A method of compounding a heterogeneous metal material

Abstract

This invention discloses a method for composite materials of dissimilar metals. The method includes: S1, obtaining a target stainless steel plate and fixing it using a contour cooling fixture; S2, using laser direct energy deposition (LDED) to load metal powder into a powder feeder and perform metal composite deposition on a preset working area; wherein the metal powder is copper powder or a composite copper powder containing alloy powder; the ratio of the width of the preset working area to the diameter of the laser head spot is 1:(1.0~1.5); S3, after deposition, holding the target stainless steel plate at 300~450℃ for 1~3 hours to complete the composite of copper and stainless steel or the composite of copper alloy and stainless steel. This invention reduces the welding process between the original copper ring and stainless steel and the use of precious metal solder in the welding process by laser deposition of pure copper or copper alloy as a transition layer on stainless steel, and improves the welding strength and gas density with ceramics.

Description

Technical Field

[0001] This invention belongs to the field of heterogeneous material composite technology, and specifically relates to a method for composite heterogeneous metal materials. Background Technology

[0002] In medium- and high-voltage vacuum switches, to ensure safety and reliability, vacuum interrupters are required to have high vacuum levels, airtightness, and long mechanical life. Alumina ceramics, as excellent insulating materials, are widely used in the shells of vacuum interrupters. However, the low coefficient of thermal expansion of ceramics makes direct welding with stainless steel during the sealing process difficult. Therefore, currently, in the welding process of vacuum interrupters, especially the stainless steel cover plates at both ends, when welding to ceramics, it is necessary to first weld a copper ring onto the stainless steel surface using silver-copper solder for an effective transition before welding to the ceramics, in order to ensure weld strength and airtightness.

[0003] Driven by the current development of intelligent technology and the rapid growth of AI data, the price of silver has increased rapidly. Other solders cannot achieve the welding performance of silver-copper solder. Therefore, the large-scale use of silver-copper solder has led to a significant increase in the production cost of medium and high voltage vacuum switches and the consumption of precious metals.

[0004] Most copper / stainless steel composites are manufactured using traditional hot-rolling or welding methods. Chinese patent CN120055292A discloses a method for hollow ring laser additive manufacturing of copper alloy-stainless steel heterostructures. This patent primarily designs and develops a ring laser for copper / stainless steel additive manufacturing, clearly defining the related processes and the technical challenges of thin-walled composites. Chinese patent CN119187593A discloses a laser additive manufacturing method for 316L+xCu functionally graded composite materials. This method uses different proportions of 316L powder and Cu powder to prepare the composite material through a layer-by-layer gradient transition. The process is complex and costly. However, the patent does not specify clear process requirements or demonstrate a solution for thin-walled material composites.

[0005] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, this invention provides a method for compositing heterogeneous metallic materials. The technical problem to be solved by this invention is achieved through the following technical solution: This invention provides a method for compositing heterogeneous metallic materials, comprising the following steps: S1. Obtain the target stainless steel plate and fix it with a contour cooling fixture, wherein the contour cooling fixture exposes the preset working area of ​​the target stainless steel plate; S2. Using laser direct energy deposition (EDD) technology, metal powder is loaded into a powder feeder, and metal composite is applied to the preset working area in an inert atmosphere; wherein, the metal powder is copper powder or composite copper powder containing alloy powder; the distance between the laser head and the preset working area is 10-50 mm, and the ratio of the width of the preset working area to the spot diameter of the laser head is 1:(1.0-1.5). S3. After deposition, the target stainless steel plate is kept at 300-450℃ for 1-3 hours to relieve stress and form a metal composite layer in the preset working area, thus completing the composite of copper and stainless steel or the composite of copper alloy and stainless steel.

[0007] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention uses powder-feeding laser additive manufacturing technology to replace the traditional copper and stainless steel welding process. By rapidly laser-depositing a layer of pure copper or copper alloy on the surface of thin-walled stainless steel as a transition layer for welding stainless steel and ceramics, the welding process between copper and stainless steel and the use of precious metal silver-copper solder in the welding process are reduced.

[0008] 2. Adding trace elements to copper powder allows for the use of low-silver or silver-free solder when welding copper alloys to ceramics, further reducing the use and waste of silver, and resulting in higher welding strength and better air density with ceramics.

