Brazing filler metal for welding copper-clad aluminum busbar, preparation method and welding method

Abstract

The invention relates to brazing filler metal for welding a copper-clad aluminum busbar, a preparation method and a welding method, and belongs to the technical field of copper-clad aluminum busbar composites.The brazing filler metal comprises a tin-zinc brazing filler metal layer on the core portion and a copper brazing filler metal layer on the outer layer; the tin-zinc brazing filler metal layer is made of a tin-zinc material, and the tin-zinc material is composed of, by weight, 13%-15% of Zn, 0.5%-1% of In, 0.6% of Sb, 1% of Bi and the balance Sn. The copper brazing filler metal layer is made of a copper coating material, and the copper coating material is composed of, by weight, 0.05% of Sn, 0.1% of Mn, 0.01% of Ag, 0.015% of P and the balance pure copper. The brazing filler metal is of an inner-layer and outer-layer structure, welding of core aluminum and welding of a copper layer can be met at the same time, and meanwhile a welded joint has good conductivity, corrosion resistance and other performance.

Description

Technical Field

[0001] This invention belongs to the field of copper-clad aluminum busbar composite material technology, specifically relating to a brazing filler metal, its preparation method, and its welding method for welding copper-clad aluminum busbars. Background Technology

[0002] Copper-clad aluminum busbars are a novel bimetallic composite material with an aluminum core and an outer copper cladding, forming a permanent interatomic metallurgical bond between the aluminum core and the copper outer layer. Currently, the welding method for copper-clad aluminum busbars involves argon arc welding of the aluminum core and cold spraying of the copper outer layer. This method is not only complex in terms of pre-welding processing but also results in low copper layer density after welding, leading to poor salt spray corrosion resistance and reduced electrical conductivity. Furthermore, the current brazing filler metal structure is limited and cannot meet the welding requirements of copper-clad aluminum busbars. Summary of the Invention

[0003] The purpose of this invention is to provide a brazing filler metal, a preparation method, and a welding method for welding copper-clad aluminum busbars, which can simultaneously satisfy the welding of the core aluminum and the copper layer, while also giving the welded joint good electrical conductivity and corrosion resistance.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] In a first aspect, the present invention provides a brazing filler metal for welding copper-clad aluminum busbars, the brazing filler metal comprising a tin-zinc brazing filler metal layer in the core and an outer copper brazing filler metal layer;

[0006] The tin-zinc solder layer is made of tin-zinc material, which is composed of the following components by weight percentage:

[0007] Zn 13-15%, In 0.5-1%, Sb 0.6%, Bi 1%, the remainder being Sn;

[0008] The copper solder layer is made of copper cladding material, which is composed of the following components by weight percentage:

[0009] Sn 0.05%, Mn 0.1%, Ag 0.01%, P 0.015%, the remainder is pure copper.

[0010] Preferably, the thickness of the brazing filler metal is less than or equal to 0.2 mm.

[0011] Preferably, the performance parameters of the tin-zinc solder layer in the core satisfy at least one of the following:

[0012] (a) The coefficient of linear expansion is 21-22, and the unit is 10. -6 / K;

[0013] (b) Heating to 210-250℃ and holding at that temperature, with a surface tension of 602-619 mN / m.

[0014] (c) Complete melting temperature: 180-205℃.

[0015] Secondly, the present invention also proposes a method for preparing a brazing filler metal for welding copper-clad aluminum busbars. The method includes preparing a tin-zinc brazing filler metal layer in the core and a copper brazing filler metal layer in the outer layer, and welding the prepared tin-zinc brazing filler metal layer and copper brazing filler metal layer into a brazing filler metal for welding copper-clad aluminum busbars.

[0016] The preparation of the tin-zinc solder layer includes the following steps:

[0017] (1) Prepare tin, zinc, indium, antimony and bismuth with a purity of 99.9% in a certain proportion and remove surface impurities;

[0018] (2) First, add tin to the induction furnace and heat it to 250-300°C until it is completely melted;

[0019] (3) Continue to add antimony to the induction furnace and heat the induction furnace to 400-450°C. Stir constantly to completely melt the antimony.

[0020] (4) Continue to add zinc to the induction furnace and keep the temperature of the induction furnace at 400-450℃. Stir evenly and then introduce nitrogen for protection.

