Copper-steel bimetallic material and preparation method thereof

Abstract

The invention discloses a copper-steel bimetallic material and a preparation method thereof, and relates to the technical field of copper-steel bimetallic products. The method specifically comprises the following steps that a, a steel matrix is prepared, specifically, steel is machined into the steel matrix; b) preparing a copper alloy pressed blank: performing compression molding on copper-based powder through a powder metallurgy process to obtain the copper alloy pressed blank; c) assembling: placing the copper alloy pressed compact on a steel substrate to form a to-be-welded compact; and d) diffusion welding: placing the to-be-welded compact on a lower electrode of diffusion welding equipment, controlling an upper electrode of the diffusion welding equipment to extrude the to-be-welded compact and electrify the to-be-welded compact, monitoring the displacement of the upper electrode when the upper electrode pressurizes and heats the to-be-welded compact through the compact, and cutting off the current when the displacement meets a preset condition to finish welding. The invention aims to improve the production process of the existing copper-steel bimetallic material and reduce the processing cost.

Description

Technical Field

[0001] The present invention relates to the technical field of copper-steel bimetallic products, and particularly relates to a copper-steel bimetallic material and a preparation method thereof. Background Art

[0002] Copper-steel bimetallic materials refer to composite materials with a steel layer as the matrix and a copper alloy layer as the surface or working layer. The matrix layer of such materials is made of steel, having high hardness and strength, while the surface layer or working layer uses copper alloy, having good tribological properties. Due to their unique properties, copper-steel bimetallic materials have been widely used in multiple industrial fields. For example, they are used to manufacture high-performance mechanical components, automotive parts, electronic components, etc.

[0003] Currently, the diffusion welding process is one of the common methods for preparing copper-steel bimetallic materials. The diffusion welding process enables the atomic diffusion of the copper alloy layer and the steel matrix material at high temperature, thereby achieving good bonding of the two materials. This process has advantages such as low production cost and simple operation, and is particularly suitable for mass production of copper-steel bimetallic composites. In the patent application document CN202311658934.X, a method for preparing copper-steel bimetallic materials using the diffusion welding process is disclosed. In the embodiment, the material grade of the copper alloy layer used is CuSn10Pb10. When making plates with CuSn10Pb10 copper alloy, the finished product rate is low, and the unit price of the plates is about 50% higher than that of the bars. In order to reduce costs, bars are usually purchased during production, and then the bars are formed by sawing or wire cutting, and further grinding is carried out according to needs. Since copper alloy does not have magnetism and it is difficult to fix the workpiece through traditional magnetic devices, in the processing of copper alloy, relatively complex fixing and clamping devices are often required, which not only increases the processing difficulty but also greatly reduces the production efficiency.

[0004] Therefore, how to improve the existing production process of copper-steel bimetallic materials and reduce the processing cost has become an urgent technical problem to be solved. Summary of the Invention

[0005] The main object of the present invention is to provide a copper-steel bimetallic material and a preparation method thereof, aiming to improve the existing production process of copper-steel bimetallic materials and reduce the processing cost.

[0006] To achieve the above object, the present invention provides a preparation method of a copper-steel bimetallic material, including the following steps: a) Steel matrix preparation: Processing steel into a steel matrix; b) Copper alloy green compact preparation: Compacting and molding using copper-based powder through powder metallurgy process to obtain a copper alloy pressed green compact; c) Assembly: Placing the copper alloy pressed green compact on the steel matrix to form a green compact to be welded; d) Diffusion welding: Place the green compact to be welded on the lower electrode of the diffusion welding equipment, control the upper electrode of the diffusion welding equipment to extrude the green compact to be welded and apply electricity, monitor the displacement of the upper electrode on the green compact during pressurization and heating of the green compact to be welded, and cut off the current when the displacement meets the preset conditions to complete the welding.

[0007] In an embodiment of the present application, after processing the steel into a steel matrix, the following steps are further included: By turning or milling, a groove is machined on the surface of the steel matrix that contacts the copper alloy green compact. The depth of the groove is the first depth, and the thickness of the groove edge is the first thickness; define the first depth as A, where 3 mm ≥ A ≥ 1 mm; define the first thickness as B, where 1.5 mm ≥ B ≥ 0.5 mm.

