Method and device for improving forming quality and performance uniformity of laser deposition forming thin-wall part

Abstract

The invention relates to a method and device for improving the forming quality and performance uniformity of a laser deposition forming thin-walled workpiece. The device comprises a clamping assembly, a laser metal deposition system, a liquid nitrogen active cooling system and an auxiliary forming assembly, and the clamping assembly is used for clamping a base body of the deposition forming thin-walled workpiece; the laser metal deposition system is used for generating high-energy laser for a deposition area of the substrate to form a laser deposition area, providing a protective atmosphere for the laser deposition area and feeding deposition powder; the liquid nitrogen active cooling system is used for cooling and dissipating heat for a base body forming the laser deposition molten pool, the auxiliary forming assembly comprises two ceramic plates which are oppositely arranged, and the opposite faces of the two ceramic plates and the deposition face of the top of the base body form a deposition groove so as to assist in setting of a deposition layer. The cooling rate and the solidification speed of the molten pool can be increased, then the effects of reducing the microstructure size of a cladding layer and refining grains are achieved, and the forming efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of laser additive manufacturing, and in particular to a method and a device for improving the forming quality and performance uniformity of thin-walled parts formed by laser deposition. Background Art

[0002] Additive manufacturing technology for metal materials is a process method that uses high-power laser beam melting / rapid solidification to grow layer by layer by discretizing the CAD model, using metal powder, particles, metal wire, etc. as raw materials, and directly completing the near-net-shape manufacturing of high-performance parts from the part digital model. Laser deposition manufacturing technology (LDM) is an organic combination of rapid prototyping technology and laser cladding technology. It uses metal powder as raw material and high-energy laser beam as heat source. According to the scanning path planned by the layered slicing information of the CAD model of the formed part, the metal powder is melted, rapidly solidified, and deposited layer by layer, thereby realizing the direct manufacturing of the entire metal part. Laser deposition technology uses a coaxial powder feeding processing method, with a laser beam as a heat source, to synchronously transport the molten powder material to the substrate, and deposit it layer by layer according to a pre-set path, and finally obtains a processing method for parts. It often has a high deposition rate and high density, and can prepare large metal structures. Compared with traditional forming processes, laser additive manufacturing has the advantages of not requiring molds during part forming, no restrictions on forming dimensions, short production cycle, high material utilization, uniform forming structure, excellent mechanical properties, and the ability to realize the design and manufacturing of gradient materials.

[0003] The LDM system mainly includes: laser and optical path system, water chiller and cooling system, CNC machine tool system, powder feeder and powder feeding system, inert gas protection system, laser melting deposition chamber and process monitoring system. LDM technology integrates the characteristics of rapid prototyping technology and laser cladding technology, and has the following advantages: (1) No large equipment and molds are required, the parts are nearly net-shaped, and the material utilization rate is high; (2) The process flow and manufacturing cycle are short, and the manufacturing cost is low; (3) The parts have no macro-segregation, the structure is fine and dense, and the mechanical properties reach the level of forgings; (4) The forming size is not limited, and large-sized parts can be manufactured; (5) The laser beam has high energy density, which can achieve near-net-shaped forming of refractory and difficult-to-process materials; (6) Failed and damaged parts can be quickly repaired, and directional structure repair and manufacturing can be achieved.

