Method for surface density modification of mixed powder sintered copper-chromium contact based on SLM and copper-chromium contact

Abstract

The present application discloses a method for modifying the surface density of a mixed powder sintered copper-chromium contact based on SLM and a copper-chromium contact, and relates to the technical field of copper-chromium contact preparation. The method comprises: machining the mixed powder sintered CuCr contact and placing it in the printing chamber of a 3D printing device; establishing a 3D printing model, and designing the printing parameters of the area to be printed according to the surface size of the CuCr contact; the area to be printed includes the front arc burning surface and the back welding surface, the front arc burning surface includes the contact center plane area and the edge chamfered arc area, and the back welding surface includes the welding area; the printing chamber is sealed and evacuated, and a protective gas is introduced for washing; SLM is used for printing according to the 3D printing model and the printing parameters of the area to be printed, and the result is obtained after cooling. The present application can greatly improve the surface density of the CuCr contact, avoid the problem of arc extinguishing chamber failure caused by the solder climbing to the contact surface, and at the same time improve printing efficiency and reduce costs.

Description

Technical Field

[0001] The present application relates to the technical field of copper-chromium contact preparation, and in particular to a method for modifying the surface density of a mixed powder sintered copper-chromium contact based on SLM and a copper-chromium contact. Background Art

[0002] CuCr materials are widely used in medium and high voltage vacuum circuit breaker contact materials due to their good breaking, pressure resistance and anti-welding properties. Common methods for preparing CuCr contacts include mixed powder sintering, vacuum infiltration, vacuum casting and arc melting. Since the mixed powder sintering method uses solid phase sintering, its particle bonding strength is relatively low. During the interruption process of the arc chamber, the CuCr contact is disconnected from the matrix, making it easier to pull the CuCr contact apart. Its anti-welding performance is also the best among these processes. In addition, the mixed powder sintered CuCr contact has a high material utilization rate during the preparation process, so the cost is relatively low. It is currently widely used in vacuum interrupters of 10kV and below.

[0003] However, since the mixed powder sintered CuCr contact is solid phase sintered, the density of the contact is relatively low, generally 97%. The process of installing the CuCr contact into the arc extinguishing chamber is used together with the contact cup and the conductive rod. These accessories are usually connected by brazing technology before. During the brazing process, the contact density is low, and the solder will penetrate into the inside of the contact through the capillary effect, and some will even penetrate into the contact surface, resulting in the failure of the CuCr contact arc extinguishing chamber to break. In addition, in production, the mixed powder sintered CuCr contact needs to be aged during the process of being installed in the arc extinguishing chamber. This process uses discharge to remove the residual gas, impurities and processing burrs on the electrode surface and passivate the electrode surface. Whether the aging is thorough is directly related to the dynamic medium recovery of the vacuum arc extinguishing chamber after the arc. At present, the aging process can be divided into current aging and voltage aging according to different discharge forms. The former is through arc discharge and the latter is glow discharge or spark discharge. However, there is a problem that the arc extinguishing chamber aging process is long, generally 7 to 8 hours, and the cost is expensive, resulting in high cost. Based on this, the present application proposes a method for modifying the surface density of mixed powder sintered copper-chromium contacts based on SLM. Summary of the invention

[0004] The main purpose of this application is to provide a method for modifying the surface density of mixed powder sintered copper-chromium contacts based on SLM and a copper-chromium contact, aiming to solve the technical problems of low surface densification and high production cost of existing mixed powder sintered copper-chromium contacts.

[0005] To achieve the above purpose, the present application proposes a method for modifying the surface density of a mixed powder sintered copper-chromium contact based on SLM, comprising the following steps:

[0006] The mixed powder sintered CuCr contact is machined and placed in the printing chamber of the 3D printing equipment;

[0007] A 3D printing model is established, and printing parameters of the area to be printed are designed according to the surface size of the CuCr contact; wherein the area to be printed includes a front arc burning surface and a back welding surface, the front arc burning surface includes a contact center plane area and an edge chamfered arc area, and the back welding surface includes a welding area; the printing power and the number of printing layers of the contact center plane area are less than those of the edge chamfered arc area;

[0008] After the printing chamber is sealed, it is evacuated, and then protective gas is introduced for washing to complete positive pressure protection;

[0009] According to the 3D printing model and the printing parameters of the area to be printed, the front arc burning surface and the back welding surface are printed using SLM laser selective melting molding technology to form a remelting layer, and then after cooling, the modified CuCr contact is obtained.

[0010] Optionally, in the step of establishing a 3D printing model and designing printing parameters of the area to be printed according to the surface size of the CuCr contact, the printing parameters of the contact center plane area include:

[0011] The printing power is 200W-300W, the printing speed is 1300mm / s-1500mm / s, the blowing angle is 250°-300°, the spot spacing is 0.10-0.15, and the number of printing layers is 1-2 layers.

[0012] Optionally, in the step of establishing a 3D printing model and designing printing parameters of the area to be printed according to the surface size of the CuCr contact, the printing parameters of the contact center plane area include:

[0013] The printing power is 240W-260W, the printing speed is 1350mm / s-1450mm / s, the blowing angle is 270°-280°, the spot spacing is 0.12-0.14, and the number of printing layers is 2.

[0014] Optionally, in the step of establishing a 3D printing model and designing printing parameters of the area to be printed according to the surface size of the CuCr contact, the printing parameters of the edge chamfered arc area include:

[0015] The printing power is 300W-400W, the printing speed is 800mm / s-1300mm / s, the blowing angle is 250°-300°, the spot spacing is 0.05-0.10, and the number of printing layers is 3-5 layers.

[0016] Optionally, in the step of establishing a 3D printing model and designing printing parameters of the area to be printed according to the surface size of the CuCr contact, the printing parameters of the edge chamfered arc area include:

[0017] The printing power is 340W-360W, the printing speed is 1000mm / s-1100mm / s, the blowing angle is 270°-280°, the spot spacing is 0.07-0.09, and the number of printing layers is 4.

[0018] Optionally, in the step of establishing a 3D printing model and designing printing parameters of the area to be printed according to the surface size of the CuCr contact, the printing parameters of the welding area include:

[0019] The printing power is 300W-400W, the printing speed is 800mm / s-1300mm / s, the blowing angle is 250°-300°, the spot spacing is 0.05-0.10, and the number of printing layers is 3-5 layers.

