Graphite box for sintering neodymium iron boron magnetic steel and method for preventing magnetic steel material from being bent

Abstract

The invention discloses a graphite box for neodymium iron boron magnetic steel sintering and a method for preventing a magnetic steel material from being bent, the graphite box for neodymium iron boron magnetic steel sintering comprises a box body, the top of the box body is open, and a plurality of long partition plates are evenly and detachably arranged in the box body in the width direction of the box body at intervals so as to divide the box body into a plurality of first material cavities; a first air hole is formed in the long partition plate; and the cover plate is movably inserted into the open end of the box body. Compared with the prior art, the novel graphite box has the beneficial effects that in order to solve the problem of position deviation of magnetic steel caused by abnormal movement of the graphite box in the transfer process, the long partition plates are adopted in the novel graphite box to form the appropriate stacking material cavity, convenience and high efficiency in the stacking process are improved, independence and the exhaust effect of the stacking material cavity are guaranteed, and the magnetic steel stacking efficiency is improved. The problem of adhesion of the sintered magnetic steel is fundamentally solved, and meanwhile, the risk of material bending can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of rare earth permanent magnet materials, and more specifically, to a graphite box for sintering NdFeB magnets and a method for preventing magnet material from bending. Background Art

[0002] As the third generation of rare earth permanent magnet materials, sintered NdFeB is known as the "king of magnets" because of its extremely excellent magnetic properties. It is widely used in high-tech fields such as new energy vehicle drive motors, wind power system generators, 3C products and intelligent manufacturing. With the continuous improvement and perfection of the performance of NdFeB permanent magnet materials, the application field continues to expand, and higher requirements are also put forward for the magnetic properties of sintered NdFeB magnets. Grain boundary diffusion technology is increasingly used in the preparation of high-performance sintered NdFeB materials. Its advantage is that while the intrinsic coercivity of the material is greatly improved, the remanence is almost not reduced, and the use of heavy rare earth is greatly reduced, which not only reduces production costs, but also saves resources. In recent years, common grain boundary diffusion technologies mainly include roller coating, screen printing and spraying. Although each has its own advantages, the magnetic steel coated by these methods needs to be stacked in a graphite box whether it is stacked flat or vertically, and then it must go through several transfer processes before it can be sent to the sintering furnace for heat treatment. Several rows of magnet groups are usually stacked in a graphite box, and there are usually gaps between the ends of adjacent magnet groups. The graphite box will inevitably be affected by vibration and impact during transportation, so it is easy for the position of the magnets in the box to shift, especially there is a risk of contact between the ends of adjacent magnet groups. When the ends of adjacent magnet groups are in contact, adhesion is likely to occur during the sintering process. Therefore, using existing graphite boxes to stack magnets and transport them to the sintering furnace for sintering will greatly increase the possibility of magnet adhesion after sintering, causing unnecessary economic losses.

[0003] In addition, the grain boundary diffusion of sintered NdFeB can be divided into oriented diffusion and non-oriented diffusion. Most high coercivity products are oriented diffusion, that is, the NdFeB blank is oriented and formed in the direction of grain boundary diffusion, which is processed into thin sheets of different specifications. However, some products are limited by customer requirements, blank specifications and processing dimensions, and non-oriented diffusion is required. The same ordinary graphite box and row stacking method as oriented diffusion are used for them, especially for products with a magnetic steel thickness of less than 5mm. After sintering, the material is extremely prone to bending and cannot be saved, resulting in batch scrapping of products. Summary of the invention

[0004] One object of the present invention is to solve at least the above-mentioned problems and to provide a graphite box for sintering NdFeB magnets. In order to solve the problem of positional displacement of the magnets due to the movement of the graphite box during transportation, partitions of different specifications are combined in the graphite box to form a suitable stacking cavity, which not only increases the convenience and efficiency of the stacking process, but also ensures the independence of the stacking cavities and the exhaust effect of the stacking cavities, thereby fundamentally solving the problem of adhesion of the magnets after sintering. At the same time, the present invention also provides a method for preventing bending of magnet materials. Stacking magnets with the graphite box of the present invention can effectively reduce the risk of bending of the magnet materials and reduce the economic losses caused by bending of the magnet materials.

[0005] In order to achieve these purposes and other advantages according to the present invention, a graphite box for sintering NdFeB magnets is provided, comprising: A box body, with an open top, wherein a plurality of long partitions are evenly spaced and detachably provided in the box body along the width direction thereof, so as to divide the box body into a plurality of first material chambers, and the long partitions are provided with first air holes; A cover plate is movably inserted at the open end of the box body.

[0006] Preferably, a plurality of sub-partitions are evenly spaced and detachably provided in the first material cavity along the length direction of the box body to divide the first material cavity into a plurality of second material cavities, and second air holes are provided on the sub-partitions.

[0007] Preferably, a plurality of first grooves corresponding to each other and having opposite notches are vertically opened on both side walls in the width direction of the box body, and the plurality of first grooves on each side wall are spaced apart along the width direction of the box body, and the top and bottom of the first grooves are open, and the plurality of pairs of first grooves correspond to a plurality of long partitions one by one, and the two ends of the long partitions are respectively matched with the corresponding pair of first grooves, so that the long partitions can be inserted into the corresponding pair of first grooves from the top of the corresponding pair of first grooves.

[0008] Preferably, a plurality of second grooves corresponding to each other and having opposite notches are vertically opened on both side walls in the length direction of the box body, the plurality of second grooves on each side wall are evenly spaced along the length direction of the box body, and the top and bottom of the second grooves are open; the plurality of sub-partitions in each first material cavity correspond to each other, the plurality of sub-partitions corresponding to each other in the plurality of first material cavities are sequentially connected and integrally formed to form a short partition, the plurality of short partitions correspond to the plurality of pairs of second grooves one by one, and the two ends of the short partitions are respectively adapted to the corresponding pair of second grooves; Among them, a plurality of first card slots are vertically opened at the bottom of the long partition, and the plurality of first card slots are spaced along the length direction of the long partition, and the two ends of the first card slots perpendicular to the length direction of the long partition are open; a plurality of second card slots are vertically opened at the top of the short partition, and the plurality of second card slots are spaced along the length direction of the short partition, and the two ends of the second card slots are open perpendicular to the length direction of the short partition; the side wall of the long partition between the bottom of the first card slot and the top of the long partition is adapted to the second card slot, and the side wall of the short partition between the bottom of the second card slot and the bottom of the short partition is adapted to the first card slot.

