Steel for steel-copper composite base material and manufacturing method thereof

Abstract

The invention relates to the technical field of metal composite materials, and discloses steel for a steel-copper composite base material and a manufacturing method thereof.The manufacturing method comprises the steps that a layer of amorphous boron film is deposited on the to-be-composited surface of the steel to serve as an interface reaction triggering layer; and overlapping the steel plate with the film and the copper plate, and heating to 650-800 DEG C while applying the pressure of 1-5 MPa to carry out heat-preservation compounding. Components such as phosphorus, nickel, antimony and rare earth are set in the steel and have a synergistic effect with an amorphous boron film trigger layer in the manufacturing method, an instantaneous liquid phase is formed in situ on a steel-copper interface, and high-strength metallurgical bonding at low temperature and low pressure is achieved. The prepared steel-copper composite board is high in interface bonding strength and low in interface thermal resistance and contact resistance, and the technical problems that in a traditional process, brittle phases are likely to be generated on an interface, and the process conditions are harsh are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of metal composite materials technology, specifically to a steel for steel-copper composite matrix and its manufacturing method. Background Technology

[0002] Steel-copper composites combine the strength, structural support, and low cost of steel with the electrical, thermal, and corrosion-resistant properties of copper, making them widely used in power transmission and distribution, chemical equipment, kitchenware manufacturing, and electronic packaging. Currently, common industrial methods for preparing steel-copper composites include explosive bonding, rolling bonding, and casting bonding.

[0003] However, due to the significant differences in physical and chemical properties between iron and copper, and their limited mutual solubility in the solid state, controlling the microstructure and properties of the interfacial region during composite processing using traditional hot working methods presents technical challenges. To achieve effective interatomic diffusion and metallurgical bonding, high processing temperatures and significant deformation pressures are typically required. Under these conditions, the steel-copper interface readily reacts, forming one or more layers of hard and brittle iron-copper intermetallic compounds. The presence of this brittle phase layer disrupts the continuity and toughness of the interface, becoming the root cause of crack initiation during the composite material's use, significantly reducing the interfacial bonding strength and the overall mechanical properties of the material.

[0004] To suppress the excessive growth of brittle phases, precise control of process parameters such as temperature, pressure, and time during hot working is required, which narrows the manufacturing process window. Inappropriate selection of process parameters or insufficient energy input can prevent the formation of a continuous metallurgical bond at the interface, resulting in defects such as voids and incomplete bonding; conversely, excessive energy input accelerates the thickening of the brittle phase. Therefore, under current technological conditions, achieving a high-strength metallurgical bond between steel and copper at relatively low temperatures and pressures, while effectively controlling the phase structure at the interface, is a technical problem to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a steel for steel-copper composite materials and its manufacturing method. This solves the problem that existing steel-copper composite material preparation technologies typically require harsh process conditions such as high temperature and high pressure, which easily lead to the formation of brittle intermetallic compounds at the interface that weaken the bonding performance, resulting in a narrow manufacturing process window and difficulty in precise control.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a steel for steel-copper composite base material and its manufacturing method, comprising, by weight, the following components: carbon ≤ 0.08 parts; silicon ≤ 0.2 parts; manganese 0.4-0.8 parts; phosphorus 0.06-0.12 parts; nickel 1.5-2.5 parts; rare earth 0.02-0.05 parts; antimony 0.005-0.02 parts; sulfur ≤ 0.02 parts; balance iron.

[0007] During the hot-pressing process with copper plates, the design of the above-mentioned chemical composition can achieve the following technical effects:

[0008] When heated at the steel-copper interface, the phosphorus and nickel components in the steel react with iron at a temperature below the melting points of steel and copper, forming a transient liquid phase in situ. This transient liquid phase acts as a medium for atomic diffusion, accelerating the migration of atoms between the steel and copper interfaces.

[0009] The antimony component in the steel is configured to partially dissolve in the transient liquid phase during its formation, thereby altering the viscosity of the liquid phase and influencing the atomic diffusion rate. This configuration is used to regulate the kinetics of the interfacial reaction, controlling the scope and uniformity of the reaction.

[0010] The rare earth component in the steel is configured to clean the steel surface before lamination. During the hot-pressing process, the rare earth component also reacts chemically with phosphorus enriched in the interface region, resulting in the in-situ generation of dispersed rare earth phosphide particles with high thermal stability in the final bond layer.

