A double laser welding method for high-precision shaft tooth structure

Abstract

The application provides a double laser welding method for high-precision shaft tooth structure, belongs to the double laser welding wire filling technical field, and adjusts the coaxial combination of the continuous and pulse lasers before welding starts, the laser beam axis and the welding plane are 90 DEG, the wire feeding angle is set to 18 DEG, the continuous and pulse defocusing amounts are both 0mm, the current of the continuous laser, the current and frequency of the pulse laser are regulated and controlled, the wire feeding speed is regulated and controlled to be 900mm / min, the welding speed and the laser action position are adjusted by the computer general control, the combination of the low continuous laser power and the pulse laser is realized under the premise of guaranteeing the weld penetration, the problems of the excessively large heat affected zone of the arc welding and the poor performance of the structural member are solved on the one hand, the heat input of the continuous laser is reduced, the use range of the continuous laser low power is improved, the welding deformation of the shaft body and the gear is reduced, and the mechanical properties of the weld joint are improved.

Description

Technical Field

[0001] This invention relates to the field of laser welding methods, and more specifically to a dual-laser welding method for high-precision shaft and gear structures. Background Technology

[0002] How to connect shafts and gears is a crucial research issue affecting the development of mechanical parts. Currently, the main connection methods include: 1) connecting the shaft and gear with bolts; 2) assembling them by welding. When connecting with bolts, the shaft and gear need to be thickened at the threaded positions, thus generally increasing the overall mass after assembly, which is not conducive to lightweight design. Welding is a newer connection method. Removing the threaded holes of the shaft and gear reduces the number of machining steps, and while ensuring the strength of the parts, it can reduce the wall thickness to a certain extent, thus optimizing the overall mass and cost of the parts. Compared with arc welding, laser welding has the advantages of high energy density, strong welding penetration, and fast welding speed, resulting in a narrow heat-affected zone and a high weld depth-to-width ratio, making it particularly suitable for the working characteristics of gear parts. Laser welding produces welds with smooth, flat surfaces free of defects such as porosity.

[0003] However, due to the small spot diameter of a single continuous laser, achieving the required penetration depth requires further increases in laser heat input power, resulting in a larger heat-affected zone. For the base metal of the shaft, materials such as QT500 and QT600 are commonly used. These materials are highly susceptible to carbon migration, leading to the formation of ledeburite and martensite in the weld area. This can cause cracks during use, ultimately leading to workpiece failure.

[0004] Therefore, a new welding method is needed to achieve high-precision welding of shaft gear structures.

[0005] Dual-laser beam welding is an emerging welding technology that uses continuous-pulse dual laser beams for composite welding. It can effectively improve the surface quality of the weld, reduce the hardness of the weld and the sensitivity to centerline cracking. Due to the addition of pulsed laser, the molten pool can achieve a stirring effect, and the filler metal is more uniform. While meeting the requirements of deep welding, it reduces the input power of continuous laser and reduces welding deformation.

[0006] Based on the aforementioned research status, this invention proposes a dual-laser beam welding method for high-precision shaft gear weld joints. This method uses a combination of continuous laser and pulsed laser welding as the welding heat source. The angle between the welding wire and the surface to be welded is adjusted using a fixture to ensure uniform filling of the weld seam. The laser spot is adjusted to fully melt the welding wire, improving the droplet state and minimizing laser heat absorption by the base metal of the workpiece. By adjusting the laser's focus, power, and position, a small-spot heat source is maintained, establishing a combined use of low-continuous laser and pulsed laser. The heat input to different base materials on both sides is optimized by shifting the laser's position, allowing for more precise control of the heat-affected zone on the shaft side. Under certain penetration depth conditions, this reduces heat input to the base material on the shaft side, solving the problem of poor mechanical properties that easily occurs when welding and assembling high-precision shaft gear structures. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a dual-laser welding method for high-precision shaft and gear structures. This invention primarily utilizes a dual-laser beam welding method, an emerging welding technology. By employing a continuous-pulsed dual-laser beam composite welding process, the surface quality of the weld is effectively improved, and the hardness and centerline cracking sensitivity of the weld are reduced. The addition of the pulsed laser enhances the stirring effect of the molten pool, resulting in more uniform filler metal. While achieving deeper welds, the input power of the continuous laser is reduced, minimizing welding deformation. Based on the current research, this invention proposes a dual-laser beam welding method for high-precision shaft and gear structure weld joints. On one hand, it solves the problems of excessively large heat-affected zones in traditional arc welding, which easily lead to deformation, cracks, and porosity during welding. On the other hand, it reduces the heat input during laser welding. By precisely controlling the welding heat, the heat input on the shaft side is reduced, improving the mechanical properties of high-precision shaft and gear structure weld joints. This method uses a combination of continuous laser and pulsed laser welding as the welding heat source. By adjusting the angle between the welding wire and the plane to be welded, it ensures that the welding wire can fill the weld uniformly. Adjusting the laser spot size on the welding wire allows for complete melting, improving the droplet state and minimizing the laser heat absorption of the base metal of the workpiece. By adjusting the laser's focus, power, and position, maintaining a small-spot heat source, a combined use scheme of low-continuous laser and pulsed laser is established. Optimizing the heat input to different base materials on both sides through laser position shifting allows for more precise control of the heat-affected zone on the shaft side. Under certain penetration depth conditions, this reduces the heat input to the base material on the shaft side, solving the problem of poor mechanical properties that easily occurs in high-precision shaft gear structures when welded and assembled.

