Stainless steel and aluminum alloy welding method

Abstract

The invention provides a stainless steel and aluminum alloy welding method which comprises the following steps: (1) sequentially carrying out acid washing and alkali washing on a stainless steel raw material and an aluminum alloy raw material to obtain a first stainless steel raw material and a first aluminum alloy raw material; (2) electroplating a nickel layer on the outer surface of the first stainless steel raw material to obtain a second stainless steel raw material; and (3) the second stainless steel raw material and the first aluminum alloy raw material are subjected to vacuum brazing treatment, and a welding assembly is obtained. The welding method is easy to operate, the aluminum-silicon welding flux well fills the assembling gap between the stainless steel pipe and the aluminum alloy plate, the welding binding rate is high, it is guaranteed that the environment where a cooling medium is located is not polluted, and the service life of cooling equipment can be prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of metal welding, and in particular to a welding method for stainless steel and aluminum alloy. Background Art

[0002] Both semiconductor PVD and CVD equipment need to operate under high temperature and high pressure environments, and the equipment needs to be cooled and precisely controlled in order to operate stably for a long time. The existing technology processes flow channels inside aluminum alloys or stainless steel and injects medium for cooling. However, the thermal conductivity of stainless steel cannot meet the cooling requirements, and aluminum alloys are prone to oxidation and corrosion in liquid media and high temperatures for a long time. Therefore, the use of pre-buried stainless steel pipes in cooling equipment can ensure that the cooling medium is not contaminated, and the aluminum alloy transfers heat relatively quickly, which can meet the use requirements. However, due to the different welding parameters of different metals, welding of two dissimilar metals, aluminum alloy and stainless steel, is difficult and not easy to achieve.

[0003] CN111889874A discloses a stirring welding method for aluminum alloy and stainless steel. The stirring welding device comprises a first stirring welding mechanism and a second stirring welding mechanism, wherein the first stirring welding mechanism is provided with a first stirring welding head, and the second stirring welding mechanism is provided with a second stirring welding head. When the stirring welding device is in operation, the first stirring welding mechanism and the second stirring welding mechanism are driven to move toward the weld respectively. The first stirring welding head and the second stirring head are provided to stir-weld the receiving part and the embedded part of the embedded welding part respectively, and the first stirring welding head is first screwed into the receiving part overlapped on the stainless steel to be welded to heat the receiving part, and the stainless steel to be welded is preheated by the heat. Since the stainless steel to be welded is preheated in advance, the stainless steel to be welded can reach a thermoplastic state at the same time as the aluminum alloy to be welded, thereby ensuring that the weld formed after the stirring welding is completed is smoother and has better connection performance.

[0004] CN106271069A discloses a laser welding method for stainless steel and aluminum alloy, the process of which is: respectively treating the plate-shaped stainless steel workpiece and aluminum alloy workpiece to be welded so that their surfaces are free of any impurities and dry, closely fitting and stacking the treated stainless steel workpiece and aluminum alloy workpiece together, using a nanosecond infrared laser to output laser and scanning the surface of the stainless steel workpiece or aluminum alloy workpiece along a welding track to weld them, the thickness of the scanned stainless steel workpiece or aluminum alloy workpiece is 0.05-0.5mm, and during welding, the laser output by the nanosecond infrared laser is perpendicular to the surface of the scanned stainless steel workpiece or aluminum alloy workpiece.

[0005] CN102794561A discloses a reaction stir friction welding method suitable for connecting aluminum alloy and stainless steel. After a Ni-Cu coating is formed on the welding surface of the stainless steel base material, a metal bond or a strong chemical bond is formed at the interface of the layer under the action of stir friction, so that the mediums of each layer have a strong bonding force, and the strength of the connection surface is improved; at the same time, the Al2O3 bond between the aluminum alloy and / or stainless steel dissimilar materials is limited by the barrier delay effect. 13 The amount of brittle compounds such as Fe4, AlFe, and AlFe3 generated increases, thereby improving the plasticity of the connection surface.

