Method for preparing gradient transition copper / steel composite layer through diffusion melting method

Abstract

A method for preparing a gradient transition copper / steel composite layer through a diffusion melting method comprises the steps that the surface of a forged 42CrMoA stainless steel base material is treated and then heated, then a transition layer and a copper alloy layer are prepared on the surface of the forged 42CrMoA stainless steel through a laser fuse technology, nickel elements are transited to the surface layer of the copper / steel composite layer in a gradient mode through laser melting diffusion, and the gradient transition copper / steel composite layer is obtained. The problems that pores and cracks exist in a copper-steel composite copper alloy layer, metallurgical bonding is difficult, the material utilization rate is low, the production cost is high and the like are solved, the prepared copper-steel composite material has excellent mechanical performance, and meanwhile the surface layer components of the alloy layer meet the requirement of CuSn12Ni2.

Description

Technical Field

[0001] The present invention relates to the technical field of metal additive manufacturing, and particularly to a method for preparing a gradient transition copper / steel composite layer by a diffusion melting method. The method uses ENiCu-7 as a transition layer and CuSn12 as a cladding layer to finally obtain a copper-steel composite layer with a composition of CuSn12Ni2. Background Art

[0002] As a bearing material, tin bronze CuSn12Ni2 usually needs to be compounded with a steel substrate to form a tin bronze / steel bimetallic composite material in order to combine the advantageous properties of both. Its main chemical components are: Cu 84% - 87%, Sn 11% - 13%, Ni 1.5% - 2.5%. The material of CuSn12Ni2 has good electrical conductivity, plasticity and thermal conductivity, and also has good machining and mechanical properties. Tin can dissolve in the copper matrix to form α-solid solution and δ-phase (Cu 79 Sn 19 Ni2). The α-solid solution has a face-centered cubic structure and is the main constituent phase in tin bronze. The δ-phase has a complex cubic structure, is hard and brittle. These two phases improve the strength, hardness and corrosion resistance of the alloy. The addition of nickel can enhance the strength, wear resistance and plasticity of the alloy, and at the same time, Ni can also reduce the stress corrosion sensitivity of copper alloys. Based on the above characteristics, tin bronze CuSn12Ni2 is widely used in layered metal composite structures including bearings, washers, bushings, main shaft bearings, machine tool bearings, crane bearings, sliding bearings for wind power gearboxes, thrust bearings, etc. However, the production and processing of tin bronze CuSn12Ni2 alloy powder still face some challenges. The preparation cost of the powder is relatively high, the control of the fluidity and uniformity of the powder is relatively complex, and currently there is only European standard tin bronze CuSn12Ni2 powder on the market and no wire of this grade.

[0003] With the development of material preparation technologies and equipment, in recent years, researchers have developed many advanced preparation processes for laminated metal composite materials, including arc spraying, cold spraying, high-velocity oxy-fuel spraying, plasma surfacing, laser cladding, etc. The composite layers prepared by arc spraying and high-velocity oxy-fuel spraying technologies have defects such as oxidation, pores, and unmelted particles. Although the cold spraying process overcomes the problems of oxidation and thermal deformation brought by traditional thermal deposition processes, the coating and the substrate do not achieve metallurgical bonding and the coating has a certain porosity. Although the laser powder melting process has many advantages such as metallurgical bonding of the cladding layer, controllable thickness, fine grains, small heat input, small heat affected zone, and high efficiency, the preparation process of the alloy powder used in laser cladding is relatively complex, and impurities are easily introduced during the preparation process, resulting in defects such as pores and cracks in the subsequent preparation process of laminated composite materials. At the same time, during the laser cladding process, metal powder may be wasted due to flying and incomplete melting, resulting in low material utilization rate. In actual production, the treatment and recycling of metal powder are more complex than those of metal wire. The flying powder may pollute the working environment and requires a better dust control and recycling system. On the other hand, the powder used in laser cladding has high quality requirements, which significantly increases the production cost. Compared with laser wire melting, laser powder melting has higher requirements for laser equipment, and the powder feeding speed and laser parameters need to be precisely controlled to ensure the quality of the cladding layer. The paper "Understanding the formation of laser-induced melt pools with both wire and powder feeding in directed energy deposition" proposes that the characteristics of the powder such as particle size distribution and fluidity have a significant impact on the formation and deposition quality of the melt pool, and these characteristics require more precise equipment control and detection. In addition, the high reflectivity and low absorptivity of the powder also increase the difficulty of process development. Summary of the Invention