[0021] (5) Lower the temperature to 250-300℃, add bismuth and indium, stir until completely dissolved, and purge with nitrogen gas for protection to obtain a liquid alloy.

[0022] (6) Remove the gas and oxide residue from the liquid alloy and let it stand for 2-5 minutes. Then, lower the temperature to slightly above the melting point of the alloy and pour it into a preheated cast iron mold. The ingot is rolled into a tin-zinc brazing filler layer.

[0023] The specific process for preparing the copper solder layer is as follows:

[0024] Add 0.015% P, 0.05% Sn, 0.01% Ag, 0.15% Mn and 0.01% Ag to pure copper. After complete melting, pour the mixture into a preheated cast iron mold and roll it into a copper brazing filler layer.

[0025] Thirdly, the present invention also proposes a welding method for applying the brazing filler metal described in the first or second aspect to copper-clad aluminum busbars, the welding method comprising the following steps:

[0026] (1) After clamping the copper-clad aluminum busbar workpiece to be welded with the brazing filler metal, spot welding is used to fix the weld joint;

[0027] (2) Based on the different models of the copper-clad aluminum busbars to be welded, set the corresponding welding process parameters, melt the copper brazing filler layer of the brazing filler and weld it to form a continuous and sealed copper weld.

[0028] (3) After the copper brazing layer is welded, the core aluminum of the copper-clad aluminum busbar to be welded is heated by brazing equipment. When the temperature is heated to 210-250℃, it is kept at the temperature for 5-30 seconds to obtain the welded copper-clad aluminum busbar.

[0029] The beneficial effects of this invention are:

[0030] This invention provides a brazing filler metal for welding copper-clad aluminum busbars, a preparation method, and a welding method. Firstly, the linear expansion coefficient of the tin-zinc brazing filler metal layer in the core of this invention is 21-22 (10). -6 The similar coefficient of linear expansion ( / K) can reduce welding stress, ensure joint sealing, and improve joint reliability. Secondly, the present invention can simultaneously satisfy the welding of the core aluminum and the welding of the copper layer, and can make the welded joint have good conductivity and corrosion resistance. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the brazing filler metal proposed in this invention for welding copper-clad aluminum busbars.

[0032] Explanation of reference numerals in the attached diagram: 1: Tin-zinc brazing filler layer, 2: Copper brazing filler layer, 3: Interface joint. Detailed Implementation

[0033] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0034] like Figure 1 As shown, the brazing filler metal used for welding copper-clad aluminum busbars in Examples 1-3 includes a tin-zinc brazing filler metal layer 1 with a low-temperature soft brazing filler metal core and a copper brazing filler metal layer 2 with a high-temperature hard brazing filler metal outer layer, as well as an interface bonding area 3 located between the tin-zinc brazing filler metal layer 1 and the copper brazing filler metal layer 2.

[0035] The tin-zinc solder layer 1 is made of tin-zinc material, which is composed of the following components by weight percentage:

[0036] Zn 13-15%, In 0.5-1%, Sb 0.6%, Bi 1%, the remainder being Sn;

[0037] The copper solder layer 2 is made of copper cladding material, which is composed of the following components by weight percentage:

[0038] Sn 0.05%, Mn 0.1%, Ag 0.01%, P 0.015%, the remainder is pure copper.

[0039] In this embodiment, the brazing filler metal thickness is ≤0.2mm; the overall size of the brazing filler metal is consistent with the cross-sectional size of the copper-clad aluminum busbar; the outer copper layer size: taking a copper layer cross-sectional width of 2mm as an example, the brazing filler metal copper layer width is ≤1.8mm to avoid penetrating the copper layer during welding, thereby forming a dense weld; the core brazing filler metal size: the size is greater than the cross-sectional size of the copper-clad aluminum busbar core aluminum, and can be connected with the outer copper layer to form a complete brazing filler metal.

[0040] In this embodiment, the maximum temperature of the copper-clad aluminum busbar under thermal shock is 150°C; the heat treatment temperature should not be too high to avoid material softening; the melting temperature of the tin-zinc brazing filler metal in the core of this invention is 180-205°C, and the brazing temperature is 210-250°C.