[0004] Laser deposition manufacturing (LDM) is a technology for rapidly manufacturing near-net-shape three-dimensional metal specimens. It has the advantages of low dilution rate, small heat-affected zone, fast cooling rate and high degree of automation. LDM can be used to form functional gradient specimens with complex geometric configurations or repair complex structural components, which is difficult to achieve with traditional methods. However, LDM technology is restricted by process parameters and various physical processes. These parameters interact with each other, resulting in limited manufacturing of LDM process under various conditions, causing cracks, metallurgical defects and poor surface quality in the formed parts. The poor surface quality of additively manufactured parts has a negative impact on the geometric accuracy and mechanical properties of the finished specimens. In order to achieve qualified surface quality, several post-processing steps are often added, which increases time and operating costs. The surface quality of the deposited parts is mainly affected by process parameters and physical processes. In order to improve the surface quality of additively manufactured parts, domestic and foreign scholars have conducted a lot of research work. (Reference: Yang Guang, Li Xintong, Wang Yushi, et al. Research on the prediction and control method of surface roughness of laser deposition manufactured parts [J]. Aviation Manufacturing Technology, 2024, 67(14): 14-23.) Laser additive manufacturing technology uses laser as a heat source and is based on the principle of layered manufacturing. It accumulates materials layer by layer through melting and solidification to finally obtain three-dimensional solid components. At present, laser additive manufacturing technology for metal parts is mainly divided into laser deposition manufacturing technology (LDM) and laser selective melting technology (SLM) according to the different feeding methods during the forming process. LDM-formed components are large in size and high in efficiency, but the forming accuracy is low, and subsequent mechanical processing is often required to meet the precision requirements of the parts. SLM-formed components have high precision, and non-matching surfaces can be free of subsequent processing, but the size of the formed parts is limited and the efficiency is low. The melt channel is the most basic unit of laser additive manufacturing components. The smaller the size of the melt channel, the higher the accuracy of the components formed by accumulation and overlap. The size of the molten pool and the properties of the powder fed into the molten pool during the forming process directly determine the size and morphology of the melt channel. To this end, the National Defense Key Discipline Laboratory of Aeronautical Manufacturing Technology Digitalization of Shenyang Aerospace University independently developed a small molten pool laser deposition manufacturing process that uses small-particle powder used in SLM technology as raw materials, uses a small spot to melt the powder, and uses the LDM process method to stack layer by layer to complete the high-precision forming of large components. The diameter of the molten pool formed by this process is only about 1.5mm, which not only retains the high efficiency of LDM technology, but also takes into account the high precision of SLM technology. It can achieve high-precision forming of large components and make the precision of some non-matching surfaces reach the level of free machining. Thin-walled parts are the most common LDM deposition specimens. The dimensional control of the wall thickness of thin-walled parts is the basis for studying the forming accuracy of small molten pool laser deposition, and the process parameters are the key factors affecting the deposition width of LDM thin-walled parts. (References; Qin Lanyun, Lin Pengxiang, Yang Guang, et al. Model prediction and experimental study on the deposition width of thin-walled parts manufactured by small molten pool laser deposition [J]. Aviation Manufacturing Technology, 2024, 67(03):32-37.) Laser deposition technology has been applied to the manufacture of some important large parts, but there are still many problems in the manufacture of thin-walled metal components. For example, the residual stress concentration caused by the interlayer heat accumulation during the laser deposition process leads to deformation and cracking of thin-walled parts (Reference 1: Wu Zhipeng, Wu Rikaixi Ayi, Zhang Yutao. Numerical simulation and experimental study of thin-plate laser cladding under synchronous gas cooling [J / OL]. Surface Technology, 1-12 [2024-09-23].), and this study uses numerical simulation and experimental verification methods to show that liquid nitrogen cooling is beneficial to reducing residual stress and deformation in the laser additive process of thin-walled parts; excessive segregation caused by excessive dilution rate leads to quality problems and coarse grains of formed structure lead to insufficient structure strength (Reference 2: Zhou Jianzhong, Wang Songtao, Xu Jiale, et al. Effect of liquid nitrogen forced cooling on the microstructure and properties of WC / Ni60A coating prepared by laser cladding on Ti6Al4V surface [J]. Rare Metal Materials and Engineering, 2019, 48(02): 500-508.), and the study showed that the dilution rate of the deposited layer under liquid nitrogen cooling was significantly lower than that under air cooling conditions, and that there were strengthening mechanisms such as fine grain strengthening, solid solution strengthening and dispersion strengthening in the structure under liquid nitrogen cooling conditions. The microhardness and wear resistance were increased by 1.61 times and 1.77 times respectively compared with those under air cooling conditions. In the process of laser additive manufacturing, when the formed parts are stacked layer by layer to a certain height, the temperature gradient from top to bottom inside the formed parts decreases, which causes the molten pool to be unable to maintain the temperature gradient from top to bottom during solidification, thus affecting the integrity of the columnar crystals. The interruption of the columnar crystal structure will affect the mechanical properties of the formed parts to a certain extent, and the dendrite spacing is increased compared with the bottom, and there are miscellaneous crystals in different directions, which leads to a decrease in the microhardness value and increases the possibility of organizational segregation (Reference 3: He Bin, Li Dichen, Zhang Anfeng, et al. Effect of liquid argon cooling on the structure and microhardness of 316L laser metal direct forming parts [J]. Chinese Laser, 2011, 38(10): 94-99.); As the number of deposition layers increases, the efficiency of heat transfer decreases, resulting in an increase in the size of the molten pool and the interlayer temperature. This phenomenon will have the following adverse consequences: uneven material distribution along the additive direction, large differences in the size of the molten pool, collapse of the additive structure, etc. At the same time, the plasma arc working process is accompanied by huge heat input, which leads to residual stress and deformation of the parts. How to reduce or weaken the interlayer heat accumulation effect in the plasma arc additive process is the key to achieving shape control. At present, the most common way to prevent heat accumulation is to increase the interlayer cooling time (interlayer pause time), but this will also seriously reduce the additive efficiency; another is to use a water-cooled fixture to promote the heat dissipation of the substrate, and the disadvantage of this method is that the heat dissipation is still conducted through the substrate, and the cooling rate of the deposition process is still unstable. (References: Zhao Yuhui, Wang Zhiguo, Zhao Jibin, et al. Study on the influence of cooling conditions on the microstructure and properties of 316L stainless steel by plasma arc powder feeding additive [J]. Rare Metals, 2021, 45(09): 1062-1069.) In summary, during the metal deposition process, the temperature accumulation inside the formed part, the layer-by-layer decrease in the temperature gradient of the molten pool, and the increase in the dendrite spacing are the main reasons for the reduction in the performance of the metal deposition formed organization. While ensuring that the laser deposition parameters remain unchanged, the efficiency of heat transfer decreases with the increase in the number of deposition layers, resulting in an increase in the size of the molten pool and the temperature between layers, which will lead to large differences in the size of the molten pool and the collapse of additive structural parts. Specifically, it is because the accumulation of temperature causes the liquid metal to exist for too long, resulting in liquid metal flow, and the accumulation of forming errors ultimately leads to problems with the shape accuracy of the formed part. In addition, the problem of uneven organizational properties caused by the different solidification temperature states of each deposition layer during laser deposition is also worth considering.

[0005] Therefore, it is necessary to provide a method and device for improving the forming quality and performance uniformity of thin-walled parts formed by laser deposition to solve the above problems. Summary of the invention

[0006] The present invention provides a method and device for improving the forming quality and performance uniformity of thin-walled parts formed by laser deposition, so as to solve the existing problems that the liquid metal exists for too long due to temperature accumulation, resulting in liquid metal flowing, and the accumulation of forming errors ultimately leads to the shape accuracy problem of the formed parts, and the problem of uneven organizational performance caused by the different solidification temperature states of each deposition layer during the laser deposition process.

[0007] The device for improving the forming quality and performance uniformity of thin-walled parts formed by laser deposition of the present invention adopts the following technical scheme, including: A clamping assembly, used for clamping a substrate of a deposition-formed thin-walled part; A laser metal deposition system, which is used to generate high-energy laser light in the deposition area of ​​the substrate to form a laser deposition area, provide a protective atmosphere for the laser deposition area, and feed the deposition powder; A liquid nitrogen active cooling system is used to cool and dissipate heat for a substrate forming a laser deposition molten pool, and comprises: a support frame connected to a laser deposition cladding head of a laser metal deposition system, on which a plurality of liquid nitrogen nozzles connected to a liquid nitrogen tank are arranged, the plurality of liquid nitrogen nozzles are symmetrically distributed on both sides of the substrate, the injection ends of every two symmetrical liquid nitrogen nozzles are opposite, and the symmetry center of the two symmetrical liquid nitrogen nozzles is the position where the laser deposition molten pool is formed; Auxiliary molding component, the auxiliary molding component includes: a linear drive component, an angle adjustment component and two ceramic plates arranged on a support frame, the two ceramic plates are arranged opposite to each other, the back faces of the two ceramic plates are arranged on both sides of the substrate, and the back faces of the two ceramic plates are rotatably connected to the output end of the linear drive component, and the angle adjustment component is used to drive the ceramic plate to rotate at the output end of the linear drive component to adjust the shape of the deposition groove formed by the opposite faces of the two ceramic plates and the deposition surface on the top of the substrate; And a control system, which is used to control the auxiliary forming components of the auxiliary forming components and the angle adjustment component to adjust the inclination angle of the ceramic plate and the distance between the two ceramic plates according to the shape of the formed thin-walled part, so that the shape of the deposition groove formed by the two ceramic plates and the top deposition surface of the substrate is consistent with the shape of the formed thin-walled part.

