Preparation method of large-size thin-wall structure based on magnetic field regulation and control laser additive manufacturing

Abstract

The invention belongs to the technical field of metal additive manufacturing, and relates to a preparation method of a large-size thin-wall structure based on magnetic field regulation and control of laser directional energy deposition. According to the method, the part forming area is filled with the protective gas, the oxygen content of the forming area is 100 ppm or below, and oxidation and inclusion pollution of alloy in the forming process are avoided. By starting the electromagnetic field generator, a stable uniform magnetic field is formed in a part forming area, the metallurgical behavior of a molten pool is regulated and controlled through the thermal damping effect and the thermal electromagnetic convection effect generated by the magnetic field in the molten pool, and optimization of the grain structure is achieved. A laser cladding head is started, powder metal materials are conveyed to the position of a molten pool through powder carrying gas, and the powder metal materials are molten through laser to form a stable molten pool; and a laser cladding head is controlled to scan in a uniform magnetic field area according to a set track to carry out circulating deposition, and light stopping is carried out every time deposition of one layer is completed, so that heat of a deposition layer is released, and heat accumulation is reduced until part forming is completed.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal additive manufacturing and relates to a method for preparing a large-size thin-walled structure based on magnetic field-controlled laser directional energy deposition. Background Art

[0002] AlSi10Mg alloy is the most typical type of lightweight aluminum alloy in additive manufacturing research. Its composition is equivalent to the national standard ZL104 casting alloy and the American standard A360 die-cast aluminum alloy. It has the characteristics of low density, high specific strength, good corrosion resistance and excellent thermal conductivity. It is an important material for the manufacture of thin-walled complex lightweight aluminum alloy components.

[0003] Laser directed energy deposition is a coaxial powder feeding metal additive manufacturing technology. Laser directed energy deposition, abbreviated as LDED, has broad application prospects in fields such as aviation and aerospace due to its advantages such as high manufacturing efficiency and large forming size.

[0004] Due to the high laser reflectivity of aluminum alloy, fast thermal conductivity of the material, unstable laser absorption; the oxide film on the surface of aluminum alloy affects the stability of the melting process; the relatively poor fluidity of aluminum alloy powder and the low viscosity of aluminum alloy lead to a narrow process window for single-wall laser directed energy deposition of AlSi10Mg aluminum alloy. When the laser power is too small or the laser scanning speed is too fast, the forming defect of powder not being fused is easy to occur; when the laser power is too large or the scanning speed is too slow, as the deposition layer increases, the heat accumulation becomes larger and larger, and the deposition layer collapses and other forming defects are easy to occur, and large-sized thin-walled structural parts cannot be deposited stably. In addition, during the LDED forming process, the temperature of the micro-melting pool changes from 10³K / s to 10 6 K / s, due to the extraordinary metallurgical characteristics of the micro-molten pool, such as ultra-fast cooling, large temperature gradient and directional heat transfer, and the cyclic heating and cooling characteristics of layer-by-layer accumulation, metallurgical defects such as coarse grains, directional growth, segregation and significant residual stress appear in the formed parts, which seriously affect the mechanical properties and shape accuracy of the parts, thus limiting the promotion and application of this technology.

[0005] In order to improve the performance of aluminum alloy additive manufacturing, the prior art adopts methods such as post-processing and adding reinforcing particles, and the reinforcing particles include SiC and TiC. Although the microstructure and mechanical properties of the formed parts are improved by the above methods, brittle inclusions are introduced, which will lead to a decrease in the strength of the formed parts.

[0006] In summary, in the existing additive manufacturing technology, the formed parts have problems such as coarse grains, directional growth, segregation and poor mechanical properties. Summary of the invention

[0007] The purpose of the present invention is to provide a method for preparing large-size thin-walled structures based on magnetic field-controlled laser directional energy deposition, so as to solve the technical problems of coarse grains, directional growth, segregation and poor mechanical properties of formed parts in additive manufacturing technology. The present invention can effectively influence and improve the solidification structure and mechanical properties of formed parts through magnetic field, avoiding the problems of coarse grains, directional growth and segregation.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention discloses a method for preparing a large-size thin-walled structure based on magnetic field-controlled laser directional energy deposition, comprising the following steps: Turn on the protective gas to fill the part forming area with the protective gas and keep the oxygen content in the forming area below 100ppm; Start the electromagnetic field generator to form a stable uniform magnetic field in the part forming area; The laser cladding head is turned on, the powder metal material is transported to the molten pool position through the powder-carrying gas, and the powder metal material is melted by the laser to form a stable molten pool; The laser cladding head is controlled to scan along a set trajectory in a uniform magnetic field for cyclic deposition, and the laser is stopped after each layer of deposition is completed until the part is formed.

