A method of welding an aluminium alloy profile

Abstract

The application discloses a welding method of aluminum alloy profiles, which comprises a top forging step and a welding step. In the top forging step, a small current is passed and a large pressure is applied, so as to form a conductive boss in the welding area of the first profile, and the first profile is forced to separate from the second profile, and only the conductive boss is in contact with the second profile. In the welding step, a large current is passed to increase the current density, and a small pressure is applied to avoid the wear of the electrode head and the excessive extrusion of the conductive boss, so as to keep the conduction through the conductive boss only. The size of the second conduction path limited by the conductive boss is small, which plays a role in forcibly concentrating the current, reduces the influence caused by the corrosion and wear of the end surface of the electrode cap, increases the current density and welding heat of the welding area, improves the stability and reliability of the welding, and improves the quality of the welding product.

Description

Technical Field

[0001] This invention relates to the field of profile welding technology, and in particular to a welding method for aluminum alloy profiles. Background Technology

[0002] Aluminum alloys have high electrical conductivity and heat dissipation. When spot welding aluminum alloy sheets, the resulting electrical path is too large, making it difficult to concentrate heat. Only by rapidly applying a very large current for a short time can a qualified weld be formed.

[0003] like Figure 1-3 As shown, the existing method for welding aluminum alloy sheets involves stacking two aluminum alloy sheets 1', placing two electrode caps 2' on the upper and lower sides of the two sheets 1', and then applying a constant pressure or clamping force F. A large current is applied to the two electrode caps 2' to initiate welding, with the current path 3' determined by the area of ​​the ends of the electrode caps 2'. Aluminum alloys (e.g., copper-aluminum) undergo a eutectic reaction at high temperatures, forming metallic compounds. Therefore, after welding a certain number of points on the electrode caps 2', a compound layer 21' (e.g., a copper-aluminum compound layer) will cover the middle of its end face, and it will lose its curvature, becoming flat. The compound layer 21' has high resistance, and its accumulation in the middle of the electrode caps 2' hinders current flow, resulting in a decrease in current in the central welding area. The presence of the compound layer 21′ makes the end face of the electrode cap 2′ relatively flat compared to before, resulting in a larger area being pressed together during spot welding. As a result, the current path 3′ becomes larger. The central region 31′ of the current path 3′ suffers from a severe lack of current density due to the presence of the compound layer 21′. The surrounding region 32′ around the central region 31′ also experiences a reduction in current density due to the increased size of the current path 3′. This leads to insufficient current density and insufficient welding heat in the welding area, resulting in poor quality and instability of the aluminum alloy spot welding. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a welding method for aluminum alloy profiles, including an upsetting step and a welding step. In the upsetting step, a small current is passed through and a large pressure is applied, thereby forming a conductive boss in the welding area of ​​the first profile. This allows for the forced concentration of current in the welding step, reducing the impact of corrosion and wear on the end face of the electrode cap, greatly improving the stability and reliability of the welding, and enhancing the quality of the welded products.

[0005] The present invention provides a welding method for aluminum alloy profiles, comprising the following steps:

[0006] The steps for arranging the profiles are as follows: stack the first profile and the second profile in a predetermined position; the steps for arranging the electrode caps are as follows: assemble the first electrode cap on the top surface of the first profile and assemble the second electrode cap on the bottom surface of the second profile;

[0007] Upsetting step: The first electrode cap and the second electrode cap are energized and clamp the first profile and the second profile;

[0008] By pressing the first profile with the first electrode cap, the area of ​​the first profile pressed by the first electrode cap bends and protrudes towards the second profile and forms a conductive protrusion. At the same time, the first profile and the second profile are forcibly separated to form a gap, with only the conductive protrusion in contact with the second profile.

[0009] Welding steps: Increase the current and decrease the clamping force. The current passes through the conductive boss, and the first profile and the second profile are welded together.

[0010] In one of the alternative technical solutions, a shaping step is also included: reducing the current and increasing the clamping force, clamping the welding area of ​​the first profile and the second profile with the first electrode cap and the second electrode cap, thereby completing the shaping of the welding area.

[0011] In one of the alternative technical solutions, the ends of the first electrode cap and the second electrode cap are both spherical caps, and the cross-section of the conductive protrusion is arc-shaped.

