Cu-la alloy electric contact material for low voltage circuit breaker and preparation method thereof

Abstract

A Cu-La alloy electric contact material for low-voltage circuit breaker and a preparation method thereof relate to a Cu alloy electric contact material for low-voltage circuit breaker and a preparation method thereof.The present application is to solve the technical problems that the existing copper-based electric contact is prone to have the problems of increased contact resistance, increased material loss and insufficient breaking capacity in the process of repeated on-off and high current breaking.The present application forms a fine and dispersed Cu6La second phase in the Cu matrix through micro La alloying, improves the uniformity of the damage of the organization and surface under the action of the electric arc while keeping the advantages of simple composition and good conductivity and heat conductivity of the copper-based material.Under the same test conditions of 380V / 60A and 1000 times of on-off, the contact resistance of the Cu-0.2La alloy is about 2.1mΩ, and the cumulative mass loss is about 2.5mg, which are significantly lower than those of the commercial Cu-diamond composite contact; the limit breaking current of the Cu-0.2La alloy is about 7575A.

Description

Technical Field

[0001] This invention relates to a Cu alloy electrical contact material for low-voltage circuit breakers and its preparation method. Background Technology

[0002] Electrical contacts in low-voltage circuit breakers, relays, contactors, and switching devices must withstand mechanical contact, current-carrying temperature rise, arcing during operation, localized melting, material migration, surface oxidation, and welding during service. The contact resistance stability, resistance to welding, resistance to arc erosion, and breaking capacity of the contact materials directly affect the reliability and service life of the electrical equipment.

[0003] Silver-based electrical contact materials offer good overall electrical contact performance, but their material cost is relatively high. Copper and copper alloys, with their excellent electrical and thermal conductivity, machinability, and cost advantages, are important candidates for low-cost electrical contact materials. However, ordinary copper materials are prone to localized melting, splashing, rapid solidification, and material transfer under repeated switching and high-current impact conditions, leading to increased contact resistance, roughened contact surface, increased tendency to weld, and decreased breaking reliability.

[0004] Existing copper-based electrical contacts typically improve arc damage resistance by introducing refractory metals, carbon materials, oxides, or other reinforcing phases, but this can lead to problems such as complex fabrication processes, unstable interfacial bonding, or decreased electrical and thermal conductivity. Therefore, there is a need for a copper-based electrical contact material with relatively simple composition, controllable processing, and the ability to balance contact resistance stability, material loss, and high current breaking capacity. Summary of the Invention

[0005] The present invention aims to solve the technical problems of existing copper-based electrical contacts, which are prone to increased contact resistance, increased material loss and insufficient breaking capacity during repeated switching and high-current breaking processes, and provides a Cu-La alloy electrical contact material for low-voltage circuit breakers and its preparation method.

[0006] The Cu-La alloy electrical contact material for low-voltage circuit breakers of the present invention consists of 0.18% to 0.22% La by mass percentage, with the balance being Cu and unavoidable impurities.

[0007] The Cu-La alloy electrical contact has a Cu6La second phase dispersed in the Cu matrix. The Cu6La second phase is nearly spherical or blunt blocky with an equivalent diameter of 0.2 μm to 3 μm.

[0008] The equivalent diameter refers to the diameter of a circle whose two-dimensional projected area is equal to that of the particle.

[0009] The preparation method of the Cu-La alloy electrical contact material for low-voltage circuit breakers of the present invention is carried out according to the following steps:

[0010] 1. Weigh out Cu and La raw materials according to the target composition;

[0011] 2. Melt and cast Cu and La raw materials under vacuum conditions to obtain Cu-La alloy ingots;

[0012] 3. Homogenize the Cu-La alloy ingot;

[0013] IV. Plastic deformation processing of the homogenized Cu-La alloy;

[0014] 5. Use a special blanking die to stamp the plastically deformed Cu-La alloy into electrical contact components.

[0015] The Cu-La alloy electrical contacts prepared by this invention can be used in low-voltage circuit breakers, relays, contactors, or switching devices.