[0009] Furthermore, the protective gas and the powder-carrying gas are both inert gases.

[0010] Furthermore, the strength of the uniform magnetic field is less than or equal to 0.25T.

[0011] Furthermore, the powder metal material contains Al, Fe, Ni and Ti, the particle size of the powder metal material ranges from 53 μm to 150 μm, and the average particle size of the powder metal material is from 60 μm to 100 μm.

[0012] Furthermore, the powdered metal material is dried in a vacuum drying chamber at 120° C. to 150° C. for 2 to 4 hours before use.

[0013] Furthermore, the powder metal material is transported to the molten pool position by the powder-carrying gas, and the powder feeding amount of the powder metal material is 3g / min~6g / min.

[0014] Furthermore, the powdered metal material is melted by laser to form a stable molten pool, the laser power is 1200W~1800W, and the laser spot diameter is 3mm.

[0015] Furthermore, the laser cladding head is controlled to scan and perform cyclic deposition according to a set track in the uniform magnetic field region, wherein the scanning speed of the laser cladding head is 10 mm / s to 16.6 mm / s, the overlap rate between adjacent scanning tracks is 50%, and the lifting amount of the laser cladding head is controlled to be 0.15 mm to 0.4 mm.

[0016] Furthermore, the light is stopped after each layer of deposition is completed, and the light stopping time is 5 seconds to 10 seconds.

[0017] Based on the above method, the present invention also discloses a preparation device for a large-size thin-walled structure based on magnetic field-controlled laser directional energy deposition, and a preparation method for a large-size thin-walled structure based on magnetic field-controlled laser directional energy deposition, comprising a liftable workbench, a forming substrate being provided on the liftable workbench, a laser cladding head being provided above the forming substrate, an electromagnetic field generator being provided on the periphery of the forming substrate, and the electromagnetic field generator being used to form a uniform magnetic field between the forming substrate and the laser cladding head.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention turns on the protective gas so that the protective gas fills the part forming area, and the oxygen content in the forming area is below 100ppm, thereby avoiding oxidation and inclusion contamination of the alloy during the forming process. By starting the electromagnetic field generator, a stable uniform magnetic field is formed in the part forming area, and the thermal damping effect and thermal electromagnetic convection effect generated by the magnetic field in the molten pool are used to regulate the metallurgical behavior of the molten pool and optimize the grain structure. By turning on the laser cladding head, the powder metal material is transported to the molten pool position through the powder-carrying gas, and the powder metal material is melted by the laser to form a stable molten pool; by controlling the laser cladding head to scan according to the set trajectory in the uniform magnetic field area for cyclic deposition, the laser is stopped after each layer of deposition is completed, so as to release the heat of the deposition layer and reduce heat accumulation until the part is formed. The present invention effectively releases excess heat by increasing the stop time, and regulates the metallurgical behavior of the molten pool through the magnetic field, which can effectively affect and improve the solidification structure and mechanical properties of the formed parts, optimize the grain structure, avoid the problems of coarse grains, directional growth and segregation, and at the same time, avoid the problem of brittle inclusions caused by the method of adding reinforcing particles.

[0019] 2. Before use, the present invention performs vacuum drying on the powdered metal material to remove the moisture absorbed by the powdered metal material.

[0020] 3. The device of the present invention includes a liftable workbench, on which a forming substrate is provided. The liftable workbench is used to adjust the height of the forming substrate to ensure that the multi-layer metal molten deposition and the molten pool are always in the magnetic field. A laser cladding head is provided above the forming substrate, and the laser cladding head is used to emit laser to melt the powdered metal material by laser to form a stable molten pool. An electromagnetic field generator is provided on the periphery of the forming substrate, and the electromagnetic field generator is used to form a uniform magnetic field between the forming substrate and the laser cladding head. The thermal damping effect and thermal electromagnetic convection effect generated by the magnetic field in the molten pool are used to regulate the metallurgical behavior of the molten pool and achieve the optimization of the grain structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a flow chart of the method of the present invention; Figure 2 This is a physical picture of a large-sized thin-walled structural part deposited by laser directional energy deposition according to the present invention; Figure 3 It is a grain structure diagram of AlSi10Mg alloy deposited by laser directional energy deposition; a is a grain structure diagram of AlSi10Mg alloy deposited by laser directional energy deposition without magnetic field assistance; b is a grain structure diagram of AlSi10Mg alloy deposited by laser directional energy deposition with magnetic field assistance; Figure 4 The present invention is an application device diagram of the method of the present invention.

