Coaxial composite laser welding method and welding method of flat wire motor winding

Abstract

The invention discloses a coaxial composite laser welding method and a welding method of a flat wire motor winding, and relates to the technical field of laser welding, coaxial composite laser beams are adopted to act on the surface of a high-reflection material to form a welding pool, the coaxial composite laser beams comprise 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 core laser beam; the core laser beam is a continuous laser beam, the continuous laser beam forms a main molten pool, the pulse laser beam forms an auxiliary molten pool, and the main molten pool and the auxiliary molten pool have overlapped parts. The continuous laser and the pulse laser are combined, the main molten pool formed by the continuous laser and the auxiliary molten pool formed by the pulse laser are communicated in an overlapped mode, the pulse laser disturbs molten metal in the auxiliary molten pool and drives the molten metal in the main molten pool to achieve the oscillation stirring effect, and the laser energy absorption efficiency of the high-reflection material can be improved; and the energy distribution of the heat source can be optimized by adjusting the energy proportion and the focus point position, the energy state of the heat source is accurately controlled, and zero splashing is achieved.

Description

Technical Field

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

[0002] With the rapid development of industrial manufacturing in my country, laser welding technology has been applied to manufacturing fields such as petroleum, chemical industry, atomic energy engineering, aerospace, etc. It has shown excellent performance in welding conventional materials such as carbon structural steel, stainless steel, aluminum alloy, etc. Domestic and foreign scholars have conducted a large number of experimental studies and accumulated a lot of theoretical experience. However, there is a lack of research on laser welding of highly reflective materials. Highly reflective materials refer to materials that can reflect most of the incident light back within a specific wavelength range and usually have a high reflectivity. Since highly reflective materials have a high reflectivity to lasers, which can reach more than 90%, most of the laser energy irradiated to the surface of the parts is reflected during laser welding, resulting in a waste of laser energy and a very low yield rate, which has an adverse effect on the application of laser welding to components made of highly reflective materials.

[0003] In the development and production of flat wire motor windings, how to achieve precise welding of a large number of flat wires in a small space is an important research topic. In addition to the requirements of long-term mechanical stability, it is also very important to reduce spatter during welding and increase the penetration depth of the welded joint. Spatter generated during welding may cause the winding to short-circuit. The commonly used material for motor winding flat wire is copper alloy, which is a highly reflective material with high reflectivity and low absorption rate for near-infrared lasers. The absorption rate at 1064nm is less than 5%. If you want to achieve the penetration depth requirements, you need to further increase the laser heat input power, which will cause the heat affected zone to become larger and cause 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 object of the present invention is to provide a coaxial composite laser welding method and a flat wire motor winding welding method to solve the problems existing in the above-mentioned prior art and avoid spattering while ensuring the welding penetration of highly reflective materials.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A coaxial composite laser welding method uses a coaxial composite laser beam to act on the surface of a high-reflective material to form a welding molten 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 molten pool, and the pulsed laser beam forms an auxiliary molten pool. The main molten pool and the auxiliary molten pool have an overlapping portion.

[0008] The present invention also provides a method for welding a flat wire motor winding, which adopts the above-mentioned coaxial composite laser welding method and comprises the following steps:

[0009] S1: pre-process the flat wire;

[0010] S2: Fix the two flat wires to be welded together, and arrange the end planes of the two flat wires side by side to form a surface to be welded;

[0011] 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;

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

[0013] S5: start welding;

[0014] S6: Welding is completed and the coaxial composite laser beam is turned off.

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

[0016] In an exemplary embodiment, the insulation paint is removed by a length of 10 to 15 mm; the stain cleaning includes oil cleaning and oxidation layer elimination processing.

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

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

[0019] In an exemplary embodiment, in S4, the welding trajectory is one or more of a circular, rectangular and "sun" shape, and the circular, rectangular and "sun" shaped welding trajectory covers 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 track is used, and a semicircular track is added on the lower side;

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

[0023] When there is a fore-and-aft offset between the two flat wires to be welded together, an elliptical welding trajectory is used.

[0024] In an exemplary embodiment, during the welding process, a shielding gas is sprayed to cover the welding area, and the shielding gas nozzle is located at the rear end in the welding direction.

