Device and method for preparing metal workpiece through laser powder bed melting technology under high-intensity magnetic field

Abstract

The invention discloses a device and method for preparing a metal workpiece through a laser powder bed melting technology under a high-intensity magnetic field, and relates to the technical field of additive equipment.The device for preparing the metal workpiece through the laser powder bed melting technology under the high-intensity magnetic field comprises additive equipment and a superconducting strong magnet, and the additive equipment prepares the metal workpiece through the laser powder bed melting technology; the additive equipment is provided with a printing area; the superconducting strong magnet comprises a superconducting coil used for generating a magnetic field, and the superconducting coil is wound outside the printing area. The method effectively solves the problems of uneven grain morphology and columnar crystal growth and orientation in the traditional L-PBF (laser powder bed melting technology) process, and obviously improves the strength, ductility and fatigue performance of the metal workpiece, so that the material performance is improved, and the production efficiency and the material utilization rate are obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of additive equipment, and in particular to a device and method for preparing a metal workpiece by using a laser powder bed melting technology under a strong magnetic field. Background Art

[0002] Laser powder bed fusion (L-PBF) technology is an advanced metal additive manufacturing process that can efficiently manufacture complex structures. However, due to the rapid solidification and complex thermal history in the L-PBF process, microstructural defects such as uneven structure, columnar crystal growth, microcracks and single crystal orientation are prone to occur, which will reduce the mechanical properties and reliability of the material. In addition, the residual stress caused by rapid cooling is also a major challenge in the L-PBF process. The melting of the metal in the L-PBF process, the flow of the molten metal in the molten pool and the subsequent solidification process determine the microstructure and properties of the alloy, and will also affect the subsequent plastic processing and heat treatment processes. Summary of the invention

[0003] The purpose of the present invention is to provide a device and method for preparing metal workpieces by laser powder bed melting technology under a strong magnetic field, so as to solve the problems existing in the above-mentioned prior art and improve the workpiece quality and additive efficiency.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] The invention provides a device for preparing a metal workpiece by using a laser powder bed melting technology under a strong magnetic field, comprising: an additive device and a superconducting strong magnet, wherein the additive device prepares the metal workpiece by using the laser powder bed melting technology; the additive device has a printing area; the superconducting strong magnet comprises a superconducting coil and an annular liquid helium device for generating a magnetic field, wherein the annular liquid helium device has an annular cavity, wherein the annular cavity is used to accommodate liquid helium and the superconducting coil, wherein a low-temperature cooling interface is arranged on the annular liquid helium device, wherein the low-temperature cooling interface is connected to the annular cavity, wherein the annular cavity is arranged around the printing area, and wherein the annular liquid helium device is used to maintain a temperature in the annular cavity lower than 25K so as to enable the superconducting strong magnet to generate an ultra-strong magnetic field of 0.5-20T after a current is passed through the superconducting strong magnet.

[0006] Preferably, the additive equipment includes a laser, a printing base, a powder roller, a powder box, a powder conveying assembly, a printing bin and a lifting drive device; the printing base is arranged in the printing bin, the printing area is located on the printing base, the powder box is used to accommodate metal powder, the powder conveying assembly can convey the metal powder in the powder box to the powder roller, the powder roller transports the metal powder to the printing base and spreads the metal powder evenly; the laser is used to irradiate the flattened metal powder with laser to melt the powder; the printing base is located in the superconducting coil, and the lifting drive device can drive the printing base to rise and fall.

[0007] Preferably, the axis of the superconducting coil is parallel or perpendicular to the printing base, the current range of the superconducting coil is 0-500A, the generated magnetic induction intensity range is 0.5-20T, and the magnetic field uniformity area is greater than 75mm.

[0008] Preferably, the axes of the superconducting coil and the superconducting strong magnet are parallel to the printing base, and holes are respectively left at the top and bottom of the superconducting strong magnet. The top hole is used for allowing the high-energy laser emitted by the laser to irradiate into the printing area, and the bottom hole is used for allowing the telescopic rod of the lifting drive device to extend into the superconducting coil to drive the printing base to rise and fall.

