Method for processing aluminum alloy case frame body with complex cooling runner

Abstract

The application discloses a processing method of an aluminum alloy machine case frame body with a complex cooling flow channel, and comprises the following steps: welding mode, machining sequence and allowance design, and steps of selecting a filler metal, trimming the filler metal, cleaning the to-be-welded part and the filler metal, protecting the to-be-welded part and the filler metal, assembling the filler metal, assembling a cover plate, loading into a furnace, welding, sealing test and the like. The application can realize integrated manufacturing of the aluminum alloy machine case frame body with the complex cooling flow channel, adopts a combination of brazing and diffusion welding to realize the welding of the machine case by adopting the sequence of twice welding and thrice machining, solves the problem that the simple diffusion welding cannot realize high-strength welding of the machine case, and also solves the problems of insufficient strength, more defects and deformation caused by the argon arc welding.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy heat sink welding technology, specifically relating to a diffusion brazing process for an aluminum alloy chassis frame with complex cooling channels. Background Technology

[0002] Aluminum alloy chassis with built-in cooling are increasingly used in electronic devices. Currently, aluminum alloy chassis frames are mostly achieved by brazing or a combination of brazing and TIG welding, with diffusion welding being less common. All three welding methods have significant drawbacks:

[0003] First, it is difficult to achieve one-piece brazing of the three sides of the chassis by simply using the brazing process. If it is one-piece brazing, one or two of the three sides of the chassis will be vertical surfaces during brazing, which is not conducive to applying pressure to the brazing surface and is prone to brazing defects, such as incomplete welding, voids, and discontinuous welding.

[0004] Secondly, diffusion welding alone cannot achieve the desired chassis welding. This is because the structural characteristics of aluminum alloy chassis are unsuitable for diffusion welding, or rather, diffusion welding of aluminum alloys itself has technical flaws. Simply put, diffusion welding involves heating and pressurizing to achieve atomic diffusion between the surfaces of two contacting parts, thus bonding them together. Since the connection is at the atomic level, the connection strength should be very high. However, aluminum alloy surfaces have a surface oxide layer. To achieve atomic-level diffusion, this oxide film needs to be broken. However, the oxide film broken during the diffusion process cannot be expelled on its own; it all integrates into the aluminum alloy bonding diffusion layer, affecting the connection strength and resulting in low post-weld connection strength—in other words, it is technically unreasonable.

[0005] Third, if the chassis cover plates are brazed separately, the industry often uses argon arc welding to combine multiple cover plates of the chassis frame. However, argon arc welding results in large deformation after welding, making it difficult to guarantee the chassis size after welding. At the same time, when the brazing position of the cover plate is close to the argon arc welding position, the high heat input of argon arc welding can easily cause secondary heating of the brazed weld seam, resulting in defects.

[0006] For the reasons mentioned above, it is necessary to design a processing method to improve the welding quality of aluminum alloy chassis frames with complex cooling channels, avoid post-weld defects, reduce welding deformation, and improve welding strength. Summary of the Invention

[0007] In response to the problems mentioned in the background art, the present invention aims to provide a processing method for an aluminum alloy chassis frame with complex cooling channels, which solves the problems of the inability to weld the chassis by diffusion welding alone (mainly due to insufficient strength after welding), the brazing defects that exist when welding multiple cover plates of the aluminum alloy chassis frame by brazing alone, and the deformation problems caused by the combination of argon arc welding and brazing, thereby improving the welding quality of the aluminum alloy chassis frame and reducing or even eliminating brazing defects.

[0008] The solution proposed in this invention is a welding method that combines brazing and diffusion welding equipment, and adopts a processing flow of "machining-welding-machining-welding-re-machining" to improve the brazing quality of aluminum alloy chassis frames with complex cooling channels and reduce welding deformation.

