Neodymium-iron-boron magnetic steel extrusion forming machine tool and method

Abstract

The neodymium iron boron magnetic steel extrusion forming machine tool comprises a supporting frame and a controller, a layer crack type shock wave generator is installed on the supporting frame, a forming die is installed above the layer crack type shock wave generator, the periphery of the forming die is sleeved with a space-time synchronous magnetic field assembly, and a profiling piston mechanism is installed in the forming die; the forming mold comprises a magnetofluid inner wall, a space defined by the magnetofluid inner wall is a forming cavity, the space-time synchronous magnetic field assembly coaxially sleeves the forming mold, the profiling piston mechanism comprises a piston head in sliding sleeving fit with the magnetofluid inner wall, and the bottom of the piston head is vertically, upwards and fixedly connected with a vacuumizing opening in a penetrating mode. The invention relates to the technical field of neodymium iron boron magnets. According to the method, the problem that the magnetic performance of the material cannot reach the theoretical limit due to the fact that a formed magnetic powder orientation structure is damaged by traditional mechanical pressing in the neodymium-iron-boron magnet forming process is solved.

Description

Technical Field

[0001] This invention relates to the field of neodymium iron boron magnet technology, and in particular to a neodymium iron boron magnet extrusion molding machine and method. Background Technology

[0002] Neodymium iron boron (NdFeB) magnets, as the highest-performance permanent magnet materials, are widely used in key fields such as new energy vehicles, wind power, and electronic information. As high-end equipment develops towards miniaturization and high efficiency, market demands for their magnetic properties continue to rise. However, the actual magnetic properties of products fall far short of theoretical limits. The core bottleneck lies in the synergistic contradiction between the stability of magnetic powder orientation and densification during molding.

[0003] Traditional molding processes primarily utilize mechanical pressing, such as die pressing and isostatic pressing. First, a pre-polarized magnetic field is used to orient the magnetic powder, followed by mechanical pressure for densification. However, the transmission of mechanical pressure is delayed and uneven. During loading, the magnetic powder is subjected to extrusion and shear forces, disrupting the already formed ordered orientation structure. Furthermore, the slow loading rate prevents densification from being completed within the orientation stabilization window, leading to magnetic domain disorder and limited magnetic properties. Simultaneously, traditional processes also suffer from insufficient densification, limited magnetic field control, difficulty in achieving balanced molding constraints, and susceptibility to magnetic powder oxidation.

[0004] Although the industry has attempted to improve the situation by optimizing magnetic field strength and refining molds, the core contradiction between mechanical pressing and orientation stability has not been fundamentally resolved, limiting the improvement of magnetic properties. Therefore, we have developed a neodymium iron boron magnet extrusion molding machine and method. Summary of the Invention

[0005] To address the problem that traditional mechanical pressing during the NdFeB magnet forming process destroys the already formed magnetic powder orientation structure, thus preventing the material's magnetic properties from reaching their theoretical limits, the present invention aims to provide a NdFeB magnet extrusion forming machine tool and method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a neodymium iron boron magnet extrusion molding machine tool, comprising a support frame and a controller, a split-type shock wave generator is installed on the support frame, a molding die is installed above the split-type shock wave generator, a spatiotemporal synchronous magnetic field component is sleeved on the outer periphery of the molding die, and a forming piston mechanism is installed in the molding die; The molding die includes a magnetic fluid inner wall, and the space enclosed by the magnetic fluid inner wall is a molding cavity. The spatiotemporal synchronization magnetic field component is coaxially sleeved on the outside of the molding die. The molding piston mechanism includes a piston head that is slidably sleeved with the inner wall of the magnetic fluid, and a vacuum port is fixedly connected to the bottom of the piston head vertically upward. Among them, the layered shock wave generator is used to generate planar shock waves that are vertically transmitted into the molding cavity from bottom to top; the spatiotemporal synchronous magnetic field component is used to generate a dynamic magnetic field that is synchronized with the shock wave front during the pressing process; the magnetofluid inner wall is used to provide rigid constraints when the shock wave is loaded and switch to a flexible state when unloaded; and the pressing piston mechanism is used to provide dynamic reverse pressure when the shock wave arrives.

[0007] Preferably, the support frame includes a base plate, on which a bearing platform and a gantry are fixedly mounted respectively; the split-type shock wave generator is fixedly mounted on the base plate of the support frame, the bottom of the forming mold is fixedly mounted on the bearing platform, and the forming piston mechanism is fixedly mounted on the gantry.

