A coaxial composite laser welding method and a welding method for a flat wire motor winding

Abstract

The application discloses a coaxial composite laser welding method and a welding method of a flat wire motor winding, relates to the technical field of laser welding, and adopts a coaxial composite laser beam to act on the surface of high-reflectivity material to form a welding molten pool. The coaxial composite laser beam comprises an outer ring laser beam and a core laser beam. The outer ring laser beam is a pulse laser beam, and the core laser beam is a continuous laser beam. The continuous laser beam forms a main molten pool, and the pulse laser beam forms an auxiliary molten pool. The main molten pool and the auxiliary molten pool have an overlapping portion. The application combines the continuous laser and the pulse laser, the main molten pool formed by the continuous laser is in overlapping communication with the auxiliary molten pool formed by the pulse laser, the pulse laser forms disturbance to the molten metal in the auxiliary molten pool, drives the molten metal in the main molten pool to have an oscillation stirring effect, can increase the laser energy absorption efficiency of the high-reflectivity material, improves the welding penetration, can optimize the energy distribution of a heat source by adjusting the energy proportion and the focus point position, accurately controls the energy state of the heat source, and realizes zero spatter.

Description

Technical Field

[0001] This invention relates to the field of laser welding technology, and in particular to a coaxial composite laser welding method and a welding method for flat wire motor windings. Background Technology

[0002] With the rapid development of my country's industrial manufacturing, laser welding technology has been applied to manufacturing fields such as petroleum, chemical, nuclear energy engineering, and aerospace. It has demonstrated excellent performance in welding conventional materials such as carbon structural steel, stainless steel, and aluminum alloys, and scholars both domestically and internationally have conducted extensive experimental research, accumulating a wealth of theoretical experience. However, research on laser welding of highly reflective materials is relatively scarce. Highly reflective materials are those that can reflect most of the incident light within a specific wavelength range, typically exhibiting high reflectivity. Because highly reflective materials have a reflectivity to laser light that can reach over 90%, during laser welding, most of the laser energy irradiating the surface of the part is reflected, resulting in wasted laser energy and a very low yield rate. This negatively impacts the application of laser welding to components made of highly reflective materials.

[0003] In the research and production of flat wire motor windings, achieving precise welding of a large number of flat wires within a limited space is a crucial research topic. Besides the requirement for long-term mechanical stability, reducing spatter and increasing weld penetration are also essential, as spatter can cause short circuits in the windings. Copper alloys are commonly used for the flat wires in motor windings. Copper alloys are highly reflective materials with high reflectivity and low absorptivity to near-infrared lasers, with an absorptivity of less than 5% at 1064nm. To achieve the required penetration depth, the laser heat input power needs to be further increased, leading to a larger heat-affected zone and increased spatter.

[0004] Therefore, a new laser welding method is urgently needed to achieve high-quality welding of highly reflective materials. Summary of the Invention

[0005] The purpose of this invention is to provide a coaxial composite laser welding method and a welding method for flat wire motor windings to solve the problems existing in the prior art and avoid spatter while ensuring the welding penetration of high reflective materials.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A coaxial composite laser welding method uses a coaxial composite laser beam to act on the surface of a highly reflective material to form a weld pool. The coaxial composite laser beam includes an outer ring laser beam and a core laser beam. The outer ring laser beam is a pulsed laser beam, and the core laser beam is a continuous laser beam. The continuous laser beam forms a main weld pool, and the pulsed laser beam forms an auxiliary weld pool. The main weld pool and the auxiliary weld pool have an overlapping portion.

[0008] The present invention also provides a welding method for a flat wire motor winding. Using the above coaxial composite laser welding method, it includes the following steps:

[0009] S1: Pretreat the flat wire;

[0010] S2: Fix two flat wires to be welded together. The end planes of the two flat wires are arranged side by side to form a welding surface to be welded;

[0011] S3: Adjust the angle of the coaxial composite laser beam so that the coaxial composite laser beam forms an included angle with the normal direction of the welding surface to be welded;

[0012] S4: Adjust the power of the coaxial composite laser beam and the defocus amount acting on the flat wire, and set the welding path and welding speed;

[0013] S5: Start welding;

[0014] S6: After welding is completed, turn off the coaxial composite laser beam.

