High conductivity flux cored brazing sheet

Abstract

The invention discloses a high-conductivity flux-cored brazing sheet, which belongs to the field of brazing, especially the field of aluminum alloy brazing, and includes a metal and a brazing filler metal. The melting point of the brazing filler metal is lower than the melting point of the metal. The metal is wound and connected with the brazing filler metal or the metal is made into metal particles and filled into the brazing filler metal, which is pressed into a sheet shape. A certain amount of high-melting-point metal material is provided and placed in the sheet-shaped brazing filler metal alloy to penetrate the two sides of the sheet-shaped brazing filler metal to form a stable conductive channel. These channel materials do not melt during the welding process, and after welding, these channel materials remain in the welding seam and do not affect the joint strength. In this way, the conductivity of the entire welding process is guaranteed, sparks, splashes and explosions of the welding materials in a large current are avoided, and the welding quality is guaranteed.

Description

Technical Field

[0001] The invention belongs to the field of brazing, in particular to the field of aluminum alloy brazing, and specifically relates to a high-conductivity flux-cored brazing sheet. Background Art

[0002] Aluminum motors are a development direction in the current motor industry. Using aluminum instead of copper as the coil material for large motors has the advantages of being cheap, light, and easy to construct. The coil is composed of a large number of aluminum wires with rectangular cross-sections. During the assembly stage, the aluminum wires are installed one by one and then connected end to end. The connection of the wires needs to be welded to ensure conductivity and strength.

[0003] The main method currently used is fusion welding (argon arc welding), which can ensure welding strength and conductivity.

[0004] However, the efficiency of argon arc welding is relatively low, and each joint needs to consume several minutes. In a motor with more than one thousand joints, argon arc welding undoubtedly greatly limits production efficiency.

[0005] A more serious disadvantage is that in order to save space, the aluminum wires are arranged very tightly and the wire joints are very close to each other. It is difficult for the argon arc welding torch to pass through the other wire joints and reach into the assembly space to weld the welds inside. To solve this problem, the designer must adjust the design and sacrifice motor performance to ensure welding.

[0006] Another major drawback is that the temperature of argon arc welding is very high, with the local arc temperature reaching tens of thousands of degrees Celsius. After welding one or two joints in succession, the temperature of the wire will be very high, which can easily damage the adjacent insulating coating materials. In order to solve this problem, the process design must wait for the joint temperature to drop after the welding is completed before coating the local insulating material. This seriously affects the coating quality and production efficiency.

[0007] In the production of traditional copper motors ， Practitioners generally use the resistance heating brazing process. It uses a fixture made of conductive graphite to clamp the copper coil joint, and a copper-phosphorus brazing alloy is pre-placed between the joints. After power is turned on, the graphite clamp is heated by the huge current, which in turn heats the copper material, and then heats the copper-phosphorus brazing alloy. After reaching the melting point of the alloy, the brazing alloy liquid is connected to the copper material under the action of the phosphorus element in the copper-phosphorus brazing alloy, and a good joint is formed after cooling, completing the brazing. Compared with argon arc welding, this process is convenient to construct, has high efficiency, and low temperature.

[0008] However, this process is difficult to achieve in the production of aluminum motors. This is because among the available materials for aluminum brazing, there is no "self-brazing" brazing alloy like copper-phosphorus alloy. Aluminum brazing requires additional flux, but flux powder is insulating. If the flux is applied to the surface of the aluminum brazing alloy according to the general scheme, no current path can be formed when the joint is heated, and the graphite chuck cannot be heated, so the brazing cannot be completed.

[0009] Therefore, there is a need for an aluminum alloy brazing material that is both electrically conductive and can provide sufficient brazing aid.

[0010] The applicant of the present invention came up with a way to make a pill-shaped aluminum alloy brazing filler metal during the research and development process. The brazing filler metal is made into a flat tube with flux powder inside, or a thin flux-cored welding wire is coiled into a flat ring shaped like a paper clip or "S". These two brazing filler metal shaping methods can theoretically solve the problem. However, in actual use, sparks and explosions occur, and the brazing filler metal cannot be used at all.

