be used to meet the molding requirements of castings with varying complexity. The mold preheating temperature is 250℃ to reduce the temperature difference between the molten metal and the mold, thereby reducing thermal stress and preventing cracks and deformation in the casting. Besides uniformly heating the mold using electric heating rods or gas heaters, induction heating can be used for rapid and precise localized or overall preheating; or indirect heating can be achieved using hot oil or hot air circulation systems to achieve more stable temperature control.

[0060] The die-casting pressure is 8–10 MPa, and the holding time is 15 seconds. This is to ensure that the molten alloy fully fills the mold cavity and applies continuous pressure to the casting during solidification to compensate for solidification shrinkage, reduce defects such as shrinkage cavities and porosity, and thus improve the density of the casting. Besides precisely controlling the die-casting pressure and holding time through a hydraulic system, a servo motor-driven injection system can be used to achieve finer pressure curve control and more accurate holding time; or a real-time pressure sensor and closed-loop control system can be combined to dynamically adjust the pressure according to the solidification state of the melt. After forming, water cooling to room temperature to obtain the matrix blank is a rapid cooling method aimed at refining the grain structure and improving the mechanical properties of the matrix blank.

[0061] Besides directly immersing the casting in a water bath for cooling, spray cooling can also be used, employing water mist or jets to uniformly cool the casting surface; alternatively, a circulating water cooling system can be used to ensure stable cooling medium temperature and improve cooling efficiency. The density of the matrix blank, ≥99.5%, is a key indicator for evaluating casting quality. In addition to measuring density using non-destructive testing methods such as Archimedes' displacement method or X-ray transmission method, the internal structure of the casting can be observed using a metallographic microscope to assess porosity; or ultrasonic testing technology can be used to detect internal defects and indirectly assess density.

[0062] This application's solution optimizes the preparation process of copper-based alloy matrices, aiming to solve the problems of excessively high impurity content and insufficient density that may occur in traditional preparation processes, thereby ensuring that the matrix possesses high electrical conductivity and mechanical properties. The solution first employs a vacuum induction melting process, melting electrolytic copper within a strictly controlled temperature range of 1180–1220℃ and a vacuum degree of ≤5 Pa.

[0063] This high-vacuum environment effectively isolates oxygen and nitrogen from the air, preventing the copper melt from oxidizing at high temperatures and minimizing the introduction of gaseous impurities, thus laying a pure foundation for the uniform distribution of subsequent alloying elements. Subsequently, chromium blocks, zirconium wire, and silver granules are added sequentially. These trace alloying elements are continuously stirred in the copper melt at a stirring speed of 50 r / min for 30 min to ensure complete dissolution and uniform dispersion, avoiding component segregation. This is crucial for the uniform precipitation of strengthening phases during subsequent heat treatment, thereby ensuring the matrix achieves a synergistic performance of high hardness and high conductivity. The molten alloy is then immediately subjected to low-pressure die casting. During this process, the mold is preheated to 250°C to reduce the temperature difference between the alloy melt and the mold, improving the fluidity of the alloy melt and allowing it to smoothly and fully fill the mold cavity, while avoiding casting defects caused by thermal stress.

[0064] The die-casting pressure is controlled at 8–10 MPa and maintained for 15 seconds. This ensures that the molten alloy is continuously subjected to pressure during solidification, effectively compensating for solidification shrinkage and minimizing the generation of internal defects such as shrinkage cavities and porosity. The formed matrix blank is then rapidly cooled to room temperature by water cooling. This rapid cooling helps refine the grain structure and form a supersaturated solid solution, providing a favorable microstructure for subsequent solution treatment and aging treatment.

[0065] Ultimately, through this series of precisely controlled manufacturing processes, a substrate blank with a density of ≥99.5% was obtained. This high-density substrate blank not only has very few internal defects, ensuring the continuity of the conductive channels and the stability of mechanical strength, but also provides a smooth, non-porous, high-quality substrate for subsequent surface pretreatment and gradient diffusion plating processes. This avoids the problem of weak adhesion between the plating layer and the substrate, thus enabling the entire plug manufacturing method to synergistically achieve excellent conductivity, wear resistance, and long service life.

[0066] The following is a specific example. In preparing a copper-based alloy matrix, a vacuum induction melting furnace equipped with a medium-frequency induction heating power supply and a high-vacuum pump system (e.g., a vacuum system consisting of a mechanical pump, a Roots pump, and a diffusion pump) can be used. First, high-purity electrolytic copper blocks are placed in a graphite crucible. The vacuum pump system is started to evacuate the furnace cavity to a vacuum level below 5 Pa. Then, the medium-frequency power supply is turned on to heat the electrolytic copper to 1200°C and maintain a stable temperature. After the electrolytic copper has completely melted, pre-weighed chromium blocks, zirconium wire, and silver granules are sequentially added through the feeding mechanism on the furnace top.

[0067] After the alloying elements are added, the melt is stirred using electromagnetic force generated by an induction coil at a speed of 50 r / min for 30 minutes to ensure uniform alloy composition. After stirring, the molten alloy is poured into the holding furnace of a low-pressure die-casting machine via a tilting mechanism. This low-pressure die-casting machine is equipped with a steel mold preheated to 250°C. Through the control system, the molten alloy is forced into the mold cavity at a pressure of 8 MPa and maintained at this pressure for 15 seconds to ensure the casting is fully filled and to compensate for solidification shrinkage. After the pressure holding period, the mold is opened, the formed casting is removed, and it is immediately immersed in a room-temperature water bath for rapid cooling until the casting temperature drops to room temperature. The cooled casting serves as the base blank. X-ray non-destructive testing or metallographic analysis confirms that its density reaches over 99.5%, and that its internal structure is uniform and free of obvious defects.

[0068] Through the above technical solution, this application effectively solves the technical problems of excessively high impurity content and insufficient density in the preparation of copper-based alloy matrices. By employing a vacuum induction melting process, electrolytic copper is melted and alloying elements are added under strictly controlled temperature and high vacuum conditions, which can minimize oxidation and impurity introduction, ensuring high purity of the matrix material.

[0069] Meanwhile, by precisely controlling the stirring speed and time, the uniform distribution of trace alloying elements in the copper matrix was ensured, avoiding compositional segregation. In addition, the low-pressure die casting process, combined with mold preheating, precise die casting pressure and holding time, and post-forming water cooling treatment, effectively improved the density of the matrix blank, reduced internal defects, and refined the grain structure.

[0070] These measures work together to give the obtained substrate blank excellent electrical conductivity and mechanical strength, providing a high-quality substrate for subsequent heat treatment and surface composite plating. This lays a solid foundation for the final fabrication of meter connector plugs that combine high conductivity, high wear resistance, and long service life. Compared with solutions relying solely on the basic substrate, this approach, through refined control of the substrate material source, fundamentally improves the intrinsic quality of the material. This allows subsequent solution aging treatment to play a more effective role, precipitating a uniform strengthening phase and ensuring stronger adhesion between the composite plating layer and the substrate, thereby significantly improving the overall performance and reliability of the plug.

[0071] In some of the solutions described above in this application, a pretreatment is proposed to clean and activate the substrate surface. However, if the treatment parameters are not specific during the implementation process, residual oil, oxide layer or impurities may remain on the surface, affecting the adhesion and uniformity of the subsequent plating layer, thereby reducing the wear resistance and electrical conductivity stability of the plug.

[0072] In this regard, this application further proposes that the pretreatment in step S3 specifically includes: alkaline degreasing: using an alkaline degreasing agent containing 50 g / L NaOH and 30 g / L Na2CO3, treating at 60°C for 15 min; pickling: using a 10% dilute sulfuric acid solution, soaking at 25°C for 3 min; activation: using a 5% hydrochloric acid solution, soaking for 1 min.

[0073] The specific formulation of the alkaline degreasing agent, containing 50g / L NaOH and 30g / L Na₂CO₃, is designed to efficiently remove oil stains from the substrate surface. NaOH, as a strong alkali, effectively saponifies animal and vegetable oils and emulsifies mineral oils; Na₂CO₃ acts as a detergent builder, providing an alkaline environment and aiding in the dispersion and suspension of dirt. Besides this formulation, alkaline degreasing agents using sodium silicate, sodium phosphate, or other additives, or composite alkaline degreasing agents containing surfactants, can also be used. A treatment temperature of 60℃ is used to enhance the activity of the degreasing agent and the dissolution rate of the oil stains, while avoiding excessively high temperatures that could accelerate oxidation of the substrate surface.

[0074] In practice, the process can also be carried out within a temperature range of 40-70℃, or by using ultrasonic-assisted heating for degreasing. A processing time of 15 minutes ensures that the oil stains are fully removed, achieving the required surface cleanliness. Depending on the type and thickness of the oil stains, the processing time can be adjusted to 10-20 minutes, or a multi-stage degreasing method can be used, with each stage having a shorter processing time.

[0075] In the pickling step, a 10% dilute sulfuric acid solution is used to gently and effectively remove the oxide film and minor rust from the substrate surface. Sulfuric acid, as a strong acid, performs well in removing oxides in its dilute form, and its corrosion of copper-based alloys is relatively controllable. Alternatively, a 5%-15% dilute hydrochloric acid solution, or a dilute sulfuric acid solution containing a small amount of corrosion inhibitor, can be used.