[0015] In an exemplary embodiment, in S1, the pretreatment includes removing the insulating paint film and cleaning the stains on the surface of the flat wire.

[0016] In an exemplary embodiment, the removal length of the insulating paint film is 10 - 15 mm; the stain cleaning includes oil stain cleaning and oxide layer elimination treatment.

[0017] In an exemplary embodiment, in S3, the included angle between the coaxial composite laser beam and the normal direction of the welding surface to be welded is 5° - 15°.

[0018] In an exemplary embodiment, in S4, the power of the continuous laser is 1400 - 2000 W, and the average power of the pulsed laser is 200 - 500 W; the defocus amount of the coaxial composite laser beam acting on the flat wire is -4 - 0 mm; the welding speed is 50 - 250 mm / min.

[0019] In an exemplary embodiment, in S4, the welding path is one or more of a circle, a rectangle, and a "day" shape. The circular, rectangular, and "day" - shaped welding paths cover the end planes of the two flat wires to be welded together.

[0020] In an exemplary embodiment, in S4:

[0021] When there is a height difference between the two flat wires to be welded together, a circular welding path is adopted, and a semi - circular path is additionally welded on the lower side;

[0022] When there is a gap between the two flat wires to be welded together, a circular welding path is adopted, and the diameter of the circular welding path is increased;

[0023] When there is a forward or backward offset between the two flat wires to be welded together, an elliptical welding trajectory is used.

[0024] In one exemplary embodiment, during the welding process, a protective gas is sprayed to cover the welding area, with the protective gas nozzle positioned at the rear end of the welding direction.

[0025] In an exemplary embodiment, the flow rate of the protective gas is 10 to 20 L / min.

[0026] The present invention achieves the following technical effects compared to the prior art:

[0027] In laser welding, continuous lasers can provide stable heat input, making them suitable for deep penetration welding and high-speed welding. However, when welding highly reflective materials, the high reflectivity causes the continuous laser energy to be reflected, requiring higher power to achieve welding. But high power can easily lead to problems such as spatter and excessively large heat-affected zones. Pulsed lasers, on the other hand, achieve localized rapid heating and cooling through intermittent high-energy pulses, making them suitable for precision welding. However, they are difficult to meet the needs of large-scale welding when used alone.

[0028] This invention combines two technologies to form a coaxial composite laser. The core laser beam of the coaxial composite laser is a continuous laser, which provides the basic energy through stable heat input, forming a main molten pool in the center. The outer laser beam of the coaxial composite laser is a pulsed laser, forming an auxiliary molten pool around the main molten pool. By adjusting the size of the spot in the center and the ring spot around the center, the main molten pool and the auxiliary molten pool overlap and connect. The pulsed laser disturbs the molten metal in the auxiliary molten pool, thereby driving the molten metal in the connected main molten pool to achieve an oscillating and stirring effect. This can increase the laser energy absorption efficiency of highly reflective materials and significantly improve the welding penetration depth. The principle is that the precise control capability of pulsed lasers superimposes high-energy pulses in key areas, accurately controlling the dynamic behavior of the molten pool (such as weld depth and weld width). By adjusting the energy ratio and focal point position of the two lasers, the energy distribution of the heat source can be optimized, achieving precise control of the heat source energy state for welding. By reasonably adjusting the energy distribution, the flow direction and speed of the liquid metal in the molten pool can be controlled. For example, the energy distribution can promote the liquid metal to flow towards the center of the weld instead of splashing outwards. The orderly flow of liquid metal in the molten pool helps to stabilize the welding process and further achieve a zero-splash state.

[0029] Other technical solutions disclosed in this invention also have the following technical advantages:

[0030] By employing a coaxial composite laser welding method, continuous laser and pulsed laser are combined as the welding heat source for flat wire motor windings. By adjusting the average power of the continuous laser and pulsed laser, the heat input can be reasonably distributed, and the laser output can be kept as a small spot heat source. By establishing a scheme for the combined use of continuous laser and pulsed laser, the heat absorption of the base metal can be precisely controlled, improving the forming morphology of the flat copper wire welded joint, avoiding defects such as porosity and incomplete penetration, and enhancing the performance of the weld joint to ensure good forming of the flat wire welded joint.

