External magnetic field assisted duplex stainless steel laser-MIG composite welding method

Abstract

The invention discloses an external magnetic field assisted duplex stainless steel laser-MIG composite welding method which at least comprises the following steps: under the magnetic field condition, welding a workpiece in a composite mode that laser is in front and electric arc is in back; wherein the magnetic field intensity is smaller than or equal to 0.8 mT, the included angle between the center line of the laser beam and the normal perpendicular to the surface of the workpiece ranges from 0 degree to 10 degrees, and the included angle between the welding torch and the center line of the laser beam ranges from 30 degrees to 60 degrees. According to the welding method, welding defects can be restrained, welding seam forming is improved, welding seam quality is guaranteed, the problem that the proportion of a ferrite phase (alpha) and an austenite phase (gamma) in a welded joint area is unbalanced in existing duplex stainless steel welding is effectively solved, and the using performance of a welded joint is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of welding, and in particular relates to a laser-MIG composite welding method for duplex stainless steel assisted by an external magnetic field. Background Art

[0002] Laser-arc hybrid welding process is a fusion welding process that combines laser and arc. Compared with single heat source welding method, laser-arc hybrid welding can combine the advantages of laser beam welding and arc welding. Compared with other technologies, laser hybrid welding has incomparable advantages. When laser and arc act on the surface of the material at the same time, the high-energy laser beam guides the arc and accelerates the generation of anode spots, making the hybrid welding have deep and narrow welds, and at the same time has the characteristics of high production efficiency, high arc stability, and few welding defects, truly realizing the effect of "1+1>2".

[0003] Duplex stainless steel has good mechanical properties and corrosion resistance, and is widely used in important fields such as marine engineering, petrochemicals, and pressure vessels. The room temperature structure of duplex stainless steel is composed of ferrite phase (α) and austenite phase (γ), and the ratio of the two phases is close to 1:1. Compared with ferritic stainless steel, duplex stainless steel has higher plasticity and toughness, better weldability and intergranular corrosion resistance. Compared with austenitic stainless steel, it has higher strength and better resistance to chloride stress corrosion. Duplex stainless steel has the advantages of both ferritic stainless steel and austenitic stainless steel, and its comprehensive performance is very excellent.

[0004] However, duplex stainless steel welding easily produces two-phase imbalance in the joint structure, which is mainly manifested as follows: the ferrite content of the weld structure is much greater than the austenite content, which will have an adverse effect on the performance of the weld, and when the temperature of the heat-affected zone exceeds the solution treatment temperature during welding, it will cause the grains to grow significantly, the austenite phase to decrease, and the ferrite phase content to increase. When the cooling rate is too fast, the two-phase ratio of the heat-affected zone will be unbalanced, affecting the performance of the steel.

[0005] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0006] The purpose of the present invention is to provide a laser-MIG hybrid welding method for duplex stainless steel assisted by an external magnetic field, which can solve the problem in the existing welding technology that the imbalance of the two-phase ratio of ferrite phase (α) and austenite phase (γ) in the joint area after welding affects the performance of the welded joint.

[0007] In order to achieve the above object, a technical solution provided by a specific embodiment of the present invention is as follows:

[0008] An external magnetic field assisted duplex stainless steel laser-MIG composite welding method at least comprises: welding the workpiece in a composite manner of laser in front and arc in the back under magnetic field conditions;

[0009] Among them, the magnetic field intensity is less than or equal to 0.8 mT, the angle between the center line of the laser beam and the normal line perpendicular to the workpiece surface is 0 to 10°, and the angle between the welding torch and the center line of the laser beam is 30° to 60°.

[0010] In one or more embodiments of the present invention, the welding parameters are: laser power 3600-4200W.

[0011] In one or more embodiments of the present invention, the welding parameters are: welding current 200-220A, welding voltage 18-20V.

[0012] In one or more embodiments of the present invention, the welding parameters are: welding speed 6-12 mm / s.

[0013] In one or more embodiments of the present invention, the welding parameters are: the wire spacing is 2 to 4 mm.

[0014] In one or more embodiments of the present invention, the welding parameters are: a defocus amount of 2 to 5 mm.

