Preparation method of high temperature resistant sintered NdFeB magnet based on copper roller speed control

Abstract

The present invention relates to the technical field of magnetic material preparation, and proposes a method for preparing a high-temperature sintered NdFeB magnet based on copper roller speed control, including: sealing, vacuuming, heating, melting and rapidly solidifying the raw materials of the high-temperature sintered NdFeB magnet, obtaining alloy flakes, and obtaining first and second temperature data; obtaining the matching degree of the copper roller cooling rate of the second temperature data; obtaining the abnormal score of the first temperature data, and then obtaining the copper roller speed adjustment coefficient, obtaining the copper roller speed adjustment sequence; obtaining the copper roller speed allocation coefficient; obtaining the speed of the copper roller according to the copper roller speed adjustment sequence and the copper roller speed allocation coefficient, realizing the control of the copper roller speed, and obtaining high-performance high-temperature sintered NdFeB magnets through hydrogen crushing, air flow milling, magnetic field pressing, sintering, heat treatment and performance testing processes. The present invention aims to solve the problem that the process equipment parameter setting using the rapid solidification casting method is difficult to cope with changes in the preparation process due to dependence on prior parameters.

Description

Technical Field

[0001] The invention relates to the technical field of magnetic material preparation, and in particular to a method for preparing a high-temperature sintered NdFeB magnet based on copper roller rotation speed regulation. Background Art

[0002] High temperature sintered NdFeB magnet is a permanent magnetic material. At present, the industrial preparation of NdFeB magnet smelting casting mainly adopts the rapid solidification casting method. The principle of the rapid solidification casting method is to melt the prepared metal raw materials into molten metal, and then cast the molten metal onto a rotating copper roller for rapid cooling and solidification. Compared with the traditional ingot casting process, the rapid solidification casting method has a more uniform composition, the main phase and the Nd-rich phase are distributed alternately, and there is no α-Fe segregation. Therefore, the rapid solidification casting process is widely used to prepare high-performance NdFeB magnets. However, the thickness and grain microstructure of the casting prepared by the rapid solidification casting process have an important influence on the performance of the magnet. At the same time, the performance of the magnet is also affected by the preparation process, such as the temperature of the molten metal casting, the casting speed, and the rotation speed of the copper roller. At present, the parameter setting of the rapid solidification casting process equipment mainly depends on the prior parameters of the experimental test data. However, due to the preparation environment, the operating status of the preparation equipment and equipment differences, relying on a priori parameter settings is difficult to cope with changes in the preparation process and can easily cause production losses. Summary of the invention

[0003] The present invention provides a method for preparing a high temperature sintered NdFeB magnet based on copper roller speed control, so as to solve the problem that when a rapid solidification casting method is used to prepare a high temperature sintered NdFeB magnet, the parameter setting of the process equipment depends on the prior parameters, which makes it difficult to cope with the changes in the preparation process. The technical solution adopted is as follows:

[0004] An embodiment of the present invention provides a method for preparing a high temperature sintered NdFeB magnet based on copper roller speed control, the method comprising the following steps:

[0005] Put the raw materials for preparing NdFeB magnets into the crucible of the vacuum melting casting furnace according to the proportion, evacuate the furnace, heat up and melt under the protection of high-purity argon, adjust the rotation speed of the copper roller, and after melting, cast the molten metal in the crucible through the tundish into the water-cooled copper roller for rapid solidification to obtain the NdFeB alloy sheet, collect the temperature data in the vacuum melting casting furnace, and obtain the cooling initial temperature sequence, cooling completion temperature sequence, first temperature data and second temperature data;

[0006] Obtaining the floating probability and floating probability weight of the second temperature data, and obtaining the copper roller cooling rate matching degree of the second temperature data according to the floating probability and floating probability weight of the second temperature data;

[0007] According to the first temperature data included in the cooling initial temperature sequence, the abnormal score of the first temperature data is obtained; according to the abnormal score of all the first temperature data included in the cooling initial temperature sequence and the copper roller cooling rate matching degree of the second temperature data, the copper roller speed adjustment coefficient of the second temperature data is obtained, and the copper roller speed adjustment sequence is obtained;

