Method for preparing CuCr contact material through ultrahigh-pressure high-temperature sintering

Abstract

The invention relates to the technical field of preparation of copper-based composite materials, in particular to a method for preparing a CuCr contact material through ultrahigh-pressure high-temperature sintering, which comprises the steps of burdening and powder mixing, vacuum sintering, vacuum self-consuming arc melting and ultrahigh-pressure high-temperature sintering. The preparation process combining vacuum consumable arc melting and ultrahigh-pressure high-temperature sintering is adopted, the problem of poor material density of a traditional preparation process can be effectively solved, the density of a CuCr50 sintered body is remarkably improved, the density is improved to 99.8%, the distribution of a second phase of a Cr phase is more uniform, the interface bonding force of a Cu matrix and the Cr phase is enhanced, and the two-phase interface bonding strength is improved. Through the ultrahigh-pressure preparation technology, the problem of synergistic improvement of the strength and plasticity of the CuCr50 material is solved, and the tensile strength, yield strength and other mechanical properties of an ultrahigh-pressure sintered body are obviously improved.

Description

Technical Field

[0001] The invention relates to the technical field of copper-based composite material preparation, in particular to a method for preparing a CuCr contact material by ultra-high pressure and high temperature sintering. Background Art

[0002] The contact is the key core component of the vacuum interrupter. It must have both the high current carrying capacity to reliably conduct the load current for a long time and the ability to resist erosion and ablation caused by high arc energy when breaking fault current.

[0003] A lot of research has been done at home and abroad on the preparation process, performance characterization and application of contact materials in circuit breaker switches. The most common contact material is CuCr alloy.

[0004] The research on contact material CuCr alloy started early. A variety of preparation methods have been developed, such as powder sintering, infiltration and arc melting, as well as emerging preparation technologies such as vacuum induction melting, self-propagating casting, mechanical alloying, laser surface alloying, electric spark sintering, and original growth composite method in recent years.

[0005] Among them, the CuCr contact material prepared by arc melting has high purity and strong bonding between the two phases, but it also has the disadvantages of complex arc melting process, high energy consumption and cost in the capacity process, and easy component segregation in the cooling process. In addition, there are still some quality problems in the production of CuCr contact materials, such as excessive gas content in the material, too large and difficult to control Cr phase particle size in the material, difficulty in densification of sintered body, and insufficient ablation resistance of the material.

[0006] Therefore, how to solve the problems of microstructure optimization, ablation resistance improvement and preparation process stability of CuCr contact materials through new preparation processes and material modification technologies, and further explore the optimization of alloy composition and doping strengthening mechanism to meet the needs of high voltage and high current vacuum circuit breakers, has become an urgent research direction. Summary of the invention

[0007] The present invention provides a method for preparing CuCr contact material by arc melting-ultra-high pressure and high temperature, which aims to solve the problems of insufficient density, poor mechanical strength, low mechanical properties and high production cost of traditional contact materials in ultra-high / extra-high voltage vacuum circuit breaker switch equipment.

[0008] In order to solve the above technical problems, the technical solutions provided by the present invention are as follows:

[0009] A method for preparing a CuCr contact material by ultra-high pressure and high temperature sintering comprises the following steps:

[0010] S1. Mixing ingredients

[0011] The ingredients used are Cu powder and Cr powder. The two are added to a ball mill in proportion for mixing. After mixing evenly, they are added to a mold, and a cold isostatic press is used to press the loaded powder into a pre-sintered blank sample.

[0012] S2. Vacuum sintering

[0013] The pressed blank sample is placed in a vacuum sintering furnace for sintering.

[0014] S3. Vacuum consumable arc melting

[0015] The sintered bar is subjected to vacuum consumable arc melting.

[0016] S4. Ultra-high pressure and high-temperature sintering

[0017] The melted bar is subjected to ultra-high pressure and high-temperature sintering.

[0018] As an improvement, the ratio between the Cu powder and the Cr powder in step S1 is 4:6 - 6:4.

[0019] As an improvement, the powder particle size of the Cu powder in step S1 is 35 - 50 μm, and the powder particle size of the Cr powder is 30 - 60 μm.

[0020] As an improvement, the mixing ratio of the ball mill in step S1 is 1:1; the grinding balls used for mixing are Al2O3 ceramic balls, and the particle sizes are divided into three types: 3 mm, 5 mm, and 8 mm. The proportion of balls with different particle sizes is: 3:2:1.

[0021] As an improvement, the mold in step S1 is a circular barrel-shaped mold, and the material is H13 hot work die steel.

[0022] As an improvement, the method of vacuum sintering in step S2 is to keep the temperature at 600 ± 20 °C for 240 ± 20 min.