[0041] In this embodiment, the coefficient of linear expansion of 1-series aluminum is 24 (10). -6 In this embodiment, the coefficient of linear expansion of the tin-zinc solder in the core is 21-22 (10 K). -6 The similar coefficient of linear expansion ( / K) can reduce welding stress, ensure joint sealing, and improve joint reliability. In the temperature range of 210-250℃, the surface tension of the tin-zinc brazing filler metal in the core of this embodiment is 602-619mN / m, which is much smaller than the critical surface tension of aluminum (800-1000mN / m), resulting in good wetting effect.

[0042] Example 1

[0043] The brazing filler metal used in this embodiment for welding copper-clad aluminum busbars includes a core tin-zinc brazing filler metal layer 1 and an outer copper brazing filler metal layer 2, as well as an interface bonding area 3 located between the tin-zinc brazing filler metal layer 1 and the outer copper brazing filler metal layer 2.

[0044] The tin-zinc solder layer 1 is made of tin-zinc material, which is composed of the following components by weight percentage:

[0045] Zn 13%, In 0.5%, Sb 0.6%, Bi 1%, the remainder being Sn;

[0046] The copper solder layer 2 is made of copper cladding material, which is composed of the following components by weight percentage:

[0047] Sn 0.05%, Mn 0.1%, Ag 0.01%, P 0.015%, the remainder is pure copper.

[0048] This embodiment also proposes a method for preparing brazing filler metal for welding copper-clad aluminum busbars. The method includes the preparation of a core tin-zinc brazing filler layer 1 and an outer copper brazing filler layer 2. The preparation of the tin-zinc brazing filler layer 1 includes the following steps:

[0049] (1) Prepare tin, zinc, indium, antimony and bismuth with a purity of 99.9% in a certain proportion and remove surface impurities;

[0050] (2) First, add tin to the induction furnace and heat it to 250-300°C until it is completely melted;

[0051] (3) Continue to add antimony to the induction furnace and heat the induction furnace to 400-450°C. Stir constantly to completely melt the antimony.

[0052] (4) Continue to add zinc to the induction furnace and keep the temperature of the induction furnace at 400-450℃. Stir evenly and then introduce nitrogen for protection.

[0053] (5) Lower the temperature to 250-300℃, add bismuth and indium, stir until completely dissolved, and purge with nitrogen gas for protection to obtain a liquid alloy.

[0054] (6) Remove the gas and oxide slag from the liquid alloy and let it stand for 2-5 minutes. Then, lower the temperature to slightly above the alloy melting point (about 210-250°C) and pour it into a preheated cast iron mold. Roll the ingot into a tin-zinc brazing filler layer 1. Note that before pouring into the cast iron mold, the mold should be cleaned and coated with graphite powder. At the same time, pour it slowly during casting to avoid creating air holes.

[0055] In this embodiment, the performance parameters of the core tin-zinc solder satisfy at least one of the following:

[0056] (a) The coefficient of linear expansion is 21.08, in units of 10⁻⁸. -6 / K;

[0057] (b) Heating to 210-250℃ and holding at that temperature, with a surface tension of 605-618mN / m.

[0058] (c) Complete melting temperature 201℃.

[0059] The specific preparation process of copper solder layer 2 is as follows:

[0060] Add 0.015% P, 0.05% Sn, 0.01% Ag, 0.15% Mn and 0.01% Ag to pure copper. After complete melting, pour the mixture into a preheated cast iron mold and roll the ingot to form copper brazing filler layer 2.

[0061] In this embodiment, during the preparation of the copper brazing filler layer 2, the melting point of the brazing filler is lower than that of the base material, and it has good fluidity and wetting and spreading properties. Therefore, adding 0.015% P to pure copper is to lower the melting point and improve the fluidity of the molten brazing filler. Adding 0.05% Sn and 0.01% Ag is to improve the wettability of the molten brazing filler. Adding 0.15% Mn and 0.01% Ag can avoid the formation of brittle phases due to excessive alloying elements. At the same time, Mn and Ag can refine the brazing seam structure.

[0062] In this embodiment, a graphite rod is used to continuously stir the tin-zinc brazing filler layer throughout the preparation process to ensure that the components are mixed evenly. After the alloy is completely melted, a small amount of ammonium chloride or a special brazing filler degassing agent can be added to remove the gas and oxide slag in the melt. After standing for 2 to 5 minutes, the surface slag is skimmed off.