[0008] Preferably, the clamping assembly comprises: A positioning base, the top of which is provided with a through slot along its length direction; A limit block is arranged on the inner bottom surface of the through slot; And two positioning blocks are arranged on the two side walls of the through slot through positioning screws, and are used for positioning and clamping the base.

[0009] Preferably, a through hole is provided in the positioning block, a brass pipe for liquid nitrogen to pass through is provided in the through hole, and the inlet and outlet ends of the brass pipe are connected to the liquid nitrogen tank to form a closed loop.

[0010] Preferably, the laser metal deposition system comprises: a robotic arm, a nitrogen tank, a laser generator, a powder feeder and a control system, wherein the laser deposition cladding head is arranged at the output end of the robotic arm, the control system is used to control the robotic arm to run according to the motion trajectory of laser deposition, and is used to control the nitrogen sprayed from the nitrogen tank to enter the powder feeder, and the nitrogen drives the deposition powder in the powder feeder to reach the laser deposition cladding head together, and the laser head of the laser deposition cladding head converges to the deposition area, and at the same time controls the laser generator to generate high-energy laser on the deposition powder in the deposition area to form a laser deposition area.

[0011] Preferably, the support frame comprises: Two connecting cross bars are horizontally and symmetrically arranged on both sides of the laser deposition cladding head, and the ends of the connecting cross bars facing away from the laser deposition cladding head are connected with horizontal supporting bars arranged horizontally; And a plurality of distance adjustment components are vertically and evenly arranged on the horizontal support rod, one end of which is connected to the horizontal support rod, and the other end of which is connected to the liquid nitrogen nozzle.

[0012] Preferably, the distance adjustment assembly includes: a threaded rod, one end of which is threadedly connected to the horizontal support rod, and the end connected to the horizontal support rod is provided with an adjusting nut after passing through the horizontal support rod, and a connecting ring is provided at one end of the threaded rod away from the horizontal support rod, and the connecting ring is connected to the liquid nitrogen nozzle through a thread.

[0013] Preferably, the ceramic plate is made of nano-alumina ceramic material.

[0014] Preferably, the liquid nitrogen active cooling system also includes: a temperature feedback device, a computer control system and an electromagnetic control valve, the electromagnetic control valve and the temperature feedback device are electrically connected to the computer control system, wherein each liquid nitrogen nozzle is connected to the main pipeline arranged at the outlet of the liquid nitrogen tank through a branch pipeline, the electromagnetic control valve is arranged on the main pipeline, the temperature feedback device is arranged on one end side of the substrate, the temperature feedback device is used to collect the temperature of the laser deposition molten pool in real time, and the computer control system is used to control the switch, time and flow rate of the electromagnetic control valve spraying liquid nitrogen from the liquid nitrogen nozzle according to the temperature of the laser deposition molten pool and the working conditions until the temperature of the laser deposition molten pool reaches the expected temperature required by the working conditions.

[0015] Preferably, the angle adjustment component includes: a servo, whose output end is provided with a driving gear, wherein a transmission rod is rotatably provided at the output end of the linear drive component, the transmission rod is connected to the ceramic plate through a support, and a transmission gear meshing with the driving gear is provided on the transmission rod.

[0016] A method for improving the forming quality and performance uniformity of a thin-walled part formed by laser deposition, comprising: Obtain an STL model of the expected thin-walled part, select the layer thickness according to the shape and size of the thin-walled part, and use layering software to perform layering on the STL model; Clamp the substrate through the clamping assembly, control the robotic arm to drive the laser deposition cladding head to align with the center of the substrate, and perform position calibration for laser deposition manufacturing; turn on the laser generator, nitrogen tank, powder feeder, and control system in sequence to put the laser generator, nitrogen tank, powder feeder, and control system in working condition; The laser power, powder feeding amount, scanning speed and deposition height of the laser deposition layer are determined according to the layering results of the STL model. The spacing between the two ceramic plates and the tilt angle of the ceramic plates are adjusted according to the shape of the formed thin-walled part, so that the spacing between the two ceramic plates is consistent with the width of the formed thin-walled part, and the tilt angle is consistent with the tilt angle of the formed thin-walled part. When depositing each layer of laser cladding, the laser deposition area is cooled by the liquid nitrogen active cooling system. At the same time, when depositing each layer, the temperature feedback device is used to collect the temperature of the molten pool of each layer in real time. When depositing the next layer, the switch time of the electromagnetic control valve and the liquid nitrogen flow rate are controlled to control the molten pool temperature to be consistent with the molten pool temperature of the previous layer, that is, to complete the task of each layer of deposition; After completing the task of depositing one deposition layer, the control system controls the robotic arm to rise in the vertical direction to the height of each deposition layer after the STL model is layered according to the layering software, and completes the laser deposition task of the current deposition layer until the laser deposition task of the entire thin-walled part is completed.

[0017] The beneficial effects of the present invention are: 1. The active cooling system in this device can actively cool the laser cladding deposit layer in real time by spraying liquid nitrogen, which can not only effectively solve the problem of thermal stress accumulation cracking caused by the cumulative increase in the temperature of the deposited layer, but also greatly increase the cooling rate and solidification rate of the molten pool, thereby reducing the microstructure size of the cladding layer and refining the grains. In addition, the deposition process does not require a slow cooling process, and can achieve uninterrupted laser cladding forming, thereby improving the forming efficiency.

