A copper-chromium-tellurium alloy strip, a method for preparing the same and an application thereof

Abstract

This invention discloses a copper-chromium-tellurium alloy strip, comprising Cr, Te, P, Cu, and unavoidable impurities, with the sum of the mass percentages of all elements being 100%, wherein Cr: 0.05~0.50 wt%, Te: 0.05~0.50 wt%, and P: 0.001~0.020 wt%. The copper-chromium-tellurium alloy strip comprises a matrix and a second phase, the second phase being a chromium-tellurium intermetallic compound with an average size of 0.5~3.0 μm. This invention, by controlling the Cr and Te content and the size of the chromium-tellurium intermetallic compound, alters the distribution of cathode spots under arc erosion, thereby improving the arc erosion resistance of the copper-chromium-tellurium alloy, making the copper-chromium-tellurium alloy strip suitable for preparing vacuum switch contact materials.

Description

Technical Field

[0001] This invention relates to the field of copper alloy technology, specifically to a copper-chromium-tellurium alloy strip, its preparation method, and its applications. Background Technology

[0002] Vacuum switches are core switching devices in medium and high voltage power transmission and distribution systems, and their performance and reliability are directly related to the safe and stable operation of the entire power system. The contact material of a vacuum switch is one of the key factors that determines its performance, and it needs to have the following characteristics: (1) conductivity to reduce on-state losses and temperature rise; (2) excellent resistance to arc erosion to withstand the erosion of multiple opening and closing arcs; (3) good resistance to welding to prevent the contacts from sticking together under fault current; (4) appropriate mechanical strength and hardness to ensure the structural stability and deformation resistance of the contacts; and (5) good processing performance to facilitate the manufacture of contact parts with complex shapes and precise dimensions.

[0003] Currently, the main materials used for commercial vacuum switch contacts are copper-chromium alloys (such as CuCr25 and CuCr50). The addition of chromium significantly improves the material's resistance to arc erosion and its resistance to welding, but its conductivity decreases accordingly (typically to 70-80% IACS). Furthermore, high chromium content (e.g., 25-50 wt%) leads to high material hardness, difficulty in plastic processing, and higher costs. Tellurium copper alloys (such as C14500) are known for their excellent conductivity (>90% IACS) and improved machinability, but they have poor arc erosion resistance and weak resistance to welding, making them prone to failure under the high-load conditions of vacuum switches. Therefore, a single copper-chromium or copper-tellurium alloy cannot fully meet the comprehensive performance requirements of vacuum switch contact materials.

[0004] In recent years, researchers have attempted to improve the performance of copper-based contact materials through multi-element microalloying. For example, Chinese patent document CN116970836B discloses a high-strength tellurium-copper alloy, in which Fe is added to enhance strength, but the conductivity is only about 77% IACS. Chinese patent document CN110814500A discloses a copper electrode material suitable for resistance spot welding of aluminum alloys and its preparation method. This copper electrode material mainly includes 0.19~0.72wt% chromium and 0.40~1.33wt% tellurium, with the balance being copper. The preparation method includes melting and mixing chromium particles, tellurium particles, and copper particles to obtain a molten metal; pouring the molten metal into a mold to obtain an ingot; cutting the ingot to obtain a cut ingot; subjecting the cut ingot to solution treatment and quenching; and then performing aging treatment. However, the copper electrode material prepared by this method does not consider its ablation resistance.

[0005] In summary, existing copper-based contact materials struggle to achieve an ideal balance between conductivity, arc erosion resistance, weldability, machinability, and cost. Therefore, developing a novel copper alloy contact material with superior overall performance is crucial for advancing vacuum switch technology towards higher performance, greater reliability, and greater economy. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a copper-chromium-tellurium alloy strip containing Cr-Te intermetallic compounds with an average size of 0.5~3.0 μm. This ensures that the conductivity of the copper-chromium-tellurium alloy is ≥90% IACS while achieving the optimal balance between the arc resistance and conductivity of the copper-chromium-tellurium alloy.

[0007] A copper-chromium-tellurium alloy strip comprises Cr, Te, P, Cu, and unavoidable impurities, with the sum of the mass percentages of all elements being 100%, wherein Cr: 0.05~0.50 wt%, Te: 0.05~0.50 wt%, and P: 0.001~0.020 wt%; The copper-chromium-tellurium alloy strip comprises a matrix and a second phase, the second phase comprising chromium-tellurium intermetallic compounds with an average size of 0.5~3.0 μm.

