Laser reflow welding method

Abstract

The invention provides a laser reflow welding method, and belongs to the technical field of laser welding. Comprising the following steps: providing at least two layers of to-be-welded vehicle door materials, and treating the surface of a to-be-welded area; at least two to-be-welded vehicle door materials are stacked up and down, the at least two to-be-welded vehicle door materials are clamped through a clamp, and the to-be-welded areas of the at least two to-be-welded vehicle door materials are tightly attached together; configuring process parameters of a first welding seam and process parameters of a second welding seam according to the thickness of the at least two layers of vehicle door materials and the width requirement of the joint surface; the galvanometer welding head sequentially welds the first welding seam and the second welding seam according to the technological parameters, the length of the second welding seam is not smaller than that of the first welding seam, and the second welding seam is opposite in direction. Through two independent laser deep penetration welding and reflow welding, the appearance of a welding seam is guaranteed, the problem that the quality of the welding seam is reduced due to the fact that no follow-up shielding gas exists in the flying welding process or the galvanometer welding curve track can be solved, and the design difficulty of the clamp can be simplified.

Description

Technical Field

[0001] The invention relates to the technical field of laser welding, and in particular to a laser melting back welding method. Background Art

[0002] The aluminum laser welding technology for car bodies has been applied in the production lines of many automobile brands at home and abroad. By taking advantage of the advantages of laser welding, the lightweight, high strength and high quality of all-aluminum or mixed material car bodies have been achieved. In the process of laser welding of commonly used materials for automobile door window frames and inner panels, a protective gas atmosphere of inert gases such as argon or nitrogen is often required. The protective gas can prevent the oxidation of materials in the molten pool area and take away the heat generated by the welding part. With the increasing production cycle and the increasing complexity of the weld trajectory, the protective gas cannot effectively follow and protect the front and back of the weld in real time during the galvanometer flight welding process; in addition, when the protective gas is output to the welding trajectory area on the fixture supporting the automobile door window frame and inner panel, there is also the problem of being unable to ventilate in real time following the welding trajectory, and the continuous output of protective gas leads to serious waste of protective gas. The improvement of the process method of door welding without protective gas is very urgent for various manufacturers. The self-melting welding method without protective gas atmosphere does not require the use of protective gas during the welding process, reduces the difficulty of fixture design, and can also beautify the weld and improve the welding quality. It has been increasingly widely used.

[0003] In traditional single laser welding head autogenous welding, an arc pit is formed by the collapse and closure of the laser deep melting welding keyhole at the end of the weld. The arc pit is reduced by extending the weld length and slowly reducing the power, which will cause insufficient penetration at the end of the weld, greatly reducing the effective weld length, and failing to effectively connect the car door window frame and inner panel. Therefore, it is very necessary to propose a laser remelting welding method that ensures the appearance of the weld and the welding quality of the welding part without using protective gas. Summary of the invention

[0004] In view of this, the present invention proposes a laser remelting welding method which does not use a protective atmosphere, reduces the difficulty of fixture design, welds two layers of door materials by deep fusion welding, and covers the first weld with a second weld to optimize the weld appearance.

[0005] The present invention provides a laser reflow welding method, comprising the following steps:

[0006] Provide at least two layers of door material to be welded and prepare the surface of the welding area;

[0007] Stacking at least two layers of door materials to be welded up and down, clamping the at least two layers of door materials to be welded with a clamp, and making the at least two layers of door materials to be welded closely together;

[0008] According to the requirements of thickness and joint width of at least two layers of door materials, configure the process parameters of the first weld and the second weld;

[0009] The galvanometer welding head welds the first weld and the second weld in sequence according to the process parameters. The length of the second weld is not less than that of the first weld and the direction is opposite.

[0010] On the basis of the above technical solution, preferably, the first weld adopts laser deep penetration welding, penetrates at least one layer of door material along the set direction of the first weld, and makes the melting depth of the bottom layer of door material exceed 30% of the thickness of the bottom layer of door material; the second weld adopts laser remelting welding, and the melting depth of the second weld is different from that of the first weld; the swinging mode of the first weld is not exactly the same as the swinging mode of the second weld.

