Laser end welding method for restraining instability based on gas constraint molten pool

Abstract

The invention relates to a laser end welding method for restraining instability based on a gas constraint molten pool, and belongs to the technical field of laser welding. According to the technical scheme, a coaxial shielding gas nozzle is arranged on the outer side of a laser beam, and shielding gas is introduced; in the welding direction, a front shielding gas nozzle and a rear shielding gas nozzle are arranged on the front side and the rear side of a laser beam correspondingly, and shielding gas is introduced into the front shielding gas nozzle and the rear shielding gas nozzle; protective gas is directly blown to the molten pool through the coaxial protective gas nozzle, the front protective gas nozzle and the rear protective gas nozzle according to preset parameters, and a gas stable field is formed around the molten pool. By optimizing the flowing mode and flow distribution of the protective gas, forced constraint and accurate regulation and control of the shape and flowing behavior of the molten pool are achieved, dynamic instability caused by intense oscillation or insufficient flowing of the molten pool is effectively restrained, and therefore the defects of splashing and air holes are reduced, and the stable welding speed is increased to more than two times that of the prior art.

Description

Technical Field

[0001] This invention relates to a laser end-welding method based on gas-confined molten pool to suppress instability, specifically a laser end-welding method that uses the morphology of a gas-confined molten pool to suppress instability and achieve high-speed welding, belonging to the field of laser welding technology. Background Technology

[0002] As a core component of transformer cooling systems, plate-type radiators are widely used in power, industry, transportation, and special environments due to their excellent heat dissipation and compact structure. Among these, the end weld of the radiator fins is a critical weld affecting production efficiency and product quality, characterized by high workload and stringent forming requirements. Currently, the mainstream end welding process is TIG welding, but TIG welding has several shortcomings in end joint applications: it requires extremely strict workpiece cleanliness, and poor cleaning will seriously affect weld quality; the penetration depth is shallow and the welding speed is low, with existing end welding speeds for plate-type radiators for transformers typically below 0.9 m / min, and in some cases even below 0.7 m / min, resulting in low welding productivity; furthermore, due to the limited current-carrying capacity of the tungsten electrode, high current conditions easily cause the tungsten electrode to melt and evaporate, contaminating the weld, and the high cost of inert gas further increases production costs. More importantly, TIG welding is sensitive to the end gap, and the molten metal tends to flow downwards, resulting in poor weld formation or even failure to weld. Furthermore, the high heat input leads to significant workpiece deformation after welding, affecting product quality. Therefore, the industry urgently needs to develop efficient and high-quality new welding methods to address current production bottlenecks.

[0003] Compared to TIG welding, laser welding exhibits significant technological advantages due to its highly concentrated energy. For end joints with a thickness of less than 3mm, laser welding speed can be 3 to 5 times faster than TIG welding, significantly reducing the processing time per piece. Simultaneously, laser beam welding offers high precision, allowing for accurate control of the molten pool morphology, resulting in a smooth and flat weld surface. This reduces subsequent processing steps and ensures consistency in the appearance and dimensions of the joint. However, laser welding of heat sink end joints is extremely sensitive to assembly precision, especially in thin-plate end joints. Ensuring tight fit between plates and process stability becomes a key technical challenge. Furthermore, laser welding is prone to producing keyhole-type pores, affecting the heat sink's sealing performance and quality. To address these issues, Chinese patent application CN201510990030.6 proposes a laser welding method for synchronous rolling of thin-plate end joints. This method uses rollers on both sides of the weld to achieve rolling alignment, thereby suppressing assembly gaps. However, this solution has complex equipment control and weak tolerance. It is prone to defects such as discontinuous forming and uneven surface during high-speed welding. Furthermore, due to the limitations of the roller structure, it is difficult to apply to the end welding requirements of special structures such as plate heat sinks.

[0004] Based on existing laser welding technology, the applicant previously proposed a "laser termination welding method for plate heat sinks for transformers" (Chinese patent application number CN202511316012X). This method forms a stable molten pool in the weld area by oscillating the laser beam, effectively improving welding speed and weld formation consistency, and avoiding process instability problems caused by high-speed conditions. However, this technology still has limitations: large defocusing leads to insufficient laser energy density, making it impossible to form a stable molten pool at higher welding speeds; at the same time, this technology limits the power to below 4kW, and further increasing the power will cause increased molten pool fluctuations, both of which limit further increases in welding speed. In addition, when the misalignment of the workpiece end faces is too large, the height of the molten pools on the two plates is inconsistent, making it difficult for the molten pool metal to converge towards the center during higher-speed welding, resulting in formation difficulties. Summary of the Invention

[0005] The purpose of this invention is to provide a laser end-welding method based on gas-confined molten pool instability suppression. By setting multiple sets of shielding gases above the molten pool and precisely designing their flow patterns, the molten pool morphology and flow behavior are forcibly constrained and actively controlled, thereby stabilizing the molten pool shape. This method achieves high-speed welding while ensuring good weld surface formation and maintaining stable and reliable weld quality during long-term continuous operation, thus solving the problems existing in the prior art.

