Copper-tungsten alloy-copper-steel composite electrical contact and preparation method thereof

Abstract

The invention discloses a copper-tungsten alloy-copper-steel composite electrical contact and a preparation method thereof, and relates to the technical field of alloy material preparation. Comprising the following steps: performing compression molding on tungsten powder to obtain a blank block; pre-sintering the briquette to prepare a framework, so as to obtain a tungsten framework; the theoretical copper infiltration weight is calculated according to the weight of the tungsten framework, copper infiltration is conducted on the tungsten framework according to 1.2-1.4 times of the theoretical copper infiltration weight, and the copper-tungsten alloy is obtained; the method comprises the following steps: respectively machining and cleaning a copper-tungsten alloy, a steel part and a copper part, then assembling, placing a chromium-copper alloy on the top of the assembled copper part, vacuumizing, sintering at 1250-1300 DEG C, and cooling to obtain a blank; and carrying out heat treatment on the blank to obtain the copper-tungsten alloy-copper-steel composite electrical contact. According to the method, the copper-tungsten alloy, the copper and the steel are combined, the bonding strength between matrixes is improved, the consistency and the stability of the quality of a welded product are guaranteed, and the air hole defect of a bonding surface is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of alloy material preparation, and in particular to a copper-tungsten alloy-copper-steel composite electrical contact and a preparation method thereof. Background Art

[0002] Copper-tungsten alloy is a commonly used electrical contact material. It is widely used in high-voltage switchgear due to its excellent electrical conductivity, thermal conductivity, arc erosion resistance and high-temperature strength. At present, the welding method between copper-tungsten alloy and steel special-shaped parts is mostly brazing process. Usually, vacuum brazing and induction brazing are used to achieve the combination of copper-tungsten alloy and steel. However, in these two brazing processes, the wettability of the solder with the parent steel and copper-tungsten alloy is poor, and the welding is not reliable. After welding, large holes visible to the naked eye will appear at the joint surface, the brazing rate is low, and dangerous phenomena such as tungsten head falling off are prone to occur during the processing of the finished product. At the same time, the high temperature environment of welding will cause the steel to soften, and the bonding strength between the substrates is low. It is difficult to ensure the consistency and stability of the product quality after the three materials of copper-tungsten alloy, copper and steel are combined, which is not conducive to subsequent use. Based on this, the present application proposes a copper-tungsten alloy-copper-steel composite electrical contact and a preparation method thereof. Summary of the invention

[0003] The main purpose of the present application is to provide a copper-tungsten alloy-copper-steel composite electrical contact and a preparation method thereof, aiming to solve the technical problem that the existing process is difficult to ensure the quality of copper-tungsten alloy-copper-steel after welding.

[0004] To achieve the above object, the present application proposes a method for preparing a copper-tungsten alloy-copper-steel composite electrical contact, comprising the following steps:

[0005] The tungsten powder is pressed into a shape to obtain a compact; the compact is pre-sintered to form a skeleton to obtain a tungsten skeleton;

[0006] Calculating a theoretical copper infiltration weight according to the weight of the tungsten skeleton, and infiltrating the tungsten skeleton with copper at 1.2-1.4 times the theoretical copper infiltration weight to obtain a copper-tungsten alloy;

[0007] The copper-tungsten alloy, the steel part and the copper part are machined separately, cleaned and assembled, and a chromium-copper alloy is placed on the top of the assembled copper part, vacuumed, sintered at 1250-1300° C., and cooled to obtain a blank;

[0008] The blank is heat treated to obtain a copper-tungsten alloy-copper-steel composite electrical contact.

[0009] Optionally, in the step of compacting the tungsten powder to obtain a compact, tungsten powder with a particle size of 4-6 μm is used.

[0010] Optionally, in the step of pre-sintering the blank to form a skeleton to obtain a tungsten skeleton, the whole process is evacuated to a vacuum degree of 10-20 Pa, the pre-sintering temperature is 1300-1400° C., and the holding time is 1.5-2.5 h.

