A silver-copper composite strip without punching and its preparation method

Abstract

The present invention belongs to the technical field of melt materials for fuses, and particularly relates to a silver-copper composite strip without pre-punching and a preparation method thereof. The silver-copper composite strip without pre-punching of the present invention includes a first oxygen-free copper strip, a first pure silver strip, a BAg72Al strip, a second pure silver strip, and a second oxygen-free copper strip arranged in sequence along the width direction. The present invention arranges the BAg72Al strip in the center of the silver-copper composite strip, and utilizes the high resistivity of the BAg72Al strip to achieve the purpose of circuit disconnection. The silver-copper composite strip provided by the present invention does not need to be pre-punched before use. The BAg72Al in the core plays the role of circuit disconnection, which not only saves silver materials but also avoids the cumbersome punching process. Moreover, the interface bonding strength of the composite strip of the present invention is high, there are few defects such as interface inclusions and pores, the quality of the composite strip is stable and the bonding quality is good, and it has a wide application prospect in the field of melt materials for fuses.

Description

Technical Field

[0001] The present invention belongs to the technical field of melt materials for fuses, and particularly relates to a silver-copper composite strip without punching and a preparation method thereof. Background Art

[0002] As a substitute material for pure silver strips, silver-copper composite strips have been widely used in low-voltage electrical appliances and fuses. For example, Chinese patents with publication numbers CN109585235B, CN216928470U, CN209454299U, and CN207602503U all use silver-copper composite strips to replace pure silver strip materials. The silver-copper composite strip not only maintains the fast-fusing characteristic of the original pure silver strip but also saves material costs, making it an ideal material to replace pure silver fuses.

[0003] Currently, silver-copper composite strips are usually provided to manufacturers in the form of conventional composite strips. When used as melt materials, manufacturers need to pre-punch numerous densely distributed through-holes along the length direction in the center of the silver strip for use. The purpose of setting the through-holes is to utilize the skin effect of the current, so that the current concentrates on the edge of the holes after the circuit is connected, and then the heat at the edge of the holes rises rapidly, and the connection part between the holes is melted under appropriate conditions to achieve the purpose of disconnecting the circuit. However, after the silver-copper composite strip products are supplied to the using manufacturers, the subsequent punching process increases the processing procedures of the manufacturers, and has very high requirements for the straightness of the silver strip and copper strip in the composite strip, and also causes waste of pure silver precious metals in the using manufacturers.

[0004] In addition, the existing preparation methods of silver-copper composite strips are mainly brazing composite and mechanical inlay composite. The former brazing composite has high requirements for the quality of the brazing seam, and it is very difficult for the brazing strength to meet the requirements of subsequent repeated rolling; the latter mechanical inlay composite has poor strip quality, many defects such as pores and inclusions, and the quality of the composite strip is unstable.

[0005] To solve the above deficiencies, it is necessary to develop a silver-copper composite strip without punching and a preparation method thereof, which can not only overcome the pre-punching process cost and waste phenomenon of conventional silver-copper composite strips in using manufacturers, but also meet the requirements of subsequent rolling and achieve high-quality bonding of silver-copper composite strips. Summary of the Invention

[0006] The first object of the present invention is to provide a silver-copper composite strip without punching, which does not need to be punched before use, and has high interface strength and excellent composite quality of the composite strip.

[0007] The second object of the present invention is to provide a preparation method of a silver-copper composite strip without punching, which is simple to operate and easy to implement, and the prepared composite strip has good interface quality and is suitable for industrial preparation of silver-copper composite strips.

[0008] To achieve the above objects, the technical solution adopted for the silver-copper composite strip without punching of the present invention is:

[0009] A non-punched silver-copper composite strip, comprising a first oxygen-free copper strip, a first pure silver strip, a BAg72Al strip, a second pure silver strip, and a second oxygen-free copper strip arranged in sequence along the width direction.

[0010] For the non-punched silver-copper composite strip provided by the present invention, the center is a BAg72Al strip, the two sides of the center are pure silver strips, and the two sides of the pure silver strips are oxygen-free copper strips. In the present invention, the BAg72Al strip is arranged at the center of the silver-copper composite strip. By utilizing the high resistivity of the BAg72Al strip (the resistivity is higher than that of silver and copper, the resistivity of silver is 1.65×10 -8 Ω·m, the resistivity of copper is 1.75×10 -8 Ω·m, and the resistivity of BAg72Al is 1.98×10 -8 Ω·m), when the current in the circuit exceeds a certain value, the BAg72Al foil generates resistive heat, which has a high heat quantity and a low melting temperature. The heat preferentially melts on the BAg72Al strip, thereby achieving the purpose of disconnecting the circuit.