[0011] The reason for the spark explosion problem is that during the specific construction, due to the fluctuations of factors such as people, machines, materials, methods, and environment, the flow state of the melted solder is unstable in the small space of the joint, and the flux sandwiched in the tubular solder cannot flow out in time, and the oxides on the metal surface cannot be dissolved in time. This causes local poor conductivity during the gradual softening and flow of the solder, and the local current is too large due to the small contact area, which is quickly vaporized by Joule heat. Then, a local arc is triggered due to the extremely short electrical gap. This arc will impact and burn local materials, especially the brazing additive will decompose and vaporize in the case of instantaneous overheating. This causes the surface of the parent material to change color, or even overburn and melt. In the case of light, the brazing cannot be completed, and in the case of heavy, the parent material is scrapped.

[0012] Therefore, there is an urgent need for a sheet aluminum alloy brazing material that can stably conduct electricity, does not spark, and can provide enough flux. Summary of the invention

[0013] The purpose of the present invention is to provide a sheet-shaped aluminum alloy brazing material which can stably conduct electricity, does not produce sparks, and can provide enough flux.

[0014] In order to solve the above problems, the material design scheme adopted is to provide some high melting point metal materials in the sheet solder alloy to penetrate the two sides of the sheet solder to form a stable conductive channel with a certain area. These channel materials do not melt during the welding process. After welding, these channel materials remain in the welding interface and will not affect the joint strength. In this way, it is impossible to have a situation where the conductive contact area is too small, and the welding quality and conductivity can also be well guaranteed.

[0015] Specifically: When the low melting point solder is a zinc-aluminum alloy, the soldering auxiliary agent is the FB502S soldering auxiliary agent powder in the JB / T 6045-2017 "Soldering Flux for Brazing" standard. The high melting point metal is a zinc alloy or aluminum alloy whose liquidus is more than 20 degrees Celsius higher than the liquidus of the low melting point solder.

[0016] The zinc-aluminum alloy as the low melting point solder is preferably Zn78-98% and Al2-22%, for example: Zn98%Al2% alloy, Zn95%Al5% alloy, Zn85%Al15%, and Zn78%Al22% alloy.

[0017] The aluminum alloy used as the high melting point metal to be combined with the zinc-aluminum alloy is preferably BAl95Si, BAl92Si, BAl90Si and BAl88Si in GB / T 13815-2008 "Aluminum-based solder".

[0018] When the low melting point brazing filler metal is aluminum silicon alloy, the brazing auxiliary agent is selected as FB501S brazing auxiliary powder in the JB / T 6045-2017 "Brazing Flux for Brazing" standard. The high melting point metal is selected as an aluminum alloy whose liquidus is more than 20 degrees Celsius higher than the liquidus of the low melting point brazing filler metal.

[0019] The aluminum-silicon alloy used as the low melting point solder is preferably BAl88Si, BAl90Si, and BAl92Si in GB / T 13815-2008 "Aluminum-based solder".

[0020] The aluminum alloy used as the high melting point metal in conjunction with the aluminum-silicon alloy is preferably SAl 1070 in GB / T 10858-2008 "Aluminum and aluminum alloy welding wire".

[0021] In addition, the present invention also discloses a method for preparing a highly conductive flux-cored brazing sheet.

[0022] Production method: A hollow pipe is set in a low melting point alloy, and then a brazing aid is canned in the pipe to make a seamless flux-cored welding wire, wherein the brazing aid content is 5%-20% (the brazing aid accounts for the total weight of the seamless flux-cored welding wire). The seamless flux-cored welding wire is wound with a high melting point metal wire. The wound body is then rolled into a sheet by a calender.

[0023] Preferably, the material is selected as a high melting point metal wire and one to three seamless flux-cored welding wires made of low melting point metals intertwined with each other. Preferably, a high melting point metal wire and a seamless flux-cored welding wire made of low melting point metals are intertwined with each other.

[0024] Preferably, the winding method is that a seamless flux-cored welding wire made of a low-melting-point metal is tightly wound around a central high-melting-point metal wire.