[0011] Optionally, the step of infiltrating the tungsten skeleton with copper according to 1.2-1.4 times the theoretical copper infiltration weight to obtain the copper-tungsten alloy comprises:

[0012] The tungsten skeleton is infiltrated with copper according to 1.3 times of the theoretical copper infiltration weight, and the vacuum is evacuated to a vacuum degree of 30-40Pa. The infiltration temperature is 1350-1450°C and kept warm for 4-6 hours to obtain a copper-tungsten alloy.

[0013] Optionally, the step of machining the copper-tungsten alloy, the steel part and the copper part respectively comprises:

[0014] The surface of the copper-tungsten alloy is sandblasted, and the infiltration surface of the copper-tungsten alloy is milled;

[0015] Milling of steel and copper parts to the required dimensions.

[0016] Optionally, in the step of milling the copper-tungsten alloy infiltration surface, a copper layer of 1-2 mm is left on the copper-tungsten alloy infiltration surface after milling.

[0017] Optionally, the steps of assembling, placing a chromium-copper alloy on the top of the assembled copper part, evacuating the copper part, sintering the copper part at 1250-1300° C., and cooling the copper part to obtain a blank include:

[0018] After the cleaned copper-tungsten alloy, steel parts and copper parts are assembled, they are placed in a vacuum sintering furnace, and chromium-copper alloy is placed on the top of the assembled copper parts. The vacuum is evacuated to ≤8Pa, and then the temperature is raised to 1250-1300℃ at a rate of 3-5℃ / min and kept warm for 1.5-2.5h. After cooling to 650-750℃ with the furnace, nitrogen is filled in, and the blank is taken out of the furnace after cooling to <200℃.

[0019] Optionally, the chromium content in the blank is 0.25-0.35%.

[0020] Optionally, the step of heat treating the blank to obtain the copper-tungsten alloy-copper-steel composite electrical contact comprises:

[0021] The blank is heated to 800-900° C. and kept warm for 0.5-1.5 hours, water-cooled, then heated to 450-500° C. and kept warm for 3-5 hours, and then air-cooled to obtain a copper-tungsten alloy-copper-steel composite electrical contact.

[0022] The present application also proposes a copper-tungsten alloy-copper-steel composite electrical contact, which is obtained by the above-mentioned method for preparing the copper-tungsten alloy-copper-steel composite electrical contact.

[0023] This application includes at least the following beneficial effects:

[0024] In the present application, after the tungsten powder is pressed into shape, the pressed green block is pre-sintered to improve the green block strength and prepare a tungsten skeleton. Then, the theoretical copper infiltration weight that can saturate the tungsten skeleton is calculated according to the weight of the tungsten skeleton, and copper infiltration is performed at 1.2-1.4 times the theoretical copper infiltration weight, so that a copper layer of a certain thickness is left on the surface of the copper-tungsten alloy after infiltration. When sintering with pure copper and chromium-copper alloy in the subsequent process, the copper-tungsten alloy can be better combined with pure copper, thereby improving the bonding strength of the matrix, reducing the pore defects on the bonding surface, and avoiding the dangerous phenomenon of tungsten head falling off in the subsequent processing process. Then, the copper-tungsten alloy, steel parts and copper parts are machined separately so that the three can be better. The chromium-copper alloy is assembled with pure copper. After sintering, the pure copper becomes a low-chromium copper alloy containing chromium. The matrix exhibits a low-chromium copper structure. After subsequent heat treatment, the doping of chromium can further improve the hardness and strength of the matrix compared to the pure copper matrix, and can also avoid softening of the matrix steel, thereby realizing the combination of the three materials of copper-tungsten alloy, copper and steel. The present application adopts vacuum sintering to connect copper-tungsten alloy, copper and steel, which not only solves the defects of traditional welding process, improves the bonding strength between the substrates, ensures the quality consistency and stability of welding products, and reduces the porosity defects on the bonding surface, but also the prepared copper-tungsten alloy-copper-steel composite electrical contact has a high hardness and strength of the matrix copper. The hardness of the matrix copper can reach more than 90HB, and the electrical conductivity can reach more than 52Ms / m. At the same time, the strength of the matrix steel is also improved, and the hardness can reach more than 30HRC, which is much higher than the hardness of the matrix copper and matrix steel in the composite electrical contacts prepared by the current brazing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. It is obvious that the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0026] Figure 1This is a flow chart of a method for preparing a copper-tungsten alloy-copper-steel composite electrical contact according to an embodiment of the present application;