[0008] The roles of each alloying element in this invention are as follows: Cr: The addition of Cr can, on the one hand, form Cr-Te intermetallic compounds (such as CrTe and Cr2Te3) with Te. These second phases remain stable at high arc temperatures, effectively hindering arc erosion and material migration. On the other hand, the addition of Cr can inhibit grain growth, promote the formation of equiaxed grains, and purify grain boundaries, reducing impurity segregation, thereby improving the weld resistance and high-temperature strength of copper-chromium-tellurium alloys. When the Cr content is below 0.05 wt%, the amount of Cr-Te intermetallic compounds formed is insufficient (below 1.5 × 10⁻⁶). 3 pcs / mm 2 The improvement in arc resistance is limited. When the Cr content is higher than 0.5 wt%, the Cr solid solution in the copper matrix increases electron scattering, and the average size of the formed Cr-Te intermetallic compound is too large, which significantly reduces the conductivity of the copper-chromium-tellurium alloy and leads to increased hardness and decreased plasticity, making it difficult to process. Therefore, this invention controls the Cr content within the range of 0.05~0.50 wt%, which can ensure that the conductivity of the copper-chromium-tellurium alloy is ≥90% IACS while forming a sufficiently dispersed and fine second phase, thereby achieving the best balance between arc resistance and conductivity of the copper-chromium-tellurium alloy.

[0009] Te: The addition of Te can effectively purify the copper matrix and reduce the scattering of electrons by impurities such as oxygen and sulfur, thereby improving the conductivity of copper-chromium-tellurium alloys. Firstly, Te can combine with Cr to form fine, dispersed Cr-Te intermetallic compounds, thus improving arc resistance. Simultaneously, these second phases are small in size and uniformly distributed, having little impact on the conductivity of copper-chromium-tellurium alloys. When the Te content is too low (<0.05 wt%), the improvement in arc erosion resistance is not significant, and the amount of second phases formed with Cr is insufficient (less than 1.5 × 10⁻⁶). 3 pcs / mm 2 While excessive Te content (>0.5 wt%) can improve the arc erosion resistance of copper-chromium-tellurium alloys, it can also lead to the formation of coarse or discontinuous telluride phases, which deteriorates the arc resistance and causes hot working brittleness. Therefore, this invention controls the Te content within the range of 0.05~0.5 wt%. This allows Te to fully exert its conductivity-enhancing effect and form a suitable amount of fine second phase with Cr, synergistically improving arc resistance. Furthermore, the addition of a small amount of Te improves the machinability and cold working properties of copper-chromium-tellurium alloys, making them suitable for precision machining of complex contact parts.

[0010] P: As a deoxidizer and grain refiner, phosphorus (P) helps purify the melt and refine the as-cast microstructure. The addition of P not only inhibits grain growth during casting, contributing to a uniform and refined as-cast microstructure and providing a good foundation for subsequent processing, but also acts as a deoxidizer, preventing excessive oxygen content in the copper-chromium-tellurium alloy from causing cracking during processing. Therefore, in this invention, the P content is controlled at 0.005~0.015 wt%, ensuring both deoxidation and grain refinement effects while avoiding damage to plasticity and conductivity caused by brittle phosphides due to excessive P content.

[0011] In this invention, the chromium-tellurium intermetallic compound plays a crucial role in the arc erosion resistance of copper-chromium-tellurium alloys. On one hand, under vacuum arc erosion, the cathode spots formed on the contact surface have extremely high energy density, which is the main source of ablation in copper-chromium-tellurium alloys. The 0.5–3.0 μm chromium-tellurium intermetallic compound produced by this invention can refine and disperse the cathode spots generated by the arc, forming uniformly distributed micro-spots. This significantly reduces the energy density and penetration depth of individual spots, thereby greatly mitigating localized over-vaporization and splashing of the copper-chromium-tellurium alloy material, thus reducing the degree of ablation. On the other hand, chromium-tellurium intermetallic compounds have higher melting points and high-temperature strength than copper matrices. Under the action of high-temperature electric arcs, although the copper matrix will melt and vaporize, these fine second-phase particles can still exist in solid or semi-solid form, forming a tiny corrosion-resistant skeleton in the molten pool. This skeleton can not only hinder the flow and splashing of liquid copper under the action of high-temperature electric arcs, but also serve as a heterogeneous nucleation core during the solidification process after the arc is extinguished, refining the solidification structure and reducing the coarse casting structure caused by repeated melting and solidification, thereby improving the arc erosion resistance stability of copper-chromium-tellurium alloys.

