Aluminum pipe with lap joint internal thread and brazing layer

Abstract

This utility model relates to an lap-type internally threaded aluminum round tube with a composite brazing layer, comprising a tubular body formed by embossing and rolling cold-rolled aluminum strip. An lap portion is provided along the axial direction of the tubular body. The lap portion includes an upper slope and a lower slope, with the upper slope covering the outer side of the lower slope. The upper and lower slopes are staggered and stacked to form a stepped lap surface. After the tube body expands, the upper and lower slopes fit tightly together to form a self-locking sealing structure. The upper slope is formed on one side of the cold-rolled aluminum strip with the composite brazing layer, and the lower slope is formed on the other side. The advantages of this utility model are: through integrated forming of "embossing-lap-internal expansion," the high-frequency welding step is completely eliminated, removing defects such as weld buildup and slag spatter, significantly reducing energy consumption and equipment investment, and making it particularly suitable for small-diameter mass production.

Description

Technical Field

[0001] This utility model relates to an lap-jointed internally threaded aluminum round tube with a composite brazing layer, belonging to the field of aluminum tubes. Background Technology

[0002] Currently, there are three main types of materials and processes used for internally threaded round tubes in air conditioning heat exchangers: extruded copper tubes, extruded aluminum tubes, and cold-rolled composite aluminum tubes with brazed layers and high-frequency welded aluminum tubes. Among them, the high price of copper in extruded copper tubes leads to high overall costs; although extruded aluminum tubes can reduce costs, they are prone to defects such as uneven wall thickness, poor corrosion resistance, and limited internal thread forming due to the limitations of the extrusion process itself, making it difficult to meet the requirements of high-performance air conditioners.

[0003] In recent years, to balance lightweighting and cost, the industry has begun to adopt aluminum tubes made from "cold-rolled composite aluminum with brazed layers + high-frequency welding" to replace the two types of extruded tubes mentioned above. This approach improves the material's density and mechanical properties through continuous cold rolling, and then uses high-frequency welding to roll the cold-rolled composite aluminum strip with brazed layers into tubes. However, high-frequency welding is prone to weld buildup and slag spatter at the weld seam. Furthermore, the smaller the outer diameter of the round tube, the more difficult it is to concentrate high-frequency energy, resulting in a significantly increased welding defect rate, a narrow process window, and low yield, further increasing the difficulty of cost control for small-diameter products.

[0004] Therefore, there is an urgent need in this field for a new type of internally threaded composite brazed aluminum round tube that can completely get rid of high-frequency welding and its inherent defects while maintaining the excellent comprehensive performance of cold-rolled composite brazed aluminum material, and taking into account small diameter, low cost and high reliability. Utility Model Content

[0005] To overcome the shortcomings of existing technologies, this utility model provides a lap-jointed internally threaded aluminum round tube with a composite brazing layer. The technical solution of this utility model is as follows:

[0006] A composite brazed layer lap-type internally threaded aluminum round tube includes a tubular body (1) formed by embossing and rolling a cold-rolled aluminum strip with a brazed layer. An lap portion is provided on the tubular body (1) along the axial direction of the tubular body (1). The lap portion includes an upper slope (2) and a lower slope (3). The upper slope (2) covers the outside of the lower slope (3). The upper slope (2) and the lower slope (3) are stacked in a staggered manner to form a stepped lap surface (4). After the tube body is expanded, the upper slope (2) and the lower slope (3) are tightly fitted to form a self-locking sealing structure. The upper slope is formed on one side edge of the cold-rolled aluminum strip with a brazed layer, and the lower slope is formed on the other side edge.

[0007] The angle α between the upper slope (2) and the inner wall plane of the tubular body is 30°-60°, and the angle β between the lower slope (3) and the tube wall plane is 30°-60°. The coverage width W1 of the upper slope (2) and the width W2 of the lower slope (3) satisfy: W1 / W2=1.2-1.8.

[0008] The overlap length L of the stepped lap surface (4) is 0.3-1.2mm, and the thickness T of the lap area and the wall thickness t satisfy: T / t=1.8-2.5.

[0009] The outer diameter of the tubular body is 4-20mm, the wall thickness is 0.2-0.8mm, and when the outer diameter is ≤8mm, the overlap length L of the joint is ≤0.6mm.

[0010] The lower slope (3) has a downwardly bent limiting protrusion (21) at its end, and the upper slope (2) has a limiting groove (31) at its starting end to limit the limiting protrusion (21).