[0011] Preferably, the swinging mode of the first weld is: a spiral trajectory with a point on the center line of the weld as a way point, a sinusoidal wave trajectory with a point on the center line of the weld as a way point, or a circular trajectory with a point on the center line of the weld as the center of the circle; the swinging mode of the second weld is: a spiral trajectory with a point on the center line of the weld as a way point, a sinusoidal wave trajectory with a point on the center line of the weld as a way point, a circular trajectory with a point on the center line of the weld as the center of the circle, a broken line trajectory passing through discrete points equally spaced on the center line of the weld, or an 8-shaped trajectory surrounding discrete points on the center line of the weld.

[0012] Further preferably, the galvanometer welding head includes a laser fiber, a dynamic focusing mechanism, a collimator, a fixed reflector, an XY galvanometer and a field mirror arranged in sequence; the laser fiber is arranged in a vertical direction for outputting a laser beam; the dynamic focusing mechanism is arranged on the output optical path of the laser fiber, and the dynamic focusing mechanism moves along the axial direction of the laser fiber, a collimator is fixedly arranged at the center of the dynamic focusing mechanism, and the collimator is coaxially arranged with the laser fiber; the fixed reflector is arranged on the light-emitting side direction of the collimator and is connected to the collimator optical path; the XY galvanometer is arranged on the light-emitting side direction of the fixed reflector, a fulcrum is arranged on the XY galvanometer, and the XY galvanometer is swung relative to the fulcrum to change the position of the laser beam spot; the field mirror is arranged on the light-emitting side direction of the XY galvanometer for outputting a laser beam; wherein the dynamic focusing mechanism drives the collimator to move to change the spot size of the laser beam acting on the door material.

[0013] More preferably, the spot size of the laser beam acting on the door material is calculated according to the following formula:

[0014] If the focus of the laser beam is on the surface of the door material, the spot size of the laser beam acting on the door material is Where D 焦点 is the spot size at the focus of the laser beam output by the galvanometer welding head; f聚焦焦距 f is the focal length of the field lens of the galvanometer welding head; 准直焦距 is the focal length of the collimator lens of the galvanometer welding head; d 芯径 is the fiber diameter;

[0015] If there is a defocus distance Z between the focus of the laser beam and the surface of the door material, the Rayleigh length Z r for Where λ is the wavelength of the laser beam; M 2 is the beam quality; at this time, the spot size of the laser beam acting on the door material is

[0016] Still further preferably, the total thickness of the at least two layers of door material is in the range of [1 mm, 5 mm].

[0017] More preferably, at least two layers of the vehicle door material are both non-ferrous metal material or ferrous metal material.

[0018] Further preferably, when at least two layers of door materials are non-ferrous metal materials, the range of the laser beam power of the given first weld is [1500W, 5000W]; the range of the welding speed of the first weld is [40mm / s, 150mm / s]; the spot size of the laser beam of the first weld acting on the door material is [0.2mm, 1mm]; the range of the spot swing amplitude A1 of the first weld is [0.2mm, 1.6mm]; the range of the spot swing frequency of the first weld is [60Hz, 25 0Hz]; the power of the given second weld is in the range of [500W, 4000W]; the welding speed of the second weld is in the range of [60mm / s, 300mm / s]; the spot size of the laser beam of the second weld acting on the door material is [1mm, 3mm]; the spot swing amplitude A2 of the second weld is in the range of A1+[0, 2mm]; the spot swing frequency of the second weld is in the range of [100Hz, 500Hz]; the length of the second weld at the beginning and end is longer than that of the first weld by [0, 5mm] respectively.

