Diamond wire laser welding method and system

Abstract

The present invention provides a diamond wire laser welding method and a system. The method comprises: positioning two ends of a broken wire to make the two ends opposite to each other; respectively carrying out section shearing and cleaning on the two ends; acquiring pictures of the two ends by using a visual detection module, detecting and calculating the concentricity of the two ends, and controlling the two ends to automatically adjust the positions thereof to make the two ends concentric; aligning a target heating light spot of a laser generation module to a molten pool part composed of the two ends and a limited space around the two ends, and starting laser heating welding; monitoring a real-time temperature and a real-time crystal phase of the molten pool part, adjusting the heating power of the laser generation module on the basis of the real-time temperature, determining whether the degree of match between a real-time crystal phase image and a target crystal phase image is greater than a first threshold, and if yes, stopping welding; and polishing the weld, performing annealing and completing welding. The welding method of the present invention has a high degree of automation, laser welding is carried out by using the laser generation module, heating is fast, efficiency is high, and accurate and automatic welding is achieved by determining a crystal phase image.

Description

Diamond wire laser welding method and system Technical Field

[0001] The present invention belongs to the technical field of diamond wire welding, and in particular relates to a diamond wire laser welding method and system. Background Art

[0002] During the production of single-crystal silicon wafers, silicon rods are cut in both forward and reverse directions using a multi-wire diamond wire mesh with acceleration and deceleration. During the cutting process, diamond wire breakage often occurs due to mechanical, electrical, process parameters, and electronic control software system matching reasons. After the diamond wire breaks, the staff needs to weld or replace the diamond wire.

[0003] Current diamond wire welding methods include:

[0004] Resistance welding is a common welding method in the industry. However, this welding process has the disadvantages of low welding success rate, long welding time, poor welding appearance, and low tensile strength. These disadvantages greatly affect the efficiency and yield of silicon wafer production.

[0005] Brazing is a method of joining metals by simultaneously heating a filler metal (lower than the melting point of the workpieces) and the workpieces to their melting point. The liquid filler metal then fills the gaps between the solid workpieces, creating a smooth, aesthetically pleasing joint. However, the weld has relatively low tensile strength and is prone to re-fracture, impacting subsequent use.

[0006] Regardless of the welding method, manual welding operations are required throughout the process, with a low degree of automation. In addition, the welding method is unreliable, inefficient, and has low tensile strength at the welding position.

[0007] Summary of the Invention

[0008] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a diamond wire laser welding method and system, which solves the defects of the prior art in that the broken diamond wire cannot be welded with high quality and high efficiency.

[0009] In a first aspect, the present invention provides a diamond wire laser welding method, comprising:

[0010] Position the two ends of the broken wire so that the two ends face each other;

[0011] Perform cross-section shearing and cleaning on both ends respectively;

[0012] The visual inspection module is used to collect images of the two ends, detect and calculate the concentricity of the two ends, and control the two ends to automatically adjust their positions to make the two ends concentric;

[0013] Aim the target heating spot of the laser generating module at the molten pool consisting of the two ends and the limited space around them, and start laser heating welding;

[0014] Monitor the real-time temperature and real-time crystal phase of the molten pool, adjust the heating power of the laser generating module according to the real-time temperature, and determine whether the matching degree between the real-time crystal phase image and the target crystal phase image is greater than a first threshold. If so, stop welding;

[0015] Grind the weld, anneal, and complete the weld.

[0016] In some embodiments, when performing laser heating welding, the target heating spot is aimed at the molten pool to melt and vaporize the metal to form a heated hole. The visual detection module is used to determine whether the steam pressure in the heated hole is balanced with the surface tension and gravity of the liquid metal. If balanced, the target heating spot is controlled to move along the welding direction of the two ends to form a weld.

[0017] In some embodiments, a near-infrared thermal imaging module is used to monitor the molten pool to obtain a near-infrared image and a thermal imaging image. The switching duty cycle parameters of the laser generating module are determined based on the grayscale of the near-infrared image and the heat distribution coefficient of the thermal imaging image, and the heating power of the laser generating module is adjusted based on the switching duty cycle parameters.

[0018] In some embodiments, the welding cycle is divided into several stages. According to the diamond wire of different materials, for each stage, the grayscale constant of the corresponding near-infrared image and the thermal distribution coefficient constant of the thermal imaging image are determined, the corresponding switch duty cycle parameters are set, and the two ends of the broken wire are welded in stages.