[0009] Preferably, the axes of the superconducting coil and the superconducting strong magnet are perpendicular to the printing base, the top opening of the superconducting strong magnet is used for allowing the high-energy laser emitted by the laser to irradiate into the printing area, and the bottom opening is used for allowing the telescopic rod of the lifting drive device to extend into the superconducting coil to drive the printing base to rise and fall.

[0010] Preferably, both inner and outer surfaces of the annular liquid helium device are coated with a thermal insulation layer.

[0011] Preferably, air inlet and outlet holes are provided on the printing chamber, and an oxygen content sensor is arranged in the printing chamber.

[0012] Preferably, the powder roller, powder box, powder conveying assembly, printing bin and lifting drive device are all made of aluminum alloy to avoid the influence of strong magnetic field during the printing process.

[0013] Preferably, the superconducting strong magnet is connected to the printing chamber via a connector.

[0014] The present invention also provides a method for preparing a metal workpiece by laser powder bed melting technology under a strong magnetic field, comprising:

[0015] Preparation steps: selecting metal powder suitable for laser powder bed melting; preparing the device for preparing metal workpieces by laser powder bed melting technology under a strong magnetic field as described above;

[0016] Printing steps:

[0017] S1. Pass current into the superconducting strong magnet, pass liquid helium into the annular liquid helium device to maintain it below 25K, and generate a strong magnetic field; fill the powder box with high-flowability and uniform particle size metal powder; the powder conveying component conveys the metal powder to the powder roller; and the powder roller is used to evenly spread the metal powder on the printing base;

[0018] S2, the laser emits a high-energy laser beam, which shines on the printing base to melt the powder;

[0019] Repeat the steps of S1, using a powder roller to evenly spread the metal powder on the printing base, and S2 until the entire additive process is completed.

[0020] Compared with the prior art, the present invention has achieved the following technical effects:

[0021] The strong magnetic field generated by the superconducting strong magnet in the solution provided by the present invention significantly affects the solidification process of the metal through magnetoplastic effect, thermoelectromagnetic effect and magnetoresistance effect, thereby regulating the grain growth behavior and orientation. Grain refinement, texture orientation adjustment and micro defect reduction are achieved. The present invention effectively solves the problems of uneven grain morphology, columnar crystal growth and orientation in the traditional L-PBF (i.e. laser powder bed fusion technology) process, significantly improves the strength, ductility and fatigue performance of metal workpieces, thereby improving material performance, and significantly improving production efficiency and material utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 A schematic diagram of the structure of a device for preparing a metal workpiece by laser powder bed melting technology under a strong magnetic field in which the axis of the superconducting coil provided in an embodiment of the present invention is parallel to a printing base;

[0024] Figure 2 for Figure 1 The front view of the interior of the printing chamber and the superconducting strong magnet;

[0025] Figure 3 A schematic diagram of the structure of a device for preparing a metal workpiece by laser powder bed melting technology under a strong magnetic field in which the axis of the superconducting coil provided in an embodiment of the present invention is perpendicular to a printing base;

[0026] Figure 4 for Figure 3The front view of the interior of the printing chamber and the superconducting strong magnet;

[0027] In the figure: 1-superconducting strong magnet; 2-inlet and outlet holes; 3-printing base; 4-laser; 5-powder box; 6-gas stop valve; 7-powder roller; 8-oxygen content sensor; 9-annular liquid helium device; 10-superconducting coil; 11-telescopic rod; 12-base; 13-powder conveying assembly; 14-top hole; 15-connector; 16-insulation layer; 17-low-temperature cooling interface; 18-flow meter. DETAILED DESCRIPTION