[0011] A method for manufacturing steel for steel-copper composite materials includes the following steps:

[0012] S1. Provide a steel plate made of steel for steel-copper composite base material, and a copper plate;

[0013] S2. An amorphous boron thin film is deposited on the surface of the steel plate to be composited. This thin film is used as an interface reaction triggering layer.

[0014] S3. The steel plate with the amorphous boron thin film is stacked with the copper plate, and the stacked assembly is placed in a vacuum or inert atmosphere protection environment.

[0015] S4. While applying a preset pressure to the component, heat it to a predetermined temperature and keep it at that temperature to complete the low-temperature reaction composite.

[0016] S5. Cool the composite components.

[0017] In one specific embodiment, the preset pressure in step S4 is 1-5 MPa, the preset temperature is 650-800°C, and the heat preservation time is 30-60 minutes.

[0018] In one specific embodiment, the thickness of the amorphous boron film deposited in step S2 is 1–5 μm. The deposition method for this amorphous boron film can be magnetron sputtering.

[0019] During the heating process in step S4, the amorphous boron film undergoes a solid-state exothermic reaction with the iron and nickel on the surface of the steel plate. The localized heat released by this reaction provides the triggering energy for the formation of the transient liquid phase at the interface of phosphorus, nickel, and iron elements in the steel plate.

[0020] In one specific embodiment, the method may further include a step of preparing steel for the steel-copper composite base material before step S1. This preparation step is achieved by vacuum induction melting, the process of which is as follows: after industrial pure iron is melted, ferrosilicon, electrolytic manganese, nickel plate, ferrophosphorus and antimony ingots are added in sequence according to a predetermined ratio, and rare earth metals are pressed in for alloying before tapping, and finally cast into ingots and rolled into plates.

[0021] This invention provides a steel for steel-copper composite materials and a method for manufacturing the same. It offers the following advantages:

[0022] 1. This invention sets specific amounts of phosphorus and nickel components in steel and combines this with setting an amorphous boron thin film on the surface of the steel plate as a reaction trigger layer, so that the manufacturing process of steel-copper composite can be completed in a lower temperature range of 650-800℃ and a lower pressure range of 1-5MPa, reducing the requirements of external energy supply and high-pressure equipment in the manufacturing process.

[0023] 2. This invention, through the design of the chemical composition of steel, especially the presence of nickel and the formation of a controlled transient liquid phase at the interface, promotes the formation of a gradient bonding layer with a smooth transition of composition at the steel-copper interface, replacing the brittle iron-copper intermetallic compound layer with obvious interface demarcation that is easily generated in traditional processes, thereby changing the microstructure of the interface region.

[0024] 3. The present invention adds a specific amount of rare earth components to steel. During the hot pressing composite process, the rare earth components undergo an in-situ chemical reaction with phosphorus enriched at the interface, generating highly thermally stable rare earth phosphide particles in the final bonding layer. These particles serve as an endogenous reinforcing phase and are distributed in the interface matrix. Detailed Implementation

[0025] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example:

[0027] Example 1

[0028] This embodiment provides a method for preparing a steel-copper composite plate.

[0029] Preparation of steel for steel-copper composite base materials

[0030] Chemical composition:

[0031] A steel for preparing a steel-copper composite base material is prepared by weight, and its chemical composition includes: 0.05 parts carbon, 0.1 parts silicon, 0.6 parts manganese, 0.09 parts phosphorus, 2.0 parts nickel, 0.035 parts rare earth, 0.012 parts antimony, ≤0.02 parts sulfur, and the balance being iron.

[0032] Smelting and rolling:

[0033] Industrial pure iron, electrolytic manganese, nickel plates, ferrophosphorus, industrial ferrosilicon, antimony ingots, and lanthanum-cerium mixed rare earth metals were used as raw materials and placed in a vacuum induction melting furnace. The materials were batched and smelted according to the aforementioned chemical composition. The melting temperature was controlled at 1620℃. The molten steel was poured into steel ingots and then homogenized and annealed at 1200℃ for 3 hours. The annealed ingots were heated to 1150℃ and subjected to multiple hot rolling passes, with the final rolling temperature controlled at 900℃, ultimately yielding a steel plate with a thickness of 5mm.

[0034] Manufacturing of steel-copper composite plates

[0035] Surface pretreatment:

[0036] Take the steel plate prepared above and a 5mm thick T2 copper plate, and sandblast the surfaces to be laminated. Then, ultrasonically clean them sequentially in acetone and anhydrous ethanol for 15 minutes each. Pickle the steel plate in a 12 vol.% hydrochloric acid aqueous solution at 50°C for 8 minutes, and pickle the copper plate in an 8 vol.% sulfuric acid aqueous solution at room temperature for 2 minutes. After treatment, rinse with deionized water and dry with high-purity nitrogen.