[0076] Immersion at 25℃ is considered normal operating temperature, designed to control the pickling reaction rate and prevent excessive corrosion of the substrate due to high temperatures. In practical applications, pickling can be performed within a temperature range of 20-30℃, or a cooling device can be used to maintain the solution temperature at a lower level. A 3-minute immersion time ensures thorough removal of the oxide film while minimizing corrosion of the substrate itself. Depending on the thickness and type of oxide film, the immersion time can be adjusted to 2-5 minutes, or a spray pickling method can be used to shorten the processing time.

[0077] In the activation step, a 5% hydrochloric acid solution is used to remove any passivation film that may form after pickling and to slightly roughen the substrate surface, thereby improving surface activity. The chloride ions in hydrochloric acid have a strong activating effect. Besides hydrochloric acid, a 2%-8% dilute nitric acid solution, or an acidic solution containing a small amount of activator, can also be used. The immersion time of 1 minute aims to quickly activate the metal surface while avoiding excessive corrosion. Depending on the substrate material and the desired level of activation, the immersion time can be adjusted to 30 seconds to 2 minutes, or an electrochemical activation method can be used.

[0078] The solution proposed in this application ensures that the subsequent gradient diffusion plating process can form a composite diffusion layer with strong adhesion and good uniformity by performing a refined pretreatment on the surface of the heat-treated substrate. Specifically, the pretreatment step S3 first involves alkaline degreasing using a specific ratio of alkaline degreasing agent at 60°C for 15 minutes. This step aims to efficiently remove various oil stains that may remain on the surface of the copper-based alloy substrate during manufacturing and heat treatment. The strong alkalinity of sodium hydroxide is responsible for saponifying and emulsifying the oil stains, while sodium carbonate assists in providing an alkaline environment and dispersing the dirt. The temperature of 60°C accelerates the chemical reaction and dissolution of the oil stains, and the precise 15-minute time ensures thorough removal of the oil stains while avoiding excessive corrosion of the substrate. A pickling treatment is then performed, using a 10% dilute sulfuric acid solution to soak the substrate at 25°C for 3 minutes.

[0079] The main purpose of this step is to gently remove the thin oxide film that may form after alkaline degreasing, as well as any minor rust present on the substrate surface. A 10% dilute sulfuric acid concentration and a room temperature of 25°C, combined with a short immersion of 3 minutes, ensure effective removal of oxides while minimizing corrosion of the substrate itself, maintaining its original conductivity and surface smoothness. Finally, an activation treatment is performed, involving immersion in a 5% hydrochloric acid solution for 1 minute.

[0080] This step is a crucial activation process. Chloride ions in hydrochloric acid can rapidly remove any remaining extremely thin passivation film after pickling and moderately roughen the substrate surface at the microscale. This micro-roughening increases the effective surface area and active sites of the substrate, providing an ideal "anchoring" foundation for the copper-tungsten transition layer formed in the subsequent S41 ion plating process, greatly enhancing the physical bonding between the transition layer and the substrate. Through the synergistic effect of the above alkaline degreasing, pickling, and activation treatments, this scheme ensures that the copper-based alloy substrate surface reaches a highly clean, oxidation-free, and highly active state before entering the gradient plating stage.

[0081] This precisely controlled pretreatment process, in close coordination with the subsequent plasma diffusion plating to form a copper-tungsten transition layer and low-temperature diffusion plating to form a hard chromium wear-resistant layer, enables the composite diffusion plating layer to firmly adhere to the substrate surface and uniformly cover it. This effectively avoids problems such as weak coating adhesion, easy peeling, and uneven contact resistance in traditional processes, providing excellent wear resistance and stable conductivity for the plug-in posts of meter connectors.

[0082] The following is a specific example. When pre-treating the surface of a heat-treated copper-based alloy substrate, the substrate can first be immersed in an alkaline degreasing tank prepared with sodium hydroxide and sodium carbonate in a specific ratio. For example, the solution in this degreasing tank can be prepared to contain 50 grams of sodium hydroxide and 30 grams of sodium carbonate per liter. To ensure effective degreasing, the temperature of the degreasing tank can be precisely controlled at 60°C, and the substrate should remain in the solution for 15 minutes to thoroughly remove various organic contaminants adhering to the surface.

[0083] After alkaline degreasing, the substrate is removed and thoroughly rinsed with water, then transferred to an acid pickling tank. This tank can hold a 10% dilute sulfuric acid solution. To avoid excessive corrosion of the substrate, the acid pickling process can be carried out at room temperature, such as 25°C, with an immersion time of 3 minutes. After acid pickling, the substrate is thoroughly rinsed again with water and then quickly immersed in an activation tank. A 5% hydrochloric acid solution can be used in the activation tank. The activation process is usually short, such as immersion for 1 minute, to quickly remove the surface passivation layer and improve the activity of the metal surface. After this series of pretreatment steps, the substrate surface will be clean and activated, ready for the subsequent gradient plating process.

[0084] Through the above technical solution, this application effectively solves the problem that the lack of specific pretreatment parameters in traditional methods leads to residual oil, oxide layers, or impurities on the surface, which in turn affects the adhesion and uniformity of subsequent plating layers. The specific ratio of the alkaline degreasing agent and precise temperature and time control ensure the complete removal of oil from the substrate surface, avoiding interference from residual oil in subsequent treatments. Mild pickling conditions effectively remove oxides and minor rust, providing a clean substrate for activation.

[0085] The precise activation treatment, through appropriate roughening and removal of the passivation film, significantly enhances the activity of the substrate surface. This allows the copper-tungsten transition layer formed by subsequent plasma plating to form an extremely strong physical bond with the substrate, laying the foundation for the uniform coverage of the hard chrome wear-resistant layer. This refined pretreatment process, in close coordination with the copper-based alloy substrate and the gradient plating process, ensures high adhesion and high uniformity between the composite plating layer and the substrate. This significantly improves the wear resistance and conductivity stability of the meter connector pins, effectively extending their service life and avoiding measurement inaccuracies and safety hazards caused by plating peeling or increased contact resistance.

[0086] Traditional meter connectors suffer from an inherent contradiction between conductivity and wear resistance when subjected to repeated insertion and removal wear and stable conduction under high current conditions. This is compounded by the limitations of existing technologies and performance bottlenecks in current solutions. While some solutions in this application propose plasma plating to form a copper-tungsten transition layer on the substrate surface to improve wear resistance and conductivity, improper parameter settings can lead to insufficient adhesion, uneven thickness, or compositional deviations, affecting the stability and overall performance of the transition layer. Consequently, these methods fail to effectively address the long-term reliability issues of the connectors under repeated insertion and removal conditions.

[0087] In this regard, this application further proposes that the parameters of the plasma diffusion process in step S41 are as follows: Cu-30%W target material, diffusion temperature 400℃, vacuum degree 10~20Pa, target current 2A, and diffusion time 90min.

[0088] Plasma infiltration is a surface modification technology that utilizes plasma to activate and accelerate atomic diffusion and deposition processes. Its core function is to form a coating with specific composition, structure, and properties on the substrate surface by precisely controlling process parameters, thereby improving the material's wear resistance, corrosion resistance, or conductivity. This process achieves good adhesion between the coating and the substrate and allows for effective control over the coating thickness and uniformity. The target material is the source of the deposition material in plasma infiltration. Using a Cu-W alloy as the target material aims to co-deposit copper and tungsten onto the substrate surface to form a composite coating.

[0089] Copper typically provides excellent electrical conductivity, while tungsten enhances the mechanical properties of the coating with its high hardness and wear resistance. The ratio of copper to tungsten in the target material is a key factor determining the composition and performance of the resulting coating. For example, different copper-tungsten ratios can be selected based on the desired hardness, conductivity, and bonding characteristics with the substrate. Alternatively, other metals or alloys, such as copper-molybdenum alloy targets, can be chosen to form a copper-molybdenum transition layer. Plasma deposition temperature is a crucial parameter affecting the atomic diffusion rate, deposition efficiency, and the bonding quality between the coating and the substrate during plasma deposition. An appropriate deposition temperature promotes the migration and rearrangement of deposited atoms on the substrate surface, resulting in a dense and well-bonded coating. Excessively high temperatures may lead to substrate degradation or a coarse coating structure, while excessively low temperatures may result in slow deposition rates, a less dense coating, or poor adhesion. For example, the deposition temperature can be adjusted based on factors such as the thermal stability of the substrate material, the desired microstructure of the coating, and deposition efficiency; it can be selected within the range of 350°C to 450°C.

[0090] Vacuum level is a key parameter for controlling the purity and stability of the plasma environment in plasma diffusion deposition processes. At an appropriate vacuum level, interference from gas molecules on the deposition process can be effectively reduced, preventing impurities from being incorporated into the coating, thus ensuring the purity and density of the coating. Simultaneously, vacuum level also affects the glow discharge characteristics and ionization efficiency of the plasma. For example, the vacuum level can be adjusted according to the type of plasma source, the size of the cavity, and the required coating quality; for instance, it can be selected within the range of 5 Pa to 30 Pa. Target current is an important parameter for controlling the intensity of plasma bombardment of the target and the deposition rate. Higher target current generally means stronger ion bombardment and a faster deposition rate, but excessively high current may lead to target overheating, sputtering instability, or increased internal stress in the coating.

[0091] By precisely controlling the target current, effective regulation of coating thickness, uniformity, and microstructure can be achieved. For example, the target current can be adjusted according to the target size, deposition efficiency requirements, and coating quality targets, and can be selected within the range of 1A to 3A. The plating time directly determines the final coating thickness. With other process parameters fixed, extending the plating time generally increases the coating thickness. A reasonable plating time should ensure the formation of a uniform and dense coating of the required thickness, while avoiding increased energy consumption or decreased coating performance due to excessive time. For example, the plating time can be adjusted according to factors such as the target coating thickness, deposition rate, and production efficiency, and can be selected within the range of 60 min to 120 min.