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

[0026] Compared with the prior art, the present invention has achieved the following technical effects:

[0027] In laser welding, continuous laser can provide stable heat input, which is suitable for deep penetration welding and high-speed welding. However, when welding highly reflective materials, the high reflectivity will cause continuous laser energy to be reflected, and higher power is required to achieve welding. However, high power is prone to cause problems such as spatter and excessive heat-affected zone. Pulsed laser uses intermittent high-energy pulses to achieve local rapid heating and cooling, which is suitable for precision welding, but it is difficult to meet large-scale welding needs when used alone.

[0028] The present invention combines the two to form a coaxial composite laser. The core laser beam of the coaxial composite laser is a continuous laser. The stable heat input of the continuous laser provides basic energy to form a main molten pool in the middle. The outer ring laser beam of the coaxial composite laser is a pulsed laser to form an auxiliary molten pool around the main molten pool. The size of the point light spot in the middle and the surrounding ring light spot are adjusted to make the main molten pool overlap and connect with the auxiliary molten pool. 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, which can increase the laser energy absorption efficiency of high-reflective materials and greatly improve the welding penetration. The principle is that the precise control capability of the pulsed laser can superimpose high-energy pulses in key areas and accurately control the dynamic behavior of the molten pool (such as melt depth and melt width). By adjusting the energy ratio and focal point position of the two lasers, the energy distribution of the heat source can be optimized, and precise control of the energy state of the heat source can be achieved 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 cause the liquid metal to flow to the center of the weld instead of splashing outward. 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 the present invention also have the following technical advantages:

[0030] By adopting the coaxial composite laser welding method, continuous laser and pulse laser are combined as the welding heat source of the flat wire motor winding. The heat input can be reasonably distributed by adjusting the average power of the continuous laser and the pulse laser, and the laser output is kept to have a small spot heat source. A coordinated use scheme of continuous laser and pulse laser is established. The heat absorption of the base metal can be accurately controlled, the forming morphology of the flat copper wire welding joint can be improved, defects such as pores and incomplete fusion can be avoided, and the performance of the weld joint can be improved to ensure that the flat wire welding joint is well formed.

[0031] By adjusting the laser welding trajectory, the heat input range of the flat wire can be optimized, and the heat-affected range can be further precisely controlled. Under the condition of meeting a certain melting depth, the heat input to the flat wire can be reduced, and the grain morphology and dislocation of the heat-affected zone of the welded joint can be further controlled. The joint resistance can be reduced to 48% of the base material, which is 35% higher than the ability to reduce resistance with single laser welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 A schematic structural diagram of a flat wire disclosed in a specific embodiment of the present invention;

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

[0035] Figure 2b It is a schematic diagram of the state where two flat wires to be welded have a height difference in the Z-axis direction;

[0036] Figure 2c It is a schematic diagram of a state in which two flat wires to be welded have a gap in the X-axis direction;

[0037] Figure 2d It is a schematic diagram of the state where two flat wires to be welded are offset in the Y-axis direction;

[0038] Figure 3 A schematic diagram of welding a flat wire of a motor winding using a coaxial composite laser according to a specific embodiment of the present invention;

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

[0040] Figure 4bA schematic diagram of a rectangular welding track in which two flat wires to be welded are fixed in a qualified state;

[0041] Figure 4c It is a schematic diagram of a "sun" shaped welding trajectory when two flat wires to be welded are fixed in a qualified state;

[0042] Figure 5a It is a schematic diagram of the welding trajectory of two flat wires to be welded in a state where there is a height difference in the Z-axis direction;

[0043] Figure 5b A schematic diagram of a welding trajectory when two flat wires to be welded have a gap in the X-axis direction;

[0044] Figure 5c A schematic diagram of a welding trajectory of two flat wires to be welded in a state where the two flat wires are offset in the Y-axis direction;

[0045] Among them, 1. Pulse laser; 2. Continuous laser; 3. Coaxial composite laser; 4. Flat wire; 5. Shielding gas nozzle; 6. Welding clamping device; 7. Insulating paint; 8. Circular welding trajectory; 9. Rectangular welding trajectory; 10. "Sun" 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 DESCRIPTION

[0046] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. People familiar with the technology can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] The purpose of the present invention is to provide a coaxial composite laser welding method and a flat wire motor winding welding method to solve the problems existing in the prior art and avoid spattering while ensuring the welding penetration of highly reflective materials.