[0018] 2. The present invention makes full use of the characteristics of laser cladding forming for additive manufacturing, and combines the clamping components, auxiliary forming components, and liquid nitrogen active cooling system in the device to achieve high-quality and efficient forming of variable thickness straight and curved thin walls, which has the advantages of saving expensive powder materials and shortening the development and manufacturing cycle of complex thin-walled parts.

[0019] 3. The present invention makes full use of the liquid nitrogen active cooling system to transform the entire laser deposition forming process into a dynamic temperature control system, so that the overall organizational properties of the formed thin-walled parts are in a stable state, and the formed thin-walled parts will not suffer local failure in the service environment.

[0020] 4. By adjusting the opening and closing size and rotation angle of the ceramic plates, it can be ensured that the laser deposition molten pool is always solidified and formed inside the double ceramic plates. This can not only break through the precision limitation of the molten pool limit size on the size of the formed thin-walled parts and improve the surface quality of the thin-walled parts, but also overcome the molten pool flow problem caused by interlayer heat accumulation by real-time control of the thin-wall thickness and forming direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 It is a schematic diagram of the overall structure of an embodiment of a device for improving the forming quality and performance uniformity of a thin-walled part formed by laser deposition according to the present invention; Figure 2 A connection diagram of the positional relationship of the components of the invented clamping assembly, auxiliary forming assembly and liquid nitrogen active cooling system; Figure 3 To invent a positional relationship diagram of the laser beam, powder path, molten pool and deposited layer during laser deposition; Figure 4 A diagram showing the positional relationship of the components in the front view of the invented device for improving the forming quality and performance uniformity of thin-walled parts formed by laser deposition; Figure 5 A diagram showing the relationship between the horizontal laser deposition direction and the spatial position of the liquid nitrogen nozzle and the ceramic plate of the invention; Figure 6 A working flow chart of the invented clamping assembly, auxiliary forming assembly and liquid nitrogen active cooling system; Figure 7 It is a schematic diagram of three adjustment modes of achieving equal wall thickness, variable wall thickness and inclined surface assisted forming by adjusting the ceramic plate of the invention; Figure 8 It is a structural schematic diagram of adjusting the distance between two ceramic plates and adjusting the angle of the ceramic plates.

[0023] In the figure: 1. Robotic arm; 2. Nitrogen tank; 3. Control system; 4. Powder feeder; 5. Water chiller; 6. Laser generator; 7. Computer control system; 8. Connecting cross bar; 9. Connecting bolt; 10. Laser deposition cladding head; 11. Adjusting nut; 12. Threaded rod; 13. Temperature feedback device; 14. Positioning block; 15. Positioning base; 16. Positioning screw; 17. Base; 18. Ceramic plate; 19. Connecting nut; 20. Limit block; 21. Brass pipe; 22. Liquid nitrogen nozzle; 23. Solenoid control valve; 24. Liquid nitrogen tank; 25. Distance adjustment assembly; 26. Servo controller; 27. Connecting rod; 28. Angle adjustment assembly; 29. ​​Transmission gear; 30. Transmission rod; 31. Thread; 32. Servo. DETAILED DESCRIPTION

[0024] 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 only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] An embodiment of the device for improving the forming quality and performance uniformity of thin-walled parts formed by laser deposition according to the present invention is as follows: Figure 1 As shown, it includes: a clamping component, a laser metal deposition system, a liquid nitrogen active cooling system, an auxiliary molding component and a control system, wherein the clamping component is used to clamp the substrate 17; the laser metal deposition system is used to generate high-energy laser on the deposition area of ​​the substrate 17 to form a laser deposition area, and provide a protective atmosphere for the laser deposition area and feed the deposition powder; the liquid nitrogen active cooling system is used to cool and dissipate the heat for the substrate 17 forming the laser deposition molten pool, and the liquid nitrogen active cooling system includes: a support frame, which is connected to the laser deposition cladding head 10 of the laser metal deposition system, The support frame is provided with a plurality of liquid nitrogen nozzles 22 connected to the liquid nitrogen tank 24. The plurality of liquid nitrogen nozzles 22 are symmetrically distributed on both sides of the substrate 17. The spray ends of each two symmetrical liquid nitrogen nozzles 22 are opposite, and the symmetry center of the two symmetrical liquid nitrogen nozzles 22 is the position where the laser deposition molten pool is formed; wherein the two symmetrical liquid nitrogen nozzles 22 and the laser head of the laser deposition cladding head 10 are in a plane perpendicular to the horizontal deposition direction of the substrate 17. The horizontal deposition direction of the substrate 17 is to use the plane where the two liquid nitrogen nozzles and the laser head are located as the front end, and the two pairs of liquid nitrogen nozzles 22 as the rear end for laser deposition manufacturing. The purpose of this is that the cooling rate of the molten pool is extremely high. In order to effectively cool and dissipate the heat of the molten pool, the high temperature generated in this way can reach the liquid nitrogen spraying area at the shortest distance for timely heat exchange. The laser deposition manufacturing is continuous and uninterrupted, and heat will be continuously generated. The remaining two pairs of liquid nitrogen nozzles can increase the cooling amount, and continuously cool and dissipate the heat during the entire laser deposition process. The auxiliary molding component includes: a linear drive component, an angle adjustment component 28 and two ceramic plates 18 arranged on the support frame, the two ceramic plates 18 are arranged opposite to each other, the back surfaces of the two ceramic plates 18 are arranged on both sides of the substrate 17, and the back surfaces of the two ceramic plates 18 are rotatably connected to the output end of the linear drive component, and the angle adjustment component is used to drive the ceramic plates 18 to rotate at the output end of the linear drive component to adjust the shape of the deposition groove formed by the opposite surfaces of the two ceramic plates 18 and the top deposition surface of the substrate 17, specifically, as Figure 8As shown, the angle adjustment component 28 includes a servo 32, and the output end of the servo 32 is connected to a driving gear, wherein the output end of the linear drive component is connected to a connecting rod 31 through a thread 31, and a transmission rod 30 perpendicular to the connecting rod 27 is passed through the end of the connecting rod 31, and the transmission rod 30 can rotate around the connecting rod 27, and the transmission rod 30 is fixedly connected to the ceramic plate 18 through a support, and a transmission gear 29 meshing with the driving gear is provided at the end of the transmission rod 30, and the transmission gear 29 is meshed with the driving gear at the output end of the servo 32 of the angle adjustment component 28. The control system is used to control the auxiliary forming components of the auxiliary forming components, the angle adjustment component 28 adjusts the inclination angle of the ceramic plate 18 and the distance between the two ceramic plates 18 according to the shape of the formed thin-walled part, so that the shape of the deposition trough formed by the two ceramic plates 18 and the top deposition surface of the substrate 17 is consistent with the shape of the formed thin-walled part.