[0004] In order to overcome the defects of the above-mentioned prior art, the purpose of the present invention is to provide a method for preparing a gradient-transition copper / steel composite layer by diffusion melting. A transition layer and a copper alloy layer are prepared on the surface of forged 42CrMoA stainless steel by laser wire melting technology, and nickel elements are gradient-transferred to the surface layer of the copper-steel composite layer by laser melting diffusion, solving the problems of pores, cracks, difficult metallurgical bonding, low material utilization rate, high production cost, etc. in the copper-steel composite copper alloy layer. The prepared copper-steel composite material has excellent mechanical properties, and at the same time, the composition of the surface layer of the alloy layer meets the requirements of tin bronze CuSn12Ni2.

[0005] In order to achieve the above purpose, the technical solution of the present invention is as follows:

[0006] A method for preparing a gradient-transition copper / steel composite layer by diffusion melting, comprising the following steps:

[0007] Step 1: Treat the surface of the forged 42CrMoA stainless steel substrate to ensure that the substrate surface is free of rust, iron filings and oil.

[0008] Step 2: Preheat the substrate

[0009] Wrap the substrate for preheating and stop heating when the surface temperature of the substrate rises to 150 - 200 °C.

[0010] Step 3: Laser cladding of the transition layer

[0011] Perform laser cladding of the transition layer on the surface of the forged 42CrMoA stainless steel substrate. The welding wire grade used for the transition layer laser cladding is ENiCu-7, and the process parameters are: laser power: 3000 - 3200 W; scanning speed: 8 - 10 mm / s; wire feeding speed: 6 m / min; overlap rate: 2.0 - 3.5 mm; shielding gas: 99.99% pure argon, flow rate 15 - 25 L / min, cladding thickness is 2.0 - 2.5 mm. After cladding, thoroughly clean the oxide layer on the surface of the cladding layer and then clean the dust.

[0012] Step 4: Laser cladding of the first layer of copper alloy

[0013] Perform the first layer of copper alloy laser cladding on the surface of the final cladding layer in Step 3. The welding wire grade used for the copper alloy layer laser cladding is CuSn12, laser power: 3500 - 4000 W, scanning speed: 8 - 10 mm / s, wire feeding speed: 6 - 8 m / min, overlap rate: 2.0 - 3.5 mm, shielding gas: 99.99% pure argon, flow rate 15 - 25 L / min; cladding thickness is 2.0 - 2.5 mm. After cladding, clean the oxide layer on the surface of the cladding layer.

[0014] Step 5: Laser cladding of the second layer of copper alloy

[0015] Perform the second layer of copper alloy laser cladding on the surface of the final cladding layer in Step 4. The welding wire grade for the second layer of copper alloy is CuSn12, laser power 4000 - 4500 W, scanning speed: 10 - 12 mm / s, wire feeding speed: 8 - 10 m / min, overlap rate: 2.0 - 3.5 mm, shielding gas: 99.99% pure argon, flow rate 15 - 25 L / min. After cladding, clean the oxide layer on the surface of the cladding layer to obtain a copper / steel composite layer.

[0016] For the copper / steel composite layer obtained, after finish machining, perform penetrant inspection on the surface of its alloy layer, and perform ultrasonic non-destructive testing on the bonding surface between the copper alloy layer and the substrate after cladding.

[0017] The diameter of the welding wire is 1.2 mm.

[0018] A gradient transition copper / steel composite layer is obtained by the above method.

