Silver-copper alloy-copper penetrating type composite belt and preparation method thereof

Abstract

The invention provides a silver-copper alloy-copper penetrating type composite belt and a preparation method thereof. The silver-copper alloy-copper penetrating type composite belt comprises a copper base body and a silver-copper alloy penetrating body arranged in the copper base body in a penetrating mode, the copper content in the silver-copper alloy penetrating body is 20 wt%-40 wt%, and a diffusion layer of 0.5-2.0 micrometers is formed between the copper base body and the silver-copper alloy penetrating body. The core technical problems that an existing silver-copper composite fusing material is poor in thermal shock stability, low in breaking consistency and unstable in interface bonding structure are solved. The invention further provides a preparation method of the silver-copper alloy-copper penetrating type composite belt.

Description

Technical Field

[0001] This invention belongs to the technical field of fusible materials and composite metal materials, specifically relating to a silver-copper alloy-copper through-type composite strip and its preparation method. Background Technology

[0002] Silver-copper alloy-copper composite strips, as core fusing materials, are widely used in low-voltage electrical appliances and circuit protection. Their thermal shock stability and breaking consistency directly determine the operational reliability and operational accuracy of circuit protection devices, making them a core focus of fusing material research and development. In existing technologies, silver-copper composite fusing materials mostly use pure silver or silver-copper alloys with no clearly defined composition as the conductor functional area, combined with a copper matrix to form a composite structure. While this can basically meet the conductivity and fusing requirements of conventional circuits, under complex operating conditions such as short-circuit breaking and repeated thermal shocks, the structural stability and operational consistency of the material are difficult to meet high-standard application requirements, becoming a key factor restricting its promotion in the field of high-end circuit protection.

[0003] The physical properties of pure silver and copper substrates are not well matched. Their coefficients of linear expansion differ significantly, and during thermal shock with rapid temperature changes, significant thermal stress concentration is likely to occur at the interface. After long-term cycling, structural damage such as microcracks and interface peeling may occur, greatly reducing the material's thermal shock resistance. When using non-eutectic silver-copper alloys to replace pure silver, new technical problems arise due to the phase transformation characteristics of the alloys themselves. These alloys have obvious solid-liquid coexistence zones during melting, and cannot achieve rapid and concentrated solid-liquid transformation during melting. This can easily lead to dispersed bridge formation and fluctuating arc root position, resulting in a decrease in the consistency of the breaking action and affecting the accuracy of circuit protection.

[0004] Meanwhile, existing silver-copper composite strip manufacturing processes lack synergistic control over composition and interfacial microstructure. The interfacial bonding between the silver-copper functional zones and the copper matrix is ​​often a simple physical composite, making it difficult to form a stable metallurgical interface. Uneven diffusion layer thickness and poor continuity are common problems. This unstable interfacial structure not only exacerbates thermal stress concentration but also affects the synchronicity of heat conduction and phase transformation during melting, further deteriorating the material's thermal shock stability and fracture consistency. In summary, how to solve the technical challenges of interfacial thermal stress concentration, diffusion layer instability, and fluctuating fracture surface formation in existing silver-copper composite fusing materials through precise alloy composition definition and effective control of interfacial microstructure, and achieve synergistic optimization of thermal shock stability and fracture consistency, has become a key technical problem urgently needing to be solved in this field. Summary of the Invention

[0005] This invention aims to at least solve one of the aforementioned technical problems existing in the prior art. To this end, this invention provides a silver-copper alloy-copper through-type composite strip, addressing the technical pain points of existing silver-copper composite fusing materials under short-circuit breaking and thermal shock conditions. These problems arise from the use of pure silver or silver-copper alloys with no clearly defined composition, and the lack of precise control over the interface diffusion layer. Specifically, this leads to interfacial thermal stress concentration due to the large difference in the thermal expansion coefficients between pure silver and the copper matrix; dispersed bridging formation and reduced breaking consistency caused by the solid-liquid coexistence zone during the melting of non-eutectic silver-copper alloys; and unstable interfacial diffusion layer leading to structural damage and further deterioration of the material's thermal shock stability and breaking performance. This invention solves the core technical problems of poor thermal shock stability, low breaking consistency, and unstable interfacial bonding structure in existing silver-copper composite fusing materials.

[0006] The present invention also provides a method for preparing a silver-copper alloy-copper through-type composite strip.

[0007] A first aspect of the present invention provides a silver-copper alloy-copper through-hole composite strip, comprising a copper substrate and a silver-copper alloy through-hole disposed in the copper substrate, wherein the copper content in the silver-copper alloy through-hole is 20wt%~40wt%, and a diffusion layer of 0.5~2.0μm is formed between the copper substrate and the silver-copper alloy through-hole.

[0008] The silver-copper alloy-copper through-type composite strip of the present invention has at least the following beneficial effects: The copper content in the silver-copper alloy penetrator is 20wt%~40wt%. Silver-copper alloys in this copper content range are close to the Ag-Cu eutectic composition. Their phase transformation can be completed at a single temperature without a significant solid-liquid coexistence region. During the melting process, the solid-liquid transformation can be completed rapidly within a narrow temperature range, forming a concentrated broken bridge structure, which effectively improves the stability of the arc root, avoids the fluctuation of the breaking action caused by the dispersion of broken bridges, and greatly improves the breaking consistency of the composite band. At the same time, the linear expansion coefficient of silver-copper alloy in this composition range is closer to that of the copper matrix, which greatly reduces the interfacial thermal mismatch stress between the two, reduces the problem of interfacial thermal stress concentration under thermal shock conditions, and improves the structural stability of the composite band under rapid temperature changes.

[0009] A diffusion layer of 0.5~2.0μm is formed between the copper substrate and the silver-copper alloy penetrator. This continuous metallurgical diffusion layer of this thickness ensures a stable metallurgical bonding effect between the copper substrate and the silver-copper alloy penetrator, improves the interfacial bonding strength between the two, avoids structural damage such as interfacial peeling and microcracks after thermal shock cycling, and enhances the thermal shock resistance of the composite band. It also prevents the diffusion layer from altering the phase transformation characteristics of the silver-copper alloy penetrator if it is too thick, or causing insufficient interfacial bonding force if it is too thin, thus ensuring the stable performance of the melting and breaking function of the silver-copper alloy penetrator and taking into account both the stability of the interfacial structure and the accuracy of melting and breaking.