[0009] To solve the above problems, the present invention adopts the following solution:

[0010] A method for processing an aluminum alloy chassis frame with complex cooling channels, wherein the aluminum alloy chassis frame includes a first surface, a second surface, and a third surface, and the first surface, the second surface, and the third surface are three non-coplanar surfaces with cooling channels connected sequentially along the circumference of the aluminum alloy chassis frame. The first surface, the second surface, and the third surface are respectively assembled and welded to a first cover plate, a second cover plate, and a third cover plate. The processing method includes the following steps:

[0011] Step 1: Machine cooling channels on the first and third surfaces of the aluminum alloy chassis frame. Then, assemble the first cover plate to the first surface and the third cover plate to the third surface. Finally, use diffusion brazing to weld the first cover plate to the first surface and the third cover plate to the third surface.

[0012] Step 2: Check the welding seal between the first cover plate and the first surface, and between the third cover plate and the third surface in Step 1. After confirming that the welding seal is qualified, process the cooling channel on the second surface. Then, assemble the second cover plate to the second surface and weld the second cover plate to the second surface by diffusion brazing.

[0013] Step 3: Perform a second welding seal check. Once the welding seal is satisfactory, perform overall shape machining on the aluminum alloy chassis frame until it meets the dimensional requirements.

[0014] Furthermore, in steps one and two, cooling channels on the first, second, and third surfaces are machined using mechanical processing methods.

[0015] Furthermore, in step three, the overall external dimensions of the aluminum alloy chassis frame are processed using machining methods.

[0016] Furthermore, in steps two and three, a water pressure method is used to check the weld sealing.

[0017] As an option,

[0018] In step one, the first surface, the third surface, the first cover plate and the third cover plate are pre-processed with machining allowance in terms of external dimensions for the overall shape processing of the aluminum alloy chassis frame in step three before welding.

[0019] In step two, the second surface and the second cover plate are pre-processed with machining allowance in terms of external dimensions to prepare for the overall shape processing of the aluminum alloy chassis frame in step three before welding.

[0020] Furthermore, during the diffusion brazing in steps one and two, the brazing filler metal is shaped and sized by wire cutting or integral punching, and the brazing filler metal is a single piece or multiple pieces spliced ​​together.

[0021] Furthermore, before diffusion brazing in steps one and two, the first surface, second surface, third surface, first cover plate, second cover plate, third cover plate and brazing filler metal are sequentially degreased, alkaline washed and acid-washed, and then placed in diethylene glycol dimethyl ether to await welding.

[0022] Furthermore, the diffusion brazing in steps one and two also includes:

[0023] During brazing, brazing filler metal is laid on the first, second, and third surfaces, and the outer contour of the brazing filler metal extends beyond the outer contour of the position to be welded on the first, second, and third surfaces by a certain margin.

[0024] The cover plate is assembled in one go, and the first cover plate, the second cover plate and the third cover plate are assembled in one go and will not be moved after assembly.

[0025] Furthermore, during the diffusion brazing in steps one and two, the diffusion brazing temperature in the vacuum furnace is set to T1. As the furnace temperature rises to T1, pressure P1 is simultaneously applied to the aluminum alloy chassis frame. When the lowest temperature of the aluminum alloy chassis frame reaches T2, the diffusion brazing temperature is gradually reduced, where T2 < T1. When the highest temperature of the aluminum alloy chassis frame reaches T3, T2 < T3 < T1, the pressure is increased to P2, where P2 > P1. The temperature is maintained at T3 and the pressure at P2, and the diffusion brazing timer begins. After welding, the aluminum alloy chassis frame is allowed to cool naturally to a temperature of T4 before the pressure is released, where T4 < T2.

[0026] further,

[0027] During diffusion brazing in step one, pressure is applied along a direction perpendicular to the first surface, the third surface, the first cover plate, and the third cover plate, and a height limiting device is set in a direction perpendicular to the first surface, the third surface, the first cover plate, and the third cover plate, wherein the height of the height limiting device is greater than or equal to the height distance between the first cover plate and the third cover plate.

[0028] During diffusion brazing in step two, pressure is applied in a direction perpendicular to the second surface and the second cover plate, and a height limiting device is set in a direction perpendicular to the second surface and the second cover plate. The height of the height limiting device is greater than or equal to the height distance between the second cover plate and the opposite surface on the aluminum alloy chassis frame.

