Method for manufacturing thin profiled magnetic steel

Abstract

The application provides a preparation method of a thin profiled magnetic steel, comprising the following steps: rapid solidification powder preparation, raw materials are sequentially subjected to a rapid solidification process, a hydrogen crushing process and an air flow grinding process to obtain mixed fine powder; molding, the mixed fine powder obtained after the rapid solidification powder preparation step is filled in a preparation mold, then a magnetic field is applied for orientation, and the green body is obtained after demolding; the preparation mold is a detachable structure, and the preparation mold comprises a mold frame and a plurality of partition plates arranged in parallel in the mold frame; sintering and tempering, the obtained green body is subjected to sintering and tempering treatment to obtain a thin profiled magnetic body. The preparation method has high magnet utilization rate and production efficiency, the magnetic performance uniformity of the prepared magnetic steel is better, and the yield is high.

Description

Technical field

[0001] The present invention relates to the technical field of magnetic steel production and preparation, and in particular to a method for preparing thin special-shaped magnetic steel. [Background Technology]

[0002] Growing environmental concerns are driving the rapid development of new energy vehicles. According to a recent International Energy Agency survey, electric motors account for approximately two-thirds of industrial electricity consumption and approximately 46% of global electricity consumption. Therefore, improving motor energy efficiency and efficiently driving them are key. Magnets, as efficient carriers for converting electrical energy into mechanical energy, are crucial to the development of the motor industry.

[0003] Sintered NdFeB magnets are known as the "King of Magnets" for their ultra-high magnetic properties. They are ideal materials for realizing micro-volume, high-efficiency new energy vehicle motors and industrial automation motors. Usually, high-performance motor magnets are mostly "tile-shaped" or "bread-shaped". However, the processing of micro-tile-shaped magnets in the prior art is mostly through traditional molding processes to obtain large-volume and mass block magnets, such as more than 300g, and then the large-volume and mass block magnets are processed through linear cutting and polishing processes to obtain micro-magnets less than 100g. The obtained magnets have poor magnetic property uniformity, low appearance defective yield, low production efficiency and low magnet utilization.

[0004] Therefore, it is necessary to provide a method for preparing thin special-shaped magnetic steel. [Summary of the invention]

[0005] The object of the present invention is to provide a method for preparing thin special-shaped magnetic steel, which has high magnet utilization and production efficiency, and the magnetic properties of the prepared magnetic steel are better uniform, have good appearance and high yield.

[0006] The technical solutions of the present invention are as follows:

[0007] The present invention provides a method for preparing thin special-shaped magnetic steel, comprising the steps of:

[0008] Rapid coagulation powder making: the raw materials are sequentially subjected to the rapid coagulation process, hydrogen crushing process and air flow grinding process to obtain mixed fine powder;

[0009] Molding, filling the mixed fine powder obtained after the rapid solidification and powder making step into a preparation mold, then applying a magnetic field for orientation, and demolding after orientation to obtain a green body; the preparation mold is a detachable structure, and the preparation mold includes a mold frame and a plurality of partitions arranged in parallel in the mold frame;

[0010] Sintering and tempering: the obtained green body is sintered and tempered to obtain a thin special-shaped magnet.

[0011] Preferably, the rapid solidification process specifically comprises: placing the raw material into a vacuum rapid solidification furnace to make a strip;

[0012] The hydrogen breaking process specifically comprises: placing the strip obtained from the rapid solidification process into a hydrogen explosion furnace, introducing hydrogen, absorbing nitrogen sufficiently, heating to 400-600℃ for 2-7h, and breaking the strip into particles of 300-800μm.

[0013] The airflow milling process specifically comprises: using airflow milling equipment to mill the particles obtained from the hydrogen breaking process to obtain the mixed fine powder; the median particle size of the obtained mixed fine powder is 1-8μm.

[0014] Preferably, the mold frame comprises upper and lower mold plates arranged in parallel and side mold plates arranged vertically between the upper and lower mold plates; the partition plates are arranged in the cavity formed by the upper and lower mold plates and the side mold plates, and the mold cavities are formed between adjacent two partition plates.

[0015] Preferably, in the molding step, the filling density is 2.0-5.0g / cm 3 Before filling the mixed fine powder obtained after the rapid solidification and powder making step into the preparation mold, mold assembly is further included; the mold assembly comprises the steps of: arranging the side mold plates vertically on the lower mold plates, arranging the partition plates between the side mold plates, and arranging a transition frame at the upper end of the side mold plates.

[0016] Preferably, the filling of the mixed fine powder obtained after the rapid solidification and powder making step into the preparation mold specifically comprises:

[0017] Weighing: weighing the corresponding mass of mixed fine powder according to the specifications of the preparation mold for filling;

[0018] Powder distribution: filling the weighed mixed fine powder into the assembled preparation mold, and the powder distribution density is 0.5-5.0g / cm 3 ;

[0019] Mold closing and pressing: installing the upper mold plate to press the floating powder into the mold cavities.

