A welding method and device for die-cast aluminum alloy, and a die-cast aluminum alloy radiator

Abstract

The present invention belongs to the technical field of die-cast aluminum alloy brazing, and specifically relates to a welding method and device for die-cast aluminum alloy, and a die-cast aluminum alloy radiator. The welding method for die-cast aluminum alloy provided by the present invention is to brush the brazing liquid on the surface to be welded, and then compound the surface to be welded, and diffuse it under a certain pressure and temperature to achieve the connection of the welding surface. The present invention adopts a combination of brushing brazing liquid and diffusion welding method, which can make the Si atoms in the die-cast aluminum alloy base material diffuse more fully, thereby effectively improving the joint strength. In addition, the present invention integrates the entire process of melting the brazing liquid, preheating the workpiece and welding the workpiece, and the welding efficiency is high. In addition, during the welding process of the present invention, the entire radiator is buried in the yellow sand, isolated from the atmosphere, and high-quality brazing is achieved; at the same time, the present invention adopts a combination of low-temperature brazing and diffusion welding, which can achieve a balance between low-temperature welding and high-strength joints, and has good application prospects in the field of die-cast aluminum alloy welding.

Description

Technical Field

[0001] The invention belongs to the technical field of die-cast aluminum alloy welding, and in particular relates to a die-cast aluminum alloy welding method and device, and a die-cast aluminum alloy radiator. Background Art

[0002] Die-cast aluminum alloy has the properties of high specific strength, corrosion resistance, electrical and thermal conductivity, and casting processing. Compared with other types of aluminum alloys, it has lower production costs and the material properties can be changed by adjusting the die-casting metal elements. It has been widely used in die-cast aluminum alloy radiators for 5G base station electronic communications.

[0003] The die-cast aluminum alloy radiator is mainly composed of two symmetrical die-cast aluminum alloy cavities with complex medium channels inside the cavities. During preparation, the two halves of the die-cast aluminum alloy cavity need to be merged together and made into a die-cast aluminum alloy radiator by welding.

[0004] At present, there are three main methods for welding die-cast aluminum alloys: fusion welding, solid-state welding and brazing. The high temperature of fusion welding often causes blistering or deformation on the surface of die-cast aluminum alloys, so it is not often used. Solid-state welding can obtain well-formed and dense solid phase welds, but its scope of use is limited and cannot meet the welding of die-cast aluminum alloy castings. In comparison, brazing is a low-temperature connection method with the advantages of high welding efficiency, easy operation, and no restrictions on the shape of the workpiece. It is particularly suitable for the connection of die-cast aluminum alloys.

[0005] However, the brazing of die-cast aluminum alloys still has the following problems: First, there is a lack of suitable brazing filler metals; if the melting temperature of the brazing filler metal is high (≥400°C), the surface of the die-cast aluminum alloy base material will bulge or deform; if the melting temperature of the brazing filler metal is low, the brazing filler metals are mostly soft solders with low strength themselves, which makes it difficult for the joint strength to meet the use requirements, that is, the existing brazing filler metals cannot meet the dual requirements of low temperature and high strength; second, the die-cast aluminum alloy itself has many casting defects, such as pores and inclusions, and the brazing process is more likely to produce defects such as pores, inclusions, and blistering, resulting in low strength of the brazed joint.

[0006] In order to solve the above-mentioned shortcomings, it is necessary to develop a new type of welding method for die-cast aluminum alloy and a matching preparation device, so as to achieve high-strength and high-reliability brazing of die-cast aluminum alloy radiators. Summary of the invention

[0007] In order to solve the above-mentioned shortcomings, the purpose of the present invention is to provide a welding method for die-cast aluminum alloy, which has high welding efficiency, low welding temperature, high strength of the welded joint, can achieve high-strength and high-reliability brazing of die-cast aluminum alloy, and is suitable for welding applications of die-cast aluminum alloy.

[0008] The present invention also aims to provide a special device for implementing the welding method of die-cast aluminum alloy, which has a simple structure and low cost and can achieve high-strength and reliable brazing of die-cast aluminum alloy.

[0009] Another object of the present invention is to provide a die-cast aluminum alloy radiator, which has high welding joint strength, few defects and high quality, and is suitable for use as a die-cast aluminum alloy radiator in a 5G base station.

