Method for infiltrating copper tungsten contact material with ultra-low chromium copper using vacuum sintering process

Abstract

This invention discloses a method for infiltrating ultra-low chromium copper into copper-tungsten contact materials using a vacuum sintering process, comprising the following steps: S1, pressing tungsten powder into a blank; S2, degumming the tungsten blank; S3, preparing the copper matrix; S4, unloading the blank; S5, sintering and infiltrating; and S6, solution treatment and aging. In the copper-tungsten contact material infiltrated with ultra-low chromium copper using the vacuum sintering process of this invention, the Cr content is approximately 0.025 wt.%. This ultra-low Cr content provides excellent strengthening of the contact material, resulting in a hardness ≥78 HB and a conductivity ≥55 Ms / m, thus compensating for the insufficient conductivity of chromium copper while meeting the hardness requirements of copper.

Description

Technical Field

[0001] This invention relates to the field of copper-tungsten contact material technology, specifically to a method for producing copper-tungsten contact materials by vacuum sintering with ultra-low chromium copper. Background Technology

[0002] Currently, copper-tungsten contacts and contact fingers used in medium and high voltage circuit breakers are mostly used for voltage levels of 126kV and 145kV. Since the voltage level is relatively low, the performance requirements of the substrate are also low. Chromium copper is expensive, so the material is mostly required to be T2Y. However, the best production process for preparing contacts and contact fingers is the integral sintering method, which requires the blank to be extruded again after sintering to meet the performance requirements. This results in a long production time and consumes a lot of manpower and resources.

[0003] After sintering, CuW / TU1 and CuW / T2 have a cast matrix. Under the condition of satisfactory electrical conductivity (≥56Ms / m), the hardness is 40-50HB. CuW / T2Y material is extruded after sintering with special extrusion tooling, but only the surface hardness can be increased to above 78HB, while the internal structure remains as cast. CuW / CuCr(Zr) material products can reach a hardness of over 110HB, but the electrical conductivity is only 46Ms / m. All of the above materials have their own shortcomings in terms of electrical conductivity and hardness. Summary of the Invention

[0004] To address the problems mentioned in the background art, the present invention provides a method for producing copper-tungsten contact materials by vacuum sintering with ultra-low chromium copper.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0006] A method for melting and infiltrating ultra-low chromium copper into copper-tungsten contact materials using a vacuum sintering process includes the following steps:

[0007] S1, Tungsten powder compact:

[0008] Take tungsten powder and add 0.3-0.5 wt.% of molding agent glue relative to the tungsten powder. Mix well and pour into a mold. Select positioning blocks according to the required tungsten billet size and press into tungsten billets under pressure in an automatic press.

[0009] S2, Debinding of tungsten billet:

[0010] The forming agent adhesive in the tungsten billet obtained from S1 was removed by sintering to facilitate subsequent pressing. The sintering temperature was 1000℃ and the sintering time was 80-90 min.

[0011] S3, Copper substrate preparation:

[0012] A CuCr0.1 material and pure copper are prepared as the copper matrix material, with a Cr content of 0.025 wt.% in the copper matrix. The CuCr0.1 material is a CuCr0.1 copper rod or a CuCr0.1 copper plate, and the pure copper is a pure copper rod or a pure copper plate.

[0013] S4. Unloading:

[0014] Place the tungsten billet obtained in S2 at the bottom of the crucible, place the pure copper rod or pure copper plate prepared in S3 on top, and then place the CuCr0.1 copper rod or CuCr0.1 copper plate on top.

[0015] S5, Sintering and Melting:

[0016] The tungsten billet, copper substrate, and crucible placed in S4 are placed into the vacuum furnace together. The furnace door is closed and the vacuum pump is started to evacuate the furnace until the vacuum level reaches 6×10⁻⁶. -1 Pa, sintering begins, sintering temperature is 1350℃, sintering time is 4-8h;

[0017] S6. Solution aging treatment:

[0018] The product obtained after sintering S5 is solution treated at 950-980℃ for 1-1.5 hours and aged at 480-500℃ for 3.5-4 hours. The hardness and electrical conductivity meet the following requirements: hardness ≥78HB, electrical conductivity ≥55Ms / m.