[0011] Therefore, for the silver-copper composite strip of the present invention, after being supplied to the user manufacturers, there is no need for punching, which avoids the trouble of additional punching for downstream manufacturers. At the same time, it can also solve the problem of waste of pre-punching of conventional silver-copper composite strips in user manufacturers. And since the present invention uses BAg72Al to replace part of the precious metal pure silver, it also achieves the purpose of saving silver materials. In particular, the interface bonding strength of the composite strip of the present invention is high, there are few defects such as interface inclusions and pores, the quality of the composite strip is stable and the composite quality is good, which is very suitable for use as a melt material in fuses.

[0012] Preferably, the first oxygen-free copper strip, the first pure silver strip, the BAg72Al strip, the second pure silver strip, and the second oxygen-free copper strip have the same length and thickness; the widths of the first oxygen-free copper strip, the second oxygen-free copper strip, and the BAg72Al strip respectively account for 1 / 4 of the total width of the non-punched silver-copper composite strip; the widths of the first pure silver strip and the second pure silver strip respectively account for 1 / 8 of the total width of the non-punched silver-copper composite strip.

[0013] Based on the consideration of ensuring the use requirements of the melt material, further, the thickness of the non-punched silver-copper composite strip is 0.1 - 0.3 mm.

[0014] Preferably, the total width of the non-punched silver-copper composite strip is 20 - 60 mm.

[0015] The preparation method of the non-punched silver-copper composite strip of the present invention adopts the following technical solution:

[0016] A preparation method of a non-punched silver-copper composite strip, comprising the following steps:

[0017] (1) Place two pure silver plates parallel to each other and fix them. A die gap is formed between the pure silver plates to obtain a casting die cavity. Then, the molten BAg72Al metal liquid after melting is injected into the die gap of the casting die cavity, and after cooling and demolding, an Ag-BAg72Al-Ag three-layer composite strip is obtained.

[0018] (2) Clamp the Ag-BAg72Al-Ag three-layer composite strip on the workbench of a surface grinder. Fix an oxygen-free copper plate on one side of the workbench. Then, make the pure silver surface on one side of the Ag-BAg72Al-Ag three-layer composite strip and the surface of the oxygen-free copper plate perform left-right feeding friction. When plastic deformation appears on the pure silver surface and the silver-copper eutectic alloy liquid flows on the silver-copper contact surface, stop the friction, apply pressure to make the Ag-BAg72Al-Ag three-layer composite strip press tightly against the oxygen-free copper plate, and after pressure holding, a composite Ag-BAg72Al-Ag-Cu four-layer composite strip is obtained.

[0019] (3) Repeat step (2) to composite the pure silver surface on the other side of the Ag-BAg72Al-Ag-Cu four-layer composite strip with another oxygen-free copper plate to obtain a Cu-Ag-BAg72Al-Ag-Cu five-layer composite strip. Flip the five-layer composite strip and perform rolling and annealing to obtain the non-punched silver-copper composite strip.

[0020] Preferably, in step (1), the fixing is carried out using a graphite plate.

[0021] The melting temperature of the BAg72Al metal liquid is 600 - 650 °C.

[0022] To avoid oxidation of the metal liquid and the strip during the casting process, further, in step (1), the melting and injection are carried out under vacuum conditions.

[0023] The present invention uses friction welding to achieve the composite of pure silver and oxygen-free copper, thereby improving the strength and quality of the composite interface. Specifically, between the pure silver surface and the oxygen-free copper surface on the outside of the Ag-BAg72Al-Ag three-layer composite strip, through friction welding, heat is generated by friction between the silver and copper surfaces to reach the eutectic temperature, and a silver-copper eutectic alloy liquid is generated between the silver and copper surfaces. Then, a pressing pressure is applied to achieve the effective composite of the silver and copper surfaces. Further preferably, in step (2), the speed of the left-right feeding friction is 180 - 300 mm / min.

[0024] Preferably, in step (2), the pressure is 15 - 30 N, and the pressure holding time is 15 - 20 min.

[0025] Further, in step (3), the flipping angle is 90°.

