A controlled pulse perforating plasma arc-non-axisymmetric rotating tungsten arc combined welding method

Abstract

The present invention relates to a controlled pulse perforation plasma arc-non-axisymmetric rotating tungsten arc combined welding method. The welding system based on it includes a PAW and NAR-GTAW combined welding gun system, a wire feeding device, and an acquisition and control system. The method includes: the NAR-GTAW welding gun and the PAW welding gun are both fixed on a movable carriage, the angle between the welding wire and the tungsten electrode is 30° to 60°, the PAW welding gun forms an angle of 2° to 5° with the vertical direction of the workpiece, and the movable carriage is adjusted so that both welding guns are located at the exact center of the groove or welding position, and the PAW welding gun is first used for base welding, and the NAR-GTAW welding gun is used for cap welding on the basis of the base welding. The present invention combines the advantages of the two welding methods by combining PAW and NAR-GTAW, effectively solves the problems of surface pores and undercuts that are prone to occur in plasma arc welding technology, eliminates welding defects, beautifies the weld surface, and ensures welding quality.

Description

Technical Field

[0001] The invention relates to a controlled pulse perforating plasma arc-non-axisymmetric rotating tungsten arc combined welding method, wherein the first heat source is a controlled pulse perforating plasma arc, and the second heat source is a non-axisymmetric tip rotating tungsten arc, and belongs to the technical field of plasma arc welding. Background Art

[0002] With the rapid development of the global heavy manufacturing industry, medium and thick plates have been widely used in shipbuilding, natural gas transportation, aerospace, bridges and nuclear industries. Traditional welding methods such as submerged arc welding have high welding efficiency, but the pre-welding preparation is complicated and the welding limitations are high; tungsten inert gas welding has high welding quality, but low welding efficiency; high-energy beam welding such as laser welding and electron beam welding, welding equipment is expensive; and plasma arc welding has high welding efficiency and good welding quality, and can form single-sided and double-sided welding without beveling, but it is very easy to have undercut defects during the welding process.

[0003] Controlled pulsed perforation plasma arc welding (PAW) is based on a specially designed pulse current waveform. Through real-time sensing of the perforation status of the molten pool, the pulsed welding current waveform parameters are adjusted online to control the periodic formation and closure of small holes, forming a "one pulse one hole" welding mode, and realizing controlled pulsed perforation plasma arc welding. For 3-14mm stainless steel plates, good connections can be achieved, and single-sided welding and double-sided forming can be realized. However, in the actual welding process, due to improper selection of welding parameters or incorrect operation methods, grooves or depressions are generated in the parent material part at the junction of the weld surface and the parent material, forming undercuts.

[0004] Non-axisymmetric rotary tungsten inert gas welding (NAR-GTAW) is a process that generates a periodic arc by applying mechanical force to make the eccentric tungsten electrode move in a circular motion, which can effectively increase the shape coefficient of the weld, obtain a weld without welding defects on the surface, increase the stirring capacity of the arc, refine the weld structure, improve the weld quality, and improve the mechanical properties of the weld. However, since the non-axisymmetric rotary tungsten inert gas welding periodically strikes the arc at the bottom and both sides of the groove during the rotation process, when the arc rotates to the two sides of the groove, the arc melts the parent material to facilitate the fusion of the side walls, and stirs the molten pool when it rotates to the bottom away from the wire feeding side to increase the penetration depth; the welding wire will only melt the welding wire when the arc rotates to the bottom close to the wire feeding side, resulting in a decrease in the melting efficiency of the welding wire due to the different positions of the rotating arc. In addition, due to the characteristics of tungsten inert gas welding, it takes about 8 welds to weld a 16mm thick steel plate. Its overall deposition efficiency is low, and the thickness of a single-layer deposition layer is limited, which is difficult to meet the requirements of high-efficiency welding.