[0015] In one or more embodiments of the present invention, welding is performed under a shielding gas, and the shielding gas flow rate is 15-20 L / min.

[0016] In one or more embodiments of the present invention, the shielding gas is a mixture of argon and nitrogen, and the volume proportion of nitrogen in the mixture is 1.5-2.5%.

[0017] In one or more embodiments of the present invention, the workpiece surface is polished and cleaned with an organic solvent before welding.

[0018] In one or more embodiments of the present invention, the workpiece is fixed on a mobile platform. During the welding process, the positions of the laser and the welding torch remain fixed, and the mobile platform drives the workpiece to move for welding.

[0019] Compared with the prior art, the present invention introduces a transverse alternating magnetic field into the laser arc hybrid welding of duplex stainless steel, and regulates the plasma morphology and the droplet transition process by applying an alternating magnetic field, and regulates the welding arc, droplet transition and the flow of liquid metal in the molten pool by applying an external magnetic field, so as to achieve weld grain refinement, reduce component heterogeneity, improve plasticity and toughness, inhibit welding defects, improve weld formation, thereby improving weld quality, and improve the current duplex stainless steel welding. The problem of imbalance in the proportion of ferrite phase (α) and austenite phase (γ) in the joint area after welding, which affects the performance of the welded joint, can also be improved. In addition, certain technical guidance can be provided for improving welding efficiency and shortening product production cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A schematic diagram of a welding system in one embodiment of the present invention;

[0022] Figure 2 This is a macroscopic morphology of the weld in Comparative Example 1 of the present invention;

[0023] Figure 3 This is a macroscopic morphology of the weld in Comparative Example 2 of the present invention;

[0024] Figure 4 A schematic diagram of a welding device in one embodiment of the present invention;

[0025] Figure 5 This is a macroscopic morphology of the weld in Example 1 of the present invention;

[0026] Figure 6 This is a macroscopic morphology of the weld in Example 2 of the present invention;

[0027] Figure 7 This is a macroscopic morphology of the weld in Example 3 of the present invention;

[0028] Figure 8 This is a cross-sectional view of a weld in Example 3 of the present invention;

[0029] Fig. 9 This is the weld structure diagram in Example 3 of the present invention;

[0030] Fig.10 This is the weld structure diagram in Example 4 of the present invention.

[0031] Description of main reference numerals:

[0032] 1. Magnetic pole and excitation coil; 2. Protective sleeve; 3. Connecting seat; 4. MIG welding torch; 5. Laser head; 6. Laser focusing lens; 7. Anti-splash protective lens; 8. Incident laser light source; 9. Welding droplet; 10. Plasma; 11. Welding pool; 12. Parent material. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0034] A specific embodiment of the present invention provides a method for laser-MIG hybrid welding of duplex stainless steel assisted by an external magnetic field, comprising steps 1-4.

[0035] Step 1: Grind the surface of the workpiece and clean it with an organic solvent.

[0036] Specifically, use a grinding machine to grind the surface of the workpiece to make the workpiece bright as a whole, remove burrs and barbs, and then use acetone and alcohol to remove surface oil, oxides and impurities to avoid defects such as pores and slag inclusions in the weld.

[0037] Step 2: Fix the workpiece on the mobile platform with a clamp and set an alternating transverse magnetic field at the weld to be welded.

[0038] Specifically, two magnetic poles are arranged on both sides of the arc welding torch, and the magnetic core material is Q235 low-carbon steel. Q235 low-carbon steel is low in price and has a high relative magnetic permeability to air, and can maintain good magnetic conductivity even at high temperatures. The excitation coil is evenly wound with enameled copper wire with a diameter of 0.3mm. After the two magnetic poles are wound, the ends of the copper wire are respectively connected to the positive and negative poles of the excitation power supply. The Tesla measuring machine is used to detect the magnetic field strength on the surface of the workpiece. The frequency and intensity of the alternating magnetic field are adjusted by changing the current and frequency of the excitation power supply. During the welding process, the mobile platform drives the workpiece to move according to the preset path while keeping the welding torch and laser head fixed in position to ensure that the area to be welded is always in the set alternating transverse magnetic field.