[0092] This application's solution, through precise control of plasma diffusion plating process parameters, aims to form a high-performance copper-tungsten transition layer. This transition layer not only serves as a bridge between the substrate and the subsequent hard chrome wear-resistant layer but also plays a crucial role in conductivity and mechanical support. Specifically, a Cu-30%W target material is used, with a carefully designed specific ratio of copper to tungsten. This ensures that the transition layer possesses sufficient hardness (e.g., reaching HV400~500) to support the upper hard chrome wear-resistant layer and prevent premature wear, while maintaining good conductivity (e.g., conductivity exceeding 60% IACS). This effectively compensates for the lower conductivity of the hard chrome layer and forms a smooth conductive gradient with the highly conductive copper-based alloy substrate, reducing interfacial contact resistance. The diffusion plating temperature is set at 400℃, which is lower than the aging treatment temperature of the copper-based alloy substrate (450±10℃). This effectively prevents the coarsening of the nano-reinforcing phases (such as CrCu2, ZrCu3) already formed in the substrate, thus protecting the original high hardness and high conductivity of the substrate from degradation. At the same time, this temperature is sufficient to provide the energy required for atomic diffusion, promoting slight mutual dissolution between copper and tungsten atoms sputtered from the target and copper atoms on the substrate surface, forming a metallurgical bond. This significantly enhances the bonding force between the transition layer and the substrate, avoiding the coating peeling problem that may be caused by simple physical deposition.

[0093] Furthermore, controlling the vacuum level within the range of 10–20 Pa ensures a pure and stable plasma environment, reducing the interference of impurities on the deposition process and resulting in a dense, pore-free transition layer structure. Precisely setting the target current to 2 A allows for stable control of the deposition rate, preventing excessive internal stress and cracking caused by overly rapid deposition.

[0094] The diffusion plating time was set to 90 min, which matched the deposition rate, ensuring that the copper-tungsten transition layer could reach the target thickness of 5-8 μm. This thickness formed a reasonable thickness ratio with the subsequent hard chrome wear-resistant layer (3-5 μm), allowing the transition layer to fully buffer the interface stress and provide a uniform and stable support base for the hard chrome wear-resistant layer, thereby ensuring the long-term stability and reliability of the entire composite diffusion plating layer.

[0095] In one specific implementation, after heat treatment and surface pretreatment of the copper-based alloy substrate, the substrate is placed in a plasma deposition apparatus. First, the apparatus chamber is evacuated to a vacuum level of 10–20 Pa to ensure a pure deposition environment. Then, the plasma source is activated, and sputtering is performed using a target composed of Cu and 30% W. The deposition temperature is precisely controlled at 400°C, and the target current is adjusted to 2A. The deposition process lasts for 90 minutes to ensure that the copper-tungsten transition layer is uniformly and densely deposited on the substrate surface, achieving a preset thickness of 5–8 μm. After deposition, the plasma source is turned off, and the substrate is removed after the chamber cools, yielding a semi-finished plug post with a copper-tungsten transition layer on its surface. This transition layer provides an excellent bonding base and conductive buffer for the subsequent hard chrome wear-resistant layer.

[0096] Through the above technical solution, this application effectively solves the problems of insufficient coating adhesion, uneven thickness, or composition deviation that may occur during the formation of the copper-tungsten transition layer, thereby significantly improving the long-term reliability of the plug-in post under repeated insertion and removal conditions. This solution achieves a synergistic balance between conductivity and hardness of the transition layer by precisely controlling the composition of the Cu-30%W target material, ensuring sufficient mechanical support while effectively compensating for conductivity loss. The setting of a 400℃ plating temperature cleverly protects the high hardness and high conductivity properties of the copper-based alloy substrate after aging treatment from degradation, while simultaneously promoting a strong metallurgical bond between the transition layer and the substrate. The coordinated control of vacuum degree, target current, and plating time ensures uniform thickness, dense structure, and no defects in the transition layer, providing a stable and functionally compatible foundation for the subsequent hard chrome wear-resistant layer. Ultimately, this solution enables the plug-in post for electricity meter connectors to maintain a strong bond, stable conductivity, and structural integrity during long-term use, significantly extending its service life and improving the accuracy of electricity metering and the safety of electricity use.

[0097] In some of the solutions described above in this application, a low-temperature diffusion plating process is proposed to form a hard chromium wear-resistant layer on the surface of a copper-tungsten transition layer. However, if the composition of the diffusion agent, temperature and time parameters are not appropriate, it may lead to insufficient coating adhesion, substandard wear resistance or affect the overall conductivity.

[0098] In this regard, this application further proposes that the parameters of the low-temperature diffusion plating process in step S42 are as follows: the diffusion agent is composed of 80% chromium powder, 5% ammonium chloride and 15% alumina by mass, the diffusion plating temperature is 550℃ and the holding time is 120min.

[0099] Chromium powder, as the main active component of the diffusion agent, is the primary source of chromium in the hard chromium wear-resistant layer. Its purity is typically high; for example, electrolytic chromium powder or atomized chromium powder with a purity of 99.5% or higher can be used, with a particle size controlled between 1 and 10 micrometers to ensure uniform diffusion and the formation of a dense coating during the diffusion plating process. Ammonium chloride acts as an activator during the diffusion plating process, decomposing at high temperatures to produce halogen gases. These gases effectively remove oxides from the surface of the copper-tungsten transition layer, activate the substrate surface, and promote the diffusion and deposition of chromium atoms.

[0100] Besides ammonium chloride, other halides such as ammonium fluoride or ammonium bromide can also be considered as activators, as they also decompose at high temperatures and provide active halogens. Alumina, as an inert filler and diluent, primarily disperses chromium powder and the activator, preventing their agglomeration at high temperatures, ensuring the uniformity of the diffusion agent, and controlling the rate of the diffusion reaction to avoid localized overheating. Furthermore, alumina provides some mechanical support to prevent the diffusion layer from collapsing. In addition to alumina, other high-temperature resistant and chemically inert powders such as silicon dioxide, silicon carbide, or boron nitride can also be used as fillers.

[0101] The plating temperature is a key parameter affecting the formation rate and quality of the plating layer. Setting it to 550℃ aims to provide sufficient energy for chromium atoms to diffuse and react on the surface of the copper-tungsten transition layer, forming a dense hard chromium layer, while avoiding excessively high temperatures that could adversely affect the microstructure and properties of the copper-based alloy substrate and the copper-tungsten transition layer. In other embodiments, the plating temperature can be fine-tuned according to the specific material system and desired properties. For example, while ensuring the plating effect, it can be appropriately reduced to 500℃ to further reduce the heat effect, or slightly increased to 580℃ if the substrate's heat resistance allows, to accelerate the plating rate. The holding time determines the thickness and uniformity of the plating layer. A holding time of 120 minutes ensures that chromium atoms have sufficient time to diffuse and form a hard chromium wear-resistant layer with a thickness of 3–5 μm, giving it good density and adhesion. If a thinner wear-resistant layer is required, the heat preservation time can be shortened appropriately, for example, to 90 minutes; if a thicker wear-resistant layer is required, the heat preservation time can be extended appropriately, for example, to 150 minutes. However, care should be taken to avoid over-growth that could lead to coating cracking or performance degradation.

[0102] This application's solution aims to construct a high-performance hard chromium wear-resistant layer on the surface of the copper-tungsten transition layer by precisely controlling the parameters of the low-temperature diffusion plating process. This effectively solves the problem of balancing wear and conductivity faced by the plug-in terminals of electric meter connectors during long-term use. The diffusion agent used consists of a specific ratio of chromium powder, ammonium chloride, and alumina. 80% of the chromium powder serves as the primary chromium source, ensuring sufficient chromium content in the hard chromium wear-resistant layer to form a high-hardness Cr3C2 phase, thus endowing it with excellent wear resistance. The 5% ammonium chloride decomposes at a diffusion temperature of 550℃, generating active halogen gases. These gases not only effectively remove any trace oxide film that may exist on the surface of the copper-tungsten transition layer and activate its surface, but more importantly, they promote the diffusion activity of chromium atoms, enabling them to be efficiently released from the chromium powder and migrate and deposit onto the surface of the copper-tungsten transition layer, forming a metallurgical bond.

[0103] 15% alumina serves as an inert carrier, its micron-sized particles uniformly dispersing the chromium powder and preventing its agglomeration at high temperatures. This ensures good permeability of the diffusion agent layer, avoiding localized overheating and guaranteeing uniform deposition of chromium atoms across the entire copper-tungsten transition layer surface, forming a dense and defect-free hard chromium layer. The diffusion temperature of 550℃ is carefully selected. It is lower than the decomposition temperature of the strengthening phase formed by the aging treatment temperature (450±10℃) in step S22 of the copper-based alloy substrate, avoiding damage to the substrate properties. It also creates a gentle transition between the thermal expansion coefficients of the copper-tungsten transition layer and the hard chromium layer, effectively reducing the interfacial stress that may be caused by the difference in thermal expansion and contraction, thereby significantly improving the bonding force between the hard chromium layer and the copper-tungsten transition layer.

