Welding method for hollow tungsten electrode coaxial mig / mag hybrid welding device

Abstract

Hollow tungsten electrode coaxial MIG / MAG composite welding device and welding method. The welding efficiency of the hollow tungsten electrode coaxial wire feeding welding technology is still low. The composition comprises: a hollow tungsten electrode (1), a tungsten electrode holder (2), a protective gas cover (3), a MIG / MAG welding wire (4), an insulating porcelain tube (5), a plasma buffer gas chamber (12), a TIG power supply (13) and a MIG / MAG power supply (14); the hollow tungsten electrode is clamped by the symmetrically arranged tungsten electrode holder, the protective gas cover is located outside the tungsten electrode holder, and the upper end of the hollow tungsten electrode is fixed with the plasma buffer gas chamber; the hollow tungsten electrode is inserted with the insulating porcelain tube, the insulating porcelain tube is inserted with the MIG / MAG welding wire, and the gap between the MIG / MAG welding wire and the hollow tungsten electrode forms an ion gas channel (15). The present application is used for hollow tungsten electrode coaxial MIG / MAG composite welding.

Description

Technical Field

[0001] This invention relates to a welding method for a hollow tungsten electrode coaxial MIG / MAG composite welding device. Background Technology

[0002] In terms of arc welding technology, traditional non-consumable electrode tungsten inert gas (TIG) welding with off-axis filler wire has long been the preferred technology for high-quality welding in certain key fields due to its unique process stability, playing a vital role in promoting the rapid development of the national economy. Compared with TIG welding, traditional gas metal arc welding (MIG / MAG welding) can simultaneously melt the filler material while using the heat of the arc to melt the base material, meeting the material filling requirements of the welding process and even enabling the control of the weld metallurgical process. This method has technical advantages such as high welding efficiency and good process robustness, but the weld quality is relatively lower. Both have played irreplaceable and unique roles in many fields. However, with the steady improvement of manufacturing technology, traditional arc welding methods face many technical challenges in some new application areas or scenarios that require further improvement and solutions. In recent years, against this backdrop, to address several technical bottlenecks in traditional tungsten inert gas (TIG) off-axis filler wire welding, hollow TIG coaxial filler wire welding technology has been developed. This technology truly achieves coaxiality between the welding wire and the arc. Compared with traditional TIG off-axis filler wire welding, this method offers advantages such as smaller welding torch space, non-directional process implementation, significantly improved process robustness, and better protection for non-ferrous metal welding. This makes it a promising market prospect in welding special materials and complex structures, as well as in arc additive manufacturing. However, the welding efficiency of hollow TIG coaxial filler wire welding technology remains relatively low. How to further improve welding efficiency without compromising welding quality is a core issue currently being focused on by both industry and academia. Summary of the Invention

[0003] The purpose of this invention is to solve the problem that the welding efficiency of hollow tungsten inert gas (TIG) coaxial filler wire welding technology is still low. This invention provides a welding method for a hollow tungsten inert gas (TIG) coaxial MIG / MAG composite welding device that changes the state and position of the hollow tungsten inert gas arc, thereby altering the coupling effect between the TIG arc and the MIG / MAG arc, and achieving precise control of the welding process.

[0004] The above objectives are achieved through the following technical solutions:

[0005] A hollow tungsten electrode coaxial MIG / MAG composite welding device, comprising a hollow tungsten electrode, a tungsten electrode clamp, a protective gas hood, a MIG / MAG welding wire, an insulating ceramic tube, a plasma buffer chamber, a TIG power supply, and a MIG / MAG power supply.

[0006] The hollow tungsten electrode is held by symmetrically arranged tungsten electrode clamps, the protective gas cover is located outside the tungsten electrode clamps, and the plasma buffer gas chamber is fixed at the upper end of the hollow tungsten electrode.

[0007] The hollow tungsten electrode is fitted with an insulating ceramic tube, and the insulating ceramic tube is fitted with a MIG / MAG welding wire. The gap between the MIG / MAG welding wire and the hollow tungsten electrode forms an ion gas channel.

[0008] The hollow tungsten electrode coaxial MIG / MAG composite welding device further includes a conductive block, which is attached to the outer side of the tungsten electrode clamp.

[0009] In the hollow tungsten electrode coaxial MIG / MAG composite welding device, the TIG power supply is electrically connected to the conductive block, and the MIG / MAG power supply is connected to the MIG / MAG welding device.

