A cast brazing silver-copper composite strip and a method for producing the same

Abstract

The present application belongs to the technical field of preparation of fuse material for fuses, and particularly relates to a fused brazing type silver-copper composite strip and a preparation method thereof. The preparation method of the fused brazing type silver-copper composite strip comprises uniformly processing a preset number of cuboid blind holes along the length direction of a block-shaped copper plate, leaving a pure copper area at both ends of the cuboid blind holes; preheating the processed block-shaped copper plate, then pouring molten silver into the blind hole groove of the preheated block-shaped copper plate for fused brazing; and taking the pure copper area as a rolling auxiliary traction section for rolling treatment. The above-mentioned preparation method of the silver-copper composite strip has low requirements for the preparation equipment and low production cost, and can effectively realize the effective preparation of the multi-interface silver-copper composite strip, so that the size of the composite strip is no longer limited by hot rolling means, and the silver-copper strip obtained by the fused brazing method has high bonding strength, good strength stability, high straightness and high yield.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fuse material preparation for fuses, and more particularly to a fused brazing type silver-copper composite strip and a preparation method thereof. BACKGROUND

[0002] In recent years, with the rapid development of high-end equipment circuits such as new energy vehicles, high-speed trains, and photovoltaic inverters, new opportunities and challenges have been brought to the development of precision fuse materials. As the core functional component of fuses, pure silver fuses have become the only choice for fuse material due to their excellent overcurrent protection capability. However, in the current environment of circuit voltage upgrade and equipment iteration, the silver-copper composite strip with silver replacing copper and forming a composite strip with silver and copper arranged in phases has become a new trend in the industry. The silver-copper composite strip has a silver-saving rate of 50-80% and has the same fast melting capability as pure silver strip, as well as good functionality and economy, and its market acceptance is also increasing. For example, Chinese patents with announcement numbers CN109585235B, CN111883400B, CN207602503U, CN216928470U, and CN209454299U all use silver-copper composite strips to replace pure silver strips and use them in low-voltage electrical appliances and fuses, thereby achieving good use effects. Therefore, the replacement of silver-copper composite strips for pure silver strips is inevitable.

[0003] Currently, the common preparation methods of silver / copper composite strips in the prior art include mechanical inlaying hot pressing and vacuum hot pressing. An invention patent application with publication number CN101053874A discloses a preparation method of a double-sided inlaying type hot-rolled composite silver-copper strip, which combines copper composite blank and silver composite blank with interference fit, and then hot-rolls and composites under argon protection, with a heating temperature of 500-900℃, a holding time of 10-100min, and a deformation of 40-90%. The above hot-rolling and compounding method is suitable for the preparation of composite strips with fewer silver-copper combination interfaces (≤3). If it is applied to the preparation of silver-copper composite strips with more interfaces (≥5), the diffusion pressure is transferred layer by layer, and the load transfer is not consistent, which leads to inconsistent deformation between silver and copper, reduced straightness of the silver-copper combination surface, and low yield. In addition, an invention patent application with publication number CN107824629A discloses a vacuum hot pressing process for silver-copper composite strips, which forms silver and copper into blocks and then realizes the diffusion compounding of silver and copper through vacuum hot pressing. However, the diffusion process using vacuum hot pressing is prone to problems such as insufficient diffusion, low interface bonding strength, and long cycle.

[0004] Therefore, there is an urgent need to develop a silver-copper composite strip preparation method that can comprehensively solve the problems of inconsistent deformation between silver and copper, reduced straightness of the silver-copper bonding surface, low strength, poor stability, low yield, and inability to accurately composite. SUMMARY

[0005] To solve the above problems, the main purpose of the present application is to provide a preparation method for a cast brazing type silver-copper composite strip, which has low requirements for equipment and low production cost, can effectively prepare multi-interface (≥5) silver-copper composite strips, and has high composite strength, high straightness, good stability, and high product yield of the prepared silver-copper composite strip.