[0010] To achieve the above object, the welding method of the die-cast aluminum alloy of the present invention adopts the following technical solution:

[0011] A method for welding a die-cast aluminum alloy comprises the following steps:

[0012] (1) preparing an electric sand bath furnace, adding yellow sand into a chamber of the electric sand bath furnace and placing a crucible therein, and keeping the yellow sand covering the crucible to a preset depth; heating the electric sand bath furnace and placing a low-temperature solder in the crucible, and then melting it into a solder liquid after keeping it warm for later use;

[0013] (2) After the soldering flux is applied to the surface to be welded of the die-cast aluminum alloy component to be welded, the component is placed in yellow sand in an electric sand bath furnace for preheating, and after preheating, solder liquid is applied to the surface to be welded of the die-cast aluminum alloy component;

[0014] (3) The surfaces to be welded of the different die-cast aluminum alloy parts obtained in step (2) are bonded together to form an assembly part, and the assembly part is placed in the yellow sand of an electric sand bath furnace, with the yellow sand covering the surfaces to be welded of the assembly part, and then pressure is applied to the assembly part, and heating is stopped after the pressure is maintained.

[0015] The welding method of die-cast aluminum alloy provided by the present invention comprises brushing the solder liquid on the surface to be welded, then compounding the surface to be welded, and diffusing under a certain pressure and temperature to achieve the connection of the welding surface. The present invention adopts a combination of brushing solder liquid-diffusion welding method, which can make Si atoms in the die-cast aluminum alloy base material diffuse more fully through diffusion under temperature and pressure, thereby effectively improving the joint strength.

[0016] At the same time, the present invention adds yellow sand as an energy storage medium into the electric sand bath furnace, which can realize multiple functions of uniformly heating the molten solder liquid, preheating the radiator and welding the radiator, integrating melting solder, preheating the workpiece and welding the workpiece, and effectively improving the welding efficiency. In addition, during the entire welding process, the entire workpiece is buried in the yellow sand to isolate the air from heating, which can prevent the gas precipitation in the cast aluminum alloy or the oxidation absorption of the brazing seam metal, thereby reducing joint defects and improving the strength of the welded joint, and is suitable for the preparation and application of die-cast aluminum alloys.

[0017] In the present invention, the material of the die-cast aluminum alloy parts is a die-cast aluminum alloy material available in the art, such as Al-Si-Cu die-cast aluminum alloy. Preferably, the grade of the die-cast aluminum alloy is ADC12.

[0018] In step (1), preferably, the particle size of the yellow sand is 0.125 to 0.25 mm.

[0019] In step (1), the crucible is a graphite crucible; and the preset depth is 2 / 3 of the height of the crucible.

[0020] Preferably, in step (1), the heating temperature is 350-380°C.

[0021] Preferably, in step (1), the low-temperature solder is one of Zn59Sn40Cu1, Zn58Sn40Cu2, and Zn57Sn40Cu3; and the insulation time is 20 to 30 minutes. The present invention adopts the above-mentioned low-temperature solder. Since the melting temperature of the solder is relatively low (300-335°C), the strength of the conventional brazing joint is relatively low. However, the present invention diffuses Si atoms in the parent material into the weld through a certain time and pressure, and becomes a dispersion-strengthened phase, thereby greatly improving the joint strength and achieving a balance between low temperature and high strength of the die-cast aluminum alloy radiator.

[0022] In step (2), preferably, the flux is cesium fluoroaluminate flux; the coating thickness of the flux is 6 to 10 μm; and the coating thickness of the solder liquid is 12 to 20 μm.

[0023] Furthermore, before applying the brazing flux, it is necessary to remove the oil stains and oxide film on the surface of the die-cast aluminum alloy component to be welded. The brazing flux can be applied by conventional brushing, such as brushing with a wire brush.

[0024] In step (2), when the die-cast aluminum alloy parts are placed in the yellow sand of the electric sand bath furnace for preheating, the burial depth of the yellow sand is 2 / 3 of the height of the die-cast aluminum alloy parts; and the preheating time is 8 to 15 minutes.

[0025] In step (3), the pressure applied is 0.8 to 3.0 MPa, and the pressure is maintained for 3 to 5 minutes.