[0037] Deposition of the interface reaction trigger layer:

[0038] A thin film of amorphous boron was deposited on the pretreated steel plate surface to be laminated using magnetron sputtering. The deposition process parameters were: base vacuum 4.0 × 10⁻⁶. -4 Pa, working gas pressure 0.5 Pa, sputtering power 200 W, and deposition time sufficient to obtain a film with a thickness of 3 μm.

[0039] Low-temperature reaction compounding:

[0040] A steel plate with an amorphous boron thin film is stacked with a pretreated copper plate and placed in a vacuum hot press furnace, where the vacuum level is evacuated to 2.0 × 10⁻⁶. -3A pressure of 3 MPa was applied to the laminated assembly, and the temperature was increased to 725°C at a rate of 15°C / min, and held at this temperature and pressure for 45 minutes. After the holding period, the pressure was released by cooling the furnace to below 200°C, and the sample was removed to obtain the steel-copper composite plate.

[0041] Example 2

[0042] This embodiment provides a method for preparing a steel-copper composite plate.

[0043] Preparation of steel for steel-copper composite base materials

[0044] Chemical composition:

[0045] A steel for preparing a steel-copper composite base material, by weight, comprises the following chemical composition: 0.03 parts carbon, 0.05 parts silicon, 0.4 parts manganese, 0.06 parts phosphorus, 1.5 parts nickel, 0.02 parts rare earth, 0.005 parts antimony, ≤0.02 parts sulfur, and the balance being iron.

[0046] Smelting and rolling:

[0047] The same raw materials and equipment as in Example 1 were used. The melting temperature was controlled at 1600°C. The molten steel was poured into steel ingots, and then homogenized and annealed at 1150°C for 4 hours. The annealed steel ingots were heated to 1100°C and subjected to multiple hot rolling passes, with the final rolling temperature controlled at 850°C, to finally obtain a steel plate with a thickness of 3 mm.

[0048] Manufacturing of steel-copper composite plates

[0049] Surface pretreatment:

[0050] Take the steel plate prepared above and a T2 copper plate with a thickness of 3 mm, and perform the same surface pretreatment as in Example 1.

[0051] Deposition of the interface reaction trigger layer:

[0052] An amorphous boron thin film was deposited on the pretreated steel plate surface to be laminated using magnetron sputtering. The deposition process parameters were: base vacuum 5.0 × 10⁻⁶. -4 Pa, working pressure 0.8 Pa, sputtering power 100 W, and deposition time sufficient to obtain a film with a thickness of 1 μm.

[0053] Low-temperature reaction compounding:

[0054] A steel plate with an amorphous boron thin film is stacked with a pretreated copper plate and placed in a vacuum hot press furnace, where the vacuum level is evacuated to 5.0 × 10⁻⁶. -3A pressure of 1 MPa is applied to the laminated assembly, and the temperature is increased to 650°C at a rate of 10°C / min, and held at this temperature and pressure for 30 minutes. After the holding period, the pressure is released by cooling the furnace to below 200°C, and the sample is removed to obtain the steel-copper composite plate.

[0055] Example 3

[0056] This embodiment provides a method for preparing a steel-copper composite plate.

[0057] Preparation of steel for steel-copper composite base materials

[0058] Chemical composition:

[0059] A steel for preparing a steel-copper composite base material, by weight, comprises the following chemical composition: 0.08 parts carbon, 0.2 parts silicon, 0.8 parts manganese, 0.12 parts phosphorus, 2.5 parts nickel, 0.05 parts rare earth, 0.02 parts antimony, ≤0.02 parts sulfur, and the balance being iron.

[0060] Smelting and rolling:

[0061] The same raw materials and equipment as in Example 1 were used. The melting temperature was controlled at 1650°C. The molten steel was poured into steel ingots, and then homogenized and annealed at 1250°C for 2 hours. The annealed steel ingots were heated to 1200°C and subjected to multiple hot rolling passes, with the final rolling temperature controlled at 950°C, to obtain a steel plate with a thickness of 10 mm.

[0062] Manufacturing of steel-copper composite plates

[0063] Surface pretreatment:

[0064] Take the steel plate prepared above and a T2 copper plate with a thickness of 10 mm, and perform the same surface pretreatment as in Example 1.

