A spray pipe and spraying device for spraying powder

Abstract

The present invention discloses a spraying pipe and a spraying device for spraying powder. The spraying pipe comprises: an outer pipe and a Laval nozzle, the Laval nozzle is arranged in the outer pipe, the side wall of the Laval nozzle is provided with a plurality of evenly spaced powder supply channels, a plurality of evenly spaced gas supply channels and an air cavity, the powder supply channel is located at the periphery of the gas supply channel, the side wall of the Laval nozzle above the gas supply channel has a circle of air cavity, the air cavity is connected to the top of the gas supply channel, each gas supply channel is connected to the inside of the Laval nozzle through a plurality of gas channels evenly spaced from top to bottom, the side wall of the outer pipe is provided with a first air inlet hole, the first air inlet hole is located above the Laval nozzle, the side wall of the outer pipe and the side wall of the Laval nozzle are provided with a through second air inlet hole, and the second air inlet hole is connected to the air cavity. The present invention realizes uniform powder feeding by adding gas supply channels and powder supply channels, improves the deposition efficiency and deposition quality of the coating, and forms a coating with uniform thickness.

Description

Technical Field

[0001] The invention relates to the technical field of powder spraying, and in particular to a spray pipe and a spraying device for spraying powder. Background Art

[0002] During the use of metal parts, due to the long-term effects of uneven loads such as external alternating stress, especially in harsh working environments, it is easy to produce surface defects such as microcracks. If metal parts with defects continue to be used, the microcrack defects on the surface will continue to expand to form a larger defect area, causing the parts to be scrapped prematurely due to failure to meet the use requirements, resulting in a huge waste of energy and resources. According to statistics, common metal parts that are scrapped prematurely due to surface defects include motor rotor blades, gears and shaft parts. Using advanced laser surface repair technology to repair defective metal surfaces can not only extend the service life of metal parts, but also reduce economic losses and time losses, especially for high value-added core components. It has important application significance.

[0003] Cold spraying technology (CS, Cold Spraying), also known as gas dynamic spraying technology, refers to the technology that when high-speed solid particles with a certain plasticity collide with the substrate, they undergo strong plastic deformation and deposit to form a coating. Under normal conditions, the general concept is that when solid particles collide with a certain substrate, the solid particles will erode the substrate.

[0004] Whether the cold spray particles can form a coating on the substrate depends mainly on the velocity of the particles before they hit the substrate, that is, the critical velocity V of the particles. p For each spray material, there is a certain critical velocity V p When the particle speed is greater than this speed, the particles collide and deposit on the substrate surface to form a coating. During the spraying process, in order to make the spraying powder reach its critical speed, the accelerating gas can be preheated and sent into the spray gun. The preheating temperature is usually less than 600°C. In addition, in order to obtain a higher particle spraying speed, the powder particle size and distribution range are required to be small, generally spherical powder of 5μm to 50μm.

[0005] However, when high-speed gas accelerates the movement of powder, the powder in the traditional nozzle is not ejected at the same speed, and the powder is relatively more in the fast speed and less in the slow speed, which causes the coating to be unevenly distributed on the cross-section of the substrate, roughly thick in the middle and thin on both sides, resulting in low deposition efficiency and seriously affecting the performance of the coating. In short, the traditional nozzle has low deposition efficiency, which limits its widespread application in industry. Summary of the invention

[0006] The embodiment of the present invention provides a spray pipe and a spraying device for spraying powder, so as to solve the problem of low spraying deposition efficiency in the prior art.