[0031] By adjusting the laser welding trajectory, the heat input range of the flat wire can be optimized, and the heat-affected zone can be further precisely controlled. Under the condition of meeting a certain penetration depth, the heat input to the flat wire can be reduced, and the grain morphology and dislocations in the heat-affected zone of the weld joint can be further controlled. The joint resistance can be reduced to 48% of the base material, which is 35% higher than the resistance reduction capability of single laser welding. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the structure of a flat wire disclosed in a specific embodiment of the present invention;

[0034] Figure 2a A schematic diagram showing the properly secured state of the two flat wires to be welded;

[0035] Figure 2b This is a schematic diagram showing the two flat wires to be welded having a height difference in the Z-axis direction.

[0036] Figure 2c This is a schematic diagram showing two flat wires to be welded with a gap in the X-axis direction.

[0037] Figure 2d This is a schematic diagram showing the state of two flat wires to be welded, which are offset in the Y-axis direction.

[0038] Figure 3 A schematic diagram of flat wires for coaxial composite laser welding of motor windings, as disclosed in a specific embodiment of the present invention;

[0039] Figure 4a A schematic diagram of a circular welding trajectory used to fix two flat wires to be welded in a qualified state;

[0040] Figure 4bSchematic diagram of the rectangular welding trajectory for two flat wires to be welded in a qualified fixed state;

[0041] Figure 4c Schematic diagram of the "day" - shaped welding trajectory for two flat wires to be welded in a qualified fixed state;

[0042] Figure 5a Schematic diagram of the welding trajectory for two flat wires to be welded with a height difference in the Z - axis direction;

[0043] Figure 5b Schematic diagram of the welding trajectory for two flat wires to be welded with a gap in the X - axis direction;

[0044] Figure 5c Schematic diagram of the welding trajectory for two flat wires to be welded with an offset in the Y - axis direction;

[0045] Among them, 1. Pulse laser; 2. Continuous laser; 3. Coaxial composite laser; 4. Flat wire; 5. Protection gas nozzle; 6. Welding clamping device; 7. Insulating paint skin; 8. Circular welding trajectory; 9. Rectangular welding trajectory; 10. "Day" - shaped welding trajectory; 11. Welding trajectory when there is a height difference in the Z - axis; 12. Welding trajectory when there is a gap in the X - axis; 13. Elliptical welding trajectory. Detailed implementation manners

[0046] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention. Those skilled in this technology can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0047] The purpose of the present invention is to provide a coaxial composite laser welding method and a welding method for a flat - wire motor winding to solve the problems existing in the prior art and avoid splashing while ensuring the welding penetration depth of high - reflection materials.

[0048] To make the above - mentioned objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners.

[0049] Embodiment 1

[0050] This embodiment provides a coaxial composite laser welding method, which uses a coaxial composite laser beam to act on the surface of a highly reflective material to form a weld pool. The coaxial composite laser beam includes an outer ring laser beam and a core laser beam. The outer ring laser beam is a pulsed laser beam, and the core laser beam is a continuous laser beam. The continuous laser beam forms the main weld pool, and the pulsed laser beam forms the auxiliary weld pool. The main weld pool and the auxiliary weld pool have an overlapping portion.

[0051] In laser welding, continuous lasers can provide stable heat input, making them suitable for deep penetration welding and high-speed welding. However, when welding highly reflective materials, the high reflectivity causes the continuous laser energy to be reflected, requiring higher power to achieve welding. But high power can easily lead to problems such as spatter and excessively large heat-affected zones. Pulsed lasers, on the other hand, achieve localized rapid heating and cooling through intermittent high-energy pulses, making them suitable for precision welding. However, they are difficult to meet the needs of large-scale welding when used alone.

