High-soldering-resistance copper-chromium contact and its preparation method

Abstract

This application discloses a high-weld-resistance copper-chromium contact and its preparation method, belonging to the field of contact material technology. The preparation method includes: using high-purity electrolytic chromium powder and electrolytic copper powder as raw materials, mixing them via acoustic resonance, and then sequentially passing them through powder pressing and cold isostatic pressing to obtain a blank; subjecting the blank to gradient sintering and finishing to obtain a copper-chromium electrode rod; then atomizing the copper-chromium electrode rod to obtain copper-chromium alloy powder; sequentially passing the copper-chromium alloy powder through cladding, heat treatment, sealing welding, and hot isostatic pressing sintering, and then removing the cladding to obtain a preform; after processing the preform, remelting the surface with a green laser to obtain a high-weld-resistance copper-chromium contact. This method improves the purity of the copper-chromium contact and optimizes the morphology and distribution of chromium particles, resulting in a contact with high purity, fine and uniformly distributed chromium particles, excellent weld resistance and breaking performance, suitable for high-voltage arc-extinguishing chambers.

Description

Technical Field

[0001] This application belongs to the field of contact material technology, specifically relating to a copper-chromium contact with high resistance to welding and its preparation method. Background Technology

[0002] Copper-chromium alloys possess a series of excellent comprehensive properties, such as strong short-circuit current breaking capacity, high dielectric strength, good ablation resistance, and low current-cutting value, making them an indispensable core component in vacuum interrupters. Their performance directly affects the operational stability and reliability of vacuum interrupters and even power equipment.

[0003] With the rapid development of the power industry, power grids are continuously moving towards higher voltage and larger capacity. In advanced high-voltage applications such as 126kV and 252kV single-break arc-extinguishing chambers and 40.5kV back-to-back capacitor banks, extremely stringent requirements are placed on the performance of copper-chromium contact materials, particularly in terms of insulation, breaking capacity, and resistance to welding. For example, during frequent switching processes with high voltage and high current, the contacts must withstand extremely high temperatures and electrical stresses. If the resistance to welding is insufficient, the contacts are prone to adhesion, leading to arc-extinguishing failure and potentially causing power accidents, seriously affecting the safe and stable operation of the power system.

[0004] Currently, the main manufacturing processes for contact materials include powder mixing and sintering, melt infiltration, casting, and arc melting. Among these, powder mixing and sintering produces contacts with low density, is time-consuming, and costly. Melt infiltration requires removing excess copper after infiltration, increasing processing costs and reducing yield. Casting and arc melting may introduce impurities during the manufacturing process, affecting material properties. Therefore, existing copper-chromium contact materials and their manufacturing methods have many shortcomings in meeting the stringent performance requirements of high-voltage applications, necessitating a manufacturing process that can significantly improve the insulation, breaking capacity, and resistance to welding of copper-chromium contact materials. Summary of the Invention

[0005] The purpose of this application is to provide a copper-chromium contact with high resistance to welding and a method for preparing the same, which can improve the purity of the copper-chromium contact material, optimize the morphology and distribution of chromium particles, and thus significantly improve its insulation performance, breaking performance and resistance to welding.

[0006] To achieve the above objectives, this application provides a method for preparing a copper-chromium contact with high resistance to welding, comprising the following steps:

[0007] Electrolytic chromium powder and electrolytic copper powder are used as raw materials to obtain a mixed powder.

[0008] The mixed powder is compacted in a rubber sleeve, and then cold isostatically pressed together with the rubber sleeve to obtain a green body;

[0009] The billet is subjected to gradient sintering to obtain a bar stock, and the bar stock is then finely machined to obtain a copper-chromium electrode rod.

[0010] The copper-chromium electrode rod is subjected to atomization powder preparation to obtain copper-chromium alloy powder.

[0011] After the copper-chromium alloy powder is encapsulated, it undergoes heat treatment, sealing welding, and hot isostatic pressing sintering. The encapsulation is then removed to obtain the copper-chromium contact preform.

[0012] After the copper-chromium contact preform is processed into a contact, the surface is remelted to obtain a copper-chromium contact with high resistance to welding.

[0013] Furthermore, the mass fractions of the electrolytic chromium powder and the electrolytic copper powder are 23%~55% and 45%~77%, respectively, the purity of the electrolytic chromium powder is ≥99.3%, and the purity of the electrolytic copper powder is ≥99.7%.

[0014] Furthermore, the mixed powder is obtained by acoustic resonance mixing, wherein the frequency of the acoustic resonance mixing is 50Hz~60Hz, the vibration acceleration is 80g~100g, the amplitude is 2mm~25mm, and the mixing time is 10min~40min.

[0015] Furthermore, the powder-pressing process includes the following steps: mechanically vibrating the rubber sleeve for 35s~45s, pressing the powder 9~10 times; after covering with the rubber sleeve plug, rolling the material for 5min~8min, tightening the rubber sleeve opening, and then pressing the powder in the reverse direction 2~3 times.

[0016] Furthermore, the pressure of the cold isostatic pressing treatment is 220MPa~230MPa, and the holding time is 5min~10min; the density of the billet is 75%~80%.

[0017] Furthermore, the gradient sintering includes the following steps:

[0018] In a vacuum environment of 0.01 Pa, the temperature was increased from room temperature to 400℃~450℃ at a rate of 3℃ / min~5℃ / min and held for 2 hours;

[0019] Then raise the temperature to 750℃~850℃ at a rate of 2℃ / min~3℃ / min and hold for 2 hours;

[0020] Then raise the temperature to 1000℃~1050℃ at a rate of 1℃ / min~2℃ / min and hold for 2.5h;

[0021] Stop heating and allow the furnace to cool to 55℃~60℃.

[0022] Furthermore, the atomization powder preparation process includes the following steps:

[0023] The vacuum environment is evacuated to a vacuum level below 5 Pa, and the copper-chromium electrode rod is melted by electromagnetic field to obtain a beam melt;

[0024] The beam melt is broken into fine droplets through an atomizing nozzle;

[0025] The tiny droplets cool and solidify at a rate of 90k / s to 130k / s to form copper-chromium alloy powder.

[0026] Furthermore, the heat treatment temperature is 525℃~575℃. After reaching the heat treatment temperature, the casing is degassed until the vacuum degree inside the casing is 1*10. -4 Pa;

[0027] The hot isostatic pressing (HIP) sintering process is carried out at a temperature of 850℃~950℃, a pressure of 120MPa~130MPa, and a holding time of 2h~4h.

[0028] Furthermore, the surface remelting method is green laser printing, wherein the printing power of the green laser printing is 200W~300W, the printing speed is 1300mm / s~1500mm / s, the blowing angle is 250°~300°, the number of printing layers is 1~2 layers, and the spot size is 0.05μm~0.1μm.

[0029] This application also discloses a copper-chromium contact with high resistance to welding, which is prepared according to the above method.