[0022] Among them: 1. Liftable workbench; 2. Forming substrate; 3. Multi-layer metal molten deposition; 4. Molten pool; 5. Magnetic field; 6. Powder conveying mechanism; 7. Laser; 8. Laser cladding head; 9. Electromagnetic field generator. DETAILED DESCRIPTION In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings 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 should fall within the scope of protection of the present invention.

[0023] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0024] The present invention is further described in detail below in conjunction with the accompanying drawings: See also Figure 1 The present invention discloses a method for preparing a large-sized thin-walled structure based on magnetic field-controlled laser directional energy deposition, comprising the following steps: S1. Turn on the protective gas to fill the part forming area with the protective gas and keep the oxygen content in the forming area below 100ppm; S2, start the electromagnetic field generator 9 to form a stable uniform magnetic field in the part forming area; Preferably, the strength of the uniform magnetic field is 0.25T.

[0025] S3, turning on the laser cladding head 8, conveying the powder metal material to the molten pool position through the powder-carrying gas, and melting the powder metal material by laser to form a stable molten pool; Preferably, the protective gas and the powder-carrying gas are both inert gases.

[0026] Preferably, the powder metal material contains Al, Fe, Ni and Ti, the particle size of the powder metal material ranges from 53 μm to 150 μm, and the average particle size of the powder metal material is from 60 μm to 100 μm.

[0027] Preferably, the powder metal material is AlSi10Mg alloy powder; Preferably, the powdered metal material is dried in a vacuum drying chamber at 120° C. to 150° C. for 2 to 4 hours before use.

[0028] Preferably, the powder metal material is transported to the molten pool position by means of a powder-carrying gas, and the powder feeding amount of the powder metal material is 3 g / min to 6 g / min.

[0029] Preferably, the powdered metal material is melted by laser to form a stable molten pool, the laser power is 1200W~1800W, and the laser spot diameter is 3mm.

[0030] S4, controlling the laser cladding head 8 to scan and perform cyclic deposition according to a set trajectory in the uniform magnetic field region, and stopping the laser after each layer of deposition is completed until the part is formed.

[0031] Preferably, the laser cladding head 8 is controlled to scan according to a set trajectory in a uniform magnetic field region for cyclic deposition, wherein the scanning speed of the laser cladding head 8 is 10 mm / s to 16.6 mm / s, the overlap rate between adjacent scanning tracks is 50%, and the lifting amount of the laser cladding head 8 is controlled to be 0.15 mm to 0.4 mm.

[0032] Preferably, the light is stopped after each layer of deposition is completed, and the light stopping time is 5 seconds to 10 seconds.

[0033] See also Figure 1 In another feasible embodiment of the present invention, the following is adaptively modified according to the situation. It includes the following steps: Turn on the shielding gas and fill the forming area of ​​the part with it. The oxygen content in the forming area is below 100ppm to prevent the powdered metal material from reacting with oxygen in the air during the laser cladding process, and to avoid oxidation and inclusion contamination of the alloy during the forming process.

[0034] The electromagnetic field generator 9 is started to form a stable uniform magnetic field in the part forming area. The metallurgical behavior of the molten pool is regulated by the thermal damping effect and thermal electromagnetic convection effect generated by the magnetic field in the molten pool to achieve the optimization of the grain structure.