[0008] In an embodiment of the present application, the difference between the height of the copper alloy green compact and the depth of the groove is C, where 1 mm ≥ C ≥ 0 mm.

[0009] In an embodiment of the present application, zinc stearate is added as a release lubricant to the copper-based powder, and the content of zinc stearate is D, where 1.5% ≥ C ≥ 0.5%.

[0010] In an embodiment of the present application, the content of zinc stearate is 0.7%.

[0011] In an embodiment of the present application, the copper-based powder is non-spherical powder.

[0012] The present application also discloses a copper-steel bimetallic material prepared according to the method described in any one of the above, including a steel matrix and a copper alloy layer. The copper alloy layer is bonded to the steel matrix by diffusion welding, and the interfacial shear strength is P, where 150 MPa ≥ P ≥ 100 MPa.

[0013] In an embodiment of the present application, the thickness of the copper alloy layer is E, where 4 mm ≥ E ≥ 1 mm.

[0014] With the above technical solution, after the steel substrate is processed with grooves, it can effectively restrict the displacement of the copper alloy pressed green compact, avoiding excessive deformation during the welding process; the copper alloy pressed green compact is formed by powder metallurgy pressing, with a short preparation cycle, high production efficiency, enabling mass production, and the production volume per minute can reach 10 to 25; the material utilization rate is increased to more than 95%, significantly reducing the production cost; during the diffusion welding process, the welding quality is controlled in real time by the displacement of the upper electrode, avoiding the inaccurate temperature measurement caused by the change of the radiation rate when using an infrared thermometer in the traditional diffusion welding process, improving the stability of the welding process and the welding quality; the obtained copper-steel bimetallic material has a dense bonding interface, no inclusions, and firm welding, and the welding shear strength can stably reach more than 100 MPa, meeting the shear strength requirements specified in the national standard GB 13238-91 "Copper-Steel Composite Steel Plate", and the comprehensive performance is significantly improved, being suitable for industrial mass production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will be described in detail below with specific embodiments and drawings, where: Figure 1 is a schematic structural diagram of the first embodiment of the present invention; Figure 2 is a scanning electron microscope photograph of the product prepared in the first embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be described in detail below with reference to the drawings and embodiments. It should be understood that the following specific embodiments are only used to explain the present invention and do not limit the present invention.

[0017] As Figure 1 shown, in order to achieve the above purpose, the present invention provides a method for preparing a copper-steel bimetallic material, including the following steps: a) Preparation of the steel substrate: Processing the steel into a steel substrate; b) Preparation of the copper alloy green compact: Using copper-based powder to be formed by powder metallurgy pressing to obtain a copper alloy pressed green compact; c) Assembly: Placing the copper alloy pressed green compact on the steel substrate to form a green compact to be welded; d) Diffusion welding: Placing the green compact to be welded on the lower electrode of the diffusion welding equipment, controlling the upper electrode of the diffusion welding equipment to extrude the green compact to be welded and energize, monitoring the displacement of the upper electrode on the green compact to be welded during pressure application and heating, and disconnecting the current when the displacement meets the preset conditions to complete the welding.

[0018] Specifically, for step a) preparation of the steel substrate: Low-carbon steel, medium-carbon steel or alloy steel is selected as the raw material for the steel. The specific grade of the steel is preferably 45 steel, and the thickness of the steel is preferably 2 mm to 20 mm, which can be specifically determined according to the actual product requirements. The steel is processed by mechanical processing equipment such as a lathe or a milling machine. During processing, the steel is processed into a steel substrate with the required shape, and the specific shape can be circular, rectangular or other special shapes. To make the copper alloy layer after welding more firmly bonded to the steel substrate, grooves can be processed on the steel substrate. The depth of the grooves is preferably 1 mm to 3 mm, and the thickness of the groove edge is 0.5 mm to 1.5 mm. Keep the inside of the grooves free of rust and oil.