[0048] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0049] Embodiment 1

[0050] The present 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 welding molten 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 molten pool, and the pulsed laser beam forms an auxiliary molten pool. The main molten pool and the auxiliary molten pool have an overlapping portion.

[0051] In laser welding, continuous laser can provide stable heat input, which is suitable for deep penetration welding and high-speed welding. However, when welding highly reflective materials, the high reflectivity will cause continuous laser energy to be reflected, and higher power is required to achieve welding. However, high power is prone to cause problems such as spatter and excessive heat-affected zone. Pulsed laser uses intermittent high-energy pulses to achieve local rapid heating and cooling, which is suitable for precision welding, but it is difficult to meet large-scale welding needs when used alone.

[0052] The present invention combines the two to form a coaxial composite laser. The core laser beam of the coaxial composite laser is a continuous laser. The stable heat input of the continuous laser provides basic energy to form a main molten pool in the middle. The outer ring laser beam of the coaxial composite laser is a pulsed laser to form an auxiliary molten pool around the main molten pool. The size of the point light spot in the middle and the surrounding ring light spot are adjusted to make the main molten pool overlap and connect with the auxiliary molten pool. 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, thereby increasing the laser energy absorption efficiency of highly reflective materials and greatly improving the welding penetration. The principle is:

[0053] First, the periodic disturbance of the pulsed laser causes dynamic fluctuations and microstructures (such as pits and ripples) on the surface of the molten metal, significantly increasing the roughness of the material surface. The rough surface will cause multiple reflections and scattering of the laser, extend the optical path length, and cause more photons to be absorbed by the material rather than directly reflected and escaped. For highly reflective materials (such as aluminum and copper), this effect can break through the energy loss bottleneck of mirror reflection.

[0054] Secondly, the high peak power of the pulsed laser instantly vaporizes the metal, forming a deep-melting keyhole structure. The light beam can directly enter the keyhole, and through the heat transfer of the keyhole, a larger welding depth can be obtained. The keyhole can also improve the quality of weld formation, reduce welding defects, and meet the welding requirements of highly reflective materials. Oscillating stirring causes the keyhole wall to fluctuate continuously, maintains the stability of the opening, and avoids keyhole collapse caused by metal vapor recoil.

[0055] Third, the forced convection of the molten metal can accelerate the transfer of heat to the bottom of the molten pool, while quickly drawing the unmelted material at the front end of the keyhole into the molten pool, breaking through the limitations of traditional heat conduction.

[0056] Fourthly, the short pulse width of the pulsed laser can suppress the plasma cloud that persists 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 a lower-power continuous laser is combined with a pulsed laser, the precision control capability of the pulsed laser can superimpose high-energy pulses in key areas, provide additional energy supplementation, and accurately control the dynamic behavior of the molten pool (such as melting depth and width). The high peak energy of the pulsed laser can instantly overcome the reflection barrier of the highly reflective material to the energy, allowing the material to quickly reach the temperature required for welding, thereby reducing the requirements for continuous laser power. In addition, the energy distribution of the heat source can be optimized by adjusting the energy ratio and focus position of the two lasers, and the energy state of the heat source can be precisely controlled 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, the appropriate energy distribution can cause the liquid metal to flow to the center of the weld instead of splashing outward. The orderly flow of liquid metal in the molten pool helps to stabilize the welding process and further achieve a zero-splash state.

[0058] Embodiment 2

[0059] This embodiment provides a method for welding a flat wire motor winding, using the coaxial composite laser welding method described in Embodiment 1, and comprising the following steps:

[0060] S1: pre-processing the flat wire 4;

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

[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 and damage to the laser when the coaxial composite laser beam acts on highly reflective materials;

[0063] S4: adjusting the power of the coaxial composite laser beam and the defocusing amount acting on the flat wire 4, and setting the welding trajectory and welding speed;

[0064] S5: start welding;

[0065] S6: Welding is completed and the coaxial composite laser beam is turned off.