[0020] Preferably, in the powder distribution process, one or more of airflow vibration, electromagnetic vibration, and mechanical vibration is used to assist powder distribution.

[0021] Preferably, the orientation is alternating current orientation combined with direct current pulse orientation, the orientation magnetic field is 1-5T, and the orientation degree of the green body is more than 97%.

[0022] Preferably, when demolding, the partition plates are taken out of the mold frame together with the oriented green body, and the sintering and tempering steps are performed.

[0023] Preferably, the sintering and tempering steps specifically include: placing the obtained green body in a sintering furnace under the protection of inert gas, and -4 Pa~1*10 -2 Pa, and heat-treating at a sintering temperature of 900-1200°C for 2-10 hours; after sintering, heat-treating at a temperature of 700-1000°C for 2-8 hours for primary tempering, and then heat-treating at a temperature of 300-650°C for 2-15 hours for secondary tempering.

[0024] After the sintering and tempering steps, the obtained thin special-shaped magnet is subjected to machining, cutting and grinding.

[0025] The beneficial effects of the present invention are as follows: the preparation method of the thin special-shaped magnetic steel of the present invention, by filling the mixed fine powder into the mold cavity formed in the preparation mold in the forming step, and obtaining a green body for sintering and tempering after the mold is closed and pressed, and the green body can directly obtain a uniformly formed thin special-shaped magnetic steel after sintering and tempering. Compared with the prior art, the preparation method of the present invention, when preparing micro-tile magnetic steel, by using the preparation mold in the forming process to pre-fill the mold cavity with the mixed fine powder of the corresponding mass and volume required for the magnetic steel to be prepared, after forming, sintering and tempering, directly obtains a product matching the target magnetic steel, and can achieve near-forming of magnetic steel below 100g, or even below 10g. Micro-tile magnetic steel is directly obtained without having to undergo linear cutting and grinding processes such as from a larger volume and mass magnet, thereby avoiding waste of magnetic material and improving the utilization rate of the magnet. The obtained micro-tile magnetic steel has better magnetic uniformity, good appearance, high yield and stable magnetic properties.

Brief Description of the Drawings

[0026] Figure 1 This is a process flow chart of the molding step described in Example 1 of the present invention;

[0027] Figure 2 This is a diagram of residual magnetization fluctuation points of tile magnetic steel obtained in different mold cavities in Example 1 of the present invention;

[0028] Figure 3 This is a diagram of the coercive force fluctuation points of the tile magnetic steel obtained in different mold cavities in Example 1 of the present invention. [Specific implementation method]

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] Example 1

[0031] A method for preparing thin special-shaped magnetic steel comprises the following steps:

[0032] The raw material is obtained by batching, mixing, smelting and ingot casting of a rare earth element raw material block, and then the raw material is subjected to a rapid solidification process, a hydrogen crushing process and an air flow milling process to obtain mixed fine powder;

[0033] The mixed fine powder obtained after the rapid solidification and powdering step is filled in a preparation mold, and the filling density is 3.0 g / cm 3 Then, a magnetic field is applied for orientation, and the green body is demolded after orientation; the preparation mold is a detachable structure, and the preparation mold comprises a mold frame 1 and a plurality of partition plates 2 arranged in parallel in the mold frame 1; the number of the partition plates 2 can be set according to the volume in the mold frame 1, and is preferably 2-200;

[0034] Sintering and tempering, the obtained green body is sintered and tempered to obtain a thin profile special-shaped magnet. Specifically, the raw material in the embodiment of the application is a NdFeB alloy material, and the obtained thin profile special-shaped magnet is a NdFeB thin profile special-shaped magnet.

[0035] The rapid solidification process specifically comprises: placing the raw material into a vacuum rapid solidification furnace to form a ribbon; the thickness of the obtained ribbon is 0.30 mm;

[0036] The hydrogen crushing process specifically comprises: placing the ribbon obtained in the rapid solidification process into a hydrogen explosion furnace, introducing hydrogen, sufficiently absorbing nitrogen, heating to 500 DEG C for 5 h, and crushing the ribbon into particles with a size of 500 μm;

[0037] The air flow milling process specifically comprises: using an air flow milling device to mill the particles obtained in the hydrogen crushing process to obtain the mixed fine powder; the median particle size of the obtained mixed fine powder is 6 μm;

[0038] As shown in Figure 1 The mold frame 1 comprises an upper mold plate 11 and a lower mold plate 12 arranged in parallel and a side mold plate 13 arranged vertically between the upper mold plate 11 and the lower mold plate 12; the partition plates 2 are arranged in the cavity surrounded by the upper mold plate 11, the lower mold plate 12 and the side mold plate 13, and a mold cavity 14 is formed between two adjacent partition plates 2; the number of the partition plates 2 and the volume of the mold cavity 14 can be set correspondingly according to the mass and volume of the magnetic steel to be prepared, which increases the applicability of the preparation mold and enables the preparation method to be applied to the preparation of magnetic steels of different specifications. The preparation mold of the application is a detachable structure, which facilitates the setting of the mold cavity 14 before forming and the demolding of the green body after forming, and improves the production efficiency.