[0027] Figure 2 This is a schematic diagram of assembling the copper-tungsten alloy, steel, copper and chromium-copper alloy described in the embodiment of the present application;

[0028] Figure 3 This is a connection diagram of the copper-tungsten alloy-copper-steel composite electrical contact product described in an embodiment of the present application;

[0029] Figure 4 This is a metallographic structure diagram of the bonding surface between the copper-tungsten alloy and copper described in the embodiment of the present application.

[0030] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0032] In view of the technical problems existing in the prior art, the embodiments of the present application provide a method for preparing a copper-tungsten alloy-copper-steel composite electrical contact, such as Figure 1 As shown, the following steps are included:

[0033] Step S10, pressing the tungsten powder into a shape to obtain a green block; pre-sintering the green block into a skeleton, evacuating the whole process to a vacuum degree of 10-20Pa, the pre-sintering temperature is 1300-1400°C, and the insulation time is 1.5-2.5h to obtain a tungsten skeleton.

[0034] In the specific implementation process, tungsten powder with a particle size of 4-6μm is used. If the particle size of the tungsten powder is larger, the pore flow channel formed by the large particles is large, there is no capillary suction effect, and the copper infiltration will be incomplete. If the particle size of the tungsten powder is smaller, the pore flow channel formed by the small particles is too small and easy to be blocked, and the copper infiltration will also be incomplete. This application limits the particle size of the tungsten powder to 4-6μm, which can form a suitable pore flow channel, which is conducive to the melting and infiltration of copper.

[0035] During the pre-sintering process of making tungsten skeleton, tungsten is easily burned when sintered under non-vacuum conditions, generating tungsten oxide inclusions, which affects the performance of copper-tungsten alloy. Therefore, the vacuum degree is controlled at 10-20Pa throughout the entire process in this application, which can avoid tungsten oxidation during the sintering process as much as possible, so that the prepared tungsten skeleton has low gas content, few inclusions, and uniform structure, thereby improving the quality of copper-tungsten alloy.

[0036] Step S20, calculating the theoretical copper infiltration weight according to the weight of the tungsten skeleton, and infiltrating the tungsten skeleton with copper at 1.2-1.4 times the theoretical copper infiltration weight, evacuating the whole process to a vacuum degree of 30-40Pa, an infiltration temperature of 1350-1450°C, and keeping warm for 4-6h to obtain a copper-tungsten alloy.

[0037] In the specific implementation process, in order to enable copper to fully infiltrate the tungsten skeleton, the present application calculates the weight of copper that can fully infiltrate the tungsten skeleton based on the weight of the tungsten skeleton, and preferably infiltrates at a copper weight that is 1.3 times the calculated infiltrated copper weight, so that a copper layer of a certain thickness can be left on the surface of the copper-tungsten alloy, thereby enabling the copper-tungsten alloy to better combine with pure copper.

[0038] Step S30, sandblasting the surface of the copper-tungsten alloy, and milling the infiltration surface of the copper-tungsten alloy; milling the steel parts and the copper parts to the required size, after cleaning, assembling the cleaned copper-tungsten alloy, steel parts and copper parts, placing them in a vacuum sintering furnace, and placing chromium-copper alloy on the top of the assembled copper parts, evacuating to ≤8Pa, and then heating to 1250-1300℃ at a rate of 3-5℃ / min, and keeping warm for 1.5-2.5h, and then cooling to 650-750℃ with the furnace, filling with nitrogen, cooling to <200℃ and then taking out of the furnace to obtain a blank.

