Silver-copper composite belt blank assembling unit, silver-copper composite belt blank and preparation method

Abstract

The invention provides a silver-copper composite belt blank assembling unit, a silver-copper composite belt blank and a preparation method. Each assembly unit is mainly a sandwich-shaped long-strip-shaped blank formed by stacking a pure copper plate, a pure silver plate and a pure copper plate in sequence, and the pure silver plate and the pure copper plate are connected in a brazed mode through silver-copper foil strip brazing filler metal. The silver-copper composite strip blank is mainly formed by transversely arranging a plurality of assembling units, and the adjacent assembling units are connected in a brazing mode through silver-copper-zinc foil strip brazing filler metal. Therefore, the composite composite belt blank is prepared mainly by adjusting the sizes of the assembling units and the corresponding number of the assembling units which are transversely and circularly arranged in the width direction, the manufacturing process is a standardized and modularized production and manufacturing process of the composite belt blank, and the problem that in the preparation process of a plurality of wide composite belt blanks, the production cost is low can be effectively solved. The problems of size deviation, dislocation or poor control precision and the like are easily caused, and the production efficiency of the composite belt blank is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of composite metal strips, and in particular to a silver-copper composite strip blank assembly unit and a preparation method thereof, and a method for further preparing the silver-copper composite strip blank using the assembly unit. Background Art

[0002] Silver-copper composite strip (hereinafter referred to as composite strip) is a composite metal strip product made by arranging pure silver matrix and pure copper matrix of equal thickness alternately along the width direction of the strip, with a thickness of usually 0.06-0.2 mm and a total width of usually 20-180 mm; the sides of pure silver and pure copper are in a metallurgical bonding state, and are usually arranged regularly with equal silver width and equal silver strip spacing. Composite strip is a raw material used to manufacture the core component of fuse - melt material. Compared with the existing pure silver strip, pure silver is retained only in the part where the diameter needs to be processed, and pure copper is used to replace pure silver in the rest of the part, which greatly saves the use of precious metal silver. It also has good circuit breaking capacity, stable resistance and melting point, which is in line with the development trend of energy conservation, emission reduction and cost reduction. Especially in the field of low-voltage fast fuses, it has become the main melt material for fuses in electrical systems such as new energy vehicles, high-speed trains, and wind and solar energy storage.

[0003] As the safety guarantee of the circuit, the fuse's fusing performance, rated voltage, rated current, and breaking capacity are related to many factors. Among them, the dimensional accuracy and stability of the melt material not only affect the resistance of the fuse piece to a certain extent, but also have a significant impact on the diameter punching process of the fuse piece. If there is a dimensional out-of-tolerance defect, it is very likely that the diameter punching will occur at the interface between pure copper and pure silver or directly punching the pure copper part, resulting in the scrapping of the fuse and even affecting the circuit safety. Therefore, the dimensional accuracy and stability of the composite strip product are important indicators to measure its qualification. With the continuous increase of current circuit power and current carrying capacity, the current carrying capacity of the fuse is also continuously improving, making its size continuously increasing, and the size of the fuse piece used is also increasing accordingly, which is manifested in the gradual increase in the width requirements of the composite strip and the number of silver bars. At the same time, with the development of new energy vehicles and wind and solar energy storage industries, the use of wide (width ≥ 60mm) and multiple (number of silver bars ≥ 3) composite strip products is increasing.

[0004] Existing composite strip processing and manufacturing processes are usually hot-pressing resistance composite, hot-rolling composite or diffusion composite, etc. These composite methods require the silver-copper interface to reach a certain composite pressure condition, and the pressure device (including pressure rod and pressure head) in such equipment is usually arranged in a vertical direction. When there are many composite strips and the width is large, the silver plates and copper plates are stacked in sequence. There are problems such as overturning and collapse caused by excessive vertical stacking and excessive weight, or interlayer slippage and uneven pressure transmission during the composite process, resulting in uneven size of the composite strip blanks, affecting the quality of the finished product after rolling. In addition to this method, some manufacturers also use hot-rolled composite technology or slotted pure silver narrow strips on the base of pure copper plate, but the hot-rolled composite technology is only suitable for the production of plate products with a thickness of ≤120 mm. For multiple composite wide band products, it not only increases the process difficulty, but also easily causes interface defects such as uneven composite and weak bonding, or even cannot be achieved; while the embedded strip method is cumbersome, the production efficiency is low, the size is difficult to control, and the embedded strip method is suitable for the production of surface composite composite strips (the silver strip is non-strip through-type, and only composited on the surface of one side of the strip), not suitable for the production of side composite composite strips. In addition, some fuse manufacturers use the method of overlapping shorter fuses to form large-width fuses during the assembly process of fuses to achieve the purpose of use by connecting them, but the overlapping method will introduce new problems, such as the reliability of the overlap solder joints and the impact on the current characteristics of the fuse. Therefore, the efficient and stable production and manufacturing process of wide-width silver-copper composite fuses is still a key link in the large-capacity and high-current fuse manufacturing industry chain. Summary of the invention

[0005] In view of this, in order to improve the efficiency and stability of the manufacturing process of wide-width silver-copper composite fuse pieces, one object of the present invention is to provide a silver-copper composite strip blank assembly unit (hereinafter referred to as the assembly unit) and a preparation method. The assembly unit can be adjusted according to the finished product size and number of strips required by different customers, by adjusting the size of the assembly unit and the corresponding number of horizontal circular arrangements in the width direction, and combined with the brazing process to achieve efficient and stable production of wide-width, multi-strip side composite composite strip blanks, while keeping their size uniform and controllable.