[0030] In summary, this application has the following advantages:

[0031] The preparation method provided in this application first uses high-purity electrolytic chromium powder and electrolytic copper powder as raw materials, which can improve the purity of the materials themselves and reduce the problem of particle breakdown caused by inclusions. Copper-chromium alloy powder is prepared by electrode induction gas atomization (EIGA) technology, which can produce alloy powder with high chromium content and powder purity, and the chromium particles in the alloy powder are finer, which can significantly improve the anti-welding performance of the contacts. Then, copper-chromium alloy rods are prepared by hot isostatic pressing. Compared with traditional cold pressing molding technology, this solves the problem of difficult forming of spherical powder prepared by EIGA, and can also produce larger-sized rods, avoiding the tonnage requirements of traditional technologies. After processing the alloy rods to obtain contact materials, surface remelting technology is used to treat the contact surface, which can form a fine chromium layer on the contact surface, further improving the anti-welding performance. Attached Figure Description

[0032] Figure 1 This is a SEM image (×1.0k) of the copper-chromium alloy powder in Example 1 of this application.

[0033] Figure 2This is a 500x metallographic photograph of the copper-chromium contact preform in Embodiment 1 of this application;

[0034] Figure 3 This is a metallographic photograph of the surface of the contact product after remelting in Embodiment 1 of this application. Detailed Implementation

[0035] The principles and features of this application are described below with reference to embodiments. The examples are for illustrative purposes only and are not intended to limit the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0036] Current research on copper-chromium contact materials has revealed that particulate breakdown is the primary factor causing reignition in these materials. Reignition ultimately leads to arc-extinguishing chamber failure, seriously threatening the safe operation of the equipment. Regarding resistance to welding, the microstructure and distribution of chromium particles have a significant impact. Studies show that the finer the chromium particles, the more dispersed their distribution, and the more spherical they are, the more significantly the material's resistance to welding is improved. Current contact material preparation processes mainly include powder mixing and sintering, melt infiltration, casting, and arc melting.

[0037] Among them, (1) the mixed powder sintering method has certain advantages in terms of anti-fusion welding performance. Its solid-state sintering characteristics make the particle bonding strength between the matrix low, and the contact surface is easy to be pulled apart from the matrix after melting. However, this method also has many defects. For example, the contact prepared by the mixed powder sintering method has a low density, usually only 97%. When it is connected with the contact cup, conductive rod and other accessories by brazing technology, the solder is easy to penetrate into the inside of the contact or even the surface due to capillary effect, causing the arc-extinguishing chamber to fail to open. At the same time, in the production process, the copper-chromium contact of mixed powder sintering needs to be aged before being put into the arc-extinguishing chamber. The residual gas, impurities and processing burrs on the electrode surface are removed and the electrode surface is passivated by current aging (arc discharge) or voltage aging (glow discharge or spark discharge). However, this process takes a long time, generally 7 to 8 hours, and is expensive. (2) The melting infiltration method requires the removal of excess metal copper after melting infiltration, which increases the process and processing cost, and also reduces the yield. (3) The casting and electric arc melting methods introduce impurities during the preparation process, which affects the material properties.

[0038] In summary, existing copper-chromium contact materials and their preparation methods have many shortcomings in meeting the stringent performance requirements of high-voltage applications. Therefore, this application provides a novel preparation process that significantly improves the insulation performance, breaking performance, and anti-welding performance of copper-chromium contact materials by increasing the purity and optimizing the morphology and distribution of chromium particles, while simplifying the production process and reducing production costs.

[0039] Specifically, in the first aspect, this application provides a method for preparing a copper-chromium contact with high resistance to welding, comprising the following steps:

[0040] S1. Electrolytic chromium powder and electrolytic copper powder are used as raw materials and mixed to obtain a mixed powder.

[0041] In a specific embodiment, the mass fractions of the electrolytic chromium powder and the electrolytic copper powder are 23%~55% and 45%~77%, respectively, the purity of the electrolytic chromium powder is ≥99.3%, and the purity of the electrolytic copper powder is ≥99.7%. Common powder-making processes in the prior art include aluminothermic chromium powder and electrolytic chromium powder. Aluminothermic chromium powder is prepared by reducing chromium oxide with aluminum, and this type of chromium powder often contains unreacted aluminum inclusions, resulting in relatively low purity. Electrolytic chromium powder is obtained by electrolyzing molten chromium salts to obtain metallic chromium; the electrolyte purity is generally high, and the resulting chromium powder also has relatively high purity. This application uses electrolytic chromium powder and electrolytic copper powder as raw materials, which can minimize inclusions (such as Fe, Si, O, etc.). These impurities are key factors causing particulate breakdown, which is the main cause of reignition and failure of copper-chromium contacts. Therefore, the high-purity raw materials of this application directly improve the insulation performance and dielectric strength of the material. Furthermore, during the subsequent EIGA powder preparation process, low-melting-point impurities (such as Pb and Sn) in the high-purity raw materials are more easily volatilized, further purifying the alloy powder and creating a synergistic effect with the EIGA process to improve purity. Simultaneously, this application controls the chromium content within the range of 23% to 55%, which can form dispersed, fine spherical chromium particles, effectively inhibiting fusion welding and ensuring a uniform chromium phase distribution during atomization, improving the sphericity and particle size consistency of the alloy powder. When the chromium content exceeds 55%, it may lead to increased material brittleness and decreased conductivity. In contrast, the copper content is controlled at 45% to 77%, ensuring good electrical conductivity (copper's conductivity is more than 10 times that of chromium), while chromium particles act as a reinforcing phase, improving hardness and ablation resistance. The formulation range of this application achieves an optimal balance between electrical and mechanical properties, making it particularly suitable for the frequent interruption requirements of high-voltage arc-extinguishing chambers. Furthermore, the proportioning range of this application can also enable the mixed powder to obtain a high-density preform during the cold isostatic pressing process, due to the synergistic effect of the plastic deformation capability of copper powder and the rigid support of chromium powder, thus providing high-quality electrode rods for subsequent EIGA powder production.