[0010] A silver-copper alloy penetrator with a copper content of 20wt%~40wt% complements a diffusion layer of 0.5~2.0μm. On the one hand, the phase transformation behavior and thermal expansion matching are optimized by controlling the alloy composition. On the other hand, the interface structure is stabilized by controlling the thickness of the diffusion layer. The core problems of thermal stress concentration, diffusion layer instability and fracture surface fluctuation in existing silver-copper composite fusing materials are solved from two dimensions: alloy bulk performance and interface bonding performance. The composite strip has excellent structural stability and can maintain precise and consistent breaking action under complex working conditions of short-circuit breaking and repeated thermal shock, which significantly improves the reliability and service life of the composite strip as a fusing material.

[0011] The diffusion layer is a metallurgical bonding transition region formed between the copper matrix and the silver-copper alloy through-body. Precise control of its thickness is a key technical means for this invention to solve the core problems of unstable interfacial bonding structure, poor thermal shock stability, and low fracture consistency in existing silver-copper composite fusing materials. It directly determines the synergistic effect of the composite band's interfacial bonding performance, structural stability, and fusing function, and is also the core guarantee for achieving bidirectional optimization of alloy bulk performance and interfacial bonding performance. The formation of the diffusion layer is the core marker of the transformation from physical adhesion to atomic-level metallurgical bonding between the copper matrix and the silver-copper alloy through-body, and precise control of its thickness is a prerequisite for achieving stable metallurgical bonding. A diffusion layer that is too thin or too thick will directly lead to the failure of the interfacial bonding structure. Specifically: When the diffusion layer is too thin (<0.5μm, or h / δ<0.00025), atomic diffusion is insufficient, and a continuous, dense metallurgical bond cannot be formed between the copper matrix and the silver-copper alloy penetrant. Physical bonding remains dominant, resulting in significantly insufficient interfacial adhesion. Under the stress and temperature changes of thermal shock cycling and short-circuit interruption, gaps and delamination easily appear at the interface, potentially even leading to displacement and fracture of the silver-copper alloy penetrant.

[0012] Excessive diffusion layer thickness (>2.0 μm, or h / δ>0.001): Excessive atomic diffusion can distort the microstructure of the interfacial bonding region, exceeding the reasonable range for metallurgical bonding. This can lead to stress concentration zones at the interface, weakening its mechanical properties. Furthermore, excessive diffusion results in an excessively large mixing area between the copper matrix and the silver-copper alloy, compromising the structural integrity of the interface. After thermal shock, even very slight stress marks may appear at the interface, demonstrating the negative impact of excessive thickness on interfacial structural stability.

[0013] Precisely controlling the diffusion layer thickness of 0.5~2.0μm allows copper and silver atoms to diffuse moderately and uniformly at the interface, forming a continuous and dense metallurgical bonding transition zone. This enables seamless bonding between the copper matrix and the silver-copper alloy through-body, significantly improving the interfacial bonding strength and laying the foundation for the structural integrity of the composite strip under complex working conditions.

[0014] According to some embodiments of the present invention, a diffusion layer of 0.5 to 1.6 μm is formed between the copper substrate and the silver-copper alloy through-body.

[0015] According to some embodiments of the present invention, the copper substrate and the silver-copper alloy through-body are formed with any value of 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1.0μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, and 1.6μm, such as 1.0μm, or any range of both, such as 0.8μm to 1.2μm.

[0016] According to some embodiments of the present invention, the copper content in the silver-copper alloy penetrator is 20wt%~30wt%.

[0017] According to some embodiments of the present invention, the copper content in the silver-copper alloy penetrator is 26wt%~30wt%.

[0018] According to some embodiments of the present invention, the copper content in the silver-copper alloy penetrator is any value of 26wt%, 27wt%, 28wt%, 29wt%, or 30wt%, such as 28wt%, or any range of two, such as 28wt% to 30wt%.

[0019] According to some embodiments of the present invention, the width of the top of the silver-copper alloy penetrator is W, the minimum cross-sectional width of the silver-copper alloy penetrator is δ, and W is 1.2 to 1.5 times δ.

[0020] The width W at the top of the silver-copper alloy through-body is set to 1.2 to 1.5 times its minimum cross-sectional width δ. This structural proportion design is compatible with the melting function, interfacial bonding characteristics, and overall mechanical properties of the composite strip of the silver-copper alloy through-body. This design allows the through-body to form a reasonable cross-sectional shape that is wider at the top and narrower at the bottom, making it easier for heat to accumulate at the minimum cross-sectional width δ during melting, accelerating the solid-liquid transformation at that location, further ensuring the formation of a concentrated broken bridge structure, avoiding multiple fractures during melting, and improving the fracture consistency of the composite strip. At the same time, it increases the contact area between the top of the through-body and the copper substrate, improving the interfacial bonding force between the two, and dispersing thermal shock and melting. The stress concentration at the interface during the process reduces the generation of structural damage such as microcracks and interface peeling, enhancing the thermal shock stability and structural integrity of the composite strip. At the same time, the cross-sectional shape of the through-body at this ratio is suitable for the hot pressing composite and rolling preparation process, which can effectively avoid the fracture and misalignment of the through-body during the composite process, and also make the stress distribution during rolling more uniform, ensuring the yield of the product during the preparation process. Moreover, the structural parameters can be precisely controlled through grooving and composite processes, which has good industrial applicability. It works synergistically with the control of silver-copper alloy composition and diffusion layer thickness to further optimize the thermal shock stability and fracture consistency of the composite strip.

[0021] According to some embodiments of the present invention, the width W of the top of the silver-copper alloy penetrating body is 4~8mm.

[0022] According to some embodiments of the present invention, the minimum cross-sectional width δ of the silver-copper alloy penetrator is 2~4 mm.

[0023] According to some embodiments of the present invention, W is any value of 1.2 times, 1.3 times, 1.4 times, or 1.5 times δ, such as 1.3 times, or a range of values ​​formed by any two of them, such as 1.3 times to 1.5 times.

[0024] According to some embodiments of the present invention, the thickness of the diffusion layer is h, the minimum cross-sectional width of the silver-copper alloy penetrator is δ, and the relationship between h and δ is 0.00025≤h / δ≤0.001.

[0025] h / δ < 0.00025: The diffusion layer is too thin, resulting in insufficient metallurgical bonding and easy interface peeling under thermal shock; h / δ > 0.001: The diffusion layer is too thick, which will change the phase transformation characteristics of the silver-copper alloy through-body and reduce the consistency of the break.

[0026] With a value of 0.00025≤h / δ≤0.001, the copper matrix and the penetrator can be stably metallurgically bonded together, while avoiding excessive growth of the diffusion layer from affecting the fusing function of the penetrator, thus achieving synergistic optimization of thermal shock stability and fracture consistency.

[0027] Furthermore, the parameter δ represents the middle width (minimum cross-sectional width) of the silver-copper alloy through-body, which is easily measured using conventional testing methods. The relationship can directly guide the control of production processes and has strong industrial applicability.