[0010] The hollow tungsten electrode coaxial MIG / MAG composite welding device has a hollow tungsten electrode bottom with a chamfered inner hole, a hollow tungsten electrode arc emission plane, and a chamfered outer surface of the hollow tungsten electrode.

[0011] A welding method for a hollow tungsten inert coaxial MIG / MAG composite welding device specifically includes the following steps:

[0012] (1) Select hollow tungsten electrodes according to the materials to be welded, and choose hollow tungsten electrodes with large inner diameter or small inner diameter;

[0013] (2) Use a tungsten electrode sample preparation tool to clean the contaminants at the electron emission end of the tungsten electrode. At the same time, pre-set the electron emission end of the tungsten electrode into a specific flared shape, install the tungsten electrode onto the welding torch, and ensure that the tungsten electrode extends 8-12mm beyond the end of the protective gas shield.

[0014] (3) The MIG / MAG welding wire is coaxially fed out through the insulating ceramic tube inside the hollow tungsten electrode, with the end of the welding wire extending 1-3 mm beyond the electron emission end of the hollow tungsten electrode;

[0015] (4) Use mechanical cleaning or chemical cleaning methods to pre-treat the workpiece end face to be welded and the surrounding 15mm area;

[0016] (5) Assemble the workpiece to be welded, use a feeler gauge to measure the size of the end face gap, control the gap within 0.8mm, and use a clamp to fix the workpiece to be welded.

[0017] (6) Check and confirm in turn that the cooling water, shielding gas, ionizing gas, welding travel mechanism, TIG power supply, and MIG / MAG power supply are in normal working condition, and set the shielding gas and ionizing gas flow rate, TIG power supply and MIG / MAG power supply polarity, TIG power supply and MIG / MAG power supply current mode, TIG power supply and MIG / MAG power supply current magnitude and welding speed according to the welding parameters.

[0018] (7) When selecting a hollow tungsten electrode with a large inner diameter, the distance between the inner wall of the hollow tungsten electrode and the welding wire is greater than the distance between the hollow tungsten electrode and the workpiece. Move the welding torch to the area to be welded to ensure that the distance between the end of the tungsten electrode and the workpiece remains unchanged.

[0019] (8) When selecting a hollow tungsten electrode with a small inner diameter, the distance between the inner wall of the hollow tungsten electrode and the welding wire is less than the distance between the hollow tungsten electrode and the workpiece. Move the welding torch to the area to be welded to ensure that the distance between the end of the tungsten electrode and the workpiece remains unchanged.

[0020] (9) After the above (7) or (8) is completed, first turn on the TIG power supply. Under the action of high frequency arc ignition, the TIG arc breaks down the air to establish a conductive channel.

[0021] (10) When the TIG arc is burning stably for 0.2~0.5s, turn on the MIG / MAG power supply. At this time, the MIG / MAG welding wire begins to be fed into the arc area until it contacts the test plate, and the MIG / MAG arc completes the contact arc ignition.

[0022] (11) After both the MIG / MAG arc and the TIG arc are burning stably, turn on the welding start button to realize the hollow tungsten electrode coaxial MIG / MAG composite welding of the workpiece to be welded.

[0023] (12) After welding is completed, first disconnect the TIG welding power supply. After the TIG arc is extinguished, disconnect the MIG welding power supply to complete the welding of the sample to be welded.

[0024] Beneficial effects:

[0025] 1. This invention feeds the welding wire for MIG / MAG welding through the inner hole of a hollow tungsten electrode, achieving coincidence between the geometric center of the welding wire and the geometric center of the hollow tungsten electrode. This means that during actual welding, the welding wire can rotate at any angle around its geometric center without changing the spatial position of the welding wire and the hollow tungsten electrode. Based on the principle of minimum voltage for flexible arcs, this method alters the state and position of the hollow tungsten electrode arc, thereby changing the coupling effect between the TIG arc and the MIG / MAG arc, achieving precise control of the welding process.

[0026] 2. The process developed by this invention based on the hollow tungsten electrode coaxial MIG / MAG composite welding device is a coaxial composite welding process. With the MIG / MAG welding wire as the center, the position of the TIG arc relative to the MIG / MAG arc will not change even when rotated at any angle.

