High-power laser welding method for medium plate

Abstract

The invention belongs to the technical field of laser welding, and discloses a medium-thickness plate high-power laser welding method which comprises the following steps: S1, measuring a butt joint gap between workpieces, and configuring a laser combination consisting of at least a first welding beam and a second welding beam; s2, the first welding light beam and the second welding light beam are output at the same time or respectively; wherein the width of the first welding light beam at least completely covers the butt joint gap, and the first welding light beam is used for cleaning an oxide layer and dirt on the to-be-welded surface of the workpiece and generating a stable molten pool with deep melting depth and large melting area on the surface of the workpiece; the second welding beam and the first welding beam are arranged in parallel, act on the rear portion of a molten pool formed by the first welding beam in the moving direction of the laser welding head and are used for gasifying materials and forming a deep melting key hole in the surface of a workpiece; the problems that when an existing laser welding process is used for welding medium and thick plates, the welding efficiency and the energy utilization rate are low, welding air holes are likely to occur, the side wall is not fused, and the welding fusion depth is unstable can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of laser welding, and in particular to a high-power laser welding method for medium and thick plates. Background Art

[0002] Medium and thick plates generally refer to steel plates with a thickness of 4.5mm to 25mm, which are widely used in industries such as shipbuilding, engineering machinery and construction engineering. The welding of medium and thick plates is an important part of the production and manufacturing process of various industries. In the shipbuilding industry, the use of medium and thick plates in some ship types exceeds 80%, and the welding workload accounts for more than 70% of the total welding workload. The welding of medium and thick plates in various industries is still mainly manual welding. The development of efficient, high-quality and low-consumption medium and thick plate welding technology is an urgent need for various industries.

[0003] At present, the welding of medium and thick plates mainly adopts narrow gap arc welding, among which narrow gap submerged arc welding and narrow gap TIG welding are the main ones. Narrow gap laser welding and laser arc hybrid welding have also been applied to the field of medium and thick plate welding. However, whether it is narrow gap arc welding or narrow gap laser wire welding, it is necessary to open the groove in advance, fill multiple welding passes, have low welding efficiency, large welding deformation, and easily appear defects such as welding pores and side wall unfusion, and unstable wire feeding welding penetration; while laser arc welding, which combines two heat sources, uses the ultra-high power density of high-power laser to form a deep melting keyhole to obtain a weld with a large depth-to-width ratio, so as to reduce the number of weld layers; the arc improves the transmission efficiency of laser energy and the absorption rate of the workpiece to the laser, so as to improve the welding efficiency; the introduction of the arc improves the problem of too small laser spot and improves the gap tolerance, but the workpiece still needs to be grooved in advance, and the groove has a greater impact on the welding quality. In addition, the bubbles in the laser keyhole do not have time to escape after closing, and pores are easily formed after cooling and solidification. In addition, the total energy input of welding is too large, which leads to overheating of the molten pool, and there is violent evaporation, spattering and deformation during the welding process. Summary of the invention

[0004] The object of the present invention is to provide a high-power laser welding method for medium and thick plates, which has high welding efficiency and energy utilization rate and can effectively reduce spatter and deformation during welding.

[0005] To achieve this object, the present invention adopts the following technical solutions: A high-power laser welding method for medium and thick plates is provided, comprising the following steps: S1: measuring the butt gap between the workpieces, and configuring a laser combination consisting of at least a first welding beam and a second welding beam; S2: Outputting the first welding beam and the second welding beam simultaneously or separately; wherein, The width of the first welding beam at least completely covers the butt gap, and is used to clean the oxide layer and dirt on the surface of the workpiece to be welded, and to generate a stable molten pool with a shallow melting depth and a large melting area on the surface of the workpiece; The second welding beam is arranged in parallel with the first welding beam, and acts on the rear part of the molten pool formed by the first welding beam along the moving direction of the laser welding head, so as to gasify the material and form a deep melting keyhole on the surface of the workpiece.

[0006] As an optional solution for the high-power laser welding method for medium and thick plates, the laser combination also includes a third welding beam, which is arranged parallel to the second welding beam and is output simultaneously or separately with the second welding beam. The third welding beam acts on the rear wall of the deep melting keyhole along the moving direction of the laser welding head to maintain the opening state of the deep melting keyhole.