[0042] In a specific embodiment, the mixed powder is obtained by acoustic resonance mixing, wherein the frequency of the acoustic resonance mixing is 50Hz~60Hz, the vibration acceleration is 80g~100g, the amplitude is 2mm~25mm, and the mixing time is 10min~40min. The acoustic resonance mixing technology of this application achieves efficient and uniform powder mixing through acoustic vibration and cavitation effects. Compared with traditional mechanical mixing (such as ball milling or double-roller screw mixers, where the mixing time is generally 2h~4h), the mixing time is shorter, and the copper and chromium powders are mixed more uniformly, ultimately controlling the filling rate to 80%~95%. The frequency of 50Hz~60Hz is close to the natural vibration frequency of the powder, easily inducing a resonance effect, promoting sufficient collision and interpenetration of copper and chromium powders at the microscopic level, reducing agglomeration. This avoids uneven mixing caused by insufficient vibration energy at low frequencies (e.g., <50Hz) or localized overheating of the powder caused by excessive energy concentration at high frequencies (e.g., >60Hz). The vibration acceleration of 80g~100g overcomes the friction and adhesion between powder particles, ensuring uniform dispersion of copper and chromium powders with significant density differences, thus preventing stratification due to density differences. This ensures "forced mixing" of particles during vigorous vibration, making it particularly suitable for uniform distribution in formulations with high chromium content (up to 55%). The amplitude of 2mm~25mm balances macro-mixing and micro-dispersion: a small amplitude (2mm) ensures uniform distribution of fine particles, while a large amplitude (25mm) promotes overall powder flow and prevents localized accumulation. Preferably, a composite vibration mode of "high-frequency small amplitude + low-frequency large amplitude" can be formed to cover powder particles of different sizes. A mixing time of 10 minutes or more ensures that the powder completely breaks down from its initial agglomeration state, while a time of less than 40 minutes avoids particle breakage due to excessive vibration (especially important for chromium powder, which is brittle and prone to fine powder formation with prolonged vibration, affecting subsequent molding). In summary, the parameter range for acoustic resonance powder mixing in this application is the result of optimization based on the physical properties (density, hardness, brittleness) of copper and chromium powders and the mixing objectives (uniformity, particle integrity). Deviations from this range will directly affect the powder mixing quality, leading to problems such as insufficient compaction of the green body, component segregation after sintering, and uneven performance during surface remelting. Ultimately, this reduces the contact's resistance to welding (e.g., increased welding force and shortened service life). Therefore, strictly controlling the parameters within the specified range is a crucial prerequisite for ensuring contact performance in this application.

[0043] S2. The mixed powder is compacted in a rubber sleeve, and then cold isostatically pressed together with the rubber sleeve to obtain a blank.

[0044] In a specific embodiment, the powder compaction process includes the following steps: mechanically vibrating the rubber sleeve for 35-45 seconds, compacting the powder 9-10 times; after covering with the rubber sleeve plug, rolling the material for 5-8 minutes, tightening the rubber sleeve opening, and then compacting the powder in the reverse direction 2-3 times. The rubber sleeve is preferably made of polyurethane, which can uniformly transmit pressure during compaction and cold isostatic pressing, avoiding stress concentration-induced cracks in the green body. Furthermore, polyurethane exhibits good chemical stability to copper and chromium powders and will not chemically react with the metal powders during cold isostatic pressing. Simultaneously, its tensile strength and elongation at break are high, effectively preventing powder leakage and ensuring uniform density of the green body. This application employs a multi-stage vibration and compaction synergistic effect. First, mechanical vibration initially arranges the powder particles; then, forward compaction achieves graded filling of copper and chromium powders; next, rolling eliminates powder agglomeration through shear force, thereby improving mixing uniformity. Finally, reverse compaction balances the internal stress of the rubber sleeve, preventing stratification before cold isostatic pressing.

[0045] In a specific embodiment, the cold isostatic pressing treatment is carried out at a pressure of 220 MPa to 230 MPa, and the holding time is 5 min to 10 min; the density of the preform is 75% to 80%. The copper-chromium powder of this application undergoes plastic deformation under a pressure of 220 MPa to 230 MPa, increasing the contact area between particles (from point contact to surface contact). Holding the pressure allows for sufficient stress relaxation, preventing the preform from springing back after pressure relief, thereby controlling the final density to reach 75% to 80%, providing an ideal electrode rod preform for subsequent EIGA powder production.

[0046] S3. The blank is subjected to gradient sintering to obtain a bar stock, and the bar stock is then finely machined to obtain a copper-chromium electrode rod.

[0047] In a specific implementation, gradient sintering includes the following steps:

[0048] S301. In a vacuum environment of 0.01 Pa, the temperature is increased from room temperature to 400℃~450℃ at a rate of 3℃ / min~5℃ / min, and held for 2 hours. This step is the low-temperature stage, during which the lubricant on the surface of the copper powder can decompose and volatilize, preventing the formation of porosity in the subsequent high-temperature stage. Furthermore, the internal stress of the billet can be gradually relaxed during the heating process, preventing cracking due to thermal stress. The entire gradient sintering process must be carried out in a vacuum environment, which can effectively inhibit copper oxidation and accelerate the diffusion rate of residual gas in the billet, improving degassing efficiency and thus reducing the diffusion rate of the bar stock.

[0049] S302, then heat to 750℃~850℃ at a rate of 2℃ / min~3℃ / min and hold for 2 hours. This step is the medium-temperature stage, where copper begins to diffuse across grain boundaries, promoting the formation of initial sintering necks between copper particles (referring to the neck-like connection structure formed in the early stages of powder metallurgy sintering, where atomic diffusion gradually increases the particle contact interface). At this point, the porosity is high and the grain size is stable. As the holding time and subsequent sintering proceed, the neck region gradually expands and promotes the densification process, thereby improving the strength of the billet. At the same time, low-melting-point impurities in the chromium powder (such as Pb and Sn) are gradually volatilized and removed during this process, thereby improving the purity of the bar stock.

[0050] S303, then heat to 1000℃~1050℃ at a rate of 1℃ / min~2℃ / min, and hold for 2.5h. This step is the high-temperature stage, during which a local liquid phase will form on the surface of the copper particles. The capillary force of the liquid phase promotes particle rearrangement, thereby increasing the density. The holding process ensures that the chromium particles are uniformly dispersed in the copper matrix.

[0051] S304. Stop heating and cool with the furnace to 55℃~60℃. During furnace cooling, supersaturated chromium atoms in the copper matrix slowly precipitate, forming uniformly distributed nanoscale Cr precipitates. These precipitates pin dislocations, thereby increasing the hardness of the bar stock. Furthermore, they can eliminate residual stress within the bar stock, ensuring dimensional stability and machining accuracy during subsequent processing.

[0052] Furthermore, the gradient sintering method of this application can form a uniform microstructure, making the droplet breakage during the atomization powder production process more uniform. At the same time, the low porosity and high purity of the rod stock can also ensure good bonding between the 3D printed remelted layer and the matrix, high interfacial shear strength, and low porosity in the remelted layer, thereby significantly improving the anti-welding performance of the contact surface.

[0053] In a specific implementation, after finishing, an electrode rod with a specification of Φ90~100(0,+0.3) (mm)*800(0,+0.3) (mm) can be obtained.

[0054] S4. The copper-chromium electrode rod is subjected to atomization powder preparation to obtain copper-chromium alloy powder.

[0055] In a specific embodiment, the atomization powder preparation process includes the following steps: creating a vacuum environment to a vacuum level below 5 Pa, melting the copper-chromium electrode rod under the action of an electromagnetic field to obtain a beam melt; breaking the beam melt into fine droplets through an atomizing nozzle; and cooling and solidifying the fine droplets at a speed of 90 k / s to 130 k / s to form copper-chromium alloy powder. In this application, creating a vacuum level of <5 Pa can reduce the oxygen partial pressure to 10. -3The pressure is below 100 Pa, effectively suppressing copper-chromium oxidation during the smelting process. Furthermore, the vapor pressure of low-melting-point impurities (such as Pb, Sn, and Zn) in the electrode rod increases significantly during vacuum induction melting, allowing these impurities to preferentially volatilize and be removed, further improving the purity of the alloy powder. Next, the electromagnetic field generated by the ring induction coil creates a strong eddy current in the molten pool of the electrode rod, ensuring the chromium particles are fully dissolved and dispersed in the copper liquid, improving the uniformity of chromium distribution. Finally, rapid solidification suppresses the coarsening and segregation of the Cr phase, resulting in chromium particles being dispersed in the copper matrix, increasing the density of the alloy powder. Moreover, compared to the VIGA process (using a crucible for melting), EIGA uses electromagnetic levitation to keep the molten pool and the water-cooled copper crucible in a non-contact state, avoiding contamination of the crucible material (such as alumina and zirconium oxide).