[0065] Deposition of the interface reaction trigger layer:

[0066] A thin film of amorphous boron was deposited on the pretreated steel plate surface to be laminated using magnetron sputtering. The deposition process parameters were: base vacuum 2.0 × 10⁻⁶. -4 Pa, working gas pressure 0.2 Pa, sputtering power 300 W, and deposition time sufficient to obtain a film with a thickness of 5 μm.

[0067] Low-temperature reaction compounding:

[0068] A steel plate with an amorphous boron thin film is stacked with a pretreated copper plate and placed in a vacuum hot press furnace, where the vacuum level is evacuated to 1.0 × 10⁻¹. -3A pressure of 5 MPa is applied to the laminated assembly, and the temperature is increased to 800°C at a rate of 20°C / min, and held at this temperature and pressure for 60 minutes. After the holding period, the assembly is cooled to below 200°C in the furnace, the pressure is released, and the sample is removed to obtain the steel-copper composite plate.

[0069] Comparative Example 1

[0070] Compared with Example 1, the difference is that the steel used in step 1 is conventional Q235 low carbon steel, whose chemical composition by weight includes: 0.18 parts carbon, 0.20 parts silicon, 0.45 parts manganese, ≤0.04 parts phosphorus, and ≤0.04 parts sulfur, and does not contain the nickel, rare earth and antimony components as defined in this invention; the remaining steps, including all process parameters for surface pretreatment, deposition of the interface reaction trigger layer and low-temperature reaction composite, are exactly the same as in Example 1.

[0071] Comparative Example 2

[0072] Compared with Example 1, the difference is that in the chemical composition of the steel used in the steel-copper composite base material prepared in step 1, the phosphorus content is controlled at the level of conventional impurities, specifically 0.015 parts, while the content of other components such as nickel, rare earth, and antimony, as well as all manufacturing steps and process parameters, are exactly the same as in Example 1.

[0073] Comparative Example 3

[0074] Compared with Example 1, the difference is that the steel used in the steel-copper composite base material prepared in step 1 does not contain antimony components in its chemical composition, while the content of other components such as phosphorus, nickel, and rare earth, as well as all manufacturing steps and process parameters, are exactly the same as in Example 1.

[0075] Comparative Example 4

[0076] Compared with Example 1, the difference is that the steel used in the steel-copper composite base material prepared in step 1 does not contain rare earth components in its chemical composition, while the content of other components such as phosphorus, nickel, and antimony, as well as all manufacturing steps and process parameters, are exactly the same as in Example 1.

[0077] Comparative Example 5

[0078] Compared with Example 1, the difference is that the deposition of the interface reaction trigger layer is omitted in the manufacturing process. That is, after the surface pretreatment of the steel plate, the amorphous boron film is not deposited, and it is directly laminated with the pretreated copper plate and the subsequent low-temperature reaction composite step is performed. All other steps and process parameters are exactly the same as those in Example 1.

[0079] Test Example 1: Interface Bond Strength Shear Test

[0080] This test example is used to detect the interfacial shear strength of the steel-copper composite plates prepared in Examples 1-3 and Comparative Examples 1-5.

[0081] Experimental steps:

[0082] Sample preparation: Rectangular shear samples with dimensions of 25 mm × 10 mm were cut from the composite plates prepared in Examples 1-3 and Comparative Examples 1-5 using a wire EDM machine along a direction perpendicular to the rolling direction of the plate. The composite interface was ensured to be parallel to the 25 mm length of the sample. Five valid samples were prepared for each group.

[0083] Test equipment and fixtures: The test was conducted on a universal testing machine. A dedicated shear fixture was used, which could separately fix the steel and copper layers of the specimen and ensure that the load applied by the testing machine was parallel to the steel-copper composite interface.

[0084] Test execution: The specimen is clamped in the shear fixture, the loading rate of the testing machine is set to 1 mm / min, the testing machine is started and the load is applied until shear separation occurs at the interface or significant plastic deformation occurs on one side of the material. During the test, the system automatically records the load-displacement curve.

[0085] Data Processing: The peak load, i.e., the maximum shear force, is read from the recorded load-displacement curves. The actual shear area at the interface of each specimen is accurately measured using vernier calipers. The interfacial shear strength of each specimen is calculated using the formula: Interfacial Shear Strength = Maximum Shear Force / Shear Area.