[0007] As an optional solution for the high-power laser welding method for medium and thick plates, the light output mode, light output power, beam width and spot shape of each welding light beam are independently controlled and adjustable in real time.

[0008] As an optional solution for the high-power laser welding method for medium and thick plates, the width of each welding beam is determined according to the requirement of the weld width, and the weld width is greater than or equal to the butt gap.

[0009] As an optional solution for the high-power laser welding method for medium and thick plates, the laser combination is composed of a multi-channel laser output by a laser based on an array fiber. The laser based on the array fiber includes a plurality of laser modules. The output optical fibers 30 of the plurality of laser modules are arranged in an array to form a fiber array. The plurality of laser modules are independently controlled and adjustable in real time.

[0010] As an optional solution for the high-power laser welding method for medium and thick plates, the width of each welding beam is determined by the single-point spot diameter and spacing of the multi-channel laser; The single spot diameter and spacing of the multi-path laser are determined by the core and outer cladding diameters of the output optical fibers 30 of the plurality of laser modules and the collimation and focusing ratio of the laser welding head.

[0011] As an optional solution for the high-power laser welding method for medium and thick plates, the first welding beam completely covers the entire welding area of ​​the workpiece.

[0012] As an optional solution of the high-power laser welding method for medium and thick plates, the width of the first welding beam is greater than the width of the second welding beam; The width of the third welding beam is greater than the width of the second welding beam and / or smaller than the width of the first welding beam.

[0013] As an optional solution for the high-power laser welding method for medium and thick plates, the power of the second welding beam is greater than the power of the first welding beam and the third welding beam; preferably, the power of the second welding beam is configured to achieve a required welding depth, and the power of the first welding beam and the third welding beam is configured to melt through the welding wire without melting through the plate.

[0014] As an optional solution of the high-power laser welding method for medium and thick plates, the first welding beam and the third welding beam jointly form a 'Y'-shaped large keyhole around the second welding beam.

[0015] As described above, the present invention provides a high-power laser welding method for medium and thick plates, which uses a laser combination consisting of at least a first welding beam and a second welding beam, and outputs the first welding beam and the second welding beam simultaneously or separately to weld the medium and thick plates, wherein the width of the first welding beam at least completely covers the butt joint gap, is used to clean the oxide layer and dirt on the surface of the workpiece to be welded, and generates a stable molten pool with shallow melting depth and large melting area on the surface of the workpiece, and the molten welding wire liquid and the workpiece are fully fused in the molten pool and filled into the butt joint gap; the second welding beam is arranged in parallel with the first welding beam, and acts on the rear part of the molten pool formed by the first welding beam along the moving direction of the laser welding head, and is used to gasify the material and form a deep melting keyhole on the surface of the workpiece. Since the workpiece surface and the welding wire are already in a molten state after the first welding beam acts, the energy of the second welding beam can be fully utilized at this time, and almost all the laser energy can be absorbed by the molten metal, and a larger melting depth can be obtained by using a lower laser energy. The material around the deep melting keyhole is melted by heat conduction, and the second welding beam and the first welding beam work together to form a deep melting keyhole. Under the action of the first welding beam, the front wall of the keyhole is deeply melted, maintaining a large opening state, and the metal vapor in the keyhole escapes to the surrounding areas along the side walls of the keyhole, reducing the shielding effect on the laser, thereby improving energy utilization and welding efficiency.

[0016] In addition, this welding method does not require the workpiece to be beveled in advance, nor does it require the workpiece to be cleaned before welding, which can effectively improve the welding efficiency. Multiple groups of laser beams are welded in parallel, which improves the tolerance of the assembly gap. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a welding schematic diagram of a high-power laser welding method for medium and thick plates provided in a specific embodiment of the present invention; Figure 2 It is a schematic diagram of a laser combination provided in a specific embodiment of the present invention; Figure 3 It is a side view of the welding process of the medium and thick plate high-power laser welding method provided in the specific implementation example of the present invention; Figure 4is a microscope image of the front side of a weld formed by using welding parameters in an example in a specific embodiment of the present invention; Figure 5 is a microscope image of the reverse side of a weld formed by using welding parameters in an example in a specific embodiment of the present invention; Figure 6 is a metallographic diagram of a molten pool formed by welding parameters in an example according to a specific embodiment of the present invention.