[0020] Optionally, in the step of establishing a 3D printing model and designing printing parameters of the area to be printed according to the surface size of the CuCr contact, the printing parameters of the welding area include:

[0021] The printing power is 340W-360W, the printing speed is 1000mm / s-1100mm / s, the blowing angle is 270°-280°, the spot spacing is 0.07-0.09, and the number of printing layers is 4.

[0022] Optionally, the thickness of the remelted layer is 50 μm-100 μm.

[0023] Optionally, the raw material of the mixed powder sintered CuCr contact is at least one of copper-chromium mixed powder, copper-chromium alloy powder and copper-chromium-tellurium alloy powder.

[0024] Optionally, the mixed powder sintered CuCr contact is prepared by one of a double pressing and double sintering process, a single pressing and single sintering process, and a single pressing and single sintering combined with hot isostatic pressing densification process.

[0025] Optionally, in the step of machining the mixed powder sintered CuCr contact and placing it in a printing chamber of a 3D printing device, the machining method includes dry machining, oil machining, surface degreasing, deburring, anti-oxidation treatment and sandblasting.

[0026] Optionally, an automatic gripping robot is provided inside the 3D printing device, and the automatic gripping robot can realize continuous loading and unloading in the printing chamber.

[0027] Optionally, the number of laser heads of the 3D printing device is 2-3.

[0028] Optionally, in the step of introducing protective gas for purging, the protective gas is argon and the purging time is 15 minutes to 25 minutes.

[0029] The present application also proposes a copper-chromium contact obtained by modification using the above method.

[0030] This application includes at least the following beneficial effects:

[0031] In order to improve the density of the surface of the mixed powder sintered copper-chromium contact, the present application uses the SLM laser selective melting molding technology to print the surface of the mixed powder sintered CuCr contact, and designs the printing parameters of the area to be printed on the surface of the CuCr contact according to the arc ablation degree of the CuCr contact in the vacuum arc extinguishing chamber, and 3D prints the front arc burning surface and the back welding surface respectively to form a dense remelting layer, which divides the front arc burning surface into a contact center plane area and an edge chamfered arc area. Since the arc ablation degree of the contact center plane area is relatively light, its printing power and printing layer number are less than those of the edge chamfered arc area, while the edge chamfered arc area is severely ablated, so the printing power and printing layer number are appropriately increased, which can not only improve the printing efficiency, but also save electricity and reduce the printing cost, and form a dense remelting layer in the contact center plane area and the edge chamfered arc area; the back welding surface can be divided into a welding area and a non-welding area. The present application only prints the welding area to form a dense layer on the contact welding surface, which can reduce costs and improve printing efficiency;

[0032] In addition, the dense layer formed in the welding area can effectively reduce the solder climbing problem caused by the non-density of the mixed powder sintered CuCr contact itself, thereby reducing the arc extinguishing chamber breaking failure problem caused by the solder climbing to the contact surface during the use of the mixed powder sintered CuCr contact;

[0033] Moreover, the present invention forms a dense remelting layer on both the front arcing surface and the back welding surface of the CuCr contact, which can effectively remove the tip, burr and processing traces of the arcing surface of the CuCr contact, so that the protrusions and depressions on the surface of the CuCr contact are flattened and impurities are removed, thereby effectively replacing the arc extinguishing chamber aging process and avoiding the problems of long aging process time and high cost;

[0034] After the surface of the mixed powder sintered CuCr contact is modified by the method of the present application, the surface density of the CuCr contact can be greatly improved. It has been verified that the solder is almost enriched below the remelting layer of the CuCr contact and no longer penetrates into the interior of the CuCr contact matrix. At the same time, it can improve printing efficiency and reduce costs, and is suitable for industrial production applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] 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.

[0036] Figure 1 This is a flow chart of a method for modifying the surface density of a mixed powder sintered copper-chromium contact based on SLM as described in an embodiment of the present application;

[0037] Figure 2 A schematic diagram of the front arcing surface of the CuCr contact according to an embodiment of the present application;

[0038] Figure 3 A schematic diagram of the back welding surface of the CuCr contact according to an embodiment of the present application;

[0039] Figure 4 A schematic diagram of the front arcing surface and the back welding surface of the CuCr contact according to the embodiment of the present application;

[0040] Figure 5 This is a scanning electron microscope image of the CuCr contact after welding described in the embodiment of the present application.

[0041] 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

[0042] 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.

[0043] Contact material is an electrical contact material used for switches, relays, electrical connections and electrical connectors. CuCr composite materials are mixed according to a certain proportion and process and then arc remelted in a vacuum (after arc remelting, its metallographic structure is greatly improved, and the material performance is closer to "alloy". Since the vacuum switch is a docking type, very stringent requirements are placed on the contact material's resistance to welding, gas content, through-current thermal conductivity, and current cutoff level ("current cutoff" means that the arc current is not forcibly interrupted at the zero point). CuCr material has good comprehensive characteristics, such as strong short-circuit current breaking capacity, high dielectric strength, ablation resistance, low current cutoff, etc., and the CuCr material has a greater suction effect than the degassing effect, so it has a better dynamic vacuum degree than other materials, so it can be widely used in medium and high voltage vacuum circuit breaker contact materials.

[0044] However, due to the great difference in physical properties such as density and melting point between Cu and Cr, it is extremely difficult to produce CuCr alloy using conventional casting technology, and powder metallurgy must be used. At present, the methods for preparing CuCr contacts are generally mixed powder sintering, vacuum infiltration, vacuum casting, and arc melting. Since the CuCr contacts prepared by the mixed powder sintering method adopt solid phase sintering, their particle bonding strength is relatively low. During the interruption process of the arc chamber, the CuCr contacts are disconnected from the matrix, making the CuCr contacts easier to be pulled apart. Its anti-welding performance is also the best among these processes. In addition, the mixed powder sintered CuCr contacts have a high material utilization rate during the preparation process, so the cost is relatively low. At present, they are widely used in vacuum arc chambers of 10kV and below.