[0006] The technical solution of this invention is: A laser termination welding method based on gas-confined molten pool instability suppression involves aligning the ends of two workpieces to be welded to form bevel-free end faces. Laser welding is performed at the transverse welding position of the end faces, where the laser beam melts the end faces to form a molten pool, which solidifies to form the termination weld. A coaxial shielding gas nozzle is provided outside the laser beam and a shielding gas is supplied through it. Along the welding direction, a front shielding gas nozzle and a rear shielding gas nozzle are respectively set on the front and rear sides of the laser beam, and shielding gas is supplied through both nozzles. The shielding gas is blown directly onto the molten pool through a coaxial shielding gas nozzle, a front shielding gas nozzle, and a rear shielding gas nozzle according to preset parameters, forming a stable gas field around the molten pool. This achieves forced constraint and precise control over the morphology and flow behavior of the molten pool, suppressing dynamic instability caused by intense oscillations or insufficient flow in the molten pool under high-speed welding conditions, thereby realizing high-speed laser end welding. The power of the laser beam is 4kW to 8kW, the defocusing amount is +20mm to +120mm, and the welding speed is 2m / min to 8m / min.

[0007] Further, the preset parameters include: the angle α between the centerline of the coaxial shielding gas nozzle and the end face to be welded is 45° to 135°; the angle β between the centerline of the front shielding gas nozzle and the centerline of the coaxial shielding gas nozzle is 20° to 60°; the angle γ between the centerline of the rear shielding gas nozzle and the centerline of the coaxial shielding gas nozzle is 20° to 60°; the distance h1 between the lower edge of the front shielding gas nozzle and the end face to be welded is 5 to 20 mm; the distance h2 between the lower edge of the coaxial shielding gas nozzle and the end face to be welded is 5 to 25 mm; and the distance h2 between the lower edge of the rear shielding gas nozzle and the end face to be welded is... The distance h3 between the ends to be welded is 10-30 mm; the gas flow rate of the protective gas in the pre-mounted protective gas nozzle is 0-50 m / s; the gas flow rate of the protective gas in the coaxial protective gas nozzle is 0-10 m / s; the gas flow rate of the protective gas in the post-mounted protective gas nozzle is 50-150 m / s; the flow rates of the protective gas in the pre-mounted, post-mounted, and coaxial protective gas nozzles satisfy the following relationship: the flow rate of the protective gas in the post-mounted protective gas nozzle ≥ the flow rate of the protective gas in the pre-mounted protective gas nozzle ≥ the flow rate of the protective gas in the coaxial protective gas nozzle.

[0008] Furthermore, there is only one front protective gas nozzle and one rear protective gas nozzle, namely, front protective gas nozzle two and rear protective gas nozzle one.

[0009] Furthermore, there are two front protective gas nozzles and two rear protective gas nozzles. The two front protective gas nozzles are designated as front protective gas nozzle one and front protective gas nozzle two, and the two rear protective gas nozzles are designated as rear protective gas nozzle one and rear protective gas nozzle two.

[0010] Furthermore, the distance d1 between the extended lines of the center lines of the second pre-mounted protective gas nozzle and the coaxial protective gas nozzle on the end face to be welded is 2mm to 15mm, and the distance d2 between the extended lines of the center lines of the first rear-mounted protective gas nozzle and the coaxial protective gas nozzle on the end face to be welded is 0mm to 10mm.

[0011] Furthermore, the spot of the laser beam oscillates at high speed on the end face to be welded according to a predetermined laser trajectory, forming a laser beam spot trajectory. The laser beam spot trajectory can be circular, elliptical, straight, or rectangular. The width D1 of the laser beam spot trajectory perpendicular to the welding direction on the weld surface is 0-10 mm, and the width D2 of the laser beam spot trajectory along the welding direction on the weld surface is 0-10 mm. The laser oscillation frequency is 5 Hz to 300 Hz.

[0012] Furthermore, the protective gas is argon, a mixture of argon and CO2, CO2, or nitrogen, and the gas pressure is 0.2~0.8 MPa.

[0013] Furthermore, the thickness of the first workpiece to be welded is W1, the thickness of the second workpiece to be welded is W2, and the thickness of the plate material W = W1 + W2 is 1mm to 5mm, so there is no need to set a bevel.