[0025] Preferably, the diameter of the middle high-melting-point metal wire is larger than the diameter of the seamless flux-cored welding wire made of low-melting-point metal, but smaller than twice the diameter of the seamless flux-cored welding wire made of low-melting-point metal.

[0026] In addition, the present invention also discloses another method for preparing a highly conductive flux-cored brazing sheet.

[0027] Take solder and metal, make the metal into metal particles, place them inside the solder; and use a calender to calender them into sheets.

[0028] Compared with the prior art, the high-conductivity flux-cored brazing sheet of the present invention can stably conduct electricity without sparks and can provide sufficient flux. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic structural diagram of embodiments 1 to 10 of the high-conductivity flux-cored brazing sheet of the present invention.

[0030] Figure 2 Schematic diagram of the structure of the eleventh embodiment of the high conductivity flux cored brazing sheet of the present invention

[0031] Figure 3 It is a metallographic diagram of the welding interface of Example 1.

[0032] Figure 4 It is an enlarged metallographic view of Example 1.

[0033] Figure 5 It is the metallographic diagram of embodiment 1.

[0034] Figure 6 What is shown is the metallographic diagram of the eleventh embodiment corresponding to the first embodiment. DETAILED DESCRIPTION

[0035] The specific implementation modes of the present invention are further described in detail below by means of specific examples in combination with the accompanying drawings. However, the following specific examples are only used to help understand the present invention and cannot be understood as further limiting the present invention.

[0036] Embodiment 1:

[0037] Figure 1 As shown, a high-conductivity flux-cored brazing sheet includes a metal and a brazing material, wherein the melting point of the brazing material is lower than the melting point of the metal, and the brazing material is wound and connected with the metal and pressed into a sheet.

[0038] The high melting point metal is an aluminum alloy, and the aluminum alloy is BAl95Si in GB / T 13815-2008 "Aluminum-based brazing filler metal".

[0039] The low melting point solder is a zinc-aluminum alloy, wherein Zn accounts for 98% and Al accounts for 2%.

[0040] The flux in the flux cored solder is FB502S brazing auxiliary powder in the JB / T 6045-2017 "Brazing Flux for Brazing" standard.

[0041] Figure 3 As shown in the figure, area A is the base material to be welded, which is industrial pure aluminum. Area B is the metal component Zn98Al alloy in the flux-cored brazing filler metal, and area C is BAl95Si metal. It can be seen that the filling effect of the entire brazing interface is outstanding, and each transition layer is also well diffused.

[0042] Figure 4 As shown, further observation of the metallographic changes shows that the Zn98Al2 alloy and B A Transition diffusion layer between al95Si alloy.

[0043] Figure 5 As shown, better brazing effect is also obtained in a wider area of ​​Al95Si.

[0044] Embodiment 2:

[0045] Figure 1 As shown, a high-conductivity flux-cored brazing sheet includes a metal and a brazing material, wherein the melting point of the brazing material is lower than the melting point of the metal, and the brazing material is wound and connected with the metal and pressed into a sheet.

[0046] The high melting point metal is an aluminum alloy, and the aluminum alloy is BAl92Si in GB / T 13815-2008 "Aluminum-based brazing filler metal".

[0047] The low melting point solder is a zinc-aluminum alloy, wherein Zn accounts for 95% and Al accounts for 5%.

[0048] The flux in the flux cored solder is FB502S brazing auxiliary powder in the JB / T 6045-2017 "Brazing Flux for Brazing" standard.

[0049] Embodiment three:

[0050] Figure 1 As shown, a high-conductivity flux-cored brazing sheet includes a metal and a brazing material, wherein the melting point of the brazing material is lower than the melting point of the metal, and the brazing material is wound and connected with the metal and pressed into a sheet.

[0051] The high melting point metal is an aluminum alloy, and the aluminum alloy is BAl90Si in GB / T 13815-2008 "Aluminum-based brazing filler metal".

[0052] The low melting point solder is a zinc-aluminum alloy, wherein Zn accounts for 85% and Al accounts for 15%.

