Hollow tungsten electrode coaxial filler wire welding device and control and welding method

Abstract

Hollow tungsten electrode coaxial wire welding device and control and welding method. The welding efficiency of the current hollow tungsten electrode coaxial wire welding technology is still relatively low. The present invention comprises: a hollow tungsten electrode (1), a tungsten electrode clamp (2), a protective gas cover (3), a welding wire (4), an insulating porcelain tube (5), and an ion buffer filter air chamber (12); the hollow tungsten electrode is clamped by symmetrically arranged tungsten electrode clamps, the protective gas cover is located outside the tungsten electrode clamp, and the upper end of the hollow tungsten electrode is fixed with an ion buffer filter air chamber; the hollow tungsten electrode has a step inside, the insulating porcelain tube is inserted into the step inside the hollow tungsten electrode, the insulating porcelain tube is inserted with a welding wire, and the gap between the welding wire and the hollow tungsten electrode forms an ion gas channel (15); an ion gas filter (14) is fixed inside the ion buffer filter air chamber, and a porous medium material (13) is filled in the closed space formed by the ion gas filter and the ion gas buffer air chamber. The present invention is used for hollow tungsten electrode coaxial wire welding.

Description

Technical Field

[0001] The invention relates to a hollow tungsten electrode coaxial wire-filling welding device and a control and welding method. Background Art

[0002] Traditional tungsten inert gas arc welding (TIG) with side-by-side filler wire, due to its unique process stability, has long been the preferred choice for high-quality welding solutions in certain fields, playing an irreplaceable and unique role in promoting many key areas of national economic development. However, traditional TIG welding with side-by-side filler wire has drawbacks such as large welding gun dimensions, limited arc heat for effective wire melting, high weld deposit dilution, directional process implementation, and poor weld protection for non-ferrous metals. These drawbacks significantly limit its application in welding special materials and complex structures, or in arc additive manufacturing.

[0003] Hollow tungsten electrode coaxial wire welding utilizes machining to create a hole in the center of a conventional tungsten electrode. The welding wire is then passed through the inner hole of the hollow tungsten electrode, aligning the geometric center axes of the tungsten electrode and the welding wire. This technology overcomes the directional limitations of conventional tungsten electrode argon arc side-by-side wire welding. Furthermore, by coaxially feeding the tungsten electrode and welding wire directly into the high-temperature zone at the center of the arc, it significantly enhances the arc's fusing capacity and improves deposition efficiency. The invention patent with patent number CN201710512517.2 achieves insulation between the tungsten electrode and the welding wire by coating an insulating layer on the inner walls of two half-split tungsten electrodes, and then merges the two half-split tungsten electrodes into one tungsten electrode, ultimately achieving the purpose of coaxiality of the tungsten electrode and the welding wire. However, this method increases the difficulty of implementing the welding process, and the assembly problem and the conductive uniformity problem between the two tungsten electrodes cannot be solved; the patent with patent number 201610998677.8 provides a hollow tungsten electrode coaxial wire-filled TIG welding device and its welding gun. This patent feeds the welding wire from the inner hole of the hollow tungsten electrode, and connects the inner hole of the tungsten electrode and the protective gas cavity by punching a hole in the side wall of the tungsten electrode to achieve the effect of gas-wire combined feeding. However, this method does not take into account the uniformity of gas feeding and the insulation problem between the welding wire and the inner hole of the tungsten electrode. During the implementation of the process, it is very easy for the welding wire and tungsten electrode to conduct electricity at the same time, making it impossible to ensure the stability of the welding process and the controllability of the process. Summary of the Invention

[0004] The purpose of the present invention is to solve the problem that the current hollow tungsten electrode coaxial wire welding method does not take into account the uniformity of gas feeding and the insulation problem between the welding wire and the inner hole of the tungsten electrode. A method is provided based on the arc formation principle of tungsten electrode argon arc welding, which controls the arc shape by changing the shape characteristics of the electron emitting end of the hollow tungsten electrode. While meeting the requirements of hollow tungsten electrode coaxial wire welding, the spatial temperature gradient of the arc column area is regulated to ensure that the welding wire coaxially and stably fed out of the inner hole of the tungsten electrode enters the arc column area in the form of a high-temperature solid state and then enters the molten pool in the form of a liquid bridge transition, thereby reducing the interference of liquid metal transition on the flow of the molten pool and the stability of the arc, and meeting the requirements of efficient and stable argon arc wire welding. Hollow tungsten electrode coaxial wire welding device and control and welding method.

[0005] The above purpose is achieved through the following technical solutions:

[0006] A hollow tungsten electrode coaxial wire-filling welding device comprises a hollow tungsten electrode, a tungsten electrode clamp, a protective gas cover, a welding wire, an insulating porcelain tube, and an ion buffer filter air chamber;

[0007] The hollow tungsten electrode is clamped by symmetrically arranged tungsten electrode clamps, the protective gas cover is located outside the tungsten electrode clamps, and the plasma buffer filter air chamber is fixed to the upper end of the hollow tungsten electrode;

[0008] The hollow tungsten electrode has a step inside, the insulating porcelain tube is inserted into the step inside the hollow tungsten electrode, the welding wire is inserted into the insulating porcelain tube, and the gap between the welding wire and the hollow tungsten electrode forms an ion gas channel;

[0009] An ion gas filter screen is fixed inside the ion gas buffer filter chamber, and a porous medium material is filled in the closed space formed by the ion gas filter screen and the ion gas buffer chamber.

