Follow-up electromagnetic induction heating assisted laser directional energy deposition method

Abstract

The invention provides a follow-up electromagnetic induction heating-assisted laser directional energy deposition method, which is characterized in that an induction coil and a laser beam jointly perform laser energy deposition and synchronous induction heating coupling action on a substrate, and a pyrometer monitors the temperature of the substrate under the heating coupling action in real time. Wherein the nozzle arranged below the cylindrical optical system and used for feeding and the induction coil are both arranged in the Z-axis direction, meanwhile, according to real-time temperature data collected by the pyrometer, the temperature feedback circuit controls the lead screw to do reciprocating motion, and then the induction coil is driven to move up and down in the Z direction so as to control the distance between the induction coil and the substrate; the coupling effect of laser energy deposition and synchronous induction heating is controlled, so that accurate control over thermal field distribution in the machining process is guaranteed, the temperature gradient of a molten pool and the periphery and the cooling rate of the periphery of the molten pool are controlled, and then thermal stress in the printing process and residual stress in the cooling process are controlled; and finally, the effect of inhibiting the deformation of the printing component is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of laser powder additive manufacturing, and in particular to a follow-up electromagnetic induction heating assisted laser directional energy deposition method. Background Art

[0002] The laser directed energy deposition manufacturing process uses a focused laser beam to melt metal powder or wire and deposit it layer by layer to form the desired geometry. Due to its unique advantages in manufacturing flexibility, material utilization and component repair, it is widely used in aerospace, defense, marine and offshore industries.

[0003] Electromagnetic induction heating is a non-contact heating process that can locally heat components without contaminating foreign matter. In the laser powder feeding additive manufacturing process, the addition of an auxiliary heat source for local preheating can significantly reduce the temperature gradient around the molten pool and help reduce thermal stress. Therefore, the laser is combined with synchronous induction heating to develop a synchronous induction-assisted laser deposition device to achieve directional thermal management of the deposition process. The leading edge of the induction coil locally preheats the substrate and establishes a uniform thermal environment, creating favorable conditions for subsequent material melting and solidification. The trailing edge of the coil continues to slowly cool the newly formed deposited layer, which helps to suppress the thermal stress generated by rapid solidification, thereby effectively controlling the accumulation of residual stress.

[0004] Patent CN202210900429.0 reports a method and device for anisotropy and crack suppression of high-temperature alloys by laser energy deposition. Before manufacturing, a carbon medium-wave infrared radiation heating device is used to preheat the substrate; during the additive manufacturing process, a high-frequency induction heating device is used to generate a changing magnetic field in the forming area to heat the solidified layer and the substrate; however, it is difficult to achieve synchronous preheating and slow cooling, and synchronous movement following the changing scanning path of the laser head.

[0005] Patent ZL201610284077.5 reports a laser selective melting electromagnetic induction three-dimensional heating system, in which a graphite block is provided between the induction coil and the inner body of the forming cylinder. The induction coil heats the graphite block, and the graphite block conducts the high temperature to the inner body of the forming cylinder, reducing the cooling and solidification rate and the temperature gradient between processing layers; however, induction heating of a specific area cannot be achieved.

[0006] Patent ZL201910067776.8 reports a device and method for electromagnetic induction heating-assisted laser additive manufacturing of titanium-based composite materials. The electromagnetic induction coil and the laser head are synchronously moved through a steering and height adjustment mechanism to synchronously preheat and slowly cool the substrate and the deposited titanium-based composite material layer. However, the position between the electromagnetic induction coil and the laser head is relatively fixed. As the heat accumulation of the deposited layer increases, the auxiliary heating effect of the coil should change in real time with the change of the temperature field of the deposited tissue. The regulation of the coil working distance can realize rapid regulation of the temperature field of the deposited tissue, thereby realizing directional thermal management of the deposition process. Summary of the invention

[0007] The purpose of the technical solution of the present invention is: to preheat the substrate by induction heating before molding, and to control the overall temperature field distribution by matching the dual heat sources of laser and induction heating during the molding process. At the same time, the working distance between the induction coil and the part can be fed back according to the temperature of the molten pool to achieve the purpose of real-time regulation, and then the cooling rate of the component is slowed down by induction heating after molding, thereby effectively adjusting the deformation of the component.