[0019] Compared with the prior art, the advantages of the present invention are as follows:

[0020] (1) By strictly controlling the laser power, the present invention uses ENiCu-7 as the transition layer to achieve the gradient transition effect of nickel element in the composite layer, and CuSn12 as the cladding layer, and finally obtains the target of the CuSn12Ni2 cladding layer with the composition, solving the problems of pores, cracks and difficult metallurgical bonding in the copper-steel composite copper alloy layer.

[0021] (2) The welding wires used in the present invention are all commercial welding wires. Compared with the laser powder melting (CuSn12Ni2 powder laser cladding) process, the material utilization rate is high and the material cost is low, greatly reducing the production cost.

[0022] (3) After the copper alloy layer fails in the present invention, the failed copper alloy layer can be machined off and remelted, so as to realize remanufacturing, which helps to extend the service life of parts and reduce the maintenance cost.

[0023] In summary, the present invention uses laser wire diffusion melting to prepare the CuSn12Ni2 / steel composite layer, which not only saves costs, but also avoids environmental pollution and waste of raw materials, has good economic benefits, solves the problems of pores, cracks, etc. existing in the existing process, the density of the alloy layer is greater than or equal to 99.8%, the shear strength of the alloy layer reaches 450 MPa, far exceeding the industry standard requirement of 230 MPa, realizes the metallurgical bonding between the tin bronze and the steel substrate, and this bonding method has a very high bonding strength, reaching 600 MPa, further improving the performance of the copper-steel composite layer. Description of the Drawings

[0024] Figure 1 It is the metallographic structure diagram of the copper alloy layer of Example 1 under 500 times magnification.

[0025] Figure 2 It is the microscopic structure diagram of the molten pool of the copper alloy layer of Example 2. Detailed Embodiments

[0026] Example 1

[0027] This example includes the following steps:

[0028] The first step: surface treatment of the forging 42CrMoA substrate to ensure that the substrate surface is free of rust, iron filings and oil.

[0029] Use a 42CrMoA substrate with a diameter of 150 mm. First, use a brush and compressed air to remove surface rust and iron filings impurities. Subsequently, use a cotton cloth dipped in acetone, alcohol or cleaning agent to wipe and remove the oil stain on the surface of the substrate to be processed, ensuring that the surface of the substrate is free of rust, iron filings and oil stains.

[0030] Step 2: Preheat the substrate

[0031] Use an LCD crawler ceramic heater to wrap the substrate for preheating. During the preheating process, use a temperature measuring gun to detect the temperature of the substrate. Stop heating when the surface temperature of the substrate rises to 150 °C.

[0032] Step 3: Laser cladding of the transition layer

[0033] Perform laser cladding of the transition layer on the surface of the forged 42CrMoA stainless steel substrate; the welding wire grade for laser cladding of the transition layer is ENiCu-7, the wire diameter is 1.2 mm, adjust the laser power to 3000 W, scanning speed: 8 mm / s, wire feeding speed: 6 m / min, overlap rate: 2.0 mm, shielding gas: 99.99% pure argon, flow rate 15 L / min. Use these process parameters to perform laser cladding of ENiCu-7 on the surface of the substrate. After cladding, use a brush to thoroughly clean the oxide layer on the surface of the cladding layer and then use compressed air to clean the dust. The cladding thickness of the transition layer is 2.0 mm.

[0034] Step 4: Laser cladding of the first layer of copper alloy

[0035] Perform laser cladding of the first layer of copper alloy on the surface of the final cladding layer in Step 3; the welding wire grade for laser cladding of the copper alloy layer is CuSn12, the wire diameter is 1.2 mm, adjust the laser power to 3500 W, scanning speed: 8 mm / s, wire feeding speed: 6 m / min, overlap rate: 2.0 mm, shielding gas: 99.99% pure argon, flow rate 15 L / min. Use these process parameters to perform laser cladding of CuSn12 on the surface of the transition layer. After cladding, use a brush to thoroughly clean the oxide layer on the surface of the cladding layer and then use compressed air to clean the dust. After measurement, the cladding thickness of the first layer of copper alloy layer is 2.2 mm.