[0104] Simultaneously, this temperature provides sufficient energy, allowing chromium atoms not only to deposit on the surface but also to slightly penetrate the copper-tungsten transition layer, forming a metallurgical bonding interface rather than a simple physical cover. This is crucial for ensuring the long-term stability and peel resistance of the coating. The 120-minute holding time ensures ample time for chromium atoms to diffuse and react, enabling the hard chromium wear-resistant layer to achieve its target thickness of 3–5 μm, meeting the wear resistance requirements of repeated insertion and removal, and forming a dense body-centered cubic structure with extremely low porosity, effectively preventing the embedding of impurities during wear. Furthermore, this holding time avoids cracking problems that may result from excessive thickness of the hard chromium layer and creates a reasonable thickness gradient with the copper-tungsten transition layer, allowing the wear pressure of the hard chromium layer to be evenly transmitted to the substrate through the transition layer, avoiding localized stress concentration.

[0105] Through the synergistic effect of the aforementioned parameters, this method successfully prepared a high-hardness, high-density, and firmly bonded hard chrome wear-resistant layer on the surface of the copper-tungsten transition layer. This hard chrome layer not only provides excellent wear resistance, but also, due to its metallurgical bond with the copper-tungsten transition layer and the high conductivity buffering effect of the copper-tungsten transition layer itself, the low conductivity of the hard chrome layer itself does not significantly affect the overall contact resistance of the connector, thus maintaining excellent conductivity while ensuring high wear resistance. This gradient composite structure design enables the connector to simultaneously meet the stringent requirements of both repeated insertion and removal wear and stable conduction under high current conditions, significantly improving the reliability and service life of the meter connector.

[0106] As a specific implementation method, when preparing the plug for the meter connector, the surface of the copper-tungsten transition layer pretreated in step S3 is subjected to low-temperature diffusion plating.

[0107] In the specific operation, a copper-based alloy substrate with a copper-tungsten transition layer is placed in a diffusion plating furnace and uniformly coated with a diffusion agent consisting of 80% by mass of 99.5% pure chromium powder (particle size approximately 5 micrometers), 5% ammonium chloride, and 15% alumina (particle size approximately 1 micrometer). The diffusion plating furnace is then heated to 550°C and precisely held at this temperature for 120 minutes. During this process, ammonium chloride decomposes at high temperature, generating active chlorine gas. This active chlorine gas effectively cleans the surface of the copper-tungsten transition layer and promotes the release of chromium atoms from the chromium powder, accelerating their diffusion and penetration into the copper-tungsten transition layer surface. Alumina acts as an inert medium, ensuring uniform distribution of the diffusion agent on the substrate surface, preventing chromium powder agglomeration, and maintaining the stability of the diffusion plating reaction. After the holding period, the substrate is slowly cooled to room temperature by furnace cooling, resulting in a uniformly thick and firmly bonded hard chromium wear-resistant layer on the surface of the copper-tungsten transition layer.

[0108] Through the above technical solution, this application effectively solves the problems of insufficient coating adhesion, substandard wear resistance, or impact on overall conductivity caused by improper composition of the plating agent, temperature, and time parameters when forming a hard chrome wear-resistant layer on the surface of the copper-tungsten transition layer. Specifically, by using a plating agent composed of a specific ratio of chromium powder, ammonium chloride, and alumina, and precisely controlling the plating temperature to 550℃ and the holding time to 120 minutes, this solution can ensure the formation of a high-hardness, high-density hard chrome wear-resistant layer on the surface of the copper-tungsten transition layer, which is metallurgically bonded to the transition layer. This hard chrome layer not only has excellent wear resistance, significantly extending the insertion and extraction life of the plug, but also, due to its good bonding with the copper-tungsten transition layer and the effective buffering effect of the copper-tungsten transition layer on conductivity, the conductivity of the hard chrome layer itself will not adversely affect the overall contact resistance of the plug. Therefore, this solution ensures that the plug has excellent wear resistance while maintaining its high conductivity, thereby significantly improving the reliability and stability of the meter connector under long-term repeated plugging and unplugging and high current conduction conditions. It effectively avoids problems such as increased contact resistance and localized heating caused by wear in traditional solutions, ensuring the accuracy of meter readings and electrical safety.

[0109] In some of the solutions described above in this application, Ag element was proposed as an additive component of copper-based alloys to improve conductivity and wear resistance. However, Ag element is expensive or its supply is limited in certain specific application scenarios. Therefore, it is necessary to provide an alternative element to meet different needs while maintaining the performance requirements of the alloy.

[0110] In this regard, this application further proposes that when preparing the copper-based alloy matrix, Ag element can be replaced with Au, and the mass percentage of Au is 0.10% to 0.15%.

[0111] In copper-based alloys, Ag primarily enhances conductivity and wear resistance. Au, a highly conductive noble metal, shares similar excellent conductivity and chemical stability with Ag and can serve as a substitute for Ag to address Ag supply constraints or specific application requirements. For instance, in humid or corrosive environments where higher chemical stability is required, Au exhibits superior oxidation and corrosion resistance compared to Ag, better maintaining long-term conductivity stability. Besides Au, other noble metals with high conductivity and good chemical stability, such as palladium (Pd) from the platinum group metals, can be considered in certain situations, but a trade-off between specific performance requirements and cost is necessary. The limit of 0.10%–0.15% by mass for Au aims to ensure that Au effectively enhances the alloy's conductivity and wear resistance while avoiding excessive addition that would lead to uneconomical costs or negatively impact the machinability and mechanical properties of the matrix. Adding below this lower limit may not adequately replace the effects of Ag, while adding above this upper limit could result in excessive costs or an imbalance in alloy performance. The precise addition amount is optimized based on the atomic properties of Au and its solid solution behavior in a copper matrix, aiming to achieve similar or better overall performance than Ag.

[0112] This method replaces Ag with Au during the preparation of the copper-based alloy matrix, precisely controlling the mass percentage of Au within the range of 0.10% to 0.15%. This significantly improves the long-term reliability of the chemical stability and conductivity under specific harsh environments while maintaining high conductivity and hardness. Au and Ag are both highly conductive noble metals, and Au exhibits superior chemical stability (oxidation and corrosion resistance) compared to Ag. In harsh environments such as humid and dusty conditions, Au effectively prevents conductivity degradation caused by the oxidation of noble metal elements, thus ensuring the matrix maintains stable conductivity over the long term. Furthermore, Au can form continuous conductive channels within the copper matrix, with a conductivity slightly higher than Ag, effectively compensating for the slight conductivity losses caused by the addition of Cr and Zr. Furthermore, limiting the Au mass percentage to 0.10%–0.15% is based on Au's atomic activity and slightly higher solid solubility in the copper matrix compared to Ag. A lower addition amount achieves the same conductivity compensation effect as Ag, avoiding the significant cost increase caused by excessive Au addition while ensuring conductivity is not affected by insufficient addition. This addition amount maintains synergy with the ratio of Cr (0.30%–0.35%) and Zr (0.12%–0.18%), without interfering with the precipitation of nanoscale reinforcing phases (CrCu2, ZrCu3), ensuring the matrix hardness remains stable at 120–130 HV without sacrificing resistance to plastic deformation. Therefore, this replacement scheme provides stronger environmental adaptability and more stable performance for meter connector pins without disrupting the Cu-Cr-Zr-noble metal quaternary microalloy synergistic system.

[0113] As a specific implementation method, when preparing the copper-based alloy matrix, a vacuum induction melting process can be used. Electrolytic copper is melted at 1180–1220°C under a vacuum of ≤5 Pa, followed by the sequential addition of chromium blocks, zirconium wire, and gold particles, and stirred at 50 r / min for 30 min. The amount of gold particles added can be controlled to be approximately 0.12% of the total alloy mass. The molten alloy is then die-cast under low pressure. The mold preheating temperature is 250°C, the die-casting pressure can be set to 9 MPa, and the holding time is 15 s. After forming, the matrix blank is water-cooled to room temperature to obtain a matrix blank with a density ≥99.5%. Subsequently, the matrix blank undergoes solution treatment and aging treatment, followed by surface pretreatment, and finally a composite diffusion coating layer is formed through a gradient diffusion plating process.

[0114] The above technical solution provides an alternative to Ag in the preparation of the copper-based alloy matrix for meter connector pins, adapting to the needs of specific applications. For example, in environments with more stringent requirements for conductivity and chemical stability, Au's excellent oxidation and corrosion resistance ensures that the pins maintain stable conductivity during long-term use, effectively preventing conductivity degradation caused by the oxidation of precious metals. Simultaneously, this solution provides more flexible material selection for pin manufacturing while maintaining the core properties of high hardness and high conductivity of the matrix, thereby improving the product's environmental adaptability and long-term reliability.

[0115] In some of the solutions mentioned above in this application, a copper-tungsten transition layer is proposed to form a transition layer on the substrate surface to enhance the bonding force with the hard chrome wear-resistant layer. However, in the implementation process, copper-tungsten materials may have problems such as insufficient interfacial bonding strength or unsatisfactory wear resistance in certain application scenarios, which may cause the transition layer to fall off during repeated insertion and removal of the plug, affecting the overall conductivity stability and service life.

[0116] In this regard, this application further proposes that in step S41, the copper-tungsten transition layer can be replaced with a copper-molybdenum transition layer, wherein the mass percentage of Mo in the copper-molybdenum transition layer is 25% to 35% and the thickness is 5 to 8 μm.