[0045] However, the density of the mixed powder sintered CuCr contact is relatively low due to solid phase sintering, and the density is generally 97%. Although the density is beneficial to improving the contact's resistance to welding, the reason is that the lower the density, the lower the contact's tensile strength. During the arc extinguishing chamber's breaking process, the contact is more likely to break from the matrix, which enables the arc extinguishing chamber to smoothly achieve the breaking process. However, the process of installing the CuCr contact into the arc extinguishing chamber is used together with the contact cup and the conductive rod. These accessories were usually connected by brazing technology before. During the brazing process, the contact density is low, and the solder will penetrate into the contact through the capillary effect, and some will even penetrate into the contact. The surface of the head causes the interruption failure of the CuCr contact arc extinguishing chamber; and in the production, the mixed powder sintered CuCr contacts need to be aged during the process of being installed in the arc extinguishing chamber. This process uses discharge to remove residual gas, impurities and processing burrs on the electrode surface and passivate the electrode surface. Whether the aging is thorough is directly related to the dynamic medium recovery of the vacuum arc extinguishing chamber after the arc. At present, the aging process can be divided into current aging and voltage aging according to different discharge forms. The former is through arc discharge and the latter is glow discharge or spark discharge. However, there is a problem that the arc extinguishing chamber aging process is relatively long, generally taking 7 to 8 hours, and the cost is expensive, resulting in high cost.

[0046] Selective laser melting (SLM) is a 3D printing technology that uses metal powder to directly print metal parts. During printing, a scraper spreads a layer of metal powder on the base of the forming cylinder, and the laser beam selectively melts the powder according to the cross-sectional contours of each layer of the part to process the current layer; after one layer is sintered, the lifting system descends to the height of a cross-sectional layer, and the powder roller spreads another layer of metal powder on the formed cross-sectional layer, and sintering the next layer, and so on, until the entire part is sintered. The entire forming process is carried out in a processing chamber that is evacuated or filled with protective gas to prevent the metal from reacting with other gases at high temperatures. Printing copper-chromium alloy contacts by SLM technology can improve the surface properties of copper-chromium alloy contacts. There are also some existing technologies that use SLM technology to produce copper-chromium alloy contacts. For example, patent CN111636061A discloses a method for batch laser cladding production of CuCr composite contacts. The patent is to clad the required material powder on the copper base surface, and the finished product is a machined blank, which achieves a certain cost saving effect, but still cannot solve the solder climbing problem caused by the non-density of the mixed powder CuCr contact itself; in patent CN117690742 A discloses a method for surface modification of copper-chromium contacts using SLM printing technology. Specifically, the arcing surface of the copper-chromium contact is printed using SLM laser selective melting 3D printing technology, thereby forming a remelting layer on the arcing surface of the copper-chromium alloy contact. However, it is mainly aimed at improving the surface properties of copper-chromium contacts prepared by vacuum infiltration, vacuum casting or vacuum consumable arc melting, but cannot solve the problem of arc extinguishing chamber breaking failure caused by solder climbing to the contact surface during the use of mixed powder contacts. In addition, it is not designed for the printing area, and the printing efficiency is not high enough.

[0047] In view of the technical problems existing in the existing mixed powder sintered CuCr contacts, the embodiments of the present application provide a method for modifying the surface density of mixed powder sintered copper-chromium contacts based on SLM, such as Figure 1 As shown, the following steps are included:

[0048] The mixed powder sintered CuCr contact is machined and placed in the printing chamber of the 3D printing equipment;

[0049] A 3D printing model is established, and printing parameters of the area to be printed are designed according to the surface size of the CuCr contact; wherein the area to be printed includes a front arc burning surface and a back welding surface, the front arc burning surface includes a contact center plane area and an edge chamfered arc area, and the back welding surface includes a welding area; the printing power and the number of printing layers of the contact center plane area are less than those of the edge chamfered arc area;

[0050] After the printing chamber is sealed, it is evacuated, and then protective gas is introduced for washing to complete positive pressure protection;

[0051] According to the 3D printing model and the printing parameters of the area to be printed, the front arc burning surface and the back welding surface are printed using SLM laser selective melting molding technology to form a remelting layer, and then after cooling, the modified CuCr contact is obtained.

[0052] In order to improve the density of the surface of the mixed powder sintered copper-chromium contact, the SLM laser selective melting molding technology is used to print the surface of the prepared mixed powder sintered CuCr contact, and the printing parameters of the area to be printed on the CuCr contact surface are designed in different regions according to the arc ablation degree of the CuCr contact in the vacuum arc extinguishing chamber, and the front arc burning surface and the back welding surface are 3D printed respectively to form a dense remelting layer, which divides the front arc burning surface into the contact center plane area and the edge chamfered arc area, such as Figure 2 As shown in the figure, the printing power and number of printing layers in the center plane area of ​​the contact are smaller than those in the edge chamfered arc area due to the lighter arc ablation. However, since the edge chamfered arc area has more serious ablation, the printing power and number of printing layers should be increased appropriately. This can not only improve the printing efficiency, but also save electricity and reduce the printing cost. A dense remelting layer can be formed in the center plane area of ​​the contact and the edge chamfered arc area. The back welding surface can be divided into welding area and non-welding area, such as Figure 3 As shown, the present application only prints the welding area, and forms a dense layer on the contact welding surface, which can reduce costs and improve printing efficiency. The dense layer formed in the welding area can effectively reduce the solder climbing problem caused by the non-density of the mixed powder sintered CuCr contact itself, thereby reducing the arc extinguishing chamber breaking failure problem caused by the solder climbing to the contact surface during the use of the mixed powder sintered CuCr contact. In addition, the present application forms a dense remelting layer on both the front arc burning surface and the back welding surface of the CuCr contact, which can effectively remove the tip, burr and processing marks of the CuCr contact arc burning surface, so that the protrusions and depressions on the surface of the CuCr contact are flattened and impurities are removed, thereby effectively replacing the arc extinguishing chamber aging process, avoiding the problems of long aging process time and high cost. After the surface of the mixed powder sintered CuCr contact is modified by the method of the present application, the surface density of the CuCr contact can be greatly improved. It has been verified that the solder is almost enriched below the remelting layer of the CuCr contact and no longer penetrates into the interior of the CuCr contact matrix. At the same time, it can improve printing efficiency and reduce costs, and is suitable for industrial production applications.