[0028] A second aspect of the present invention provides a method for preparing the aforementioned silver-copper alloy-copper through-type composite strip, comprising the following steps: S1: Select the copper substrate as the base material, and perform grooving on the first surface of the copper substrate along the thickness extension direction of the copper substrate to obtain the first receiving groove. S2: The silver-copper alloy through-body is fitted into the first receiving groove, and the composite billet after fitting is subjected to the first hot pressing composite treatment and the first rolling and shaping treatment in sequence. S3: The copper substrate that has been processed in S2 is flipped over. Along the thickness extension direction of the copper substrate, a groove is made on the second surface of the copper substrate at the position opposite to the first receiving groove to obtain the second receiving groove. The groove depth is extended to expose the silver-copper alloy penetrating body in the first receiving groove. S4: The silver-copper alloy through-body is fitted into the second accommodating groove, and the composite blank after the second fitting is subjected to a second hot pressing composite treatment and a second rolling and shaping treatment in sequence. After slitting, the silver-copper alloy-copper through-body composite strip is obtained.

[0029] The method for preparing the silver-copper alloy-copper through-type composite strip of the present invention has at least the following beneficial effects: Receiving grooves are opened on both the front and back surfaces along the thickness extension direction of the copper substrate, and the secondary groove depth extends to expose the silver-copper alloy penetrator that was first installed. This ensures that the silver-copper alloy penetrator forms a continuous and complete penetrating structure in the copper substrate, avoiding forming defects such as penetrator breakage and misalignment. It also ensures that the silver-copper alloy penetrator can accurately perform its fusing function when the composite strip is melted, providing a structural basis for consistent separation. At the same time, the adaptive installation method allows for a higher degree of fit between the silver-copper alloy penetrator and the groove in the copper substrate, reducing the interface gap and creating favorable conditions for the subsequent formation of a uniform and stable diffusion layer.

[0030] The step-by-step hot-pressing composite and rolling forming process involves hot-pressing composite and rolling forming of the composite billets after single and double embedding, respectively. The step-by-step hot-pressing composite can gradually achieve metallurgical bonding between the silver-copper alloy and the copper matrix. Combined with rolling forming, it can effectively control the bonding tightness of the interface between the two, avoiding the problems of uneven interface bonding and stress concentration caused by single composite forming. It can also precisely control the growth of the interface diffusion layer, stabilizing it within the optimal thickness range of 0.5~2.0μm, ensuring a stable metallurgical bonding effect between the copper matrix and the silver-copper alloy through-body, improving the interface bonding strength, and enhancing the thermal shock stability of the composite strip.

[0031] This method, by eliminating the annealing process, leverages the superior diffusion properties between silver-copper alloys and copper. Through the synergistic effect of hot pressing and rolling, a diffusion layer meeting the requirements can be formed without additional annealing. This significantly simplifies the preparation process, shortens the production cycle, and reduces energy consumption and manufacturing costs. Simultaneously, it avoids problems such as excessively thick diffusion layers and silver-copper alloy composition segregation caused by improper temperature control during annealing. This ensures the phase transformation characteristics of the silver-copper alloy through-body and the structural properties of the copper matrix, guaranteeing that the composite strip possesses both excellent thermal shock stability and fracture consistency.

[0032] The process and material properties of this invention are highly compatible. The entire preparation method is designed around a silver-copper alloy through-body with a copper content of 20wt%~40wt%. The process parameters of the step-by-step hot pressing and rolling can match the thermal expansion and phase transformation characteristics of the silver-copper alloy with this composition, effectively reducing the interfacial thermal mismatch stress generated during the preparation process, reducing the generation of microcracks inside the composite strip, and further improving the structural stability of the finished composite strip. Moreover, the final slitting step can ensure the dimensional accuracy of the finished composite strip, meeting the requirements for industrial application of fusing materials.

[0033] The overall process is highly practical and controllable, with clear operation steps and easily controllable parameters. Grooving, embedding, hot pressing, and rolling are all mature metal processing technologies that do not require the introduction of special equipment. They can be directly adapted to existing metal composite strip production lines for industrial production, which is conducive to large-scale promotion. At the same time, through precise control of each process, silver-copper alloy-copper through-type composite strips with optimized thermal shock stability and fracture consistency can be stably produced, improving product yield and performance consistency.

[0034] The preparation method of the present invention does not require expensive equipment and complex process control, the reaction conditions are not harsh, the raw materials are readily available, the production cost is low, and it is easy to industrialize.

[0035] According to some embodiments of the present invention, the temperature of the first hot-pressing composite treatment is 450°C to 600°C.

[0036] This temperature range is highly compatible with the material properties of the silver-copper alloy and the copper substrate, as well as the composite process of this invention. It ensures that the copper substrate and the silver-copper alloy penetrate form a suitable interfacial bonding state, while avoiding process and performance defects caused by excessively high or low temperatures. Specifically, 450℃ to 600℃ is the suitable temperature range for atomic diffusion between the silver-copper alloy and the copper substrate. At this temperature, the atomic diffusion rate is moderate, which can promote the formation of a continuous metallurgical diffusion layer at the interface, meeting the basic requirements for the stability of the composite band structure. It can also avoid excessively rapid atomic diffusion and excessive growth of the diffusion layer beyond the limited range of 0.5~2.0μm due to excessively high temperatures, and can also prevent insufficient atomic diffusion, excessively thin or discontinuous diffusion layers caused by excessively low temperatures, ensuring precise and controllable diffusion layer thickness. Furthermore, the copper content of the silver-copper alloy through-body used in this invention is 20wt%~40wt% (close to the eutectic composition), and the temperature of 450℃~600℃ is far below its phase transformation temperature of approximately 780℃. Hot pressing at this temperature does not alter the composition and microstructure of the silver-copper alloy, fully preserving its core melting characteristics of having no obvious solid-liquid coexistence zone and being able to quickly complete the solid-liquid transformation. This ensures that the fracture consistency of the finished composite strip is not affected by the manufacturing process. Moreover, the mild hot pressing temperature of 450℃~600℃ prevents excessive thermal deformation differences between the copper matrix and the silver-copper alloy through-body due to sudden temperature increases, effectively reducing thermal stress concentration at the interface and avoiding forming defects such as microcracks, interface peeling, and warping in the composite billet during hot pressing. This ensures the adhesion between the silver-copper alloy through-body and the copper matrix, laying a good structural foundation for subsequent rolling and shaping processes. Furthermore, the diffusion bonding efficiency of silver-copper alloys with copper is higher at temperatures between 450℃ and 600℃. Compared to the composite of pure silver and copper, a stable metallurgical bonding surface can be formed without subsequent additional annealing, significantly simplifying the preparation process, shortening the production cycle, and reducing production energy consumption and manufacturing costs. At the same time, hot-pressing composites in this temperature range, combined with subsequent rolling, can further improve the interfacial bonding tightness, ensuring that the bonding strength of the diffusion layer meets the requirements for use in complex conditions such as thermal shock and short-circuit breaking. The composite billet after hot pressing at 450℃ to 600℃ possesses suitable plasticity and interfacial bonding state, which is highly compatible with subsequent rolling and shaping processes. During rolling, there will be no problems such as interfacial cracking, breakage or misalignment of the silver-copper alloy penetrating body. This ensures that the silver-copper alloy penetrating body forms a continuous and regular penetrating structure in the copper matrix, and rolling can further refine the interfacial structure, improving the overall structural stability and thermal shock resistance of the composite strip.