[0006] Another purpose of the present application is to provide a cast brazing type silver-copper composite strip with high composite strength, high straightness, and good stability.

[0007] To achieve the above purpose, the preparation method for a cast brazing type silver-copper composite strip adopted by the present application is as follows:

[0008] A preparation method for a cast brazing type silver-copper composite strip, comprising the following steps:

[0009] (1) uniformly process a preset number of cuboid blind holes along the length direction of the block-shaped copper plate, leaving unprocessed pure copper regions at both ends of the cuboid blind holes;

[0010] (2) preheat the block-shaped copper plate processed in step (1), then pour the molten silver metal liquid into the blind hole groove of the preheated block-shaped copper plate for cast brazing, and obtain a silver-copper composite blank after heat preservation;

[0011] (3) using the unprocessed pure copper region in the silver-copper composite blank as a rolling auxiliary traction section for rolling treatment, to obtain a cast brazing type silver-copper composite strip.

[0012] The preparation method for a cast brazing type silver-copper composite strip of the present application processes pouring grooves on the copper plate, further combines the cast brazing method to obtain a composite blank, which can better guarantee the straightness of the silver-copper bonding surface during the later rolling process, thereby effectively improving the straightness and yield of the composite strip. At the same time, the cast brazing method has low requirements for the preparation equipment, low production cost, and can effectively prepare multi-interface (≥5) silver-copper composite strips, so that the size of the composite strip is no longer limited by hot rolling means, and experiments have proved that the silver-copper interface obtained by the cast brazing method has high bonding strength and straightness, and good strength stability.

[0013] In addition, the present application leaves an unprocessed pure copper rolling auxiliary region at both ends of the blank obtained by cast brazing, which can avoid traction of the finished product section during the finishing rolling process, further improving the yield of the silver-copper composite strip.

[0014] In step (1), the number of cuboid blind holes corresponds to the number of silver strips in the silver-copper composite strip, and the present application does not make special limitations thereon. Preferably, in order to better embody the effect of the present application on the multi-interface silver-copper compounding, the preset number of the cuboid blind holes is ≥ 3, i.e., the number of silver strips in the finished product is ≥ 3. The silver-copper composite strip with ≥ 3 silver strips corresponds to ≥ 5 silver-copper bonding interfaces, which can better embody the advantages of the present application for the preparation of the composite strip product.

[0015] The processing mode of the cuboid blind hole can be a conventional processing mode, and more preferably is milling processing. The size precision of the pouring groove milled on the copper plate is high, and the straightness of the silver-copper bonding surface can be better ensured in the later rolling process, thereby effectively improving the straightness of the composite strip and the yield.

[0016] The un-milled pure copper area at both ends of the cuboid blind hole serves as a rolling auxiliary area for traction, avoiding the use of finished product sections for traction, and effectively improving the yield in the finish rolling process. Preferably, in step (1), the length of the un-processed pure copper area is 50-70 mm.

[0017] The present application does not make special limitations on the size of the block copper plate and the cuboid blind hole, which can be selected according to the demand for the preparation quantity and the use size of the composite strip. Preferably, in step (1), the length, width and height of the block copper plate are 450-500 mm, 60-300 mm and 68-72 mm, respectively; the length, width and height of the cuboid blind hole are 350-420 mm, 3-5 mm and 63-66 mm, respectively; and the interval of each cuboid blind hole is 4-6 mm.

[0018] Further, in order to improve the rolling efficiency, after obtaining the silver-copper composite blank in step (2), the method further comprises the step of butt welding two or more silver-copper composite blanks together by using a solder to obtain a butt-jointed silver-copper composite blank. The present application butt welds two or more silver-copper composite blanks together to obtain a composite blank, which helps to reduce the frequent loading and unloading of the silver-copper composite strip on the winding device of the rolling mill in the rolling process, improves the work efficiency, and reduces the waste of materials.