[0053] In the specific implementation process, when establishing a 3D printing model, it is necessary to slice and layer the three-dimensional design model through magics software to obtain the contour data of each section, and then generate a filling scan path based on the contour data, save this program file, that is, the file to be printed, and then import the file to be printed and the printing parameter settings into the 3D printing device. The 3D printing device can use LIM-X260 equipment (depending on the size of the batch, other types of SLM equipment can also be selected), select a substrate of the same or similar material as the CuCr contact to be printed, fix the substrate on a liftable workbench, and perform leveling. Evenly lay a layer of metal powder on the surface of the substrate, and then control the high-energy laser beam to scan along the planned path, melt the metal powder and wait for it to solidify, process a remelting layer, and then move the substrate down one layer to start a new round of powder laying and scanning. In this way, layer by layer processing is completed to complete the printing of the remelting layer, thereby obtaining a CuCr contact with a densified surface, thereby avoiding the problem of solder climbing to the contact surface during the use of the mixed powder sintered CuCr contact.

[0054] As an implementable embodiment of the present application, in the step of establishing a 3D printing model and designing printing parameters of the area to be printed according to the surface size of the CuCr contact, the printing parameters of the contact center plane area include:

[0055] The printing power is 200W-300W, the printing speed is 1300mm / s-1500mm / s, the blowing angle is 250°-300°, the spot spacing is 0.10-0.15, and the number of printing layers is 1-2 layers.

[0056] Furthermore, the printing parameters of the contact center plane area are preferably:

[0057] The printing power is 240W-260W, the printing speed is 1350mm / s-1450mm / s, the blowing angle is 270°-280°, the spot spacing is 0.12-0.14, and the number of printing layers is 2.

[0058] The printing parameters of the contact center plane area are further preferably:

[0059] The printing power is 250W, the printing speed is 1400mm / s, the blowing angle is 275°, the spot spacing is 0.13, and the number of printing layers is 2.

[0060] As an implementable embodiment of the present application, in the step of establishing a 3D printing model and designing printing parameters of the area to be printed according to the surface size of the CuCr contact, the printing parameters of the edge chamfer area include:

[0061] The printing power is 300W-400W, the printing speed is 800mm / s-1300mm / s, the blowing angle is 250°-300°, the spot spacing is 0.05-0.10, and the number of printing layers is 3-5 layers.

[0062] Furthermore, the printing parameters of the edge rounded area are preferably:

[0063] The printing power is 340W-360W, the printing speed is 1000mm / s-1100mm / s, the blowing angle is 270°-280°, the spot spacing is 0.07-0.09, and the number of printing layers is 4.

[0064] The printing parameters of the edge rounded area are further preferably:

[0065] The printing power is 350W, the printing speed is 1050mm / s, the blowing angle is 275°, the spot spacing is 0.08, and the number of printing layers is 4.

[0066] As an implementable embodiment of the present application, in the step of establishing a 3D printing model and designing printing parameters of the area to be printed according to the surface size of the CuCr contact, the printing parameters of the welding area include:

[0067] The printing power is 300W-400W, the printing speed is 800mm / s-1300mm / s, the blowing angle is 250°-300°, the spot spacing is 0.05-0.10, and the number of printing layers is 3-5 layers.

[0068] Furthermore, the printing parameters of the welding area are:

[0069] The printing power is 340W-360W, the printing speed is 1000mm / s-1100mm / s, the blowing angle is 270°-280°, the spot spacing is 0.07-0.09, and the number of printing layers is 4.

[0070] The printing parameters of the welding area are further preferably:

[0071] The printing power is 350W, the printing speed is 1050mm / s, the blowing angle is 275°, the spot spacing is 0.08, and the number of printing layers is 4.

[0072] In the specific implementation process, the present application designs the printing parameters of the area to be printed according to the surface size of the CuCr contact, and designs the area to be printed on the surface of the CuCr contact in different regions according to the arc ablation degree of the CuCr contact in the vacuum interrupter, such as Figure 4As shown, the front arc burning surface is divided into a contact center plane area and an edge chamfered arc area. Since the arc ablation degree of the contact center plane area is relatively light, its printing power and printing layer number are smaller than those of the edge chamfered arc area. Since the ablation of the edge chamfered arc area is relatively serious, the printing power and printing layer number are appropriately increased. By designing the printing parameters by area, the printing efficiency can be improved. After reducing the printing power and printing layer number of the contact center plane area, electric energy can be saved and printing cost can be reduced. After 3D printing with the printing parameters designed in this application, a dense remelting layer can be formed in the contact center plane area and the edge chamfered arc area, thereby effectively replacing the arc extinguishing chamber aging process and saving costs. In addition, the dense layer formed on the contact welding surface can also effectively reduce the solder climbing problem caused by the non-density of the mixed powder sintered CuCr contact itself.

[0073] As an implementation method of the present application, the thickness of the remelted layer is 50 μm-100 μm.

[0074] The present application forms a dense remelting layer on the front arcing surface and the back welding surface, which not only effectively removes the tip, burr and processing marks of the arcing surface of the CuCr contact, but also flattens the protrusions and depressions on the surface of the CuCr contact and removes impurities. At the same time, the remelting layer with a thickness of 50μm-100μm can effectively reduce the problem of solder climbing to the contact surface of the mixed powder CuCr contact during use, and greatly improves the density of the surface of the mixed powder CuCr contact, thereby avoiding the problem of arc extinguishing chamber breaking failure.

[0075] As an implementation method of the present application, the raw material of the mixed powder sintered CuCr contact is at least one of copper-chromium mixed powder, copper-chromium alloy powder and copper-chromium-tellurium alloy powder.

[0076] Specifically, the present application uses copper-chromium mixed powder, copper-chromium alloy powder and copper-chromium-tellurium alloy powder to replace the pure Cu layer, which can effectively improve the strength of the contact and prevent it from being deformed due to impact during service.

[0077] As an implementation method of the present application, the mixed powder sintered CuCr contact is prepared by one of the following processes: a double pressing and double sintering process, a single pressing and single sintering process, and a single pressing and single sintering combined with hot isostatic pressing and densification process.

[0078] Specifically, the double pressing and double firing process refers to the process of deforming and solidifying the original material by pressing and sintering under high temperature and high pressure conditions to obtain CuCr contacts. Due to the re-pressing and re-high temperature sintering, the bonding force between the material particles is enhanced, and a dense structure and uniform grain boundaries are formed under high temperature conditions, thereby improving the mechanical properties and chemical stability of the contact material, thereby processing the original material into a CuCr contact material with high strength, high hardness and high wear resistance; the single pressing and single firing process is also the process of deforming and solidifying the original material by pressing and sintering under high temperature and high pressure conditions, but only one pressing and high temperature sintering are performed; the single pressing and single firing combined with hot isostatic pressing densification process is to put the metal powder into a mold, and then apply high pressure and high temperature to cause diffusion and bonding between the metal particles to form a dense structure, which can produce CuCr contacts with high density, high strength and high hardness, and the metal powder can fully fill every corner of the mold under high temperature and high pressure, thereby realizing the processing of complex shapes, and can also achieve mass production, improve production efficiency and reduce costs.