[0008] According to the second temperature data included in the cooling completion temperature sequence and the standard temperature of the solidified molten metal, the upper floating interval of the molten metal cooling completion temperature and the lower floating interval of the molten metal cooling completion temperature are obtained, and the upper floating probability and the lower floating probability of the second temperature data are obtained. According to the upper floating probability and the lower floating probability of all the second temperature data in the cooling completion temperature sequence, the molten metal cooling completion temperature floating index is obtained, and the copper roller speed adjustment coefficient is obtained according to the molten metal cooling completion temperature floating index;

[0009] The speed of the copper roller is obtained according to the copper roller speed adjustment sequence and the copper roller speed adjustment coefficient, and the speed of the copper roller is controlled to complete the rapid solidification casting. The obtained NdFeB alloy sheets are subjected to hydrogen crushing, air flow grinding, magnetic field pressing, sintering, heat treatment and performance testing to obtain high-performance high-temperature resistant sintered NdFeB magnets.

[0010] Furthermore, the NdFeB magnet is composed of the following components in mass percentage: Pr-Nd: 29.5-32%, Dy: 0-5%, Cu: 0.01%-0.5%, Co: 0.6%-2%, Al: 0.2-0.8%, B: 1%-5.5% and Nb: 0-3.5%, with the remainder being Fe.

[0011] Furthermore, the purity of the Pr-Nd is greater than 99%, the Pr content is 20%-30%, the Dy is added in the form of a Dy-Fe alloy, wherein the Dy content is 80%, the Nb is added in the form of a Nb-Fe alloy, wherein the Nb content is 65%, and the B is added in the form of a B-Fe alloy, wherein the B content is 18.3-20.4%.

[0012] Furthermore, the vacuum operation makes the vacuum degree in the vacuum melting casting furnace reach Pa.

[0013] Furthermore, the copper roller has a rotation speed of 1-2.5 m / s.

[0014] Furthermore, the average thickness of the NdFeB alloy sheet obtained after rapid solidification is 0.25 to 0.5 mm.

[0015] Further, the floating probability and floating probability weight of the second temperature data are obtained, and the copper roller cooling rate matching degree of the second temperature data is obtained according to the floating probability and floating probability weight of the second temperature data, including the specific method of:

[0016] Record each second temperature data in the cooling completion temperature sequence as primary temperature data;

[0017] Recording the number of all temperature data from the first second temperature data to the first level temperature data in the cooling completion temperature sequence as the first number of the first level temperature data;

[0018] The ratio of the frequency of occurrence of the first-level temperature data in the cooling completion temperature sequence to the first quantity of the first-level temperature data is recorded as the floating probability of the first-level temperature data;

[0019] The absolute value of the difference between the second temperature data in the cooling completion temperature sequence and the standard temperature of the solidified molten metal is recorded as the floating probability weight of the second temperature data;

[0020] The product of the floating probability of the primary temperature data and the floating probability weight is recorded as the floating probability product of the primary temperature data;

[0021] The mean of the floating probability products of the first second temperature data to the first-level temperature data in the cooling completion temperature sequence is recorded as the mean of the floating probability products of the first-level temperature data;

[0022] The power with the natural constant as the base and the opposite number of the mean of the floating probability product of the primary temperature data as the exponent is recorded as the copper roller cooling rate matching degree of the primary temperature data.

[0023] Further, the method of obtaining the abnormal score of the first temperature data according to the first temperature data included in the cooling initial temperature sequence, and obtaining the copper roller speed adjustment coefficient of the second temperature data according to the abnormal scores of all the first temperature data included in the cooling initial temperature sequence and the copper roller cooling rate matching degree of the second temperature data, includes the following specific methods:

[0024] Using an anomaly detection algorithm on the first temperature data in the cooling initial temperature sequence to obtain anomaly scores of all first temperature data;

[0025] Record the difference between the abnormal score of the first temperature data and the average of the abnormal scores of all the first temperature data included in the cooling initial temperature sequence as the abnormal score difference of the first temperature data;

[0026] Recording the abnormal score difference of the first temperature data in the cooling initial temperature sequence at the same time as the acquisition time of the second temperature data as the first abnormal score difference of the second temperature data;

[0027] The ratio of the abnormal score difference of the second temperature data to the matching degree of the copper roller cooling rate is recorded as the copper roller speed adjustment coefficient of the second temperature data.

[0028] Further, the obtaining of the upward floating probability and the downward floating probability of the second temperature data includes the following specific methods:

[0029] The number of the first second temperature data to the first level temperature data in the cooling completion temperature sequence that is within the upper floating range of the metal liquid cooling completion temperature is recorded as the upper floating number of the first level temperature data;

[0030] The ratio of the upward floating quantity of the first-level temperature data to the first quantity of the first-level temperature data is recorded as the upward floating probability of the first-level temperature data.