[0008] In order to achieve the above-mentioned invention object, the technical solution of the present invention provides a method for assisted laser directional energy deposition by electromagnetic induction heating, which is applied to a device for assisted laser directional energy deposition by electromagnetic induction heating. The device comprises: an induction component, a transformer, a lead screw, a loading fixture, a lead screw guide slot, an induction coil, a magnetic flux controller, a nozzle and a pyrometer;

[0009] The induction component is connected to the transformer, the transformer is connected to one end of the lead screw, the loading fixture is vertically connected to the lead screw slot to control the lead screw to reciprocate along the gravity direction, the other end of the lead screw is connected to the connection end of the induction coil at an angle, a magnetic flux controller is arranged around the action end of the induction coil, the lead screw slot is connected to one end of the pyrometer through a temperature feedback circuit, the other end of the pyrometer penetrates into one end of the cylindrical optical system, a laser beam channel is arranged in the center of the optical system to emit a laser beam, powder is stored around the laser beam channel, a hollow nozzle is arranged at the other end of the cylindrical optical system, the laser beam is emitted from the hollow part, and powder is sprayed around the hollow part;

[0010] The method comprises the following steps:

[0011] Obtain target workpiece data, determine the material and substrate shape according to the workpiece data to be processed, and place the substrate;

[0012] Determine the shape of the induction coil, the size of the induction coil, and the working distance between the induction coil and the substrate according to the target workpiece data and the state of the target workpiece;

[0013] According to the target workpiece data, material and substrate shape, the laser beam power, target spot diameter, powder injection rate, induction current of the induction coil and induction current frequency are set;

[0014] The magnetic flux controller is located above the substrate, the nozzle is located above the magnetic flux controller, the induction coil and the nozzle move coaxially, the substrate is preheated first, after the nozzle sprays powder according to the powder spraying rate, the cylindrical optical system emits a laser beam and the induction coil controls the magnetic flux controller to heat the substrate together;

[0015] The pyrometer obtains the substrate heating temperature in real time, and controls the reciprocating motion of the lead screw through the temperature feedback circuit according to the substrate heating temperature, so as to indirectly adjust the laser beam and the magnetic flux controller to heat the substrate together, thereby controlling the temperature gradient and solidification speed of the molten pool and the surrounding area, controlling the residual stress and deformation, and further controlling the substrate deposition layer.

[0016] Preferably, the shape of the active end of the induction coil is annular, the diameter of the active end of the induction coil is 50 mm to 80 mm, and the working distance between the active end of the induction coil and the substrate is 2 mm to 5 mm.

[0017] Preferably, the induction coil is a copper tube with a square cross-section of 6 mm to 12 mm in side length and a wall thickness of 1.5 mm.

[0018] Preferably, the laser beam power is 300W to 3000W, the target spot diameter is 2mm to 2.5mm, the powder injection rate is 4g / min to 6g / min, the induction current of the induction coil is 20A to 100A, and the induction current frequency is 10KHz to 20KHz.

[0019] Preferably, the laser is limited to a laser beam

[0020] Preferably, thermoelastic-plastic mechanics is used as a theoretical basis, and the birth-death unit method is adopted to optimize the laser beam power, the target spot diameter, the induced current of the induction coil, and the induced current frequency with the minimum temperature gradient at the highest temperature of the molten pool as the optimization target.

[0021] The technical solution of the present invention proposes a method for laser directional energy deposition assisted by follow-up electromagnetic induction heating. By coupling laser energy deposition and synchronous induction heating, the temperature gradient of the molten pool and its surroundings, as well as the cooling rate around the molten pool, are controlled, thereby controlling the thermal stress in the printing process and the residual stress in the cooling process, ultimately achieving the effect of suppressing the deformation of the printed component. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the structure of a deformation suppression process device according to an embodiment of the present invention;

[0023] Figure 2 It is a real-time feedback flow chart of the temperature field of the molten pool of induction heating assisted laser directed energy deposition;

[0024] Figure 3 This is the deformation diagram of the formed component without induction heating;

[0025] Figure 4 This is the deformation diagram of the formed component by induction heating assisted laser cladding;

[0027] 1-sensing component; 2-flexible extension cable; 3-transformer; 4-temperature feedback circuit; 5-pyrometer; 6-mounting plate; 7-nozzle; 8-magnetic flux controller; 9-light spot; 10-loading substrate fixture, 11-induction coil, 12-screw lead slide, 13-loading fixture. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0029] The embodiment of the present invention provides a method for laser directional energy deposition assisted by electromagnetic induction heating, comprising the following steps:

[0030] Step 1. According to the shape requirements of the target material and its substrate, the corresponding temperature field control parameters of the laser energy beam and the induction heating dual heat source synchronous heating should be set. These parameters include the coupling relationship between the induction coil parameters and the laser heating parameters. The temperature field control parameters include laser power, moving speed, induction coil size, induced current, induced current frequency, and the working distance between the induction coil and the part. At the same time, the heating efficiency of the induction coil is optimized by the screw lead slot, so as to achieve precise temperature field control. The magnetic flux controller (MFC) can adjust the direction according to the directional heating position. By setting a screw lead slot that can slide in the Z direction on the mounting plate, real-time control based on the molten pool temperature is realized, which effectively stabilizes the temperature distribution during the deposition process, thereby optimizing the thermal stress management of the component. When forming a single-layer cladding, an induction coil with a circular cladding action position is selected.

[0031] The induction coil is placed coaxially with the nozzle and is used for preheating the processing area, assisting laser energy deposition, and slow cooling of the processing area.

[0032] The induction coil is formed by bending a copper tube with a cross section of 6mm to 12mm side length and a wall thickness of 1.5mm. The middle section of the copper tube is bent into a ring shape as the action position of the induction coil, and the copper tubes at the non-action position are put together. A magnetic flux controller is arranged around the ring-shaped coil at the action position. The induction coil includes a single-turn or multi-turn disc coil, and the geometric size is determined according to the part to be formed.

[0033] During the deposition process, the lead screw guide groove sliding along the Z direction adjusts the up and down movement of the lead screw according to the real-time feedback of the molten pool temperature field, thereby adjusting the distance between the induction coil and the substrate, and then adjusting the induced current on the substrate to achieve effective management of the induction heat.

[0034] 1.1 Selection of induction coil parameters

[0035] Select a suitable induction coil according to the shape of the geometric part; when repairing parts, choose a circular induction coil with a coil diameter of 50mm to 80mm. During processing, place the induction coil above the processing plane and set the distance between the induction coil and the substrate at 2mm to 5mm. Connect the induction coil to the induction processor.

[0036] 1.2 Selection of dual heat source parameters

[0037] The embodiment of the present invention adopts a laser energy beam, and the dual heat source heating parameters include laser beam parameters and induction heating parameters, wherein the laser beam parameters are 300W to 3000W, the spot diameter is 2mm to 2.5mm, and the induction heating parameters are selected. The induction current control range is between 20A and 100A, and the induction current frequency control range is between 10KHz and 20KHz.

[0038] Step 2: Place the target material substrate into a fixture to clamp one end of the substrate and place the other end freely, and perform deposition according to the parameters in step 1.

[0039] Step 3, set the nozzle feed rate at 4g / min to 6g / min, turn on the optical system and induction coil for synchronous heating according to the laser parameters and induction heater parameters set in step 1, obtain the real-time temperature of the temperature field generated by the substrate according to the pyrometer, and then adjust the lead screw with real-time feedback.

[0040] Step 4: Turn off the laser and induction heater and let the part cool to room temperature in air.

[0041] The laser used in the present invention is limited to laser beam.

[0042] The feeding method is powder feeding.

[0043] The reference for matching the deformation of the free end of the part with the control parameters of the temperature field and stress field of the dual heat source synchronous heating in the embodiment of the present invention is:

[0044] Through numerical simulation, the minimum temperature gradient at the highest temperature of the molten pool is taken as the optimization target, and the matching of laser parameters and induction parameters is corrected to achieve the minimum temperature gradient at the highest temperature of the molten pool and the minimum residual stress. This method is based on the theory of thermoelastic-plastic mechanics and uses the birth-death unit method for numerical simulation to determine the best matching processing parameters of the laser beam and the induction heating dual heat source, thereby establishing the corresponding relationship between the dual heat source parameters and the deformation, thereby saving the experimental materials and time required for designing process parameters.

[0045] Figure 1 This is a schematic diagram of the structure of the device for the deformation suppression process of an embodiment of the present invention. Under the action of the laser beam, the powder material undergoes a local rapid melting and rapid solidification process, accompanied by the melting of the substrate material. These complex thermal processes are unevenly distributed in time and space, and residual stress is formed in the formed metal. The present invention inputs the implementation parameters into the induction heating device 1. During the processing, the induction coil 11 moves coaxially with the nozzle 7 to achieve preheating of the substrate before printing, heat treatment of the cladding layer after printing, and simultaneous reduction of the large temperature gradient and residual stress during the printing process, thereby reducing the deformation of the substrate. In addition, the movable lead screw can help adjust the distance between the induction coil and the substrate to achieve controllable induction heat input, thereby further optimizing the thermal field distribution and reducing residual stress. The deformation of the repaired parts can be reduced by regulating the temperature field, thereby achieving defect-free printing.