[0029] In the processing method of this invention, the welding process is not diffusion welding, but brazing. The difference lies in the addition of pressure to braze the material, which promotes the brazing reaction and increases the brazing strength. Compared with existing processing methods, the processing method of this invention has the following characteristics:

[0030] 1. During the processing, the welding of the three continuous surfaces of the aluminum alloy chassis frame is achieved through a combination of machining and welding.

[0031] 2. The welding process is a combination of diffusion welding (pressure welding) and brazing;

[0032] 3. Effective height limits were implemented during the welding process, and reasonable welding parameters were determined;

[0033] 4. Chemical treatment was used to avoid the influence of oxide film on the surface of the workpiece to be welded, to limit the generation of aluminum alloy oxide scale after pickling, and to improve the welding strength.

[0034] Compared with the prior art, the present invention realizes the integrated manufacturing of aluminum alloy chassis frame with complex cooling channels. The chassis welding is achieved by using diffusion brazing, which combines brazing and diffusion welding. This solves the problem of weld performance in diffusion welding chassis, as well as the problem of insufficient structural strength and many defects in chassis frame welded by brazing alone. It also overcomes the deformation problem caused by argon arc welding. Attached Figure Description

[0035] Figure 1 It is a schematic diagram of an aluminum alloy chassis frame structure with complex cooling channels;

[0036] Figure 2 This is a schematic diagram of the aluminum alloy chassis frame, the first cover plate, and the third cover plate.

[0037] Figure 3 This is a schematic diagram of the structure of an aluminum alloy chassis after the first and third cover plates are welded together and then welded to the second cover plate.

[0038] Figure 4 This is a schematic diagram of the aluminum alloy chassis frame being loaded into the diffusion welding equipment.

[0039] In the diagram: 1-First cover plate, 2-Second cover plate, 3-Third cover plate, 4-Chassis. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, it should not be construed that the scope of the subject matter of the present invention is limited to the following embodiments. All modifications, substitutions and alterations made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention are included within the scope of the present invention.

[0041] like Figures 1-4As shown, this invention presents a method for manufacturing an aluminum alloy chassis frame with complex cooling channels. The method employs two diffusion brazing processes and three machining operations to achieve the manufacturing of an aluminum alloy chassis frame with complex cooling channels on three sides (the structure of the aluminum alloy chassis frame with complex cooling channels is shown below). Figure 1 This invention employs a combination of brazing and diffusion welding to ensure the strength of the joints in the aluminum alloy chassis frame. The processing method of this invention includes the following:

[0042] (A) Welding, machining sequence and allowance design: Three adjacent surfaces on the aluminum alloy chassis frame ( Figure 1 The surfaces referred to as the first, second, and third surfaces respectively all have complex flow channels. Figure 1 (Not shown in the diagram), first use a five-axis machining center to machine the cooling channels on the opposite first and third surfaces, forming two opposing surfaces with cooling channels, 4 ( Figure 2 Then, diffusion brazing was used to bond the chassis 4 ( Figure 2 ) and the first cover plate 1 ( Figure 2 ), third cover plate 3 ( Figure 2 After welding, the weld seal was tested using a water pressure test. Following the test, the remaining cooling channels on the second surface were machined, and then the chassis 4 ( ) was again joined using diffusion brazing. Figure 2 First cover plate 1 ( Figure 2 ), third cover plate 3 ( Figure 2 ) Post-welding assembly and second cover plate 2 ( Figure 3 Welding is performed, and the weld sealing is tested by water pressure after welding. After passing the test, the entire aluminum alloy chassis frame is machined. A 2mm machining allowance should be left in height between the three welded surfaces (first surface, second surface, and third surface) of the aluminum alloy chassis frame and the first cover plate 1, second cover plate 2, and third cover plate 3. The assembly gap between the three welded surfaces (first surface, second surface, and third surface) of the aluminum alloy chassis frame and the first cover plate 1, second cover plate 2, and third cover plate 3 should be controlled between 1 and 1.5mm.