[0019] Note: In this invention, the copper-tungsten contact material with ultra-low chromium copper is infiltrated through a vacuum sintering process. The Cr content is about 0.025 wt.%. The ultra-low Cr content can play a very good strengthening role for the contact material. Experimental studies have found that the solubility of Cr in Cu at room temperature is <0.03%. When the Cr content is about 0.03%, the electrical conductivity and hardness of the matrix are in a balance. The electrical conductivity is lower than that of pure copper but higher than that of chromium copper, and the hardness is lower than that of chromium copper but higher than that of pure copper.

[0020] Furthermore, in the above scheme, in step S1, the tungsten powder particle size is selected from 1 to 100 μm. The tungsten powder is spread in layers, and each layer is compacted after being spread. There are a total of n layers. The weight ratio of each layer of tungsten powder is 1 / n of the total weight of the tungsten powder, where n = 3 to 10. In order from bottom to top, the first layer of tungsten powder has the smallest particle size, the nth layer has the largest particle size, and the particle size of the (n-1)th layer of tungsten powder is between the particle size of the first layer and the particle size of the second layer.

[0021] Explanation: Tungsten powder of various particle sizes is used and spread according to particle size. The tungsten powder in the lower layer has a smaller particle size, resulting in a more compact compaction. The tungsten powder in the upper layer has a larger particle size, providing sufficient porosity for the melting and infiltration of the copper matrix material on the tungsten billet. At the same time, by controlling the particle size of the (n-1)th layer to be between the particle size of the tungsten powder in the first layer and the particle size of the tungsten powder in the second layer, sufficient porosity is provided for the melting and infiltration of the copper matrix material, while also ensuring the density of the upper layer material and improving the overall hardness of the finished material.

[0022] Furthermore, in the above scheme, n=5, and the particle size of the tungsten powder in each layer from bottom to top is as follows: 1~5μm, 20~40μm, 50~80μm, 6~20μm, 50~100μm.

[0023] Note: By layering tungsten powder of five different particle sizes, extremely high sintering density can be achieved while ensuring uniform grain structure.

[0024] Furthermore, in the above scheme, in step S1, the tungsten powder is dried before being pressed.

[0025] Note: Drying the tungsten billet before pressing it makes the billet denser.

[0026] Furthermore, in the above scheme, the drying process is as follows: add deionized water equivalent to 5 to 20 times the weight of tungsten powder to the tungsten powder, perform ultrasonic dispersion under ultrasonic conditions to obtain a mixture, then perform spray drying on the mixture using a spray drying method, and then place it in a vacuum drying oven for drying to obtain dried tungsten powder.

[0027] Note: The above drying method can remove residual oil and other contaminants from the surface of tungsten powder.

[0028] Furthermore, in the above scheme, the temperature inside the vacuum drying oven is 80–150°C, and the drying time is 30–100 min.

[0029] Furthermore, in the above scheme, in step S1, the molding agent adhesive is SBP adhesive.

[0030] Note: SBP adhesive is a molding adhesive added during powder mixing to help form tungsten blanks.

[0031] Furthermore, in the above scheme, in step S1, the pressing pressure of the automatic press is 260-280 MPa, and the pressing time is 3-5 min.

[0032] Note: The pressure and time can be adjusted according to the required size of the tungsten billet.

[0033] Furthermore, in the above scheme, in step S2, the sintering temperature is increased from 0 to 500-600℃ within 10 minutes, held for 20 minutes, and then increased from 500-600℃ to 1000℃ within 5 minutes, held for 65 minutes.

[0034] Note: Sintering using a gradient heating process results in better removal of the molding agent adhesive.

[0035] Furthermore, in the above scheme, in step S5, the sintering and melting process consists of three stages of heating and three stages of holding, with the following temperature / time parameters: heating (0~600℃) / 2min, holding at 600℃ / 5min, heating (600~1000℃) / 8min, holding at 1000℃ / 15min, heating (1000~1350℃) / 30min, and holding at 1350℃ / 3~7h.

[0036] Explanation: The three-stage heating and three-stage holding heating sintering melting process can refine the grains of copper-tungsten contact material, resulting in a more uniform distribution of various elements and a better crystal structure.