[0039] In the specific implementation process, by sandblasting the surface of the copper-tungsten alloy, compared with lathe lathe, it can not only achieve the effect of making the surface of the copper-tungsten alloy smooth, but also improve production efficiency. When the copper-tungsten alloy infiltration surface is milled, a 1-2mm copper layer is left on the copper-tungsten alloy infiltration surface. Since there may still be excess copper residue on the surface of the copper-tungsten alloy after infiltration, it is necessary to remove the excess infiltration copper by milling, and retain a 1-2mm copper layer to allow the copper-tungsten alloy to better combine with pure copper.

[0040] The present application adopts a slow heating method, controlling the heating rate to 3-5°C / min, and heating to 1250-1300°C to ensure that the base copper has enough time to melt, so that the molten copper liquid can bond the copper-tungsten alloy and the steel bonding surface to achieve a bonding effect. The slow heating also helps to remove gases and impurities on the surface and inside of the workpiece, improve the purity and density of the material, and thereby improve the quality and performance of the composite electrical contact.

[0041] In the specific implementation process, the chromium content in the blank is 0.25-0.35%. The present application uses chromium-copper alloy and pure copper for vacuum sintering, so that the matrix after sintering exhibits a low-chromium copper structure, in which the chromium content is 0.25-0.35%. Chromium doping is beneficial to improve the strength of the matrix, thereby improving product quality.

[0042] Step S40, heating the blank to 800-900°C and keeping it warm for 0.5-1.5h, water cooling, then heating to 450-500°C and keeping it warm for 3-5h, and air cooling to obtain a copper-tungsten alloy-copper-steel composite electrical contact.

[0043] In the specific implementation process, the blank is heated to 800-900℃ and kept warm for 0.5-1.5h, and then quickly cooled with water to promote the full dissolution of the excess phase into the solid solution, followed by rapid cooling to obtain a supersaturated solid solution. The blank is then heated to 450-500℃ and kept warm for 3-5h, and then naturally cooled by air cooling. The process of heating, keeping warm and cooling promotes rapid expansion and contraction of the metal, which is beneficial to improve the hardness and strength of the matrix, reduce residual stress, and improve the stability of the internal structure of the composite electrical contact product.

[0044] The embodiment of the present application further provides a copper-tungsten alloy-copper-steel composite electrical contact, which is obtained by the above-mentioned method for preparing the copper-tungsten alloy-copper-steel composite electrical contact.

[0045] The base copper in the copper-tungsten alloy-copper-steel composite electrical contact prepared in the present application has high hardness and strength. The hardness of the base copper can reach above 90HB, and the electrical conductivity can reach above 52Ms / m. At the same time, the strength of the base steel is also improved, and the hardness can reach above 30HRC, which is much higher than the hardness of the base copper and base steel in the composite electrical contact prepared by the current brazing process.

[0046] The above technical solution of the present application is described in detail below in conjunction with specific embodiments.

[0047] Example 1

[0048] A method for preparing a copper-tungsten alloy-copper-steel composite electrical contact comprises the following steps:

[0049] The tungsten powder with a particle size of 5 μm is pressed into a shape to obtain a green block; the green block is pre-sintered to form a skeleton, and the vacuum is evacuated to a vacuum degree of 15 Pa throughout the process, the pre-sintering temperature is 1350°C, and the heat preservation time is 2 hours to obtain a tungsten skeleton;

[0050] The theoretical copper infiltration weight is calculated according to the weight of the tungsten skeleton, and the tungsten skeleton is infiltrated with copper according to 1.3 times of the theoretical copper infiltration weight, and the vacuum is evacuated to a vacuum degree of 35 Pa, the infiltration temperature is 1400° C., and the temperature is kept for 5 hours to obtain a copper-tungsten alloy;

[0051] The surface of the copper-tungsten alloy is sandblasted, and the infiltration surface of the copper-tungsten alloy is milled, so that a 1.5 mm copper layer is left on the infiltration surface of the copper-tungsten alloy; the steel part and the copper part are milled to the required size;