[0053] The flux in the flux cored solder is FB502S brazing auxiliary powder in the JB / T 6045-2017 "Brazing Flux for Brazing" standard.

[0054] Embodiment 4:

[0055] Figure 1 As shown, a high-conductivity flux-cored brazing sheet includes a metal and a brazing material, wherein the melting point of the brazing material is lower than the melting point of the metal, and the brazing material is wound and connected with the metal and pressed into a sheet.

[0056] The high melting point metal is an aluminum alloy, and the aluminum alloy is BAl88Si in GB / T 13815-2008 "Aluminum-based brazing filler metal".

[0057] The low melting point solder is a zinc-aluminum alloy, in which Zn accounts for 78% and Al accounts for 22%.

[0058] The flux in the flux cored solder is FB502S brazing auxiliary powder in the JB / T 6045-2017 "Brazing Flux for Brazing" standard.

[0059] Embodiment five:

[0060] Figure 1 As shown, a high-conductivity flux-cored brazing sheet includes a metal and a brazing material, wherein the melting point of the brazing material is lower than the melting point of the metal, and the brazing material is wound and connected with the metal and pressed into a sheet.

[0061] The high melting point metal is an aluminum alloy, and the aluminum alloy is SAl 1070 in GB / T 10858-2008 "Aluminum and aluminum alloy welding wire".

[0062] The low melting point solder is a silicon aluminum alloy, and the silicon aluminum alloy is BAl88Si in GB / T 13815-2008 "Aluminum-based solder".

[0063] The flux in the flux cored solder is FB501S brazing auxiliary powder in the JB / T 6045-2017 "Brazing Flux for Brazing" standard.

[0064] Embodiment six:

[0065] Figure 1 As shown, a high-conductivity flux-cored brazing sheet includes a metal and a brazing material, wherein the melting point of the brazing material is lower than the melting point of the metal, and the brazing material is wound and connected with the metal and pressed into a sheet.

[0066] The high melting point metal is an aluminum alloy, and the aluminum alloy is SAl 1070 in GB / T 10858-2008 "Aluminum and aluminum alloy welding wire".

[0067] The low melting point solder is a silicon aluminum alloy, and the silicon aluminum alloy is BAl90Si in GB / T 13815-2008 "Aluminum-based solder".

[0068] The flux in the flux cored solder is FB501S brazing auxiliary powder in the JB / T 6045-2017 "Brazing Flux for Brazing" standard.

[0069] Embodiment seven:

[0070] Figure 1 As shown, a high-conductivity flux-cored brazing sheet includes a metal and a brazing material, wherein the melting point of the brazing material is lower than the melting point of the metal, and the brazing material is wound and connected with the metal and pressed into a sheet.

[0071] The high melting point metal is an aluminum alloy, and the aluminum alloy is SAl 1070 in GB / T 10858-2008 "Aluminum and aluminum alloy welding wire".

[0072] The low melting point solder is a silicon aluminum alloy, and the silicon aluminum alloy is BAl92Si in GB / T 13815-2008 "Aluminum-based solder".

[0073] The flux in the flux cored solder is FB501S brazing auxiliary powder in the JB / T 6045-2017 "Brazing Flux for Brazing" standard.

[0074] In addition, the present invention also discloses a method for preparing a high-conductivity flux-cored brazing sheet, and a specific embodiment is as follows:

[0075] Embodiment eight:

[0076] Figure 1 As shown, a low melting point brazing material is placed in a hollow tube, and then a brazing aid is canned in the tube to make a seamless flux-cored welding wire, wherein the brazing aid accounts for 5% of the total weight of the seamless flux-cored welding wire. The seamless flux-cored welding wire is wound with a high melting point metal wire. The wound body is then rolled into a sheet by a calender.

[0077] The material selected is a high melting point metal wire and three seamless flux-cored welding wires made of low melting point metals wound together.

[0078] The diameter of the middle high-melting-point metal wire is twice the diameter of the seamless flux-cored welding wire made of low-melting-point metal.