[0006] However, the above-mentioned welding method of aluminum alloy and stainless steel still has problems such as high welding cost and low welding bonding rate. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a welding method for stainless steel and aluminum alloy. After electroplating a nickel layer on the outer surface of the stainless steel, the stainless steel and the aluminum alloy are firmly welded by vacuum brazing. The welding process time is short, and the solder can well fill the assembly gap between the stainless steel tube and the aluminum alloy plate to achieve a tight fit, thereby meeting the use requirements of the cooling equipment.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for welding stainless steel and aluminum alloy, the welding method comprising the following steps:

[0010] (1) The stainless steel raw material and the aluminum alloy raw material are successively pickled and alkali washed to obtain a first stainless steel raw material and a first aluminum alloy raw material;

[0011] (2) electroplating a nickel layer on the outer surface of the first stainless steel raw material to obtain a second stainless steel raw material;

[0012] (3) The second stainless steel raw material and the first aluminum alloy raw material are vacuum brazed to obtain a welded assembly.

[0013] The welding method of stainless steel and aluminum alloy of the present invention uses vacuum brazing to well combine stainless steel and aluminum alloy, with a short production cycle. When the solder melts, it can fill the assembly gap between the stainless steel tube and the aluminum alloy plate to achieve a tight fit, ensuring that the environment where the cooling medium is located is not polluted, and can extend the service life. The brazing method of the present invention electroplates a nickel layer on the outer surface of the first stainless steel raw material, effectively ensuring a good welding bonding rate between the stainless steel and the aluminum alloy.

[0014] Preferably, the stainless steel raw material in step (1) comprises a stainless steel tube.

[0015] Preferably, the aluminum alloy raw material includes an aluminum alloy plate.

[0016] The structural schematic diagram of the welding assembly obtained by the welding method of the present invention is as follows Figure 1 As shown, the stainless steel tube 1 is welded inside the aluminum alloy plate 2. Before vacuum brazing, a welding piece can be placed between the upper and lower aluminum alloy plates, and the welding piece is profiled and cut to avoid the stainless steel tube in the middle.

[0017] Preferably, the thickness uniformity of the aluminum alloy plate is <0.1, for example, it can be 0.09, 0.08, 0.07, 0.05, 0.04, 0.03 or 0.01, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] Preferably, the acid solution used for pickling in step (1) includes nitric acid with a concentration of 15% to 25%, for example, it can be 15%, 16%, 18%, 20%, 21%, 23% or 25%, etc., but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable; and hydrofluoric acid with a concentration of 1% to 3%, for example, it can be 1%, 1.5%, 2%, 2.3%, 2.5%, 2.8% or 3%, etc., but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0019] Preferably, the volume ratio of nitric acid to hydrofluoric acid is (1-3):1, for example, 1:1, 1.3:1, 1.5:1, 1.8:1, 2:1, 2.5:1 or 3:1, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] Preferably, the pickling temperature is 80-85°C, for example, 80°C, 80.5°C, 81°C, 82°C, 83°C or 85°C, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable;

[0021] The time is 45 to 50 seconds, for example, 45 seconds, 46 seconds, 47 seconds, 48 ​​seconds, 49 seconds or 50 seconds, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0022] Preferably, the alkali solution used for the alkali washing includes sodium hydroxide with a concentration of 1% to 3%, for example, it can be 1%, 1.5%, 2%, 2.5%, 2.7%, 2.9% or 3%, etc., but it is not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable; sodium carbonate with a concentration of 3% to 5%, for example, it can be 3%, 3.5%, 4%, 4.5%, 4.8%, 4.9% or 5%, etc., but it is not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable; and trisodium phosphate with a concentration of 2% to 4%, for example, it can be 2%, 2.2%, 2.5%, 3%, 3.5%, 3.7% or 4%, etc., but it is not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable.