[0010] The hollow tungsten electrode coaxial wire-filling welding device has a bell-shaped bottom and a circular ring-shaped end face. The hollow tungsten electrode is cut radially to form a plurality of arc emission points in a stepped petal-shaped manner.

[0011] In the hollow tungsten electrode coaxial wire-filling welding device, the step of the stepped hole inside the stepped petal-shaped hollow tungsten electrode is located 10 to 20 mm above the end of the hollow tungsten electrode.

[0012] The hollow tungsten electrode coaxial wire-filling welding device and the petal-shaped hollow tungsten electrode generally have 2 to 8 petals.

[0013] In the hollow tungsten electrode coaxial wire-filling welding device, the width of the ion gas channel is 0.2 to 0.3 mm.

[0014] In the hollow tungsten electrode coaxial wire-filling welding device, the porous medium material is a sponge material.

[0015] A method for controlling a hollow tungsten electrode coaxial filler wire welding device comprises the following steps:

[0016] (1) The shape of the hollow tungsten pole electron emitting end is prefabricated. A bell-mouth shape is machined on the inner hole of the hollow tungsten pole electron emitting end with an outer diameter of D1 and an inner hole diameter of D4. The inner surface of the bell-mouth is called the inner wall, and the diameter of the inner wall is D2. A bevel is machined on the outer diameter of the hollow tungsten pole electron emitting end. The annular surface formed by the bevel is called the outer wall. The unmachined end surface of the electron emitting end is used to emit electrons. This end surface is called the tungsten pole electron emitting end plane, or end plane for short. Its radial width is calculated by the following formula:

[0017]

[0018] (2) Control of spatial temperature gradient in the arc column area;

[0019] The diameter D2 of the inner wall of the bell mouth is used to change the distance between the inner edge of the arc and the welding wire, thereby adjusting the shape of the arc irradiation area. The diameter D3 of the outer wall of the electron emission end is changed to change the width w of the electron emission end.

[0020] (3) Effective control of arc stability;

[0021] Based on the principle of electron tip emission, the smaller the w value, the better the arc stability. When the current is large, the degree of tungsten electrode burning increases.

[0022] (4) Control of arc preheating wire and melting wire position;

[0023] When the welding current is constant, the spatial morphology distribution characteristics of the arc column area during the wire feeding process can be precisely controlled by changing the value of the inner wall diameter D2 of the bell mouth.

[0024] (5) Precise control of the spatial morphology and distribution characteristics of the arc column area;

[0025] When the welding current remains unchanged, changing the D2 value means changing the position of the electron emission end, thereby regulating the distance between the welding wire and the arc. The larger the D2 value, the farther the inner edge of the arc is from the welding wire, the weaker the irradiation effect on the welding wire, and the lower the preheating effect of the arc on the welding wire. On the contrary, the preheating effect of the arc on the welding wire is enhanced.

[0026] Adjust the distance between the tungsten electrode electron emission plane and the test plate, that is, the distance between the hollow tungsten electrode and the workpiece, and control the distance between the position where the welding wire begins to melt and the test plate.

[0027] A welding method for a hollow tungsten electrode coaxial filler wire welding device, the method comprising the following steps:

[0028] (1) Use the tungsten electrode sample preparation tool to clean the contaminants on the tungsten electrode electron emitter, then install it on the welding gun, extend the tungsten electrode electron emitter out of the protective gas shield, and control the distance between the two ends to be 8-10mm;

[0029] (2) Decontamination of the welding area on the workpiece surface and the area 15 mm nearby by mechanical cleaning or chemical cleaning;

[0030] (3) Fine-tune the welding gun posture to ensure that the center axis of the tungsten electrode is perpendicular to the surface of the welding sample, and adjust the distance between the welding gun and the workpiece;

[0031] (4) Check and confirm that the cooling water, shielding gas, ion gas, wire feeding device, welding travel mechanism and welding power supply are in normal working condition, and set the shielding gas flow, wire feeding speed, welding arc mode, welding current and welding speed according to the welding parameters.

[0032] (5) Press the start button to prepare the hollow tungsten electrode coaxial filler wire welding layer at a high wire feeding speed of the workpiece to be welded.