[0052] Then use 75% or more ethanol to clean the copper-tungsten alloy, steel welding surface and copper parts to make them free of oxidation and pollution. Figure 2 Assemble as shown, and place chromium-copper alloy on the top of the assembled copper part, then place it in a vacuum sintering furnace and evacuate to ≤8Pa, heat it to 1275℃ at a rate of 4℃ / min, and keep it warm for 2.0h, then cool it to 700℃ with the furnace, fill it with nitrogen, cool it to <200℃ and then take it out of the furnace to obtain a blank, the chromium content in the blank is 0.3%;

[0053] The blank is heated to 850°C and kept at this temperature for 1 hour, water-cooled, then heated to 475°C and kept at this temperature for 4 hours, and then air-cooled to obtain a copper-tungsten alloy-copper-steel composite electrical contact product, such as Figure 3 shown.

[0054] The hardness of the base copper in the copper-tungsten alloy-copper-steel composite electrical contact obtained by the above method is 95HB, the electrical conductivity is 58Ms / m, and the hardness of the base steel is 35HRC.

[0055] Example 2

[0056] A method for preparing a copper-tungsten alloy-copper-steel composite electrical contact comprises the following steps:

[0057] Tungsten powder with a particle size of 4 μm is pressed into a shape to obtain a compact; the compact is pre-sintered to form a skeleton, and the vacuum is evacuated to a vacuum degree of 10 Pa throughout the process, the pre-sintering temperature is 1300° C., and the heat preservation time is 2.5 hours to obtain a tungsten skeleton;

[0058] The theoretical copper infiltration weight is calculated according to the weight of the tungsten skeleton, and the tungsten skeleton is infiltrated with copper according to 1.2 times of the theoretical copper infiltration weight, and the vacuum is evacuated to a vacuum degree of 30 Pa, the infiltration temperature is 1350° C., and the temperature is kept for 6 hours to obtain a copper-tungsten alloy;

[0059] The surface of the copper-tungsten alloy is sandblasted, and the infiltration surface of the copper-tungsten alloy is milled, so that a 1 mm copper layer is left on the infiltration surface of the copper-tungsten alloy; the steel part and the copper part are milled to the required size;

[0060] Then use 75% or more ethanol to clean the copper-tungsten alloy, steel welding surface and copper parts to make them free of oxidation and pollution. Figure 2 Assemble as shown, and place chromium-copper alloy on the top of the assembled copper part, then place it in a vacuum sintering furnace and evacuate to ≤8Pa, heat it to 1250℃ at a rate of 3℃ / min, and keep it warm for 2.5h, then cool it to 650℃ with the furnace, fill it with nitrogen, cool it to <200℃ and then take it out of the furnace to obtain a blank, the chromium content in the blank is 0.25%;

[0061] The blank is heated to 800°C and kept at this temperature for 1.5 hours, water-cooled, and then heated to 450°C and kept at this temperature for 5 hours, and then air-cooled to obtain a copper-tungsten alloy-copper-steel composite electrical contact. The metallographic structure of the bonding surface between the copper-tungsten alloy and the copper in the copper-tungsten alloy-copper-steel composite electrical contact is shown in FIG. Figure 4 shown.

[0062] Depend on Figure 4 It can be seen that there is no hole defect on the bonding surface between copper-tungsten alloy and copper, the connection is uniform, there is no intermetallic compound at the interface, there is no abnormal phase, and the copper-tungsten alloy does not have poor infiltration, and the grain structure is evenly distributed and fine.

[0063] The hardness of the base copper in the copper-tungsten alloy-copper-steel composite electrical contact obtained by the above method is 92HB, the electrical conductivity is 51Ms / m, and the hardness of the base steel is 33HRC.