[0023] Preferably, the volume ratio of the sodium hydroxide, sodium carbonate and trisodium phosphate is (4-6):(1-3):(1-3):, for example, it can be 4:1:1, 4.3:1:1.2, 4.5:1:1.5, 4.8:1.5:1, 5:2:1, 5.5:2:1.4 or 6:3:1, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] Preferably, the temperature of the alkali washing is 80-85°C, for example, 80°C, 80.5°C, 81°C, 82°C, 83°C or 85°C, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable;

[0025] The time is 45 to 50 seconds, for example, 45 seconds, 46 seconds, 47 seconds, 48 ​​seconds, 49 seconds or 50 seconds, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0026] Preferably, the electroplating current in step (2) is 1 to 5 A / dm 2 , for example, it can be 1A / dm 2 , 1.5A / dm 2 , 2A / dm 2 , 2.5A / dm 2 、3A / dm 2 , 4A / dm 2 or 5A / dm 2 The above range is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0027] Preferably, the electroplating temperature is 55-65°C, for example, 55°C, 55.5°C, 56°C, 58°C, 60°C or 65°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0028] Preferably, the thickness of the nickel layer in step (2) is 7 to 9 μm, for example, 7 μm, 7.3 μm, 7.5 μm, 8 μm, 8.5 μm, 8.8 μm or 9 μm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] Preferably, the solder used in the vacuum brazing process in step (3) comprises aluminum silicon solder.

[0030] Preferably, the temperature of the vacuum brazing treatment in step (3) is 550-570°C, for example, it can be 550°C, 552°C, 555°C, 560°C, 565°C or 570°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] The preferred temperature of the vacuum brazing treatment of the present invention is 550-570°C to ensure that the aluminum-silicon solder fills the gap well and improves the welding bonding rate of stainless steel and aluminum alloy. When the temperature of the vacuum brazing treatment is low, the solder fluidity is insufficient, affecting the filling of the weld; when the temperature of the vacuum brazing treatment is high, the solder is excessively lost, affecting the welding quality.

[0032] Preferably, the pressure of the vacuum brazing treatment in step (3) is 4 to 5 MPa, for example, 4MPa, 4.2MPa, 4.3MPa, 4.5MPa, 4.8MPa or 5MPa, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] Preferably, the holding time of the vacuum brazing treatment is 180 to 200 min, for example, it can be 180 min, 185 min, 188 min, 190 min, 193 min, 195 min or 200 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] Preferably, the vacuum degree of the vacuum brazing process in step (3) is ≤3.0×10 -3 MPa, for example, can be 3.0×10 -3 MPa, 2.9×10 -3 MPa, 2.5×10 -3 MPa, 2.2×10 -3 MPa, 2.0×10 -3 MPa or 1.0×10 -3 MPa, etc., but are not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] The vacuum degree of the vacuum brazing treatment is preferably ≤3.0×10-3 MPa, to avoid low vacuum, which leads to more oxygen and other gases in the welding area, thereby increasing the possibility of oxidation and gas porosity, resulting in poor welding effect.

[0036] As a preferred technical solution of the present invention, the welding method comprises the following steps:

[0037] (1) The stainless steel raw material and the aluminum alloy raw material are successively subjected to acid washing at a temperature of 80 to 85° C. for 45 to 50 seconds and alkali washing at a temperature of 80 to 85° C. for 45 to 50 seconds to obtain a first stainless steel raw material and a first aluminum alloy raw material;

[0038] The stainless steel raw material includes a stainless steel tube; the aluminum alloy raw material includes an aluminum alloy plate; the thickness uniformity of the aluminum alloy plate is less than 0.1; the acid solution used in the pickling includes nitric acid with a concentration of 15% to 25% and hydrofluoric acid with a concentration of 1% to 3%; the alkali solution used in the alkali washing includes sodium hydroxide with a concentration of 1% to 3%, sodium carbonate with a concentration of 3% to 5%, and trisodium phosphate with a concentration of 2% to 4%;

[0039] (2) electroplating a nickel layer with a thickness of 7 to 9 μm on the outer surface of the first stainless steel raw material to obtain a second stainless steel raw material;

[0040] The electroplating current is 1-5A / dm 2 ; The electroplating temperature is 55-65°C;

[0041] (3) The second stainless steel raw material and the first aluminum alloy raw material are subjected to a temperature of 550-570°C, a pressure of 4-5 MPa, a holding time of 180-200 min, and a vacuum degree of ≤3.0×10 -3 MPa vacuum brazing treatment to obtain a welded assembly;

[0042] The solder used in the vacuum brazing process includes aluminum silicon solder.