[0033] Beneficial effects:

[0034] 1. The present invention is based on the arc formation principle used in tungsten inert gas (TIG) welding. By modifying the shape characteristics of the electron-emitting end of the hollow tungsten electrode, the arc shape is controlled. While meeting the requirements of hollow tungsten electrode coaxial wire welding, the spatial temperature gradient of the arc column region is regulated. This ensures that the welding wire, coaxially and stably delivered from the inner hole of the tungsten electrode, enters the arc column region in a high-temperature solid state and then enters the molten pool in the form of a liquid bridge transition. This reduces the interference of the liquid metal transition with the molten pool flow and arc stability, thus meeting the basic process characteristics required for efficient and stable argon arc welding technology. In addition, when the welding wire and the workpiece are in contact, the welding wire and the workpiece have the same potential, and the welding arc burns between the welding wire and the inner hole of the tungsten electrode. At this time, the TIG arc acts as a preheating wire, which is extremely beneficial for improving the welding wire's deposition efficiency and further reducing the heat input to the base material. At the same time, the design of the ion gas channel ensures that the high-temperature welding wire inside the hollow tungsten electrode and the liquid molten pool in the welding arc action area are always well protected, effectively preventing oxidizing gas contamination of the liquid metal, which is beneficial for improving welding quality.

[0035] 2. This invention eliminates the directional problem of traditional tungsten electrode argon arc side-axis filler wire welding, and the addition of the porcelain tube effectively solves the insulation problem between the welding wire and the tungsten electrode, making it possible to weld various complex curved surfaces of components;

[0036] 3. Compared with the method of coating the inner part of the half-split tungsten electrode with an insulating layer, the present invention adopts a high-temperature resistant and wear-resistant boron nitride porcelain tube for insulation, which significantly reduces the failure problem caused by friction between the welding wire and the insulating material during long-term transportation of the welding wire. The design of the insulating porcelain tube not only reduces the manufacturing cost, but also is more convenient to replace and has higher reliability, greatly improving the stability of the hollow tungsten electrode coaxial filler wire welding process during implementation.

[0037] 4. The petal-shaped characteristic tungsten electrode with several arc emission points adopted in the present invention can effectively burn several points where the current is concentrated, compared with the conventional ring-shaped hollow tungsten electrode, prevent the damage to the porcelain tube caused by the high-temperature arc and the heat conduction of the tungsten electrode at the arc emission end, stabilize the arc, and increase the welding speed.

[0038] 5. The inner hole of the hollow tungsten electrode of the present invention has a step, so that the relative position between the porcelain tube and the tungsten electrode does not shift, and the step serves as a reference. The position of the porcelain tube will be highly consistent each time it is installed, which provides a guarantee for the consistency of the hollow tungsten electrode coaxial wire welding process.

[0039] 6. The present invention realizes laminar flow of ion gas before it reaches the welding area through the ion gas buffer chamber, porous medium material, ion gas filter and ion gas channel, which plays a good synergistic control role in the stable combustion of the flexible arc. In addition, the stable flow of ion gas plays a vital role in protecting the end of the high-temperature welding wire and the high-temperature area of ​​the welding pool.

[0040] 7. The present invention adopts a steady flow design of the ion gas flow through the gas path, which not only realizes the protection of the high temperature area of ​​the welding wire and the molten pool, but also the vertical downward flow of the airflow will promote the transition of the molten droplet at the end of the welding wire to a certain extent, which is of great significance for regulating the filling process during welding.

[0041] 8. The present invention uses a large-diameter hollow tungsten electrode, which increases the surface area of ​​the electron emission zone while significantly reducing the current density in the arc column region. This increases the area of ​​the arc column irradiated on the workpiece surface while also reducing the arc's ability to melt the base material. This is extremely beneficial for reducing the dilution rate of the base material in the deposited metal and improving the performance of the deposited metal in the weld layer.

[0042] 9. The electron emission area of ​​the hollow tungsten electrode of the present invention is surface emission. This increases the arc irradiation area while ensuring the electron density and arc temperature in the arc column. Therefore, under the premise of effectively ensuring the heat in the central area, the arc's ability to melt the welding wire per unit time is enhanced, and the wire feeding speed can be further increased, laying the foundation for significantly improving welding efficiency.

[0043] 10. The shape of the tungsten electrode electron emission end of the present invention is processed into a "funnel", which can move the electron emission area away from the central axis of the tungsten electrode and the welding wire, reduce the heat radiation effect of the high-temperature arc on the welding wire inside the tungsten electrode, and prevent the welding wire from melting inside the tungsten electrode, causing damage to the tungsten electrode or poor wire feeding. In addition, each micro-area on the electron emission end surface is a bell-shaped arc formation area. The annular arc surrounded by countless micro-areas forming the bell-shaped arc presents the characteristics of an annular "M"-shaped heat source, in which the heat in the center area of ​​the "M"-shaped heat source is used to melt the welding wire, and the arc near the edge of the "M"-shaped heat source is used to preheat the welding wire. This is extremely beneficial for improving the melting efficiency of the welding wire and controlling the liquid metal after the welding wire melts to enter the liquid molten pool in the form of a liquid bridge.