[0019] For step b) preparation of the copper alloy green compact: Pure copper powder or copper-based alloy powder is selected as the raw material. The specific composition of the copper-based alloy powder can be selected according to actual needs. For example, it can be CuSn10Pb10 copper alloy powder, electrolytic copper powder, CuSn8 or other copper alloy powders. To improve the pressing performance, zinc stearate is added to the copper-based powder as a mold release agent. The addition amount of zinc stearate is preferably 0.5% to 1.5% of the total weight of the copper-based powder, and the optimal addition amount is 0.7%. After the copper-based powder and zinc stearate are mixed evenly, powder metallurgy pressing equipment is used for pressing and forming. Specifically, the copper-based powder is loaded into a mold and pressed at a pressing pressure of 400 MPa to 800 MPa for 10 seconds to 30 seconds to obtain a copper alloy pressed green compact with the required shape. The difference between the height of the copper alloy pressed green compact and the depth of the grooves processed on the steel substrate is 0 mm to 1 mm, and the shape of the copper alloy pressed green compact is the same as the shape of the grooves on the steel substrate to achieve the best assembly effect. After the copper alloy pressed green compact is pressed, it can be directly used for welding without sintering.

[0020] For step c) assembly: The copper alloy pressed green compact is placed on the surface-treated steel substrate. Specifically, the copper alloy pressed green compact is accurately placed inside the grooves of the steel substrate to form a green compact to be welded. During the assembly process, no solder paste or other auxiliary welding materials are required, and no copper plating treatment is required on the surface of the steel substrate. It can be directly welded in the air. Ensure that the copper alloy pressed green compact is in close contact with the grooves of the steel substrate without obvious gaps to obtain an ideal welding effect.

[0021] Step d) Diffusion welding: Place the green compact to be welded on the lower electrode of the diffusion welding equipment. The diffusion welding equipment includes an upper electrode, a lower electrode, a hydraulic cylinder or a pneumatic cylinder, a displacement monitoring device, and a current control device. At the beginning of welding, drive the upper electrode to move downward through the pneumatic cylinder or the hydraulic cylinder to apply pressure to the green compact to be welded. At the same time, pass a direct current or an alternating current through the upper and lower electrodes to heat the green compact to be welded. During the welding process, monitor the displacement of the upper electrode after applying pressure and heating to the green compact to be welded through the displacement monitoring device. The monitoring of the displacement is realized by a grating ruler or a laser displacement sensor. The preset condition is that the displacement of the upper electrode reaches 0.02 mm to 0.2 mm, and the optimal displacement is 0.1 mm. When it is monitored that the displacement of the upper electrode meets the above preset condition, the current control device automatically cuts off the welding current to end the welding process. After welding is completed, naturally cool the copper-steel bimetallic material to room temperature to obtain the required finished copper-steel bimetallic material.

[0022] Adopting the above technical solution, after the steel matrix is processed by the groove, it can effectively limit the displacement of the copper alloy pressing green compact and avoid excessive deformation during the welding process. The copper alloy pressing green compact adopts the powder metallurgy pressing forming process, which has a short preparation cycle, high production efficiency, can realize batch production, and the production volume per minute can reach 10 to 25. The material utilization rate is increased to more than 95%, significantly reducing the production cost. The diffusion welding process uses the displacement of the upper electrode to control the welding quality in real time, avoiding the inaccurate temperature measurement caused by the change of the radiation rate when using an infrared thermometer in the traditional diffusion welding process, improving the stability of the welding process and the welding quality. The obtained copper-steel bimetallic material has a dense bonding interface, no inclusions, and firm welding. The welding shear strength can stably reach more than 100 MPa, meeting the shear strength requirements specified in the national standard GB 13238-91 "Copper-Steel Composite Steel Plate", and the comprehensive performance is significantly improved, which is suitable for industrial batch production and application.

[0023] In an embodiment of the present application, after the steel is processed into a steel matrix, the following steps are further included: Through turning or milling, process a groove on the surface of the steel matrix that contacts the copper alloy pressing green compact. The depth of the groove is the first depth, and the thickness of the groove edge is the first thickness. Define the first depth as A, where 3 mm ≥ A ≥ 1 mm; define the first thickness as B, where 1.5 mm ≥ B ≥ 0.5 mm.

