Coaxial powder feeding laser cladding nozzle

Abstract

The utility model discloses a coaxial powder feeding laser cladding nozzle which comprises an assembly body, an inner shielding gas inlet, a powder inlet, an upper powder cavity, a powder distributing pipe, a powder cavity, an outer shielding gas inlet and a cooling water pipeline. Through the proper dip angle structure, radius and outlet gap of the powder cavity, powder convergence is good, it is guaranteed that powder at the outlet of the nozzle cannot be melted due to heat radiation to block the nozzle, the powder cannot block a laser light path to cause the scattering phenomenon of laser, and through the space structure of the upper powder cavity, the powder is not prone to being blocked in the powder cavity. By arranging a cooling water pipeline, cooling water circulation with a good effect is achieved, it is guaranteed that the coaxial powder feeding nozzle cannot be damaged in a high-temperature environment, and by arranging an inner protective gas inlet and an outer protective gas inlet, powder particles are prevented from being oxidized in the high-temperature environment; and after leaving the coaxial powder feeding nozzle, the powder particles always move in the environment filled with the protective gas atmosphere.

Description

Technical Field

[0001] The utility model relates to the relevant field of laser cladding, in particular to a coaxial powder feeding laser cladding nozzle. Background Art

[0002] By laser irradiation, a molten pool is formed on the substrate, and powder is gathered at the laser focus, so that the metal powder becomes molten, so that the metal powder is well metallurgically bonded with the substrate material.

[0003] During the parts processing process, the quality of the cladding layer depends on parameters such as powder feeding concentration, speed, continuity, and uniformity. However, the existing laser cladding nozzles currently have problems such as easy blockage of the nozzle outlet, unstable powder feeding, and low powder utilization. Utility Model Content

[0004] Therefore, in order to solve the above-mentioned shortcomings, the utility model provides a coaxial powder feeding laser cladding nozzle.

[0005] In order to achieve the above-mentioned purpose, the utility model adopts the following technical scheme: a coaxial powder feeding laser cladding nozzle, comprising a coaxial powder feeding nozzle;

[0006] The coaxial powder feeding nozzle comprises an assembly, an inner protective gas inlet, a powder inlet, an upper powder chamber, a powder distribution pipe, a powder chamber, an outer protective gas inlet, and a cooling water pipeline;

[0007] An inner protective gas inlet is provided on the outer side of the top of the assembly, and the upper powder chamber is arranged in the middle of the assembly and has a powder inlet provided therein;

[0008] The top end of the powder distributing tube is connected to the upper powder chamber, and the top end of the powder chamber is connected to the powder distributing tube;

[0009] The external protective gas inlet is arranged on the outside of the middle part of the assembly, and the cooling water pipeline is opened on the inside of the bottom end of the assembly.

[0010] Preferably, a laser beam channel is opened in the middle of the assembly.

[0011] It is further preferred that there is an angled structure between the inner and outer walls of the powder chamber, and the angled structure determines the angle of powder spraying and the focal distance of convergence. A suitable powder chamber inclination ensures that the powder will neither diverge due to insufficient stiffness nor be blown away by the internal protective gas because it is too close to the outlet of the coaxial powder feeding nozzle.

[0012] In a further preferred embodiment, the cross section of the upper powder cavity is rectangular, so as to solve the problem of clogging of the original nozzle powder inside the nozzle and uneven dispersion.

[0013] It is further preferred that the coaxial powder feeding nozzle is used to transport powder and laser beam, the laser beam is emitted by an external laser to a reflective focusing mirror, and then the laser beam is reflected to the coaxial powder feeding nozzle by the reflective focusing mirror, the powder beam and the laser beam arrive at the outlet of the coaxial powder feeding nozzle at the same time to form a molten pool, and form a deposition layer after solidification, and the CNC workbench is a working platform for operation, and a substrate is placed on the top thereof.

[0014] In a further embodiment, the optimum inclination angle of the powder chamber is 19°.

[0015] In a further embodiment, the optimum radius of the powder cavity is 6.3 mm.

[0016] In a further embodiment, the outlet gap of the powder chamber is preferably 0.44 mm.