[0026] The special device of the present invention adopts the following technical solution:

[0027] A special device for implementing the above-mentioned welding method of die-cast aluminum alloy comprises an electric sand bath furnace and a crucible; the electric sand bath furnace is provided with a cavity, and the crucible is placed inside the electric sand bath furnace.

[0028] Preferably, the crucible is a graphite crucible, and the electric sand bath furnace has a heating function.

[0029] The device of the present invention has a simple structure and low cost, and is suitable for welding applications of die-cast aluminum alloys.

[0030] The die-cast aluminum alloy radiator of the present invention adopts the following technical solution:

[0031] A die-cast aluminum alloy radiator is obtained by welding using the die-cast aluminum alloy welding method as described above; the die-cast aluminum alloy component is a die-cast aluminum alloy cavity with two halves that are symmetrical.

[0032] The die-cast aluminum alloy radiator of the present invention welds two symmetrical halves of the die-cast aluminum alloy cavity by brushing on solder liquid-diffusion welding method, and during the entire welding process, the entire workpiece is buried in yellow sand to isolate it from air heating, thereby effectively improving the joint strength and improving the welding quality at a low welding temperature, and is suitable for use in 5G base station die-cast aluminum alloy radiators.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] (1) The present invention integrates the entire process of melting solder liquid, preheating workpieces and welding workpieces for the first time, with high welding efficiency; and during the welding process, the entire radiator is buried in the yellow sand, isolated from the atmosphere, achieving high-quality brazing.

[0035] (2) The present invention uses low-temperature brazing filler metal for welding, which meets the welding requirements of die-cast aluminum alloys (bulging or deformation of the base material above 400°C), and through the assisted diffusion of pressure and temperature, Si atoms in the base material migrate into the weld, thereby improving the strength of the joint, thereby achieving a balance between low-temperature welding and high-strength joints, and has good application prospects in the field of die-cast aluminum alloy welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic structural diagram of a preparation device used in the welding method of die-cast aluminum alloy of the present invention;

[0037] Figure 2 This is a macroscopic morphology of a die-cast aluminum alloy base material obtained by welding the die-cast aluminum alloy according to the welding method of Comparative Example 1;

[0038] Figure 3 This is a macroscopic morphology of a welded joint obtained by the welding method of the die-cast aluminum alloy of Comparative Example 2;

[0039] Figure 4 For Example 1 of the present invention ( Figure 4 a) and Comparative Example 3 ( Figure 4 b) Microscopic morphology of the welded joint obtained by the welding method of the die-cast aluminum alloy;

[0040] Figure 5 This is an appearance diagram of a finished die-cast aluminum alloy radiator obtained by welding the die-cast aluminum alloy by the welding method of Example 1 of the present invention;

[0041] Figure 6 This is a macroscopic morphology of a welded joint obtained by the welding method of die-cast aluminum alloy in Example 1 of the present invention;

[0042] in, Figure 1 Middle: 1-Electric sand bath furnace, 2-Crucible, 3-Die-casting aluminum alloy parts. DETAILED DESCRIPTION

[0043] In order to more clearly illustrate the technical solution of the present invention, the implementation scheme of the present invention will be described in detail with reference to examples below. However, it should be understood by those skilled in the art that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0044] In the following examples, the yellow sand used has a particle size of 0.125-0.25 mm and is of fine river sand purchased from Qingyuan Jinfeng River Sand Co., Ltd.

[0045] The structural schematic diagram of the preparation device used in the welding method of die-cast aluminum alloy according to the present invention is as follows Figure 1 As shown. The device comprises an electric sand bath furnace 1 and a crucible 2; the electric sand bath furnace 1 is provided with a cavity, and the crucible 2 is placed inside the electric sand bath furnace 1. When welding the die-cast aluminum alloy, yellow sand and the die-cast aluminum alloy parts 3 are placed inside the cavity of the electric sand bath furnace 1. In the following embodiments, the electric sand bath furnace 1 has a heating function. The crucible 2 is a graphite crucible.

