Dual-beam laser welding method for exhaust pipe barrel and flange

Abstract

The present invention relates to a dual-beam laser welding method for an exhaust pipe barrel and a flange, comprising the following steps: step one: processing the welding edges of the exhaust pipe barrel and the flange into annular welding edges respectively; step two: planning the geometric position and shape of dual-beam laser welding and the welding path according to the design parameters of the annular welding edge; step three: determining the dual-beam laser welding parameters; step four: performing dual-beam laser welding on the flange and the exhaust pipe barrel according to the dual-beam laser welding parameters; step one includes: preparing an annular groove on the inner side of the welding edge of the flange, the radial height of the annular groove of the flange is consistent with the wall thickness of the exhaust pipe barrel; the welding edge of the exhaust pipe barrel is inserted and assembled in the annular groove of the flange. The present invention realizes reliable welding of the butt joint area of ​​the flange and the exhaust pipe barrel and full fusion of the interface of the overlap area, which significantly improves the weld formation.

Description

Technical Field

[0001] The invention relates to the technical field of aircraft engine exhaust pipe welding, and in particular to a double-beam laser welding method for an exhaust pipe barrel and a flange. Background Art

[0002] The engine exhaust pipe of a large fire-fighting / water rescue amphibious aircraft includes flanges, exhaust pipe barrels, reinforcement rings and other parts. The flange is usually set at the end of the exhaust pipe and installed near the engine through fasteners; the flange is an annular machined part, and the thickness of the part connected to the exhaust pipe barrel ranges from 4mm to 8mm. The exhaust pipe barrel is a thin-walled shell structure, usually manufactured by sheet metal method, with the axis as a spatial curve and a wall thickness range of 0.8mm-1.5mm. The reinforcement ring is usually set at the tail of the exhaust pipe and is also installed on the body through fasteners. The length of the exhaust pipe ranges from 500mm to 2000mm, and the cross-sectional diameter of the exhaust pipe ranges from Φ300mm to Φ1000mm.

[0003] The exhaust pipe is the main channel for the exhaust gas of the engine to be discharged outside the cabin. The exhaust gas not only flows fast but also has a high temperature, so the service environment of the exhaust pipe is very harsh. In order to ensure the smooth exhaust function of the exhaust pipe, the inner wall of the exhaust pipe should be as smooth as possible. At the same time, in order to be as close to the design life of the exhaust pipe as possible, that is, to ensure the service reliability of the exhaust pipe, the geometric dimensional accuracy of the exhaust pipe should also be controlled within a strict tolerance range.

[0004] Due to the large difference in the thickness of the annular connection edge of the exhaust pipe flange and the exhaust pipe barrel, three methods are usually used to connect the two. Figure 1-3 As shown in the first method, the welding edge of the flange is processed to be as thick as the exhaust pipe body and the inner surfaces of the two are basically flush, and then the two are butt-connected by argon arc welding. The formed argon arc weld 3 is shown in the attached figure. Figure 1 As shown; the second is to install the inner sleeve of the welding edge of the exhaust pipe barrel on the welding edge of the flange, with an overlap of about 5mm-20mm, and realize the overlap connection of the two by argon arc welding method; the third (patent application number 202110109084.2) is to process the welding edge of the flange and the exhaust pipe barrel into a preset annular welding edge, and use the strong penetration of laser welding and the fluidity of the molten metal of the upper parent material to realize the connection between the two and make the welded joint have both butt and overlap characteristics.

[0005] The first and second welding methods both use argon arc welding to achieve the annular connection between the exhaust pipe flange and the cylinder. Due to the large heat input and wide weld width of argon arc welding, the welding deformation is large, and the roundness tolerance of the exhaust pipe after welding can only be controlled within the range of ±3mm, resulting in a large deviation between the actual service life of the exhaust pipe and the design life; the residual stress of argon arc welding is large, and stress relief annealing must be performed after welding; while the weld width of the argon arc weld is wide, the collapse of the back of the weld is also relatively large, resulting in a large weld grinding strength on the inner wall of the exhaust pipe. Compared with the first connection method, although the second connection method can slightly reduce the welding deformation of the exhaust pipe, it not only increases the geometric size mutation of the inner wall of the exhaust pipe, which will have a certain impact on the exhaust function of the exhaust pipe to a certain extent, but also the unfused interface inside the lap joint is very easy to accelerate crack initiation and expansion under fatigue load and reduce the service reliability of the structure. The third connection technology is limited by the small laser beam spot diameter and small welding pool, resulting in a narrow welding process margin. When the laser beam movement trajectory deviates from the preset trajectory by more than 0.2mm, it is easy to cause problems such as insufficient melting of the top edge of the flange welding edge and undercutting of the weld toe in the overlap area of ​​the flange and cylinder welding joint. Figure 3 As shown, the laser weld 4 and weld toe undercut 41 are formed. Summary of the invention

[0006] (1) Technical issues to be solved

[0007] An embodiment of the present invention provides a dual-beam laser welding method for an exhaust pipe barrel and a flange, comprising processing the welding edges of the exhaust pipe barrel and the flange into annular welding edges respectively; planning the dual-beam laser welding geometric position morphology and welding path according to the design parameters of the annular welding edge; determining the dual-beam laser welding parameters; and performing dual-beam laser welding on the flange and the exhaust pipe barrel according to the dual-beam laser welding parameters. The present invention realizes reliable welding of the butt joint area of ​​the flange and the exhaust pipe barrel and sufficient fusion of the interface of the overlap area, thereby significantly improving the weld formation.

[0008] (2) Technical solution

[0009] An embodiment of the present invention provides a dual-beam laser welding method for an exhaust pipe barrel and a flange, comprising the following steps:

[0010] Step 1: respectively processing the welding edges of the exhaust pipe barrel and the flange into annular welding edges;

[0011] Step 2: planning the geometric position and welding path of the dual-beam laser welding according to the design parameters of the annular welding edge;

[0012] Step 3: Determine dual-beam laser welding parameters;

[0013] Step 4: performing double-beam laser welding on the flange and the exhaust pipe barrel according to double-beam laser welding parameters;

[0014] Step one includes: preparing an annular groove on the inner side of the welding edge of the flange, wherein the radial height of the annular groove of the flange is consistent with the wall thickness of the exhaust pipe barrel; and inserting and assembling the welding edge of the exhaust pipe barrel into the annular groove of the flange.