[0052] This invention combines two technologies to form a coaxial composite laser. The core laser beam of the coaxial composite laser is a continuous laser, whose stable heat input provides the basic energy, forming a main molten pool in the center. The outer laser beam of the coaxial composite laser is a pulsed laser, forming an auxiliary molten pool around the main molten pool. By adjusting the size of the spot in the center and the surrounding ring spot, the main molten pool and the auxiliary molten pool overlap and connect. The pulsed laser disturbs the molten metal in the auxiliary molten pool, thereby stirring the molten metal in the connected main molten pool, achieving an oscillating and stirring effect. This increases the laser energy absorption efficiency of highly reflective materials and significantly improves the welding penetration. The principle is as follows:

[0053] First, the periodic perturbation of pulsed lasers causes dynamic fluctuations and microstructures (such as pits and ripples) on the surface of molten metal, significantly increasing the surface roughness of the material. This roughness triggers multiple reflections and scattering of the laser, lengthening the optical path and causing more photons to be absorbed by the material rather than directly reflected. For highly reflective materials (such as aluminum and copper), this effect can overcome the energy loss bottleneck of specular reflection.

[0054] Secondly, the high peak power of the pulsed laser instantly vaporizes the metal, forming a deep-penetration keyhole structure. The beam can directly enter the keyhole, and through heat transfer within the keyhole, a greater weld penetration depth is achieved. The keyhole also improves weld formation quality, reduces welding defects, and meets the welding requirements of highly reflective materials. Oscillating stirring causes continuous fluctuations in the keyhole wall, maintaining opening stability and preventing keyhole collapse due to metal vapor backflow.

[0055] Third, the forced convection of the molten metal can accelerate the transfer of heat to the bottom of the molten pool, while simultaneously drawing unmelted material from the front of the keyhole into the molten pool, thus overcoming the limitations of traditional heat conduction.

[0056] Fourth, the short pulse width of pulsed lasers can suppress the persistent plasma cloud in continuous laser welding. By adjusting the pulse frequency and duty cycle, the shielding effect of the plasma on the incident laser can be reduced while maintaining the continuity of the molten pool.

[0057] When using a combination of low-power continuous laser and pulsed laser, the precise control capability of the pulsed laser allows for the superposition of high-energy pulses in critical areas, providing additional energy and precisely controlling the dynamic behavior of the molten pool (such as weld depth and width). The high peak energy of the pulsed laser can instantly overcome the energy reflection barrier of highly reflective materials, enabling the material to quickly reach the temperature required for welding, thereby reducing the power requirements of the continuous laser. Furthermore, by adjusting the energy ratio and focal point position of the two lasers, the energy distribution of the heat source can be optimized, achieving precise control of the heat source energy state for welding. By reasonably adjusting the energy distribution, the flow direction and speed of the liquid metal in the molten pool can also be controlled. For example, a suitable energy distribution can cause the liquid metal to flow towards the center of the weld instead of splashing outwards. The orderly flow of the liquid metal in the molten pool helps stabilize the welding process, further achieving a zero-splatter state.

[0058] Example 2

[0059] This embodiment provides a welding method for flat wire motor windings, employing the coaxial composite laser welding method described in Embodiment 1, including the following steps:

[0060] S1: Preprocess flat wire 4;

[0061] S2: Fix the two flat wires 4 to be welded together, with the end planes of the two flat wires 4 side by side to form the welding surface;

[0062] S3: Adjust the angle of the coaxial composite laser beam so that the coaxial composite laser beam forms an angle with the normal direction of the surface to be welded, so as to avoid laser reflection damage to the laser when the coaxial composite laser beam acts on the highly reflective material;

[0063] S4: Adjust the power of the coaxial composite laser beam and the amount of defocusing applied to the flat wire 4, and set the welding trajectory and welding speed;

[0064] S5: Start welding;

[0065] S6: Welding complete, shut down the coaxial composite laser beam.

[0066] In this embodiment, the coaxial composite laser welding method described in Embodiment 1 is adopted, and continuous laser and pulsed laser are combined as the welding heat source for the joint of the flat wire 4. By adjusting the average power of the continuous laser and the pulsed laser, reasonable distribution of heat input can be achieved, and a small-spot heat source output by the laser can be maintained. A cooperation scheme for the continuous laser and the pulsed laser is established, which can precisely control the heat absorption of the base metal, improve the forming morphology of the welded joint of the flat copper wire, avoid defects such as pores and incomplete penetration, and enhance the performance of the weld joint to ensure good forming of the welded joint of the flat wire 4.

[0067] Further, in S1, the pretreatment includes removing the insulating paint layer 7 and cleaning the stains on the surface of the flat wire 4. Specifically, the removal length range of the insulating paint layer 7 is 10 - 15 mm; the stain cleaning includes oil cleaning and oxide layer removal treatment.