[0026] It should be noted that the ceramic plate 18 is made of nano-alumina ceramic material, which has the characteristics of high melting point (2015°C), high room temperature and high temperature strength, high chemical stability, high hardness and good wear resistance. The width of the ceramic plate 18 is consistent with the thickness of the substrate 17. The deposition powder is melted under the high temperature of the high-energy laser beam and cooled in the deposition tank to form. First, the auxiliary molding components and angle adjustment components of the auxiliary molding components are controlled according to the shape of the formed thin-walled part to be formed to adjust the inclination angle of the ceramic plate 18 and the spacing between the two ceramic plates 18, and the inclination angle of the ceramic plate 18 and the spacing between the two ceramic plates 18 are adjusted so that the shape of the deposition tank formed between the two ceramic plates 18 is consistent with the shape of the formed thin-walled part to be formed. The two ceramic plates 18 move synchronously with the laser deposition cladding head 10, and the deposition layers are accumulated layer by layer. The two ceramic plates 18 stabilize the shape of each deposition layer within a certain range, and finally the overall shape error of the formed thin-walled part will not be too large, thereby ensuring the forming accuracy of the formed thin-walled part. Secondly, the control system is a computer control system 7, which controls the servo controller 26 of the linear drive assembly to control the linear motor to drive the ceramic plate 18 to move relatively, so as to adjust the wall thickness and the inclined surface of the thin-walled parts. Figure 7 As shown in a, the wall thickness adjustment of the formed thin-walled part can be achieved by only driving the two ceramic plates 18 to move relative to each other through the linear drive assembly, such as Figure 7 b and Figure 7 As shown in FIG. 3 , the two ceramic plates 18 are first driven to move relative to each other by a linear drive assembly, and then the driving gear 29 is meshed by controlling the steering gear 32 to drive the rotation of the transmission gear 29, thereby driving the ceramic plate 18 to adjust the angle from a straight surface to an inclined surface. The two ceramic plates 18 that move synchronously with the laser deposition cladding head 10 also avoid the problem of low shape accuracy of the substrate 17 caused by the flow of the molten pool due to heat accumulation between the deposition layers during the process of regulating the layer thickness, layer width and forming angle of the deposition layer.

[0027] Specifically, the clamping assembly includes: a positioning base 15, a stopper block 20 and two positioning blocks 14. The top of the positioning base 15 is provided with a through slot along its length direction; the stopper block 20 is arranged on the inner bottom surface of the through slot; the two positioning blocks 14 are arranged on the two side walls of the through slot by positioning screws 16, and the two positioning blocks 14 are used to position and clamp the substrate 17. In order to further cool and dissipate the residual heat of the molten pool after liquid nitrogen cooling, a through hole is provided in the positioning block 14 of this embodiment, and a brass pipe 21 for liquid nitrogen to pass through is provided in the through hole. The inlet and outlet ends of the brass pipe 21 are provided with connecting nuts 19 connected to the pipe of the liquid nitrogen tank 24, and the inlet and outlet ends of the brass pipe 21 are connected to the liquid nitrogen tank 24 to form a closed loop, which continuously provides an extremely low temperature liquid nitrogen cooling environment for cooling the substrate 17, thereby realizing cooling of the deposited formed thin-walled parts on the substrate 17. That is, by introducing liquid nitrogen into the brass pipe 21 and spraying liquid nitrogen from the liquid nitrogen nozzle 22 to rapidly cool the high-temperature molten pool during the laser deposition process, it is possible to avoid the accumulation of thermal stress and cracking between the deposited layers and the coarsening of the microstructure grains, thereby avoiding the problem of low productivity caused by the molten pool existing for too long.

[0028] Specifically, the laser metal deposition system includes: a robot arm 1, a nitrogen tank 2, a laser generator 6, a powder feeder 4 and a control system 3, wherein the laser generator 6 is cooled by a water cooler 5, and a laser deposition cladding head 10 is arranged at the output end of the robot arm 1; the control system 3 is used to control the robot arm 1 to run according to the motion trajectory of laser deposition, to control the nitrogen tank 2 to provide a protective atmosphere for the laser deposition area, to control the powder feeder 4 to feed the deposited powder, and to control the laser generator 6 to generate high-energy laser to the deposition area to form a laser deposition area; it should be noted that the laser metal deposition system The control system 3 also regulates the powder feeding amount, laser power, scanning rate and vertical (Z-axis) rising amount of the robot arm 1 in the laser deposition process. The control system 3 is the control system of the laser metal deposition system. The control system 3 controls the robot arm 1 to perform high-precision trajectory operation. The control system 3 controls the nitrogen gas sprayed from the nitrogen tank 2 to be transported to the powder feeder 4 through the air pipe, driving the metal powder in the powder feeder 4 to reach the laser head of the robot arm 1 with the laser deposition cladding head 10. Through the convergence of the laser head, the nitrogen gas wraps the metal powder and converges to a convergence point a distance below the laser head. At the same time, the high-energy laser beam generated by the laser generator 6 is transmitted from the middle of the laser head through the optical path. Most of the laser energy is irradiated on the metal powder to melt quickly, and the remaining energy is irradiated on the substrate 17. The irradiated part of the substrate 17 is also melted at high temperature, and is cooled and solidified together with the molten powder to form a metallurgical deposition layer.

