Laser termination welding method for sheet-type radiator of transformer

Abstract

The present application relates to a kind of laser termination welding methods of sheet type radiator for transformer, belong to the laser welding technical field of sheet type radiator for transformer.The technical scheme is: the thickness of the workpiece to be welded one is W1, the thickness of the workpiece to be welded two is W2;The end of the workpiece to be welded one and the workpiece to be welded two are aligned to form the end face to be welded, and the thickness of the end face to be welded is W, W=W1+W2;The end face to be welded has no groove;Laser welding is carried out at the transverse welding position of the end face to be welded, the spot of laser beam is swung at high speed according to predetermined track on the end face to be welded, to form laser beam spot track, and the laser defocusing amount is positive;Laser melts the end face to be welded to form laser molten pool, and forms termination weld after solidification.The present application melts the end face of heat dissipation sheet by swinging laser beam and forms stable molten pool, combined with the parameter of large defocusing amount laser beam, significantly improves the tolerance to assembly gap, and high-quality end face welding of heat dissipation sheet can be realized without the aid of pressing wheel, which improves production efficiency while ensuring excellent welding quality.

Description

TECHNICAL FIELD

[0001] The present application relates to a laser termination welding method for sheet-type radiators of transformers, and belongs to the technical field of laser welding of sheet-type radiators of transformers. BACKGROUND

[0002] The sheet-type radiator of a transformer is a key component for cooling the transformer, mainly composed of radiating fins and a collecting tube, and is widely used in the fields of electric power, industry, transportation and special environments. The sheet-type radiator adopts a self-cooling mode, relies on the circulation of transformer oil between the radiator and the oil tank to achieve efficient heat exchange. The end face weld of the radiating fin is a key weld that affects the production efficiency and product quality of the radiator, and has a large workload and high weld forming requirements. At present, the existing technology mainly adopts the TIG welding process. However, this process has obvious shortcomings: it is sensitive to gaps, the molten pool metal is prone to sag, resulting in poor weld forming or even inability to weld; it is extremely sensitive to the cleanliness of the workpiece, and poor cleaning can seriously affect the weld quality; the penetration is shallow, and the welding speed is low (usually less than 0.7 m / min), resulting in low production efficiency; the heat input is large, and the workpiece deforms greatly after welding, affecting the product quality; the tungsten electrode has limited current-carrying capacity, and a large current can cause the tungsten electrode to melt and contaminate the weld, and the cost of inert gas is relatively high, further increasing the production cost. Therefore, there is an urgent need to develop a new type of welding method with high efficiency and high quality to address the current bottleneck.

[0003] Compared with TIG welding, laser welding has the advantages of high energy density, fast welding speed, and stable process. It can form a deep penetration weld pool instantaneously, achieving efficient "one-step forming" welding. The focusing precision of the laser beam is high, and the heat-affected zone is only 1 / 5-1 / 10 of that of TIG welding. The weld surface is smooth and flat, and no finishing is required to meet the high-precision assembly requirements, significantly reducing the subsequent process and ensuring the consistency of the joint. However, when using laser welding to weld the end joint of the radiating fin, it is extremely sensitive to assembly precision, especially in thin plate end joint, ensuring close contact between the plates and process stability becomes a key technical problem. At the same time, the laser weld is narrow and prone to "spoon hole" porosity, affecting the sealing and quality. In view of this problem, Chinese patent application CN201510990030.6 proposes a laser welding method for synchronous rolling of thin plate end joint, which realizes rolling centering by setting rollers on both sides of the weld to suppress the assembly gap. However, this scheme has complex equipment control and weak tolerance ability, and is prone to defects such as discontinuous forming and uneven surface during high-speed welding. Moreover, due to the limitation of the roller structure, it cannot be applied to the end welding requirements of special structures such as sheet-type radiators. SUMMARY

[0004] The purpose of the present application is to provide a laser butt welding method for sheet-type radiators of transformers, which ensures uniform energy distribution of the laser on the weld by rapidly swinging the laser beam on the butt surface of the plate to achieve the effect of stabilizing the molten pool, while achieving high-speed welding and taking into account the aesthetic surface forming, ensuring stable and reliable weld quality for long-term welding operations; significantly improving the adaptability to assembly gaps, achieving high-quality end welding of the sheet-type radiator fins without the need for real-time compression wheel assistance, greatly reducing the requirements for jig precision and assembly, and being suitable for a wider range of industrial scenarios, solving the above technical problems existing in the prior art.

[0005] The technical solution of the present application is:

[0006] A laser butt welding method for sheet-type radiators of transformers, comprising the following steps:

[0007] The two to-be-welded fins are respectively to-be-welded workpiece one and to-be-welded workpiece two, the thickness of the to-be-welded workpiece one is W1, and the thickness of the to-be-welded workpiece two is W2; the end portions of the to-be-welded workpiece one and the to-be-welded workpiece two are aligned to form a to-be-welded end surface, the thickness of the to-be-welded end surface is W, W=W1+W2; the to-be-welded end surface has no groove; laser welding is performed at the transverse welding position of the to-be-welded end surface, the spot of the laser beam swings at high speed on the to-be-welded end surface according to a predetermined track to form a laser beam spot track, and the laser defocusing amount is positive; the to-be-welded end surface is melted by the laser to form a laser molten pool, and after solidification, an end-welded weld is formed.