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

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] The magnetic field strength and operating efficiency of superconducting strong magnets are much higher than those of traditional electromagnets, and they are widely used in occasions requiring high-intensity and stable magnetic fields, such as particle accelerators, nuclear fusion reactors, and materials science research. In the research and modification of metal materials, strong magnetic fields can affect the growth behavior and orientation of metal grains, thereby changing the internal grain structure. For example, strong magnetic fields can guide metals to form a crystal structure with preferential orientation, thereby improving their electrical conductivity and mechanical properties. In addition, the magnetoplastic effect generated by strong magnetic fields can affect the plastic deformation behavior of magnetic or weakly magnetic metals (such as iron, nickel, cobalt, etc.) by changing the magnetic domain arrangement of magnetic or weakly magnetic metals (such as iron, nickel, cobalt, etc.), thereby improving their mechanical properties. And strong magnets can accelerate the phase change of metals by compensating Gibbs free energy with magnetization free energy. Superconducting strong magnets can also provide auxiliary effects in the smelting, solidification and heat treatment of metals to optimize the physical properties of metal materials. By applying a strong magnetic field during solidification or heat treatment, an excellent microstructure can be obtained. This method has been used to a certain extent in the preparation of high-performance alloys. For example, by annealing Ti64 alloy under a strong magnetic field, martensite is quickly decomposed and the crystal orientation of the α phase in the alloy is affected, which significantly improves the plasticity. In addition, special effects such as the thermoelectromagnetic effect and magnetoresistance effect generated in a strong magnetic field also have a significant impact on the metal solidification process. Therefore, the rational use of superconducting strong magnetic fields can make significant progress in the processing and performance optimization of metal materials, providing a unique research method for the development of new high-performance metal materials.

[0031] Research has found that for Fe-Ni-C steel, a 1.9T magnetic field can increase the martensitic transformation temperature by about 6K. At a temperature of -60°C, a 2T magnetic field increases the isothermal martensitic phase transformation rate of Fe-Ni-Mn alloy by about two times. Strong magnetic fields affect the magnetic energy of the system, and the driving force of phase transformation changes. For Cu-Co alloys, the magnetic field can suppress convection in the melt, so that the Cu-Co alloy obtains a Cu-rich phase solidification structure with consistent size. Moreover, during directional solidification and ingot solidification, strong magnetic fields can suppress convection in the melt.

[0032] Combine the following Figures 1 to 4 , describing an embodiment of the present invention.

[0033] The present invention provides a device for preparing a metal workpiece by using a laser powder bed melting technology under a strong magnetic field, comprising: an additive device and a superconducting strong magnet 1, wherein the additive device prepares the metal workpiece by using the laser powder bed melting technology; the additive device has a printing area; the superconducting strong magnet 1 comprises a superconducting coil 10 and an annular liquid helium device 9 for generating a magnetic field, wherein the annular liquid helium device 9 has an annular cavity, wherein the annular cavity is used to accommodate liquid helium and the superconducting coil 10, wherein a low-temperature cooling interface 17 is arranged on the annular liquid helium device 9, wherein the low-temperature cooling interface 17 is connected to the annular cavity, wherein the annular cavity is arranged around the printing area, and wherein the annular liquid helium device 9 is used to maintain a temperature in the annular cavity lower than 25K so as to enable the superconducting strong magnet 1 to generate an ultra-strong magnetic field of 0.5-20T after a current is passed through it.

[0034] The strong magnetic field generated by the superconducting strong magnet 1 in the solution provided by the present invention significantly affects the solidification process of the metal through magnetoplastic effect, thermoelectromagnetic effect and magnetoresistance effect, thereby regulating the grain growth behavior and orientation. Grain refinement, texture orientation adjustment and micro defect reduction are achieved. The present invention effectively solves the problems of uneven grain morphology, columnar crystal growth and orientation in the traditional L-PBF (i.e. laser powder bed melting technology) process, significantly improves the strength, ductility and fatigue performance of metal workpieces, thereby improving material performance, and significantly improving production efficiency and material utilization.