[0023] As an improvement, the parameters of the vacuum consumable arc melting in step S3 are: vacuum degree: ≤1×10-3 Pa, protective gas: high-purity argon, pressure: 0.02–0.05 MPa, melting current: 500–2000 A, melting voltage: 20–30 V, arc length: 2–5 mm, melting rate: 50–200 g / min, electrode rotation speed: 10–50 rpm.

[0024] As an improvement, the equipment used for ultra-high pressure and high-temperature sintering in step S4 is a 650 mm cylinder diameter forging six-sided top press; the cylinder thrust of the six-sided top press is 33.2 MN, and the heating method of the six-sided top is: high-frequency electromagnetic induction heating.

[0025] The advantages of the present invention are:

[0026] 1. The present invention can effectively solve the problem of poor density of materials in the traditional preparation process, significantly improve the density of the CuCr50 sintered body, increase the density to 99.8%, make the distribution of the Cr-phase second phase more uniform, enhance the interfacial bonding force between the Cu matrix and the Cr phase, and improve the interfacial bonding strength of the two phases.

[0027] 2. Through the ultra-high pressure preparation technology, the present invention solves the problem of the simultaneous improvement of the strength and plasticity of the CuCr50 material. The mechanical properties such as the tensile strength and yield strength of the ultra-high pressure sintered body are significantly improved. The yield strength and tensile strength reach 237.6 MPa and 348.3 MPa respectively, and a relatively high ductility of 32.08% is maintained. During the extreme service process, the strength, plasticity and mechanical strength of the material are comprehensively improved, and the material life is extended.

[0028] 3. The present invention can effectively improve the anti-arc erosion ability of the material, greatly improve the reliability of high-voltage switchgear, reduce the frequency of replacement and maintenance, and comprehensively extend the service life of the material.

[0029] 4. Compared with the traditional process, the present invention adopts an integrated and process-optimized arc melting and ultra-high pressure and high temperature composite preparation process, which effectively improves the production efficiency, enhances the comprehensive performance of the product, and reduces the high cost of arc melting at the same time.

[0030] 5. The present invention can effectively improve the consistency of physical properties and chemical compositions, and significantly improve the quality stability of the product. The present invention can effectively solve the performance bottleneck of traditional contact materials in ultra-high / extra-high voltage equipment, bring a technological breakthrough to the vacuum circuit breaker industry, help the industry upgrade to higher voltage levels and higher reliability, not only meet the needs of the high-end market, but also enhance the competitiveness of the product in the international market. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 FIG. is the SEM image of the ultra-high pressure sintered bulk material of the present invention.

[0032] Figure 2 For the present invention Figure 1 The enlarged view of the structure at position A in the present invention, where point 1 is the Cr nano-precipitation phase, point 2 is the Cu matrix material, point 3 indicates the pinning and knotting of the Cr nano-phase and the surrounding dislocations, and point 4 indicates the dislocation movement in the region. DETAILED DESCRIPTION OF THE INVENTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0034] Example 1

[0035] This embodiment discloses a method for preparing CuCr contact material by arc melting-ultra-high pressure and high temperature, comprising the following steps:

[0036] S1. Mixing ingredients

[0037] The ingredients used in this embodiment are Cu powder and Cr powder, the mass ratio of the two is 50% each, the powder size of Cu powder is 40μm, and the powder size of Cr powder is 45μm.

[0038] After the ingredients are mixed, add them to the ball mill and mix them in a ratio of 1:1 for 6 hours. The grinding balls used for mixing are Al2O3 ceramic balls with particle sizes of 3mm, 5mm, and 8mm. The ratio of balls of different particle sizes is 3:2:1.

[0039] After being evenly mixed, the mixture is added into a round barrel mold made of H13 hot working die steel. A cold isostatic press is then used to press the loaded powder into a pre-sintered blank sample.

[0040] S2. Vacuum sintering

[0041] The pressed green sample is placed in a vacuum sintering furnace at 600±20°C for 240±20 minutes to form a sintered rod;

[0042] S3. Vacuum consumable arc melting

[0043] The sintered rods are subjected to vacuum consumable arc melting, and the process parameters are: vacuum degree: ≤1×10-3Pa, protective gas: high-purity argon, pressure 0.03MPa, melting current: 1000A, melting voltage: 25V, arc length: 3mm, melting rate: 100g / min, electrode rotation speed: 30rpm.

[0044] S4.Ultra-high pressure and high temperature sintering

[0045] The smelted rods were prepared by ultra-high pressure and high temperature sintering process, with pressure: 4.5 GPa, sintering temperature: 800°C, heating rate: 50°C / min, holding time: 40min, cooling rate: 400°C / min.