[0005] Chinese patent document CN103567652A discloses a DC plasma arc-tungsten inert gas arc composite welding method for aluminum alloy based on pulse coordinated control, wherein a tungsten inert gas arc welding gun is applied on one side of a plasma arc welding gun, and the tungsten inert gas arc welding gun is used to clean the surface oxide film of the aluminum alloy in front during welding, and the DC plasma arc welding gun is used to weld in the back. In order to prevent electromagnetic interference between the plasma arc and the tungsten inert gas arc during welding, when the plasma arc current is in the pulse base value arc maintenance, the pulse signal controller is triggered to adjust the tungsten inert gas arc current to the negative half-wave peak value to clean the surface oxide film of the aluminum alloy; when the plasma arc current is in the pulse peak welding stage, the tungsten inert gas arc current is adjusted to the pulse base value output by the pulse signal controller, and so on and so forth. However, this patent is a welding method specifically for aluminum and aluminum alloys, which has limitations in welding materials, and does not solve the problem of surface pores and undercut welding defects that are prone to occur during plasma arc welding. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a controlled pulse perforation plasma arc-non-axisymmetric rotating tungsten arc combined welding method, which can effectively solve the problems of surface pores and undercut welding defects on the surface of plasma arc welding welds.

[0007] The technical solution of the present invention is as follows:

[0008] A controlled pulsed perforating plasma arc-non-axisymmetric rotating tungsten arc combined welding method, based on a welding system including a PAW and NAR-GTAW combined welding gun system, a wire feeding device, and a collection and control system;

[0009] The PAW and NAR-GTAW combined welding gun system comprises a NAR-GTAW welding power source, a PAW welding power source, a NAR-GTAW welding gun and a PAW welding gun; the NAR-GTAW welding gun comprises a central rotating shaft, a motor system, and an external motor control box, the external motor control box controls the switch of the motor and the rotation rate of the central rotating shaft, the central rotating shaft is connected to a tungsten pole, one end of the tungsten pole is a non-axisymmetric tip; the tungsten pole rotates with the rotation of the central rotating shaft, and the arc generated between the tungsten pole tip and the base material can periodically heat the base material and melt the welding wire; the NAR-GTAW welding gun and the PAW welding gun are both fixed on a movable carriage;

[0010] The wire feeding device is located at the front side of the NAR-GTAW welding gun and is used for feeding wire during welding;

[0011] The data acquisition and control system includes an electromagnetic relay, a Hall current sensor, a Hall voltage sensor, a tail flame voltage sensor, a data acquisition card and a PAW closed-loop control system;

[0012] The combined welding method comprises the following steps:

[0013] (1) Open an I-shaped groove on the workpiece to be welded and weld it by butt welding, or weld it directly without opening a groove. Before welding, pre-treat the surface of the workpiece groove or the welding position to be welded to clean the oil and dust;

[0014] (2) Arrange the PAW welding gun and the NAR-GTAW welding gun in front and back along the welding direction, adjust the angle of the NAR-GTAW welding gun to be perpendicular to the workpiece to be welded, place the wire feeding device in front of the NAR-GTAW welding gun, use the front wire feeding method, and the angle between the welding wire and the tungsten electrode is α, which is 30° to 60°; adjust the angle of the PAW welding gun to form an angle of 2° to 5° with the vertical direction of the workpiece to be welded;

[0015] (3) Before welding, adjust the distance between the PAW welding gun and the workpiece to be welded, adjust the distance between the tungsten electrode of the NAR-GTAW welding gun and the workpiece to be welded, set it to supply air in advance, exhaust the air at the groove or the welding position before welding, adjust the movable slide to align the PAW welding gun and the NAR-GTAW welding gun, so that both welding guns are located in the center of the groove or the welding position; set the wire feeding device to delay wire feeding and draw the wire in advance;

[0016] (4) DC welding is used. First, the base welding is performed using a PAW welding gun, and then the cover welding is performed using a NAR-GTAW welding gun based on the base welding to complete the welding.

[0017] According to the preferred embodiment of the present invention, the PAW closed-loop control system includes a plasma arc welding machine, an interface circuit and a main control computer. The main control computer controls the input switching signal, output switching signal and output analog signal of the data acquisition card; the input and output of the switching signal are realized through the electromagnetic relay switch circuit to control the arc starting and arc ending functions; the acquisition card obtains the welding current, voltage and tail flame voltage signals in real time through the Hall current sensor, Hall sensor and tail flame voltage sensor, and then outputs the analog signal to the welding power supply through the acquisition card after computer processing to control the next stage of the welding process.