[0015] Furthermore, in step one, the thickness range of the first welding edge wall thickness δ1 of the flange is 2mm-4mm, the length L of the first welding edge of the flange in the state of the first welding edge wall thickness δ1 is not less than 3mm, and the depth a of the annular groove of the flange is 0.2mm-1.5mm.

[0016] Furthermore, after the flange and the exhaust pipe barrel are assembled by insertion, the inner surfaces between the two are flush and the local maximum assembly gap △x between the two should not be greater than a / 2.

[0017] Furthermore, step two includes: during the welding process, the inclination angle range between the central axis of the first laser beam and the normal of the flange surface is ±10°; a second laser beam is set at a side perpendicular to the laser welding direction of the first laser beam and away from the flange, and the focal position of the second laser beam is located on the side of the flange welding edge.

[0018] Furthermore, step two includes: during the welding process, the distance between the central axis of the first laser beam and the axial welding end face of the annular groove of the flange is b, b=0-a / 2, the first laser beam is negatively defocused and the defocus amount △f range is (δ2-δ1)-(δ2-δ1) / 2.

[0019] Furthermore, step 2 includes: the inclination angle between the central axis of the second laser beam and the normal direction of the flange surface is 30°-60°, and the distance between the focus position of the second laser beam and the surface of the flange is 0 to -Δf.

[0020] Furthermore, the first laser beam and the second laser beam act on the same molten pool.

[0021] Furthermore, step 2 also includes: the welding action point of the second laser beam is located behind the laser action point of the first laser beam, and the second laser beam and the first laser beam act on different molten pools.

[0022] Furthermore, determining the dual-beam laser welding parameters in step 3 includes:

[0023] The first laser beam and the second laser beam are fiber lasers or YAG lasers, the focal lengths of the first laser beam and the second laser beam are in the range of 150 mm to 500 mm, and the focal spot diameters are in the range of 0.2 mm to 0.6 mm; when conventional laser welding is used, the welding parameters include welding speed and laser power;

[0024] When scanning laser beam welding is adopted, the welding parameters include welding speed, laser power, scanning trajectory, scanning amplitude and scanning frequency. The scanning trajectory of the first laser beam is circular, the scanning frequency adjustment range is 30Hz-200Hz, and the scanning amplitude is not greater than b; the scanning trajectory of the second laser beam is vertical, the scanning frequency is the same as that of the first laser beam, and the scanning amplitude range is δ1-δ2.

[0025] Furthermore, in step three, inert gas protection is used during arc welding, and the inert gas protection also includes a back protection type.

[0026] (3) Beneficial effects

[0027] The present invention makes full use of the strong penetration of the first laser beam welding and the auxiliary heating and stirring effect of the second laser beam to fully melt the top edge of the flange welding edge and fully spread the liquid molten pool, thereby achieving reliable welding of the butt joint area of ​​the flange and the exhaust pipe barrel and interface fusion of the overlapping area, avoiding the occurrence of weld toe undercut, greatly alleviating stress concentration at the weld toe, and significantly improving weld formation. It not only solves the technical problems of low precision and poor service reliability in argon arc welding of exhaust pipes, but also significantly expands the welding process margin and process feasibility of the exhaust pipe.

[0028] In addition, the cross-sectional morphology of the dual-beam laser welded joint obtained by the present invention realizes the smooth transition of the butt welding of plates of unequal thickness between the flange and the exhaust pipe barrel, with butt welding characteristics as the main feature and lap welding characteristics as the auxiliary feature, combining the advantages of the two welding methods, making it possible for dual-beam laser welding to replace conventional argon arc welding and conventional laser welding.

[0029] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments of the present invention are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 It is a schematic diagram of a welding method in the prior art.

[0032] Figure 2 It is a schematic diagram of another welding method in the prior art.

[0033] Figure 3 It is another schematic diagram of a welding method in the prior art.

[0034] Figure 4 It is a schematic diagram of welding an exhaust pipe barrel and a flange in one embodiment of the present invention.

[0035] Figure 5 Schematic diagram of the cross section of dual-beam laser welding in one embodiment of the present invention.

[0036] Figure 6 1 is a timing diagram of scanning trajectories of the first laser beam and the second laser beam in one embodiment of the present invention.

[0037] Figure 7 Schematic diagram of the scanning trajectory of the first laser beam in one embodiment of the present invention.

[0038] Figure 8 Schematic diagram of the scanning trajectory of the second laser beam in one embodiment of the present invention.

[0039] Fig. 9 It is a structural schematic diagram of the welding process of the flange and the exhaust pipe barrel in one embodiment of the present invention.

[0040] Fig.10 1 is a top view of a dual-beam laser welding path in one embodiment of the present invention.

[0041] Fig.11 It is a schematic diagram of the chamfered state allowed to exist when the flange and the exhaust pipe barrel are assembled in one embodiment of the present invention.

[0042] Fig.12 1 is a flow chart of a dual-beam laser welding method according to an embodiment of the present invention.

[0043] Fig.13 It is a schematic diagram of a welding torch clamping dual laser heads in one embodiment of the present invention.

[0044] In the figure: flange 1, exhaust pipe barrel 2, argon arc weld 3, laser weld 4, weld toe bite 41, end flange axis 5, first laser beam 6, first position 61, second position 62, third position 63, fourth position 64, circular scanning direction 65, first scanning trajectory 66, second laser beam 7, fifth position 71, sixth position 72, seventh position 73, second scanning trajectory 76, dual-beam laser welded joint 8, steering knuckle 9, welding fixture 10, spot action point 11, laser beam motion trajectory 12, first laser head 13, second laser head 14, laser head sliding trajectory 15, welding edge 16, vertical scanning trajectory 17. DETAILED DESCRIPTION

[0045] The following is a further detailed description of the embodiments of the present invention in conjunction with the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to exemplarily illustrate the principles of the present invention, but cannot be used to limit the scope of the present invention, that is, the present invention is not limited to the described embodiments, and covers any modification, replacement and improvement of parts, components and connection modes without departing from the spirit of the present invention.

[0046] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0047] The following will refer to the attached Figure 1 -Attached Fig.13 The present application is described in detail with reference to embodiments.