[0014] The beneficial effects of this invention are as follows: Based on galvanometer-oscillating laser welding, this invention introduces a technique of forcibly constraining the molten pool morphology with protective gas, significantly improving the speed and forming quality of laser end-welding. By optimizing the flow pattern and flow distribution of the protective gas, this invention forms a stable gas field around the molten pool, achieving forced constraint and precise control of the molten pool morphology and flow behavior. This effectively suppresses dynamic instability caused by intense molten pool oscillation or insufficient flow, thereby reducing spatter and porosity defects and increasing the stable welding speed to more than twice that of existing technologies. Simultaneously, this invention exhibits excellent tolerance to assembly errors, resulting in a smooth, uniform weld surface, providing a new path for the efficient and high-quality production of plate-type heat sinks. Attached Figure Description

[0015] Figure 1 This is a front view illustrating the principle of the invention; Figure 2 This is a top view illustrating the principle of the invention; Figure 3 This is a side view illustrating the principle of the invention; Figure 4 This is a photograph of the weld surface in Embodiment 1 of the present invention; Figure 5 This is a macroscopic photograph of the weld cross-section in Embodiment 1 of the present invention; Figure 6 This is a photograph of the weld surface in Embodiment 2 of the present invention; Figure 7 This is a macroscopic photograph of the weld cross-section in Embodiment 2 of the present invention; Figure 8 This is a photograph of the weld surface in Embodiment 3 of the present invention; Figure 9 This is a macroscopic photograph of the weld cross-section in Embodiment 3 of the present invention; Figure 10 This is a photograph of the weld surface in Embodiment 4 of the present invention; Figure 11 This is a macroscopic photograph of the weld cross-section in Embodiment 4 of the present invention; Figure 12 This is a photograph of the weld surface in Embodiment 5 of the present invention; Figure 13 This is a macroscopic photograph of the weld cross-section in Embodiment 5 of the present invention; Figure 14 This is a photograph of the weld surface in Embodiment Six of the present invention; Figure 15 This is a macroscopic photograph of the weld cross-section in Embodiment Six of the present invention; Figure 16 This is a photograph of the weld surface in Embodiment 7 of the present invention; Figure 17This is a macroscopic photograph of the weld cross-section in Embodiment 7 of the present invention; Figure 18 This is a photograph of the weld surface in Embodiment 8 of the present invention; Figure 19 This is a macroscopic photograph of the weld cross-section in Embodiment 8 of the present invention; Figure 20 This is a photograph of the weld surface in Embodiment 9 of the present invention; Figure 21 This is a macroscopic photograph of the weld cross-section in Embodiment 9 of the present invention; Figure 22 This is a photograph of the weld surface in Embodiment 10 of the present invention; Figure 23 This is a macroscopic photograph of the weld cross-section in Embodiment 10 of the present invention; In the figure: 1. Front protective gas nozzle 1, 2. Front protective gas nozzle 2, 3. Rear protective gas nozzle 1, 4. Rear protective gas nozzle 2, 5. Coaxial protective gas nozzle, 6. Laser beam, 7. Laser trajectory, 8. Molten pool, 9. Welded workpiece 1, 10. Workpiece 2, 11. Detailed Implementation

[0016] The invention will be further illustrated below with reference to the accompanying drawings and examples.

[0017] See attached document Figure 1 , 2 3. A laser termination welding method based on gas-confined molten pool instability suppression, wherein the ends of workpiece 10 and workpiece 11 are aligned to form a bevel-free end face for welding, and laser welding is performed at the horizontal welding position of the end face. The laser beam 6 melts the end face to form a molten pool 8, and after solidification, a termination weld 9 is formed; a coaxial shielding gas nozzle 5 is provided on the outside of the laser beam 6 and a shielding gas is introduced; along the welding direction, a front shielding gas nozzle and a rear shielding gas nozzle are respectively set on the front and rear sides of the laser beam 6, and both the front and rear shielding gas nozzles are filled with shielding gas. Shielding gas; the shielding gas is blown directly onto the molten pool 8 through the coaxial shielding gas nozzle 5, the front shielding gas nozzle and the rear shielding gas nozzle according to preset parameters, forming a stable gas field around the molten pool 8, realizing forced constraint and precise control of the morphology and flow behavior of the molten pool 8, suppressing dynamic instability caused by intense oscillation or insufficient flow of the molten pool 8 under high-speed welding conditions, thereby realizing high-speed laser end welding; the power of the laser beam 6 is 4kW~8kW, the defocusing amount is +20mm~+120mm, and the welding speed is 2m / min~8m / min.