[0027] 3. By adjusting the diameter of the hollow tungsten electrode's inner hole, this invention can conveniently adjust the distance between the inner wall of the tungsten electrode and the welding wire relative to the distance between the electron emission end of the tungsten electrode and the workpiece, thereby changing the position of the tungsten inert gas arc. It is suitable for welding metals with different physical properties and can meet the high-quality connection requirements of different metals in different application environments, greatly expanding the application scope of this technology.

[0028] 4. For non-ferrous metals such as aluminum alloys and magnesium alloys that are difficult to weld due to their dense, high-melting-point oxide films, this invention uses a hollow tungsten electrode with a large inner diameter to separate the MIG arc and TIG arc. By precisely controlling the TIG arc mode and using an AC or AC + pulse combination, the oxide film on the surface of the welded metal can be cleaned. This is of great significance for simplifying the cleaning process, reducing production costs, and improving the welding quality of non-ferrous metals.

[0029] 5. For metal components with high carbon equivalent or high restraint, this invention, by selecting a hollow tungsten electrode with a large inner diameter and matching an appropriate welding current and arc mode, can regulate the preheating and post-weld slow cooling zones and temperatures of the component to be welded. This achieves precise control of the thermal cycle curve of the welded component, meeting the requirements of consistent welding quality in mass production. The method has a simple process flow and significantly reduces processing costs.

[0030] 6. In this invention, when the inner diameter of the hollow tungsten electrode is small, the arc formed between the electron emitting end of the hollow tungsten electrode and the workpiece gradually shifts to the space between the inner wall of the hollow tungsten electrode and the welding wire of the MIG / MAG arc as the MIG / MAG arc is ignited. This phenomenon increases the temperature at the molten end of the welding wire, reduces the surface tension between the solid welding wire end and the molten droplet, and allows the droplet to stably transition into the liquid pool in the form of small droplets under the action of plasma flow force, gravity, and ion blowing force. This is of great significance for improving deposition efficiency, stabilizing the welding process, and improving welding quality. Furthermore, the direct action of the tungsten arc on the welding wire significantly improves welding efficiency while reducing heat input in the weld area, positively promoting grain growth and improving weld performance. Attached Figure Description

[0031] Appendix Figure 1 This is a schematic diagram of a hollow tungsten electrode coaxial MIG / MAG composite welding device;

[0032] In the diagram: 1. Hollow tungsten electrode; 2. Tungsten electrode clamp; 3. Shielding gas hood; 4. MIG / MAG welding wire; 5. Insulating ceramic tube; 6. Tungsten inert gas (TIG) arc; 7. Droplet; 8. Weld layer; 9. Sample; 10. Conductive block; 11. Ionizing gas inlet; 12. Ionizing gas buffer chamber; 13. TIG power supply; 14. MIG / MAG power supply; 15. Ionizing gas channel; 20. MIG / MAG arc.

[0033] Appendix Figure 2 This is a schematic diagram of a stepped hollow tungsten electrode;

[0034] In the diagram: 16. Hollow tungsten electrode step; 17. Chamfer on the inner hole of the hollow tungsten electrode; 18. Arc emission plane of the hollow tungsten electrode; 19. Chamfer on the outer surface of the hollow tungsten electrode;

[0035] Where: D represents the diameter of the welding wire, D0 represents the distance between the welding wire and the inner wall of the tungsten electrode, D1 represents the diameter of the inner hole of the hollow tungsten electrode, D2 represents the diameter of the chamfered edge of the inner hole of the hollow tungsten electrode, D3 represents the diameter of the chamfered edge of the outer side of the hollow tungsten electrode, D4 ​​represents the diameter of the hollow tungsten electrode, b represents the distance between the inner hole of the tungsten electrode and the surface of the welding wire, and w represents the width of the electron emission end face of the tungsten electrode.

[0036] Appendix Figure 3 This is a schematic diagram of the composite welding process of hollow tungsten inert gas (TIG) argon arc and MIG / MAG arc when the inner diameter of the hollow tungsten inert gas electrode is small.

[0037] Appendix Figure 4 This is a schematic diagram of the composite welding process of hollow tungsten inert gas (TIG) argon arc welding and MIG / MAG arc welding when the inner diameter of the hollow tungsten electrode is relatively large. Detailed implementation method:

[0038] Example 1:

[0039] A hollow tungsten electrode coaxial MIG / MAG composite welding device, comprising a hollow tungsten electrode 1, a tungsten electrode clamp 2, a protective gas hood 3, a MIG / MAG welding wire 4, an insulating ceramic tube 5, a plasma buffer chamber 12, a TIG power supply 13, and a MIG / MAG power supply 14.

