Aluminum alloy door and window welding method

Abstract

The application discloses a kind of aluminum alloy door and window welding methods, including step one, profile polishing oil pretreatment, step two, fixed clamping and control joint gap and diagonal line deviation, step three, high-frequency induction gradient preheating, step four, ultrasonic wave auxiliary friction stir welding, step five, controllable cooling and heat treatment after welding;The application reduces the deformation resistance of aluminum alloy by electromagnetic induction preheating, combines the cavitation effect and acoustic streaming effect of ultrasonic wave, effectively avoids the generation of oxide film in the welding process, refines the dynamic recrystallization grain, solves the technical problems of large thermal deformation, easy to produce hole and crack in traditional welding method, greatly improves the corner connection strength and air-tight / water-tight performance of aluminum alloy door and window.

Description

Technical Field

[0001] This invention relates to the field of door and window manufacturing technology, and in particular to a welding method for aluminum alloy doors and windows. Background Technology

[0002] Aluminum alloy doors and windows are widely used in modern buildings due to their advantages such as light weight, corrosion resistance, and high strength. Traditional aluminum alloy connection methods mostly use mechanical riveting or corner bracket splicing, but after being subjected to large wind pressure or long-term use, the connection is prone to loosening and deformation, resulting in a decrease in air tightness and water tightness.

[0003] Currently, for long straight welds or corner welds of aluminum alloys, the commonly used welding methods are gas metal arc welding (GMAW) and friction stir welding. The former has a large heat input, which can easily lead to severe thermal warping deformation of aluminum alloy profiles, and the weld surface is prone to fish scale pattern, affecting the appearance. It usually requires a lot of grinding and correction work. Although the latter is a solid-state welding with small thermal deformation, when welding aluminum alloys (especially 6-series aluminum alloys), due to the poor plasticity of the material, it is easy to produce defects such as "incomplete penetration" and "tunnel-type holes". In addition, the large axial upsetting force may cause instability of thin-walled profiles. Therefore, this invention proposes a welding method for aluminum alloy doors and windows to solve the problems existing in the prior art. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to propose a welding method for aluminum alloy doors and windows. This welding method reduces the deformation resistance of aluminum alloys through electromagnetic induction preheating, and effectively avoids the formation of oxide films during the welding process by combining the cavitation and acoustic flow effects of ultrasound. It also refines the dynamic recrystallized grains, solving the technical problems of large thermal deformation and easy formation of holes and cracks in traditional welding methods. This significantly improves the corner connection strength and airtight / watertight performance of aluminum alloy doors and windows.

[0005] To achieve the objectives of this invention, the invention is implemented through the following technical solution: a welding method for aluminum alloy doors and windows, comprising the following steps:

[0006] Step 1: Chemically clean and mechanically grind the areas of the aluminum alloy door and window profiles to be welded to remove oil and surface oxide layers.

[0007] Step 2: After the profiles are joined together, fix them on the tooling fixture and control the gap and diagonal deviation;

[0008] Step 3: Use a high-frequency induction heating device to perform non-contact gradient preheating on the area of ​​the aluminum alloy profile to be welded;

[0009] Step 4: Start the friction stir welding spindle and simultaneously turn on the ultrasonic generator so that the stirring head can weld the preheated aluminum alloy profile under the assistance of ultrasonic vibration. When the welding is finished, the stirring head is withdrawn using a stepped decompression method.

[0010] Step 5: After welding, the weld area is subjected to controlled cooling treatment, and finally heat treatment is performed to obtain the welded aluminum alloy doors and windows.

[0011] Further improvements are made in the following: In step one, mechanical grinding is performed using a stainless steel wire brush or a carbide rotary file until a metallic luster is exposed, and the grinding width is not less than 20mm on each side of the bevel.

[0012] Further improvements include: applying an anti-oxidation protective agent to the back of the welding groove in step two; controlling the butt joint gap to be ≤0.2mm and the diagonal deviation to be ≤0.4mm during fixing.

