Method of simulated laser fusion welding of aluminum and its alloys

Abstract

The present application relates to a kind of aluminum and its alloy's imitation laser melting welding method, including workpiece welding preparation, adjusting welding parameter etc step, when first pressing welding torch switch, first pulse arc is generated between tungsten electrode and workpiece, base metal forms molten pool below tungsten electrode, welding wire is sent to the edge of molten pool, and second pulse arc is generated;When the moment of second pulse arc generation, welding torch moves forward, and welding wire tip is melted with base material to form first filling wire welding process;When again needing to press welding torch switch, welding torch needs to retreat 1-2mm again to ignite arc, and part of filling weld is re-melted;Welding wire is again sent to the edge of new molten pool, and the tip of welding wire and base material are again melted using the second second pulse arc to form second filling wire welding process;So repeatedly press welding torch switch to realize the continuous welding of long weld;Solve the difficult problem of weld forming of aluminum and its alloy below 2mm wall thickness.

Description

Technical Field

[0001] This invention belongs to the field of welding production, specifically relating to a laser-simulated melting welding method for aluminum and its alloys, which is particularly suitable for small thin-walled parts with a wall thickness of less than 2mm. Background Technology

[0002] The melting and welding of aluminum and its alloys is relatively more difficult than that of steel due to numerous problems such as oxide film, cracks, deformation, porosity, and low joint strength. In particular, the treatment of the oxide film requires rigorous pre-weld cleaning and continuous removal of the oxide film formed on the molten pool surface during welding. Because the melting point of the oxide film is much higher than that of aluminum itself, cleaning the oxide film during melting and welding of aluminum requires chemical methods or cathodic arc atomization. For gas shielded welding, the oxide film is usually cleaned using cathodic atomization, which utilizes positive ions in the arc to impact and break the oxide film. Therefore, reverse polarity is used in gas metal arc welding, while AC welding is required for non-consumable electrode welding. Currently, AC tungsten inert gas (TIG) welding of aluminum uses rectangular wave constant current or pulsed current welding with secondary inversion, which features arc stability and good weld formation. However, for welding some micro-sized and thin-walled structural components, these welding methods cannot guarantee good weld formation.

[0003] For welding thin metal parts, a laser-like welding process is currently popular. This is a discontinuous arc spot welding method with precise control of welding time, achieving continuous welding through a series of overlapping spot welds. This laser-like welding is mainly used for repairing residual defects or minor damage in cast iron, stainless steel, and carbon steel workpieces. However, its application in welding thin aluminum and its alloy structures or repairing defects is rare. This is primarily because the field generally believes that laser-like welding of aluminum and its alloys presents the following technical challenges: welding aluminum itself requires AC arc welding, which protects and reduces tungsten electrode burn-off and utilizes positive ions in the arc to remove the oxide film formed during the aluminum welding process; while laser-like welding technology is precisely controlled pulse welding, allowing for millisecond-level adjustment of the pulse duration. Current traditional techniques consider that the pulsed arc combustion process in laser-like welding only lasts a few cycles, making it difficult to achieve the melting process of the base material and the removal of the oxide film. Due to their high thermal conductivity, aluminum and its alloys require a hard-mode (characterized by high current and short duration) heat input process for welding. Aluminum and its alloys show little color change in their molten state at high temperatures, and the molten pool has low surface tension and low high-temperature solid-state strength. Using soft-mode heating easily leads to collapse or burn-through. Therefore, welding thin-walled, small structural components is extremely difficult, and such applications are currently rare.

[0004] In addition, the process of adding welding wire is more difficult than that of steel welding wire during aluminum welding. This is mainly because aluminum welding wire has a lower melting point and a smaller end size, making it easier to melt under the radiation of the electric arc. In contrast, the base material has a relatively large volume and good thermal conductivity, making it difficult to melt. As a result, the welding wire melts in advance and forms a spherical shape, which is not easily blown into the molten pool by the shielding gas. Summary of the Invention