[0039] In the molding step, the mixed fine powder obtained after the rapid powdering step is filled into the preparation mold, and the molding step further comprises a mold assembly step; the mold assembly step comprises the steps of: vertically arranging the side mold plate 13 on the lower mold plate 12, and arranging the partition plate 2 between the side mold plate 13; preferably, the side mold plate 13 is arranged corresponding to the edge area of the lower mold plate 12, and a transition frame 3 is arranged at the upper end of the side mold plate 13.

[0040] The upper end of the transition frame 3 has a larger cross-sectional area than the lower end, so that the mixed fine powder is more easily filled into the preparation mold.

[0041] The filling of the mixed fine powder obtained after the rapid powdering step into the preparation mold specifically comprises:

[0042] The mixed fine powder is weighed according to the size of the preparation mold, and the mixed fine powder is filled into the mold cavity 14 of the preparation mold; the transition frame 3 prevents the mixed fine powder from overflowing during pouring, avoids the loss of the mass of the mixed fine powder after weighing, ensures the accuracy of preparation, and prevents the waste of the mixed fine powder.

[0043] The mixed fine powder is filled into the mold cavity 14 of the preparation mold, and the powder distribution density is 2.5g / cm 3 It should be noted that the powder distribution density is a preferred range suitable for the operation process of the embodiment of the present application, but cannot be understood as the only limitation of the powder distribution density;

[0044] The powder distribution process is assisted by one or more of air flow vibration, electromagnetic vibration, and mechanical vibration.

[0045] The mold is closed and pressed to press the floating powder into the mold cavity 14; the pressing method comprises one-way pressing or two-way floating pressing, and the pressing method is not specifically limited in the embodiment of the present application, and can be selected according to the specific operation.

[0046] The orientation is alternating current orientation mixed with direct current pulse orientation, the orientation magnetic field is 2.5T, and the orientation degree of the green body is more than 97%.

[0047] As an option, the demolding process can remove the oriented temperature green body by disassembling the mold frame 1, or a robot can be used to take out the oriented green body from the mold cavity; when demolding, the partition plate 2 is taken out from the mold frame 1 together with the oriented green body, and the sintering and tempering steps are performed;

[0048] The sintering and tempering steps specifically comprise: under the protection of inert gas, the obtained green body is placed in a sintering furnace, and the furnace is vacuumized to a pressure of 0.8*10 -4Pa is sintered at 1030℃ for 5h, and then is first tempered at 900℃ for 5h and second tempered at 500℃ for 6h.

[0049] The sintering and tempering process is followed by a machining step, which includes cutting and grinding processes.

[0050] The preparation method of the thin profiled magnetic steel of the present application fills the mixed fine powder into the mold cavity formed in the preparation mold in the forming step, and then obtains the green body for sintering and tempering after compression molding. The green body can directly obtain the uniformly formed thin profiled magnetic steel after sintering and tempering. Compared with the prior art, the preparation method of the present application directly obtains the product matching the target magnetic steel after forming, sintering and tempering by filling the corresponding mass and volume of mixed fine powder required for the preparation of the magnetic steel in the mold cavity in the forming process. The near net shape of the magnetic steel below 100g, even below 10g, can be realized. The micro-tile magnetic steel is directly prepared without linear cutting and grinding processes of larger volume and mass magnets, thereby avoiding waste of magnet material and improving the utilization rate of the magnet. The volume and mass of the obtained micro-tile magnetic steel are uniform, the formed product is not easy to break, the magnetic performance uniformity is good, the appearance is good, the yield is high, and the magnetic performance is stable.

[0051] Compared with the preparation method of the prior art, the preparation method of the present application does not include the isostatic pressing process. The green body is taken out from the mold frame together with the separator, and then is directly sintered, thereby saving the preparation steps and realizing full automation of the forming and sintering.

[0052] In the present application, the utilization rate of the magnet is higher than 80%, which is greatly improved compared with the prior art.

[0053] Taking the 1 out of 27 continuous preparation mold as an example, the fluctuation of the magnetic steel obtained in different mold cavities under different filling densities is used to evaluate the quality fluctuation of the magnetic steel obtained by the preparation method of the present application. The 1 out of 27 continuous mold is a mold cavity formed in the preparation mold, and the number of the finally prepared magnetic steel is 27. The mass, mass average, filling density and mass fluctuation percentage obtained in the 1 out of 27 continuous preparation mold are shown in the following table. As can be seen from the table, the quality distribution of the thin profiled magnetic steel obtained by the technical solution of the present application is uniform, the fluctuation value is small, and the yield is high.