[0008] Preferably, the lamination shock wave generator includes a pulse drive source independently installed outside the support frame. The output end of the pulse drive source is connected to an energy transmission and focusing component. The energy transmission and focusing component is fixedly installed on a substrate directly below the forming mold. The beam emitting lens of the energy transmission and focusing component is fixedly connected to a corrugated telescopic tube. An annular plate is fixedly connected to the top port of the corrugated telescopic tube. A groove is formed at the center of the bottom of the forming mold, and a detachable modulation plate is embedded in the groove. The annular plate is fixedly installed at the port of the groove at the bottom of the forming mold by bolts. The top end face of the annular plate abuts against the bottom surface of the modulation plate. The energy transmission and focusing component is configured to apply laser pulses from the pulse drive source vertically and uniformly to the lower surface of the modulation plate in a non-contact manner to induce controllable lamination of its surface material. The modulation plate is made of high-purity oxygen-free copper.

[0009] Preferably, the inner wall of the magnetofluid includes an annular cavity with an open inner wall. A cylindrical wall is fixedly attached to the opening of the inner wall of the annular cavity. The cylindrical wall is made of polyimide film, and the inner surface of the polyimide film is coated with a low-friction and wear-resistant coating. The cavity between the cylindrical wall and the annular cavity is filled with magnetofluid. An excitation coil is fixedly sleeved on the outer wall of the annular cavity. The winding plane of the excitation coil is perpendicular to the axis of the forming cavity of the forming mold. The excitation coil is configured to generate a radial magnetic field when energized, so as to change the rheological state of the magnetofluid and realize the active control of its constraint stiffness. An annular groove is opened on the inner wall of the forming mold. The upper and lower end faces of the annular cavity are fixedly connected to the upper and lower surfaces of the annular groove. The excitation coil is located inside the annular groove. The inner wall of the cylindrical wall is flush with the inner wall of the forming mold. The outer wall of the piston head is slidably sleeved with the inner wall of the cylindrical wall.

[0010] Preferably, the spatiotemporal synchronous magnetic field assembly includes a sleeve fixedly fitted onto the outer wall of the molding die. The sleeve has an internal cavity, in which a pre-polarized steady magnetic field coil and a high-intensity pulsed magnetic field coil are fixedly fitted. A high-permeability soft magnetic shielding cylinder is fixedly fitted onto the inner wall of the annular cavity of the sleeve to isolate the magnetic field generated by the excitation coil from the magnetic field generated by the spatiotemporal synchronous magnetic field assembly. Both the pre-polarized steady magnetic field coil and the high-intensity pulsed magnetic field coil are hollow solenoids. The two ends of the pre-polarized steady magnetic field coil are connected to a cooling water supply pipe and a cooling water discharge pipe, respectively. The two ends of the high-intensity pulsed magnetic field coil are connected to a liquid nitrogen supply pipe and a liquid nitrogen discharge pipe, respectively. The pre-polarized steady magnetic field coil is fitted onto the outer periphery of the high-intensity pulsed magnetic field coil. The pre-polarized steady magnetic field coil is connected to a steady power supply to generate an axial steady magnetic field to pre-orient the magnetic powder after powder loading and before impact. The high-intensity pulsed magnetic field coil is connected to a pulsed power supply to generate an axial pulsed magnetic field synchronized with the wavefront during shock wave loading.

[0011] Preferably, the compression piston mechanism includes a cylinder fixedly installed on the side wall at the center of the top of the gantry frame. A pressure sensor is fixedly connected to the telescopic end at the bottom of the cylinder. The monitoring end of the pressure sensor is fixedly connected to the center of the top of the piston head. The bottom of the vacuum port is flush with the bottom of the piston head. The top port of the vacuum port is located above the piston head and is connected to a vacuum pump. A fixed plate is fixedly connected to the inner wall of the vacuum port. A valve block is slidably sleeved on the inner wall of the vacuum port below the fixed plate. A guide rod is fixedly connected to the top of the valve block. The guide rod slides vertically upward through the fixed plate and is fixedly connected to a baffle. The bottom of the baffle is in a stop fit with the top surface of the fixed plate. A spring is sleeved on the outer wall of the guide rod between the fixed plate and the valve block. The two ends of the spring are respectively pressed against the fixed plate and the valve block. A guide groove is opened on the inner wall of the vacuum port near the bottom port. The bottom surface of the valve block is flush with the bottom end face of the vacuum port.