[0026] The preparation method of the non-punched silver-copper composite strip of the present invention forms a die gap by combining pure silver plates, and vacuum-casts to form a three-layer sandwich strip with BAg72Al in the core and pure silver on the outer layer, i.e., Ag-BAg72Al-Ag. Then, by using left and right feeding friction extrusion welding, the composite of the sandwich strip and the upper and lower oxygen-free copper strips is realized. Through the above method of the present invention, heat is generated by friction between the sandwich strip and the copper strip, causing the pure silver to have thermoplastic flow and being welded together by extrusion. It does not require inert gas protection or vacuum protection, has low requirements for equipment, and the strip length is not limited by the equipment size. In particular, there are few defects such as pores and inclusions at the composite interface, and the interface bonding quality is high, which is suitable for the industrial preparation of silver-copper composite strips.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) The non-punched silver-copper composite strip of the present invention does not require pre-punching before use. The BAg72Al in the core plays the role of circuit disconnection, which not only saves silver materials but also avoids the cumbersome punching process. Moreover, the interface bonding strength of the composite strip of the present invention is high, there are few defects such as interface inclusions and pores, the quality of the composite strip is stable and the composite quality is good, which is very suitable for use in the melt material for fuses.

[0029] (2) The present invention uses friction extrusion welding to realize the composite of the three-layer sandwich strip and the oxygen-free copper strip under the atmosphere, without conditions such as vacuum or inert gas protection. The interface quality of the composite strip is good, and the size of the composite strip is not limited by the equipment size, which has a wide application prospect in the field of preparing melt materials for fuses. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic structural diagram of the non-punched silver-copper composite strip of the present invention;

[0031] Figure 2 is a schematic structural diagram of the casting mold cavity involved in the preparation of the non-punched silver-copper composite strip of the present invention;

[0032] Figure 3 is the non-punched silver-copper composite strip of Example 1 of the present invention ( Figure 3 left figure) and the silver-copper composite strip of Comparative Example 5 ( Figure 3 right figure) of the microscopic morphology diagram of the silver-copper interface;

[0033] Among them, Figures 1 - 2 in: 1 - oxygen-free copper strip, 2 - BAg72Al strip, 3 - pure silver strip, 4 - die gap, 5 - side graphite plate, 6 - pure silver plate, 7 - bottom graphite plate. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The technical solution of the present invention will be further described below in conjunction with specific embodiments. However, those skilled in the art should understand that the following embodiments are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. The specific conditions not specified in the embodiments are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are all conventional products obtained through commercial channels.

[0035] Among them, in the following embodiments, the material composition of BAg72Al (by mass percentage) is: Ag 72 ± 1%, and the balance is Al. The oxygen content of oxygen-free copper is not more than 0.003%, the total impurity content is not more than 0.05%, and the purity of copper is greater than 99.95%; the Ag content in pure silver is greater than 99.99%, the Pb content is not more than 0.01%, the Pd content is not more than 0.01%, and the total impurity content is not more than 0.1%.

[0036] The non-punched silver-copper composite strip involved in the following embodiments has a structural schematic diagram as Figure 1 shown. Figure 1 In, the non-punched silver-copper composite strip is sequentially provided with an oxygen-free copper strip 1, a pure silver strip 3, a BAg72Al strip 2, a pure silver strip 3, and an oxygen-free copper strip 1 along the width direction; among them, the materials and sizes of the two outermost oxygen-free copper strips are the same, and the materials and sizes of the two pure silver strips inside the copper strip are also the same.

[0037] The casting mold cavity involved in the following embodiments has a structural schematic diagram as Figure 2 shown. The casting mold cavity is composed of two pure silver plates and three graphite plates. Among them, the two pure silver plates 6 are placed in parallel, and the side of the pure silver strip is fixed by two side graphite plates 5 and the bottom is fixed by one bottom graphite plate 7, and a mold gap 4 for casting molten metal is formed between the two pure silver plates 6.

[0038] I. Embodiment

[0039] Embodiment 1

[0040] The non-punched silver-copper composite strip of this embodiment is sequentially provided with a first oxygen-free copper strip, a first pure silver strip, a BAg72Al strip, a second pure silver strip, and a second oxygen-free copper strip along the width direction.

[0041] Among them, the total width of the non-punched silver-copper composite strip is 20 mm, and the thickness is 0.1 mm.

[0042] The first oxygen-free copper strip, the first pure silver strip, the BAg72Al strip, the second pure silver strip, and the second oxygen-free copper strip have the same length and thickness; the widths of the first oxygen-free copper strip, the second oxygen-free copper strip, and the BAg72Al strip respectively account for 1 / 4 of the total width of the non-punched silver-copper composite strip, all of which are 5 mm; the widths of the first pure silver strip and the second pure silver strip respectively account for 1 / 8 of the total width of the non-punched silver-copper composite strip, all of which are 2.5 mm.