[0037] According to some embodiments of the present invention, the temperature of the first hot-pressing composite treatment is any value among 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, and 600°C, such as 550°C, or any range formed by both, such as 500°C to 550°C.

[0038] According to some embodiments of the present invention, the reduction rate of the first hot-pressing composite treatment is 30% to 60%.

[0039] According to some embodiments of the present invention, the reduction rate of the first hot-pressing composite treatment is any value of 30%, 35%, 40%, 42%, 45%, 48%, 50%, 55%, 60%, such as 45%, or any range of two, such as 40% to 50%.

[0040] This reduction rate range is compatible with the hot-pressing temperature of 450℃ to 600℃, and also matches the material plasticity of the silver-copper alloy and the copper substrate. This allows for a tight bond at the interface and precise control of the diffusion layer, while avoiding process defects and performance problems caused by excessively high or low reduction rates. Firstly, a reduction rate of 30% to 60% provides suitable compressive stress at the bonding surface between the silver-copper alloy penetrator and the copper substrate, effectively eliminating interfacial gaps after embedding. This allows the two materials to achieve an atomically tight bond, creating the necessary conditions for atomic diffusion at 450℃ to 600℃. This ensures the formation of a continuous and uniform metallurgical diffusion layer, rather than a simple physical bond, thus enhancing the basic strength of the interfacial bond. Secondly, this reduction rate range, in conjunction with the hot-pressing temperature, can control the rate and range of atomic diffusion. Too low a reduction rate results in insufficient compressive stress and inadequate atomic diffusion momentum, easily leading to an excessively thin and discontinuous diffusion layer. Too high a reduction rate causes excessive plastic deformation at the interface, resulting in excessive atomic diffusion and a diffusion layer thickness exceeding the limit. A reduction rate of 30% to 60% allows the diffusion layer to grow stably within the optimal thickness range of 0.5 to 2.0 μm, balancing interfacial bonding strength and the melting function of the silver-copper alloy penetrator. Third, the copper matrix and the silver-copper alloy with a copper content of 20wt% to 40wt% used in this invention exhibit good plasticity in the hot state at 450℃ to 600℃. A reduction rate of 30% to 60% falls within the suitable plastic deformation range for both materials. Excessive reduction rate will not cause warping or cracking of the copper matrix, or breakage or misalignment of the silver-copper alloy penetrator; nor will insufficient plasticity of the composite billet due to an excessively low reduction rate, leading to interfacial delamination during subsequent rolling, thus ensuring the structural integrity of the billet after the first hot-pressing composite. Fourth, after a reduction rate of 30%–60%, the composite billet exhibits a fixed and tightly bonded relative position between the silver-copper alloy through-body and the copper substrate. This prevents misalignment during subsequent flipping and second grooving and lamination, ensuring the continuity and regularity of the through-body after the second lamination. Simultaneously, the moderate plastic deformation resulting from this reduction rate provides the billet with uniform thickness and microstructure, perfectly matching subsequent rolling and shaping processes, further enhancing the dimensional accuracy and structural stability of the finished composite strip. Finally, the tight bonding and suitable diffusion achieved by the 30%–60% reduction rate ensure a seamless connection between the metallurgical diffusion layer and the materials on both sides, significantly improving the interfacial bonding strength between the copper substrate and the silver-copper alloy through-body. This effectively reduces interfacial thermal stress concentration caused by the difference in their thermal expansion coefficients, preventing interfacial delamination and microcracks during thermal shock cycling, and significantly improving the thermal shock stability of the finished product.

[0041] According to some embodiments of the present invention, the temperature of the second hot-pressing composite treatment is 400°C to 600°C.

[0042] This temperature range is compatible with the material properties of the silver-copper alloy and the copper substrate, and it synergizes with the process of the first hot-pressing composite temperature. This ensures a stable bond between the secondary-embedded silver-copper alloy through-body and the copper substrate, as well as the first composite silver-copper alloy through-body, while also allowing for precise control of the overall interface diffusion layer growth, avoiding process and performance defects caused by abnormal temperatures. Specifically, 400℃~600℃ is the suitable temperature for atomic diffusion between the silver-copper alloy and the copper substrate. At this temperature, atomic diffusion occurs between the secondary-embedded silver-copper alloy through-body, the inner wall of the second accommodating groove in the copper substrate, and the exposed end face of the first composite silver-copper alloy through-body, forming a continuous metallurgical bond. This avoids gaps or weak bonds at the secondary composite point, ensuring that the silver-copper alloy through-body forms a complete, unbroken through-structure in the copper substrate, providing a reliable structural basis for concentrated breakage when the composite strip melts. Furthermore, the second hot-pressing temperature is matched with the first hot-pressing temperature of 450℃ to 600℃, which is within the range of mild diffusion between the silver-copper alloy and copper atoms. This not only further enhances the interfacial metallurgical bonding effect through the second hot-pressing, but also prevents excessive atomic diffusion due to excessive temperature, which would cause the diffusion layer thickness between the copper substrate and the silver-copper alloy penetrating body to exceed the limited range of 0.5~2.0μm. At the same time, the lower limit of 400℃ can also ensure that the atoms have sufficient diffusion motive force, avoiding the diffusion layer being too thin or discontinuous, and ensuring that the diffusion layer thickness is stable within the optimal range, thus balancing the interfacial bonding strength and the melting function of the silver-copper alloy penetrating body. Furthermore, the copper matrix and the silver-copper alloy with a copper content of 20wt%~40wt% still possess good plasticity in the hot state of 400℃~600℃. This temperature range will not cause excessive thermal deformation of the copper matrix due to high temperature, nor will it cause compositional segregation or microstructure distortion in the silver-copper alloy through-body that has already undergone primary composite. It can also prevent the secondary-embedded silver-copper alloy through-body from breaking or misaligning during hot pressing, effectively ensuring the structural integrity of the billet after secondary composite and avoiding forming defects such as warping, interface delamination, and through-body displacement. Furthermore, the temperature of 400℃~600℃ is much lower than the eutectic phase transformation temperature of the silver-copper alloy (copper content 20wt%~40%) of about 780℃. Secondary hot composite is carried out at this temperature without changing the composition and microstructure of the silver-copper alloy. It can completely retain its core melting characteristics of having no obvious solid-liquid coexistence region and being able to quickly complete the solid-liquid transformation in a narrow temperature range, ensuring that the finished composite strip can form a concentrated broken bridge structure when short-circuited, ensuring arc root stability and fracture consistency.