[0009] Preferably, a card end is protruding from the bottom of the cover plate, the card end is square, and the length and width of the card end are slightly smaller than the opening of the box body, so that the cover plate can be plugged into the box body.

[0010] Preferably, a sealing ring is sleeved on the card end to enable the cover plate to be sealed and plugged with the box body; a suction port is opened on the side wall of the box body, and the suction port is movably connected to the dust collection device; Among them, when the box body needs to be cleaned, the sealing ring is put on the card end and the cover plate is sealed and plugged into the box body, and then the suction port is connected to the dust suction device, and the dust suction device cleans the inside of the box body; when the magnet needs to be sintered, the sealing ring is removed, the magnet is stacked into the box body, the cover plate is covered, and it can be transported to the sintering furnace.

[0011] Preferably, the bottom end of the first air hole is open to communicate with the bottom of the box body, so that when the box body is cleaned, impurities inside the box body flow to the dust suction port.

[0012] Preferably, each first material chamber side wall is provided with a through hole, the through hole is connected with a spiral tube, the spiral tube is located outside the box body, and an abutting screw is screwed onto the spiral tube; one of the through holes forms the suction port.

[0013] The method for preventing the bending of the magnetic steel material is to place the non-oriented diffused magnetic steel in the graphite box for sintering the NdFeB magnetic steel, and then transport and sinter it.

[0014] Preferably, the specific steps of placing the non-oriented diffused magnetic steel code in the graphite box for sintering the NdFeB magnetic steel are as follows: S1. According to the required specifications and dimensions of the non-oriented diffused magnetic steel, the number of short partitions and long partitions is adaptively selected to make the size of the stacking cavity match the required specifications and dimensions of the non-oriented diffused magnetic steel; the stacking cavity is the first cavity or the second cavity; S2. For each stacking cavity, vertically stack a plurality of non-oriented diffused magnetic steels in the stacking cavity until the stacking cavity is full; S3, repeat step S2 until all the stacking cavities are filled with non-oriented diffused magnetic steel, and then cover the cover plate.

[0015] Preferably, the graphite box is made by graphitizing a long carbon product, wherein the long carbon product is a combination of Russian larch, yellow pine and red eucalyptus, with a mass ratio of 1:2~3:2~3. The long carbon product is compressed into a cylindrical shape, heated to 2700°C with an electric current, maintained for 3~5 hours, then heated to 2850°C, maintained for 3~5 hours, and then maintained between 2800°C~2850°C, maintained for 4~6 hours, and then cooled at a rate of 3~4°C / minute. When cooled to 1500°C~1700°C, it is maintained for 10~20 hours.

[0016] The graphite box manufactured in this way is more resistant to high temperatures, making the NdFeB magnets placed in it more stable and will not bend or deform due to contact with the graphite box.

[0017] The method for preventing the bending of the magnetic steel material is to place the non-oriented diffused magnetic steel in the graphite box for sintering the NdFeB magnetic steel, and then transport and sinter it.

[0018] The present invention has at least the following beneficial effects: First, the present invention provides a graphite box for sintering NdFeB magnets. To solve the problem of positional displacement of the magnets due to the movement of the graphite box during transportation, partitions of different specifications are combined in the new graphite box to form a suitable stacking cavity, which not only increases the convenience and efficiency of the stacking process, but also ensures the independence of the partitions and the exhaust effect of the stacking cavity, fundamentally solving the problem of adhesion of the magnets after sintering.

[0019] Second, the present invention provides a method for preventing bending of magnetic steel materials. Compared with the traditional method of "stacking several rows of long strip-shaped magnetic steel groups in an ordinary graphite box so that the position cannot be accurately fixed", the present method can effectively improve the external force from unfair directions received by non-oriented magnetic steels due to position bias, and then combined with the new graphite box structure, the traditional long row of magnetic steel groups is divided into multiple small magnetic steel groups, so that the multiple small magnetic steel groups are independent in different stacking cavities, further reducing the mutual influence between the magnetic steels in the entire graphite box, and effectively reducing the risk of material bending. The method of the present invention is applicable to all non-oriented diffused magnetic steels.

[0020] Thirdly, the present invention provides a sealing ring and a suction port. When the box body needs to be cleaned, the sealing ring is sleeved on the card end and the cover plate is sealed and plugged into the box body. Then the suction port is connected to the dust suction device, and the dust suction device cleans the inside of the box body. When the magnetic steel needs to be sintered, the sealing ring is removed, the magnetic steel is stacked into the box body, the cover plate is covered, and it can be transported to the sintering furnace. As a whole, it is convenient to clean the isolation powder and other impurities inside the box body, keep the inside of the box body clean, and facilitate the next sintering.

[0021] Fourth, the present invention provides a structure for maintaining the vertical state of the magnetic steel by setting a through hole, a spiral tube and a screw rod, which can keep the magnetic steel in a vertical state as much as possible during sintering in the sintering furnace, and further reduce the curvature of the magnetic steel.

[0022] Fifth, the present invention further reduces the material curvature of the magnetic steel by manufacturing a graphite box that is more resistant to high temperatures.

[0023] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a structural schematic diagram of a graphite box for sintering NdFeB magnets according to one of the technical solutions of the present invention (a structural diagram of a combination of a long partition and a short partition); Figure 2 This is a schematic diagram of the structure of a graphite box for sintering NdFeB magnets according to one of the technical solutions of the present invention (a structural diagram containing only a long partition); Figure 3 This is a schematic diagram of the structure of the box body described in one of the technical solutions of the present invention; Figure 4 This is a schematic diagram of the structure of the cover plate described in one of the technical solutions of the present invention; Figure 5 This is a schematic diagram of the structure of a graphite box for sintering NdFeB magnets during vacuum sintering according to one of the technical solutions of the present invention; Figure 6 This is a schematic diagram of the structure of the graphite box for sintering NdFeB magnets described in one of the technical solutions of the present invention when cleaning the inside of the box.