[0037] Compared with the prior art, the beneficial effects of the present invention are reflected in the following aspects:

[0038] First, the present invention uses a vacuum sintering and melting method to place the product in a vacuum environment, so that the bonding surface will not be oxidized and the bonding strength between CuW and the matrix is ​​higher after vacuum sintering.

[0039] Secondly, this invention innovatively uses tungsten powder of various particle sizes to spread the powder according to the particle size. The tungsten powder in the lower layer has a smaller particle size, so it is compacted more densely. The tungsten powder in the upper layer has a larger particle size, which provides sufficient porosity for the melting and infiltration of the copper matrix material on the tungsten blank. At the same time, by controlling the particle size of the (n-1)th layer to be between the particle size of the tungsten powder in the first layer and the particle size of the tungsten powder in the second layer, it ensures that sufficient porosity is provided for the melting and infiltration of the copper matrix material, while also ensuring the density of the upper layer material and improving the hardness of the overall finished material.

[0040] Third, in the copper-tungsten contact material of the present invention, which is infiltrated with ultra-low chromium copper through vacuum sintering process, the Cr content is about 0.025 wt.%. The ultra-low Cr content can play a very good strengthening role for the contact material, making the contact material hardness ≥78HB and electrical conductivity ≥55Ms / m. This satisfies the hardness requirement of copper material and also makes up for the lack of electrical conductivity of chromium copper. Detailed Implementation

[0041] Example 1

[0042] A method for melting and infiltrating ultra-low chromium copper into copper-tungsten contact materials using a vacuum sintering process includes the following steps:

[0043] S1, Tungsten powder compact:

[0044] Take tungsten powder with a particle size of 1-60 μm, add 0.4 wt.% SBP glue relative to the tungsten powder, mix well, pour into a mold, select positioning blocks according to the required tungsten billet size, and press into tungsten billets under an automatic press; the automatic press has a pressing pressure of 270 MPa and a pressing time of 3 min.

[0045] S2, Debinding of tungsten billet:

[0046] The forming agent adhesive in the tungsten billet obtained from S1 was removed by sintering to facilitate subsequent pressing. The sintering temperature was 1000℃ and the sintering time was 80min.

[0047] S3, Copper substrate preparation:

[0048] A CuCr0.1 material and pure copper are prepared as the copper matrix material, with a Cr content of 0.025 wt.% in the copper matrix. The CuCr0.1 material is a CuCr0.1 copper rod or a CuCr0.1 copper plate, and the pure copper is a pure copper rod or a pure copper plate.

[0049] S4. Unloading:

[0050] Place the tungsten billet obtained in S2 at the bottom of the crucible, place the pure copper rod or pure copper plate prepared in S3 on top, and then place the CuCr0.1 copper rod or CuCr0.1 copper plate on top.

[0051] S5, Sintering and Melting:

[0052] The tungsten billet, copper substrate, and crucible placed in S4 are placed into the vacuum furnace together. The furnace door is closed and the vacuum pump is started to evacuate the furnace until the vacuum level reaches 6×10⁻⁶. -1 Pa, sintering begins, sintering temperature is 1350℃, sintering time is 5h;

[0053] S6. Solution aging treatment:

[0054] The product obtained after sintering S5 was solution treated at 960℃ for 1.5h and then aged at 500℃ for 3.5h.

[0055] Example 2

[0056] A method for melting and infiltrating ultra-low chromium copper into copper-tungsten contact materials using a vacuum sintering process includes the following steps:

[0057] S1, Tungsten powder compact:

[0058] Take tungsten powder with a particle size of 10-80 μm, add 0.3 wt.% SBP glue relative to the tungsten powder, mix well, pour into a mold, select positioning blocks according to the required tungsten billet size, and press into tungsten billets under an automatic press; the automatic press has a pressing pressure of 260 MPa and a pressing time of 3 min.

[0059] S2, Debinding of tungsten billet:

[0060] The forming agent adhesive in the tungsten billet obtained from S1 was removed by sintering to facilitate subsequent pressing. The sintering temperature was 1000℃ and the sintering time was 80min.

[0061] S3, Copper substrate preparation:

[0062] A CuCr0.1 material and pure copper are prepared as the copper matrix material, with a Cr content of 0.025 wt.% in the copper matrix. The CuCr0.1 material is a CuCr0.1 copper rod or a CuCr0.1 copper plate, and the pure copper is a pure copper rod or a pure copper plate.