[0086] Results Recording: Record the interfacial shear strength calculation results of the five effective specimens in each group, and calculate their arithmetic mean as the final cross-sectional shear strength of the specimens in that group.

[0087] Experimental data:

[0088] Table 1. Interfacial shear strength test results of the examples and comparative examples.

[0089] Sample number Interfacial shear strength Example 1 235.4 Example 2 218.9 Example 3 242.1 Comparative Example 1 45.7 Comparative Example 2 65.3 Comparative Example 3 98.6 Comparative Example 4 121.5 Comparative Example 5 38.2

[0090] Results analysis:

[0091] The test data in Table 1 show that the composite plates prepared in Examples 1, 2, and 3 have significantly higher interfacial shear strength values ​​than those prepared in Comparative Examples 1 to 5. Comparative Example 1 uses conventional low-carbon steel, while Comparative Example 5 does not have an interfacial reaction triggering layer; both have the lowest interfacial shear strength values. This indicates that the steel containing specific chemical components designed in this invention, together with the amorphous boron thin film at the interface, forms the basis for a high-strength metallurgical bond. The amorphous boron thin film, acting as a reaction triggering layer, provides the necessary energy input for the in-situ interfacial reaction.

[0092] Comparing the data from Example 1 with those from Comparative Examples 2 and 3, significant differences in interfacial bonding strength can be observed. In Comparative Example 2, due to the lack of a specific amount of phosphorus, a transient liquid phase serving as a medium for rapid atomic diffusion failed to form at the interface under the set hot-pressing process conditions. The low solid-state atomic diffusion efficiency prevented the formation of a continuous and dense metallurgical bonding layer. In Comparative Example 3, the lack of antimony resulted in a lack of effective control over the kinetics of the transient liquid phase reaction at the interface, potentially leading to uneven reaction or excessive erosion of the substrate. This, in turn, affected the integrity of the final bonding interface, resulting in a lower shear strength value than in Example 1.

[0093] Comparing the data from Example 1 and Comparative Example 4, there is a significant difference in the interfacial shear strength values. This is attributed to the fact that in the steel of Example 1, the rare earth components reacted chemically with the phosphorus enriched in the interfacial region during the hot-pressing composite process, resulting in the in-situ formation of dispersed rare earth phosphide reinforcing phases in the final bonding layer. The presence of these hard phases provides microscopic reinforcement to the interfacial bonding layer. Therefore, the high cross-sectional shear strength of Examples 1-3 is a direct reflection of the synergistic effect of the steel's chemical composition and various technical features in the manufacturing process.

[0094] Test Example 2: Interfacial Bond Strength Tensile Test

[0095] This test example is used to test the tensile strength of each group of steel-copper composite plates prepared in Examples 1-3 and Comparative Examples 1-5 in the direction perpendicular to the interface.

[0096] Experimental steps:

[0097] Specimen preparation: Cylindrical tensile specimens perpendicular to the composite interface were prepared from the composite plates prepared in Examples 1-3 and Comparative Examples 1-5 by machining. The gauge length of the specimen was 5 mm in diameter, and the composite interface was located in the middle of the gauge length. Five valid specimens were prepared for each group.

[0098] Test equipment and fixtures: The test was conducted on a universal testing machine. Standard tensile fixtures were used to hold the specimens, ensuring that the applied tensile load was perpendicular to the steel-copper composite interface.

[0099] Test execution: The specimen is clamped on the testing machine, the tensile rate of the testing machine is set to 0.5 mm / min, the testing machine is started and a tensile load is applied until the specimen breaks. During the test, the system automatically records the load displacement data.

[0100] Data Processing: Examine the fracture location of each specimen. Only specimens where the fracture occurred at the steel-copper interface are selected as valid data. Record the maximum tensile force at fracture. Calculate the interfacial tensile strength of each valid specimen using the formula: Interfacial Tensile Strength = Maximum Tensile Force / Original Cross-sectional Area.

[0101] Results Recording: Record the interfacial tensile strength calculation results of the 5 valid specimens in each group, and calculate their arithmetic mean as the final interfacial tensile strength of the sample group.

[0102] Experimental data:

[0103] Table 2. Interfacial tensile strength test results of the examples and comparative examples.