[0035] This embodiment maintains the cryogenic state of the superconducting coil 10 by means of the annular liquid helium device 9, which is filled with liquid helium, and the liquid helium can maintain the operating temperature of the superconducting coil 10 below 25 K. The superconducting coil 10 can achieve an ultra-strong magnetic field of 0.5-20 T at an operating temperature below 25 K.

[0036] In some embodiments, the additive device includes a laser 4, a printing base 3, a powder roller 7, a powder box 5, a powder conveying assembly 13, a printing bin and a lifting drive device; the printing base 3 is arranged in the printing bin, the printing area is located on the printing base 3, the powder box 5 is used to contain metal powder, the powder conveying assembly 13 can convey the metal powder in the powder box 5 to the powder roller 7, the powder roller 7 transports the metal powder to the printing base 3 and spreads the metal powder evenly; the laser 4 is used to irradiate the laser on the flattened metal powder to melt the powder; the printing base 3 is located in the superconducting coil 10, and the lifting drive device can drive the printing base 3 to rise and fall.

[0037] In this embodiment, the laser 4 outputs high-energy laser irradiation. During the printing process, the lifting drive device drives the printing base 3 to rise and fall to achieve layer-by-layer printing, thereby realizing the preparation of parts under a strong magnetic field.

[0038] In some examples, the additive equipment can be the AF-250MD-PLUS metal 3D printer produced by Suzhou Shuangen Intelligent Technology Co., Ltd.

[0039] In some embodiments, the axis of the superconducting coil 10 is parallel or perpendicular to the printing base 3, the current range of the superconducting coil 10 is 0-500A, the generated magnetic induction intensity range is 0.5-20T, and the magnetic field uniformity area is greater than 75mm.

[0040] like Figure 2 and Figure 4 As shown. A strong magnetic field is applied perpendicularly or parallel to the laser scanning direction, which can regulate the solute migration behavior in the molten pool, promote grain refinement and improve the formation of texture in the additive direction. Cooling and solidification: Under the action of a strong magnetic field, the cooling rate of the molten pool is controlled, so that the crystal growth direction and grain size are effectively controlled, and a metal workpiece with excellent microstructure is obtained.

[0041] In some embodiments, the axes of the superconducting coil 10 and the superconducting strong magnet 1 are parallel to the printing base 3, and holes are respectively left at the top and bottom of the superconducting strong magnet 1. The top hole 14 is used for allowing the high-energy laser emitted by the laser 4 to irradiate into the printing area, and the bottom hole is used for allowing the telescopic rod 11 of the lifting drive device to extend into the superconducting coil 10 to drive the printing base 3 to rise and fall.

[0042] It should be understood that the hole in this embodiment is opened on the annular liquid helium device 9, so the superconducting coil 10 in the superconducting strong magnet 1 needs to avoid the position of the hole when winding.

[0043] In some embodiments, the axes of the superconducting coil 10 and the superconducting strong magnet 1 are perpendicular to the printing base 3, the top opening of the superconducting strong magnet 1 is used for allowing the high-energy laser emitted by the laser 4 to irradiate into the printing area, and the bottom opening is used for allowing the telescopic rod 11 of the lifting drive device to extend into the superconducting coil 10 to drive the printing base 3 to rise and fall.

[0044] In some embodiments, both the inner and outer surfaces of the annular liquid helium device 9 are coated with a heat insulating layer 16 .

[0045] In some embodiments, air inlet and outlet holes 2 are provided on the printing chamber, and an oxygen content sensor 8 is provided in the printing chamber.

[0046] In this embodiment, argon gas is introduced into the printing chamber through some of the inlet and outlet holes 2 and exhausted through other inlet and outlet holes 2 to reduce the oxygen content in the printing chamber, and the oxygen content in the printing chamber is maintained below 500 ppm. The oxygen content sensor 8 is used to detect the oxygen content in the printing chamber to realize the visualization of the oxygen content.

