Medium plate welding process without beveling

Abstract

The invention belongs to the technical field of laser welding, and discloses a medium-thickness plate welding process without beveling, three groups of laser arrays are adopted for welding, the first laser array completely covers a butt joint gap to generate a stable molten pool with shallow depth and large melting area, and the second laser array melts and gasifies materials to form a deep melting key hole. The third laser array acts on the rear wall of the deep melting key hole to maintain the opening state of the key hole, and the third laser array, the first laser array and the second laser array jointly act to form a Y-shaped large key hole; due to the fact that the three sets of laser arrays are adopted for parallel machining, the total welding input energy can be accurately controlled, large-penetration-depth single-time welding of pure laser is achieved, and meanwhile the problems of welding deformation and incomplete penetration during multi-pass welding are solved; the to-be-welded workpiece does not need to be beveled in advance, the workpiece does not need to be cleaned before welding, and the welding efficiency can be effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of laser welding, and in particular to a welding process for medium and thick plates without the need for beveling. 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 invention aims to provide a medium and thick plate welding process without beveling, without the need for beveling in advance, and with high welding efficiency and energy utilization.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] A medium and thick plate welding process without beveling is provided, comprising the following steps:

[0007] S1: Butt two workpieces to be welded and fix them on the welding fixture;

[0008] S2: Fix the laser welding head on the robot or the three-axis welding platform, set the collimation and focusing ratio of the laser welding head; fix the wire feeding structure, and select the wire feeding method and welding wire type;

[0009] S3: measuring the butt gap between the two workpieces and setting the width of the laser array combination, wherein the laser array combination includes a first laser array, a second laser array and a third laser array;

[0010] S4: adjusting the position of the laser welding head so that the projection of the first laser array on the horizontal plane is perpendicular to the butt joint gap and can completely cover the butt joint gap along the width direction of the butt joint gap;

[0011] S5: Starting welding, the first laser array emits light, the wire feeding structure feeds the welding wire into the laser operation area synchronously, the workpiece and the welding wire melt, and after being fully fused, they are filled into the butt gap;

[0012] S6: After a preset time interval, the second laser array and the third laser array emit light at the same time; at the same time, the laser welding head is moved, and the first laser array, the second laser array, and the third laser array are combined to complete the welding process.

[0013] As an optional solution for the medium and thick plate welding process without beveling, the second laser array is arranged in parallel with the first laser array, and along the moving direction of the laser welding head, the second laser array is located 0.5 mm-1 mm behind the first laser array;

[0014] The third laser array is arranged in parallel with the second laser array, and along the moving direction of the laser welding head, the third laser array is located 0.5 mm-1 mm behind the second laser array.

[0015] As an optional solution for the medium and thick plate welding process without beveling, the powers of the first laser array, the second laser array and the third laser array are set separately; the first laser array and the third laser array can melt the welding wire and the penetration depth does not exceed one third of the thickness of the workpiece;

[0016] The power of the second laser array is greater than that of the first laser array and the third laser array, and can reach a set welding depth.

[0017] As an optional solution for the medium and thick plate welding process without beveling, the light emission modes of the first laser array, the second laser array and the third laser array are continuous mode or pulse mode.

[0018] As an optional solution for the medium and thick plate welding process without beveling, in S2, the collimation and focusing ratio of the laser welding head is 1:2, 1:2.5 or 1:3, preferably 1:2.

[0019] As an optional solution for the medium and thick plate welding process without beveling, in S2, the wire feeding method is front wire feeding or rear wire feeding, preferably front wire feeding.

[0020] As an optional solution for the medium and thick plate welding process without beveling, in S3, the width of the third laser array is larger than the second laser array and smaller than the first laser array.

[0021] As an optional solution for the medium and thick plate welding process without beveling, in S6, the preset time depends on the stabilization time of the molten pool.

[0022] As an optional solution for the medium and thick plate welding process without beveling, in S3, the laser welding head is tilted, and the angle between the axis of the laser welding head and the vertical direction is 5°-10°.

[0023] As an optional solution for the welding process of medium and thick plates without beveling, in S4, the welding process parameters of the laser welding head are set, the adjustment range of the welding defocus amount is -10mm to 10mm, and the welding speed is 0.3m / min-3m / min.