[0029] Specifically, the support frame includes: two connecting cross bars 8, and a distance adjustment component 25, the two connecting cross bars 8 are horizontally symmetrically arranged on both sides of the laser deposition cladding head 10, one end of the connecting cross bar 8 is connected to the laser deposition cladding head 10 through a connecting bolt 9, and the end of the connecting cross bar 8 away from the laser deposition cladding head 10 is connected to a horizontally arranged horizontal support rod; a plurality of distance adjustment components 25 are evenly arranged on the horizontal support rod along the length direction of the horizontal support rod, wherein the distance adjustment component 25 includes: a threaded rod 12, one end of the threaded rod 12 is threadedly connected to the horizontal support rod, the end of the threaded rod 12 connected to the horizontal support rod is provided with an adjustment nut 11 after passing through the horizontal support rod, and a connecting ring is provided at one end of the threaded rod 12 away from the horizontal support rod, and the connecting ring is connected to the liquid nitrogen nozzle 22 through a thread, and the laser head of the laser deposition cladding head 10, the connecting cross bar 8, the threaded rod 12 and the liquid nitrogen nozzle 22 are connected into one piece. The four are connected to form a "C" shape, with the deposition workpiece as the symmetry axis, and the same structure is also present on the other side of the workpiece, forming an "O" shape as a whole, wherein the positional relationship between the liquid nitrogen nozzle 22, the molten pool and the deposition direction of each deposition layer is as follows: Figure 5 As shown; it should be noted that the liquid nitrogen nozzle 22 and the connecting ring of the threaded rod 12 are connected by a section of thread, and the length of this section of thread is the adjustable distance of the liquid nitrogen nozzle 22, which respectively adjusts the horizontal and vertical distances of the liquid nitrogen nozzle 22 from the substrate 17. It is used for adjusting the distance of the liquid nitrogen nozzle 22 from the molten pool on the substrate 17 under the initial conditions to adapt to different working conditions. The position relationship diagram of the thread adjustment area is shown in Figure 4 and 5 shown.

[0030] Specifically, the liquid nitrogen active cooling system also includes: a temperature feedback device 13, a computer control system 7 and an electromagnetic control valve 23. The electromagnetic control valve 23 and the temperature feedback device 13 are electrically connected to the computer control system 7. The temperature feedback device 13 uses a temperature imager. Each liquid nitrogen nozzle 22 is connected to the main pipeline provided at the outlet of the liquid nitrogen tank 24 through a branch pipeline. The electromagnetic control valve 23 is provided on the main pipeline. The temperature feedback device 13 is provided at one end of the substrate 17. The temperature feedback device 13 is used to collect the temperature of the laser deposition molten pool in real time. The computer control system 7 is used to collect the temperature of the laser deposition molten pool in real time according to the temperature of the laser deposition molten pool and the process. The working condition requires that the electromagnetic control valve 23 control the switch, time and flow rate of liquid nitrogen sprayed from the liquid nitrogen nozzle 22 until the temperature of the laser deposition molten pool reaches the expected temperature required by the working condition, that is, the temperature in the laser deposition process is monitored in real time through the temperature feedback device 13, and the temperature data is transmitted to the computer control system 7 for analysis and storage, and the temperature data with better morphology quality of the deposited layer is stored. When depositing the next deposited layer, the switch of the electromagnetic control valve is controlled to adjust the cooling temperature, thereby playing a stabilizing role in regulating the temperature of each deposited layer, and finally making the overall organizational properties of the deposited layer stable. There are six liquid nitrogen nozzles 22 in this embodiment. The distance adjustment assembly 25 arranges the liquid nitrogen nozzles 22 on both sides of the substrate 17. There are three liquid nitrogen nozzles 22 on each side of the substrate 17 and they correspond to each other. The center of the line connecting the two opposite liquid nitrogen nozzles 22 is used as the position where the laser deposition molten pool is formed. In this way, the high temperature generated by the molten pool can be evenly cooled and dissipated by the liquid nitrogen sprayed by the liquid nitrogen nozzles on both sides, so as to prevent the difference in the microstructure and performance on both sides of the formed thin-walled parts from being too large, and to avoid the problem of local failure of the formed thin-walled parts during service and huge deformation caused by different residual stresses on both sides during deposition. It should be noted that, through the liquid nitrogen active cooling system, since the liquid nitrogen active cooling system is bolted to the laser deposition cladding head, during the deposition process, the liquid nitrogen nozzle of the liquid nitrogen active cooling system moves together with the laser deposition cladding head, so that the distance between the liquid nitrogen nozzle and the molten pool is dynamically stable, so that the cooling source of the liquid nitrogen sprayed by the liquid nitrogen nozzle is always stable within a certain range from the molten pool, so as to ensure the stability of the cooling rate of the molten pool, and thus ensure the uniformity of the overall performance of the formed thin-walled parts.

[0031] A method for improving the forming quality and performance uniformity of a thin-walled part formed by laser deposition, comprising: Step 1: Use 3D modeling software to perform CAD 3D modeling on the shape and size of the expected thin-walled part, extract the STL model of the thin-walled part, and then select the layer thickness according to the shape, size and manufacturing accuracy of the structural part. H (n=1,2,3‥), use the slicing and stratification software to stratify the STL model and determine the stratification width of each layer W (n=1,2,3‥) and thin-wall forming inclination angle Ln (n=1,2,3‥), one layered slice is equivalent to one process, and there are n processes in total.