[0016] The beneficial effects of this invention are as follows:

[0017] Compared to ordinary copper materials and existing copper-based electrical contact materials, this invention forms a fine, dispersed Cu6La second phase in the Cu matrix through trace La alloying. This maintains the simple composition and electrical and thermal conductivity advantages of copper-based materials while improving the uniformity of microstructure and surface damage under arcing. Under the same test conditions of 380V / 60A and 1000 switching cycles, the contact resistance of the Cu-0.2La alloy prepared by this invention is approximately 2.1mΩ, and the cumulative mass loss is approximately 2.5mg, both significantly lower than that of commercial Cu-diamond composite contacts. The ultimate breaking current of the Cu-0.2La alloy prepared by this invention is approximately 7575A, higher than that of Cu-0.2Zr, Cu-0.2Al, and commercial Cu-diamond composite contacts.

[0018] Although Cu-0.2Te exhibits a high breaking current and a low maximum welding force, its contact resistance after 1000 on / off cycles is higher than that of Cu-0.2La prepared in this invention. Cu-0.2Zr shows a significant cumulative mass loss, while Cu-0.2Al exhibits a low breaking current. This indicates that the Cu-0.2La prepared in this invention achieves a good overall balance between contact resistance, material loss, welding force, and breaking capacity. Attached Figure Description

[0019] Figure 1 Microstructure and second phase identification diagram of the Cu-0.2La alloy obtained in Experiment 1;

[0020] Figure 2A performance comparison chart of Cu-0.2La, Cu-0.2Zr, Cu-0.2Al, Cu-0.2Te alloys and commercial Cu-diamond composite contacts in 380V / 60A, 1000 switching cycles;

[0021] Figure 3 A comparison of the ultimate breaking currents of Cu-0.2La, Cu-0.2Zr, Cu-0.2Al, Cu-0.2Te alloys and commercial Cu-diamond composite contacts. Detailed Implementation

[0022] Specific implementation method one: This implementation method is a Cu-La alloy electrical contact material for low-voltage circuit breakers, which is composed of 0.18%~0.22% La by mass percentage, with the balance being Cu and unavoidable impurities.

[0023] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the mass percentage of La is 0.2%. Everything else is the same as in Specific Implementation Method One.

[0024] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the Cu-La alloy electrical contact material contains a Cu6La second phase dispersedly distributed within the Cu matrix. Everything else is the same as in Specific Implementation Method One or Two.

[0025] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the Cu6La second phase is nearly spherical or blunt blocky, with an equivalent diameter of 0.2 μm to 3 μm. Everything else is the same as in Specific Implementation Methods One to Three.

[0026] Specific Implementation Method Five: This implementation method differs from Specific Implementation Method Four in that the Cu6La second phase forms segregated clusters with a size of less than 5 μm. Everything else is the same as in Specific Implementation Method Four.

[0027] Specific Implementation Method Six: This implementation method is the preparation method of Cu-La alloy electrical contact material for low-voltage circuit breakers in Specific Implementation Method One, and is carried out according to the following steps:

[0028] 1. Weigh out Cu and La raw materials according to the target composition;

[0029] 2. Melt and cast Cu and La raw materials under vacuum conditions to obtain Cu-La alloy ingots;

[0030] 3. Homogenize the Cu-La alloy ingot;

[0031] IV. Plastic deformation processing of the homogenized Cu-La alloy;

[0032] 5. Use a special blanking die to stamp the plastically deformed Cu-La alloy into electrical contact components.

[0033] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method Six in that the Cu and La raw materials mentioned in step one are corresponding pure metal blocks, both with a purity greater than 99.9 wt.%. Everything else is the same as in Specific Implementation Method Six.

[0034] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method Seven in that the vacuum melting described in step two is replaced by vacuum induction melting. Everything else is the same as in Specific Implementation Method Seven.

[0035] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Method Eight in that the homogenization treatment temperature in step three is 800℃~950℃, and the holding time is 4h~24h. Everything else is the same as in Specific Implementation Method Eight.

[0036] Specific Implementation Method 10: This implementation method differs from Specific Implementation Method 9 in that the plastic deformation processing described in step four is one or more of cold rolling, hot rolling, cold drawing, or extrusion, and the total deformation is 50% to 90%.

[0037] The electrical contacts mentioned in step five are moving contacts, stationary contacts, contact plates, contact bridges, or contact rivets. Everything else is the same as in specific implementation method nine.