[0068] In S3, the angle between the coaxial composite laser beam and the normal direction of the surface to be welded is 5° - 15°.

[0069] In S4, the power of the continuous laser is 1400 - 2000 W, and the average power of the pulsed laser is 200 - 500 W; the defocus amount of the coaxial composite laser beam acting on the flat wire 4 is -4 - 0 mm; the welding speed is 50 - 250 mm / min.

[0070] In S4, when the two flat wires 4 to be welded are fixed qualified, the welding trajectory is one or more of the circular welding trajectory 8, the rectangular welding trajectory 9, and the "day" - shaped welding trajectory 10, and the circular welding trajectory 8, the rectangular welding trajectory 9, and the "day" - shaped welding trajectory 10 cover the end planes of the two flat wires 4 to be welded together;

[0071] When there are defects in the fixation of the two flat wires 4 to be welded, for example:

[0072] When there is a height difference between the two flat wires 4 to be welded together, the circular welding trajectory 8 is adopted, and a semi - circular trajectory is additionally welded on the lower side;

[0073] When there is a gap between the two flat wires 4 to be welded together, the circular welding trajectory 8 is adopted, and the diameter of the circular welding trajectory 8 is increased;

[0074] When there is a front - to - back offset between the two flat wires 4 to be welded together, an elliptical welding trajectory is adopted.

[0075] As a preferred solution of this embodiment, during the welding process, a shielding gas covering the welding area is sprayed, the shielding gas nozzle 5 is at the rear end of the welding direction, and the flow rate of the shielding gas is 10 - 20 L / min.

[0076] The following section details the method for coaxial composite laser welding of the flat wire 4 of the motor winding, using specific experiments. The flat wire 4 used in the experiment is T2 copper with good conductivity and machinability, with a cross-sectional size of 1.5×3mm. The continuous laser 2 is a fiber laser with a rated power of 2kW, and the pulsed laser 1 is a fiber laser with a rated power of 800W. The protective gas used is argon gas with a purity of 99.99%.

[0077] Experiment 1

[0078] Under ideal fixed conditions before welding, that is, the two flat wires 4 to be welded are fixed in a qualified manner, as shown in Figure 2(a), the flat wire motor winding is welded by coaxial composite laser welding.

[0079] S1: According to actual needs, cut the selected flat wire 4 into 58mm long strips, remove 10mm of the insulating varnish 7 from one end of the flat wire 4, and then clean the surface of the flat wire 4 with a cleaning agent. Figure 1 As shown;

[0080] S2: Place the pre-treated flat wire 4 on the welding clamping device 6, remove the paint from one end and place them side by side to form the welding surface, and tighten them to ensure the welding effect.

[0081] S3: Pulsed laser 1 emits pulsed laser light, and continuous laser 2 emits continuous laser light. The pulsed and continuous laser lights pass through coaxial composite laser 3 to form a coaxial composite laser beam. The angle of coaxial composite laser 3 is adjusted so that the angle θ between the coaxial composite laser beam and the normal direction of the surface to be welded is 5°. Figure 3 As shown;

[0082] S4: Adjust the vertical distance between the coaxial composite laser 3 and the end of the flat wire 4 so that the defocusing amount of the coaxial composite laser beam acting on the flat wire 4 is -1mm;

[0083] The current and frequency of the power of the pulsed laser 1 and the continuous laser 2 are uniformly controlled so that the average power of the pulsed laser 1 is 360W and the power of the continuous laser 2 is 1700W, thereby improving the forming morphology of the flat wire 4. At the same time, while ensuring that the weld of the flat wire 4 is fully penetrated, it achieves better conductivity.

[0084] The welding speed is set to 50 mm / min, and the welding trajectory can be set to a circular welding trajectory (e.g., 8). Figure 4a As shown), rectangular welding trajectory 9 (as shown) Figure 4b (as shown) and the "sun" shaped welding trajectory 10 (as shown) Figure 4c As shown), the size of the welding trajectory is selected according to the size of the welding end of the flat wire 4, preferably a circular welding trajectory 8 with a diameter of 1.9 mm, located at the center of the surface to be welded, such as... Figure 3 As shown;

[0085] S5: Adjust the position of the protective gas nozzle 5 so that the protective gas can fully protect the welding area. The flow rates of the protective gas in the welding area and the protective gas in the laser lens are both set to 10L / min.