[0043] The preparation method of the non-punched silver-copper composite strip of this embodiment includes the following steps:

[0044] (1) Place two pure silver plates in parallel and fix them with graphite plates to form a die gap in the middle of the pure silver plates, obtaining a casting die cavity; place the casting die cavity in a vacuum melting furnace, and then melt the BAg72Al metal into a metal liquid under vacuum and at a melting temperature of 600 - 650 °C. Inject the melted BAg72Al metal liquid into the die gap of the casting die cavity, cool and demold to obtain an Ag-BAg72Al-Ag three-layer composite strip; wherein, in this step, the thickness of the pure silver plate is 2.5 mm, and the thickness of the pure silver plate corresponds to the width of the pure silver strip in the non-punched silver-copper composite strip; the thickness of the die gap is 5 mm, and the thickness of the die gap corresponds to the width of the BAg72Al strip in the non-punched silver-copper composite strip;

[0045] (2) Clamp the Ag-BAg72Al-Ag three-layer composite strip on the workbench of a surface grinder, fix an oxygen-free copper plate above, and then turn on the power of the surface grinder to make the pure silver surface on one side of the Ag-BAg72Al-Ag three-layer composite strip and the surface of the oxygen-free copper plate perform left-right feeding friction; when obvious plastic deformation appears on the pure silver surface and the silver-copper eutectic alloy liquid flows on the silver-copper contact surface, stop the friction, and at the same time apply pressure to the Ag-BAg72Al-Ag three-layer composite strip below to press against the oxygen-free copper plate above. After pressure holding, obtain a composite Ag-BAg72Al-Ag-Cu four-layer composite strip; wherein, the speed of the left-right feeding friction is 180 mm / min; the pressure applied to the Ag-BAg72Al-Ag three-layer composite strip is 15 N, and the pressure holding time is 15 min;

[0046] (3) Repeat step (2) to composite the pure silver surface on the other side of the Ag-BAg72Al-Ag-Cu four-layer composite strip with another oxygen-free copper plate to obtain a Cu-Ag-BAg72Al-Ag-Cu five-layer composite strip; then turn the five-layer composite strip by 90°, and then perform multi-pass rough rolling, annealing, and finish rolling to obtain the non-punched silver-copper composite strip of Embodiment 1. Among them, in the five-layer composite strip of this step, the widths of the pure silver strips on both sides are the same, both being 2.5 mm; the widths of the outermost oxygen-free copper strips are the same, both being 5 mm; the thickness of the BAg72Al strip is 5 mm; except for the different widths, the lengths and thicknesses of each single strip are the same.

[0047] Embodiment 2

[0048] The non-punched silver-copper composite strip of this embodiment is sequentially provided with a first oxygen-free copper strip, a first pure silver strip, a BAg72Al strip, a second pure silver strip, and a second oxygen-free copper strip along the width direction.

[0049] Among them, the total width of the non-punched silver-copper composite strip is 24 mm, and the thickness is 0.2 mm.

[0050] The lengths and thicknesses of the first oxygen-free copper strip, the first pure silver strip, the BAg72Al strip, the second pure silver strip, and the second oxygen-free copper strip are the same; the widths of the first oxygen-free copper strip, the second oxygen-free copper strip, and the BAg72Al strip respectively account for 1 / 4 of the total width of the non-punched silver-copper composite strip, all being 6 mm; the widths of the first pure silver strip and the second pure silver strip respectively account for 1 / 8 of the total width of the non-punched silver-copper composite strip, all being 3 mm.

[0051] The preparation method of the non-punched silver-copper composite strip in this embodiment is basically the same as that in Embodiment 1, and the difference between the two is that:

[0052] In step (1), the thickness of the pure silver plate is 3 mm, and the thickness of the pure silver plate corresponds to the width of the pure silver strip in the non-punched silver-copper composite strip; the thickness of the die gap is 6 mm, and the thickness of the die gap corresponds to the width of the BAg72Al strip in the non-punched silver-copper composite strip;

[0053] In step (2), the speed of the left and right feeding friction is 200 mm / min; the pressure applied to the Ag-BAg72Al-Ag three-layer composite strip is 18 N, and the pressure holding time is 16 min;

[0054] In the five-layer composite strip of step (3), the widths of the two pure silver strips on both sides are the same, both being 3 mm; the widths of the outermost oxygen-free copper strips are the same, both being 6 mm; the thickness of the BAg72Al strip is 6 mm; except for the different widths, the lengths and thicknesses of each single strip are the same.