[0024] Beneficial effects of the present invention:

[0025] The present invention provides a medium and thick plate welding process without beveling, which adopts three groups of laser arrays for welding. The first laser array acts on the to-be-welded area of ​​the workpiece, and along the width direction of the butt gap between the two workpieces, the first laser array can cover the butt gap to generate a stable molten pool with shallow depth and large melting area. The molten welding wire liquid and the workpiece are fully fused in the molten pool and then filled into the butt gap. Along the welding direction, the second laser array acts on the rear of the molten pool formed by the first laser array 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. Since the workpiece surface and the welding wire are already in a molten state after the first laser array acts, the energy of the second laser array can be fully utilized at this time, and almost all the laser energy can be absorbed by the molten metal. A greater 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 laser array and the first laser array work together to form a deep melting keyhole. Under the action of the first laser array, 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.

[0026] The third laser array acts on the rear wall of the deep melting keyhole. When the first laser array and the second laser array move along the extension direction of the butt gap, the metal behind the keyhole continues to solidify to form a weld. The third laser array can maintain the opening state of the keyhole, and work together with the first laser array and the second laser array to form a "Y"-shaped large keyhole, which can reduce the pressure of the metal vapor in the keyhole, reduce the solidification rate of the molten pool, slow down the cooling rate of the molten pool, and reduce the difficulty of gas escape, thereby effectively avoiding spatter and weld pores during welding, which is conducive to optimizing weld formation. Due to the use of three groups of laser arrays for parallel processing, the total welding input energy can be accurately controlled, achieving pure laser single welding with large melting depth, while avoiding welding deformation and the problem of incomplete penetration during multi-pass welding. This welding process does not require the workpiece to be welded to be grooved in advance, nor does it require the workpiece to be cleaned before welding, which can effectively improve welding efficiency. At the same time, multiple groups of laser arrays are welded in parallel to improve the tolerance of assembly gaps. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a welding schematic diagram of a medium and thick plate welding process without beveling provided in a specific embodiment of the present invention;

[0028] Figure 2 It is a schematic diagram of a laser array assembly provided in a specific embodiment of the present invention;

[0029] Figure 3 It is a side view of the welding process of a medium and thick plate welding process without beveling provided in a specific embodiment of the present invention;

[0030] Figure 4 is 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;

[0031] 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;

[0032] 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.

[0033] In the figure:

[0034] 100, workpiece; 101, butt gap; 102, molten pool; 103, weld; 104, keyhole;

[0035] 1. Laser welding head; 2. Wire feeding structure;

[0036] 3. Laser array combination; 31. First laser array; 32. Second laser array; 33. Third laser array. DETAILED DESCRIPTION

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0042] like Figures 1 to 6 As shown, this embodiment provides a medium-thick plate welding process without beveling, which is used to weld 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:

[0043] S1: butt-join two workpieces 100 to be welded and fix them on a welding jig;

[0044] The above steps are specific to this embodiment, refer to Figure 1 , two workpieces 100 to be welded are butted and fixed on a welding fixture. Specifically, the two workpieces 100 are butted tightly, and the butt gap 101 in an ideal state is 0 mm, and in practice the butt gap 101 can be controlled within 1.5 mm.

[0045] Exemplarily, the welding jig is a structure that has been disclosed in the prior art, and its specific structure refers to the prior art and will not be described in detail here.

[0046] S2: Fix the laser welding head 1 on the robot or the three-axis welding platform, set the collimation and focusing ratio of the laser welding head 1; fix the wire feeding structure 2, and select the wire feeding method and welding wire type;

[0047] In the above steps, specifically in this embodiment, the laser welding head 1 is fixed on a robot or a three-axis welding platform to facilitate the movement of the laser welding head 1. Specifically, the robot and the three-axis welding platform are structures disclosed in the prior art, as long as they can drive the laser welding head 1 to move.

[0048] Then set the collimation and focusing ratio of the laser welding head 1 (collimation and focusing ratio=focusing lens focal length / collimation lens focal length). Optionally, the collimation and focusing ratio of the laser welding head 1 is 1:2, 1:2.5 or 1:3, preferably 1:2.

[0049] Then fix the wire feeding structure 2, and select the wire feeding method and the type of welding wire. Optionally, the wire feeding method is front wire feeding or rear wire feeding, preferably front wire feeding. 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 amount of wire feeding per unit time. If the thickness of the workpiece 100 is large or the butt gap 101 between the two workpieces 100 is large, the welding wire needs to be thickened accordingly, and the laser power required to melt the welding wire should also be increased.