[0043] Compared with the prior art, the present invention has at least the following beneficial effects:

[0044] The welding method of stainless steel and aluminum alloy provided by the present invention is simple to operate and has a short production cycle. The aluminum-silicon solder can well fill the assembly gap between the stainless steel tube and the aluminum alloy plate. The welding bonding rate is high, which ensures that the environment where the cooling medium is located is not polluted, and can extend the service life of the cooling equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the welding assembly in the present invention.

[0046] In the figure: 1- stainless steel pipe; 2- aluminum alloy plate. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0048] The present invention is further described in detail below. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0049] Example 1

[0050] This embodiment provides a method for welding stainless steel and aluminum alloy, the welding method comprising the following steps:

[0051] (1) The stainless steel tube and the aluminum alloy plate are successively subjected to acid washing at a temperature of 83° C. for 47 seconds and alkaline washing at a temperature of 84° C. for 46 seconds to obtain a first stainless steel tube and a first aluminum alloy plate;

[0052] The thickness uniformity of the aluminum alloy plate is 0.08; the acid solution used in the pickling is 30% nitric acid and 2% hydrofluoric acid, and the volume ratio of the two is 1:1; the alkali solution used in the alkali washing is 2% sodium hydroxide, 4% sodium carbonate and 3% trisodium phosphate, and the volume ratio of the three is 5:3:1;

[0053] (2) electroplating a nickel layer with a thickness of 8 μm on the outer surface of the first stainless steel tube to obtain a second stainless steel tube;

[0054] The electroplating current is 3A / dm 2 ; The electroplating temperature is 60°C;

[0055] (3) The second stainless steel tube and the first aluminum alloy plate were subjected to a temperature of 560°C, a pressure of 4.5 MPa, a holding time of 190 min, and a vacuum degree of 2×10 -3 MPa vacuum brazing treatment to obtain a welded assembly;

[0056] The solder used in the vacuum brazing process is aluminum silicon solder, and the model is BAL95Si.

[0057] Example 2

[0058] This embodiment provides a method for welding stainless steel and aluminum alloy, the welding method comprising the following steps:

[0059] (1) The stainless steel tube and the aluminum alloy plate are successively subjected to acid washing at a temperature of 80° C. for 50 seconds and alkaline washing at a temperature of 80° C. for 45 seconds to obtain a first stainless steel tube and a first aluminum alloy plate;

[0060] The thickness uniformity of the aluminum alloy plate is 0.01; the acid solution used in the pickling is 15% nitric acid and 3% hydrofluoric acid, and the volume ratio of the two is 2:1; the alkali solution used in the alkali washing is 3% sodium hydroxide, 3% sodium carbonate and 2% trisodium phosphate, and the volume ratio of the three is 6:1:2;

[0061] (2) electroplating a nickel layer with a thickness of 7 μm on the outer surface of the first stainless steel tube to obtain a second stainless steel tube;

[0062] The electroplating current is 1A / dm 2 ; The electroplating temperature is 65°C;

[0063] (3) The second stainless steel tube and the first aluminum alloy plate were subjected to a temperature of 550°C, a pressure of 5 MPa, a holding time of 200 min, and a vacuum degree of 1×10 -3 MPa vacuum brazing treatment to obtain a welded assembly;

[0064] The solder used in the vacuum brazing process includes aluminum silicon solder, model BAL95Si.

[0065] Example 3

[0066] This embodiment provides a method for welding stainless steel and aluminum alloy, the welding method comprising the following steps:

[0067] (1) The stainless steel tube and the aluminum alloy plate are successively subjected to acid washing at a temperature of 82° C. for 47 seconds and alkaline washing at a temperature of 83° C. for 47 seconds to obtain a first stainless steel tube and a first aluminum alloy plate;

[0068] The thickness uniformity of the aluminum alloy plate is 0.06; the acid solution used in the pickling is 17% nitric acid and 1.5% hydrofluoric acid, and the volume ratio of the two is 2.2:1; the alkali solution used in the alkali washing is 1.8% sodium hydroxide, 3.5% sodium carbonate and 2.4% trisodium phosphate, and the volume ratio of the three is 4.6:1.8:2.7;

[0069] (2) electroplating a nickel layer with a thickness of 7.7 μm on the outer surface of the first stainless steel tube to obtain a second stainless steel tube;

[0070] The electroplating current is 1.6A / dm 2 ; The electroplating temperature is 58°C.