[0063] S4. Unloading:

[0064] Place the tungsten billet obtained in S2 at the bottom of the crucible, place the pure copper rod or pure copper plate prepared in S3 on top, and then place the CuCr0.1 copper rod or CuCr0.1 copper plate on top.

[0065] S5, Sintering and Melting:

[0066] The tungsten billet, copper substrate, and crucible placed in S4 are placed into the vacuum furnace together. The furnace door is closed and the vacuum pump is started to evacuate the furnace until the vacuum level reaches 6×10⁻⁶. -1 Pa, sintering begins, sintering temperature is 1350℃, sintering time is 4h;

[0067] S6. Solution aging treatment:

[0068] The product obtained after sintering S5 was solution treated at 950℃ for 1 hour and aged at 480℃ for 3.5 hours.

[0069] Example 3

[0070] A method for melting and infiltrating ultra-low chromium copper into copper-tungsten contact materials using a vacuum sintering process includes the following steps:

[0071] S1, Tungsten powder compact:

[0072] Take tungsten powder with a particle size of 30-100μm, add 0.5wt.% SBP glue relative to the tungsten powder, mix well, pour into a mold, select positioning blocks according to the required tungsten billet size, and press into tungsten billets under an automatic press; the automatic press has a pressing pressure of 280MP and a pressing time of 5min.

[0073] S2, Debinding of tungsten billet:

[0074] The forming agent adhesive in the tungsten billet obtained from S1 was removed by sintering to facilitate subsequent pressing. The sintering temperature was 1000℃ and the sintering time was 90min.

[0075] S3, Copper substrate preparation:

[0076] A CuCr0.1 material and pure copper are prepared as the copper matrix material, with a Cr content of 0.025 wt.% in the copper matrix. The CuCr0.1 material is a CuCr0.1 copper rod or a CuCr0.1 copper plate, and the pure copper is a pure copper rod or a pure copper plate.

[0077] S4. Unloading:

[0078] Place the tungsten billet obtained in S2 at the bottom of the crucible, place the pure copper rod or pure copper plate prepared in S3 on top, and then place the CuCr0.1 copper rod or CuCr0.1 copper plate on top.

[0079] S5, Sintering and Melting:

[0080] The tungsten billet, copper substrate, and crucible placed in S4 are placed into the vacuum furnace together. The furnace door is closed and the vacuum pump is started to evacuate the furnace until the vacuum level reaches 6×10⁻⁶. -1 Pa, sintering begins, sintering temperature is 1350℃, sintering time is 8h;

[0081] S6. Solution aging treatment:

[0082] The product obtained after sintering S5 was solution treated at 980℃ for 1.5 hours and then aged at 500℃ for 4 hours.

[0083] Example 4

[0084] The difference from Example 1 is that in step S1, the tungsten powder is spread in layers, and each layer of tungsten powder is compacted after it is spread. There are a total of 3 layers, and the weight of each layer of tungsten powder accounts for 1 / 3 of the total weight of tungsten powder. The particle size of each layer of tungsten powder is 1-20 μm, 30-50 μm, and 60-100 μm from bottom to top.

[0085] Example 5

[0086] The difference from Example 4 is that n=5, and the particle size of the tungsten powder in each layer from bottom to top is as follows: 1-5μm, 20-40μm, 50-80μm, 6-20μm, 50-100μm.

[0087] Example 6

[0088] The difference from Example 4 is that n=10, and the particle size of the tungsten powder in each layer from bottom to top is as follows: 1-5μm, 10-15μm, 20-30μm, 35-40μm, 45-50μm, 55-60μm, 65-70μm, 75-80μm, 6-10μm, 85-100μm.

[0089] Tungsten powder of various particle sizes is spread according to particle size. The tungsten powder in the lower layer has a smaller particle size, resulting in a more compact compaction. The tungsten powder in the upper layer has a larger particle size, providing sufficient porosity for the melting and infiltration of the copper matrix material on the tungsten blank. At the same time, by controlling the particle size of the (n-1)th layer to be between the particle size of the tungsten powder in the first layer and the particle size of the tungsten powder in the second layer, sufficient porosity is provided for the melting and infiltration of the copper matrix material, while ensuring the density of the upper layer material and improving the hardness of the overall finished material.