[0086] S6: Turn on the laser cooling device and perform welding according to the welding trajectory and welding speed set in step S4;

[0087] S7: After welding is completed, turn off pulsed laser 1, continuous laser 2, coaxial composite laser 3, laser cooling device and protective gas nozzle 5.

[0088] Experiment 2

[0089] Before welding the ends of the flat wire motor windings, several common defects may occur due to improper clamping and other reasons. Figure 2(b) shows the state when there is a height difference in the Z-axis direction. In this state, coaxial composite laser welding of the flat wire motor windings is used.

[0090] S1: According to actual needs, cut the selected flat wire 4 into 58mm long strips, remove 12mm of the insulating varnish 7 from one end of the flat wire 4, and then clean the surface of the flat wire 4 with a cleaning agent. Figure 1 As shown;

[0091] S2: Place the pre-treated flat wire 4 on the welding clamping device 6, remove the paint from one end and place them side by side to form the welding surface, tighten them, and leave a height difference of 1mm in the Z-axis direction.

[0092] S3: Pulsed laser 1 emits pulsed laser light, and continuous laser 2 emits continuous laser light. The pulsed and continuous laser lights pass through coaxial composite laser 3 to form a coaxial composite laser beam. The angle of coaxial composite laser 3 is adjusted so that the angle θ between the coaxial composite laser beam and the normal direction of the surface to be welded is 10°. Figure 3 As shown;

[0093] S4: Adjust the vertical distance between the coaxial composite laser 3 and the end of the flat wire 4 so that the defocusing amount of the coaxial composite laser beam acting on the flat wire 4 is -2mm;

[0094] The power of pulsed laser 1 and continuous laser 2 is uniformly controlled so that the average power of pulsed laser 1 is 300W and the power of continuous laser 2 is 1500W, thereby improving the forming morphology of flat wire 4. At the same time, while ensuring that the weld of flat wire 4 is fully penetrated, the heat input is adjusted to achieve better conductivity.

[0095] The welding speed is set to 100 mm / min. Based on the height difference defect fixed before welding, the welding path is adjusted. The preferred path is a circular welding trajectory 8. A semi-circular trajectory is added to the lower side. The large circle diameter is 1.9 mm and the semi-circular radius is 0.5 mm. It is located at the center of the surface to be welded, as shown in Figure 5(a).

[0096] S5: Adjust the position of the protective gas nozzle 5 so that the protective gas can fully protect the welding area. The flow rates of the protective gas in the welding area and the protective gas in the laser lens are both set to 12L / min.

[0097] S6: Turn on the laser cooling device and perform welding according to the welding trajectory and welding speed set in step S4;

[0098] S7: After welding is completed, turn off pulsed laser 1, continuous laser 2, coaxial composite laser 3, laser cooling device and protective gas nozzle 5.

[0099] Experiment 3

[0100] Before welding the ends of the flat wire motor windings, several common defects may occur due to improper clamping and other reasons. Figure 2(c) shows the state when there is a gap in the X-axis direction. In this state, coaxial composite laser welding of the flat wire motor windings is used.

[0101] S1: According to actual needs, cut the selected flat wire 4 into 58mm long strips, remove 14mm of the insulating varnish 7 from one end of the flat wire 4, and then clean the surface of the flat wire 4 with a cleaning agent. Figure 1 As shown;

[0102] S2: Place the pre-treated flat wire 4 on the welding clamping device 6, remove the paint from one end and place them side by side to form the welding surface, tighten them, and leave a 1mm gap in the X-axis direction.

[0103] S3: Pulsed laser 1 emits pulsed laser light, and continuous laser 2 emits continuous laser light. The pulsed and continuous laser lights pass through coaxial composite laser 3 to form a coaxial composite laser beam. The angle of coaxial composite laser 3 is adjusted so that the angle θ between the coaxial composite laser beam and the normal direction of the surface to be welded is 12°. Figure 3 As shown;

[0104] S4: Adjust the vertical distance between the coaxial composite laser 3 and the end of the flat wire 4 so that the defocusing amount of the coaxial composite laser beam acting on the flat wire 4 is -3mm;

[0105] The power of pulsed laser 1 and continuous laser 2 is uniformly controlled so that the average power of pulsed laser 1 is 400W and the power of continuous laser 2 is 1900W, thereby improving the forming morphology of flat wire 4. At the same time, while ensuring that the weld of flat wire 4 is fully penetrated, the heat input is adjusted to achieve better conductivity.