[0035] Turn on the laser cladding head 8, transport the powder metal material to the molten pool position through the powder-carrying gas, and melt the powder metal material through the laser to form a stable molten pool; The laser cladding head 8 is controlled to scan along the set trajectory in the uniform magnetic field area for cyclic deposition, and the laser is stopped after each layer of deposition is completed, that is, the laser cladding head 8 is turned off after each layer of deposition is completed, so as to release the heat of the deposition layer and reduce heat accumulation until the part is formed. After the deposition printing is completed, the laser, magnetic field, protective gas and powder conveying are turned off in sequence. The present invention effectively releases excess heat and reduces heat accumulation by increasing the stop time, thereby achieving stable deposition of large-size thin-walled structures. The metallurgical behavior of the molten pool is regulated by the magnetic field, which can effectively affect and improve the solidification structure and mechanical properties of the formed parts. The thermal damping effect and thermo-electromagnetic convection effect generated by the magnetic field inside the molten pool can significantly refine the size and structure of the solidified grains, thereby improving the forming performance of the parts, optimizing the grain structure, and avoiding the problems of coarse grains, directional growth and segregation. At the same time, the problem of brittle inclusions caused by the method of adding reinforcing particles is avoided, see Figure 2 This is a real picture of a large-sized thin-walled structural component deposited by laser directed energy deposition according to the present invention.

[0036] Embodiment 1: This embodiment provides a method for preparing a large-sized thin-walled structure based on magnetic field-controlled laser directional energy deposition, comprising the following steps: S1. Turn on the protective gas to fill the part forming area with the protective gas and keep the oxygen content in the forming area below 100ppm; S2, start the electromagnetic field generator 9 to form a stable uniform magnetic field in the part forming area; Preferably, the strength of the uniform magnetic field is 0.05T.

[0037] S3, turning on the laser cladding head 8, conveying the powder metal material to the molten pool position through the powder-carrying gas, and melting the powder metal material by laser to form a stable molten pool; Preferably, the protective gas and the powder-carrying gas are both inert gases.

[0038] Preferably, the powder metal material contains Al, Fe, Ni and Ti, the particle size of the powder metal material ranges from 53 μm to 150 μm, and the average particle size of the powder metal material is from 60 μm to 100 μm.

[0039] Preferably, the powder metal material is AlSi10Mg alloy powder; Preferably, the powdered metal material is dried in a vacuum drying chamber at 120° C. for 2 hours before use.

[0040] Preferably, the powder metal material is transported to the molten pool position by means of a powder-carrying gas, and the powder feeding amount of the powder metal material is 3 g / min.

[0041] Preferably, the powdered metal material is melted by laser to form a stable molten pool, the laser power is 1200 W, and the laser spot diameter is 3 mm.

[0042] S4, controlling the laser cladding head 8 to scan and perform cyclic deposition according to a set trajectory in the uniform magnetic field region, and stopping the laser after each layer of deposition is completed until the part is formed.

[0043] Preferably, the laser cladding head 8 is controlled to scan according to a set track in the uniform magnetic field region for cyclic deposition, wherein the scanning speed of the laser cladding head 8 is 10 mm / s, the overlap rate between adjacent scanning tracks is 50%, and the lifting amount of the laser cladding head 8 is controlled to be 0.15 mm~0.4 mm.

[0044] Preferably, the light is stopped after each layer of deposition is completed, and the light stopping time is 5 seconds.

[0045] Embodiment 2: This embodiment provides a method for preparing a large-sized thin-walled structure based on magnetic field-controlled laser directional energy deposition, comprising the following steps: S1. Turn on the protective gas to fill the part forming area with the protective gas and keep the oxygen content in the forming area below 100ppm; S2, start the electromagnetic field generator 9 to form a stable uniform magnetic field in the part forming area; Preferably, the strength of the uniform magnetic field is 0.1T.

[0046] S3, turning on the laser cladding head 8, conveying the powder metal material to the molten pool position through the powder-carrying gas, and melting the powder metal material by laser to form a stable molten pool; Preferably, the protective gas and the powder-carrying gas are both inert gases.

[0047] Preferably, the powder metal material contains Al, Fe, Ni and Ti, the particle size of the powder metal material ranges from 53 μm to 150 μm, and the average particle size of the powder metal material is from 60 μm to 100 μm.

[0048] Preferably, the powder metal material is AlSi10Mg alloy powder; Preferably, the powdered metal material is dried in a vacuum drying chamber at 135° C. for 3 hours before use.

[0049] Preferably, the powder metal material is transported to the molten pool position by means of a powder-carrying gas, and the powder feeding amount of the powder metal material is 4.5 g / min.

[0050] Preferably, the powdered metal material is melted by laser to form a stable molten pool, the laser power is 1600 W, and the laser spot diameter is 3 mm.

[0051] S4, controlling the laser cladding head 8 to scan and perform cyclic deposition according to a set trajectory in the uniform magnetic field region, and stopping the laser after each layer of deposition is completed until the part is formed.