[0009] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0010] Figure 1 This is a schematic flowchart of a composite method for heterogeneous metal materials provided in an embodiment of the present invention; Figure 2 This is a schematic cross-sectional view of the copper alloy-stainless steel composite workpiece prepared in Example 1 of the present invention; Figure 3 This is a schematic cross-sectional view of the copper alloy-stainless steel composite workpiece prepared in Example 2 of the present invention.

[0011] The attached figures are labeled as follows: 1-Target stainless steel plate; 2-Shaped cooling fixture; 21-Water inlet; 22-Water outlet; 3-Metal composite layer. Detailed Implementation

[0012] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following describes in detail a composite method for heterogeneous metal materials proposed according to the present invention, in conjunction with the accompanying drawings and specific embodiments.

[0013] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of the present invention.

[0014] It should be noted that, in this document, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0015] In related technologies, when manufacturing the vacuum interrupter, a core component of medium- and high-voltage vacuum switches, the stainless steel cover plate and copper transition ring are welded together using AgCu28 solder. Then, the nickel-plated ceramic shell is welded to the copper transition ring using AgCu28 solder. This process wastes precious metals and has high production costs. In the solution provided by this invention, a metal composite layer 3 is laser-laminated onto the area (preset working area) of the stainless steel surface using laser additive manufacturing. This metal composite layer 3 can be a layer of pure copper, replacing the traditional welding process. Alternatively, the metal composite layer 3 can be pure copper with added trace elements to improve its weldability, allowing the use of low-silver-content solder or silver-free solder during the subsequent welding of the metal composite layer 3 to the ceramic shell.

[0016] This invention provides a method for compositing heterogeneous metal materials, such as... Figure 1 As shown, it includes the following steps S1 to S3.

[0017] S1. Obtain the target stainless steel plate 1 and fix it with the contour cooling fixture 2. The contour cooling fixture 2 exposes the preset working area of ​​the target stainless steel plate 1.

[0018] In one example, the shape of the contour cooling fixture 2 is complementary to that of the target stainless steel plate 1. The contour cooling fixture 2 has a hollow structure, with a water inlet 21 at one end and a water outlet 22 at the other end. The target stainless steel plate 1 is relatively thin, typically only 1-1.5 mm thick. When using a laser to melt and bond metal powder to the surface of the target stainless steel plate 1, deformation or even burn-through can easily occur. This invention employs a contouring fixture design. Based on the structure of the target stainless steel plate, a contour cooling fixture 2 is fabricated. The fixture is hollow, allowing for water cooling within its hollow interior. During operation, the target stainless steel plate 1 is tightly fitted to the contour cooling fixture 2, ensuring the temperature is controlled between 20-50°C. This provides a good heat dissipation environment for the target stainless steel plate 1, thereby preventing deformation caused by localized high temperatures during laser deposition.

[0019] In one example, the target stainless steel plate 1 is a pre-treated stainless steel plate. The pretreatment includes: obtaining a hydrochloric acid solution with a volume concentration of 3-5%, spraying it onto a predetermined working area of ​​the target stainless steel plate 1, and shielding non-predetermined working areas with a tetrafluoroethylene film; placing it at a temperature of 20-50°C for 20-30 minutes, cleaning the predetermined working area, and obtaining the pre-treated stainless steel plate. In other words, this embodiment uses hydrochloric acid solution to corrode and roughen the predetermined working area of ​​the pre-treated stainless steel plate, forming a blackened layer. By roughening the predetermined working area, the laser absorption rate of the stainless steel surface can be increased, and the contact area with the metal powder can be expanded. Thus, while ensuring composite strength and gas density, the minimum laser energy can be used for the composite of dissimilar metals, avoiding deformation or burn-through of the stainless steel.

[0020] In one example, the thickness of the preset working area of ​​the target stainless steel plate 1 is 1 to 1.5 mm.