[0018] In the embodiment: the angle between the centerline of the coaxial shielding gas nozzle 5 and the end face to be welded is α; the angle between the centerline of the front shielding gas nozzle and the centerline of the coaxial shielding gas nozzle 5 is β; the angle between the centerline of the rear shielding gas nozzle and the centerline of the coaxial shielding gas nozzle 5 is γ; the distance from the lower edge of the coaxial shielding gas nozzle 5 to the end face to be welded is h2; the distance from the lower edge of the rear shielding gas nozzle to the end face to be welded is h3; the distance between the extension lines of the centerlines of the second front shielding gas nozzle 2 and the coaxial shielding gas nozzle 5 on the end face to be welded is d1; the distance between the extension lines of the centerlines of the first rear shielding gas nozzle 3 and the coaxial shielding gas nozzle 5 on the end face to be welded is d2; the width of the laser beam spot trajectory perpendicular to the welding direction on the weld surface is D1; ​​the width of the laser beam spot trajectory along the welding direction on the weld surface is D2; the thickness of the workpiece 10 to be welded is W1; the thickness of the second workpiece 11 to be welded is W2.

[0019] Example 1

[0020] The thicknesses W1 and W2 of the workpieces to be welded 10 and 11 are both 1mm. A protective gas nozzle is set on each side of the laser beam 6, namely the front protective gas nozzle 2 and the rear protective gas nozzle 3. Protective gas is passed through both the protective gas nozzle 2 and the rear protective gas nozzle 3.

[0021] The angle α between the centerline of the coaxial shielding gas nozzle 5 and the end face to be welded is 70°; the angle β between the centerline of the front shielding gas nozzle 2 and the centerline of the coaxial shielding gas nozzle 5 is 20°; and the angle γ between the centerline of the rear shielding gas nozzle 3 and the centerline of the coaxial shielding gas nozzle 5 is 20°. The distance h1 between the lower edge of the front shielding gas nozzle 2 and the end face to be welded is 12mm; the distance h2 between the lower edge of the coaxial shielding gas nozzle 5 and the end face to be welded is 15mm; and the distance h2 between the lower edge of the rear shielding gas nozzle 3 and the end face to be welded is... The distance h3 between the welding ends is 18mm; the gas flow rate of the front shielding gas nozzle 2 is 5m / s; the gas flow rate of the shielding gas in the coaxial shielding gas nozzle 5 is 5m / s; the gas flow rate of the shielding gas in the rear shielding gas nozzle 3 is 50m / s; the distance d1 between the extended lines of the center lines of the front shielding gas nozzle 2 and the coaxial shielding gas nozzle 5 on the welding end face is 5mm; and the distance d2 between the extended lines of the center lines of the rear shielding gas nozzle 3 and the coaxial shielding gas nozzle 5 on the welding end face is 3mm.

[0022] The laser beam spot trajectory is circular with a diameter of 1 mm. That is, the width D1 of the laser beam spot trajectory on the weld surface perpendicular to the welding direction is 1 mm, and the width D2 of the laser beam spot trajectory on the weld surface along the welding direction is 1 mm. The laser oscillation frequency is 50 Hz.

[0023] The laser beam power is 4kW, the defocusing distance is +40mm, and the welding speed is 3m / min.

[0024] The protective gas is argon, with a pressure of 0.4 MPa.

[0025] Welding effect as Figure 4 , Figure 5 As shown.

[0026] Example 2

[0027] The thicknesses W1 and W2 of the workpieces to be welded 10 and 11 are both 1mm. Two protective gas nozzles are set on each side of the laser beam 6, namely front protective gas nozzle 1 and front protective gas nozzle 2, and rear protective gas nozzle 3 and rear protective gas nozzle 4, all of which are filled with protective gas.

[0028] The angle α between the centerline of the coaxial shielding gas nozzle 5 and the end face to be welded is 60°; the angle β between the centerline of the front shielding gas nozzle 2 and the centerline of the coaxial shielding gas nozzle 5 is 25°; the angle γ between the centerline of the rear shielding gas nozzle 3 and the centerline of the coaxial shielding gas nozzle 5 is 25°; the distance h1 between the lower edge of the front shielding gas nozzle 2 and the end face to be welded is 15mm; the distance h2 between the lower edge of the coaxial shielding gas nozzle 5 and the end face to be welded is 18mm; the distance h3 between the lower edge of the rear shielding gas nozzle 3 and the end face to be welded is 20mm; the shielding gas inside the front shielding gas nozzle 1... The gas flow rate is 8 m / s. The gas flow rate of the protective gas in the pre-mounted protective gas nozzle 2 is 10 m / s. The gas flow rate of the protective gas in the coaxial protective gas nozzle 5 is 5 m / s. The gas flow rate of the protective gas in the rear protective gas nozzle 3 is 100 m / s. The gas flow rate of the protective gas in the rear protective gas nozzle 4 is 120 m / s. The distance d1 between the extended lines of the center lines of the pre-mounted protective gas nozzle 2 and the coaxial protective gas nozzle 5 on the end face to be welded is 3 mm. The distance d2 between the extended lines of the center lines of the rear protective gas nozzle 3 and the coaxial protective gas nozzle 5 on the end face to be welded is 5 mm.