[0038] The invention was verified using the following experiments:

[0039] Experiment 1: This experiment demonstrates a method for preparing a Cu-0.2La alloy electrical contact material, specifically carried out according to the following steps:

[0040] 1. Weigh out Cu and La raw materials according to the target composition. The La content is 0.2 wt.%, and the balance is Cu and unavoidable impurities.

[0041] The Cu and La raw materials are corresponding pure metal blocks, each with a purity greater than 99.9 wt.%.

[0042] 2. Place the Cu and La raw materials weighed in step 1 into a vacuum induction melting furnace for melting and casting to obtain Cu-La alloy ingots;

[0043] 3. Homogenize the Cu-La alloy ingot;

[0044] The homogenization treatment was carried out at a temperature of 900℃ for 12 hours.

[0045] 4. The homogenized Cu-La alloy is cold-rolled with a total reduction rate of 80%.

[0046] 5. Use a special blanking die to stamp the plastically deformed Cu-0.2La alloy into electrical contact components.

[0047] Figure 1 The microstructure and second-phase identification of the Cu-0.2La alloy obtained in Experiment 1 are shown in Figure a). Figure a) shows the backscattered electron image and Cu and La elemental distribution diagrams; Figure b) shows the high-angle annular dark-field image, selected area electron diffraction pattern, and Cu and La elemental distribution diagrams of the La-enriched particles. As shown in Figure a), bright-colored particles are distributed in the Cu matrix of the Cu-0.2La alloy, and the Cu and La elemental distribution results indicate that the particles are La-enriched phases. As shown in Figure b), high-angle annular dark-field imaging, selected area electron diffraction, and elemental distribution analysis of the La-enriched particles confirmed that the particles are Cu6La second phases. The Cu6La second phase is nearly spherical, with an equivalent diameter of approximately 0.2~3 μm, and is diffusely distributed in the Cu matrix without forming a continuous network structure.

[0048] On / off performance test

[0049] The Cu-0.2La electrical contact components obtained in Experiment 1, along with each comparative contact sample, were assembled on the same test platform. Except for the material type, the contact structure, assembly method, and test conditions remained consistent. 1000 on / off cycles were performed at 380V / 60A, and the maximum welding force and contact resistance were recorded at the predetermined number of on / off cycles. The cumulative mass loss was also measured. The test results are shown below. Figure 2 The Cu-La in the figure is the sample from Experiment 1. Figure 2 It can be seen that after 1000 switching cycles, the maximum welding force of the Cu-0.2La contact is approximately 6.7 N, the contact resistance is approximately 2.1 mΩ, and the cumulative mass loss is approximately 2.5 mg. The contact resistance and cumulative mass loss of the Cu-0.2La contact are significantly lower than those of commercial Cu-diamond composite contacts, and remain relatively stable throughout the test.

[0050] Limit breaking capacity test

[0051] Using the same contact structure, assembly method, and test procedure, the ultimate breaking capacity of Test 1 and each comparison contact was tested. The ultimate breaking current for each material is shown in [reference needed]. Figure 3 The Cu-La in the figure is the sample of Experiment 1. It can be seen that the breaking current of Cu-0.2La contact is 7575A; the breaking current of commercial Cu-diamond composite contact is 4900A, and Cu-0.2La contact is about 1.55 times that.

[0052] Comparative Example 1: Cu-0.2Zr Alloy Electrical Contact Material

[0053] Cu-0.2Zr alloy electrical contact samples were prepared using the same process as in Experiment 1, replacing La with Zr. Figure 2 and Figure 3 It is known that the contact resistance of the material after 1000 switching cycles is approximately 2.3 mΩ, the cumulative mass loss is approximately 6.5 mg, and the ultimate breaking current is 5816 A.

[0054] Comparative Example 2: Cu-0.2Al Alloy Electrical Contact Material

[0055] Al was used instead of La, and Cu-0.2Al alloy electrical contact samples were prepared using the same process as in Experiment 1. Figure 2 and Figure 3 It is known that the contact resistance of the material after 1000 switching cycles is approximately 3.2 mΩ, the cumulative mass loss is approximately 2.3 mg, and the ultimate breaking current is 4762 A.