[0040] The hollow tungsten electrode is held by symmetrically arranged tungsten electrode clamps, the protective gas cover is located outside the tungsten electrode clamps, and the plasma buffer gas chamber is fixed at the upper end of the hollow tungsten electrode.

[0041] The hollow tungsten electrode is fitted with an insulating ceramic tube, and the insulating ceramic tube is fitted with a MIG / MAG welding wire. The gap between the MIG / MAG welding wire and the hollow tungsten electrode forms an ion gas channel 15.

[0042] Example 2:

[0043] According to the hollow tungsten electrode coaxial MIG / MAG composite welding device described in Example 1, the hollow tungsten electrode coaxial MIG / MAG composite welding device further includes a conductive block 10, which is attached to the outer side of the tungsten electrode clamp.

[0044] Example 3:

[0045] According to the hollow tungsten electrode coaxial MIG / MAG composite welding apparatus described in Embodiment 1 or 2, the TIG power supply is electrically connected to the conductive block, and the MIG / MAG power supply is connected to the MIG / MAG welding apparatus.

[0046] Example 4:

[0047] According to the hollow tungsten electrode coaxial MIG / MAG composite welding device described in Example 3, the bottom of the hollow tungsten electrode has a hollow tungsten electrode inner hole chamfer, a hollow tungsten electrode arc emission plane, and a hollow tungsten electrode outer surface chamfer.

[0048] Example 5:

[0049] For 5A06 aluminum alloy, a large hollow tungsten electrode inner diameter is used to implement a hollow tungsten electrode coaxial MIG welding process. The welding material size is 300×200×3mm. Before welding, only the oxide film on the end face of the aluminum alloy to be welded is mechanically cleaned. The plate within 15mm of the area to be welded is not treated in any way. Argon is used for both the shielding gas and the ionizing gas. The specific implementation steps are as follows:

[0050] Step 1: Clean the contaminants on the electron emission end of the tungsten electrode using a tungsten electrode sample preparation tool. At the same time, pre-shape the electron emission end of the tungsten electrode into a specific flared shape. The inner diameter D1 of the hollow tungsten electrode is 16mm, the hollow tungsten electrode diameter D4 is 20mm, the diameter D2 of the chamfered edge of the inner hole of the hollow tungsten electrode is 17mm, the diameter D3 of the chamfered edge of the outer side of the hollow tungsten electrode is 19mm, and the width w of the electron emission end face of the tungsten electrode is 1mm. Install the tungsten electrode into the welding torch, ensuring that the tungsten electrode extends 10mm beyond the end of the protective gas shield.

[0051] Step 2: The diameter D of the welding wire is 1.2mm, the welding wire grade is ER5083, the distance b between the inner hole of the tungsten electrode and the surface of the welding wire is 7.2mm. The MIG welding wire is coaxially fed out through the insulating ceramic tube inside the hollow tungsten electrode, and the end of the welding wire extends 1-3mm beyond the electron emission end of the hollow tungsten electrode.

[0052] Step 3: Use mechanical cleaning methods to treat the end face of the workpiece to be welded, without treating the surrounding area;

[0053] Step 4: Assemble the workpieces to be welded, use feeler gauges and other tools to measure the size of the end face gap, control the gap within 0.8mm, and use clamps to fix the workpieces to be welded.

[0054] Step 5: Check and confirm that the cooling water, shielding gas, ionizing gas, welding travel mechanism, TIG power supply, and MIG / MAG power supply are all in normal working order. Set the flow rates of the shielding gas and ionizing gas to 20 L / min and 10 mL / min respectively, according to the welding parameters. Use AC mode for the TIG power supply and DC reverse polarity for the MIG power supply. Set the MIG welding current to 230 A, the initial welding current to 100-150 A, the arc ignition time to 0.2-0.5 s, and the arc termination current to 150-180 A. Set the shielding gas delay time after welding to 5-10 s. Set the TIG welding current to 300 A, using sinusoidal AC output mode at 120 Hz. Control the TIG welding current to 200-150 A, the arc ignition time to 0.3-0.6 s, and the arc termination current to 150-180 A. Set the shielding gas delay time after welding to 8-10 s. The welding speed is set to 0.7 m / min.