[0079] As an implementable embodiment of the present application, in the step of machining the mixed powder sintered CuCr contact and placing it in a printing chamber of a 3D printing device, the machining method includes dry machining, oil machining, surface degreasing, deburring, anti-oxidation treatment and sandblasting.

[0080] Specifically, by performing dry machining, oil machining, surface degreasing, deburring, anti-oxidation treatment and sandblasting on the mixed powder sintered CuCr contact, a large number of burrs, tips, protrusions, etc. on the surface of the mixed powder sintered CuCr contact can be removed, and certain impurities can be removed, which is beneficial to the subsequent printing on the front arc burning surface and the back welding surface of the mixed powder sintered CuCr contact, thereby forming a dense remelting layer.

[0081] As an implementable embodiment of the present application, an automatic gripping robot is provided inside the 3D printing device, and the automatic gripping robot can realize continuous loading and unloading in the printing chamber.

[0082] Specifically, in order to further improve the printing efficiency, the present application sets an automatic gripping robot inside the 3D printing equipment. After a batch of CuCr contacts are printed, the automatic gripping robot can realize continuous loading and unloading in the printing chamber. This process does not require opening the printing chamber, thus avoiding the process of re-vacuuming and washing for positive pressure protection, thereby greatly improving the printing efficiency and saving printing costs.

[0083] As an implementation method of the present application, the number of laser heads of the 3D printing device is 2-3. By setting multiple laser heads for synchronous printing, the printing efficiency of the CuCr contact surface can be further improved.

[0084] As an implementation method of the present application, in the step of introducing a protective gas for purging, the protective gas is argon, and the purging time is 15 minutes to 25 minutes.

[0085] Specifically, during the entire printing process, it is necessary to prevent the metal from reacting with other gases at high temperatures. Therefore, the present application introduces inert gas argon into the printing chamber after evacuating it to vacuum before performing subsequent 3D printing steps to prevent oxidation reactions of copper and chromium metals.

[0086] The embodiment of the present application also provides a copper-chromium contact obtained by modification using the above method.

[0087] The above technical solution of the present application is described in detail below in conjunction with specific embodiments.

[0088] Example 1

[0089] A method for modifying the surface density of a mixed powder sintered copper-chromium contact based on SLM, comprising the following steps:

[0090] S1. After dry processing, surface degreasing, deburring, anti-oxidation treatment and sandblasting treatment, the mixed powder sintered CuCr contact is placed in the printing chamber of the 3D printing device. The 3D printing device is equipped with an automatic grabbing manipulator to realize continuous loading and unloading in the printing chamber through the automatic grabbing manipulator;

[0091] The raw materials of the mixed powder sintered CuCr contact are a mixture of copper-chromium mixed powder, copper-chromium alloy powder and copper-chromium-tellurium alloy powder; the mixed powder sintered CuCr contact is prepared by single pressing and single sintering combined with hot isostatic pressing densification process;

[0092] S2. Establish a 3D printing model and design printing parameters of the area to be printed according to the surface size of the CuCr contact;

[0093] Wherein, the area to be printed includes a front arc burning surface and a back welding surface, the front arc burning surface includes a contact center plane area and an edge chamfered arc area, and the back welding surface includes a welding area;

[0094] The printing parameters of the contact center plane area are:

[0095] The printing power is 250W, the printing speed is 1400mm / s, the blowing angle is 275°, the spot spacing is 0.13, and the number of printing layers is 2;

[0096] The printing parameters of the edge chamfer area are:

[0097] The printing power is 350W, the printing speed is 1050mm / s, the blowing angle is 275°, the spot spacing is 0.07, and the number of printing layers is 4;

[0098] The printing parameters of the welding area are:

[0099] The printing power is 350W, the printing speed is 1050mm / s, the blowing angle is 275°, the spot spacing is 0.07, and the number of printing layers is 4;

[0100] S3, after the printing chamber is sealed, evacuate it, and then introduce argon gas for washing. The washing time is 20 minutes to complete the positive pressure protection;

[0101] S4. According to the 3D printing model and the printing parameters of the area to be printed, the SLM laser selective melting molding technology is used to print the front arc burning surface and the back welding surface. The laser heads of the 3D printing equipment are set to 3. After the remelting layer is formed on the front arc burning surface and the back welding surface, the modified CuCr contact is obtained after cooling and vacuum encapsulation.

[0102] Example 2

[0103] A method for modifying the surface density of a mixed powder sintered copper-chromium contact based on SLM, comprising the following steps:

[0104] S1. After dry processing, surface degreasing, deburring, anti-oxidation treatment and sandblasting treatment, the mixed powder sintered CuCr contact is placed in the printing chamber of the 3D printing device. The 3D printing device is equipped with an automatic grabbing manipulator to realize continuous loading and unloading in the printing chamber through the automatic grabbing manipulator;

[0105] The raw materials of the mixed powder sintered CuCr contact are a mixture of copper-chromium mixed powder and copper-chromium alloy powder; the mixed powder sintered CuCr contact is prepared by a double pressing and double firing process;

[0106] S2. Establish a 3D printing model and design printing parameters of the area to be printed according to the surface size of the CuCr contact;

[0107] The area to be printed includes a front arc burning surface and a back welding surface, the front arc burning surface includes a contact center plane area and an edge chamfered arc area, and the back welding surface includes a welding area; the printing power and the number of printing layers of the contact center plane area are less than those of the edge chamfered arc area;

[0108] The printing parameters of the contact center plane area are:

[0109] The printing power is 200W, the printing speed is 1500mm / s, the blowing angle is 250°, the spot spacing is 0.10, and the number of printing layers is 1;

[0110] The printing parameters of the edge chamfer area are:

[0111] The printing power is 300W, the printing speed is 1300mm / s, the blowing angle is 250°, the spot spacing is 0.05, and the number of printing layers is 3;

[0112] The printing parameters of the welding area are:

[0113] The printing power is 300W, the printing speed is 1300mm / s, the blowing angle is 250°, the spot spacing is 0.05, and the number of printing layers is 3;

[0114] S3, after the printing chamber is sealed, evacuate it, and then introduce argon gas for washing. The washing time is 15 minutes to complete the positive pressure protection;

[0115] S4. According to the 3D printing model and the printing parameters of the area to be printed, the front arc burning surface and the back welding surface are printed by SLM laser selective melting molding technology. The laser heads of the 3D printing equipment are set to 2. After the remelting layer is formed on the front arc burning surface and the back welding surface, the modified CuCr contact is obtained after cooling and vacuum encapsulation.