[0029] The laser beam spot trajectory is elliptical. The width D1 of the laser beam spot trajectory on the weld surface perpendicular to the welding direction is 1.5 mm, and the width D2 of the laser beam spot trajectory on the weld surface along the welding direction is 1 mm. The laser oscillation frequency is 50 Hz.

[0030] The laser beam power is 5kW, the defocusing distance is +50mm, and the welding speed is 5m / min.

[0031] The protective gas is argon, with a pressure of 0.4 MPa.

[0032] Welding effect as Figure 6 , Figure 7 As shown.

[0033] Example 3

[0034] The thicknesses W1 and W2 of the workpieces to be welded 10 and 11 are both 1mm. Two protective gas nozzles are set on each side of the laser beam 6, namely front protective gas nozzle 1 and front protective gas nozzle 2, and rear protective gas nozzle 3 and rear protective gas nozzle 4, all of which are filled with protective gas.

[0035] The laser beam spot trajectory is rectangular. The width D1 of the laser beam spot trajectory on the weld surface perpendicular to the welding direction is 1.5 mm, and the width D2 of the laser beam spot trajectory on the weld surface along the welding direction is 1 mm. The laser oscillation frequency is 80 Hz.

[0036] The laser beam power is 6kW, the defocusing distance is +60mm, and the welding speed is 6m / min.

[0037] The remaining parameters are the same as in Example 2.

[0038] Welding effect as Figure 8 , Figure 9 As shown.

[0039] Example 4

[0040] The thicknesses W1 and W2 of the workpieces to be welded 10 and 11 are both 1mm. A protective gas nozzle is set before and after the laser beam 6, namely the front protective gas nozzle 2 and the rear protective gas nozzle 3, both of which are filled with protective gas.

[0041] The laser beam spot trajectory is rectangular. The width D1 of the laser beam spot trajectory on the weld surface perpendicular to the welding direction is 1.5 mm, and the width D2 of the laser beam spot trajectory on the weld surface along the welding direction is 3 mm. The laser oscillation frequency is 80 Hz.

[0042] The laser beam power is 6kW, the defocusing distance is +50mm, and the welding speed is 5m / min.

[0043] The remaining parameters are the same as in Example 1.

[0044] Welding effect as Figure 10 , Figure 11 As shown.

[0045] Example 5

[0046] The thicknesses W1 and W2 of the workpieces to be welded 10 and 11 are both 1mm. Two protective gas nozzles are set on each side of the laser beam 6, namely front protective gas nozzle 1 and front protective gas nozzle 2, and rear protective gas nozzle 3 and rear protective gas nozzle 4, all of which are filled with protective gas.

[0047] The laser beam spot trajectory is linear. The width D1 of the laser beam spot trajectory on the weld surface perpendicular to the welding direction is 0, and the width D2 of the laser beam spot trajectory on the weld surface along the welding direction is 1.5 mm. The laser oscillation frequency is 100 Hz.

[0048] The laser beam power is 8kW, the defocusing distance is +20mm, and the welding speed is 8m / min.

[0049] The remaining parameters are the same as in Example 2.

[0050] Welding effect as Figure 12 , Figure 13 As shown.

[0051] Example 6

[0052] The thicknesses W1 and W2 of the workpieces to be welded 10 and 11 are both 1mm. Two protective gas nozzles are set on each side of the laser beam 6, namely front protective gas nozzle 1 and front protective gas nozzle 2, and rear protective gas nozzle 3 and rear protective gas nozzle 4, all of which are filled with protective gas.