[0012] Preferably, the average amount of the chromium-tellurium intermetallic compound per unit area is 1.5 × 10⁻⁶. 3 ~2.5×10 3 pcs / mm 2 .

[0013] In this invention, the chromium-tellurium intermetallic compound is mainly defined by the content of chromium and tellurium. If the content of both is less than 0.05 wt%, the amount of chromium-tellurium intermetallic compound formed will be less than 1.5 × 10⁻⁶. 3 pcs / mm 2 However, this has limited effect on improving the arc resistance of the alloy.

[0014] Preferably, the microstructure of the copper-chromium-tellurium alloy strip includes recrystallized grains and elongated grains, wherein the recrystallized grains account for 70% to 90% of the total volume, and the elongated grains account for 10% to 30% of the total volume; The size of the recrystallized grains is 15~30 μm; The aspect ratio of the elongated grains is 3.3 to 10.0, the length dimension is 20 to 50 μm, and the width dimension is 5 to 15 μm.

[0015] In this invention, the copper-chromium-tellurium alloy strip contains recrystallized grains and elongated grains, with the majority being recrystallized grains. The fine recrystallized grains (15~30 μm) provide strength and ablation resistance to the copper-chromium-tellurium alloy. Compared to recrystallized grains, the elongated grains, which are not recrystallized, have a lower internal dislocation density and retain the rolling texture. In certain crystal orientations, there is less electron scattering. The elongated grains provide a fast conduction path for electrons, thereby compensating to some extent for the conductivity loss caused by fine grain strengthening and the precipitation of a large amount of second phase, achieving a balance between strength, ablation resistance, and conductivity in the copper-chromium-tellurium alloy.

[0016] Preferably, the copper-chromium-tellurium alloy strip has a conductivity of 81~85% IACS, an arc erosion rate of 1.9~2.4μg / C, a hardness of 100~135 HV, and a tensile strength of 360~455 MPa. Under 180° bending conditions, the copper-chromium-tellurium alloy strip satisfies R / t≤3.0 without cracking both perpendicular and parallel to the rolling direction, where R is the bending radius and t is the strip thickness.

[0017] The present invention also provides a method for preparing the above-mentioned copper-chromium-tellurium alloy strip, comprising the following steps: smelting → semi-continuous casting → hot rolling → milling → homogenization annealing → cold rolling and annealing; In the smelting process, electrolytic copper, copper-chromium (Cu-Cr) master alloy, copper-tellurium intermetallic alloy and phosphorus copper (Cu-P) master alloy are placed in a smelting furnace for melting, and a protective atmosphere (such as high-purity argon) is used for blowing.

[0018] More preferably, the specific steps of the smelting process are as follows: first, melt the electrolytic copper matrix, and after it is completely melted and heated to 1250~1350 ℃, add copper-chromium master alloy and stir thoroughly and blow air to keep it warm for 1~2 hours. Then, lower the furnace temperature to 1200~1250 ℃ and add copper-tellurium (Cu-Te) master alloy. Finally, add copper-phosphorus master alloy, stir thoroughly after adding, and keep it warm for 10~30 minutes.

[0019] In this invention, the blowing step aims to utilize high temperature and an inert atmosphere (Ar gas) to deeply remove harmful components such as oxygen from the melt, purifying the melt and reducing subsequent oxidation inclusions. Te element has a high vapor pressure; adding it at excessively high temperatures can easily lead to severe burn-off and compositional imbalance. Adding it later at a relatively lower melting temperature maximizes the effective yield of Te and ensures accurate composition. After addition, the mixture is thoroughly stirred and held at that temperature for 10-30 minutes to ensure uniform diffusion of all elements and homogeneous melt composition. After sampling and analysis confirming the composition is acceptable, the melt is ready for casting.

