A method of follow-on electromagnetic induction heating assisted laser directed energy deposition

Abstract

The application provides a kind of follow-up electromagnetic induction heating auxiliary laser directional energy deposition method, in the method, induction coil and laser beam are deposited on substrate together laser energy and synchronous induction heating coupling effect, pyrometer real-time monitoring substrate under heating coupling effect temperature.Induction coil and nozzle for feeding arranged in Z-axis direction are arranged below cylindrical optical system, at the same time, according to the real-time temperature data collected by pyrometer, the temperature feedback circuit is controlled to reciprocate screw, and then induction coil moves up and down in Z direction to control the distance between induction coil and substrate, control laser energy deposition and synchronous induction heating coupling effect, to ensure the accurate control of heat field distribution in the process, to control the temperature gradient of molten pool and periphery, and the cooling rate around molten pool, to control thermal stress in printing process and residual stress in cooling process, and finally achieve the effect of inhibiting the deformation of printed component.

Description

Technical Field

[0001] This invention relates to the field of laser powder additive manufacturing technology, specifically to a method for laser directional energy deposition assisted by follow-up electromagnetic induction heating. Background Technology

[0002] Laser-directed energy deposition (LDED) manufacturing processes use a focused laser beam to melt metal powder or filament, depositing 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 laser powder feeding additive manufacturing, adding an auxiliary heat source for local preheating can significantly reduce the temperature gradient around the molten pool, helping to reduce thermal stress. Therefore, by combining laser with synchronous induction heating, a synchronous induction-assisted laser deposition device was developed, enabling 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, helping to suppress thermal stress generated by rapid solidification, thereby effectively controlling the accumulation of residual stress.

[0004] Patent CN202210900429.0 reports a method and apparatus for anisotropy and crack suppression of high-temperature alloys by laser energy deposition. Before manufacturing, a carbon mid-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 laser head's variable scanning path.

[0005] Patent ZL201610284077.5 reports a laser selective melting electromagnetic induction three-dimensional heating system, in which a graphite block is placed 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 solidification rate and the temperature gradient between processing layers; however, it cannot achieve induction heating in a specific area.

[0006] Patent ZL201910067776.8 discloses an apparatus and method for electromagnetic induction heating-assisted laser additive manufacturing of titanium-based composite materials. The electromagnetic induction coil and the laser head move synchronously through a steering and height adjustment mechanism to simultaneously 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 adjustment of the working distance of the coil can realize the rapid control 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 this invention is to preheat the substrate using induction heating before molding, and to regulate the overall temperature field distribution by matching the laser and induction heating dual heat sources during molding. 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 real-time regulation. Then, after molding, the cooling rate of the component is slowed down by induction heating, thereby effectively regulating the deformation of the component.

[0008] To achieve the above-mentioned objectives, the present invention provides a method for laser-directed energy deposition assisted by electromagnetic induction heating. The method is applied to a laser-directed energy deposition apparatus assisted by electromagnetic induction heating. The apparatus includes: a sensing component, a transformer, a lead screw, a loading fixture, a lead screw lead groove, an induction coil, a magnetic flux controller, a nozzle, and a pyrometer.

[0009] The sensing component is connected to the transformer, the transformer is connected to one end of the lead screw, the loading fixture is perpendicularly connected to the lead screw guide groove to control the lead screw to reciprocate along the direction of gravity, the other end of the lead screw is connected at an angle to the connection end of the induction coil, the induction coil is surrounded by a magnetic flux controller, the lead screw guide groove is connected to one end of the pyrometer through a temperature feedback circuit, the other end of the pyrometer is inserted into one end of the cylindrical optical system, the optical system has a laser beam channel in the center to emit a laser beam, and powder is stored around the laser beam channel, the other end of the cylindrical optical system has a hollow nozzle, the hollow part emits a laser beam, and powder is sprayed around the hollow part;

[0010] The method includes the following steps:

[0011] Acquire the target workpiece data, determine the material and substrate shape based on the workpiece data, and place the substrate;

[0012] Based on the target workpiece data and the state of the target workpiece, determine the shape of the induction coil, the size of the induction coil, and the working distance between the induction coil and the substrate;

[0013] Based on the target workpiece data, material, and substrate shape, set the laser beam power, target spot diameter, powder jetting rate, induction coil current, and induction current frequency;

[0014] The magnetic flux controller is located above the substrate, and the nozzle is located above the magnetic flux controller. The induction coil moves coaxially with the nozzle. The substrate is preheated first. After the nozzle sprays powder at 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 acquires the substrate heating temperature in real time. Based on the substrate heating temperature, the lead screw is controlled to reciprocate through the temperature feedback circuit. This allows the laser beam and the magnetic flux controller to be adjusted to heat the substrate together, thereby controlling the temperature gradient and solidification rate of the molten pool and surrounding area, controlling residual stress and deformation, and thus controlling the substrate deposition layer.