[0019] Further preferably, when at least two layers of door material are both ferrous metal materials, the power of the given first weld is in the range of [1500W, 5000W]; the welding speed of the first weld is in the range of [20mm / s, 200mm / s]; the spot size of the laser beam of the first weld acting on the door material is [0.2mm, 1mm]; the power of the given second weld is in the range of [1000W, 3000W]; the welding speed of the second weld is in the range of [50mm / s, 300mm / s]; the spot size of the laser beam of the second weld acting on the door material is [0.6mm, 3mm]; the length of the second weld at the beginning and end is respectively longer than that of the first weld by [0, 5mm].

[0020] More preferably, the power of the laser beam of the first weld is greater than the power of the laser beam of the second weld, and the penetration depth of the first weld is greater than the penetration depth of the second weld; the spot size of the second weld is greater than the spot size of the first weld.

[0021] The laser reflow welding method provided by the present invention has the following beneficial effects compared with the prior art:

[0022] The laser remelting welding method provided by the embodiment of the present invention performs the first welding according to the thickness of the two-layer door material by adapting the laser welding processing parameters. The first weld adopts laser deep melting welding to ensure the welding depth and the width of the joint surface. The second weld adopts remelting welding. The remelting welding process parameters control the laser energy density to achieve laser thermal conduction welding, cover the first weld, and ensure the weld appearance. It can solve the problem of weld quality degradation caused by the flight welding process or the galvanometer welding curve trajectory without follow-up protective gas. In addition, the focus position can also be adjusted through the galvanometer welding head, thereby changing the size of the light spot projected on the door material to meet the welding requirements of the two welds. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A schematic diagram of the weld direction of a laser remelting welding method of the present invention;

[0025] Figure 2 A schematic diagram of an optical path in which the focus of a laser beam of a galvanometer welding head in a laser reflow welding method of the present invention is located on the surface of a vehicle door material;

[0026] Figure 3 A schematic diagram of an optical path in which the focus of a laser beam of a galvanometer welding head deviates from the surface of a door material in a laser reflow welding method of the present invention;

[0027] Figure 4 It is a front view of the first weld of Example 1 of a laser melting back welding method of the present invention;

[0028] Figure 5 This is a stereoscopic diagram of the effect of laser reflow welding in Example 1 of a laser reflow welding method of the present invention;

[0029] Figure 6 A three-dimensional diagram of the first weld of Example 2 of a laser melting back welding method of the present invention;

[0030] Figure 7 This is a stereoscopic diagram of the effect of laser reflow welding in Example 2 of a laser reflow welding method of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] In traditional single laser autogenous welding, an arc pit is formed at the end of the weld due to the collapse and closure of the laser deep melting keyhole. The arc pit can be reduced by extending the weld length and slowly reducing the power. This will result in insufficient penetration at the end of the weld, greatly reducing the effective weld length, and making it impossible to effectively connect the car door window frame and inner panel. Figure 1 As shown, the present invention provides a laser reflow welding method, comprising the following steps:

[0033] S1: Provide at least two layers of door material to be welded and prepare the surface of the welding area.

[0034] The content of surface treatment is to remove oil stains and dirt on the surface of the material. If necessary, further surface grinding can be performed. The total thickness of at least two layers of door materials is in the range of [1mm, 5mm]. At least two sides of the door material include two layers, or more than two layers. The total thickness cannot be too thick, otherwise there is a risk of poor welding.

[0035] S2: stacking at least two layers of door material to be welded up and down, clamping the at least two layers of door material to be welded with a clamp, and making the at least two layers of door material to be welded closely attached to each other.

[0036] The fixture is used to maintain the relative position of the two layers of door material unchanged during the welding process. A conventional pneumatic flip fixture or manual caliper is used on the fixed base. The fixed base is also equipped with a ball guide post for limiting the position. The ball guide post is abutted against the end face of the door material. The fixture and the ball guide post work together to prevent the position of the two layers of door material from moving.

[0037] S3: According to the thickness of at least two layers of door material and the requirement of the width of the joint surface, configure the process parameters of the first weld and the process parameters of the second weld.