[0039] Step 3: Adjust the welding torch and laser head to the preset position, and perform teaching programming on the mobile platform so that the workpiece moves along the preset path.

[0040] Specifically, the angle between the center line of the laser beam and the normal line perpendicular to the workpiece surface is set to 0° to 10°, and the angle between the welding torch and the center line of the laser beam is set to 30° to 60°. By controlling the angle, it is beneficial to utilize the laser energy, so that the welding torch and laser work together to ensure the welding effect.

[0041] Step 4, using a composite method of laser in front and arc in the back, welding the workpiece under a shielding gas, with set welding parameters, and according to a preset motion path.

[0042] Specifically, the laser heats the workpiece before laser-assisted arc welding, which can reduce the oxidation reaction during the welding process and improve the quality of the weld.

[0043] During welding, the magnetic field strength is controlled to be less than or equal to 0.8mT, and the welding parameters are: laser power 3600~4200W, welding current 200~220A, welding voltage 18~20V, welding speed 6~12mm / s, filament spacing 2~4mm, and defocus 2~5mm. By controlling the magnetic field strength and welding parameters, welding defects can be suppressed, the imbalance of the ferrite phase (α) and austenite phase (γ) in the joint area after welding can be improved, and the quality of the weld can be improved. The shielding gas is a mixture of argon and nitrogen, and the volume proportion of nitrogen in the mixture is 1.5~2.5%. Because nitrogen is an austenite-forming element, the use of a mixture of argon and nitrogen can ensure the ratio of austenite and ferrite in the welded joint.

[0044] The present invention is further described in detail below in conjunction with specific embodiments.

[0045] like Figure 1 As shown, the instruments used in the welding system of the present invention include Shandong Aotai Pulse MIG-630PH inverter pulse MIG / MAG arc welding power supply; RFL-C6000 fiber laser produced by Hanrui Technology Co., Ltd., with a maximum output power of 6.0kW, an output mode of continuously adjustable output, a laser wavelength of 1070-1080nm, and the laser is transmitted to the laser head through an optical fiber with a core diameter of 150um. The diameter of the light spot generated after focusing by the lens is 0.6mm; at the same time, a Hanli HL-8000 laser water cooler is used to provide cooling water for the laser equipment, and also includes a mobile platform, a walking mechanism, an excitation power supply and a magnetic pole system.

[0046] The duplex stainless steel used in the present invention is UNS 32750 duplex stainless steel, the plate is supplied in the state of solid solution and pickling, and the specification is 125×64×8mm; the filler wire adopts ER2594 stainless steel solid wire with a diameter of 1.2mm, and the chemical composition of the base material and the welding wire is shown in Table 1 and Table 2. It can be seen from the table that the element content of UNS 32750 duplex stainless steel and ER2594 welding wire is substantially the same, which can reduce the problem of decreased weld performance caused by the difference in element ratio.

[0047] Table 1 Chemical composition of UNS 32750 duplex stainless steel (wt%)

[0048]

[0049] Table 2 Chemical composition of GTS-2594 welding material (wt%)

[0050]

[0051] Example 1

[0052] The laser-MIG hybrid welding method of duplex stainless steel assisted by an external magnetic field comprises:

[0053] The surface of the duplex stainless steel test plate was polished with a grinding wheel to make the workpiece bright as a whole, and burrs and barbs were removed. Then acetone and alcohol were used to remove oil and impurities on the workpiece surface.

[0054] The test plate is clamped and fixed on the welding mobile platform with a rigid fixture, a transverse alternating magnetic field is set at the weld to be welded, and two magnetic poles are set on both sides of the arc welding torch.

[0055] The shielding gas is set to a mixture of 98% argon and 2% nitrogen, and compressed air is turned on to side-blow the spatter generated during welding to effectively protect the laser lens.

[0056] MIG arc welding uses a DC reverse connection method, the laser beam is perpendicular to the test plate surface, and the arc welding torch and the laser head are at an angle of 45°.