[0020] Preferably, in the semi-continuous casting process, the casting temperature is 1150~1200 ℃ and the casting speed is 60~100 mm / min.

[0021] Preferably, in the hot rolling process, the initial temperature of hot rolling is 800~860 ℃, the holding time is 1~3 hours, the total processing rate of hot rolling is ≥80%, the final rolling temperature is not lower than 700 ℃, and then the temperature is reduced to below 200 ℃ at a cooling rate of ≥300 ℃ / min.

[0022] In this invention, the hot rolling process employs rapid cooling to retain the supersaturated solid solution at room temperature, creating conditions for the precipitation of nano- or submicron-sized dispersed second phases during subsequent cold rolling and finished product annealing. If the cooling rate is lower than 300 ℃ / min, the Cr-Te intermetallic compounds will grow excessively and aggregate along grain boundaries or specific interfaces, forming large (e.g., >5 μm) and unevenly distributed coarse second phases, which will severely impair the toughness, uniformity, and final properties of the copper-chromium-tellurium alloy.

[0023] Preferably, in the milling process, the thickness of the upper and lower surfaces is 0.5~0.7 mm. This process is mainly to remove the oxide scale, surface defects and decarburized layer generated in the hot rolling process, to obtain a clean and bright metal surface, and to prevent these surface defects from being pressed into the copper-chromium-tellurium alloy in the subsequent cold rolling process, becoming crack sources or weak points in performance.

[0024] Preferably, in the homogenization annealing process, the annealing temperature is 700~750 ℃ ​​and the time is 4~12 hours.

[0025] In this invention, a high-temperature (700~750 ℃) and long-term (4~12 hours) homogenization annealing process essentially eliminates dendritic segregation caused by non-equilibrium solidification in the ingot, making the distribution of Cr, Te, and P elements in the copper matrix more uniform. This creates a uniform compositional starting point for subsequent hot working and uniform precipitation of fine second phases, and also lays the foundation for obtaining good bending performance. Simultaneously, this process effectively prevents uneven microstructure or cracking caused by segregation during subsequent processing. Besides the second phase, grain size is a key factor affecting bending performance. The aforementioned high-temperature homogenization annealing process reduces excessive grain growth, thus laying the foundation for grain control in subsequent annealing processes.

[0026] Preferably, the cold rolling and annealing process includes at least two cycles of cold rolling and annealing.

[0027] More preferably, in the cold rolling and annealing process, the processing rate of the first cold rolling is 50% to 80%. In this invention, controlling the processing rate of the first cold rolling serves two purposes: firstly, to reserve sufficient deformation energy for further refining the final grain size, serving as the driving force for subsequent recrystallization; and secondly, to allow the material to undergo strong plastic deformation through a processing rate of 50% to 80%, further promoting the diffusion of solid solution atoms (such as Cr) and inducing strain-induced precipitation of extremely fine second phases.

[0028] More preferably, in the cold rolling and annealing process, the temperature of the first annealing is 600~700 ℃, and the time is 1~5 hours. Utilizing the deformation energy stored in the first cold rolling, the material is driven to undergo complete recrystallization. During this process, the fibrous deformed structure is replaced by new, undistorted equiaxed fine grains, and the internal stress is basically eliminated, resulting in a uniform and soft intermediate structure. This process not only restores the plasticity of the material for subsequent cold rolling of the finished product, but also ensures that the grains are all recrystallized grains through the first annealing process. The average grain size of the recrystallized grains can be controlled at 20~40 μm, laying the foundation for obtaining a fine and uniform grain structure in the final product.

[0029] More preferably, in the cold rolling and annealing process, the processing rate of the second cold rolling is 15% to 40% to achieve the final finished product thickness and the required work hardening state.

[0030] More preferably, in the cold rolling and annealing process, the temperature of the second annealing process is 300~380 ℃, and the time is 5~10 hours.