[0046] Example 1

[0047] The welding method of the die-cast aluminum alloy provided in this embodiment comprises the following steps:

[0048] (1) An electric sand bath furnace is prepared, yellow sand is added into the chamber of the electric sand bath furnace and a graphite crucible is placed therein, and the height of the yellow sand buried is maintained to be 2 / 3 of the height of the graphite crucible; the electric sand bath furnace is heated and a low-temperature solder is placed in the graphite crucible, and after heat preservation, it is melted into a solder liquid for standby use; wherein, the heating temperature of the electric sand bath furnace is 350° C.; the low-temperature solder is Zn59Sn40Cu1; and the heat preservation time is 20 min.

[0049] (2) After removing the oil stains and oxide film from the surfaces of the two symmetrical halves of the die-cast aluminum alloy cavity to be welded, apply cesium fluoroaluminate brazing flux, and then place the die-cast aluminum alloy cavity in yellow sand in an electric sand bath furnace for preheating, wherein the burial depth of the yellow sand is 2 / 3 of the height of the die-cast aluminum alloy cavity; after preheating, use a wire brush to brush the brazing liquid of step (1) on the surfaces of the die-cast aluminum alloy cavity to be welded; wherein the coating thickness of the cesium fluoroaluminate brazing flux is 6 μm; the brushing thickness of the brazing liquid is 12 μm; and the preheating time is 8 min.

[0050] (3) The surface to be welded of the die-cast aluminum alloy cavity obtained in step (2) is bonded to form an assembly, and the assembly is placed in the yellow sand of the electric sand bath furnace, and the yellow sand is kept to cover the surface to be welded of the assembly, and then pressure is applied to the assembly, and the solder liquid diffuses into the inside of the parent material to form a weld, and the electric sand bath furnace is stopped from heating after the pressure is maintained. When the temperature of the sand bath furnace drops below 100°C, the workpiece is taken out to obtain a finished die-cast aluminum alloy radiator. The pressure applied is 0.8MPa, and the pressure holding time is 3min.

[0051] The die-cast aluminum alloy heat sink provided in this embodiment is prepared by the above method.

[0052] Example 2

[0053] The welding method of the die-cast aluminum alloy provided in this embodiment is basically the same as that in Embodiment 1, except that:

[0054] In step (1), the heating temperature of the electric sand bath furnace is 360° C.; the holding time is 22 min; in step (2), the coating thickness of the cesium fluoroaluminate brazing agent is 8 μm; the brush coating thickness of the brazing liquid is 15 μm; the preheating time is 10 min; in step (3), the applied pressure is 1.0 MPa; and the holding time is 4 min.

[0055] The die-cast aluminum alloy heat sink provided in this embodiment is prepared by the above method.

[0056] Example 3

[0057] The welding method of the die-cast aluminum alloy provided in this embodiment is basically the same as that in Embodiment 1, except that:

[0058] In step (1), the heating temperature of the electric sand bath furnace is 370°C; the low-temperature solder is Zn57Sn40Cu3; the insulation time is 26 minutes; in step (2), the coating thickness of the cesium fluoroaluminate solder is 9 μm; the brush coating thickness of the solder liquid is 18 μm; the preheating time is 12 minutes; in step (3), the applied pressure is 1.5 MPa; and the pressure holding time is 5 minutes.

[0059] The die-cast aluminum alloy heat sink provided in this embodiment is prepared by the above method.

[0060] Example 4

[0061] The welding method of the die-cast aluminum alloy provided in this embodiment is basically the same as that in Embodiment 1, except that:

[0062] In step (1), the heating temperature of the electric sand bath furnace is 380°C; the low-temperature solder is Zn58Sn40Cu2; the insulation time is 30 minutes; in step (2), the coating thickness of the cesium fluoroaluminate solder is 10 μm; the brush coating thickness of the solder liquid is 20 μm; the preheating time is 15 minutes; in step (3), the applied pressure is 3.0 MPa; and the pressure holding time is 5 minutes.

[0063] The die-cast aluminum alloy heat sink provided in this embodiment is prepared by the above method.

[0064] Comparative Example 1

[0065] The welding method of the die-cast aluminum alloy provided in Comparative Example 1 is basically the same as that in Example 1, except that: in step (1), the heating temperature of the electric sand bath furnace is 430°C; the low-temperature solder is Zn98Al (melting point is 385-405°C), and the other steps are the same to obtain the finished die-cast aluminum alloy radiator of Comparative Example 1.