[0047] In some embodiments, the powder roller 7, the powder box 5, the powder conveying assembly 13, the printing chamber and the lifting drive device are all made of aluminum alloy to avoid the influence of strong magnetic fields during the printing process.

[0048] In some embodiments, the superconducting strong magnet 1 is connected to the printing chamber via a connector 15 .

[0049] In some embodiments, an air stop valve 6 is provided on the top of the powder box 5. When the air stop valve 6 is opened, metal powder can be filled into the powder box 5. After the powder filling is completed, the air stop valve 6 is closed to prevent air from entering the printing chamber.

[0050] The influence formula of the change of metal orientation behavior under strong magnetic field is:

[0051]

[0052] Here χ a,b and χ c Represent the magnetic susceptibility of the crystal a, b and c axes, μ 0 is the vacuum magnetic permeability, B is the magnetic induction intensity;

[0053] The influence formula of phase change of metal under strong magnetic field is:

[0054] ΔG=ΔG 0 -(μ 0 / 2)H 2 Δ(xV)

[0055] Here, ΔG 0 is the free energy under the condition of no magnetic field, and the second term on the right side is the change of magnetic Gibbs free energy, μ 0is the magnetic field constant (4π×10 -7 H·m -1 ), H is the magnetic field intensity, χ is the magnetic permeability, and V is the molar volume of the substance. It can be found that when the same magnetic field is applied, the greater the magnetic permeability of the substance, the more obvious the change in the total Gibbs free energy.

[0056] The present invention also provides a method for preparing a metal workpiece by laser powder bed melting technology under a strong magnetic field, comprising:

[0057] Preparation steps: selecting metal powder suitable for laser powder bed melting; preparing the above-mentioned device for preparing metal workpieces by laser powder bed melting technology under a strong magnetic field;

[0058] Printing steps:

[0059] S1, pass current into the superconducting strong magnet 1, pass liquid helium into the annular liquid helium device 9 to maintain it below 25K, and generate a strong magnetic field; fill the powder box 5 with metal powder with high fluidity and uniform particle size; the powder conveying component 13 conveys the metal powder to the powder roller 7; and the powder roller 7 is used to evenly spread the metal powder on the printing base 3;

[0060] S2, the laser 4 emits a high-energy laser beam, which is irradiated onto the printing base 3 to melt the powder;

[0061] Repeat the steps of S1 to evenly spread the metal powder on the printing base 3 using the powder roller 7 and S2 until the entire additive process is completed.

[0062] It should be noted that the superconducting strong magnet 1 is an electromagnet made of a low-temperature superconductor with a low critical transition temperature. The low-temperature superconducting material can generate a strong magnetic field, mainly based on its zero resistance characteristic, allowing current to flow continuously without loss. Therefore, when the superconducting material is made into a coil and an electric current is passed through liquid helium, according to Ampere's law, the flowing current will generate a magnetic field in the surrounding space. The superconducting strong magnet 1 can carry extremely high current density, and the magnetic field generated is correspondingly very strong. In addition, the complete anti-magnetism (Meissner effect) of the superconducting strong magnet 1 enables it to repel external magnetic fields, further enhancing its advantages in strong magnetic field applications.

[0063] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A device for preparing metal workpieces by laser powder bed melting technology under a strong magnetic field, characterized in that: include: Additive equipment and superconducting strong magnet, wherein the additive equipment uses laser powder bed fusion technology to prepare metal workpieces; The additive device has a printing area; The superconducting strong magnet comprises a superconducting coil and an annular liquid helium device for generating a magnetic field, wherein the annular liquid helium device has an annular cavity, wherein the annular cavity is used to accommodate liquid helium and the superconducting coil, and the annular liquid helium device is provided with a low-temperature cooling interface, wherein the low-temperature cooling interface is connected to the annular cavity, wherein the annular cavity is arranged around the printing area, and the annular liquid helium device is used to maintain the temperature in the annular cavity below 25K so as to enable the superconducting strong magnet to generate an ultra-strong magnetic field of 0.5-20T after a current is passed through it.