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

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

[0018] Preferably, the laser beam power is 300W to 3000W, the target spot diameter is 2mm to 2.5mm, the powder spraying 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 the theoretical basis, and the birth-death element 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 by taking the minimum temperature gradient at the highest temperature of the molten pool as the optimization target.

[0021] The present invention proposes a follow-up electromagnetic induction heating-assisted laser directional energy deposition method. By coupling the 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. This controls the thermal stress during the printing process and the residual stress during the cooling process, ultimately achieving the effect of suppressing the deformation of the printed component. Attached Figure Description

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

[0023] Figure 2 This is a flowchart of the real-time feedback process for the temperature field of the molten pool in induction heating-assisted laser-directed energy deposition.

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

[0025] Figure 4 Deformation diagram of the formed component for induction heating-assisted laser cladding;

[0026] 1-Sensing component; 2-Flexible extension cable; 3-Transformer; 4-Temperature feedback circuit; 5-Temperature meter; 6-Mounting plate; 7-Nozzle; 8-Magnetic flux controller; 9-Light spot; 10-Loading substrate clamp; 11-Induction coil; 12-Lead screw lead groove; 13-Loading clamp. Detailed Implementation

[0027] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0028] This invention provides a method for laser-directed energy deposition assisted by electromagnetic induction heating, comprising the following steps:

[0029] Step 1: Based on the shape requirements of the target material and its substrate, appropriate temperature field control parameters for simultaneous heating from both laser energy beam and induction heating sources should be set. These parameters include the coupling relationship between the induction coil parameters and the laser heating parameters. 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. Simultaneously, the heating efficiency of the induction coil is optimized using a lead screw guide groove, thereby achieving precise temperature field control. The magnetic flux controller (MFC) can adjust the direction according to the directional heating position. By setting a lead screw guide groove that can slide along the Z-direction on the mounting plate, real-time control based on the molten pool temperature is achieved, effectively stabilizing the temperature distribution during the deposition process and thus 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.

[0030] The induction coil is placed coaxially with the nozzle and is used for preheating the processing area, assisting in laser energy deposition, and slow cooling of the processing area.

[0031] The induction coil is made of a copper tube with a square cross-section of 6mm to 12mm and a wall thickness of 1.5mm. The middle section of the copper tube is bent into a ring shape as the active position of the induction coil. The copper tubes in the non-active positions are joined together. A magnetic flux controller is arranged around the ring-shaped coil at the active position. The induction coil includes a single-turn or multi-turn disc coil, and its geometry is determined according to the part to be formed.

[0032] During the deposition process, the lead screw sliding along the Z-direction adjusts the up-and-down movement of the lead screw based on the real-time feedback of the molten pool temperature field, thereby controlling the distance between the induction coil and the substrate, and thus adjusting the induced current on the substrate to achieve effective management of induced heat.

[0033] 1.1 Selection of Induction Coil Parameters

[0034] Select a suitable induction coil based on the shape of the geometrically formed part; when repairing parts, choose a circular induction coil with a 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 to 2mm to 5mm. Connect the induction coil to the induction processing machine.

[0035] 1.2 Selection of parameters for dual heat sources

[0036] The embodiments of the present invention use a laser energy beam. The dual heat source heating parameters include laser beam parameters and induction heating parameters. The laser beam parameters are 300W to 3000W and the spot diameter is 2mm to 2.5mm. The selection of induction heating parameters includes an induction current control range of 20A to 100A and an induction current frequency control range of 10KHz to 20KHz.

[0037] Step 2: Place the target material substrate into the fixture and hold one end of the substrate, while leaving the other end free. Deposit the substrate according to the parameters in Step 1.

[0038] Step 3: Set the nozzle feed rate to 4g / min to 6g / min. According to the laser parameters and induction heater parameters set in Step 1, turn on the optical system and induction coil to heat synchronously. Obtain the real-time temperature of the temperature field generated by the substrate based on the pyrometer, and then adjust the lead screw in real time.

[0039] Step 4: Turn off the laser and induction heater, and place the part in the air to cool to room temperature.

[0040] The laser used in this invention is limited to laser beams.

[0041] The feeding method is powder feeding.