[0044] 11. During welding, when the droplet at the end of the welding wire contacts the workpiece, the welding wire and the workpiece have the same potential, and the welding arc gradually transfers from the workpiece to the inner hole of the tungsten electrode. At this time, the heat of the TIG arc is basically used to preheat the welding wire, which is extremely beneficial to improving the welding wire deposition efficiency. In addition, the transfer of the arc further significantly reduces the heat input to the base material, preventing the coarsening of grains and affecting the mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a schematic diagram of the structure of a hollow tungsten electrode coaxial wire-filled welding device;

[0046] Figure: 1. Hollow tungsten electrode; 2. Tungsten electrode clamp; 3. Shielding gas hood; 4. Welding wire; 5. Insulating porcelain tube; 6. Welding arc; 7. Molten droplet; 8. Welding layer; 9. Test specimen; 10. Conductive block; 11. Ion gas inlet; 12. Ion buffer filter chamber; 13. Porous dielectric material; 14. Ion gas filter; 15. Ion gas channel.

[0047] Figure 2 It is a schematic diagram of a stepped hollow tungsten electrode;

[0048] In the figure: 16, hollow tungsten electrode step; 17, hollow tungsten electrode inner hole chamfer; 18, hollow tungsten electrode arc emission plane; 19, hollow tungsten electrode outer side chamfer;

[0049] Figure 3 This is a schematic diagram of the end surface of a conventional annular hollow tungsten core;

[0050] In the figure: D1 is the inner diameter of the arc emitting end of the hollow tungsten electrode; D2 is the outer diameter of the chamfer of the inner hole of the core tungsten electrode; D3 is the outer diameter of the arc emitting plane of the core tungsten electrode; D4 is the diameter of the hollow tungsten electrode;

[0051] Figure 4 This is a schematic diagram of the petal-shaped tungsten extreme surface;

[0052] Figure 5 This is a diagram of the arc shape of the hollow tungsten electrode and its electron emitting end;

[0053] In the figure: 20, inner hole of hollow tungsten electrode; 21, arc irradiation area; 22, bell mouth. DETAILED DESCRIPTION

[0054] Example 1:

[0055] A hollow tungsten electrode coaxial wire-filling welding device, comprising a hollow tungsten electrode 1, a tungsten electrode clamp 2, a protective gas cover 3, a welding wire 4, an insulating porcelain tube 5, and a plasma buffer filter air chamber 12;

[0056] The hollow tungsten electrode is clamped by symmetrically arranged tungsten electrode clamps, the protective gas cover is located outside the tungsten electrode clamps, and the plasma buffer filter air chamber is fixed to the upper end of the hollow tungsten electrode;

[0057] The hollow tungsten electrode has a step inside, the insulating porcelain tube is inserted into the step inside the hollow tungsten electrode, the welding wire is inserted into the insulating porcelain tube, and the gap between the welding wire and the hollow tungsten electrode forms an ion gas channel 15;

[0058] The gas passes through the ion gas channel and the porous material inside the ion gas buffer chamber to control the uniformity of the airflow. Then the ion gas passes through the porous ion gas filter and mesh, so that the airflow enters the ion gas channel in a laminar flow and stability.

[0059] The ion gas channel is installed together with the ceramic tube, and has an internal gas chamber that can stabilize the gas flow state. The gas chamber introduces ion gas into the hollow tungsten electrode through two air inlet pipes, achieving effective protection for the welding wire and the high-temperature liquid molten pool, preventing problems such as oxidation in the weld seam that affect the reliability of the weld layer during service.

[0060] The welding wire 4 is fed steadily at a certain wire feeding speed by a wire feeder and is fed out through the inner hole of the porcelain tube 5. The welding wire 4 can be in the form of a solid welding wire or a twisted wire.

[0061] The insulating porcelain tube is made of high-melting-point boron nitride. When installed inside the hollow tungsten electrode, the step at the arc burning end of the hollow tungsten electrode is used to constrain the installation position. The outer diameter of the porcelain tube is slightly smaller than the inner hole size of the hollow tungsten electrode, with a difference of 0.05 to 0.15 mm. The distance between the end of the insulating porcelain tube and the electron emission end of the tungsten electrode is between 12 and 15 mm. The melting point of this material is as high as 3000 ° C, and the resistivity can reach 4.5×10 at 1494 ° C. 3 Ω·cm, and its thermal conductivity is also excellent among ceramics at 41.8W·(m·k) -1 , the maximum operating temperature in an inert atmosphere is up to 2800℃;

[0062] An ion gas filter screen 14 is fixed inside the ion gas buffer filter chamber, and a porous medium material 13 is filled in the closed space formed by the ion gas filter screen and the ion gas buffer chamber.

[0063] Example 2:

[0064] According to the hollow tungsten electrode coaxial wire-filling welding device described in Example 1, the bottom of the hollow tungsten electrode is a bell-mouth, the end face is annular, and the hollow tungsten electrode with stepped petal-shaped structure is cut radially to form multiple arc emission points.