[0106] The welding speed is set to 200 mm / min. The welding path is adjusted according to the gap defect fixed before welding. The preferred path is a circular welding trajectory 8. The diameter of the circular welding trajectory 8 is adjusted to 2 mm according to the gap width of 1 mm, and it is located at the center of the surface to be welded, as shown in Figure 5(b).

[0107] S5: Adjust the position of the protective gas nozzle 5 so that the protective gas can fully protect the welding area. The flow rates of the protective gas in the welding area and the protective gas in the laser lens are both set to 15L / min.

[0108] S6: Turn on the laser cooling device and perform welding according to the welding trajectory and welding speed set in step S4;

[0109] S7: After welding is completed, turn off pulsed laser 1, continuous laser 2, coaxial composite laser 3, laser cooling device and protective gas nozzle 5.

[0110] Experiment 4

[0111] Before welding the ends of the flat wire motor windings, several common defects may occur due to improper clamping and other reasons. Figure 2(d) shows the state when there is a deviation in the Y-axis direction. In this state, coaxial composite laser welding of the flat wire motor windings is used.

[0112] S1: According to actual needs, cut the selected flat wire 4 into 58mm long strips, remove 15mm of the insulating varnish 7 from one end of the flat wire 4, and then clean the surface of the flat wire 4 with a cleaning agent. Figure 1 As shown;

[0113] S2: Place the pre-treated flat wire 4 on the welding clamping device 6, remove the paint from one end and place them side by side to form the welding surface, tighten them, and leave an offset of 1mm in the Y-axis direction;

[0114] S3: Pulsed laser 1 emits pulsed laser light, and continuous laser 2 emits continuous laser light. The pulsed and continuous laser lights pass through coaxial composite laser 3 to form a coaxial composite laser beam. The angle of coaxial composite laser 3 is adjusted so that the angle θ between the coaxial composite laser beam and the normal direction of the surface to be welded is 15°. Figure 3 As shown;

[0115] S4: Adjust the vertical distance between the coaxial composite laser 3 and the end of the flat wire 4 so that the defocusing amount of the coaxial composite laser beam acting on the flat wire 4 is -4mm.

[0116] The power of pulsed laser 1 and continuous laser 2 is uniformly controlled so that the average power of pulsed laser 1 is 370W and the power of continuous laser 2 is 1750W, thereby improving the forming morphology of flat wire 4. At the same time, while ensuring that the weld of flat wire 4 is fully penetrated, the heat input is adjusted to achieve better conductivity.

[0117] The welding speed is set to 250 mm / min. Based on the pre-welding fixed offset defect, the welding path is adjusted. The preferred welding path is an elliptical welding trajectory 8. Based on the offset of 1 mm, the major axis of the ellipse is adjusted to 3.2 mm and the minor axis to 1.5 mm, which is located at the center of the surface to be welded, as shown in Figure 5(c).

[0118] S5: Adjust the position of the protective gas nozzle 5 so that the protective gas can fully protect the welding area. The flow rates of the protective gas in the welding area and the protective gas in the laser lens are both set to 20L / min.

[0119] S6: Turn on the laser cooling device and perform welding according to the welding trajectory and welding speed set in step S4;

[0120] S7: After welding is completed, turn off pulsed laser 1, continuous laser 2, coaxial composite laser 3, laser cooling device and protective gas nozzle 5.

[0121] After the welding test was completed, the flat wire obtained had excellent shape. No spatter was generated during the welding process, and no defects such as pores, inclusions and cracks were found. The laser did not damage the insulation varnish of the flat wire. The conductivity test of the joint showed that the conductivity of the joint met the production requirements.

[0122] In the description of this invention, it should be understood that the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0123] In the description of this invention, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0124] If this invention discloses or relates to components or structural parts that are fixedly connected to each other, then, unless otherwise stated, a fixed connection can be understood as: a fixed connection that can be detached (e.g., using bolts or screws), or a fixed connection that cannot be detached (e.g., riveting, welding). Of course, a fixed connection can also be replaced by an integral structure (e.g., manufactured in one piece using a casting process) (except where it is obviously impossible to use an integral molding process).