[0056] Specifically, the atomization powder preparation process includes the following steps: After evacuating the atomization equipment to below 5 Pa, the CuCr electrode rod is inserted into the annular induction coil inside the atomization equipment. Under the action of the electromagnetic field, the electrode rod melts and drips into the atomization nozzle (orifice diameter 6mm~8mm). Then, the inert gas valve is opened, the gas pressure is adjusted, and the gas is introduced into the atomizer, breaking the molten metal into a large number of fine droplets and solidifying them at a cooling rate of 90k / s~130k / s (where k / s is Kelvin / second, the third unit of cooling rate) to form CuCr alloy powder. These powders also need to be sieved through a 300-1000 mesh sieve before being used for subsequent contact preparation.

[0057] S5. After the copper-chromium alloy powder is encapsulated, it is subjected to heat treatment, sealing welding, and hot isostatic pressing sintering. The encapsulation is then removed to obtain the copper-chromium contact preform.

[0058] Among them, the preferred material for the sleeve is copper (a mixture of copper and copper-chromium alloy). Compared with stainless steel sleeves, copper sleeves can be reused, saving material waste during the removal of the sleeve.

[0059] In a specific embodiment, the heat treatment temperature is 525℃~575℃. After reaching the heat treatment temperature, the cladding is degassed (12h~15h) until the vacuum degree inside the cladding is 1*10⁻⁶. -4 Pa, and then the casing is sealed using argon arc welding. This application utilizes heating degassing to thoroughly remove adsorbed gases and trace volatiles from the mixture inside the casing, adjusting the internal vacuum level of the casing to 1*10. -4 The high pressure effectively avoids defects such as porosity and looseness inside the material caused by residual gas during hot isostatic pressing, ensuring the density and mechanical properties of the product. Finally, argon arc welding under high vacuum prevents air from re-entering the casing, thus ensuring a stable vacuum environment inside the casing. This provides a good foundation for subsequent hot isostatic pressing processes, reduces the risk of impurity introduction, and helps improve the purity and performance uniformity of the final product.

[0060] In a specific embodiment, the hot isostatic pressing (HIP) sintering temperature is 850℃~950℃, the pressure is 120MPa~130MPa, and the holding time is 2h~4h. HIP sintering further refines and uniformly disperses chromium particles within the copper matrix, effectively suppressing molten pool flow under arcing and reducing welding tendency. Synchronous shrinkage of the cladding and the billet reduces residual stress within the material after HIP sintering, thereby improving the fatigue resistance of the contact during high-frequency breaking. The processing temperature of 850℃~950℃ promotes diffusion welding of copper-chromium alloy powder. The temperature range of 850℃~950℃ keeps the copper phase in a relatively plastic state (close to semi-molten), while preventing excessive grain growth of the chromium phase. Through diffusion, the particles achieve tight bonding, increasing the density of the billet. Furthermore, at moderate temperatures, copper atoms have strong diffusion capabilities, which can fill the pores between powder particles and simultaneously inhibit the coarsening of the chromium phase caused by high temperatures, ensuring a uniform alloy structure (fine and evenly distributed chromium particles), thus laying the foundation for subsequent weld resistance. If the temperature is below 850℃, the copper phase lacks plasticity, the atomic diffusion rate decreases, and it becomes difficult for powder particles to achieve tight bonding through diffusion and plastic deformation, resulting in insufficient compactness of the billet and a large number of residual pores. Subsequently, the contacts are prone to fusion welding due to local electric field concentration during switching. If the temperature is above 950℃, the copper phase softens excessively or even melts locally, which may lead to copper phase loss or aggregation under pressure, resulting in uneven distribution of chromium particles (local enrichment or sparseness), destroying the uniformity of the structure, and reducing weld resistance (fusion welding is more likely to occur in copper phase enrichment areas).

[0061] At high temperatures, isostatic pressing at 120MPa to 130MPa applies uniform pressure to the powder compact, promoting plastic deformation and close contact of the particles, rapidly eliminating internal pores, thereby increasing density and reducing defects (such as microcracks and porosity). Moderate pressure ensures densification without excessively compressing and breaking chromium particles or causing copper phase loss, maintaining a reasonable ratio and distribution of the copper and chromium phases. If the pressure is below 120MPa, it cannot effectively drive the plastic deformation and pore closure of the powder particles, resulting in poor densification, leaving more pores and porosity inside the compact. This leads to decreased electrical and thermal conductivity (prone to localized overheating when current passes through), and reduced resistance to welding (arc concentration points easily form at pore locations). If the pressure exceeds 130 MPa, excessive pressure will cause the chromium particles to be squeezed and broken, forming a fine chromium powder aggregate, which will disrupt the original particle distribution balance and may also cause the copper phase to be squeezed out of the particle gaps, resulting in local component segregation (insufficient copper phase or excessive concentration of chromium phase), leading to uneven contact hardness, increased wear during switching, or an increased risk of local fusion welding.

[0062] The holding time of 2-4 hours, combined with temperature and pressure, allows sufficient time for copper and chromium atoms to complete long-range diffusion, ensuring full fusion of the interparticle interfaces, completely eliminating residual porosity, and preventing localized porosity due to insufficient time. Too short a time results in insufficient densification, while too long a time increases energy consumption and may cause slow growth of chromium phase grains. This range balances effectiveness with economic efficiency. Holding times below 2 hours result in insufficient diffusion and densification, incomplete elimination of porosity, low compaction of the billet, and numerous micro-defects in the microstructure, affecting electrical conductivity and mechanical strength, and making it prone to fusion welding under arc conditions (melt pools easily form at defects). Holding times above 4 hours cause chromium phase grains to continue growing at prolonged high temperatures, leading to decreased alloy toughness and increased brittleness, making the contacts prone to fracture under mechanical or thermal shock. Energy consumption increases significantly, production efficiency decreases, and excessive copper phase diffusion may cause localized compositional inhomogeneity, affecting the stability of weld resistance. Therefore, the parameter range of hot isostatic pressing (850℃~950℃, 120MPa~130MPa, 2h~4h) is determined by balancing the diffusion behavior, densification efficiency and microstructure stability of the copper-chromium two phases. Deviation from this range will directly affect the density, microstructure uniformity and anti-welding performance of the contacts, leading to an increased risk of product failure.

[0063] S6. After the copper-chromium contact preform is processed into a contact, the surface is remelted to obtain a copper-chromium contact with high resistance to welding.