[0104] Sample number Interfacial tensile strength Example 1 152.8 Example 2 141.3 Example 3 160.7 Comparative Example 1 28.3 Comparative Example 2 42.8 Comparative Example 3 61.5 Comparative Example 4 83.2 Comparative Example 5 21.6

[0105] Results analysis:

[0106] Table 2 clearly shows that the composite plates prepared in Examples 1, 2, and 3 all have higher interfacial tensile strength values ​​than those in Comparative Examples 1 to 5. The interfacial tensile strength values ​​in Comparative Examples 1 and 5 are at the lowest level, which confirms that the specific chemical composition of the steel and the amorphous boron thin film trigger layer used in this invention are two fundamental prerequisites for achieving effective interfacial bonding. Without either one, the interface cannot form a metallurgical structure capable of resisting vertical tensile stress under the set low-temperature process.

[0107] The interfacial tensile strength values ​​of Example 1 differ significantly from those of Comparative Examples 2 and 3. In Comparative Example 2, due to the lack of synergistic effects of phosphorus and nickel in the steel, a transient liquid phase cannot form at the interface. The interatomic bonding relies on slow solid-state diffusion, and the resulting bonding force is insufficient to resist effective tensile loads. In Comparative Example 3, although a transient liquid phase is formed, the lack of antimony component to regulate the physical properties of this liquid phase prevents the uniformity of the interfacial reaction from being guaranteed. This may lead to defects in localized areas of the interface, which become stress concentration points during the tensile process, resulting in premature interface failure.

[0108] The interfacial tensile strength of Example 1 is higher than that of Comparative Example 4. This is because the steel in Example 1 contains rare earth elements. During the interfacial reaction, these elements react in situ with phosphorus, generating a dispersed hard reinforcing phase within the interfacial bonding layer. The presence of these reinforcing phases allows the interfacial bonding layer to more effectively suppress the initiation and propagation of microcracks when subjected to vertical tensile stress. The high interfacial tensile strength of Examples 1-3 is the result of the synergistic effect of multiple technical characteristics between their steel composition and manufacturing process.

[0109] Test Example 3: Interface Thermal Resistance Test

[0110] This test example is used to detect the interfacial thermal resistance of the steel-copper composite plates prepared in Examples 1-3 and Comparative Examples 1-5.

[0111] Experimental steps:

[0112] Sample preparation: Circular thin-film samples with a diameter of 12.7 mm and a thickness of 2 mm were cut from the composite plates prepared in Examples 1-3 and Comparative Examples 1-5 using a wire EDM machine. Ensure that the two circular surfaces of the sample are parallel to the steel-copper composite interface. Three valid samples were prepared for each group.

[0113] Measurement of thermophysical parameters:

[0114] The thermal diffusivity (α) of each sample was measured at room temperature along the direction perpendicular to the interface using a laser flare thermal conductivity meter.

[0115] The specific heat capacity (Cp) of the corresponding materials for each group of samples was measured using a differential scanning calorimeter.

[0116] The density (ρ) of each group of samples was measured using Archimedes' displacement method.

[0117] Equivalent thermal conductivity calculation: According to the formula: Equivalent thermal conductivity (λ) eff The equivalent thermal conductivity of each composite plate sample is calculated by α×ρ×Cp.

[0118] Interfacial thermal resistance calculation:

[0119] According to the formula: Total thermal resistance (R) total )=L / λ eff Calculate the total thermal resistance of the sample, where L is the total thickness of the sample.

[0120] Calculate the thermal resistance of the steel layer and the copper layer separately: R steel =L steel / λ steel R copper =L copper / λ copper L steel and L copper Let λ be the thickness of each layer. steel and λ copper This represents the intrinsic thermal conductivity of the corresponding material.

[0121] According to the formula: Interfacial thermal resistance (R) interface ) = R total -R steel -R copper The thermal resistance of the steel-copper interface was calculated.

[0122] Results Recording: Record the interfacial thermal resistance calculation results of the three effective samples in each group, and calculate their arithmetic mean as the final interfacial thermal resistance of the sample group.

[0123] Experimental data:

[0124] Table 3. Interfacial thermal resistance test results of the examples and comparative examples.

[0125] Sample number <![CDATA[Interface thermal resistance (10 -6 m 2 ·K / W)]]> Example 1 8.7 Example 2 9.9 Example 3 8.1 Comparative Example 1 155.6 Comparative Example 2 112.4 Comparative Example 3 78.3 Comparative Example 4 45.1 Comparative Example 5 182.3

[0126] Results analysis:

[0127] The test data in Table 3 show that the composite plates prepared in Examples 1, 2, and 3 have relatively low interfacial thermal resistance values, while the interfacial thermal resistance values ​​of Comparative Examples 1 to 5 are significantly higher. Comparative Examples 1 and 5 have the highest interfacial thermal resistance values, indicating that in the absence of the specific chemical composition steel designed in this invention or the amorphous boron thin film trigger layer, the steel and copper only form a physical bond primarily based on mechanical contact. At such interfaces, heat transfer is hindered by numerous microscopic voids and discontinuous contact points, resulting in extremely high phonon scattering, thus manifesting as high interfacial thermal resistance.