[0019] In some embodiments, the laser generating module is a picosecond laser generator, which uses a laser with a wavelength of 600nm to 700nm to perform staged welding on the two ends of the broken wire.

[0020] In some embodiments, target crystal phase images are set for diamond wires of different materials and specifications. The target crystal phase image is configured to select a diamond wire, align the target heating spot of the laser generating module with a part of the diamond wire, achieve a balance between the vapor pressure and the surface tension and gravity of the liquid metal in the part, and complete heating along the radial direction, and then collect the resulting crystal phase image.

[0021] In some embodiments, the two ends of the broken wire are placed on a magnetic platform provided with a V-groove, and the broken wire is pressed from top to bottom by a pressing block, so that the ends of the broken wire are extended out of the magnetic platform to set an extension distance, and the pressure F applied to the pressing block by the cylinder is <[78500*N / (cos a / 2)]-(m1+m)*g, wherein the mass of the pressing block is m, the mass of the broken wire in contact with the magnetic platform per unit area is m1, the angle of the V-groove in the magnetic platform is a, and the number of diamond particles on the contact surface between the broken wire and the magnetic platform is N.

[0022] In some embodiments, when performing cross-sectional shearing on both ends, a double-edged circular cutting tool is used to simultaneously apply shearing force inward along the radial direction of a certain section of the broken wire to form a welding section perpendicular to the axial centerline of the broken wire at the end.

[0023] In some embodiments, when grinding the weld, a grinding mechanism is used to wrap the weld formed on the molten pool. Diamond abrasive is embedded in the contact surface between the grinding mechanism and the weld. The grinding mechanism is controlled to perform high-hertz micro-amplitude cross-frequency vibration to eliminate surface bubbles and impurities in the weld.

[0024] In a second aspect, the present invention provides a welding system applied to the above-mentioned diamond wire laser welding method, comprising:

[0025] A positioning mechanism for positioning the ends of the broken wire so that the two ends face each other;

[0026] A shearing mechanism, used for shearing the two ends respectively;

[0027] A cleaning mechanism, used for cleaning both ends respectively;

[0028] The visual inspection module is used to collect images of the two ends, detect and calculate the concentricity of the two ends, and control the positioning mechanism to drive the two ends to automatically adjust their positions so that the two ends are concentric;

[0029] The laser generating module is used to generate a target heating spot aimed at the molten pool composed of the two ends and the limited space around them, and perform laser heating welding;

[0030] a detection module for monitoring the real-time temperature and real-time crystal phase of the molten pool, adjusting the heating power of the laser generating module according to the real-time temperature, and determining whether the matching degree between the real-time crystal phase image and the target crystal phase image is greater than a first threshold. If so, controlling the laser generating module to stop welding;

[0031] A grinding mechanism, used for grinding the weld;

[0032] The annealing mechanism is used to anneal the broken wires after welding and grinding.

[0033] Compared with the prior art, the beneficial effects of the present invention include at least:

[0034] When positioning the two ends of the broken wire, the visual inspection module collects images of the two ends, controls the two ends to automatically adjust their positions on three axes, and ensures concentricity; and uses the target heating spot to align with the molten pool, so that the real-time crystal phase image formed on the molten pool matches the target crystal phase image to a greater than a first threshold value. The welding process is completed through automatic control and detection, and finally polishing and annealing are performed to complete the welding. This welding method has a high degree of automation and uses a laser generation module for laser welding, which has fast heating and high efficiency. Precise automatic welding is achieved through the judgment of the crystal phase image. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention is further described with reference to the accompanying drawings. However, the embodiments in the accompanying drawings do not constitute any limitation to the present invention. A person skilled in the art can obtain other drawings based on the following drawings without creative effort.

[0036] FIG1 is a schematic flow chart of a diamond wire laser welding method according to an embodiment.

[0037] FIG2 is a schematic diagram of a process flow during laser heating welding in one embodiment.

[0038] FIG3 is a schematic structural diagram of a positioning mechanism in an embodiment.

[0039] FIG4 is a schematic diagram of a pressing block pressing a broken wire onto a V-shaped groove of a magnetic platform in an embodiment.

[0040] FIG5 is a schematic structural diagram of an annealing mechanism in an embodiment. DETAILED DESCRIPTION

[0041] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0042] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0043] In the description of the present invention, when a specific device is described as being located between a first device and a second device, an intervening device may or may not be present between the specific device and the first device or the second device. When a specific device is described as being connected to another device, the specific device may be directly connected to the other device without an intervening device, or may be directly connected to the other device but with an intervening device.