[0031] Further, the copper roller speed is obtained according to the copper roller speed adjustment sequence and the copper roller speed adjustment coefficient, the copper roller speed is controlled, the rapid solidification casting is completed, and then the obtained NdFeB alloy sheet is subjected to hydrogen crushing, air flow grinding, magnetic field pressing, sintering, heat treatment and performance testing respectively to obtain a high-performance high-temperature resistant sintered NdFeB magnet, including the specific method:

[0032] Input the copper roller speed adjustment sequence into the neural network to obtain the copper roller speed control ratio value, wherein the neural network can use the BP neural network and the optimization algorithm can use the SGD algorithm;

[0033] The copper roller speed control ratio value of the temperature data and the copper roller speed adjustment coefficient are input into the PID controller to obtain the speed of the copper roller;

[0034] The rotation speed of the copper roller is obtained as the actual rotation speed of the copper roller to realize the control of the rotation speed of the copper roller, complete the rapid solidification casting, and obtain the NdFeB alloy sheet;

[0035] The obtained NdFeB alloy flakes are subjected to hydrogen crushing and then dehydrogenation treatment;

[0036] The hydrogen-crushed product is then ground into a NdFeB alloy powder of a predetermined size using argon gas in a jet mill;

[0037] The NdFeB alloy powder of a preset size is subjected to magnetic field pressing, wherein the magnetic field pressing includes but is not limited to two stages of forming and isostatic pressing, to obtain a green body;

[0038] After the pressing and forming, the green body is sintered, and the sintering includes but is not limited to the two processes of heating and heat preservation. After the sintering is completed, a rapid cooling treatment is performed;

[0039] The green body obtained after the rapid cooling treatment is heat-treated to obtain a high-temperature sintered NdFeB magnet; the high-temperature sintered NdFeB magnet is subjected to performance testing, including but not limited to magnetic properties, microstructure observation of the rapid solidification casting belt, micro-region composition and fracture morphology analysis, particle size distribution measurement and magnet average grain size measurement, to obtain a comprehensive performance evaluation of the high-temperature sintered NdFeB magnet;

[0040] According to the comprehensive evaluation of high temperature resistant sintered NdFeB magnets performance, high performance high temperature resistant sintered NdFeB magnets are obtained.

[0041] The beneficial effects of the present invention are:

[0042] The present invention collects temperature data of the molten metal at the tundish pouring port and the NdFeB alloy thin sheet obtained at the discharge port of the vacuum melting casting furnace, obtains the cooling initial temperature sequence, the cooling completion temperature sequence, the first temperature data and the second temperature data, firstly, according to the principle that the initial temperature of the molten metal has certain fluctuations and different initial temperatures require different cooling rates for matching, the copper roller cooling rate matching degree of the second temperature data is obtained; secondly, the matching degree between the current rotation speed of the copper roller and the current cooling demand is evaluated, and the copper roller rotation speed adjustment coefficient of the second temperature data is obtained according to the abnormal score of the first temperature data and the copper roller cooling rate matching degree of the second temperature data, and then the copper roller rotation speed adjustment sequence is obtained; then, the metal liquid cooling completion temperature sequence is set according to the standard temperature of the solidified metal liquid. The floating range of the degree is obtained, and then the copper roller speed adjustment coefficient is obtained. The degree to which the copper roller speed should be increased or decreased is determined according to the copper roller speed adjustment coefficient. Finally, the speed of the copper roller is obtained according to the copper roller speed adjustment sequence and the copper roller speed adjustment coefficient, so as to realize the control of the copper roller speed. After the rapid solidification casting is completed, the obtained NdFeB alloy sheet is subjected to hydrogen crushing, air flow grinding, magnetic field pressing, sintering, heat treatment and performance testing processes to obtain high-performance high-temperature resistant sintered NdFeB magnets, so as to solve the problem that when the rapid solidification casting method is used to prepare high-temperature resistant sintered NdFeB magnets, the parameter setting of the process equipment depends on the prior parameters, which makes it difficult to cope with the changes in the preparation process. The speed of the copper roller is controlled according to the initial temperature of the molten metal cooling and the completion temperature of the molten metal cooling, so as to improve the preparation quality of the high-temperature resistant sintered NdFeB magnets. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0044] Figure 1 A schematic flow chart of a method for preparing a high temperature sintered NdFeB magnet based on copper roller speed control provided by one embodiment of the present invention;