[0005] This invention addresses the technical biases in the prior art by providing a laser-simulated melting welding method for aluminum and its alloys, solving the problem of difficult weld formation for aluminum and its alloys with a wall thickness of less than 2mm. The method specifically includes the following steps: Step 1: Pre-welding preparation of the workpiece, cleaning the welding area of ​​the workpiece; Step 2, workpiece assembly: During welding, backing plates are used on the back of the workpieces and welding fixtures are used to assemble the weldment to ensure that the joint gap and misalignment meet the welding requirements. Step 3, Welding machine connection: Connect the precision pulse controller in series to the welding torch control switch circuit of the tungsten inert gas welding machine; Step 4: Connect the water, electricity, and gas to the tungsten inert gas (TIG) welding machine, connect the power supply to the precision pulse controller, turn on the power switch, and adjust the control mode to continuous welding mode. Adjust the pulse frequency to 2 Hz, use 2Hz pulses, and the pulse duty cycle to between 30% and 50%. Adjust the TIG welding method to AC mode and switch the control mode switch on the welding machine panel to short welding 2T mode. Step 5: Adjust the output current of the tungsten inert gas (TIG) welding machine according to the size and thickness of the workpiece. The flow rate of the shielding gas argon needs to be adjusted to a laminar flow state according to the nozzle diameter. Step 6: Move the welding torch to the welding start position, hold the welding torch firmly with one hand and keep the distance between the tungsten electrode and the workpiece between 0.5 and 1 mm, and hold the welding wire with the other hand to feed it to 2 to 3 mm in front of the tungsten electrode of the welding torch, at an angle of 10 to 15° with the base material and stick it to the surface of the base material. Step 7: When the welding gun switch is pressed for the first time, the first pulsed arc is generated between the tungsten electrode and the workpiece. A molten pool is formed in the base material below the tungsten electrode. The welding wire is then fed to the edge of the molten pool, waiting for the second pulsed arc to be generated. At the instant the second pulsed arc is generated, the welding gun moves forward 2-3 mm. This second pulse will melt the tip of the welding wire and the base material to form the first filler wire welding process, thus completing the first welding cycle. When the welding gun switch needs to be pressed again, the welding gun needs to be retracted 1-2 mm to re-ignite the arc. This re-ignition of the arc will re-melt part of the filler weld. The welding wire is fed to the edge of the new molten pool again, and the second pulsed arc is used to melt the tip of the welding wire and the base material again to form the second filler wire welding process. By repeatedly pressing the welding gun switch, continuous welding of long welds can be achieved.

[0006] In step 1, the workpiece is a thin-walled structural component of aluminum and its alloys with a wall thickness of 0.1-2 mm.

[0007] In step 2, the gap between the joints is 0-0.1 times the plate thickness, and the misalignment is 0-0.1 times the plate thickness.

[0008] In step 3, the tungsten inert gas (TIG) welding machine is an AC / DC TIG welding machine with IGBT inverter.

[0009] In step 5, when the workpiece has a wall thickness of 0.1-2mm, the welding current is 80-180A, the pulse duty cycle is 30%-50%, the oxide film cleaning time duty cycle is 40-60%, and the protective gas argon flow rate is 8-12L / min with a 10mm diameter nozzle.

[0010] The advantages of this invention are: it employs precise pulse welding, with two pulsed arcs advancing and retreating in a coordinated manner, rapidly heating and melting the base metal and the tip of the welding wire; the molten pool has a short duration, resulting in minimal loss of alloying elements in the molten metal; and the molten pool volume is small, correspondingly reducing the heat-affected zone. For high-strength aluminum alloys, the joint performance is also less affected. Furthermore, due to the small molten pool volume, short duration, and shallow penetration, harmful gases from the arc dissolve into the molten metal. Additionally, the mutual influence of the two pulsed arc heating processes facilitates the rapid escape of dissolved gases from the weld, thus reducing the likelihood of porosity. Because the arc is initiated and melted in a regular, periodic advance and retreat motion, the probability of the welding wire forming a spherical shape is low, the filling process is relatively simple and easy, and it is easy to feed the welding wire into the arc area to melt and form a weld. In the dual-pulse arc heating welding process, the initial pulsed arc heating not only overcomes the spherical shape formation of the welding wire during the filling process but also preheats and removes the oxide film on the base metal surface, which is beneficial for the welding wire to melt and integrate into the molten pool in the next pulsed arc to form filler wire. Then, while melting the welding wire, the pulsed arc reheats and melts the base material, promoting better fusion. This facilitates weld formation and the release of dissolved gases after the molten pool crystallizes. Furthermore, this application increases the current value and reduces the pulsed arc burning time during laser-like welding, meeting the requirement for a strong and rapid heat input process during welding of aluminum and its alloys due to their high thermal conductivity. Detailed Implementation