[0116] Example 3

[0117] A method for modifying the surface density of a mixed powder sintered copper-chromium contact based on SLM, comprising the following steps:

[0118] S1. After the mixed powder sintered CuCr contact is subjected to oil processing, surface degreasing, deburring, anti-oxidation treatment and sandblasting, it is placed in the printing chamber of the 3D printing device. The 3D printing device is provided with an automatic grabbing manipulator inside, and continuous loading and unloading is realized in the printing chamber through the automatic grabbing manipulator;

[0119] The raw materials of the mixed powder sintered CuCr contact are a mixture of copper-chromium alloy powder and copper-chromium-tellurium alloy powder; the mixed powder sintered CuCr contact is prepared by a single pressing and single sintering process;

[0120] S2. Establish a 3D printing model and design printing parameters of the area to be printed according to the surface size of the CuCr contact;

[0121] The area to be printed includes a front arc burning surface and a back welding surface, the front arc burning surface includes a contact center plane area and an edge chamfered arc area, and the back welding surface includes a welding area; the printing power and the number of printing layers of the contact center plane area are less than those of the edge chamfered arc area;

[0122] The printing parameters of the contact center plane area are:

[0123] The printing power is 300W, the printing speed is 1300mm / s, the blowing angle is 300°, the spot spacing is 0.15, and the number of printing layers is 2;

[0124] The printing parameters of the edge chamfer area are:

[0125] The printing power is 400W, the printing speed is 800mm / s, the blowing angle is 300°, the spot spacing is 0.10, and the number of printing layers is 5;

[0126] The printing parameters of the welding area are:

[0127] The printing power is 400W, the printing speed is 800mm / s, the blowing angle is 300°, the spot spacing is 0.10, and the number of printing layers is 5;

[0128] S3, after the printing chamber is sealed, evacuate it, and then introduce argon gas for washing. The washing time is 25 minutes to complete the positive pressure protection;

[0129] S4. According to the 3D printing model and the printing parameters of the area to be printed, the SLM laser selective melting molding technology is used to print the front arc burning surface and the back welding surface. The laser heads of the 3D printing equipment are set to 3. After the remelting layer is formed on the front arc burning surface and the back welding surface, the modified CuCr contact is obtained after cooling and vacuum packaging.

[0130] Example 4

[0131] A method for modifying the surface density of a mixed powder sintered copper-chromium contact based on SLM, comprising the following steps:

[0132] S1. After dry processing, surface degreasing, deburring, anti-oxidation treatment and sandblasting treatment, the mixed powder sintered CuCr contact is placed in the printing chamber of the 3D printing device. The 3D printing device is equipped with an automatic grabbing manipulator to realize continuous loading and unloading in the printing chamber through the automatic grabbing manipulator;

[0133] The raw material of the mixed powder sintered CuCr contact is copper-chromium mixed powder; the mixed powder sintered CuCr contact is prepared by single pressing and single sintering combined with hot isostatic pressing densification process;

[0134] S2. Establish a 3D printing model and design printing parameters of the area to be printed according to the surface size of the CuCr contact;

[0135] The area to be printed includes a front arc burning surface and a back welding surface, the front arc burning surface includes a contact center plane area and an edge chamfered arc area, and the back welding surface includes a welding area; the printing power and the number of printing layers of the contact center plane area are less than those of the edge chamfered arc area;

[0136] The printing parameters of the contact center plane area are:

[0137] The printing power is 240W, the printing speed is 1450mm / s, the blowing angle is 260°, the spot spacing is 0.12, and the number of printing layers is 1;

[0138] The printing parameters of the edge chamfer area are:

[0139] The printing power is 340W, the printing speed is 1100mm / s, the blowing angle is 260°, the spot spacing is 0.07, and the number of printing layers is 3;

[0140] The printing parameters of the welding area are:

[0141] The printing power is 340W, the printing speed is 1100mm / s, the blowing angle is 260°, the spot spacing is 0.07, and the number of printing layers is 3;

[0142] S3, after the printing chamber is sealed, evacuate it, and then introduce argon gas for washing. The washing time is 18 minutes to complete the positive pressure protection;

[0143] S4. According to the 3D printing model and the printing parameters of the area to be printed, the front arc burning surface and the back welding surface are printed by SLM laser selective melting molding technology. The laser heads of the 3D printing equipment are set to 2. After the remelting layer is formed on the front arc burning surface and the back welding surface, the modified CuCr contact is obtained after cooling and vacuum encapsulation.

[0144] Example 5

[0145] A method for modifying the surface density of a mixed powder sintered copper-chromium contact based on SLM, comprising the following steps:

[0146] S1. After the mixed powder sintered CuCr contact is subjected to oil processing, surface degreasing, deburring, anti-oxidation treatment and sandblasting, it is placed in the printing chamber of the 3D printing device. The 3D printing device is provided with an automatic grabbing manipulator inside, and continuous loading and unloading is realized in the printing chamber through the automatic grabbing manipulator;

[0147] The raw materials of the mixed powder sintered CuCr contact are a mixture of copper-chromium alloy powder and copper-chromium-tellurium alloy powder; the mixed powder sintered CuCr contact is prepared by a single pressing and single sintering process;

[0148] S2. Establish a 3D printing model and design printing parameters of the area to be printed according to the surface size of the CuCr contact;

[0149] The area to be printed includes a front arc burning surface and a back welding surface, the front arc burning surface includes a contact center plane area and an edge chamfered arc area, and the back welding surface includes a welding area; the printing power and the number of printing layers of the contact center plane area are less than those of the edge chamfered arc area;

[0150] The printing parameters of the contact center plane area are:

[0151] The printing power is 260W, the printing speed is 1450mm / s, the blowing angle is 270°, the spot spacing is 0.14, and the number of printing layers is 2;

[0152] The printing parameters of the edge chamfer area are:

[0153] The printing power is 360W, the printing speed is 1100mm / s, the blowing angle is 270°, the spot spacing is 0.07, and the number of printing layers is 4;

[0154] The printing parameters of the welding area are:

[0155] The printing power is 360W, the printing speed is 1100mm / s, the blowing angle is 270°, the spot spacing is 0.07, and the number of printing layers is 4;

[0156] S3, after the printing chamber is sealed, evacuate it, and then introduce argon gas for washing. The washing time is 22 minutes to complete the positive pressure protection;

[0157] S4. According to the 3D printing model and the printing parameters of the area to be printed, the front arc burning surface and the back welding surface are printed by SLM laser selective melting molding technology. The laser heads of the 3D printing equipment are set to 2. After the remelting layer is formed on the front arc burning surface and the back welding surface, the modified CuCr contact is obtained after cooling and vacuum encapsulation.