[0008] The technical means employed in this invention are as follows:

[0009] A dual-laser welding method for high-precision shaft gear structures includes the following steps:

[0010] S1: Process the pre-made bevels on both sides of the workpiece to be welded;

[0011] S2: Fix the workpiece to be welded on the welding platform;

[0012] S3: Fix the laser and the wire feeding device to make them move synchronously; the laser emits pulsed laser and continuous laser, and the pulsed laser and continuous laser coaxially combine to form a composite laser beam; adjust the position of the laser, and then adjust the angle between the axis of the composite laser beam and the plane to be welded, and adjust the angle between the wire feeding device and the plane to be welded, so that the welding wire is fed into the center of the laser spot;

[0013] S4: Adjust the vertical distance between the laser and the plane to be welded, thereby adjusting the defocusing amount of the composite laser beam acting on the workpiece to be welded; fine-tune the center point of the laser spot to make it biased towards the gear side, reducing the heat input to the metal on the shaft side;

[0014] S5: Before starting welding, turn on the laser cooling device and set the welding speed and wire feed speed;

[0015] S6: Adjust the position of the shielding gas nozzle to ensure that the shielding gas fully protects the weld.

[0016] S7: The power of the continuous laser, the current and frequency of the pulsed laser are uniformly controlled to adjust the state of the molten droplets of the welding wire and the uniformity of filling, thereby improving the surface morphology of the weld. At the same time, while ensuring that the weld of the workpiece to be welded is fully penetrated, the heat input is reduced to prevent the workpiece from deforming after welding due to excessive laser power. Welding is carried out according to the welding speed and wire feeding speed set in step S5.

[0017] S8: After welding is completed, turn off the laser, wire feeder, cooling device and protective gas nozzle, and grind the surface of the weld to remove fumes.

[0018] Preferably, in step S1, the angle of the precast bevel is 8~12°, and more preferably 10°.

[0019] Preferably, in step S2, before the workpiece to be welded is fixed on the welding platform, the surface oil stains of the workpiece to be welded are cleaned and the oxide layer is removed.

[0020] Preferably, in step S3, the position of the laser is adjusted so that the axis of the composite laser beam is perpendicular to the plane to be welded, and the angle between the wire feeding device and the plane to be welded is adjusted to 16~20°, preferably 18°; the extension length of the welding wire is 8~15 mm.

[0021] Preferably, in step S4, the vertical distance between the laser and the plane to be welded is adjusted so that the defocusing amount of the composite laser beam acting on the workpiece to be welded is -2 to 2 mm, preferably 0 mm; the center point of the laser spot is finely adjusted so that it is biased towards the gear side by 0.1 to 0.3 mm, preferably 0.2 mm.

[0022] Preferably, in step S5, the welding speed is 200~300 mm / min, more preferably 250 mm / min, and the wire feeding speed is 800~1000 mm / min, more preferably 900 mm / min.

[0023] Preferably, in step S6, the protective gas flow rate is 10~20 L / min, and more preferably 15 L / min.

[0024] Preferably, in step S7, the power of the continuous laser is 1450~1550 W, more preferably 1500 W, the current of the pulsed laser is 90~110 A, more preferably 100 A, and the frequency of the pulsed laser is 35~45 Hz, more preferably 40 Hz.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1. This invention uses a coaxial combination of continuous laser and pulsed laser as a heat source. By utilizing the energy gradient and density distribution changes formed by different lasers on the coaxial axis, the energy state of the heat source is precisely controlled for welding. By achieving the combined use of lower continuous laser power and pulsed laser, the working range of the continuous laser is increased, the surface morphology of the weld is improved, the welding deformation caused by excessive heat input during the welding process is reduced, defects such as porosity and incomplete penetration are avoided, and the performance of the weld joint is improved.