[0065] The shape of the hollow tungsten electron emitter consists of three parts: ① A bell-shaped shape with a certain angle is machined on the inner hole of the hollow tungsten electron emitter with an outer diameter of D1 and an inner diameter of D4. The inner surface of the bell-shaped shape is called the inner wall, and the inner wall diameter is D2; ② An inclined surface with a certain chamfer is machined on the outer diameter of the hollow tungsten electron emitter. The circular surface formed by the inclined surface is called the outer wall; ③ The unmachined end surface of the electron emitter is used to emit electrons. This end surface is called the tungsten electron emitter plane, or simply the end plane. Its radial width is calculated by the following formula:

[0066] The method for controlling the spatial temperature gradient in the arc column region is achieved by changing the inner wall diameter D2 of the electron emission end bell mouth and the outer wall diameter D3 of the electron emission end. The purpose of changing the inner wall diameter D2 of the bell mouth is to change the distance between the inner edge position of the arc and the welding wire, that is, to adjust the shape of the arc irradiation zone, thereby achieving the purpose of accurately controlling the degree of arc preheating of the welding wire and the position of the arc melting fuse; the purpose of changing the outer wall diameter D3 of the electron emission end is to change the size of the electron emission end width w, thereby achieving effective control of the welding layer width and the arc stability during the welding process.

[0067] Example 3:

[0068] According to the hollow tungsten electrode coaxial wire-filling welding device described in Example 1 or 2, the step of the stepped hole inside the stepped petal-shaped hollow tungsten electrode is located 10 to 20 mm above the end of the hollow tungsten electrode.

[0069] Example 4:

[0070] According to the hollow tungsten electrode coaxial welding device with filler wire described in embodiment 1, 2 or 3, the petal-shaped hollow tungsten electrode generally has 2 to 8 petals.

[0071] Example 5:

[0072] According to the hollow tungsten electrode coaxial filler wire welding device described in embodiment 1, 2, 3 or 4, the width of the ion gas channel is 0.2 to 0.3 mm.

[0073] Example 6:

[0074] According to the hollow tungsten electrode coaxial filler wire welding device described in Example 1, 2, 3, 4, or 5, the porous medium material is a sponge material.

[0075] Installation method: Fix the stepped ring-shaped or petal-shaped hollow tungsten electrode in the hollow tungsten electrode coaxial wire feeding TIG welding gun through the tungsten electrode clamp. Set the distance between the tungsten end face and the workpiece between 3 and 10 mm. Slowly insert the porcelain tube into the hollow tungsten electrode through the side without the step hole of the hollow tungsten electrode until the end face of the porcelain tube contacts the step surface of the inner hole of the tungsten electrode. Then, the ion gas buffer chamber is fixed to the end of the porcelain tube with an interference fit. During welding, the ion gas enters the ion gas buffer chamber through the gas inlet, flows through the porous medium material, and then enters the ion gas channel composed of the porcelain tube, tungsten electrode and welding wire through the ion gas filter. Before entering the welding wire and arc irradiation area, it plays a good protective role on the high-temperature area of ​​the welding wire and the liquid molten pool. The type and flow rate of the ion gas can be set according to the actual working conditions. The conductive block on the outside of the tungsten electrode clamp is in close contact with the tungsten electrode clamp. Its function is to transfer the electric energy required for welding to the tungsten electrode through the tungsten electrode clamp, and complete the arc ignition between the tungsten electrode and the workpiece by high-frequency arc ignition, forming a high-temperature arc with stable combustion.

[0076] The petal-shaped hollow tungsten electrode with steps has a width of 0.15 to 0.25 mm. In order to prevent the damage of the porcelain tube caused by the heat conduction between the high-temperature arc and the tungsten electrode at the arc emission end, the distance between the step position and the end surface of the tungsten electrode at the arc emission end is between 12 and 15 mm.

[0077] Ion gas types include commonly used argon, helium, hydrogen, oxygen, nitrogen, and mixed gases obtained by mixing the above different gases in a certain proportion; the flow rate of the ion gas can be set according to actual needs, generally set between 10 and 2000 mL;

[0078] The ion gas filter can be made of copper alloy, and the mesh size of the copper mesh is between 100 and 200 meshes. The ion gas channel consists of two parts: the front section consists of the inner wall of the porcelain tube and the welding wire, and the rear section consists of the inner wall of the tungsten electrode and the welding wire. In order to ensure the straightness and uniformity of the wire when it is fed out, the size of the gap is generally set between 0.2 and 0.3 mm.

[0079] During actual welding, if the welding current is large and the arc straightness is good, the ion gas flow rate can be appropriately increased to improve the protection effect and promote the uniform transition of the molten droplets at the end of the welding wire. At the same time, a larger ion gas flow rate can also take away a large amount of heat, playing the role of a high-temperature tungsten electrode in the cold zone.

[0080] When the welding current is large or a high-frequency pulse arc is used, the arc straightness is better. At this time, in order to prevent the high-temperature arc from burning the tungsten electrode and causing tungsten clamping in the weld, the size w of the arc emission plane 18 can be appropriately increased. In order to increase the w value, the chamfer diameter D2 of the outer side of the tungsten electrode can be appropriately reduced, or the outer edge diameter D3 of the hollow tungsten electrode arc emission plane can be appropriately increased.