[0042] In this embodiment of the invention, the reference for matching the deformation of the free end of the part with the temperature field and stress field control parameters of the dual-heat-source synchronous heating is as follows:

[0043] This method uses numerical simulation to optimize the matching of laser and induction heating parameters, aiming to minimize both the temperature gradient at the highest temperature of the molten pool and the residual stress. Based on thermo-elastic-plastic mechanics, the method employs the birth-and-death element method to determine the optimal matching parameters between the laser beam and induction heating dual heat sources. This establishes the correlation between the dual heat source parameters and the deformation, thereby saving experimental materials and time required for designing process parameters.

[0044] Figure 1 This is a schematic diagram of the deformation suppression device according to an embodiment of the present invention. Under the action of a laser beam, the powder material undergoes a localized rapid melting and solidification process, accompanied by the melting of the substrate material. These complex thermal processes are unevenly distributed in space and time, resulting in residual stress in the formed metal. The present invention inputs implementation parameters into the induction heating device 1. During processing, the induction coil 11 and the nozzle 7 move coaxially, preheating the substrate before printing and heat-treating the cladding layer after printing. This simultaneously reduces the large temperature gradient and residual stress during printing, thereby reducing substrate deformation. Furthermore, a movable lead screw helps adjust the distance between the induction coil and the substrate, achieving controllable induction heat input, further optimizing the thermal field distribution and reducing residual stress. By controlling the temperature field, deformation of the repaired parts is reduced, thus achieving defect-free printing.

[0045] Figure 2 This is a flowchart illustrating the real-time feedback of the molten pool temperature field in induction heating-assisted laser-guided energy deposition (LAD). With the goal of minimizing free-end deformation, the molten pool temperature field is controlled in real-time by altering the distance between the substrate and the induction coil. Furthermore, it allows for the study and optimization of microstructure and properties while ensuring successful deposition.

[0046] This invention, through the addition of a synchronous auxiliary heating device around the laser processing location, controls the thermal behavior of the molten pool and its surrounding area, such as the temperature gradient and solidification rate, via the coupling effect of the two heat sources. This, in turn, controls the high residual stress and deformation generated in the formed material. Notably, this invention utilizes a real-time temperature adjustment screw based on molten pool feedback to move the induction coil in the Z-direction, thereby achieving 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 deformation of the component to be suppressed.

[0047] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0048] (1) The embodiments of the present invention can suppress the thermal stress caused by heating and cooling, and regulate the deformation by adjusting the parameters of induction heating through temperature feedback, thereby improving the quality of the molded parts;

[0049] (2) The composite heat source system of the present invention not only shows its advantages in a single direction, but also has multi-axial efficiency, and can precisely control the manufacturing process at different angles and directions.

[0050] (3) The present invention achieves real-time control of the amount of 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.

[0051] Specifically, Example 1 is as follows:

[0052] 1. Based on the target workpiece and the simulated process parameters, obtain the laser power and powder feeding rate;

[0053] 2. Adjust nozzle 7 to the working range, and then adjust both the light and powder to be within the range;

[0054] 3. Enter the set parameters;

[0055] 4. Simultaneously activate the cylindrical optical system when the nozzle is turned on to feed the powder. The laser irradiates the substrate and powder surface, melting on the substrate to form a cladding layer, thus achieving single heat source printing.

[0056] 5. After printing the cylindrical optical system, turn it off and allow it to cool to room temperature; alternatively, after printing, perform slow cooling and heat treatment, and then use inverse imaging technology to reconstruct the model. The final model will look like this. Figure 3 As shown, the deformation at its free end is 1.1 mm.

[0057] Example 2 is as follows:

[0058] 1. Based on the target workpiece and the simulated process parameters, obtain the laser power and powder feeding rate;

[0059] 2. The induction heating parameters obtained from numerical simulation include the induction current, induction frequency, and distance between the induction coil 11 and the substrate;

[0060] 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~5mm);

[0061] 4. Set the parameters;

[0062] 5. When the nozzle feeding is turned on, the cylindrical optical system is turned on at the same time, and the induction coil is also turned on simultaneously. The two heat sources move synchronously on the substrate surface to achieve synchronous printing of the two heat sources.

[0063] 6. After printing, both heat sources are turned off simultaneously, allowing the printer to cool to room temperature. Slow cooling and heat treatment can also be performed after printing. Comparing Case 1 and Case 2, the warping of the free ends demonstrates the significant impact of induction heating on residual deformation.

[0064] Example 3 is as follows:

[0065] 1. Input parameters such as laser power and powder feeding rate based on the target workpiece and the simulated process parameters;

[0066] 2. Adjust the current, induction frequency, and effective heating efficiency based on the induction coil heating parameters obtained from numerical simulation;

[0067] 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 powder are simultaneously within the focal length of the cylindrical optical system.