[0038] like Figure 1 As shown, the first weld adopts laser deep penetration welding, and at least one layer of door material is welded through along the set direction of the first weld, and the melting depth of the bottom layer of door material exceeds 30% of the thickness of the bottom layer of door material; the second weld adopts laser remelting welding, and the melting depth of the second weld is different from that of the first weld; the swinging mode of the first weld is not exactly the same as the swinging mode of the second weld.

[0039] As a further improvement of this embodiment, the swinging mode of the first weld is: a spiral trajectory with a point on the center line of the weld as a path point, a sinusoidal wave trajectory with a point on the center line of the weld as a path point, and a circular trajectory with a point on the center line of the weld as the center of the circle; the swinging mode of the second weld is: a spiral trajectory with a point on the center line of the weld as a path point, a sinusoidal wave trajectory with a point on the center line of the weld as a path point, a circular trajectory with a point on the center line of the weld as the center of the circle, a broken line trajectory passing through discrete points equally spaced on the center line of the weld, or an 8-shaped trajectory surrounding discrete points on the center line of the weld.

[0040] like Figure 2 and Figure 3 As shown, the galvanometer welding head of the present invention comprises a laser fiber, a dynamic focusing mechanism, a collimator, a fixed reflector, an XY galvanometer and a field mirror which are arranged in sequence; the laser fiber is arranged in a vertical direction for outputting a laser beam; the dynamic focusing mechanism is arranged on the output optical path of the laser fiber, and the dynamic focusing mechanism moves along the axial direction of the laser fiber, a collimator is fixedly arranged at the center of the dynamic focusing mechanism, and the collimator is coaxially arranged with the laser fiber; the fixed reflector is arranged in the light-emitting side direction of the collimator, and is connected to the collimator optical path; the XY galvanometer is arranged in the light-emitting side direction of the fixed reflector, a fulcrum is arranged on the XY galvanometer, and the XY galvanometer is swung relative to the fulcrum to change the position of the laser beam spot; the field mirror is arranged in the light-emitting side direction of the XY galvanometer for outputting a laser beam; wherein the dynamic focusing mechanism drives the collimator to move to change the spot size of the laser beam acting on the door material.

[0041] like Figure 2 and Figure 3 As shown, the spot size of the laser beam acting on the door material is calculated according to the following formula:

[0042] If the focus of the laser beam is on the surface of the door material, the spot size of the laser beam acting on the door material is Where D 焦点 is the spot size at the focus of the laser beam output by the galvanometer welding head; f 准直焦距 f is the focal length of the field lens of the galvanometer welding head; 准直焦距 is the focal length of the collimator lens of the galvanometer welding head; d 芯径 is the fiber diameter;

[0043] If there is a defocus distance Z between the focus of the laser beam and the surface of the door material, the Rayleigh length Z r for Where λ is the wavelength of the laser beam; M 2 is the beam quality; at this time, the spot size of the laser beam acting on the door material is

[0044] In the present invention, at least two layers of door materials are non-ferrous metal materials or ferrous metal materials. The process parameters of the first weld and the process parameters of the second weld under different material conditions are now described.

[0045] 1) When at least two layers of door materials are non-ferrous metal materials, the range of the laser beam power of the given first weld is [1500W, 5000W]; the range of the welding speed of the first weld is [40mm / s, 150mm / s]; the spot size of the laser beam of the first weld acting on the door material is [0.2mm, 1mm]; the range of the spot swing amplitude A1 of the first weld is [0.2mm, 1.6mm]; the range of the spot swing frequency of the first weld is [60Hz, 250Hz] ; The power of the given second weld is in the range of [500W, 4000W]; the welding speed of the second weld is in the range of [60mm / s, 300mm / s]; the spot size of the laser beam of the second weld acting on the door material is [1mm, 3mm]; the spot swing amplitude A2 of the second weld is in the range of A1+[0, 2mm]; the spot swing frequency of the second weld is in the range of [100Hz, 500Hz]; the length of the second weld at the beginning and end is longer than that of the first weld by [0, 5mm] respectively.