[0081] Example 7:

[0082] A method for controlling a hollow tungsten electrode coaxial filler wire welding device comprises the following steps:

[0083] (1) The shape of the hollow tungsten pole electron emitting end is prefabricated. A bell-mouth shape is machined on the inner hole of the hollow tungsten pole electron emitting end with an outer diameter of D1 and an inner hole diameter of D4. The inner surface of the bell-mouth is called the inner wall, and the diameter of the inner wall is D2. A bevel is machined on the outer diameter of the hollow tungsten pole electron emitting end. The annular surface formed by the bevel is called the outer wall. The unmachined end surface of the electron emitting end is used to emit electrons. This end surface is called the tungsten pole electron emitting end plane, or end plane for short. Its radial width is calculated by the following formula:

[0084]

[0085] (2) Control of spatial temperature gradient in the arc column area;

[0086] The diameter D2 of the inner wall of the bell mouth is used to change the distance between the inner edge of the arc and the welding wire, thereby adjusting the shape of the arc irradiation area. The diameter D3 of the outer wall of the electron emission end is changed to change the width w of the electron emission end.

[0087] (3) Effective control of arc stability;

[0088] Based on the principle of electron tip emission, the smaller the w value, the better the arc stability. When the current is large, the degree of tungsten electrode burning increases.

[0089] (4) Control of arc preheating wire and melting wire position;

[0090] When the welding current is constant, the spatial morphology distribution characteristics of the arc column area during the wire feeding process can be precisely controlled by changing the value of the inner wall diameter D2 of the bell mouth.

[0091] (5) Precise control of the spatial morphology and distribution characteristics of the arc column area;

[0092] When the welding current remains unchanged, changing the D2 value means changing the position of the electron emission end, thereby regulating the distance between the welding wire and the arc. The larger the D2 value, the farther the inner edge of the arc is from the welding wire, the weaker the irradiation effect on the welding wire, and the lower the preheating effect of the arc on the welding wire. On the contrary, the preheating effect of the arc on the welding wire is enhanced.

[0093] Adjust the distance between the tungsten electrode electron emission plane and the test plate, that is, the distance between the hollow tungsten electrode and the workpiece, and control the distance between the position where the welding wire begins to melt and the test plate.

[0094] Example 8:

[0095] A welding method for a hollow tungsten electrode coaxial wire welding device is described. Q235 carbon steel is used as the base material, and 308L stainless steel welding wire with a diameter of 1.2 mm is used. A hollow tungsten electrode coaxial wire surface welding experiment is conducted on a 300×200×20 mm carbon steel sample. The specific implementation steps are as follows:

[0096] Step 1: Use a tungsten electrode sample preparation tool to clean the contaminants on the electron emitting end of the tungsten electrode. Pre-set the electron emitting end of the hollow tungsten electrode with an outer diameter D4 of 6mm and an inner hole diameter D1 of 3mm into a specific bell-mouth shape. Control the bell-mouth diameter D2 between 3.5 and 3.6mm, and the outer wall diameter D3 between 5.0 and 5.1mm. Install the processed hollow tungsten electrode on the welding gun using a tungsten electrode clamp. The electron emitting end of the tungsten electrode needs to extend out of the protective gas shield. The vertical distance between the electron emitting end of the hollow tungsten electrode and the end of the protective gas shield should be kept at 8-10mm.

[0097] Step 2: Decontaminate the weld area and the surrounding 15 mm area on the surface of a 300 × 200 × 20 mm carbon steel specimen using mechanical or chemical cleaning methods;

[0098] Step 3: Fine-tune the welding gun posture to ensure that the center axis of the tungsten electrode is perpendicular to the surface of the welding sample. At the same time, adjust the distance between the welding gun and the workpiece so that the distance between the electron emission end of the tungsten electrode and the workpiece is set to 3-6mm;

[0099] Step 4: Check and confirm in sequence that the cooling water, shielding gas, wire feeding device, welding travel mechanism and welding power supply are in normal working condition, and set the shielding gas flow, wire feeding speed, welding arc mode (continuous, pulse), welding current and welding speed according to the welding parameters. The welding mode is set to continuous welding mode, the welding current is set to 400-600A, the wire feeding speed is set to 3-4m / min, the shielding gas flow is set to 18-20L / min, the ion gas flow is set to 10mL / min, the welding speed is set to 0.3m / min, the starting current is controlled at 450-650A, the arc starting time is set to 0.2-0.5s, the arc ending current is set to 250-300A, and the shielding gas delay gas supply time is set to 5-10s after welding is completed.

[0100] Step 5: Press the start button to prepare the hollow tungsten electrode coaxial filler wire welding layer at a high wire feeding speed of the workpiece to be welded.

[0101] The different stages of the wire feeding process are based on the different ways in which the wire is heated during transportation, and can be divided into three stages: first, before the wire is fed out of the inner hole of the hollow tungsten electrode, the thermal radiation effect of the high-temperature inner hole of the tungsten electrode will preheat the wire to a certain extent; second, just before the wire is fed out of the inner hole of the tungsten electrode and enters the arc area, it will first enter the arc irradiation zone 15. In the area surrounded by the edge of the high-temperature annular arc, the thermal radiation effect will further preheat the wire; finally, when the end of the wire preheated to a higher temperature enters the arc column area, the wire immediately reaches the melting point and begins to melt stably to form liquid metal.