[0158] Example 6

[0159] A method for modifying the surface density of a mixed powder sintered copper-chromium contact based on SLM, comprising the following steps:

[0160] S1. After dry processing, surface degreasing, deburring, anti-oxidation treatment and sandblasting treatment, the mixed powder sintered CuCr contact is placed in the printing chamber of the 3D printing device. The 3D printing device is equipped with an automatic grabbing manipulator to realize continuous loading and unloading in the printing chamber through the automatic grabbing manipulator;

[0161] The raw materials of the mixed powder sintered CuCr contact are a mixture of copper-chromium mixed powder and copper-chromium-tellurium alloy powder; the mixed powder sintered CuCr contact is prepared by a single pressing and single sintering process;

[0162] S2. Establish a 3D printing model and design printing parameters of the area to be printed according to the surface size of the CuCr contact;

[0163] The area to be printed includes a front arc burning surface and a back welding surface, the front arc burning surface includes a contact center plane area and an edge chamfered arc area, and the back welding surface includes a welding area; the printing power and the number of printing layers of the contact center plane area are less than those of the edge chamfered arc area;

[0164] The printing parameters of the contact center plane area are:

[0165] The printing power is 270W, the printing speed is 1380mm / s, the blowing angle is 260°, the spot spacing is 0.12, and the number of printing layers is 1;

[0166] The printing parameters of the edge chamfer area are:

[0167] The printing power is 370W, the printing speed is 900mm / s, the blowing angle is 260°, the spot spacing is 0.06, and the number of printing layers is 3;

[0168] The printing parameters of the welding area are:

[0169] The printing power is 370W, the printing speed is 900mm / s, the blowing angle is 260°, the spot spacing is 0.06, and the number of printing layers is 3;

[0170] S3, after the printing chamber is sealed, evacuate it, and then introduce argon gas for washing. The washing time is 17 minutes to complete the positive pressure protection;

[0171] S4. According to the 3D printing model and the printing parameters of the area to be printed, the SLM laser selective melting molding technology is used to print the front arc burning surface and the back welding surface. The laser heads of the 3D printing equipment are set to 3. After the remelting layer is formed on the front arc burning surface and the back welding surface, the modified CuCr contact is obtained after cooling and vacuum packaging.

[0172] Example 7

[0173] A method for modifying the surface density of a mixed powder sintered copper-chromium contact based on SLM, comprising the following steps:

[0174] S1. After the mixed powder sintered CuCr contact is subjected to oil processing, surface degreasing, deburring, anti-oxidation treatment and sandblasting, it is placed in the printing chamber of the 3D printing device. The 3D printing device is provided with an automatic grabbing manipulator inside, and continuous loading and unloading is realized in the printing chamber through the automatic grabbing manipulator;

[0175] The raw materials of the mixed powder sintered CuCr contact are a mixture of copper-chromium alloy powder and copper-chromium-tellurium alloy powder; the mixed powder sintered CuCr contact is prepared by a single pressing and single sintering process;

[0176] S2. Establish a 3D printing model and design printing parameters of the area to be printed according to the surface size of the CuCr contact;

[0177] The area to be printed includes a front arc burning surface and a back welding surface, the front arc burning surface includes a contact center plane area and an edge chamfered arc area, and the back welding surface includes a welding area; the printing power and the number of printing layers of the contact center plane area are less than those of the edge chamfered arc area;

[0178] The printing parameters of the contact center plane area are:

[0179] The printing power is 250W, the printing speed is 1400mm / s, the blowing angle is 250°, the spot spacing is 0.14, and the number of printing layers is 1;

[0180] The printing parameters of the edge chamfer area are:

[0181] The printing power is 360W, the printing speed is 1100mm / s, the blowing angle is 250°, the spot spacing is 0.08, and the number of printing layers is 4;

[0182] The printing parameters of the welding area are:

[0183] The printing power is 360W, the printing speed is 1100mm / s, the blowing angle is 250°, the spot spacing is 0.08, and the number of printing layers is 4;

[0184] S3, after the printing chamber is sealed, evacuate it, and then introduce argon gas for washing. The washing time is 24 minutes to complete the positive pressure protection;

[0185] S4. According to the 3D printing model and the printing parameters of the area to be printed, the SLM laser selective melting molding technology is used to print the front arc burning surface and the back welding surface. The laser heads of the 3D printing equipment are set to 3. After the remelting layer is formed on the front arc burning surface and the back welding surface, the modified CuCr contact is obtained after cooling and vacuum packaging.

[0186] Test example

[0187] The surface density of the CuCr contact obtained after modification in Example 1 of the present application was analyzed. The CuCr contact modified in Example 1 and the conductive rod were connected by AgCu 28 The Ni solder was vacuum brazed at a maximum temperature of 830°C and kept warm for 5 minutes. After the brazing was completed, the welding effect was observed under a 200μm scanning electron microscope. The scanning electron microscope image was as follows: Figure 5 shown.

[0188] Depend on Figure 5It can be seen that the solder is almost enriched below the remelting layer of the CuCr contact and no longer penetrates into the interior of the CuCr contact matrix. After testing, after laser remelting, the solder diffuses at most in the remelting layer with a diffusion height of ≤40μm. It hardly climbs in the matrix and climbs along the grain boundaries in pure copper with a climbing height of about 120μm, effectively reducing the solder climbing on the surface of the mixed powder CuCr contact. This shows that the present application performs 3D printing on the center plane area, edge chamfered arc area and welding area of ​​the contact respectively, which can form a dense layer on the surface of the mixed powder sintered CuCr contact, avoiding the solder climbing problem caused by the non-denseness of the mixed powder sintered CuCr contact itself, thereby improving the use effect of the mixed powder sintered CuCr contact.