[0057] The welding operation in this embodiment is: welding a duplex stainless steel test plate with a thickness of 8 mm, using a composite method of laser in front and arc in the back, and performing laser and MIG arc composite welding simultaneously. The welding parameters are: laser power 4200W, welding current 220A, welding voltage 18V, welding speed 8mm / s, filament spacing 2mm, defocusing amount -3mm, shielding gas flow 15L / min, and the magnetic field strength in the center of the welding area is controlled to be 0.2mT by adjusting the excitation power supply.

[0058] Example 2

[0059] The laser-MIG hybrid welding method of duplex stainless steel assisted by an external magnetic field comprises:

[0060] The surface of the duplex stainless steel test plate was polished with a grinding wheel to make the workpiece bright as a whole, and burrs and barbs were removed. Then acetone and alcohol were used to remove oil and impurities on the workpiece surface.

[0061] The test plate is clamped and fixed on the welding mobile platform with a rigid fixture, a transverse alternating magnetic field is set at the weld to be welded, and two magnetic poles are set on both sides of the arc welding torch.

[0062] The shielding gas is set to a mixture of 98% argon and 2% nitrogen, and compressed air is turned on to side-blow the spatter generated during welding to effectively protect the laser lens.

[0063] MIG arc welding uses a DC reverse connection method, the laser beam is perpendicular to the test plate surface, and the arc welding torch and the laser head are at an angle of 45°.

[0064] The welding operation in this embodiment is: welding a duplex stainless steel test plate with a thickness of 8 mm, using a composite method of laser in front and arc in the back, and performing laser and MIG arc composite welding simultaneously. The welding parameters are: laser power 4200W, welding current 220A, welding voltage 18V, welding speed 8mm / s, filament spacing 2mm, defocusing amount -3mm, shielding gas flow 15L / min, and the magnetic field strength in the center of the welding area is controlled to be 0.4mT by adjusting the excitation power supply.

[0065] Example 3

[0066] The laser-MIG hybrid welding method of duplex stainless steel assisted by an external magnetic field comprises:

[0067] The surface of the duplex stainless steel test plate was polished with a grinding wheel to make the workpiece bright as a whole, and burrs and barbs were removed. Then acetone and alcohol were used to remove oil and impurities on the workpiece surface.

[0068] The test plate is clamped and fixed on the welding mobile platform with a rigid fixture, a transverse alternating magnetic field is set at the weld to be welded, and two magnetic poles are set on both sides of the arc welding torch.

[0069] The shielding gas is set to a mixture of 98% argon and 2% nitrogen, and compressed air is turned on to side-blow the spatter generated during welding to effectively protect the laser lens.

[0070] MIG arc welding uses a DC reverse connection method, the laser beam is perpendicular to the test plate surface, and the arc welding torch and the laser head are at an angle of 45°.

[0071] The welding operation in this embodiment is: welding a duplex stainless steel test plate with a thickness of 8 mm, using a composite method of laser in front and arc in the back, and performing laser and MIG arc composite welding simultaneously. The welding parameters are: laser power 4200W, welding current 220A, welding voltage 18V, welding speed 8mm / s, filament spacing 2mm, defocusing amount -3mm, shielding gas flow 15L / min, and the magnetic field strength in the center of the welding area is controlled to be 0.6mT by adjusting the excitation power supply.

[0072] Example 4

[0073] The laser-MIG hybrid welding method of duplex stainless steel assisted by an external magnetic field comprises:

[0074] The surface of the duplex stainless steel test plate was polished with a grinding wheel to make the workpiece bright as a whole, and burrs and barbs were removed. Then acetone and alcohol were used to remove oil and impurities on the workpiece surface.

[0075] The test plate is clamped and fixed on the welding mobile platform with a rigid fixture, a transverse alternating magnetic field is set at the weld to be welded, and two magnetic poles are set on both sides of the arc welding torch.

[0076] The shielding gas is set to a mixture of 98% argon and 2% nitrogen, and compressed air is turned on to side-blow the spatter generated during welding to effectively protect the laser lens.

[0077] MIG arc welding uses a DC reverse connection method, the laser beam is perpendicular to the test plate surface, and the arc welding torch and the laser head are at an angle of 45°.