[0045] Figure 2 Schematic diagram of temperature floating range. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] See also Figure 1 , which shows a flow chart of a method for preparing a high temperature sintered NdFeB magnet based on copper roller speed control provided by an embodiment of the present invention, the method comprising the following steps:

[0048] Step S001, put the raw materials for preparing NdFeB magnets into the crucible of the vacuum melting and casting furnace according to the proportion, evacuate the vacuum, heat up and melt under the protection of high-purity argon, adjust the rotation speed of the copper roller, and after melting, cast the molten metal in the crucible through the tundish into the water-cooled copper roller for rapid solidification to obtain the NdFeB alloy sheet, collect the temperature data in the vacuum melting and casting furnace, and obtain the cooling initial temperature sequence, cooling completion temperature sequence, first temperature data and second temperature data.

[0049] Raw materials for preparing NdFeB magnets are weighed according to the mass percentage of Pr-Nd: 31wt%, Dy: 0.8wt%, Cu: 0.2wt%, Co: 0.9wt%, Al: 0.4%, B: 1.02wt%, Nb: 0.3wt% and Fe: 65.38wt%, and then put into a crucible of a vacuum melting casting furnace in a certain order according to the melting points, wherein the purity of Pr-Nd is greater than 99%, and the content of Pr in the Pr-Nd alloy is 25%; Dy is added in the form of Dy-Fe alloy, and the content of Dy in Dy-Fe is 80%; Nb is added in the form of Nb-Fe alloy, and the content of Nb in the Nb-Fe alloy is 65%; B is added in the form of B-Fe alloy, and the content of B in the B-Fe alloy is 20%; other raw materials are analytically pure metals.

[0050] Then close the vacuum melting casting furnace and start to evacuate. When the vacuum degree in the vacuum melting casting furnace reaches Pa, stop vacuuming and start filling with high-purity argon. When the argon pressure in the vacuum melting and casting furnace is 0.04MPa, start smelting. Control the smelting temperature at 1500℃. After the above raw materials are completely melted, let them stand and refine for 2 minutes. Adjust the speed of the copper roller to 2m / s, cast the molten metal in the crucible through the tundish onto the water-cooled copper roller for rapid condensation and solidification, and obtain NdFeB alloy sheet with a thickness of 0.35mm.

[0051] Among them, a B-type PtRh30-PtRh6 thermocouple temperature sensor is set in the vacuum melting casting furnace. During the preparation process of the NdFeB alloy thin sheet, the temperature data of the molten metal at the tundish pouring port and the NdFeB alloy thin sheet at the discharge port of the vacuum melting casting furnace are collected. The temperature of the molten metal at the tundish pouring port is the initial temperature of the molten metal cooling, and the temperature of the NdFeB alloy thin sheet at the discharge port of the vacuum melting casting furnace is recorded as the completion temperature of the molten metal cooling.

[0052] Temperature data is collected from two temperature sensors once at every time interval T. The temperature data of the temperature sensors at the molten metal position at the tundish pouring gate are arranged according to the temperature data collection time to obtain the initial cooling temperature sequence. The temperature data of the temperature sensors of the NdFeB alloy sheet at the discharge port of the vacuum melting casting furnace are arranged according to the temperature data collection time to obtain the cooling completion temperature sequence.

[0053] The empirical value of the interval time T is 0.5 seconds, and the empirical values ​​of the number of temperature data included in the cooling initial temperature sequence and the cooling completion temperature sequence are both first empirical values. The empirical value of the first empirical value is 500.

[0054] The temperature data in the cooling initial temperature sequence is recorded as the first temperature data, and the temperature data in the cooling completion temperature sequence is recorded as the second temperature data.

[0055] At this point, the cooling initial temperature sequence, the cooling completion temperature sequence, the first temperature data and the second temperature data are acquired.

[0056] Step S002: Obtain the floating probability and floating probability weight of the second temperature data, and obtain the copper roller cooling rate matching degree of the second temperature data according to the floating probability and floating probability weight of the second temperature data.