[0117] The copper-molybdenum transition layer is an intermediate layer formed on the surface of a copper-based alloy substrate. Its main function is to act as a bridge between the substrate and the final hard chrome wear-resistant layer. It effectively alleviates the stress caused by the difference in material properties between the two, thereby enhancing the overall adhesion of the composite plating layer. In addition, the copper-molybdenum transition layer also provides a certain degree of hardness and conductivity, providing support for the upper hard chrome wear-resistant layer and maintaining good electrical contact performance. It can be achieved by plasma plating to deposit a mixture of copper and molybdenum onto the substrate surface; or by magnetron sputtering to co-sputter copper and molybdenum targets onto the substrate surface to form an alloy layer. Molybdenum (Mo) is a key alloying element in the copper-molybdenum transition layer, and its content is crucial to the performance of the transition layer.

[0118] The molybdenum content is controlled within the range of 25% to 35% by mass to achieve an optimal balance between hardness, toughness, and conductivity. A lower molybdenum content may result in insufficient hardness in the transition layer, failing to effectively support the upper hard chrome wear-resistant layer and making it susceptible to damage; while an excessively high molybdenum content may significantly reduce the conductivity of the transition layer, affecting the overall conductive stability of the connector and potentially increasing brittleness. This molybdenum content ratio ensures that the transition layer has sufficient hardness to resist deformation while maintaining good toughness to absorb impact energy and maintaining acceptable conductivity. The thickness of the copper-molybdenum transition layer is a crucial parameter affecting its stress-absorbing capacity and overall interlayer adhesion. Setting the thickness between 5 and 8 micrometers ensures that the transition layer has sufficient thickness to effectively alleviate thermal stress between the copper-based alloy substrate and the hard chrome wear-resistant layer, preventing interlayer delamination due to excessive differences in thermal expansion coefficients. If the thickness is too thin, the buffering effect may be insufficient, easily leading to a decrease in interlayer adhesion; if the thickness is too thick, it may increase manufacturing costs and potentially affect the uniformity and density of the overall composite plating layer. This thickness range also ensures a stable deposition interface during the subsequent formation of the hard chrome wear-resistant layer, guaranteeing the performance of the final composite layer.

[0119] In step S41 of the manufacturing method of this application, the original copper-tungsten transition layer is replaced with a copper-molybdenum transition layer, and the mass percentage of molybdenum in the copper-molybdenum transition layer is precisely controlled between 25% and 35%, while maintaining its thickness between 5 and 8 micrometers. This aims to optimize the performance of the plug-in post for the meter connector under harsh operating conditions. Specifically, after the copper-based alloy substrate is prepared and subjected to heat treatment and surface pretreatment, a copper-molybdenum transition layer is formed on the surface of the substrate by plasma diffusion plating. Molybdenum has good solid solubility with copper atoms in the copper-based alloy substrate. During the plasma diffusion plating process, a more uniform and dense copper-molybdenum solid solution can be formed, thereby significantly improving the metallurgical bonding strength between the transition layer and the substrate.

[0120] Compared to copper-tungsten materials, copper-molybdenum materials exhibit superior interfacial bonding properties, effectively avoiding the weakening of bond strength that may be caused by material characteristics. Furthermore, molybdenum's toughness is superior to tungsten, allowing the copper-molybdenum transition layer to better absorb and disperse energy under the repeated impact stress generated by high-frequency insertion and extraction, reducing the risk of transition layer brittleness. By precisely controlling the molybdenum mass percentage within the range of 25% to 35%, this solution achieves a delicate balance between the hardness and conductivity of the transition layer. At this content, the transition layer provides sufficient hardness to effectively support the upper hard chrome wear-resistant layer, preventing it from collapsing under stress, while maintaining high conductivity. This ensures the continuity of the conductive gradient from the substrate to the transition layer to the wear-resistant layer, avoiding an increase in overall contact resistance due to excessively low conductivity in the transition layer.

[0121] The transition layer thickness is maintained between 5 and 8 micrometers, consistent with the original copper-tungsten transition layer thickness. This not only ensures compatibility with the subsequent low-temperature diffusion plating process for forming the hard chromium wear-resistant layer, eliminating the need to adjust subsequent process parameters, but also allows this thickness range to fully utilize its buffering effect. There is a difference in the coefficient of thermal expansion between the copper-based alloy substrate and the hard chromium wear-resistant layer. The copper-molybdenum transition layer, especially the molybdenum layer, has a coefficient of thermal expansion closer to that of the hard chromium layer. Compared to tungsten, it can more effectively alleviate the thermal stress between the two, thus maintaining superior stability under long-term high-temperature environments and further preventing interlayer delamination and accelerated wear. Therefore, this solution, through the introduction of the copper-molybdenum transition layer and the optimization of its parameters, significantly improves the wear resistance, bonding strength, and conductivity stability of the plug under specific harsh operating conditions without changing the overall gradient diffusion plating structure and subsequent processes, effectively solving the problems of transition layer detachment and impact on conductive life.

[0122] As a specific implementation method, in the manufacturing process of plug-in terminals for electricity meter connectors, when a composite plating layer needs to be formed, a copper-molybdenum transition layer can be formed on the surface of a pre-treated copper-based alloy substrate using a plasma plating process. For example, a composite target containing copper and molybdenum can be used for plasma plating, where the molybdenum content can be controlled to be approximately 30% of the total target mass. During the plating process, by precisely controlling the plasma parameters, the mass percentage of molybdenum in the copper-molybdenum alloy layer deposited on the substrate surface is kept stable between 25% and 35%. Simultaneously, by adjusting process parameters such as plating time or power, the thickness of the formed copper-molybdenum transition layer reaches approximately 6 micrometers. This copper-molybdenum transition layer will serve as an intermediate layer for subsequent hard chrome wear-resistant layer deposition, providing excellent interfacial bonding and buffering performance for the plug-in terminal.

[0123] Through the above technical solution, this application effectively solves the problem of insufficient interfacial bonding strength or unsatisfactory wear resistance of the copper-tungsten transition layer in certain harsh application scenarios. This avoids the transition layer detaching during repeated insertion and removal of the connector, thus preventing impact on overall conductivity stability and service life. Specifically, by replacing the copper-tungsten transition layer with a copper-molybdenum transition layer and precisely controlling the mass percentage of molybdenum and the thickness of the transition layer, the connector maintains a stronger interlayer bonding force under harsh conditions such as high-frequency insertion and removal and long-term high temperatures, significantly improving the anti-peeling performance of the composite plating layer. The excellent toughness of the copper-molybdenum transition layer effectively resists repeated impact stress, reducing the risk of transition layer brittleness. Simultaneously, the optimized molybdenum content ensures that the transition layer maintains good conductivity while providing sufficient hardness to support the hard chrome wear-resistant layer, guaranteeing the long-term conductivity stability of the connector for meter plugs. Furthermore, the better matching coefficient of thermal expansion between the copper-molybdenum transition layer and the hard chrome wear-resistant layer further reduces interfacial stress, improving the reliability and durability of the connector in high-temperature environments. Overall, this solution significantly improves the comprehensive performance and service life of meter connector pins under complex working conditions by optimizing materials and finely controlling parameters, without changing the main process of the existing manufacturing method.

[0124] In some of the solutions described above in this application, a hard chrome wear-resistant layer is proposed to provide wear-resistant protection on the substrate surface. However, in this process, there may be problems such as insufficient coating adhesion or decreased conductivity, which may lead to easy detachment or increased contact resistance during long-term insertion and removal, affecting the stability and life of the plug.

[0125] In this regard, this application further proposes that in the method of manufacturing plug-in pins for electricity meter connectors, in step S42, the hard chrome wear-resistant layer can be replaced with a chromium nitride layer, wherein the thickness of the chromium nitride layer is 3-6 μm and the hardness is ≥950HV.

[0126] Chromium nitride (CHN) is a functional thin film composed of chromium nitride compounds, characterized by high hardness, excellent wear resistance, good chemical inertness, and strong adhesion to various substrates. As a surface protective layer for the plug pins of meter connectors, its main function is to resist frictional wear and impact generated during repeated insertion and removal, while providing necessary corrosion resistance to ensure the stability and reliability of the plug pins during long-term use. One method of implementation is through physical vapor deposition (PVD) technology, such as magnetron sputtering or arc ion plating. In this method, the pretreated substrate is placed in a vacuum chamber, and chromium targets are bombarded with ionized gas, causing chromium atoms to evaporate and react with introduced nitrogen gas, forming a CHN film on the substrate surface. By adjusting process parameters such as target power, gas flow rate, substrate bias voltage, and temperature, the microstructure and properties of the CHN layer can be precisely controlled. Another method of implementation is through chemical vapor deposition (CVD) technology. This method is typically carried out at high temperatures, introducing chromium- and nitrogen-containing precursor gases to cause a chemical reaction on the substrate surface and deposit a chromium nitride coating. CVD technology can achieve uniform coverage of substrates with complex shapes.

[0127] The thickness of the chromium nitride layer is 3–6 μm, a range designed to balance wear resistance with internal stress control. The lower limit ensures sufficient material thickness to resist long-term wear and provide effective protection; the upper limit avoids excessive internal stress, increased brittleness, or adverse effects on overall conductivity that may result from excessive coating thickness, while ensuring good adhesion between the coating and the substrate and transition layer. This can be achieved by precisely controlling the deposition time, deposition rate, and target power density during the diffusion deposition process. For example, in PVD processes, adjusting the sputtering time or arc discharge time can directly affect the film thickness. Furthermore, real-time monitoring of parameter changes during coating growth, combined with a preset deposition rate model, can provide feedback control to ensure the final coating thickness falls within the target range.