[0012] In one of the alternative technical solutions, during the upsetting step, the pressure acting on the first profile is F1, the current is I1, and the duration is T1;

[0013] In the welding step, the pressure acting on the first profile is F2, the current is I2, and the duration is T2, where F2 < F1, I2 > I1, and T2 > T1.

[0014] In one of the alternative technical solutions, during the upsetting step, the pressure acting on the first profile is F1, the current is I1, and the duration is T1;

[0015] In the welding step, the pressure acting on the first profile is F2, the current is I2, and the duration is T2, where F2 < F1, I2 > I1, and T2 > T1.

[0016] In the shaping step, the pressure acting on the first profile is F3, the current is I3, and the duration is T3, where F3 > F2 and I3 < I2.

[0017] In one of the alternative technical solutions, F3 = F1, I3 = I1, and T3 = T1.

[0018] In one of the alternative technical solutions, the thickness of the first profile is between 0.8 and 4 mm;

[0019] The value range of F1 is 3 to 12 kN, the value range of I1 is 20 to 50 kA, and the value range of T1 is 60 to 100 mS.

[0020] In one of the optional technical solutions, the value of F2 ranges from 2 to 9 kN, the value of I2 ranges from 25 to 55 kA, and the value of T2 ranges from 100 to 160 mS.

[0021] In one of the alternative technical solutions, the first electrode cap and the second electrode cap are spot welded together.

[0022] In one of the alternative technical solutions, during the electrode cap arrangement step, the second electrode cap is arranged coaxially with the first electrode cap.

[0023] The above technical solution has the following beneficial effects:

[0024] The welding method for aluminum alloy profiles provided by this invention includes an upsetting step and a welding step. In the upsetting step, a small current is applied and a large pressure is applied to form a conductive boss in the welding area of ​​the first profile, while forcibly separating the first profile from the second profile, with only the conductive boss in contact with the second profile. In the welding step, a large current is applied to increase the current density, and a small pressure is applied to avoid wear on the electrode head and excessive compression of the conductive boss, ensuring that conductivity is maintained only through the conductive boss. The size of the second current path formed by the conductive boss is small, which plays a role in forcibly concentrating the current, reducing the impact of corrosion and wear on the end face of the electrode cap, increasing the current density and welding heat in the welding area, improving the stability and reliability of the welding, and enhancing the quality of the welded product. Attached Figure Description

[0025] The disclosure of this invention will become more readily understood by referring to the accompanying drawings. It should be understood that these drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings:

[0026] Figure 1 This is a schematic diagram of the current path formed between two electrode caps when welding aluminum alloy profiles in the prior art;

[0027] Figure 2 This is a schematic diagram illustrating how the formation of a compound layer at the end of the electrode cap in the prior art results in insufficient current density in the middle part of the current path.

[0028] Figure 3 This is a schematic diagram of the current curve and pressure curve when welding aluminum alloy profiles in the prior art;

[0029] Figure 4A schematic diagram of an electrical path formed between a first electrode cap and a second electrode cap during the upsetting stage of a welding method for aluminum alloy profiles provided in an embodiment of the present invention.

[0030] Figure 5 A schematic diagram of a welding method for aluminum alloy profiles provided in an embodiment of the present invention, wherein a first profile is formed with a downwardly protruding conductive boss during the upsetting stage;

[0031] Figure 6 This is a schematic diagram of a welding method for aluminum alloy profiles provided in an embodiment of the present invention, showing the current-carrying path formed between the first electrode cap and the second electrode cap during the welding stage.

[0032] Figure 7 This is a schematic diagram of the current and pressure curves during the upsetting, welding, and shaping stages of a welding method for aluminum alloy profiles provided in an embodiment of the present invention. Detailed Implementation

[0033] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. Identical components are indicated by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, while the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0034] like Figure 4-7 As shown, an embodiment of the present invention provides a welding method for aluminum alloy profiles, comprising the following steps:

[0035] The steps for arranging the profiles are as follows: Stack the first profile 1 and the second profile 2 in the predetermined position.

[0036] Electrode cap arrangement steps: assemble the first electrode cap 3 onto the top surface of the first profile 1, and assemble the second electrode cap 4 onto the bottom surface of the second profile 2.

[0037] Upsetting step: The first electrode cap 3 and the second electrode cap 4 are energized and clamp the first profile 1 and the second profile 2.

[0038] The first electrode cap 3 presses against the first profile 1, causing the area of ​​the first profile 1 pressed by the first electrode cap 3 to bend and protrude toward the second profile 2 and form a conductive protrusion 11. At the same time, the first profile 1 and the second profile 2 are forcibly separated to form a gap, with only the conductive protrusion 11 in contact with the second profile 2.