[0046] The equipment used for ultra-high pressure is a forging six-sided top press with a cylinder diameter of 650 mm. The thrust of the six-sided top press cylinder is 33.2 MN. The heating method of the six-sided top is high-frequency electromagnetic induction heating. This heating method can directly act on the sample or heating element to achieve rapid temperature rise and precise control. The pressure-bearing components used are, from outside to inside: pyrophyllite blocks, dolomite, graphite sleeves, salt tubes, and tantalum cups. Inside the tantalum cup is a CuCr50 bulk material sintered in a vacuum sintering furnace.

[0047] In this embodiment, the CuCr50 sintered body prepared by the combined process of arc melting and ultra-high pressure and high-temperature sintering has a significantly improved material density under ultra-high pressure pressing conditions. The strength, plasticity, and mechanical strength of the prepared product are significantly improved, and the ablation resistance of the material is also improved synchronously.

[0048] Table 1 Mechanical property indexes of CuCr contact materials prepared by ultra-high pressure

[0049]

[0050] As can be seen from Table 1, the yield strength and tensile strength of the material prepared by the present invention reach 237.6 MPa and 348.3 MPa respectively. While the yield strength and tensile strength of the traditional arc melting method are only 162 MPa and 258.3 MPa respectively. The present invention can significantly improve the mechanical properties of the material compared with the traditional arc melting process. At the same time, in terms of elongation, the elongation of the present invention is 32.08%, which is comparable to the traditional process, and both maintain good ductility.

[0051] As Figure 1 shown, through the ultra-high pressure preparation technology of the present invention, the problem of poor material density in traditional preparation processes such as powder sintering, infiltration, and arc melting is solved. The density of the CuCr50 sintered body is significantly improved, and the density is increased to 99.8%. This makes the distribution of the Cr second phase more uniform, enhances the interfacial bonding force between the Cu matrix and the Cr phase, and improves the interfacial bonding strength of the two phases.

[0052] As Figure 2 shown, Figure 2 in position 1 in Figure 2 is the precipitation of Cr nano-phase in the Cu matrix, Figure 2 in position 3 in

[0053] Example 2

[0054] This embodiment discloses a method for preparing CuCr contact materials by arc melting - ultra-high pressure and high temperature, including the following steps:

[0055] S1. Mixing powders

[0056] The ingredients used in this example are Cu powder and Cr powder, with their mass ratios each accounting for 50%. The powder particle size of Cu powder is 35 μm, and the powder particle size of Cr powder is 30 μm.

[0057] After the ingredients are prepared, they are added to a ball mill and mixed according to a ball-to-material ratio of 1:1 for 6 hours. The grinding balls used for mixing are Al2O3 ceramic balls with diameters of 3 mm, 5 mm, and 8 mm, and the proportion of balls with different diameters is 3:2:1.

[0058] After being uniformly mixed, they are added to a circular barrel-shaped mold. The material of the circular barrel-shaped mold is H13 hot work die steel. Then, a cold isostatic press is used to press the loaded powder into a pre-sintered blank sample.

[0059] S2. Vacuum sintering

[0060] The pressed blank sample is placed in a vacuum sintering furnace and sintered at a temperature of 600 ± 20 °C for 240 ± 20 minutes to form a sintered bar.

[0061] S3. Vacuum consumable arc melting

[0062] The sintered bar is subjected to vacuum consumable arc melting. Process parameters: Vacuum degree: ≤1 × 10-3 Pa, protective gas: high-purity argon gas with a pressure of 0.02 MPa, melting current: 500 A, melting voltage: 20 V, arc length: 2 mm, melting rate: 50 g / min, electrode rotation speed: 10 rpm.

[0063] S4. Ultra-high pressure and high temperature sintering

[0064] The melted bar is prepared by an ultra-high pressure and high temperature sintering process. Pressure: 4 GPa, sintering temperature: 600 °C, heating rate: 40 °C / min, holding time: 20 minutes, cooling rate: 300 °C / min.

[0065] The equipment used for ultra-high pressure is a 650 mm cylinder diameter forged six-sided top press. The cylinder thrust of the six-sided top press is 33.2 MN. The heating method of the six-sided top is high-frequency electromagnetic induction heating. This heating method can directly act on the sample or heating element to achieve rapid temperature increase and precise control. The pressure-bearing components used are, from the outside to the inside: pyrophyllite blocks, dolomite, graphite sleeves, salt tubes, and tantalum cups. Inside the tantalum cup is a CuCr50 bulk material sintered in a vacuum sintering furnace.