[0025] Description of the drawings; 1-box body; 2-first side wall; 3-second side wall; 4-first material cavity; 5-second material cavity; 6-cover plate; 601-card end; 7-first groove; 8-second groove; 9-long partition; 10-short partition; 11-first air hole; 12-second air hole; 13-first card slot; 14-second card slot; 15-screw tube; 16-screw; 17-sealing ring; 18-through hole; 19-magnetic steel. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0027] It should be understood that the terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

[0028] like Figure 1-6As shown, the present invention provides a graphite box for sintering NdFeB magnets, comprising: A box body 1, with an open top, is provided with a plurality of long partitions 9 evenly spaced and detachable along the width direction of the box body 1 to divide the box body 1 into a plurality of first material chambers 4, and the long partitions 9 are provided with first air holes 11; A cover plate 6, which is movably inserted at the open end of the box body 1; In the above technical scheme, the box body 1 is a square trough body with an open top, and a cover plate 6 is movably inserted on the open end of the box body 1; a plurality of long partitions 9 are arranged in the box body 1, and the long partitions 9 are arranged vertically, and the plurality of long partitions 9 are arranged at intervals along the length direction of the box body 1, and the long partitions 9 are vertically connected to the two side walls (hereinafter referred to as the first side walls 2) of the width direction of the box body 1, and the two ends of the long partitions 9 are detachably connected to the adjacent first side walls 2, and the detachable connection method can be snap-on, and the plurality of long partitions 9 divide the box body 1 into a plurality of first material chambers 4, that is, the plurality of first material chambers 4 are arranged in sequence along the width direction of the box body 1; wherein, the long partitions 9 are provided with first air holes 11, and the materials of the box body 1, the long partitions 9 and the cover plate 6 are all graphite; In this technical solution, during use, the number of long partitions 9 is adaptively selected according to the size of the magnetic steel to be stacked, so that the size of the first material cavity 4 separated by the long partition 9 is suitable for stacking the magnetic steel, and then the magnetic steel to be stacked is vertically stacked in the first material cavity 4 in sequence until the first material cavity 4 is full. When the first material cavity 4 is full of magnetic steel, the multiple magnetic steels in the first material cavity 4 are not loose. For ease of understanding, a more specific use process is listed here: Figure 2 As shown, the first material cavity 4 separated by the long partition 9 is in the shape of a long strip, and the magnetic steel is in the shape of a vertical sheet. The width of the first material cavity 4 can be designed to be compatible with the length of the magnetic steel, so that when the magnetic steel is stacked vertically in sequence along the length direction of the first material cavity 4 until the first material cavity 4 is full, the long strip magnetic steel group formed by the multiple stacked vertical magnetic steels in the first material cavity 4 is attached to or spaced apart by a gap of 1 to 3 mm at both ends of its own width direction with the side walls of the first material cavity 4 at both ends of its width direction; The beneficial effect obtained by adopting this technical solution is that a new type of graphite box for sintering NdFeB magnets is provided by arranging a box body 1, a cover plate 6, a long partition plate 9, a first material chamber 4, and a first air hole 11. In order to solve the problem of position displacement of the magnets due to the movement of the graphite box during transportation, a long partition plate 9 is used in the new graphite box to form a suitable stacking material chamber (i.e., the first material chamber 4). This can avoid the possibility of contact between the ends of the magnets during transportation and sintering, and at the same time increase the convenience and efficiency of the stacking process, ensure the independence and exhaust effect of the stacking material chamber, and effectively solve the problem of adhesion of the magnets after sintering. At the same time, the use of the graphite box to stack non-oriented diffused magnetic steel can minimize the phenomenon of material bending of the non-oriented diffused magnetic steel during sintering.

[0029] In another technical solution, a plurality of sub-partitions are evenly spaced and detachably provided in the first material chamber 4 along the length direction of the box body 1 to divide the first material chamber 4 into a plurality of second material chambers 5, and a second air vent 12 is provided on the sub-partition; specifically, a plurality of sub-partitions are provided in the first material chamber 4, and the plurality of sub-partitions are arranged along the length direction of the first material chamber 4 (the length direction of the first material chamber 4 is consistent with the length direction of the box body 1), the sub-partitions are arranged perpendicular to the side walls of the first material chamber 4, and the sub-partitions are detachably connected to the side walls of the first material chamber 4, and the detachable connection is preferably a snap connection; In this technical solution, during use, the number of long partitions 9 and sub-partitions is adaptively selected in advance according to the specifications and performance of the magnetic steel to be stacked, and a suitable material cavity is combined, and then the magnetic steel is stacked vertically or flatly to fill the material cavity; The beneficial effects obtained by adopting this technical solution are as follows: Figure 1~2 As shown, by setting sub-partitions, a new type of graphite box is provided. By selecting long partitions 9 and the number of sub-partitions, more material cavities of different sizes for stacking magnetic steel can be combined. For example, only long partitions 9 can be selected, and different numbers of long partitions can be used to combine to obtain the first material cavity 4 of different sizes. The first material cavity 4 is usually in the shape of a long strip, which is suitable for vertically stacking magnetic steel in rows. For example, multiple long partitions 9 and multiple sub-partitions can be selected to obtain a second material cavity 5 of another size. The second material cavity 5 is usually in the shape of a small grid, which can be used to stack magnetic steel flatly or vertically, but is more suitable for flat stacking. On the whole, by designing long partitions 9 and sub-partitions, material cavities of various specifications for stacking magnetic steel can be combined, which is more practical and has a wider range of applications.