[0018] In the figure: 100, workpiece; 101, butt gap; 102, molten pool; 103, weld; 104, keyhole; 1. Laser welding head; 2. Wire feeding structure; 3. Laser combination; 30. Output optical fiber; 31. First welding beam; 32. Second welding beam; 33. Third welding beam. DETAILED DESCRIPTION

[0019] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0020] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0021] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0022] In the description of this embodiment, the terms "upper", "lower", "right" and other directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplified operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0023] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0024] like Figures 1 to 6 As shown, this embodiment provides a medium-thick plate high-power laser welding method for welding a workpiece 100. The workpiece 100 to be welded can be various grades of carbon steel, stainless steel, alloy steel and aluminum alloy disclosed in the prior art, with a thickness of 4.5mm-25mm. The method comprises the following steps: S1: measuring the butt gap 101 between the workpieces 100 and configuring a laser combination 3 consisting of at least a first welding beam 31 and a second welding beam 32 .

[0025] The above steps, specifically in this embodiment, are to butt-join two workpieces 100 to be welded, measure the width of the butt-joint gap 101 between the two workpieces 100 to be welded, and configure the laser combination 3 according to the width of the butt-joint gap 101. The laser combination 3 is composed of at least a first welding beam 31 and a second welding beam 32.

[0026] S2: Output the first welding beam 31 and the second welding beam 32 simultaneously or separately; wherein the width of the first welding beam 31 at least completely covers the butt gap 101, and is used to clean the oxide layer and dirt on the surface of the workpiece 100 to be welded, and to generate a stable molten pool 102 with a shallow melting depth and a large melting area on the surface of the workpiece 100; the second welding beam 32 is arranged in parallel with the first welding beam 31, and acts on the rear part of the molten pool 102 formed by the first welding beam 31 along the moving direction of the laser welding head 1, and is used to vaporize the material and form a deep melting keyhole 104 on the surface of the workpiece 100.

[0027] In the above steps, specifically in this embodiment, the width of the first welding beam 31 at least completely covers the butt joint gap 101, which is used to clean the oxide layer and dirt on the surface of the workpiece 100 to be welded, and to generate a stable molten pool 102 with a shallow melting depth and a large melting area on the surface of the workpiece 100. After the molten welding wire liquid and the workpiece 100 are fully fused in the molten pool 102, they are filled into the butt joint gap 101; the second welding beam 32 is arranged in parallel with the first welding beam 31, and acts on the rear part of the molten pool 102 formed by the first welding beam 31 along the moving direction of the laser welding head 1, which is used to gasify the material and form a deep melting keyhole 104 on the surface of the workpiece 100. Since the surface of the workpiece 100 and the welding wire are already in a molten state after the first welding beam 31 acts, the energy of the second welding beam 32 can be fully utilized at this time, and almost all the laser energy can be absorbed by the molten metal, and a larger melting depth can be obtained by using a lower laser energy. The material around the deep melting keyhole 104 is melted by heat conduction, and the second welding beam 32 and the first welding beam 31 work together to form a deep melting keyhole 104. Under the action of the first welding beam 31, the front wall of the keyhole 104 is deeply melted, and the state of the large opening is maintained. The metal vapor in the keyhole 104 escapes to the surroundings along the side walls of the keyhole 104, reducing the shielding effect on the laser and improving the laser energy utilization rate and welding efficiency. The first welding beam 31 and the second welding beam 32 can emit light simultaneously or at intervals of preset time. The selection of the light emission time depends on the time required for the molten pool 102 to stabilize. If the time required for the molten pool 102 to stabilize is short, the light emission can be selected to be simultaneous. If the molten pool 102 stabilizes for a long time, the first welding beam 31 and the second welding beam 32 are selected to emit light at intervals of preset time. After the molten pool 102 stabilizes, the second welding beam 32 emits light to ensure that the laser energy of the second welding beam 32 is fully utilized. A larger melting depth can be obtained using lower energy. The preset time is greater than or equal to the stabilization time of the molten pool 102.