[0036] Step 5: Laser cladding of the second layer of copper alloy

[0037] A second layer of copper alloy laser cladding is performed on the surface of the final cladding layer in step four; the welding wire brand used is CuSn12, the welding wire diameter is 1.2mm, the laser power is adjusted to 4000W, the scanning speed is 10mm / s, the wire feeding speed is 8m / min, and the overlap rate is 2.0mm; the shielding gas is 99.99% pure argon, and the flow rate is 15L / min. The process parameters are used to continue the copper alloy layer CuSn12 laser cladding on the surface of the first copper alloy cladding layer. After cladding, the surface oxide layer of the cladding layer is thoroughly cleaned with a plate brush, and then the dust is cleaned with compressed air to obtain a copper / steel composite layer; the cladding thickness of the second copper alloy layer is measured to be 2.3mm.

[0038] The copper / steel composite layer is not allowed to have defects such as pores, cracks, sand holes, cold shuts, shrinkage, scratches and pieces of needle-shaped small holes on the surface of the alloy layer after fine processing. The surface of the copper alloy layer after fine processing is subjected to penetrant flaw detection, and the bonding surface of the copper alloy layer with the substrate after cladding is subjected to ultrasonic non-destructive testing.

[0039] Figure 1 The metallographic structure of the copper alloy layer of Example 1 is 500 times smaller, the alloy layer has a grain size of 8 to 9, the alloy layer has a density greater than or equal to 99.8%, and the second phase (Cu 79 Sn 19 Ni2) precipitates along the grain boundaries in long strips and plays a role in grain boundary strengthening. The shear strength of the copper alloy layer obtained in this embodiment is greater than 435MPa, the bonding strength between the copper alloy layer and the transition layer is about 570MPa, the tensile strength of the copper alloy layer is greater than 480MPa, and the chemical composition of the surface copper alloy layer meets the requirements of CuSn12Ni2.

[0040] Example 2

[0041] This embodiment includes the following steps:

[0042] Step 1: Surface treatment of forged 42CrMoA substrate to ensure that the substrate surface is free of rust, iron filings and oil stains.

[0043] Use a 42CrMoA substrate with a diameter of 150mm, use a scrub brush and compressed air to remove surface rust and impurities such as iron filings, then use a cotton cloth dipped in acetone, alcohol or detergent to wipe and remove oil stains on the surface of the substrate to be processed.

[0044] Step 2: Preheating the substrate

[0045] Use LCD crawler ceramic heater to wrap the substrate for preheating. Use temperature measuring gun to detect the temperature of the substrate during preheating. When the surface temperature of the substrate rises to 200℃, stop heating.

[0046] Step 3: Transition layer laser cladding

[0047] The transition layer was laser clad on the surface of the forged 42CrMoA stainless steel substrate; the welding wire used for the transition layer laser cladding was ENiCu-7, and the wire diameter was 1.2mm; the laser power was adjusted to 3200W, the scanning speed was 10mm / s, the wire feeding speed was 6m / min, the overlap rate was 3.0mm, the shielding gas was 99.99% pure argon, and the flow rate was 20L / min. The process parameters were used to perform ENiCu-7 laser cladding on the substrate surface. After cladding, the oxide layer on the surface of the cladding layer was thoroughly cleaned with a brush and then the dust was cleaned with compressed air. The thickness of the transition layer cladding was about 2.3mm.

[0048] Step 4: First layer of copper alloy laser cladding

[0049] The first layer of copper alloy laser cladding is performed on the surface of the final cladding layer in step three; the welding wire brand used for laser cladding of the copper alloy layer is CuSn12, the welding wire diameter is 1.2mm, the laser power is adjusted to 4000W, the scanning speed is 10mm / s, the wire feeding speed is 6m / min, the overlap rate is 3.0mm, the shielding gas is 99.99% pure argon, the flow rate is 20L / min, and the process parameters are used to perform CuSn12 laser cladding of the copper alloy layer on the surface of the transition layer. After cladding, the oxide layer on the surface of the cladding layer is thoroughly cleaned with a plate brush and then the dust is cleaned with compressed air. It is measured that the cladding thickness of the second copper alloy layer is about 2.5mm.