[0018] Preferably according to the present invention, the welding system further comprises a self-adjusting system, and the self-adjusting system comprises an arc length control system and a laser control system.

[0019] Preferably, according to the present invention, the arc length control system includes an arc length automatic controller and an arc voltage height adjustment controller. The arc length automatic controller is used to adjust the height of the welding gun to ensure that the arc length remains unchanged. By utilizing the constant current characteristics of the welding machine power supply, during the welding process, the current in the circuit is always equal to the current set on the control panel, and the arc voltage changes with the change of the distance from the tungsten electrode tip to the base material. When the welding gun is raised, the arc length increases, and the arc voltage increases accordingly; conversely, when the height of the welding gun is lowered, the arc voltage decreases. The arc voltage height adjustment controller detects the change in arc voltage and then controls the lifting motor of the welding gun to adjust the distance between the welding gun and the workpiece to be welded, ensuring that the detected arc voltage is consistent with the set voltage, thereby controlling the distance between the tungsten electrode tip and the workpiece to be welded to remain constant.

[0020] Preferably, according to the present invention, the laser control system includes a laser and a CCD industrial camera, the laser is arranged on the PAW welding gun, and the CCD industrial camera is set up in front of the welding of the workpiece to be welded. The laser emits a laser, which is filtered by the lens and the cylindrical mirror, and a clear and bright laser stripe is formed on the surface of the workpiece to be welded. The laser irradiates the surface of the narrow gap groove, and it will be interrupted at the weld, and discontinuity will occur. At this time, the CCD industrial camera collects the laser image to extract the feature point information, and obtains the size data of the contour after algorithm processing to obtain the position information of the tungsten electrode, and obtains the feedback information by comparing it with the set position information, and then adjusts the lateral position of the welding gun to maintain the welding gun in the welding process. The center of the weld can always be maintained, making the equipment more flexible, and timely adjustments can be made when welding complex welds to ensure weld formation.

[0021] Preferably, according to the present invention, in step (2), the distance between the NAR-GTAW welding gun and the PAW welding gun is 100 to 300 mm.

[0022] Preferably, according to the present invention, in step (3), the distance between the PAW welding gun and the workpiece to be welded is 5 to 8 mm; the distance between the tungsten electrode of the NAR-GTAW welding gun and the workpiece to be welded is 3 to 4 mm.

[0023] Preferably, according to the present invention, in step (3), the time for delayed wire feeding is 0.2 to 0.4 s, and the time for advance wire drawing is 0.2 to 0.4 s.

[0024] Preferably, according to the present invention, in step (4), the process parameters of the base welding performed by the PAW welding gun are as follows: the PAW tungsten electrode retraction amount is 1.3-1.5 mm, the DC pulse plasma arc base current is 180-210 A, the peak current is 200-220 A, and the ion gas flow rate is 2-3 L / min.

[0025] Preferably, in step (4), the process parameters for cap welding by the NAR-GTAW welding gun are: the rotation speed of the tungsten electrode is 250-350 r / min, the shielding gas flow rate is 20-30 L / min, the tungsten electrode diameter is 2.5-3.5 mm, the welding current is 120-180 A, the welding voltage is 12-16 V, the welding speed is 80-120 mm / min, and the wire feeding speed is 1000-1200 mm / min.

[0026] Preferably, according to the present invention, in step (4), during welding, an electromagnetic pulse protection device is added between two welding guns to reduce mutual interference between magnetic fields during welding.

[0027] The purpose of the present invention is achieved based on:

[0028] The PAW welding method has a unique "pinhole effect". Compared with the NAR-GTAW welding method, its welding speed and welding efficiency are greatly improved, and the weld heat affected zone is narrow, the workpiece deformation and residual stress are small, the joint quality is good, and there is basically no internal defect. However, due to improper selection of welding parameters and other reasons, grooves or depressions are generated in the parent material part at the junction of the weld surface and the parent material during the welding process; while the NAR-GTAW welding arc rotates periodically with the rotation of the tungsten tip, and the arc is forced to rotate due to the external mechanical force, so that the stirring effect of the arc on the molten pool is enhanced, which can effectively increase the shape coefficient of the weld, so that the molten pool is completely spread out, and a beautiful weld can be obtained, so it is suitable for cap welding; at the same time, NAR-GTAW can be used for capping while PAW welding, which can improve welding efficiency. The present invention fully combines the advantages of the two, and uses PAW for welding and NAR-GTAW for capping welding at the same time, which can effectively solve the undercut problem caused by PAW welding, obtain a beautiful weld, and appropriately improve production efficiency, which has great application value in actual production.