[0128] The interfacial thermal resistance of Example 1 was significantly lower than that of Comparative Examples 2 and 3. In Comparative Example 2, due to the lack of synergistic effect of the phosphorus-nickel components, a transient liquid phase could not be formed at the interface, the metallurgical bonding between atoms was insufficient, and a large number of lattice mismatches and microscopic defects existed at the interface. These defects, acting as scattering centers for hot carriers, increased the resistance to heat transfer across the interface. In Comparative Example 3, although a transient liquid phase was formed, the lack of antimony components to regulate reaction kinetics resulted in an interfacial bonding layer that may have uneven thickness or disordered structure, similarly hindering heat transfer and making its interfacial thermal resistance higher than that of Example 1.

[0129] The interfacial thermal resistance of Example 1 is lower than that of Comparative Example 4. In Example 1, the rare earth components in the steel not only purify the interface and reduce the scattering of phonons by impurity atoms, but also, together with the dispersed rare earth phosphides generated in situ by phosphorus, construct a gradient transition layer with a more ordered structure and better atomic matching. This gradient transition layer mitigates the phonon spectrum mismatch, providing a channel for effective heat conduction between the steel and copper. Therefore, the low interfacial thermal resistance of Examples 1-3 is a direct result of the synergistic effect of the steel components and manufacturing process, which forms a continuous, dense, and structurally ordered metallurgical bonding interface.

[0130] Test Example 4: Interface Contact Resistance Test

[0131] This test example is used to detect the interfacial contact resistance of the steel-copper composite plates prepared in Examples 1-3 and Comparative Examples 1-5.

[0132] Experimental steps:

[0133] Sample preparation: Rectangular samples with dimensions of 20mm × 5mm × 5mm were cut from the composite plates prepared in Examples 1-3 and Comparative Examples 1-5 using a wire EDM machine. The cross-sections of the samples were mechanically ground and polished to ensure a smooth surface and expose a clear steel-copper interface.

[0134] Test equipment and setup: A four-probe tester was used, equipped with a constant DC current source and a high-precision micro-ohmmeter. Four equally spaced tungsten carbide probes were vertically pressed onto the polished sample cross-section.

[0135] Probe Arrangement: Adjust the probe positions so that their connecting lines are perpendicular to the steel-copper interface. Place the two outer probes as current input terminals in the steel and copper regions respectively. Arrange the two inner probes as voltage measurement terminals close to both sides of the interface to span the entire interface area.

[0136] Test execution: A constant DC current of 1A is applied to the outer probe through a current source. Simultaneously, the voltage drop (ΔV) between the two inner voltage probes is accurately measured using a micro-ohmmeter.

[0137] Data processing and calculation: According to the formula: Interfacial contact resistivity (Ω·m) 2 The interfacial contact resistivity is calculated as follows: )=(ΔV×A) / |. Where ΔV is the measured voltage drop (V), | is the applied current (A), and A is the cross-sectional area of ​​the sample.

[0138] Results Recording: Record the interfacial contact resistivity calculation results of 5 effective samples in each group, and calculate their arithmetic mean as the final interfacial contact resistivity of the sample group.

[0139] Experimental data:

[0140] Table 4. Interfacial contact resistivity test results of the examples and comparative examples.

[0141] Sample number <![CDATA[Interface contact resistivity (10 -9 Ω·m 2 )]]> Example 1 1.57 Example 2 1.82 Example 3 1.49 Comparative Example 1 231.5 Comparative Example 2 168.9 Comparative Example 3 95.2 Comparative Example 4 53.6 Comparative Example 5 288.4

[0142] Results analysis:

[0143] The test data in Table 4 show that the interfacial contact resistivity values ​​of Examples 1, 2, and 3 are significantly lower than those of all comparative examples. Comparative Examples 1 and 5 have the highest interfacial contact resistivity values, indicating that when the steel chemical composition designed in this invention is not used or the amorphous boron thin film trigger layer is not used, the interface formed between steel and copper is electrically discontinuous. This interface contains a large number of microscopic voids and oxide inclusions, which constitute a strong scattering barrier for charge carriers, resulting in extremely high resistance.