[0063] After the above process is completed, the tin-zinc brazing alloy and copper brazing alloy ingots are rolled to the required thickness, cut to the required size, and then joined together by welding or mechanical methods for use in the welding of copper-clad aluminum busbars.

[0064] This embodiment also proposes a welding method for applying the above-mentioned brazing filler metal to copper-clad aluminum busbars, the welding method comprising the following steps:

[0065] (1) After clamping the copper-clad aluminum busbar workpiece to be welded with the brazing filler metal, spot welding is used to fix the weld joint;

[0066] (2) Based on the different models of the copper-clad aluminum busbars to be welded, set the corresponding welding process parameters, melt the copper brazing layer of the brazing filler and weld it to form a continuous, sealed, and good copper weld. After the outer layer is welded, the weld shrinks, which can form a closed space inside, avoid the oxidation of the brazing filler during tin-zinc brazing, and the welding of the outer copper layer has a preheating effect on the core aluminum, which is beneficial to subsequent brazing.

[0067] (3) After the copper brazing layer is welded, the core aluminum of the copper-clad aluminum busbar to be welded is heated by brazing equipment. When the temperature is heated to 210-250℃, it is kept at the temperature for 5-30 seconds to obtain the welded copper-clad aluminum busbar.

[0068] In the following embodiments, the preparation method and welding method are the same as in Example 1, except that the weight percentage of the tin core material is different.

[0069] Example 2

[0070] The brazing filler metal used in this embodiment for welding copper-clad aluminum busbars includes a core tin-zinc brazing filler metal layer 1 and an outer copper brazing filler metal layer 2, as well as an interface bonding area 3 located between the tin-zinc brazing filler metal layer 1 and the outer copper brazing filler metal layer 2.

[0071] The tin-zinc solder layer is made of tin-zinc material, which is composed of the following components by weight percentage:

[0072] Zn 15%, In 0.5%, Sb 0.6%, Bi 1%, the remainder being Sn;

[0073] The copper solder layer is made of copper cladding material, which is composed of the following components by weight percentage:

[0074] Sn 0.05%, Mn 0.1%, Ag 0.01%, P 0.015%, the remainder is pure copper.

[0075] In this embodiment, the performance parameters of the core tin-zinc solder satisfy at least one of the following:

[0076] (a) The coefficient of linear expansion is 21.18, in units of 10⁻⁶. -6 / K;

[0077] (b) Heating to 210-250℃ and holding at that temperature, with a surface tension of 606-618mN / m.

[0078] (c) Complete melting temperature 203℃.

[0079] Example 3

[0080] The brazing filler metal used in this embodiment for welding copper-clad aluminum busbars includes a core tin-zinc brazing filler metal layer 1 and an outer copper brazing filler metal layer 2, as well as an interface bonding area 3 located between the tin-zinc brazing filler metal layer 1 and the outer copper brazing filler metal layer 2.

[0081] The tin-zinc solder layer is made of tin-zinc material, which is composed of the following components by weight percentage:

[0082] Zn 13%, In 1%, Sb 0.6%, Bi 1%, the remainder being Sn;

[0083] The copper solder layer is made of copper cladding material, which is composed of the following components by weight percentage:

[0084] Sn 0.05%, Mn 0.1%, Ag 0.01%, P 0.015%, the remainder is pure copper.

[0085] In this embodiment, the performance parameters of the core tin-zinc solder satisfy at least one of the following:

[0086] (a) The coefficient of linear expansion is 21.15, in units of 10⁻⁶. -6 / K;

[0087] (b) Heating to 210-250℃ and holding at that temperature, with a surface tension of 605-618mN / m.

[0088] (c) Complete melting temperature 201℃.

[0089] Example 4

[0090] The brazing filler metal used in this embodiment for welding copper-clad aluminum busbars includes a core tin-zinc brazing filler metal layer 1 and an outer copper brazing filler metal layer 2, as well as an interface bonding area 3 located between the tin-zinc brazing filler metal layer 1 and the outer copper brazing filler metal layer 2.

