A method for preparing a low-cost hard contact material for vacuum switch

Abstract

The present invention discloses a method for manufacturing a low-cost hard contact material for vacuum switches, and relates to the technical field of design and preparation of electrical contact materials. The method comprises the following steps: Step 1: Mixing materials in a V-shaped heating mixer, wherein the mixed materials are mainly tungsten powder, tungsten carbide powder, and a trace amount of copper powder and iron powder, etc. The mixing time is several hours, and the mixed raw material powder is subjected to multiple cycles of heat treatment, pressing and crushing. Step 2: Pre-burning treatment. Step 3: Melt infiltration process. Step 4: After the product is out of the furnace, the surface of the product is roughly processed, and the ferroalloy side is machined to a shape and size that meets the performance requirements, and the product can be shipped out of the factory. The present invention adopts an integrated process of melt infiltration and welding to produce low-cost contact materials for vacuum switches, which reduces the production cost of the product and the welding cost of downstream enterprises, and has important social benefits for achieving energy conservation, environmental protection, and a low-carbon economy.

Description

Technical Field

[0001] The invention belongs to the technical field of design and preparation of electric contact materials, and in particular relates to a method for manufacturing a low-cost hard contact material for a vacuum switch. Background Art

[0002] Vacuum switches play a very important role in the safe operation of power grids. Their working mechanism is to use insulating and arc-extinguishing media to achieve current interruption. The working performance and electrical life of vacuum switches are closely related to the materials of their core components, the electrical contacts. The quality of the contact materials directly determines the reliability and safety of the vacuum switch operation. Therefore, the contact materials are required to have good electrical and thermal conductivity, large current breaking capacity, withstand voltage strength, low cutoff value, high resistance to welding, low arc burnout rate, and good mechanical properties.

[0003] However, in the process of implementing the prior art solution, the inventors of this application found that the above technology has at least the following technical problems:

[0004] 1. Early vacuum switches generally used refractory pure metals such as W and Mo as contact materials. Although they have the advantages of appropriate breaking capacity and long contact life, they still have the disadvantages of high breaking current and interception level, which limits the use scenarios of vacuum switches.

[0005] 2. Cu has excellent electrical and thermal conductivity and has also been used as a contact material, but its current interception level is low and its resistance to welding is poor.

[0006] 3. Although the CuBi contact material has good resistance to welding, Bi has a low melting point, is easily volatile, has low strength, and is prone to electrical corrosion, so it cannot be used in high-load vacuum circuit breakers.

[0007] 4. CuCr has high voltage resistance, excellent arc erosion resistance and breaking performance, but due to the incompatibility of Cu and Cr, when the alloy solidifies, the Cr phase tends to eutecticize and is prone to component segregation.

[0008] 5. CuW alloy has good breaking capacity and conductivity, and is often used as the contact material of high-voltage vacuum switches. The conductive rod part is usually made of copper or copper-chromium alloy. The material cost has always been high, which limits the development of high-voltage switches. Summary of the invention

[0009] Based on the above shortcomings, the purpose of the present invention is to provide a new low-cost vacuum circuit breaker contact material, which has high insulation strength and mechanical strength, good resistance to welding, low current cutoff value and high interrupting voltage power supply capacity, and can be used in vacuum circuit breakers of higher voltage levels.

[0010] The embodiment of the present application provides a method for manufacturing a hard contact material for a vacuum switch at a low cost, characterized in that the method comprises the following steps:

[0011] Step 1: Mix the materials in a V-shaped heating mixer. The mixture includes tungsten powder, tungsten carbide powder, and a small amount of copper powder and iron powder. The mixing time is several hours. The mixed raw material powder is subjected to multiple cycles of heat treatment, pressing and crushing.

[0012] Step 2: Pre-sintering treatment, and ensure that after pre-sintering treatment, copper and tungsten carbide and tungsten particles are in a good infiltration state, which can well induce the subsequent copper infiltration process.

[0013] Step 3: Infiltration process, copper infiltration and sintering in a vacuum furnace, covering the surface of the pre-fired pressed green sheet with a specified weight of pure copper sheet, and then covering the surface of the pure copper sheet with a specified weight of ferroalloy to form a sandwich structure, put it into a graphite crucible, fill it with alumina powder around to prevent oxidation, and place it in an atmosphere heating furnace for infiltration-welding integrated heat treatment process. During the furnace heating process, the copper sheet reaches the melting point and begins to melt, and the copper liquid penetrates into the pores in the green sheet through capillary action. At the same time, a high-strength welding connection between the ferroalloy and the tungsten-copper contact is achieved.

[0014] Step 4: After the product is out of the furnace, the product surface is roughly processed, and the ferroalloy side is machined to a shape and size that meets the performance requirements. The product can then be shipped out of the factory.

[0015] Preferably, the average particle size of the tungsten carbide powder in step 1 is less than 5 microns, the average particle size of the copper powder is less than 50 microns, and the average particle size of the iron powder and the nickel powder is less than 30 microns.

[0016] Preferably, the heat treatment temperature in step 1 is 500-750° C. and the time is 2-5 hours.

[0017] Preferably, the temperature of the pre-sintering treatment in step 2 is 1000°C to 1200°C.

[0018] Preferably, in step 3, the weight content of the copper sheet and the iron alloy in the mixture is 5-20%.

[0019] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0020] 1. The final product performance obtained by the preparation method provided by the present invention is: density 12±0.2g / cm 3 ; Hardness is; Conductivity is 18±2MS / m.