[0043] (B) Selection of brazing filler metal: The brazing filler metal grade is 4004 and the brazing filler metal thickness is 0.1mm.

[0044] (C) Trimming the Brazing Filler Metal: The brazing filler metal is trimmed using wire cutting (or integral punching). If wire cutting is used, because the filler metal is thin and soft, two flat stainless steel plates with a thickness of at least 0.5mm are used to sandwich the filler metal between them, and clamps or steel clips are used to hold the plates to prevent slippage during the cutting process. To ensure sufficient filler metal while preventing excessive filler metal from flowing into the cooling channels and blocking them, the width of the filler metal should be 0.2–0.4mm wider than the width of the welding position. If the width of the filler metal is less than 4mm of the chassis width, the filler metal can be cut in sections and spliced ​​during brazing.

[0045] (D) Cleaning the parts to be welded and the brazing filler metal: Before welding, the parts to be welded (first surface, third surface, first cover plate 1, third cover plate 3) should be degreased, alkaline washed, and acid-washed to remove surface rust, oil, oxide film, and other contaminants. The alkaline washing time for the parts to be welded is 5 seconds, and the alkaline washing time for the brazing filler metal is 50 seconds. During the cleaning process, the surfaces to be welded should not be bumped or scratched.

[0046] (E) Protection of workpieces and brazing filler metal: After cleaning, workpieces and brazing filler metal often cannot be welded immediately. In order to ensure the diffusion brazing effect, the cleaned workpieces and brazing filler metal should be quickly immersed in diethylene glycol dimethyl ether to prevent the regeneration of the oxide film on their surface.

[0047] (F) Solder assembly: Assemble the solder into the chassis 4 ( Figure 2 On the ), ensure the brazing filler metal corresponds to the shape of the area to be soldered, and assemble it to the center of the area to be soldered, maintaining consistent allowance on both sides. To ensure smooth brazing, along the 4 ( Figure 2 An additional piece of solder about 5mm wide is placed around the outermost edge. If there are joints in the solder, the width of the solder overlap at the joint should be 5mm to 10mm.

[0048] (G) Cover plate assembly: The first cover plate 1 and the second cover plate 3 are assembled onto the chassis 4. They should be assembled in one go. After assembly, the first cover plate 1 and the third cover plate 3 should not be moved to avoid the brazing filler metal from shifting away from the welding position during the process of moving the cover plates.

[0049] (H) Furnace Loading: Move the assembled chassis 4, first cover plate 1, and third cover plate 3 into the diffusion welding furnace, ensuring that chassis 4 is not tilted and is located at the center of the diffusion welding head. Place two height-limiting fixtures of the same height and appropriate size on both sides of chassis 4. Figure 4 ).

[0050] (I) Welding: The temperature inside the vacuum furnace during diffusion welding is set to 630℃. During the furnace temperature rise, a pressure of 0.01T is applied to the workpiece to be welded. When the minimum temperature of the workpiece to be welded reaches 580℃, the welding temperature is gradually reduced. When the temperature of the workpiece to be welded reaches a suitable temperature (this suitable temperature is an empirical temperature, obtained through experiments, generally a value lower than 630℃ but higher than 580℃, determined according to the conditions of the vacuum furnace and the workpiece to be welded), the pressure is increased to 0.3T and the welding time is started. The welding time is not less than 60 minutes. After welding, the workpiece is allowed to cool naturally to a temperature of 250℃ before the pressure is released.

[0051] (J) Sealing test: The weld is tested for leakage by filling with water pressure.

[0052] (K) The chassis 4, after the welding of the first cover plate 1 and the third cover plate 3, is defined as the post-welded chassis assembly. Figure 3 Then process the welded assembly of the chassis and the second cover plate 2 ( Figure 3 The cooling channels on the second surface corresponding to the second cover plate 2 on the welded assembly of the chassis are processed using machining equipment, and the assembly gap between the two is controlled according to the requirements of step (A) to control the machining dimensions.