[0012] A method for using a neodymium iron boron magnet extrusion molding machine includes the following steps: S1, NdFeB magnetic powder is loaded into the molding cavity of the molding die; S2, the piston head descends and fits into the inner wall of the top port of the molding die, and the air in the molding cavity of the molding die is extracted through the vacuum port; S3, after the vacuum is completed, the piston head descends to level and pre-press the top of the neodymium iron boron magnetic powder; S4, activate the spatiotemporal synchronous magnetic field component to generate an axial pre-oriented steady magnetic field in the molding cavity; at the same time, activate the magnetorheological inner wall to change the rheological state of the magnetorheological material of the magnetorheological inner wall, thereby transforming the inner wall into a rigid constraint state. S5, Shockwave Synchronous Loading: The controller synchronization coordination triggers the following events: S51, triggers a layered shock wave generator to generate a planar shock wave that is vertically transmitted from bottom to top into the molding cavity; S52, during the shock wave loading period, the control spatiotemporal synchronization magnetic field component is switched to generate an axial pulse magnetic field synchronized with the shock wave front. S53, at the instant the shock wave front reaches the bottom surface of the piston head, controls the compression piston mechanism to make the piston head perform a preset dynamic reverse pressure. S6, sequentially close the spatiotemporal synchronization magnetic field component and the magnetofluid inner wall, so that the inner wall constraint returns to a flexible state; control the piston head of the molding piston mechanism to reset and lift; then the NdFeB blank that has completed densification and orientation can be taken out from the molding cavity.

[0013] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: 1. This invention achieves initial orientation by pre-polarized steady magnetic field and final magnetic moment locking by synchronous high-intensity pulsed magnetic field at the instant of shock wave compression of powder, realizing that the orientation is determined by the densification. This process avoids harmful particle slippage and improves the magnetic powder orientation of the compact to near single crystal level, laying the foundation for the preparation of magnets with ultra-high remanence.

[0014] 2. In this invention, the shock wave applies GPa-level pressure to the powder instantaneously and as a whole, resulting in extremely high energy transfer efficiency, enabling the compact to reach high density within microseconds. At the same time, the uniform lateral boundary provided by the magnetic fluid intelligent constraint effectively avoids the pressure gradient and friction loss in traditional pressing, resulting in an extremely uniform density distribution inside the compact, which significantly improves the consistency of the product and the stability of subsequent sintering.

[0015] 3. This invention, by having the piston perform dynamic reverse pressurization at the moment the shock wave arrives, actively cancels out the harmful rarefaction waves reflected from the free surface, transforming the unloading process from severe stress to a smooth release under quasi-isostatic pressure, eliminating defects such as delamination, springback, and microcracks caused by the unloading wave, and ensuring that the high-density compact has extremely high structural integrity. Attached Figure Description

[0016] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Figure 1 This is a schematic cross-sectional view of the entire structure of the present invention; Figure 2 For the present invention Figure 1 A schematic diagram of the structure of part A; Figure 3 This is a schematic diagram of the piston head structure of the present invention; Figure 4 This is a schematic diagram of the vacuum port structure of the present invention.

[0017] In the diagram: 1. Support frame; 11. Base plate; 12. Bearing platform; 13. Gantry frame; 2. Layered shock wave generator; 21. Pulse drive source; 22. Energy transmission and focusing component; 23. Corrugated telescopic tube; 24. Annular plate; 25. Modulation plate; 3. Molding mold; 31. Magnetofluid inner wall; 311. Annular cavity; 312. Cylindrical wall; 313. Magnetofluid; 314. Excitation coil; 4. Spatiotemporal synchronous magnetic field assembly; 41. Sleeve; 42. Prepolarized steady magnetic field coil; 43. High-intensity pulsed magnetic field coil; 44. High permeability soft magnetic shielding cylinder; 5. Press-formed piston mechanism; 51. Piston head; 52. Cylinder; 53. Pressure sensor; 54. Vacuum port; 541. Fixing plate; 542. Valve block; 543. Guide rod; 544. Baffle; 545. Spring; 546. Guide groove. Detailed Implementation

[0018] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0019] Please see Figures 1 to 4 It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding and reading. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed in this invention. Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0020] Example 1: A neodymium iron boron magnet extrusion molding machine tool, wherein a support frame 1 constitutes the installation foundation and load-bearing skeleton of the entire equipment. The support frame 1 includes a horizontally arranged heavy-duty base plate 11, which serves as the installation reference surface for the entire equipment. A solid bearing platform 12 is fixed at one end of the base plate 11 for precise support and positioning of the molding die 3. A rigid gantry frame 13 spans above the base plate 11, with its crossbeam located above the bearing platform 12.

[0021] On this support frame, each functional subsystem is precisely installed and aligned. The molding piston mechanism 5 is directly fixed to the center of the crossbeam of the gantry 13. The molding die 3 is rigidly connected to the top surface of the support platform 12 via its bottom. The spatiotemporal synchronization magnetic field assembly 4 is coaxially fitted onto the outside of the molding die 3. The main body of the split-wave shock wave generator 2 is mounted on the base plate 11, with its energy output end precisely aligned with the geometric center of the bottom of the molding die 3. All electrical wiring, control signal lines, and cooling and vacuum piping are rationally arranged along the support frame 1. A central controller is connected to the drive units and sensor signals of all subsystems, responsible for the logical decision-making and femtosecond-level synchronous timing control of the entire process.