[0031] On the one hand, this annealing process eliminates the residual internal stress generated by the second cold rolling, improving dimensional stability and resistance to stress relaxation. Simultaneously, it promotes the slow and uniform precipitation of supersaturated Cr and Te atoms retained in the matrix during hot rolling, rapid cooling, and subsequent processes, as Cr-Te intermetallic compounds. After low-temperature, long-term annealing, these readily form second-phase particles with an average size of 0.5–3.0 μm and a uniformly dispersed distribution. On the other hand, the use of a larger second cold rolling amount combined with a lower second annealing temperature further refines the grains, resulting in a "bimodal grain structure" in the copper-chromium-tellurium alloy, containing both recrystallized and non-recrystallized elongated grains. The fine recrystallized grains (15–30 μm) provide strength and ablation resistance to the copper-chromium-tellurium alloy; compared to recrystallized grains, the non-recrystallized elongated grains have a lower internal dislocation density and retain the rolling texture. The combination of fine second-phase particles and the bimodal grain structure achieves a balance between strength, ablation resistance, and electrical conductivity in the copper-chromium-tellurium alloy. At the same time, this process can ensure the ratio of elongated grains to recrystallized grains, avoiding the decrease in bending performance caused by excessive elongated grains, and can also control the size of recrystallized grains, thereby improving the bending performance of the material by refining the grains.

[0032] The present invention also provides the application of the above-mentioned copper-chromium-tellurium alloy strip in the preparation of vacuum switch contact materials.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows: In this invention, by controlling the content of Cr and Te elements and the size of the chromium-tellurium intermetallic compound, the distribution of cathode spots under arc erosion is changed, thereby providing the arc erosion resistance of copper-chromium-tellurium alloy, making copper-chromium-tellurium alloy strip suitable for preparing vacuum switch contact materials. Attached Figure Description

[0034] Figure 1 This is a scanning electron microscope image of the chromium-tellurium intermetallic compound after the second annealing in Example 1.

[0035] Figure 2 Metallographic images of recrystallized and elongated grains after the second annealing in Example 1 (scale bar: 100 μm). Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited to the following embodiments.

[0037] All raw materials used in this invention are commercially available.

[0038] Example 1 (1) Smelting: First, melt the electrolytic copper plate. After it is completely melted and the temperature is raised to 1320 ℃, add the copper-chromium master alloy and stir it thoroughly. Then, blow air to keep it warm for 1 hour. After that, lower the furnace temperature to 1240 ℃ and add the copper-tellurium (Cu-Te) master alloy. Finally, add the copper-phosphorus master alloy. After adding it, stir it thoroughly and keep it warm for 30 minutes. After the composition is qualified, start casting.

[0039] (2) Semi-continuous casting: The casting temperature is 1180 ℃ and the casting speed is 80 mm / min.

[0040] (3) Hot rolling: The homogenized ingot is heated to 850 ℃ and held for 2 hours. Then, it is hot rolled in multiple passes with a total processing rate of ≥80% and a final rolling temperature of not less than 700 ℃. After hot rolling, rapid cooling is adopted with a cooling rate of about 300 ℃ / min.

[0041] (4) Milling: The thickness of the upper and lower surfaces is 0.6 mm each, thereby removing oxide scale and other foreign matter from the surface of the hot-rolled billet.

[0042] (5) Homogenization annealing: The annealing temperature is 720 ℃ and the holding time is 8 h.

[0043] (6) First cold rolling: The processing rate of the first cold rolling is 75%.

[0044] (7) First annealing: The temperature of the second annealing is 610 ℃ and the holding time is 5 h.

[0045] (8) Second cold rolling: The processing rate of the second cold rolling is 21%.

[0046] (9) Second annealing: temperature is 360 ℃, holding time is 8 h.

[0047] The preparation methods of Examples 2-10 and Comparative Examples 1-9 are the same as those of Example 1, with the differences shown in Tables 1 and 2.

[0048] Table 1: Elemental composition of copper-chromium-tellurium alloys prepared in the examples and comparative examples Table 2: Key process parameters for copper-chromium-tellurium alloys prepared in the examples and comparative examples The difference between Comparative Example 1 and Example 1 is that the Cr content is 1.00 wt%.

[0049] The difference between Comparative Example 2 and Example 1 is that the Te element content is 0.85 wt%.

[0050] The difference between Comparative Example 3 and Example 1 is that the hot rolling temperature is 920°C.

[0051] The difference between Comparative Example 4 and Example 1 is that no water spraying and rapid cooling are performed after hot rolling, and the cooling rate is 100 °C / min.

[0052] The difference between Comparative Example 5 and Example 1 is that the homogenization annealing temperature is 800°C.