[0055] Step 6: Move the welding torch to the area to be welded in a certain posture, ensuring that the distance between the tungsten electrode tip and the workpiece is 3~3.5mm;

[0056] Step 7: After all the above steps have been performed, first turn on the TIG power supply. Under the action of high-frequency arc ignition, the TIG arc breaks down the air to establish a conductive channel.

[0057] Step 8: After the TIG arc is burning stably, turn on the MIG power supply. At this time, the MIG welding wire will start to be fed into the arc area until it contacts the test plate, and the MIG arc will complete the contact and arc ignition.

[0058] Step 9: Once both the MIG arc and the TIG arc are burning stably, turn on the welding start button to achieve hollow tungsten inert gas coaxial MIG composite welding of the workpiece to be welded.

[0059] Step 10: After welding is completed, first disconnect the TIG welding power supply. After the TIG arc is extinguished for 0.1~0.3ms, disconnect the MIG welding power supply to complete the welding of 5A06 aluminum alloy material.

[0060] Compared to conventional single-heat-source MIG arc welding and single-heat-source TIG filler wire welding, hollow tungsten inert gas (TIG) coaxial MIG hybrid welding of 5A06 aluminum alloy eliminates the need for cleaning the area near the weld, simplifying the welding process and reducing costs. Furthermore, its welding speed is increased by 30% and 250% compared to MIG and TIG welding, respectively, and it produces excellent weld quality, with tensile strength reaching approximately 87% of the base metal, which is 6% and 12% higher than TIG filler wire and MIG welding, respectively.

[0061] Example 6:

[0062] Taking 304 stainless steel as an example, hollow tungsten inert gas (TIG) coaxial MAG composite welding is performed. The tungsten inert gas used is a hollow tungsten inert gas with a small inner diameter, and the dimensions of the welding material are 300×150×2mm. Before welding, the oxide film on the end face of the area to be welded and the plate within 15mm of the area to be welded is cleaned. The shielding gas is argon, and the ionizing gas is a mixture of argon and carbon dioxide. The specific implementation steps are as follows:

[0063] Step 1: Clean the contaminants on the electron emission end of the tungsten electrode using a tungsten electrode sample preparation tool. At the same time, pre-shape the electron emission end of the tungsten electrode into a specific flared shape. The inner diameter D1 of the hollow tungsten electrode is 4mm, the hollow tungsten electrode diameter D4 is 8mm, the diameter D2 of the chamfered edge of the inner hole of the hollow tungsten electrode is 5mm, the diameter D3 of the chamfered edge of the outer side of the hollow tungsten electrode is 7mm, and the width w of the electron emission end face of the tungsten electrode is 1mm. Install the tungsten electrode into the welding torch, ensuring that the tungsten electrode extends 10mm beyond the end of the protective gas shield.

[0064] Step 2: The diameter D of the welding wire is 1.2mm, the welding wire grade is ER308L, the distance b between the inner hole of the tungsten electrode and the surface of the welding wire is 1.4mm, and the MAG welding wire is coaxially fed out through the insulating ceramic tube inside the hollow tungsten electrode. The end of the welding wire extends 1-3mm beyond the electron emission end of the hollow tungsten electrode.

[0065] Step 3: Use mechanical cleaning methods to treat the end face of the workpiece to be welded, without treating the surrounding area;

[0066] Step 4: Assemble the workpieces to be welded, use feeler gauges and other tools to measure the size of the end face gap, control the gap within 0.5mm, and use clamps to fix the workpieces to be welded.

[0067] Step 5: Check and confirm that the cooling water, shielding gas, ionizing gas, welding travel mechanism, TIG power supply, and MAG power supply are all in normal working order. Set the flow rates of the shielding gas and ionizing gas to 20 L / min and 10 mL / min respectively, according to the welding parameters. The ionizing gas should be a mixture of 98% argon and 2% carbon dioxide by volume, and the shielding gas should be argon. Set the TIG power supply to DC positive polarity mode and the MAG power supply to DC reverse polarity mode. Set the MAG welding current to 200 A, the initial welding current to 120-160 A, the arc ignition time to 0.4-0.6 s, the arc termination current to 150-170 A, and the shielding gas delay time after welding to 5-10 s. The TIG welding machine current is set to 200A, the initial welding current is controlled between 100 and 150A, the arc start time is set to 0.3 to 0.6 seconds, the arc end current is set to 150 to 180A, and the shielding gas delay time after welding is set to 8 to 10 seconds. The welding speed is set to 0.6 m / min.

