Thin plate laser lap welding method, laser device and laser welding equipment

Abstract

The invention belongs to the technical field of laser welding, and discloses a thin plate laser lap joint welding method, a laser device and laser welding equipment. The power of the laser acting on the surface of the upper plate and the power of the laser acting on the lower plate are both smaller than the power of the laser acting on the center of the weld joint, the laser power is in a low-high-low change trend in the direction from the upper plate to the center of the weld joint to the lower plate, and it is ensured that the laser in the center of the weld joint can penetrate through the upper plate. Laser on the two sides of the center of the welding seam is controlled in a state of not penetrating through the plate, so that energy input in different subareas of the welding seam is accurately controlled, the controllable and different fusion depths of all the subareas are ensured, the problems that the fusion depths are unstable, the contour of a molten pool is discontinuous and the lower plate is easy to penetrate are solved, the welding seam is good in consistency and free of inward concave or outward convex, and continuous smooth transition is achieved; the size measurement of the molten pool meets the standard requirements, the welding quality and the welding efficiency are effectively improved, welding wires are not needed, and the cost is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of laser welding, and in particular to a thin plate laser lap welding method, a laser and laser welding equipment. Background Art

[0002] The core of an LNG carrier is the LNG storage tank, which must safely store liquefied natural gas at -163°C, preventing leakage while also ensuring a low evaporation rate. This is why LNG carriers are also known as offshore super freezers. Currently, mainstream ship storage tank systems are divided into two types: self-supporting and membrane types. Membrane liquid cargo systems primarily consist of membrane-type MARK III and No. 96 tanks. The No. 96 tank, primarily made of cryogenic invar steel, has a low market share due to its high material cost and difficulty in onboard operation. Therefore, membrane tank systems primarily utilize MARK III tanks.

[0003] The film metal used for the main barrier of the MARK III liquid cargo tank is 1.2mm corrugated 304L stainless steel. The secondary barrier is made of a three-layer composite film, and the insulation material is reinforced polyurethane foam. The welding results of the 304L stainless steel corrugated plate determine the integrity of the main barrier and are the key to the successful construction of the LNG ship containment system. However, due to the characteristics of 304L stainless steel with high electrical resistance, large expansion coefficient and low thermal conductivity, it is prone to adverse consequences such as coarse grains and large thermal stress after welding. At the same time, due to the high content of alloying elements, the melt viscosity is high, which is prone to pores and weld undercuts. TIG welding and metal inert gas shielded welding (MIG welding) are commonly used welding methods. These two welding methods require filler wire and have low welding efficiency. Manual secondary welding is often required, and the overall cost is high. Therefore, laser welding is more widely used.

[0004] The laser lap welding method in the existing technology, single laser non-swing welding is simple to operate, but this welding method mainly relies on the fluidity of the material itself for fusion, and is suitable for welding scenarios with narrow welds (such as about 0.1mm). It is very difficult to increase the weld width. For materials with wider welds (such as more than 0.3mm), the liquid in the molten pool may not be fully fused, and welding defects such as pores and sand holes are prone to occur; while single laser oscillating welding controls the swing of the laser beam in a single direction (such as the X-axis or Y-axis) through the galvanometer motor, thereby achieving precise movement of the laser beam, which can easily widen the weld width, reduce the penetration depth, and effectively improve welding defects (such as pores, cracks, etc.), but as Figure 6As shown in the figure, since a single laser cannot adjust the energy in real time according to the position, when the laser acts on the lower plate, the energy is large and it is easy to penetrate, but when it acts on the upper plate, the penetration depth is insufficient and cannot meet the size requirements; then, since the large-scale swing will limit the increase in the swing frequency, when the laser moves along the weld to be welded, the swing frequency in the direction perpendicular to the weld is low, which will cause the material to not be fully melted. Finally, it appears as an independent and discontinuous keyhole on the cross-section, and an overall molten pool is not formed. The penetration depth at the weld is unstable and uneven concave and convex are prone to occur, curling and unfused edges are prone to occur at the upper plate, and unstable biting edges are prone to occur at the lower plate, which seriously affect the weld quality. Summary of the Invention

[0005] The purpose of the present invention is to provide a thin plate laser lap welding method, laser and laser welding equipment, which use multi-channel lasers to perform self-melting welding on the overlap of the upper plate and the lower plate. While ensuring the weld width, it can optimize the laser energy distribution, the weld is well formed, the bottom plate has no undercut, and the welding efficiency is high and the cost is low.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, a thin plate laser lap welding method is provided, comprising the following steps:

[0008] S1: Overlap the upper plate and the lower plate to be welded, fix them on a welding jig, and pre-weld at least one welding point between the upper plate and the lower plate;

[0009] S2: Select the number of laser paths according to the weld width and set the parameters of the laser array; wherein the laser power at the center of the laser array is greater than the laser power at the two sides;

[0010] S3: Adjust the position of the laser welding head relative to the weld so that the center of the laser array is located inside the edge of the upper plate near the overlap, and the long axis of the laser array is set at an angle to the welding direction;

[0011] S4: the laser array emits light, the laser welding head moves along the overlap of the upper plate and the lower plate, and swings along the long axis direction of the laser array to weld to form an overlap weld.

[0012] As an optional solution for the thin plate laser lap welding method, in S2, the parameters of the laser array include the power of each single laser, the output spot diameter and the collimation and focusing ratio. The power of each single laser of the laser array is independently adjustable. The central laser power of the laser array is controlled to be able to melt through the upper plate without penetrating the lower plate, and the laser power on both sides of the laser array is controlled to be not able to penetrate the single layer of plate.

[0013] As an optional solution for the thin plate laser lap welding method, in S3, the edge of the upper plate near the lap is the center of the weld, and the center of the laser array is placed on the upper plate perpendicular to the weld center and 0.2mm-0.4mm away from the weld center.

[0014] As an optional solution for the thin plate laser lap welding method, in S3, the angle between the long axis of the laser array and the welding movement direction is 60° to 90°, preferably 90°.

[0015] As an optional solution for the thin plate laser lap welding method, in S3, the laser welding head is tilted, and the angle between the axis of the laser welding head and the vertical direction is 10°-15°.

[0016] As an optional solution for the thin plate laser lap welding method, the upper surface of the upper plate is defined as the 0 focus position, and the focus of the laser array is adjusted to -2 mm to 0 mm.

[0017] As an optional solution for the thin plate laser lap welding method, in S4, the swing trajectory of the laser welding head is an "8" shape or a circle, and adjacent light spots are circumscribed, preferably an "8" shape.

[0018] As an alternative to the thin plate laser lap welding method, the swing amplitude W of the laser welding head is W =Dd f , where D is the center distance between two adjacent laser beams, and the diameter of the focused spot d is f =d*(F f / F c ), F f is the focal length of the focusing lens, F c is the focal length of the collimator, d is the output spot diameter;

[0019] And / or, it is preferred to set the oscillation frequency of the laser array (3) to be not less than 30 times the welding speed, and the oscillation frequency*oscillation amplitude<the limit speed of the oscillation motor of the laser welding head.

[0020] As an optional solution for the thin plate laser lap welding method, the welding speed is set to 15mm / s-50mm / s; the laser welding head can deliver shielding gas to the welding position, and the flow rate of the shielding gas is 15L / min-25L / min.

[0021] In a second aspect, a laser is provided, which can output a laser array, and the laser array is used for welding overlapping upper and lower plates. The laser array includes multiple lasers, and the laser power at the center of the laser array is greater than the laser power on both sides. The laser array can swing along the long axis direction.

[0022] As an optional solution for the laser, the laser at the center of the laser array is used to melt through the upper plate without penetrating the lower plate, and the lasers on both sides of the laser array are used not to penetrate the upper plate and the lower plate respectively.

[0023] In a third aspect, a laser welding device is provided, comprising the above-mentioned laser.

[0024] In a fourth aspect, a laser welding device is provided, comprising a laser welding head capable of outputting a laser array, the laser array comprising multiple lasers, the laser power at the center of the laser array being greater than the laser power at the sides, and the laser array being capable of swinging along its long axis. The laser welding device can be used to perform the aforementioned thin plate laser lap welding method.

[0025] Beneficial effects of the present invention:

[0026] The present invention provides a thin plate laser lap welding method and laser welding equipment, which uses multiple lasers to perform autogenous welding on the overlap of the upper plate and the lower plate. The use of multiple lasers can be applied to a wider weld seam. At the same time, the power of the laser acting on the surface of the upper plate and the power of the laser acting on the lower plate are both smaller than the power of the laser acting on the center of the weld seam, that is, along the direction from the upper plate to the center of the weld seam to the lower plate, the laser power shows a low-high-low variation trend. By such an arrangement, it can be ensured that the laser in the center of the weld seam can penetrate the upper plate, while the lasers on both sides of the center of the weld seam are controlled to be within the range of not being able to penetrate the plate. state, in order to achieve precise control of the energy input in different zones of the weld, ensuring that the penetration depth of each zone is controllable and different, and the lower plate has no undercut and no penetration; during the welding process, the multi-channel laser setting can effectively increase the laser coverage weld width to form a wider molten pool, so that when the multi-channel laser swings according to the preset motion trajectory, the laser swing amplitude can be reduced and the swing frequency can be increased. Through such a setting, the laser energy is evenly distributed, the base material in the center of the weld is melted a lot and flows down naturally under the action of gravity, the weld is well formed, the lower plate has no undercut, and the energy concentration effectively improves the welding efficiency. The cross-section of the weld after forming is as follows Figure 1 and Figure 7 As shown, the weld transitions smoothly from the upper plate to the lower plate, with a smooth surface and good consistency, no inner concavity or outer convexity, and a continuous and smooth transition. The molten pool size measurement meets the standard requirements, effectively improving the welding quality and welding efficiency. No filler wire is required, which can effectively reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the outline of a corrugated stainless steel lap weld in actual ship operation provided by an embodiment of the present invention;

[0028] Figure 2 Schematic diagram of the relative positions of the laser array and the weld provided in a specific embodiment of the present invention;

[0029] Figure 3 Schematic diagram of an "8"-shaped trajectory of a laser array swing trajectory provided by an embodiment of a specific embodiment of the present invention;

[0030] Figure 4 Schematic diagram of a circular laser array oscillation trajectory provided by an embodiment of the present invention;

[0031] Figure 5 This is a schematic diagram of the laser array arrangement provided in a specific embodiment of the present invention;

[0032] Figure 6 It is the metallographic diagram of the weld seam of single laser oscillation welding;

[0033] Figure 7 It is an actual weld metallographic diagram provided by an embodiment of the specific implementation of the present invention.

[0034] In the picture:

[0035] 1. Upper plate; 2. Lower plate; 3. Laser array; 4. Weld center. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0037] In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention in specific circumstances.

[0038] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0039] In the description of this embodiment, terms such as "upper," "lower," and "right" are used to refer to positions or locations based on the positions or locations shown in the accompanying drawings. These terms are intended solely to facilitate description and simplify operation, and are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meaning.

[0040] Combined with the visual inspection, metallographic inspection and specimen geometric data analysis standards for corrugated stainless steel welding, the lap weld between the upper plate 1 and the lower plate 2 should meet the following standards:

[0041] 1. The weld surface should be as smooth as possible, with a smooth transition from the upper plate 1 to the lower plate 2, and there should be no weld-through defects on the back;

[0042] 2. Metallographic photography can show a clear and smooth weld curve on the base material, and the weld must have a slight back arc surface. That is, the weld surface must have a slight smooth transition convexity, such as Figure 7 If the weld cross section is concave, or the weld pool profile is circular or not fully penetrated, it does not meet the standards. Figure 6 As shown;

[0043] 3. Combination Figure 1 , the molten pool profile of the lap weld must meet the parameter standards shown in Table 1.

[0044] Table 1

[0045]

[0046] Single laser non-oscillating welding has a large depth-to-width ratio, making it easy to obtain a large penetration depth. However, it is very difficult to significantly increase the penetration width while ensuring welding quality and stability, and it is impossible to obtain a qualified weld that meets the standards in Table 1.

[0047] like Figure 6 As shown, single-laser oscillating welding, by introducing scanning laser welding, allows for easier control of weld width. However, as the oscillation amplitude increases, insufficient energy is likely to occur at the weld center (4), leading to uneven concavities and convexities in the weld. Unfused edges are prone to curling at the upper plate (1), and unstable undercuts are common at the lower plate (2). The weld pool also struggles to form a continuous and uniform overall structure, particularly due to insufficient penetration at the weld center (4). Furthermore, welding efficiency is severely limited by the oscillation speed. As laser power increases, the stability of the entire welding process and weld quality destabilize, making it difficult to obtain a qualified weld that meets the standards in Table 1.

[0048] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0049] First, as Figures 2 to 5 As shown, this embodiment provides a thin plate laser lap welding method and laser welding equipment, which are applied to thin plates that require precision welding and high welding quality. For example, the thin plates to be welded in this embodiment are made of corrugated 304L stainless steel, that is, the upper plate 1 and the lower plate 2 are both made of corrugated 304L stainless steel. The method includes the following steps:

[0050] S1: The upper plate 1 and the lower plate 2 to be welded are overlapped and fixed on a welding jig, and at least one welding point is pre-welded between the upper plate 1 and the lower plate 2.