[0027] 2. This invention, by changing the offset of the laser action position, rationally distributes the heat input and precisely controls the heat absorption of the base metal on the shaft side, thereby improving the migration of carbon elements, further optimizing mechanical properties, and increasing tensile strength by 27%.

[0028] 3. This invention controls the wire feeding speed, laser power, and welding speed during the welding process through a welding control module, enabling high-precision shaft and gear materials to achieve a high-quality connection. Furthermore, this welding device is an efficient improvement on single-laser wire-filling welding, with simple and easy-to-implement process control. It is a high-quality welding method suitable for high-precision shaft and gear structures.

[0029] Based on the above reasons, this invention can be widely applied in fields such as shaft and gear welding. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the prefabricated bevel angle in a specific embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram of laser composite in a specific embodiment of the present invention.

[0033] Figure 3 This is a schematic diagram of dual-laser filler wire welding in a specific embodiment of the present invention.

[0034] Figure 4 This is a schematic diagram showing the offset of the laser action position in a specific embodiment of the present invention.

[0035] In the diagram: 1. Pulsed laser; 2. Continuous laser; 3. Condenser lens; 4. Workpiece to be welded; 5. Laser composite equipment; 6. Composite laser beam; 7. Welding wire; 8. Shielding gas nozzle; 9. Pre-formed bevel; 10. Welding fixture; 11. Gear material; 12. Shaft material. Detailed Implementation

[0036] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0039] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0040] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0041] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0042] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0043] like Figures 1-4 As shown, a dual-laser welding method for high-precision shaft gear structures includes the following steps:

[0044] S1: Process the pre-fabricated bevels 9 on both sides of the workpiece 4 to be welded, so that the angle α of the pre-fabricated bevel 9 is 10°, such as... Figure 1 As shown;

[0045] S2: Clean the surface oil stains and remove the oxide layer of the workpiece 4 to be welded, and then fix the workpiece 4 to be welded on the welding platform using the welding fixture 10; during the fixing process, ensure that the shaft material 12 and the gear material 11 are assembled without gaps to ensure the precision of the workpiece;

[0046] S3: Fix the laser combining device 5 of the laser to the wire feeding device so that they move synchronously; the laser emits pulsed laser and continuous laser, and the pulsed laser 1 and continuous laser 2 are coaxially combined through the laser combining device 5 to form a composite laser beam 6. The composite laser beam 6 forms a laser spot (e.g., under the action of the focusing lens 3) Figure 2 As shown); Figure 3 As shown, adjust the position of the laser, thereby adjusting the axis of the composite laser beam to be perpendicular to the plane to be welded, and adjust the angle β between the wire feeding device and the plane to be welded to 18°, so that the welding wire 7 is fed into the center of the laser spot; the extension length of the welding wire is 8~15 mm.

[0047] S4: As Figure 4 As shown, the vertical distance between the laser and the plane to be welded is adjusted, thereby adjusting the defocusing amount of the composite laser beam 6 acting on the workpiece 4 to be welded to 0mm; the center point of the laser spot is finely adjusted so that its offset L towards the gear material 11 side is 0.2mm, reducing the heat input to the metal on the shaft material 12 side;

[0048] S5: Before starting welding, turn on the laser cooling device, set the welding speed to 250 mm / min and the wire feed speed to 900 mm / min;

[0049] S6: Adjust the position of the shielding gas nozzle 8 to ensure that the shielding gas fully protects the weld. The flow rates of both the weld shielding gas and the laser lens shielding gas are set to 15 L / min.

[0050] S7: The power of continuous laser 2 and the current and frequency of pulsed laser 1 are uniformly controlled to make the power of continuous laser 2 1500W, the current of pulsed laser 1 100A, and the frequency of pulsed laser 1 40Hz. This adjusts the state of the molten droplets and the uniformity of the filling, improves the surface morphology of the weld, and at the same time reduces the heat input to prevent the workpiece from deforming after welding due to excessive laser power, while ensuring that the weld of the workpiece 4 to be welded is fully penetrated. Welding is then carried out according to the welding speed and wire feeding speed set in step S5.

[0051] S8: After welding is completed, turn off the laser, wire feeder, cooling device and protective gas nozzle 8, and use a wire brush to grind the fumes on the weld surface.