[0066] Example 3

[0067] This example discloses a method for preparing a CuCr contact material by arc melting - ultra-high pressure and high temperature, including the following steps:

[0068] S1. Ingredients preparation and powder mixing

[0069] The ingredients used in this embodiment are Cu powder and Cr powder, and the mass ratio of the two accounts for 50% each. The powder particle size of Cu powder is 50μm, and the powder particle size of Cr powder is 60μm

[0070] After the ingredients are prepared, they are added to a ball mill and mixed according to a ball-to-material ratio of 1:1 for 6 hours. The grinding balls used for mixing are Al2O3 ceramic balls with particle sizes of 3mm, 5mm, and 8mm, and the proportion of balls with different particle sizes is 3:2:1

[0071] After being mixed evenly, they are added to a circular barrel-shaped mold. The material of the circular barrel-shaped mold is H13 hot work die steel. Then, a cold isostatic press is used to press the loaded powder into a pre-sintered blank

[0072] S2. Vacuum sintering

[0073] The pressed blank is placed in a vacuum sintering furnace and sintered at a temperature of 600±20°C for 240±20 minutes to form a sintered bar

[0074] S3. Vacuum consumable arc melting

[0075] The sintered bar is subjected to vacuum consumable arc melting. Process parameters: Vacuum degree: ≤1×10-3Pa, protective gas: high-purity argon, pressure: 0.05MPa, melting current: 2000A, melting voltage: 30V, arc length: 5mm, melting rate: 200g / min, electrode rotation speed: 50rpm

[0076] S4. Ultra-high pressure and high-temperature sintering

[0077] The melted bar is prepared by ultra-high pressure and high-temperature sintering process. Pressure: 5GPa, sintering temperature: 1000°C, heating rate: 60°C / min, holding time: 60min, cooling rate: 500°C / min

[0078] The equipment used for ultra-high pressure is a 650mm cylinder diameter forged six-sided top press. The cylinder thrust of the six-sided top press is 33.2MN. The heating method of the six-sided top is high-frequency electromagnetic induction heating. This heating method can directly act on the sample or heating element to achieve rapid temperature increase and precise control. The pressure-bearing components used are, from outside to inside: pyrophyllite blocks, dolomite, graphite sleeves, salt tubes, and metal tantalum cups. Inside the tantalum cup is the CuCr50 bulk material sintered in a vacuum sintering furnace

[0079] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes should be covered within the protection scope of the present invention.

Claims

1. A method for preparing CuCr contact material by ultra-high pressure and high temperature sintering, characterized in that: The steps include: S1. Mixing ingredients The ingredients used are Cu powder and Cr powder, which are added to a ball mill in proportion and mixed, and then added to a mold. A cold isostatic press is used to press the loaded powder into a pre-sintered blank sample. S2. Vacuum sintering The pressed green sample is placed in a vacuum sintering furnace for sintering; S3. Vacuum consumable arc melting The sintered rods are subjected to vacuum consumable arc melting; S4.Ultra-high pressure and high temperature sintering The smelted rods are sintered at ultra-high pressure and high temperature.

2. The method for preparing CuCr contact material by ultra-high pressure and high temperature sintering according to claim 1, characterized in that: The mass ratio between the Cu powder and the Cr powder in step S1 is 1:

1.

3. The method for preparing CuCr contact material by ultra-high pressure and high temperature sintering according to claim 1, characterized in that: In step S1, the powder particle size of the Cu powder is 35-50 μm, and the powder particle size of the Cr powder is 30-60 μm.

4. The method for preparing CuCr contact material by ultra-high pressure and high temperature sintering according to claim 1, characterized in that: The mixing ratio of the ball mill in step S1 is 1:1; the grinding balls used for mixing are Al2O3 ceramic balls, and the particle sizes are divided into three types: 3mm, 5mm, and 8mm, and the proportions of balls of different particle sizes are: 3:2:

1.

5. The method for preparing CuCr contact material by ultra-high pressure and high temperature sintering according to claim 1, characterized in that: The mold in step S1 is a round barrel mold made of H13 hot working die steel.

6. The method for preparing CuCr contact material by ultra-high pressure and high temperature sintering according to claim 1, characterized in that: The vacuum sintering method in step S2 is to maintain the temperature at 600±20° C. for 240±20 min.

7. The method for preparing CuCr contact material by ultra-high pressure and high temperature sintering according to claim 1, characterized in that: The parameters of the vacuum consumable arc melting in step S3 are: vacuum degree: ≤1×10-3Pa, protective gas: high-purity argon, pressure of 0.02-0.05MPa, melting current: 500-2000A, melting voltage: 20-30V, arc length: 2-5mm, melting rate: 50-200g / min, electrode rotation speed: 10-50rpm.

8. The method for preparing CuCr contact material by ultra-high pressure and high temperature sintering according to claim 1, characterized in that: The equipment used for ultra-high pressure and high temperature sintering in step S4 is a 650mm cylinder diameter forged six-sided top press; the six-sided top press cylinder thrust is 33.2MN, and the six-sided top heating method is: high-frequency electromagnetic induction heating.

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