[0021] S2. Using laser direct energy deposition (LDED), metal powder is loaded into a powder feeder and, in an inert atmosphere, metal composite is applied to a preset working area. The metal powder is copper powder or a composite copper powder containing alloy powder. The distance between the laser head and the preset working area is 10–50 mm, and the ratio of the width of the preset working area to the laser spot diameter is 1:(1.1–1.3). In the high-voltage field of a vacuum interrupter, even tiny burrs and dust can cause breakdown. To ensure that the metal powder is effectively deposited in the preset working area without contaminating the surrounding area, this embodiment adjusts and optimizes the laser spot according to a ratio of the width of the preset working area to the laser spot diameter of 1:(1.0–1.5). This ensures effective deposition while preventing copper powder from escaping to non-preset working areas and causing burr and dust contamination. Simultaneously, additive composite under inert gas protection effectively reduces copper oxidation.

[0022] In one example, the laser direct energy deposition process uses a laser power of 1–4 kW, a powder feeding rate of 100–300 g / min, and a scanning speed of 200–600 mm / min. This process combines copper (or copper containing alloy powder) with stainless steel via additive manufacturing, achieving high production efficiency (0.6–2 kg / h), low cost, and a simple process, making it suitable for large-scale industrial production.

[0023] For example, the angle between the central axis of the laser head and the plane of the preset working area is 45° to 90°.

[0024] In some examples, the copper powder has a particle size of 20–200 micrometers and a flow rate of less than 20 s / 50 g.

[0025] In other examples, the copper powder in the composite copper powder has a particle size of 20–200 micrometers and a flow rate of less than 20 s / 50 g; the alloy powder has a particle size of 0.1–200 micrometers. The mass ratio of alloy powder to copper powder in the composite copper powder is (0.05–0.1):1.

[0026] In some embodiments, the alloy powder is at least one of Ni, Sn, Al, Si, Zn, Ti, or Zr to improve the flowability or welding strength of the composite copper powder. For example, the particle size of Ti and Zr can be 50–200 micrometers, and the particle size of Ni and Si can be 0.1–100 micrometers. Adding Sn and Al to the copper powder can lower the melting point of copper, while adding metals such as Ti and Ni can improve the high-temperature weldability and welding strength with nickel on the ceramic surface. Therefore, by optimizing the added elements, solders with low silver content (Ag content below 10%) or silver-free solders can be used for welding with ceramics.

[0027] In one example, a pretreatment process for the copper powder is also included. This pretreatment process includes: adding graphite powder (smaller than 800 mesh) to the copper powder at a mass ratio of 1-3% to obtain a mixed powder; ball milling the mixed powder and grinding media at a mass ratio of 1:1 for 6-8 hours; and then sieving through a sieve (smaller than 300 mesh) to remove excess graphite powder, obtaining graphite-coated copper powder. Because pure copper has extremely high thermal conductivity and reflectivity, this embodiment uniformly coats the outer surface of the copper powder with a layer of graphite, increasing the laser absorption rate of the copper powder from the original 5% to over 63%. This allows the copper powder to effectively absorb energy and fully melt under low-power laser energy, achieving composite with stainless steel.

[0028] Furthermore, the distance between the laser head and the preset working area is 20-25mm.

[0029] Further, the ratio of the width of the preset working area to the diameter of the laser spot is 1:(1.1 to 1.3). Preferably, the ratio of the width of the preset working area to the diameter of the laser spot is 1:1.2.

[0030] S3. After deposition, the target stainless steel plate 1 is kept at 300-450℃ for 1-3 hours to relieve stress and form a metal composite layer 3 in the preset working area, thus completing the composite of copper and stainless steel or the composite of copper alloy and stainless steel.

[0031] For example, the thickness of the metal composite layer 3 is 1 to 5 mm; the metal composite layer 3 includes at least one deposited metal layer with a thickness of 0.5 to 1.0 mm.

[0032] The composite method for dissimilar metal materials provided in this invention is an alternative to the current method of welding stainless steel cover plates and ceramics using silver-copper solder in the fabrication of high-voltage vacuum switch interrupters. In the composite preparation method provided by this invention, pure copper or copper alloy is prepared as a transition layer on the stainless steel surface using laser additive manufacturing technology, eliminating the need for silver-copper solder required for welding the transition copper ring to stainless steel. Simultaneously, this transition layer improves the weldability of stainless steel and ceramics, thereby enhancing the welding efficiency and strength of the vacuum interrupter while reducing the use of precious metals. Furthermore, the alloying components added to the pure copper further improve the welding strength and airtightness between the ceramics and stainless steel.