[0052] Preferably, the laser cladding head 8 is controlled to scan according to a set track in the uniform magnetic field region for cyclic deposition, wherein the scanning speed of the laser cladding head 8 is 13.3 mm / s, the overlap rate between adjacent scanning tracks is 50%, and the lifting amount of the laser cladding head 8 is controlled to be 0.15 mm~0.4 mm.

[0053] Preferably, the light is stopped after each layer of deposition is completed, and the light stopping time is 7.5 seconds.

[0054] Embodiment three: This embodiment provides a method for preparing a large-sized thin-walled structure based on magnetic field-controlled laser directional energy deposition, comprising the following steps: S1. Turn on the protective gas to fill the part forming area with the protective gas and keep the oxygen content in the forming area below 100ppm; S2, start the electromagnetic field generator 9 to form a stable uniform magnetic field in the part forming area; Preferably, the strength of the uniform magnetic field is 0.25T.

[0055] S3, turning on the laser cladding head 8, conveying the powder metal material to the molten pool position through the powder-carrying gas, and melting the powder metal material by laser to form a stable molten pool; Preferably, the protective gas and the powder-carrying gas are both inert gases.

[0056] Preferably, the powder metal material contains Al, Fe, Ni and Ti, the particle size of the powder metal material ranges from 53 μm to 150 μm, and the average particle size of the powder metal material is from 60 μm to 100 μm.

[0057] Preferably, the powder metal material is AlSi10Mg alloy powder; Preferably, the powdered metal material is dried in a vacuum drying chamber at 150° C. for 4 hours before use.

[0058] Preferably, the powder metal material is transported to the molten pool position by means of a powder-carrying gas, and the powder feeding amount of the powder metal material is 6 g / min.

[0059] Preferably, the powdered metal material is melted by laser to form a stable molten pool, the laser power is 1200W~1800W, and the laser spot diameter is 3mm.

[0060] S4, controlling the laser cladding head 8 to scan and perform cyclic deposition according to a set trajectory in the uniform magnetic field region, and stopping the laser after each layer of deposition is completed until the part is formed.

[0061] Preferably, the laser cladding head 8 is controlled to scan according to a set track in the uniform magnetic field region for cyclic deposition, wherein the scanning speed of the laser cladding head 8 is 16.6 mm / s, the overlap rate between adjacent scanning tracks is 50%, and the lifting amount of the laser cladding head 8 is controlled to be 0.15 mm~0.4 mm.

[0062] Preferably, the light is stopped after each layer of deposition is completed, and the light stopping time is 10 seconds.

[0063] Embodiment 4: This embodiment provides a method for preparing a large-sized thin-walled structure based on magnetic field-controlled laser directed energy deposition. The method can achieve stable deposition of large-sized thin-walled structures. At the same time, the AlSi10Mg alloy prepared by magnetic field-assisted laser directed energy deposition has a more uniform equiaxed crystal structure.

[0064] S1. Prepare the equipment and ensure that the laser, magnetic field and powder metal material are focused at the same location, i.e. the molten pool location.

[0065] S2. The powder used in this method may contain metals or alloys such as Al, Fe, Ni and Ti, and the powder particle size ranges from 53μm to 150μm. Before the deposition test, the powder needs to be dried to remove the moisture absorbed by the powder, and the powder filling and substrate setting are completed.

[0066] S3. Start the protective gas to prevent oxidation and inclusion contamination of the alloy during the forming process. High-purity inert gas is selected as the powder carrier gas and protective gas. When the set magnetic field strength is reached, the powder conveying is started and the laser is started to form a stable molten pool on the substrate. The laser process parameters are determined by the characteristics of the powder material and the structural parts.

[0067] S4. By controlling the laser cladding head 8 to move in the magnetic field area, single-pass, multi-pass and multi-layer deposition begins. When depositing large-sized thin-walled structural parts, the stop time of each layer is determined according to the characteristics of the structural parts and powder materials to eliminate heat accumulation and avoid molten pool collapse, so as to achieve stable deposition of large-sized thin-walled structures.

[0068] S5. According to the specific forming requirements, multi-pass and multi-layer cyclic deposition is carried out until the part is formed.

[0069] S6. After the deposition printing is completed, turn off the laser, magnetic field, protective gas and powder delivery in sequence.