[0071] (3) The second stainless steel tube and the first aluminum alloy plate were subjected to a temperature of 557°C, a pressure of 4.3 MPa, a holding time of 184 min, and a vacuum degree of 2.1×10 -3 MPa vacuum brazing treatment to obtain a welded assembly;

[0072] The solder used in the vacuum brazing process includes aluminum silicon solder, model BAL95Si.

[0073] Example 4

[0074] This embodiment provides a method for welding stainless steel and aluminum alloy, the welding method comprising the following steps:

[0075] (1) The stainless steel tube and the aluminum alloy plate are successively subjected to acid washing at a temperature of 85° C. for 45 seconds and alkaline washing at a temperature of 85° C. for 45 seconds to obtain a first stainless steel tube and a first aluminum alloy plate;

[0076] The thickness uniformity of the aluminum alloy plate is 0.031; the acid solution used in the pickling is 25% nitric acid and 1% hydrofluoric acid, and the volume ratio of the two is 3:1; the alkali solution used in the alkali washing is 1% sodium hydroxide, 5% sodium carbonate and 4% trisodium phosphate, and the volume ratio of the three is 6:3:1;

[0077] (2) electroplating a nickel layer with a thickness of 9 μm on the outer surface of the first stainless steel tube to obtain a second stainless steel tube;

[0078] The electroplating current is 5A / dm 2 ; The electroplating temperature is 65°C;

[0079] (3) The second stainless steel tube and the first aluminum alloy plate were subjected to a temperature of 570°C, a pressure of 4 MPa, a holding time of 180 min, and a vacuum degree of 3.0×10 -3 MPa vacuum brazing treatment to obtain a welded assembly;

[0080] The solder used in the vacuum brazing process includes aluminum silicon solder, model BAL95Si.

[0081] It can be seen from Examples 1 to 4 that the welding method of stainless steel and aluminum alloy provided by the present invention is simple to operate and has a short production cycle. The aluminum-silicon solder can well fill the assembly gap between the stainless steel tube and the aluminum alloy plate. The welding bonding rate is high, the welding effect is good, and the service life of the cooling equipment is extended.

[0082] Example 5

[0083] This embodiment provides a method for welding stainless steel and aluminum alloy. The welding method is the same as that of Embodiment 1 except that the temperature of the vacuum brazing treatment in step (3) is replaced with 520°C.

[0084] Example 6

[0085] This embodiment provides a method for welding stainless steel and aluminum alloy. The welding method is the same as that of Embodiment 1 except that the temperature of the vacuum brazing treatment in step (3) is replaced with 600°C.

[0086] Combining Example 1 with Examples 5 to 6, it can be seen that in Example 5, due to the relatively low temperature of the vacuum brazing process, the fluidity of the solder is insufficient, which affects the filling of the weld and reduces the welding bonding rate; in Example 6, due to the relatively high temperature of the vacuum brazing process, the solder is excessively lost and the welding bonding rate is reduced.

[0087] Example 7

[0088] This embodiment provides a method for welding stainless steel and aluminum alloy. In the welding method, the vacuum degree of the vacuum brazing process in step (3) is replaced by 4×10 -3 Except for MPa, the rest are the same as in Example 1.

[0089] In this embodiment, due to the low vacuum degree of vacuum brazing, there will be more oxygen and other gases in the welding area, which will increase the possibility of oxidation and gas porosity, resulting in a decrease in the welding bonding rate.

[0090] Comparative Example 1

[0091] This comparative example provides a method for welding stainless steel and aluminum alloy. The welding method is the same as Example 1 except that step (2) is not performed, that is, the first stainless steel tube and the first aluminum alloy plate are directly vacuum brazed.