[0011] Example

[0012] Step 1: Pre-welding preparation of the workpiece. Since oil and oxide film at the welding area significantly affect the aluminum welding process, cleaning is necessary. For small workpieces, oil can be cleaned with solvents such as gasoline, acetone, ethyl acetate, or carbon tetrachloride. Oxide film can be cleaned using a chemical cleaning method involving alkaline cleaning followed by acid cleaning, and then rinsed with clean water and dried. For larger workpieces that are difficult to clean chemically, or workpieces that are locally contaminated after chemical cleaning, mechanical cleaning methods can be used. Generally, a stainless steel wire wheel or scraper with a wire diameter ≤0.3mm is used to clean the surface of the area to be welded.

[0013] In step 1, during alkaline cleaning, the alkaline solution is a NaOH solution at a temperature of 40-50℃, wherein the mass percentage of NaOH in the NaOH solution is 6%-10%. The rinsing time for pure aluminum is 10-20 minutes, and for aluminum alloys, it is 5-7 minutes. After alkaline cleaning, rinse with cold water for 2 minutes, and then rinse with HNO3 solution (30% HNO3) at room temperature for 2-3 minutes, wherein the mass percentage of HNO3 in the HNO3 solution is 30%. Finally, rinse with cold water for 2-3 minutes. After chemical cleaning, the area to be welded should be baked at 100-150℃, or air-dried.

[0014] Step 2, workpiece assembly: To prevent aluminum welding deformation and ensure forming, backing plates are needed on the workpieces during welding, and special tooling fixtures are used to assemble the welded parts to ensure that the joint gap and misalignment meet the welding requirements. The joint gap is 0-0.1 times the plate thickness, and the misalignment is 0-0.1 times the plate thickness.

[0015] Step 3, Welding machine connection: Connect the precision pulse controller in series to the welding torch control switch circuit of the tungsten inert gas (TIG) welding machine; the TIG welding machine is an AC / DC TIG welding machine with IGBT inverter; the precision pulse controller is a digital display precision controller with easy-to-adjust touch keys.

[0016] Step 4: Connect the water, electricity, and gas to the tungsten inert gas (TIG) welding machine, connect the power supply to the precision pulse controller, turn on the power switch, and adjust the control mode to continuous welding mode. Adjust the pulse frequency to 2 Hz, use 2Hz pulses, and the pulse duty cycle to between 30% and 50%. Adjust the TIG welding method to AC mode and switch the control mode switch on the welding machine panel to short welding 2T mode. Step 5: Adjust the output current of the tungsten inert gas (TIG) welding machine according to the size and thickness of the workpiece. When the workpiece thickness is 0.1-2mm, the welding current should be 80-180A, the pulse duty cycle should be between 30% and 50%, the oxide film cleaning time should be 40-60%, and the shielding gas argon flow rate should be adjusted according to the nozzle diameter to achieve laminar flow. Generally, a 10mm diameter nozzle is selected, and the gas flow rate should be 8-12L / min.

[0017] Step 6: Move the welding torch to the welding start position, hold the welding torch firmly with your right hand and keep the distance between the tungsten electrode and the workpiece between 0.5 and 1 mm, hold the welding wire and feed it to 2 to 3 mm in front of the tungsten electrode of the welding torch, at an angle of 10 to 15° with the base material and stick it to the surface of the base material. Step 7: When the welding torch switch is pressed for the first time, the first pulsed arc is generated between the tungsten electrode and the workpiece. A molten pool quickly forms in the base material below the tungsten electrode. Then, one hand feeds the welding wire to the edge of the molten pool, waiting for the second pulsed arc to occur. At the instant the second pulsed arc occurs, the welding torch moves forward 2-3 mm. This second pulse melts the welding wire tip and the base material, forming the first filler welding process, thus completing the first welding cycle. When the welding torch switch needs to be pressed again, the welding torch needs to be retracted 1-2 mm to re-ignite the arc. This re-ignition of the arc re-melts part of the filler weld. The welding wire is fed again to the edge of the new molten pool, and the second pulsed arc melts the welding wire tip and the base material again, forming the second filler welding process. Repeating this process of pressing the welding torch switch allows for continuous welding of long welds.

[0018] Application Example 1 A φ6mm 7075 aluminum tube with a wall thickness of 2mm was welded to a φ6mm 6063 aluminum rod to form a T-joint, and the weld formation was good. The welding parameters were: welding current 150A, pulse duty cycle 40%, frequency 2, oxide film cleaning time up to 50%, argon flow rate 12L / min, and welding wire diameter 1.2mm.