[0057] Due to the measurement error of the molten metal temperature after solidification and the occurrence of temperature anomalies, the initial temperature of the molten metal fluctuates to a certain extent. Different initial temperatures require different cooling rates to match. Therefore, the cooling rate needs to be determined according to the cooling completion temperature of the molten metal to ensure the quality of the NdFeB alloy sheet.

[0058] Each second temperature data in the cooling completion temperature sequence is recorded as primary temperature data for analysis, and the number of all temperature data from the first second temperature data to the primary temperature data in the cooling completion temperature sequence is recorded as the first number of primary temperature data.

[0059] The ratio of the frequency of occurrence of the primary temperature data in the cooling completion temperature sequence to the first quantity of the primary temperature data is recorded as the floating probability of the primary temperature data.

[0060] The absolute value of the difference between the second temperature data in the cooling completion temperature sequence and the standard temperature of the solidified molten metal is recorded as the floating probability weight of the second temperature data, wherein the standard temperature of the solidified molten metal is 30°C.

[0061] The copper roller cooling rate matching degree of the second temperature data is obtained according to the floating probability and floating probability weight of the second temperature data in the cooling completion temperature sequence.

[0062]

[0063] In the formula, The first temperature in the cooling completion temperature sequence The matching degree of the copper roller cooling rate of the second temperature data; For the a first number of second temperature data; The first temperature in the cooling completion sequence Second temperature data; The first temperature in the cooling completion temperature sequence The floating probability of the second temperature data; The first temperature in the cooling completion temperature sequence floating probability weight for each second temperature data; is an exponential function with a natural constant as its base.

[0064] When the floating probability and floating probability weight of the second temperature data in the cooling completion temperature sequence are greater, the matching degree of the copper roller cooling rate of the second temperature data is smaller, that is, the deviation between the second temperature data in the cooling completion temperature sequence and the standard temperature of the solidified molten metal is greater, the current rotation speed of the copper roller is less matched with the current cooling demand, and the rotation speed of the copper roller needs to be adjusted to improve the production quality of high temperature resistant sintered NdFeB magnets.

[0065] At this point, the matching degree of the copper roller cooling rate of the second temperature data is obtained.

[0066] Step S003, obtaining the abnormal score of the first temperature data according to the first temperature data contained in the cooling initial temperature sequence, obtaining the copper roller speed adjustment coefficient of the second temperature data according to the abnormal scores of all first temperature data contained in the cooling initial temperature sequence and the copper roller cooling rate matching degree of the second temperature data, and obtaining the copper roller speed adjustment sequence.

[0067] The LOF anomaly detection algorithm is used for the first temperature data in the cooling initial temperature sequence to obtain the anomaly scores of all the first temperature data, wherein the hyperparameter K of the LOF anomaly detection algorithm is 3.

[0068] The copper roller rotation speed adjustment coefficient of the second temperature data is obtained according to the abnormal scores of all the first temperature data included in the cooling initial temperature sequence and the copper roller cooling rate matching degree of the second temperature data.

[0069]

[0070] In the formula, The first temperature in the cooling completion temperature sequence The copper roller speed adjustment coefficient of the second temperature data; The first temperature in the cooling initial temperature sequence The anomaly score of the first temperature data; is the mean of the anomaly scores of all first temperature data contained in the cooling initial temperature sequence; The first temperature in the cooling completion temperature sequence The copper roller cooling rate matching of the second temperature data.

[0071] The greater the difference between the abnormal score of the first temperature data in the cooling initial temperature sequence and the mean abnormal score of all the first temperature data contained in the cooling initial temperature sequence, the smaller the matching degree of the copper roller cooling rate of the second temperature data at the same time as the acquisition time of the first temperature data, the greater the adjustment coefficient of the copper roller speed of the second temperature data at the same time as the acquisition time of the first temperature data, that is, the less the current rotation speed of the copper roller matches the current cooling demand, and the more it is necessary to adjust the rotation speed of the copper roller to improve the production quality of high temperature resistant sintered NdFeB magnets.

[0072] Arrange the copper roller speed adjustment coefficients of the second temperature data in the cooling completion temperature sequence according to the order in which the temperature data are obtained to obtain the copper roller speed adjustment sequence.

[0073] At this point, the copper roller speed adjustment coefficient and the copper roller speed adjustment sequence of the second temperature data are obtained.