[0048] See attached Fig.12 As shown, a dual-beam laser welding method for an exhaust pipe barrel 2 and a flange 1 according to an embodiment of the present invention comprises the following steps:

[0049] Step 1: Processing the welding edges of the exhaust pipe barrel 2 and the flange 1 into annular welding edges respectively;

[0050] Step 2: planning the geometric position and welding path of the dual-beam laser welding according to the design parameters of the annular welding edge;

[0051] Step 3: Determine dual-beam laser welding parameters;

[0052] Step 4: performing double-beam laser welding on the flange 1 and the exhaust pipe barrel 2 according to double-beam laser welding parameters;

[0053] Step 1 of the embodiment of the present invention includes: preparing an annular groove on the inner side of the welding edge of the flange 1, the radial height of the annular groove of the flange 1 being consistent with the wall thickness of the exhaust pipe barrel 2; and the welding edge of the exhaust pipe barrel 2 is inserted and assembled in the annular groove of the flange 1.

[0054] The embodiment of the present invention proposes a dual-beam laser welding method for an exhaust pipe barrel 2 and a flange 1. In the plug-in design of the flange 1 and the exhaust pipe barrel 2, the inner surfaces of the flange 1 and the exhaust pipe barrel 2 are basically flush. At the same time, a dual-beam laser welding geometric position and welding path planning are proposed. The strong penetration of the first laser beam 6 welding and the auxiliary heating and stirring effect of the second laser beam 7 are fully utilized to fully melt the top edge of the flange 1 welding edge and fully spread the liquid molten pool, so as to achieve reliable welding of the butt joint area of ​​the flange 1 and the exhaust pipe barrel 2 and interface fusion of the overlap area, thereby avoiding the occurrence of the following problems Figure 3The weld toe undercut 41 shown greatly alleviates stress concentration at the weld toe and also significantly improves weld formation, thereby solving the technical problems of low precision and poor service reliability during argon arc welding of exhaust pipes and significantly expanding the welding process margin and process feasibility of the exhaust pipes.

[0055] At the same time, the embodiment of the present invention utilizes the outer part of the flange 1 to melt under the irradiation of the dual-beam laser to make up for the local gap between the flange 1 and the exhaust pipe barrel 2 due to the low assembly accuracy, significantly reducing the machining accuracy requirements of the welding edge and effectively supplementing the liquid metal in the molten pool. Under the auxiliary heating and stirring action of the second laser beam 7, when the laser is close to the edge of the flange 1, it is more conducive to the melting of the top edge of the welding edge of the flange 1. When the laser is close to the exhaust pipe barrel 2, it further intensifies the melting of the parent material in the overlapping area of ​​the exhaust pipe barrel 2 and the flange 1, that is, the wettability of this part is increased, which is more conducive to the molten pool flowing from the higher position of the flange 1 side to the exhaust pipe barrel 2 side and achieving full spreading. Therefore, the upper surfaces of the flange 1 and the exhaust pipe barrel 2 have better welding forming and overlapping effects under the action of the dual-beam laser welding heat source. At the same time, under the combined action of the dual beams, the liquid molten pool on the flange 1 side flows to the exhaust pipe barrel 2 side, the welding thickness is relatively thinned, and the influence of the dual laser beam on the back penetration of the weld is relatively enhanced.

[0056] In addition, the cross-sectional morphology of the dual-beam laser welded joint obtained in the embodiment of the present invention realizes the smooth transition of the butt welding of the unequal thickness plates of the flange 1 and the exhaust pipe barrel 2, with butt welding characteristics as the main feature and lap welding characteristics as the auxiliary feature, combining the advantages of the two welding methods, making it possible for dual-beam laser welding to replace conventional argon arc welding and conventional laser welding.

[0057] For details, see the attached Figure 4As shown, according to a dual-beam laser welding method of an exhaust pipe barrel 2 and a flange 1 according to an embodiment of the present invention, in step 1, the thickness range of the first welding edge wall thickness δ1 of the flange 1 is 2mm-4mm, the first welding edge length L of the first welding edge wall thickness of the flange 1 in the state of δ1 is not less than 3mm, and the depth a of the annular groove of the flange 1 is 0.2mm-1.5mm. In the embodiment of the present invention, according to the actual situation of the aircraft engine exhaust pipe, the thickness range of the first welding edge wall thickness δ1 of the flange 1 is generally 2mm-4mm, specifically, it can be 2mm, it can also be 4mm, and it can also be 3mm. The first welding edge length L of the first welding edge wall thickness of the flange 1 in the state of δ1 is not less than 3mm, so L is at least 3mm, and it can also be 4mm, etc. At the same time, the depth a of the annular groove of the flange 1 can be 0.2mm-1.5mm, specifically, the depth a of the annular groove of the flange 1 can be 0.2mm, it can also be 1.0mm, it can also be 1.5mm, etc. In the embodiment of the present invention, the thickness range of the first welding edge wall thickness δ1 of the flange 1, the first welding edge length L of the flange 1 in the state of the first welding edge wall thickness δ1, and the depth a of the annular groove of the flange 1 can be determined according to the actual situation of the aircraft engine exhaust pipe, and should not constitute a limitation to the present application. In addition, in the embodiment of the present invention, the radial height of the annular groove of the flange 1 is consistent with the second welding edge wall thickness δ2 of the exhaust pipe barrel 2, so that when the exhaust pipe barrel 2 is inserted into the annular groove of the flange 1, it can be ensured that the inner walls of the flange 1 and the exhaust pipe barrel 2 remain flush, so that the exhaust pipe has less resistance when exhausting, and the exhaust of the exhaust pipe is smoother.

[0058] For details, see the attached Figure 4 As shown, according to a dual-beam laser welding method of an exhaust pipe barrel 2 and a flange 1 according to an embodiment of the present invention, after the flange 1 and the exhaust pipe barrel 2 are inserted and assembled, the inner surfaces between the two are flush and the local maximum assembly gap △x between the two should be no greater than a / 2. In the embodiment of the present invention, after the exhaust pipe barrel 2 is inserted and assembled into the flange 1, in order to ensure the welding quality, the exhaust pipe barrel 2 is kept flush with the inner wall of the flange 1 and the local maximum assembly gap △x between the exhaust pipe barrel 2 and the flange 1 should be minimized, so as to ensure that the molten liquid molten pool is fully spread between the end of the exhaust pipe barrel 2 and the end of the flange 1, and then the two are connected together after the molten pool solidifies. Therefore, the local maximum assembly gap △x between the two should not be greater than a / 2. When the local maximum assembly gap △x between the exhaust pipe barrel 2 and the flange 1 is greater than a / 2, it is easy for the liquid molten pool to be unable to fully spread between the end of the exhaust pipe barrel 2 and the end of the flange 1 due to excessive "lack of meat" in the welding base material, and the liquid molten pool cannot connect the exhaust pipe barrel 2 and the flange 1 on both sides of the assembly gap.