[0043] The billet after secondary hot pressing and composite at 400℃~600℃ has a tight interface bond and suitable overall hot plasticity, which is highly compatible with the subsequent secondary rolling and shaping process. During the rolling process, there will be no problems such as secondary composite interface cracking or silver-copper alloy through-body displacement. Rolling can further refine the interface structure and improve the dimensional accuracy of the billet, ultimately ensuring the structural regularity and performance stability of the finished composite strip.

[0044] According to some embodiments of the present invention, the temperature of the second hot-pressing composite treatment is any value among 400°C, 450°C, 500°C, 550°C, and 600°C, such as 550°C, or any range formed by both, such as 500°C to 600°C.

[0045] According to some embodiments of the present invention, the reduction rate of the second hot-pressing composite treatment is 30% to 60%.

[0046] The reduction rate of the second hot-pressing composite treatment is limited to 30%–60%. This reduction rate range is compatible with the second hot-pressing composite temperature of 400℃–600℃ and forms a process synergy with the reduction rate of the first hot-pressing composite. On the one hand, it can provide suitable compressive stress for the bonding surface between the secondary embedded silver-copper alloy penetrator and the copper substrate, as well as the silver-copper alloy penetrator of the first composite, effectively eliminating interfacial gaps, promoting full atomic diffusion, and achieving stable metallurgical bonding at the secondary composite site. This ensures that the silver-copper alloy penetrator forms a complete and continuous penetrating structure in the copper substrate. At the same time, it precisely controls the overall interfacial diffusion layer thickness in coordination with temperature, stabilizing it within the optimal range of 0.5–2.0 μm, avoiding insufficient bonding due to an excessively thin diffusion layer or affecting fusing performance due to an excessively thick diffusion layer. On the other hand, this… The reduction rate is matched with the hot plasticity characteristics of the copper matrix and the silver-copper alloy with a copper content of 20wt%~40wt%, which will not cause the billet to warp, crack, or breakage and misalignment of the silver-copper alloy through-body. This ensures the structural integrity of the billet after secondary composite and lays a good foundation for subsequent secondary rolling and shaping. It also prevents problems such as interface cracking and through-body displacement during the rolling process. At the same time, relying on the good diffusion characteristics of the silver-copper alloy and copper, this reduction rate, combined with the hot composite temperature, can achieve a stable overall interface bonding without additional annealing. This fits the short-process design, simplifies the process, reduces costs, and further strengthens the interface bonding strength between the copper matrix and the silver-copper alloy through-body, reduces interface thermal stress concentration, and improves the overall thermal shock stability and fracture consistency of the composite strip.

[0047] According to some embodiments of the present invention, the reduction rate of the second hot-pressing composite treatment is any value of 30%, 35%, 40%, 42%, 45%, 48%, 50%, 55%, 60%, such as 45%, or any range of two, such as 40% to 50%.

[0048] According to some embodiments of the present invention, before the first hot-pressing composite treatment and the second hot-pressing composite treatment, the first accommodating groove and the second accommodating groove are respectively cleaned.

[0049] According to some embodiments of the present invention, after the first rolling and shaping process and the second rolling and shaping process, a degreasing process is performed respectively. Attached Figure Description

[0050] Figure 1 This is a cross-sectional view of the silver-copper alloy-copper through-type composite strip of Example 1.

[0051] Figure 2 This is a line scan of the interface elements of the silver-copper alloy-copper through-type composite strip in Example 1.

[0052] Figure 3 This is a SEM image of the contact surface between the copper matrix and the silver-copper alloy through-body in the composite strip of Example 1. Detailed Implementation

[0053] The following will describe the concept and technical effects of the present invention clearly and completely with reference to the embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0054] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0055] Unless otherwise specified, "room temperature" in this invention means 25℃±5℃.

[0056] Unless otherwise specified, "about" in this invention means that the allowable error is within ±2%.

[0057] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0058] The coefficient of linear expansion of copper is 16.5~17×10⁻⁶. -6 / K.

[0059] The coefficient of linear expansion of pure silver is 19~20×10⁻⁶. -6 / K.

[0060] The coefficient of linear expansion of the silver-copper alloy (copper content 28wt%) is 17~18×10⁻⁶. -6 / K (varies slightly with temperature).

[0061] Example 1 A silver-copper alloy-copper through-type composite strip was prepared, with the structure as follows: Figure 1 As shown, it includes a copper substrate and a silver-copper alloy penetrator penetrating the copper substrate. The copper content in the silver-copper alloy penetrator is 25wt%, and a 1.0μm diffusion layer is formed between the copper substrate and the silver-copper alloy penetrator.

[0062] The width W of the silver-copper alloy penetrating the top of the body is 5mm.

[0063] The minimum cross-sectional width δ of the silver-copper alloy penetrator is 3.5 mm.

[0064] The specific preparation steps are as follows: S1: Select a copper substrate as the base material, and perform grooving on the first surface of the copper substrate along the thickness extension direction of the copper substrate to obtain the first accommodating groove. S2: The silver-copper alloy through-body is fitted into the first receiving groove, and the composite blank after fitting is subjected to the first hot pressing composite treatment and the first rolling and shaping treatment in sequence. S3: The copper substrate that has been processed in S2 is flipped over. Along the thickness extension direction of the copper substrate, a groove is made on the second surface of the copper substrate at the position opposite to the first receiving groove to obtain the second receiving groove. The groove depth extends to expose the silver-copper alloy penetrating body in the first receiving groove. S4: The silver-copper alloy through-body is fitted into the second receiving groove. The composite blank after the second fitting is subjected to a second hot pressing composite treatment and a second rolling and shaping treatment. After slitting, the silver-copper alloy-copper through-body composite strip is obtained.

[0065] The temperature of the first hot-pressing composite treatment was 500℃, and the reduction rate of the first hot-pressing composite treatment was 42%.

[0066] The temperature of the second hot-pressing composite treatment was 500℃, and the reduction rate of the second hot-pressing composite treatment was 42%.