[0053] The difference between Comparative Example 6 and Example 1 is that the first annealing temperature is 500°C.

[0054] The difference between Comparative Example 7 and Example 1 is that the second cold rolling process rate is 10%.

[0055] The difference between Comparative Example 8 and Example 1 is that the second annealing temperature is 400°C.

[0056] The difference between Comparative Example 9 and Example 1 is that the processing rate of the second cold rolling is 35%.

[0057] The microstructure, hardness, tensile strength, conductivity, bending properties, and arc ablation rate of the copper-chromium-tellurium alloy strips prepared in Examples 1-10 and Comparative Examples 1-9 were analyzed. Microstructure testing: Grain size and grain size were determined under a metallographic microscope according to GB / T 13298-2020 "Methods for Examination of Microstructure of Metals". The sample area was 10×10 mm, and after polishing, it was etched with a ferric chloride mixed solution. The morphology and size of the second phase were analyzed using a field emission scanning electron microscope (FESEM) JSM-IT700HR, with the second phase particle size retained to one significant figure.

[0058] Hardness test: The test shall be conducted in accordance with the requirements of GB / T 4340.0~2009 Metallic materials Vickers hardness test - Part 1: Test method. The test sample size is 30 mm × 30 mm.

[0059] Tensile strength test: The room temperature tensile test was conducted on an electronic universal mechanical performance testing machine in accordance with GB / T 228.1-2010 Metallic materials, tensile testing - Part 1: Room temperature test method. The test specimen was dumbbell-shaped, the width of the tensile specimen was 20 mm, and the tensile speed was 5 mm / min. Conductivity testing: The test shall be conducted in accordance with the requirements of GB / T 32791-2016 Test method for conductivity of copper and copper alloys by eddy current, and the test strip size shall be 100 mm × 100 mm.

[0060] Bending performance test: According to GB / T 232-2010 Metallic Materials Bending Test Method, the samples were bent at 180° perpendicular to the rolling direction and parallel to the rolling direction on a universal testing machine using the corresponding bending die. The sample width was 10 mm and the length was 50 mm.

[0061] Arc erosion rate test: Arc erosion testing was conducted on the material under vacuum conditions according to the relevant methods in GB / T 1984-2014 "Electrical Life Test Methods for High Voltage AC Circuit Breakers". Flat plate electrodes were used, with a vacuum degree ≤1.0×10⁻⁶. -3 The average ablation rate was measured under the conditions of Pa, DC current of 10 kA, arcing time of 10 ms, and 50 interruption cycles.

[0062] Table 3: Microstructure of copper-chromium-tellurium alloys prepared in the examples and comparative examples Depend on Figure 1 It can be seen that, through a specific deformation heat treatment process, the size of the second-phase compound (i.e., the labeled "chromium-tellurium phase") in the alloy strip can be reduced to approximately 3 μm. Figure 2It can be seen that the microstructure of the alloy strip is mainly composed of round and elliptical recrystallized grains (with an average size of 10 μm and an area of ​​80%), and a small number of lath-shaped elongated grains in some areas (with an average size of 49 μm in the length direction, an average size of 6 μm in the width direction, and an area of ​​20%).

[0063] As shown in Tables 1 to 4, through Comparative Example 1, when the Cr content is high, the particles of the second phase are larger, which will seriously deteriorate the conductivity of the strip. At the same time, the copper-chromium-tellurium alloy has high hardness and strength, which does not meet the working conditions of the processed products. Comparative Example 2 shows that when the Te content is 0.85 wt%, the plasticity of the material decreases sharply and cannot meet the processing requirements. As can be seen from Comparative Example 3, when the hot rolling temperature is 920 ℃, the recrystallization grain size of the material is large due to the high hot rolling temperature. Although a larger first cold rolling process is used in the later stage, it is still not possible to effectively break the grains. The grain size of the material is 35 μm, which leads to poor bending performance of the alloy.

[0064] As shown in Comparative Example 4, when hot rolling is not followed by rapid cooling, the final size of the second phase and the recrystallized grains are both large, resulting in a significant decrease in its bending performance and resistance to arc erosion.

[0065] As can be seen from Comparative Example 5, when the homogenization annealing temperature is 800 ℃, the annealing temperature is high, the length-to-width ratio of the elongated grains is small, and the bimodal grain structure is not obvious, which affects the bending performance of the alloy and the strength of the strip is also low.