[0068] Step 6: Move the welding torch to the area to be welded in a certain posture, ensuring that the distance between the tungsten electrode tip and the workpiece is 3.0~3.5mm;

[0069] Step 7: After all the above steps have been performed, first turn on the TIG power supply. Under the action of high-frequency arc ignition, the TIG arc breaks down the air to establish a conductive channel.

[0070] Step 8: After the TIG arc is burning stably, turn on the MAG power supply. At this time, the MAG welding wire will start to be fed into the arc area until it contacts the test plate, and the MAG arc will complete the contact and arc ignition.

[0071] Step 9: After the MAG arc is ignited, the conductive path of the TIG arc will shift from between the electron emitter and the workpiece to between the inner wall of the hollow tungsten electrode and the welding wire. At this time, turn on the welding start button to realize the coaxial MAG composite welding of the hollow tungsten electrode to be welded.

[0072] Step 10: After welding is completed, first disconnect the TIG welding power supply. After the TIG arc is extinguished for 0.1~0.2ms, disconnect the MAG welding power supply to complete the hollow tungsten inert gas coaxial MAG welding of 304 stainless steel.

[0073] The welding speed of hollow tungsten inert gas coaxial MAG composite welding of 304 stainless steel is comparable to that of conventional MAG welding of stainless steel, but its welding quality is close to that of TIG filler wire welding, with excellent weld formation quality and tensile strength reaching about 92% of the base material.

[0074] The coupling mechanism between the TIG and MIG / MAG arcs is modified as follows: when using a small-diameter hollow tungsten electrode, the distance between the tip of the tungsten electrode and the workpiece is greater than the distance between the inner wall of the hollow tungsten electrode and the welding wire. After the MIG / MAG welding wire and the workpiece are ignited, according to the principle of minimum voltage, the welding arc will change its position of action, gradually shifting from the workpiece surface to the welding wire. At this time, the conductive channel is between the inner wall of the tungsten electrode and the welding wire. The heat generated by the TIG arc is used to heat the welding wire. Because the annular surface area of ​​the inner wall of the tungsten electrode is relatively large, the current density of the TIG arc is relatively small. This can significantly increase the temperature of the welding wire tip before melting without melting the welding wire. This is of great significance for improving the deposition efficiency of MIG / MAG welding wires without increasing the welding heat input.

[0075] By altering the coupling mechanism of the TIG and MIG / MAG arcs, when the inner diameter of the hollow tungsten electrode is large, the distance between the inner wall of the tungsten electrode and the welding wire is greater, making the argon arc generated by the tungsten electrode and the arc generated by the MIG / MAG welding wire independent. In this case, the annular argon arc generated by the hollow tungsten electrode can serve as preheating before welding and slow cooling after welding, which is of great significance for difficult-to-weld metals with high carbon equivalent. Precise control of the temperature field during welding can be achieved by controlling the size of the hollow tungsten electrode and the current. Simultaneously, by changing the electrode polarity during welding, a cathodic breakage effect is achieved on the sample surface. Without adding other processes, oil and oxides on the sample surface can be removed, ensuring that the molten metal formed after melting is not contaminated. This is extremely beneficial for improving the mechanical properties of the weld metal.

[0076] The welding power source for hollow tungsten inert gas (TIG) arc combustion and the power source for MIG / MAG welding are two dedicated power sources with independent functions. The welding process of each can be adjusted and controlled through an independent welding power source control system.

[0077] The aforementioned TIG welding power source and MIG / MAG welding power source can be configured with welding parameters that match different actual application scenarios and applied in the hollow tungsten inert coaxial MIG / MAG composite welding process.

[0078] Welding wire types include various flux-cored welding wires, solid welding wires, and stranded welding wires.