[0019] Application Example 2: A butt welding test was conducted on a 1060 pure aluminum plate with dimensions of 150mm*100mm and a thickness of 1.5mm. The weld formation was good. The welding parameters were: welding current 120A, pulse duty cycle 50%, frequency 2, oxide film cleaning time up to 40%, argon flow rate 10L / min, and welding wire diameter 1.2mm.

[0020] This application is mainly applicable to thin-walled structural components of aluminum and its alloys with a wall thickness of 0.1-2mm; it can also be applied to welding repairs of aluminum and its alloys with a wall thickness of more than 2mm. For example, surface welding tests were conducted on 1060 pure aluminum plates with surface scratches (deep 1-2mm, width 2-5mm, length 10-8mm) measuring 150mm*100mm and a thickness of 5mm, and the weld formation was good. The welding parameters were: welding current 280A, pulse duty cycle 50%, frequency 2, oxide film cleaning time up to 40%, argon flow rate 12L / min, and welding wire diameter 2.4mm.

[0021] 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 laser-simulated melting welding method for aluminum and its alloys, characterized in that... Includes the following steps: Step 1, Pre-welding preparation of the workpiece: Clean the area of ​​the workpiece to be welded, and remove the surface oxide film and oil stains; the workpiece is a thin-walled structural part of aluminum and its alloy with a wall thickness of 0.1-2mm; Step 2, workpiece assembly: During welding, a backing plate is set on the workpiece, and the workpiece to be welded is assembled using welding fixtures to ensure that the joint gap and misalignment meet the welding process requirements. Step 3, Welding machine connection: Connect the precision pulse controller in series with the welding torch control switch circuit of the tungsten inert gas welding machine; Step 4: Connect the water, electricity, and gas supply to the tungsten inert gas (TIG) welding machine and the power supply to the precision pulse controller. Turn on the power switch and adjust the control mode to continuous welding mode. Adjust the pulse frequency to 2Hz and the pulse duty cycle to 30%–50%. Adjust the welding type of the TIG welding machine to AC mode and switch the control mode of the welding machine panel to the welding torch switch jog control mode. Step 5: Adjust the output current of the tungsten inert gas (TIG) welding machine according to the size and thickness of the workpiece. The flow rate of the shielding gas argon needs to be adjusted to a laminar flow state according to the nozzle diameter. When the workpiece has a wall thickness of 0.1-2mm, the welding current is 80-180A, the oxide film cleaning duty cycle is 40-60%, and the shielding gas argon flow rate is 8-12L / min for a 10mm diameter nozzle. Step 6: Move the welding torch to the welding start position, hold the welding torch firmly with one hand and keep the distance between the tungsten electrode and the workpiece at 0.5-1mm, and hold the welding wire with the other hand to feed it to 2-3mm in front of the tungsten electrode of the welding torch. The welding wire should be at an angle of 10-15° to the base material and attached to the surface of the base material. Step 7: When the welding gun switch is pressed for the first time, the first pulsed arc is generated between the tungsten electrode and the workpiece. A molten pool is formed in the base material below the tungsten electrode. The welding wire is then fed to the edge of the molten pool, waiting for the second pulsed arc to be generated. At the instant the second pulsed arc is generated, the welding gun moves forward 2-3 mm. The second pulse will melt the tip of the welding wire and the base material to form the first filler wire welding process, thus completing the first welding cycle. When the welding gun switch needs to be pressed again, the welding gun retracts 1-2 mm and then re-ignites the arc. The re-ignited arc will remelt part of the already filled weld. The welding wire is fed to the edge of the new molten pool again, and the second pulsed arc is used to melt the tip of the welding wire and the base material again to form the second filler wire welding process. By repeatedly pressing the welding gun switch, continuous welding of long welds can be achieved.

2. The laser-simulated melting welding method for aluminum and its alloys according to claim 1, characterized in that, In step 2, the gap between the joints is 0-0.1 times the plate thickness, and the misalignment is 0-0.1 times the plate thickness.

3. The laser-simulated melting welding method for aluminum and its alloys according to claim 1, characterized in that, In step 3, the tungsten inert gas (TIG) welding machine is an AC / DC TIG welding machine with IGBT inverter.