[0019] Further preferably, step (3) is specifically: processing the upper and lower end faces of the silver-copper composite blank obtained in step (2), then cold rolling and annealing treatment to obtain a pre-product composite strip, then finish rolling treatment by taking the un-processed pure copper area on the pre-product composite strip as a rolling auxiliary traction section, and finally cutting to obtain a cast-brazing silver-copper composite strip.

[0020] Still further, in step (2), the preheating temperature of the block copper plate is 950-970℃. The present application adopts this preheating temperature, which helps to the atomic diffusion of the silver metal liquid and the copper plate interface, so that the silver-copper bonding surface is more fully bonded.

[0021] Preferably, in step (2), the holding time is 5-10 min.

[0022] In the above scheme of the present application, the two silver-copper composite blanks are welded together by using the filler metal, which can effectively improve the efficiency of subsequent rolling. Preferably, the filler metal is silver-based filler metal BAg56CuZnSn. The specific composition of the filler metal is: Ag 55%-57%, Cu 21%-23%, Zn 15%-19%, and Sn 4.5%-5.5%. The melting point is 620-650℃. The filler metal is green and cadmium-free, easy to recycle, and the surface of the welded joint after brazing is smooth, and the strength of the brazed joint is high.

[0023] Preferably, in step (3), the rolling treatment is: using a six-roll rolling mill, using the unprocessed pure copper area as the rolling auxiliary traction section for reciprocating rolling until the thickness of the composite strip is 0.1-0.3mm.

[0024] Further, the cutting is to cut off the pure copper area at both ends of the composite strip after the finish rolling treatment and / or the middle butt joint brazing site.

[0025] The present application provides a melt-cast brazing type silver-copper composite strip, and the technical scheme adopted is as follows:

[0026] The melt-cast brazing type silver-copper composite strip is prepared by the above preparation method, and is composed of copper strips and silver strips arranged in sequence along the width direction. The number of copper strips is greater than the number of silver strips by 1, and the outermost side of the silver-copper composite strip is a copper strip. The total width of the melt-cast brazing type silver-copper composite strip is ≥20mm, and the thickness is 0.1-0.3mm.

[0027] The number of silver strips is not specifically limited in the present application, and any number of silver strips can be used. In order to further embody the product advantages of the present application, preferably, the number of silver strips is ≥3.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] (1) The preparation method of the melt-cast brazing type silver-copper composite strip of the present application adopts a melt-cast brazing method, which can better ensure the straightness of the silver-copper bonding surface during the later rolling process, thereby effectively improving the straightness and yield of the composite strip. The silver-copper interface obtained by the melt-cast brazing method has high bonding strength and good strength stability.

[0030] (2) The melt-cast brazing method has low requirements for the preparation equipment and low production cost, and can effectively prepare a silver-copper composite strip with multiple interfaces (≥5), so that the size of the composite strip is no longer limited by hot rolling.

[0031] (3) The application can weld two or more initially obtained silver-copper composite billets and then roll them, which not only has a simple process, but also can effectively improve the rolling efficiency. Meanwhile, the application leaves unprocessed pure copper rolling auxiliary areas at both ends of the billet obtained by melting and casting brazing, which can avoid the traction of the finished product section during the process of finishing the finished product, and effectively improve the yield of the silver-copper composite strip.

[0032] In summary, the silver-copper composite material prepared by the preparation method has multiple advantages of sufficient silver-copper contact, good stability, high interface bonding strength, short production cycle, high efficiency, high straightness of the composite strip, and high yield, which can effectively overcome the problems of low silver-copper interface bonding strength, long cycle, low processing efficiency, low straightness, and low yield of the silver-copper composite strip made by the existing ordinary hot rolling or vacuum hot pressing composite method, and has a wide application prospect in the field of fuse material preparation. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The figure is a preparation schematic diagram of the preparation method of the melting and casting brazing type silver-copper composite strip of the application;

[0034] Figure 2 The figure is an appearance diagram of the finished product of the melting and casting brazing type silver-copper composite strip of the application;

[0035] Among them, Figure 1 The figure is a preparation schematic diagram of the preparation method of the melting and casting brazing type silver-copper composite strip of the application; DETAILED DESCRIPTION

[0036] The technical solutions of the application are further described below in combination with specific embodiments. However, those skilled in the art should understand that the following examples are only used to illustrate the application and should not be regarded as limiting the application.