[0007] In a first aspect, a spray nozzle for spraying powder is provided, comprising: an outer tube and a Laval nozzle, wherein the Laval nozzle is arranged in the outer tube, the top end of the Laval nozzle is lower than the top end of the outer tube, the side wall of the Laval nozzle is provided with a plurality of evenly spaced powder supply channels, a plurality of evenly spaced air supply channels and an air cavity, the powder supply channels are located at the periphery of the air supply channels, the powder supply channels and the air supply channels are arranged alternately, each of the powder supply channels runs from the top end of the side wall of the Laval nozzle to the bottom end of the side wall of the Laval nozzle, the top end of the air supply channel is lower than the top end of the air supply channel The top of the powder channel, the bottom end of the air supply channel is higher than the bottom end of the Laval nozzle, the side wall of the Laval nozzle above the air supply channel has a circle of air cavity, the air cavity is connected with the top of the air supply channel, each of the air supply channels is connected with the interior of the Laval nozzle through a plurality of gas channels evenly spaced from top to bottom, the side wall of the outer tube is provided with a first air inlet hole, the first air inlet hole is located above the Laval nozzle, the side wall of the outer tube and the side wall of the Laval nozzle are provided with a through second air inlet hole, the second air inlet hole is connected with the air cavity.

[0008] Furthermore, the spray pipe for spraying powder also includes: an air supply pipe arranged outside the outer pipe, the air supply pipe includes: a main air supply pipe, a first branch air supply pipe and a second branch air supply pipe, one end of the main air supply pipe is respectively connected with one end of the first branch air supply pipe and one end of the second branch air supply pipe, the other end of the first branch air supply pipe is connected with the first air inlet hole, and the other end of the second branch air supply pipe is connected with the second air inlet hole.

[0009] Further: the gas channel is a downwardly inclined channel.

[0010] Further: the inner diameter of the top end of the Laval nozzle is larger than the inner diameter of the contraction tube of the Laval nozzle.

[0011] In the second aspect, a spraying device is provided, comprising: a first mounting plate, a shell, a plurality of lasers and a nozzle as described in the embodiment of the first aspect; the first mounting plate is provided with a mounting hole, the shell is inserted into the mounting hole, the shell is a hollow structure, one end of the outer tube is inserted into the hollow structure, the second air inlet is located above the shell, the outer surface of the side wall of the outer tube located in the hollow structure is covered with an insulation layer, the outer surface of the insulation layer is wrapped with a cooling water pipe, one end of the cooling water pipe is connected to a cooling joint, the other end of the cooling water pipe extends out of the shell, the outer surface of the cooling water pipe is wrapped with a resistance wire, one end of the resistance wire is electrically connected to the insulation joint, and a plurality of the lasers are evenly spaced and installed on the lower surface of the first mounting plate.

[0012] Further: the lower surface of the first mounting plate is connected to a plurality of U-shaped mounting seats, and each of the lasers is rotatably mounted in the U-shaped mounting seat.

[0013] Further: the U-shaped mounting seat is mounted on the lower surface of the first mounting plate through adjustable bolts.

[0014] Further: one end of the first mounting plate is connected to one end of the connecting plate, the other end of the connecting plate is connected to the second mounting plate, and the cooling joint and the insulation joint are installed on the second mounting plate.

[0015] Further: one end of the second mounting plate is connected to one end of the third mounting plate.

[0016] Thus, the embodiment of the present invention increases the supply of powder at the slow speed by adding an air supply channel and a powder supply channel, thereby achieving uniform powder delivery, thereby improving the deposition efficiency and deposition quality of the coating and forming a coating with uniform thickness. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0018] Figure 1 2 is a cross-sectional view of a nozzle for spraying powder according to an embodiment of the present invention. Figure 1 ;

[0019] Figure 2 2 is a cross-sectional view of a nozzle for spraying powder according to an embodiment of the present invention. Figure 2 ;

[0020] Figure 3is a three-dimensional diagram of a spray pipe for spraying powder according to an embodiment of the present invention;

[0021] Figure 4 is a bottom view of an outlet of a spray pipe for spraying powder according to an embodiment of the present invention;

[0022] Figure 5 The structure of the spraying device of the embodiment of the present invention is shown in FIG. Figure 1 ;

[0023] Figure 6 The structure of the spraying device of the embodiment of the present invention is shown in FIG. Figure 2 ;

[0024] Figure 7 is a cross-sectional view of a Laval nozzle of the prior art;

[0025] Figure 8 is a bottom view of the outlet of a Laval nozzle of the prior art;

[0026] Fig. 9 is a schematic diagram of a coating formed by spraying with a Laval nozzle in the prior art;