[0028] In addition, this welding method does not require the workpiece to be beveled in advance, nor does it require the workpiece to be cleaned before welding, which can effectively improve the welding efficiency. Multiple groups of laser beams are welded in parallel, which improves the tolerance of the assembly gap.

[0029] Optionally, the laser combination 3 also includes a third welding beam 33, which is arranged in parallel with the second welding beam 32, and is output simultaneously or separately with the second welding beam 32. The third welding beam 33 acts on the rear wall of the deep melting keyhole 104 along the moving direction of the laser welding head 1 to maintain the opening state of the deep melting keyhole 104.

[0030] Specifically, in this embodiment, refer to Figure 1 and Figure 2, the third welding beam 33 acts on the rear wall of the deep-melting keyhole 104, and when the first welding beam 31 and the second welding beam 32 move along the extension direction of the butt gap 101, the metal behind the keyhole 104 continuously solidifies to form a weld 103. The third welding beam 33 can maintain the opening state of the keyhole 104, and work together with the first welding beam 31 and the second welding beam 32 to form a "Y"-shaped large keyhole 104, which can reduce the pressure of the metal vapor in the keyhole 104, reduce the solidification speed of the molten pool 102, slow down the cooling rate of the molten pool 102, and reduce the difficulty of gas escape, thereby effectively avoiding spatter during welding and the generation of pores in the weld 103, which is conducive to optimizing the formation of the weld 103. The third welding beam 33 and the second welding beam 32 are output simultaneously or separately. If the time required for the molten pool 102 to stabilize is short, they can be selected to emit light simultaneously. If the molten pool 102 stabilizes for a long time, the third welding beam 33 and the second welding beam 32 are selected to emit light separately with a preset time interval. After the molten pool 102 is stabilized, the third welding beam 33 emits light to ensure that the laser energy of the second welding beam 32 is fully utilized, while avoiding rapid solidification of the molten pool 102, extending the gas escape time, and preventing spatter.

[0031] Specifically, the wire feeding method is front wire feeding or rear wire feeding, preferably front wire feeding. In the present embodiment, the wire feeding method is front wire feeding. The welding wire is in front and the laser is in the back. The welding wire absorbs the energy of the first welding beam 31 and then melts. After the molten droplets enter the molten pool 102, the second welding beam 32 and the third welding beam 33 begin to work. The molten state lasts for a long time, the fusion of the workpiece 100 and the welding wire will be more complete, and the weld 103 will be better formed. In the rear wire feeding method, the laser is in front and the welding wire is in the back. The welding wire mainly absorbs the energy of the third welding beam 33. As the laser welding head 1 continues to move, the welding wire droplets enter the molten pool 102 and begin to cool, resulting in a poorer cladding effect. The type of welding wire can be selected as needed according to the material of the workpiece 100 to be welded. Specifically, the diameter of solid welding wire is generally 0.8mm, 1.0mm, 1.2mm and 1.6mm. The diameter of the welding wire will also affect the wire feeding amount per unit time. If the workpiece 100 is thick or the butt gap 101 between the two workpieces 100 is large, the welding wire needs to be thickened accordingly. At the same time, the laser power required to melt the welding wire also needs to be increased.

[0032] Optionally, the light output mode, light output power, beam width and spot shape of each welding beam are independently controlled and adjustable in real time.