[0053] The angle α between the centerline of the coaxial shielding gas nozzle 5 and the end face to be welded is 45°; the angle β between the centerline of the front shielding gas nozzle 2 and the centerline of the coaxial shielding gas nozzle 5 is 25°; the angle γ between the centerline of the rear shielding gas nozzle 3 and the centerline of the coaxial shielding gas nozzle 5 is 25°; the distance h1 between the lower edge of the front shielding gas nozzle 2 and the end face to be welded is 10mm; the distance h2 between the lower edge of the coaxial shielding gas nozzle 5 and the end face to be welded is 13mm; the distance h3 between the lower edge of the rear shielding gas nozzle 3 and the end face to be welded is 15mm; the gas flow rate of the shielding gas inside the front shielding gas nozzle 1 is... The gas flow rate of the protective gas in the front protective gas nozzle 2 is 20 m / s; the gas flow rate of the protective gas in the coaxial protective gas nozzle 5 is 10 m / s; the gas flow rate of the protective gas in the rear protective gas nozzle 3 is 130 m / s; the gas flow rate of the protective gas in the rear protective gas nozzle 4 is 150 m / s; the distance d1 between the extension lines of the center lines of the front protective gas nozzle 2 and the coaxial protective gas nozzle 5 on the end face to be welded is 8 mm; the distance d2 between the extension lines of the center lines of the rear protective gas nozzle 3 and the coaxial protective gas nozzle 5 on the end face to be welded is 10 mm.

[0054] The remaining parameters are the same as in Example 2.

[0055] Welding effect as Figure 14 , Figure 15 As shown.

[0056] Example 7

[0057] The thicknesses W1 and W2 of the workpieces to be welded 10 and 11 are both 1.2 mm. A protective gas nozzle is set on each side of the laser beam 6, namely the front protective gas nozzle 2 and the rear protective gas nozzle 3, both of which are filled with protective gas.

[0058] The laser beam spot trajectory is circular. The width D1 of the laser beam spot trajectory on the weld surface perpendicular to the welding direction is 1.5 mm, and the width D2 of the laser beam spot trajectory on the weld surface along the welding direction is 1.5 mm. The laser oscillation frequency is 80 Hz.

[0059] The laser beam power is 5kW, the defocusing distance is +40mm, and the welding speed is 5m / min.

[0060] The remaining parameters are the same as in Example 1.

[0061] Welding effect as Figure 16 , Figure 17 As shown.

[0062] Example 8

[0063] The thicknesses W1 and W2 of the workpieces to be welded 10 and 11 are both 1.2 mm. Two protective gas nozzles are set on each side of the laser beam 6, namely front protective gas nozzle 1 and front protective gas nozzle 2, and rear protective gas nozzle 3 and rear protective gas nozzle 4, all of which are filled with protective gas.

[0064] The laser beam spot trajectory is circular. The width D1 of the laser beam spot trajectory on the weld surface perpendicular to the welding direction is 1.5 mm, and the width D2 of the laser beam spot trajectory on the weld surface along the welding direction is 1.5 mm. The laser oscillation frequency is 150 Hz.

[0065] The laser beam power is 6kW, the defocusing distance is +80mm, and the welding speed is 6m / min.

[0066] The remaining parameters are the same as in Example 1.

[0067] Welding effect as Figure 18 , Figure 19 As shown.

[0068] Example 9

[0069] The thicknesses W1 and W2 of the workpieces to be welded 10 and 11 are both 2mm. One protective gas nozzle is set on each side of the laser beam 6, namely the front protective gas nozzle 2 and the rear protective gas nozzle 3, and both are filled with protective gas.

[0070] The angle α between the centerline of the coaxial shielding gas nozzle 5 and the end face to be welded is 45°; the angle β between the centerline of the front shielding gas nozzle 2 and the centerline of the coaxial shielding gas nozzle 5 is 20°; the angle γ between the centerline of the rear shielding gas nozzle 3 and the centerline of the coaxial shielding gas nozzle 5 is 20°; the distance h1 from the lower edge of the front shielding gas nozzle 2 to the end face to be welded is 15mm; the distance h2 from the lower edge of the coaxial shielding gas nozzle 5 to the end face to be welded is 18mm; the distance h2 from the lower edge of the rear shielding gas nozzle 3 to the end face to be welded is... The distance from h3 is 23mm; the gas flow rate of the protective gas in the front protective gas nozzle 2 is 50m / s; the gas flow rate of the protective gas in the coaxial protective gas nozzle 5 is 10m / s; the gas flow rate of the protective gas in the rear protective gas nozzle 3 is 130m / s; the distance d1 between the extension lines of the center lines of the front protective gas nozzle 2 and the coaxial protective gas nozzle 5 on the end face to be welded is 4mm; the distance d2 between the extension lines of the center lines of the rear protective gas nozzle 3 and the coaxial protective gas nozzle 5 on the end face to be welded is 3mm.

[0071] The laser beam spot trajectory is circular. The width D1 of the laser beam spot trajectory on the weld surface perpendicular to the welding direction is 1.5 mm, and the width D2 of the laser beam spot trajectory on the weld surface along the welding direction is 1.5 mm. The laser oscillation frequency is 150 Hz.