[0006] Another object of the present invention is to provide a silver-copper composite strip blank (hereinafter referred to as blank) and a preparation method thereof. The blank is formed by horizontally splicing and brazing the above-mentioned assembly units. During the brazing process, the assembly units are placed horizontally. By adjusting the pressure of the tooling fixture, the pressure on the brazing surface can be made even, and the size and the number of silver strips can be flexibly controlled, thereby avoiding dimensional deviations or blank defects caused by traditional composite processes. In addition, the brazing time is short and the efficiency is high. After welding, only the weld needs to be polished before it can be transferred to the subsequent rolling stage. The method is simple.

[0007] Among them, "horizontal" in the present invention means that the assembly units are arranged vertically, that is, the direction perpendicular to the gravity direction of the assembly units, such as "horizontal splicing" and "horizontal arrangement"; "longitudinal" means that the assembly units are arranged flat, that is, the direction parallel to the gravity direction of the assembly units.

[0008] To achieve the above object, the technical solution provided by the present invention is as follows: A silver-copper composite strip blank assembly unit is mainly composed of a sandwich-shaped long strip blank formed by stacking a pure copper plate-a pure silver plate-a pure copper plate in sequence, wherein the pure silver plate and the pure copper plate are brazed and connected by a silver-copper foil strip brazing material.

[0009] A method for preparing the above-mentioned assembly unit includes the steps of: firstly stacking and assembling the pure copper plate, the pure silver plate and the foil solder neatly in the order of "pure copper plate-foil solder-pure silver plate-foil solder-pure copper plate" to obtain assembly unit assembly parts; and then brazing the assembly unit assembly parts.

[0010] The brazing connection method includes existing welding methods such as gas shielded brazing and vacuum brazing. The gas shielded brazing method includes: placing the assembly unit assembly in the uniform temperature zone of the gas shielded furnace, and introducing nitrogen for 15 to 30 minutes, and if necessary, the gas shielded furnace can be cleaned 2 to 3 times; then stop introducing nitrogen, and raise the temperature in the gas shielded furnace to 820 to 880°C at a heating rate of 5 to 10°C / min, keep warm for 10 to 30 minutes, and then cool.

[0011] The vacuum brazing method comprises: firstly placing the assembly unit assembly in the center of the graphite platform in the vacuum chamber, and then evacuating the vacuum chamber to 3.0×10 -3 ~8.0×10 -4 Pa, then heat to 820-880℃ and keep warm for 10-30 min, then cool.

[0012] A silver-copper composite strip blank is mainly composed of a plurality of the above-mentioned assembly units arranged transversely, and adjacent assembly units are brazed and connected by using silver-copper-zinc foil strip brazing material.

[0013] A method for preparing the above-mentioned silver-copper composite strip blank comprises the steps of: Workpiece assembly: First, multiple assembly units are stacked horizontally, and silver-copper-zinc foil brazing materials are inserted between adjacent assembly units to form blank assembly parts; Blank preparation: The blank assembly parts are brazed to connect adjacent assembly units by brazing to form a composite strip blank.

[0014] In the workpiece assembly step, a plane clamp is used to fix multiple assembly units. The plane clamp includes a plane bottom plate, a left clamp, a right clamp, and multiple locking bolts. The plane bottom plate is provided with multiple T-slots. The left clamp and the right clamp are movably mounted on the plane floor through the cooperation of the locking bolts and the T-slots, and can move along the T-slots. In this way, the spacing between the left clamp and the right clamp can be adjusted and fixed to the plane floor along the T-slots through the locking bolts. The left clamp and the right clamp can be slidably fixed on the upper surface of the horizontal bottom plate, and cooperate to clamp the multiple assembly units and the foil strip solder located between adjacent assembly units to form a blank assembly part.

[0015] The step of preparing the blank comprises: brazing the blank assembly parts by gas shielded brazing or vacuum brazing to connect adjacent assembly units by brazing to form the composite strip blank.

[0016] The gas shielded brazing method comprises: placing the blank assembly and the flat fixture together in a uniform temperature zone in a gas shielded furnace, and introducing nitrogen for 15 to 30 minutes. If necessary, the gas shielded furnace can be cleaned 2 to 3 times; then the introduction of nitrogen is stopped, and the temperature in the gas shielded furnace is increased to 680 to 760°C at a heating rate of 5 to 10°C / min, the insulation time is 10 to 30 minutes, and then cooled.

[0017] The vacuum brazing method comprises: firstly placing the blank assembly and its plane fixture together at the center of the graphite platform in the vacuum chamber, and then evacuating the vacuum chamber to 3.0×10 -3 ~8.0×10 -4 Pa, then heat to 680-760℃ and keep warm for 10-30min, then cool.

[0018] Therefore, the assembly unit provided by the present invention is a three-layer composite plate composed of a pure copper plate-a pure silver plate-a pure copper plate, and its size and precision are stable and controllable, which is beneficial to ensuring the size and precision of each silver bar in the wide width and multiple composite strip blanks obtained by subsequent brazing.

[0019] The assembly unit provided by the present invention is mainly prepared by gas shielded brazing or vacuum brazing, and the preparation method is simple, easy to operate and highly controllable.

[0020] The composite strip blank provided by the present invention is based on the copper-silver-copper assembly unit, and can be prepared according to the finished product size and number of strips required by different customers by adjusting the size of the assembly unit and the number of horizontal circular arrangements, thereby avoiding the influence of its own gravity on the pressure during the traditional vertical preparation when producing composite strip blanks with a thickness of ≥120 mm; and the assembly units are brazed into a whole by gas shielded brazing or vacuum brazing. During the brazing process, the contact pressure between the assembly units can be made more uniform by adjusting the pressure of the plane clamp in the horizontal direction, so that the size change of the silver bars in each assembly unit is stable and controllable; and the process flow is short and the efficiency is high. After welding, only the weld seam on the surface of the composite strip blank needs to be polished or the surface milled flat before it can be transferred to the subsequent rolling link.