[0013] The further improvement is that: in step three, the non-contact gradient preheating is specifically controlled by controlling the relative position of the high-frequency induction coil and the welding spindle, so that the induction coil is always located 50-100mm in front of the stirring head in the forward direction. By adjusting the output power of the high-frequency induction heating device, the temperature of the base material in the welding area is maintained between 150℃ and 250℃.

[0014] The high-frequency induction heating device outputs a current frequency of 10kHz-50kHz and adopts a pulse heating mode with a duty cycle of 20%-80% and a pulse heating modulation frequency of 5Hz-20Hz. By adjusting the ratio of current conduction and cutoff time, the induction coil maintains an intermittent working state during the heating process.

[0015] A further improvement is that: in step four, the frequency of the ultrasonic wave during ultrasonic vibration assistance is set to 20kHz-40kHz, and the output power is 500W-2000W.

[0016] The direction of ultrasonic vibration is coaxial with the axis of the friction stir welding spindle, and the ultrasonic vibration is turned on 0.5s-1s before the stirring head contacts the surface of the aluminum alloy profile and turned off 0.5s-1s after the stirring head is completely withdrawn from the material.

[0017] Further improvements are made in the following: in step four, the parameters for friction stir welding are controlled as follows: the spindle speed is controlled between 800-1500 rpm, the welding speed is controlled between 100-400 mm / min, and the axial welding pressure is controlled between 3000-6000 N.

[0018] During the welding process, an inert gas is continuously applied to the interface between the stirring head and the material for protection. The inert gas is selected from one or more combinations of nitrogen or argon, and the gas flow rate is 10-25 L / min.

[0019] When the inert gas is a mixture of nitrogen and argon, the volume ratio is 7-8:2-3.

[0020] The further improvement is as follows: In step four, the step-by-step pressure reduction method is specifically implemented by keeping the ultrasonic vibration on when the welding reaches the end point, linearly reducing the axial pressure from the first preset value to the second preset value, maintaining the second preset value pressure for 0.5-2 seconds, and then lifting the stirring head away from the workpiece, wherein the second preset value is 20%-40% of the first preset value.

[0021] A further improvement is that the controllable cooling treatment in step five specifically involves covering the weld and its heat-affected zone with heat insulation material within 3 minutes after welding, controlling the cooling rate of the weld area to not exceed 15℃ / min, until the temperature drops below 100℃.

[0022] The further improvement is that the heat treatment in step five specifically involves placing the welded door and window frame as a whole into an aging furnace for artificial aging treatment at an aging temperature of 160℃-180℃ and a holding time of 2h-4h.

[0023] The beneficial effects of the present invention are as follows: The present invention effectively eliminates the thermal stress concentration in the thick-thin transition zone by high-frequency induction gradient preheating, fundamentally suppressing the warping deformation of the profile. At the same time, the acoustic flow effect and cavitation effect generated by ultrasonic-assisted stir friction welding avoid the alumina film at the fusion interface and refine the grains, which greatly improves the tensile strength of the weld and solves the hidden dangers of micropores and brittle fracture that are easy to occur in conventional welding.

[0024] Secondly, by using a stepped decompression and closed-loop temperature control slow cooling process, near-net-shape forming is achieved and a large number of grinding processes are eliminated, while significantly improving the air tightness, water tightness and wind pressure resistance of the corners of doors and windows. Attached Figure Description

[0025] Figure 1 This is a flowchart of the welding method of the present invention. Detailed Implementation

[0026] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0027] Example

[0028] according to Figure 1 As shown, this embodiment provides a welding method for aluminum alloy doors and windows, including the following steps:

[0029] Step 1: Chemically clean and mechanically grind the areas of the aluminum alloy door and window profiles to be welded to remove oil and surface oxide layers.

[0030] Mechanical grinding uses a stainless steel wire brush or a carbide rotary file to grind until the metal luster is exposed, and the grinding width is not less than 20mm on each side of the bevel.