[0030] In another technical solution, a plurality of first grooves 7 corresponding to each other and having opposite notches are vertically opened on both side walls in the width direction of the box body 1. The plurality of first grooves 7 on each side wall are spaced apart along the width direction of the box body 1. The top and bottom of the first grooves 7 are open. Multiple pairs of first grooves 7 correspond to multiple long partitions 9 one by one. Both ends of the long partitions 9 are matched with the corresponding pair of first grooves 7 so that the long partitions 9 can be inserted into the corresponding pair of first grooves 7 from the top of the corresponding pair of first grooves 7. Specifically, the side walls in the width direction of the box body 1 refer to the side walls arranged along the width direction of the box body 1 itself, that is, the first side walls 2. Multiple first grooves 7 are vertically opened on each first side wall 2. The first grooves 7 are evenly spaced along the width direction of the box body 1, and the multiple first grooves 7 on a pair of first side walls 2 correspond to each other one by one, and the notches of each pair of corresponding first grooves 7 are close to each other (that is, the notches are opposite), and the top and bottom (that is, the two ends in the vertical direction of the notch) of the first grooves 7 are open, so that the long partition 9 can be inserted into the corresponding pair of first grooves 7 from the top of the corresponding pair of first grooves 7 to complete the detachable connection; when in use, the long partition 9 can be directly extended into the corresponding pair of first grooves 7 from the top open part of the corresponding pair of first grooves 7; the technical solution has the beneficial effect that, by designing the first grooves 7, a method for detachable connection between the long partition 9 and the box body 1 is provided, and installation and disassembly are relatively convenient.

[0031] In another technical solution, a plurality of second grooves 8 corresponding to each other and having opposite notches are vertically opened on both side walls of the box body 1 in the length direction, and the plurality of second grooves 8 on each side wall are evenly spaced along the length direction of the box body 1, and the top and bottom of the second grooves 8 are open; the plurality of sub-partitions in each first material cavity 4 correspond to each other, and the plurality of sub-partitions corresponding to each other in the plurality of first material cavities 4 are sequentially connected and integrally formed to form a short partition 10, and the plurality of short partitions 10 correspond to the plurality of pairs of second grooves 8 one by one, and the two ends of the short partition 10 are respectively adapted to the corresponding pair of second grooves 8; Among them, a plurality of first card slots 13 are vertically opened at the bottom of the long partition 9, and the plurality of first card slots 13 are arranged at intervals along the length direction of the long partition 9, and the first card slots 13 are open at both ends of the length direction of the long partition 9; a plurality of second card slots 14 are vertically opened at the top of the short partition 10, and the plurality of second card slots 14 are arranged at intervals along the length direction of the short partition 10, and the second card slots 14 are open at both ends of the length direction of the short partition 10; the side wall of the long partition 9 between the bottom of the first card slot 13 and the top of the long partition 9 is matched with the second card slot 14, and the side wall of the short partition 10 between the bottom of the second card slot 14 and the bottom of the short partition 10 is matched with the first card slot 13; In the above technical solution, the number of sub-partitions in each first material cavity 4 is the same and corresponds one to one, and the sub-partitions of the multiple corresponding first material cavities 4 are sequentially connected and integrally formed to form a short partition 10; the side wall of the box body 1 in the length direction refers to the side wall of the box body 1 itself arranged along its length direction, and the side wall is the second side wall 3, and the second side wall 3 is perpendicular to the first side wall 2. A plurality of second grooves 8 are vertically opened on each second side wall 3, and the plurality of second grooves 8 are evenly spaced along the length direction of the box body 1, and the top and bottom of the second grooves 8 are open, so that the short partition 10 can be extended from the top of the corresponding pair of second grooves 8 into the corresponding pair of second grooves 8, so as to complete the detachable connection between the short partition 10 and the box body 1; A plurality of first card slots 13 are provided at the bottom of the long partition 9, and the plurality of first card slots 13 are arranged at intervals along the length direction of the long partition 9 (that is, the length direction of the box body 1), the notches of the first card slots 13 face downward, and both ends of each first card slot 13 perpendicular to the length direction of the long partition 9 are open; a plurality of second card slots 14 are provided at the top of the short partition 10, and the plurality of second card slots 14 are arranged at intervals along the length direction of the short partition 10 (that is, the width direction of the box body 1), the notches of the second card slots 14 face upward, and both ends of each second card slot 14 perpendicular to the length direction of the short partition 10 are open, so as to cooperate with the first card slots 13 on the long partition 9 for installation and disassembly. More specifically, on the long partition 9, the side wall of the long partition 9 (the first card wall described below) located between the bottom of the first card slot 13 and the top of the long partition 9 is adapted to the second card slot 14, and on the short partition 10, the bottom of the second card slot 14 and the short partition 10 are adapted to the second card slot 14. The side wall of the short partition 10 between the bottom (hereinafter referred to as the second card wall) is adapted to the first card slot 13, so that when in use, the short partition 10 is first installed in the box body 1, and then the long partition 9 is inserted into the corresponding pair of first grooves 7. At this time, the long partition 9 is located above the short partition 10, and the second card slot 14 is located above the corresponding first card wall, and the second card wall is located above the corresponding first card slot 13. After the long partition 9 is inserted into the corresponding pair of first grooves 7, the first card slot 13 is clamped on the corresponding second card wall, and the second card slot 14 is clamped on the corresponding first card wall to complete the installation of the long partition 9 and the short partition 10; the number of the first card slots 13 on each long partition 9 is not less than the number of the short partition 10 so that the long partition 9 can be flatly clamped on the short partition 10, and the number of the second card slots 14 on each short partition 10 is adaptively designed according to the actual required size of the second material cavity 5; In this technical solution, when in use, the number of short partitions 10 and long partitions 9 is adaptively selected according to the size of the magnetic steel, so as to obtain the first material cavity 4 or the second material cavity 5 of appropriate size (here, the number of short partitions 10 can also be zero or it is selected not to install the short partitions 10). When the second material cavity 5 is needed, the short partition 10 is first installed in the box body 1, and then the long partition 9 is installed on the box body 1 in accordance with the first groove 7, and the long partition 9 and the short partition 10 are in a clamping state; when stacking the magnetic steel, the magnetic steel is stacked in the first material cavity 4 or the second material cavity 5; when actually designing the size of the graphite box, the following design can be used: Figure 1 As a reference, the length direction of the first side wall 2 is recorded as the left-right direction, and the horizontal and vertical connection direction between the two pairs of first side walls 2 is the front-to-back direction. When designing the box body 1, the length of the first side wall 2 along the left-right direction is 240mm, the height along the up-down direction is 42mm, and the thickness along the front-to-back direction is 10mm; the length of the second side wall 3 along the front-to-back direction is 300mm, the height along the up-down direction is 42mm, and the thickness along the left-to-right direction is 10mm; the length of the long partition 9 along the front-to-back direction is 286mm, the height along the up-down direction is 28mm, and the thickness along the left-to-right direction is 6mm; the length of the short partition 10 along the left-to-right direction is 226mm, the height along the up-down direction is 28mm, and the thickness along the front-to-back direction is 6mm.