[0053] (L) Post-welding assembly of the welded chassis ( Figure 3 ) and second cover plate 2 ( Figure 3 And test the sealing performance: Repeat steps (C) to (J), wherein in step (C), the brazing filler metal should be applied according to the assembly of the chassis after welding. Figure 3 Cutting at the welding position, (H) step, height-limiting fixture ( Figure 4 The height of the assembly should be consistent with that of the welded chassis components. Figure 3 The height should be appropriate. It is important to note that when welding the first cover plate 1, the third cover plate 3, and the second cover plate 2, the brazing pressure direction should be perpendicular to the horizontal plane. That is, after welding the first and third surfaces, the orientation of the chassis 4 needs to be adjusted before welding the second surface, i.e., like... Figure 4 As in the previous example, during each diffusion brazing, the first, second, and third surfaces remain horizontal (this is achieved by rotating the housing 4 to ensure the aforementioned surfaces are always parallel to the horizontal plane). The pressure head applies pressure perpendicular to the horizontal plane, and graphite paper is placed between the first cover plate 1 (or the second cover plate 2 or the third cover plate 3) and the pressure head. A load coupler is installed at the center of the workpiece to be welded for temperature measurement. Height-limiting fixtures are placed on both sides of the workpiece to be welded. Figure 4 The text also indicates the high-speed compression amount of the welding height. This compression amount is determined based on the deformation of the workpiece after pressure is applied, the deformation of the height-limiting tooling, and the external dimensions of the aluminum alloy chassis frame. The goal is to ensure that the external dimensions of the aluminum alloy chassis frame meet the requirements after diffusion brazing.

[0054] The diffusion brazing of this invention focuses on brazing (because of the use of brazing filler metal), and its diffusion emphasizes that the pressure applied during the brazing process promotes atomic diffusion.

[0055] The above processing method uses two diffusion brazing and three machining operations to weld the aluminum alloy chassis frame with complex flow channels on three adjacent surfaces, while reserving appropriate machining allowance to ensure that the machined chassis meets the design dimensions after welding.

[0056] The above processing method uses diethylene glycol dimethyl ether (DME) to prevent the formation of an oxide film on the surface of the aluminum alloy workpiece and the brazing filler metal. Before the brazing reaction, the surface oxide film needs to be removed. Once broken, the oxide film melts into the welding reaction layer, reducing the strength of the brazed joint. Immersing the workpiece and brazing filler metal in DME reduces or avoids the formation of the surface oxide film, thereby reducing the degree to which the oxide film melts into the welding reaction layer and ultimately improving the strength of the aluminum alloy weld joint.

[0057] The above processing method increases pressure while brazing the aluminum alloy chassis frame, achieving a combination of brazing and diffusion welding, thus avoiding the problem that brazing alone cannot guarantee the strength of the welded joint.

[0058] The above processing method uses height-limiting tooling to ensure the height of the welded parts during the pressure welding process, avoiding problems such as the welded parts being crushed or the height being too small after welding due to pressure fluctuations or excessive pressure during the welding process.

[0059] The above description is merely one specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for processing an aluminum alloy chassis frame with complex cooling channels, wherein the aluminum alloy chassis frame includes a first surface, a second surface, and a third surface, and the first surface, the second surface, and the third surface are three non-coplanar surfaces with cooling channels connected sequentially along the circumference of the aluminum alloy chassis frame, and the first surface, the second surface, and the third surface are respectively assembled and welded to a first cover plate (1), a second cover plate (2), and a third cover plate (3), characterized in that: The processing method includes the following steps: Step 1: Cooling channels are machined on the first and third surfaces of the aluminum alloy chassis frame. Then, the first cover plate (1) is assembled to the first surface, and the third cover plate (3) is assembled to the third surface. Then, the first cover plate (1) is welded to the first surface and the third cover plate (3) is welded to the third surface by diffusion brazing. Step 2: Check the welding seal between the first cover plate (1) and the first surface, and between the third cover plate (3) and the third surface in Step 1. After confirming that the welding seal is qualified, process the cooling channel on the second surface. Then assemble the second cover plate (2) to the second surface and weld the second cover plate (2) to the second surface by diffusion brazing. Step 3: Perform a second welding seal check. Once the welding seal is satisfactory, perform overall shape machining on the aluminum alloy chassis frame until it meets the dimensional requirements.

