Carbon steel / copper composite plates, their spark plasma hot pressing sintering method and applications

Abstract

This invention provides a carbon steel / copper composite plate, its spark plasma hot pressing sintering method, and its application, belonging to the field of metal layered composite material processing technology. The preparation method of the carbon steel / copper composite plate includes: selecting carbon steel plate and pure copper plate as composite substrates; sequentially performing degreasing, grinding, micro-roughening, acid pickling activation, cleaning, and drying treatments on the surfaces to be composited on the carbon steel plate and pure copper plate; stacking and assembling them in a graphite mold according to a preset lamination method; placing the assembled graphite mold in a spark plasma hot pressing sintering device, applying axial pressure and heating for sintering and holding under vacuum or a protective atmosphere; cooling with the furnace after sintering and holding; and aging the resulting composite plate after cooling to obtain the steel / pure copper composite plate. This method achieves a continuous and dense metallurgical bond between the carbon steel and pure copper interface through spark plasma hot pressing sintering technology, resulting in a composite plate that combines the high strength, low cost, and good electrical conductivity of carbon steel.

Description

Technical Field

[0001] This invention relates to composite sheet technology, and more particularly to a carbon steel / copper composite sheet, its spark plasma hot pressing sintering method, and its application. Background Technology

[0002] Steel, with its wide availability, low price, high strength, and good weldability and machinability, is one of the most widely used basic structural materials in fields such as power equipment, rail transportation, engineering machinery, and metallurgical equipment. However, steel's electrical conductivity, thermal conductivity, and corrosion resistance are relatively limited, making it difficult to directly meet the comprehensive requirements of electrical conductivity, thermal conductivity, and complex service environments. Pure copper possesses excellent electrical conductivity, thermal conductivity, corrosion resistance, and good plasticity, and is widely used in electrical connections, heat dissipation substrates, busbars, contact components, wear-resistant conductive sliding parts, and thermal management structural components, but its price is relatively high. Therefore, preparing layered composite plates from steel and pure copper can fully leverage the advantages of steel, such as low cost, high strength, and ease of processing, while utilizing the excellent electrical and thermal conductivity of pure copper. Steel / pure copper composite plates show promising application prospects in areas such as flow guide plates, electrical connection plates, wear-resistant conductive plates, heat dissipation plates, and electrical equipment connection components.

[0003] Currently, common methods for preparing steel / pure copper composite plates include rolling composite, explosive composite, and brazing composite. Rolling composite is suitable for continuous production and has high production efficiency, but the significant differences in deformation resistance, thermal expansion coefficients, and plastic flow behavior between steel and pure copper make it difficult to coordinate interface deformation during the composite process, easily leading to problems such as local non-bonding and edge cracking. Explosive composite can form steel-copper composite plates under instantaneous high-energy impact; however, this method has high requirements for site conditions, safety protection, and process control. Although brazing composite has a relatively low process temperature, which can reduce the risk of matrix melting and deformation, it usually requires the introduction of brazing filler metal or an intermediate layer. The interfacial bonding strength and high-temperature service stability are greatly affected by the brazing filler metal composition, wettability, and degree of interfacial reaction. Conventional hot-press diffusion bonding can achieve good metallurgical bonding, but it often suffers from problems such as long heating time, low diffusion efficiency, insufficient interface densification, and high energy consumption. Cladding or welding can achieve surface functionalization by depositing a pure copper layer on the steel substrate. However, due to the significant differences in melting point, thermal conductivity, wettability, and miscibility between steel and copper, problems such as excessive dilution, component segregation, porosity, cracks, uneven interface structure, and coarsening of the heat-affected zone are prone to occur during the cladding process.