[0008] Further, the range of W is 1.5mm-3mm.

[0009] Further, the angle α between the laser beam and the horizontal direction is 0-20°, the angle β between the laser beam and the normal direction of the weld is 0-40°, the laser power is 500W-4000W, and the defocusing amount is +50mm-+150mm.

[0010] Further, the laser beam spot track is of any shape, the track width of the laser beam spot on the weld surface perpendicular to the welding direction is D1, and the range of D1 is: W≥D1≥W-0.6mm; the track width of the laser beam spot on the weld surface along the welding direction is D2, and D2 is 0-3mm, and the laser swinging frequency is 100Hz-300Hz.

[0011] Further, the laser molten pool needs to be protected by gas, the protective gas is a mixture of Ar and CO2, the volume ratio of Ar in the mixed gas is 0-30%, the protective gas pressure is 0.2MPa-0.8MPa; the protective gas flow is 10L / min-40L / min; and the welding speed is 1.5m / min-4m / min.

[0012] The positive effect of the present application: by swinging the laser beam to melt the fin end face and form a stable molten pool, combined with the large defocusing amount laser beam parameters, the tolerance to assembly gap is significantly improved, and high-quality end face welding of the fin can be realized without the aid of a compression wheel, which significantly improves the production efficiency while ensuring excellent welding quality. In addition, the present application can achieve good welding by using a mixed gas containing a small proportion of Ar gas, which significantly reduces the welding cost. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is the principle front view of the present application;

[0014] Figure 2 is the principle top view of the present application;

[0015] Figure 3 is the principle side view of the present application;

[0016] Figure 4 is the weld surface forming photo in embodiment one of the present application;

[0017] Figure 5 is the weld cross-section macro photo in embodiment one of the present application;

[0018] Figure 6 is the weld surface forming photo in embodiment two of the present application;

[0019] Figure 7 is the weld cross-section macro photo in embodiment two of the present application;

[0020] Figure 8 is the weld surface forming photo in embodiment three of the present application;

[0021] Figure 9 is the weld cross-section macro photo in embodiment three of the present application;

[0022] Figure 10 is the weld surface forming photo in embodiment four of the present application;

[0023] Figure 11 is the weld cross-section macro photo in embodiment four of the present application;

[0024] In the figure: 1, laser beam, 2, laser molten pool, 3, workpiece to be welded one, 4, workpiece to be welded two, 5, laser beam spot trajectory, 6, weld. DETAILED DESCRIPTION

[0025] The present application will be further described by embodiments in combination with the accompanying drawings.

[0026] As Figure 1 , 2As shown in FIGS. 3, a laser termination welding method for sheet-type radiators of transformers is used to weld radiators of common materials and thicknesses; two radiators to be welded are respectively a first workpiece 3 to be welded and a second workpiece 4 to be welded; in this embodiment: W1 is the thickness of the first workpiece 3 to be welded, W2 is the thickness of the second workpiece 4 to be welded, the end portions of the first workpiece 3 to be welded and the second workpiece 4 to be welded are aligned to form a welding end face, W is the thickness of the welding end face, W = W1 + W2, a is the included angle between the laser beam 1 and the horizontal direction, β is the included angle between the laser beam 1 and the normal direction of the weld, D1 is the track width of the laser beam spot on the surface of the weld perpendicular to the welding direction, and D2 is the track width of the laser beam spot on the surface of the weld along the welding direction. The welding end face is not beveled; laser welding is performed at the transverse welding position of the welding end face, the laser beam spot on the welding end face is swung at a high speed according to a predetermined track to form a laser beam spot track 5, and the defocusing amount of the laser is positive; the laser melts the welding end face to form a laser molten pool 2, and the solidification forms a terminated weld 6.

[0027] Embodiment One

[0028] The thicknesses W1 and W2 of the first workpiece 3 to be welded and the second workpiece 4 to be welded are both 1 mm, and the thickness W of the welding end face is 2 mm.

[0029] The included angle a between the laser beam 1 and the horizontal direction is 0°, the included angle β between the laser beam 1 and the normal direction of the weld is 20°, the laser power is 3000 W, the defocusing amount is +80 mm, the laser beam spot track 5 is elliptical, the track width D1 of the laser beam spot on the surface of the weld perpendicular to the welding direction is 2 mm, i.e., W - (0 mm), the track width D2 of the laser beam spot on the surface of the weld along the welding direction is 3 mm, and the laser swinging frequency is 100 Hz.

[0030] The laser molten pool 2 needs to be protected by a gas, the protective gas is pure CO2 (i.e., the Ar proportion in the mixed gas of Ar and CO2 is 0%), the protective gas pressure is 0.5 MPa, the protective gas flow is 30 L / min, and the welding speed is 3 m / min.