[0032] Step 2: Layer thickness according to step 1 H (n=1,2,3‥), layer width W (n=1,2,3‥), thin-wall forming inclination angle L n (n=1,2,3‥), determine the motion trajectory of the laser head of the current layer, assemble the liquid nitrogen active cooling system according to the pre-designed system, and debug the computer control system 7, the temperature feedback device 13, and the electromagnetic control valve 23 to be in working condition. The substrate 17 is clamped by the clamping assembly, and the liquid nitrogen nozzle cools the substrate 17 with liquid nitrogen to avoid the collapse of the substrate 17 caused by the temperature accumulation of the deposition layer, the cracking due to thermal stress accumulation, the coarse microstructure, and the insufficient strength. At the same time, the computer control system 7 controls the linear drive assembly to drive the two pick pieces 18 to adjust the spacing between the two ceramic plates 18 to the thickness of the formed thin-walled part. Then, the computer control system 7 controls the rotation of the steering gear 32 to adjust the inclination angle of the ceramic plate 18, so that the inclination angle of the ceramic plate 18 is consistent with the inclination angle of the formed thin-walled part. Finally, the shape of the deposition trough formed by the two ceramic plates 18 and the top deposition surface of the substrate 17 is consistent with the shape of the formed thin-walled part. That is, according to the thickness of each layer of the formed thin-walled part H (n=1,2,3‥), width W (n=1,2,3‥), thin-wall forming inclination angle L n (n=1,2,3‥). The servo controller 26 is controlled by the computer control system 7 to control the linear motor and the steering gear 32, so as to adjust the distance between the two ceramic plates 18 moving synchronously with the laser deposition cladding head and the inclination angle with the ceramic plates 18, so that the distance between the two ceramic plates 18 moving synchronously with the laser deposition cladding head is consistent with the wall thickness of the formed thin-walled part, so that the inclination angle of the two ceramic plates 18 is adjusted in real time to be consistent with the inclination angle of the shape of the formed thin-walled part, and ensure that the laser deposition molten pool is always solidified between the two ceramic plates 18.

[0033] Step 3: Control the robot arm 1 to drive the laser deposition cladding head 10 to align with the center of the substrate 17 to perform position calibration for laser deposition manufacturing; turn on the laser generator 6, the nitrogen tank 2, the powder feeder 4, and the control system 3 in sequence, so that the laser generator 6, the nitrogen tank 2, the powder feeder 4, and the control system 3 are in working state. The control system 3 controls the laser power and the amount of powder fed during the laser deposition process. The running trajectory and scanning speed of the laser deposition cladding head 10 are used to deposit and manufacture each layer of the slice deposition layer, and the slice layer thickness is optimized to meet the requirements. H (n=1,2,3‥), width W (n=1,2,3‥), thin-wall forming inclination angle Ln (n=1,2,3‥), including laser power, powder feeding amount, nitrogen flow rate, feed rate, overlap rate, and switching time of the electromagnetic control valve. The specific steps of the optimization scheme are as follows: observe the macroscopic morphology of the deposited layer obtained under a certain process parameter, first eliminate the situation of unmelted powder and overburned powder, analyze the influence of parameters and adjust them to avoid such problems; secondly, on the basis of no unmelted powder and overburned powder, check the surface flatness of the deposited layer, adjust the overlap rate, etc. to meet the requirements; finally, observe the microstructure of the deposited layer to check for fine cracks, and then adjust the relevant parameters to avoid them. Laser deposition is a thermal processing process. Temperature is an important parameter to characterize the rationality of various process parameters. Recording the real-time temperature of the deposited layer that meets the design requirements is of great significance to the regulation of the shape and performance of the deposited layer. At the same time, the temperature feedback device (temperature camera) measures the temperature of the molten pool at this moment. Tn (n=1,2,3‥) for recording.

[0034] Step 4: According to the slice thickness in step 1 H (n=1,2,3‥), adjust the laser deposition cladding head 10 to rise the same distance H (n=1,2,3). According to the specific shape of each slice, the relative distance and tilt angle of the two ceramic plates 18 are readjusted. According to the temperature of the molten pool of the previous deposition layer Tn (n=1,2,3‥), the deposition manufacturing process parameters of this deposition layer are adjusted by control system 3 so that the molten pool temperature of this deposition layer Tn +1 (n=1,2,3‥) and the molten pool temperature of the previous deposition layer Tn (n=1,2,3‥) are equal, that is, when depositing each deposition layer, the temperature feedback device 13 is used to collect the molten pool temperature of each deposition layer in real time, and when depositing the next deposition layer, the switching time of the electromagnetic control valve 23 and the liquid nitrogen flow rate are controlled to control the molten pool temperature to be consistent with the molten pool temperature of the previous deposition layer, that is, the task of depositing one deposition layer is completed; Step 5: When performing each deposition layer task, the temperature of the molten pool of the current deposition layer is controlled by controlling the switch time of the electromagnetic control valve 23 and the liquid nitrogen flow rate. Tn +1 (n=1,2,3‥) and the molten pool temperature of the previous deposition layer Tn(n=1,2,3‥) are equal, so that the molten pool temperature of each deposition layer in the entire manufacturing process is maintained at a stable state. After completing the task of each deposition layer, the control system 3 controls the robot arm 1 to rise in the (vertical direction) Z-axis direction according to the layer height of each deposition layer after the STL model is layered by the layering software, and completes the laser deposition task of the current deposition layer until the laser deposition task of the entire formed thin-walled part is completed.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A device for improving the forming quality and performance uniformity of thin-walled parts formed by laser deposition, characterized in that: include: A clamping assembly, used for clamping a substrate of a deposition-formed thin-walled part; A laser metal deposition system, which is used to generate high-energy laser light in the deposition area of ​​the substrate to form a laser deposition area, provide a protective atmosphere for the laser deposition area, and feed the deposition powder; A liquid nitrogen active cooling system is used to cool and dissipate heat for a substrate forming a laser deposition molten pool, and comprises: a support frame connected to a laser deposition cladding head of a laser metal deposition system, on which a plurality of liquid nitrogen nozzles connected to a liquid nitrogen tank are arranged, the plurality of liquid nitrogen nozzles are symmetrically distributed on both sides of the substrate, the injection ends of every two symmetrical liquid nitrogen nozzles are opposite, and the symmetry center of the two symmetrical liquid nitrogen nozzles is the position where the laser deposition molten pool is formed; An auxiliary forming component, comprising: a linear drive component, an angle adjustment component and two ceramic plates arranged on a support frame, the two ceramic plates being arranged opposite to each other, the opposite back surfaces of the two ceramic plates being arranged on both sides of the substrate, and the opposite back surfaces of the two ceramic plates being rotatably connected to the output end of the linear drive component, and the angle adjustment component being used to drive the ceramic plates to rotate at the output end of the linear drive component to adjust the shape of a deposition groove formed by the opposite surfaces of the two ceramic plates and the deposition surface on the top of the substrate; And a control system, which is used to control the auxiliary forming components of the auxiliary forming components and the angle adjustment component to adjust the inclination angle of the ceramic plate and the distance between the two ceramic plates according to the shape of the formed thin-walled part, so that the shape of the deposition groove formed by the two ceramic plates and the top deposition surface of the substrate is consistent with the shape of the formed thin-walled part.