[0051] Specifically, in this embodiment, the above steps involve overlapping the upper plate 1 and lower plate 2 and securing them to a welding jig, ensuring a tight fit. At least one pre-weld spot is then applied along the overlap to secure the plates and prevent welding deformation that could cause excessive gaps. For example, the welding jig is a structure already known in the prior art. Its specific structure is referenced in the prior art and will not be further described here.

[0052] S2: Select the number of laser paths according to the weld width and set the parameters of the laser array 3; wherein the laser array 3 includes multiple laser paths, and the laser power at the center of the laser array 3 is greater than the laser power at both sides.

[0053] Specifically, in this embodiment, the above steps involve selecting the number of laser paths based on the weld seam width to ensure that laser array 3 at least completely covers the weld seam. The parameters of a single-column laser array 3 are set based on the material of the plates to be welded, the weld seam width, and the laser oscillation amplitude. The laser power at the center of laser array 3 is greater than the laser power at the sides. Specifically, the laser power varies from low to high to low along the direction from upper plate 1 to weld seam center 4 to lower plate 2. This ensures that the laser light at the center of laser array 3 penetrates upper plate 1, while the laser light at the sides is controlled to prevent penetration. In particular, the laser light acting on lower plate 2 requires precise power regulation to avoid problems with penetration.

[0054] Optionally, the parameters of the laser array 3 include the power of each single laser channel, and the power of each laser channel of the laser array 3 is independently adjustable. Specifically, the maximum power of a single laser channel supports 500W / 1000W / 1500W / 2000W, which can be adjusted from 10% to 100%, and meets the precise control of the single-channel output power, so as to achieve precise control of the energy input in different zones of the weld. The laser power at the center of the laser array 3 is controlled to be able to melt through the upper plate 1 without penetrating the lower plate 2, while the laser power on both sides of the laser array 3 is controlled to be in a state where it does not penetrate a single layer of plate, that is, the lasers on both sides do not penetrate the upper plate 1 or the lower plate 2. This ensures that the penetration depth of each zone is controllable, thereby solving the problems of unstable penetration depth, discontinuous molten pool contour, and easy penetration of the lower plate 2.

[0055] Specifically, the laser array 3 is generated by laser welding equipment, has a width of 2mm-4mm, and supports up to nine lasers with real-time adjustable parameters. The array laser passes through a collimating lens, a first oscillating mirror, a second oscillating mirror, and a focusing lens before acting at a specific angle on the joint between the upper and lower plates 1 and 2.

[0056] Optionally, the parameters of the laser array 3 include an output spot diameter. The output spot diameter is related to the properties of the laser welding equipment. The output spot diameter is usually 0.02 mm-1.5 mm, preferably 0.02 mm or 0.05 mm.

[0057] Optionally, the parameters of the laser array 3 include a collimation and focusing ratio (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.

[0058] S3: Adjust the position of the laser welding head relative to the weld so that the center of the laser array 3 is placed inside the edge of the upper plate 1 close to the overlap, and the long axis of the laser array 3 is set at an angle to the welding direction.

[0059] In the above steps, specifically in this embodiment, the position of the laser welding head relative to the weld is adjusted so that the center of the laser array 3 is placed on the inner side of the edge of the upper plate 1 near the overlap. Figure 2 As shown, the edge of the upper plate 1 near the overlap is defined as the weld center 4, and the center of the laser array 3 is placed 10.2mm-0.6mm from the weld center 4 to the upper plate, that is, the distance x ranges from 0.2mm to 0.6mm, to ensure a large amount of melting of the parent material of the upper plate 1, which is conducive to the formation of the raised back arc surface of the weld.

[0060] The long axis of the laser array 3 is set at an angle to the welding moving direction. Specifically, continue to refer to Figure 2 The angle α is between 60° and 90°, preferably 90°. This means that the long axis of the laser array 3 is preferably perpendicular to the welding direction. Adjusting the angle α allows for fine-tuning of the weld width. When the laser array 3 is tilted relative to the weld, the projected length perpendicular to the weld decreases as the angle α decreases. However, due to the tilt of the laser array 3, the arrival time of each laser beam perpendicular to the weld may vary. Therefore, the angle α should not be too large.