[0078] The welding operation in this embodiment is: welding a duplex stainless steel test plate with a thickness of 8 mm, using a composite method of laser in front and arc in the back, and performing laser and MIG arc composite welding simultaneously. The welding parameters are: laser power 4200W, welding current 220A, welding voltage 18V, welding speed 8mm / s, filament spacing 2mm, defocusing amount -3mm, shielding gas flow 15L / min, and the magnetic field strength in the center of the welding area is controlled to be 0.8mT by adjusting the excitation power supply.

[0079] Comparative Example 1

[0080] The laser-MIG hybrid welding method of duplex stainless steel assisted by an external magnetic field comprises:

[0081] The surface of the duplex stainless steel test plate was polished with a grinding wheel to make the workpiece bright as a whole, and burrs and barbs were removed. Then acetone and alcohol were used to remove oil and impurities on the workpiece surface.

[0082] The test plate is clamped and fixed on the welding mobile platform with a rigid fixture, a transverse alternating magnetic field is set at the weld to be welded, and two magnetic poles are set on both sides of the arc welding torch.

[0083] The shielding gas is set to a mixture of 98% argon and 2% nitrogen, and compressed air is turned on to side-blow the spatter generated during welding to effectively protect the laser lens.

[0084] MIG arc welding uses a DC reverse connection method, the laser beam is perpendicular to the test plate surface, and the arc welding torch and the laser head are at an angle of 45°.

[0085] The welding operation in this embodiment is: welding a duplex stainless steel test plate with a thickness of 8 mm, using a composite method of laser in front and arc in the back, and performing laser and MIG arc composite welding simultaneously. The welding parameters are: laser power 4200W, welding current 220A, welding voltage 18V, welding speed 8mm / s, filament spacing 2mm, defocusing amount -3mm, shielding gas flow 15L / min, and the magnetic field strength in the center of the welding area is controlled to be 0mT by adjusting the excitation power supply.

[0086] Comparative Example 2

[0087] The laser-MIG hybrid welding method of duplex stainless steel assisted by an external magnetic field comprises:

[0088] The surface of the duplex stainless steel test plate was polished with a grinding wheel to make the workpiece bright as a whole, and burrs and barbs were removed. Then acetone and alcohol were used to remove oil and impurities on the workpiece surface.

[0089] The test plate is clamped and fixed on the welding mobile platform with a rigid fixture, a transverse alternating magnetic field is set at the weld to be welded, and two magnetic poles are set on both sides of the arc welding torch.

[0090] The shielding gas is set to a mixture of 98% argon and 2% nitrogen, and compressed air is turned on to side-blow the spatter generated during welding to effectively protect the laser lens.

[0091] MIG arc welding uses a DC reverse connection method, the laser beam is perpendicular to the test plate surface, and the arc welding torch and the laser head are at an angle of 45°.

[0092] The welding operation in this comparative example is: welding a duplex stainless steel test plate with a thickness of 8 mm, using a composite method of laser in front and arc in the back, and performing laser and MIG arc composite welding simultaneously. The welding parameters are: laser power 4200W, welding current 220A, welding voltage 18V, welding speed 8mm / s, light wire spacing 2mm, defocusing amount -3mm, shielding gas flow 15L / min, and the magnetic field intensity in the center of the welding area is controlled to be 1.0mT by adjusting the excitation power supply.

[0093] In Comparative Example 1, the magnetic field strength is 0 mT. Figure 2 It can be seen that the weld bead is bent to a certain extent, and the weld formation is poor. Analysis shows that the coupling effect is poor due to the compression and attraction effect of the laser on the arc, which is manifested as poor weld formation. Figure 3 In Comparative Example 2, the magnetic field strength reaches 1.0 mT. The magnetic field strength is too large, causing the composite plasma to be unstable. It rotates at high speed under the action of the magnetic field, making the welding process unstable and the weld formation not meeting the requirements.

[0094] In embodiments 1-4, an alternating transverse magnetic field is provided, such as Figure 4 As shown, a welding torch is installed using a connecting seat, a protective sleeve is provided on the connecting seat, a magnetic pole and an excitation coil are arranged in the protective sleeve to generate an alternating transverse magnetic field, the laser head is arranged vertically so that the incident laser light source is perpendicular to the workpiece, and the welding torch is welded at a set angle. During the welding process, the arc swings, the fluidity of the welding molten pool is relatively increased, and the weld grains are refined, thereby improving the ratio of the ferrite phase (α) and the austenite phase (γ) in the joint area after welding.