[0032] The beneficial effect of adopting this technical solution is that, by setting the second groove 8 and the short partition 10, a method of detachably connecting the long partition 9 and the sub-partition with the graphite box is provided, which is not only convenient for processing and use, but also convenient for installation and disassembly and easy to use.

[0033] In another technical solution, a card end 601 is protruded from the bottom of the cover plate 6, and the card end 601 is square. The length and width of the card end 601 are slightly smaller than the opening of the box body 1, so that the cover plate 6 can be inserted into the box body 1; specifically, the length and width of the card end 601 are slightly smaller than the opening of the box body 1, such as the length and width are 0.5~1.5cm smaller; the technical solution has the beneficial effect that, by designing the card end 601, a detachable connection method (card connection) between the cover plate 6 and the box body 1 is provided, which is convenient to manufacture and use.

[0034] In another technical solution, the number of the long partitions 9 and the number of the short partitions 10 are both two; the beneficial effect obtained by adopting this technical solution is that two long partitions 9 and two short partitions 10 are selected to separate the second material chambers 5 into nine independent second material chambers. This form of layout is more commonly used and has wider applicability.

[0035] In another technical solution, a sealing ring 17 is sleeved on the card end 601 to seal the cover plate 6 and the box body 1; a suction port is opened on the side wall of the box body 1, and the suction port is movably connected to the dust collection device; When the box body 1 needs to be cleaned, the sealing ring 17 is sleeved on the clamping end 601, and the cover plate 6 is sealed and plugged on the box body 1, and then the suction port is connected to the dust collection device, and the dust collection device cleans the inside of the box body 1; when the magnetic steel 19 needs to be sintered, the sealing ring 17 is removed, the magnetic steel 19 is stacked in the box body 1, and the cover plate 6 is covered, and then it can be transported to the sintering furnace; In this technical solution, a sealing ring 17 is sleeved on the card end 601, and the sealing ring 17 is movably connected to the card end 601, that is, the sealing ring 17 can be removed from the card end 601, and a suction port is provided on the side wall of the box body 1, and the suction port is connected to the dust collection device; when in use, when it is necessary to sinter the magnetic steel 19, the sealing ring 17 is removed from the card end 601, the magnetic steel 19 is stacked in the box body 1, and the isolation powder is sprinkled, and then the cover plate 6 is covered. At this time, the interior of the box body 1 is not completely closed. After the graphite box is transported to the sintering furnace, the sintering furnace is vacuumed, and the interior of the box body 1 is connected through the first air vent 11, which is convenient for vacuuming the interior of the box body 1. After the vacuum is drawn, After it is empty, sintering can begin; when the box body 1 needs to be cleaned, the sealing ring 17 is sleeved on the card end 601 and the cover plate 6 is sealed and plugged into the box body 1, and then the suction port is connected with the dust suction device. Through the suction pressure of the dust suction device, the impurities inside the box body 1 can be easily sucked out from the suction port (the inside of the box body 1 is connected through the first air vent 11, so the isolation powder and other impurities can pass through the first air vent 11 and finally be sucked out of the inside of the box body 1 from the suction port), avoiding the problem of large cleaning workload and many dead angles caused by directly cleaning the inside of the box body 1; it is easy to clean the isolation powder and other impurities inside the box body 1 as a whole, keep the inside of the box body 1 clean, which is conducive to the next test.

[0036] In another technical solution, the bottom end of the first air hole 11 is open to communicate with the bottom of the box body 1, so that when the box body 1 is cleaned, impurities inside the box body 1 flow to the dust suction port; specifically, each first air hole 11 is designed to have a bottom that is connected to the bottom of the box body 1, so that when cleaning the inside of the box body 1, impurities such as isolation powder inside the box body 1 can more easily flow to the suction port through the first air hole 11, thereby maximizing the cleaning strength and cleaning effect.

[0037] In another technical solution, a through hole 18 is provided on the side wall of each first material cavity 4, and the through hole 18 is connected with a horizontal spiral tube 15, and the spiral tube 15 is located outside the box body 1, and the spiral tube 15 is screwed with an abutting screw 16; one of the through holes 18 forms the suction port; in this technical solution, a through hole 18 is provided on one of the first side walls 2 where each first material cavity 4 is located, and the through hole 18 is connected with a spiral tube 15, and the spiral tube 15 is located outside the box body 1 (that is, the outside world), and the spiral tube 15 is screwed with an abutting screw 16, and one of the through holes 18 forms the suction port. In this way, when in use, after the magnetic steel 19 is placed in the first material cavity 4, there is usually a certain gap between the outermost magnetic steel 19 and the first side wall 2. These gaps are also the main factors causing the magnetic steel 19 to bend during the sintering process. By The rod 16 is screwed into the box body 1 until the abutting screw 16 abuts against the nearby magnetic steel 19, so that the long row of magnetic steels 19 inside the first material chamber 4 can be kept vertical as much as possible to avoid bending of the material due to the instability and tilt of the magnetic steel 19 during transportation and sintering. The bending rate of the magnetic steel 19 can be further reduced as a whole. When cleaning the inside of the box body 1, all the abutting screws 16 are unscrewed from the tube 15, and then one of the spiral tubes 15 is connected to the dust collection device, and the remaining spiral tubes 15 are sealed by the sealing plug, and then the sealing ring 17 is put on the card end 601, and the cover plate 6 is sealed and inserted at the open end of the box body 1. The dust collection device is started, and the impurities inside the box body 1 can be sucked out, so that the inside of the box body 1 is convenient to clean. In actual use, the abutting screws 16 and the spiral tubes 15 are made of graphite material or made of materials resistant to vacuum sintering temperature.