[0037] The figure is a preparation schematic diagram of the preparation method of the melting and casting brazing type silver-copper composite strip of the application; Figure 1 The figure is a preparation schematic diagram of the preparation method of the melting and casting brazing type silver-copper composite strip of the application; along the length direction of the block-shaped copper plate 1, a preset number (5) of cuboid blind holes 2 are uniformly milled, and unprocessed pure copper areas 3 are left at both ends of the cuboid blind holes; then the processed block-shaped copper plate is preheated, the melted silver metal liquid is poured into the blind hole groove of the preheated block-shaped copper plate for melting and casting brazing, and after heat preservation, a silver-copper composite billet is obtained; then the silver-copper composite billet is welded together by brazing through the weld 4 of two or more silver-copper composite billets, and a butt-jointed silver-copper composite billet is obtained; further, the upper and lower end faces of the butt-jointed silver-copper composite billet are milled, and then cold-rolled and annealed to obtain a pre-product composite strip; then the unprocessed pure copper area is used as a rolling auxiliary traction section to perform finish rolling on the pre-product composite strip, and finally, the melting and casting brazing type silver-copper composite strip is obtained by cutting.

[0038] In other embodiments, the preset number of cuboid blind holes can be regularly selected. In other embodiments, the brazing filler metal can not be used for butt brazing between the two silver-copper composite blanks, and only the single silver-copper composite blank can be processed.

[0039] The embodiments of the melt-cast brazing type silver-copper composite strip and the preparation method thereof are specifically described below.

[0040] Embodiment 1

[0041] The preparation method of the melt-cast brazing type silver-copper composite strip of the embodiment is specifically as follows:

[0042] (1) A block-shaped copper plate (length 460 mm, width 60 mm, height 70 mm) is milled along the length direction to form five cuboid blind holes (length 400 mm, width 4 mm, height 65 mm) which are uniformly distributed and have smooth inner surfaces, the blind holes are spaced by 5 mm, and the two ends of the blind holes have a 60 mm long unprocessed pure copper region.

[0043] (2) The block-shaped copper plate processed in step (1) is cleaned with a degreasing agent, and then is preheated to 950-970 ℃ in an induction device, while a silver ingot is put into a smelting furnace for smelting. After smelting, the silver metal liquid is poured into the blind hole groove of the preheated copper plate for melt-cast brazing, and is kept for 6 min, and then is taken out after cooling to 350 ℃ to obtain a silver-copper composite blank. Then, the silver-copper composite blank is butt brazed together by using a silver-based brazing filler metal BAg56CuZnSn and an induction brazing method to obtain a butt joint silver-copper composite blank.

[0044] (3) The butt joint silver-copper composite blank obtained in step (2) is placed on a milling machine to mill the upper and lower end surfaces to be able to see the silver-copper phase distribution, and then is cleaned to obtain a silver-copper composite blank for rolling, which has a pure copper region at both ends. Then, the silver-copper composite blank for rolling is rolled on a two-roll mill for 3 times, and then is annealed, pickled, alcohol cleaned and air dried to obtain a pre-product composite strip. The pre-product composite strip is rolled on a four-roll mill for 5 times, and when the thickness of the composite strip is rolled to below 0.8 mm, the six-roll mill is used, the un-milled pure copper region at both ends of the silver-copper composite strip is used as a rolling auxiliary traction section, and the reciprocating rolling is performed multiple times until the thickness of the composite strip is rolled to 0.15 mm. Then, the silver-copper composite strip with a width of 50 mm is cut on a cutting machine, and finally, the pure copper (traction region) at both ends of the composite strip and the middle butt joint brazing part are cut off to obtain the melt-cast brazing type silver-copper composite strip product of embodiment 1.