[0033] Specifically, in this embodiment, the butt gap 101 between the two workpieces 100 is measured, and the parameters of each welding beam of the laser combination 3 are set according to the width of the butt gap 101. The parameters include light output mode, light output power, beam width and spot shape. Each parameter is independently controlled and adjustable in real time. During the adjustment process, the light emitting mode, light emitting power, beam width and spot shape of the first laser beam 31 are determined according to the width of the butt gap 101, the thickness of the medium and thick plate to be welded, combined with the single spot shape, spot diameter, spacing of the first welding beam 31 and the collimation and focusing ratio of the laser welding head 1, so that the total width of the first welding beam 31 at least completely covers the butt gap 101, and the power of the first laser beam 31 can melt through the welding wire without melting through the workpiece 100; the light emitting mode, light emitting power, beam width and spot shape of the second laser beam 32 are determined in combination with the single spot shape, spot diameter, spacing of the second welding beam 32 and the collimation and focusing ratio of the laser welding head 1, so that the total width of the second welding beam 32 is smaller than that of the first laser beam 31 but needs to completely cover the butt gap 101, and the power of the second laser beam 32 can reach the required welding depth, and the light The spots are arranged linearly, the second welding beam 32 is arranged parallel to the first welding beam 31, and along the moving direction of the laser welding head 1, the second welding beam 32 is located 0.5mm-1mm behind the first welding beam 31; combined with the single spot shape, spot diameter, spacing of the third welding beam 33 and the collimation and focusing ratio of the laser welding head 1, the light output mode, light output power, beam width and spot shape of the third welding beam 33 are confirmed, so that the total width of the third welding beam 33 is slightly larger than the first laser beam 31, and at the same time, the power of the third laser beam 33 is less than the power of the first laser beam 31, which can melt through the welding wire without melting through the workpiece 100, and the spots are arranged linearly, the third welding beam 33 is arranged parallel to the second welding beam 32, and along the moving direction of the laser welding head 1, the third welding beam 33 is located 0.5mm-1mm behind the second welding beam 32.

[0034] Optionally, the light emission modes of the first welding beam 31, the second welding beam 32 and the third welding beam 33 are continuous mode or pulse mode. Specifically, in this embodiment, they are all continuous mode, and the stability of the molten pool 102 is better in the continuous mode.

[0035] Optionally, the laser combination 3 is composed of a multi-channel laser output by a laser based on an array fiber, the laser based on the array fiber includes a plurality of laser modules, the output optical fibers 30 of the plurality of laser modules are arranged in an array to form a fiber array, and the plurality of laser modules are independently controlled and adjustable in real time.

[0036] Specifically, the first welding beam 31, the second welding beam 32 and the third welding beam 33 are formed by lasers of different output optical fibers 30. The single-point spot diameter and spacing of the first welding beam 31, the second welding beam 32 and the third welding beam 33 depend on the core and outer cladding diameter of the pigtail fiber ultimately output by the single-channel laser, as well as the collimation and focusing ratio of the laser welding head 1.

[0037] Optionally, the width of each welding beam is determined by the single-point spot diameter and spacing of the multi-channel laser; the single-point spot diameter and spacing of the multi-channel laser are determined by the core and outer cladding diameters of the output optical fibers 30 of several laser modules and the collimation and focusing ratio of the laser welding head 1.

[0038] Specifically, the spot diameter = fiber core × (focusing lens focal length / collimating lens focal length), and the spot spacing = outer cladding diameter × (focusing lens focal length / collimating lens focal length). For example, the fiber core is generally 20 μm, 50 μm, 100 μm, and the outer cladding is generally 250 μm or 400 μm. The collimation and focusing ratio of the laser welding head 1 is 1:2, 1:2.5 or 1:3, preferably 1:2.

[0039] Optionally, the width of the first welding beam 31 is greater than the width of the second welding beam 32 ; the width of the third welding beam 33 is greater than the width of the second welding beam 32 , and / or, smaller than the width of the first welding beam 31 .

[0040] Specifically, the total width of the first welding beam 31 needs to cover the butt gap 101, and preferably also the edge of the workpiece 100. On the one hand, it can play a role in welding cleaning before deep melting, and on the other hand, it can also fully fuse the molten droplets of the workpiece 100 and the welding wire. The total width of the second welding beam 32 is smaller than the total width of the first welding beam 31, but it also needs to cover the butt gap 101 to ensure the depth and width of the molten pool 102 to avoid the problem of incomplete melting at the edge of the weld 103. The width of the third welding beam 33 is generally slightly wider than the width of the second welding beam 32 to effectively avoid the collapse of the keyhole 104. For example, the butt gap 101 is 1.5 mm wide and the spot spacing is 0.5 mm. Then, the first welding beam 31 needs at least four beams to emit light simultaneously, and the second welding beam 32 is preferably two beams considering that the gap is relatively large.