[0055] Embodiment 3

[0056] The non-punched silver-copper composite strip of this embodiment is provided with a first oxygen-free copper strip, a first pure silver strip, a BAg72Al strip, a second pure silver strip, and a second oxygen-free copper strip in sequence along the width direction.

[0057] Among them, the total width of the non-punched silver-copper composite strip is 32 mm, and the thickness is 0.3 mm.

[0058] The lengths and thicknesses of the first oxygen-free copper strip, the first pure silver strip, the BAg72Al strip, the second pure silver strip, and the second oxygen-free copper strip are the same; the widths of the first oxygen-free copper strip, the second oxygen-free copper strip, and the BAg72Al strip respectively account for 1 / 4 of the total width of the non-punched silver-copper composite strip, all being 8 mm; the widths of the first pure silver strip and the second pure silver strip respectively account for 1 / 8 of the total width of the non-punched silver-copper composite strip, all being 4 mm.

[0059] The preparation method of the non-punched silver-copper composite strip in this embodiment is basically the same as that in Embodiment 1, and the difference between the two is that:

[0060] In step (1), the thickness of the pure silver plate is 4 mm, and the thickness of the pure silver plate corresponds to the width of the pure silver strip in the non-punched silver-copper composite strip; the thickness of the die gap is 8 mm, and the thickness of the die gap corresponds to the width of the BAg72Al strip in the non-punched silver-copper composite strip.

[0061] In step (2), the speed of the left and right feed friction is 240 mm / min; the pressure applied to the Ag-BAg72Al-Ag three-layer composite strip is 22 N, and the pressure holding time is 18 min.

[0062] In the five-layer composite strip of step (3), the widths of the two pure silver strips on both sides are the same, both being 4 mm; the widths of the outermost oxygen-free copper strips are the same, both being 8 mm; the thickness of the BAg72Al strip is 8 mm; except for the different widths, the lengths and thicknesses of each single strip are the same.

[0063] Example 4

[0064] In the non-punched silver-copper composite strip of this example, a first oxygen-free copper strip, a first pure silver strip, a BAg72Al strip, a second pure silver strip, and a second oxygen-free copper strip are arranged in sequence along the width direction.

[0065] Among them, the total width of the non-punched silver-copper composite strip is 40 mm, and the thickness is 0.1 mm.

[0066] The lengths and thicknesses of the first oxygen-free copper strip, the first pure silver strip, the BAg72Al strip, the second pure silver strip, and the second oxygen-free copper strip are the same; the widths of the first oxygen-free copper strip, the second oxygen-free copper strip, and the BAg72Al strip respectively account for 1 / 4 of the total width of the non-punched silver-copper composite strip, all being 10 mm; the widths of the first pure silver strip and the second pure silver strip respectively account for 1 / 8 of the total width of the non-punched silver-copper composite strip, all being 5 mm.

[0067] The preparation method of the non-punched silver-copper composite strip of this example is basically the same as that of Example 1, and the difference between the two is that:

[0068] In step (1), the thickness of the pure silver plate is 5 mm, and the thickness of the pure silver plate corresponds to the width of the pure silver strip in the non-punched silver-copper composite strip; the thickness of the die gap is 10 mm, and the thickness of the die gap corresponds to the width of the BAg72Al strip in the non-punched silver-copper composite strip.

[0069] In step (2), the speed of the left and right feed friction is 280 mm / min; the pressure applied to the Ag-BAg72Al-Ag three-layer composite strip is 26 N, and the pressure holding time is 19 min.

[0070] In the five-layer composite strip of step (3), the widths of the two pure silver strips on both sides are the same, both being 5 mm; the widths of the outermost oxygen-free copper strips are the same, both being 10 mm; the thickness of the BAg72Al strip is 10 mm; except for the different widths, the lengths and thicknesses of each single strip are the same.

[0071] Example 5

[0072] In the non-punched silver-copper composite strip of this example, a first oxygen-free copper strip, a first pure silver strip, a BAg72Al strip, a second pure silver strip, and a second oxygen-free copper strip are arranged in sequence along the width direction.

[0073] Among them, the total width of the non-punched silver-copper composite strip is 60 mm, and the thickness is 0.3 mm.

[0074] The lengths and thicknesses of the first oxygen-free copper strip, the first pure silver strip, the BAg72Al strip, the second pure silver strip, and the second oxygen-free copper strip are the same; the widths of the first oxygen-free copper strip, the second oxygen-free copper strip, and the BAg72Al strip respectively account for 1 / 4 of the total width of the non-punched silver-copper composite strip, all being 15 mm; the widths of the first pure silver strip and the second pure silver strip respectively account for 1 / 8 of the total width of the non-punched silver-copper composite strip, all being 7.5 mm.