[0070] The present invention realizes the LDED forming of large-sized thin-walled structures with uniform organization by changing the generation mode of magnetic field. The changes of the application mode of magnetic field, the form of laser heat source, the stop time of each layer, the laser scanning speed and strategy, the type of powder material and other related details are all within the scope of the present invention.

[0071] Embodiment five: This embodiment provides a method for preparing a large-sized thin-walled structure based on magnetic field-controlled laser directional energy deposition. The present invention realizes the forming of a large-sized thin-walled structure LDED with uniform structure by changing the way the magnetic field is generated. The present invention improves the microstructure and mechanical properties of the parts through the relevant details such as the way the magnetic field is applied, the form of the laser heat source, the time for stopping the light for each layer, the laser scanning speed and strategy, and the type of powder material.

[0072] S1. Basis Figure 1 Principle shown, prepare the equipment and ensure that the laser, magnetic field and powder metal material are focused at the same location, that is, the molten pool location.

[0073] S2. Adjust the power supply, movable rails and lifting platform to achieve the expected magnetic field strength, and the uniform magnetic field strength is set to 0.2 T. The particle size range of AlSi10Mg alloy powder is 53μm to 150μm, and the average particle size is 60μm to 100μm. Before the deposition test, it is necessary to dry it at 120℃ in a vacuum drying chamber for 3 hours to remove the absorbed moisture, and complete the powder filling, substrate setting and pre-filling of protective gas.

[0074] S3. Start the shielding gas to prevent oxidation and inclusion contamination of the alloy during the forming process. High-purity argon is used as the powder carrier gas and shielding gas. The shielding gas fills the forming area of ​​the part, and the oxygen content in the forming area is below 100ppm. Start the electromagnetic field generator 9, adjust the current and voltage to achieve the set magnetic field strength, and start the powder delivery at the same time, and set the powder delivery rate to 5g / min. Start the laser to form a stable molten pool on the substrate. The parameters of laser directional energy deposition include: laser power 1800W, scanning speed 10mm / s, spot diameter 3mm, overlap rate between adjacent tracks 50%, and laser cladding head 8 lifting amount 0.15mm~0.4mm.

[0075] S4. Start single-pass, multi-pass and multi-layer deposition by controlling the laser cladding head 8 to move in the uniform magnetic field region. When depositing a large-size thin-walled structure of AlSi10Mg aluminum alloy, stop the laser for 10 seconds per layer to release excess heat and reduce heat accumulation.

[0076] S5. According to the specific forming requirements, multi-pass and multi-layer cyclic deposition is carried out until the part is formed.

[0077] S6. After the deposition printing is completed, the laser, magnetic field, protective gas and powder delivery are turned off in sequence.

[0078] The present invention effectively releases excess heat and reduces heat accumulation by increasing the light-off time, thereby achieving stable deposition of large-size thin-walled structures, such as Figure 2 The size of the part is 80mm×51mm×5mm.

[0079] Using magnetic field to improve the structure of LDED parts. The present invention uses the thermal damping effect and thermal electromagnetic convection effect generated by the magnetic field in the molten pool to regulate the metallurgical behavior of the molten pool and optimize the grain structure. Taking AlSi10Mg alloy as an example, the effectiveness of magnetic field regulation on metal grains is verified. Figure 3As shown in a, in the absence of a magnetic field, AlSi10Mg presents a coarse columnar crystal structure; under the action of a magnetic field, the device effectively refines the grain structure of AlSi10Mg to form a fine equiaxed crystal structure, as shown in Figure 3 The process of the present invention is simple and can improve the solidification structure and mechanical properties of the AlSi10Mg alloy in the LDED additive manufacturing process.

[0080] The present invention has strong operability and applicability. In actual application, different laser and magnetic field process matching parameters can be selected according to specific forming requirements of different metal parts.