[0045] The cast brazing silver-copper composite strip of the embodiment is prepared by the above method, and is composed of copper strips and silver strips arranged in turn along the width direction, the number of copper strips is one more than that of silver strips, and the outermost side of the silver-copper composite strip is a copper strip; the number of silver strips is 5; the width of the silver-copper composite strip is 50 mm, and the thickness is 0.15 mm.

[0046] Example 2

[0047] The preparation method of the cast brazing silver-copper composite strip of the embodiment is as follows:

[0048] (1) A block-shaped copper plate (length 460 mm, width 165 mm, height 70 mm) is milled along the length direction to form 15 cuboid blind holes (length 400 mm, width 4 mm, height 65 mm) which are uniformly distributed and have smooth inner surfaces, the blind holes are spaced 5 mm apart, and 60 mm long unprocessed pure copper regions are left at both ends of the blind holes.

[0049] (2) The block-shaped copper plate processed in step (1) is cleaned with a degreasing agent, and then is preheated to 950-970°C in an induction device, while silver ingots are put into a smelting furnace for smelting, after smelting, the silver liquid metal is poured into the preheated copper plate blind hole groove for cast brazing, and is kept for 7 min, and then is taken out after cooling to 350°C to obtain a silver-copper composite blank; then, using silver-based brazing filler metal BAg56CuZnSn, the two silver-copper composite blanks are butt-jointed and brazed together by induction brazing to obtain a butt-jointed silver-copper composite blank.

[0050] (3) The butt-jointed silver-copper composite blank is placed on a milling machine to mill the upper and lower end surfaces flat until the silver-copper phase distribution can be seen, and then is cleaned to obtain a silver-copper composite blank for rolling, which has pure copper regions at both ends; then the silver-copper composite blank for rolling is rolled 3 times on a two-high rolling mill, and then is annealed, pickled, alcohol cleaned and air dried to obtain a pre-product composite strip, which is rolled 5 times on a four-high rolling mill, and when the thickness of the composite strip is rolled to below 0.8 mm, the six-high rolling mill is used, the unprocessed pure copper regions at both ends of the silver-copper composite strip are used as auxiliary traction sections for rolling, and the rolling is carried out back and forth for multiple times, until the thickness of the composite strip is rolled to 0.10 mm, then the silver-copper composite strip with a width of 145 mm is cut on a shearing machine, and finally the pure copper (traction region) at both ends of the composite strip and the middle butt-jointed brazing part are cut off, to obtain the cast brazing silver-copper composite strip product of Example 2.

[0051] The cast brazing silver-copper composite strip of the embodiment is prepared by the above method, and is composed of copper strips and silver strips arranged in turn along the width direction, the number of copper strips is one more than that of silver strips, and the outermost side of the silver-copper composite strip is a copper strip; the number of silver strips is 5; the width of the silver-copper composite strip is 50 mm, and the thickness is 0.15 mm.

[0052] Example 3

[0053] The preparation method of the cast brazing type silver-copper composite strip of the present example is as follows:

[0054] (1) A block-shaped copper plate (length 460 mm, width 227 mm, height 70 mm) was milled along the length direction to form 24 uniformly distributed and smooth inner surface cuboid blind holes (length 400 mm, width 4 mm, height 65 mm), with a blind hole interval of 5 mm, and a 60 mm long unprocessed pure copper region at both ends of the blind holes.

[0055] (2) The block-shaped copper plate processed in step (1) was cleaned with a degreasing agent, and then preheated to 950-970°C in an induction device, while silver ingots were placed in a smelting furnace for smelting. After smelting, the silver liquid metal was poured into the preheated copper plate blind hole groove for cast brazing, and the temperature was maintained for 8 min. After cooling to 350°C, the cooled silver-copper composite blank was obtained. Then, using silver-based filler metal BAg56CuZnSn, the two silver-copper composite blanks were butt-jointed and brazed together by induction brazing to obtain a butt-jointed silver-copper composite blank.