[0052] In this specific embodiment, a 4 mm thick thin plate was selected as the test piece for the study, with dimensions of 100×60×4 mm. The shaft and gear materials were QT500 or QT600 and 20MnCr5, respectively. ERNICR-3 nickel-chromium-iron alloy welding wire with a diameter of 1.0 mm was selected. The continuous and pulsed lasers were fiber lasers with a rated power of 2 kW and 800 W. The laser beam focus was on the welding wire and no more than 0.3 mm away from the plane to be welded. The welding wire extension length was 8~15 mm, the wire feeding angle β was 18°, and the shielding gas was argon with a purity of 99.99%.

[0053] The welding parameters used in specific embodiments are shown in Table 1:

[0054]

[0055] In the welding process of ductile iron and 20MnCr5, without the addition of pulsed laser, a large continuous laser power is required to achieve uniform and high-quality weld filling. This results in more pronounced carbon diffusion within the heat-affected zone of the ductile iron, leading to numerous carbon-enriched areas. By introducing pulsed laser, while ensuring sufficient weld penetration, the heat input is significantly reduced, mechanical properties are improved, and the joint performance is further optimized through precise control of the laser's application position.

[0056] After the welding test was completed, the weld formation was excellent, and no defects such as porosity, inclusions and cracks were found. The specimen did not undergo significant deformation. Through mechanical property tests on the weld, the tensile strength at the joint met the production requirements.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dual-laser welding method for high-precision shaft gear structures, characterized in that, The steps include the following: S1: Process the pre-made bevels on both sides of the workpiece to be welded; S2: Fix the workpiece to be welded on the welding platform; S3: Fix the laser and the wire feeding device to achieve synchronous movement; the laser emits coaxial pulsed laser and continuous laser, which coaxially combine to form a composite laser beam, which forms a laser spot under the action of the focusing lens; adjust the position of the laser, thereby adjusting the angle between the axis of the composite laser beam and the plane to be welded, and adjusting the angle between the wire feeding device and the plane to be welded, so that the welding wire is fed into the center of the laser spot. The welding wire is ERNICR-3 nickel-chromium-iron alloy welding wire with a diameter of 1.0 mm. S4: Adjust the vertical distance between the laser and the plane to be welded, thereby adjusting the defocus of the composite laser beam acting on the workpiece to be welded, so that the defocus of the composite laser beam acting on the workpiece to be welded is -2~2mm; fine-tune the center point of the laser spot, making it deflected towards the gear side by 0.1~0.3mm, reducing the heat input to the metal on the shaft side. The shaft and gear materials are QT500 or QT600 and 20MnCr5, respectively. S5: Before starting welding, turn on the laser cooling device, set the welding speed and wire feed speed. The welding speed is 200~300mm / min, and the wire feed speed is 800~1000mm / min. S6: Adjust the position of the shielding gas nozzle to ensure that the shielding gas fully protects the weld. S7: The power of the continuous laser, the current of the pulsed laser, and the frequency are uniformly controlled. The power of the continuous laser is 1450~1550W, the current of the pulsed laser is 90~110A, and the frequency of the pulsed laser is 35~45Hz. This adjusts the state of the molten droplets and the uniformity of the filling, improves the surface morphology of the weld, and reduces heat input to prevent deformation of the workpiece after welding due to excessive laser power, while ensuring sufficient weld penetration. Welding is then performed according to the welding speed and wire feed speed set in step S5. S8: After welding is completed, turn off the laser, wire feeder, cooling device and protective gas nozzle, and grind the surface of the weld to remove fumes.

2. The dual-laser welding method for high-precision shaft gear structures according to claim 1, characterized in that, In step S1, the angle of the precast bevel is 8~12°.

3. The dual laser welding method for high-precision shaft gear structures according to claim 1, characterized in that, In step S2, before the workpiece to be welded is fixed on the welding platform, the surface oil stains on the workpiece to be welded are cleaned and the oxide layer is removed.

4. The dual-laser welding method for high-precision shaft gear structures according to claim 1, characterized in that, In step S3, the position of the laser is adjusted so that the axis of the composite laser beam is perpendicular to the plane to be welded, the angle between the wire feeding device and the plane to be welded is adjusted to 16~20°, and the extension length of the welding wire is 8~15mm.

5. The dual-laser welding method for high-precision shaft gear structures according to claim 1, characterized in that, In step S6, the protective gas flow rate is 10~20L / min.

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