[0004] Spark plasma sintering (SPS) for preparing composite plates offers significant advantages, including rapid heating, low sintering temperature, and short holding time. It effectively suppresses grain coarsening and excessive interfacial reactions, preserving the fine-grained structure of the material. Furthermore, plasma activation breaks down surface oxide films and purifies the bonding interface, achieving a reliable bond with high strength and density between dissimilar materials. Therefore, there is an urgent need to develop a spark plasma hot-pressing sintering method for preparing steel / pure copper composite plates. This method, through interfacial activation, rapid densification, and short-time diffusion bonding, achieves a stable, continuous, and dense metallurgical bond between steel and copper or pure copper plates, resulting in steel / copper composite plates that possess both structural load-bearing capacity and electrical and thermal conductivity. This technology is expected to solve problems such as unstable interfacial bonding, difficult process control, and difficulty in achieving synergistic microstructure and properties in traditional rolling composite, explosive composite, cladding composite, and conventional hot-pressing diffusion bonding methods, and has high engineering application value. Summary of the Invention

[0005] The purpose of this invention is to address the problems of unstable interfacial bonding quality, complex processes, long preparation cycles, and underutilization of the conductivity of copper layers in existing carbon steel / copper composite plates. This invention proposes a spark plasma hot pressing (SPHT) method for carbon steel / copper composite plates. This method utilizes the interfacial activation effect of pulsed current, the synergistic effect of rapid heating and axial pressure, to achieve a continuous and dense metallurgical bond between carbon steel and pure copper under vacuum or a protective atmosphere. This effectively suppresses the excessive growth of brittle intermetallic compounds at the interface, reduces interfacial porosity and delamination defects, and results in a steel / copper composite plate that combines the high strength and low-cost load-bearing advantages of carbon steel with the excellent electrical and thermal conductivity of pure copper.

[0006] It should be noted that, in this invention, unless otherwise specified, the specific meaning of "comprising" in relation to composition and description includes both open-ended meanings such as "comprising," "including," etc., and closed-ended meanings such as "composed of," "consisting of," etc., and similar meanings.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: a spark plasma hot pressing sintering method for carbon steel / copper composite plates, comprising the following steps:

[0008] S1: Surface pretreatment, the carbon steel plate and pure copper plate to be composite are sequentially degreased, polished, pickled and activated and dried to remove surface oxide scale, passivation film and oil stains.

[0009] S2: Laminated assembly, where pre-treated carbon steel plates and pure copper plates are laminated and assembled in a preset lamination method to form a layered prefabricated body;

[0010] S3: Molding and pre-pressing: The layered preform is placed in a graphite mold and an axial pre-pressure of 5-20 MPa is applied to make the carbon steel plate and the pure copper plate fit tightly together, so as to increase the actual contact area of ​​the steel and copper metal interfaces and reduce the interface porosity.

[0011] S4: Plasma hot pressing sintering. The assembled graphite mold is placed in the discharge plasma hot pressing sintering equipment. Under vacuum or protective atmosphere, axial pressure is applied and a segmented heating system is used for heating, sintering and heat preservation, so that a metallurgical bonding layer is formed at the interface between the carbon steel plate and the pure copper plate. After cooling, the initial carbon steel / copper composite plate is obtained.

[0012] S5: Aging treatment, the initial carbon steel / copper composite plate is kept at 350-550℃ for 15-120 minutes, and then cooled to room temperature to obtain the carbon steel / copper composite plate.

[0013] Furthermore, the carbon steel plate is one or more of Q235, Q345, or 20 steel.

[0014] Furthermore, the pure copper plate is one of T2, TU1 or TU2 pure copper, and the purity of the pure copper is not less than 99.9%.

[0015] Further, in step S1, the degreasing is performed by ultrasonic cleaning with anhydrous ethanol, acetone, deionized water or a combination thereof, and the cleaning time is 5 to 30 minutes; the grinding and roughening is performed by one or more of sandblasting, sandpaper grinding, mechanical polishing or wire brush treatment, preferably, sandblasting roughening is performed with brown fused alumina or white fused alumina abrasive particles; the acid pickling activation is performed by one or more of hydrofluoric acid, nitric acid, oxalic acid or hydrochloric acid solution.

[0016] Furthermore, in step S2, the lamination method is a two-layer steel / pure copper structure, a three-layer steel / pure copper / steel symmetrical structure, a three-layer pure copper / steel / pure copper structure, or a multi-layer alternating stacked structure.