[0029] The beneficial effects of the present invention are:

[0030] 1. The present invention combines the advantages of the two welding methods by combining PAW and NAR-GTAW, effectively solves the problem of undercutting that is easy to occur in plasma arc welding technology, eliminates welding defects, beautifies the weld surface, and ensures welding quality. In addition, the non-axisymmetric rotating tungsten electrode welding process uses external mechanical force to make the eccentric tungsten electrode tip move in a circular motion, increases the stirring capacity of the arc, and can effectively increase the shape coefficient of the weld, so that the surface obtains a beautiful weld, and at the same time can refine the structure, improve the weld quality, and increase the impact toughness of the weld.

[0031] 2. Compared with the existing PAW-GTAW composite welding method, the present invention adopts non-axisymmetric rotation tungsten electrode argon arc welding to replace ordinary tungsten electrode argon arc welding. In the existing PAW-GTAW composite welding method, under the condition of the same weld width, the welding electrical parameters of the ordinary tungsten electrode are relatively large, and the large input will damage the mechanical properties of the welded joint. When applied to thick stainless steel plates, it will change the physical and chemical properties of the stainless steel and reduce its corrosion resistance. However, NAR-GTAW can meet the requirements under smaller electrical parameters, reduce welding heat input, reduce thermal stress and welding deformation, and obtain a larger weld coefficient. While ensuring the physical and chemical properties of the weld, it can save costs and reduce consumables. In addition, the non-axisymmetric rotation characteristics will refine the weld structure and improve the surface mechanical properties.

[0032] 3. By adopting the technical solution of the present invention, a weld with dense fish-scale strip-like morphology can be formed. The arc will rotate along with the periodic rotation of the tungsten electrode, which will have a strong stirring effect on the molten pool, so that the molten pool can be spread evenly when cooling, increasing the shape coefficient of the weld. At the same time, the molten pool will also move forward steadily to form an aesthetically pleasing weld.

[0033] 4. The welding process of the present invention is stable, and an arc length control system and a laser control system are added to the welding system. On the one hand, the arc length control system can maintain the arc length near a predetermined value without causing large fluctuations, so that the equipment is stable in the direction perpendicular to the weld; on the other hand, the laser control system is used to keep the welding gun at the center of the weld at all times, so that the welding equipment is stable along the weld.

[0034] 5. The present invention sets the distance between the NAR-GTAW welding gun and the PAW welding gun to 100-300 mm, which can effectively prevent the mutual influence between the arcs and avoid the coupling of the arcs when the distance between the two arcs is too close during the PAW and NAR-GTAW combined welding process. The two arcs will be affected by the Lorentz force. The greater the current, the greater the magnetic field intensity generated by the arc, and the greater the attraction between the two arcs, which may cause the following problems: First, because NAR-GTAW is a rotating arc, when the arc approaches the PAW arc, it will be attracted by the PAW arc to produce a coupling phenomenon. When the arc follows the rotation of the tungsten pole and moves away from the PAW arc, the NAR-GTAW arc will experience arc creep on the PAW arc, which results in the heat generated by the NAR-GTAW arc being unable to effectively act on the workpiece, the stirring effect of the rotating arc being unable to be maximized, and the weld surface being unable to be formed; Second, when the PAW and NAR-GTAW arcs are coupled, the NAR-GTAW arc cannot effectively heat the welding wire, and thus the weld surface cannot be formed. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1A schematic diagram of a PAW and NAR-GTAW combined welding gun of the present invention;

[0036] Figure 2 It is a schematic diagram of the relative position between the PAW welding gun and the workpiece;

[0037] Figure 3 Schematic diagram of the relative position of the PAW welding gun and the laser.