[0017] Beneficial effects of the utility model:

[0018] The utility model has good powder convergence through the appropriate inclination structure, radius and outlet gap of the powder chamber, the focusing radius is between 3-4mm, the powder focusing distance is appropriate, and it is ensured that the powder at the nozzle outlet will not melt and block the nozzle due to heat radiation, and the powder will not block the laser light path and cause laser scattering.

[0019] The utility model makes it difficult for the powder to be blocked inside and cause the problem of uneven dispersion through the spatial structure of the upper powder cavity.

[0020] The utility model has a cooling water circulation with good effect by arranging the cooling water pipeline, and ensures that the coaxial powder feeding nozzle will not be damaged in a high temperature environment.

[0021] The utility model prevents the powder particles from being oxidized in a high temperature environment by arranging an inner protective gas inlet and an outer protective gas inlet, so that the powder particles always move in an environment full of protective gas atmosphere after leaving the coaxial powder feeding nozzle. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the cross-sectional structure of the coaxial powder feeding nozzle of the utility model;

[0023] Figure 2 It is the process flow chart of the utility model;

[0024] Figure 3 It is a velocity field distribution cloud diagram and vector diagram of the nozzle of the utility model in the z=0 section in the mesh coordinate system;

[0025] Figure 4 It is a gas velocity diagram in the vertical direction of the axis of the coaxial powder feeding nozzle and the outlet of the coaxial powder feeding nozzle of the utility model;

[0026] Figure 5 This is a diagram showing the powder gathering effect of different powder chamber inclination angles of the utility model;

[0027] Figure 6 It is the inclination angle powder convergence chart of the utility model;

[0028] Figure 7 This is a comparison diagram between the utility model and the original nozzle structure;

[0029] Figure 8 It is a graph showing the recovery rate of powder of the present utility model.

[0030] Among them: CNC workbench-1, substrate-2, accumulation layer-3, reflective focusing mirror-4, laser beam-5, coaxial powder feeding nozzle-6, powder beam-7, molten pool-8, assembly-61, inner protective gas inlet-62, powder inlet-63, upper powder chamber-64, powder distribution pipe-65, powder chamber-66, outer protective gas inlet-67, cooling water pipeline-68. DETAILED DESCRIPTION

[0031] In order to further explain the technical solution of the present utility model, it is described in detail through specific embodiments below.

[0032] See also Figure 1-8 The utility model provides a coaxial powder feeding laser cladding nozzle, including a coaxial powder feeding nozzle 6; the coaxial powder feeding nozzle 6 includes an assembly 61, an inner shielding gas inlet 62, a powder inlet 63, an upper powder chamber 64, a powder distribution pipe 65, a powder chamber 66, an outer shielding gas inlet 67, and a cooling water pipeline 68; the inner shielding gas inlet 62 is opened on the outer side of the top of the assembly 61, the upper powder chamber 64 is arranged in the middle of the assembly 61, and the powder inlet 63 is opened inside the upper powder chamber 64; the top of the powder distribution pipe 65 is connected with the upper powder chamber 64, and the top of the powder chamber 66 is connected with the powder distribution pipe 65; the outer shielding gas inlet 67 is arranged on the outer side of the middle of the assembly 61, and the cooling water pipeline 68 is opened on the inner side of the bottom end of the assembly 61.

[0033] In this embodiment, a laser beam channel is provided in the middle of the assembly 61, and an angled structure is provided between the inner and outer walls of the powder chamber 66. The angled structure determines the angle at which the powder is ejected and the focal distance of convergence. A suitable angle of the powder chamber 66 ensures that the powder will neither be dispersed due to insufficient stiffness nor be blown away by the internal protective gas due to being too close to the outlet of the coaxial powder feeding nozzle 6. The cross-section of the upper powder chamber 64 is rectangular, which solves the problem of clogging of the original nozzle powder inside the nozzle and uneven dispersion.

[0034] It is further preferred that the coaxial powder feeding nozzle 6 is used to transport powder and laser beam 5. The laser beam 5 is emitted by an external laser to the reflective focusing mirror 4, and then the reflective focusing mirror 4 reflects the laser beam 5 to the coaxial powder feeding nozzle 6. The powder beam 7 and the laser beam 5 arrive at the outlet of the coaxial powder feeding nozzle 6 at the same time to form a molten pool 8, which forms a deposition layer 3 after solidification. The CNC workbench 1 is a working platform for operation, and a substrate 2 is placed on the top thereof.