[0059] Specifically, in the attached Figure 4 As shown, during actual processing, the flange 1 can be placed horizontally, the first laser beam 6 is irradiated along the A direction, and the flange 1 is moved to a suitable position along the B direction, so that the distance between the exhaust pipe barrel 2 and the flange 1 reaches the above-mentioned local maximum assembly gap △x, and the end flange axis 5 of the flange 1 is set horizontally. Fig. 9 As shown, this makes it easy for the turntable to clamp, fix and drive the flange 1 to rotate through the steering knuckle 9 on one side.

[0060] For details, see the attached Figure 4 As shown, according to another dual-beam laser welding method of the exhaust pipe barrel 2 and the flange 1 according to an embodiment of the present invention, step 2 includes: during the welding process, the inclination angle range between the central axis of the first laser beam 6 and the normal direction of the surface of the flange 1 is ±10°; a second laser beam 7 is arranged on the side perpendicular to the laser welding direction of the first laser beam 6 and away from the flange 1, and the focus position of the second laser beam 7 is located on the side of the welding edge of the flange 1. In the embodiment of the present invention, the first laser beam 6 performs laser welding on the connection part of the flange 1 and the exhaust pipe barrel 2 around the normal direction of the flange 1 surface; the second laser beam 7 performs laser-assisted welding on the connection part of the flange 1 and the exhaust pipe barrel 2 on the side of the first laser beam 6. Through the composite welding of the first laser beam 6 and the second laser beam 7, the first laser beam 6 can be fully utilized to achieve deep penetration welding, accompanied by the liquid molten pool flowing from the higher flange 1 side to the exhaust pipe barrel 2. At the same time, under the scanning action of the second laser beam 7, on the one hand, it is more conducive to fully melting the top edge of the welding side of the flange 1, and on the other hand, the second laser beam 7 accelerates the stirring of the molten pool, further intensifies the liquid molten pool from the higher flange 1 side to the lower exhaust pipe barrel 2 side, and at the same time further overcomes the surface tension of the liquid molten pool, so that the liquid molten pool on the flange 1 side is more conducive to spreading to the exhaust pipe barrel 2 side and promoting the interface fusion of the molten pool and the upper surface of the exhaust pipe barrel 2, overcoming the occurrence of the attached Figure 3 The defect of the undercut 41 at the weld toe is eliminated, thereby greatly alleviating the stress concentration at the weld toe. At the same time, under the action of the dual laser welding heat source of the embodiment of the present invention, when the liquid metal flows from the flange 1 side to the exhaust pipe barrel 2 side, the weld thickness at the action position of the first laser beam 6 is reduced, so it is more conducive to the effect of the first laser beam 6 on the back of the weld joint, that is, the penetration of the first laser beam 6 is relatively enhanced. Even if the laser beam motion trajectory deviates from the preset trajectory by more than 0.2mm, the effect on the weld formation will be significantly reduced. In summary, compared with the existing single laser welding, dual-beam laser welding not only makes the front of the weld better, but also has a very favorable effect on the back of the weld.

[0061] For details, see the attached Figure 4As shown, according to another dual-beam laser welding method of an exhaust pipe barrel 2 and a flange 1 according to an embodiment of the present invention, step 2 includes: during the welding process, the distance between the central axis of the first laser beam 6 and the axial welding end face of the annular groove of the flange 1 is b, b=0-a / 2, the first laser beam 6 is negatively defocused and the defocus amount △f range is (δ2-δ1)-(δ2-δ1) / 2. As mentioned above, after the flange 1 and the exhaust pipe barrel 2 are inserted and assembled, the inner surfaces between the two are flush and the local maximum assembly gap △x between the two should not be greater than a / 2. Therefore, the depth of the exhaust pipe barrel 2 inserted and assembled into the flange 1 should be no less than a / 2, so combined with the attached Figure 4 As shown in FIG. 1 , the range of the distance b between the central axis of the first laser beam 6 and the axial welding end face of the annular groove of the flange 1 is set between 0 and a / 2, which can ensure that the welding energy of the first laser beam 6 is concentrated on the overlapping area of ​​the flange 1 and the exhaust pipe barrel 2. In this way, the strong penetration of the laser welding of the first laser beam 6 can be fully utilized to fully melt the top edge of the welding edge of the flange 1 and fully spread the liquid molten pool, so as to achieve reliable welding of the butt joint area of ​​the flange 1 and the overlapping area of ​​the exhaust pipe barrel 2 (see FIG. 1 ). Figure 4 The interface of part b) is fully fused to avoid the formation of Figure 3 The weld toe undercut 41 shown greatly alleviates stress concentration at the weld toe and also significantly improves weld formation, thereby solving the technical problems of low precision and poor service reliability during argon arc welding of exhaust pipes and significantly expanding the welding process margin and process feasibility of the exhaust pipes.

[0062] In the embodiment of the present invention, the first laser beam 6 is negatively defocused and the defocus amount Δf is in the range of (δ2-δ1)-(δ2-δ1) / 2. During the welding process, the liquid molten pool flows from the higher flange 1 side to the lower exhaust pipe barrel 2 side. Figure 4 As shown, the laser beam focus gradually acts on the surface of the liquid molten pool or a position close to the surface. At this time, the high energy density at the laser beam focus further enhances the welding penetration.