[0021] Therefore, the above-mentioned assembly unit and preparation method, the blank using the assembly unit and the preparation method provided by the present invention improve the production efficiency of the composite strip blank, and are a standardized and modular production and manufacturing process for the composite strip blank, which can effectively solve the problems of dimensional deviation, misalignment or poor control accuracy that are prone to occur during the preparation process of wide-width and multi-strip composite strip blanks. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of the three-dimensional structure of a planar clamp used in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the silver-copper assembly unit; Figure 3 It is a structural schematic diagram of a composite strip blank assembly; Figure 4 for Figure 3 A schematic diagram of the arrangement of assembly units and foil strip solder in the composite strip blank assembly shown; Figure 5 This is a photo of a silver-copper composite strip product made from the silver-copper composite strip blank provided in Example 4 of the present invention.

[0023] Among them, the component symbols in each figure are: 1. pure copper plate, 2. pure silver plate, 3. foil strip solder, 4. plane clamp, 41. left clamp, 42. right clamp, 43. plane bottom plate, 44. T-slot, 45. locking bolt, 46. reinforcing rib. DETAILED DESCRIPTION

[0024] The terms used in the present invention are all commonly used terms in the relevant field. The raw materials, equipment, preparation processes, testing methods, etc. used are all prior arts in the relevant field unless otherwise specified.

[0025] In order to improve the efficiency and stability of the production process of wide-width silver-copper composite fuse pieces, the present invention adjusts the size of the assembly unit and the corresponding number of its transverse circular arrangement in the width direction, and combines the brazing process to achieve efficient and stable production of wide-width, multi-strip side-composite composite strip blanks while maintaining uniform and controllable size.

[0026] A silver-copper composite strip assembly unit is mainly composed of a sandwich-shaped long strip blank formed by stacking a pure copper plate-a pure silver plate-a pure copper plate in sequence, wherein the pure silver plate and the pure copper plate are brazed and connected by a silver-copper foil strip brazing material.

[0027] In order to avoid introducing impurity elements that affect the electrical properties of the finished composite strip and causing large fluctuations in size, the silver-copper foil solder is preferably 0.03-0.08 mm thick and 20-25 mm wide. The silver-copper foil solder includes BAg50Cu, BAg72Cu, BAg85Cu, BAg92Cu, etc. in the GB / T 10046 national standard.

[0028] Taking into account the size of commercially available products and the limitations of equipment and process conditions, the size of the pure copper plate is preferably a long strip with a thickness of 4 to 12 mm, a length of 300 to 800 mm, and a width of 20 to 25 mm.

[0029] Taking into account the size of commercially available products and the limitations of equipment and process conditions, the size of the pure silver plate is preferably a long strip with a thickness of 2 to 5 mm, a length of 300 to 800 mm, and a width of 20 to 25 mm.

[0030] A method for preparing the above-mentioned assembly unit includes the steps of: firstly stacking and assembling the pure copper plate, the pure silver plate and the foil solder neatly in the order of "pure copper plate-foil solder-pure silver plate-foil solder-pure copper plate" to obtain an assembly unit assembly part; and then welding the assembly unit assembly part.

[0031] To ensure good bonding and interface stability between the silver plate and the copper plate in the assembly unit, the pure copper plate and the pure silver plate also include the steps of pickling to remove oxide scale on the surface of the pure copper plate and cleaning to remove oil stains on the surface of the pure copper plate and the pure silver plate before assembly.

[0032] The welding treatment method includes existing welding processes such as gas shielded brazing and vacuum brazing. The gas shielded brazing method includes: placing the assembly unit assembly in a uniform temperature zone in a gas shielded furnace, and introducing nitrogen for 15 to 30 minutes. If necessary, the gas shielded furnace can be cleaned 2 to 3 times; then stop introducing nitrogen, raise the temperature in the gas shielded furnace to 820 to 880°C at a heating rate of 5 to 10°C / min, keep warm for 10 to 30 minutes, and then cool.

[0033] The vacuum brazing method comprises: firstly placing the assembly unit assembly in the center of the graphite platform in the vacuum chamber, and then evacuating the vacuum chamber to 3.0×10 -3 ~8.0×10 -4 Pa, then heat to 820-880℃ and keep warm for 10-30 min, then cool.

[0034] The assembly unit parts are cooled to room temperature in the furnace after the welding process, and then taken out of the furnace for surface cleaning and milling until the surface is smooth, thus forming the assembly unit.

[0035] A silver-copper composite strip blank is mainly composed of a plurality of the above-mentioned assembly units arranged transversely, and adjacent assembly units are brazed and connected by using silver-copper-zinc foil strip brazing material, wherein silver brazing agent is used as an auxiliary when necessary.

[0036] The reason why silver-copper-zinc foil brazing alloy is selected in the silver-copper composite strip blank is mainly because its welding temperature is lower than the welding problem of the silver-copper foil brazing alloy in the assembly unit. This can prevent the brazing alloy in the assembly unit from melting again during the brazing process of preparing the silver-copper composite strip blank, affecting the weld quality and the dimensional consistency and stability of the composite strip blank. Silver-copper-zinc foil brazing alloys include BAg25CuZn, BAg30CuZn, BAg35CuZn, BAg44CuZn, BAg45CuZn, BAg50CuZn, etc. in the national standard GB / T 10046.

[0037] When the assembly units are brazed by gas shielding, silver brazing agent is coated on both sides of the silver-copper-zinc foil brazing material. The silver brazing agent can be in the form of paste or powder. The silver brazing agent can be selected from QJ101, QJ102, QJ112, etc., and is mainly prepared with borate, fluoride, boric acid or other auxiliary materials as the main ingredients.

[0038] A method for preparing the above-mentioned silver-copper composite strip blank comprises the steps of: Workpiece assembly: firstly, a plurality of assembly units are stacked transversely, and silver-copper-zinc foil strip solder is inserted between adjacent assembly units to form a blank assembly part, wherein, if necessary, both surfaces of the foil strip solder are evenly coated with silver solder; Blank preparation: The blank assembly parts are brazed to connect adjacent assembly units by brazing to form a composite strip blank.