[0075] The preparation method of the non-punched silver-copper composite strip of this example is basically the same as that of Example 1, and the difference between the two is that:

[0076] In step (1), the thickness of the pure silver plate is 7.5 mm, and the thickness of the pure silver plate corresponds to the width of the pure silver strip in the non-punched silver-copper composite strip; the thickness of the die gap is 15 mm, and the thickness of the die gap corresponds to the width of the BAg72Al strip in the non-punched silver-copper composite strip;

[0077] In step (2), the speed of the left and right feeding friction is 300 mm / min; the pressure applied to the Ag-BAg72Al-Ag three-layer composite strip is 30 N, and the pressure holding time is 20 min;

[0078] In the five-layer composite strip of step (3), the widths of the two pure silver strips on both sides are the same, both being 7.5 mm; the widths of the outermost oxygen-free copper strips are the same, both being 15 mm; the thickness of the BAg72Al strip is 15 mm; except for the different widths, the lengths and thicknesses of each single strip are the same.

[0079] II. Comparative Example

[0080] Comparative Example 1

[0081] The non-punched silver-copper composite strip provided in Comparative Example 1 is successively provided with a first oxygen-free copper strip, a first pure silver strip, a BAg80Al strip (BAg80Al is in mass percentage, and the material composition is: Ag 80±1%, the balance is Al), a second pure silver strip, and a second oxygen-free copper strip along the width direction. That is, in the silver-copper composite strip of this comparative example, the BAg80Al strip is used to replace the BAg72Al strip in Example 1, and the remaining parameters are the same correspondingly.

[0082] The preparation method of the non-punched silver-copper composite strip of this comparative example is basically the same as that of Example 1, except that in step (1), the BAg80Al metal is melted into a metal liquid under vacuum, and the melting temperature is 700-750°C, and the remaining steps and parameters are the same.

[0083] Comparative Example 2

[0084] The non-punched silver-copper composite strip provided in Comparative Example 2 is successively provided with a first oxygen-free copper strip, a first pure silver strip, a BAg50Al strip (BAg50Al is in mass percentage, and the material composition is: Ag 50±1%, the balance is Al), a second pure silver strip, and a second oxygen-free copper strip along the width direction. That is, in the silver-copper composite strip of this comparative example, the BAg50Al strip is used to replace the BAg72Al strip in Example 1, and the remaining parameters are the same correspondingly.

[0085] The preparation method of the non-punched silver-copper composite strip of this comparative example is basically the same as that of Example 1, except that in step (1), the BAg50Al metal is melted into a metal liquid under vacuum, and the melting temperature is 620-680°C, and the remaining steps and parameters are the same.

[0086] Comparative Example 3

[0087] The non-punched silver-copper composite strip provided in Comparative Example 3 is successively provided with a first oxygen-free copper strip, a first pure silver strip, a BAg72Cu strip (BAg72Cu is in mass percentage, and the material composition is: Ag 72±1%, the balance is Cu), a second pure silver strip, and a second oxygen-free copper strip along the width direction. That is, in the silver-copper composite strip of this comparative example, the BAg72Cu strip is used to replace the BAg72Al strip in Example 1, and the remaining parameters are the same correspondingly.

[0088] The preparation method of the non-punched silver-copper composite strip of this comparative example is basically the same as that of Example 1, except that in step (1), the BAg72Cu metal is melted into a metal liquid under vacuum, and the melting temperature is 800-850°C, and the remaining steps and parameters are the same.

[0089] Comparative Example 4

[0090] The non-punched silver-copper composite strip provided in Comparative Example 4 is successively provided with a first oxygen-free copper strip, a first pure silver strip, a BAl88Si strip (BAl88Si is in mass percentage, and the material composition is: Al 88±1%, with the balance being Si), a second pure silver strip, and a second oxygen-free copper strip along the width direction. That is, in the silver-copper composite strip of this comparative example, the BAl88Si strip is used to replace the BAg72Al strip in Example 1, and the remaining parameters are the same correspondingly.

[0091] The preparation method of the non-punched silver-copper composite strip of this comparative example is basically the same as that of Example 1, except that in step (1), the BAl88Si metal is melted into a metal liquid under vacuum, and the melting temperature is 600-650°C, and the remaining steps and parameters are the same.