[0033] The method provided by the present invention will be further described below with reference to specific embodiments.

[0034] Example 1 In this embodiment, such as Figure 2 As shown, target stainless steel plate 1 is a 316 stainless steel workpiece.

[0035] Step 1: Spray a 3% hydrochloric acid solution onto the surface of the preset working area of ​​the 316 stainless steel workpiece, and then place the 316 stainless steel workpiece in a ventilated environment at 30°C for 30 minutes to allow the working surface to be corroded and roughened, forming a blackened corrosion layer.

[0036] Step 2: Add graphite powder to copper powder with a particle size of 100-200 micrometers to obtain a mixed powder; the mass content of graphite powder in the mixed powder is 1%. Use a ball mill to ball mill the mixed powder and grinding media at a mass ratio of 1:1 for 8 hours. Sieve to remove excess graphite powder to obtain graphite-coated copper powder.

[0037] Step 3: Add Sn powder and Ni powder to the graphite-coated copper powder and mix for 4 hours to obtain composite copper powder; wherein the mass content of Sn powder in the composite copper powder is 1.5% and the mass content of Ni powder is 5%.

[0038] Step 4: Install the 316 stainless steel workpiece into the contour cooling fixture 2, and place the composite copper powder into the laser powder feeding bucket.

[0039] Step 5: Adjust the laser spot size to 1.6mm, and adjust the angle between the central axis of the laser head and the plane of the preset working area to 45 degrees, so that metal deposition can occur simultaneously in the preset working area. Figure 2 Metal deposition was also performed on the outer surface shown in the diagram (note) Figure 2 The structure of the middle metal composite layer 3 does not represent the actual deposition thickness and is only a schematic diagram.

[0040] Step 6: Adjust the distance between the laser head and the deposition area to 20mm; adjust the laser power to 1.3kw, the powder feeding speed to 120g / min, the steady-state speed to 300mm / min, and then perform surface laser deposition.

[0041] Step 7: Place the laser-deposited 316 stainless steel workpiece into a vacuum furnace for stress relief treatment at 300 degrees Celsius for 1.2 hours, then allow it to cool naturally.

[0042] Step 8: Perform precision machining on the heat-treated 316 stainless steel workpiece to the dimensions required by the drawing, thus obtaining the desired result. Figure 3 The copper alloy-stainless steel composite workpiece shown.

[0043] Using the copper alloy-stainless steel composite workpiece obtained in Example 1, a vacuum interrupter was prepared. The welding strength and vacuum leakage rate were tested, and the results are shown in Table 1. The welding strength was 203 MPa, and the vacuum leakage rate was 6.8 × 10⁻⁶. -10 Pa·m 3 / s.

[0044] Example 2 In this embodiment, such as Figure 3 As shown, target stainless steel plate 1 is a 304 stainless steel workpiece.

[0045] Step 1: Spray a 3% hydrochloric acid solution onto the surface of the preset working area of ​​the 304 stainless steel workpiece, and then place the 304 stainless steel workpiece in a ventilated environment at 50°C for 25 minutes to allow the working surface to be corroded and roughened, forming a blackened corrosion layer.

[0046] Step 2: Add graphite powder to copper powder with a particle size of 50-150 micrometers to obtain a mixed powder; the mass content of graphite powder in the mixed powder is 2.3%. Use a ball mill to ball mill the mixed powder and grinding media at a mass ratio of 1:1 for 7 hours. Sieve to remove excess graphite powder to obtain graphite-coated copper powder.

[0047] Step 3: Add Sn powder, Ni powder and Si powder to the graphite-coated copper powder and mix for 4 hours to obtain composite copper powder; in the composite copper powder, the mass content of Sn powder is 3%, the mass content of Ni powder is 2%, and the mass content of Si powder is 3%.

[0048] Step 4: Install the 304 stainless steel workpiece into the contour cooling fixture 2, and place the composite copper powder into the laser powder feeding bucket.

[0049] Step 5: Adjust the laser spot size to 2.2mm, and adjust the angle between the central axis of the laser head and the plane of the preset working area to 90 degrees to ensure effective coverage of the deposition area.