[0066] Comparative Example 2

[0067] The welding method of the die-cast aluminum alloy provided in Comparative Example 2 is basically the same as that in Example 1, except that: in step (1), the heating temperature of the electric sand bath furnace is 230°C; the low-temperature solder is Sn91Zn (melting point is 199°C), and the other steps are the same to obtain the finished die-cast aluminum alloy radiator of Comparative Example 2.

[0068] Comparative Example 3

[0069] The welding method of the die-cast aluminum alloy provided in Comparative Example 3 is basically the same as that of Example 1, except that: in step (3), the surface to be welded of the die-cast aluminum alloy cavity obtained in step (2) is bonded to form an assembly part, and the assembly part is placed in a box-type furnace for insulated diffusion welding. The temperature of the insulated diffusion welding is 350°C and the time is 15 minutes, thereby obtaining the finished die-cast aluminum alloy radiator of Comparative Example 3.

[0070] Test example

[0071] The performance and morphology of the die-cast aluminum alloy radiator prepared by the welding method of the die-cast aluminum alloy of Examples 1 to 4 of the present invention and Comparative Examples 1 to 3 were tested. The specific test method is: the die-cast aluminum alloy radiator welded by Examples 1 to 4 and Comparative Examples 1 to 3 is selected as the comparison object, and the standard specimens of the same size are taken to test the tensile strength of the joint and the brazing rate, and then the morphology of the parent material and the weld is observed. Among them, the tensile strength test of the joint refers to the provisions of GB / T 11363. The brazing rate refers to the percentage of the actual welding area (the area after removing defects such as inclusions and pores) to the nominal welding area. The brazing rate test process is: the brazing seam is pulled apart on a tensile testing machine, placed on a stereo microscope, and the actual welding area and the nominal welding area are measured using a computer three-dimensional drawing software, and the brazing rate is calculated. The test results of tensile strength and brazing rate are shown in Table 1.

[0072] The test results of base metal and weld morphology are as follows: Figures 2 to 6 As shown. Among them, Figure 2 This is a macroscopic morphology of a die-cast aluminum alloy base material obtained by welding the die-cast aluminum alloy according to the welding method of Comparative Example 1; Figure 3 This is a macroscopic morphology of a welded joint obtained by the welding method of the die-cast aluminum alloy of Comparative Example 2; Figure 4 For Example 1 of the present invention ( Figure 4 a) and Comparative Example 3 ( Figure 4 b) Microscopic morphology of the welded joint obtained by the welding method of the die-cast aluminum alloy; Figure 5 This is an appearance diagram of a finished die-cast aluminum alloy radiator obtained by welding the die-cast aluminum alloy by the welding method of Example 1 of the present invention; Figure 6 This is a macroscopic morphology of a welded joint obtained by the welding method of die-cast aluminum alloy in Example 1 of the present invention.

[0073] Table 1 Performance of die-cast aluminum alloy radiators obtained by welding of Examples 1 to 4 and Comparative Examples 1 to 3

[0074]

[0075] Combined with Table 1 Figures 2 to 4 It can be seen that compared with the welded joints obtained in Comparative Examples 1 to 3, the brazing rate of the brazed joints of Examples 1 to 4 of the present invention is high, reaching 85 to 89%, and the tensile strength of the joints is relatively high, reaching 68.5 to 88 MPa, which is significantly improved compared with Comparative Examples 1 to 3.

[0076] After the experiment, it was found that the reason for the above test results is that: Comparative Example 1 uses Zn98Al solder, the melting temperature of the solder is relatively high, the welding temperature exceeds 400°C, and the surface of the base material obviously bulges and softens (see Figure 2), resulting in low joint strength. Comparative Example 2 uses soft solder Sn91Zn, which has a low brazing temperature and meets the low temperature requirement of brazing. However, due to the low strength of Sn91Zn itself, the strengthening effect of trace Si atoms cannot change the low strength of the solder itself, resulting in low joint strength, and cracks will occur after bending (see Figure 3 ), which cannot meet the use requirements for strength. In addition, comparative example 3 uses a box-type resistance furnace for diffusion welding. Although the brazing material, brazing flux and operation steps are basically the same as those in Example 1, the components are heated in the box-type resistance furnace without protection. The entire high-temperature process is under the atmosphere, and the brazing seam is easily oxidized, resulting in defects such as slag inclusions and pores (see Figure 4 b), resulting in low joint strength. The die-cast aluminum alloy product obtained by the present invention has uniform welding morphology, no defects such as slag inclusions and pores, high welding quality, and high joint strength (see Figure 4 a).