[0035] In this embodiment, due to the complex structure of the coaxial powder feeding nozzle 6, high processing precision requirements, and high material costs, it is difficult to verify the rationality of the nozzle structure and optimize the structural size parameters of the nozzle through a large number of experiments. The optimized nozzle structure parameters are obtained through numerical simulation, and the powder feeding nozzle is manufactured and the powder feeding experiment is conducted, which can effectively reduce the design cost and improve the design efficiency.

[0036] In this embodiment, due to the characteristics of coaxial powder feeding, the discrete model is selected to simulate the powder flow field and the following assumptions are adopted:

[0037] (1) The carrier gas and powder enter the nozzle at the same speed;

[0038] (2) Ignore the collision between particles and the impact on the shielding gas;

[0039] (3) The influence of laser radiation, substrate on laser reflection and other heat sources and particle phases are ignored;

[0040] (4) Assume that the particles are uniform spherical with a diameter of 100 μm;

[0041] (5) A steady-state solver is used, so the powder concentration distribution does not change with time.

[0042] In the continuous phase model, the gas is assumed to be an ideal incompressible fluid by default. The basic control equations of turbulence include the continuity equation and the momentum equation. The turbulence model uses the standard model. In the model, the mass conservation equation of the continuous phase is:

[0043]

[0044] Where: ρ is the gas density, μi is the gas velocity.

[0045] The momentum conservation equation for the continuous phase is:

[0046]

[0047] Where: p represents pressure, μ is the fluid dynamic viscosity coefficient, and μi is the turbulent viscosity.

[0048] In this embodiment, the numerical simulation and analysis of the powder feeding process of the coaxial powder feeding nozzle 6 are as follows:

[0049] The gas velocity flow field diagram refers to the flow velocity, direction, pressure and other parameters of the powder-carrying gas and the shielding gas at various locations during the powder feeding process of the nozzle. The movement state of the gas determines the movement state of the powder. Figure 3 The velocity field distribution cloud map and vector map of the nozzle in the z=0 section in the mesh coordinate system.

[0050] It can be seen that the gas velocity at the outlet of the powder chamber 66 is relatively high, and the velocity decreases and part of the gas diverges after being ejected from the coaxial powder feeding nozzle 6. The higher carrier gas velocity can make the powder and the carrier gas have better stiffness and obtain a better convergence effect. After the carrier gas flow is ejected from the coaxial powder feeding nozzle 6, it is exposed to the external environment and the dispersion degree increases. However, due to the rectification effect of the external protective gas, the carrier gas near the outlet converges to the internal protective gas, which is conducive to the convergence of the powder and can make the powder evenly distributed at the laser focal point.

[0051] However, the inclination angle and flow rate of the external shielding gas outlet should not be too large, otherwise the powder may converge prematurely and the powder concentration in the center may be too high, resulting in poor cladding quality, premature melting of the powder, and splashing to the outlet of the coaxial powder feeding nozzle 6, causing the coaxial powder feeding nozzle 6 to be blocked. The shielding gas converges toward the internal shielding gas at the outlet of the coaxial powder feeding nozzle 6. The external shielding gas can protect the powder particles from oxidation, improve the uniformity of the powder at the convergence point, and improve the utilization rate of the powder.

[0052] Therefore, the effect of adding a protective gas layer with a suitable flow rate and inclination angle outside the coaxial powder feeding nozzle 6 is obvious. Figure 4 It is a gas velocity diagram in the vertical direction of the axis of the coaxial powder feeding nozzle 6 and the outlet of the coaxial powder feeding nozzle 6.