[0056] (3) The butt-jointed silver-copper composite blank was placed on a milling machine to mill the upper and lower end surfaces to be able to see the distribution of silver-copper phases, and then cleaned to obtain a silver-copper composite blank for rolling, with pure copper regions at both ends. The silver-copper composite blank for rolling was rolled 3 times on a two-high rolling mill, and then annealed, pickled, alcohol cleaned and air dried to obtain a pre-product composite strip. The pre-product composite strip was rolled 5 times on a four-high rolling mill, and when the thickness of the composite strip was rolled to below 0.8 mm, it was rolled on a six-high rolling mill, with the un-milled pure copper regions at both ends of the silver-copper composite strip serving as auxiliary traction sections for rolling, and the rolling was repeated multiple times until the thickness of the composite strip was rolled to 0.10 mm. Then, the silver-copper composite strip with a width of 221 mm was cut on a shearing machine, and finally the pure copper (traction region) at both ends of the composite strip and the middle butt-jointed brazing site were cut off to obtain the finished cast brazing type silver-copper composite strip of Example 3.

[0057] The cast brazing type silver-copper composite strip of the present example was prepared by the above method, and was composed of copper strips and silver strips arranged in sequence along the width direction, with the number of copper strips being one more than the number of silver strips, and the outermost side of the silver-copper composite strip being a copper strip. The number of silver strips was 24. The width of the silver-copper composite strip was 221 mm, and the thickness was 0.10 mm.

[0058] Comparative Example 1

[0059] The silver-copper composite strip provided by Comparative Example 1 was composed of copper strips and silver strips arranged in sequence along the width direction, with the number of copper strips being one more than the number of silver strips, and the outermost side of the silver-copper composite strip being a copper strip. The number of silver strips was 24. The width of the silver-copper composite strip was 221 mm.

[0060] The silver-copper composite tape of the present comparative example was prepared by a hot rolling method, and the specific preparation process and process parameters were as follows:

[0061] (1) The silver ingot was processed into a silver plate blank with a thickness of 400 mm, a width of 4 mm, and a height of 65 mm. A block-shaped copper plate (460 mm long, 227 mm wide, and 70 mm high) was milled along the length direction to form 24 uniformly distributed and smooth inner surface rectangular blind holes (400 mm long, 4 mm wide, and 65 mm high), with a blind hole spacing of 5 mm. The two ends of the blind hole had a 60 mm long unmilled pure copper region.

[0062] (2) The silver plate blank was inserted into the blind hole on the block-shaped copper plate to form an interference fit, thereby forming a composite blank.

[0063] (3) The composite blank formed by the interference fit was placed on a milling machine to mill the upper and lower end surfaces to be able to see the silver-copper phase distribution, and then cleaned to obtain a silver-copper composite blank to be rolled, which had a pure copper region at both ends. The silver-copper composite blank to be rolled was heated to 900°C for 10 minutes under the protection of argon, and then hot rolled 3 times on a hot rolling mill. Then, the silver-copper composite blank was annealed, pickled, alcohol cleaned, and air dried to obtain a pre-product composite tape. The pre-product composite tape was rolled 5 times on a four-roll mill, and when the thickness of the composite tape was rolled to 0.8 mm or less, the six-roll mill was used, and the unmilled pure copper region at both ends of the silver-copper composite tape was used as a rolling auxiliary traction section for repeated rolling. The thickness of the composite tape was rolled to 0.10 mm, and then cut into a silver-copper composite tape with a width of 221 mm on a shearing machine to obtain a silver-copper composite tape product by a hot rolling method.

[0064] Comparative Example 2

[0065] The silver-copper composite tape provided in Comparative Example 2 was basically the same as the preparation process of Example 3, except that the temperature of the block-shaped copper plate in step (2) was adjusted to 1050-1100°C in the preheating of the induction device, and the remaining steps were the same.