[0044] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0045] The applicant's research found that:

[0046] When a diamond wire breaks, existing techniques typically use resistance welding or brazing to weld the broken wire. Both methods require manual welding, resulting in low welding efficiency, poor consistency, and a low degree of automation. Various welding factors can affect the quality of the welded diamond wire, significantly reducing cutting performance. This is particularly true for high-carbon steel (0.92% to 0.98%) or tungsten steel, which, due to their poor plasticity, are prone to cracking and exhibit poor weldability. Furthermore, the melting point of tungsten steel diamond wire is above 2850°C, making conventional welding machines incapable of meeting these requirements.

[0047] In view of this, referring to FIG. 1 , in a first aspect, a diamond wire laser welding method is provided in an embodiment of the present disclosure, comprising:

[0048] Position the two ends of the broken wire so that they face each other and are spaced a certain distance apart.

[0049] Cut the two ends of the wire separately so that the two sections have the same cross-sectional area, clean and remove the oxide film and oil stains on the surface of the two ends of the broken wire;

[0050] The visual inspection module is used to capture images of both ends, detect and calculate the concentricity of the two ends, and control the two ends to automatically adjust their positions so that the two ends are concentric. It should be noted that the two ends of the broken wire are respectively fixed by a positioning mechanism. The positioning mechanism has a three-axis servo centering function and can automatically align the cross-section of the end according to the concentricity detection and calculation results.

[0051] Aim the target heating spot of the laser generating module at the molten pool formed by the two ends and the limited space around them, and start laser heating welding. It should be noted that before laser heating welding, since the two ends are separated, when welding starts, the two ends are first irradiated with the target heating spot. In addition to covering the cross-sections of the two ends, the target heating spot also covers a section of the line behind the cross-section. Under the laser heating of the target heating spot, the molten pool formed by the two ends and the limited space around them begins to melt.

[0052] Monitor the real-time temperature and real-time crystal phase of the molten pool, adjust the heating power of the laser generating module according to the real-time temperature, control the temperature of the molten pool to be greater than the melting point of the wire, and judge whether the matching degree between the real-time crystal phase image and the target crystal phase image is greater than a first threshold value. If so, stop welding. Specifically, the target crystal phase image is tested in advance, and the broken wires of different diamond wire materials and specifications are welded respectively through the combination of several groups of laser frequency parameters and power parameters to obtain multiple groups of diamond wire welding joints, and each group of diamond wire welding joints is strength tested. For each material and specification, the best target crystal phase image and corresponding welding control parameters are determined. During the welding process, the corresponding welding control parameters are set according to the specific diamond wire material and specification, and the matching degree between the real-time crystal phase image and the target crystal phase image is calculated. Only when the matching degree is greater than the first threshold value can it be judged that the molten pool has been melted through and the ideal crystal phase state has been reached, and then stop welding.

[0053] Then the welded joints of the welded diamond wires are ground and annealed to complete the welding.

[0054] The laser welding method in the above embodiment changes the traditional manual welding method by means of visual detection and automatic control, realizes automatic welding, and improves welding efficiency.

[0055] Referring to Figure 2, as an embodiment, during laser heating welding, the target heating spot is aimed at the molten pool, causing the metal to melt and vaporize to form a heated hole. During this process, the liquid metal flows outside the heated hole wall, and the surface tension of the wall layer and the steam pressure continuously generated in the heated hole cavity must be in a stalemate and maintain a dynamic balance. As the light beam continues to enter the heated hole, the metal material outside the heated hole maintains a continuous flow. When the equilibrium state is reached, the heated hole is always in a stable state of flow.

[0056] Therefore, the visual inspection module is used to determine whether the steam pressure in the heated hole is balanced with the surface tension and gravity of the liquid metal. By judging whether the state of the heated hole remains stable, the overall size does not expand, and the metal material outside the heated hole remains in continuous flow within the first time interval, if so, the current heated hole is judged to be balanced, and the target heating spot is controlled to move along the welding direction of the two ends. As the light beam moves, the heated hole is always in a stable state of flow. That is to say, the heated hole and the molten metal surrounding the heated hole wall move along the moving direction of the target heating spot. The molten metal fills the gap left after the heated hole is removed to form a weld.

[0057] The laser welding method in this embodiment achieves a deeper penetration and a larger aspect ratio. This method compensates for the welding characteristics of high-carbon steel by generating less thermal stress through more concentrated heat energy. This significantly improves the welding success rate of high-carbon steel diamond wire, shortens the welding time, and reduces the reliance on welding skills during welding, effectively increasing the degree of automation. Furthermore, the high energy density of the laser can be used to weld tungsten steel diamond wire with a melting point above 2850°C.