[0064] In a specific embodiment, the surface remelting method is green laser printing. The green laser printing power is 200W~300W, the printing speed is 1300mm / s~1500mm / s, the blowing angle is 250°~300°, the spot spacing is 0.10mm~0.15mm, the number of printing layers is 1~2 layers, and the spot size is 0.05μm~0.1μm. This application selects green laser (wavelength around 532nm), as copper alloys have a significantly higher absorption rate of green laser than red laser (wavelength 1064nm). At the same printing power, green laser can more efficiently convert energy into heat in the molten pool, reducing energy loss and thus increasing the remelted area per unit time, directly improving printing efficiency and reducing energy consumption cost per unit area. Simultaneously, the short wavelength characteristic of green laser results in higher focusing accuracy, which, combined with precise energy control, reduces the surface roughness of the contact after remelting. Low-roughness surfaces can reduce electric field concentration effects, avoiding excessively high local field strength caused by surface tip discharge, thereby significantly improving the breaking performance and insulation stability of the contacts. Green laser remelting can form submicron-sized chromium particles in the remelted layer, uniformly dispersed within the copper matrix. This fine-grained structure significantly improves the material's resistance to welding, greatly reducing welding force compared to unremelted surfaces, thus effectively preventing contact adhesion problems during frequent breaking processes. Furthermore, 3D printing the remelted layer can eliminate tool marks, microcracks, adsorbent gases, and contaminants on the product surface, forming a dense remelted layer that achieves a certain aging effect. This can reduce aging time and even replace traditional aging processes in some scenarios, significantly reducing the manufacturing cost and production cycle of the arc-extinguishing chamber.

[0065] Secondly, based on a general inventive concept, this application also provides a copper-chromium contact with high resistance to welding, obtained according to the above-described preparation method.

[0066] In summary, this application provides a copper-chromium contact with high resistance to welding and its preparation method. Through the synergistic optimization of multiple process steps, it achieves a comprehensive improvement in material properties. Specifically:

[0067] (1) First, high-purity electrolytic chromium powder (purity ≥99.3%) and electrolytic copper powder (purity ≥99.7%) are selected as raw materials. This selection is the basis for improving the material performance. High-purity raw materials can reduce the problem of particle breakdown caused by inclusions from the source, and lay a pure material foundation for the subsequent process to prepare high-quality contact materials.

[0068] (2) Based on the above raw materials, copper-chromium electrode rods are first prepared by cold isostatic pressing. This process enables the mixed powder to be initially shaped and obtain a blank with a certain density, providing qualified electrode rod raw materials for the next step of EIGA powder preparation and ensuring the stability of the subsequent powder preparation process.

[0069] (3) The EIGA process for preparing copper-chromium alloy powder, compared with the traditional VIGA (vacuum induction gas atomization powder preparation), does not require the use of a crucible, thus avoiding the contamination caused by the crucible and enabling the preparation of copper-chromium alloy powder with a high chromium content. At the same time, low-melting-point impurities and gaseous elements will volatilize during the powder preparation process, further improving the purity of the powder. More importantly, this process can refine the chromium particles in the alloy powder to the micron level, which has a significant effect on improving the anti-welding performance of the contacts. It is a further optimization of the material properties based on the cold isostatic pressing process.

[0070] (4) After obtaining copper-chromium alloy powder, copper-chromium alloy rods are prepared by hot isostatic pressing. This process effectively solves the problem of difficult forming of spherical powder prepared by EIGA. Compared with traditional cold pressing technology, it can not only produce larger rods, but also avoids the requirement for press tonnage. While ensuring the quality of material forming, it expands the range of rod specifications and provides a suitable blank for subsequent processing into contact materials.

[0071] (5) After the alloy rod is processed to obtain the contact material, the contact surface is finally treated by 3D printing remelting technology. Based on the aforementioned process, the contact performance can be further improved: a submicron-level fine chromium layer is formed on the contact surface, which significantly enhances the anti-welding performance; at the same time, the 3D printed remelting layer can eliminate tool marks, adsorbed gases and contaminants on the product surface, play a certain aging role, reduce aging time or even replace the aging process, thereby saving the manufacturing cost of the arc-extinguishing chamber, which is a dual optimization of contact material performance and production efficiency.

[0072] The technical solutions described above in this application will be explained in detail below with reference to specific embodiments.

[0073] Example 1

[0074] This embodiment provides a method for preparing a copper-chromium contact with high resistance to welding, including the following steps:

[0075] (1) Weigh 52wt% of electrolytic chromium powder and the remainder of electrolytic copper powder for mixing.

[0076] (2) Select a frequency of 60Hz, a vibration acceleration of 100g, and an amplitude of 25mm to mix the raw materials with acoustic resonance for 10min. The filling rate is controlled at 80%~95% to obtain mixed powder.

[0077] (3) Load the mixed powder into the polyurethane sleeve, first mechanically vibrate the sleeve for 40 seconds, then pound the powder 9 times, and then cover the sleeve and roll the material for 6 minutes. Use a steel clip to tighten the sleeve opening, turn the sleeve opening downwards, and then pound the powder in the opposite direction 2 times.

[0078] (4) After the powder is pressed, the rubber sleeve and the mixed powder therein are subjected to cold isostatic pressing at 225 MPa and held for 8 minutes to obtain a blank with a density of 75%~80%.

[0079] (5) The billet is placed in a vacuum sintering furnace for gradient sintering to obtain a bar stock, including: heating from room temperature to 400°C at a rate of 4°C / min in a vacuum environment of 0.01Pa and holding for 2 hours;

[0080] Then raise the temperature to 800℃ at a rate of 2.5℃ / min and hold for 2 hours;

[0081] Then raise the temperature to 1020℃ at a rate of 1.8℃ / min and hold for 2.5 hours;

[0082] Stop heating and allow the furnace to cool to 60°C before removing it from the furnace.

[0083] (6) The rod is precision machined to obtain copper-chromium electrode rods with specifications of Φ90~100(0,+0.3) (mm)×800(0,+0.3) (mm).

[0084] (7) After evacuating the atomizing equipment to below 5 Pa, the copper-chromium electrode rod is inserted into the annular induction coil inside the atomizing equipment. Under the action of the electromagnetic field, the electrode rod melts and drips into the atomizing nozzle. Then, the inert gas valve is opened, the gas pressure is adjusted to 1 MPa and introduced into the atomizer, breaking the molten metal into a large number of fine droplets and solidifying them at a cooling rate of 100 k / s to form CuCr alloy powder. The metallographic photograph of the obtained CuCr alloy powder is shown below. Figure 1 As shown, the Cr particle size is between 1 μm and 2 μm, while the alloy powder particle size is approximately 60 μm.

[0085] (8) After sieving the CuCr alloy powder through a 300-mesh sieve, pack it into a copper sheath, place it in a heat treatment furnace and heat it to 550°C, then degas for 14 hours until the vacuum degree inside the sheath reaches 1*10. -4 Pa, the sheath is sealed using argon arc welding.