[0074] Step S004, according to the second temperature data included in the cooling completion temperature sequence and the standard temperature of the solidified molten metal, obtain the upper floating range of the molten metal cooling completion temperature and the lower floating range of the molten metal cooling completion temperature, obtain the upper floating probability and the lower floating probability of the second temperature data, obtain the molten metal cooling completion temperature floating index according to the upper floating probability and the lower floating probability of all the second temperature data in the cooling completion temperature sequence, and obtain the copper roller speed adjustment coefficient according to the molten metal cooling completion temperature floating index.

[0075] Too fast or too slow rotation speed of the copper roller will lead to a decrease in the quality of the prepared high-temperature resistant sintered NdFeB magnets. Therefore, it is necessary to set the floating range of the metal liquid cooling completion temperature according to the standard temperature of the solidified metal liquid.

[0076] Get the maximum value of the second temperature data in the cooling completion temperature sequence and minimum value ,Will As the metal liquid cools down and the temperature rises, As the floating range of the metal liquid cooling completion temperature. is the standard temperature of the solidified molten metal. The temperature floating range diagram is as follows: Figure 2 shown.

[0077] The number of the first second temperature data to the first-level temperature data in the cooling completion temperature sequence that are within the upper floating range of the molten metal cooling completion temperature is recorded as the upper floating number of the first-level temperature data, and the ratio of the upper floating number of the first-level temperature data to the first number of the first-level temperature data is recorded as the upper floating probability of the first-level temperature data.

[0078] The number of the first second temperature data to the first level temperature data in the cooling completion temperature sequence that are within the floating range of the molten metal cooling completion temperature is recorded as the downward floating number of the first level temperature data, and the ratio of the downward floating number of the first level temperature data to the first number of the first level temperature data is recorded as the downward floating probability of the first level temperature data.

[0079] The metal liquid cooling completion temperature fluctuation index is obtained according to the upward fluctuation probability and the downward fluctuation probability of all the second temperature data in the cooling completion temperature sequence.

[0080]

[0081] In the formula, Complete temperature floating index for molten metal cooling; The first temperature in the cooling completion temperature sequence Second temperature data; For the The upward floating probability of the second temperature data; For the The downward floating probability of the second temperature data; is a first empirical value, the empirical value is 500, that is, the number of second temperature data included in the cooling completion temperature sequence; It is the first preset value, and the empirical value is 1.

[0082] When the probability of upward floating in the temperature data of the completion of molten metal cooling is smaller than the probability of downward floating, the temperature floating index of the completion of molten metal cooling is less than 0, and the speed of the copper roller should be reduced; when the probability of upward floating in the temperature data of the completion of molten metal cooling is larger than the probability of downward floating, the temperature floating index of the completion of molten metal cooling is greater than 0, and the speed of the copper roller should be increased.

[0083] The power with the natural constant as the base and the temperature fluctuation index of the metal liquid cooling completion as the exponent is recorded as the copper roller speed adjustment coefficient.

[0084] When the temperature fluctuation index of the metal liquid is larger, the copper roller speed adjustment coefficient is larger. When the copper roller speed adjustment coefficient is greater than 0, the copper roller speed should increase; when the copper roller speed adjustment coefficient is less than 0, the copper roller speed should decrease; when the copper roller speed adjustment coefficient is equal to 0, the copper roller speed should remain unchanged.

[0085] In particular, it should be noted that when the maximum value of the second temperature data in the cooling completion temperature sequence is less than the standard temperature of the molten metal after solidification, it is considered that the cooling rate of the copper roller is much greater than the cooling requirement, and the copper roller speed adjustment coefficient is assigned to the second preset value. At this time, the copper roller speed should be reduced; when the minimum value of the second temperature data in the cooling completion temperature sequence is greater than the standard temperature of the molten metal after solidification, it is considered that the cooling rate of the copper roller is much less than the cooling requirement, and the copper roller speed adjustment coefficient is assigned to the third preset value. At this time, the copper roller speed should be increased.

[0086] Among them, the second preset value is an integer less than -1, and the empirical value is -3; the third preset value is an integer greater than 1, and the empirical value is 3.

[0087] At this point, the copper roller speed adjustment coefficient is obtained.

[0088] Step S005, obtain the speed of the copper roller according to the copper roller speed adjustment sequence and the copper roller speed adjustment coefficient, realize the control of the copper roller speed, complete the rapid solidification casting, and subject the obtained NdFeB alloy sheets to hydrogen crushing, air flow grinding, magnetic field pressing, sintering, heat treatment and performance testing to obtain high-performance high-temperature resistant sintered NdFeB magnets.