[0066] Comparative Example 3

[0067] The silver-copper composite tape provided in Comparative Example 3 was basically the same as the preparation process of Example 3, except that the temperature of the block-shaped copper plate in step (2) was adjusted to 800-850°C in the preheating of the induction device, and the remaining steps were the same.

[0068] Comparative Example 4

[0069] The silver-copper composite strip provided by Comparative Example 4 is prepared by the same process as that of Example 3, except that in step (1), a block-shaped copper plate (460 mm in length, 227 mm in width, and 70 mm in height) is milled along the length direction to form 24 cuboid blind holes (450 mm in length, 4 mm in width, and 65 mm in height) that are evenly distributed, smooth in inner surface, and almost equal in length to the block-shaped copper plate, with a spacing of 5 mm. That is, a small amount of pure copper region is left at both ends of the blind holes.

[0070] Comparative Example 5

[0071] The silver-copper composite strip provided by Comparative Example 5 is prepared by the same process as that of Example 3, except that in step (2), the two silver-copper composite blanks are not brazed together using silver-based brazing filler metal, and step (3) is directly performed using a single silver-copper composite blank, and the remaining steps are the same.

[0072] Interface strength of Example 1

[0073] In this test example, the interface bonding strength of the silver-copper composite strip prepared by the preparation method of the silver-copper composite strip by melting and casting brazing of Example 3 and the silver-copper composite strip prepared by the composite method of Comparative Examples 1-5 is investigated. The interface strength test is performed on a universal testing machine. The specific test process is as follows: a 10 mm wide silver-copper composite strip is taken from the silver-copper composite strip of the same thickness on the tensile testing machine, and the average value of five test results at different positions of the same composite strip is taken as the result. The test results of the bonding strength of the silver-copper composite strip are shown in Table 1.

[0074] Table 1 Interface bonding strength of silver-copper composite strip

[0075]

[0076] As can be seen from Table 1, compared with the interference fit- hot rolling composite method of Comparative Example 1, the silver-copper composite strip prepared by the melting and casting brazing method of the present application has a better bonding interface.

[0077] Straightness, rolling efficiency and yield of Example 2

[0078] In this test example, the straightness, rolling efficiency and yield of the silver-copper composite strip prepared by the preparation method of the silver-copper composite strip by melting and casting brazing of Example 3 and the silver-copper composite strip prepared by the composite method of Comparative Examples 1-5 are investigated. The straightness test method is as follows: the straightness is measured by a laser interferometer by a straight line method. The rolling efficiency is calculated based on the time required to prepare 40 kg of product. The yield is the percentage of qualified products in the total amount of composite strips prepared in the same amount. The results are shown in Table 2.

[0079] Table 2 Straightness of silver-copper composite strip product

[0080]

[0081]

[0082] As shown in Table 2, the preparation method of the cast soldering type silver-copper composite strip provided by the application can improve the dimensional accuracy of the corresponding casting groove when the silver liquid metal is cast on the copper plate, so that the straightness of the silver-copper bonding surface can be better ensured in the later rolling process, and the rolling efficiency and yield are also high, thereby greatly avoiding the problems of inconsistent deformation between silver and copper, reduced straightness of the silver-copper bonding surface, low yield, and inability to accurately composite in the hot rolling process.

[0083] Further, Figure 2 The appearance diagram of the prepared cast soldering type silver-copper composite strip product by the preparation method of the cast soldering type silver-copper composite strip. Figure 2 The leftmost silver-copper composite strip in the figure corresponds to the composite strip product of Example 3 of the application.