[0027] Fig.10 Schematic diagram of a coating formed by spraying with a nozzle for spraying powder according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The present invention discloses a spray nozzle for spraying powder. Figures 1 to 4As shown, the nozzle includes the following structure: an outer tube 1 and a Laval nozzle 2. Among them, the Laval nozzle 2 is arranged in the outer tube 1. The top of the Laval nozzle 2 is lower than the top of the outer tube 1, that is, the inlet of the Laval nozzle 2 is lower than the inlet of the outer tube 1. The Laval nozzle 2 is composed of two conical tubes, the upper end of which is a contraction tube and the lower end is an expansion tube. Preferably, the inner diameter of the top of the Laval nozzle 2 is larger than the inner diameter of the contraction tube of the Laval nozzle 2, so that the powder can enter the Laval nozzle 2; the outlet at the bottom end of the Laval nozzle 2 is circular, and the bottom end of the Laval nozzle 2 is flush with the bottom end of the outer tube 1, that is, the outlets of the two are flush. The side wall of the Laval nozzle 2 is provided with a plurality of evenly spaced powder replenishment channels 3, a plurality of evenly spaced air replenishment channels 4 and an air cavity 5. Therefore, the Laval nozzle 2 is located in the center, and the powder replenishment channel 3 and the air replenishment channel 4 are both surrounded by the periphery of the Laval nozzle 2. The powder replenishment channel 3 is located on the periphery of the air replenishment channel 4. The powder replenishing channel 3 and the air replenishing channel 4 are arranged alternately. It should be understood that the alternate arrangement refers to being on the circumference. Each powder replenishing channel 3 runs from the top of the side wall of the Laval nozzle 2 to the bottom of the side wall of the Laval nozzle 2. Therefore, the inlet of the powder replenishing channel 3 is connected to the inlet of the outer tube 1. After the powder enters the outer tube 1, it will not only enter the Laval nozzle 2, but also enter the powder replenishing channel 3. The powder flow rate in the Laval nozzle 2 is large. The powder in the powder replenishing channel 3 is mainly used to replenish powder from all sides to solve the problem of uneven powder spraying in the Laval nozzle 2. The top of the air replenishing channel 4 is lower than the top of the powder replenishing channel 3. There is a circle of air cavity 5 in the side wall of the Laval nozzle 2 above the air replenishing channel 4. The air cavity 5 is connected to the top of the air replenishing channel 4. It should be understood that the top of the air cavity 5 is closed, that is, it will not be connected to the outer tube 1. In this way, unlike the powder replenishing channel 3, the inlet of the air replenishing channel 4 is not connected to the inlet of the outer tube 1. Each gas supplement channel 4 is connected to the interior of the Laval nozzle 2 through a plurality of gas channels 6 evenly spaced from top to bottom. Preferably, the gas channel 6 is a downwardly inclined channel. The bottom end of the gas supplement channel 4 is higher than the bottom end of the Laval nozzle 2, so that the airflow direction at the outlet is downward along the Laval nozzle 2, avoiding the airflow from damaging the powder flow direction at the outlet. Preferably, the diameter of the outer tube 1 near the bottom gradually decreases. The side wall of the outer tube 1 is provided with a first air inlet 7. The first air inlet 7 is located above the Laval nozzle 2. The side wall of the outer tube 1 and the side wall of the Laval nozzle 2 are provided with a second air inlet that is connected. It should be understood that the second air inlet is not higher than the Laval nozzle 2, and can generally be the same height as the air cavity 5. The connection only means that the side wall of the outer tube 1 where the second air inlet is located and the side wall of the Laval nozzle 2 are connected. The second air inlet is connected to the air cavity 5, so that the gas can be transported to all the gas supplement channels 4. The first air inlet hole 7 and the second air inlet hole are used to pass high-pressure gas to the structures connected to each other.