[0050] Step 5: Second layer of copper alloy laser cladding

[0051] A second layer of copper alloy laser cladding is performed on the surface of the final cladding layer in step 4; the welding wire brand used is CuSn12, the welding wire diameter is 1.2mm, the laser power is adjusted to 4500W, the scanning speed is 12mm / s, the wire feeding speed is 10m / min, and the overlap rate is 3.0mm; the shielding gas is 99.99% pure argon, and the flow rate is 20L / min. The process parameters are used to continue the copper alloy layer CuSn12 laser cladding on the surface of the first copper alloy cladding layer. After cladding, the surface oxide layer of the cladding layer is thoroughly cleaned with a plate brush, and then the dust is cleaned with compressed air to obtain a copper / steel composite layer; the cladding thickness of the second copper alloy layer is measured to be 2.4mm.

[0052] The copper / steel composite layer is not allowed to have defects such as pores, cracks, sand holes, cold shuts, shrinkage, scratches and pieces of needle-shaped small holes on the surface of the alloy layer after fine processing. The surface of the copper alloy layer after fine processing is subjected to penetrant flaw detection, and the bonding surface of the copper alloy layer with the substrate after cladding is subjected to ultrasonic non-destructive testing.

[0053] Figure 2For the microstructure of the copper alloy layer in Example 2, the melt pool parameters are as follows: the melt depth is 0.75 mm, the melt width is 4.3 mm, the reinforcement height is 1.7 mm, and the travel distance is 4.3 mm. The grain size of the obtained alloy layer is 8 - 9 grades, and the density of the alloy layer is greater than or equal to 99.8%. The content of nickel element melted and diffused from the transition layer to the first-layer copper alloy layer is 5% - 6%, and the content of nickel element melted and diffused from the transition layer to the second-layer copper alloy layer is 1.5% - 2.5%, meeting the component requirements of European standard CuSn12Ni2. The copper alloy layer obtained in this example has the best performance in all aspects, with a shear strength greater than 450 MPa, the bonding strength between the copper alloy layer and the transition layer is about 600 MPa, and the tensile strength of the copper alloy layer is greater than 500 MPa.

[0054] Example 3

[0055] This example includes the following steps:

[0056] First step: Surface treatment of the forged 42CrMoA substrate to ensure that the substrate surface is free of rust, iron filings, and oil stains.

[0057] Use a 42CrMoA substrate with a diameter of 180 mm. First, use a wire brush and compressed air to remove surface rust and iron filings impurities, and then use a cotton cloth dipped in acetone, alcohol, or cleaning agent to wipe and remove the oil stains on the surface of the substrate to be processed, ensuring that the substrate surface is free of rust, iron filings, and oil stains.

[0058] Second step: Substrate preheating

[0059] Use an LCD crawler ceramic heater to wrap the substrate for preheating. During the preheating process, use a temperature measuring gun to detect the temperature of the substrate, and stop heating when the surface temperature of the substrate rises to 150 °C.

[0060] Third step: Laser cladding of the transition layer

[0061] Laser cladding of the transition layer on the surface of the forged 42CrMoA stainless steel substrate; the welding wire grade used for laser cladding of the transition layer is ENiCu - 7, the wire diameter is 1.2 mm, adjust the laser power to 3100 W, the scanning speed: 9 mm / s, the wire feeding speed: 6 m / min, the overlap rate: 3.0 mm, the shielding gas: 99.99% pure argon, the flow rate is 20 L / min. Use these process parameters to perform laser cladding of ENiCu - 7 on the substrate surface. After cladding, use a wire brush to thoroughly clean the oxide layer on the surface of the cladding layer, and then use compressed air to clean the dust. The cladding thickness of the transition layer is 2.2 mm.