[0024] Specifically, the specific method of processing the steel into a steel matrix is as follows: First, process the steel into the required specific shape through a lathe or a milling machine, which can be processed into a circular shape, a rectangular shape, or other special shapes determined according to actual use requirements. After the shape of the steel matrix is processed, on the surface of the steel matrix that contacts the subsequently prepared copper alloy pressing green compact, use the lathe or the milling machine for secondary processing again to form the required groove structure.

[0025] The specific steps for processing the groove are as follows: In the first step, firmly clamp the steel substrate on the fixture of a lathe or milling machine processing equipment, adjust the operating parameters of the equipment, and set the corresponding rotational speed of the motor; In the second step, according to the shape and size requirements of the groove to be processed, select an appropriate processing position on the surface of the steel substrate, and gradually process the required groove structure through a lathe or milling machine; the depth of the groove is processed to the required first depth A, and the specific numerical range of the first depth A is 1 mm to 3 mm; the edge thickness of the groove is processed to the required first thickness B, and the specific numerical range of the first thickness B is 0.5 mm to 1.5 mm; In the third step, the specific processing process is carried out in a layer-by-layer processing manner. The cutting amount per layer is preferably controlled between 0.1 mm and 0.5 mm, and the groove depth A and edge thickness B are finally obtained through layer-by-layer cutting; In the fourth step, after the groove is processed, use a measuring tool to measure the depth A and edge thickness B of the groove to ensure that the technical requirements are met.

[0026] By adopting the above technical solution, the groove structure processed on the steel substrate ensures that the subsequent copper alloy pressed green compact can be positioned on the surface of the steel substrate, significantly improves the contact tightness and positioning accuracy between the copper alloy and the steel substrate, effectively prevents displacement and deformation problems during subsequent processing and welding, and improves the welding quality and overall performance of the finally prepared copper-steel bimetallic material, which is suitable for industrial mass production.

[0027] In an embodiment of the present application, the difference between the height of the copper alloy pressed green compact and the groove depth is C, and 1 mm ≥ C ≥ 0 mm.

[0028] Specifically, the copper alloy pressed green compact described in the present invention refers to a copper alloy structural part prepared by a powder metallurgy process, which specifically includes a copper-based alloy powder (such as electrolytic copper powder, CuSn10Pb10 alloy powder or other copper-based alloy powders) mixed with a zinc stearate release agent, and then pressed and formed on a pressing equipment (such as a powder metallurgy hydraulic press) at a pressure of 400 MPa to 800 MPa to obtain a green compact.

[0029] The height of the copper alloy pressed green compact specifically refers to the dimension of the copper alloy pressed green compact in the direction perpendicular to the bottom surface of the groove of the steel substrate; the groove depth refers to the depth dimension of the groove formed on the steel substrate by mechanical processing in the direction perpendicular to the surface of the steel substrate.

[0030] The height difference between the height of the copper alloy pressed green compact and the depth of the groove in the steel matrix is defined as C, and the specific numerical range of the difference C is from 0 mm to 1 mm, that is, the height of the copper alloy pressed green compact is greater than or equal to the groove depth. Specifically, when the copper alloy pressed green compact is placed into the groove, the upper surface of the copper alloy pressed green compact is slightly higher than the surface of the steel matrix or flush with the surface of the steel matrix. The height difference C can be adjusted according to specific welding process requirements. The adjustment method is to control the final height of the copper alloy pressed green compact by changing the filling amount of the copper-based alloy powder in the pressing die when the copper alloy pressed green compact is pressed and formed, so that the height difference C meets the range requirements.

[0031] Adopting the above technical solution, by reasonably setting the difference C between the height of the copper alloy pressed green compact and the depth of the groove in the steel matrix, when welding subsequently, the copper alloy pressed green compact can be in full and close contact with the bottom and side walls of the groove in the steel matrix, which can effectively ensure the tight combination of the material interfaces during diffusion welding, avoid the occurrence of pores, inclusions and welding defects at the interface joint, and thus effectively improve the shear strength and overall mechanical properties of the welding interface of the copper-steel bimetallic material.