[0090] Example 7

[0091] The difference from Example 1 is that in step S1, the tungsten powder is dried before being pressed. The drying method is as follows: deionized water equivalent to 10 times the weight of the tungsten powder is added to the tungsten powder, and ultrasonic dispersion is performed under ultrasonic conditions to obtain a mixture. Then, the mixture is spray-dried using a spray drying method, and then placed in a vacuum drying oven for drying. The temperature in the vacuum drying oven is 120°C, and the drying time is 60 minutes to obtain dried tungsten powder.

[0092] Example 8

[0093] The difference from Example 7 is that deionized water equivalent to 5 times the weight of the tungsten powder was added to the tungsten powder.

[0094] The temperature inside the vacuum drying oven is 80℃, and the drying time is 30 minutes.

[0095] Example 9

[0096] The difference from Example 7 is that deionized water equivalent to 20 times the weight of the tungsten powder was added to the tungsten powder.

[0097] The temperature inside the vacuum drying oven is 150℃, and the drying time is 100 minutes.

[0098] Example 10

[0099] The difference from Example 1 is that in step S2, the sintering temperature is increased from 0 to 500°C within 10 minutes, held for 20 minutes, and then increased from 500°C to 1000°C within 5 minutes, held for 65 minutes.

[0100] Example 11

[0101] The difference from Example 10 is that the sintering temperature is increased from 0 to 600°C within 10 minutes, held for 20 minutes, and then increased from 600°C to 1000°C within 5 minutes, held for 65 minutes.

[0102] Example 12

[0103] The difference from Example 8 is that in step S5, the sintering and melting process consists of three stages of heating and three stages of holding, with the following temperature / time parameters: heating (0~600℃) / 2min, holding at 600℃ / 5min, heating (600~1000℃) / 8min, holding at 1000℃ / 15min, heating (1000~1350℃) / 30min, and holding at 1350℃ / 3h.

[0104] Example 13

[0105] The difference from Example 11 is that in step S5, the heat preservation time in the last stage is 7 hours.

[0106] The properties of the copper-tungsten contact materials prepared by the methods in Examples 1-13 above were tested, and the test results are shown in Table 1.

[0107] Table 1. Performance test results of copper-tungsten contact materials in Examples 1-11

[0108]

[0109]

[0110] Based on the data in Table 1, it can be seen from the comparison of Examples 1-3 that Example 1 is the best example.

[0111] By comparing Examples 1 with Examples 4-6, it can be seen that using tungsten powder of various particle sizes and spreading it according to particle size results in smaller particle size in the lower layer of tungsten powder, which is more compacted, while larger particle size in the upper layer of tungsten powder provides sufficient porosity for the melting and infiltration of the copper matrix material on the tungsten billet. At the same time, by controlling the particle size of the (n-1)th layer to be between the particle size of the tungsten powder in the first layer and the particle size of the tungsten powder in the second layer, sufficient porosity is provided for the melting and infiltration of the copper matrix material, while ensuring the density of the upper layer material and improving the hardness of the overall finished material. Among them, Example 6 is the preferred embodiment.

[0112] Furthermore, by comparing Example 1 with Examples 7-9, it can be seen that the drying method of the present invention can remove residual oil and other contaminants from the surface of tungsten powder, thereby further improving product performance. Among them, Example 9 is a preferred embodiment.

[0113] By comparing Example 1 with Examples 10-11, it can be seen that in step S2, the sintering is carried out using a gradient heating process, which improves the removal effect of the molding agent adhesive and thus further improves the product performance. Example 11 is the preferred example.

[0114] By comparing Example 1 with Examples 12-13, it can be seen that in step S5, the heating and sintering melting process of three-stage heating and three-stage holding can refine the grains of the copper-tungsten contact material, making the distribution of various elements more uniform and the crystal structure better. Example 13 is a preferred example.