[0079] Embodiment nine:

[0080] Figure 1As shown, a low melting point brazing material is placed in a hollow tube, and then a brazing aid is canned in the tube to make a seamless flux-cored welding wire, wherein the brazing aid accounts for 20% of the total weight of the seamless flux-cored welding wire. The seamless flux-cored welding wire is wound with a high melting point metal wire. The wound body is then rolled into a sheet by a calender.

[0081] A high melting point metal wire is wound around a seamless flux cored wire made of a low melting point metal.

[0082] The diameter of the middle high-melting-point metal wire is slightly larger than the diameter of the seamless flux-cored welding wire made of low-melting-point metal.

[0083] Embodiment ten:

[0084] Figure 1 As shown, a low melting point brazing material is placed in a hollow tube, and then a brazing aid is canned in the tube to make a seamless flux-cored welding wire, wherein the brazing aid accounts for 15% of the total weight of the seamless flux-cored welding wire. The seamless flux-cored welding wire is wound with a high melting point metal wire. The wound body is then rolled into a sheet by a calender.

[0085] The winding method is that a seamless flux-cored welding wire made of a low-melting-point metal is tightly wound around a high-melting-point metal wire in the center.

[0086] The diameter of the middle high-melting-point metal wire is 1.5 times the diameter of the seamless flux-cored welding wire made of low-melting-point metal.

[0087] Embodiment eleven:

[0088] Figure 2 As shown, this embodiment corresponds to the first to tenth embodiments, and the difference is that the winding connection between the metal and the solder is replaced by filling the metal into metal particles in the solder and pressing it into a sheet.

[0089] Figure 6 As shown in the figure, when replacing Example 1, an obvious granular BAl95Si can be observed in the joint (C). The number of particles actually observed is lower than the number we added, and in the metallographic image, it can be observed that obvious silicon-rich concentrated crystals appear (D). This may be because many particles are dissolved by the zinc-aluminum alloy due to heat problems, so the boundaries are not obvious.

[0090] Blank case 1:

[0091] Using flame brazing, a flux-cored brazing rod made of Zn98Al alloy is held in hand to continuously fill the brazing seam during the heating process until the brazing seam is fully filled. After testing the tensile strength, the section is dissected and the metallographic structure is tested. Samples that are fully filled and have no obvious macroscopic defects are selected as qualified samples.

[0092] Blank Case 2:

[0093] The low melting point solder is made into thin sheets and heated by the above resistance brazing heating process. During heating, the two aluminum conductors are tied with aluminum wire as an external conductive path to prevent sparks and splashes. After testing the tensile strength, the section is dissected and the metallographic structure is tested. The samples that are fully filled and have no obvious macroscopic defects are selected as qualified samples.

[0094] The low melting point solder is a zinc-aluminum alloy, wherein Zn accounts for 98% and Al accounts for 2%.

[0095] The flux in the flux cored solder is FB502S brazing auxiliary powder in the JB / T 6045-2017 "Brazing Flux for Brazing" standard.

[0096] Strength test: The sheet material is 0.7mm thick, 11.5mm wide and 28mm long. Two 10mm thick and 12.5mm wide aluminum wires are overlapped, and the overlap length is 28mm. The above heating method is used to form a 28mm*12.5mm joint.

[0097] Strength value: (GB / T 228.1-2010 "Tensile test of metal materials") take the average of three times.

[0098]

[0099]

[0100] The inspection of metallographic effect mainly focuses on whether there are microscopic defects, the state of the diffusion layer, and the composition of the interface. Microscopic defects are difficult to avoid in brazing, but the reliability of application can be guaranteed if the defects are few, small, and discontinuous.

[0101] In order to achieve industrial application, the material must be able to be mass-produced smoothly and at an acceptable cost. In this technology, the main processing technology problems encountered in the actual production process are: 1. The affinity between different metals has a great influence. After high-pressure bonding, the bonding surfaces between different metals need to have a certain bonding strength to ensure the integrity during the grinding process. 2. Since this technology is a sheet material obtained by grinding, the stress caused by different materials in the grinding process is too large due to different ductility, resulting in material deformation. 3. During the metal grinding process, different metals experience changes such as fatigue, and annealing treatment is required. The more annealing times, the more unstable the material is and the higher the cost. 4. The relationship between the compression and extension forces of the wound material at different positions during the grinding process is asymmetric, which leads to different lower limits of the material grinding thickness.