[0038] In the figure: 1. PAW welding gun, 2. NAR-GTAW welding gun, 3. Mobile slide, 4. Wire feeding device, 5. Laser, 6. Protective gas hood, 7. Tungsten electrode. DETAILED DESCRIPTION

[0039] The present invention will be further described below through specific implementation modes in conjunction with the accompanying drawings, but is not limited thereto.

[0040] Example 1

[0041] like Figures 1 to 3 As shown, a controlled pulse perforating plasma arc-non-axisymmetric rotating tungsten arc combined welding method is based on a welding system including a PAW and NAR-GTAW combined welding gun system, a wire feeding device, and a collection and control system; the welding material in this embodiment is 2507 super duplex stainless steel, and the plate thickness is 10 mm.

[0042] The PAW and NAR-GTAW combined welding gun system comprises a NAR-GTAW welding power source, a PAW welding power source, a NAR-GTAW welding gun and a PAW welding gun; the NAR-GTAW welding gun comprises a central rotating shaft, a motor system, and an external motor control box, the external motor control box controls the switch of the motor and the rotation rate of the central rotating shaft, the central rotating shaft is connected to a tungsten pole, one end of the tungsten pole is a non-axisymmetric tip; the tungsten pole rotates with the rotation of the central rotating shaft, and due to the asymmetry of its rotation, the arc can always periodically heat the base material and melt the welding wire according to the minimum voltage principle; the NAR-GTAW welding gun and the PAW welding gun are both fixed on a movable carriage;

[0043] The wire feeding device is located at the front side of the NAR-GTAW welding gun and is used for feeding wire during welding;

[0044] The acquisition and control system includes an electromagnetic relay, a Hall current sensor, a Hall voltage sensor, a tail flame voltage sensor, a data acquisition card and a PAW closed-loop control system; the PAW closed-loop control system includes a plasma arc welder, an interface circuit and a main control computer. The main control computer controls the input switching signal, output switching signal and output analog signal of the data acquisition card; the input and output of the switching signal are realized through the electromagnetic relay switch circuit to control the arc starting and arc ending functions; the acquisition card obtains the welding current, voltage and tail flame voltage signals in real time through the Hall current sensor, the Hall sensor and the tail flame voltage sensor, and then outputs the analog signal to the welding power supply through the acquisition card after computer processing to control the next stage of the welding process.

[0045] The welding method comprises the following steps:

[0046] (1) Medium and thick plates of 2507 super duplex stainless steel do not have grooves. Pre-treat the workpiece to be welded and remove the oil, rust and dust inside and on the surface of the welding position. Perform anti-deformation treatment on the workpiece to be welded and reinforce it with spot welding, and fix the workpiece to be welded on the workbench with a fixture;

[0047] (2) Arrange the PAW welding gun and the NAR-GTAW welding gun in front and back along the welding direction, with a welding gun spacing of 100 mm. Adjust the angle of the NAR-GTAW welding gun to be perpendicular to the workpiece to be welded. The wire feeding device is placed in front of the NAR-GTAW welding gun. The wire feeding method is front wire feeding. The angle between the welding wire and the tungsten electrode is α, and α is 60°. Adjust the angle of the PAW welding gun to form an angle of 5° with the vertical direction of the workpiece to be welded.

[0048] (3) Before welding, adjust the distance between the PAW welding gun and the workpiece to be welded to 8 mm, adjust the angle of the NAR-GTAW welding gun to slightly tilt the workpiece to be welded, and the distance between the welding gun and the upper end of the blunt edge of the workpiece is 3.5 mm; set the two welding power sources to supply gas in advance, and exhaust the air at the position to be welded before welding to ensure that the weld is filled with protective gas; adjust the movable slide to align the PAW welding gun and the NAR-GTAW welding gun so that the two welding guns are in the center of the position to be welded; set the wire feeding device to delay wire feeding by 0.3 s and draw wire in advance by 0.3 s;

[0049] (4) DC welding is used. First, the base welding is performed using a PAW welding gun, and then the cover welding is performed using a NAR-GTAW welding gun based on the base welding to complete the welding.

[0050] Among them, the PAW welding process parameters are set as follows: the PAW tungsten electrode retraction is 1.4 mm, the DC pulse plasma arc base current is 210 A, the peak current is 210 A, and the ion gas flow rate is 2 L / min.