[0053] The gas velocity at the nozzle axis at the outlet of the coaxial powder feeding nozzle 6 is relatively small. As the distance from the coaxial powder feeding nozzle 6 increases, the gas velocity gradually increases. The gas velocity reaches the maximum at 1.5 mm from the coaxial powder feeding nozzle 6, and then the gas velocity is maintained at about 2.3 m / s until the gas velocity at 6 mm from the coaxial powder feeding nozzle 6 begins to drop rapidly. This is because the gas flow at the nozzle axis at the outlet of the coaxial powder feeding nozzle 6 is mainly internal protective gas. As the distance from the nozzle increases, the powder-carrying gas ejected from the outlet of the coaxial powder feeding nozzle 6 also partially diffuses to the axis of the coaxial powder feeding nozzle 6, resulting in an increase in the gas velocity at the axis. The maximum velocity at 1.5 mm is due to the powder convergence here, and the powder-carrying gas, external protective gas, and internal protective gas all converge at the axis. After that, the gas velocity remains average, indicating that the central area of ​​the gas has a good stiffness and can transport the powder to the convergence plane without divergence. At 6 mm, the gas quickly escapes and the velocity drops sharply. At the outlet of the coaxial powder feeding nozzle 6, the air flow velocity in the vertical direction of the outlet of the coaxial powder feeding nozzle 6 is 3.3m / s. The velocity drops sharply after the gas leaves the coaxial powder feeding nozzle 6, and then the gas velocity remains at about 1.5m / s. The gas velocity rises slightly at a distance of 5.5mm from the coaxial powder feeding nozzle 6 and then drops sharply. This indicates that the gas stiffness of the process is good. Good gas stiffness helps prevent powder from dispersing. Therefore, a suitable shielding gas flow rate should be selected to ensure the stiffness of the shielding gas after leaving the coaxial powder feeding nozzle 6 to ensure that the powder is better gathered on the focal plane.

[0054] In this embodiment, during the laser cladding process, the inclination angle of the powder chamber 66 in the coaxial powder feeding nozzle 6 is the most important factor affecting the powder convergence. The size of the inclination angle of the powder chamber 66 determines the angle of powder ejection and the focal distance of convergence. Figure 5 This is a diagram showing the powder gathering effect at different powder chamber 66 inclination angles.

[0055] When the inclination angle of the powder chamber 66 is 15° and 25°, the concentration of the powder at the focal plane is significantly lower than that when the inclination angle of the powder chamber is 20°. Therefore, a suitable inclination angle of the powder chamber 66 should be selected to ensure that the powder will not be dispersed due to insufficient stiffness and will not be blown away by the internal protective gas due to being too close to the outlet of the coaxial powder feeding nozzle 6. In addition, the radius of the powder when it converges is too large, resulting in a low powder concentration at the convergence point.

[0056] The best range of powder convergence distance is 8-12mm, so the optimal value of powder convergence distance is 10mm. As for the powder convergence diameter, the smaller the value, the better, which can improve the quality of the cladding layer. Under normal circumstances, the laser spot diameter is about 3mm, so the powder convergence diameter should not be greater than 3mm. Using Design Expert, RSM prediction of the optimal values ​​of the powder cavity 66 radius, powder cavity 66 gap, and powder cavity 66 inclination angle was performed. The optimal values ​​obtained were a powder cavity 66 radius of 5.39mm, a powder cavity 66 inclination angle of 18°, and an outlet gap of 0.44mm.

[0057] Compared with the original nozzle structure, the powder convergence diameter before optimization was 4.251mm, the powder convergence diameter after optimization was 3.069mm, and the powder convergence focal distance after optimization was 9.479mm.

[0058] The powder concentration after optimization is higher than that before optimization, and the powder concentration distribution in the central area is more uniform, and the powder distribution is closer to a circle. This shows that the optimization of the nozzle structure and structural parameters in this paper is successful.

[0059] The final determined inclination angle of the powder chamber 66 is 19°, the radius of the powder chamber 66 is 6.3 mm, the inclination angle of the external protective gas is 35°, and the optimal flow rate of the external protective gas is 1.5 m / s.

[0060] In this embodiment, the prototype and the result verification are as follows:

[0061] This coaxial powder feeding nozzle 6 is integrally printed using 3D printing technology, without any parts, and will not cause problems such as powder moisture or blockage due to gas leakage or cooling water leakage. M5 copper internal threads are embedded in the powder inlet 63, the external shielding gas inlet 67, the internal shielding gas inlet 62, and the cooling water pipeline 68 inlet to facilitate the connection of pneumatic pipe joints.