[0050] Step 6: Adjust the distance between the laser head and the deposition area to 30mm; adjust the laser power to 2.6kw, the powder feeding speed to 200g / min, the steady-state speed to 350mm / min, and then perform surface laser deposition; Step 7: Place the laser-deposited 304 stainless steel workpiece into a vacuum furnace for stress relief treatment at 350 degrees Celsius for 1.5 hours, then allow it to cool naturally.

[0051] Step 8: Perform precision machining on the heat-treated 304 stainless steel workpiece to the dimensions required by the drawing, such as... Figure 3 As shown, a copper alloy-stainless steel composite workpiece is obtained.

[0052] Using the copper alloy-stainless steel composite workpiece obtained in Example 2, a vacuum interrupter was prepared. The welding strength and vacuum leakage rate were tested, and the results are shown in Table 1. The welding strength was 220 MPa, and the vacuum leakage rate was 5.3 × 10⁻⁶. -10 Pa·m 3 / s.

[0053] Example 3 In this embodiment, such as Figure 2 As shown, target stainless steel plate 1 is a 304 stainless steel workpiece.

[0054] Step 1: Spray a 3% hydrochloric acid solution onto the surface of the preset working area of ​​the 304 stainless steel workpiece, and then place the 304 stainless steel workpiece in a ventilated environment at 50°C for 30 minutes to allow the working surface to be corroded and roughened, forming a blackened corrosion layer.

[0055] Step 2: Add graphite powder to copper powder with a particle size of 30-120 micrometers to obtain a mixed powder; the mass content of graphite powder in the mixed powder is 2.0%. Use a ball mill to ball mill the mixed powder and grinding media at a mass ratio of 1:1 for 8 hours. Sieve to remove excess graphite powder to obtain graphite-coated copper powder.

[0056] Step 3: Add Ti powder, Zn powder and Ni powder to the graphite-coated copper powder and mix for 4 hours to obtain composite copper powder; in the composite copper powder, the mass content of Sn powder is 2.5%, the mass content of Ni powder is 4%, and the mass content of Zn powder is 2%.

[0057] Step 4: Install the 304 stainless steel workpiece into the contour cooling fixture 2, and place the composite copper powder into the laser powder feeding bucket.

[0058] Step 5: Adjust the laser spot size to 1.8mm, and adjust the angle between the central axis of the laser head and the plane of the preset working area to 75 degrees, so that metal deposition can occur simultaneously in the preset working area. Figure 2 Metal deposition was also performed on the outer surface shown in the diagram (note) Figure 2 The structure of the middle metal composite layer 3 does not represent the actual deposition thickness and is only a schematic diagram.

[0059] Step 6: Adjust the distance between the laser head and the deposition area to 25mm; adjust the laser power to 2.4kw, the powder feeding speed to 150g / min, the steady-state speed to 320mm / min, and then perform surface laser deposition; Step 7: Place the laser-deposited 304 stainless steel workpiece into a vacuum furnace for stress relief treatment at 300 degrees Celsius for 1.5 hours, then allow it to cool naturally.

[0060] Step 8: Perform precision machining on the heat-treated 304 stainless steel workpiece to the dimensions required by the drawing, such as... Figure 3 As shown, a copper alloy-stainless steel composite workpiece is obtained.

[0061] Using the copper alloy-stainless steel composite workpiece obtained in Example 3, a vacuum interrupter was prepared. The welding strength and vacuum leakage rate were tested, and the results are shown in Table 1. The welding strength was 205 MPa, and the vacuum leakage rate was 6.5 × 10⁻⁶. -10 Pa·m 3 / s.

[0062] Comparative Example Taking the target stainless steel plate 1 in Example 2 as an example, without setting the contour cooling fixture 2, a copper transition ring is welded to the same position on the target stainless steel plate 1 using AgCu28 solder; then, the copper transition ring is connected to the ceramic shell using AgCu28 solder to prepare a vacuum interrupter. The welding strength and vacuum leakage rate of the vacuum interrupter prepared in the comparative example are tested, and the results are shown in Table 1. The welding strength is 190 MPa, and the vacuum leakage rate is 7.2 × 10⁻⁶. -10 Pa·m 3 / s.

[0063] Table 1. Comparison of detection indicators between Examples 1-3 and comparative examples.