[0017] Furthermore, in step S3, a graphite paper, carbon paper, or boron nitride release layer is provided between the layered preform and the pressure head of the graphite mold, and / or on the inner wall of the graphite mold. That is, a graphite paper, carbon paper, or boron nitride release layer is used to separate the laminated preform from the upper and lower pressure heads.

[0018] Furthermore, in step S3, the layered preform is placed at the center of the graphite mold.

[0019] Further, in step S4, the sintering temperature is 700–950℃, preferably 780–880℃; the sintering pressure is 20–80 MPa, preferably 30–60 MPa; the holding time is 5–30 min, preferably 8–15 min; and the vacuum degree is ≤10. -1 Pa.

[0020] Further, in step S4, the segmented heating regime is as follows: the temperature is increased from room temperature to 550-650°C at a heating rate of 80-150°C / min and held for 3-10 minutes, and then increased to the sintering temperature of 700-950°C at a heating rate of 30-80°C / min.

[0021] Further, in step S4, the protective atmosphere is one or more of argon, nitrogen, or an argon-hydrogen mixture.

[0022] Furthermore, in step S4, the cooling rate of the furnace cooling is 50–200 °C / h.

[0023] Another objective of this invention is to disclose a carbon steel / copper composite plate, which is prepared using the above-described preparation method.

[0024] Furthermore, a continuous and dense diffusion metallurgical bonding interface is formed between the carbon steel layer and the pure copper layer.

[0025] Furthermore, the carbon steel / copper composite plate is a two-layer composite structure or a three-layer composite structure.

[0026] Furthermore, the single-layer thickness of the carbon steel layer is 4–10 mm, and the single-layer thickness of the pure copper layer is 2–6 mm.

[0027] Furthermore, when it is a two-layer composite structure, the total thickness is 6–16 mm; when it is a three-layer composite structure, the total thickness is 10–26 mm.

[0028] Another objective of this invention is to disclose a discharge plasma hot pressing sintering device for carbon steel / copper composite plates, comprising: a discharge plasma sintering furnace cavity (4) connected to a vacuum system and a protective atmosphere inlet system;

[0029] The upper electrode (1) and the lower electrode (9) are respectively disposed at the top and bottom of the discharge plasma sintering furnace cavity (4) and are electrically connected to the pulsed DC power supply.

[0030] The upper pressure head (2) and the lower pressure head (8) are connected to the upper electrode and the lower electrode respectively and are arranged coaxially. They can move relative to each other along the axial direction to apply axial pressure to the workpiece to be sintered.

[0031] A graphite mold (3) is detachably set between the upper and lower pressure heads to accommodate the layered preform of carbon steel / copper composite plate.

[0032] Furthermore, the equipment also includes a temperature and pressure control unit, which is configured to execute a segmented sintering procedure: first, the temperature is raised from room temperature to 550-650°C at a first heating rate and a first pre-pressure is applied; then, the temperature is raised to a sintering temperature of 700-950°C at a second heating rate and the pressure is increased to a sintering pressure of 20-80 MPa; after holding at this temperature for 5-30 minutes, the equipment is cooled with the furnace.

[0033] Furthermore, the upper pressure head (2) and the lower pressure head (8) are made of graphite, and in use, a release isolation layer is sandwiched between the layered preform and the upper and lower pressure heads. The release isolation layer is graphite paper, carbon paper or graphite sheet coated with boron nitride isolation coating.

[0034] Furthermore, the vacuum system is connected to the discharge plasma sintering furnace cavity (4) and is used to evacuate the vacuum degree of the discharge plasma sintering furnace cavity to ≤10. -1 Pa.

[0035] Furthermore, the protective atmosphere system is connected to the discharge plasma sintering furnace cavity (4) and is used to introduce a protective atmosphere into the discharge plasma sintering furnace cavity.

[0036] Furthermore, the upper pressure head (2) and the lower pressure head (8) are provided with positioning grooves or positioning steps on their end faces to limit the radial displacement of the graphite mold (3) so that the layered preform is located at the center of the graphite mold.