[0061] If the weld width is adjusted by increasing or decreasing the number of laser paths, the range of weld width adjustment is larger. Assuming the collimation and focusing ratio is 100:200, then for each additional laser path, the total width of the laser array 3 increases by 0.5mm, so adjusting the number of paths is only suitable for coarse adjustment of the weld width. Fine-tuning the angle α can achieve the effect of fine-tuning the weld width. The thermal conductivity of the material is not considered, only the effective width of the laser array 3 is considered. The theoretical weld width when the laser array 3 is tilted = the total width of the laser array 3 * sinα, which is the maximum when α is 90° and 0.866 times when α is 60°. Assuming the total width of the laser array 3 is 2.1mm, the adjustment range of the weld width by fine-tuning the angle α is between 1.8mm and 2.1mm.

[0062] Optionally, the laser welding head is tilted, with the angle between the axis of the laser welding head and the vertical direction being 10°-15°, so that the laser array 3 is tilted to the weld, which can reduce the problem of unfused upper and lower plates 1 and curling of the upper plate 1. Specifically, when a single-channel laser is placed on the lower plate 2 near the edge of the upper plate 1, since the focused beam is not incident vertically, part of the laser will be blocked by the upper plate 1, resulting in the lower plate 2 at the overlap being not fully melted, thus causing the problem of unfused overlap. At the same time, the molten droplets of the upper plate 1 tend to gather inward due to surface tension, forming curling. In addition, the focus of the upper plate 1 and the lower plate 2 is also prone to inconsistency, and tilting the laser welding head at a certain angle can improve the above problems. In addition, although stainless steel is not a highly reflective material, it also has a certain reflectivity. At the same time, there will inevitably be some spatter during the stainless steel welding process. Tilting at a certain angle can better protect the laser welding head and extend the service life of the laser welding head.

[0063] Optionally, the upper surface of the upper plate 1 is defined as the zero focus position, and the focus of the laser array 3 is adjusted from -2 mm to 0 mm to ensure that the penetration depth of the weld meets the requirements.

[0064] S4: The laser array 3 emits light, and the laser welding head moves along the overlap of the upper plate 1 and the lower plate 2, and swings along the long axis direction of the laser array 3 to form an overlap weld;

[0065] In the above steps, specifically in this embodiment, the laser array 3 emits light, and the laser welding head moves along the overlap of the upper plate 1 and the lower plate 2, and swings and welds to form the overlap weld. Specifically, the swing trajectory of the laser welding head is as follows: Figure 3 The "8" shape shown or Figure 4 The circular shape shown, and the adjacent light spots are circumscribed, preferably in the shape of an "8", so as to achieve more uniform heating of the weld and effectively reduce welding defects such as porosity and cracks.

[0066] Furthermore, the swing amplitude of the laser welding head is the laser center distance minus the focus spot diameter, that is, WW =Dd f Among them, refer to Figure 5 , D is the center distance between two adjacent lasers, which is generally the setting value of the equipment, and the focus spot diameter d f =d*(F f / F c ), F f is the focal length of the focusing lens, F c is the focal length of the collimator, and d is the output spot diameter. Specifically, the output spot diameter is usually 0.02 mm-1.5 mm, preferably 0.02 mm or 0.05 mm. The collimation-focusing ratio is 1:2, 1:2.5 or 1:3, preferably 1:2.

[0067] Compared with single laser oscillation welding, the oscillation amplitude of laser array 3 oscillation welding is the single laser oscillation amplitude / number of laser arrays 3. When welding to obtain welds of the same width, laser array 3 can achieve a smaller oscillation amplitude, thereby improving the quality of the weld. During single laser welding, the larger oscillation amplitude makes the material inside the oscillation track ineffective for laser action, and the internal material can only be melted by heat conduction. It is easy to have a shallow penetration depth or even unmelted plate, which leads to poor weld quality. The reduction of the oscillation amplitude of laser array 3 can optimize the energy distribution of laser array 3, ensuring sufficient energy at the center 4 of the weld, so that the amount of parent material melted at the center 4 of the weld is large and flows down naturally under the action of gravity, ensuring sufficient penetration depth at the center 4 of the weld, good weld formation, and no undercut on the lower plate 2, effectively avoiding uneven concave and convex welds.

[0068] Optionally, the oscillation frequency of the laser array 3 is the single laser oscillation frequency * the number of laser arrays 3, which can achieve higher frequency welding compared to single laser beam welding. It is preferred to set the oscillation frequency of the laser array 3 to be no less than 30 times the welding speed so that the energy of the laser can be evenly delivered to the weld. At the same time, the welding efficiency can be effectively improved. In addition, the oscillation frequency of the laser array 3 * the oscillation amplitude < the maximum speed of the laser welding head oscillation motor. Specifically, the oscillation frequency of the laser welding head depends on its specific hardware parameters, and the oscillation of the laser welding head is achieved by rotating the reflective lens through two oscillating motors. The maximum speed of the oscillating motor will limit the oscillation frequency and amplitude of the laser welding head, that is, the oscillation frequency * the oscillation amplitude < the maximum speed of the oscillating motor. In the prior art, the maximum speed of the oscillating motor generally does not exceed 3000 mm / s. In addition, in actual applications, the oscillation amplitude is usually determined first and then the oscillation frequency is determined to achieve small-amplitude, high-frequency, and high-speed welding, thereby improving the quality of the weld.