[0051] The NAR-GTAW welding process parameters were set as follows: the rotation speed of the tungsten electrode was 300 r / min, the shielding gas flow rate was 25 L / min, the tungsten electrode diameter was 3 mm, the welding current was 150 A, the welding voltage was 14 V, the welding speed was 100 mm / min, and the wire feeding speed was 1100 mm / min.

[0052] This embodiment can achieve the welding of 10mm medium and thick plates of 2507 super duplex stainless steel. By performing PAW base welding, consumables and welding time are greatly saved, welding efficiency is greatly improved, welding residual stress is reduced, and the quality of the welded joint is guaranteed; by performing NAR-GTAW cap welding, the defects of the actual production of PAW welding of medium and thick plates are compensated, and a beautiful weld surface and a relatively fine weld structure can be obtained, and the low-temperature impact toughness of the weld is improved; and because the heat input of the entire welding process is small, the two-phase ratio of the duplex stainless steel can be guaranteed, thereby ensuring the corrosion resistance of the duplex stainless steel.

[0053] Embodiment 2:

[0054] A controlled pulse perforating plasma arc-non-axisymmetric rotating tungsten arc combined welding method, wherein the basic system is as described in Example 1, except that the welding system based thereon further includes a self-adjusting system; the self-adjusting system includes an arc length control system and a laser control system;

[0055] The arc length control system includes an arc length automatic controller and an arc voltage height adjustment controller. The arc length automatic controller is used to adjust the height of the welding gun to ensure that the arc length remains unchanged. By utilizing the constant current characteristics of the welding machine power supply, during the welding process, the current in the circuit is always equal to the current set on the control panel, and the arc voltage changes with the change of the distance from the tungsten electrode tip to the base material. When the welding gun is raised, the arc length increases, and the arc voltage increases accordingly; conversely, when the height of the welding gun is lowered, the arc voltage decreases. The arc voltage height adjustment controller detects the change in arc voltage and then controls the lifting motor of the welding gun to adjust the distance between the welding gun and the workpiece to be welded, ensuring that the detected arc voltage is consistent with the set voltage, thereby controlling the distance between the tungsten electrode tip and the workpiece to be welded to remain constant.

[0056] The laser control system includes a laser and a CCD industrial camera, and the laser is arranged on the PAW welding gun. The CCD industrial camera is set up in front of the welding frame, and then the laser emits a laser, which is filtered by the lens and the cylindrical mirror, and a clear and bright laser stripe is formed on the surface of the workpiece to be welded. When the laser is irradiated on the surface of the narrow gap groove, it will be interrupted at the weld and discontinuous. At this time, the CCD industrial camera collects the laser image to extract the feature point information, and obtains the size data of the contour after algorithm processing to obtain the position information of the tungsten electrode. By comparing with the set position information, feedback information is obtained, and then the lateral position of the welding gun is adjusted to maintain the welding gun in the center of the weld at all times during the welding process, so that the equipment is more flexible, and timely adjustments can be made when welding complex welds to ensure weld formation.

[0057] Embodiment 3:

[0058] A controlled pulse perforating plasma arc-non-axisymmetric rotating tungsten arc combined welding method, wherein the basic system is as described in Example 1, except that in step (1), a butt welding method is adopted for opening an I-shaped groove of a medium-thick plate of 2507 super duplex stainless steel;

[0059] In step (2), the distance between the PAW welding gun and the NAR-GTAW welding gun is 300 mm, the angle between the welding wire and the tungsten electrode is 45°, and the angle of the PAW welding gun is adjusted to form an angle of 2° with the vertical direction of the workpiece.

[0060] Embodiment 4:

[0061] A controlled pulse perforating plasma arc-non-axisymmetric rotating tungsten arc combined welding method, wherein the basic system is as described in Example 1, except that in step (1), a butt welding method is adopted for opening an I-shaped groove of a medium-thick plate of 2507 super duplex stainless steel;

[0062] In step (2), the distance between the PAW welding gun and the NAR-GTAW welding gun is 200 mm, the angle between the welding wire and the tungsten electrode is adjusted to 30°, and the angle of the PAW welding gun is adjusted to form an angle of 3° with the vertical direction of the workpiece.