[0063] For details, see the attached Figure 4As shown, according to another dual-beam laser welding method of the exhaust pipe barrel 2 and the flange 1 of an embodiment of the present invention, step 2 includes: the inclination angle between the central axis of the second laser beam 7 and the normal direction of the surface of the flange 1 is 30°-60°, and the focal position of the second laser beam 7 is 0 to -△f away from the surface of the flange 1. In this way, it can be ensured that the second laser beam 7 provides a laser-assisted welding method for the same molten pool on the side of the first laser beam 6. During the welding process, the first laser beam 6 realizes deep melting and penetration welding, and the liquid molten pool flows from the higher flange 1 side to the exhaust pipe barrel 2 side. At the same time, under the scanning action of the second laser beam 7, on the one hand, it is more conducive to fully melting the top edge of the welding edge of the flange 1, and on the other hand, the second laser beam 7 accelerates the stirring of the molten pool, further intensifies the liquid molten pool from the higher flange 1 side to the exhaust pipe barrel 2 side, and also further overcomes the surface tension of the liquid molten pool, so that the liquid molten pool on the flange 1 side is more conducive to spreading to the exhaust pipe barrel 2 side and promoting the interface fusion of the molten pool and the surface of the exhaust pipe barrel 2, overcoming the above-mentioned Figure 3 The weld toe bite edge 41 defect shown in the figure can greatly alleviate the stress concentration at the weld toe. At the same time, under the action of the dual laser welding heat source, when the liquid metal flows from the flange 1 side to the exhaust pipe barrel 2 side, the weld thickness at the action position of the first laser beam 6 decreases, so it is more conducive to the influence of the first laser beam 6 on the back of the weld joint, that is, the penetration of the first laser beam 6 is relatively enhanced. Even if the laser beam motion trajectory deviates from the preset trajectory by more than 0.2mm, the influence on the weld formation will be significantly reduced. In summary, compared with the existing single laser welding, dual-beam laser welding not only makes the front of the weld better, but also has a very favorable influence on the back of the weld.

[0064] For details, see the attached Figure 7 and attached Fig.10 As shown, according to another dual-beam laser welding method for exhaust pipe barrel 2 and flange 1 according to an embodiment of the present invention, the first laser beam 6 and the second laser beam 7 act on the same molten pool. Fig.10 The movement trajectory of the first laser beam 6 and the second laser beam 7 is the laser beam movement trajectory 12. The first laser beam 6 and the second laser beam 7 act on the same molten pool to form a light spot action point 11, so that it can be ensured that the double-beam laser welding formed by the first laser beam 6 and the second laser beam 7 acts on the same molten pool, improves the energy concentration of the molten pool, uses the first laser beam 6 to achieve deep penetration welding, and uses the second laser beam 7 to perform scanning laser irradiation on the molten pool, which is more conducive to fully melting the top edge of the welding side of the flange 1, and at the same time can accelerate the stirring of the molten pool, further intensifies the liquid molten pool from the higher flange 1 side to the exhaust pipe barrel 2 side, so that the liquid molten pool on the flange 1 side is more conducive to spreading to the exhaust pipe barrel 2 side and promoting the interface fusion of the molten pool and the surface of the exhaust pipe barrel 2, thereby greatly alleviating the stress concentration at the weld toe. Figure 7The v in represents the moving direction of the first laser beam 6, Figure 7 and Fig.10 In each case, v represents the moving direction of the second laser beam 7 .

[0065] Furthermore, the plane formed by the central axis of the first laser beam 6 and the central axis of the second laser beam 7 is perpendicular to the welding direction. Figure 4 , Attachment Fig. 9 and attached Fig.11 As shown, when the plane formed by the central axis of the first laser beam 6 and the central axis of the second laser beam 7 is perpendicular to the welding direction, it can ensure that the laser rays of the first laser beam 6 and the second laser beam 7 are vertically irradiated to the part to be welded, and the irradiation position can be conveniently operated and accurately adjusted during use.

[0066] Specifically, according to another dual-beam laser welding method of the exhaust pipe barrel 2 and the flange 1 of an embodiment of the present invention, step 2 also includes: the welding point of the second laser beam 7 is located behind the laser action point of the first laser beam 6, and the second laser beam 7 and the first laser beam 6 act on different molten pools. At this time, the laser welding of the first laser beam 6 mainly affects the welding penetration and the back formation of the weld, and the second laser beam 7 mainly acts on the front of the weld and plays a role in modifying the welding. Of course, it should be noted that the modified welding is also more conducive to promoting the interface fusion of the molten pool of the flange 1 and the upper surface of the exhaust pipe barrel 2, overcoming the problems such as the attached Figure 3 The weld toe undercut 41 defect shown significantly relieves stress concentration at the weld toe.

[0067] Specifically, according to a dual-beam laser welding method for an exhaust pipe barrel 2 and a flange 1 according to an embodiment of the present invention, the dual-beam laser welding parameters determined in step 3 include: the first laser beam 6 and the second laser beam 7 are fiber lasers or YAG lasers, the focal length range of the first laser beam 6 and the second laser beam 7 is 150mm-500mm, and the focal spot diameter range is 0.2mm-0.6mm; when conventional laser welding is adopted, the welding parameters include welding speed and laser power; when scanning laser beam welding is adopted, the welding parameters include welding speed, laser power, scanning trajectory, scanning amplitude and scanning frequency, the scanning trajectory of the first laser beam 6 is circular, the scanning frequency adjustment range is 30Hz-200Hz, and the scanning amplitude is not greater than b; the scanning trajectory of the second laser beam 7 is vertical, the scanning frequency is the same as the first laser beam 6, and the scanning amplitude range is δ1-δ2. Of course, it should be noted that the type of the first laser beam 6, the focal length range, the focal spot diameter range, the scanning frequency adjustment range, etc. can be set as needed, and the specific numerical range should not constitute a limitation to the present application. Of course, the scanning trajectory of the second laser beam 7 can be the same as the scanning trajectory of the first laser beam 6, that is, both are circular; at the same time, the scanning trajectory of the second laser beam 7 can also be selected to be a vertical line as described above according to needs.

[0068] Specifically, according to a dual-beam laser welding method for an exhaust pipe barrel 2 and a flange 1 according to an embodiment of the present invention, in step 3, inert gas protection is used during arc welding, and the inert gas protection also includes a back protection type. Fig. 9 As shown, the welding torch is used to realize the output of the dual-beam laser, the manipulator is used to adjust the position of the welding torch, the laser is used to output the laser to the welding torch, and the welding torch is used to output the first laser beam 6 and the second laser beam 7. Fig.13 As shown, the welding torch can be used to clamp the first laser head 13 and the second laser head 14; the first laser head 13 and the second laser head 14 generate the first laser beam 6 and the second laser beam 7 respectively, and the movement trajectories of the first laser head 13 and the second laser head 14 are shown in the attached figure. Fig.13 The laser head sliding track 15 is shown in the figure. The turntable is used to adjust the steering knuckle 9, and the turntable drives the welding fixture 10 through the steering knuckle 9 to achieve stable rotation, and the back protection can be provided by the welding fixture 10. The back protection can be provided by a horizontal blowing air curtain, and the inert protective gas is used to achieve forced cooling so that the back of the weld is basically flush, that is, to ensure the streamline of the inner surface of the exhaust pipe; at the same time, the back can also adopt a ceramic pad or a forced cooling pad with cooling water to achieve forced forming of the back of the weld to ensure the streamline of the inner surface of the exhaust pipe.