[0102] Precise control of the spatial morphological distribution characteristics of the arc column region is achieved in the following manner. When the welding current remains unchanged, changing the D2 value essentially changes the position of the electron emission end, thereby regulating the distance between the welding wire and the arc. The larger the D2 value, the farther the inner edge of the arc is from the welding wire, the weaker the irradiation effect on the welding wire, and the arc's preheating effect on the welding wire decreases. Conversely, the arc's preheating effect on the welding wire increases. At the same time, the distance between the tungsten electrode electron emission plane and the test plate is adjusted, that is, the distance between the hollow tungsten electrode and the workpiece (generally 3 to 6 mm), and the highest point of the arc center is controlled to be between 1.0 and 2.5 mm above the plate surface, that is, the position where the welding wire begins to melt is controlled to be 1.0 to 2.5 mm away from the test plate. This is extremely beneficial for the melting process of the welding wire during liquid bridge transition.

[0103] The above-mentioned control of the highest point of the arc center position between 1.0 and 2.5 mm above the plate surface is extremely beneficial for the liquid metal formed after the welding wire melts to enter the molten pool in the form of a liquid bridge transition. The basis is that after the end of the welding wire, which has been preheated to a certain temperature, contacts the highest point of the arc center position, the welding wire will begin to melt to form droplets, and the diameter of the droplets under the action of surface tension, gravity, etc. is about 1.3 mm. According to different wire feeding speeds, by controlling the appropriate position of the highest point of the arc center, the molten droplets at the end of the welding wire can be accurately achieved to enter the molten pool in the form of a liquid bridge transition.

[0104] The liquid metal formed after the welding wire melts enters the molten pool in the form of a liquid bridge transition. This means that the liquid metal formed after the high-temperature welding wire melts after entering the high-temperature arc column area will contact the surface of the liquid molten pool before dripping into the molten pool in the form of drops. Under the action of the surface tension of the liquid metal, the liquid metal stably transitions into the molten pool, completing the filling process.

[0105] The width of the welding layer prepared by this method is 14 to 20 mm, the depth of matrix melting is only 0.8 to 1.0 mm, and the dilution rate of the matrix to the deposited metal is extremely low. The wire feeding speed under this method is 2 to 4 times the wire feeding speed of conventional traditional tungsten inert argon arc welding, and the welding speed is 1.5 to 2 times that of conventional similar welding methods.

[0106] Example 9:

[0107] Using TC4 titanium alloy as the base material, a hollow tungsten electrode coaxial filler wire welding experiment was carried out on a 200×150×3mm titanium alloy specimen using a TC4 welding wire of the same material and a diameter of 1.2mm. The specific implementation steps are as follows:

[0108] Step 1: Use a tungsten electrode sample preparation tool to clean the contaminants on the electron emitting end of the tungsten electrode. Pre-set the electron emitting end of the hollow tungsten electrode with an outer diameter D4 of 6mm and an inner hole diameter D1 of 3mm into a specific bell-mouth shape. Control the bell-mouth diameter D2 between 3.6 and 3.7mm, and the outer wall diameter D3 between 5.2 and 5.3mm. Install the processed hollow tungsten electrode on the welding gun using a tungsten electrode clamp. The electron emitting end of the tungsten electrode needs to extend out of the protective gas shield. The vertical distance between the electron emitting end of the hollow tungsten electrode and the end of the protective gas shield should be kept at 8-10mm.

[0109] Step 2: Use mechanical cleaning or chemical cleaning to decontaminate the end face of the 200×150×3mm titanium alloy sample to be welded and the surrounding 15mm area, wipe it clean with alcohol, and air dry it for later use;

[0110] Step 3: Fine-tune the welding gun posture to ensure that the center axis of the tungsten electrode is perpendicular to the surface of the welding sample. At the same time, adjust the distance between the welding gun and the workpiece so that the distance between the electron emission end of the tungsten electrode and the workpiece is set to 4-5mm;

[0111] Step 4: Check and confirm in sequence that the cooling water, shielding gas, wire feeding device, welding travel mechanism and welding power supply are in normal working condition, and set the shielding gas flow, wire feeding speed, welding arc mode (continuous, pulse), welding current and welding speed according to the welding parameters. The welding mode is set to continuous welding mode, the welding current is set to 450A, the wire feeding speed is set to 4.5m / min, the shielding gas flow is set to 18-20L / min, the ion gas flow is set to 5mL / min, the welding speed is set to 0.5m / min, the starting current is controlled at 500A, the arc starting time is set to 0.5s, the arc ending current is set to 180A, the arc ending time is set to 2s, and the shielding gas delay gas supply time after welding is completed is set to 10s.

[0112] Step 5: Pressing the start button completes single-sided welding and double-sided forming of a 3mm-thick titanium alloy hollow tungsten electrode coaxial filler wire. This method produces a uniform surface finish on the titanium alloy, increasing welding efficiency by 1.3 to 2 times compared to conventional solid tungsten electrode argon arc welding. The weld surface is silvery white, free of yellow or blue oxidation colors, and the mechanical properties of the welded joint reach 96% of those of the parent material.