[0058] As an embodiment, when monitoring the real-time crystal phase of the molten pool, a scanning electron microscope is used to collect real-time crystal phase images of the molten pool, and cluster analysis is performed on the real-time crystal phase images to confirm two results:

[0059] The first result is obtained based on solid-state crystal phase clustering. The first-level clustering is performed based on the distribution position of the solid-state crystal phase, and then the structural feature clustering is performed on the first-level clustering results to obtain the first result.

[0060] The second result is the result obtained based on liquid crystal phase clustering. The first-level clustering is performed based on the distribution position of the liquid crystal phase, and then the structural feature clustering is performed based on the first-level clustering result to obtain the second result.

[0061] Performing crystal distribution feature extraction on the first result to obtain solid crystal phase position feature information;

[0062] Performing crystal distribution feature extraction on the second result to obtain liquid crystal phase position feature information;

[0063] The solid crystal phase position characteristic information and the liquid crystal phase position characteristic information represent position distribution information of the solid crystal phase and the liquid crystal phase in the real-time crystal phase image, and a first ratio of the liquid crystal phase distribution area to the real-time crystal phase image is calculated;

[0064] In the same way, for a specific diamond wire material and specification, the above cluster analysis is performed according to the target crystal phase image obtained according to the preset optimal welding control parameters, and the second proportion of the liquid crystal phase distribution area in the target crystal phase image is also obtained;

[0065] By automatic detection and judgment, only when the ratio of the first ratio to the second ratio is greater than the first threshold value, preferably, the first threshold value is 98%, it is proved in actual laser welding that the diamond wire molten pool has been melted through and welding can be stopped.

[0066] It should be noted that since diamond wire is primarily composed of silicon, with some carbon or tungsten, all components exist in a solid state before laser heating. Once laser heating melts them, they exist in a liquid state. The solid and liquid phases have distinct structural characteristics, making cluster analysis possible. Preferably, the above cluster analysis is performed for silicon.

[0067] Therefore, in this embodiment, after the target heating spot is aligned with the molten pool, the visual detection module is first used to collect an image of the molten pool to determine whether the steam pressure in the heated hole is balanced with the surface tension and gravity of the liquid metal. If balanced, the target heating spot is moved to form a weld. Then, a scanning electron microscope is used to collect a real-time crystal phase image of the molten pool, and a cluster analysis is performed on the real-time crystal phase image including at least a portion of the weld. The first proportion of the liquid crystal phase distribution area in the real-time crystal phase image is calculated, and then compared with the second proportion of the liquid crystal phase distribution area in the target crystal phase image in the target crystal phase image. When the ratio of the first proportion to the second proportion is greater than 98%, it proves that the molten pool of the diamond wire has been fully melted and the liquid crystal phase distribution is ideal. After the welding is stopped and the cooling is stopped, a good weld quality can be achieved.

[0068] Preferably, target crystal phase images are set respectively for diamond wires of different materials and specifications, and the target crystal phase images are obtained through the following steps: a selected diamond wire with specific materials and specifications is selected, and the target heating spot of the laser generating module is aimed at a part of the diamond wire. It should be noted that this part is a complete part of the diamond wire, and the metal is melted and vaporized on this part to form a heated hole. The heated hole is observed by a visual detection module until the steam pressure in the heated hole is balanced with the surface tension and gravity of the liquid metal. The heating is completed along the radial direction of the diamond wire to form a weld, and the crystal phase image of the weld is collected using a scanning electron microscope to obtain the target crystal phase image.

[0069] The reason why a complete part of the diamond wire is selected for welding is that this laser welding does not require additional welding materials. It only requires melting the raw materials at both ends of the broken wire and fusing the two raw materials. In order to improve the quality of the weld, it is compared with the weld formed after laser heating on the complete diamond wire. This can ensure that after the broken wire is welded, the relevant physical parameters of the diamond wire still meet the requirements of the single crystal silicon wafer cutting process, and the tensile strength of the welding position basically reaches the level of the original diamond wire.

[0070] Since the target crystal phase image has been determined in advance according to the specific diamond wire specifications, the target crystal phase image includes the distribution area of ​​the liquid silicon crystal phase and the ideal structural characteristics. The ratio of the liquid crystal phase distribution area is determined by image comparison, and manual visual verification can be added. After confirmation, welding is stopped.