[0041] In addition, the number of paths of each laser combination 3 is selected based on the requirements for the width of the weld 103 and whether the gap can be completely covered. The width of the laser combination 3 can be changed by adjusting the number of paths, and the width of the weld 103 can be fine-tuned in combination with the welding angle of the laser combination 3. When adjusting the welding angle of the laser combination 3 and the width of the laser combination 3, the projection of the first welding beam 31 on the horizontal plane must be perpendicular to the butt gap 101, thereby ensuring that the second welding beam 32 and the third welding beam 33 are both perpendicular to the butt gap 101, so as to ensure that the two workpieces 100 can be welded together, and at the same time ensure that the projection width of the laser combination 3 on the horizontal plane completely covers the gap.

[0042] Optionally, the power of the second welding beam 32 is greater than the power of the first welding beam 31 and the third welding beam 33; preferably, the power of the second welding beam 32 is configured to achieve a required welding depth, and the power of the first welding beam 31 and the third welding beam 33 is configured to melt through the welding wire without melting through the plate.

[0043] Specifically, the setting of a single laser power depends on the thickness of the workpiece 100 that actually needs to be welded. The first welding beam 31 and the third welding beam 33 are only auxiliary and need to melt the welding wire without melting through the workpiece 100. The penetration depth only needs to reach one third of the thickness of the workpiece 100. The second welding beam 32 is the main welding heat source and needs to reach the set welding depth.

[0044] Exemplarily, in this embodiment, the first welding beam 31 is composed of multiple lasers with a wavelength of 1080nm, which are arranged in parallel perpendicular to the welding direction, and the power of each laser is independently adjustable between 0-2000W; the second welding beam 32 is composed of multiple high-power lasers with a wavelength of 1080nm, which are placed 0.5mm-1mm behind the first welding beam 31, and the power of each laser is independently adjustable between 0-6000W; the third welding beam 33 is composed of multiple lasers with a wavelength of 1080nm, which are placed 0.5mm-1mm behind the second welding beam 32, and the power of each laser is independently adjustable between 0-2000W.

[0045] Optionally, the first welding beam 31 and the third welding beam 33 together form a 'Y'-shaped large keyhole 104 around the second welding beam 32 .

[0046] Specifically, the spacing between the first welding beam 31 and the second welding beam 32, and the spacing between the second welding beam 32 and the third welding beam 33 are generally 0.5 mm-1 mm, and the spacing setting is related to the stability of the keyhole 104. If the spacing between the two groups of laser beams is too small, the opening at the upper end of the keyhole 104 will not be large enough, and the pores and spatters will still be obvious; if the spacing is too large, the keyhole 104 will change from a "Y" shape to an independent "W" shape, and it will not be possible to form an integral keyhole 104, and the keyholes 104 of the first welding beam 31 and the second welding beam 32 will interfere with each other.

[0047] Alternatively, if Figure 3 As shown, the laser welding head 1 is tilted, and the angle between the axis of the laser welding head 1 and the vertical direction is 5°-10°, so as to ensure that during high-power welding, the reflected light will not directly enter the laser welding head 1 and damage the lens or laser.

[0048] Optionally, the welding process parameters of the laser welding head 1 are set, wherein the adjustment range of the welding defocus is from -10mm to +10mm. The increase in the welding defocus will lead to a decrease in the penetration depth and an increase in the laser power density at the positive focus. Therefore, increasing the welding defocus can improve the stability of the welding process and optimize the formation of the weld 103. The welding speed is 0.3m / min-3m / min. The size of the welding speed can not only affect the width of the weld 103, but also the penetration depth. Too slow a welding depth will result in excessive heat input per unit time, making the welding state unstable; and too fast a welding speed may result in insufficient welding fusion. The specific welding speed needs to be adjusted according to the actual welding effect and welding rhythm.

[0049] Optionally, the laser welding head 1 can also deliver shielding gas to the welding position, and the shielding gas is nitrogen, argon or helium to protect the workpiece 100 to be welded from being contaminated by other gases and impurities, ensure the welding quality, and at the same time, affect the penetration depth and width of the weld 103. Specifically, the flow rate of shielding gas for high-power welding is generally 10L / min-30L / min. The specific value of the flow rate is related to the size of the gas outlet and the distance between the gas outlet and the welding position, and it also needs to be adjusted in real time according to the actual effect. Specifically, in this embodiment, the shielding gas is blown in coaxially with the laser.