[0039] The assembly of the workpiece affects the dimensional accuracy, production efficiency and stability of the final composite strip blank, so the consistency and efficiency of the assembly process should be ensured. For this purpose, a planar fixture is used to fix multiple assembly units in the workpiece assembly step.

[0040] Among them, the planar clamp includes a planar base plate, a left clamping plate, a right clamping plate, and a plurality of locking bolts, and a plurality of T-slots are arranged on the planar base plate; the left clamping plate and the right clamping plate are movably mounted on the planar floor through the cooperation of the locking bolts and the T-slots, and can move along the T-slots; in this way, the spacing between the left clamping plate and the right clamping plate can be adjusted and fixed to the planar floor along the T-slots through the locking bolts; the left clamping plate and the right clamping plate can be slidably fixed on the upper surface of the horizontal base plate, and are used to clamp a plurality of the assembly units and the foil solder located between adjacent assembly units to form a blank assembly part.

[0041] Preferably, the left and right clamping plates have the same structure, and each clamping plate includes a blank clamping surface, a fixing surface and a plurality of reinforcing ribs. The blank clamping surface is perpendicular to the planar bottom plate, and the fixing surface is arranged on the back of the blank clamping surface and forms an L-shape with the blank clamping surface. The fixing surface is fixed to the planar bottom plate by the locking bolt. Each reinforcing rib is fixed to the back and fixing surface of the blank clamping surface at the same time. The locking bolt is arranged between adjacent reinforcing ribs. The blank clamping surfaces of the left and right clamping plates are arranged opposite to each other, and the area of ​​the blank clamping surface is slightly larger than the contact area of ​​the assembly unit in contact with it; the distance between the left and right clamping plates is controlled by controlling the distance between the two blank clamping surfaces, so that the planar clamp can be used for the assembly of composite strip blanks of different sizes. In order to ensure that the blank assembly parts are evenly stressed during the assembly process and to ensure their stability and dimensional uniformity, preferably, the locking bolts and reinforcing ribs are symmetrically distributed.

[0042] The steps of assembling the workpiece include: placing multiple assembly units and foil solder inserted between the assembly units between the left and right clamps in the plane fixture according to a predetermined design, and fixing them between the left and right clamps by locking bolts, so as to form the blank assembly. Before assembly, the pure copper joint surface of the assembly unit is first cleaned with an ultrasonic cleaner to remove impurities such as oil stains and foreign matter; the foil solder is cut into square sheets of the same size as the pure copper joint surface, wherein a layer of silver solder is evenly applied on both sides of the foil solder with a soft brush when gas shielded brazing is used, and no silver solder is required when vacuum brazing is used; the silver-copper-zinc foil solder is assembled between the joint surfaces of the two assembly units, and the edges are aligned; after all the assembly is completed, the left and right clamps are used to fix them on both sides, and the clamping force is controlled appropriately, so that the assembly unit does not slide or shift.

[0043] The step of preparing the blank includes: brazing the blank assembly parts by gas shielded brazing or vacuum brazing to connect adjacent assembly units by brazing to form the composite strip blank. During the brazing process, the brazing temperature is determined according to the silver-copper-zinc brazing alloy.

[0044] The gas shielded brazing method comprises: placing the blank assembly and the flat fixture together in a uniform temperature zone in a gas shielded furnace, and introducing nitrogen for 15 to 30 minutes. If necessary, the gas shielded furnace can be cleaned 2 to 3 times; then the introduction of nitrogen is stopped, and the temperature in the gas shielded furnace is increased to 680 to 760°C at a heating rate of 5 to 10°C / min, the insulation time is 10 to 30 minutes, and then cooled.

[0045] The vacuum brazing method comprises: firstly placing the blank assembly and its plane fixture together at the center of the graphite platform in the vacuum chamber, and then evacuating the vacuum chamber to 3.0×10 -3 ~8.0×10 -4 Pa, then heat to 680-760℃ and keep warm for 10-30min, then cool.

[0046] The present invention also provides an application of the silver-copper composite strip blank in preparing a melt material for a fuse.

[0047] Therefore, the assembly unit provided by the present invention is a three-layer composite plate composed of a pure copper plate-a pure silver plate-a pure copper plate, and its size and precision are stable and controllable, which is beneficial to ensuring the size and precision of each silver bar in the wide width and multiple composite strip blanks obtained by subsequent brazing.

[0048] The assembly unit provided by the present invention is mainly prepared by gas shielded brazing or vacuum brazing, and the preparation method is simple, easy to operate and highly controllable.

[0049] The composite strip blank provided by the present invention is based on the copper-silver-copper assembly unit, and can be prepared according to the finished product size and number of strips required by different customers by adjusting the size of the assembly unit and the number of horizontal circular arrangements, thereby avoiding the influence of its own gravity on the pressure during traditional vertical preparation; and the assembly units are brazed into a whole by gas shielded brazing or vacuum brazing. During the brazing process, the contact pressure between the assembly units can be made more uniform by adjusting the plane clamp pressure in the horizontal direction, so that the size change of the silver bars in each assembly unit is stable and controllable; and the process flow is short and the efficiency is high. After welding, only the weld seam on the surface of the composite strip blank needs to be polished and smoothed before it can be transferred to the subsequent rolling link.

[0050] Therefore, the above-mentioned assembly unit and preparation method, the blank using the assembly unit and the preparation method provided by the present invention improve the production efficiency of the composite strip blank, and are a standardized and modular production and manufacturing process for the composite strip blank, which can effectively solve the problems of dimensional deviation, misalignment or poor control accuracy that are prone to occur during the preparation process of wide-width and multi-strip composite strip blanks.