[0084] As shown in Table 2, the preparation method of the cast soldering type silver-copper composite strip provided by the application can improve the dimensional accuracy of the corresponding casting groove when the silver liquid metal is cast on the copper plate, so that the straightness of the silver-copper bonding surface can be better ensured in the later rolling process, and the rolling efficiency and yield are also high, thereby greatly avoiding the problems of inconsistent deformation between silver and copper, reduced straightness of the silver-copper bonding surface, low yield, and inability to accurately composite in the hot rolling process. Figure 2 It can be seen that the number of silver strips in the silver-copper composite strip obtained by hot rolling in the prior art is usually 1-4, and when the number of composite silver strips reaches 24 by using the preparation method of the cast soldering type silver-copper composite strip of the application, the straightness and composite strength can still be maintained, the comprehensive quality is good, and it is very suitable for the preparation of fuse material, especially for the preparation of high-voltage DC circuit fuse material.

Claims

1. A method for producing a cast brazing silver-copper composite strip, characterized by, The method comprises the following steps: (1) uniformly processing a preset number of cuboid blind holes along the length direction of a block-shaped copper plate, and leaving unprocessed pure copper areas at both ends of the cuboid blind holes; (2) preheating the block-shaped copper plate processed in step (1), then pouring molten silver metal liquid into the blind hole groove of the preheated block-shaped copper plate to perform fusion casting brazing, and obtaining a silver-copper composite blank after heat preservation; (3) taking the unprocessed pure copper area in the silver-copper composite blank as a rolling auxiliary traction section to perform rolling treatment, and obtaining a fusion casting brazing type silver-copper composite strip. In step (2), the preheating temperature of the block-shaped copper plate is 950-970℃; and the heat preservation time is 5-10min.

2. The method of producing a cast brazing silver copper composite strip according to claim 1, wherein In step (1), the length of the unprocessed pure copper area is 50-70mm.

3. The method for preparing the fused cast brazed silver-copper composite strip as described in claim 1, characterized in that, In step (1), the length, width and height of the block-shaped copper plate are 450-500mm, 60-300mm and 68-72mm respectively; the length, width and height of the cuboid blind hole are 350-420mm, 3-5mm and 63-66mm respectively; and the interval of each cuboid blind hole is 4-6mm.

4. The method of claim 1, wherein the cast brazing silver-copper composite strip is prepared by the steps of: preparing a silver-copper composite strip by mixing silver and copper powders, and sintering the mixed powders; and coating the silver-copper composite strip with a fluxing agent. In step (2), after obtaining the silver-copper composite blank, the method further comprises the step of butt brazing two or more silver-copper composite blanks together by using a brazing filler metal to obtain a butt-jointed silver-copper composite blank.

5. The method of producing a cast brazing silver copper composite strip according to claim 1 or 4, characterized in that, Step (3) is specifically: processing the upper and lower end faces of the silver-copper composite blank obtained in step (2), then performing cold rolling and annealing treatment to obtain a pre-product composite strip, then taking the unprocessed pure copper area on the pre-product composite strip as a rolling auxiliary traction section to perform finish rolling treatment, and finally cutting to obtain a fusion casting brazing type silver-copper composite strip.

6. The method of claim 4, wherein the silver-copper composite strip is prepared by the steps of: preparing a silver-copper composite strip by the method of claim 1; and heating the silver-copper composite strip to a temperature of 400 to 600°C in a non-oxidizing atmosphere. The brazing filler metal is a silver-based brazing filler metal BAg56CuZnSn.

7. The method of producing a cast brazing silver-copper composite strip according to any one of claims 1 to 4, characterized in that, In step (3), the rolling treatment is: using a six-roll rolling mill to perform reciprocating rolling by taking the unprocessed pure copper area as a rolling auxiliary traction section until the thickness of the composite strip is 0.1-0.3mm.

8. The silver-copper composite strip for cast-brazing produced by the production method according to any one of claims 1 to 7, characterized by The fusion casting brazing type silver-copper composite strip is composed of copper strips and silver strips arranged in sequence along the width direction, the number of the copper strips is greater than the number of the silver strips by 1, and the outermost side of the silver-copper composite strip is a copper strip; the total width of the fusion casting brazing type silver-copper composite strip is ≥20mm, and the thickness is 0.1-0.3mm.

9. The cast brazing silver-copper composite strip of claim 8 wherein, The number of the silver strips is ≥3.

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