[0022] The spallation shock wave generator 2 is responsible for generating the high-quality planar shock wave required for densification. Its pulse drive source 21 is a high-power nanosecond pulsed laser, typically placed independently to isolate vibration. The energy transfer and focusing component 22 is mounted on the substrate 11, which collimates and focuses the laser beam. The outlet of this focusing component is connected to an annular plate 24 via a section of corrugated metal telescopic tube 23. This design allows for minute centering adjustments and isolates vibration. A circular groove is machined at the center of the bottom of the molding die 3, into which a replaceable modulation plate 25 made of high-purity oxygen-free copper is embedded. The aforementioned annular plate 24 is tightly fixed to the groove port plane at the bottom of the die with bolts, ensuring that its top surface forms a full-plane tight contact with the lower surface of the modulation plate 25. The laser pulse ultimately passes through the light-transmitting hole in the center of the annular plate 24, acting vertically and uniformly on the lower surface of the modulation plate 25, inducing a spallation effect and generating high-speed flying fragments that impact the die, thereby exciting a planar shock wave in the powder.

[0023] The core innovation of the molding die 3 lies in its magnetofluid inner wall 31, which possesses active variable stiffness capability. The die body is a cylindrical structure with an annular groove machined into its inner wall. An independent magnetofluid inner wall module 31 is prefabricated and embedded in this groove. This module includes a non-magnetic annular cavity 311, the outer wall of which is tightly wound with an excitation coil 314, the winding plane of which is strictly perpendicular to the die axis. The inner opening of the annular cavity 311 is covered and sealed with a flexible cylindrical wall 312, which in this example is made of polyimide film and coated with a low-friction, wear-resistant coating on its inner side. The sealed cavity formed between the annular cavity 311 and the flexible cylindrical wall 312 is filled with magnetofluid 313 with high magnetic saturation intensity. After the entire module is installed, the inner surface of the flexible cylindrical wall 312 is smoothly flush with the inner walls of the upper and lower sections of the die, together forming the final molding cavity. When a strong instantaneous current is applied to the excitation coil 314, the resulting radial magnetic field causes a dramatic change in the rheological state of the magnetofluid 313, which becomes solidified, thus giving the mold sidewall a rigid constraint state. After the power is cut off, the magnetic field disappears, the magnetofluid 313 returns to the liquid state, and the sidewall returns to its flexible state.

[0024] The spatiotemporal synchronization magnetic field component 4 is used to provide a dynamic orientation magnetic field that is precisely synchronized with the shock wave. A sleeve 41 made of insulating material is fixedly fitted onto the outside of the molding die 3. A high-permeability soft magnetic shielding cylinder 44 is tightly attached to the inner wall of the sleeve 41 to isolate the internal and external magnetic fields. Inside the high-permeability soft magnetic shielding cylinder 44, two independent hollow solenoids are coaxially nested: a high-intensity pulsed magnetic field coil 43 on the inner side and a pre-polarized steady magnetic field coil 42 on the outer side. The pre-polarized steady magnetic field coil 42 is connected to a conventional cooling water circuit for heat dissipation during long-term operation; the high-intensity pulsed magnetic field coil 43 is connected to a liquid nitrogen cooling pipeline to cope with the extreme thermal load generated by instantaneous ultra-high current. In terms of operating sequence, the pre-polarized steady magnetic field coil 42 is turned on first to pre-orient the powder; at the instant the shock wave is triggered, the controller turns it off and synchronously starts the high-intensity pulsed magnetic field coil 43, generating a high-intensity pulsed magnetic field that spatiotemporally follows the shock wave front to achieve final magnetic moment locking at the instant the powder is compressed.

[0025] The molding piston mechanism 5 integrates cavity sealing, vacuuming, and dynamic pressure management functions. A high-frequency response servo cylinder 52 is fixed to the crossbeam of the gantry 13. A pressure sensor 53 is connected to the end of the piston rod of the cylinder 52, and the lower part of the pressure sensor 53 is rigidly connected to the piston head 51. The outer diameter of the piston head 51 is precisely slidingly fitted with the inner diameter of the cylindrical wall 312 of the magnetofluidic inner wall 31. A key innovative design is the self-sealing vacuum port 54 that runs through the piston head 51. The bottom of the vacuum port 54 is flush with the bottom surface of the piston head 51, and a fixed plate 541 is provided inside it. Below the fixed plate 541 is a sliding valve block 542. The valve block 542 is connected to the top baffle 544 through the guide rod 543, and a downward force is applied by the spring 545 to seal the bottom port under normal conditions. A guide groove 546 is opened on the lower side wall of the vacuum port 54. The piston head 51 descends and fits into the inner wall at the top port of the molding mold 3. The vacuum pump extracts the air from the molding cavity of the molding mold 3 through the vacuum port 54. At this time, the valve block 542 rises and the guide groove 546 opens, allowing the vacuum pump to extract air. After the vacuum is completed, the vacuum pump reverses the air flow, and the valve block 542 falls back and closes under the action of the spring 545. At the same time, the air pressure presses against the valve block 542. Then the piston head 51 descends to level and pre-press the top of the neodymium iron boron magnetic powder.