[0051] It should be noted that in actual silver-copper composite strip products, after the composite strip is punched into narrow strips, the two ends of the narrow strips need to be welded to the contacts at both ends of the fuse during the assembly process of the fuse, so the outermost copper strips at both ends of the narrow strips are usually wider. When the composite strip blank is prepared by the method provided by the present invention, the size of the assembly units on both sides and the middle assembly unit is slightly different, which is subject to the actual customer requirements.

[0052] The technical solution of the present invention is further described in detail below through specific implementation methods.

[0053] In the process of preparing the composite strip blank in the following embodiments of the present invention, Figure 1 The plane clamp 4 comprises a plane bottom plate 43, a left clamping plate 41 and a right clamping plate 42 slidably fixed on the plane bottom plate 43, and four locking bolts 45. The plane bottom plate 43 has a horizontal upper surface and is provided with two T-shaped slots 44.

[0054] The left clamping plate 41 and the right clamping plate 42 in the planar clamp 4 have the same structure. Each of the left clamping plate 41 and the right clamping plate 42 includes a blank clamping surface, a fixing surface and three reinforcing ribs. The blank clamping surface is perpendicular to the planar bottom plate 43, and the fixing surface is arranged on the back of the blank clamping surface and forms an L shape with the blank clamping surface, and the fixing surface is fixed to the planar bottom plate 43 by two symmetrically arranged locking bolts 45. Three reinforcing ribs 46 are arranged on the back of the blank clamping surface, and the reinforcing ribs 46 are respectively fixed to the blank clamping surface and the fixing surface. The locking bolts 45 are arranged between adjacent reinforcing ribs 46. The locking bolts 45 and the reinforcing ribs 46 are symmetrically distributed to ensure uniform force on the composite strip blank assembly parts.

[0055] The blank clamping surfaces of the left clamping plate 41 and the right clamping plate 42 are arranged opposite to each other, and the area of ​​the blank clamping surface is slightly larger than the contact area of ​​the assembly unit in contact with it; the distance between the two blank clamping surfaces is controlled to adjust the spacing between the left clamping plate 41 and the right clamping plate 42, so that the plane clamp can be used for the assembly of composite strip blanks of different sizes. The left clamping plate 41 and the right clamping plate 42 are respectively fixed to the plane bottom plate 43 along the T-slot 44 by two symmetrically arranged locking bolts 45, so as to uniformly press the composite strip blank assembly parts when the plane clamp is used for assembly, and ensure its stability and dimensional uniformity.

[0056] Example 1 This embodiment provides an assembly unit and a preparation method thereof, a composite strip blank using the assembly unit and a preparation method thereof, the specific contents of which are as follows: (1) Assembling unit: Select pure copper plate with size of 300 mm×20 mm×6 mm, pure silver plate with size of 300 mm×20 mm×4 mm, and BAg72Cu foil strip with size of 300 mm×20 mm×0.05 mm as raw materials, and prepare the assembly unit by gas shielded brazing. The specific preparation method includes the following steps: First, the surface of the pure copper plate is pickled to remove the oxide scale, and the pure silver plate and the pure copper plate are cleaned with alcohol to remove the oil stains. Then, after the silver solder QJ101 is applied on both sides of the foil solder, the layers are neatly stacked and assembled in the order of "pure copper plate-foil solder-pure silver plate-foil solder-pure copper plate" to obtain an assembly unit assembly. Place the assembled assembly unit assembly parts flatly in the middle temperature zone of the gas shielded brazing furnace, introduce nitrogen for about 20 minutes to wash the furnace, and wash the furnace three times; then close the nitrogen valve, raise the furnace temperature to 830℃ at a heating rate of 7-9℃ / min, keep it warm for 15 minutes, and then cool it with the furnace; take out the assembly unit for surface cleaning, and mill it flat to make an assembly unit with a size of 300 mm×20 mm×16.05±0.05 mm, such as Figure 2 As shown, the pure copper plate 1 and the pure silver plate 2 in the assembly unit are connected together by brazing to form a sandwich-shaped long strip composite plate with a "pure copper plate-pure silver plate-pure copper plate" structure.

[0057] (2) The composite strip blank is mainly composed of 8 of the above-mentioned assembly units arranged in a horizontal cycle and brazed. Please refer to Figure 3 and Figure 4 The specific preparation method of the composite strip blank comprises the following steps: Workpiece assembly: The foil solder 3 can be commercially available BAg45CuZn, and the silver solder can be commercially available QJ101; during pre-welding treatment, the pure copper plate bonding surface of the assembly unit is cleaned with an ultrasonic cleaner to remove impurities such as oil, foreign matter, etc.; the BAg45CuZn foil solder is cut into square sheets of the same size as the pure copper plate bonding surface, and a layer of silver solder QJ101 is evenly applied on both sides with a soft brush; during assembly, the 8 components are assembled in the order of "assembly unit-foil solder 3-..." The assembly units are arranged and assembled in sequence along the thickness direction thereof, a single layer of BAg45CuZn foil strip solder coated with QJ101 silver solder is stacked between every two assembly units, and the entire blank assembly is placed between the left and right clamping plates 41 and 42 in the plane fixture 4, keeping the edges aligned; then the spacing between the left and right clamping plates 41 and 42 is adjusted, and the locking bolts 45 are fixed in the appropriate position of the T-slot 44, so that the clamping force is appropriate and the assembly units do not slide or shift, thus forming a composite strip blank assembly; Composite strip blank formation: The assembled blank assembly together with the plane fixture is placed in the uniform temperature zone of the gas-shielded brazing furnace, and nitrogen is introduced for 20 minutes, and the furnace is washed three times; then the nitrogen valve is closed, the furnace temperature is raised to 700°C at a heating rate of 7°C / min, and kept warm for 20 minutes, and then the heating power is turned off to cool with the furnace. After the workpiece temperature cools to below 100°C, the workpiece is taken out, the residual brazing flux on the surface is cleaned, and after milling and flattening, a composite strip blank with a furnace size of 300 mm×20 mm×128.80 mm is obtained, of which the silver bar width is 4.00 mm±0.05 mm, the silver bar spacing is 16.05 mm±0.05 mm, and the total width of the blank is 128.80 mm±0.05 mm.