[0031] The welding effect is as shown in FIGS. 4 and 5. Figure 4 and Figure 5

[0032] Embodiment Two

[0033] The thicknesses W1 and W2 of the first workpiece 3 to be welded and the second workpiece 4 to be welded are both 1 mm, and the thickness W of the welding end face is 2 mm.

[0034] ​The angle a between the laser beam 1 and the horizontal direction is 10°, the angle β between the laser beam 1 and the normal direction of the weld is 30°, the laser power is 3500W, and the defocusing amount is +50mm; the laser beam spot track 5 is circular, the track width D1 of the laser beam spot on the surface of the weld perpendicular to the welding direction is 1.4mm, i.e., W-(0.6mm), the track width D2 of the laser beam spot on the surface of the weld along the welding direction is 1.4mm, and the laser oscillation frequency is 150Hz. The laser molten pool 2 is protected by a mixed gas of Ar and CO2, the proportion of Ar in the mixed gas is 10%, the protective gas pressure is 0.4MPa, and the protective gas flow is 30L / min; the welding speed is 3.5m / min.

[0035] The welding effect is shown in Figure 6 and Figure 7 .

[0036] Example Three

[0037] The thicknesses W1 and W2 of the workpieces 3 and 4 to be welded are both 1.2mm, and the thickness W of the end face to be welded is 2.4mm.

[0038] The angle a between the laser beam 1 and the horizontal direction is 0°, the angle β between the laser beam 1 and the normal direction of the weld is 25°, the laser power is 3500W, and the defocusing amount is +120mm; the laser beam spot track 5 is rectangular, the track width D1 of the laser beam spot on the surface of the weld perpendicular to the welding direction is 2mm, i.e., W-(0.4mm), the track width D2 of the laser beam spot on the surface of the weld along the welding direction is 3mm, and the laser oscillation frequency is 250Hz.

[0039] The laser molten pool 2 is protected by a mixed gas of Ar and CO2, the proportion of Ar in the mixed gas is 20%, the protective gas pressure is 0.3MPa, and the protective gas flow is 20L / min; the welding speed is 2m / min.

[0040] The welding effect is shown in Figure 8 and Figure 9 .

[0041] Example Four

[0042] The thicknesses W1 and W2 of the workpieces 3 and 4 to be welded are both 1.2mm, and the thickness W of the end face to be welded is 2.4mm.

[0043] The angle a between the laser beam 1 and the horizontal direction is 15°, the angle β between the laser beam 1 and the normal direction of the weld is 40°, the laser power is 2800W, and the defocusing amount is +150mm; the laser beam spot track 5 is an ellipse, the track width D1 of the laser beam spot on the weld surface perpendicular to the welding direction is 2mm, i.e., W-(0.4mm), the track width D2 of the laser beam spot on the weld surface along the welding direction is 3mm, and the laser oscillation frequency is 150Hz.

[0044] The laser molten pool 2 is protected by a mixed gas of Ar and CO2, the proportion of Ar in the mixed gas is 20%, the protective gas pressure is 0.4MPa, and the protective gas flow is 35L / min; the welding speed is 1.8m / min.

[0045] The welding effect is shown in Figure 10 and Figure 11 .

Claims

1. A laser termination welding method for a plate-type heat sink for a transformer, characterized in that... It includes the following steps: The two heat sinks to be welded are workpiece one (3) and workpiece two (4), with the thickness of workpiece one (3) being W1 and the thickness of workpiece two (4) being W2. The ends of workpiece one (3) and workpiece two (4) are aligned to form a weldable end face with a thickness of W, where W = W1 + W2. The weldable end face has no bevel. Laser welding is performed at the horizontal welding position of the weldable end face. The spot of the laser beam (1) oscillates at high speed on the weldable end face according to a predetermined trajectory, forming a laser beam spot trajectory (5). The laser defocusing amount is positive. The laser melts the weldable end face to form a laser molten pool (2), which solidifies to form a weld seam (6) at the end. The laser beam (1) has an angle α of 0-20° with the horizontal direction and an angle β of 0-40° with the weld normal direction. The laser power is 500W-4000W and the defocusing amount is +50mm-+150mm. The laser beam spot trajectory (5) is circular or rectangular. The width of the laser beam spot trajectory perpendicular to the welding direction on the weld surface is D1. The range of D1 is: W≥D1≥W-0.6mm. The width of the laser beam spot trajectory along the welding direction on the weld surface is D2 of 0-3mm. The laser oscillation frequency is 150Hz-300Hz. The welding speed is 1.8m / min-4m / min.

2. The laser termination welding method for a transformer plate heat sink according to claim 1, characterized in that: The range of W is 1.5mm-3mm.

3. The laser termination welding method for a transformer plate heat sink according to claim 1, characterized in that: The laser melting pool (2) needs to be protected by gas. The protective gas is a mixture of Ar and CO2. The volume ratio of Ar in the mixture is 0-30%, the protective gas pressure is 0.2MPa-0.8MPa, and the protective gas flow rate is 10L / min-40L / min.

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