[0031] Step 2: After the profiles are joined together, fix them on the tooling fixture and control the gap and diagonal deviation. Control the gap to 0.1mm and the diagonal deviation to 0.2mm; and apply an anti-oxidation protective agent to the back of the weld bevel.

[0032] Step 3: Use a high-frequency induction heating device to perform non-contact gradient preheating on the area of ​​the aluminum alloy profile to be welded;

[0033] Non-contact gradient preheating specifically involves controlling the relative position of the high-frequency induction coil and the welding spindle, ensuring that the induction coil is always located 80mm in front of the stirring head in the forward direction. By adjusting the output power of the high-frequency induction heating device, the temperature of the base material in the welding area is maintained between 200℃ and 210℃.

[0034] The high-frequency induction heating device outputs a current frequency of 25kHz and adopts a pulse heating mode with a duty cycle of 70% and a pulse heating modulation frequency of 15Hz. By adjusting the ratio of current conduction and cutoff time, the induction coil maintains an intermittent working state during the heating process to avoid overheating of the aluminum alloy surface due to the skin effect.

[0035] Step 4: Start the friction stir welding spindle and simultaneously turn on the ultrasonic generator so that the stirring head can weld the preheated aluminum alloy profile under the assistance of ultrasonic vibration. When the welding is finished, the stirring head is withdrawn using a stepped decompression method.

[0036] When using ultrasonic vibration assistance, the frequency of the ultrasonic wave is set to 40kHz and the output power is 1500W. The direction of ultrasonic vibration is coaxial with the axis of the friction stir welding spindle. The ultrasonic vibration is turned on 1 second before the stirring head contacts the surface of the aluminum alloy profile and turned off 0.5 seconds after the stirring head completely withdraws from the material.

[0037] Its integrated structure is that ultrasonic vibration is rigidly connected to the main shaft housing of the stirring head through a flange-type transducer. The ultrasonic vibration is transmitted to the clamping end of the stirring head through the amplitude transformer. Axial high-frequency vibration is applied while the stirring head is rotating. An insulating and heat-insulating gasket is provided between the transducer and the rotating main shaft.

[0038] The parameters for friction stir welding are: spindle speed controlled at 1500 rpm, welding speed controlled at 300 mm / min, and axial welding pressure controlled at 5000 N.

[0039] During the welding process, a nitrogen and argon mixture with a volume ratio of 7:3 is continuously applied to the interface between the stirring head and the material for protection, with a gas flow rate of 20 L / min.

[0040] The step-by-step pressure reduction method is as follows: when the welding reaches the end point, the ultrasonic vibration is kept on, the servo valve receives the PLC signal, and the pressure of the hydraulic circuit is linearly reduced from the first preset value to the second preset value. The pressure drop rate is controlled at 1000 N / s. After maintaining the second preset value pressure for 1.5s, the stirring head is lifted and removed from the workpiece. The second preset value is 35% of the first preset value.

[0041] Step 5: After welding, the weld area is subjected to controlled cooling treatment, and finally heat treatment is performed to obtain the welded aluminum alloy doors and windows;

[0042] The controlled cooling process specifically involves covering the weld and its heat-affected zone with heat insulation material within 3 minutes after welding, controlling the cooling rate of the weld area at 13℃ / min until the temperature drops below 100℃.

[0043] The heat treatment specifically involves placing the welded door and window frame as a whole into an aging furnace for artificial aging treatment at an aging temperature of 180℃ and a holding time of 2.5h.

[0044] Application examples

[0045] This application example provides a welding method for a 1.4mm thick 6063-T5 aluminum alloy sliding window frame. The specific steps are as follows:

[0046] Step 1: Profile Pretreatment

[0047] Select commercially available 6063-T5 aluminum alloy profiles and cut them into horizontal beams and vertical mullions with a length of 1500mm.