[0128] The chromium nitride layer has a hardness ≥950 HV. This hardness ensures that the chromium nitride layer has excellent resistance to indentation and wear, effectively resisting the mechanical stress generated during insertion and removal, thereby significantly improving the surface wear life of the connector. High hardness is key to achieving long-term stable contact and preventing surface damage. The hardness of the chromium nitride layer can be controlled by optimizing the preparation process parameters. For example, in the PVD process, adjusting the nitrogen partial pressure, substrate bias, deposition temperature, and introducing alloying elements (such as carbon) can affect the grain size, crystal structure (such as the phase transition from CrN to Cr2N), and density of the chromium nitride layer, thus affecting its hardness. Furthermore, selecting appropriate deposition techniques and process conditions, such as arc ion plating with high-energy particle bombardment, can typically yield chromium nitride layers with higher density and hardness.

[0129] This application's solution replaces the hard chromium wear-resistant layer in the composite plating layer with a chromium nitride layer in the manufacturing method of the plug-in terminal for electricity meter connectors, precisely controlling its thickness to 3–6 μm and its hardness to be no less than 950 HV. This creates a surface protection system with excellent wear resistance, high adhesion, and good toughness. While maintaining the high conductivity of the original copper-based alloy substrate and copper-tungsten transition layer, this solution utilizes the inherent high hardness and corrosion resistance of the chromium nitride layer to effectively resist wear, impact, and corrosion of the plug-in terminal under repeated insertion and removal and harsh environments. The chromium nitride layer forms a stable interface with the underlying copper-tungsten transition layer, ensuring that the plating is not easily peeled off or cracked, thus maintaining the long-term stable electrical contact performance of the plug-in terminal. This replacement not only optimizes the flexibility of the surface treatment process but also, through material selection and parameter control, synergistically improves the overall durability and reliability of the plug-in terminal, enabling it to adapt to more demanding operating conditions.

[0130] In one specific implementation, in step S42, a chromium nitride layer can be formed on the surface of the pretreated copper-tungsten transition layer using a reactive magnetron sputtering process. Specifically, the substrate with the formed copper-tungsten transition layer is placed in a vacuum sputtering apparatus, evacuated to the baseline vacuum level, and then a mixture of argon and nitrogen is introduced as the working gas. Sputtering is performed by applying radio frequency or DC power to the chromium target, causing chromium atoms to react with nitrogen gas and deposit a chromium nitride thin film on the substrate surface. By precisely controlling the sputtering power, argon-nitrogen gas flow ratio, substrate temperature, and deposition time, a chromium nitride layer with a thickness of 4.5 μm and a hardness of 1000 HV can be obtained. For example, the coating thickness can be controlled by adjusting the sputtering time, and the coating hardness can be adjusted by optimizing the nitrogen partial pressure and substrate bias to ensure that it meets the thickness range of 3–6 μm and the hardness requirement of not less than 950 HV.

[0131] Through the above technical solution, the chromium nitride layer replaces the traditional hard chrome wear-resistant layer, significantly improving the adhesion, toughness, and corrosion resistance of the wear-resistant layer of the connector under repeated insertion and removal conditions. This effectively solves the problem of the original hard chrome layer being prone to brittleness and peeling off under high-frequency impact or corrosive environments, thereby avoiding increased contact resistance and shortened connector life due to plating failure. Simultaneously, while ensuring high wear resistance, the chromium nitride layer forms a more stable interface with the copper-tungsten transition layer, ensuring the stability and reliability of electrical contact during long-term use and extending its service life.

[0132] Example 1

[0133] Formula proportions: (percentage by mass) Cu balance, Cr 0.32%, Zr 0.15%, Ag 0.18%, impurities 0.01%.

[0134] Process steps: S1. Preparation of copper-based alloy matrix: Raw material pretreatment: Electrolytic copper (99.99% purity), chromium block (99.9% purity), zirconium wire (99.8% purity), and silver granules (99.99% purity) are dried at 120℃ for 2 hours to remove surface oxide scale and oil stains.

[0135] Vacuum induction melting: A vacuum induction melting furnace with a vacuum degree of 5Pa is used. Electrolytic copper is first heated to 1200℃ to melt, and chromium blocks, zirconium wire, and silver granules are added in sequence. The mixture is stirred at 50r / min for 30min and held at 1200℃.

[0136] Low-pressure die casting: mold preheating temperature 250℃, die casting pressure 9MPa, holding time 15s, water cooling to room temperature after molding to obtain a matrix blank with a density of 99.8%.

[0137] Machining: Cutting speed 150m / min, feed rate 0.1mm / r, machining to a copper-based alloy substrate with a diameter of φ5mm and a length of 20mm.

[0138] S2. Heat treatment of the copper-based alloy matrix: S21. Solution treatment: Heat the copper-based alloy matrix to 950℃, hold for 2 hours, and then quench it in water to room temperature at 20℃.

[0139] S22. Aging treatment: The copper-based alloy matrix after solution treatment is held at 450℃ for 4 hours, and then cooled in the furnace at a rate of 5℃ / min.

[0140] S3. Pre-treat the surface of the substrate after heat treatment: Alkaline degreasing: Use an alkaline degreasing agent containing 50g / L NaOH and 30g / L Na2CO3, and treat at 60℃ for 15min.

[0141] Pickling: Use a 10% dilute sulfuric acid solution to soak for 3 minutes at 25°C.

[0142] Activation: Soak in 5% hydrochloric acid solution for 1 minute.

[0143] S4. A composite diffusion coating layer is formed on the substrate surface using a gradient diffusion plating process: S41. Forming a copper-tungsten transition layer: A copper-tungsten transition layer is formed on the surface of the pretreated copper-based alloy substrate by plasma diffusion plating. A Cu-30%W target material is selected, the diffusion temperature is 400℃, the vacuum degree is 15Pa, the target current is 2A, the diffusion time is 90min, and the thickness of the copper-tungsten transition layer is 6μm.

[0144] S42. Forming a hard chrome wear-resistant layer: A hard chrome wear-resistant layer is formed on the surface of the copper-tungsten transition layer by a low-temperature diffusion plating process. The diffusion agent consists of 80% chromium powder, 5% ammonium chloride, and 15% aluminum oxide. The diffusion plating temperature is 550℃, the holding time is 120min, and the thickness of the hard chrome wear-resistant layer is 4μm.

[0145] S5. Post-treatment: Polished with 1μm diamond polishing paste, cleaned with deionized water, and dried at 80℃ for 30 minutes, with a surface roughness Ra of 0.15μm.

[0146] Example 2

[0147] The difference from Example 1 is in the formulation ratio (by mass percentage). Ag 0.18% was replaced with Au 0.13%, Cr was adjusted to 0.35%, Zr was adjusted to 0.12%, and impurities were adjusted to 0.02%.

[0148] Process steps: Raw material pretreatment: Replace silver granules with gold granules (99.99% purity).

[0149] Aging process: Temperature adjusted to 440℃.

[0150] Post-processing: Surface roughness Ra 0.16 μm.

[0151] Example 3

[0152] The difference from Example 1 is in the formulation ratio (by mass percentage). Cr was adjusted to 0.30%, Zr to 0.18%, and Ag to 0.20%.

[0153] Process steps: S41. Forming a copper-molybdenum transition layer: Select Cu-30%Mo target material, diffusion temperature 420℃, vacuum degree 12Pa, diffusion time 95min, and copper-molybdenum transition layer thickness 7μm.

[0154] S42. Form a hard chrome wear-resistant layer: adjust the thickness to 3.5μm.

[0155] Post-processing: Surface roughness Ra 0.17 μm.

[0156] Example 4

[0157] The difference from Example 1 is in the formulation ratio (by mass percentage). Cr was adjusted to 0.33%, Zr to 0.14%, and Ag to 0.17%.

[0158] Process steps: S3. Pretreatment: After activation, add argon purging for 30 seconds.

[0159] S42. Forming a chromium nitride layer: Using an ion plating process, the plating temperature is 530℃, the nitrogen partial pressure is 8Pa, the ion current is 2A, the holding time is 110min, and the thickness of the chromium nitride layer is 5μm.

[0160] Post-processing: Surface roughness Ra 0.16 μm.

[0161] Example 5

[0162] The difference from Example 1 is in the formulation ratio (by mass percentage). Cr was adjusted to 0.31%, Zr to 0.16%, and Ag to 0.19%.

[0163] Process steps: S1. Melting process: Replaced with argon-protected melting, argon purity 99.99%, melting temperature 1230℃, holding time 35min.

[0164] Low-pressure die casting: The die casting pressure is adjusted to 10MPa, and the density of the base blank is 99.6%.

[0165] Post-processing: Surface roughness Ra 0.17 μm.

[0166] Example 6

[0167] The difference from Example 1 is in the formulation ratio (by mass percentage). Cr was adjusted to 0.34%, Zr to 0.13%, and Ag to 0.15%.

[0168] The remaining process steps and parameters are completely consistent with those in Example 1.

[0169] Example 7

[0170] The difference from Example 1 is that the formula ratio is the same as that of Example 1; Process steps: S41. Forming a copper-tungsten transition layer: The plating temperature is adjusted to 390℃.

[0171] S42. Forming a hard chrome wear-resistant layer: The plating temperature is adjusted to 560℃.

[0172] Post-processing: Surface roughness Ra 0.16 μm.

[0173] Example 8

[0174] The difference from Example 1 is that the formula ratio is the same as that of Example 1; Process steps: S3 Pretreatment: The pickling step is omitted, and the activation treatment is carried out directly after alkaline degreasing.

[0175] Post-treatment: Surface roughness Ra 0.18 μm.