[0067] Before the first and second hot-pressing composite treatments, the first and second receiving grooves are cleaned respectively. After the first and second rolling and shaping treatments, degreasing treatments are performed respectively.

[0068] Example 2 A silver-copper alloy-copper through-type composite strip was prepared, with the structure as follows: Figure 1 As shown, it includes a copper substrate and a silver-copper alloy penetrator penetrating the copper substrate. The copper content in the silver-copper alloy penetrator is 28wt%, and a 1.6μm diffusion layer is formed between the copper substrate and the silver-copper alloy penetrator.

[0069] The width W of the silver-copper alloy penetrating the top of the body is 5mm.

[0070] The minimum cross-sectional width δ of the silver-copper alloy penetrator is 4 mm.

[0071] The specific preparation steps are as follows: S1: Select a copper substrate as the base material, and perform grooving on the first surface of the copper substrate along the thickness extension direction of the copper substrate to obtain the first accommodating groove. S2: The silver-copper alloy through-body is fitted into the first receiving groove, and the composite blank after fitting is subjected to the first hot pressing composite treatment and the first rolling and shaping treatment in sequence. S3: The copper substrate that has been processed in S2 is flipped over. Along the thickness extension direction of the copper substrate, a groove is made on the second surface of the copper substrate at the position opposite to the first receiving groove to obtain the second receiving groove. The groove depth extends to expose the silver-copper alloy penetrating body in the first receiving groove. S4: The silver-copper alloy through-body is fitted into the second receiving groove. The composite blank after the second fitting is subjected to a second hot pressing composite treatment and a second rolling and shaping treatment. After slitting, the silver-copper alloy-copper through-body composite strip is obtained.

[0072] The temperature of the first hot-pressing composite treatment was 550℃, and the reduction rate of the first hot-pressing composite treatment was 45%.

[0073] The temperature of the second hot-pressing composite treatment was 550℃, and the reduction rate of the second hot-pressing composite treatment was 45%.

[0074] Before the first and second hot-pressing composite treatments, the first and second receiving grooves are cleaned respectively. After the first and second rolling and shaping treatments, degreasing treatments are performed respectively.

[0075] Example 3 A silver-copper alloy-copper through-type composite strip was prepared, with the structure as follows: Figure 1 As shown, it includes a copper substrate and a silver-copper alloy penetrator penetrating the copper substrate. The copper content in the silver-copper alloy penetrator is 30wt%, and a 2μm diffusion layer is formed between the copper substrate and the silver-copper alloy penetrator.

[0076] The width W of the silver-copper alloy penetrating the top of the body is 5.5 mm.

[0077] The minimum cross-sectional width δ of the silver-copper alloy penetrator is 4 mm.

[0078] The specific preparation steps are as follows: S1: Select a copper substrate as the base material, and perform grooving on the first surface of the copper substrate along the thickness extension direction of the copper substrate to obtain the first accommodating groove. S2: The silver-copper alloy through-body is fitted into the first receiving groove, and the composite blank after fitting is subjected to the first hot pressing composite treatment and the first rolling and shaping treatment in sequence. S3: The copper substrate that has been processed in S2 is flipped over. Along the thickness extension direction of the copper substrate, a groove is made on the second surface of the copper substrate at the position opposite to the first receiving groove to obtain the second receiving groove. The groove depth extends to expose the silver-copper alloy penetrating body in the first receiving groove. S4: The silver-copper alloy through-body is fitted into the second receiving groove. The composite blank after the second fitting is subjected to a second hot pressing composite treatment and a second rolling and shaping treatment. After slitting, the silver-copper alloy-copper through-body composite strip is obtained.

[0079] The temperature of the first hot-pressing composite treatment was 600℃, and the reduction rate of the first hot-pressing composite treatment was 48%.

[0080] The temperature of the second hot-pressing composite treatment was 600℃, and the reduction rate of the second hot-pressing composite treatment was 48%.

[0081] Before the first and second hot-pressing composite treatments, the first and second receiving grooves are cleaned respectively. After the first and second rolling and shaping treatments, degreasing treatments are performed respectively.

[0082] Comparative Example 1 The difference from Example 1 is that the penetrating body is a pure silver penetrating body.

[0083] Comparative Example 2 The difference from Example 1 is that the copper content in the silver-copper alloy penetrator is 50 wt%.

[0084] Comparative Example 3 The difference from Example 1 is that the minimum cross-sectional width δ of the silver-copper alloy penetrator is 0.8 mm.

[0085] Comparative Example 4 The difference from Example 1 is that the minimum cross-sectional width δ of the silver-copper alloy penetrator is 5 mm.

[0086] Performance testing (1) Thermal shock cycling test (GB / T 2423.22-2012 Environmental Testing Part 2: Test Methods Test N: Temperature Change): -40℃ The composite band was evaluated at 150℃ for 1000 cycles.

[0087] (2) Discontinuity test: Record the arc duration and calculate the discreteness for analysis and comparison.

[0088] The test results are shown in Table 1.

[0089] Table 1

[0090] Table 1 shows the thermal shock cycling test results (-40℃). The core performance of the composite strips in the embodiments of the present invention was compared with that of the comparative examples using tests at 150℃ and 1000 cycles (arc duration and dispersion). This clearly demonstrates the key influence of silver-copper alloy composition, structural parameters, and diffusion layer control on the thermal shock stability and fracture consistency of the composite strips. It also verifies the superiority of the technical solution of the present invention. The specific analysis is as follows: After 1000 thermal shock cycles, Examples 1-3 showed no obvious cracks or interface peeling (only Example 3 showed very slight stress traces), and the structural integrity was good. In the fracture test, the arc duration was concentrated in 2-5ms with small dispersion, and the fracture action was precise and consistent. Among them, Example 2 was the best example because the silver-copper alloy had a copper content of 28wt%, which is a near-eutectic composition, and the diffusion layer thickness, W / δ ratio, and h / δ ratio were all in the optimal range. There was no structural damage from thermal shock, the arc duration was 3-4ms, and the fracture consistency was the best.

[0091] In Example 3, the diffusion layer thickness was 2 μm. Slight stress marks appeared under thermal shock, and the fracture consistency was slightly inferior to that of Examples 1 and 2. Reasonable diffusion layer parameters ensure the metallurgical bonding strength between the copper substrate and the silver-copper alloy, avoid interfacial delamination under thermal shock, and do not change the melting phase transformation characteristics of the silver-copper alloy due to excessive diffusion layer thickness, thus balancing structural stability and melting accuracy.

[0092] Comparative Example 1 (pure silver penetrator) showed good consistency in fracture, but had significant defects in thermal shock stability. The arc duration of the pure silver penetrator was 2-3 ms with small dispersion, but its thermal expansion coefficient differed greatly from that of the copper matrix. After 1000 thermal shocks, obvious micro-cracks appeared in the narrow diameter, highlighting the problem of thermal stress concentration at the interface.