[0144] The interfacial contact resistivity of Example 1 was significantly lower than that of Comparative Examples 2 and 3. This directly reflects the influence of differences in interfacial microstructure on electron transport properties. In Comparative Example 2, due to the lack of synergistic effect of phosphorus and nickel components in the steel, a transient liquid phase could not be formed at the interface, thus failing to establish a continuous metal atom bonding network. Electrons had to overcome a large number of lattice mismatches and defect barriers when crossing the interface. In Comparative Example 3, the lack of antimony component to regulate the interfacial reaction resulted in a bonding layer that may have compositional segregation or structural inhomogeneity. These inhomogeneities also constituted additional electron scattering centers, increasing the interfacial resistivity.

[0145] The interfacial contact resistivity of Example 1 is lower than that of Comparative Example 4. This difference is attributed to the effect of the rare earth components. During the interfacial reaction, the rare earth components, on the one hand, remove impurity atoms such as oxygen and sulfur from the interfacial region, reducing the scattering of conductive electrons by these impurities; on the other hand, the rare earth phosphides formed in situ with phosphorus are dispersed in the interfacial layer, contributing to the formation of a region with a smoother transition in composition and structure. This gradient transition layer provides a more unobstructed transport path for electrons. Therefore, the low interfacial contact resistivity of Examples 1-3 is a direct reflection of the physically dense, chemically clean, and structurally continuous metallurgical bonding interface formed by the synergistic effect of the steel components and manufacturing process.

Claims

1. A steel for steel-copper clad base material, characterized by, The steel copper composite base steel is made of raw materials including the following weight parts: Carbon: ≤0.08 parts; Silicon: ≤0.2 parts; Manganese: 0.4-0.8 parts; Phosphorus: 0.06-0.12 parts; Nickel: 1.5-2.5 parts; Rare earth: 0.02-0.05 parts; Antimony: 0.005-0.02 parts; Sulfur: ≤0.02 parts; Iron: the rest.

2. A steel for steel-copper composite base material according to claim 1, characterized by The phosphorus and the nickel cooperate to form a transient liquid phase at the interface with copper through in-situ reaction, as a medium for atomic diffusion.

3. The steel of claim 1, wherein The rare earth is used to purify the interface to be compounded and to have a secondary reaction with the phosphorus enriched at the interface during the compounding process, to generate in-situ dispersed rare earth phosphide as a reinforcing phase.

4. The steel of claim 1, wherein The antimony is used as a transient liquid phase reaction stabilizer to regulate the physical properties of the transient liquid phase when it is formed, to control the kinetic process of the interface reaction.

5. A method of manufacturing a steel for steel-copper clad base material according to any one of claims 1 to 4, characterized in that, The method comprises the following steps: S1, providing a steel plate made of steel and a copper plate for a steel copper composite base; S2, depositing an amorphous boron film on the surface of the steel plate to be compounded as an interface reaction trigger layer; S3, stacking the steel plate with the amorphous boron film and the copper plate and placing them in a vacuum or inert atmosphere protection environment; S4, heating the stacked assembly to a predetermined temperature while applying pressure to it, to complete the low-temperature reaction compounding; S5, cooling the compounded assembly.

6. The method of producing a steel for steel-copper composite base material according to claim 5, characterized by, The pressure in step S4 is 1-5 MPa, the predetermined temperature is 650-800℃, and the holding time is 30-60 minutes.

7. The method of producing a steel for steel-copper composite base material according to claim 5, characterized by, The thickness of the amorphous boron film deposited in step S2 is 1-5 μm.

8. The method of producing a steel for steel-copper composite base material according to claim 5, characterized by, In step S4, the amorphous boron film has a solid-state exothermic reaction with iron and nickel in the steel plate, which provides trigger energy for the phosphorus, nickel and iron elements in the steel plate to form a transient liquid phase at the interface.

9. The method of producing a steel for steel-copper composite base material according to claim 5, characterized by, The method for depositing the amorphous boron film in step S2 is a magnetron sputtering method.

10. The method of producing a steel for steel-copper composite base material according to claim 5, characterized by, The method further comprises a step of preparing the steel copper composite base steel before step S1, which is: using vacuum induction melting to melt industrial pure iron, then adding silicon iron, electrolytic manganese, nickel plate, phosphorus iron and metal antimony ingot in sequence, and finally pressing rare earth metal before tapping for alloying.