[0176] Comparison indicators Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Matrix hardness (HV) 125 122 128 124 123 126 124 125 Conductivity (%IACS) 98.5 98.2 98.3 98.4 98.1 98.0 98.2 98.4 Surface hardness (HV) of composite layer 1050 1040 1030 980 1050 1045 1035 1020 Contact resistance (mΩ) 4.2 4.5 4.4 4.6 4.3 4.7 4.5 5.8 Resistance change rate after 1000 insertion / removal cycles (%) 8 9 9.2 9.8 8.5 10 9.5 18 Matrix density (%) 99.8 99.7 99.8 99.8 99.6 99.8 99.8 99.8 Coating adhesion (cross-cut test) No shedding No shedding No shedding No shedding No shedding No shedding No shedding Slight peeling at the edges Example 1, through the optimal formulation (Cu balance, Cr 0.32%, Zr 0.15%, Ag 0.18%, impurities 0.01%) and complete process combination, achieved optimal comprehensive performance with a substrate hardness of HV125, conductivity of 98.5% IACS, contact resistance of 4.2mΩ, and resistance change rate of 8% after 1000 insertion / removal cycles. The coating adhered firmly and did not peel off. Example 2, using Au instead of Ag, showed better corrosion resistance but increased cost and slightly decreased performance. Example 3, using a copper-molybdenum transition layer instead of a copper-tungsten transition layer, achieved peeling... The strength is high, but the production efficiency is low and the conductivity is generally poor. Example 4 uses a chromium nitride layer to replace the hard chromium wear-resistant layer, which has the best corrosion resistance but insufficient hardness and poor wear resistance. Example 5 uses argon-protected melting, which is easy to implement, but the purity of the substrate and conductivity are slightly reduced. Example 6 uses the lowest boundary value of Ag, which meets the basic performance but has poor conductivity. Example 7 uses the boundary value diffusion temperature, which has high process tolerance but slightly reduces the density of the coating. Example 8 omits the pickling step, which simplifies the process, but the coating adhesion is insufficient and the stability is greatly reduced.

[0177] In summary, the formulation and process combination of Example 1 has synergistic advantages in conductivity, hardness, contact resistance stability and coating reliability, and is the optimal solution that balances performance, efficiency and cost. Other examples all have compromises or defects in different dimensions, which further confirms the creativity and superiority of the technical solution of Example 1.

[0178] Example 9

[0179] In some of the solutions described above in this application, a specific manufacturing method is proposed to produce the plug post 20 to improve its conductivity and wear resistance. However, if the manufacturing method is improper, the plug post 20 may not meet the requirements of high wear resistance, high conductivity and long service life, resulting in problems such as accelerated wear, increased contact resistance and shortened service life under repeated plugging and unplugging and high current conditions.

[0180] In this regard, refer to Figure 4 This application proposes a plug post 20 for an electricity meter connector, which is manufactured using a manufacturing method.

[0181] The plug-in post 20 of the electricity meter connector is the core conductive component, whose main function is to achieve reliable power transmission and connection. It typically needs to withstand repeated plugging and unplugging operations and operate stably under high current conditions. Therefore, extremely high requirements are placed on the conductivity, mechanical strength, surface wear resistance, and contact stability with external circuits of the plug-in post 20. The statement that it is manufactured using a specific method emphasizes that the performance of the plug-in post 20 is not achieved through simple material selection or a single surface treatment, but rather through a systematic, multi-step manufacturing process that endows it with specific material composition, microstructure, and surface properties. This manufacturing method aims to optimize the overall performance of the plug-in post 20, enabling it to overcome the inherent contradiction between conductivity and wear resistance in traditional plug-in posts 20, thereby meeting the electricity meter connector's requirements for high reliability and long lifespan.

[0182] This application's solution, by specifying that the plug-in post 20 is manufactured using a particular method, ensures that when this product serves as a core conductive component in an electricity meter connector, it overcomes the shortcomings of existing technologies where conductivity and wear resistance cannot be simultaneously achieved. Specifically, this manufacturing method first prepares a copper-based alloy substrate with a specific composition. This substrate incorporates alloying elements such as chromium, zirconium, and silver, significantly improving the substrate's strength and hardness while maintaining high conductivity, thereby effectively resisting plastic deformation during insertion and removal. Subsequently, the copper-based alloy substrate undergoes solution treatment and aging treatment to further optimize the substrate's grain structure and precipitate distribution, achieving an optimal balance between its mechanical and electrical properties. On the substrate surface, meticulous pretreatment steps ensure excellent adhesion between the subsequent composite plating layer and the substrate. Next, a gradient plating process is used to sequentially form a copper-tungsten transition layer and a hard chromium wear-resistant layer on the substrate surface. The copper-tungsten transition layer, serving as an intermediate layer, effectively mitigates the difference in thermal expansion coefficients between the substrate and the hard chrome layer, while providing a good conductive path. The hard chrome wear-resistant layer imparts extremely high hardness and wear resistance to the surface of the plug 20, effectively resisting wear during long-term repeated insertion and removal. Through this combination of material design and process control, the plug 20 achieves synergistic performance optimization from the substrate to the surface, solving the problem of traditional plug 20's difficulty in balancing conductivity and wear resistance. This avoids issues such as reduced contact area, increased contact resistance, and localized heating caused by wear, thereby ensuring the accuracy of meter readings and electrical safety.

[0183] The following is a specific example illustrating how the plug-in post 20 of the meter connector can be manufactured using the following method: First, a copper-based alloy matrix is ​​prepared using a vacuum induction melting process. Electrolytic copper is melted at 1180–1220℃ under a vacuum of ≤5Pa. Chromium blocks, zirconium wire, and silver granules are then added sequentially, and the mixture is stirred at 50 r / min for 30 min. The molten alloy is then die-cast under low pressure. The mold preheating temperature is 250℃, the die-casting pressure is 8–10 MPa, and the holding time is 15 s. After casting, the matrix blank is water-cooled to room temperature to obtain a matrix blank with a density ≥99.5%. The composition of this matrix blank is: Cr 0.30%–0.35%, Zr 0.12%–0.18%, Ag 0.15%–0.20%, with the balance being Cu and unavoidable impurities, wherein the impurity content is ≤0.01%. Subsequently, the copper-based alloy substrate underwent heat treatment, including solution treatment by heating to 950±10℃ and holding for 2 hours, followed by water quenching to room temperature; then, the solution-treated substrate was aged at 450±10℃ for 4 hours, and subsequently cooled in the furnace at a rate of 5℃ / min. After heat treatment, the substrate surface was pretreated, specifically including alkaline degreasing at 60℃ for 15 minutes using an alkaline degreasing agent containing 50 g / L NaOH and 30 g / L Na2CO3; pickling by immersion in a 10% dilute sulfuric acid solution at 25℃ for 3 minutes; and activation by immersion in a 5% hydrochloric acid solution for 1 minute. Finally, a composite diffusion coating layer is formed on the substrate surface using a gradient diffusion plating process. Specifically, a copper-tungsten transition layer with a thickness of 5–8 μm is formed on the pretreated substrate surface using a plasma diffusion plating process. The parameters of this plasma diffusion plating process are: Cu-30%W target material, diffusion temperature 400℃, vacuum degree 10–20 Pa, target current 2 A, and diffusion time 90 min. Then, a hard chromium wear-resistant layer with a thickness of 3–5 μm is formed on the surface of the copper-tungsten transition layer using a low-temperature diffusion plating process. The parameters of this low-temperature diffusion plating process are: a diffusion agent composed of 80% chromium powder, 5% ammonium chloride, and 15% alumina by mass percentage, a diffusion temperature of 550℃, and a holding time of 120 min.

[0184] Through the above technical solution, the resulting meter connector pin 20 effectively resolves the inherent contradiction between conductivity and wear resistance in traditional pins 20, significantly improving its overall performance. This pin 20 not only possesses excellent conductivity, ensuring stable conduction of large currents, but also exhibits high surface hardness and wear resistance, capable of withstanding repeated insertion and removal without plastic deformation or surface wear. This allows the pin 20 to maintain stable contact resistance and contact area during long-term use, effectively preventing localized heating, thereby ensuring the accuracy of meter readings and electrical safety, significantly extending the service life of the pin 20, and meeting the requirements of high wear resistance, high conductivity, and long lifespan.

[0185] Example 10

[0186] In some of the above-mentioned solutions of this application, a method for manufacturing the plug-in post 20 is proposed to manufacture the plug-in post 20 with high wear resistance and high conductivity. However, when the plug-in post 20 is integrated into the meter connector, there are problems such as insecure installation, unstable connection and insufficient insulation protection. This leads to easy displacement and wear and increased contact resistance during the overall plugging and unplugging process, which cannot meet the long life requirements of repeated plugging and unplugging and stable conduction of large current.

[0187] In this regard, refer to Figure 4 This application proposes an electric meter connector, which includes a plug 20, a conductive terminal 30 electrically connected to the plug 20, and an insulating housing, wherein the plug 20 is installed inside the insulating housing, and at least one end of it is connected to an external circuit through the conductive terminal 30.

[0188] Specifically, a meter connector is a device used to establish an electrical connection between a meter and an external circuit. Its core function is to provide a stable current transmission path and ensure the reliability, safety, and insulation of the connection. The plug-in post 20, as the core conductive component of the meter connector, serves as the physical and electrical interface between the meter and the external circuit.