[0026] During the shock wave loading process, the core function of the piston head 51 is to act as a momentum trap: at the instant the shock wave front reaches its bottom surface, the controller drives the cylinder 52 to execute a specific dynamic pressure curve based on the feedback from the pressure sensor 53 and the preset model, applying reverse dynamic pressure to counteract the unloading wave and protect the integrity of the compact.

[0027] Example 2: The core of this invention lies in its radical innovation of the traditional physical process of slow orientation followed by mechanical pressing of NdFeB magnetic powder. It creatively introduces instantaneous densification using shock waves, achieving femtosecond-level synchronization with dynamic magnetic field orientation, intelligent constraint, and active unloading in space and time. Its working principle is not a simple superposition of the functions of each subsystem, but a dynamic closed-loop process of precise coordination and interlocking of multiple physical fields, aiming to resolve the fundamental contradiction between densification and orientation in one go.

[0028] A method for using a neodymium iron boron magnet extrusion molding machine includes the following steps; S1, neodymium iron boron magnetic powder is loaded into the molding cavity of the molding mold 3.

[0029] S2, the controller commands the high-frequency servo cylinder 52 of the forming piston mechanism 5 to move, driving the piston head 51 to descend and fit into the inner wall at the top port of the forming mold 3. The controller starts the vacuum pump connected to the vacuum port 54 on the piston head 51. At this time, the valve block 542 rises under the action of negative pressure, the guide groove 546 opens, and the air in the forming cavity of the forming mold 3 is continuously extracted through the guide groove 546 at the bottom of the vacuum port 54.

[0030] S3, after vacuuming is completed, the vacuum pump reverses its direction, and valve block 542 falls back and closes under the action of spring 545. At the same time, the air pressure presses against valve block 542, completing self-sealing. To obtain a more uniform initial powder bed density, the controller can further instruct cylinder 52 to apply a small, controllable pressure to piston head 51 to level and slightly pre-compact the top of the powder. The pressure in this step is much lower than the subsequent shock wave pressure and is only for process optimization.

[0031] S4, Applying a pre-orientation magnetic field: The controller activates the pre-polarized steady magnetic field coil 42 in the spatiotemporal synchronization magnetic field component 4; the coil is supplied with a steady current, generating a uniform axial steady magnetic field with a direction parallel to the cavity axis throughout the entire space of the molding cavity, with an intensity of 0.5-1.2T; under the action of this magnetic field, the magnetic moments of the sheet-like particles of neodymium iron boron magnetic powder rotate, and they are initially aligned along the axial direction, completing the pre-orientation; Activating rigid constraints: Simultaneously, the controller outputs a strong current pulse to the excitation coil 314 of the inner wall 31 of the magnetofluid; the radial magnetic field generated by the coil penetrates the annular cavity 311, causing a sudden change in the rheological state of the magnetofluid 313 inside: the magnetic particles instantly arrange themselves into chains, resulting in a sharp increase in the apparent viscosity or shear stress of the magnetofluid by several orders of magnitude, and rapid solidification on a macroscopic scale. This state is transmitted through the flexible cylindrical wall 312, transforming the entire mold sidewall from a passive support to an active, high-rigidity rigid constraint, firmly confining the powder within a defined geometric space; S5, Shockwave Synchronous Loading: The controller synchronization coordination triggers the following events: S51, triggering shock wave densification: The controller sends a trigger signal to the pulse drive source 21 of the split shock wave generator 2. The high-energy laser pulse passes through the energy transmission and focusing component 22 and the corrugated telescopic tube 23 and acts vertically on the lower surface of the modulation plate 25, inducing its splitting to generate a high-speed flying piece. The flying piece hits the bottom of the mold, thereby generating a high-intensity planar shock wave with excellent flatness that propagates from bottom to top in the powder. This shock wave, as the only active force source, causes the powder particles to undergo extremely high pressure and plastic deformation within the microsecond range, achieving instantaneous and overall densification. S52, Switch to Synchronous Pulsed Magnetic Field: At the same moment as the shock wave trigger signal is emitted or at the precise delay calculated according to the shock wave propagation model, the controller performs magnetic field switching: cuts off the power supply to the pre-polarized steady magnetic field coil 42 and simultaneously starts the high-intensity pulsed magnetic field coil 43; under the protection of liquid nitrogen cooling, this coil releases an axial pulsed magnetic field with greater intensity and shorter pulse width; the activation of this magnetic field is synchronized with the propagation position of the shock wave front in time and space; its core function is: at the moment when the powder particles are compressed to the densest point by the shock wave and the internal frictional resistance is minimal, the ultimate orientation force is applied to freeze the magnetic moment of the particles on the final ideal orientation, thus completing the time and space synchronization of orientation and densification; S53, Activate Momentum Sink Back Pressure: The controller monitors the shock wave propagation status in real time through model calculation or a transient pressure sensor installed at the bottom of the mold. When the shock wave front is predicted or detected to reach the bottom surface of the piston head 51, the controller immediately commands the high-frequency response servo cylinder 52 of the forming piston mechanism 5. Based on the preset dynamic pressure curve model, the cylinder 52 drives the piston head 51 to perform a rapid and precise reverse pressurization action. The purpose of this action is not pre-pressurization, but to act as an active momentum sink to generate a reverse pressure wave to actively counteract the rarefaction wave reflected from the free surface, thereby suppressing the springback, delamination, or internal damage of the compact and ensuring high integrity. S6, sequentially close the spatiotemporal synchronization magnetic field component 4 and the magnetofluid inner wall 31, so that the inner wall constraint returns to a flexible state; control the piston head 51 of the molding piston mechanism 5 to reset and lift; then the NdFeB blank that has completed densification and orientation can be taken out from the molding cavity.