[0069] Optionally, the welding speed can be set to 15mm / s to 50mm / s. Furthermore, while the laser welding head emits laser light, it can also deliver shielding gas, such as nitrogen or argon, to the weld seam to protect the upper and lower plates 1 and 2 to be welded from contamination by other gases and impurities, thereby ensuring welding quality. For example, the shielding gas flow rate is 15L / min to 25L / min. The specific flow rate is related to the size of the gas outlet and the distance from the gas outlet to the welding position, and needs to be adjusted in real time based on the actual effect.

[0070] After welding, a portion of the weld is cut for metallographic mapping to observe the molten pool morphology. If the molten pool morphology is not continuously and smoothly transitioned, and there are concave or convex parts, the power of the laser array 3 needs to be further adjusted.

[0071] Specifically, in this embodiment, the weld seam is cut after completion, and metallographic mapping is performed to observe the molten pool morphology. If the molten pool morphology is not continuously and smoothly transitioned, with internal concavity or external convexity, the power of laser array 3 is further adjusted based on the actual situation. In other words, if the parameters of the weld cross section do not meet the standards in Table 1, the power of laser array 3 needs to be further adjusted.

[0072] For example, the upper plate 1 and the lower plate 2 to be welded are both made of 1.2 mm thick corrugated 304L stainless steel. The steps of lap welding are as follows:

[0073] Overlap the upper and lower plates 1 and 2 with a 10mm overlap width. Secure them in a welding jig using a rigid, dedicated clamp. Ensure the upper and lower plates 1 and 2 are pressed snugly together, with a gap of no more than 0.2mm after compression. Pre-weld at least one spot every 20mm along the overlap to secure the upper and lower plates 1 and 2, preventing welding deformation and excessive gaps. Pre-weld at 20mm intervals along the welding direction to prevent warping during welding due to thin plates and long weld lengths.

[0074] The laser array 3 of the laser welding equipment is set to have 5 light outputs, the maximum power of a single laser is 1500W, the output spot diameter is 0.05mm, the collimating lens focal length of the laser welding head is 100mm, the focusing lens focal length is 200mm, the focusing spot diameter is 0.1mm, the single laser spacing is 0.5mm, and the total width of the laser array 3 is 2.1mm; in other embodiments, a larger weld width can also be obtained by increasing the number of laser paths.

[0075] Then, according to the placement angles of the upper plate 1 and the lower plate 2, the position of the laser array 3 is adjusted so that the long axis of the laser array 3 is perpendicular to the weld. In other embodiments, the angle α between the long axis of the laser array 3 and the weld can also be adjusted to fine-tune the weld width.

[0076] The axis of the laser welding head is deviated from the vertical direction by 10°, so that the laser array 3 is incident on the weld at an angle; the center of the laser array 3 is moved to a position 0.4 mm inside the upper plate 1 from the weld center 4; and the focus of the laser array 3 is adjusted to -2 mm.

[0077] Specifically, along the direction from the upper plate 1 to the lower plate 2, the first, second, and third lasers act on the upper plate 1, the fourth laser acts on the overlap between the lower plate 2 and the upper plate 1, and the fifth laser acts on the lower plate 2. The power of the first laser is set to 150W, the power of the second laser is set to 250W, the power of the third laser is set to 300W, the power of the fourth laser is set to 150W, and the power of the fifth laser is set to 100W. The swing trajectory of the laser welding head is set to an "8" shape, and the long axis of the "8" shape is perpendicular to the weld, the swing amplitude is set to 0.4mm, and the swing frequency is set to 500Hz. After the swing, part of the fourth laser acts on the upper plate 1, and the other part acts on the lower plate 2.

[0078] The welding speed was set to 15 mm / s. At the same time, the shielding gas delivered to the weld was argon with a flow rate of 15 L / min.

[0079] The laser array 3 emits light, and the laser welding head moves along the welding direction and the preset swing trajectory to form a lap weld and complete the lap welding.