[0071] As an implementation method, during the welding process, a near-infrared thermal imaging module is used to monitor the molten pool portion to obtain a near-infrared image and a thermal imaging image, which are then transmitted to an imaging processing module for processing to obtain the grayscale of the near-infrared image and the thermal distribution coefficient of the thermal imaging image. The grayscale and the thermal distribution coefficient are analyzed and processed to determine which position in the molten pool portion has uneven heat distribution. For areas where heat is concentrated, the switching duty cycle parameters of the laser generating module are adjusted to reduce the heating power of the laser generating module. For areas where heat is insufficient, the switching duty cycle parameters of the laser generating module are adjusted to increase the heating power of the laser generating module, so that the total power of the diamond wire is maintained at a relatively stable level during the welding process to ensure the quality consistency of the weld.

[0072] As an implementation method, the welding cycle is divided into several stages. According to the different materials of diamond wire, for each stage, the grayscale constant of the corresponding near-infrared image and the thermal distribution coefficient constant of the thermal imaging image are determined, the corresponding switch duty cycle parameters are set, and the two ends of the broken wire are welded in stages.

[0073] Among them, the welding cycle can be divided into five welding stages: preheating, cleaning, welding, tempering, and quenching and tempering. According to the specific material and specifications of the diamond wire, for each welding stage, the welding control parameters are set in advance. After multiple sets of tests, the set of parameters with the best welding quality is obtained as the optimal welding control parameters. The optimal laser welding power is determined for each stage, and the corresponding switching duty cycle parameters are obtained; in addition, by conducting advance tests on the five welding stages, the ideal near-infrared image grayscale constant and the thermal distribution coefficient constant of the thermal imaging image can be determined for each stage. These are used for comparison with the near-infrared image and thermal imaging image obtained by the near-infrared thermal imaging module during the welding process, thereby achieving precise heating control in multiple welding stages.

[0074] Optionally, the laser generating module is a picosecond laser generator, which uses a laser with a wavelength of 600nm to 700nm to perform staged welding on the two ends of the broken wire.

[0075] Among them, for the five welding stages of preheating, cleaning, welding, tempering, and quenching and tempering, welding is performed with an appropriate laser according to the demand for heat and temperature rise. For example, in the preheating stage, the demand for heat is not too high, and a laser with a lower frequency and lower energy density can be emitted; in the welding stage, the demand for heat is high and rapid temperature rise is required, and a laser with a higher frequency and higher energy density can be emitted; in the tempering and quenching and tempering stages, a relatively stable heat needs to be maintained to fine-tune the welding quality, and a laser with a higher frequency and moderate energy density can be emitted.

[0076] The above laser adjustment function can automatically switch to different laser frequencies and energy densities according to the welding stage through program preset, thereby improving the refined control of welding. Moreover, through staged laser welding control, the appearance and diameter consistency of the diamond wire after welding can be improved. Since no additional welding materials are added, in order to achieve immediate use after welding, the control of the welding process is particularly important. Among them, in the tempering stage, the diameter of the weld can be adjusted with a laser with a higher frequency and moderate energy density to keep the outer diameter basically consistent.

[0077] During the welding process, very high requirements are placed on the fixing stability of the two ends of the broken wire. If the two ends become loose during the welding process, the welding quality will be affected, which will directly lead to inconsistency in the appearance and diameter of the diamond wire. Therefore, in order to solve the above problems, this embodiment places the two ends of the broken wire on a magnetic platform provided with a V-shaped groove. It should be noted that the top end of the broken wire still exceeds the top of the V-shaped groove, and then a pressure block is used to press the broken wire from top to bottom. The pressure block is made of polyurethane and presses vertically to the broken wire to ensure that the diamond wire is subjected to force as evenly as possible when under pressure, and to prevent the diamond wire from moving in a circle around the center when subjected to oblique force, thereby reducing the tensile strength of the diamond wire. At the same time, the polyurethane pressure block applies a reasonable pressure value to the diamond wire, and the polyurethane pressure block has a reasonable hardness value to ensure that when the pressure block positions the diamond wire, the diamond particles on the diamond wire will not penetrate the polyurethane body, and the pressure block will not crush the diamond particles.