[0039] Welding steps: Increase the current and decrease the clamping force. The current passes through the conductive boss 11, and the first profile 1 and the second profile 2 are welded together.

[0040] The welding method provided by this invention is mainly used for welding aluminum alloy profiles (sheets) on vehicle bodies, such as aluminum-copper profiles. The thickness of the aluminum alloy profiles (sheets) on the vehicle body is generally less than 5mm.

[0041] Welding is performed using existing welding fixtures and a servo welding system with variable pressure and current.

[0042] Before the actual welding, the profiles and electrode caps should be positioned as follows:

[0043] The first profile 1 and the second profile 2 are stacked in a preset position on the welding fixture. For example, they are placed on the operating platform of the welding fixture. Limiting plates or limiting blocks can be arranged at both ends of the operating platform. The limiting plates or limiting blocks have upward-opening sliding grooves. The two ends of the first profile 1 and the second profile 2 are placed in the sliding grooves. When the first profile 1 forms a downward conductive protrusion 11, the main body of the first profile 1 (except for the area of ​​the conductive protrusion 11) is lifted by the conductive protrusion 11, thereby separating it from the second profile 2 to form a gap and avoid contact to disperse the current density.

[0044] The first profile 1 is positioned above the second profile 2, and the two are attached together.

[0045] Two electrode caps are used. The electrode caps are components of the servo welding system. The current can be adjusted by a current regulator (e.g., a variable resistor) in the servo welding system. The clamping force or pressure can be adjusted by two clamping arms with two electrode caps installed.

[0046] After arranging the first profile 1 and the second profile 2, the first electrode cap 3 is fitted onto the top surface of the first profile 1, with its end abutting against the top surface of the welding area of ​​the first profile 1. The second electrode cap 4 is fitted onto the bottom surface of the second profile 2, with its end abutting against the bottom surface of the welding area of ​​the second profile 2. The second electrode cap 4 is positioned below the first electrode cap 3, forming a first electrical path 5 between them. The radius / area of ​​the first electrical path 5 is larger than the radius / area of ​​the contact area between the first electrode cap 3 / second electrode cap 4 and the first profile 1 / second profile 2. When the first electrode cap 3 and the second electrode cap 4 clamp the profiles, they can be moved and clamped simultaneously, or the second electrode cap 4 can be kept fixed, and the first electrode cap 3 can be moved only towards the second electrode cap 4.

[0047] After energization, the process is divided into an upsetting stage and a welding stage. The purpose of the upsetting stage is to first apply a small current and a large pressure, thereby forming a conductive boss 11 that bends and protrudes towards the second profile 2 in the welding area of ​​the first profile 1. Simultaneously, under the action of the conductive boss 11, the first profile 1 and the second profile 2 are forcibly separated. The main body of the first profile 1 (excluding the area with the conductive boss 11) is lifted by the conductive boss 11, thus separating it from the second profile 2 and forming a gap to avoid contact and disperse the current density. At this point, only the conductive boss 11 is in contact with the second profile 2. The second energizing path 6 between the second electrode cap 4 and the first electrode cap 3 is constrained by the conductive boss 11. The radius / area of ​​the second energizing path 6 is smaller than the radius / area of ​​the first energizing path 5, which facilitates increasing the current density in the welding area and enhancing the welding heat during subsequent welding.

[0048] During the welding stage, a large current is applied to increase the current density, while a small pressure is applied to avoid wear on the electrode cap and to prevent excessive compression of the conductive boss 11. At the same time, the first profile 1 and the second profile 2 are not pressed together. At this time, the conductivity is only achieved through the conductive boss 11. The conductive boss 11 limits the size of the second current path 6 formed by the second current path 6 to a small size, which plays a role in forcibly concentrating the current. This reduces the impact of corrosion and wear on the end face of the electrode cap, increases the current density and welding heat in the welding area, improves the stability and reliability of the welding, and enhances the quality of the welded product.

[0049] In one embodiment, the thickness of the first profile 1 is less than or equal to the thickness of the second profile 2. The thickness of the first profile 1 is not greater than the thickness of the second profile 2. Preferably, the thickness of the first profile 1 is less than the thickness of the second profile 2, and the first profile 1 is thinner than the second profile 2, so that it is easier to deform under heat and pressure, thereby forming the conductive protrusion 11.