[0030] In addition, the nozzle also includes: an air supply pipe arranged outside the outer tube 1. The air supply pipe includes: a main air supply pipe 8, a first branch air supply pipe 9 and a second branch air supply pipe 10. One end of the main air supply pipe 8 is connected with one end of the first branch air supply pipe 9 and one end of the second branch air supply pipe 10 respectively. The other end of the first branch air supply pipe 9 is connected to the first air inlet 7. The other end of the second branch air supply pipe 10 is connected to the second air inlet. The other end of the main air supply pipe 8 can be connected to a high-pressure gas storage tank so as to pass high-pressure gas into the nozzle. Nitrogen is generally used as the high-pressure gas.

[0031] When in use, the powder enters from the top of the outer tube 1, then enters the Laval nozzle 2, and is sprayed out from the outlet at the bottom of the Laval nozzle 2. Part of the powder enters the powder replenishing channel 3 and is sprayed out from the powder replenishing channel 3 to replenish the powder around the coating formed by spraying the Laval nozzle 2 to improve the problem of uneven coating thickness. In addition, during the spraying process, high-pressure gas enters the outer tube 1 through the first air inlet 7 and enters the air replenishing channel 4 through the second air inlet. The high-pressure gas entering the outer tube 1 accelerates the powder in the outer tube 1 and the Laval nozzle 2, and the high-pressure gas entering the air replenishing channel 4 further accelerates the powder in the Laval nozzle 2, increasing the supply of powder at the slow speed, achieving uniform powder delivery, thereby improving the deposition efficiency of the coating and forming a coating with uniform thickness.

[0032] The embodiment of the present invention also discloses a spraying device. Figures 1 to 6 As shown, the spraying device comprises: a first mounting plate 11, a housing 12, a plurality of lasers 13 and a nozzle as described in the above embodiment. The nozzle structure is not described in detail here.

[0033] The first mounting plate 11 is provided with a mounting hole. The shell 12 is inserted into the mounting hole. The shell 12 is a hollow structure. One end of the outer tube 1 is inserted into the hollow structure. The bottom end of the outer tube 1 is flush with the bottom end of the hollow structure. The second air inlet is located above the shell 12. The outer surface of the side wall of the outer tube 1 located in the hollow structure is covered with a thermal insulation layer 14. A cooling water pipe 15 is wound around the outer surface of the thermal insulation layer 14. One end of the cooling water pipe 15 is connected to the cooling joint 16. The other end of the cooling water pipe 15 extends out of the shell 12 and can be connected to an external pipe so as to discharge the cooling water. A resistance wire is wound around the outer surface of the cooling water pipe 15. One end of the resistance wire is electrically connected to the thermal insulation joint 17. It should be understood that in order to achieve the connection between the cooling water pipe 15 and the cooling joint 16 and the external pipe, and the electrical connection between the resistance wire and the thermal insulation joint 17, the shell 12 must be provided with a corresponding outlet for the corresponding components to extend out. Specifically, one end of the first mounting plate 11 is connected to one end of the connecting plate 18 so that the two form an L shape. The other end of the connecting plate 18 is connected to the second mounting plate 19 so that the two form an L shape or a T shape. The cooling joint 16 and the insulation joint 17 are installed on the second mounting plate 19. Among them, the cooling joint 16 is connected to an external cooling device (such as a water tank), and the insulation joint 1 is connected to an external insulation device. A liquid with a large specific heat capacity can pass through the cooling water pipe 15. Before spraying and during spraying, the external insulation device can be started, and the resistance wire can be heated by the insulation joint 17. The heat generated by the resistance wire heats the insulation layer 14. The insulation layer 14 disperses the heat evenly, so that the nozzle is evenly heated, so as to preheat the nozzle before spraying, and heat the nozzle during the spraying process, thereby heating the powder in the nozzle, which is beneficial to the spraying effect. After spraying is completed, the external cooling device is started, and cooling water is introduced into the cooling water pipeline 15 through the cooling joint to cool the nozzle, insulation layer 14 and other related components to room temperature in order to protect the corresponding components.