[0064] Example 3

[0065] A method for preparing a copper-tungsten alloy-copper-steel composite electrical contact comprises the following steps:

[0066] Tungsten powder with a particle size of 6 μm is pressed into a shape to obtain a compact; the compact is pre-sintered to form a skeleton, and the vacuum is evacuated to a vacuum degree of 20 Pa throughout the process, the pre-sintering temperature is 1400° C., and the heat preservation time is 1.5 hours to obtain a tungsten skeleton;

[0067] The theoretical copper infiltration weight is calculated according to the weight of the tungsten skeleton, and the tungsten skeleton is infiltrated with copper according to 1.4 times of the theoretical copper infiltration weight, and the vacuum is evacuated to a vacuum degree of 40Pa, the infiltration temperature is 1450°C, and the temperature is kept for 4 hours to obtain a copper-tungsten alloy;

[0068] The surface of the copper-tungsten alloy is sandblasted, and the infiltration surface of the copper-tungsten alloy is milled, so that a 2 mm copper layer is left on the infiltration surface of the copper-tungsten alloy; the steel part and the copper part are milled to the required size;

[0069] Then use 75% or more ethanol to clean the copper-tungsten alloy, steel welding surface and copper parts to make them free of oxidation and pollution. Figure 2 Assemble as shown, and place chromium-copper alloy on the top of the assembled copper part, then place it in a vacuum sintering furnace and evacuate to ≤8Pa, heat it to 1300℃ at a rate of 5℃ / min, and keep it warm for 1.5h, then cool it to 750℃ with the furnace, fill it with nitrogen, cool it to <200℃ and then take it out of the furnace to obtain a blank, the chromium content in the blank is 0.35%;

[0070] The blank is heated to 900° C. and kept at this temperature for 0.5 h, water-cooled, then heated to 500° C. and kept at this temperature for 3 h, and then air-cooled to obtain a copper-tungsten alloy-copper-steel composite electrical contact.

[0071] The hardness of the base copper in the copper-tungsten alloy-copper-steel composite electrical contact obtained by the above method is 91HB, the electrical conductivity is 53Ms / m, and the hardness of the base steel is 32HRC.

[0072] Example 4

[0073] A method for preparing a copper-tungsten alloy-copper-steel composite electrical contact comprises the following steps:

[0074] Tungsten powder with a particle size of 5 μm is pressed into a shape to obtain a compact; the compact is pre-sintered to form a skeleton, and the vacuum is evacuated to a vacuum degree of 17 Pa throughout the process, the pre-sintering temperature is 1380° C., and the holding time is 1.8 hours to obtain a tungsten skeleton;

[0075] The theoretical copper infiltration weight is calculated according to the weight of the tungsten skeleton, and the tungsten skeleton is infiltrated with copper according to 1.3 times of the theoretical copper infiltration weight, and the vacuum is evacuated to a vacuum degree of 33 Pa, the infiltration temperature is 1370° C., and the temperature is kept for 5.5 hours to obtain a copper-tungsten alloy;

[0076] The surface of the copper-tungsten alloy is sandblasted, and the infiltration surface of the copper-tungsten alloy is milled, so that a 1.7 mm copper layer is left on the infiltration surface of the copper-tungsten alloy; the steel part and the copper part are milled to the required size;

[0077] Then use 75% or more ethanol to clean the copper-tungsten alloy, steel welding surface and copper parts to make them free of oxidation and pollution. Figure 2 Assemble as shown, and place chromium-copper alloy on the top of the assembled copper part, then place it in a vacuum sintering furnace and evacuate to ≤8Pa, heat it to 1260℃ at a rate of 4.5℃ / min, and keep it warm for 2.2h, then cool it to 675℃ with the furnace, fill it with nitrogen, cool it to <200℃ and then take it out of the furnace to obtain a blank, the chromium content in the blank is 0.33%;

[0078] The blank is heated to 880° C. and kept at this temperature for 0.7 h, water-cooled, then heated to 480° C. and kept at this temperature for 4 h, and then air-cooled to obtain a copper-tungsten alloy-copper-steel composite electrical contact.

[0079] The hardness of the base copper in the copper-tungsten alloy-copper-steel composite electrical contact obtained by the above method is 93HB, the electrical conductivity is 50Ms / m, and the hardness of the base steel is 32HRC.