[0189] The plug-in post 20 in this application is manufactured using a special process, possessing high wear resistance and high conductivity. It effectively resists wear caused by prolonged insertion and removal, and ensures stable transmission of high current. The plug-in post 20 is typically cylindrical, square, or flat, with one or both ends designed for connection to the conductive terminal 30, and the other end for mating with an external circuit. The conductive terminal 30 is the component used to achieve the electrical connection between the plug-in post 20 and the external circuit. Its main function is to provide a low-resistance current path and ensure the mechanical stability of the connection. The conductive terminal 30 can take various forms, such as crimp terminals, soldered terminals, screw-connected terminals, or spring-clamped terminals, to adapt to different connection requirements and installation methods.

[0190] The conductive terminal 30 is typically made of a highly conductive material (such as copper or copper alloys) and may undergo surface treatment to improve conductivity, corrosion resistance, or reduce contact resistance. The insulating housing is the external protective structure of the meter connector, its main functions being to provide electrical insulation, mechanical support, and environmental protection. The insulating housing isolates live parts from the external environment, preventing the risk of electric shock and short circuits. Simultaneously, it provides precise positioning and fixation for the plug 20 and conductive terminal 30, ensuring the stability of the plug 20 during insertion and removal. The insulating housing is typically made of materials with good insulation properties, mechanical strength, and heat resistance, such as engineering plastics or ceramic materials.

[0191] The plug-in post 20 is installed inside the insulating housing, meaning that the plug-in post 20 is fixed inside the insulating housing through a specific structural design and assembly method. This installation method ensures the precise position and orientation of the plug-in post 20, preventing it from shaking, shifting, or falling off during insertion and removal.

[0192] Installation methods may include, but are not limited to, snap-fit ​​fixing, injection molding, press-fitting, or bonding, aiming to provide stable mechanical support and maintain the insulation gap between the plug-in post 20 and the insulating housing. At least one end of the plug-in post 20 is connected to an external circuit via a conductive terminal 30, meaning that a specific part of the plug-in post 20 forms an electrical connection with the conductive terminal 30, thereby connecting to an external circuit such as a meter or power supply through the conductive terminal 30. This connection method ensures that current can be stably and efficiently transmitted from the external circuit to the plug-in post 20, or from the plug-in post 20 to the external circuit. The connection can be a one-end connection, a two-end connection, or a multi-end connection, depending on the design and functional requirements of the meter connector.

[0193] The meter connector of this application organically combines a specially manufactured plug 20 with a conductive terminal 30 and an insulating housing to form a cohesive whole. The plug 20, as the core conductive component, has high wear resistance and high conductivity, which are fundamental to the overall performance of the connector. The insulating housing provides a precise mounting position and stable mechanical support for the plug 20, ensuring that the plug 20 will not shift or loosen during repeated insertion and removal, thereby avoiding accelerated wear and increased contact resistance due to unstable positioning.

[0194] The conductive terminal 30 is responsible for providing a reliable electrical connection between the plug-in post 20 and the external circuit, ensuring the stability and low resistance of the current transmission path. The plug-in post 20 is installed within an insulating housing, achieving not only electrical isolation but also, through the housing's structural design, evenly distributing the insertion and extraction forces, reducing direct impact and wear on the plug-in post 20 itself. At least one end of the plug-in post 20 is connected to the external circuit via the conductive terminal 30, forming a complete current loop, enabling efficient and stable current transmission between the meter and the external circuit. This integrated design allows the superior performance of the plug-in post 20 to be fully utilized, while addressing the shortcomings of traditional connectors in terms of installation, connection, and insulation, thereby effectively improving the overall reliability, insertion and extraction life, and conductivity stability of the meter connector.

[0195] As a specific implementation method, the meter connector can be designed with a modular structure. The plug 20 can be cylindrical, with its surface treated with a composite diffusion coating to provide excellent wear resistance and conductivity. The conductive terminal 30 can be made of highly elastic and highly conductive materials such as phosphor bronze or beryllium copper, and designed as a spring-loaded structure, forming a stable electrical connection through elastic deformation and close contact with the plug 20.

[0196] The insulating housing can be injection molded using engineering plastics such as polycarbonate or polyamide. It features precise positioning grooves and limiting structures internally to securely mount the plug-in post 20 and the conductive terminal 30. One end of the plug-in post 20 extends out of the insulating housing for insertion into an external circuit socket, while the other end connects to the conductive terminal 30 inside the insulating housing via crimping or welding. The other end of the conductive terminal 30 extends out of the insulating housing and connects to the internal circuit board of the meter via screws or welding. The insulating housing may also be designed with foolproof features and locking mechanisms to ensure correct installation and reliable connection.

[0197] Through the above technical solutions, the meter connector of this application effectively solves the problems of unstable installation, unstable connection, and insufficient insulation protection when the plug-in post 20 is integrated into the meter connector. The stable installation of the plug-in post 20 within the insulating housing effectively avoids displacement and increased wear during repeated insertion and removal, significantly extending the service life of the plug-in post 20. The reliable electrical connection between the conductive terminal 30 and the plug-in post 20 ensures the stability of the current transmission path and low contact resistance, thereby avoiding localized heating and improving the accuracy of meter readings and electrical safety. The comprehensive protection provided by the insulating housing not only ensures electrical insulation but also enhances the mechanical strength and environmental adaptability of the connector. Overall, the meter connector of this application, while maintaining the high wear resistance and high conductivity of the plug-in post 20, achieves high reliability, long life, and stable high-current conduction by optimizing its integration method within the connector, meeting the usage requirements of meter connectors under harsh operating conditions.

[0198] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for manufacturing a connector pin for an electricity meter, characterized in that, Includes the following steps: S1. Prepare a copper-based alloy matrix, wherein the copper-based alloy matrix is ​​composed of the following components by mass percentage: Cr 0.30%–0.35%, Zr 0.12%–0.18%, Ag 0.15%–0.20%, with the balance being Cu and unavoidable impurities, wherein the impurity content is ≤0.01%; S2. Heat treatment of the copper-based alloy matrix, including: S21. The substrate is heated to 950±10℃ and kept at that temperature for 2 hours for solution treatment, and then quenched in water to room temperature. S22. The solution-treated matrix is ​​kept at 450±10℃ for 4 hours for aging treatment, and then cooled in the furnace at a rate of 5℃ / min. S3. Pre-treat the surface of the substrate after heat treatment, including alkaline degreasing, pickling and activation treatment in sequence; S4. A composite diffusion coating layer is formed on the substrate surface using a gradient diffusion plating process, including: S41. A copper-tungsten transition layer is formed on the surface of the pretreated substrate by plasma diffusion plating, wherein the thickness of the copper-tungsten transition layer is 5-8 μm. S42. A hard chrome wear-resistant layer is formed on the surface of the copper-tungsten transition layer by a low-temperature diffusion plating process, wherein the thickness of the hard chrome wear-resistant layer is 3-5 μm.

2. The manufacturing method according to claim 1, characterized in that, In step S1, the preparation of the copper-based alloy matrix includes: The process involves melting electrolytic copper at 1180–1220℃ and a vacuum of ≤5Pa using a vacuum induction melting process. Chromium blocks, zirconium wires, and silver granules are then added sequentially, and the mixture is stirred at 50 r / min for 30 min. The molten alloy liquid is formed by low-pressure die casting. The mold preheating temperature is 250℃, the die casting pressure is 8~10MPa, the holding time is 15s, and after forming, it is water-cooled to room temperature to obtain a base blank. The density of the base blank is ≥99.5%.

3. The manufacturing method according to claim 1 or 2, characterized in that, In step S3, the preprocessing specifically includes: Alkaline degreasing: Use an alkaline degreasing agent containing 50 g / L NaOH and 30 g / L Na2CO3, and treat at 60℃ for 15 min; Pickling: Immerse in a 10% dilute sulfuric acid solution at 25°C for 3 minutes; Activation: Soak in 5% hydrochloric acid solution for 1 minute.

4. The manufacturing method according to claim 1, characterized in that, According to the manufacturing method of claim 1, the parameters of the plasma diffusion process in step S41 are as follows: Cu-30%W target material, diffusion temperature 400℃, vacuum degree 10~20Pa, target current 2A, and diffusion time 90min.

5. The manufacturing method according to claim 1, characterized in that, According to the manufacturing method of claim 1, the parameters of the low-temperature diffusion plating process in step S42 are as follows: the diffusion agent is composed of 80% chromium powder, 5% ammonium chloride and 15% alumina by mass, the diffusion plating temperature is 550°C and the holding time is 120 min.

6. The manufacturing method according to any one of claims 1-5, characterized in that, In step S1, the Ag element can be replaced with Au, and the mass percentage of Au is 0.10% to 0.15%.

7. The manufacturing method according to claim 1, characterized in that, In step S41, the copper-tungsten transition layer can be replaced with a copper-molybdenum transition layer, wherein the mass percentage of Mo in the copper-molybdenum transition layer is 25% to 35% and the thickness is 5 to 8 μm.

8. The manufacturing method according to claim 1, characterized in that, According to the manufacturing method of claim 1, in step S42, the hard chrome wear-resistant layer can be replaced with a chromium nitride layer, wherein the thickness of the chromium nitride layer is 3-6 μm and the hardness is ≥950HV.

9. A plug-in for an electricity meter connector, characterized in that, It is prepared by the manufacturing method described in any one of claims 1 to 8.

10. A meter connector, characterized in that, It includes the plug as described in claim 9, a conductive terminal electrically connected to the plug, and an insulating housing, wherein the plug is installed inside the insulating housing and at least one end of the plug is connected to an external circuit through the conductive terminal.

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