[0011] The outer wall of the tubular body (1) is covered with a brazing layer.

[0012] The advantages of this utility model are:

[0013] 1. Integrated molding completely eliminates the high-frequency welding step, eliminating defects such as weld buildup, weld spatter, and aluminum chips, significantly reducing energy consumption and equipment investment, and is especially suitable for small-diameter mass production.

[0014] 2. Reliable structure and improved performance: The sloping staggered lap joint increases the joint area, and after internal expansion, a dense metallurgical bond is formed. The weld strength is close to that of the base material, the pipe wall thickness is uniform, and the pressure resistance and corrosion resistance are better than traditional extruded aluminum pipes. In addition, the pipe wall lap joint can extend freely, and the thread is no longer affected by extrusion deformation during the expansion process, resulting in higher heat exchange efficiency.

[0015] 3. High material utilization and strong adaptability: Cold-rolled aluminum strip is continuously rolled and formed, with no chip loss; the overlap width can be flexibly adjusted according to the pipe diameter, and multiple specifications can be quickly switched on the same production line to meet the development needs of lightweight and diversified air conditioners. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the main structure of this utility model.

[0017] Figure 2 This is a schematic diagram of the cold-rolled aluminum strip forming process of this utility model.

[0018] Figure 3 This is a first state diagram during the processing of this utility model.

[0019] Figure 4This is a second state diagram during the processing of this utility model.

[0020] Figure 5 This is the third state diagram during the processing of this utility model.

[0021] Figure 6 This is the fourth state diagram during the processing of this utility model.

[0022] Figure 7 This is the fifth state diagram during the processing of this utility model. Detailed Implementation

[0023] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer as a result of the description. However, these embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solution of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope of the present invention.

[0024] See Figures 1 to 7 This utility model relates to an overlapping internally threaded aluminum round tube with a composite brazing layer, comprising a tubular body 1 formed by embossing and rolling a cold-rolled aluminum strip with a composite brazing layer. An overlapping portion is provided on the tubular body 1 along its axial direction. The overlapping portion includes an upper slope 2 and a lower slope 3, with the upper slope 2 covering the outside of the lower slope 3. The upper slope 2 and lower slope 3 are staggered and stacked to form a stepped overlapping surface 4. After the tube body expands, the upper slope 2 and lower slope 3 are tightly fitted to form a self-locking sealing structure. The upper slope is formed on one side of the cold-rolled aluminum strip with the composite brazing layer, and the lower slope is formed on the other side. The outer wall of the tubular body 1 is coated with a brazing layer, while the inner wall is not coated with a brazing layer.

[0025] Based on the above structural design, the following advantages are achieved:

[0026] 1. The upper and lower sloping surfaces are staggered and stacked to form a stepped lap joint. When the tube expands, the two sloping surfaces are wedge-tightened and self-locked under the action of radial force, which not only eliminates the micro-gap leakage common in high-frequency welds, but also makes the contact stress at the joint evenly distributed.

[0027] 2. The cold-rolled composite aluminum strip with brazed layer is reinforced by embossing before rolling. After tube expansion, the overlap area achieves a dual metallurgical-mechanical bond with the base material, resulting in a local increase in actual wall thickness. At the same time, there is no weld slag residue, and the risk of electrochemical corrosion is greatly reduced.

[0028] 3. The overlap width can be linearly scaled with the pipe diameter, the slope angle is formed in one step by the mold, and the internal thread can be directly rolled onto the aluminum strip surface before pipe making, effectively improving the heat transfer coefficient.

[0029] 4. It eliminates the need for high-frequency welding equipment, welding wire, and shielding gas consumption, thus shortening the production line cycle time.

[0030] The angle α between the upper slope surface 2 and the inner wall plane of the tubular body is 30°-60°, and the angle β between the lower slope surface 3 and the tube wall plane is 30°-60°. The coverage width W1 of the upper slope surface 2 and the width W2 of the lower slope surface 3 satisfy: W1 / W2=1.2-1.8.

[0031] Under the aforementioned angle and width ratio constraints, the following advantages are achieved:

[0032] The coordinated design of the slope angle and width ratio allows the overlapping surface to quickly wedge and self-lock during tube expansion, while also evenly distributing stress, taking into account sealing, strength and forming stability, which is significantly better than fixed width or single-angle structures.