[0058] Example 2 This embodiment provides an assembly unit and a preparation method thereof, a composite strip blank using the assembly unit and a preparation method thereof, the specific contents of which are as follows: (1) Assembly unit. The structure of the assembly unit of this embodiment is basically the same as that of embodiment 1, with the main difference being that this embodiment uses BAg50Cu as foil solder, and the brazing temperature during the preparation process is 830° C. and the temperature is kept for 20 min.

[0059] (2) Composite strip blank. The structure and preparation method of the composite strip blank of this embodiment are basically the same as those of embodiment 1, except that: in this embodiment, BAg25CuZn is used as foil brazing material, and the composite strip blank is prepared by vacuum brazing method without using brazing flux; the vacuum brazing method comprises: placing the blank assembly and its flat fixture together at the center of the graphite platform in the vacuum chamber, closing the furnace door and locking it; evacuating to 1.0×10 -3 Pa, heated to the brazing temperature of 700 ° C and kept warm for 20 minutes, then cooled to below 100 ° C with the furnace and taken out of the furnace, cleaned, and milled to obtain a composite strip blank with a size of 300 mm × 20 mm × 128.80 mm, a silver bar width of 4.00 mm ± 0.05 mm, a silver bar spacing of 16.05 mm ± 0.05 mm, and a total billet width of 128.80 mm ± 0.05 mm.

[0060] Example 3 This embodiment provides an assembly unit and a preparation method thereof, a composite strip blank using the assembly unit and a preparation method thereof, the specific contents of which are as follows: (1) Assembly unit. The structure and preparation method of the "assembly unit" provided in this embodiment are basically the same as those in Example 1, with the main difference being that the size of the pure copper plate used in this embodiment is 300 mm × 20 mm × 10 mm, the size of the pure silver plate is 300 mm × 20 mm × 3 mm, and the size of the BAg92Cu foil strip solder is 300 mm × 20 mm × 0.05 mm, and the assembly unit is prepared by vacuum brazing. The vacuum brazing method includes: placing the assembly unit assembly parts in the center of the graphite platform in the vacuum chamber, closing the furnace door and locking it; evacuating to 1.5 × 10 -3 Pa, heat up to the brazing temperature of 860℃ and keep it for 20 min, then cool with the furnace; take out the assembly unit, clean the surface, and mill it flat to make an assembly unit with a size of 300 mm×20 mm×23.05±0.05 mm.

[0061] (2) Composite strip blank. The composite strip blank provided in this embodiment is composed of 8 of the above-mentioned assembly units arranged in a transverse cycle and brazed. The preparation method thereof is basically the same as the preparation method of the composite strip blank provided in Example 1, with the main difference being that: in this embodiment, BAg30CuZn is used as foil brazing material, QJ112 is used as silver brazing agent, and the brazing temperature during the preparation of the composite strip blank is 730°C. Finally, a composite strip blank with a size of 300 mm×20 mm×184.80 mm is obtained, wherein the width of the silver strip is 3.00 mm±0.05 mm, the spacing between the silver strips is 23.05 mm±0.05 mm, and the total width of the blank is 184.80 mm±0.05 mm.

[0062] Example 4 This embodiment provides an assembly unit and a preparation method thereof, a composite strip blank using the assembly unit and a preparation method thereof, the specific contents of which are as follows: (1) Assembly unit. The structure and preparation method of the assembly unit of this embodiment are basically the same as those of Example 3, with the main difference being that the size of the pure copper plate used in this embodiment is 300 mm×20 mm×8 mm, the size of the pure silver plate is 300 mm×20 mm×4 mm, the size of the BAg85Cu foil strip solder is 300 mm×20 mm×0.05 mm, the brazing temperature during the preparation of the assembly unit is 820°C, and the specification of the obtained assembly unit is 300 mm×20 mm×20.05±0.05 mm.

[0063] (2) Composite strip blank. The composite strip blank provided in this embodiment is formed by brazing the 10 assembly units mentioned above which are arranged in a horizontal circular pattern and the two outermost pure copper plates with a size of 300 mm×20 mm×15 mm located on the outermost side of the 10 assembly units. The preparation method is basically the same as the preparation method of the composite strip blank provided in Example 2, with the main difference being that: in this embodiment, BAg44CuZn is used as the foil brazing material, and the brazing temperature during the preparation of the composite strip blank is 690°C. Finally, a composite strip blank with a size of 300 mm×20 mm×231.00 mm is obtained, wherein the silver bar width is 4.00 mm±0.05 mm, the silver bar spacing is 20.05 mm±0.05 mm, and the total width of the blank is 231.00 mm±0.05 mm.

[0064] Comparative Example 1 In this comparative example, a composite strip blank is prepared by a one-step gas shielded brazing forming method.

[0065] In order to keep the same size selection of the plate raw material as in Example 1, a total of 9 pure copper plates were used, including 2 pure copper plates with a size of 300 mm×20mm×6mm at the outermost side and 7 pure copper plates with a size of 300 mm×20mm×12mm in the middle; 8 pure silver plates were used with a size of 300mm×20mm×4mm; 16 pieces of BAg72Cu foil strip brazing material cut into a size of 300mm×20mm×0.05mm were used; the above-mentioned pure copper plates, pure silver plates and foil strip brazing material were brazed without assembly units, and directly stacked alternately in the thickness direction in the order of "pure copper plate-foil strip brazing material-pure silver plate-foil strip brazing material-pure copper plate-..." to form a blank assembly. The preparation method with the same gas shielded brazing process steps and parameters as in Example 1 was used to finally obtain a silver-copper composite strip blank with a furnace size of 300 mm×20 mm×128.80±0.1 mm.