[0032] To further explain, the synergistic working principle of the components of the spallation shock wave generator 2 is an energy transfer chain that precisely converts high-energy pulses into high-quality planar shock waves. Its core lies in the efficient conversion of electrical or light energy into mechanical kinetic energy through a controlled "split-wave" effect. The working principles of each component are as follows: Pulse drive source 21: As the energy starting point of the system, its core function is to instantaneously release its stored electrical or optical energy in the form of extremely high power within a very short time, on the order of nanoseconds to microseconds, after receiving a trigger signal from the controller. If it is a pulsed laser, it generates high-energy laser pulses; if it is an electrical pulse source such as a Marx generator, it generates high-voltage, high-current electrical pulses. It provides the necessary instantaneous high-power input for the entire shock wave generation process.

[0033] Energy transfer and focusing component 22: Responsible for receiving the raw high-energy pulse from the drive source 21 and directing and spatially shaping it. For the laser path, it focuses the laser beam onto a specific area on the back of the modulation plate 25 through a lens group, concentrating the energy to increase power density. For the electrical pulse path, it conducts the current pulse to the target area with minimal loss and waveform distortion through a coaxial transmission line. The aim is to ensure that energy is delivered to the interface with optimal spatial distribution and minimal loss.

[0034] Corrugated expansion tube 23 and annular plate 24: This is a mechanical and sealing coupling module. The flexible structure of the corrugated expansion tube 23 allows for slight expansion and contraction and offset in its axial direction to compensate for unavoidable alignment errors during equipment manufacturing and assembly, and to isolate equipment vibration. The annular plate 24 is fixed to the bottom of the mold, with a light-transmitting window or electrode interface at its center. Its top surface is precisely fitted to the back of the modulation plate 25, forming a sealed and flat mechanical coupling interface. Its core function is to ensure that pulse energy can pass through without damage and to rigidly transfer the mechanical effects of subsequent delamination to the mold, while maintaining a vacuum or specific atmosphere environment in the working chamber.

[0035] The modulation plate 25 is an energy-momentum converter, a key material carrier for achieving the "stripping" effect, typically made of ductile metals such as high-purity oxygen-free copper. Its working principle consists of three stages: Energy deposition: Extremely high power density pulsed energy lasers or currents from upstream are absorbed on its back side in a very short time, causing the surface material to vaporize and ionize instantly, forming high-temperature and high-pressure plasma.

[0036] Stress wave generation and spalling: The plasma expands rapidly, generating a high-intensity compressive stress wave that propagates inward within the modulation plate 25. When this wave reaches the front surface of the modulation plate 25, i.e., the free surface in contact with the mold, it is reflected. The reflected wave superimposes with the subsequent compressive wave, forming extremely strong tensile stress in the region near the front surface.

[0037] Flake formation: When the tensile stress exceeds the dynamic tensile strength of the material, a layer of material on the front side of the modulation plate 25 will be "peeled off" as a complete, high-speed solid sheet. This phenomenon is called delamination.

[0038] Overall collaborative workflow: Ultimately, the flying blade, accelerated to thousands of meters per second, acts as a perfect "planar piston," violently impacting the mold base tightly attached to it. This impact generates a shock wave with extremely high flatness, a very steep leading edge, and controllable intensity within the mold and the powder inside. This shock wave propagates vertically into the powder bed, becoming the sole active force source for achieving instantaneous overall densification of the powder.