[0189] In summary, the present application designs the printing parameters of the area to be printed on the surface of the CuCr contact by dividing the area by area according to the arc ablation degree of the CuCr contact in the vacuum arc extinguishing chamber. The arc ablation degree of the central plane area of ​​the contact is relatively light, while the ablation of the edge chamfered arc area is relatively serious. Therefore, the printing power and the number of printing layers of the central plane area of ​​the contact are smaller than those of the edge chamfered arc area, which not only improves the printing efficiency but also saves electricity and reduces the printing cost, and forms a dense remelting layer in the central plane area and the edge chamfered arc area of ​​the contact; and the present application only prints the welding area of ​​the back welding surface to form a dense layer on the welding surface of the contact, which can not only reduce the cost and improve the printing efficiency, but also the dense layer formed in the welding area can effectively reduce the solder climbing problem caused by the non-density of the mixed powder sintered CuCr contact itself, thereby reducing the arc extinguishing chamber breaking failure problem caused by the solder climbing to the contact surface during the use of the mixed powder sintered CuCr contact. At the same time, the present application forms a dense remelting layer on both the front arcing surface and the back welding surface of the CuCr contact, which can effectively remove the tips, burrs and processing marks on the arcing surface of the CuCr contact, so that the protrusions and depressions on the surface of the CuCr contact are flattened, and impurities on the surface of the CuCr contact are removed, thereby effectively replacing the arc extinguishing chamber aging process and avoiding the problems of long aging process time and high cost.

[0190] 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 modifying the surface density of mixed powder sintered copper-chromium contacts based on SLM, characterized in that: The following steps are involved: The mixed powder sintered CuCr contact is machined and placed in the printing chamber of the 3D printing equipment; A 3D printing model is established, and printing parameters of the area to be printed are designed according to the surface size of the CuCr contact; wherein the area to be printed includes a front arc burning surface and a back welding surface, the front arc burning surface includes a contact center plane area and an edge chamfered arc area, and the back welding surface includes a welding area; the printing power and the number of printing layers of the contact center plane area are less than those of the edge chamfered arc area; The printing parameters of the contact center plane area include: The printing power is 200W-300W, the printing speed is 1300mm / s-1500mm / s, the blowing angle is 250°-300°, the spot spacing is 0.10-0.15, and the number of printing layers is 1-2 layers; The printing parameters of the edge chamfer area include: Printing power is 300W-400W, printing speed is 800mm / s-1300mm / s, blowing angle is 250°-300°, spot spacing is 0.05-0.10, and the number of printing layers is 3-5 layers; The printing parameters of the welding area include: Printing power is 300W-400W, printing speed is 800mm / s-1300mm / s, blowing angle is 250°-300°, spot spacing is 0.05-0.10, and the number of printing layers is 3-5 layers; After the printing chamber is sealed, it is evacuated, and then protective gas is introduced for washing to complete positive pressure protection; According to the 3D printing model and the printing parameters of the area to be printed, the front arc burning surface and the back welding surface are printed using SLM laser selective melting molding technology to form a remelting layer, and then after cooling, the modified CuCr contact is obtained.

2. The method for modifying the surface density of mixed powder sintered copper-chromium contacts based on SLM according to claim 1, characterized in that: In the step of establishing a 3D printing model and designing printing parameters of the area to be printed according to the surface size of the CuCr contact, the printing parameters of the contact center plane area include: The printing power is 240W-260W, the printing speed is 1350mm / s-1450mm / s, the blowing angle is 270°-280°, the spot spacing is 0.12-0.14, and the number of printing layers is 2.

3. The method for modifying the surface density of mixed powder sintered copper-chromium contacts based on SLM according to claim 1, characterized in that: In the step of establishing a 3D printing model and designing printing parameters of the area to be printed according to the surface size of the CuCr contact, the printing parameters of the edge chamfered arc area include: The printing power is 340W-360W, the printing speed is 1000mm / s-1100mm / s, the blowing angle is 270°-280°, the spot spacing is 0.07-0.09, and the number of printing layers is 4.

4. The method for modifying the surface density of mixed powder sintered copper-chromium contacts based on SLM according to claim 1, characterized in that: In the step of establishing a 3D printing model and designing printing parameters of the area to be printed according to the surface size of the CuCr contact, the printing parameters of the welding area include: The printing power is 340W-360W, the printing speed is 1000mm / s-1100mm / s, the blowing angle is 270°-280°, the spot spacing is 0.07-0.09, and the number of printing layers is 4.

5. The method for modifying the surface density of mixed powder sintered copper-chromium contacts based on SLM according to claim 1, characterized in that: The thickness of the remelted layer is 50 μm-100 μm.

6. The method for modifying the surface density of mixed powder sintered copper-chromium contacts based on SLM according to claim 1, characterized in that: The raw material of the mixed powder sintered CuCr contact is at least one of copper-chromium mixed powder, copper-chromium alloy powder and copper-chromium-tellurium alloy powder.

7. The method for modifying the surface density of mixed powder sintered copper-chromium contacts based on SLM according to claim 1, characterized in that: The mixed powder sintered CuCr contact is prepared by one of a double pressing and double firing process, a single pressing and single firing process, and a single pressing and single firing combined with hot isostatic pressing and densification process.

8. The method for modifying the surface density of mixed powder sintered copper-chromium contacts based on SLM according to claim 1, characterized in that: In the step of machining the mixed powder sintered CuCr contact and placing it in a printing chamber of a 3D printing device, the machining method includes dry machining, oil machining, surface degreasing, deburring, anti-oxidation treatment and sandblasting.

9. The method for modifying the surface density of mixed powder sintered copper-chromium contacts based on SLM according to claim 1, characterized in that: An automatic grabbing robot is provided inside the 3D printing device, and the automatic grabbing robot can realize continuous loading and unloading in the printing chamber.

10. The method for modifying the surface density of mixed powder sintered copper-chromium contacts based on SLM according to claim 1, characterized in that: The number of laser heads of the 3D printing device is 2-3.

11. The method for modifying the surface density of mixed powder sintered copper-chromium contacts based on SLM according to claim 1, characterized in that: In the step of introducing protective gas for purging, the protective gas is argon and the purging time is 15 minutes to 25 minutes.

12. A copper-chromium contact, characterized in that: The copper-chromium contact is obtained by modification using the method described in any one of claims 1 to 11.

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