[0066] Comparative Example 2 In this comparative example, the composite strip blank was prepared by a one-step hot pressing resistance welding forming method. In order to keep the same plate material size selection as in Example 1, the raw materials used were: 2 pure copper plates (outermost) with a size of 300 mm×20 mm×6 mm, 7 pure copper plates (middle) with a size of 300 mm×20 mm×12 mm, 8 pure silver plates with a size of 300 mm×20 mm×4 mm, and 16 BAg72Cu foil strip brazing materials with a size of 300 mm×20 mm×0.05 mm.

[0067] The above pure copper plates and pure silver plates are directly stacked alternately in the thickness direction in the order of "pure copper plate-foil brazing material-pure silver plate-foil brazing material-pure copper plate-..." without brazing the assembly unit to form a blank assembly. The blank assembly is compounded by hot pressure resistance welding process. The process parameters are set to a current density of 4.6 to 4.8A / cm 2 , pressure 5 MPa, welding temperature 475℃, welding time 20 min. Finally, the composite strip blank with the size of 300 mm×20 mm×122.30±0.5 mm was obtained.

[0068] Comparative Example 3 In this comparative example, a composite strip blank is prepared by hot rolling. In order to keep the same size selection of the plate raw material as in Example 1, two outermost pure copper plates on both sides with a size of 300 mm×20 mm×6 mm (total), seven middle pure copper plates with a size of 300 mm×20 mm×12 mm and eight pure silver plates with a size of 300 mm×20 mm×4 mm are selected. Without brazing of the assembly unit, the blank assembly is formed by alternatingly stacking them in the thickness direction in the order of "pure copper plate-foil strip brazing material-pure silver plate-foil strip brazing material-pure copper plate-...". The blank is hot rolled and composited according to the conventional hot rolling process steps, the roll preheating temperature is 690℃~700℃, the rolling force is 3000±100 KN, and the composite plate is annealed at 350℃ in a vacuum annealing furnace for 45min after rolling, and finally a composite strip blank with a size of 300 mm×20 mm×115.20±0.5 mm is obtained.

[0069] Comparative Example 4 This comparative example adopts a one-time vacuum diffusion welding forming method to prepare a composite strip blank. In order to keep the same plate material size selection as that of Example 4, the raw materials used are: 2 pieces of 300 mm×20 mm×10 mm pure copper plates (outermost), 7 pieces of 300 mm×20 mm×20 mm pure copper plates (middle), and 8 pieces of 300 mm×20 mm×3 mm pure silver plates.

[0070] The above pure copper plates and pure silver plates are directly stacked alternately in the order of "pure copper plate-pure silver plate-pure copper plate-..." along the thickness direction without brazing the assembly unit to form a blank assembly. The blank assembly is compounded by vacuum diffusion welding process. The process parameters are set as follows: the vacuum degree of the vacuum chamber is ≤1×10 2 Pa, the pressure head pressure was 1 MPa, the vacuum chamber heating temperature was 680 °C, and the holding time was 5 h. Finally, a composite strip blank with a size of 300 mm × 20 mm × 176.52 ± 0.2 mm was obtained.

[0071] Performance Verification The composite strip blanks prepared in Examples 1 to 4 and Comparative Examples 1 to 4 were measured for the dimensions of the silver bars, copper bars and blank widths using a SteREO Discovery.VS research-grade stereo microscope and a vernier caliper. The results are shown in Table 1.

[0072] Ultrasonic nondestructive testing was performed on the weld bonding conditions of the composite strip blanks provided in each embodiment and comparative example, and the results are shown in Table 2.

[0073] The composite strip blanks provided in Examples 1 to 4 and Comparative Examples 1 to 4 were subjected to the same cold rolling process to obtain composite strip finished products with a thickness of 0.12 mm. The main parameters of the cold rolling process are as follows: the composite strip blanks were roughly rolled to a thickness of 12 mm, with a single rolling pressure not exceeding 10%, and then subjected to 400°C gas protection annealing for 4 h before being transferred to subsequent rolling; the single rolling pressure was not more than 10%, and after rolling to 1.5 mm, it was subjected to 400°C vacuum annealing for 4 h; the single rolling pressure of the finished product was not more than 6%, and the finished product was rolled to a final thickness of 0.12 mm. Among them, the composite strip finished product prepared in Example 4 is as follows Figure 5 shown.

[0074] The resistance of the finished composite tape sample was measured and the resistivity was calculated using a Tonghui TH2516 DC low resistance tester, as shown in Table 2.

[0075] Table 1 Billet size and appearance measurement results Table 2 Billet defect situation and resistivity stability results From the results in Table 1: In terms of dimensional stability, the results of Examples 1-2 and Comparative Examples 1-3, and Examples 3-4 and Comparative Example 4 are compared. The composite strip blank prepared by the assembly unit assembly method has stable dimensions and a small dimensional tolerance of the silver bar. In addition, Figure 5 In the finished composite belt shown in , the widths of the copper strips and silver strips in the middle portion are uniform, further proving that the method provided in the embodiment of the present invention can stably prepare wide-width, multiple-strip silver-copper composite belt finished products.

[0076] The size of the blank obtained in Comparative Example 1 is similar to that in Example 1, but all welds need to be brazed at one time. When brazing large-sized pure copper plates and pure silver plates, the overall heating and cooling efficiency of the assembly is slightly slower than that in Example 1, and the silver bar width tolerance is slightly higher than that in Example 1. Comparative Example 2 uses hot pressing resistance welding to compositely form all pure copper plates and pure silver plates. Since hot pressing sintering has a high material compression rate, usually between 7% and 10%, defects such as material bulging or deformation often occur at the edge of the plate. During subsequent turning and flattening, the material loss is high and the dimensional controllability is poor. In addition, when the size of the pure copper plate and pure silver plate increases, the corresponding current density requirement is higher and the energy consumption of the equipment increases.