[0086] (9) The sealed sheath was subjected to hot isostatic pressing at 900℃ and 120MPa for 3 hours. After completion, the sheath was removed to obtain a copper-chromium contact preform with a diameter of 85mm~90mm. The properties of the obtained copper-chromium contact preform are shown in Table 1, and the metallographic features are as follows. Figure 2 As shown.

[0087] (10) The obtained copper-chromium contact preform is processed into contact material according to the drawing requirements, and the contact surface is remelted by laser printing technology. Specifically, a green laser is selected for laser printing, with a printing power of 300W, a printing speed of 1300mm / s, a blowing angle of 250°, a spot spacing of 0.10, two printing layers, and a spot size of 0.1μm. The resulting metallographic structure of the laser-remelted contact surface is as follows: Figure 3 As shown. It can be seen that the CuCr remelted layer (i.e. Figure 3 The thickness of the area circled in red is about 20 μm, and the size of the chromium particles in the remelted layer is 1 μm to 2 μm, or even submicron.

[0088] Example 2

[0089] This embodiment provides a method for preparing a copper-chromium contact with high resistance to welding, including the following steps:

[0090] (1) Weigh 23wt% of electrolytic chromium powder and the remainder of electrolytic copper powder for mixing.

[0091] (2) Select a frequency of 50Hz, a vibration acceleration of 80g, and an amplitude of 2mm to mix the raw materials with acoustic resonance for 40min. The filling rate is controlled at 80%~95% to obtain mixed powder.

[0092] (3) Load the mixed powder into the polyurethane sleeve, first mechanically vibrate the sleeve for 40 seconds, then pound the powder 9 times, and then cover the sleeve and roll the material for 6 minutes. Use a steel clip to tighten the sleeve opening, turn the sleeve opening downwards, and then pound the powder in the opposite direction 2 times.

[0093] (4) After the powder is pressed, the rubber sleeve and the mixed powder therein are subjected to cold isostatic pressing at 225 MPa and held for 8 minutes to obtain a blank with a density of 75%~80%.

[0094] (5) The billet is placed in a vacuum sintering furnace for gradient sintering to obtain a bar stock, including: heating from room temperature to 400°C at a rate of 5°C / min in a vacuum environment of 0.01Pa and holding for 2 hours;

[0095] Then raise the temperature to 850℃ at a rate of 3℃ / min and hold for 2 hours;

[0096] Then raise the temperature to 1000℃ at a rate of 1℃ / min and hold for 2.5h;

[0097] Stop heating and allow the furnace to cool to 60°C.

[0098] (6) The rod is precision machined to obtain copper-chromium electrode rods with specifications of Φ90~100(0,+0.3) (mm)×800(0,+0.3) (mm).

[0099] (7) After evacuating the atomizing equipment to below 5Pa, the copper-chromium electrode rod is sent into the ring induction coil inside the atomizing equipment. Under the action of the electromagnetic field, the electrode rod melts and drips into the atomizing nozzle. Then, the inert gas valve is opened, the gas pressure is adjusted to 2MPa and introduced into the atomizer, breaking the metal liquid into a large number of fine droplets and solidifying at a cooling rate of 130k / s to form CuCr alloy powder.

[0100] (8) After sieving the CuCr alloy powder through a 1000-mesh sieve, pack it into a copper sheath, place it in a heat treatment furnace and heat it to 550°C, then degas for 14 hours until the vacuum degree inside the sheath reaches 1*10. -4 Pa, the sheath is sealed using argon arc welding.

[0101] (9) The sealed sheath is hot isostatically sintered at 950°C and 130MPa for 2 hours. After completion, the sheath is removed to obtain a copper-chromium contact preform with a diameter of 85mm~90mm.

[0102] (10) The obtained copper-chromium contact preform is processed into contact material according to the drawing requirements, and the contact surface is remelted by laser printing technology. Among them, green laser is selected for laser printing, the printing power is 200W, the printing speed is 1500mm / s, the blowing angle is 300°, the spot spacing is 0.15, the number of printing layers is 1, and the spot size is 0.05μm.

[0103] Example 3

[0104] This embodiment provides a method for preparing a copper-chromium contact with high resistance to welding, including the following steps:

[0105] (1) Weigh 40wt% of electrolytic chromium powder and the remainder of electrolytic copper powder for mixing.

[0106] (2) Select a frequency of 60Hz, a vibration acceleration of 100g, and an amplitude of 15mm to mix the raw materials with acoustic resonance for 20min. The filling rate is controlled at 80%~95% to obtain mixed powder.

[0107] (3) Load the mixed powder into the polyurethane sleeve, first mechanically vibrate the sleeve for 40 seconds, then pound the powder 9 times, and then cover the sleeve and roll the material for 6 minutes. Use a steel clip to tighten the sleeve opening, turn the sleeve opening downwards, and then pound the powder in the opposite direction 2 times.

[0108] (4) After the powder is pressed, the rubber sleeve and the mixed powder therein are subjected to cold isostatic pressing at 225 MPa and held for 8 minutes to obtain a blank with a density of 75%~80%.

[0109] (5) The billet is placed in a vacuum sintering furnace for gradient sintering to obtain a bar stock, including: heating from room temperature to 400°C at a rate of 3°C / min in a vacuum environment of 0.01Pa and holding for 2 hours;

[0110] Then raise the temperature to 850℃ at a rate of 2℃ / min and hold for 2 hours;

[0111] Then raise the temperature to 1020℃ at a rate of 1℃ / min and hold for 2.5h;

[0112] Stop heating and allow the furnace to cool to 60°C.

[0113] (6) The rod is precision machined to obtain copper-chromium electrode rods with specifications of Φ90~100(0,+0.3) (mm)×800(0,+0.3) (mm).

[0114] (7) After evacuating the atomizing equipment to below 5 Pa, the copper-chromium electrode rod is sent into the ring induction coil inside the atomizing equipment. Under the action of the electromagnetic field, the electrode rod melts and drips into the atomizing nozzle. Then, the inert gas valve is opened, the gas pressure is adjusted to 4 MPa and introduced into the atomizer, breaking the liquid metal into a large number of fine droplets and solidifying them at a cooling rate of 90 k / s to form CuCr alloy powder.

[0115] (8) After sieving the CuCr alloy powder through a 500-mesh sieve, pack it into a copper sheath, place it in a heat treatment furnace and heat it to 550°C, then degas for 14 hours until the vacuum degree inside the sheath reaches 1*10. -4 Pa, the sheath is sealed using argon arc welding.

[0116] (9) The sealed sheath is hot isostatically sintered at 900℃ and 130MPa for 2 hours. After completion, the sheath is removed to obtain a copper-chromium contact preform with a diameter of 85mm~90mm.

[0117] (10) The obtained copper-chromium contact preform is processed into contact material according to the drawing requirements, and the contact surface is remelted by laser printing technology. Among them, green laser is selected for laser printing, the printing power is 200W, the printing speed is 1300mm / s, the blowing angle is 300°, the spot spacing is 0.10, the number of printing layers is 2, and the spot size is 0.1μm.