[0066] This embodiment adopts the coaxial composite laser welding method described in Embodiment 1, and uses a composite of continuous laser and pulsed laser as the welding heat source for the flat wire 4 joint. The heat input can be reasonably distributed by adjusting the average power of the continuous laser and the pulsed laser, and the laser output is kept to have a small spot heat source. A coordinated use scheme of the continuous laser and the pulsed laser is established, which can accurately control the heat absorption of the base metal, improve the forming morphology of the flat copper wire welding joint, avoid defects such as pores and incomplete fusion, and enhance the performance of the weld joint to ensure that the flat wire 4 welding joint is well formed.

[0067] Furthermore, in S1, the pretreatment includes removing the insulating paint 7 and cleaning the stains on the surface of the flat wire 4. Specifically, the insulating paint 7 is removed by a length ranging from 10 to 15 mm; the stain cleaning includes oil cleaning and oxide layer elimination.

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

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

[0070] In S4, when the two flat wires 4 to be welded are fixed and qualified, the welding track is one or more of a circular welding track 8, a rectangular welding track 9 and a "sun" shaped welding track 10, and the circular welding track 8, the rectangular welding track 9 and the "sun" shaped welding track 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, a circular welding track 8 is used, and a semicircular track is welded on the lower side;

[0073] When there is a gap between the two flat wires 4 to be welded together, a circular welding track 8 is used and the diameter of the circular welding track 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 used.

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

[0076] The following is a detailed description of the method of coaxial composite laser welding of motor winding flat wire 4 in combination with specific experiments. The flat wire 4 selected in the experiment is T2 copper with good electrical conductivity and processing performance, with a cross-sectional size of 1.5×3mm, the continuous laser 2 is a fiber laser with a rated power of 2kW, the pulse laser 1 is a fiber laser with a rated power of 800W, and the shielding gas is argon with a purity of 99.99%.

[0077] Experiment 1

[0078] In the ideal fixing state before welding, that is, the two flat wires 4 to be welded are fixed properly, as shown in FIG. 2( a ), the flat wire motor winding is welded by coaxial composite laser.

[0079] S1: According to actual needs, the selected flat wire 4 is cut into 58 mm long strips, and the insulating paint 7 with a length of 10 mm at one end of the flat wire 4 is removed, and then the stains on the surface of the flat wire 4 are scrubbed clean with a cleaning agent, such as Figure 1 As shown;

[0080] S2: placing the pre-treated flat wire 4 on the welding clamping device 6, arranging the ends of the wires with the paint removed side by side to form the surfaces to be welded, and tightening the wires to ensure the welding effect;

[0081] S3: The pulse laser 1 emits a pulse laser, and the continuous laser 2 emits a continuous laser. The pulse laser and the continuous laser pass through the coaxial composite laser 3 to form a coaxial composite laser beam. The angle of the 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: adjusting 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 -1 mm;

[0083] The current and frequency of the pulse laser 1 and the continuous laser 2 are uniformly regulated, so that the average power of the pulse laser 1 is 360W and the power of the continuous laser 2 is 1700W, thereby improving the forming morphology of the flat wire 4 and achieving better conductive properties while ensuring that the weld of the flat wire 4 is fully penetrated;

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

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

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

[0087] S7: After welding is completed, the pulse laser 1, the continuous laser 2, the coaxial composite laser 3, the cooling device of the laser and the protective gas nozzle 5 are turned off.

[0088] Experiment 2

[0089] Before the ends of the flat wire motor windings are welded, several common defects may occur due to various reasons such as improper clamping. Figure 2(b) shows the state when a height difference occurs in the Z-axis direction. In this state, the flat wire motor windings are welded using coaxial composite laser.