2. The device for improving the forming quality and performance uniformity of thin-walled parts formed by laser deposition according to claim 1, characterized in that: The clamping assembly includes: A positioning base, the top of which is provided with a through slot along its length direction; A limit block is arranged on the inner bottom surface of the through slot; And two positioning blocks are arranged on the two side walls of the through slot through positioning screws, and are used for positioning and clamping the base.

3. The device for improving the forming quality and performance uniformity of thin-walled parts formed by laser deposition according to claim 2, characterized in that: A through hole is provided in the positioning block, and a brass pipe for liquid nitrogen to pass through is arranged in the through hole. The inlet end and the outlet end of the brass pipe are connected with the liquid nitrogen tank to form a closed loop.

4. The device for improving the forming quality and performance uniformity of thin-walled parts formed by laser deposition according to claim 1, characterized in that: The laser metal deposition system includes: a robotic arm, a nitrogen tank, a laser generator, a powder feeder and a control system, wherein the laser deposition cladding head is arranged at the output end of the robotic arm, the control system is used to control the robotic arm to run according to the motion trajectory of laser deposition, and is used to control the nitrogen sprayed from the nitrogen tank to enter the powder feeder, and the nitrogen drives the deposition powder in the powder feeder to reach the laser deposition cladding head together, and the laser head of the laser deposition cladding head converges to the deposition area, and at the same time controls the laser generator to generate high-energy laser to the deposition powder in the deposition area to form a laser deposition area.

5. The device for improving the forming quality and performance uniformity of thin-walled parts formed by laser deposition according to claim 4, characterized in that: The support frame includes: Two connecting cross bars are horizontally and symmetrically arranged on both sides of the laser deposition cladding head, and the ends of the connecting cross bars facing away from the laser deposition cladding head are connected with horizontal supporting bars arranged horizontally; And a plurality of distance adjustment components are vertically and evenly arranged on the horizontal support rod, one end of which is connected to the horizontal support rod, and the other end of which is connected to the liquid nitrogen nozzle.

6. The device for improving the forming quality and performance uniformity of thin-walled parts formed by laser deposition according to claim 5, characterized in that: The distance adjustment assembly includes: a threaded rod, one end of which is threadedly connected to the horizontal support rod, and the end connected to the horizontal support rod is provided with an adjustment nut after passing through the horizontal support rod, and a connecting ring is provided at one end of the threaded rod away from the horizontal support rod, and the connecting ring is connected to the liquid nitrogen nozzle through a thread.

7. The device for improving the forming quality and performance uniformity of thin-walled parts formed by laser deposition according to claim 1, characterized in that: The ceramic plate is made of nano-alumina ceramic material.

8. The device for improving the forming quality and performance uniformity of thin-walled parts formed by laser deposition according to claim 1, characterized in that: The liquid nitrogen active cooling system also includes: a temperature feedback device, a computer control system and an electromagnetic control valve. The electromagnetic control valve and the temperature feedback device are electrically connected to the computer control system, wherein each liquid nitrogen nozzle is connected to the main pipeline arranged at the outlet of the liquid nitrogen tank through a branch pipeline, the electromagnetic control valve is arranged on the main pipeline, and the temperature feedback device is arranged on one end side of the substrate. The temperature feedback device is used to collect the temperature of the laser deposition molten pool in real time, and the computer control system is used to control the switch, time and flow rate of the electromagnetic control valve for spraying liquid nitrogen from the liquid nitrogen nozzle according to the temperature of the laser deposition molten pool and the working conditions until the temperature of the laser deposition molten pool reaches the expected temperature required by the working conditions.

9. The device for improving the forming quality and performance uniformity of thin-walled parts formed by laser deposition according to claim 1, characterized in that: The angle adjustment component includes: a servo, an output end of which is provided with a driving gear, and the output end of the linear drive component is rotatably provided with a transmission rod, the transmission rod is connected to the ceramic plate through a support, and the transmission rod is provided with a transmission gear meshing with the driving gear.

10. A method for improving the forming quality and performance uniformity of thin-walled parts formed by laser deposition, characterized in that: include: Obtain an STL model of the expected thin-walled part, select the layer thickness according to the shape and size of the thin-walled part, and perform layer processing on the STL model using layering software; Clamp the substrate through the clamping assembly, control the robotic arm to drive the laser deposition cladding head to align with the center of the substrate, and perform position calibration for laser deposition manufacturing; turn on the laser generator, nitrogen tank, powder feeder, and control system in sequence to put the laser generator, nitrogen tank, powder feeder, and control system in working condition; The laser power, powder feeding amount, scanning speed and deposition height of the laser deposition layer are determined according to the layering results of the STL model. The spacing between the two ceramic plates and the tilt angle of the ceramic plates are adjusted according to the shape of the formed thin-walled part, so that the spacing between the two ceramic plates is consistent with the width of the formed thin-walled part, and the tilt angle is consistent with the tilt angle of the formed thin-walled part. When depositing each layer of laser cladding, the laser deposition area is cooled by the liquid nitrogen active cooling system. At the same time, when depositing each layer, the temperature feedback device is used to collect the temperature of the molten pool of each layer in real time. When depositing the next layer, the switch time of the electromagnetic control valve and the liquid nitrogen flow rate are controlled to control the molten pool temperature to be consistent with the molten pool temperature of the previous layer, that is, to complete the task of each layer of deposition; After completing the task of depositing one deposition layer, the control system controls the robotic arm to rise in the vertical direction to the height of each deposition layer after the STL model is layered according to the layering software, and completes the laser deposition task of the current deposition layer until the laser deposition task of the entire thin-walled part is completed.

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