[0037] Furthermore, the device is also equipped with a pressure sensor and a thermocouple. The pressure sensor is installed at the upper or lower pressure head to monitor the axial loading pressure in real time. The thermocouple is attached to the outer wall of the graphite mold or inserted into the temperature measuring hole of the mold to monitor the sintering temperature and feeds the signal back to the temperature and pressure control unit to achieve closed-loop control.

[0038] Another objective of this invention is to disclose the application of a carbon steel / copper composite plate in the preparation of flow guide plates, power connection plates, wear-resistant conductive plates, heat dissipation plates, or power equipment connection components.

[0039] The carbon steel / copper composite plate, its spark plasma hot pressing sintering method, and its application, as described in this invention, have the following advantages compared to existing technologies:

[0040] 1) This invention utilizes the synergistic effect of pulsed current, rapid heating, and pressure during the spark plasma hot pressing sintering process to promote the breakage of the interfacial oxide film, surface activation, and short-range diffusion of Fe and Cu elements, thereby forming a continuous and dense diffusion-bonded interface between the steel and copper plates. This method can significantly inhibit the excessive growth of brittle intermetallic compounds, improve the interfacial bonding strength and service stability of the composite plate, and achieve rapid diffusion bonding and stable metallurgical bonding of dissimilar metals such as steel and copper.

[0041] 2) This invention employs spark plasma hot pressing sintering to achieve interface densification and diffusion metallurgical bonding in a single step. This method features a simple process flow, low heat input, short preparation cycle, and low energy consumption, making it easy to achieve industrial-scale production and widespread application.

[0042] 3) The Vickers hardness of the carbon steel layer in the steel / copper composite plate obtained by the present invention reaches 210~280 HV, which provides high load-bearing capacity for the composite plate; at the same time, it combines the low cost advantage of carbon steel with the excellent conductivity of copper layer.

[0043] The carbon steel / copper composite plate of this invention has good application prospects and large-scale promotion potential in the field of preparing flow guide plates, power connection plates, wear-resistant conductive plates, heat dissipation plates or power equipment connection components. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the structure of the discharge plasma hot pressing sintering equipment used in Example 1.

[0045] Figure 2 Metallographic photograph of the carbon steel / copper plate / carbon steel composite plate prepared in Example 1.

[0046] Figure 3 The energy dispersive spectroscopy (EDS) results are for the carbon steel / copper plate / carbon steel composite material prepared in Example 1.

[0047] Figure 4 Metallographic photograph of the carbon steel / copper composite plate prepared in Example 2.

[0048] Figure 5 The energy dispersive spectroscopy (EDS) results are for the carbon steel / copper composite plate prepared in Example 2. Detailed Implementation

[0049] The present invention will be further described below with reference to embodiments. The description of the technical features described below is based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that:

[0050] Unless otherwise stated, all units used in this specification are international standard units, and all numerical values ​​and ranges appearing in this invention should be understood to include systematic errors that are unavoidable in industrial production.

[0051] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0052] In this specification, the numerical range indicated by "above" or "below" refers to the numerical range that includes the stated number.

[0053] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0054] In this specification, the terms "optional" or "optional" are used to indicate the use or omission of certain substances, components, procedures, application conditions, etc.

[0055] In this instruction manual, when "room temperature" or "room temperature" is used, the temperature can be 15-25℃.

[0056] Unless otherwise specified, all reagents or instruments used in this instruction manual are commercially available products.

[0057] Example 1:

[0058] This embodiment discloses a carbon steel / copper plate / carbon steel composite plate, the preparation method of which is as follows:

[0059] (1) Raw material preparation

[0060] Commercially available hot-rolled Q235B steel plate and T2 pure copper plate were selected as composite raw materials. The steel plate dimensions were 40mm × 4mm, and the pure copper plate dimensions were 40mm × 2mm. The steel plate composition conformed to GB / T700 standard; the T2 pure copper plate composition conformed to GB / T5231 standard, with a Cu content of not less than 99.90%, and the balance being unavoidable impurities. The two steel plates were placed on the upper and lower sides of the pure copper plate, respectively, forming a three-layer symmetrical structure of carbon steel / copper plate / carbon steel.