[0039] In short, the working principle of the generator is as follows: the drive source 21 provides instantaneous high energy → the transmission focusing component 22 guides and concentrates the energy → the energy is deposited on the back of the modulation plate 25 to induce stress waves → the stress waves are reflected on the front of the modulation plate 25, causing delamination and generating high-speed flying pieces → the flying pieces hit the mold and are converted into planar shock waves.

[0040] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A neodymium-iron-boron magnetic steel extrusion forming machine tool comprising a support frame (1) and a controller, characterized in that: The support frame (1) is provided with a layer cracking shock wave generator (2), the layer cracking shock wave generator (2) is provided with a forming die (3) above, the forming die (3) is provided with a space-time synchronous magnetic field assembly (4) outside, and the forming die (3) is provided with a pressure type piston mechanism (5); The forming die (3) comprises a magnetic fluid inner wall (31), the space formed by the magnetic fluid inner wall (31) is a forming cavity, the space-time synchronous magnetic field assembly (4) is coaxially sleeved outside the forming die (3), and the pressure type piston mechanism (5) comprises a piston head (51) which is slidably connected with the inner wall of the magnetic fluid inner wall (31); the bottom of the piston head (51) is vertically upwardly fixed and penetrates the vacuum port (54); The layer cracking shock wave generator (2) is used for generating a plane shock wave vertically transmitted into the forming cavity from bottom to top; the space-time synchronous magnetic field assembly (4) is used for generating a dynamic magnetic field synchronous with the shock wave front during the pressing process; the magnetic fluid inner wall (31) is used for providing rigid constraint when the shock wave is loaded and switching to a flexible state when the shock wave is unloaded; and the pressure type piston mechanism (5) is used for providing dynamic reverse pressure when the shock wave arrives.

2. The neodymium-iron-boron magnet extrusion machine of claim 1, wherein: The support frame (1) comprises a base plate (11), the base plate (11) is respectively provided with a bearing table (12) and a gantry (13) fixedly installed thereon; the layer cracking shock wave generator (2) is fixedly installed on the base plate (11) of the support frame (1), the bottom of the forming die (3) is fixedly installed on the bearing table (12), and the pressure type piston mechanism (5) is fixedly installed on the gantry (13).

3. The neodymium-iron-boron magnet extrusion machine of claim 2, wherein: The layer cracking shock wave generator (2) comprises a pulse driving source (21) independently installed outside the support frame (1), the output end of the pulse driving source (21) is connected with an energy transmission and focusing component (22), the energy transmission and focusing component (22) is fixedly installed on the base plate (11) below the forming die (3), the light beam emitting lens of the energy transmission and focusing component (22) is fixedly connected with a corrugated expansion pipe (23), the top port of the corrugated expansion pipe (23) is fixedly connected with a ring plate (24), a recess is formed in the center of the bottom of the forming die (3), and a detachable modulation plate (25) is embedded in the recess; the ring plate (24) is fixedly installed at the port of the recess in the bottom of the forming die (3) through bolts, the end surface of the top of the ring plate (24) abuts against the bottom surface of the modulation plate (25), the energy transmission and focusing component (22) is configured to vertically and uniformly act on the lower surface of the modulation plate (25) in a non-contact manner to induce controllable layer cracking of the surface layer material of the modulation plate (25), and the modulation plate (25) is made of high-purity oxygen-free copper.

4. The neodymium-iron-boron magnet extrusion machine of claim 1, wherein: The inner wall of the magnetic fluid (31) comprises an annular cavity (311) with an open inner side wall, the open inner side wall of the annular cavity (311) is fixedly attached with a cylindrical wall (312), the material of the cylindrical wall (312) is polyimide film, the inner surface of the polyimide film is coated with a low-friction wear-resistant coating, the cavity between the cylindrical wall (312) and the annular cavity (311) is filled with magnetic fluid (313), the outer wall of the annular cavity (311) is fixedly sleeved with an excitation coil (314), the winding plane of the excitation coil (314) is perpendicular to the axis of the forming cavity of the forming die (3), the excitation coil (314) is configured to generate a radial magnetic field when energized to change the rheological state of the magnetic fluid (313) to achieve active regulation of its constraint stiffness; the inner wall of the forming die (3) is provided with an annular groove, the upper and lower end faces of the annular cavity (311) are fixedly connected with the upper and lower faces of the annular groove, the excitation coil (314) is located inside the annular groove, the inner wall of the cylindrical wall (312) is flush with the inner wall of the forming die (3), and the outer wall of the piston head (51) is in sliding sleeve connection with the inner wall of the cylindrical wall (312).