[0092] In this comparative example, since the nickel layer is not electroplated on the outer surface of the first stainless steel tube, the welding effect between the stainless steel and the aluminum alloy will be significantly deteriorated, and the welding bonding rate will be greatly reduced.

[0093] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for welding stainless steel and aluminum alloy, characterized in that: The welding method comprises the following steps: (1) The stainless steel raw material and the aluminum alloy raw material are successively pickled and alkali washed to obtain a first stainless steel raw material and a first aluminum alloy raw material; (2) electroplating a nickel layer on the outer surface of the first stainless steel raw material to obtain a second stainless steel raw material; (3) The second stainless steel raw material and the first aluminum alloy raw material are vacuum brazed to obtain a welded assembly.

2. The welding method according to claim 1, characterized in that: The stainless steel raw material in step (1) comprises a stainless steel tube; Preferably, the aluminum alloy raw material comprises an aluminum alloy plate; Preferably, the thickness uniformity of the aluminum alloy plate is <0.

1.

3. The welding method according to claim 1 or 2, characterized in that: The acid solution used for pickling in step (1) includes nitric acid with a concentration of 15% to 25% and hydrofluoric acid with a concentration of 1% to 3%; Preferably, the pickling temperature is 80-85°C and the time is 45-50s; Preferably, the alkali solution used in the alkali washing includes sodium hydroxide with a concentration of 1% to 3%, sodium carbonate with a concentration of 3% to 5%, and trisodium phosphate with a concentration of 2% to 4%; Preferably, the alkali washing is carried out at a temperature of 80 to 85° C. and for a time of 45 to 50 seconds.

4. The welding method according to any one of claims 1 to 3, characterized in that: The electroplating current in step (2) is 1 to 5 A / dm 2 ; Preferably, the electroplating temperature is 55-65°C.

5. The welding method according to any one of claims 1 to 4, characterized in that: The thickness of the nickel layer in step (2) is 7 to 9 μm.

6. The welding method according to any one of claims 1 to 5, characterized in that: The solder used in the vacuum brazing process in step (3) includes aluminum silicon solder.

7. The welding method according to any one of claims 1 to 6, characterized in that: The temperature of the vacuum brazing treatment in step (3) is 550-570°C.

8. The welding method according to any one of claims 1 to 7, characterized in that: The pressure of the vacuum brazing process in step (3) is 4-5 MPa; Preferably, the holding time of the vacuum brazing process is 180 to 200 minutes.

9. The welding method according to any one of claims 1 to 8, characterized in that: The vacuum degree of the vacuum brazing treatment in step (3) is ≤3.0×10 -3 MPa.

10. The welding method according to any one of claims 1 to 9, characterized in that: The welding method comprises the following steps: (1) The stainless steel raw material and the aluminum alloy raw material are successively subjected to acid washing at a temperature of 80 to 85° C. for 45 to 50 seconds and alkali washing at a temperature of 80 to 85° C. for 45 to 50 seconds to obtain a first stainless steel raw material and a first aluminum alloy raw material; The stainless steel raw material includes a stainless steel tube; the aluminum alloy raw material includes an aluminum alloy plate; the thickness uniformity of the aluminum alloy plate is less than 0.1; the acid solution used in the pickling includes nitric acid with a concentration of 15% to 25% and hydrofluoric acid with a concentration of 1% to 3%; the alkali solution used in the alkali washing includes sodium hydroxide with a concentration of 1% to 3%, sodium carbonate with a concentration of 3% to 5%, and trisodium phosphate with a concentration of 2% to 4%; (2) electroplating a nickel layer with a thickness of 7 to 9 μm on the outer surface of the first stainless steel raw material to obtain a second stainless steel raw material; The electroplating current is 1-5A / dm 2 ; The electroplating temperature is 55-65°C; (3) The second stainless steel raw material and the first aluminum alloy raw material are subjected to a temperature of 550-570°C, a pressure of 4-5 MPa, a holding time of 180-200 min, and a vacuum degree of ≤3.0×10 -3 MPa vacuum brazing treatment to obtain a welded assembly; The solder used in the vacuum brazing process includes aluminum silicon solder.

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