[0118] Comparative Example 1

[0119] This comparative example provides a method for preparing a copper-chromium contact with high resistance to welding, comprising the following steps:

[0120] (1) Weigh 52wt% of aluminothermic chromium powder and the remainder of electrolytic copper powder for mixing.

[0121] (2) Select a frequency of 60Hz, a vibration acceleration of 100g, and an amplitude of 25mm to mix the raw materials with acoustic resonance for 10min. The filling rate is controlled at 80%~95% to obtain mixed powder.

[0122] (3) Load the mixed powder into the polyurethane sleeve, first mechanically vibrate the sleeve for 40 seconds, then pound the powder 9 times, and then cover the sleeve and roll the material for 6 minutes. Use a steel clip to tighten the sleeve opening, turn the sleeve opening downwards, and then pound the powder in the opposite direction 2 times.

[0123] (4) After the powder is pressed, the rubber sleeve and the mixed powder therein are subjected to cold isostatic pressing at 225 MPa and held for 8 minutes to obtain a blank with a density of 75%~80%.

[0124] (5) The billet is placed in a vacuum sintering furnace for gradient sintering to obtain a bar stock, including: heating from room temperature to 400°C at a rate of 4°C / min in a vacuum environment of 0.01Pa and holding for 2 hours;

[0125] Then raise the temperature to 800℃ at a rate of 2.5℃ / min and hold for 2 hours;

[0126] Then raise the temperature to 1020℃ at a rate of 1.8℃ / min and hold for 2.5 hours;

[0127] Stop heating and allow the furnace to cool to 60°C before removing it from the furnace.

[0128] (6) The rod is precision machined to obtain copper-chromium electrode rods with specifications of Φ90~100(0,+0.3) (mm)×800(0,+0.3) (mm).

[0129] (7) After evacuating the atomizing equipment to below 5 Pa, the copper-chromium electrode rod is sent into the ring induction coil inside the atomizing equipment. Under the action of the electromagnetic field, the electrode rod melts and drips into the atomizing nozzle. Then, the inert gas valve is opened, the gas pressure is adjusted to 1 MPa and introduced into the atomizer, breaking the metal liquid into a large number of fine droplets and solidifying at a cooling rate of 100 k / s to form CuCr alloy powder.

[0130] (8) After sieving the CuCr alloy powder through a 300-mesh sieve, pack it into a copper sheath, place it in a heat treatment furnace and heat it to 550°C, then degas for 14 hours until the vacuum degree inside the sheath reaches 1*10. -4 Pa, the sheath is sealed using argon arc welding.

[0131] (9) The sealed sheath is hot isostatically sintered at 900℃ and 120MPa for 3 hours. After completion, the sheath is removed to obtain a copper-chromium contact preform with a diameter of 85mm~90mm.

[0132] (10) The obtained copper-chromium contact preform is processed into contact material according to the drawing requirements, and the contact surface is remelted by laser printing technology. Among them, green laser is selected for laser printing, the printing power is 300W, the printing speed is 1300mm / s, the blowing angle is 250°, the spot spacing is 0.10, the number of printing layers is 2, and the spot size is 0.1μm.

[0133] Comparative Example 2

[0134] This comparative example provides a method for preparing a copper-chromium contact with high resistance to welding, comprising the following steps:

[0135] (1) Weigh 52wt% of electrolytic chromium powder and the remainder of electrolytic copper powder for mixing.

[0136] (2) The mixed powder is obtained by ball milling, wherein the ball milling speed is 800 rpm and the time is 1 h.

[0137] (3) Load the mixed powder into the polyurethane sleeve, first mechanically vibrate the sleeve for 40 seconds, then pound the powder 9 times, and then cover the sleeve and roll the material for 6 minutes. Use a steel clip to tighten the sleeve opening, turn the sleeve opening downwards, and then pound the powder in the opposite direction 2 times.

[0138] (4) After the powder is pressed, the rubber sleeve and the mixed powder therein are subjected to cold isostatic pressing at 225 MPa and held for 8 minutes to obtain a blank with a density of 75%~80%.

[0139] (5) The billet is placed in a vacuum sintering furnace for gradient sintering to obtain a bar stock, including: heating from room temperature to 400°C at a rate of 4°C / min in a vacuum environment of 0.01Pa and holding for 2 hours;

[0140] Then raise the temperature to 800℃ at a rate of 2.5℃ / min and hold for 2 hours;

[0141] Then raise the temperature to 1020℃ at a rate of 1.8℃ / min and hold for 2.5 hours;

[0142] Stop heating and allow the furnace to cool to 60°C before removing it from the furnace.

[0143] (6) The rod is precision machined to obtain copper-chromium electrode rods with specifications of Φ90~100(0,+0.3) (mm)×800(0,+0.3) (mm).

[0144] (7) After evacuating the atomizing equipment to below 5Pa, the copper-chromium electrode rod is sent into the ring induction coil inside the atomizing equipment. Under the action of the electromagnetic field, the electrode rod melts and drips into the atomizing nozzle. Then, the inert gas valve is opened, the gas pressure is adjusted to 2MPa and introduced into the atomizer, breaking the metal liquid into a large number of fine droplets and solidifying at a cooling rate of 130k / s to form CuCr alloy powder.

[0145] (8) After sieving the CuCr alloy powder through a 300-mesh sieve, pack it into a copper sheath, place it in a heat treatment furnace and heat it to 550°C, then degas for 14 hours until the vacuum degree inside the sheath reaches 1*10. -4 Pa, the sheath is sealed using argon arc welding.

[0146] (9) The sealed sheath is hot isostatically sintered at 900℃ and 120MPa for 3 hours. After completion, the sheath is removed to obtain a copper-chromium contact preform with a diameter of 85mm~90mm.

[0147] (10) The obtained copper-chromium contact preform is processed into contact material according to the drawing requirements, and the contact surface is remelted by laser printing technology. Among them, green laser is selected for laser printing, the printing power is 300W, the printing speed is 1300mm / s, the blowing angle is 250°, the spot spacing is 0.10, the number of printing layers is 2, and the spot size is 0.1μm.

[0148] Comparative Example 3

[0149] This comparative example provides a method for preparing a copper-chromium contact with high resistance to welding, comprising the following steps:

[0150] (1) Weigh 52wt% of aluminothermic chromium powder and the remainder of electrolytic copper powder for mixing.

[0151] (2) Select a frequency of 60Hz, a vibration acceleration of 100g, and an amplitude of 25mm to mix the raw materials with acoustic resonance for 10min. The filling rate is controlled at 80%~95% to obtain mixed powder.

[0152] (3) Load the mixed powder into the polyurethane sleeve, first mechanically vibrate the sleeve for 40 seconds, then pound the powder 9 times, and then cover the sleeve and roll the material for 6 minutes. Use a steel clip to tighten the sleeve opening, turn the sleeve opening downwards, and then pound the powder in the opposite direction 2 times.