[0080] Comparative Example 1

[0081] Compared with Example 1, no chromium-copper alloy is added during vacuum sintering, and the remaining steps are the same.

[0082] The hardness of the base copper in the copper-tungsten alloy-copper-steel composite electrical contact obtained by the above method is 81HB, the electrical conductivity is 42Ms / m, and the hardness of the base steel is 25HRC.

[0083] Comparative Example 2

[0084] Compared with Example 1, after the copper-tungsten alloy is prepared, the copper-tungsten alloy, the steel part and the copper part are connected by the existing vacuum brazing process, and the remaining steps are the same as those in Example 1.

[0085] The hardness of the base copper in the copper-tungsten alloy-copper-steel composite electrical contact obtained by the above method is 65HB, the electrical conductivity is 37Ms / m, and the hardness of the base steel is 21HRC.

[0086] Comparative Example 3

[0087] Compared with Example 1, after the copper-tungsten alloy is prepared, the copper-tungsten alloy, the steel part and the copper part are connected by the existing induction brazing process, and the remaining steps are the same as those in Example 1.

[0088] The hardness of the base copper in the copper-tungsten alloy-copper-steel composite electrical contact obtained by the above method is 68HB, the electrical conductivity is 34Ms / m, and the hardness of the base steel is 23HRC.

[0089] In summary, the copper-tungsten alloy-copper-steel composite electrical contact of the present application has at least the following beneficial effects compared with the prior art:

[0090] In the present application, after the tungsten powder is pressed into shape, the pressed green block is pre-sintered to improve the green block strength and prepare a tungsten skeleton. Then, the theoretical copper infiltration weight that can saturate the tungsten skeleton is calculated according to the weight of the tungsten skeleton, and copper infiltration is performed at 1.2-1.4 times the theoretical copper infiltration weight, so that a copper layer of a certain thickness is left on the surface of the copper-tungsten alloy after infiltration. When sintering with pure copper and chromium-copper alloy in the subsequent process, the copper-tungsten alloy can be better combined with pure copper, thereby improving the bonding strength of the matrix, reducing the pore defects on the bonding surface, and avoiding the dangerous phenomenon of tungsten head falling off in the subsequent processing process. Then, the copper-tungsten alloy, steel parts and copper parts are machined separately so that the three can be better. The invention relates to a method for assembling copper tungsten alloy, a steel part and a copper part, and placing a chromium-copper alloy on the top of the copper part to sinter them together. The molten copper liquid bonds the copper tungsten and steel joint surfaces at a high temperature of 1250-1300°C to achieve a bonding effect. The chromium-copper alloy is matched with pure copper. After sintering, the pure copper becomes a low-chromium copper alloy containing chromium. The matrix exhibits a low-chromium copper structure. After subsequent heat treatment, compared with the pure copper matrix, the chromium doping can further improve the hardness and strength of the matrix, and can also avoid the softening of the matrix steel, thereby realizing the combination of the three materials of copper tungsten alloy, copper and steel. The invention adopts vacuum sintering to connect copper tungsten alloy, copper and steel, which not only solves the defects of traditional welding process, but also improves the bonding strength between the matrix, ensures the quality consistency and stability of the welding product, and reduces the porosity defects of the joint surface.

[0091] The base copper in the copper-tungsten alloy-copper-steel composite electrical contact prepared in the present application has high hardness and strength. The hardness of the base copper can reach above 90HB, and the electrical conductivity can reach above 52Ms / m. At the same time, the strength of the base steel is also improved, and the hardness can reach above 30HRC, which is much higher than the hardness of the base copper and base steel in the composite electrical contact prepared by the current brazing process.