[0034] A plurality of lasers 13 are evenly spaced and mounted on the lower surface of the first mounting plate 11. For example, the number of lasers 13 is three. Preferably, a plurality of U-shaped mounting seats 20 are connected to the lower surface of the first mounting plate 11. Each laser 13 is rotatably mounted in the U-shaped mounting seat 20 so as to adjust the angle of the laser 13. Specifically, the housing of the laser 13 can be connected to the two side walls of the U-shaped mounting seat 20 through a rotating shaft. The rotating shaft can rotate, thereby driving the laser 13 to rotate. A nut can be sleeved on the rotating shaft, and the rotating shaft can be locked by the nut so as to lock the posture of the laser 13 after the angle of the laser 13 is adjusted. Preferably, the U-shaped mounting seat 20 is mounted on the lower surface of the first mounting plate 11 by an adjustable bolt 21. Therefore, by changing the length of the adjustable bolt 21, the height of the U-shaped mounting seat 20 can be changed, thereby adjusting the height of the laser 13.

[0035] By setting multiple lasers 13, if the hardness of the powder or substrate material is too large, multiple lasers 13 will focus on the powder spot to soften the substrate and powder and improve the bonding strength between the powder spot and the substrate. In addition, before spraying, the laser beam is pre-emitted to clean, roughen and preheat the surface of the workpiece to be sprayed. Laser cleaning is used to eliminate the adverse effects of oil stains, oxide films, etc. on the surface of the substrate on the deposited coating. Laser roughening is used to eliminate the effects of residues caused by sandblasting, increase the roughness and preheat the substrate to promote the bonding between the coating and the substrate; the lateral laser spot overlaps with the sprayed powder spot, and the deposited powder and the substrate are heated and softened simultaneously, reducing the critical deposition speed of the powder, improving the deposition efficiency of the powder, and improving the bonding strength of the coating. After spraying, the laser beam is emitted to remelt the top area of ​​the deposited coating, eliminate the internal pores of the coating, and reduce the roughness of the coating surface, while the middle and lower parts of the coating still maintain the structure and properties of the original powder.

[0036] In addition, one end of the second mounting plate 19 is connected to one end of the third mounting plate 22, so that the second mounting plate 19 and the third mounting plate 22 form an L shape. The third mounting plate 22 may be provided with a universal connection hole so that the third mounting plate 22 can be connected to an industrial robot commonly used for cold spraying through the connection hole.

[0037] When in use, first set the power parameters, powder feeding rate and resistance wire temperature of the laser 13. Connect the high-pressure gas storage bottle to the main air supply pipe 8, and the carrier gas type is nitrogen. Adjust the position of the laser 13 so that the laser 13 is facing the position to be sprayed, so as to heat the sprayed powder and the position to be sprayed to achieve the aforementioned function. Turn on the carrier gas switch, and the powder flows from the storage box into the outer tube 1, and enters the Laval nozzle 2 and the powder supply channel 3 respectively, and the high-pressure gas enters the outer tube 1 and the air supply channel 4 respectively. Spray the position to be sprayed to form a uniform coating. During the spraying process, the spraying device can be moved so that the spray covers all the positions to be sprayed.

[0038] The spraying effect of the embodiment of the present invention is described below with reference to a specific embodiment.

[0039] Example 1

[0040] use Figure 7 and 8 The Laval nozzle 23 of the prior art shown in the figure is used to prepare the coating. The pretreated workpiece 24 is fixed on the workbench. Before spraying, the powder is dried (dried at 120°C for 1 hour), then loaded into the powder feeder, and the cold spraying parameters are set on the control panel of the cold spraying equipment. The carrier gas type is nitrogen, the carrier gas pressure is 4MPa, the carrier gas preheating temperature is 500°C, the powder feeding rate is 1.5rpm / min, the spraying distance is 30mm, the nozzle scanning speed is 10mm / s, and the laser power is 500W. Form the following on the workpiece 24 Figure 7 and9 A coating 25 of non-uniform thickness is shown.

[0041] Example 2

[0042] The coating is prepared by using the spraying device of the embodiment of the present invention. Fix the pretreated workpiece 24 on the workbench, dry the powder (dry at 120°C for 1 hour) before spraying, and then load it into the powder feeder. Set the cold spraying parameters on the control panel of the cold spraying equipment. The carrier gas type is nitrogen, the carrier gas pressure is 4MPa, the carrier gas preheating temperature is 500°C, the powder feeding rate is 1.5rpm / min, the spraying distance is 30mm, the nozzle scanning speed is 10mm / s, and the laser power is 500W. Form the following on the workpiece 24 Figure 1 and 10 The uniform coating 26 shown has a surface layer thickness of 2 mm.