[0091] The tin-zinc solder layer is made of tin-zinc material, which is composed of the following components by weight percentage:

[0092] Zn 15%, In 1%, Sb 0.6%, Bi 1%, the remainder being Sn;

[0093] The copper solder layer is made of copper cladding material, which is composed of the following components by weight percentage:

[0094] Sn 0.05%, Mn 0.1%, Ag 0.01%, P 0.015%, the remainder is pure copper.

[0095] In this embodiment, the performance parameters of the core tin-zinc solder satisfy at least one of the following:

[0096] (a) The coefficient of linear expansion is 21.24, with units of 10⁻⁴. -6 / K;

[0097] (b) Heating to 210-250℃ and holding at that temperature, with a surface tension of 606-619 mN / m.

[0098] (c) Complete melting temperature 202℃.

[0099] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A brazing filler metal for welding copper-clad aluminum busbars, characterized in that, The brazing filler metal includes a tin-zinc core layer and an outer copper core layer; The tin-zinc solder layer is made of tin-zinc material, which is composed of the following components by weight percentage: Zn 13-15%, In 0.5-1%, Sb 0.6%, Bi 1%, the remainder being Sn; The copper solder layer is made of copper cladding material, which is composed of the following components by weight percentage: Sn 0.05%, Mn 0.1%, Ag 0.01%, P 0.015%, the remainder is pure copper.

2. The brazing filler metal for welding copper-clad aluminum busbars according to claim 1, characterized in that, The thickness of the brazing filler metal is less than or equal to 0.2 mm.

3. The brazing filler metal for welding copper-clad aluminum busbars according to claim 1, characterized in that, The performance parameters of the tin-zinc solder layer in the core satisfy at least one of the following: (a) The coefficient of linear expansion is 21-22, and the unit is 10. -6 / K; (b) Heat to 210-250℃ and hold at that temperature, with a surface tension of 602-619 mN / m; (c) Complete melting temperature: 180-205℃.

4. A method for preparing brazing filler metal for welding copper-clad aluminum busbars, characterized in that, The method includes the preparation of a core tin-zinc brazing filler layer and an outer copper brazing filler layer, and the preparation of the tin-zinc brazing filler layer and the copper brazing filler layer are welded into a brazing filler for welding copper-clad aluminum busbars. The preparation of the tin-zinc solder layer includes the following steps: (1) Prepare tin, zinc, indium, antimony and bismuth with a purity of 99.9% in a certain proportion and remove surface impurities; (2) First, add tin to the induction furnace and heat it to 250-300°C until it is completely melted; (3) Continue to add antimony to the induction furnace and heat the induction furnace to 400-450°C. Stir constantly to completely melt the antimony. (4) Continue to add zinc to the induction furnace and keep the temperature of the induction furnace at 400-450℃. Stir evenly and then introduce nitrogen for protection. (5) Reduce the temperature to 250-300℃, add bismuth and indium, stir until completely dissolved, and purge with nitrogen gas for protection to obtain a liquid alloy. (6) Remove the gas and oxide residue from the liquid alloy and let it stand for 2-5 minutes. Then, lower the temperature to slightly above the melting point of the alloy and pour it into a preheated cast iron mold. The ingot is rolled into a tin-zinc brazing filler layer. The specific process for preparing the copper solder layer is as follows: Add 0.015% P, 0.05% Sn, 0.01% Ag, 0.15% Mn and 0.01% Ag to pure copper. After complete melting, pour the mixture into a preheated cast iron mold and roll it into a copper brazing filler layer.

5. A method for welding copper-clad aluminum busbars using a brazing filler metal as described in any one of claims 1-3 or a brazing filler metal prepared by the preparation method as described in claim 4, characterized in that, The welding method includes the following steps: (1) After clamping the copper-clad aluminum busbar workpiece to be welded with the brazing filler metal, spot welding is used to fix the weld joint; (2) Based on the different models of the copper-clad aluminum busbars to be welded, set the corresponding welding process parameters, melt the copper brazing filler layer of the brazing filler and weld it to form a continuous and sealed copper weld. (3) After the copper brazing layer is welded, the core aluminum of the copper-clad aluminum busbar to be welded is heated by brazing equipment. When the temperature is heated to 210-250℃, it is kept at the temperature for 5-30 seconds to obtain the welded copper-clad aluminum busbar.

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