Claims

1. A method for sintering ultra-low chromium copper into copper-tungsten contact materials using a vacuum sintering process, characterized in that, Includes the following steps: S1, Tungsten powder compact: Take tungsten powder and add 0.3~0.5 wt.% of molding agent glue relative to the tungsten powder. Mix well and pour into a mold. Select positioning blocks according to the required tungsten billet size and press into tungsten billets under automatic press. S2, Debinding of tungsten billet: The forming agent binder in the tungsten billet obtained from S1 was removed by sintering at a temperature of 980~1000℃ for 80~90min. S3, Copper substrate preparation: A CuCr0.1 material and pure copper are prepared as the copper matrix material, with a Cr content of 0.025 wt.% in the copper matrix. The CuCr0.1 material is a CuCr0.1 copper rod or a CuCr0.1 copper plate, and the pure copper is a pure copper rod or a pure copper plate. S4. Unloading: Place the tungsten billet obtained in S2 at the bottom of the crucible, place the pure copper rod or pure copper plate prepared in S3 on top, and then place the CuCr0.1 copper rod or CuCr0.1 copper plate on top. S5, Sintering and Melting: The tungsten billet, copper substrate, and crucible placed in S4 are placed into the vacuum furnace together. The furnace door is closed and the vacuum pump is started to evacuate the furnace until the vacuum level reaches 6×10⁻⁶. -1 Pa, sintering begins, sintering temperature is 1350℃, sintering time is 4~8h; S6. Solution aging treatment: The product obtained after sintering S5 was solution treated at 950~980℃ for 1~1.5h and aged at 480~500℃ for 3.5~4h. In step S1, the tungsten powder particle size is selected from 1 to 100 μm. The tungsten powder is spread in layers, and each layer is compacted after being spread. There are a total of n layers. The weight ratio of each layer of tungsten powder is 1 / n of the total weight of tungsten powder, where n = 5 to 10. In order from bottom to top, the first layer of tungsten powder has the smallest particle size, the nth layer has the largest particle size, and the particle size of the (n-1)th layer of tungsten powder is between the particle size of the first layer and the particle size of the second layer. With n=5, the particle size of each layer of tungsten powder from bottom to top is: 1~5μm, 20~40μm, 50~80μm, 6~20μm, and 50~100μm. By layering tungsten powder of five different particle sizes, extremely high sintering density can be obtained while ensuring the uniformity of the grain structure. In step S1, the tungsten powder is dried and then pressed. The drying process is as follows: add 5 to 20 times the weight of the tungsten powder to the tungsten powder, disperse it under ultrasonic conditions to obtain a mixture, then spray dry the mixture using a spray drying method, and then place it in a vacuum drying oven for drying to obtain dried tungsten powder.

2. The method for melting and infiltrating ultra-low chromium copper into copper-tungsten contact material using vacuum sintering process according to claim 1, characterized in that, The temperature inside the vacuum drying oven is 80~150℃, and the drying time is 30~100min.

3. The method for melting and infiltrating ultra-low chromium copper into copper-tungsten contact material using a vacuum sintering process according to claim 1, characterized in that, In step S1, the molding agent adhesive is SBP adhesive.

4. The method for melting and infiltrating ultra-low chromium copper into copper-tungsten contact material using vacuum sintering process according to claim 1, characterized in that, In step S1, the automatic press applies a pressure of 260-280 MPa and a pressing time of 3-5 seconds.

5. The method for melting and infiltrating ultra-low chromium copper into copper-tungsten contact material using vacuum sintering process according to claim 1, characterized in that, In step S2, the sintering temperature is increased from 0 to 500-600℃ within 10 minutes, held for 20 minutes, and then increased from 500-600℃ to 1000℃ within 5 minutes, held for 65 minutes.

6. The method for melting and infiltrating ultra-low chromium copper into copper-tungsten contact material using a vacuum sintering process according to claim 1, characterized in that, In step S5, the sintering and melting process consists of three stages of heating and three stages of holding. The temperature / time parameters are: heating (0~600℃) / 2min, holding at 600℃ / 5min, heating (600~1000℃) / 8min, holding at 1000℃ / 15min, heating (1000~1350℃) / 30min, and holding at 1350℃ / 3~7h. Following the heating and sintering melting process of three stages of heating and three stages of holding can refine the grains of the copper-tungsten contact material, making the distribution of various elements more uniform and the crystal structure better.

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