[0069] Specifically, after the exhaust pipe double-beam laser welding is completed, the post-weld stress relief annealing treatment may not be performed, or may be performed. The specific treatment may be performed according to the welding effect.

[0070] Specifically, the exhaust pipe material includes stainless steel, titanium alloy or high temperature alloy. When welding titanium alloy or high temperature alloy, it is also necessary to consider setting a shield gas protection to prevent high temperature oxidation after the weld solidifies.

[0071] For details, see the attached Fig.11 As shown, the welding edges of the flange 1 and the exhaust pipe barrel 2 can be designed with chamfers in addition to a right-angle design, and the two should match, that is, the inner chamfer size of the annular groove of the flange 1 is not larger than the chamfer size of the outer side of the exhaust pipe barrel 2 and is not larger than (1 / 3)δ1. The chamfer size of the inner side of the exhaust pipe barrel 2 is recommended to be an oblique chamfer and not larger than (1 / 4)δ2, which facilitates the insertion assembly of the flange 1 and the exhaust pipe barrel 2.

[0072] Further, in step 3, both the first laser beam 6 and the second laser beam 7 are welded by sinusoidal scanning laser beams. Although the scanning frequencies are the same, their timing control is specifically as follows: Figure 6 , Attachment Figure 7 and attached Figure 8 As shown, when the first scanning track 66 of the first laser beam 6 is at the farthest distance D from the welding edge 16 of the flange 1, that is, when the first laser beam 6 is located at the first position 61, the scanning track 76 of the second laser beam 7 is closest to the welding edge 16 of the flange 1, and the second laser beam 7 is located at the fifth position 71. Similarly, when the first scanning track 66 of the first laser beam 6 is at the closest distance D from the welding edge 16 of the flange 1, that is, when the first laser beam 6 is located at the third position 63, the scanning track 76 of the second laser beam 7 is farthest from the welding edge 16 of the flange 1, and the second laser beam 7 is located at the seventh position 73. As shown in the attached figure Figure 7 As shown in FIG. 1 , the second position 62, the third position 63, and the fourth position 64 are respectively the scanning path trajectories of the first laser beam 6 along the circular scanning direction 65. Figure 8 As shown, the sixth position 72 and the seventh position 73 are the scanning path trajectories of the second laser beam 7 along the vertical scanning trajectory 17. In this embodiment, both the first laser beam 6 and the second laser beam 7 are welded by sinusoidal scanning laser beams, but the timing control is different as described above.

[0073] Furthermore, in the welding process of step 4, the first laser beam 6 realizes deep penetration welding, and the liquid molten pool flows from the higher flange 1 side to the exhaust pipe barrel 2 side. At the same time, under the scanning action of the second laser beam 7, on the one hand, it is more conducive to fully melting the top edge of the welding edge of the flange 1, and on the other hand, the second laser beam 7 accelerates the stirring of the molten pool, further intensifies the liquid molten pool from the higher flange 1 side to the exhaust pipe barrel 2 side, and also further overcomes the surface tension of the liquid molten pool, so that the liquid molten pool on the flange 1 side is more conducive to spreading to the exhaust pipe barrel 2 side and promoting the interface fusion of the molten pool and the upper surface of the exhaust pipe barrel 2, overcoming the occurrence of attachment Figure 3 The weld toe bite edge 41 defect shown in the figure can greatly alleviate the stress concentration at the weld toe. At the same time, under the action of the dual laser welding heat source, when the liquid metal flows from the flange 1 side to the exhaust pipe barrel 2 side, the weld thickness at the action position of the first laser beam 6 decreases, so it is more conducive to the influence of the first laser beam 6 on the back of the weld joint, that is, the penetration of the first laser beam 6 is relatively enhanced. Even if the laser beam motion trajectory deviates from the preset trajectory by more than 0.2mm, the influence on the weld formation will be significantly reduced. In summary, compared with the existing single laser welding, dual-beam laser welding not only makes the front of the weld better, but also has a very favorable influence on the back of the weld.

[0074] The following is combined with Figure 1-13 , the present invention is explained by taking an aircraft engine exhaust pipe as an example.

[0075] Embodiment 1:

[0076] See attached Figure 1 -Attached Fig.13 As shown, an aircraft engine exhaust pipe is made of 0Cr18Ni9 stainless steel, the initial welding edge of the flange 1 is 5 mm, and the welding edge of the exhaust pipe barrel 2 is 1 mm. The double-beam laser welding method of the exhaust pipe barrel 2 and the flange 1 is implemented by using the above embodiment of the present invention, which mainly includes the following steps:

[0077] Step 1: Process the welding edge of flange 1 and exhaust pipe barrel 2 into an annular welding edge. The welding edge of flange 1 is based on the inner wall of exhaust pipe barrel 2 and is processed to a wall thickness of δ1 = 3mm. The length of δ1 wall thickness state is L = 5mm. An annular groove is prepared on the inner side of the welding edge of flange 1 to form an inserted type assembly with the welding edge of exhaust pipe barrel 2; the depth of the annular groove a = 1.2mm, and the radial height of the annular groove is consistent with the wall thickness δ2 of exhaust pipe barrel 2, that is, 1mm. When the welding edges of flange 1 and exhaust pipe barrel 2 are assembled, the inner surfaces between the two are basically flush and the assembly gap between the two should not be greater than 0.6mm.

[0078] Step 2: According to the design parameters of the annular welding edge, plan the geometric position and shape of the dual-beam laser welding, the welding path and perform pre-welding cleaning. During the welding process, the distance b between the central axis of the first laser beam 6 and the axial welding end face of the annular groove of the flange 1 is 0.5mm; the central axis of the first laser beam 6 coincides with the normal of the flange 1 surface, the first laser beam 6 adopts negative defocus and the defocus amount △f is -1.0mm; on the side perpendicular to the welding direction and away from the flange 1, a second laser beam 7 is set, the focus position of the second laser beam 7 is located on the side of the welding edge of the flange 1 and the distance from the upper surface is 0.5mm, and the inclination angle of the central axis of the second laser beam 7 to the vertical direction (i.e., the normal of the workpiece surface) is 45°. Pre-welding cleaning includes chemical cleaning, mechanical grinding and scraping cleaning.