[0050] In one embodiment, such as Figure 7 As shown, the welding method of the aluminum alloy profile also includes a shaping step: reducing the current and increasing the clamping force, clamping the welding area of ​​the first profile 1 and the second profile 2 by the first electrode cap 3 and the second electrode cap 4, and completing the shaping of the welding area.

[0051] In this embodiment, a shaping stage is added after the welding stage. Due to the large coefficient of thermal expansion of aluminum, a small current and high pressure are used for forced shaping in the later stage of welding, which improves the density of the welded area. Otherwise, defects such as shrinkage cavities are prone to occur at the weld joint, resulting in insufficient strength.

[0052] In one embodiment, such as Figure 4-6 As shown, the ends of the first electrode cap 3 and the second electrode cap 4 are both spherical caps, and the cross-section of the conductive protrusion 11 is arc-shaped.

[0053] In this embodiment, the first electrode cap 3 and the second electrode cap 4 respectively include a cylindrical main body and a spherical crown or spherical crown portion connected to the end of the main body. The spherical crown or spherical crown portion is a small part of a sphere, and its surface is part of a spherical surface. On the one hand, it can reduce the area / radius of the first power path 5. On the other hand, it makes the cross-section of the curved and convex conductive protrusion 11 approximately arc-shaped, and the bottom surface is curved rather than flat. Its contact area with the second profile 2 is small, so the area / radius of the second power path 6 can be reduced.

[0054] In one embodiment, during the upsetting step, the pressure acting on the first profile 1 is F1, the current is I1, and the duration is T1.

[0055] During the welding process, the pressure acting on the first profile 1 is F2, the current is I2, and the duration is T2, where F2 < F1, I2 > I1, and T2 > T1.

[0056] In this embodiment, the current I1 in the upsetting stage is less than the current I2 in the welding stage, while the pressure F1 in the upsetting stage is greater than the pressure F2 in the welding stage. The purpose of applying a small current and a large pressure in the upsetting stage is to cause local deformation of the welding area of ​​the first profile 1, so that it bends and protrudes downwards when the first electrode cap 3 is pressed down. The purpose of applying a large current and a small pressure in the welding stage is to increase the current density and welding heat, while avoiding wear on the electrode head due to excessive pressure, avoiding flattening the conductive protrusion 11 due to excessive pressure, thus increasing its area / radius and dispersing the current density, and also avoiding pressing the first profile 1 and the second profile 2 into contact due to excessive pressure, which would severely disperse the current density. The welding stage time T2 is longer than the upsetting stage time T1 to achieve more complete welding.

[0057] In one embodiment, during the upsetting step, the pressure acting on the first profile 1 is F1, the current is I1, and the duration is T1.

[0058] During the welding process, the pressure acting on the first profile 1 is F2, the current is I2, and the duration is T2, where F2 < F1, I2 > I1, and T2 > T1.

[0059] In the shaping step, the pressure acting on the first profile 1 is F3, the current is I3, and the duration is T3, where F3 > F2 and I3 < I2.

[0060] In this embodiment, a shaping stage is added after the aforementioned upsetting and welding stages. The current I3 in the shaping stage is less than the current I2 in the welding stage to maintain a certain amount of heat without further welding. The pressure F3 in the shaping stage is greater than the pressure F2 in the welding stage, using greater pressure or clamping force to ensure the density of the welded area.

[0061] In one embodiment, F3 = F1, I3 = I1, and T3 = T1. In this embodiment, the parameters of the forming stage can be referenced from the parameters of the upsetting stage.

[0062] In one embodiment, the thickness of the first profile 1 is between 0.8 and 4 mm.

[0063] The value range of F1 is 3 to 12 kN, the value range of I1 is 20 to 50 kA, and the value range of T1 is 60 to 100 mS.

[0064] In this embodiment, if the thickness of the first profile 1 is between 0.8 and 4 mm, then F1 can be taken in the range of 3 to 12 kN, I1 can be taken in the range of 20 to 50 kA, and T1 can be taken in the range of 60 to 100 ms.

[0065] In one embodiment, the value of F2 ranges from 2 to 9 kN, the value of I2 ranges from 25 to 55 kA, and the value of T2 ranges from 100 to 160 mS.