[0048] Then, use an angle grinder with louvers to mechanically grind the mating surfaces to remove the surface oxide layer, followed by wiping with anhydrous ethanol to degrease.

[0049] Step 2: Clamping and Clearance Control

[0050] The profile is placed on a gantry-type friction stir welding machine with a vacuum adsorption platform, and clamped from the inner wall of the profile using a special pneumatic clamp to ensure that the gap between the butt joints is controlled within 0.1mm and the diagonal deviation does not exceed 0.2mm.

[0051] Step 3: High-frequency induction gradient preheating

[0052] Start the high-frequency induction heating system; use a copper tube with an inner diameter of 8mm to wind an induction coil that conforms to the shape of the weld seam, and the coil cross-section is rectangular.

[0053] Spatial arrangement: The induction coil is fixed on the side of the main shaft box of the stirring head, located 80mm in front of the stirring needle in the direction of forward movement.

[0054] Parameter settings: The heating power frequency is set to 25kHz, and the output power is 3.2kW. To prevent the aluminum alloy surface from overheating instantaneously due to the skin effect, pulse heating is used with a modulation frequency of 10Hz (i.e., 10 on / off cycles per second) and a duty cycle of 60%.

[0055] Temperature control feedback: The temperature of the preheating zone is monitored in real time using an infrared thermometer, and the power is automatically adjusted through a PID algorithm to keep the preheating temperature stable at 200℃±10℃.

[0056] Step 4: Ultrasonic Assisted Friction Stir Welding

[0057] The stirring head is made of H13 hot work die steel with a shoulder diameter of 10mm and a stirring needle length of 1.2mm (with double spiral grooves). The ultrasonic transducer is rigidly connected to the main shaft housing through a flange. The lower end of the amplitude transformer is connected to the clamping end of the stirring head through an insulating and heat-insulating ceramic gasket to prevent heat back-transmission from damaging the piezoelectric ceramic.

[0058] Start the spindle and set the speed to 1000 rpm; at the same time, turn on the ultrasonic generator, set the frequency to 28 kHz and the power to 1000 W; the ultrasonic generator is turned on 0.8 seconds before the stirring head contacts the material.

[0059] The spindle presses down, and the axial pressure is precisely controlled by the electro-hydraulic servo control system. When the spindle shoulder is pressed into the material surface by 0.1mm, it begins to move at a welding speed of 200mm / min. During the welding process, nitrogen gas with a purity of 99.99% is sprayed onto the back of the weld at a flow rate of 18L / min.

[0060] When the welding reaches the end point (5mm from the edge), the PLC sends a signal, and the electro-hydraulic servo valve actuates, linearly reducing the axial pressure from the initial 4800N to 1500N (approximately 31% of the initial value) at a rate of 800N / s. After maintaining this low-pressure state for 1 second, the spindle lifts up, and the ultrasonic wave is delayed by 0.5 seconds to shut off, completing the stepped exit.

[0061] Step 5: Post-weld heat treatment

[0062] After welding, immediately cover the weld and the heat-affected zone on both sides with a ceramic fiber insulation blanket to allow it to cool naturally and slowly. The measured cooling rate was 8℃ / min. After the frame cools to room temperature, remove the clamps.

[0063] To eliminate residual welding stress and restore strength, the entire window frame was sent into an aging furnace for artificial aging treatment. The process parameters were: 170℃ for 3 hours, followed by air cooling.

[0064] The resulting window frame weld surface has a silvery-white metallic luster and is free of cracks and holes; the difference in diagonal length of the window frame is only 0.25mm, and the flatness error is 0.08mm / m.

[0065] Tensile tests were conducted on samples taken along the weld seam, and the tensile strength of the joint was measured to be 215 MPa, which is 92% of the strength of the base material (6063-T5).