[0050] For example, the material of the workpiece 100 to be welded is 10 mm thick Q235 carbon steel. After laser cutting, no groove is opened, and no grinding and cleaning are performed. The welding steps are as follows: After two workpieces 100 to be welded are butt-jointed, they are placed on a welding jig and fixed on the welding jig using a rigid clamp.

[0051] The laser welding head 1 is fixed on the robot, and the collimation and focusing ratio of the laser welding head 1 is 100mm:200mm; the wire feeding structure 2 is fixed on the robot, and the wire feeding method of front wire feeding is adopted, and the welding wire is MG70S-6 welding wire with a diameter of 1.2mm.

[0052] Measure the butt gap 101 between two workpieces 100 to be welded, and select a suitable laser beam width. The first welding beam 31 uses 5 lasers, which are set to continuous light output mode. The power of each laser is 600W. The spots are arranged linearly. The diameter of a single spot is 0.1mm and the spacing is 0.5mm. The total width of the first welding beam 31 is 2.1mm, which can completely cover the butt gap 101. The second welding beam 32 uses 2 lasers, which are set to continuous light output mode. The power of each laser is 5000W. The spots are arranged linearly, and the second welding beam 32 is arranged parallel to the first welding beam 31. The diameter of a single spot is 0.2mm and the spacing is 0.8mm. The third welding beam 33 uses 4 lasers, which are set to continuous light output mode. The power of each laser is 1000W. After linear arrangement, they are arranged parallel to the second welding beam 32. The diameter of a single spot is 0.1mm and the spacing is 0.5mm.

[0053] Adjust the posture of the robot so that the first welding beam 31, the second welding beam 32 and the third welding beam 33 are perpendicular to the butt gap 101 between the workpieces 100 to be welded. Tilt the laser welding head 1 by 10° to avoid damage to the laser welding head 1. Set the welding process parameters: welding defocus amount -4mm, welding speed 1.8m / min. Nitrogen is used as the shielding gas, and the flow rate of the shielding gas is 30L / min.

[0054] The robot controller is used to control the moving path of the laser welding head 1, the switch of the laser, and the wire feeding of the wire feeding structure 2. First, the first welding beam 31 emits light, and the welding wire is synchronously fed into the laser operation area to melt the workpiece 100 and the welding wire, and fill the butt joint gap 101 after full fusion; after an interval of 0.1s, when the molten pool 102 is stable, the second welding beam 32 and the third welding beam 33 emit light at the same time, and at the same time, the robot moves along the direction of the butt joint gap 101 between the workpieces 100 to be welded to complete the welding.

[0055] Reference Figure 4 , is a microscope image of the front side of the weld 103 after welding is completed; Figure 5 , is a microscope image of the reverse side of the weld 103 after welding is completed; Figure 6 , which is a metallographic diagram of the molten pool 102 .

[0056] The method uses three groups of laser beams for welding. The first welding beam 31 acts on the area to be welded of the workpiece 100 and is set to medium and low power, which can clean the oxide layer and dirt on the surface of the workpiece 100. At the same time, multiple low-power combinations form the first welding beam 31, generating a stable molten pool 102 with a shallow depth and a large melting area. The molten welding wire liquid and the workpiece 100 are fully fused in the molten pool 102 and then filled into the butt gap 101. Along the welding direction, the second welding beam 32 acts on the rear of the molten pool 102 formed by the first welding beam 31 and is set to high power to melt and vaporize the material. The metal vapor exerts a greater pressure on the surrounding liquid metal, overcomes the surface tension of the material, and then forms a deep melting keyhole 104. After the first welding beam 31 acts, the surface of the workpiece 100 and the welding wire are already in a molten state. At this time, the energy of the second welding beam 32 can be fully utilized, and almost all of the laser energy can be absorbed by the molten metal. Using lower laser energy can obtain a greater melting depth. The material around the deep-melting keyhole 104 is melted by heat conduction, and the second welding beam 32 and the first welding beam 31 work together to form a deep-melting keyhole 104. The front wall of the deep-melting keyhole 104 is maintained in a large opening state under the action of the first welding beam 31. The welding shielding gas is blown into the center of the molten pool 102, and the large opening keyhole 104 significantly reduces the difficulty of gas escape. The metal vapor in the keyhole 104 escapes to the surroundings along the side wall of the keyhole 104, reducing the shielding effect on the laser, thereby improving the energy utilization rate.