[0061] (2) Surface pretreatment

[0062] First, the steel plate and pure copper plate were ultrasonically cleaned with acetone for 10 minutes to remove surface oil and adsorbed impurities. Then, the steel plate surface to be laminated was roughened by sandblasting with 80-mesh brown corundum to expose the fresh metal substrate. The pure copper plate surface to be laminated was progressively polished with 800#, 1200#, and 2000# sandpaper to achieve a surface roughness Ra ≤ 0.8 μm. After polishing, both plates were ultrasonically cleaned with anhydrous ethanol for 5 minutes and then dried with hot air. The steel plate was further activated by acid pickling with a 5% (w / w) dilute sulfuric acid solution for 30 seconds to remove the surface oxide film and passivation layer; the pure copper plate was activated by a 10% (v / v) dilute hydrochloric acid solution for 20 seconds. Both were then rinsed with deionized water and dried. After pretreatment, the lamination assembly was completed within 15 minutes.

[0063] (3) Laminated assembly

[0064] The processed steel plate and pure copper plate are stacked and assembled in a steel plate / pure copper plate / steel plate structure and placed in the center of a graphite mold. Graphite paper is used to separate the composite blank from the upper and lower graphite pressure heads, and the outside of the graphite mold is covered with graphite felt for insulation. An axial preload of 10 MPa is applied to the laminated blank to ensure a tight fit between the steel plate and the pure copper plate, thereby increasing the actual contact area at the interface and reducing interfacial porosity.

[0065] (4) Discharge plasma hot pressing sintering

[0066] The assembled and pre-pressed composite preform, along with the graphite mold, is placed in a spark plasma hot pressing sintering equipment (such as...). Figure 1 As shown in the figure, the discharge plasma sintering furnace chamber was first evacuated to below 5 Pa and maintained under vacuum. Then, a pulsed DC current was applied, employing a segmented heating regime: the temperature was increased from room temperature to 600℃ at a rate of 100℃ / min, held for 5 min, and then increased to the sintering temperature of 850℃ at a rate of 50℃ / min. During the 600℃ holding stage, a preload pressure of 15 MPa was applied. When the temperature reached 850℃, the axial pressure was increased to 50 MPa and held for 10 min to promote the breakdown of the interfacial oxide film and the diffusion of Fe and Cu atoms. After the holding period, the pressure was gradually released, and the furnace was cooled to room temperature to obtain the initial carbon steel / copper plate / carbon steel composite plate.

[0067] (5) Timeliness processing

[0068] The resulting carbon steel / copper plate / carbon steel composite plate was kept at 450℃ for 20 minutes and then cooled in the furnace to obtain a carbon steel / copper plate / carbon steel composite plate with excellent electrical conductivity, thermal conductivity and mechanical properties.

[0069] Figure 1 This is a schematic diagram of the structure of the spark plasma hot pressing sintering equipment used in Example 1; in the figure, 1 is the upper electrode, 2 is the upper pressure head, 3 is the graphite mold, 4 is the spark plasma sintering furnace cavity, 5 is the upper steel plate, 6 is the copper plate, 7 is the lower steel plate, 8 is the lower pressure head, and 9 is the lower electrode.

[0070] The spark plasma hot pressing sintering equipment used in Example 1 is as follows: Figure 1 As shown, the device includes:

[0071] The discharge plasma sintering furnace cavity (4) is connected to a vacuum system and a protective atmosphere inlet system, which are used to provide a vacuum or inert protective atmosphere environment during the sintering process.

[0072] The upper electrode (1) and the lower electrode (9) are respectively set at the top and bottom of the discharge plasma sintering furnace cavity (4) and are electrically connected to the pulsed DC power supply to transmit pulsed current to the workpiece to be sintered.

[0073] The upper pressure head (2) and the lower pressure head (8) are connected to the upper electrode and the lower electrode respectively and are arranged coaxially. They can move relative to each other along the axial direction to apply axial pressure to the layered preform. The upper pressure head (2) and the lower pressure head (8) are made of graphite material. Their end faces are provided with positioning grooves or positioning steps to limit the radial displacement of the graphite mold (3) so that the layered preform is located at the center of the graphite mold.