[0079] Step 3: Determine the dual-beam laser welding parameters. The first laser beam 6 is a conventional laser beam, and the second laser beam 7 is a scanning laser beam. The first laser beam 6 and the second laser beam 7 are fiber lasers with a focal length of 300 mm and a focal spot diameter of The welding parameters of the first laser beam 6 include: welding speed v ranges from 1.2m / min to 1.5m / min; laser power P ranges from 2000W to 2600W. The welding parameters of the second laser beam 7 include: laser power P ranges from 2000W to 2600W; circular scanning trajectory, clockwise rotation scanning, scanning amplitude of 1.0mm, scanning frequency of 100Hz. The first laser beam 6 and the second laser beam 7 both use coaxial protective covers to provide inert protective gas, and the gas flow adjustment range is 15L / min-30L / min. The inert protective gas is argon. See the attached Fig.11 In the present invention, when argon (Ar) is used as the protective gas for welding with the first laser beam 6 and the second laser beam 7, the possibility of oxidation of the welded parts can be avoided, thereby improving the welding quality.

[0080] Step 4: According to the dual-beam laser welding parameters, the flange 1 and the exhaust pipe barrel 2 are welded. Fig. 9 As shown, the welding edge of the flange 1 and the exhaust pipe barrel 2 is assembled in the welding fixture 10, which is connected to the turntable through the steering knuckle 9. The turntable drives the welding fixture 10 to achieve stable rotation. During the welding process, the welding fixture 10 uses a horizontal air curtain to provide inert protective gas to the back of the weld. The inert protective gas flow rate is 20L / min-25L / min. The first laser beam 6 and the second laser beam 7 are installed and fixed in the welding torch. Driven by the manipulator execution end, the dual-beam laser is kept to achieve synchronous movement, that is, the welding speed is the same. The dual-beam laser welding is carried out using optimized welding parameters, and the attached Fig. 9 The double-beam laser welded joint 8 in the deep penetration state shown in the figure achieves a good single-sided welding and double-sided forming effect. The weld width of the laser weld 4 of the flange 1 and the exhaust pipe barrel 2 is about 2mm-3.5mm, the welding deformation is very small, and the roundness tolerance of the exhaust pipe after welding can be controlled within the range of ±1mm.

[0081] It has been verified that, compared with the existing laser welding method, the dual-beam laser welding method of the present invention has a significantly larger welding process margin and process feasibility. The present invention can completely melt the butt and overlap connection interface of the flange 1 and the exhaust pipe barrel 2, completely avoid the weld toe undercut 41, and the front and back welds are well formed, so it is easy to obtain a welded joint without excessive defects.

[0082] Embodiment 2:

[0083] See attached Figure 1 -Attached Fig.13 As shown, an aircraft engine exhaust pipe is made of 0Cr18Ni9 stainless steel, the initial welding edge of the flange 1 is 5 mm, and the welding edge of the exhaust pipe barrel 2 is 1 mm. The double-beam laser welding method of the flange 1 and the exhaust pipe barrel 2 is implemented by using the embodiment of the present invention, which mainly includes the following steps:

[0084] Step 1: Process the welding edge of flange 1 and exhaust pipe barrel 2 into an annular welding edge. The welding edge of flange 1 is based on the inner wall of exhaust pipe barrel 2 and is processed to a wall thickness of δ1 = 3mm. The length of δ1 wall thickness state is L = 5mm. An annular groove is prepared on the inner side of the welding edge of flange 1 to form an inserted type assembly with the welding edge of exhaust pipe barrel 2; the depth of the annular groove a = 1.2mm, and the radial height of the annular groove is consistent with the wall thickness δ2 of exhaust pipe barrel 2, that is, 1mm. When the welding edges of flange 1 and exhaust pipe barrel 2 are assembled, the inner surfaces between the two are basically flush and the assembly gap between the two should not be greater than 0.6mm.

[0085] Step 2: According to the design parameters of the annular welding edge, plan the geometric position and shape of the dual-beam laser welding, the welding path and perform pre-welding cleaning. During the welding process, the distance b between the central axis of the first laser beam 6 and the axial welding end face of the annular groove of the flange 1 is 0.5mm; the central axis of the first laser beam 6 coincides with the normal of the flange 1 surface, the first laser beam 6 adopts negative defocus and the defocus amount △f is -1.0mm; on the side perpendicular to the welding direction and away from the flange 1, a second laser beam 7 is set, the focus position of the second laser beam 7 is located on the side of the welding edge of the flange 1 and the distance from the upper surface is 0.5mm, and the inclination angle of the central axis of the second laser beam 7 to the vertical direction (i.e., the normal of the workpiece surface) is 45°. Pre-welding cleaning includes chemical cleaning, mechanical grinding and scraping cleaning.

[0086] Step 3: Determine the dual-beam laser welding parameters. The first laser beam 6 and the second laser beam 7 are both scanning fiber laser beams with a focal length of 300 mm and a focal spot diameter of The welding parameters of the first laser beam 6 include: welding speed v ranges from 1.2m / min to 1.5m / min; laser power P ranges from 2000W to 2600W; circular scanning trajectory, clockwise rotation scanning, scanning amplitude of 0.5mm, scanning frequency of 100Hz. The welding parameters of the second laser beam 7 include: laser power P ranges from 2000W to 2600W; vertical scanning trajectory 17, scanning frequency of 100Hz, scanning amplitude of 1.6mm. Both the first laser beam 6 and the second laser beam 7 use a coaxial protective cover to provide an inert protective gas, and the gas flow adjustment range is 15L / min-30L / min. The inert protective gas is argon.

[0087] Step 4: According to the dual-beam laser welding parameters, the flange 1 and the exhaust pipe barrel 2 are welded. Fig. 9 As shown, the welding edge of the flange 1 and the exhaust pipe barrel 2 is assembled in the welding fixture 10, which is connected to the turntable through the steering knuckle 9. The turntable drives the welding fixture 10 to achieve stable rotation. During the welding process, the welding fixture 10 uses a horizontal air curtain to provide inert protective gas to the back of the weld. The inert protective gas flow rate is 20L / min-25L / min. The first laser beam 6 and the second laser beam 7 are installed and fixed in the welding torch. Driven by the manipulator execution end, the dual-beam laser is kept to achieve synchronous movement, that is, the welding speed is the same. The dual-beam laser welding is carried out using optimized welding parameters, and the attached Fig. 9 The double-beam laser welded joint 8 in the deep penetration state shown in the figure achieves a good single-sided welding and double-sided forming effect. The weld width of the laser weld 4 of the flange 1 and the exhaust pipe barrel 2 is about 2mm-3.5mm, the welding deformation is very small, and the roundness tolerance of the exhaust pipe after welding can be controlled within the range of ±1mm.