[0046] 2) When at least two layers of door materials are made of ferrous metal, the power of the first weld is in the range of [1500W, 5000W]; the welding speed of the first weld is in the range of [20mm / s, 200mm / s]; the spot size of the laser beam of the first weld acting on the door material is [0.2mm, 1mm]; the power of the second weld is in the range of [1000W, 3000W]; the welding speed of the second weld is in the range of [50mm / s, 300mm / s]; the spot size of the laser beam of the second weld acting on the door material is [0.6mm, 3mm]; the length of the second weld at the beginning and the end is longer than that of the first weld by [0, 5mm] respectively.

[0047] S4: The galvanometer welding head performs welding of the first weld and the second weld in sequence according to the process parameters. The length of the second weld is not less than the length of the first weld and the direction is opposite.

[0048] In the two welds with different directions, the first weld adopts laser deep fusion welding to ensure the welding depth and the width of the joint surface; the second weld adopts reflow welding, and the reflow welding process parameters control the laser energy density to achieve laser thermal conduction welding, covering the first weld and ensuring the appearance of the weld. Since no protective atmosphere is used, there is no need to use protective gas, and the difficulty of fixture design can be reduced, and there is no need to blow protective gas following the weld position.

[0049] In actual operation, it is necessary to ensure that the power of the laser beam of the first weld is greater than the power of the laser beam of the second weld, and the penetration depth of the first weld is greater than the penetration depth of the second weld; the spot size of the second weld is greater than the spot size of the first weld.

[0050] The specific contents of the present invention are described below in conjunction with specific embodiments and drawings.

[0051] Embodiment 1: A two-layer door material is selected; both the upper door material and the lower door material are non-ferrous metal materials, wherein the upper door material is a 2 mm thick 5182 aluminum alloy plate, and the lower door material is a 1.5 mm thick 6061 aluminum alloy plate.

[0052] Use a clamp to press the two layers of door material tightly together. According to the material thickness and connection width requirements, set the laser welding processing parameters to weld the first weld. The optical fiber core diameter is 200μm, the collimator focal length is 116mm, and the focusing lens focal length is 420mm. The specifications of the galvanometer welding head in the subsequent embodiments remain unchanged. Only the XY galvanometer swing amplitude and the position of the dynamic focusing mechanism are changed to adjust the defocus amount, the spot size and the swing trajectory of the spot. The spot size of the laser beam on the surface of the upper door material is 0.72mm; the laser power of the first weld is 4000W, the welding speed is 80mm / s, the swing mode of the first weld is circular, the swing amplitude is 0.8mm, the frequency is 200Hz, and the welding direction is positive. Here we define Figure 1 The welding direction from left to right is the positive direction, and the welding direction from right to left is the reverse direction. Ensure that the penetration depth of the lower door material is 1 / 2 of the lower door material plate thickness. The welding result of the first weld is shown in Figure 4 ; Then call the second weld, i.e., the reflow welding parameters, adjust the position of the dynamic focus mechanism, so that the spot size of the laser beam on the surface of the upper door material is 1.5mm; the laser power of the second weld is 3800W, the welding speed is 200mm / s, the swing mode is circular, the swing amplitude is 1.2mm, the frequency is 200Hz, the welding direction is reversed, and the length of the second weld is 2mm longer than the first. According to this laser reflow welding method, the aluminum alloy door weld can be well-formed and free of arc pits. The results after the second welding are shown in Figure 5 .

[0053] Embodiment 2: A two-layer door material is selected; both the upper door material and the lower door material are non-ferrous metal materials, wherein the upper door material is a 1.5 mm thick 5182 aluminum alloy plate, and the lower door material is a 2.5 mm thick 6061 aluminum alloy plate.