[0068] 4. Set the motion trajectory and the deposition parameters for laser cladding.

[0069] 5. As heat accumulates, the deposition layer gradually thickens, and the working lift also changes accordingly. The distance between the induction coil 11 (equipped with a magnetic flux controller 8) and the substrate can be adjusted in real time based on the temperature feedback from the pyrometer to regulate the heat input of the induction coil, thereby achieving multi-path control of the heating working distance of the induction coil.

[0070] 6. Simultaneously activate the nozzle feeding system, the cylindrical optical system, and the induction coil. The two heat sources move synchronously on the substrate surface to achieve synchronous printing with dual heat sources.

[0071] 7. After printing, both heat sources are simultaneously turned off, and the parts are cooled to room temperature. Slow cooling and heat treatment can also be performed after printing. Comparing Case 1 and Case 2, the warpage at the free ends demonstrates the significant impact of induction heating on residual deformation. The improved reconstructed model of the molded part is shown below. Figure 4 As shown, the deformation at its free end is 0.5 mm.

Claims

1. A method of guided electromagnetic induction heating assisted laser directed energy deposition, characterized in that, The method is applied to a follow-up electromagnetic induction heating auxiliary laser directional energy deposition device, and the device comprises an induction component, a transformer, a lead screw, a loading clamp, a lead screw lead groove, an induction coil, a magnetic flux controller, a nozzle and a pyrometer; The induction component is connected with the transformer, the transformer is connected with one end of the lead screw, the loading clamp is connected with the lead screw lead groove in a vertical manner to control the reciprocating movement of the lead screw along the direction of gravity, the other end of the lead screw is connected with the induction coil in an angle, the magnetic flux controller is connected around the action end of the induction coil to enable the magnetic flux controller to move around the induction coil, the lead screw lead groove is connected with one end of the pyrometer through a temperature feedback circuit, and the other end of the pyrometer is inserted into one end of a cylindrical optical system, the laser beam is emitted from the center of the cylindrical optical system, the powder is stored around the channel of the laser beam, the other end of the cylindrical optical system is provided with a hollow nozzle, the laser beam is emitted from the hollow part, and the powder is sprayed around the hollow part. The method comprises the following steps: acquiring target workpiece data, determining the material and the shape of the substrate according to the data of the workpiece to be machined, and placing the substrate; determining the shape, size and working distance of the induction coil according to the target workpiece data and the state of the target workpiece; setting the laser beam power, target spot diameter, powder spraying rate, induction current and induction current frequency of the induction coil according to the target workpiece data, material and substrate shape; 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 the powder at the powder spraying rate, the cylindrical optical system emits the laser beam and the induction coil controls the magnetic flux controller to heat the substrate together; The pyrometer acquires the heating temperature of the substrate in real time, controls the reciprocating movement of the lead screw through the temperature feedback circuit according to the heating temperature of the substrate, indirectly adjusts the laser beam and the magnetic flux controller to heat the substrate together through the adjustment of the magnetic flux controller, realizes the adjustment of the temperature gradient of the molten pool and the surrounding area and the solidification speed of the molten pool, controls the residual stress and deformation, and then adjusts and controls the deposition layer of the substrate.

2. A method of a follow-up electromagnetic induction heating assisted laser directed energy deposition as claimed in claim 1, wherein, The shape of the action end of the induction coil is a circular ring, the diameter of the action end of the induction coil is 50mm-80mm, and the working distance between the action end of the induction coil and the substrate is 2mm-5mm.

3. A method of follow-up electromagnetic induction heating assisted laser directed energy deposition as claimed in claim 2, wherein, The induction coil is a copper pipe with a square cross section with a side length of 6mm-12mm and a wall thickness of 1.5mm.

4. A method of electromagnetic induction heating assisted laser directed energy deposition as claimed in claim 1, wherein, The laser beam power is 300W-3000W, the target spot diameter is 2mm-2.5mm, the powder spraying 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. A method of a follow-up electromagnetic induction heating assisted laser directed energy deposition as claimed in claim 1, wherein, The laser is limited to the laser beam.

6. A method of a follow-up electromagnetic induction heating assisted laser directed energy deposition as claimed in claim 1, wherein, Based on thermal elastoplasticity, the laser beam power, the target spot diameter, the induction current of the induction coil and the induction current frequency are optimized by taking the minimum temperature gradient at the highest temperature of the molten pool as the optimization target.

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