[0062] Fourth step: Laser cladding of the first-layer copper alloy

[0063] The first layer of copper alloy laser cladding is performed on the surface of the final cladding layer in step three; the welding wire brand used for laser cladding of the copper alloy layer is CuSn12, the welding wire diameter is 1.2mm, the laser power is adjusted to 3800W, the scanning speed is 9mm / s, the wire feeding speed is 7m / min, the overlap rate is 2.5mm, the shielding gas is 99.99% pure argon, the flow rate is 22L / min, and the process parameters are used to perform CuSn12 laser cladding of the copper alloy layer on the surface of the transition layer. After cladding, the oxide layer on the surface of the cladding layer is thoroughly cleaned with a plate brush and then the dust is cleaned with compressed air. The cladding thickness of the first copper alloy layer is measured to be 2.6mm.

[0064] Step 5: Second layer of copper alloy laser cladding

[0065] A second layer of copper alloy laser cladding is performed on the surface of the final cladding layer in step four; the welding wire brand used is CuSn12, the welding wire diameter is 1.2mm, the laser power is adjusted to 4500W, the scanning speed is 11mm / s, the wire feeding speed is 9m / min, and the overlap rate is 3.0mm; the shielding gas is 99.99% pure argon, and the flow rate is 21L / min. The process parameters are used to continue the copper alloy layer CuSn12 laser cladding on the surface of the first copper alloy cladding layer. After cladding, the surface oxide layer of the cladding layer is thoroughly cleaned with a plate brush, and then the dust is cleaned with compressed air to obtain a copper / steel composite layer; the cladding thickness of the second copper alloy layer is measured to be 2.2mm.

[0066] The copper / steel composite layer is not allowed to have defects such as pores, cracks, sand holes, cold shuts, shrinkage, scratches and pieces of needle-shaped small holes on the surface of the alloy layer after fine processing. The surface of the copper alloy layer after fine processing is subjected to penetrant flaw detection, and the bonding surface of the copper alloy layer with the substrate after cladding is subjected to ultrasonic non-destructive testing.

[0067] The grain size of the alloy layer obtained in Example 3 is 8 to 9, the density of the alloy layer is greater than or equal to 99.8%, the chemical composition of the surface copper alloy layer meets the European standard CuSn12Ni2 requirements, the shear strength of the copper alloy layer obtained in this example is greater than 440MPa, the bonding strength between the copper alloy layer and the transition layer is about 590MPa, and the tensile strength of the copper alloy layer is greater than 485MPa.

Claims

1. A method for preparing a gradient-transition copper / steel composite layer by diffusion melting method, characterized in that, It includes the following steps: Step 1: Treat the surface of the forged 42CrMoA stainless steel substrate to ensure that there is no rust, iron filings, or oil on the substrate surface; Step 2: Preheat the substrate Wrap the substrate for preheating and stop heating when the surface temperature of the substrate rises to 150 - 200 °C; Step 3: Laser cladding of the transition layer Perform laser cladding of the transition layer on the surface of the forged 42CrMoA stainless steel substrate; the welding wire grade used for laser cladding of the transition layer is ENiCu - 7, and the process parameters are: laser power: 3000 - 3200 W; scanning speed: 8 - 10 mm / s; wire feeding speed: 6 m / min; overlap rate: 2.0 - 3.5 mm; shielding gas: 99.99% pure argon, flow rate 15 - 25 L / min, cladding thickness is 2.0 - 2.5 mm. After cladding, thoroughly clean the oxide layer on the surface of the cladding layer and then clean the dust; Step 4: Laser cladding of the first layer of copper alloy Perform laser cladding of the first layer of copper alloy on the surface of the final cladding layer in Step 3; the welding wire grade used for laser cladding of the copper alloy layer is CuSn12, laser power: 3500 - 4000 W, scanning speed: 8 - 10 mm / s, wire feeding speed: 6 - 8 m / min, overlap rate: 2.0 - 3.5 mm, shielding gas: 99.99% pure argon, flow rate 15 - 25 L / min; cladding thickness is 2.0 - 2.5 mm. After cladding, clean the oxide layer on the surface of the cladding layer; Step 5: Laser cladding of the second layer of copper alloy Perform laser cladding of the second layer of copper alloy on the surface of the final cladding layer in Step 4; the welding wire grade for the second layer of copper alloy is CuSn12, laser power 4000 - 4500 W, scanning speed: 10 - 12 mm / s, wire feeding speed: 8 - 10 m / min, overlap rate: 2.0 - 3.5 mm, shielding gas: 99.99% pure argon, flow rate 15 - 25 L / min. After cladding, clean the oxide layer on the surface of the cladding layer to obtain a copper / steel composite layer.