[0072] The laser beam power is 7kW, the defocusing distance is +80mm, and the welding speed is 6m / min.

[0073] The protective gas is carbon dioxide at a pressure of 0.6 MPa.

[0074] Welding effect as Figure 20 , Figure 21 As shown.

[0075] Example 10

[0076] The thicknesses W1 and W2 of the workpieces to be welded 10 and 11 are both 2.5 mm. Two protective gas nozzles are set on each side of the laser beam 6, namely front protective gas nozzle 1 and front protective gas nozzle 2, and rear protective gas nozzle 3 and rear protective gas nozzle 4, all of which are filled with protective gas.

[0077] The angle α between the centerline of the coaxial shielding gas nozzle 5 and the end face to be welded is 45°; the angle β between the centerline of the front shielding gas nozzle 2 and the centerline of the coaxial shielding gas nozzle 5 is 20°; the angle γ between the centerline of the rear shielding gas nozzle 3 and the centerline of the coaxial shielding gas nozzle 5 is 20°; the distance h1 between the lower edge of the front shielding gas nozzle 2 and the end face to be welded is 15mm; the distance h2 between the lower edge of the coaxial shielding gas nozzle 5 and the end face to be welded is 18mm; the distance h3 between the lower edge of the rear shielding gas nozzle 3 and the end face to be welded is 23mm; the gas flow of the shielding gas inside the front shielding gas nozzle 1... The gas flow rate is 30 m / s. The gas flow rate of the protective gas in the front protective gas nozzle 2 is 50 m / s. The gas flow rate of the protective gas in the coaxial protective gas nozzle 5 is 10 m / s. The gas flow rate of the protective gas in the rear protective gas nozzle 3 is 130 m / s. The gas flow rate of the protective gas in the rear protective gas nozzle 4 is 150 m / s. The distance d1 between the extended lines of the center lines of the front protective gas nozzle 2 and the coaxial protective gas nozzle 5 on the end face to be welded is 12 mm. The distance d2 between the extended lines of the center lines of the rear protective gas nozzle 3 and the coaxial protective gas nozzle 5 on the end face to be welded is 8 mm.

[0078] The laser beam spot trajectory is circular. The width D1 of the laser beam spot trajectory on the weld surface perpendicular to the welding direction is 1.5 mm, and the width D2 of the laser beam spot trajectory on the weld surface along the welding direction is 1.5 mm. The laser oscillation frequency is 300 Hz.

[0079] The laser beam power is 8kW, the defocusing distance is +50mm, and the welding speed is 7m / min.

[0080] The protective gas is carbon dioxide at a pressure of 0.8 MPa.

[0081] Welding effect as Figure 22 , Figure 23 As shown.

[0082] This invention proposes a laser end-welding method that utilizes protective gas confinement and controls the morphology and flow behavior of the molten pool 8 to suppress instability of the molten pool 8 under high-speed welding conditions, thereby avoiding welding spatter and porosity defects and achieving higher welding speeds. This invention achieves high-quality, highly consistent weld formation 9 under higher speed conditions, exhibits good adaptability to assembly errors, and breaks through the bottleneck of welding speed in existing processes. It provides a new technical path for the high-efficiency, high-quality, large-scale production of plate-type heat sinks for transformers.

[0083] This invention addresses the problems of insufficient energy density due to large defocusing in existing galvanometer-oscillating laser welding, molten pool fluctuations caused by power increases, and difficulties in metal convergence and forming due to excessive end-face misalignment during high-speed welding. Building upon galvanometer-oscillating laser welding, this invention introduces a technique of forcibly constraining the molten pool morphology with a protective gas, significantly improving the speed and forming quality of laser-welded joints. By optimizing the flow pattern and flow distribution of the protective gas, this invention creates a stable gas field around the molten pool 8, achieving forced constraint and precise control over the morphology and flow behavior of the molten pool 8. This effectively suppresses dynamic instability caused by intense oscillations or insufficient flow in the molten pool 8, thereby reducing spatter and porosity defects and increasing the stable welding speed to more than twice that of existing technologies. Simultaneously, this invention exhibits excellent tolerance for assembly errors, resulting in a smooth and consistent weld surface 9, providing a new path for the efficient and high-quality production of plate-type heat sinks.