[0038] In another technical solution, the graphite box is made by graphitizing a long carbon product, wherein the long carbon product is a combination of Russian larch, yellow pine and red eucalyptus, with a mass ratio of 1:2~3:2~3. The long carbon product is compressed into a cylindrical shape, heated to 2700°C with an electric current, maintained for 3~5 hours, then heated to 2850°C, maintained for 3~5 hours, and then maintained between 2800°C~2850°C, maintained for 4~6 hours, and then cooled at a rate of 3~4°C / minute. When cooled to 1500°C~1700°C, it is maintained for 10~20 hours. In this way, a more high-temperature resistant graphite box can be manufactured, and by manufacturing a more high-temperature resistant graphite box, the material curvature of the magnetic steel can be further reduced.

[0039] The present invention also provides a method for preventing bending of magnetic steel materials, wherein the non-oriented diffused magnetic steel is stacked in the graphite box for sintering the NdFeB magnetic steel, and then transported and sintered. The specific steps of stacking the non-oriented diffused magnetic steel are as follows: S1. According to the required specifications and dimensions of the non-oriented diffused magnetic steel, the number of short partitions 10 and long partitions 9 is adaptively selected to make the size of the stacking cavity match the required specifications and dimensions of the non-oriented diffused magnetic steel; the stacking cavity is the first cavity 4 or the second cavity 5; S2. For each stacking cavity, vertically stack a plurality of non-oriented diffused magnetic steels in the stacking cavity until the stacking cavity is full; S3, repeat step S2 until all the stacking cavities are filled with non-oriented diffused magnetic steel; then plug the cover plate into the box body, transfer the box body to the sintering furnace, evacuate the sintering furnace, and start sintering; Specifically, in the above step S1, the size of the stacking cavity can be determined in advance according to the specifications of the non-oriented diffused magnetic steel required. For example, when the magnetic steel needs to be stacked vertically in rows, only the long partition 9 can be selected, that is, only the first cavity 4 is designed. At this time, the width of the first cavity 4 can be designed to match the length of the magnetic steel (when stacked vertically, the magnetic steel is in the shape of a vertical sheet). When the magnetic steel is stacked flat, a combination of the long partition 9 and the short partition 10 can be selected, and the length and width of the second cavity 5 can be designed to match the length and width of the magnetic steel (when stacked flat, the magnetic steel is in the shape of a horizontal sheet); then, according to the size of the magnetic steel and the required stacking amount, the overall size of the first cavity 4 or the second cavity 5 is calculated, and then according to the size of the first cavity 4 or the second cavity 5 Calculate the number of long partitions 9 and short partitions 10 to be used and build them as required; for each stacking cavity, pre-coat the diffusion source on the magnetic steel and then sprinkle isolation powder to prepare the non-oriented diffused magnetic steel to be stacked, and then stack multiple non-oriented diffused magnetic steels vertically in the first cavity 4 or flatly stack / vertically stack in the second cavity 5 until the stacking cavity is full. When the stacking cavity is full of non-oriented diffused magnetic steels, the multiple non-oriented diffused magnetic steels in the stacking cavity are not loose. It should be noted that when stacking the non-oriented diffused magnetic steels, the multiple non-oriented diffused magnetic steels in each stacking cavity are stacked in sequence; repeat the above stacking steps until the graphite box is full of non-oriented diffused magnetic steels, and then it can be transported to the sintering furnace for sintering; The use of such a technical solution has the beneficial effect that, compared with the traditional method of "stacking a long row of magnetic steels in a graphite box, which makes it impossible to accurately fix the position", this method can effectively improve the external force from unfair directions exerted on the non-oriented magnetic steels due to their positional bias, and then combined with the new graphite box structure, the traditional long row of magnetic steel groups is divided into multiple small magnetic steel groups, so that the multiple small magnetic steel groups are independent of different stacking cavities, which further reduces the mutual influence between the magnetic steels in the entire graphite box, not only effectively avoiding the phenomenon of adhesion of the ends of the magnetic steels, but also more effectively reducing the risk of material bending. The method of the present invention is applicable to all non-oriented diffused magnetic steels.

[0040] The beneficial effects of the graphite box for sintering NdFeB magnets and the method for preventing bending of magnet materials of the present invention are described below with specific experimental examples.

[0041] <Experimental Example 1> This experimental example 1 mainly verifies the anti-sticking effect of the graphite box used for sintering NdFeB magnets.

[0042] 1. Selection of graphite box: In this experimental example 1, the graphite box is a graphite box with nine second material chambers, that is, there are two short partitions and two long partitions, and the nine second material chambers are of the same size; an ordinary graphite box with a specification of 300*240*42 is used as a reference; wherein, the box body size of the graphite box of the present invention and the ordinary graphite box is the same; 2. Magnetic steel stacking and sintering: Select the circular magnetic steel with the brand N46UH and the specification of φ53.6*φ15.7*5.6, carry out grain boundary diffusion in the direction of 5.6mm, sprinkle isolation powder on the surface after the diffusion source is coated, and stack it flatly into the ordinary graphite box and the graphite box of the present invention: Among them, for the new graphite box of the present invention: four layers of rings are stacked flat in each second material cavity, that is, 4*9=36 rings are stacked in the entire graphite box; for the ordinary graphite box: the same number of rings are stacked in the ordinary graphite box according to the conventional flat stacking method, and the conventional flat stacking method can be regarded as the same as the stacking method of the new graphite box of the present invention, that is, except that there is no long partition and short partition blocking, the stacking method is the same as the present invention; The two groups of graphite boxes undergo the same transportation process and transportation method. After sintering, the magnets are taken out of the graphite boxes, the number of adhesions in the whole batch of products is counted, and the adhesion rate is calculated (the adhesion of the ends of two adjacent magnets is recorded as two adhered magnets, the number of adhered magnets is counted, and the adhesion rate is calculated, adhesion rate = (number of adhered magnets / total number of magnets) * 100%). At the same time, a magnet is extracted from each of the two graphite boxes, and the magnetic performance data is measured using a permanent magnet pulsating magnetization measuring instrument. The specific data are shown in Table 1.