2. A method for preparing a gradient transition copper / steel composite layer by diffusion melting according to claim 1, wherein For the copper / steel composite layer, after finish machining, perform penetrant inspection on the surface of its alloy layer, and perform ultrasonic non - destructive testing on the bonding surface between the copper alloy layer and the substrate after cladding.

3. A method for preparing a gradient transition copper / steel composite layer by diffusion melting according to claim 1, characterized in that, The diameter of the welding wire is 1.2 mm.

4. A method for preparing a gradient-transition copper / steel composite layer by a diffusion melting method according to claim 1, characterized in that, It includes the following steps: Step 1: Treat the surface of the forged 42CrMoA stainless steel substrate to ensure that there is no rust, iron filings, or oil on the substrate surface; Step 2: Preheat the substrate Wrap the substrate for preheating and stop heating when the surface temperature of the substrate rises to 200 °C; Step 3: Laser cladding of the transition layer Laser cladding of the transition layer on the surface of the as-forged 42CrMoA stainless steel substrate; the welding wire grade for the transition layer laser cladding is ENiCu-7, and the wire diameter is 1.2 mm; adjust the laser power to 3200 W, scanning speed: 10 mm / s, wire feeding speed: 6 m / min, overlap rate: 3.0 mm, shielding gas: 99.99% pure argon, flow rate 20 L / min, and use these process parameters to perform ENiCu-7 laser cladding of the transition layer on the substrate surface. After cladding, thoroughly clean the oxide layer on the surface of the cladding layer with a brush and then clean the dust with compressed air. The cladding thickness of the transition layer is 2.3 mm; Step 4: Laser cladding of the first layer of copper alloy Perform laser cladding of the first layer of copper alloy on the surface of the final cladding layer in Step 3; the welding wire grade for the copper alloy layer laser cladding is CuSn12, and the wire diameter is 1.2 mm. Adjust the laser power to 4000 W, scanning speed: 10 mm / s, wire feeding speed: 6 m / min, overlap rate: 3.0 mm, shielding gas: 99.99% pure argon, flow rate 20 L / min, and use these process parameters to perform CuSn12 laser cladding of the copper alloy layer on the surface of the transition layer. After cladding, thoroughly clean the oxide layer on the surface of the cladding layer with a brush and then clean the dust with compressed air. After measurement, the cladding thickness of the second copper alloy layer is 2.5 mm; Step 5: Laser cladding of the second layer of copper alloy Perform laser cladding of the second layer of copper alloy on the surface of the final cladding layer in Step 4; the welding wire grade used is CuSn12, and the wire diameter is 1.2 mm. Adjust the laser power to 4500 W, scanning speed: 12 mm / s, wire feeding speed: 10 m / min, overlap rate: 3.0 mm; shielding gas: 99.99% pure argon, flow rate 20 L / min, and use these process parameters to continue performing CuSn12 laser cladding of the copper alloy layer on the surface of the first-layer copper alloy cladding layer. After cladding, thoroughly clean the oxide layer on the surface of the cladding layer with a brush and then clean the dust with compressed air. After measurement, the cladding thickness of the second copper alloy layer is 2.4 mm; obtain a copper / steel composite layer.

5. A gradient transition copper / steel composite layer, characterized in that, Obtained by any one of the methods according to the above claims 1-4.

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