[0092] Comparative Example 5

[0093] The silver-copper composite strip provided in Comparative Example 5, that is, the silver-copper composite strip prepared by the existing method (hot pressing and compounding a silver plate and a copper plate into one body in a vacuum furnace, and then rough rolling and finish rolling to obtain the silver-copper composite strip), has a pure silver strip in the center and oxygen-free copper strips on both sides, and through holes are punched on the pure silver strip. The thickness of the silver-copper composite strip is 0.1 mm, and the total width is 20 mm. Among them, the width of the pure silver strip is 10 mm, and the width of the oxygen-free copper strips on both sides is 5 mm.

[0094] III. Test Examples

[0095] Test Example 1

[0096] This test example examines the interfacial bonding quality of the silver-copper composite strip in Example 1 of the present invention and the traditional silver-copper composite strip in Comparative Example 5. Samples of the two silver-copper composite strips are taken, and the microscopic morphology of the bonding surface is compared by scanning electron microscopy. The test results of the microscopic morphology are as Figure 3 shown.

[0097] It can be seen from Figure 3 that for the silver-copper composite strip of Example 1 of the present invention, a silver-copper eutectic phase is formed at the composite interface. By friction extrusion to generate heat, a relatively wide weld seam can be formed. The weld seam is a silver-copper eutectic structure, and there are few defects such as pores and inclusions at the bonding interface ( Figure 3 left figure); while for the silver-copper composite strip of Comparative Example 5 prepared by the traditional method, the diffusion weld seam at the composite interface is relatively narrow, and there are more slag inclusions and unbonded defects at the bonding interface ( Figure 3 right figure). It can be seen that the present invention can not only form high-quality wide weld seams, which is beneficial to subsequent rolling processing, but also has few pores and inclusions at the bonding interface, and the quality of the composite strip is more stable.

[0098] The bonding strength (semi-hard state) of the silver-copper interface in Examples 1 to 5 and Comparative Example 5 was further measured, and the average value of the results of five parallel tests of the bonding strength was taken. Among them, the test method of the bonding strength was carried out in accordance with GBT 228.1, and a strip of 5 mm × 10 mm was used as the standard specimen (one end was silver and the other end was copper), and the transverse tensile strength of the strip was measured. The test results of the bonding strength are shown in Table 1.

[0099] Table 1 Interface bonding strength of silver-copper composite strips in Examples 1 to 5 and Comparative Example 5 of the present invention

[0100]

[0101] It can be seen from the test results of the bonding strength in Table 1 that for the non-punched silver-copper composite strip provided in the embodiments of the present application, the bonding strength of the silver-copper interface is relatively high. Compared with the traditional silver-copper composite strip in Comparative Example 5, the bonding strength is increased by at least 29.6% and at most 42.3%.

[0102] Test Example 2

[0103] This test example investigated the resistivity of the central materials BAg72Al in Example 1 of the present invention, BAg80Al in Comparative Example 1, BAg50Al in Comparative Example 2, BAg72Cu in Comparative Example 3, BAl88Si in Comparative Example 4, and the pure Ag central material in Comparative Example 5. Among them, the cross-sectional areas of the central materials in Example 1 and Comparative Examples 1 to 5 were the same, except that there was a row of through holes in the pure silver central material in Comparative Example 5. In an experimental environment of 20 °C, a QJ84 type digital DC bridge was used to measure the resistance of the composite strips of the same size and specification as above. To eliminate the influence of electromotive force, the current commutation method was adopted, and one forward reading and one reverse reading were taken, and the arithmetic mean of the two resistance measurement values was taken. Finally, the resistivity was calculated using the resistivity formula, ρ = R1ab / T0 (where ρ is the resistivity, a is the width of the silver strip, b is the thickness of the silver strip, and T0 is the temperature coefficient). The specific resistivity test results are shown in Table 2 below.

[0104] Table 2 Test results of resistivity of silver-copper composite strips in Example 1 and Comparative Examples 1 to 5 of the present invention

[0105]

[0106] It can be seen from the test results in Table 2 that the resistivity of the central material of the silver-copper composite strip in Example 1 is 1.98×10 -8Ω·m, which is closest to the resistivity of the center-punched silver foil of the traditional silver-copper composite strip in Comparative Example 5, and its function can be equivalently substituted. However, the resistivity of Comparative Example 1 and Comparative Example 3 is on the low side, which is closer to the resistivity of pure silver, and the difference is too small. When the current in the circuit exceeds a certain value, it cannot be melted immediately; the resistivity of Comparative Example 2 and Comparative Example 4 is on the high side. Usually, the composite strip plays the role of carrying and connecting the current. If the resistivity is too large, it will affect the current flow, and it will heat and melt under the normal working current. Therefore, in the silver-copper composite strip provided by the present invention, the BAg72Al material is used as the intermediate layer, and its resistivity is moderate, which can not only melt and disconnect immediately when the current in the circuit deviates from the normal value, but also play the role of carrying the current in the normal working current.