[0057] The third welding beam 33 acts on the rear wall of the deep-penetrating keyhole 104. When the first welding beam 31 and the second welding beam 32 move along the extension direction of the butt gap 101, the metal behind the keyhole 104 continuously solidifies to form a weld 103. The third welding beam 33 is set to a lower power to maintain the opening state of the keyhole 104, and works together with the first welding beam 31 and the second welding beam 32 to form a weld 103. Figure 6 The “Y” shaped large keyhole 104 shown reduces the solidification rate of the molten pool 102 , increases the gas escape time, slows down the cooling rate of the molten pool 102 , and optimizes the formation of the weld 103 .

[0058] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A high-power laser welding method for medium and thick plates, characterized in that: The steps include: S1: measuring a butt gap (101) between workpieces (100), and configuring a laser combination (3) consisting of at least a first welding beam (31) and a second welding beam (32); S2: Outputting the first welding light beam (31) and the second welding light beam (32) simultaneously or separately; wherein: The width of the first welding beam (31) at least completely covers the butt gap (101), and is used to clean the oxide layer and dirt on the surface of the workpiece (100) to be welded, and to generate a stable molten pool (102) with a shallow melting depth and a large melting area on the surface of the workpiece (100); The second welding beam (32) is arranged in parallel with the first welding beam (31), and acts on the rear of the molten pool (102) formed by the first welding beam (31) along the moving direction of the laser welding head (1), so as to gasify the material and form a deep melting keyhole (104) on the surface of the workpiece (100).

2. The high-power laser welding method for medium and thick plates according to claim 1, characterized in that: The laser assembly (3) further comprises a third welding beam (33), the third welding beam (33) being arranged in parallel with the second welding beam (32) and being output simultaneously or separately with the second welding beam (32), the third welding beam (33) acting on the rear wall of the deep melting keyhole (104) along the moving direction of the laser welding head (1) to maintain the opening state of the deep melting keyhole (104).

3. The high-power laser welding method for medium and thick plates according to claim 1 or 2, characterized in that: The light emission mode, light emission power, beam width and spot shape of each welding light beam are independently controlled and adjustable in real time.

4. The high-power laser welding method for medium and thick plates according to claim 1 or 2, characterized in that: The width of each welding beam is determined according to the requirement for the width of the weld (103), and the width of the weld (103) is greater than or equal to the butt gap (101).

5. The high-power laser welding method for medium and thick plates according to claim 1, characterized in that: The laser combination (3) is composed of a multi-channel laser output by a laser based on an array fiber, the laser based on an array fiber includes a plurality of laser modules, the output optical fibers (30) of the plurality of laser modules are arranged in an array to form an optical fiber array, and the plurality of laser modules are independently controlled and adjustable in real time.

6. The high-power laser welding method for medium and thick plates according to claim 5, characterized in that: The width of each welding beam is determined by the single-point spot diameter and spacing of the multi-channel laser; The single-point spot diameter and spacing of the multi-path laser are determined by the core and outer cladding diameters of the output optical fibers (30) of the plurality of laser modules and the collimation and focusing ratio of the laser welding head (1).

7. The high-power laser welding method for medium and thick plates according to claim 1, characterized in that: The first welding beam (31) completely covers the entire welding area of ​​the workpiece (100).

8. The high-power laser welding method for medium and thick plates according to claim 2, characterized in that: The width of the first welding beam (31) is greater than the width of the second welding beam (32); The width of the third welding beam (33) is greater than the width of the second welding beam (32), and / or is smaller than the width of the first welding beam (31).

9. The high-power laser welding method for medium and thick plates according to claim 2, characterized in that: The power of the second welding beam (32) is greater than the power of the first welding beam (31) and the third welding beam (33); preferably, the power of the second welding beam (32) is configured to achieve a required welding depth, and the power of the first welding beam (31) and the third welding beam (33) is configured to melt through the welding wire without melting through the plate.

10. The high-power laser welding method for medium and thick plates according to claim 9, characterized in that: The first welding beam (31) and the third welding beam (33) together form a 'Y'-shaped large keyhole (104) around the second welding beam (32).

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