[0066] As shown in Comparative Example 6, when the first annealing temperature is 500 ℃, the grain size is relatively large, and the second phase particles are also relatively large, which leads to a decrease in the alloy's hardness, strength, bending performance, and resistance to arc erosion.

[0067] As shown in Comparative Example 7, when the second cold rolling rate is 10%, the hardness and strength of the alloy decrease, failing to meet the requirements.

[0068] As can be seen from Comparative Example 8, when the second annealing temperature is 400 ℃, the second phase grows significantly, and the length-to-width ratio of the elongated grains is small, and the proportion of recrystallized grains is also high, resulting in a significant decrease in strength and arc erosion resistance.

[0069] As shown in Comparative Example 9, when the processing rate of the second cold rolling is 35%, not only does the proportion of recrystallized grains decrease, but the aspect ratio of the elongated grains in the alloy strip is also greater than 10, ultimately leading to a significant decrease in the bending performance of the material.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A copper-chromium-tellurium alloy strip, characterized in that, The composition includes Cr, Te, P, Cu, and unavoidable impurities, with the sum of the mass percentages of all elements being 100%, where Cr: 0.05~0.50 wt%, Te: 0.05~0.50 wt%, and P: 0.001~0.020 wt%. The copper-chromium-tellurium alloy strip comprises a matrix and a second phase, the second phase comprising chromium-tellurium intermetallic compounds with an average size of 0.5~3.0 μm.

2. The copper-chromium-tellurium alloy strip according to claim 1, characterized in that, The microstructure of the copper-chromium-tellurium alloy strip includes recrystallized grains and elongated grains, wherein the recrystallized grains account for 70% to 90% of the total volume, and the elongated grains account for 10% to 30% of the total volume. The average size of the recrystallized grains is 5~15 μm; The aspect ratio of the elongated grains is 3.3 to 10.0, the average size in the length direction is 20 to 50 μm, and the average size in the width direction is 5 to 15 μm.

3. The copper-chromium-tellurium alloy strip according to claim 1, characterized in that, The copper-chromium-tellurium alloy strip has a conductivity of 81~85% IACS, an arc erosion rate of 1.9~2.4 μg / C, a hardness of 100~135 HV, and a tensile strength of 360~455MPa. Under 180° bending conditions, the copper-chromium-tellurium alloy strip satisfies R / t≤3.0 without cracking both perpendicular and parallel to the rolling direction, where R is the bending radius and t is the strip thickness.

4. The method for preparing copper-chromium-tellurium alloy strip according to any one of claims 1 to 3, characterized in that, Includes the following steps: Melting → Semi-continuous casting → Hot rolling → Milling → Homogenization annealing → Cold rolling and annealing; In the hot rolling process, the initial temperature of hot rolling is 800~860 ℃, the holding time is 1~3 hours, the total processing rate of hot rolling is ≥80%, the final rolling temperature is not lower than 700 ℃, and then the temperature is cooled to below 200 ℃ at a cooling rate of ≥300 ℃ / min.

5. The method for preparing copper-chromium-tellurium alloy strip according to claim 3, characterized in that, In the homogenization annealing process, the annealing temperature is 700~750 ℃ ​​and the time is 4~12 hours.

6. The method for preparing copper-chromium-tellurium alloy strip according to claim 3, characterized in that, The cold rolling and annealing process includes at least two cycles of cold rolling and annealing.

7. The method for preparing copper-chromium-tellurium alloy strip according to claim 6, characterized in that, In the aforementioned cold rolling and annealing processes, the processing rate of the first cold rolling is 50% to 80%; and / or, The first annealing temperature is 600~700 ℃, and the time is 1~5 hours.

8. The method for preparing copper-chromium-tellurium alloy strip according to claim 6, characterized in that, In the aforementioned cold rolling and annealing process, the processing rate of the second cold rolling is 15% to 40%.

9. The method for preparing copper-chromium-tellurium alloy strip according to claim 6, characterized in that, In the aforementioned cold rolling and annealing process, the temperature of the second annealing is 300~380 ℃, and the time is 5~10 hours.

10. The application of the copper-chromium-tellurium alloy strip according to any one of claims 1 to 3 in the preparation of vacuum switch contact materials.

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