[0050] S3: Measure the butt gap 101 between the two workpieces 100 and set the width of the laser array assembly 3, such as Figure 2 As shown, the laser array assembly 3 includes a first laser array 31, a second laser array 32 and a third laser array 33. Further, the second laser array 32 is arranged in parallel with the first laser array 31, the third laser array 33 is arranged in parallel with the second laser array 32, and along the moving direction of the laser welding head 1, the second laser array 32 is located 0.5mm-1mm behind the first laser array 31, and the third laser array 33 is located 0.5mm-1mm behind the second laser array 32.

[0051] The above steps are specific to the present embodiment. The butt gap 101 between the two workpieces 100 is measured to set the width of the laser array assembly 3. The light output mode, light output power and laser paths of the first laser assembly are selected according to the single spot diameter and spacing of the first laser array 31 and the collimation and focusing ratio of the laser welding head 1, so that the total width of the first laser array 31 at least completely covers the butt gap 101; the light output mode, light output power and laser paths of the second laser assembly are selected according to the single spot diameter and spacing of the second laser array 32 and the collimation and focusing ratio of the laser welding head 1. The spots are arranged linearly. The second laser array 32 is arranged parallel to the first laser array 31, and along the moving direction of the laser welding head 1, the second laser array 32 is arranged parallel to the first laser array 31. The laser array 32 is located 0.5mm-1mm behind the first laser array 31; the light output mode, light output power and laser path number of the third laser combination are selected according to the single spot diameter and spacing of the third laser array 33 and the collimation and focusing ratio of the laser welding head 1, and the spots are arranged linearly. The third laser array 33 is arranged parallel to the second laser array 32, and along the moving direction of the laser welding head 1, the third laser array 33 is located 0.5mm-1mm behind the second laser array 32. At the same time, the width of the third laser array 33 is slightly larger than the width of the second laser array 32.

[0052] Optionally, the light emission modes of the first laser array 31, the second laser array 32 and the third laser array 33 are continuous mode or pulse mode. Specifically, in this embodiment, they are all continuous mode, and the molten pool 102 has better stability in the continuous mode.

[0053] Optionally, a laser based on an array fiber is provided in the laser welding head 1, and the laser based on the array fiber includes a plurality of laser modules, and the output fiber arrays of the plurality of laser modules are arranged to form a laser array, and the first laser array 31, the second laser array 32, and the third laser array 33 are formed by lasers of different output fibers. Specifically, the single-point spot diameter and spacing of the first laser array 31, the second laser array 32, and the third laser array 33 depend on the core and outer cladding diameter of the pigtail fiber ultimately output by the single-channel laser, and the collimation and focusing ratio of the laser welding head 1, wherein the spot diameter = core × (focusing lens focal length / collimating lens focal length), and the spot spacing = outer cladding diameter × (focusing lens focal length / collimating lens focal length). Exemplarily, the core is generally 20 μm, 50 μm, 100 μm, and the outer cladding is generally 250 μm or 400 μm.

[0054] Specifically, the spacing between the first laser array 31 and the second laser array 32, and the spacing between the second laser array 32 and the third laser array 33 are generally 0.5 mm to 1 mm, and the spacing setting is related to the stability of the keyhole 104. If the spacing between the two groups of laser arrays 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 laser array 31 and the second laser array 32 will interfere with each other.

[0055] Optionally, the power of the first laser array 31, the second laser array 32 and the third laser array 33 are set separately, wherein the first laser array 31 and the third laser array 33 can melt through the welding wire and the melting depth does not exceed one third of the thickness of the workpiece 100; the power of the second laser array 32 is greater than that of the first laser array 31 and the third laser array 33, and can reach a set welding depth. Specifically, the setting of the power of a single laser depends on the thickness of the workpiece 100 that actually needs to be welded. The first laser array 31 and the third laser array 33 are only used as auxiliary, and need to melt through the welding wire without melting through the workpiece 100, and the melting depth only needs to reach one third of the thickness of the workpiece 100; the second laser array 32 is the main welding heat source, and needs to reach a set welding depth.

[0056] Exemplarily, in this embodiment, the first laser array 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 laser array 32 is composed of multiple high-power lasers with a wavelength of 1080nm, which are placed 0.5mm-1mm behind the first laser array 31, and the power of each laser is independently adjustable between 0-6000W; the third laser array 33 is composed of multiple lasers with a wavelength of 1080nm, which are placed 0.5mm-1mm behind the second laser array 32, and the power of each laser is independently adjustable between 0-2000W.