[0153] (4) After the powder is pressed, the rubber sleeve and the mixed powder therein are subjected to cold isostatic pressing at 225 MPa and held for 8 minutes to obtain a blank with a density of 75%~80%.

[0154] (5) The billet is placed in a vacuum sintering furnace to obtain a bar stock, including: heating from room temperature to 1020°C at a rate of 3°C / min in a vacuum environment of 0.01Pa and holding for 4 hours; stopping heating and cooling with the furnace to 60°C before being taken out of the furnace.

[0155] (6) The rod is precision machined to obtain copper-chromium electrode rods with specifications of Φ90~100(0,+0.3) (mm)×800(0,+0.3) (mm).

[0156] (7) After evacuating the atomizing equipment to below 5 Pa, the copper-chromium electrode rod is sent into the ring induction coil inside the atomizing equipment. Under the action of the electromagnetic field, the electrode rod melts and drips into the atomizing nozzle. Then, the inert gas valve is opened, the gas pressure is adjusted to 0.1 MPa and introduced into the atomizer, breaking the liquid metal into a large number of fine droplets and solidifying them at a cooling rate of 100 k / s to form CuCr alloy powder.

[0157] (8) After sieving the CuCr alloy powder through a 300-mesh sieve, pack it into a copper sheath, place it in a heat treatment furnace and heat it to 550°C, then degas for 14 hours until the vacuum degree inside the sheath reaches 1*10. -4 Pa, the sheath is sealed using argon arc welding.

[0158] (9) The sealed sheath is hot isostatically sintered at 900℃ and 120MPa for 3 hours. After completion, the sheath is removed to obtain a copper-chromium contact preform with a diameter of 85mm~90mm.

[0159] (10) The obtained copper-chromium contact preform is processed into contact material according to the drawing requirements, and the contact surface is remelted by laser printing technology. Among them, green laser is selected for laser printing, the printing power is 300W, the printing speed is 1300mm / s, the blowing angle is 250°, the spot spacing is 0.10, the number of printing layers is 2, and the spot size is 0.1μm.

[0160] The performance of the copper-chromium contacts prepared in Examples 1-3 and Comparative Examples 1-3 was tested and analyzed, and the results are shown in Table 1.

[0161] Table 1

[0162]

[0163] As can be seen from Table 1, the oxygen and nitrogen contents of the aluminothermic chromium powder used in Comparative Example 1 increased because the oxygen and nitrogen content of the aluminothermic chromium powder is higher than that of the electrolytic chromium powder.

[0164] Comparative Example 2 used ball milling for powder mixing. After ball milling, the powder exhibited a near-rounded shape, resulting in relatively poor cold isostatic pressing formability. During the EIGA powder preparation process, gas in the electrode pores was released during melting and became trapped within droplets, forming hollow powder. Furthermore, the low density led to uneven heating, and localized overheating could cause melt splashing, forming irregular satellite powder. Hollow powder reduced the powder's tap density and flowability; satellite powder widened the particle size distribution, affecting the uniformity of powder spreading. Both types of defects reduced the product's density, thereby decreasing the material's gas content, electrical conductivity, and hardness.

[0165] Comparative Example 3 did not use gradient sintering, but directly heated to the end temperature at a uniform rate. The sintering lacked a degassing temperature point, resulting in a relatively high O and N content in the material, which further affected the material's performance.

[0166] While specific embodiments of this application have been described in detail, this should not be construed as limiting the scope of protection of this application. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims still fall within the scope of protection of this application.

Claims

1. A method for preparing a copper-chromium contact with high resistance to welding, characterized in that, Includes the following steps: Electrolytic chromium powder and electrolytic copper powder are mixed to obtain a mixed powder; the mass fractions of the electrolytic chromium powder and electrolytic copper powder are 23%~55% and 45%~77%, respectively, the purity of the electrolytic chromium powder is ≥99.3%, and the purity of the electrolytic copper powder is ≥99.7%. The mixed powder is compacted in a rubber sleeve, and then cold isostatically pressed together with the rubber sleeve to obtain a green body; The billet is subjected to gradient sintering to obtain a bar stock, and the bar stock is then finely machined to obtain a copper-chromium electrode rod. The copper-chromium electrode rod is subjected to atomization powder preparation to obtain copper-chromium alloy powder. After the copper-chromium alloy powder is encapsulated, it undergoes heat treatment, sealing welding, and hot isostatic pressing sintering. The encapsulation is then removed to obtain the copper-chromium contact preform. The heat treatment temperature is 525℃~575℃. After reaching the heat treatment temperature, the encapsulation is degassed until the internal vacuum degree of the encapsulation reaches 1*10⁻⁶. -4 Pa; The temperature of the hot isostatic pressing sintering treatment is 850℃~950℃, the pressure is 120MPa~130MPa, and the holding time is 2h~4h; After the copper-chromium contact preform is processed into a contact, the surface is remelted to obtain a copper-chromium contact with high resistance to welding. The gradient sintering process includes the following steps: In a vacuum environment of 0.01 Pa, the temperature was increased from room temperature to 400℃~450℃ at a rate of 3℃ / min~5℃ / min and held for 2 hours; Then raise the temperature to 750℃~850℃ at a rate of 2℃ / min~3℃ / min and hold for 2 hours; Then raise the temperature to 1000℃~1050℃ at a rate of 1℃ / min~2℃ / min and hold for 2.5h; Stop heating and allow the furnace to cool to 55℃~60℃; The atomization powder preparation process includes the following steps: The vacuum environment is evacuated to a vacuum level below 5 Pa, and the copper-chromium electrode rod is melted by electromagnetic field to obtain a beam melt; The beam melt is broken into fine droplets through an atomizing nozzle; The fine droplets are cooled and solidified at a rate of 90k / s to 130k / s to form copper-chromium alloy powder. The surface remelting method is green laser printing, with a printing power of 200W~300W, a printing speed of 1300mm / s~1500mm / s, a blowing angle of 250°~300°, a printing layer of 1~2 layers, and a spot size of 0.05μm~0.1μm.

2. The method for preparing a high-resistance weldable copper-chromium contact according to claim 1, characterized in that, The mixed powder is obtained by acoustic resonance mixing, wherein the frequency of the acoustic resonance mixing is 50Hz~60Hz, the vibration acceleration is 80g~100g, the amplitude is 2mm~25mm, and the mixing time is 10min~40min.

3. The method for preparing a high-resistance weldable copper-chromium contact according to claim 1, characterized in that, The powder-pressing process includes the following steps: mechanically vibrating the rubber sleeve for 35s~45s, pressing the powder 9~10 times; after covering with the rubber sleeve plug, rolling the material for 5min~8min, tightening the rubber sleeve opening, and then pressing the powder in the opposite direction 2~3 times.

4. The method for preparing a high-resistance weldable copper-chromium contact according to claim 1, characterized in that, The pressure of the cold isostatic pressing treatment is 220MPa~230MPa, and the holding time is 5min~10min; the density of the billet is 75%~80%.

5. A copper-chromium contact with high resistance to welding, characterized in that, The preparation method according to any one of claims 1 to 4 is used.

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