[0056] Comparative Example 3: Cu-0.2Te Alloy Electrical Contact Material

[0057] Cu-0.2Te alloy electrical contact samples were prepared using the same process as in Experiment 1, replacing La with Te. Figure 2 and Figure 3 It is known that the maximum welding force of the material after 1000 on / off cycles is about 2.9N, the contact resistance is about 4.1mΩ, the cumulative mass loss is about 2.8mg, and the ultimate breaking current is 7900A.

[0058] Comparative Example 4: Commercial Cu-Diamond Composite Contacts

[0059] Commercial Cu-diamond composite contacts were selected and tested under the same assembly method and test conditions as in Experiment 1. Figure 2 and Figure 3 It can be seen that the maximum welding force of the contact after 1000 switching cycles is about 10.8N, the contact resistance is about 8.2mΩ, the cumulative mass loss is about 10.2mg, and the ultimate breaking current is 4900A.

[0060] Comprehensive analysis

[0061] The above test results indicate that the evaluation of electrical contact materials for low-voltage circuit breakers cannot be based solely on a single performance indicator. Cu-0.2Te exhibits lower welding strength and higher ultimate breaking current, but its contact resistance is also higher; Cu-0.2Zr has a larger cumulative mass loss; Cu-0.2Al has a lower ultimate breaking current; and commercial Cu-diamond composite contacts have both higher contact resistance and cumulative mass loss. Cu-0.2La, by forming a finely dispersed Cu6La second phase, achieves a better overall balance between lower contact resistance, smaller mass loss, and higher ultimate breaking current, making it suitable as an electrical contact material for low-voltage circuit breakers and other switching devices.

Claims

1. A Cu-La alloy electrical contact material for low-voltage circuit breakers, characterized in that... The material is composed of 0.18% to 0.22% La by mass percentage, with the balance being Cu and unavoidable impurities.

2. The Cu-La alloy electrical contact material for low-voltage circuit breakers according to claim 1, characterized in that... The mass percentage of La is 0.2%.

3. The Cu-La alloy electrical contact material for low-voltage circuit breakers according to claim 1, characterized in that... The Cu-La alloy electrical contact material has a Cu6La second phase dispersed in the Cu matrix.

4. The Cu-La alloy electrical contact material for low-voltage circuit breakers according to claim 3, characterized in that... The Cu6La second phase is nearly spherical or blunt blocky, with an equivalent diameter of 0.2 μm to 3 μm.

5. The Cu-La alloy electrical contact material for low-voltage circuit breakers according to claim 4, characterized in that... The Cu6La second phase forms segregated clusters with a size of less than 5 μm.

6. The method for preparing a Cu-La alloy electrical contact material for low-voltage circuit breakers as described in claim 1, characterized in that... The method is performed according to the following steps:

1. Weigh out Cu and La raw materials according to the target composition; 2. Melt and cast Cu and La raw materials under vacuum conditions to obtain Cu-La alloy ingots; 3. Homogenize the Cu-La alloy ingot; IV. Plastic deformation processing of the homogenized Cu-La alloy; 5. Use a special blanking die to stamp the plastically deformed Cu-La alloy into electrical contact components.

7. The method for preparing a Cu-La alloy electrical contact material for a low-voltage circuit breaker according to claim 6, characterized in that... The Cu and La raw materials mentioned in step one are corresponding pure metal blocks, both with a purity greater than 99.9 wt.%.

8. The method for preparing a Cu-La alloy electrical contact material for a low-voltage circuit breaker according to claim 6, characterized in that... The melting under vacuum conditions described in step two is vacuum induction melting.

9. The method for preparing a Cu-La alloy electrical contact material for a low-voltage circuit breaker according to claim 6, characterized in that... The homogenization treatment in step three is carried out at a temperature of 800℃~950℃ for 4h~24h.

10. The method for preparing a Cu-La alloy electrical contact material for a low-voltage circuit breaker according to claim 6, characterized in that... The plastic deformation process described in step four is one or more of cold rolling, hot rolling, cold drawing, or extrusion, and the total deformation is 50% to 90%. The electrical contacts mentioned in step five are moving contacts, stationary contacts, contact plates, contact bridges, or contact rivets.

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