[0095] Reference Figure 5 When the magnetic field strength is 0.2mT, the bulge on the weld surface and the degree of weld bending are improved to a certain extent. Analysis shows that this is mainly because the charged particles in the arc plasma are affected by the Lorentz force on the arc motion state, which has a certain improvement effect on the weld formation.

[0096] Reference Figure 6 When the magnetic field intensity reaches 0.4mT, there are smaller protrusions on the weld surface, the surface is smoother, the weld transition is smoother, and the curvature of the weld is further improved.

[0097] Reference Figure 7-9 When the magnetic field intensity reaches 0.6mT, the weld surface is relatively smooth and the texture is clearer. Except for the tiny spatter on both sides, there are traces of the molten pool being dragged. This is because the arc swings perpendicular to the welding direction under the action of the alternating magnetic field. The arc has a certain pressure on the molten pool, and thus exerts a certain tangential force on the molten pool during the swinging process, which produces a certain dragging effect on the molten pool to both sides. The weld surface is relatively flat and the texture is clearer. At this time, the weld is best formed, which is the optimal process parameter. The proportion of ferrite and austenite in the weld is balanced. After testing, the ferrite accounts for 45%.

[0098] Reference Fig.10 When the magnetic field intensity reaches 0.8mT, it is found that there is a small amount of spatter attached to the weld surface. This is because when the alternating magnetic field intensity is too large, the arc swing amplitude increases, resulting in unstable arc burning, and finally causing increased spatter, affecting the weld formation, but the overall performance still meets the requirements.

[0099] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0100] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for laser-MIG composite welding of duplex stainless steel assisted by an external magnetic field, characterized in that: At least including: welding the workpiece in a composite manner with laser in front and arc in the back under magnetic field conditions; Among them, the magnetic field intensity is less than or equal to 0.8 mT, the angle between the center line of the laser beam and the normal line perpendicular to the workpiece surface is 0 to 10°, and the angle between the welding torch and the center line of the laser beam is 30° to 60°.

2. The external magnetic field assisted duplex stainless steel laser-MIG hybrid welding method according to claim 1, characterized in that: Welding parameters are: laser power 3600~4200W.

3. The method for laser-MIG hybrid welding of duplex stainless steel assisted by an external magnetic field according to claim 1, characterized in that: The welding parameters are: welding current 200~220A, welding voltage 18~20V.

4. The external magnetic field assisted duplex stainless steel laser-MIG hybrid welding method according to claim 1, characterized in that: Welding parameters are: welding speed 6~12mm / s.

5. The external magnetic field assisted duplex stainless steel laser-MIG hybrid welding method according to claim 1, characterized in that: The welding parameters are: wire spacing 2 to 4 mm.

6. The external magnetic field assisted duplex stainless steel laser-MIG hybrid welding method according to claim 1, characterized in that: The welding parameters are: defocus 2 to 5 mm.

7. The method for laser-MIG hybrid welding of duplex stainless steel assisted by an external magnetic field according to claim 1, characterized in that: Welding is carried out under shielding gas with a shielding gas flow rate of 15 to 20 L / min.

8. The method for laser-MIG hybrid welding of duplex stainless steel assisted by an external magnetic field according to claim 7, characterized in that: The shielding gas is a mixture of argon and nitrogen, with the volume proportion of nitrogen in the mixture being 1.5-2.5%.

9. The method for laser-MIG hybrid welding of duplex stainless steel assisted by an external magnetic field according to claim 1, characterized in that: Before welding, the workpiece surface is polished and cleaned with organic solvent.

10. The method for laser-MIG hybrid welding of duplex stainless steel assisted by an external magnetic field according to claim 1, characterized in that: The workpiece is fixed on the mobile platform. During the welding process, the positions of the laser and welding torch remain fixed, and the mobile platform drives the workpiece to move for welding.

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