[0081] Based on the above method, the present invention also discloses a preparation device for a large-sized thin-walled structure based on magnetic field-controlled laser directional energy deposition, and a preparation method for a large-sized thin-walled structure based on magnetic field-controlled laser directional energy deposition, see Figure 4 , including a liftable workbench 1, on which a forming substrate 2 is arranged, and the liftable workbench 1 is used to adjust the height of the forming substrate 2 to ensure that the multi-layer metal molten deposition 3 and the molten pool 4 are always located in the magnetic field 5. A laser cladding head 8 is arranged above the forming substrate 2, and the laser cladding head 8 is used to emit laser, and melt the powder metal material by laser to form a stable molten pool. At the same time, the powder metal material is transported to the location of the molten pool 4 by the powder conveying mechanism 6 and the powder-carrying gas. An electromagnetic field generator 9 is arranged on the periphery of the forming substrate 2, and the electromagnetic field generator 9 is used to form a uniform magnetic field between the forming substrate 2 and the laser cladding head 8. Through the thermal damping effect and thermal electromagnetic convection effect generated by the magnetic field in the molten pool, the metallurgical behavior of the molten pool is regulated to achieve the optimization of the grain structure.

[0082] The device of the present invention combined with the method of the present invention can realize the preparation of large-size thin-walled structures, and can effectively influence and improve the solidification structure and mechanical properties of the formed parts through the magnetic field, thereby avoiding the problem of brittle inclusions.

[0083] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a large-size thin-walled structure based on magnetic field-controlled laser directional energy deposition, characterized in that: The following steps are involved: Turn on the protective gas to fill the part forming area with the protective gas and keep the oxygen content in the forming area below 100ppm; Starting the electromagnetic field generator (9) to form a stable uniform magnetic field in the part forming area; Turning on the laser cladding head (8), conveying the powdered metal material to the molten pool position by means of the powder-carrying gas, and melting the powdered metal material by means of the laser to form a stable molten pool; The laser cladding head (8) is controlled to scan and perform cyclic deposition in a uniform magnetic field region according to a set trajectory, and the laser is stopped after each layer of deposition is completed until the part is formed.

2. The method for preparing a large-sized thin-walled structure based on magnetic field-controlled laser directional energy deposition according to claim 1, characterized in that: The protective gas and the powder-carrying gas are both inert gases.

3. The method for preparing a large-size thin-walled structure based on magnetic field-controlled laser directional energy deposition according to claim 1, characterized in that: The strength of the uniform magnetic field is less than or equal to 0.25T.

4. The method for preparing a large-sized thin-walled structure based on magnetic field-controlled laser directional energy deposition according to claim 1, characterized in that: The powder metal material contains Al, Fe, Ni and Ti. The particle size of the powder metal material ranges from 53 μm to 150 μm, and the average particle size of the powder metal material is from 60 μm to 100 μm.

5. The method for preparing a large-sized thin-walled structure based on magnetic field-controlled laser directional energy deposition according to claim 1, characterized in that: The powdered metal material is dried in a vacuum drying chamber at 120° C. to 150° C. for 2 to 4 hours before use.

6. The method for preparing a large-sized thin-walled structure based on magnetic field-controlled laser directional energy deposition according to claim 1, characterized in that: The powder metal material is transported to the molten pool position by the powder-carrying gas, and the powder feeding amount of the powder metal material is 3g / min~6g / min.

7. The method for preparing a large-sized thin-walled structure based on magnetic field-controlled laser directional energy deposition according to claim 1, characterized in that: The powdered metal material is melted by laser to form a stable molten pool, the laser power is 1200W~1800W, and the laser spot diameter is 3mm.

8. The method for preparing a large-sized thin-walled structure based on magnetic field-controlled laser directional energy deposition according to claim 1, characterized in that: The laser cladding head (8) is controlled to scan according to a set track in a uniform magnetic field region to perform cyclic deposition, wherein the scanning speed of the laser cladding head (8) is 10 mm / s to 16.6 mm / s, the overlap rate between adjacent scanning tracks is 50%, and the lifting amount of the laser cladding head (8) is controlled to be 0.15 mm to 0.4 mm.

9. The method for preparing a large-sized thin-walled structure based on magnetic field-controlled laser directional energy deposition according to claim 1, characterized in that: The light is stopped after each layer of deposition is completed, and the light stopping time is 5 seconds to 10 seconds.

10. A device for preparing large-size thin-walled structures based on magnetic field-controlled laser directional energy deposition, characterized in that: A method according to any one of claims 1 to 9 is adopted, comprising a liftable workbench (1), a forming substrate (2) being provided on the liftable workbench (1), a laser cladding head (8) being provided above the forming substrate (2), an electromagnetic field generator (9) being provided on the periphery of the forming substrate (2), the electromagnetic field generator (9) being used to form a uniform magnetic field between the forming substrate (2) and the laser cladding head (8).

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