[0090] S1: According to actual needs, cut the selected flat wire 4 into 58 mm long strips, remove the 12 mm long insulating paint 7 at one end of the flat wire 4, and then use a cleaning agent to clean the stains on the surface of the flat wire 4, such as Figure 1 As shown;

[0091] S2: Place the pre-treated flat wire 4 on the welding clamping device 6, and place the ends of the wires without the paint side by side to form the surface to be welded, and tighten them, leaving a height difference of 1 mm in the Z-axis direction;

[0092] S3: The pulse laser 1 emits a pulse laser, and the continuous laser 2 emits a continuous laser. The pulse laser and the continuous laser pass through the coaxial composite laser 3 to form a coaxial composite laser beam. The angle of the 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: adjusting 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 -2 mm;

[0094] The power of the pulse laser 1 and the continuous laser 2 are uniformly regulated, so that the average power of the pulse laser 1 is 300W and the power of the continuous laser 2 is 1500W, thereby improving the forming morphology of the flat wire 4. At the same time, under the premise of ensuring that the weld of the flat wire 4 is fully melted, the heat input is adjusted to achieve better conductivity;

[0095] The welding speed is set to 100 mm / min. According to the height difference defect fixed before welding, the welding path is adjusted, preferably a circular welding track 8, and a semicircular track is welded on the lower side. The diameter of the large circle is 1.9 mm, the radius of the semicircle is 0.5 mm, and it is located at the center of the surface to be welded, as shown in FIG5(a);

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

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

[0098] S7: After welding is completed, the pulse laser 1, the continuous laser 2, the coaxial composite laser 3, the cooling device of the laser and the protective gas nozzle 5 are turned off.

[0099] Experiment 3

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

[0101] S1: According to actual needs, cut the selected flat wire 4 into 58 mm long strips, remove the 14 mm long insulating paint 7 at one end of the flat wire 4, and then use a cleaning agent to clean the stains on the surface of the flat wire 4, such as Figure 1 As shown;

[0102] S2: Place the pre-treated flat wire 4 on the welding clamping device 6, place the ends of the flat wires without the paint in parallel to form the surface to be welded, tighten them, and leave a gap of 1 mm in the X-axis direction;

[0103] S3: The pulse laser 1 emits a pulse laser, and the continuous laser 2 emits a continuous laser. The pulse laser and the continuous laser pass through the coaxial composite laser 3 to form a coaxial composite laser beam. The angle of the 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: adjusting 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 -3 mm;

[0105] The power of the pulse laser 1 and the continuous laser 2 are uniformly regulated, so that the average power of the pulse laser 1 is 400W and the power of the continuous laser 2 is 1900W, thereby improving the forming morphology of the flat wire 4. At the same time, under the premise of ensuring that the weld of the flat wire 4 is fully melted, the heat input is adjusted to achieve better conductivity;

[0106] The welding speed is set to 200 mm / min, and the welding path is adjusted according to the gap defect fixed before welding, preferably a circular welding track 8. According to the gap width of 1 mm, the diameter of the circular welding track 8 is adjusted to 2 mm, which is located at the center of the surface to be welded, as shown in FIG5(b);

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

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

[0109] S7: After welding is completed, the pulse laser 1, the continuous laser 2, the coaxial composite laser 3, the cooling device of the laser and the protective gas nozzle 5 are turned off.

[0110] Experiment 4

[0111] Before the ends of the flat wire motor windings are welded, several common defects may occur due to various reasons such as improper clamping. Figure 2(d) shows the state when there is an offset in the Y-axis direction. In this state, the coaxial composite laser is used to weld the flat wire motor windings.

[0112] S1: According to actual needs, cut the selected flat wire 4 into 58 mm long strips, remove the 15 mm long insulating paint 7 at one end of the flat wire 4, and then use a cleaning agent to clean the stains on the surface of the flat wire 4, such as Figure 1 As shown;

[0113] S2: Place the pre-treated flat wire 4 on the welding clamping device 6, and place the ends of the flat wires 4 without the paint coating side by side to form the surface to be welded, and tighten them, leaving a 1mm offset in the Y-axis direction;

[0114] S3: The pulse laser 1 emits a pulse laser, and the continuous laser 2 emits a continuous laser. The pulse laser and the continuous laser pass through the coaxial composite laser 3 to form a coaxial composite laser beam. The angle of the 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: adjusting 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 -4 mm;

[0116] The power of the pulse laser 1 and the continuous laser 2 are uniformly regulated, so that the average power of the pulse laser 1 is 370W and the power of the continuous laser 2 is 1750W, thereby improving the forming morphology of the flat wire 4. At the same time, under the premise of ensuring that the weld of the flat wire 4 is fully melted, the heat input is adjusted to achieve better conductivity;

[0117] The welding speed is set to 250 mm / min, and the welding path is adjusted according to the offset defect fixed before welding, preferably an elliptical welding trajectory 8. According to the offset degree 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 FIG5(c);

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

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

[0120] S7: After welding is completed, the pulse laser 1, the continuous laser 2, the coaxial composite laser 3, the cooling device of the laser and the protective gas nozzle 5 are turned off.