[0033] The overlap length L of the stepped lap surface 4 is 0.3-1.2mm, and the thickness T of the lap area and the wall thickness t satisfy: T / t=1.8-2.5.

[0034] The outer diameter of the tubular body is 4-20mm, the wall thickness is 0.2-0.8mm, and when the outer diameter is ≤8mm, the overlap length L of the joint is ≤0.6mm.

[0035] The stepped overlap with local thickening achieves "thin-walled high strength" across the entire range of micro-tubes and large-diameter tubes: after tube expansion, the joint area forms a self-reinforcing ring, which avoids bulging and ensures roundness; the smaller the outer diameter, the shorter the overlap, the more precise the seal, zero material waste, one-time molding process, and significant yield and cost advantages.

[0036] The lower slope surface 3 has a downwardly bent limiting protrusion 21 at its end, and the upper slope surface 2 has a limiting groove 31 at its starting end to limit the limiting protrusion 21. The limiting protrusion and the limiting groove interlock, automatically centering and positioning during rolling to prevent overlapping and slippage; during tube expansion, the protrusion embeds into the groove to form a mechanical lock, further enhancing axial and circumferential shear resistance, and significantly improving assembly efficiency and joint reliability.

[0037] The working principle of this utility model is as follows:

[0038] 1. Embossed cold-rolled composite brazed aluminum strip: Embossed aluminum strip is formed by one-time roll forming: the two sides are respectively formed with an upper slope surface (with limiting groove) and a lower slope surface (with limiting protrusion), and the surface is simultaneously pressed with internal threads. Figure 2 ).

[0039] 2. Rolling into a tube: The embossed aluminum strip is wound into a round tube, so that the upper and lower slopes gradually approach each other ( Figures 3-6 ).

[0040] 3. Expansion and self-locking: The upper slope surface covers the outer side of the lower slope surface, and the limiting protrusion is embedded in the limiting groove to complete positioning. Radial expansion of the tubular body is then performed, and the upper and lower slope surfaces wedge tightly together, forming a self-locking sealing structure with a stepped overlapping surface. Figure 7 ).

[0041] 4. Sizing and cutting: After being rounded by a sizing die, the product is cut online to obtain the final product.

[0042] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. A composite brazed layer lap-jointed internally threaded aluminum round tube, comprising a tubular body (1) formed by embossing and rolling a cold-rolled aluminum strip with a brazed layer, characterized in that, On the tubular body (1), an overlapping part is provided along the axial direction of the tubular body (1); the overlapping part includes an upper slope surface (2) and a lower slope surface (3), the upper slope surface (2) covers the outside of the lower slope surface (3), the upper slope surface (2) and the lower slope surface (3) are stacked in a staggered manner to form a stepped overlapping surface (4), after the tubular body expands, the upper slope surface (2) and the lower slope surface (3) are tightly fitted to form a self-locking sealing structure; wherein, one side edge of the cold-rolled aluminum strip with a brazing layer forms the upper slope surface, and the other side edge forms the lower slope surface.

2. The lap-jointed internally threaded aluminum round tube with a composite brazing layer according to claim 1, characterized in that, The angle α between the upper slope (2) and the inner wall plane of the tubular body is 30°-60°, and the angle β between the lower slope (3) and the tube wall plane is 30°-60°. The coverage width W1 of the upper slope (2) and the width W2 of the lower slope (3) satisfy: W1 / W2=1.2-1.

8.

3. The lap-jointed internally threaded aluminum round tube with a composite brazing layer according to claim 1, characterized in that: The overlap length L of the stepped lap surface (4) is 0.3-1.2mm, and the thickness T of the lap area and the wall thickness t satisfy: T / t=1.8-2.

5.

4. The lap-jointed internally threaded aluminum round tube with a composite brazing layer according to claim 1, characterized in that: The outer diameter of the tubular body is 4-20mm, the wall thickness is 0.2-0.8mm, and when the outer diameter is ≤8mm, the overlap length L of the joint is ≤0.6mm.

5. The lap-jointed internally threaded aluminum round tube with a composite brazing layer according to claim 1, characterized in that, The lower slope (3) has a downwardly bent limiting protrusion (21) at its end, and the upper slope (2) has a limiting groove (31) at its starting end to limit the limiting protrusion (21).

6. The lap-jointed internally threaded aluminum round tube with a brazed layer as described in claim 1 or 5, characterized in that, The outer wall of the tubular body (1) is covered with a brazing layer.

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