[0089] The copper roller speed adjustment sequence is input into the neural network to obtain the copper roller speed control ratio value. The neural network can use the BP neural network, and the optimization algorithm can use the SGD algorithm. The training process of the neural network is a well-known technology and will not be described in detail.

[0090] The copper roller speed control ratio value of the temperature data and the copper roller speed adjustment coefficient are input into the PID controller to obtain the speed of the copper roller. The obtained speed of the copper roller is used as the actual speed of the copper roller to control the speed of the copper roller. That is, when the speed of the copper roller cannot meet the current cooling demand, the speed of the copper roller is increased according to the adjustment range; when the speed of the copper roller exceeds the current cooling demand, the speed of the copper roller is reduced according to the adjustment range.

[0091] At this point, the rotation speed of the copper roller in the vacuum melting casting furnace can be adaptively adjusted according to the current production status, and the rotation speed of the copper roller can be controlled to obtain higher quality NdFeB alloy sheets.

[0092] The obtained NdFeB alloy flakes were hydrogen crushed and dehydrogenated to obtain magnetic powder with a thickness of 2 mm;

[0093] Then, the magnetic powder is ground into NdFeB alloy powder with a particle size of 3 μm by jet milling under a gas pressure of 0.8 MPa;

[0094] In an argon atmosphere, the obtained 3μm NdFeB alloy powder was pressed into a state with a density of 4.0g / cm3 under magnetic field orientation conditions (magnetic field strength of 1.8T), and then an isostatic pressing process was used to increase the density of the formed green body. The isostatic pressing size was 200MPa, and the pressure was maintained for 2min to obtain the green body.

[0095] After pressing and forming, the green body is vacuum sintered at a temperature of 1090°C, sintered for 4 hours and kept warm for 2 hours, and then filled with high-purity argon gas and rapidly cooled to below 100°C;

[0096] Then the temperature is raised to 900℃ and kept for 2h for primary tempering. After cooling, the secondary tempering is carried out at 480℃ for 2h. After the secondary tempering, high-purity argon is filled and quickly cooled to below 100℃ to obtain high-temperature resistant sintered NdFeB magnets.

[0097] Performance test, using NIM-10000 magnetic material measurement system, the magnetic properties of the obtained high temperature sintered NdFeB magnets were tested, the digital optical microscope OLYMPUS-MX50 was used to observe the microstructure of the rapid casting strip, the JSM-5610LV scanning electron microscope was used to analyze the micro-region composition and fracture morphology, the laser particle size analyzer (HELOS) of SYMPATEC of Germany was used to determine the particle size distribution, and the Mias-2000 metallographic image analysis system dedicated software was used to determine the average grain size of the magnet, in order to obtain a comprehensive evaluation of the performance of the high temperature sintered NdFeB magnets.

[0098] The specific test content, instruments and systems used in the performance test can be set by the user as needed.

[0099] At this point, through the processes of batching, smelting and casting, hydrogen crushing, air flow grinding, magnetic field pressing, sintering, heat treatment and performance testing, high-performance high-temperature resistant sintered NdFeB magnets are produced.