[0054] Use a fixture to press the two layers of door materials together tightly. According to the material thickness and connection width requirements, set the laser welding processing parameters for the first weld. Select the galvanometer welding head with a fiber core diameter of 50μm, a collimator focal length of 125mm, a focusing lens focal length of 400mm, and a spot size of 0.16mm; laser power 3600W, welding speed 100mm / s, circular swing mode, swing amplitude 1mm, frequency 180Hz, and forward welding direction to ensure that the lower plate has a penetration depth of 1 / 2 of the underlying material; call the second remelting welding parameters, adjust the laser power to 3000W, welding speed 200mm / s, adjust the dynamic focusing mechanism, and achieve a spot size of 2mm on the workpiece, a linear swing mode, a swing amplitude of 1mm, a frequency of 220Hz, and the second weld length is the same as the first, and the welding direction is reversed. According to this laser remelting welding method, the aluminum alloy door weld can be formed with good appearance and no arc pits.

[0055] Embodiment 3: A two-layer door material is selected; the upper door material and the lower door material are both ferrous metal materials, wherein the upper door material is a 1mm thick galvanized sheet, and the lower door material is a 1mm thick galvanized sheet. The parameters of the galvanometer welding head selected are exactly the same as those in Embodiment 1.

[0056] Use a fixture to press the two layers of door material together tightly. According to the material thickness and connection width requirements, set the laser welding processing parameters to weld the first weld. The spot size of the laser beam on the surface of the upper door material is 0.7mm; the laser power of the first weld is 3600W, the welding speed is 100mm / s, and the welding direction is positive. Ensure that the penetration depth of the lower door material is 1 / 2 of the lower door material plate thickness. The spot size of the laser beam acting on the workpiece is 0.7mm. The welding result of the first weld is shown in Figure 1. Figure 6 ; The second melting welding parameters are: laser power 1800W, welding speed 200mm / s, laser beam spot size 1.2mm on the workpiece, and welding direction is reversed. According to this laser melting welding method, the galvanized sheet door weld can be well-formed, the arc pit is extremely small, and the welding quality is good. The results after the second welding are shown in Figure 7 .

[0057] It can be seen from the contents of the above embodiments that the galvanometer welding head swings when welding nonferrous metals, but the galvanometer welding head does not need to swing when welding ferrous metals. The above embodiments are described by taking two layers of car door materials as an example. The car door materials in actual welding can be more than two layers. The number of layers of car door materials in the above embodiments is not regarded as a limitation on the technical solution.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A laser reflow welding method, characterized in that: The steps include: Provide at least two layers of door material to be welded and prepare the surface of the welding area; Stacking at least two layers of door materials to be welded up and down, clamping the at least two layers of door materials to be welded with a clamp, and making the at least two layers of door materials to be welded closely together; According to the requirements of thickness and joint width of at least two layers of door materials, configure the process parameters of the first weld and the second weld; The galvanometer welding head welds the first weld and the second weld in sequence according to the process parameters. The length of the second weld is not less than that of the first weld and the direction is opposite.

2. A laser reflow welding method according to claim 1, characterized in that: The first weld adopts laser deep penetration welding, and penetrates at least one layer of door material along the set direction of the first weld, and makes the melting depth of the bottom layer of door material exceed 30% of the thickness of the bottom layer of door material; the second weld adopts laser remelting welding, and the melting depth of the second weld is different from that of the first weld; the swinging mode of the first weld is not exactly the same as that of the second weld.

3. A laser reflow welding method according to claim 2, characterized in that: The swinging mode of the first weld is: a spiral trajectory with a point on the center line of the weld as a way point, a sinusoidal trajectory with a point on the center line of the weld as a way point, and a circular trajectory with a point on the center line of the weld as the center of the circle; the swinging mode of the second weld is: a spiral trajectory with a point on the center line of the weld as a way point, a sinusoidal trajectory with a point on the center line of the weld as a way point, a circular trajectory with a point on the center line of the weld as the center of the circle, a broken line trajectory passing through discrete points equally spaced on the center line of the weld, or an 8-shaped trajectory surrounding discrete points on the center line of the weld.