[0080] After welding was completed, the weld was cut for metallographic preparation and observation of the molten pool morphology. Some areas of the molten pool were concave or convex, with a discontinuous and smooth transition. The laser powers were further adjusted to 160W for the first laser, 240W for the second, 290W for the third, 170W for the fourth, and 120W for the fifth. The above steps were repeated to obtain a new weld, and weld samples were again taken for metallographic preparation to obtain a qualified weld that met the standards for actual ship operation.

[0081] The weld welded using the above method has a smooth transition from the upper plate 1 to the lower plate 2, a smooth surface, good consistency, no inner concave or outer convex, a continuous and smooth transition, and the molten pool size measurement meets the standard requirements, effectively improving the welding quality and welding efficiency, while eliminating the need for filler wire to effectively reduce costs.

[0082] Secondly, this embodiment also provides a laser that can output a laser array 3. Laser array 3 is used for overlapping welding of upper plate 1 and lower plate 2. Laser array 3 includes multiple lasers. The laser power at the center of laser array 3 is greater than the laser power on both sides. This ensures that the laser at the center can penetrate upper plate 1, thereby ensuring smooth welding of upper plate 1 and lower plate 2. Laser array 3 can swing along its long axis to evenly output laser energy and avoid high energy concentration. At the same time, the dynamic force generated by the swinging stirs the molten pool metal, facilitating gas escape and enhancing the weld quality.

[0083] Furthermore, the laser at the center of the laser array 3 is used to melt through the upper plate 1 without penetrating the lower plate 2, and the lasers on both sides of the laser array 3 are used not to penetrate the upper plate 1 and the lower plate 2, respectively, to avoid the molten pool being too wide or causing defects such as collapse and burn-through, thereby helping to form a weld with moderate melt width, sufficient and uniform melt depth, and smooth surface.

[0084] On the third aspect, this embodiment also provides a laser welding device, including the above-mentioned laser, and used to perform the above-mentioned thin plate laser lap welding method, and has all the beneficial effects of the above-mentioned thin plate laser lap welding method and laser, which will not be repeated here.

[0085] Fourthly, this embodiment also provides a laser welding device, which includes a laser welding head, the laser welding head includes a laser array 3, the laser array 3 includes multiple lasers, the laser power in the center of the laser array 3 is greater than the laser power on both sides, and the laser array 3 can swing along the long axis direction.

[0086] In some embodiments, the maximum power of a single laser channel supports optional 500W / 1000W / 1500W / 2000W, adjustable from 10% to 100%, and meets the precise control of the single-channel output power to achieve precise control of the energy input in different zones of the weld. During the welding of thin plate overlaps, the parameters of the single-column laser array 3 are set according to the material of the plate to be welded, the weld width and the laser swing amplitude, and the number of laser channels is selected according to the weld width to ensure that the laser array 3 can at least completely cover the weld. The laser power at the center of the laser array 3 is greater than the laser power on both sides, that is: along the direction from the upper plate 1 to the weld center 4 to the lower plate 2, the laser power shows a low-high-low change trend, ensuring that the laser at the center of the laser array 3 can penetrate the upper plate 1, while the lasers on both sides are controlled in a state where they cannot penetrate the plate. In particular, the laser acting on the lower plate 2 needs to be precisely adjusted in power to avoid the problem of penetration of the lower plate 2.

[0087] In some embodiments, as Figure 2As shown, the laser array 3 oscillates along the long axis of the laser array 3. Specifically, the long axis is set at an angle with the welding movement direction, with the angle α being 60°-90°, preferably 90°. That is, the long axis of the laser array 3 is preferably perpendicular to the welding direction. By adjusting the angle α, the weld width can be fine-tuned. The oscillation frequency of the laser array 3 is the single laser oscillation frequency * the number of laser arrays 3. Compared to single laser beam welding, this enables higher-frequency welding. The oscillation frequency of the laser array 3 is preferably set to no less than 30 times the welding speed to evenly deliver the laser energy to the weld, while effectively improving welding efficiency. Furthermore, the oscillation frequency of the laser array 3 * the oscillation amplitude < the maximum speed of the laser welding head oscillation motor. Specifically, the oscillation frequency of the laser welding head depends on its specific hardware parameters. The oscillation of the laser welding head is achieved by rotating the reflective lens with two oscillating motors. The maximum speed of the oscillating motors will limit the oscillation frequency and amplitude of the laser welding head, that is, the oscillation frequency * the oscillation amplitude < the maximum speed of the oscillating motor. In the prior art, the maximum speed of an oscillating motor generally does not exceed 3000 mm / s. In practical applications, the oscillation amplitude is usually determined first and then the oscillation frequency to achieve small amplitude, high frequency and high speed welding, thereby improving weld quality.