[0032] In an embodiment of the present application, zinc stearate is added to the copper-based powder as a mold release lubricant, and the content of zinc stearate is D, where 1.5% ≥ C ≥ 0.5%.

[0033] Specifically, the copper-based powder described in the present invention is the raw material for preparing the copper alloy pressed green compact. The copper-based powder is specifically selected as electrolytic copper powder or copper-based alloy powder, such as CuSn10Pb10 copper alloy powder or other copper alloy powders suitable for powder metallurgy pressing and forming; the zinc stearate is added to the copper-based powder in weight percentage for mixing. The specific addition method is: uniformly disperse the weighed zinc stearate into the copper-based powder and mix it evenly through a mechanical mixing device; the specific addition content of the zinc stearate is defined as D, and the value range of the addition amount D of the zinc stearate is 0.5% to 1.5% of the total weight of the copper-based powder; in actual production, it is preferably to control the content of zinc stearate at about 0.7% to ensure that the copper-based powder can obtain good pressing performance and smooth mold release during pressing and forming, and at the same time avoid the adverse effects of too high a content of zinc stearate on the subsequent welding performance; the mixture of the copper-based powder and zinc stearate after being mixed evenly is used for the powder metallurgy pressing process to prepare the copper alloy pressed green compact.

[0034] Adopting the above technical solution, by adding an appropriate amount of zinc stearate to the copper-based powder, the fluidity of the powder in the mold is effectively improved, the compactness of the pressed green compact during forming is improved, the mold release resistance of the pressed green compact is significantly reduced, and the forming efficiency of the pressed green compact is improved.

[0035] In an embodiment of the present application, the content of zinc stearate is 0.7%.

[0036] Adopt the above technical solution to ensure that the copper-based powder can obtain good pressing performance and smooth demolding during pressing molding, and can avoid the adverse impact of excessive zinc stearate content on subsequent welding performance. The compactness of the pressed green compact is improved, and the demolding resistance of the pressed green compact is significantly reduced. In an embodiment of the present application, the copper-based powder is non-spherical powder.

[0037] Adopt the above technical solution. Since the particle shape of the non-spherical powder is irregular, it can be arranged more closely during stacking, which enables higher density to be obtained during pressing and facilitates the pressing molding of copper alloys.

[0038] Such as Figure 2 As shown, the present application also discloses a copper-steel bimetallic material prepared according to the method described in any one of the above. It includes a steel matrix and a copper alloy layer. The copper alloy layer is bonded to the steel matrix by diffusion welding, and the interfacial shear strength is P, where 150 MPa ≥ P ≥ 100 MPa.

[0039] Specifically, the copper-steel bimetallic material of the present invention includes a steel matrix and a copper alloy layer. The steel matrix is made of low-carbon steel, medium-carbon steel or alloy steel. Specifically, 45 steel can be selected for the steel matrix, and the thickness range of the steel matrix is preferably 2 mm to 20 mm. The copper alloy layer is a dense copper alloy material layer formed by diffusion welding of a copper alloy pressed green compact prepared by a powder metallurgy pressing process. The copper alloy layer of the copper-steel bimetallic material is firmly bonded to the steel matrix by a diffusion welding method. The diffusion welding is specifically carried out by a dedicated diffusion welding device. During the welding process, a constant pressure is applied by the upper electrode and a welding current is passed through. The welding end point is accurately determined by controlling the displacement of the upper electrode of the diffusion welding device. After welding, a tight metallurgical bonding layer is formed at the bonding interface between the copper alloy layer and the steel matrix. The interfacial strength between the copper alloy layer and the steel matrix is measured according to YS / T 485 "Determination Method for Shear Strength of Sintered Bimetallic Materials". Specifically, during implementation, the shear strength P of the interface between the copper alloy layer and the steel matrix is measured by a shear strength testing device, and the interfacial shear strength P is greater than 100 MPa.