5. The neodymium-iron-boron magnet extrusion machine of claim 1, wherein: The space-time synchronous magnetic field assembly (4) comprises a sleeve (41) fixedly sleeved on the outer wall of the forming die (3), the inside of the sleeve (41) is provided with a cavity, and the pre-polarization stable magnetic field coil (42) and the high-intensity pulsed magnetic field coil (43) are fixedly sleeved in the cavity, the inner wall of the annular cavity of the sleeve (41) is fixedly sleeved with a high-magnetic-conductivity soft magnetic shielding cylinder (44) for isolating the magnetic field generated by the excitation coil (314) from the magnetic field generated by the space-time synchronous magnetic field assembly (4); the pre-polarization stable magnetic field coil (42) and the high-intensity pulsed magnetic field coil (43) are both provided with a hollow solenoid, the two ends of the pre-polarization stable magnetic field coil (42) are respectively connected with a cooling water supply pipeline and a cooling water discharge pipeline, the two ends of the high-intensity pulsed magnetic field coil (43) are respectively connected with a liquid nitrogen supply pipeline and a liquid nitrogen discharge pipeline, the pre-polarization stable magnetic field coil (42) is sleeved on the outer periphery of the high-intensity pulsed magnetic field coil (43), the pre-polarization stable magnetic field coil (42) is connected with a stable power supply for generating an axial stable magnetic field for pre-orientation of the magnetic powder before powder loading and before impact; the high-intensity pulsed magnetic field coil (43) is connected with a pulse power supply for generating an axial pulsed magnetic field synchronized with the wave front during shock wave loading.

6. The neodymium-iron-boron magnet extrusion machine of claim 1, wherein: The profiled piston mechanism (5) comprises a cylinder (52) fixedly installed on the side wall of the top center of the portal frame (13), the bottom of the cylinder (52) is fixedly connected with a pressure sensor (53), the monitoring end of the pressure sensor (53) is fixedly connected with the top center of the piston head (51), the bottom of the vacuum extraction port (54) is flush with the bottom of the piston head (51), the top port of the vacuum extraction port (54) is located above the piston head (51), and the top port is connected with a vacuum pump; the inner wall of the vacuum extraction port (54) is fixedly connected with a fixed plate (541), the inner wall of the vacuum extraction port (54) below the fixed plate (541) is slidably sleeved with a valve block (542), the top of the valve block (542) is fixedly connected with a guide rod (543), the guide rod (543) vertically slides through the fixed plate (541), and the top of the guide rod (543) is fixedly connected with a baffle (544); the bottom of the baffle (544) is abuttingly connected with the top surface of the fixed plate (541), the outer wall of the guide rod (543) between the fixed plate (541) and the valve block (542) is sleeved with a spring (545), the two ends of the spring (545) are abuttingly connected with the fixed plate (541) and the valve block (542) respectively, the inner wall of the vacuum extraction port (54) near the bottom port is provided with a flow guide groove (546), and the bottom surface of the valve block (542) is flush with the bottom end surface of the vacuum extraction port (54).

7. A method of using a neodymium-iron-boron magnetic steel extrusion press machine tool, characterized by, The neodymium iron boron magnetic steel extrusion forming machine tool of any one of claims 1 to 6 comprises the following steps: S1, the neodymium iron boron magnetic powder is loaded into the forming cavity of the forming die (3); S2, the piston head (51) is lowered into the inner wall of the top port of the forming die (3), and the air in the forming cavity of the forming die (3) is extracted through the vacuum extraction port (54); S3, after the vacuum extraction is completed, the piston head (51) is lowered, and the top of the neodymium iron boron magnetic powder is flattened and pre-pressed; S4, the time-space synchronous magnetic field assembly (4) is started, so that an axial pre-oriented steady magnetic field is generated in the forming cavity; at the same time, the magnetic fluid inner wall (31) is started, so that the magneto-rheological material of the magnetic fluid inner wall (31) changes the rheological state, so that the inner wall changes to a rigid constraint state; S5, shock wave synchronous loading: The controller synchronously coordinates the following events: S51, the layer cracking shock wave generator (2) is triggered to generate a plane shock wave vertically transmitted into the forming cavity from bottom to top; S52, during the shock wave loading, the time-space synchronous magnetic field assembly (4) is controlled to switch to generate an axial pulse magnetic field synchronous with the shock wave front; S53, at the moment when the shock wave front reaches the bottom surface of the piston head (51), the profiled piston mechanism (5) is controlled to make the piston head (51) perform a preset dynamic reverse pressurization; S6, turn off the space-time synchronization magnetic field assembly (4) and the magnetic fluid inner wall (31) in turn, so that the inner wall is in a flexible state; control the piston head (51) of the compression piston mechanism (5) to reset and lift; the finished compactification and orientation of the neodymium iron boron compression blank can be taken out from the forming cavity.

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