[0092] The above description is only an optional embodiment of the present application, and does not limit the patent scope of the present application. All equivalent structural transformations made by using the contents of the present application specification and drawings under the inventive concept of the present application, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A method for preparing a copper-tungsten alloy-copper-steel composite electrical contact, characterized in that: The following steps are involved: The tungsten powder is pressed into a shape to obtain a compact; the compact is pre-sintered to form a skeleton to obtain a tungsten skeleton; Calculating a theoretical copper infiltration weight according to the weight of the tungsten skeleton, and infiltrating the tungsten skeleton with copper at 1.2-1.4 times the theoretical copper infiltration weight to obtain a copper-tungsten alloy; The copper-tungsten alloy, the steel part and the copper part are machined separately, cleaned and assembled, and a chromium-copper alloy is placed on the top of the assembled copper part, vacuumed, sintered at 1250-1300° C., and cooled to obtain a blank; The blank is heat treated to obtain a copper-tungsten alloy-copper-steel composite electrical contact.

2. The method for preparing the copper-tungsten alloy-copper-steel composite electrical contact according to claim 1, characterized in that: In the step of pressing the tungsten powder into a compact, tungsten powder with a particle size of 4-6 μm is used.

3. The method for preparing the copper-tungsten alloy-copper-steel composite electrical contact according to claim 1, characterized in that: In the step of pre-sintering the blank to form a skeleton and obtaining a tungsten skeleton, the whole process is evacuated to a vacuum degree of 10-20 Pa, the pre-sintering temperature is 1300-1400° C., and the holding time is 1.5-2.5 h.

4. The method for preparing the copper-tungsten alloy-copper-steel composite electrical contact according to claim 1, characterized in that: The step of infiltrating the tungsten skeleton with copper according to 1.2-1.4 times the theoretical copper infiltration weight to obtain the copper-tungsten alloy comprises: The tungsten skeleton is infiltrated with copper according to 1.3 times of the theoretical copper infiltration weight, and the vacuum is evacuated to a vacuum degree of 30-40Pa. The infiltration temperature is 1350-1450°C and kept warm for 4-6 hours to obtain a copper-tungsten alloy.

5. The method for preparing the copper-tungsten alloy-copper-steel composite electrical contact according to claim 1, characterized in that: The steps of machining the copper-tungsten alloy, the steel part and the copper part respectively include: Performing sandblasting on the surface of the copper-tungsten alloy and performing milling on the infiltrated surface of the copper-tungsten alloy; Milling of steel and copper parts to the required dimensions.

6. The method for preparing the copper-tungsten alloy-copper-steel composite electrical contact according to claim 5, characterized in that: In the step of milling the copper-tungsten alloy infiltration surface, a copper layer of 1-2 mm is left on the copper-tungsten alloy infiltration surface after milling.

7. The method for preparing the copper-tungsten alloy-copper-steel composite electrical contact according to claim 1, characterized in that: The steps of assembling, placing chromium-copper alloy on the top of the assembled copper part, evacuating the vacuum, sintering at 1250-1300° C., and cooling to obtain a blank include: After the cleaned copper-tungsten alloy, steel parts and copper parts are assembled, they are placed in a vacuum sintering furnace, and chromium-copper alloy is placed on the top of the assembled copper parts. The vacuum is evacuated to ≤8Pa, and then the temperature is raised to 1250-1300℃ at a rate of 3-5℃ / min and kept warm for 1.5-2.5h. After cooling to 650-750℃ with the furnace, nitrogen is filled in, and the blank is taken out of the furnace after cooling to <200℃.

8. The method for preparing the copper-tungsten alloy-copper-steel composite electrical contact according to claim 1, characterized in that: The chromium content in the blank is 0.25-0.35%.

9. The method for preparing the copper-tungsten alloy-copper-steel composite electrical contact according to claim 1, characterized in that: The step of heat treating the blank to obtain the copper-tungsten alloy-copper-steel composite electrical contact comprises: The blank is heated to 800-900° C. and kept warm for 0.5-1.5 hours, water-cooled, then heated to 450-500° C. and kept warm for 3-5 hours, and then air-cooled to obtain a copper-tungsten alloy-copper-steel composite electrical contact.

10. A copper-tungsten alloy-copper-steel composite electrical contact, characterized in that: The copper-tungsten alloy-copper-steel composite electrical contact is obtained by the preparation method of any one of claims 1 to 9.

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