[0043] In summary, the embodiments of the present invention increase the supply of powder at the slow speed by adding an air supply channel and a powder supply channel, thereby achieving uniform powder delivery, thereby improving the deposition efficiency and deposition quality of the coating and forming a coating with uniform thickness.

[0044] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A spray nozzle for spraying powder, characterized in that: include: An outer tube and a Laval nozzle, the Laval nozzle is arranged in the outer tube, the top of the Laval nozzle is lower than the top of the outer tube, the side wall of the Laval nozzle is provided with a plurality of evenly spaced powder replenishing channels, a plurality of evenly spaced air replenishing channels and an air cavity, the powder replenishing channel is located at the periphery of the air replenishing channel, the powder replenishing channel and the air replenishing channel are arranged alternately, each of the powder replenishing channels runs from the top of the side wall of the Laval nozzle to the bottom of the side wall of the Laval nozzle, the top of the air replenishing channel is lower than the top of the powder replenishing channel, the bottom end of the air replenishing channel is higher than the bottom end of the Laval nozzle, the air replenishing channel A circle of air cavity is provided in the side wall of the Laval nozzle above the channel, and the air cavity is connected to the top end of the air supply channel. Each of the air supply channels is connected to the interior of the Laval nozzle through a plurality of gas channels evenly spaced from top to bottom. A first air inlet hole is provided on the side wall of the outer tube, and the first air inlet hole is located above the Laval nozzle. A second air inlet hole is provided on the side wall of the outer tube and the side wall of the Laval nozzle, and the second air inlet hole is connected to the air cavity. The gas channel is a downwardly inclined channel. The inner diameter of the top end of the Laval nozzle is larger than the inner diameter of the contraction tube of the Laval nozzle.

2. The spray nozzle for spraying powder according to claim 1, characterized in that: Also includes: An air supply pipe is arranged outside the outer pipe, and the air supply pipe includes: a main air supply pipe, a first branch air supply pipe, and a second branch air supply pipe. One end of the main air supply pipe is respectively connected with one end of the first branch air supply pipe and one end of the second branch air supply pipe, the other end of the first branch air supply pipe is connected with the first air inlet hole, and the other end of the second branch air supply pipe is connected with the second air inlet hole.

3. A spraying device, characterized in that: include: A first mounting plate, a housing, a plurality of lasers and a nozzle as claimed in any one of claims 1 to 2; The first mounting plate is provided with a mounting hole, the shell is inserted into the mounting hole, the shell is a hollow structure, one end of the outer tube is inserted into the hollow structure, the second air inlet is located above the shell, the outer surface of the side wall of the outer tube located in the hollow structure is covered with an insulation layer, the outer surface of the insulation layer is wrapped with a cooling water pipe, one end of the cooling water pipe is connected to the cooling joint, the other end of the cooling water pipe extends out of the shell, the outer surface of the cooling water pipe is wrapped with a resistance wire, one end of the resistance wire is electrically connected to the insulation joint, and a plurality of the lasers are evenly spaced and installed on the lower surface of the first mounting plate.

4. The spraying device according to claim 3, characterized in that: The lower surface of the first mounting plate is connected to a plurality of U-shaped mounting seats, and each of the lasers is rotatably mounted in the U-shaped mounting seat.

5. The spraying device according to claim 4, characterized in that: The U-shaped mounting seat is mounted on the lower surface of the first mounting plate through adjustable bolts.

6. The spraying device according to claim 3, characterized in that: One end of the first mounting plate is connected to one end of the connecting plate, the other end of the connecting plate is connected to the second mounting plate, and the cooling joint and the insulation joint are mounted on the second mounting plate.

7. The spraying device according to claim 6, characterized in that: One end of the second mounting plate is connected to one end of the third mounting plate.

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