[0078] The ends of the broken wire are extended beyond the magnetic platform by a set distance. Preferably, the extension distance is a fixed value, 1.5 to 2 times its diameter. During the welding process, due to the high carbon content and impurities in the diamond wire, volatilization occurs, necessitating the feeding of diamond wire. Therefore, the magnetic platform can be moved horizontally by a three-axis servo centering mechanism. During laser welding, the target heating spot is aligned with the molten pool formed by the two ends and the limited space around them. Once the molten pool begins to melt, the two ends of the broken wire move toward each other, contacting each other, and achieving better fusion. The servo motor in the three-axis servo centering mechanism uses a quantitative feed method to extend the diamond wire forward.

[0079] In this process, in order to effectively control the broken wire and prevent the broken wire from displacement or rotation, it is assumed that:

[0080] The mass of the briquette is m;

[0081] The angle of the V-groove in the magnetic platform is a;

[0082] The two inclined surfaces of the V-groove are subjected to vertical pressures F1 and F2 respectively;

[0083] Assume that the diamond particles are cylindrical with a diameter of 0.005 mm;

[0084] The mass of the broken wire in contact with the magnetic platform per unit area is m1;

[0085] The pressure applied to the pressing block by the cylinder is F;

[0086] Assume that the compressive strength of artificial diamond is 2000Mpa;

[0087] Assume that there are N diamond particles on the contact surface;

[0088] Then we have:

[0089] [(m1+m)*g+F]*1 / 2*cos a / 2=F1=F2

[0090] [(m1+m)*g+F]*1 / 2*cos a / (N*π*0.00000625)<2000Mpa

[0091] Finally, it is concluded that the pressure F applied to the pressing block by the cylinder is less than [78500*N / (cos a / 2)]-(m1+m)*g.

[0092] The pressure F applied by the cylinder to the pressing block needs to satisfy the above formula to ensure that the diamond particles are not crushed and to maintain effective compression force to avoid twisting and displacement of the diamond wire.

[0093] Furthermore, the strength of diamond wire welding is directly proportional to the weld area and the quality of the weld pool. Therefore, ensuring the concentricity of the two ends of the wire during welding is extremely important. The relative parallelism of the two end sections, as well as the flatness of the cross-section and its edges, determine the quality of the weld. Traditionally, the wire is cut with a straight blade, which can easily deform the wire, resulting in curled edges, beveled sections, or straight lines. Consequently, the quality of the weld cannot be guaranteed when the wire is cut under these conditions.

[0094] Therefore, in this embodiment, when performing cross-section shearing on the two ends, a double-edged circular cutting tool is used to apply shear force inward simultaneously along the radial direction of a certain section of the broken wire to ensure that the outer diameter of the diamond wire is subjected to uniform and simultaneous force at the cutting point during the cutting process. Under the action of uniform radial force, stress cracks are generated along the section, and finally the diamond wire is broken along the vertical section at the end to form a welding section perpendicular to the axial center line of the broken wire, ensuring the parallelism of the welding sections at the two ends and the flatness of the section edges, thereby ensuring better fusion of the broken sections during welding and improving the welding quality.

[0095] As an implementation method, when grinding the weld, a grinding mechanism is used to wrap the weld formed on the molten pool. Diamond abrasive is embedded in the contact surface between the grinding mechanism and the weld. The grinding mechanism is controlled to perform high-Hz micro-amplitude cross-frequency vibration, and surface bubbles and impurities in the weld are eliminated during the high-frequency vibration process.

[0096] After laser welding, the broken wire has achieved a high degree of diameter consistency, and the outer diameter of the weld is slightly larger than the outer diameter of the diamond wire. At this time, fine grinding can be directly adopted. The grinding mechanism is controlled to perform slight cross-frequency vibration at a high frequency of 30 to 50 khz / s, and the embedded diamond sand is directly used for fine grinding. Moreover, at high frequency, the appearance quality of the diamond wire can be guaranteed to be in a good state, thereby achieving a low defect rate in the later silicon wafer cutting process.

[0097] 3 to 5 , in a second aspect, an embodiment of the present disclosure provides a welding system applied to the above-mentioned diamond wire laser welding method, comprising:

[0098] The positioning mechanism 11 is used to position the end 10 of the broken wire so that the two ends are opposite each other. The positioning mechanism 11 includes a magnetic platform 20 with a V-shaped groove 21, a pressure block 22 and a three-axis servo centering mechanism. The pressure block 22 presses the broken wire on the V-shaped groove 21 of the magnetic platform 20. The three-axis servo centering mechanism controls the synchronous movement of the magnetic platform 20 and the pressure block 22 to achieve centering and diamond wire feeding. FIG3 shows that a single positioning mechanism 11 fixes one end 10 of the broken wire. In order to complete diamond wire laser welding, two positioning mechanisms 11 are required to position the two ends respectively so that the two ends are opposite each other.