[0066] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A welding method for aluminum alloy doors and windows, characterized in that, Includes the following steps: Step 1: Chemically clean and mechanically grind the areas of the aluminum alloy door and window profiles to be welded to remove oil and surface oxide layers. Step 2: After the profiles are joined together, fix them on the tooling fixture and control the gap and diagonal deviation; Step 3: Use a high-frequency induction heating device to perform non-contact gradient preheating on the area of ​​the aluminum alloy profile to be welded; Step 4: Start the friction stir welding spindle and simultaneously turn on the ultrasonic generator so that the stirring head can weld the preheated aluminum alloy profile under the assistance of ultrasonic vibration. When the welding is finished, the stirring head is withdrawn using a stepped decompression method. Step 5: After welding, the weld area is subjected to controlled cooling treatment, and finally heat treatment is performed to obtain the welded aluminum alloy doors and windows.

2. The aluminum alloy door and window welding method according to claim 1, characterized in that: In step one, mechanical polishing is performed using a stainless steel wire brush or a carbide rotary file until a metallic luster is exposed, and the polishing width is not less than 20mm on each side of the bevel.

3. The aluminum alloy door and window welding method according to claim 1, characterized in that: In step two, an anti-oxidation protective agent is applied to the back of the welding groove; during fixing, the butt joint gap is controlled to be ≤0.2mm and the diagonal deviation is controlled to be ≤0.4mm.

4. The aluminum alloy door and window welding method according to claim 1, characterized in that: In step three, the non-contact gradient preheating specifically involves controlling the relative position of the high-frequency induction coil and the welding spindle, ensuring that the induction coil is always located 50-100mm in front of the stirring head in the forward direction. By adjusting the output power of the high-frequency induction heating device, the temperature of the base material in the welding area is maintained between 150℃ and 250℃. The high-frequency induction heating device outputs a current frequency of 10kHz-50kHz and adopts a pulse heating mode with a duty cycle of 20%-80% and a pulse heating modulation frequency of 5Hz-20Hz. By adjusting the ratio of current conduction and cutoff time, the induction coil maintains an intermittent working state during the heating process.

5. The aluminum alloy door and window welding method according to claim 1, characterized in that: In step four, when ultrasonic vibration is used for assistance, the frequency of the ultrasonic wave is set to 20kHz-40kHz, and the output power is 500W-2000W. The direction of ultrasonic vibration is coaxial with the axis of the friction stir welding spindle, and the ultrasonic vibration is turned on 0.5s-1s before the stirring head contacts the surface of the aluminum alloy profile and turned off 0.5s-1s after the stirring head is completely withdrawn from the material.

6. The aluminum alloy door and window welding method according to claim 1, characterized in that: In step four, the parameters for friction stir welding are: spindle speed controlled between 800-1500 rpm, welding speed controlled between 100-400 mm / min, and axial welding pressure controlled between 3000-6000 N. During the welding process, an inert gas is continuously applied to the interface between the stirring head and the material for protection. The inert gas is selected from one or more combinations of nitrogen or argon, and the gas flow rate is 10-25 L / min. When the inert gas is a mixture of nitrogen and argon, the volume ratio is 7-8:2-3.

7. The aluminum alloy door and window welding method according to claim 1, characterized in that: The step-by-step pressure reduction method in step four specifically involves keeping the ultrasonic vibration on when the welding reaches the end point, linearly reducing the axial pressure from the first preset value to the second preset value, maintaining the second preset value pressure for 0.5-2 seconds, and then lifting the stirring head away from the workpiece. The second preset value is 20%-40% of the first preset value.

8. The aluminum alloy door and window welding method according to claim 1, characterized in that: The controlled cooling process in step five specifically involves covering the weld and its heat-affected zone with heat-insulating material within 3 minutes after welding, controlling the cooling rate of the weld area to not exceed 15℃ / min, until the temperature drops below 100℃.

9. The aluminum alloy door and window welding method according to claim 1, characterized in that: In step five, the heat treatment specifically involves placing the welded door and window frame as a whole into an aging furnace for artificial aging treatment at an aging temperature of 160℃-180℃ and a holding time of 2h-4h.

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