[0046] Figure 2 This is a real-time feedback flow chart of the temperature field of the molten pool assisted by induction heating and laser directional energy deposition. With the minimum deformation of the free end as the optimization goal, the real-time regulation of the temperature field of the molten pool is achieved by changing the distance between the substrate and the induction coil. In addition, the organization performance can be studied and the optimization purpose can be achieved on the basis of ensuring the deposition formation.

[0047] The embodiment of the present invention controls the temperature gradient of the molten pool and the surrounding area, the solidification rate of the molten pool and other thermal behaviors through the coupling effect of the two heat sources, thereby controlling the high residual stress and deformation generated by the formed material. It is worth noting that the embodiment of the present invention adjusts the lead screw in real time through the temperature feedback of the molten pool to achieve the movement of the induction coil in the Z direction and thus achieve stable control of the temperature field near the molten pool. During the forming process, the matching relationship between the laser heat source and the synchronous induction heating heat source is related to the material and the deformed component that is desired to be suppressed.

[0048] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0049] (1) The embodiments of the present invention can suppress the thermal stress caused by temperature rise and temperature drop, and adjust the deformation by adjusting the parameters of induction heating through temperature feedback, thereby improving the quality of the molded parts;

[0050] (2) The composite heat source system of the embodiment of the present invention not only demonstrates its advantages in a single direction, but also has multi-axial performance and can precisely control the manufacturing process at different angles and directions.

[0051] (3) The embodiment of the present invention achieves real-time regulation of the induced heat by adjusting the distance between the induction coil and the substrate in real time, which helps to maintain the stability of the temperature field and reduce the temperature gradient of the molten pool.

[0052] Specifically, Example 1 is as follows:

[0053] 1. Obtain laser power and powder feeding rate according to the target workpiece and the process parameters obtained by simulation;

[0054] 2. Adjust the nozzle 7 to the working range, and then adjust the light and powder to be within the range;

[0055] 3. Input the set parameters;

[0056] 4. Turn on the nozzle feeding and the cylindrical optical system at the same time, the laser irradiates the substrate and the powder surface, melts on the substrate to form a cladding layer, and realizes single heat source printing;

[0057] 5. After printing, the cylindrical optical system is closed and cooled to room temperature. After printing, it can also be slowly cooled and heat treated, and the model can be reconstructed using inverse imaging technology. The specific model after molding is as follows: Figure 3 As shown, the deformation of the free end is 1.1 mm.

[0058] Example 2 is as follows:

[0059] 1. Obtain laser power and powder feeding rate according to the target workpiece and the process parameters obtained by simulation;

[0060] 2. Induction heating parameters obtained according to numerical simulation, including induction current, induction frequency and the distance between the induction coil 11 and the substrate;

[0061] 3. Place the nozzle 7 coaxially with the induction coil and adjust the distance between the nozzle and the induction coil; at the same time, adjust the induction coil so that it is also within the working range (2mm to 5mm);

[0062] 4. Set the set parameters;

[0063] 5. Turn on the nozzle feeding and the cylindrical optical system at the same time, and also turn on the induction coil synchronously. The dual heat sources move synchronously on the substrate surface to achieve dual heat source synchronous printing;

[0064] 6. After printing is completed, both heat sources are turned off at the same time and cooled to room temperature; slow cooling and heat treatment can also be performed after printing is completed. Comparing the warping of the free ends of cases 1 and 2, we can see the important influence of induction heating on residual deformation.

[0065] Example 3 is as follows:

[0066] 1. Input parameters such as laser power and powder feeding rate according to the target workpiece and the process parameters obtained by simulation;

[0067] 2. Adjust the current, induction frequency and effective heating efficiency according to the induction coil heating parameters obtained by numerical simulation;

[0068] 3. Place the nozzle 7 coaxially with the induction coil, and adjust the distance between the nozzle and the induction coil so that the light and the powder are within the focal length of the cylindrical optical system at the same time.

[0069] 4. Set the motion trajectory and deposition parameters of laser cladding.