[0093] Comparative Example 2 (silver-copper alloy containing 50wt% copper) showed no obvious defects in thermal shock, but its fracture consistency was extremely poor. The composition deviated from the eutectic range, and there was an obvious solid-liquid coexistence zone during melting, resulting in dispersed fracture bridges. The arc duration was 3-7ms with large dispersion, which could not meet the requirements for accurate fracture.

[0094] Comparative Examples 3 and 4 showed severe overall performance failure. Both failed to complete 1000 thermal shock cycles before exhibiting narrow-path fracture. The arc duration in the fracture test showed large dispersion and poor arc root stability. The core reason was that the structural parameters deviated from the limits of this invention, resulting in an imbalance in the relative thickness of the diffusion layer.

[0095] As shown in Table 1, the copper content of 20wt%~40wt% in silver-copper alloys is the core compositional condition for achieving synergistic optimization of thermal shock stability and fracture consistency. Materials deviating from this range exhibit the problem of excellent performance in one aspect but failure in another. Pure silver (Comparative Example 1) fractures quickly, but thermal expansion mismatch with the copper matrix leads to thermal shock cracking. The silver-copper alloy with 50wt% copper (Comparative Example 2) has a stable structure, but the presence of a solid-liquid coexistence region in the non-eutectic component results in dispersed fracture bridges and extremely poor fracture consistency. The copper content range of 20wt%~40wt% in silver-copper alloys is close to the Ag-Cu eutectic composition, which reduces the difference in thermal expansion coefficients with the copper matrix, alleviates interfacial thermal stress concentration (improving thermal shock stability), and enables solid-liquid transformation at a single temperature, forming concentrated fracture bridges (ensuring fracture consistency). Among these, 26wt%~30wt% is the optimal range (Example 2 with 28wt% copper and Example 3 with 30wt% copper have better performance than Example 1 with 25wt% copper).

[0096] Furthermore, the thickness of the diffusion layer and the h / δ ratio are key structural parameters for ensuring the stability of the composite strip structure and its normal fusing function. The thickness of the diffusion layer must be strictly controlled.

[0097] Furthermore, the parameter system (composition + structure + diffusion layer) of this invention achieves an optimal balance of comprehensive performance in the composite band, far superior to existing technical solutions. A single solution using pure silver or non-eutectic silver-copper alloys cannot simultaneously meet the dual requirements of high-end fusing materials for thermal shock stability and fracture consistency. This invention, through a synergistic design of precisely defined composition (20wt%~40wt% Cu), controlled structural parameters (W / δ=1.2~1.5, 0.00025≤h / δ≤0.001), and controlled diffusion layer thickness (0.5~1.6μm), solves the core pain points of existing technologies. Example 2, with all parameters within the optimal range of this invention (28wt% copper content, suitable diffusion layer thickness, and reasonable W / δ ratio), becomes the best-performing example, verifying the scientific validity and adaptability of the parameter system of this invention.

[0098] It should be noted that the excellent performance of thermal shock stability and breaking consistency of the present invention is the result of multi-parameter synergistic control. Single parameter optimization cannot achieve the same effect. Comparative methods that only change a single parameter (composition / structure) all show performance shortcomings. However, the embodiments of the present invention, through multi-dimensional synergistic control of composition, structure and diffusion layer, enable the composite strip to have sufficient structural integrity and maintain accurate and consistent breaking action under complex working conditions (repeated thermal shock + short circuit breaking), thus meeting the application requirements of high-end circuit protection fields.

[0099] Figure 2This is the line scan spectrum of the interface elements of the silver-copper alloy-copper through-type composite strip in Example 1. The horizontal axis represents the linear scan distance (μm) at the interface, and the vertical axis represents the signal intensity of each element. It can clearly reflect the distribution pattern of silver (Ag) and copper (Cu) elements at the interface. It can be seen that: In the copper matrix region, the Cu element signal intensity is high and stable, the Ag element signal intensity approaches 0, and there is no obvious silver element diffusion; In the silver-copper alloy penetrating region, Ag and Cu elements maintain stable characteristic signal intensities, and their ratio is consistent with the design composition of the silver-copper alloy penetrating body (25wt%Cu, 75wt%Ag), with uniform element distribution. In the interface transition region between the copper substrate and the silver-copper alloy through-body, there is a continuous and uniform element diffusion band. The Cu element decreases slowly from the copper substrate side to the alloy side, and the Ag element decreases slowly from the alloy side to the copper substrate side. The signal intensity of the two elements changes complementaryly without obvious abrupt changes. Moreover, the width of the diffusion band matches the 0.5~2.0μm diffusion layer thickness specified in the invention. Throughout the entire scanning range, there were no other stray peaks or abnormal element signals, no impurity enrichment at the interface, and the element diffusion was the mutual diffusion between pure metals, with no contaminants affecting the interface bonding.

[0100] Figure 2 The test results show that a continuous and uniform metallurgical diffusion layer is formed between the copper matrix and the silver-copper alloy through-body, rather than a simple physical bond. The gradient diffusion characteristics of Ag and Cu elements at the interface in the elemental line scan are direct evidence of thermal diffusion between metal atoms, proving that the present invention, through hot-pressing composite + rolling process, successfully promotes atomic-level interdiffusion at the interface between the copper matrix and the silver-copper alloy through-body, forming a metallurgical bonding interface, which lays the structural foundation for the interfacial bonding strength and thermal shock stability of the composite band.

[0101] Furthermore, Figure 2 The test results show that the thickness of the diffusion layer of the present invention is precisely controllable, meeting the invention's requirement of 0.5~2.0μm. The width of the element diffusion band at the interface is consistent with the thickness of the diffusion layer designed in the invention, without problems of excessive diffusion (diffusion layer too thick) or insufficient diffusion (diffusion layer too thin or discontinuous). This proves that the process parameters set by the present invention, such as the hot-pressing composite temperature (450℃~600℃) and the reduction rate (30%~60%), can precisely control the atomic diffusion rate and range, achieving precise control of the diffusion layer thickness.