[0102] The above four problems must all be solved to be an industrially feasible solution. The embodiments in the above table are all solutions that can achieve smooth and cost-acceptable industrial production within the processing range described.

[0103] Blank case description: Blank cases 1 and 2 are mainly for obtaining an optimal result. When metallographic inspection obtains a good welding result (good filling and no defects), it can be considered that this is the best result that this material can get in this lap joint structure. Blank case 1 is compared with the traditional process, and blank case 2 is compared with the traditional material under the resistance heating process. By adding an additional conductive channel on the outside to avoid sparks and spatter, the strength obtained in this case can be recognized as the standard result of this material under this process.

[0104] We can observe that the material obtained by this technology is not inferior to the traditional material in terms of strength data, and the added high melting point metal has no adverse effect on the brazing results.

[0105] Principle: Provide some high melting point metal materials in the sheet solder alloy and penetrate the two sides of the sheet solder to form a stable conductive channel with a certain area. These channel materials do not melt during the welding process. After welding, these channel materials remain in the welding interface and will not affect the joint strength. In this way, it is impossible to have a situation where the conductive contact area is too small, and the welding quality and conductivity can also be well guaranteed.

[0106] Compared with the prior art, the high-conductivity flux-cored brazing sheet of the present invention can stably conduct electricity without sparks and can provide sufficient flux.

[0107] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high conductivity flux-cored brazing sheet, characterized in that: It includes metal and solder, the melting point of the solder is lower than that of the metal, the metal and the solder are connected by winding, or the metal is made into metal particles and filled into the solder, and then pressed into a sheet, and a high melting point metal material is placed in the sheet solder alloy to penetrate the two sides of the sheet solder to form a stable conductive channel with a certain area, and these channel materials do not melt during the welding process.

2. The high conductivity flux-cored brazing sheet according to claim 1, characterized in that: The metal is a zinc alloy or an aluminum alloy, and the solder is a flux-cored solder.

3. The high conductivity flux-cored brazing sheet according to claim 2, characterized in that: The high melting point metal is a zinc alloy or an aluminum alloy, and the aluminum alloy is BAl95Si, BAl92Si, BAl90Si and BAl88Si in GB / T 13815-2008.

4. The high conductivity flux-cored brazing sheet according to claim 3, characterized in that: The low melting point solder is a zinc-aluminum alloy, wherein Zn accounts for 78-98% and Al accounts for 2-22%.

5. The high conductivity flux-cored brazing sheet according to claim 4, characterized in that: The flux in the flux cored solder is FB502S brazing aid powder in the JB / T 6045-2017 standard.

6. The high conductivity flux-cored brazing sheet according to claim 2, characterized in that: The high melting point metal is an aluminum alloy, and the aluminum alloy is SAl 1070 in GB / T 10858-2008.

7. The high conductivity flux-cored brazing sheet according to claim 6, characterized in that: The low melting point solder is an aluminum silicon alloy, and the aluminum silicon alloy is BAl88Si, BAl90Si, and BAl92Si in GB / T 13815-2008.

8. The high conductivity flux-cored brazing sheet according to claim 7, characterized in that: The flux in the flux-cored solder is FB501S brazing auxiliary powder in the JB / T 6045-2017 standard.

9. A method for preparing the high conductivity flux-cored brazing sheet according to claim 1, characterized in that: The preparation steps are as follows: S1: Take the brazing material and the metal, and entwine the brazing material and the metal with each other; S2: The wound body is calendered into a sheet by a calender.

10. A method for preparing the high conductivity flux-cored brazing sheet according to claim 1, characterized in that: The preparation steps are as follows: S1: Take the brazing material and metal, make the metal into metal particles, and place them inside the brazing material; S2: Calendered into sheets by a calender.

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