[0074] A graphite mold (3) is detachably clamped between the upper and lower pressure heads to accommodate the layered preform of carbon steel / copper composite plate. In use, a demolding isolation layer is sandwiched between the layered preform and the upper and lower pressure heads. The demolding isolation layer is graphite paper, carbon paper or graphite sheet coated with boron nitride isolation coating to prevent the preform from sticking to the pressure head.

[0075] The temperature and pressure control unit is configured to execute a segmented sintering program: first, the temperature is raised from room temperature to 550-650°C at a first heating rate and a first pre-pressure is applied; then, the temperature is raised to a sintering temperature of 700-950°C at a second heating rate and the pressure is increased to a sintering pressure of 20-80 MPa; after holding at the temperature for 5-30 minutes, the temperature is cooled with the furnace.

[0076] The vacuum system is connected to the discharge plasma sintering furnace cavity (4) and is used to evacuate the vacuum level of the discharge plasma sintering furnace cavity to ≤10. -1 Pa;

[0077] A protective atmosphere system is connected to the discharge plasma sintering furnace cavity (4) and is used to introduce one or more protective atmospheres, such as argon, nitrogen or argon-hydrogen mixture, into the discharge plasma sintering furnace cavity.

[0078] The pressure sensor is installed at the upper or lower pressure head to monitor the axial loading pressure in real time, and the thermocouple is attached to the outer wall of the graphite mold or inserted into the temperature measuring hole of the mold to monitor the sintering temperature and feed the monitoring signal back to the temperature and pressure control unit to realize closed-loop control of the sintering process.

[0079] Figure 2 The image shows a metallographic photograph of the carbon steel / copper plate / carbon steel composite plate prepared in Example 1, wherein the Cu layer thickness is 1.5 mm. The upper and lower layers are steel plates, and the center is a copper plate.

[0080] Figure 3 The energy dispersive spectroscopy (EDS) results are shown for the carbon steel / copper plate / carbon steel composite plate prepared in Example 1. The central yellow area represents the Cu plate, and the purple area represents the steel plate.

[0081] Depend on Figure 2As can be seen, the three-layer composite plate after spark plasma hot pressing sintering has a clear, straight, continuous, and dense interface, without cracks, pores, delamination, or other unbonded defects. A distinct diffusion metallurgical bonding layer is formed at the steel / copper interface, where Cu and Fe elements undergo a certain degree of mutual diffusion, resulting in a bond. Figure 3 The elemental distribution diagram clearly shows the distinct boundary between the copper and steel layers, with no excessive growth of harmful brittle intermetallic compounds, indicating that this method achieves high-quality and reliable bonding.

[0082] Example 2:

[0083] This embodiment provides a method for preparing a double-layer carbon steel / copper composite plate by spark plasma hot pressing sintering, the specific steps of which are as follows:

[0084] (1) Raw material preparation

[0085] Commercially available hot-rolled Q235B steel plate and T2 pure copper plate were selected as composite raw materials, with the steel plate measuring 40mm × 6mm and the pure copper plate measuring 40mm × 2mm. A double-layer pure copper / steel plate functional gradient structure was used for assembly. The steel plate composition conforms to GB / T700 standard; the T2 pure copper plate composition conforms to GB / T5231 standard, with a Cu content of not less than 99.90%, and the balance being unavoidable impurities.

[0086] (2) Surface pretreatment

[0087] First, the steel plate and pure copper plate were ultrasonically cleaned with ethanol for 15 minutes to remove surface oil and adsorbed impurities. Then, the steel plate surface to be laminated was roughened by sandblasting with 100-grit brown corundum, while the pure copper plate surface was progressively polished with 800# and 1500# sandpaper to expose the fresh metal substrate. After sandblasting, the steel plate was further activated by acid pickling with an 8% (v / v) dilute sulfuric acid solution for 25 seconds to remove the surface oxide film and passivation layer. The pure copper plate, after polishing, was activated by a 10% (v / v) dilute hydrochloric acid solution for 15 seconds. After activation, both were rinsed with deionized water and dried with hot air. After pretreatment, the lamination assembly was completed within 15 minutes.