[0062]

[0063] The original coaxial powder feeding nozzle 6 converges at about 15 mm, with a powder utilization rate of 46.59%, while the optimized coaxial powder feeding nozzle 6 has a utilization rate of 57.06%, proving that the optimized coaxial powder feeding nozzle 6 has a better powder feeding effect and a higher powder utilization rate than the original coaxial powder feeding nozzle 6. Figure 8 , it can be seen that the powder recovery rates of the original coaxial powder feeding nozzle 6 and the optimized coaxial powder feeding nozzle 6 near the focal position.

[0064] It is proved that the powder feeding effect of the optimized coaxial powder feeding nozzle 6 is greatly improved compared with the original coaxial powder feeding nozzle 6. The optimized powder convergence diameter is 2.9 mm, the powder utilization rate is about 57%, and the powder convergence focal distance is 11 mm.

[0065] See also Figure 1-Figure 2When in use, the coaxial powder feeding nozzle 6 is arranged in a conical shape on the outside of the laser beam 5, and the laser emits laser light to the reflective focusing mirror 4. Under the action of the reflective focusing mirror 4, the laser beam 5 enters the middle channel of the coaxial powder feeding nozzle 6 downward, and at the same time, the external powder feeder inputs powder from the powder inlet 63 to the upper powder chamber 64, and moves along the powder distribution pipe 65 and the powder chamber 66. When the powder is sprayed out, due to the rectification of the powder chamber 66 and the driving of the powder-carrying gas, it converges in the action area of ​​the laser beam 5 along the extension line direction of the powder chamber 66, so that the powder and the laser beam 5 reach the surface of the substrate 2 at the same time and melt at the same time to form a molten pool 8, and are deposited layer by layer into a deposition layer 3;

[0066] At the same time, the shielding gas converges toward the internal shielding gas at the outlet of the coaxial powder feeding nozzle 6. The external shielding gas can protect the powder particles from oxidation, improve the uniformity of the powder at the convergence point, and improve the utilization rate of the powder.

[0067] The control method of the present invention is to control by manually starting and closing the switch. The wiring diagram of the power element and the provision of power supply are common knowledge in the field, and the present invention is mainly used to protect mechanical devices, so the present invention will not explain the control method and wiring arrangement in detail.

[0068] The control method of the present invention is automatic control through a controller. The control circuit of the controller can be realized by simple programming by technicians in this field. The provision of power is also common knowledge in this field. The present invention is mainly used to protect mechanical devices, so the present invention will no longer explain the control method and circuit connection in detail.

[0069] The above description is only a preferred example of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions described in the above embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A coaxial powder feeding laser cladding nozzle, characterized in that: It comprises a numerical control workbench (1) and a coaxial powder feeding nozzle (6); The coaxial powder feeding nozzle (6) comprises an assembly (61), an inner protective gas inlet (62), a powder inlet (63), an upper powder chamber (64), a powder distribution pipe (65), a powder chamber (66), an outer protective gas inlet (67), and a cooling water pipeline (68); An inner protective gas inlet (62) is provided on the outer side of the top end of the assembly (61); the upper powder chamber (64) is arranged in the middle of the assembly (61) and has a powder inlet (63) therein; The top end of the powder distribution pipe (65) is in communication with the upper powder chamber (64), and the top end of the powder chamber (66) is in communication with the powder distribution pipe (65); The external protective gas inlet (67) is arranged on the outside of the middle part of the assembly (61); the cooling water pipeline (68) is opened on the inside of the bottom end of the assembly (61); a laser beam channel is opened in the middle of the assembly (61); the inner and outer walls of the powder chamber (66) have an inclined structure; and the cross-section of the upper powder chamber (64) is rectangular.

2. According to claim 1, a coaxial powder feeding laser cladding nozzle is characterized in that: The coaxial powder feeding nozzle (6) is used to transport powder and laser beam (5). The laser beam (5) is emitted by an external laser to a reflective focusing mirror (4), and then the reflective focusing mirror (4) reflects the laser beam (5) to the coaxial powder feeding nozzle (6). The powder beam (7) and the laser beam (5) arrive at the outlet of the coaxial powder feeding nozzle (6) at the same time to form a molten pool (8), which forms a deposition layer (3) after solidification. The CNC workbench (1) is a working platform for operation, and a substrate (2) is placed on the top of the CNC workbench.

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