[0063] Embodiment 5:

[0064] A controlled pulse perforating plasma arc-non-axisymmetric rotating tungsten arc combined welding method, wherein the basic system is as described in Example 1, except that the present embodiment is flat plate surfacing, the welding material is 2507 super duplex stainless steel, the plate thickness is 12 mm, and in step (4), the PAW welding process parameters are set as follows: the PAW tungsten electrode retraction amount is 1.4 mm, the DC pulse plasma arc base current is 198 A, the peak current is 208 A, and the ion gas flow rate is 3 L / min.

[0065] Set the NAR-GTAW welding process parameters: the rotation speed of the tungsten electrode is 350r / min, the shielding gas flow rate is 30L / min, the tungsten electrode diameter is 3.5mm, the welding current is 180A, the welding voltage is 16V, the welding speed is 120mm / min, and the wire feeding speed is 1200mm / min.

[0066] Embodiment 6:

[0067] A controlled pulse perforation plasma arc-non-axisymmetric rotating tungsten arc combined welding method, wherein the basic system is as described in Example 1, except that the present embodiment is a flat plate butt joint, the welding material is 430 ferritic stainless steel, the plate thickness is 4 mm, and in step (4), the PAW welding process parameters are set as follows: the PAW tungsten electrode retraction is 1.4 mm, the DC pulse plasma arc base current is 150 A, the peak current is 160 A, the ion gas flow rate is 3 L / min, the shielding gas is 20 L / min, and the welding speed is 300 mm / min.

[0068] Set the NAR-GTAW welding process parameters: the rotation speed of the tungsten electrode is 350r / min, the shielding gas flow rate is 20L / min, the tungsten electrode diameter is 3.5mm, the welding current is 100A, the welding voltage is 13V, the welding speed is 300mm / min, and the wire feeding speed is 1000mm / min.

[0069] This embodiment can achieve the welding of 430 ferritic stainless steel 4mm thick thin plates, effectively solve the problem of brittle fracture of 430 ferritic stainless steel after welding, effectively improve the toughness of 430 stainless steel, significantly improve the bending performance, and facilitate the transportation and use of 430 stainless steel.

[0070] Comparative Example 1

[0071] According to Chinese patent document CN103567652A, a pulse coordinated control-based aluminum alloy DC plasma arc-tungsten inert gas argon arc composite welding method is disclosed for welding 430 ferritic stainless steel with a plate thickness of 4 mm.

[0072] The 430 ferritic stainless steel in this comparative example has poor toughness and reduced bending properties after welding, and is very prone to brittle fracture during transportation and use.

Claims

1. A controlled pulse perforating plasma arc-non-axisymmetric rotating tungsten arc combined welding method, characterized in that: The welding system based on it includes PAW and NAR-GTAW combined welding gun system, wire feeding device, acquisition and control system; The PAW and NAR-GTAW combined welding gun system comprises a NAR-GTAW welding power source, a PAW welding power source, a NAR-GTAW welding gun and a PAW welding gun; the NAR-GTAW welding gun comprises a central rotating shaft, a motor system, and an external motor control box, the external motor control box controls the switch of the motor and the rotation rate of the central rotating shaft, the central rotating shaft is connected to a tungsten pole, one end of the tungsten pole is a non-axisymmetric tip; the tungsten pole rotates with the rotation of the central rotating shaft, and the arc generated between the tungsten pole tip and the base material can periodically heat the base material and melt the welding wire; the NAR-GTAW welding gun and the PAW welding gun are both fixed on a movable carriage; The wire feeding device is located at the front side of the NAR-GTAW welding gun and is used for feeding wire during welding; The acquisition and control system includes an electromagnetic relay, a Hall current sensor, a Hall voltage sensor, a tail flame voltage sensor, a data acquisition card and a PAW closed-loop control system; The combined welding method comprises the following steps: (1) Open an I-shaped groove on the workpiece to be welded and weld it by butt welding, or weld it directly without opening a groove. Before welding, pre-treat the surface of the workpiece around the groove or the position to be welded to clean the oil and dust; (2) Arrange the PAW welding gun and the NAR-GTAW welding gun in front and back along the welding direction, adjust the angle of the NAR-GTAW welding gun to be perpendicular to the workpiece to be welded, place the wire feeding device in front of the NAR-GTAW welding gun, use the front wire feeding method, and the angle between the welding wire and the tungsten electrode is α, which is 30° to 60°; adjust the angle of the PAW welding gun to form an angle of 2° to 5° with the vertical direction of the workpiece to be welded; (3) Before welding, adjust the distance between the PAW welding gun and the workpiece to be welded, adjust the distance between the tungsten electrode of the NAR-GTAW welding gun and the workpiece to be welded, set it to supply air in advance, exhaust the air at the groove or the welding position before welding, adjust the movable slide to align the PAW welding gun and the NAR-GTAW welding gun, so that both welding guns are located in the center of the groove or the welding position; set the wire feeding device to delay wire feeding and draw the wire in advance; (4) DC welding is used. First, the base welding is performed using a PAW welding gun, and then the cover welding is performed using a NAR-GTAW welding gun based on the base welding to complete the welding.