[0057] Optionally, the second laser array 32 is provided with at least one path, and may also be provided with two or more paths, and the specific number of paths may be set as required according to the actual width of the butt gap 101. Specifically, the total width of the first laser array 31 needs to cover the butt gap 101, and preferably also covers the edge of the workpiece 100, which can play a role in welding cleaning before deep melting on the one hand, and can also fully fuse the molten droplets of the workpiece 100 and the welding wire on the other hand. For example, if the butt gap 101 is 1.5mm wide and the spot spacing is 0.5mm, then the first laser array 31 needs at least four paths to emit light simultaneously, and the second laser array 32 is preferably two paths considering that the gap is relatively large.

[0058] Optionally, the width of the third laser array 33 is greater than that of the second laser array 32 but less than that of the first laser array 31. Specifically, the width of the third laser array 33 is generally slightly wider than that of the second laser array 32 to effectively prevent the keyhole 104 from collapsing.

[0059] In addition, the number of paths of each laser array is selected based on the requirement for the width of the weld 103 and whether the gap can be completely covered. The width of the laser array 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 array.

[0060] S4: adjusting the position of the laser welding head 1 so that the projection of the first laser array 31 on the horizontal plane is perpendicular to the butt joint gap 101 and can completely cover the butt joint gap 101 along the width direction of the butt joint gap 101;

[0061] The above steps, specifically in this embodiment, adjust the posture of the robot or move the position of the laser welding head 1 on the three-axis welding platform so that the projection of the first laser array 31 on the horizontal plane is perpendicular to the butt gap 101, and then ensure that the second laser array 32 and the third laser array 33 are perpendicular to the butt gap 101, so as to ensure that the two workpieces 100 can be welded together. Then set specific welding process parameters: welding defocus amount, welding speed.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] S5: Starting welding, the first laser array 31 emits light, and the wire feeding structure 2 feeds the welding wire into the laser area synchronously, and the workpiece 100 and the welding wire melt and are fully fused and filled into the butt gap 101;

[0066] The above steps are specific to this embodiment, using a robot or a controller of a three-axis mobile platform to control the moving path of the laser welding head 1, and to control the switch of the laser and the wire feeding of the wire feeding structure 2. First, the first laser array 31 emits light, and the welding wire is synchronously fed into the laser action area, so that the workpiece 100 and the welding wire are melted, and are fully fused and filled into the butt gap 101.

[0067] Specifically, in this 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 laser array 31 and then melts. After the molten droplets enter the molten pool 102, the second laser array 32 and the third laser array 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 back 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 laser array 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 poor cladding effect.

[0068] S6: After a preset time interval, the second laser array 32 and the third laser array 33 emit light at the same time; at the same time, the laser welding head 1 is moved, and the first laser array 31, the second laser array 32, and the third laser array 33 are combined to complete the welding process.

[0069] The above steps are specific to the present embodiment. After a preset time interval, when the molten pool 102 is stabilized, the second laser array 32 and the third laser array 33 are simultaneously emitted. At the same time, the laser welding head 3 moves along the position to be welded to complete the welding.

[0070] Optionally, the preset time depends on the stabilization time of the molten pool 102. After the molten pool 102 is stabilized, the second laser array 32 and the third laser array 33 are simultaneously emitted to ensure that the laser energy of the second laser array 32 is fully utilized, and a larger melting depth can be obtained with lower energy to form a deep melting keyhole 104; and the third laser array 33 acts on the rear wall of the deep melting keyhole 104 to maintain the opening state of the keyhole 104, avoid rapid solidification of the molten pool 102, and extend the gas escape time to prevent splashing. That is, the preset time is greater than the stabilization time of the molten pool 102.

[0071] 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:

[0072] 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.

[0073] 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.

[0074] Measure the butt gap 101 between two workpieces 100 to be welded, and select a suitable laser array width. The first laser array 31 uses 5 lasers, which are set to continuous light emission 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 laser array 31 is 2.1mm, which can completely cover the butt gap 101. The second laser array 32 uses 2 lasers, which are set to continuous light emission mode. The power of each laser is 5000W. The spots are arranged linearly, and the second laser array 32 is arranged parallel to the first laser array 31. The diameter of a single spot is 0.2mm and the spacing is 0.8mm. The third laser array 33 uses 4 lasers, which are set to continuous light emission mode. The power of each laser is 1000W. After linear arrangement, they are arranged parallel to the second laser array 32. The diameter of a single spot is 0.1mm and the spacing is 0.5mm.