[0077] Comparative Example 3 adopts a multi-layer hot rolling method, which has a complex process and is currently commonly used for the preparation of multi-layer composite materials with a width of less than 120 mm. For wider composite strip materials, the hot rolling process is complicated or exceeds the equipment limit.

[0078] Comparative Example 4 adopts a one-time diffusion welding forming method. Due to the pressure difference between the uppermost silver bar and the lowermost silver bar, the size uniformity of the obtained silver bar blank is poor. The width error between the uppermost silver bar and the lowermost silver bar is about 0.08 to 0.2 mm. After subsequent rolling, the size error will be further amplified.

[0079] From the results in Table 2: In terms of electrical properties, the resistivity of the strip is related to the proportion of pure silver. As the proportion of pure silver increases, the resistivity decreases. The proportion of silver in Example 1-2 is about 24.84%, and the proportion of silver in Example 3-4 is about 11.99%. Therefore, the measured resistance value of Example 3-4 is larger, and the calculated resistivity value is larger; compared with Example 1-2 and Comparative Examples 1 to 3, due to the large number of interface defects in Comparative Examples 1 to 3 and the weak composite, the calculated resistivity value is larger and the deviation is also larger; compared with Comparative Example 4, the resistivity of Example 3-4 is smaller, but because the diffusion welding method is pressurized composite, the blank size is reduced, so the calculated resistivity value is slightly reduced.

[0080] In summary, the composite tape assembly unit, composite tape blank and preparation method provided by the embodiments of the present invention have the characteristics of stable and controllable silver bar size and precision, and flexible assembly of large-size blanks for composite tape blanks with a width of not less than 120 mm. They can be used for the efficient and stable preparation of silver-copper composite tapes for fuses of different specifications and models, and are especially conducive to the efficient and stable preparation of wide-width, multi-strip silver-copper composite tape blanks.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A silver-copper composite strip blank assembly unit, characterized in that: It is mainly composed of a sandwich-shaped long strip blank formed by stacking a pure copper plate-a pure silver plate-a pure copper plate in sequence, and the pure silver plate and the pure copper plate are brazed and connected by silver-copper foil solder.

2. A method for preparing the assembly unit according to claim 1, comprising the steps of: firstly stacking and assembling the pure copper plate, the pure silver plate and the foil solder neatly in the order of "pure copper plate-foil solder-pure silver plate-foil solder-pure copper plate" to obtain an assembly unit assembly part; and then brazing the assembly unit assembly parts.

3. The preparation method according to claim 2, characterized in that The brazing connection method is a gas shielded brazing method, which includes: placing the assembly unit assembly parts in a uniform temperature zone in a gas shielded furnace, and introducing nitrogen for 15 to 30 minutes, and if necessary, the gas shielded furnace can be cleaned 2 to 3 times; then stop introducing nitrogen, raise the temperature in the gas shielded furnace to 820 to 880°C at a heating rate of 5 to 10°C / min, keep warm for 10 to 30 minutes, and then cool.

4. The preparation method according to claim 2, characterized in that The brazing connection method is a vacuum brazing method, which includes: first placing the assembly unit assembly in the center of the graphite platform in the vacuum chamber, and then evacuating the vacuum chamber to 3.0×10 -3 ~8.0×10 -4 Pa, then heat to 820-880℃ and keep warm for 10-30 min, then cool.

5. A silver-copper composite strip blank, mainly composed of a plurality of assembly units according to claim 1 arranged transversely, and adjacent assembly units are brazed and connected by using silver-copper-zinc foil brazing material.

6. The silver-copper composite strip blank according to claim 5, characterized in that: The silver-copper foil solder includes BAg50Cu, BAg72Cu, BAg85Cu or BAg92Cu, and the silver-copper-zinc foil solder includes BAg25CuZn, BAg30CuZn, BAg35CuZn, BAg44CuZn, BAg45CuZn or BAg50CuZn.

7. A method for preparing the silver-copper composite strip blank according to claim 5, comprising the steps of: Workpiece assembly: First, multiple assembly units are stacked horizontally, and silver-copper-zinc foil brazing materials are inserted between adjacent assembly units to form blank assembly parts; Blank preparation: The blank assembly parts are brazed to connect adjacent assembly units by brazing to form a composite strip blank.

8. The preparation method according to claim 6, characterized in that: The workpiece assembly steps include: providing a plane fixture, the plane fixture including a plane bottom plate, a left clamping plate, a right clamping plate, and a plurality of locking bolts, the plane bottom plate is provided with a plurality of T-slots; the left clamping plate and the right clamping plate are movably mounted on the plane floor through the cooperation of the locking bolts and the T-slots, and can move along the T-slots; A plurality of the assembly units and the silver-copper-zinc foil solder are placed in a cyclic and transversely stacked manner in the order of "assembly unit-silver-copper-zinc foil solder-assembly unit" between the left clamping plate and the right clamping plate, and are fixed to the horizontal bottom plate by the locking bolts to form a blank assembly.

9. The preparation method according to claim 7 or 8, characterized in that: The step of preparing the blank adopts a gas shielded brazing method for brazing treatment, and the gas shielded brazing method includes: placing the blank assembly and the plane clamp together in a uniform temperature zone in a gas shielded furnace, and introducing nitrogen for 15 to 30 minutes, and the gas shielded furnace can be cleaned 2 to 3 times if necessary; then stop introducing nitrogen, increase the temperature in the gas shielded furnace to 680 to 760°C at a heating rate of 5 to 10°C / min, keep warm for 10 to 30 minutes, and then cool.

10. The preparation method according to claim 7 or 8, characterized in that: The step of preparing the blank adopts a vacuum brazing method for brazing, and the vacuum brazing method includes: firstly placing the blank assembly and its plane fixture together at the center of the graphite platform in the vacuum chamber, and then evacuating to 3.0×10 -3 ~8.0×10 -4 Pa, then heat to 680-760℃ and keep warm for 10-30 min, then cool.

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