[0088] (3) Laminated assembly

[0089] The treated pure copper plate and steel plate are bonded and assembled in a pure copper / steel double-layer structure and placed in the central area of ​​a graphite mold. Flexible graphite sheets are used to isolate the composite blank from the upper and lower graphite pressure heads, and the outside of the graphite mold is covered with a graphite felt insulation layer. An axial preload of 8 MPa is applied to the laminated blank to ensure a tight bond between the pure copper plate and the steel plate, thereby increasing the actual contact area at the interface and reducing interface porosity.

[0090] (4) Discharge plasma hot pressing sintering

[0091] The assembled and pre-pressed composite preform, along with a graphite mold, is placed in a spark plasma hot pressing sintering apparatus. First, the spark plasma sintering furnace cavity is evacuated to below 5 Pa, and a small amount of high-purity argon is introduced as a protective atmosphere. Then, a pulsed direct current is applied, employing a segmented heating regime: the temperature is increased from room temperature to 600℃ at a rate of 100℃ / min, held for 5 min, and then increased to the sintering temperature of 800℃ at a rate of 50℃ / min. During the 600℃ holding stage, a preload pressure of 10 MPa is applied. When the temperature reaches 800℃, the axial pressure is increased to 40 MPa and held for 15 min to promote the breakdown of the interfacial oxide film and the diffusion of Fe and Cu atoms. After the holding period, the pressure is gradually released, and the furnace is cooled to room temperature to obtain the initial carbon steel / copper composite plate.

[0092] (5) Timeliness processing

[0093] The resulting carbon steel / copper composite plate was kept at 400℃ for 60 minutes and then cooled in the furnace to obtain a carbon steel / copper composite plate with excellent electrical and thermal conductivity and load-bearing capacity.

[0094] The composite plates prepared in Examples 1 and 2 were tested respectively. The test results showed that the composite plate had a continuous and dense interface with no obvious delamination, separation or through cracks. A clear diffusion transition layer was formed at the interface. The composite plate has the advantages of high strength and low cost load-bearing of steel and the excellent electrical and thermal conductivity of pure copper, and has good comprehensive performance.

[0095] Figure 4 The image shows a metallographic photograph of the carbon steel / copper composite plate prepared in Example 2, where the upper layer is a steel plate and the lower layer is a copper plate.

[0096] Figure 5 The image shows the energy dispersive spectroscopy (EDS) results of the carbon steel / copper composite plate prepared in Example 2, where the purple area corresponds to the steel plate and the yellow area corresponds to the Cu plate.

[0097] Depend on Figure 4 and Figure 5 It is evident that the double-layer pure copper / steel plate composite structure also achieved excellent interfacial bonding. After pretreatment and plasma activation, the oxide film at the interface between the pure copper and carbon steel substrates was effectively removed under the synergistic effect of different heating rates and pressure regimes, resulting in close atomic-level contact between the two metal substrates. The interfacial diffusion layer was narrow and uniform in width, with only the necessary short-range atomic interdiffusion occurring to form a metallurgical bond. This not only ensured high bonding strength but also maintained the excellent physicochemical properties of both the copper and steel layers.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for sintering a carbon steel / copper composite sheet by discharge plasma hot pressing, characterized by, Includes the following steps: S1: Surface pretreatment, the carbon steel plate and pure copper plate to be composite are sequentially degreased, polished, pickled and activated and dried; S2: Laminated assembly, where pre-treated carbon steel plates and pure copper plates are laminated and assembled in a preset lamination method to form a layered prefabricated body; S3: Molding and pre-pressing: The layered preform is placed in a graphite mold and an axial pre-pressure of 5-20 MPa is applied to make the carbon steel plate and the pure copper plate fit tightly together. S4: Plasma hot pressing sintering. The assembled graphite mold is placed in the discharge plasma hot pressing sintering equipment. Under vacuum or protective atmosphere, axial pressure is applied and a segmented heating system is used for heating, sintering and heat preservation, so that the interface between the carbon steel plate and the pure copper plate forms a metallurgical bond. After cooling, the initial carbon steel / copper composite plate is obtained. S5: Aging treatment, the initial carbon steel / copper composite plate is kept at 350-550℃ for 15-120 minutes, and then cooled to room temperature to obtain the carbon steel / copper composite plate.