[0077] Furthermore, the appearance of the die-cast aluminum alloy heat sink obtained by the die-cast aluminum alloy welding method of Example 1 of the present invention is as follows: Figure 5 The macroscopic morphology of the joint is shown in Figure 6 As shown. Figure 5 , Figure 6 It can be seen that the die-cast aluminum alloy radiator obtained by welding in the present invention has good appearance quality and no macroscopic defects, and is suitable for use in 5G base station die-cast aluminum alloy radiators.

[0078] In summary, the welding method of die-cast aluminum alloy provided by the present invention integrates the entire process of melting solder liquid, preheating workpieces and welding workpieces, and has high welding efficiency; and during the welding process, the entire radiator is buried in the yellow sand, isolated from the atmosphere, and high-quality brazing is achieved; at the same time, the present invention adopts a combination of low-temperature solder and diffusion welding, which can achieve low-temperature welding and high-strength joints, and has good application prospects in the field of die-cast aluminum alloy welding.

Claims

1. A method for welding a die-cast aluminum alloy, characterized in that: The following steps are involved: (1) preparing an electric sand bath furnace, adding yellow sand into the chamber of the electric sand bath furnace and placing a crucible therein, and keeping the crucible covered with yellow sand to a preset depth; heating the electric sand bath furnace and placing a low-temperature solder in the crucible, and melting it into a solder liquid after heat preservation for standby use; the heating temperature is 350-380° C., and the low-temperature solder is one of Zn59Sn40Cu1, Zn58Sn40Cu2, and Zn57Sn40Cu3; (2) After the soldering flux is applied to the surface to be welded of the die-cast aluminum alloy component to be welded, the component is placed in yellow sand in an electric sand bath furnace for preheating, and after preheating, solder liquid is applied to the surface to be welded of the die-cast aluminum alloy component; (3) The surfaces to be welded of the different die-cast aluminum alloy parts obtained in step (2) are bonded together to form an assembly part, and the assembly part is placed in the yellow sand of an electric sand bath furnace, with the yellow sand covering the surfaces to be welded of the assembly part, and then pressure is applied to the assembly part, and heating is stopped after the pressure is maintained.

2. The method for welding die-cast aluminum alloy according to claim 1, characterized in that: The particle size of the yellow sand is 0.125-0.25 mm.

3. The method for welding die-cast aluminum alloy according to claim 1, characterized in that: In step (1), the crucible is a graphite crucible; and the preset depth is 2 / 3 of the height of the crucible.

4. The method for welding die-cast aluminum alloy according to claim 1, characterized in that: In step (1), the insulation time is 20 to 30 minutes.

5. The method for welding a die-cast aluminum alloy according to any one of claims 1 to 4, characterized in that: In step (2), the flux is cesium fluoroaluminate flux; the coating thickness of the flux is 6 to 10 μm; and the coating thickness of the solder liquid is 12 to 20 μm.

6. The method for welding a die-cast aluminum alloy according to any one of claims 1 to 4, characterized in that: In step (2), when the die-cast aluminum alloy parts are placed in the yellow sand of the electric sand bath furnace for preheating, the burial depth of the yellow sand is 2 / 3 of the height of the die-cast aluminum alloy parts; and the preheating time is 8 to 15 minutes.

7. The method for welding a die-cast aluminum alloy according to any one of claims 1 to 4, characterized in that: In step (3), the pressure applied is 0.8 to 3.0 MPa, and the pressure is maintained for 3 to 5 minutes.

8. A die-cast aluminum alloy radiator, characterized in that: The die-cast aluminum alloy is welded by the welding method of the die-cast aluminum alloy as described in any one of claims 1 to 7; the die-cast aluminum alloy component is a die-cast aluminum alloy cavity with two halves symmetrical.

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