[0088] It has been verified that, compared with the existing laser welding method, the dual-beam laser welding method of the present invention has a significantly larger welding process margin and process feasibility. The present invention can completely melt the butt and overlap connection interface of the flange 1 and the exhaust pipe barrel 2, completely avoid the weld toe undercut 41, and the front and back welds are well formed, so it is easy to obtain a welded joint without excessive defects.

[0089] It should be clear that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. For the embodiments of the method, the relevant parts can refer to the partial description of the device embodiment. The present invention is not limited to the specific steps and structures described above and shown in the figures. In addition, for the sake of brevity, a detailed description of known method technologies is omitted here.

[0090] The above is only an embodiment of the present application and is not limited to the present application. For those skilled in the art, the present application may have various changes and variations without departing from the scope of the present invention. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A double-beam laser welding method for an exhaust pipe barrel and a flange, characterized in that: The steps include: Step 1: processing the welding edges of the exhaust pipe barrel (2) and the flange (1) into annular welding edges respectively; Step 2: planning the geometric position and welding path of the dual-beam laser welding according to the design parameters of the annular welding edge; Step 3: Determine dual-beam laser welding parameters. Both the first laser beam and the second laser beam adopt sinusoidal scanning laser beam welding. When the first scanning trajectory of the first laser beam is farthest from the welding edge of the flange, that is, when the first laser beam is located at the first position, the scanning trajectory of the second laser beam is closest to the welding edge of the flange. At this time, the second laser beam is located at the fifth position. When the first scanning trajectory of the first laser beam is closest to the welding edge of the flange, that is, when the first laser beam is located at the third position, the scanning trajectory of the second laser beam is farthest from the welding edge of the flange. At this time, the second laser beam is located at the seventh position. The first position and the third position are respectively the scanning path trajectories of the first laser beam along the circular scanning direction, and the fifth position and the seventh position are the scanning path trajectories of the second laser beam along the vertical scanning trajectory. Step 4: performing double-beam laser welding on the flange (1) and the exhaust pipe barrel (2) according to double-beam laser welding parameters; Step one comprises: preparing an annular groove on the inner side of the welding edge of the flange (1), wherein the radial height of the annular groove of the flange (1) is consistent with the wall thickness of the exhaust pipe barrel (2); and inserting and assembling the welding edge of the exhaust pipe barrel (2) into the annular groove of the flange (1).

2. A double-beam laser welding method for an exhaust pipe barrel and a flange according to claim 1, characterized in that: In step one, the thickness range of the first welding edge wall thickness δ1 of the flange (1) is 2 mm-4 mm, the length L of the first welding edge of the flange (1) in the state of the first welding edge wall thickness δ1 is not less than 3 mm, and the depth a of the annular groove of the flange (1) is 0.2 mm-1.5 mm.

3. A double-beam laser welding method for an exhaust pipe barrel and a flange according to claim 2, characterized in that: After the flange (1) and the exhaust pipe barrel (2) are assembled by insertion, the inner surfaces between the two are flush and the local maximum assembly gap △x between the two should not be greater than a / 2.

4. The double-beam laser welding method for exhaust pipe barrel and flange according to claim 2 is characterized in that: Step 2 comprises: during the welding process, the inclination angle range between the central axis of the first laser beam (6) and the normal direction of the surface of the flange (1) is ±10°; and a second laser beam (7) is arranged on the side perpendicular to the laser welding direction of the first laser beam (6) and away from the flange (1), and the focal position of the second laser beam (7) is located on the side of the welding edge of the flange (1).

5. A double-beam laser welding method for an exhaust pipe barrel and a flange according to claim 4, characterized in that: Step 2 comprises: during the welding process, the distance between the central axis of the first laser beam (6) and the axial welding end face of the annular groove of the flange (1) is b, b=0-a / 2, the first laser beam (6) is negatively defocused and the defocus amount Δf ranges from (δ2-δ1)-(δ2-δ1) / 2.

6. A double-beam laser welding method for an exhaust pipe barrel and a flange according to claim 5, characterized in that: Step 2 comprises: the inclination angle between the central axis of the second laser beam (7) and the normal direction of the flange (1) surface is 30°-60°, and the distance between the focal position of the second laser beam (7) and the surface of the flange (1) is 0 to -Δf.

7. A double-beam laser welding method for an exhaust pipe barrel and a flange according to claim 4, characterized in that: The first laser beam (6) and the second laser beam (7) act on the same molten pool.

8. The double-beam laser welding method for exhaust pipe barrel and flange according to claim 4 is characterized in that: Step 2 also includes: the welding action point of the second laser beam (7) is located behind the laser action point of the first laser beam (6), and the second laser beam (7) and the first laser beam (6) act on different molten pools.

9. The double-beam laser welding method for exhaust pipe barrel and flange according to claim 5, characterized in that: The dual-beam laser welding parameters determined in step 3 include: The first laser beam (6) and the second laser beam (7) are fiber lasers or YAG lasers, the focal lengths of the first laser beam (6) and the second laser beam (7) are in the range of 150 mm to 500 mm, and the focal spot diameters are in the range of 0.2 mm to 0.6 mm; when conventional laser welding is used, the welding parameters include welding speed and laser power; When scanning laser beam welding is adopted, the welding parameters include welding speed, laser power, scanning trajectory, scanning amplitude and scanning frequency. The scanning trajectory of the first laser beam (6) is circular, the scanning frequency adjustment range is 30 Hz-200 Hz, and the scanning amplitude is not greater than b; the scanning trajectory of the second laser beam (7) is vertical, the scanning frequency is the same as that of the first laser beam (6), and the scanning amplitude range is δ1-δ2.

10. A double-beam laser welding method for an exhaust pipe barrel and a flange according to claim 9, characterized in that: Step three: inert gas protection is used during arc welding, and the inert gas protection also includes back protection type.

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