[0121] After the welding test was completed, the flat wire was well-formed, no spatter was generated during the welding process, no defects such as pores, inclusions and cracks were found, and the laser did not damage the insulating paint of the flat wire. By conducting a conductivity test on the joint, it was found that the conductivity at the joint met production requirements.

[0122] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third" and the like are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0123] In the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0124] If the present invention discloses or involves components or structures that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (for example, connection using bolts or screws), and can also be understood as: a non-detachable fixed connection (for example, riveting, welding). Of course, the mutual fixed connection can also be replaced by an integrated structure (for example, manufactured by one-piece molding using a casting process) (except when it is obviously impossible to use an one-piece molding process).

[0125] In addition, unless otherwise stated, the terms used to indicate positional relationships or shapes in any technical solution disclosed in the present invention include states or shapes that are approximate, similar, or close thereto.

[0126] Any component provided by the present invention may be assembled from a plurality of separate components, or may be a separate component manufactured by an integral forming process.

[0127] It should be noted that the structures, proportions, sizes, etc. depicted in the drawings of this specification are only used to match the contents disclosed in the specification so that people familiar with this technology can understand and read them. They are not used to limit the conditions under which the present invention can be implemented. Therefore, they have no substantive technical significance. Any modification of the structure, change in the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0128] It should also be noted that in the embodiments of the present application, the same figure mark is used to represent the same component or the same part.

[0129] Adaptive changes made according to actual needs are all within the protection scope of the present invention.

[0130] It should be noted that it is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-restrictive from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any reference numerals in the claims should not be regarded as limiting the claims involved.

[0131] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A coaxial composite laser welding method, characterized in that: A coaxial composite laser beam is used to act on the surface of a highly reflective material to form a welding molten 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 molten pool, and the pulsed laser beam forms an auxiliary molten pool. The main molten pool and the auxiliary molten pool have an overlapping portion.

2. A method for welding a flat wire motor winding, characterized in that: The flat wire material is a highly reflective material, and the coaxial composite laser welding method according to claim 1 is adopted, comprising the following steps: S1: pre-process the flat wire; S2: Fix the two flat wires to be welded together, and arrange the end planes of the two flat wires side by side to form a surface to be welded; 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; S4: Adjust the power of the coaxial composite laser beam and the defocus amount acting on the flat wire, and set the welding trajectory and welding speed; S5: start welding; S6: Welding is completed and the coaxial composite laser beam is turned off.

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

4. The method for welding flat wire motor windings according to claim 3, characterized in that: The removal length of the insulating paint is 10 to 15 mm; stain cleaning includes oil cleaning and oxide layer elimination.

5. The method for welding flat wire motor windings according to claim 2, characterized in that: In S3, the angle between the coaxial composite laser beam and the normal direction of the surface to be welded is 5° to 15°.

6. The method for welding flat wire motor windings according to claim 2, characterized in that: In S4, the power of the continuous laser is 1400~2000W, and the average power of the pulsed laser is 200~500W; the defocusing amount of the coaxial composite laser beam acting on the flat wire is -4~0mm; and the welding speed is 50~250mm / min.

7. The method for welding flat wire motor windings according to claim 2, characterized in that: In S4, the welding track is one or more of circular, rectangular and "sun" shaped, and the circular, rectangular and "sun" shaped welding tracks cover the end planes of the two flat wires to be welded together.

8. The method for welding flat wire motor windings according to claim 2, characterized in that: In S4, 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 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 fore-and-aft offset between the two flat wires to be welded together, an elliptical welding trajectory is used.

9. The method for welding flat wire motor windings according to claim 2, characterized in that: During welding, shielding gas is sprayed to cover the welding area, and the shielding gas nozzle is at the rear end of the welding direction.

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

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