2. The spark plasma hot pressing sintering method for carbon steel / copper composite plates according to claim 1, characterized in that, In step S1, the carbon steel plate is one or more of Q235, Q345, or 20 steel; And / or, the pure copper plate is one of T2, TU1 or TU2 pure copper, and the purity of the pure copper is not less than 99.9%. And / or, the degreasing is performed by ultrasonic cleaning with anhydrous ethanol, acetone, deionized water or a combination thereof, for a cleaning time of 5 to 30 minutes; And / or, the grinding and roughening are performed by one or more of the following methods: sandblasting, sandpaper grinding, mechanical polishing, or wire brushing. And / or, the pickling activation is performed using one or more of hydrofluoric acid, nitric acid, oxalic acid, or hydrochloric acid solutions.

3. The method of claim 1, wherein the carbon steel / copper composite sheet is manufactured by a process of discharge plasma hot pressing sintering. In step S2, the lamination method is a two-layer steel / pure copper structure, a three-layer steel / pure copper / steel symmetrical structure, a three-layer pure copper / steel / pure copper structure, or a multi-layer alternating laminated structure.

4. The spark plasma hot pressing sintering method for carbon steel / copper composite plates according to claim 1, characterized in that, In step S3, a graphite paper, carbon paper, or boron nitride release layer is provided between the layered preform and the pressure head of the graphite mold, and / or on the inner wall of the graphite mold. And / or, the layered preform is placed at the center of the graphite mold.

5. The spark plasma hot pressing sintering method for carbon steel / copper composite plates according to claim 1, characterized in that, In step S4, the sintering temperature is 700–950℃; the sintering pressure is 20–80 MPa; the holding time is 5–30 min; and the vacuum degree is ≤10. -1 Pa; And / or, the segmented heating regime is as follows: heating from room temperature to 550-650°C at a heating rate of 80-150°C / min and holding at that temperature for 3-10 min, and then heating to the sintering temperature of 700-950°C at a heating rate of 30-80°C / min. And / or, in step S4, the protective atmosphere is one or more of argon, nitrogen, or an argon-hydrogen mixture; And / or, in step S4, the cooling rate of the furnace cooling is 50-200°C / h.

6. A carbon steel / copper clad sheet material, characterized by, It is prepared by the preparation method described in any one of claims 1-5.

7. The carbon steel / copper clad sheet of claim 6, wherein A continuous and dense diffusion metallurgical bonding interface is formed between the carbon steel layer and the pure copper layer.

8. The carbon steel / copper clad sheet of claim 6, wherein The carbon steel / copper composite plate has a two-layer or three-layer composite structure. And / or, the single-layer thickness of the carbon steel layer is 4-10 mm, and the single-layer thickness of the pure copper layer is 2-6 mm; And / or, when it is a two-layer composite structure, the total thickness is 6 to 16 mm; when it is a three-layer composite structure, the total thickness is 10 to 26 mm.

9. A device for preparing the carbon steel / copper composite plate material according to any one of claims 6 to 8, characterized by comprising: a discharge plasma heat press sintering device. include: The spark plasma sintering furnace cavity (4) is connected to a vacuum system and a protective atmosphere inlet system; The upper electrode (1) and the lower electrode (9) are respectively disposed at the top and bottom of the discharge plasma sintering furnace cavity (4) and are electrically connected to the pulsed DC power supply. The upper pressure head (2) and the lower pressure head (8) are connected to the upper electrode and the lower electrode respectively and are arranged coaxially. They can move relative to each other along the axial direction to apply axial pressure to the workpiece to be sintered. A graphite mold (3) is detachably set between the upper and lower pressure heads to accommodate the layered preform of carbon steel / copper composite plate.

10. The application of the carbon steel / copper composite plate according to any one of claims 6-8 in the field of preparing flow guide plates, power connection plates, wear-resistant conductive plates, heat dissipation plates or power equipment connection components.

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