[0043] Table 1 Adhesion rate and magnetic properties of different types of graphite boxes after sintering It can be seen from Table 1 that when the magnets are stacked in the graphite box in the same way and undergo the same transportation process and transportation method, the adhesion rate of the magnets after sintering out of the ordinary graphite box is 10.3%, which causes great product loss and high rescue cost. The adhesion rate of the magnets stacked using the graphite box of the present invention is 0, and there is no adhesion. There is no obvious difference in the magnetic properties of the products sintered from the two graphite boxes, indicating that the graphite box of the present invention can effectively solve the adhesion problem of the magnets after sintering.

[0044] <Experimental Example 2> This Experimental Example 2 verifies the effect of preventing the bending of non-oriented magnetic steel materials in the method of preventing the bending of magnetic steel materials of the present invention.

[0045] 1. Selection of graphite box: In Experimental Example 2, the graphite box is a graphite box with nine second material chambers, that is, there are two short partitions and two long partitions, and the nine second material chambers are of the same size; an ordinary graphite box with a specification of 300*240*42 is used as a reference; wherein, the box body size of the graphite box of the present invention and the ordinary graphite box is the same; 2. Magnetic steel stacking and sintering: Select N55H magnetic steel as the verification object, the finished product size is 8.4*3.15*1.0 (M)*5.6, the grain boundary diffusion magnetic steel size is 45.3*27.6*3.15, the non-oriented 3.15mm direction of the magnetic steel is coated with diffusion source, and then the isolation powder is sprinkled on the surface, and the magnetic steel is stacked vertically into the graphite box; Among them, for ordinary graphite boxes: according to the traditional stacking method, the magnetic steel is stacked vertically in a long row along the length direction of the graphite box until it is full; for the new graphite box of the present invention: the magnetic steel is stacked in each second material cavity until it is full; The common graphite box and the novel graphite box of the present invention undergo the same transportation process and transportation method. After sintering out of the furnace, the magnetic steel is taken out of the graphite box, and after being processed by a double-end grinder, the number of material bends of the whole batch of magnetic steel is counted, and the material bend rate is calculated. The determination of the material bend of the magnetic steel is specifically as follows: the ground magnetic steel is manually inspected and screened piece by piece, the magnetic steel that is bent is detected, the number of bent magnetic steel is counted, and the material bend rate is calculated, and the material bend rate = (the number of bent magnetic steels / the total number of magnetic steels) * 100%. In addition, a piece of magnetic steel is extracted from each of the two graphite boxes, and the magnetic performance data is measured using a permanent magnet pulsating magnetization measuring instrument. The specific data are shown in Table 2.

[0046] Table 2 Curvature and magnetic properties of different types of graphite boxes and stacking methods after sintering It can be seen from Table 2 that, under the same transportation process and transportation method, the material bending rate is as high as 63.7% when ordinary graphite boxes are used in combination with traditional stacking methods. The material bending rate is relatively high, the bent products cannot be saved, and the loss is relatively large; while the material bending rates of the graphite boxes of the present invention combined with the stacking method of the present invention are 13.1%. Compared with the two, the present invention significantly reduces the material bending ratio of the magnetic steel and reduces the economic loss, indicating that the graphite boxes of the present invention combined with the stacking method of the present invention can effectively improve the possibility of material bending due to non-oriented diffusion of the magnetic steel.

[0047] <Experimental Example 3> Raw material selection: High-quality Russian Scots Pine, Yellow Pine and Red Eucalyptus wood are selected as raw materials for long carbon products. These woods are selected for their high carbon content and good thermal stability.

[0048] Ratio and mixing: Russian larch, yellow pine and red eucalyptus are mixed in a mass ratio of 1:2.5:2.5. This ratio is optimized after many tests to obtain the best graphitization effect and mechanical properties.

[0049] Drying and crushing: The mixed wood is dried to remove moisture and then crushed to obtain uniform granular raw materials.

[0050] Compression molding: The crushed raw materials are placed in a mold and compressed by a hydraulic press to form a cylindrical long carbon product. During the compression process, it is necessary to ensure that the product has uniform density and is free of cracks and bubbles.

[0051] Preheating and degassing: Put the formed long carbon product into the graphitization furnace and first preheat it to remove the volatile matter and impurities. The preheating temperature is controlled at about 800℃ and maintained for 2 hours.

[0052] Graphitization heating: After preheating, the furnace temperature is gradually raised to 2700°C and maintained for 3.5 hours. In this stage, the rearrangement of carbon atoms and the formation of graphite structure mainly occur.

[0053] High temperature insulation: Then, the furnace temperature is raised to 2850°C and maintained for 4 hours. High temperature insulation helps to further improve the degree of graphitization and make the graphite structure more stable.

[0054] Maintaining temperature and cooling: Finally, the furnace temperature is maintained between 2800℃ and 2850℃ for 5 hours. Then, it is cooled at a cooling rate of 3.5℃ / min until the temperature drops to 1600℃. At 1600℃, it is maintained for 15 hours to ensure that the internal stress of the graphite product is fully released.

[0055] Cooling and removal: After cooling is completed, the graphite product is taken out of the furnace and allowed to cool naturally to room temperature.

[0056] Finally, the graphite box is processed into a graphite box. Through the above method, the graphite box manufactured by the present invention has higher high temperature resistance and better mechanical properties. The high temperature resistance can reach 3000°C.

[0057] <Experimental Example 4> Raw material selection: Russian Scots Pine, Yellow Pine and Red Eucalyptus are carefully selected as the core raw materials for long carbon products. These woods are selected for their high carbon content, excellent thermal stability and easy graphitization.

[0058] Precise Ratio: Russian Scots Pine, Yellow Pine and Red Eucalyptus wood are precisely mixed in a mass ratio of 1:2.75:2.25. This ratio is designed to balance structural stability and mechanical properties during graphitization.

[0059] Drying and crushing: The mixed wood is deeply dried to ensure that the moisture content is less than 5%, and then finely crushed to obtain granular raw materials with uniform particle size of about 2-5 mm.

[0060] High-density molding: Using advanced hydraulic molding technology, the crushed raw materials are compressed into cylindrical long carbon products under high pressure in the mold. During the molding process, the pressure and temperature must be strictly controlled to ensure the density and uniformity of the product.