[0070] 5. As the deposition layer gradually thickens due to the continuous accumulation of heat, the working lift amount will also change accordingly. The distance between the induction coil 11 with the magnetic flux controller 8 and the substrate can be adjusted in real time according to the temperature feedback from the pyrometer to adjust the heat input of the induction coil, thereby realizing multi-path control of the heating working distance of the induction coil.

[0071] 6. Turn on the nozzle feeding and the cylindrical optical system at the same time, and also turn on the induction coil synchronously. The dual heat sources move synchronously on the substrate surface to achieve dual heat source synchronous printing;

[0072] 7. After printing is completed, both heat sources are turned off at the same time and cooled to room temperature; slow cooling and heat treatment can also be performed after printing is completed. Comparing the warping of the free ends of cases 1 and 2, we can see the important influence of induction heating on residual deformation. The reconstructed model of the improved molded part is as follows Figure 4 As shown, the deformation of the free end is 0.5 mm.

Claims

1. A method for laser directional energy deposition assisted by electromagnetic induction heating, characterized in that: The method is applied to a follow-up electromagnetic induction heating assisted laser directional energy deposition device, the device comprising: an induction component, a transformer, a lead screw, a loading fixture, a lead screw guide slot, an induction coil, a magnetic flux controller, a nozzle and a pyrometer; The induction component is connected to the transformer, the transformer is connected to one end of the lead screw, the loading fixture is vertically connected to the lead screw slot to control the lead screw to reciprocate along the gravity direction, the other end of the lead screw is connected to the connection end of the induction coil at an angle, the action end of the induction coil is connected to a magnetic flux controller around the induction coil, so that the magnetic flux controller moves around the induction coil, the lead screw slot is connected to one end of the pyrometer through a temperature feedback circuit, the other end of the pyrometer penetrates into one end of the cylindrical optical system, the center of the cylindrical optical system emits a laser beam, and powder is stored around the laser beam channel, and a hollow nozzle is provided at the other end of the cylindrical optical system, the hollow part emits a laser beam, and powder is sprayed around the hollow part; The method comprises the following steps: Obtain target workpiece data, determine the material and substrate shape according to the workpiece data to be processed, and place the substrate; Determine the shape of the induction coil, the size of the induction coil, and the working distance between the induction coil and the substrate according to the target workpiece data and the state of the target workpiece; According to the target workpiece data, material and substrate shape, the laser beam power, target spot diameter, powder injection rate, induction current of the induction coil and induction current frequency are set; The magnetic flux controller is located above the substrate, the nozzle is located above the magnetic flux controller, the induction coil and the nozzle move coaxially, the substrate is preheated first, after the nozzle sprays powder according to the powder spraying rate, the cylindrical optical system emits a laser beam and the induction coil controls the magnetic flux controller to heat the substrate together; The pyrometer obtains the substrate heating temperature in real time, and controls the reciprocating motion of the lead screw through the temperature feedback circuit according to the substrate heating temperature, so as to indirectly adjust the laser beam and the magnetic flux controller to heat the substrate together, thereby controlling the temperature gradient and solidification speed of the molten pool and the surrounding area, controlling the residual stress and deformation, and further controlling the substrate deposition layer.

2. The method of follow-up electromagnetic induction heating assisted laser directional energy deposition according to claim 1, characterized in that: The shape of the induction coil action end is circular, the diameter of the induction coil action end is 50 mm to 80 mm, and the working distance between the induction coil action end and the substrate is 2 mm to 5 mm.

3. The method of follow-up electromagnetic induction heating assisted laser directional energy deposition as claimed in claim 2, characterized in that: The induction coil is a copper tube with a square cross section of 6 mm to 12 mm side length and a wall thickness of 1.5 mm.

4. The method of follow-up electromagnetic induction heating assisted laser directional energy deposition according to claim 1, characterized in that: The laser beam power is 300W-3000W, the target spot diameter is 2mm-2.5mm, the powder injection rate is 4g / min-6g / min, the induction current of the induction coil is 20A-100A, and the induction current frequency is 10KHz-20KHz.

5. The method for assisted laser directional energy deposition by electromagnetic induction heating according to claim 1, characterized in that: The laser is limited to a laser beam.

6. The method of follow-up electromagnetic induction heating assisted laser directional energy deposition according to claim 1, characterized in that: Taking thermoelastic-plastic mechanics as the theoretical basis, the birth-death unit method is adopted to take the minimum temperature gradient at the highest temperature of the molten pool as the optimization target, and the laser beam power, the target spot diameter, the induced current of the induction coil and the induced current frequency are optimized.

Images