2. The device for preparing metal workpieces by laser powder bed melting technology under a strong magnetic field according to claim 1, characterized in that: The additive equipment includes a laser, a printing base, a powder roller, a powder box, a powder conveying assembly, a printing bin and a lifting drive device; the printing base is arranged in the printing bin, the printing area is located on the printing base, the powder box is used to accommodate metal powder, the powder conveying assembly can convey the metal powder in the powder box to the powder roller, the powder roller transports the metal powder to the printing base and spreads the metal powder evenly; the laser is used to irradiate the laid metal powder with laser to melt the powder; the printing base is located in the superconducting coil, and the lifting drive device can drive the printing base to rise and fall.

3. The device for preparing metal workpieces by laser powder bed melting technology under a strong magnetic field according to claim 2, characterized in that: The axis of the superconducting coil is parallel or perpendicular to the printing base; the current range of the superconducting coil is 0-500A, the generated magnetic induction intensity range is 0.5-20T, and the magnetic field uniformity area is greater than 75mm.

4. The device for preparing metal workpieces by laser powder bed melting technology under a strong magnetic field according to claim 3, characterized in that: The axes of the superconducting coil and the superconducting strong magnet are parallel to the printing base. Holes are respectively left at the top and bottom of the superconducting strong magnet. The top hole is used for allowing the high-energy laser emitted by the laser to irradiate into the printing area, and the bottom hole is used for allowing the telescopic rod of the lifting drive device to extend into the superconducting coil to drive the printing base to rise and fall.

5. The device for preparing metal workpieces by laser powder bed melting technology under a strong magnetic field according to claim 3, characterized in that: The axes of the superconducting coil and the superconducting strong magnet are perpendicular to the printing base. The top opening of the superconducting strong magnet is used for allowing the high-energy laser emitted by the laser to irradiate into the printing area, and the bottom opening is used for allowing the telescopic rod of the lifting drive device to extend into the superconducting coil to drive the printing base to rise and fall.

6. The device for preparing metal workpieces by laser powder bed melting technology under a strong magnetic field according to claim 3, characterized in that: The inner and outer surfaces of the annular liquid helium device are both covered with a heat insulation layer.

7. The device for preparing metal workpieces by laser powder bed melting technology under a strong magnetic field according to claim 2, characterized in that: The printing chamber is provided with air inlet and outlet holes, and an oxygen content sensor is arranged in the printing chamber.

8. The device for preparing metal workpieces by laser powder bed melting technology under a strong magnetic field according to claim 3, characterized in that: The powder roller, powder box, powder conveying assembly, printing chamber and lifting drive device are all made of aluminum alloy.

9. The device for preparing metal workpieces by laser powder bed fusion technology under a strong magnetic field according to claim 5, characterized in that: The superconducting strong magnet is connected to the printing chamber through a connector.

10. A method for preparing a metal workpiece by laser powder bed melting technology under a strong magnetic field, characterized in that: include: Preparation steps: Select metal powder suitable for laser powder bed fusion; A device for preparing a metal workpiece by laser powder bed melting technology under a strong magnetic field as described in any one of claims 1 to 9; Printing steps: S1. Pass current into the superconducting strong magnet, pass liquid helium into the annular liquid helium device to maintain it below 25K, and generate a strong magnetic field; fill the powder box with high-flowability and uniform particle size metal powder; the powder conveying component conveys the metal powder to the powder roller; and the powder roller is used to evenly spread the metal powder on the printing base; S2, the laser emits a high-energy laser beam, which shines on the printing base to melt the powder; Repeat the steps of S1, using a powder roller to evenly spread the metal powder on the printing base, and S2 until the entire additive process is completed.

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