[0099] The shearing mechanism is used to perform cross-section shearing on both ends respectively; the shearing mechanism uses a double-edged circular cutting tool to cut the end of the diamond wire along the vertical section to form a welding section perpendicular to the axial center line of the broken wire;

[0100] The cleaning mechanism is used to clean both ends separately; by spraying alcohol, the grease on the surface of the broken wire is dissolved, the oxide film and oil stains on the broken wire end are removed, and the formation of pores and slag inclusions during welding is prevented;

[0101] The visual inspection module is used to collect images of the two ends, detect and calculate the concentricity of the two ends, and control the positioning mechanism to drive the two ends to automatically adjust their positions so that the two ends are concentric;

[0102] A laser generating module is used to generate a target heating spot aimed at the molten pool composed of the two ends and the limited space around them, and perform laser heating welding; preferably, the laser generating module is a picosecond laser generator, which uses a laser with a wavelength of 600nm to 700nm to perform staged welding on the two ends of the broken wire;

[0103] A detection module is used to monitor the real-time temperature and real-time crystal phase of the molten pool, adjust the heating power of the laser generating module according to the real-time temperature, and determine whether the matching degree between the real-time crystal phase image and the target crystal phase image is greater than a first threshold value. If so, the laser generating module is controlled to stop welding. The detection module includes a scanning electron microscope, a near-infrared thermal imaging module, and a processing module. The scanning electron microscope collects the real-time crystal phase image of the molten pool, and the processing module performs cluster analysis on the real-time crystal phase image to determine whether the matching degree between the real-time crystal phase image and the target crystal phase image is greater than a first threshold value. The near-infrared thermal imaging module monitors the molten pool to obtain a near-infrared image and a thermal imaging image, transmits the near-infrared image and the thermal imaging image to the processing module for processing, obtains the grayscale of the near-infrared image and the thermal distribution coefficient of the thermal imaging image, determines the switch duty cycle parameter of the laser generating module, and adjusts the heating power of the laser generating module according to the switch duty cycle parameter.

[0104] The grinding mechanism is used to grind the weld; the grinding mechanism wraps the weld formed on the molten pool, and the contact surface between the grinding mechanism and the weld is embedded with diamond sand. The grinding mechanism is controlled to perform high-hertz micro-amplitude cross-frequency vibration to eliminate surface bubbles and impurities in the weld.

[0105] The annealing mechanism is used to anneal the broken wire after welding and grinding; a large amount of heat will be generated during the welding process of the broken diamond wire; after welding is completed, some heat energy cannot be released during the cooling process at room temperature, resulting in thermal stress in the molten pool and the heat-affected zone of the molten pool, thereby reducing the tensile strength of the material in the molten pool and the heat-affected zone of the molten pool; as shown in Figure 5, in the annealing mechanism, the diamond wire is clamped and suspended by a clamping device 31, and the heating pole 32 of the annealing mechanism is used to contact the two ends of the molten pool. The heating pole 32 is a low-resistance alloy conductor, which heats and anneals the molten pool and the heat-affected zone. The outside of the heating pole 32 is an insulating material 33 to prevent electric shock.

[0106] Compared with the prior art, the present invention provides a diamond wire laser welding method and system. When positioning the two ends of a broken wire, the visual detection module collects images of the two end portions, controls the two end portions to automatically adjust their positions on three axes, and ensures concentricity. The target heating spot is aligned with the molten pool portion, so that the matching degree between the real-time crystal phase image formed on the molten pool portion and the target crystal phase image is greater than a first threshold value. The welding process is completed by automatic control and detection, and finally polishing and annealing are performed to complete the welding. This welding method has a high degree of automation and utilizes a laser generation module for laser welding, which has fast heating and high efficiency. Precise and automatic welding can be achieved by judging the crystal phase image.

[0107] Finally, it should be emphasized that the present invention is not limited to the above-mentioned embodiments. The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A diamond wire laser welding method, characterized in that: include: Positioning the two ends of the broken wire so that the two ends are opposite to each other; Perform cross-section shearing and cleaning on both ends respectively; The visual inspection module is used to collect images of the two ends, detect and calculate the concentricity of the two ends, and control the two ends to automatically adjust their positions so that the two ends are concentric; Aim the target heating spot of the laser generating module at the molten pool portion consisting of the two ends and the limited space around them, and start laser heating welding; Monitor the real-time temperature and real-time crystal phase of the molten pool, adjust the heating power of the laser generating module according to the real-time temperature, and determine whether the matching degree between the real-time crystal phase image and the target crystal phase image is greater than a first threshold value. If so, stop welding; Grind the weld, anneal, and complete the weld.