[0107] In summary, the non-punched silver-copper composite strip provided by the present invention does not need to be pre-punched before use. The BAg72Al in the core plays the role of circuit disconnection, which not only saves silver materials but also avoids the cumbersome punching process. Moreover, the interface bonding strength of the composite strip of the present invention is high, there are few defects such as interface inclusions and pores, the quality of the composite strip is stable and the composite quality is good, and it has a wide application prospect in the field of preparing melt materials for fuses.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the protection scope of the present invention.

Claims

1. A silver-copper composite strip without punching holes, characterized in that, It includes a first oxygen-free copper strip, a first pure silver strip, a BAg72Al strip, a second pure silver strip, and a second oxygen-free copper strip arranged in sequence along the width direction; Among them, first, an Ag-BAg72Al-Ag three-layer composite strip is prepared. Through friction welding between the pure silver surface and the oxygen-free copper surface on the outside of the Ag-BAg72Al-Ag three-layer composite strip, heat is generated by friction between the silver and copper surfaces to reach the eutectic temperature, and a silver-copper eutectic alloy liquid is generated between the silver and copper surfaces. Then, a pressing force is applied to achieve effective composite of the silver and copper surfaces.

2. The silver-copper composite strip without punching holes as claimed in claim 1, wherein The first oxygen-free copper strip, the first pure silver strip, the BAg72Al strip, the second pure silver strip, and the second oxygen-free copper strip have the same length and thickness; the widths of the first oxygen-free copper strip, the second oxygen-free copper strip, and the BAg72Al strip respectively account for 1 / 4 of the total width of the non-punched silver-copper composite strip; the widths of the first pure silver strip and the second pure silver strip respectively account for 1 / 8 of the total width of the non-punched silver-copper composite strip.

3. The non-punched silver-copper composite strip according to claim 1 or 2, characterized in that, The thickness of the non-punched silver-copper composite strip is 0.1 - 0.3 mm.

4. The non-punched silver-copper composite strip according to claim 1 or 2, characterized in that, The total width of the non-punched silver-copper composite strip is 20 - 60 mm.

5. A preparation method of the non-punched silver-copper composite strip as described in claim 1, characterized in that, It includes the following steps: (1) Place two pure silver plates parallel and fix them. A die gap is formed in the middle of the pure silver plates to obtain a casting die cavity; then, the melted BAg72Al metal liquid is injected into the die gap of the casting die cavity, cooled and demolded to obtain an Ag-BAg72Al-Ag three-layer composite strip; (2) Clamp the Ag-BAg72Al-Ag three-layer composite strip on the workbench of a surface grinder. Fix an oxygen-free copper plate on one side of the workbench, and then perform left-right feeding friction between the pure silver surface on one side of the Ag-BAg72Al-Ag three-layer composite strip and the surface of the oxygen-free copper plate; when plastic deformation appears on the pure silver surface and a silver-copper eutectic alloy liquid flows on the silver-copper contact surface, stop friction, apply pressure to make the Ag-BAg72Al-Ag three-layer composite strip press tightly against the oxygen-free copper plate, and obtain a composite Ag-BAg72Al-Ag-Cu four-layer composite strip after pressure holding; (3) Repeat step (2), and composite the pure silver surface on the other side of the Ag-BAg72Al-Ag-Cu four-layer composite strip with another oxygen-free copper plate to obtain a Cu-Ag-BAg72Al-Ag-Cu five-layer composite strip. Flip the five-layer composite strip and perform rolling and annealing to obtain the non-punched silver-copper composite strip.

6. The preparation method of the non-punched silver-copper composite strip according to claim 5, characterized in that, In step (1), the melting temperature of the BAg72Al metal liquid is 600 - 650 °C.

7. The preparation method of the non-punched silver-copper composite strip according to claim 5, characterized in that, In step (1), the melting and injection are both carried out under vacuum conditions.

8. The preparation method of the non-punched silver-copper composite strip according to any one of claims 5 to 7, characterized in that, In step (2), the speed of the left-right feeding friction is 180 - 300 mm / min.

9. The preparation method of the non-punched silver-copper composite strip according to any one of claims 5 to 7, characterized in that, In step (2), the pressure is 15 - 30 N, and the pressure holding time is 15 - 20 min.

10. The preparation method of the non-punched silver-copper composite strip according to any one of claims 5 to 7, characterized in that, In step (3), the flipping angle is 90°.

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