[0054] Referring to Figure 1 and Figure 2As shown, the remanence of the magnetic steel prepared in different mold cavities fluctuates in the range of 13.35-13.5 KGs, and the coercive force fluctuates in the range of 19.6-19.9 KOe. It is shown that the thin profiled magnetic steel in tile type obtained by the present application has good magnetic properties, and the magnetic properties of the magnetic steel obtained in different mold cavities are stable and uniform.

[0055]

[0056]

[0057] It can be understood that the preparation method of the thin profiled magnetic steel of the present application is not only suitable for near forming of the magnetic steel below 100g, but also suitable for forming and preparation of the tile magnetic steel of 500-1500g by adjusting the volume of the preparation mold and the mold cavities therein.

[0058] The above only describes the embodiments of the present application, and it should be pointed out that the ordinary skilled in the art can make improvements without departing from the inventive concept, and these all belong to the protection scope of the present application.

Claims

1. A method for manufacturing a thin profiled magnetic steel, characterized in that, The method comprises the steps of: quick-setting powdering, the raw materials are sequentially subjected to a quick-setting process, a hydrogen crushing process and an air-flow milling process to obtain mixed fine powder; molding, the mixed fine powder obtained after the quick-setting powdering step is filled into a preparation mold, a magnetic field is then applied for orientation, and the oriented green body is demolded to obtain a green body; the preparation mold is of a detachable structure, and comprises a mold frame and a plurality of partitions arranged in parallel in the mold frame; the mold frame comprises upper and lower mold plates arranged in parallel and side mold plates arranged vertically between the upper and lower mold plates; the partitions are arranged in the cavity surrounded by the upper and lower mold plates and the side mold plates, and a mold cavity is formed between two adjacent partitions; In the molding step, the powder filling density is 2.0-5.0 g / cm 3 ; the step of filling the mixed fine powder obtained after the rapid-tempering powdering step into a preparation mold further includes mold assembly; the mold assembly includes the steps of vertically arranging the side mold plates on the lower mold plate, arranging the partition plates between the side mold plates, and arranging a transition frame at the upper end of the side mold plates. the filling of the mixed fine powder obtained after the quick-setting powdering step into the preparation mold specifically comprises: weighing, the mixed fine powder of a corresponding mass is weighed according to the specifications of the preparation mold for filling; The mixed fine powder is filled into the assembled preparation mold, and the powder density is 0.5-5.0 g / cm 3 ; mold closing and pressing, the upper mold plate is installed to press the floating powder into the mold cavity; sintering and tempering, the obtained green body is subjected to sintering and tempering to obtain a thin profiled magnet steel.

2. The method according to claim 1, wherein: the quick-setting process specifically comprises placing the raw materials into a vacuum quick-setting furnace to prepare a ribbon; the hydrogen crushing process specifically comprises placing the ribbon obtained in the quick-setting process into a hydrogen explosion furnace, introducing hydrogen, sufficiently absorbing hydrogen, heating to 400-600 DEG C for 2-7 h, and crushing the ribbon into particles of 300-800 μm; the air-flow milling process specifically comprises using an air-flow milling device to mill the particles obtained in the hydrogen crushing process to obtain the mixed fine powder; the median particle size of the mixed fine powder is 1-8 μm.

3. The method of claim 1, wherein the thin profiled magnetic steel is prepared by the steps of: In the powder distribution process, one or more of air-flow vibration, electromagnetic vibration and mechanical vibration is used to assist powder distribution. ​ 4. The method of claim 1, wherein the thin profiled magnetic steel is prepared by the steps of: The orientation is AC orientation combined with DC pulse orientation, the orientation magnetic field is 1-5 T, and the orientation degree of the green body is greater than 97%. ​ 5. The method of claim 1, wherein the thin profiled magnetic steel is prepared by the steps of: When demolding, the partitions are taken out of the mold frame together with the oriented green body, and the sintering and tempering step is performed. ​ 6. The method of manufacturing a thin profiled magnetic steel of claim 1, wherein: The sintering and tempering steps specifically include: placing the obtained green body in a sintering furnace under inert gas protection, and performing heat treatment at a sintering temperature of 900-1200 ℃ under a vacuum pressure of 0.5*10 -4 Pa~1*10 -2 Pa, for 2-10 h; after sintering, performing primary tempering at a temperature of 700-1000 ℃ for 2-8 h, and then performing secondary tempering at a temperature of 300-650 ℃ for 2-15 h.

7. The method of manufacturing a thin profiled magnetic steel of claim 1, wherein: The sintering and tempering step is followed by machining, cutting and polishing of the obtained thin profiled magnet steel.

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