[0040] The test method for the shear strength P is as follows: The prepared copper-steel bimetallic material is processed into a standard shear strength specimen. The specimen size is based on the requirements of the YS / T 485 standard and is tested by a universal material testing machine. During the test process, the loading speed is controlled within a predetermined condition, and the maximum shear load at the separation of the copper-steel interface is measured. The shear strength P is calculated based on the measured shear load.

[0041] With the above technical solution, for the copper-steel bimetallic material obtained by the diffusion welding method, high-quality metallurgical bonding is achieved at the interface junction. The shear strength of the material interface is greater than 100 MPa and less than 150 MPa, fully meeting the shear strength requirements specified in GB 13238-91 "Copper-Steel Composite Steel Plate".

[0042] In an embodiment of the present application, the thickness E of the copper alloy layer satisfies 4 mm ≥ E ≥ 1 mm.

[0043] With the above technical solution, when the thickness E of the copper alloy layer is controlled within the range of 1 mm to 4 mm, the copper-steel bimetallic material can simultaneously possess the good thermal conductivity, electrical conductivity and excellent wear resistance of the copper alloy material, as well as the high strength and high stiffness characteristics of the steel matrix.

[0044] Observation of the copper-steel bonding surface: Using a Zeiss sigma300 field emission scanning electron microscope, observe whether there are pores, inclusions, etc. on the bonding surface between the copper layer and the steel matrix. Figure 2 It is a scanning electron microscope picture after diffusion welding of a copper-based compact (electrolytic copper powder added with 0.7% zinc stearate) and 45 steel. From Figure 2 it can be seen that there are no pores, inclusions, etc. on the bonding surface between the copper layer and the steel matrix, and the bonding is good. There are pores in the copper layer.

[0045] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. All equivalent structural transformations made under the inventive concept of the present invention, or direct / indirect applications in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A preparation method of a copper-steel bimetallic material, characterized in that, It includes the following steps: a) Preparation of steel substrate: Processing steel into a steel substrate; b) Preparation of copper alloy green compact: Using copper-based powder to be compacted by powder metallurgy process to obtain a copper alloy compacted green compact; c) Assembly: Placing the copper alloy compacted green compact on the steel substrate to form a green compact to be welded; d) Diffusion welding: Placing the green compact to be welded on the lower electrode of the diffusion welding equipment, controlling the upper electrode of the diffusion welding equipment to extrude the green compact to be welded and energize, monitoring the displacement of the green compact to be welded by the upper electrode during pressure application and heating, and disconnecting the current when the displacement meets the preset conditions to complete the welding.

2. The preparation method of the copper-steel bimetallic material according to claim 1, characterized in that After processing the steel into a steel substrate, it further includes the following steps: By turning or milling, a groove is machined on the surface of the steel substrate that contacts the copper alloy compacted green compact. The groove depth is the first depth, and the groove edge thickness is the first thickness; defining the first depth as A, 3mm ≥ A ≥ 1mm; defining the first thickness as B, 1.5mm ≥ B ≥ 0.5mm.

3. The preparation method of the copper-steel bimetallic material according to claim 2, characterized in that, The difference between the height of the copper alloy compacted green compact and the groove depth is C, 1mm ≥ C ≥ 0mm.

4. The preparation method of the copper-steel bimetallic material according to claim 1, characterized in that, Zinc stearate is added to the copper-based powder as a mold release lubricant, and the content of zinc stearate is D, 1.5% ≥ C ≥ 0.5%.

5. The preparation method of the copper-steel bimetallic material according to claim 4, characterized in that, The content of zinc stearate is 0.7%.

6. The preparation method of the copper-steel bimetallic material according to claim 1, characterized in that, The copper-based powder is non-spherical powder.

7. A copper-steel bimetallic material prepared by the method according to any one of claims 1 to 6, characterized in that, It includes a steel substrate and a copper alloy layer. The copper alloy layer is combined with the steel substrate by diffusion welding, and the interfacial shear strength is P, 150 MPa ≥ P ≥ 100 MPa.

8. The preparation method of the copper-steel bimetallic material according to claim 7, characterized in that, The thickness of the copper alloy layer is E, 4mm ≥ E ≥ 1mm.

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