Claims

1. A hollow tungsten coaxial MIG / MAG composite welding device, characterized by: The hollow tungsten electrode coaxial MIG / MAG composite welding device comprises a hollow tungsten electrode, a tungsten electrode holder, a shielding gas cover, a MIG / MAG welding wire, an insulating porcelain tube, a plasma buffer gas chamber, a TIG power supply and a MIG / MAG power supply. The hollow tungsten electrode is clamped by the symmetrically arranged tungsten electrode holder, the shielding gas cover is located outside the tungsten electrode holder, and the upper end of the hollow tungsten electrode is fixed with the plasma buffer gas chamber. The hollow tungsten electrode is internally inserted with the insulating porcelain tube, the insulating porcelain tube is internally inserted with the MIG / MAG welding wire, and the gap between the MIG / MAG welding wire and the hollow tungsten electrode forms an ion gas passage.

2. Hollow tungsten electrode coaxial MIG / MAG composite welding device according to claim 1, characterized in that The hollow tungsten electrode coaxial MIG / MAG composite welding device further comprises a conductive block which is attached to the outside of the tungsten electrode holder.

3. Hollow tungsten electrode coaxial MIG / MAG composite welding device according to claim 2, characterized in that The TIG power supply is electrically connected with the conductive block, and the MIG / MAG power supply is connected with the MIG / MAG welding device.

4. Hollow tungsten electrode coaxial MIG / MAG composite welding device according to claim 3, characterized in that The bottom of the hollow tungsten electrode is provided with a hollow tungsten electrode inner hole chamfer, a hollow tungsten electrode arc emission plane and a hollow tungsten electrode outer side chamfer.

5. A welding method of the hollow tungsten electrode coaxial MIG / MAG composite welding device according to any one of claims 1-4, specifically comprising the following steps: (1) selecting the hollow tungsten electrode according to the material to be welded, selecting a hollow tungsten electrode with a large inner hole diameter or a hollow tungsten electrode with a small inner hole diameter; (2) cleaning the contaminants on the electron emission end of the tungsten electrode by using a tungsten electrode sample preparation tool, pre-setting the electron emission end of the tungsten electrode into a horn-shaped shape, and installing the tungsten electrode to the welding gun, ensuring that the tungsten electrode extends 8-12 mm from the end of the shielding gas cover; (3) coaxially feeding the MIG / MAG welding wire through the insulating porcelain tube inside the hollow tungsten electrode, and extending the welding wire end 1-3 mm from the electron emission end of the hollow tungsten electrode; (4) pretreating the end face and the area within 15 mm thereof of the workpiece to be welded by using mechanical cleaning or chemical cleaning method; (5) assembling the workpiece to be welded, measuring the gap size between the end faces by using a feeler gauge tool, controlling the gap within 0.8 mm, and fixing the workpiece to be welded by using a clamp; (6) sequentially checking and confirming that the cooling water, the shielding gas, the ion gas, the welding walking mechanism, the TIG power supply and the MIG / MAG power supply are in normal working state, and setting the shielding gas and ion gas flow, the polarity of the TIG power supply and the MIG / MAG power supply, the current mode of the TIG power supply and the MIG / MAG power supply, the current size of the TIG power supply and the MIG / MAG power supply, and the welding speed according to the welding parameters; (7) when the hollow tungsten electrode with a large inner hole diameter is selected, the distance between the inner wall of the hollow tungsten electrode and the welding wire is greater than the distance between the hollow tungsten electrode and the workpiece, moving the welding gun to the area to be welded, and ensuring that the distance between the end of the tungsten electrode and the workpiece remains unchanged; (8) when the hollow tungsten electrode with a small inner hole diameter is selected, the distance between the inner wall of the hollow tungsten electrode and the welding wire is less than the distance between the hollow tungsten electrode and the workpiece, moving the welding gun to the area to be welded, and ensuring that the distance between the end of the tungsten electrode and the workpiece remains unchanged; (9) after the execution of the above (7) or (8) is completed, first turn on the TIG power supply, and under the action of high-frequency arc striking, the TIG arc breaks through the air to establish a conductive channel. (10) When the TIG arc is stable combustion for 0.2-0.5 s, the MIG / MAG power is turned on, at this time the MIG / MAG welding wire starts to feed to the arc area until it contacts the test plate, and the MIG / MAG arc completes the contact arc ignition; (11) When the MIG / MAG arc and the TIG arc are both stable combustion, the welding start button is turned on to realize the hollow tungsten coaxial MIG / MAG composite welding of the workpiece to be welded; (12) After the welding is completed, the TIG welding power is first turned off, and then the MIG welding power is turned off when the TIG arc is extinguished, and the welding of the workpiece to be welded is completed.

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