[0064] Based on the test results in Table 1, compared with the comparative example using traditional processes, the composite method of dissimilar metal materials provided by this invention, by laser additive manufacturing a 1-5 mm layer of pure copper or copper alloy on a 1-1.5 mm stainless steel surface, can effectively replace the welding process between the copper ring and stainless steel, reducing the use of precious silver-copper solder. Furthermore, it can improve welding strength and reduce the leakage rate of the vacuum interrupter. Thus, the composite method of dissimilar metal materials provided by this invention offers a new method for manufacturing high-performance, low-cost vacuum interrupters, significantly reducing the use of precious silver while improving the mechanical impact resistance and service life of the vacuum interrupter. The copper-stainless steel composite workpiece or copper alloy-stainless steel composite workpiece prepared by this invention can be applied to power switches, heat sinks, electrical materials, etc., and has advantages such as high bonding strength, high production efficiency, cost savings in welding, and simple process.

[0065] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0066] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for compositing heterogeneous metallic materials, characterized in that, Includes the following steps: S1. Obtain the target stainless steel plate and fix it with a contour cooling fixture, wherein the contour cooling fixture exposes the preset working area of ​​the target stainless steel plate; S2. Using laser direct energy deposition (EDD) technology, metal powder is loaded into a powder feeder, and metal composite is applied to the preset working area in an inert atmosphere; wherein, the metal powder is copper powder or composite copper powder containing alloy powder; the distance between the laser head and the preset working area is 10-50 mm, and the ratio of the width of the preset working area to the spot diameter of the laser head is 1:(1.0-1.5). S3. After deposition, the target stainless steel plate is kept at 300-450℃ for 1-3 hours to relieve stress and form a metal composite layer in the preset working area, thus completing the composite of copper and stainless steel or the composite of copper alloy and stainless steel.

2. The composite method for heterogeneous metal materials according to claim 1, characterized in that, The shape-following cooling fixture is complementary to the shape of the target stainless steel plate; The contour cooling fixture has a hollow structure, with a water inlet at one end and a water outlet at the other end.

3. The composite method for heterogeneous metal materials according to claim 2, characterized in that, The copper powder has a particle size of 20-200 micrometers and a flow rate of less than 20 s / 50g; In the composite copper powder, the mass content of the alloy powder is 5-10%; the particle size of the alloy powder is 0.1-200 micrometers.

4. The composite method of heterogeneous metal materials according to claim 3, characterized in that, The alloy powder is at least one of Ni, Sn, Al, Si, Zn, Ti, or Zr.

5. The method for composite materials of heterogeneous metals according to claim 1, characterized in that, It also includes the pretreatment process for copper powder; The pretreatment process includes: adding graphite powder smaller than 800 mesh to copper powder at a mass ratio of 1 to 3% to obtain a mixed powder; A ball mill was used to ball mill the mixed powder and grinding media at a mass ratio of 1:1 for 6 to 8 hours. Then, excess graphite powder was removed by sieving through a sieve with a mesh size of less than 300 to obtain graphite-coated copper powder.

6. The method for composite materials of heterogeneous metals according to claim 1, characterized in that, The target stainless steel plate is a pre-treated stainless steel plate; the pretreatment includes: A hydrochloric acid solution with a volume concentration of 3-4% is obtained and sprayed onto the predetermined working area of ​​the target stainless steel plate. Non-predetermined working areas are covered with a tetrafluoroethylene film. Place the stainless steel plate at a temperature of 20-50℃ for 20-30 minutes, clean the preset working area, and obtain the pre-treated stainless steel plate.

7. The method for composite materials of heterogeneous metals according to any one of claims 1-6, characterized in that, The thickness of the preset working area of ​​the target stainless steel plate is 1 to 1.5 mm.

8. The method for composite materials of heterogeneous metals according to claim 1, characterized in that, In step S2, the laser direct energy deposition process has a laser power of 1-4 kW, a powder feeding speed of 100-300 g / min, and a scanning speed of 200-600 mm / min.

9. The method for composite materials of heterogeneous metals according to claim 1, characterized in that, The angle between the central axis of the laser head and the plane of the preset working area is 45° to 90°.

10. The method for composite materials of heterogeneous metals according to claim 1, characterized in that, The thickness of the metal composite layer is 1–5 mm; The metal composite layer comprises at least one deposited metal layer, the thickness of which is 0.5 to 1.0 mm.

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