[0061] Preheating stage: The formed long carbon product is placed in a graphitization furnace and first preheated at 850°C for 2.5 hours to remove volatiles and impurities in the raw materials.

[0062] Graphitization heating: After preheating, the temperature is gradually raised to 2750°C and maintained for 4 hours. This stage mainly promotes the orderly arrangement of carbon atoms and the initial formation of graphite structure.

[0063] High temperature insulation: Subsequently, the furnace temperature is raised to 2875°C and maintained for 4.5 hours to further increase the degree of graphitization and enhance the mechanical strength and thermal stability of the graphite products.

[0064] Temperature maintenance and cooling: Finally, the furnace temperature was maintained in the range of 2825°C to 2875°C for 5.5 hours. Then, it was slowly cooled at a cooling rate of 3.75°C / min until the temperature dropped to 1650°C. At 1650°C, it was maintained for 17.5 hours to ensure the complete stabilization of the graphite structure and the full release of internal stress.

[0065] The cooled graphite product is processed into a graphite box and finely polished to remove surface flaws and unevenness to improve its appearance quality and performance.

[0066] The graphite cartridges are subjected to comprehensive quality inspections, including high temperature resistance tests and mechanical strength tests. The high temperature resistance can reach 3100°C.

[0067] The number of equipment and processing scale described here are used to simplify the description of the present invention. The application, modification and variation of the graphite box for sintering NdFeB magnets of the present invention will be obvious to those skilled in the art.

[0068] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A graphite box for sintering NdFeB magnets, characterized in that: include: A box body, with an open top, wherein a plurality of long partitions are evenly spaced and detachably provided in the box body along the width direction thereof, so as to divide the box body into a plurality of first material chambers, and the long partitions are provided with first air holes; A cover plate is movably inserted at the open end of the box body.

2. The graphite box for sintering NdFeB magnets according to claim 1, characterized in that: A plurality of sub-partitions are evenly spaced and detachably provided in the first material cavity along the length direction of the box body to divide the first material cavity into a plurality of second material cavities, and second air holes are provided on the sub-partitions.

3. The graphite box for sintering NdFeB magnets according to claim 2, characterized in that: Both side walls along the width direction of the box body are vertically provided with a plurality of first grooves corresponding to each other and having opposite notches. The plurality of first grooves on each side wall are spaced apart along the width direction of the box body. The top and bottom of the first grooves are open. The plurality of pairs of first grooves correspond to a plurality of long partitions one by one. The two ends of the long partitions are respectively matched with the corresponding pair of first grooves so that the long partitions can be inserted into the corresponding pair of first grooves from the top of the corresponding pair of first grooves.

4. The graphite box for sintering NdFeB magnets according to claim 3, characterized in that: A plurality of second grooves corresponding to each other and having opposite notches are vertically opened on both side walls in the length direction of the box body, and the plurality of second grooves on each side wall are evenly spaced along the length direction of the box body, and the top and bottom of the second grooves are both open; the plurality of sub-partitions in each first material cavity correspond to each other, and the plurality of sub-partitions corresponding to each other in the plurality of first material cavities are sequentially connected and integrally formed to form a short partition, and the plurality of short partitions correspond to the plurality of pairs of second grooves one by one, and the two ends of the short partitions are respectively adapted to the corresponding pair of second grooves; Among them, a plurality of first card slots are vertically opened at the bottom of the long partition, and the plurality of first card slots are spaced along the length direction of the long partition, and the two ends of the first card slots perpendicular to the length direction of the long partition are open; a plurality of second card slots are vertically opened at the top of the short partition, and the plurality of second card slots are spaced along the length direction of the short partition, and the two ends of the second card slots are open perpendicular to the length direction of the short partition; the side wall of the long partition between the bottom of the first card slot and the top of the long partition is adapted to the second card slot, and the side wall of the short partition between the bottom of the second card slot and the bottom of the short partition is adapted to the first card slot.

5. The graphite box for sintering NdFeB magnets according to claim 1, characterized in that: A card end is protruding from the bottom of the cover plate. The card end is square and the length and width of the card end are slightly smaller than the opening of the box body so that the cover plate can be plugged into the box body.

6. The graphite box for sintering NdFeB magnets according to claim 5, characterized in that: A sealing ring is sleeved on the card end to enable the cover plate to be sealed and plugged into the box body; a suction port is opened on the side wall of the box body, and the suction port is movably connected to the dust collection device; Among them, when the box body needs to be cleaned, the sealing ring is put on the card end and the cover plate is sealed and plugged into the box body, and then the suction port is connected to the dust suction device, and the dust suction device cleans the inside of the box body; when the magnet needs to be sintered, the sealing ring is removed, the magnet is stacked into the box body, the cover plate is covered, and it can be transported to the sintering furnace.

7. The graphite box for sintering NdFeB magnets according to claim 6, characterized in that: The bottom end of the first air hole is open to communicate with the bottom of the box body, so that when the box body is cleaned, impurities inside the box body flow to the dust suction port.

8. The graphite box for sintering NdFeB magnets according to claim 6, characterized in that: A through hole is opened on the side wall of each first material cavity, and the through hole is connected with a spiral tube, and the spiral tube is located outside the box body, and an abutting screw is screwed on the spiral tube; one of the through holes forms the suction port.

9. The graphite box for sintering NdFeB magnets according to claim 6, characterized in that: The graphite box is made by graphitizing a long carbon product, wherein the long carbon product is a combination of Russian larch, yellow pine and red eucalyptus, with a mass ratio of 1:2~3:2~3. The long carbon product is compressed into a cylindrical shape, heated to 2700°C with an electric current, maintained for 3~5 hours, then heated to 2850°C, maintained for 3~5 hours, then maintained between 2800°C~2850°C, maintained for 4~6 hours, then cooled at a rate of 3~4°C / minute, cooled to 1500°C~1700°C, and then maintained for 10~20 hours.

10. A method for preventing bending of magnetic steel material, characterized in that: The non-oriented diffused magnetic steel is placed in a graphite box for sintering NdFeB magnetic steel as claimed in any one of claims 4 and 8, and then transported and sintered.

Images