Claims

1. A hollow tungsten electrode coaxial filler wire welding device, characterized by: The hollow tungsten electrode coaxial wire-filling welding device comprises a hollow tungsten electrode, a tungsten electrode clamp, a protective gas cover, a welding wire, an insulating porcelain tube, and an ion buffer filter air chamber; The hollow tungsten electrode is clamped by symmetrically arranged tungsten electrode clamps, the protective gas cover is located outside the tungsten electrode clamps, and the plasma buffer filter air chamber is fixed to the upper end of the hollow tungsten electrode; The hollow tungsten electrode has a step inside, the insulating porcelain tube is inserted into the step inside the hollow tungsten electrode, the welding wire is inserted into the insulating porcelain tube, and the gap between the welding wire and the hollow tungsten electrode forms an ion gas channel; the welding wire is fed by a wire feeder, and the welding wire is a solid welding wire or a twisted strand welding wire; An ion gas filter screen is fixed inside the ion gas buffer filter chamber, and a porous medium material is filled in the closed space formed by the ion gas filter screen and the ion gas buffer chamber.

2. The hollow tungsten electrode coaxial filler wire welding device according to claim 1, characterized in that: The bottom of the hollow tungsten electrode is a bell mouth, the end face is annular, and it is cut along the radial direction to be equally divided into a plurality of arc emission points and is a hollow tungsten electrode with stepped petal shapes.

3. The hollow tungsten electrode coaxial filler wire welding device according to claim 2, characterized in that: The step of the stepped hole inside the stepped petal-shaped hollow tungsten electrode is located 10 to 20 mm above the end of the hollow tungsten electrode.

4. The hollow tungsten electrode coaxial filler wire welding device according to claim 3, characterized in that: The petal-shaped hollow tungsten electrode has 2 to 8 petals.

5. The hollow tungsten electrode coaxial filler wire welding device according to claim 4, characterized in that: The width of the ion gas channel is 0.2-0.3 mm.

6. The hollow tungsten electrode coaxial filler wire welding device according to claim 5, characterized in that: The porous medium material is a sponge material.

7. A control method for the hollow tungsten electrode coaxial filler wire welding device according to any one of claims 1 to 6, characterized in that: The specific steps include: (1) The shape of the hollow tungsten pole electron emitting end is prefabricated. A bell-mouth shape is machined on the inner hole of the hollow tungsten pole electron emitting end with an outer diameter of D1 and an inner hole diameter of D4. The inner surface of the bell-mouth is called the inner wall, and the diameter of the inner wall is D2. A bevel is machined on the outer diameter of the hollow tungsten pole electron emitting end. The annular surface formed by the bevel is called the outer wall. The unmachined end surface of the electron emitting end is used to emit electrons. This end surface is called the tungsten pole electron emitting end plane, or end plane for short. Its radial width is calculated by the following formula: (2) Control of spatial temperature gradient in the arc column area; The diameter D2 of the inner wall of the bell mouth is used to change the distance between the inner edge of the arc and the welding wire, thereby adjusting the shape of the arc irradiation area. The diameter D3 of the outer wall of the electron emission end is changed to change the width w of the electron emission end. (3) Effective control of arc stability; Based on the principle of electron tip emission, the smaller the w value, the better the arc stability. When the current is large, the degree of tungsten electrode burning increases. (4) Control of arc preheating wire and melting wire position; When the welding current is constant, the spatial morphology distribution characteristics of the arc column area during the wire feeding process can be precisely controlled by changing the value of the inner wall diameter D2 of the bell mouth. (5) Precise control of the spatial morphology and distribution characteristics of the arc column area; When the welding current remains unchanged, changing the D2 value means changing the position of the electron emission end, thereby regulating the distance between the welding wire and the arc. The larger the D2 value, the farther the inner edge of the arc is from the welding wire, the weaker the irradiation effect on the welding wire, and the lower the preheating effect of the arc on the welding wire. On the contrary, the preheating effect of the arc on the welding wire is enhanced. Adjust the distance between the tungsten electrode electron emission plane and the test plate, that is, the distance between the hollow tungsten electrode and the workpiece, and control the distance between the position where the welding wire begins to melt and the test plate.

8. A welding method for the hollow tungsten electrode coaxial filler wire welding device according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: (1) Use the tungsten electrode sample preparation tool to clean the contaminants on the tungsten electrode electron emitter, then install it on the welding gun, extend the tungsten electrode electron emitter out of the protective gas shield, and control the distance between the two ends to be 8-10mm; (2) Decontamination of the welding area on the workpiece surface and the area 15 mm nearby by mechanical cleaning or chemical cleaning; (3) Fine-tune the welding gun posture to ensure that the center axis of the tungsten electrode is perpendicular to the surface of the welding sample, and adjust the distance between the welding gun and the workpiece; (4) Check and confirm that the cooling water, shielding gas, ion gas, wire feeding device, welding travel mechanism and welding power supply are in normal working condition, and set the shielding gas flow, wire feeding speed, welding arc mode, welding current and welding speed according to the welding parameters; (5) Press the start button to prepare the hollow tungsten electrode coaxial filler wire welding layer at a high wire feeding speed of the workpiece to be welded.

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