2. A diamond wire laser welding method as claimed in claim 1, characterized in that: During laser heating welding, the target heating spot is aimed at the molten pool to melt and vaporize the metal to form a heat hole. The visual detection module is used to determine whether the steam pressure in the heat hole is balanced with the surface tension and gravity of the liquid metal. If balanced, the target heating spot is controlled to move along the welding direction of the two ends to form a weld.

3. A diamond wire laser welding method as claimed in claim 2, characterized in that: A near-infrared thermal imaging module is used to monitor the molten pool to obtain near-infrared images and thermal imaging images. The switch duty cycle parameters of the laser generating module are determined based on the grayscale of the near-infrared image and the heat distribution coefficient of the thermal imaging image. The heating power of the laser generating module is adjusted based on the switch duty cycle parameters.

4. A diamond wire laser welding method as claimed in claim 3, characterized in that: The welding cycle is divided into several stages. According to the different materials of diamond wire, for each stage, the gray level constant of the corresponding near-infrared image and the heat distribution coefficient constant of the thermal imaging image are determined, the corresponding switch duty cycle parameters are set, and the two ends of the broken wire are welded in stages.

5. A diamond wire laser welding method as claimed in claim 4, characterized in that: The laser generating module is a picosecond laser generator, which uses a laser with a wavelength of 600nm to 700nm to perform staged welding on the two ends of the broken wire.

6. A diamond wire laser welding method as claimed in claim 5, characterized in that: Target crystal phase images are set for diamond wires of different materials and specifications respectively. The target crystal phase image is configured to select a diamond wire, aim the target heating spot of the laser generating module at a part of the diamond wire, achieve a balance between the vapor pressure and the surface tension and gravity of the liquid metal in the part, and complete the heating along the radial direction, and then collect the resulting crystal phase image.

7. A diamond wire laser welding method according to any one of claims 1 to 6, characterized in that: Place the two ends of the broken wire on a magnetic platform with a V-groove, use a pressure block to press the broken wire from top to bottom, and make the ends of the broken wire extend out of the magnetic platform to set the extension distance, and apply a pressure F<[78500*N / (cos a / 2)]-(m1+m)*g to the pressure block through the cylinder, wherein the mass of the pressure block is m, the mass of the broken wire in contact with the magnetic platform per unit area is m1, the angle of the V-groove in the magnetic platform is a, and the number of diamond particles on the contact surface between the broken wire and the magnetic platform is N.

8. A diamond wire laser welding method as claimed in claim 7, characterized in that: When performing cross-section shearing on both ends, a double-edged circular cutting tool is used to simultaneously apply shearing force inward along the radial direction of a certain section of the broken wire, so that a welding section perpendicular to the axial center line of the broken wire is formed at the end.

9. A diamond wire laser welding method as claimed in claim 8, characterized in that: When grinding the weld, the weld formed on the molten pool is wrapped with a grinding mechanism, the contact surface between the grinding mechanism and the weld is embedded with corundum, and the grinding mechanism is controlled to perform high-Hz micro-amplitude cross-frequency vibration to eliminate surface bubbles and impurities in the weld.

10. A welding system applied to a diamond wire laser welding method as claimed in any one of claims 1 to 9, characterized in that: include: A positioning mechanism, used to position the ends of the broken wire so that the two ends are opposite to each other; A shearing mechanism, used for performing cross-section shearing on both ends respectively; A cleaning mechanism, used for cleaning the two ends respectively; The visual inspection module is used to collect images of the two ends, detect and calculate the concentricity of the two ends, and control the positioning mechanism to drive the two ends to automatically adjust their positions so that the two ends are concentric; A laser generating module is used to generate a target heating spot aimed at a molten pool portion composed of two end portions and a limited space around them, and perform laser heating welding; A detection module is used to monitor the real-time temperature and real-time crystal phase of the molten pool, adjust the heating power of the laser generating module according to the real-time temperature, and determine whether the matching degree between the real-time crystal phase image and the target crystal phase image is greater than a first threshold. If so, control the laser generating module to stop welding; A grinding mechanism, used for grinding the weld; The annealing mechanism is used to anneal the broken wire after welding and grinding.

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