[0021] 2. The integrated process of infiltration and welding is used to produce low-cost contact materials for vacuum switches, which reduces product production costs and welding costs of downstream companies, and has important social benefits for achieving energy conservation, environmental protection and low-carbon economy.

[0022] 3. Combining heat treatment experiments and theoretical calculations of the diffusion dynamics of copper / tungsten, the heat treatment process parameters during the infiltration of copper-tungsten contacts, interlayer copper plates and contact iron alloy plates are carefully designed to avoid excessive iron in the contact working area to form iron-tungsten brittle phases that deteriorate performance, and innovatively produce contact materials with good quality and low cost.

[0023] 4. Use the infiltration process to weld the iron alloy on the non-working surface of the copper-tungsten contact. During the hot pressing sintering process, add trace amounts of copper, Ni and other activating elements to improve the subsequent infiltration effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The metallographic structure of the tungsten-copper alloy side of the contact material of the invention is shown in FIG.

[0025] Figure 2 The present invention discloses a metallographic structure of the ferroalloy side of the contact material.

[0026] Figure 3 The present invention discloses a metallographic structure of the connection interface between tungsten copper alloy and iron alloy in the contact material. DETAILED DESCRIPTION

[0027] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0028] First, weigh tungsten powder with a weight content of about 80% tungsten, weigh copper powder with a weight content of about 15%, weigh tungsten carbide powder, iron powder, nickel powder and other additives with a weight content of about 5%, and mix them. The powder particles of tungsten carbide and tungsten are about 3 microns, and the copper powder is sieved through a 400-mesh sieve. The mixed raw material powder is heat treated at a temperature of 500-650°C for 2-5 hours, and the weight is 6-8 tons / cm 2 Pressure forming, crushing, heat treatment at 550~700℃ for 2~5 hours, 6~8 tons / cm 2 The pressure is formed, crushed, and heat treated at 600~750℃ for 2~5 hours at 6~8 tons / cm 2 The final pressing density is about 9~10g / cm 3 .

[0029] Infiltration connection is carried out in an atmosphere furnace. The compact is placed at the bottom layer of the graphite crucible. The middle layer is a pure copper sheet processed into the size of the compact. The top layer is an iron alloy, and the surrounding is filled with alumina powder to prevent oxidation. Based on the diffusion kinetics of copper and tungsten, and auxiliary heat treatment experiments are used to verify the calculation results and correct the parameters. The melt infiltration heat treatment process parameters, such as temperature and time, are carefully designed to ensure copper infiltration and iron alloy connection, so as to achieve good melt infiltration effects while meeting carbon conservation and environmental protection. The main performance indicators of the obtained tungsten-copper-iron alloy integral contact material are:

[0030] The overall contact material density of CuW60 and iron alloy is 12.8±0.5g / cm 3 , resistivity is 3.1±0.5, hardness is greater than;

[0031] (2) The overall contact material density of CuW70 and iron alloy is 13.2±0.5g / cm 3 , resistivity is 3.3±0.5, and hardness is greater than.

[0032] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0033] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for manufacturing a low-cost hard contact material for a vacuum switch, characterized in that: This feature includes the following steps: Step 1: Mixing materials in a V-shaped heating mixer, wherein the mixed materials include tungsten powder, tungsten carbide powder, and a trace amount of copper powder and iron powder. The mixing time is several hours, and the mixed raw material powder is subjected to multiple cycles of heat treatment, pressing and crushing; Step 2: Pre-sintering treatment, and ensure that after pre-sintering treatment, copper and tungsten carbide and tungsten particles are in a good infiltration state, which can well induce the subsequent copper infiltration process; Step 3: Infiltration process, copper infiltration and sintering in a vacuum furnace, a specified weight of pure copper sheet is covered on the surface of the pre-sintered pressed green sheet, and then a specified weight of iron alloy is covered on the surface of the pure copper sheet to form a sandwich structure, which is placed in a graphite crucible, surrounded by alumina powder to prevent oxidation, and placed in an atmosphere heating furnace for infiltration-welding integrated heat treatment process. During the furnace heating process, the copper sheet reaches the melting point and begins to melt, and the copper liquid penetrates into the pores in the green sheet by capillary action. At the same time, a high-strength welding connection between the iron alloy and the tungsten copper contact is achieved; Step 4: After the product is out of the furnace, the product surface is roughly processed, and the ferroalloy side is machined to a shape and size that meets the performance requirements. The product can then be shipped out of the factory.

2. The method for manufacturing a low-cost hard contact material for a vacuum switch according to claim 1, characterized in that: The average particle size of the tungsten carbide powder in step 1 is less than 5 microns, the average particle size of the copper powder is less than 50 microns, and the average particle size of the iron powder and the nickel powder is less than 30 microns.

3. The method for manufacturing a low-cost hard contact material for a vacuum switch according to claim 1, characterized in that: The heat treatment temperature in step 1 is 500-750° C. and the time is 2-5 hours.

4. The method for manufacturing a low-cost hard contact material for a vacuum switch according to claim 1, characterized in that: The temperature of the pre-sintering treatment in step 2 is 1000°C to 1200°C.

5. The method for manufacturing a low-cost hard contact material for a vacuum switch according to claim 1, characterized in that: In the step 3, the weight of the copper sheet and the iron alloy in the mixed material is 5-20%.

Images