2. The controlled pulse perforating plasma arc-non-axisymmetric rotating tungsten arc combined welding method according to claim 1, characterized in that: The PAW closed-loop control system includes a plasma arc welding machine, an interface circuit and a main control computer; the main control computer controls the input switching signal, output switching signal and output analog signal of the data acquisition card; the input and output of the switching signal are realized through the electromagnetic relay switch circuit to control the arc starting and arc ending functions; the acquisition card obtains the welding current, voltage and tail flame voltage signals in real time through the Hall current sensor, the Hall voltage sensor and the tail flame voltage sensor, and then outputs the analog signal to the welding power supply through the acquisition card after computer processing to control the next stage of the welding process.

3. The controlled pulse perforating plasma arc-non-axisymmetric rotating tungsten arc combined welding method according to claim 1, characterized in that: The based welding system also includes a self-adjusting system, which includes an arc length control system and a laser control system.

4. The controlled pulse perforating plasma arc-non-axisymmetric rotating tungsten arc combined welding method according to claim 3, characterized in that: The arc length control system includes an arc length automatic controller and an arc voltage height adjustment controller.

5. The controlled pulse perforating plasma arc-non-axisymmetric rotating tungsten arc combined welding method according to claim 3, characterized in that: The laser control system comprises a laser and a CCD industrial camera. The laser is arranged on a PAW welding gun, and the CCD industrial camera is set up in front of the workpiece to be welded.

6. The controlled pulse perforating plasma arc-non-axisymmetric rotating tungsten arc combined welding method according to claim 1, characterized in that: In step (2), the distance between the NAR-GTAW welding gun and the PAW welding gun is 100 to 300 mm.

7. The controlled pulse perforating plasma arc-non-axisymmetric rotating tungsten arc combined welding method according to claim 1, characterized in that: In step (3), the distance between the PAW welding gun and the workpiece to be welded is 5 to 8 mm; the distance between the tungsten electrode of the NAR-GTAW welding gun and the workpiece to be welded is 3 to 4 mm.

8. The controlled pulse perforating plasma arc-non-axisymmetric rotating tungsten arc combined welding method according to claim 1, characterized in that: In step (3), the time for delayed wire feeding is 0.2 to 0.4 s, and the time for advance wire drawing is 0.2 to 0.4 s.

9. The controlled pulse perforating plasma arc-non-axisymmetric rotating tungsten arc combined welding method according to claim 1, characterized in that: In step (4), the process parameters of the base welding by the PAW welding gun are as follows: the PAW tungsten electrode retraction amount is 1.3-1.5 mm, the DC pulse plasma arc base current is 180-210 A, the peak current is 200-220 A, and the ion gas flow rate is 2-3 L / min.

10. The controlled pulse perforating plasma arc-non-axisymmetric rotating tungsten arc combined welding method according to claim 1, characterized in that: In step (4), the process parameters of cap welding by NAR-GTAW welding gun are: tungsten electrode rotation speed is 250-350r / min, shielding gas flow rate is 20-30L / min, tungsten electrode diameter is 2.5-3.5mm, welding current is 120-180A, welding voltage is 12-16V, welding speed is 80-120mm / min, and wire feeding speed is 1000-1200mm / min.

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