[0102] Furthermore, Figure 2The test results also show that the composite strip of the present invention has excellent interfacial bonding quality, with no elemental segregation, interfacial gaps, or impurity contamination. The elemental gradient diffusion at the interface is smooth and without abrupt changes, and there are no impurity element signals, indicating that the copper matrix and the silver-copper alloy through-body have extremely high adhesion. The groove cleaning and hot-pressing composite processes in the preparation process effectively eliminate interfacial gaps and impurities, avoiding interfacial stress concentration and reduced bonding force caused by gaps and impurities, and ensuring the integrity of the interfacial structure. The preparation process of this invention can achieve synergistic stability of alloy composition and interface structure. The Ag and Cu element ratios in the silver-copper alloy penetrating body are stable, and there is no compositional segregation caused by hot working. This proves that the hot pressing composite temperature is much lower than the phase transformation temperature of the silver-copper alloy. While achieving interface diffusion, the bulk composition and microstructure of the silver-copper alloy penetrating body are completely preserved, ensuring that its melting characteristics are not affected by the preparation process. The element diffusion behavior verifies the optimization effect of the process of this invention on interfacial thermal matching. The continuous and uniform diffusion layer effectively alleviates the difference in thermal expansion coefficients between the copper substrate and the silver-copper alloy through-body, reducing interfacial thermal stress concentration under thermal shock conditions. This is also why the composite strip can withstand temperatures as low as -40℃. The core reason why there were no cracks or interface delamination during the 150℃ thermal shock cycle is that the present invention improves the thermal shock stability of the composite belt from the perspective of interface microstructure.

[0103] In conclusion, Figure 2 The elemental line scan results directly verified from the microscopic interface structure level that the present invention successfully prepared a silver-copper alloy-copper through-hole composite strip with a stable metallurgical diffusion layer at the interface through composition limitation and process control. At the same time, it proved the rationality and effectiveness of the preparation process of the present invention, which is the microscopic structure guarantee that the composite strip has excellent interfacial bonding strength, thermal shock stability and fracture consistency.

[0104] Figure 3This is a SEM image of the contact surface between the copper matrix and the silver-copper alloy through-body in the composite strip of Example 1. It can be seen that the contact surface between the copper matrix and the silver-copper alloy through-body achieves seamless bonding, without the gaps, voids, or other forming defects commonly seen in physical composites. The interface transition is continuous and regular. There are no obvious impurity particles, oxide layers, or microcracks in the interface area. The microstructure of the entire bonding surface is smooth and clean, without contaminant accumulation or heterogeneous structures caused by oxidation reactions. No traces of microcrack initiation or propagation due to thermal stress or processing stress were found. A uniform metallurgical bonding transition zone exists at the interface, without obvious abrupt boundary changes between the matrix and alloy phases. The grains of the copper matrix and the silver-copper alloy achieve good metallurgical bonding at the interface, with some areas showing interlocking characteristics of the grains rather than simple mechanical bonding. The microstructure on the silver-copper alloy through-body side is uniform, without grain coarsening, compositional segregation, or structural distortion caused by hot-pressing composite or rolling forming. The copper matrix side also maintains a good matrix structure morphology, indicating excellent microstructure matching at the interface. This invention verifies that the preparation process can achieve high-quality metallurgical bonding between the copper matrix and the silver-copper alloy through-body, producing a composite strip with no interface defects and excellent structural integrity. It also confirms from a microscopic perspective the core reason why the composite strip of this invention has excellent thermal shock stability and interface bonding stability.

[0105] Taking Example 2 as an example, the silver-copper alloy with a copper content of about 28% is close to the Ag-Cu eutectic composition. Its phase transformation is completed at a single temperature of about 780°C (melting temperature, which can be used as the melting temperature of the fuse), and there is no obvious solid-liquid coexistence region.

[0106] During the melting process, the eutectic material can rapidly complete the solid-liquid transformation within a narrow temperature range, forming a concentrated broken bridge structure and improving the stability of the arc root.

[0107] Meanwhile, the coefficient of linear expansion in this composition range is closer to that of the copper matrix, which reduces interfacial thermal mismatch stress and improves structural stability after thermal shock cycling.

[0108] This invention optimizes the phase transformation behavior and interfacial thermal matching of a silver-copper alloy by limiting the copper content range and combining a through-type composite structure with diffusion layer control technology, thereby improving thermal shock stability and fracture consistency.

[0109] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A silver-copper alloy-copper through-type composite strip, characterized in that, It includes a copper substrate and a silver-copper alloy penetrator penetrating the copper substrate, wherein the copper content in the silver-copper alloy penetrator is 20wt%~40wt%, and a diffusion layer of 0.5~2.0μm is formed between the copper substrate and the silver-copper alloy penetrator.

2. The silver-copper alloy-copper through-type composite strip according to claim 1, characterized in that, The copper content in the silver-copper alloy penetrator is 26wt%~30wt%.

3. The silver-copper alloy-copper through-type composite strip according to claim 1, characterized in that, The width of the top of the silver-copper alloy penetrator is W, and the minimum cross-sectional width of the silver-copper alloy penetrator is δ, where W is 1.2 to 1.5 times δ.

4. The silver-copper alloy-copper through-type composite strip according to any one of claims 1 to 3, characterized in that, The thickness of the diffusion layer is h, and the minimum cross-sectional width of the silver-copper alloy penetrator is δ. The relationship between h and δ is 0.00025≤h / δ≤0.

001.

5. A method for preparing a silver-copper alloy-copper through-type composite strip as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1: Select the copper substrate as the base material, and perform grooving on the first surface of the copper substrate along the thickness extension direction of the copper substrate to obtain the first receiving groove. S2: The silver-copper alloy through-body is fitted into the first receiving groove, and the composite billet after fitting is subjected to the first hot pressing composite treatment and the first rolling and shaping treatment in sequence. S3: The copper substrate that has been processed in S2 is flipped over. Along the thickness extension direction of the copper substrate, a groove is made on the second surface of the copper substrate at the position opposite to the first receiving groove to obtain the second receiving groove. The groove depth is extended to expose the silver-copper alloy penetrating body in the first receiving groove. S4: The silver-copper alloy through-body is fitted into the second accommodating groove, and the composite blank after the second fitting is subjected to a second hot pressing composite treatment and a second rolling and shaping treatment in sequence. After slitting, the silver-copper alloy-copper through-body composite strip is obtained.

6. The method according to claim 5, characterized in that, The temperature of the first hot-pressing composite treatment is 450℃~600℃.

7. The method according to claim 5, characterized in that, The reduction rate of the first hot-press composite treatment is 30% to 60%.

8. The method according to claim 5, characterized in that, The temperature of the second hot-pressing composite treatment is 400℃~600℃.

9. The method according to claim 5, characterized in that, The reduction rate of the second hot-press composite treatment is 30% to 60%.

10. The method according to any one of claims 5 to 9, characterized in that, Before the first hot-pressing composite treatment and the second hot-pressing composite treatment, the first accommodating groove and the second accommodating groove are cleaned respectively; and / or, after the first rolling and shaping treatment and the second rolling and shaping treatment, degreasing treatment is performed respectively.

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