[0066] In this embodiment, if the thickness of the first profile 1 is between 0.8 and 4 mm, then F2 can be taken in the range of 2 to 9 kN, I2 can be taken in the range of 25 to 55 kN, and T2 can be taken in the range of 100 to 160 ms. During this stage, F2 < F1, I2 > I1, and T2 > T1 should be maintained.

[0067] In one embodiment, the first electrode cap 3 and the second electrode cap 4 are spot welded together to reduce wear on the electrode caps.

[0068] In one embodiment, during the electrode cap arrangement step, the second electrode cap 4 and the first electrode cap 3 are arranged coaxially, so that the current-carrying path between the second electrode cap 4 and the first electrode cap 3 passes perpendicularly, the path is the shortest, the area or radius of the current-carrying path is the smallest, and the clamping force or pressure of the second electrode cap 4 and the first electrode cap 3 are concentrated together, which is beneficial to improving the welding quality.

[0069] As needed, the above technical solutions can be combined to achieve the best technical effect.

[0070] The above are merely the principles and preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several other modifications can be made based on the principles of the present invention, and these modifications should also be considered within the scope of protection of the present invention.

Claims

1. A welding method for aluminum alloy profiles, characterized in that, Includes the following steps: The steps for arranging the profiles are as follows: Stack the first profile and the second profile in the predetermined position; Electrode cap arrangement steps: assemble the first electrode cap on the top surface of the first profile and assemble the second electrode cap on the bottom surface of the second profile; a first electrical path will be formed between the second electrode cap and the first electrode cap, wherein the radius / area of ​​the first electrical path is larger than the radius / area of ​​the contact between the first electrode cap / second electrode cap and the first profile / second profile; Upsetting step: The first electrode cap and the second electrode cap are energized and a large pressure is applied to clamp the first profile and the second profile; the first electrode cap presses against the first profile, causing the area of ​​the first profile pressed by the first electrode cap to bend and protrude towards the second profile and form a conductive boss, while forcibly separating the first profile and the second profile to form a gap, with only the conductive boss in contact with the second profile; Welding steps: Increase the current and decrease the clamping force. The current passes through the conductive protrusion. The second current path between the second electrode cap and the first electrode cap is limited by the conductive protrusion. The radius / area of ​​the second current path is smaller than that of the first current path to forcibly concentrate the current, increase the current density in the welding area and increase the welding heat, and weld the first profile and the second profile together.

2. The welding method for aluminum alloy profiles according to claim 1, characterized in that, It also includes a shaping step: reducing the current and increasing the clamping force, clamping the welding area of ​​the first profile and the second profile with the first electrode cap and the second electrode cap, and completing the shaping of the welding area.

3. The welding method for aluminum alloy profiles according to claim 1 or 2, characterized in that, The ends of both the first electrode cap and the second electrode cap are spherical caps, and the cross-section of the conductive protrusion is arc-shaped.

4. The welding method for aluminum alloy profiles according to claim 1, characterized in that, In the upsetting step, the pressure acting on the first profile is F1, the current is I1, and the duration is T1; In the welding step, the pressure acting on the first profile is F2, the current is I2, and the duration is T2, where F2 < F1, I2 > I1, and T2 > T1.

5. The welding method for aluminum alloy profiles according to claim 2, characterized in that, In the upsetting step, the pressure acting on the first profile is F1, the current is I1, and the duration is T1; In the welding step, the pressure acting on the first profile is F2, the current is I2, and the duration is T2, where F2 < F1, I2 > I1, and T2 > T1; In the shaping step, the pressure acting on the first profile is F3, the current is I3, and the duration is T3, where F3 > F2 and I3 < I2.

6. The welding method for aluminum alloy profiles according to claim 5, characterized in that, F3=F1, I3=I1, T3= T1.

7. The welding method for aluminum alloy profiles according to claim 4 or 5, characterized in that, The thickness of the first profile is between 0.8 and 4 mm; The value range of F1 is 3~12kN, the value range of I1 is 20~50kA, and the value range of T1 is 60~100ms.

8. The welding method for aluminum alloy profiles according to claim 7, characterized in that, The value range of F2 is 2~9kN, the value range of I2 is 25~55kA, and the value range of T2 is 100~160ms.

9. The welding method for aluminum alloy profiles according to claim 1, characterized in that, The first electrode cap and the second electrode cap are spot welded together.

10. The welding method for aluminum alloy profiles according to claim 1, characterized in that, In the electrode cap arrangement step, the second electrode cap is arranged coaxially with the first electrode cap.

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