[0125] In addition, unless otherwise stated, the terms used in any of the technical solutions disclosed in this invention to indicate positional relationships or shapes include states or shapes that are similar to, close to, or approximate with those states or shapes.

[0126] Any component provided by this invention can be assembled from multiple individual components or can be a single component manufactured by a one-piece molding process.

[0127] It should be noted that the structures, proportions, sizes, etc., depicted in the accompanying drawings of this specification are only used to complement the content disclosed in the specification, so as to enable those skilled in the art to understand and read them, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0128] It should also be noted that in the embodiments of this application, the same reference numerals are used to denote the same component or the same part.

[0129] Any adaptive changes made according to actual needs are within the scope of protection of this invention.

[0130] It should be noted that, for those skilled in the art, it is obvious that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0131] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A coaxial hybrid laser welding method, characterized by: The coaxial composite laser beam is used to act on the surface of the high-reflectivity material to form a welding molten pool, the coaxial composite laser beam comprises an outer ring laser beam and a core laser beam, the outer ring laser beam is a pulsed laser beam, the core laser beam is a continuous laser beam, the continuous laser beam forms a main molten pool, the pulsed laser beam forms an auxiliary molten pool, and the main molten pool and the auxiliary molten pool have an overlapping portion; the pulsed laser beam forms disturbance to the molten metal in the auxiliary molten pool, and then drives the molten metal in the connected main molten pool, so as to achieve an oscillation stirring effect, increase the laser energy absorption efficiency of the high-reflectivity material, and greatly improve the welding penetration.

2. A method of welding a flat wire motor winding, characterized by: The flat wire material is a high-reflectivity material, and the coaxial composite laser welding method of claim 1 comprises the following steps: S1: pretreating the flat wire; S2: fixing two flat wires to be welded together, and arranging the end planes of the two flat wires side by side to form a welding surface; S3: adjusting the angle of the coaxial composite laser beam, so that the coaxial composite laser beam forms an angle with the normal direction of the welding surface; S4: adjusting the power of the coaxial composite laser beam and the defocusing amount acting on the flat wire, setting the welding track and the welding speed; S5: starting welding; S6: stopping welding and turning off the coaxial composite laser beam.

3. The welding method of a flat wire motor winding according to claim 2, characterized in that: In S1, the pretreatment comprises removing the insulating paint and cleaning the surface stains of the flat wire.

4. The welding method of a flat wire motor winding according to claim 3, characterized by: The removal length of the insulating paint is 10-15 mm; the stain cleaning comprises oil stain cleaning and oxidation layer elimination treatment.

5. The method of welding a flat conductor motor winding according to claim 2, characterized in that: In S3, the angle between the coaxial composite laser beam and the normal direction of the welding surface is 5-15°.

6. The method of welding a flat conductor motor winding of claim 2, wherein: In S4, the power of the continuous laser beam is 1400-2000 W, the average power of the pulsed laser beam is 200-500 W, the defocusing amount of the coaxial composite laser beam acting on the flat wire is -4-0 mm, and the welding speed is 50-250 mm / min.

7. The method of welding a flat conductor motor winding of claim 2, wherein: In S4, the welding track is one or more of a circular shape, a rectangular shape and a "sun" shape, and the circular, rectangular and "sun" welding tracks cover the end planes of the two flat wires to be welded together.

8. The method of welding a flat conductor motor winding of claim 2, wherein: When there is a height difference between the two flat wires to be welded together, a circular welding track is used, and a semicircular track is added on the lower side; When there is a gap between the two flat wires to be welded together, a circular welding track is used, and the diameter of the circular welding track is increased; When there is a front-back offset between the two flat wires to be welded together, an elliptical welding track is used.

9. The method of welding a flat conductor motor winding of claim 2, wherein: During the welding process, protective gas is sprayed to cover the welding area, and the protective gas nozzle is located at the rear end of the welding direction.

10. The welding method of a flat wire motor winding according to claim 9, characterized in that: The flow rate of the protective gas is 10-20 L / min.

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