[0088] The laser welding equipment is used to perform the above-mentioned thin plate laser lap welding method, and has all the beneficial effects of the above-mentioned thin plate laser lap welding method, which will not be described in detail here.

[0089] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. A person skilled in the art would be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A thin plate laser lap welding method, characterized in that: The steps include: S1: overlapping the upper plate (1) and the lower plate (2) to be welded, fixing them on a welding jig, and pre-welding at least one welding point between the upper plate (1) and the lower plate (2); S2: selecting the number of laser paths according to the weld width and setting the parameters of the laser array (3); wherein the laser array (3) includes multiple laser paths, and the laser power at the center of the laser array (3) is greater than the laser power at both sides; S3: adjusting the position of the laser welding head relative to the weld so that the center of the laser array (3) is placed on the inner side of the edge of the upper plate (1) close to the overlap, and the long axis of the laser array (3) is set at an angle to the welding direction; S4: The laser array (3) emits light, and the laser welding head moves along the overlap of the upper plate (1) and the lower plate (2), and swings along the long axis direction of the laser array (3) to weld and form an overlap weld.

2. The thin plate laser lap welding method according to claim 1, characterized in that: In S2, the parameters of the laser array (3) include the power of each single laser channel, the output spot diameter and the collimation and focusing ratio. The power of each single laser channel of the laser array (3) is independently adjustable. The central laser power of the laser array (3) is controlled to be able to melt through the upper plate (1) without penetrating the lower plate (2). The laser powers on both sides of the laser array (3) are controlled to be unable to penetrate a single layer of plate.

3. The thin plate laser lap welding method according to claim 1, characterized in that: In S3, the edge of the upper plate (1) near the overlap is the weld center (4), and the center of the laser array (3) is placed on the upper plate (1) perpendicular to the weld center (4) and 0.2 mm to 0.6 mm away from the weld center (4).

4. The thin plate laser lap welding method according to claim 1, characterized in that: In said S3, the angle between the long axis of the laser array (3) and the welding movement direction is 60° to 90°, preferably 90°.

5. The thin plate laser lap welding method according to claim 1, characterized in that: In S3, the laser welding head is tilted, and the angle between the axis of the laser welding head and the vertical direction is 10°-15°.

6. The thin plate laser lap welding method according to claim 1, characterized in that: The upper surface of the upper plate (1) is defined as the zero focus position, and the focus of the laser array (3) is adjusted to -2 mm to 0 mm.

7. The thin plate laser lap welding method according to claim 1, characterized in that: In the S4, the swing trajectory of the laser welding head is in the shape of an "8" or a circle, and adjacent light spots are circumscribed, preferably in the shape of an "8".

8. The thin plate laser lap welding method according to claim 7, characterized in that: The swing amplitude W of the laser welding head W =Dd f , where D is the center distance between two adjacent laser beams, and the focus spot diameter d f =d*(F f / F c ), F f is the focal length of the focusing lens, F c is the focal length of the collimator, d is the output spot diameter; And / or, it is preferred to set the oscillation frequency of the laser array (3) to be not less than 30 times the welding speed, and the oscillation frequency*oscillation amplitude<the limit speed of the oscillation motor of the laser welding head.

9. The thin plate laser lap welding method according to claim 8, characterized in that: The welding speed is set to 15mm / s-50mm / s; the laser welding head can deliver shielding gas to the welding position, and the flow rate of the shielding gas is 15L / min-25L / min.

10. A laser, characterized in that: The laser can output a laser array (3), and the laser array (3) is used for welding the overlapped upper plate (1) and lower plate (2). The laser array (3) includes multiple lasers, and the laser power at the center of the laser array (3) is greater than the laser power at both sides. The laser array (3) can swing along the long axis direction.

11. The laser according to claim 11, characterized in that The laser at the center of the laser array (3) is used to melt through the upper plate (1) without penetrating the lower plate (2), and the lasers on both sides of the laser array (3) are used not to penetrate the upper plate (1) and the lower plate (2).

12. A laser welding device, characterized in that: Comprising the laser according to claim 10 or 11.

13. A laser welding device, characterized in that: The invention comprises a laser welding head, wherein the laser welding head can output a laser array (3), wherein the laser array (3) comprises multiple lasers, wherein the laser power at the center of the laser array (3) is greater than the laser power at both sides, and the laser array (3) can swing along the long axis direction.

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