2. The processing method for an aluminum alloy chassis frame with complex cooling channels according to claim 1, characterized in that: In steps one and two, cooling channels on the first, second, and third surfaces are machined using mechanical processing methods.

3. The processing method for an aluminum alloy chassis frame with complex cooling channels according to claim 1, characterized in that: In step three, the overall external dimensions of the aluminum alloy chassis frame are processed using machining methods.

4. The processing method for an aluminum alloy chassis frame with complex cooling channels according to claim 1, characterized in that: In steps two and three, the welding sealing is checked by water pressure.

5. The processing method for an aluminum alloy chassis frame with complex cooling channels according to claim 1, characterized in that: In step one, the first surface, the third surface, the first cover plate (1) and the third cover plate (3) are provided with machining allowance in terms of external dimensions for the overall shape machining of the aluminum alloy chassis frame in step three before welding; In step two, the second surface and the second cover plate (2) are pre-processed with a machining allowance in terms of external dimensions for the overall shape processing of the aluminum alloy chassis frame in step three before welding.

6. The processing method for an aluminum alloy chassis frame with complex cooling channels according to claim 1, characterized in that: During the diffusion brazing in steps one and two, the brazing filler metal is shaped and sized by wire cutting or integral punching, and the brazing filler metal is either a single piece or multiple pieces spliced ​​together.

7. The processing method for an aluminum alloy chassis frame with complex cooling channels according to claim 1, characterized in that: Before diffusion brazing in steps one and two, the first surface, second surface, third surface, first cover plate (1), second cover plate (2), third cover plate (3) and brazing filler metal are sequentially degreased, alkaline washed and acid-washed, and then placed in diethylene glycol dimethyl ether to await welding.

8. The processing method of the aluminum alloy chassis frame with complex cooling channels according to claim 7, characterized in that: The diffusion brazing in steps one and two further includes: During brazing, brazing filler metal is laid on the first, second, and third surfaces, and the outer contour of the brazing filler metal extends beyond the outer contour of the position to be welded on the first, second, and third surfaces by a certain margin. The cover plate is assembled in one go, and the first cover plate (1), the second cover plate (2) and the third cover plate (3) are assembled in one go and will not be moved after assembly.

9. The processing method of the aluminum alloy chassis frame with complex cooling channels according to claim 1, characterized in that: During diffusion brazing in steps one and two, the diffusion brazing temperature in the vacuum furnace is set to T1. As the furnace temperature rises to T1, pressure P1 is simultaneously applied to the aluminum alloy chassis frame. When the lowest temperature of the aluminum alloy chassis frame reaches T2, the diffusion brazing temperature is gradually reduced, where T2 < T1. When the highest temperature of the aluminum alloy chassis frame reaches T3, T2 < T3 < T1, the pressure is increased to P2, where P2 > P1. The temperature is maintained at T3 and the pressure at P2, and the diffusion brazing timer begins. After welding, the aluminum alloy chassis frame is allowed to cool naturally to a temperature of T4 before the pressure is released, where T4 < T2.

10. The processing method of the aluminum alloy chassis frame with complex cooling channels according to claim 1, characterized in that: During diffusion brazing in step one, pressure is applied along the direction perpendicular to the first surface, the third surface, the first cover plate (1) and the third cover plate (3), and a height limiting device is set in the direction perpendicular to the first surface, the third surface, the first cover plate (1) and the third cover plate (3). The height of the height limiting device is greater than or equal to the height distance between the first cover plate (1) and the third cover plate (3). During diffusion brazing in step two, pressure is applied in a direction perpendicular to the second surface and the second cover plate (2), and a height limiting device is set in a direction perpendicular to the second surface and the second cover plate (2). The height of the height limiting device is greater than or equal to the height distance between the second cover plate (2) and the opposite surface on the aluminum alloy chassis frame.

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