4. The laser reflow welding method according to claim 3, characterized in that: The galvanometer welding head includes a laser fiber, a dynamic focusing mechanism, a collimator, a fixed reflector, an XY galvanometer and a field mirror which are arranged in sequence; the laser fiber is arranged in a vertical direction for outputting a laser beam; the dynamic focusing mechanism is arranged on the output optical path of the laser fiber, and the dynamic focusing mechanism moves along the axial direction of the laser fiber, a collimator is fixedly arranged at the center of the dynamic focusing mechanism, and the collimator is coaxially arranged with the laser fiber; the fixed reflector is arranged in the light-emitting side direction of the collimator and is connected to the collimator optical path; the XY galvanometer is arranged in the light-emitting side direction of the fixed reflector, a fulcrum is arranged on the XY galvanometer, and the XY galvanometer is swung relative to the fulcrum to change the position of the laser beam spot; the field mirror is arranged in the light-emitting side direction of the XY galvanometer for outputting a laser beam; wherein the dynamic focusing mechanism drives the collimator to move to change the spot size of the laser beam acting on the door material.

5. The laser reflow welding method according to claim 4, characterized in that: The spot size of the laser beam acting on the door material is calculated according to the following formula: If the focus of the laser beam is on the surface of the door material, the spot size of the laser beam acting on the door material is Where D 焦点 is the spot size at the focus of the laser beam output by the galvanometer welding head; f 聚焦焦距 f is the focal length of the field lens of the galvanometer welding head; 准直焦距 is the focal length of the collimator lens of the galvanometer welding head; d 芯径 is the fiber diameter; If there is a defocus distance Z between the focus of the laser beam and the surface of the door material, the Rayleigh length Z r for Where λ is the wavelength of the laser beam; M 2 is the beam quality; at this time, the spot size of the laser beam acting on the door material is 6. The laser reflow welding method according to claim 5, characterized in that: The total thickness of the at least two layers of door material is in the range of [1mm, 5mm].

7. The laser reflow welding method according to claim 6, characterized in that: At least two layers of door materials are made of non-ferrous metal materials or ferrous metal materials.

8. The laser reflow welding method according to claim 7, characterized in that: When at least two layers of door materials are nonferrous metal materials, the range of the laser beam power of the given first weld is [1500W, 5000W]; the range of the welding speed of the first weld is [40mm / s, 150mm / s]; the spot size of the laser beam of the first weld acting on the door material is [0.2mm, 1mm]; the range of the spot swing amplitude A1 of the first weld is [0.2mm, 1.6mm]; the range of the spot swing frequency of the first weld is [60Hz, 250Hz]; The power of the given second weld is in the range of [500W, 4000W]; the welding speed of the second weld is in the range of [60mm / s, 300mm / s]; the spot size of the laser beam of the second weld acting on the door material is [1mm, 3mm]; the spot swing amplitude A2 of the second weld is in the range of A1+[0, 2mm]; the spot swing frequency of the second weld is in the range of [100Hz, 500Hz]; the length of the second weld at the beginning and end is longer than that of the first weld by [0, 5mm] respectively.

9. The laser reflow welding method according to claim 7, characterized in that: When at least two layers of door materials are made of ferrous metal, the power of the first weld is in the range of [1500W, 5000W]; the welding speed of the first weld is in the range of [20mm / s, 200mm / s]; the spot size of the laser beam of the first weld acting on the door material is [0.2mm, 1mm]; the power of the second weld is in the range of [1000W, 3000W]; the welding speed of the second weld is in the range of [50mm / s, 300mm / s]; the spot size of the laser beam of the second weld acting on the door material is [0.6mm, 3mm]; the length of the second weld at the beginning and the end is longer than that of the first weld by [0, 5mm] respectively.

10. A laser reflow welding method according to any one of claims 8 or 9, characterized in that: The power of the laser beam of the first weld is greater than the power of the laser beam of the second weld, and the penetration depth of the first weld is greater than the penetration depth of the second weld; the spot size of the second weld is greater than the spot size of the first weld.

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