Claims

1. A laser termination welding method based on gas-confined molten pool instability suppression, wherein the ends of workpiece one (10) and workpiece two (11) are aligned to form a weldable end face without bevel, and laser welding is performed at the horizontal welding position of the end face, wherein the laser beam (6) melts the end face to form a molten pool (8), and after solidification, a termination weld (9) is formed; characterized in that: The laser beam (6) is equipped with a coaxial shielding gas nozzle (5) and is filled with shielding gas. Along the welding direction, a front shielding gas nozzle and a rear shielding gas nozzle are respectively set on the front and rear sides of the laser beam (6). The front shielding gas nozzle and the rear shielding gas nozzle are filled with shielding gas. The shielding gas is blown directly onto the molten pool (8) through the coaxial shielding gas nozzle (5), the front shielding gas nozzle and the rear shielding gas nozzle with preset parameters. A gas stabilization field is formed around the molten pool (8) to achieve forced constraint and precise control of the morphology and flow behavior of the molten pool (8). This suppresses the dynamic instability caused by the intense oscillation or insufficient flow of the molten pool (8) under high-speed welding conditions, thereby realizing high-speed laser end welding. The power of the laser beam (6) is 4kW to 8kW, the defocusing amount is +20mm to +120mm, and the welding speed is 2m / min to 8m / min.

2. The laser termination welding method based on gas-confined molten pool instability suppression according to claim 1, characterized in that: The preset parameters include: the angle α between the centerline of the coaxial protective gas nozzle (5) and the end face to be welded is 45° to 135°; the angle β between the centerline of the front protective gas nozzle and the centerline of the coaxial protective gas nozzle (5) is 20° to 60°; the angle γ between the centerline of the rear protective gas nozzle and the centerline of the coaxial protective gas nozzle (5) is 20° to 60°; the distance h1 between the lower edge of the front protective gas nozzle and the end face to be welded is 5 to 20 mm; the distance h2 between the lower edge of the coaxial protective gas nozzle (5) and the end face to be welded is 5 to 25 mm; and the distance h2 between the lower edge of the rear protective gas nozzle and the end face to be welded is 5 to 25 mm. The distance h3 between the weld ends is 10-30mm; the gas flow rate of the protective gas in the front protective gas nozzle is 0-50m / s; the gas flow rate of the protective gas in the coaxial protective gas nozzle (5) is 0-10m / s; the gas flow rate of the protective gas in the rear protective gas nozzle is 50-150m / s; the flow rates of the protective gas in the front protective gas nozzle, the rear protective gas nozzle and the coaxial protective gas nozzle (5) satisfy the following relationship: the flow rate of the protective gas in the rear protective gas nozzle ≥ the flow rate of the protective gas in the front protective gas nozzle ≥ the flow rate of the protective gas in the coaxial protective gas nozzle (5).

3. The laser termination welding method based on gas-confined molten pool instability suppression according to claim 2, characterized in that: There is one front protective gas nozzle and one rear protective gas nozzle, namely front protective gas nozzle two (2) and rear protective gas nozzle one (3).

4. The laser termination welding method based on gas-confined molten pool instability suppression according to claim 2, characterized in that: There are two front protective gas nozzles and two rear protective gas nozzles. The two front protective gas nozzles are front protective gas nozzle one (1) and front protective gas nozzle two (2), and the two rear protective gas nozzles are rear protective gas nozzle one (3) and rear protective gas nozzle two (4).

5. A laser termination welding method based on gas-confined molten pool instability suppression according to claim 3 or 4, characterized in that: The distance d1 between the extended lines of the center lines of the pre-mounted protective gas nozzle (2) and the coaxial protective gas nozzle (5) on the end face to be welded is 2mm to 15mm, and the distance d2 between the extended lines of the center lines of the rear protective gas nozzle (3) and the coaxial protective gas nozzle (5) on the end face to be welded is 0mm to 10mm.

6. A laser termination welding method based on gas-confined molten pool instability suppression according to claim 1 or 2, characterized in that: The spot of the laser beam (6) oscillates at high speed on the end face to be welded according to the predetermined laser trajectory (7) to form a laser beam spot trajectory. The laser beam spot trajectory is circular, elliptical, straight or rectangular. The width D1 of the laser beam spot on the weld surface perpendicular to the welding direction is 0 to 10 mm, and the width D2 of the laser beam spot on the weld surface along the welding direction is 0 to 10 mm. The laser oscillation frequency is 5 Hz to 300 Hz.

7. A laser termination welding method based on gas-confined molten pool instability suppression according to claim 1 or 2, characterized in that: The protective gas is argon, a mixture of argon and CO2, CO2, or nitrogen, and the gas pressure is 0.2–0.8 MPa.

8. A laser termination welding method based on gas-confined molten pool instability suppression according to claim 1 or 2, characterized in that: The thickness of the workpiece to be welded (10) is W1, the thickness of the workpiece to be welded (11) is W2, and the thickness of the plate W = W1 + W2 is 1mm to 5mm, so there is no need to set a bevel.

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