[0075] Adjust the posture of the robot so that the first laser array 31, the second laser array 32 and the third laser array 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.

[0076] 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 laser array 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 laser array 32 and the third laser array 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.

[0077] 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 .

[0078] The method uses three groups of laser arrays for welding. The first laser array 31 acts on the welding area 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 laser array 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 laser array 32 acts on the rear of the molten pool 102 formed by the first laser array 31 and is set to high power to melt and gasify 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 laser array 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 laser array 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 laser array 32 and the first laser array 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 laser array 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.

[0079] The third laser array 33 acts on the rear wall of the deep melting keyhole 104. When the first laser array 31 and the second laser array 32 move along the extension direction of the butt gap 101, the metal behind the keyhole 104 is continuously solidified to form a weld 103. The third laser array 33 is set to a lower power to maintain the opening state of the keyhole 104, and works together with the first laser array 31 and the second laser array 32 to form a weld 103. Figure 6The “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 .

[0080] 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 medium and thick plate welding process without beveling, characterized in that: The steps include: S1: butt-join two workpieces (100) to be welded and fix them on a welding jig; S2: fixing the laser welding head (1) on a robot or a three-axis welding platform, setting the collimation and focusing ratio of the laser welding head (1); fixing the wire feeding structure (2), and selecting the wire feeding method and the type of welding wire; S3: measuring a butt gap (101) between two workpieces (100), and setting a width of a laser array assembly (3), wherein the laser array assembly (3) comprises a first laser array (31), a second laser array (32), and a third laser array (33); S4: adjusting the position of the laser welding head (1) so that the projection of the first laser array (31) on a horizontal plane is perpendicular to the butt joint gap (101) and can completely cover the butt joint gap (101) along the width direction of the butt joint gap (101); S5: starting welding, the first laser array (31) emits light, the wire feeding structure (2) synchronously feeds the welding wire into the laser action area, the workpiece (100) and the welding wire are melted, and after being fully fused, they are filled into the butt gap (101); S6: After a preset time interval, the second laser array (32) and the third laser array (33) emit light simultaneously; at the same time, the laser welding head (1) is moved, and the first laser array (31), the second laser array (32), and the third laser array (33) are combined to complete the welding process.

2. The medium and thick plate welding process without beveling according to claim 1 is characterized in that: The second laser array (32) is arranged in parallel with the first laser array (31), and along the moving direction of the laser welding head (1), the second laser array (32) is located 0.5 mm to 1 mm behind the first laser array (31); The third laser array (33) is arranged in parallel with the second laser array (32), and along the moving direction of the laser welding head (1), the third laser array (33) is located 0.5 mm to 1 mm behind the second laser array (32).

3. The medium and thick plate welding process without beveling according to claim 1 is characterized in that: The powers of the first laser array (31), the second laser array (32) and the third laser array (33) are set separately; the first laser array (31) and the third laser array (33) are capable of melting the welding wire and the melting depth does not exceed one third of the thickness of the workpiece (100); The power of the second laser array (32) is greater than that of the first laser array (31) and the third laser array (33), and can achieve a set welding depth.

4. The medium and thick plate welding process without beveling according to claim 1 is characterized in that: The light emission modes of the first laser array (31), the second laser array (32) and the third laser array (33) are continuous mode or pulse mode.

5. The medium and thick plate welding process without beveling according to claim 1 is characterized in that: In S2, the collimation and focusing ratio of the laser welding head (1) is 1:2, 1:2.5 or 1:3, preferably 1:

2.

6. The medium and thick plate welding process without beveling according to claim 1 is characterized in that: In S2, the wire feeding method is front wire feeding or rear wire feeding, preferably front wire feeding.

7. The medium and thick plate welding process without beveling according to claim 1 is characterized in that: In S3, the width of the third laser array (33) is greater than that of the second laser array (32) but smaller than that of the first laser array (31).

8. The medium and thick plate welding process without beveling according to claim 1 is characterized in that: In S6, the preset time depends on the stabilization time of the molten pool (102).

9. The medium and thick plate welding process without beveling according to claim 1 is characterized in that: In S3, the laser welding head (1) is arranged at an angle, and the angle between the axis of the laser welding head (1) and the vertical direction is 5°-10°.

10. The medium and thick plate welding process without beveling according to claim 1, characterized in that: In S4, the welding process parameters of the laser welding head (1) are set, the adjustment range of the welding defocus amount is -10 mm to 10 mm, and the welding speed is 0.3 m / min to 3 m / min.

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