[0100] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a high temperature sintered NdFeB magnet based on copper roller speed control, characterized in that: The method comprises the following steps: Put the raw materials for preparing NdFeB magnets into the crucible of the vacuum melting casting furnace according to the proportion, evacuate the furnace, heat up and melt under the protection of high-purity argon, adjust the rotation speed of the copper roller, and after melting, cast the molten metal in the crucible through the tundish into the water-cooled copper roller for rapid solidification to obtain the NdFeB alloy sheet, collect the temperature data in the vacuum melting casting furnace, and obtain the cooling initial temperature sequence, cooling completion temperature sequence, first temperature data and second temperature data; Obtaining the floating probability and floating probability weight of the second temperature data, and obtaining the copper roller cooling rate matching degree of the second temperature data according to the floating probability and floating probability weight of the second temperature data; According to the first temperature data included in the cooling initial temperature sequence, the abnormal score of the first temperature data is obtained; according to the abnormal score of all the first temperature data included in the cooling initial temperature sequence and the copper roller cooling rate matching degree of the second temperature data, the copper roller speed adjustment coefficient of the second temperature data is obtained, and the copper roller speed adjustment sequence is obtained; According to the second temperature data included in the cooling completion temperature sequence and the standard temperature of the solidified molten metal, the upper floating interval of the molten metal cooling completion temperature and the lower floating interval of the molten metal cooling completion temperature are obtained, and the upper floating probability and the lower floating probability of the second temperature data are obtained. According to the upper floating probability and the lower floating probability of all the second temperature data in the cooling completion temperature sequence, the molten metal cooling completion temperature floating index is obtained, and the copper roller speed adjustment coefficient is obtained according to the molten metal cooling completion temperature floating index; The speed of the copper roller is obtained according to the copper roller speed adjustment sequence and the copper roller speed adjustment coefficient, and the speed of the copper roller is controlled to complete the rapid solidification casting. The obtained NdFeB alloy sheet is subjected to hydrogen crushing, air flow grinding, magnetic field pressing, sintering, heat treatment and performance testing to obtain a high-performance high-temperature resistant sintered NdFeB magnet; The method for obtaining the temperature data in the vacuum melting casting furnace is: A temperature sensor is arranged in the vacuum melting casting furnace, and during the preparation process of the NdFeB alloy thin sheets, the temperature data of the molten metal at the pouring port of the tundish and the NdFeB alloy thin sheets at the discharge port of the vacuum melting casting furnace are collected; The method for obtaining the abnormal score of the first temperature data is: The LOF anomaly detection algorithm is used for the first temperature data in the cooling initial temperature sequence to obtain the anomaly scores of all the first temperature data.

2. The method for preparing high temperature sintered NdFeB magnets based on copper roller speed control according to claim 1, characterized in that: The NdFeB magnet is composed of the following components in mass percentage: Pr-Nd: 29.5-32%, Dy: 0-5%, Cu: 0.01%-0.5%, Co: 0.6%-2%, Al: 0.2-0.8%, B: 1%-5.5% and Nb: 0-3.5%, and the balance is Fe.

3. The method for preparing high temperature sintered NdFeB magnets based on copper roller speed control according to claim 2, characterized in that: The purity of the Pr-Nd is greater than 99%, the Pr content is 20%-30%, the Dy is added in the form of a Dy-Fe alloy, wherein the Dy content is 80%, the Nb is added in the form of a Nb-Fe alloy, wherein the Nb content is 65%, and the B is added in the form of a B-Fe alloy, wherein the B content is 18.3-20.4%.

4. The method for preparing high temperature sintered NdFeB magnets based on copper roller speed control according to claim 1, characterized in that: The vacuum operation makes the vacuum degree in the vacuum melting casting furnace reach 1.0×10 -2 Pa.

5. The method for preparing high temperature sintered NdFeB magnets based on copper roller speed control according to claim 1, characterized in that: The copper roller has a rotation speed of 1-2.5 m / s.

6. The method for preparing high temperature sintered NdFeB magnets based on copper roller speed control according to claim 1, characterized in that: The average thickness of the NdFeB alloy sheet obtained after rapid solidification is 0.25-0.5 mm.

7. The method for preparing high temperature sintered NdFeB magnets based on copper roller speed control according to claim 1, characterized in that: The method of obtaining the floating probability and floating probability weight of the second temperature data and obtaining the copper roller cooling rate matching degree of the second temperature data according to the floating probability and floating probability weight of the second temperature data includes: Record each second temperature data in the cooling completion temperature sequence as primary temperature data; Recording the number of all temperature data from the first second temperature data to the first level temperature data in the cooling completion temperature sequence as the first number of the first level temperature data; The ratio of the frequency of occurrence of the first-level temperature data in the cooling completion temperature sequence to the first quantity of the first-level temperature data is recorded as the floating probability of the first-level temperature data; The absolute value of the difference between the second temperature data in the cooling completion temperature sequence and the standard temperature of the solidified molten metal is recorded as the floating probability weight of the second temperature data; The product of the floating probability of the primary temperature data and the floating probability weight is recorded as the floating probability product of the primary temperature data; The mean of the floating probability products of the first second temperature data to the first-level temperature data in the cooling completion temperature sequence is recorded as the mean of the floating probability products of the first-level temperature data; The power with the natural constant as the base and the opposite number of the mean of the floating probability product of the primary temperature data as the exponent is recorded as the copper roller cooling rate matching degree of the primary temperature data.

8. The method for preparing high temperature sintered NdFeB magnets based on copper roller speed control according to claim 7, characterized in that: The specific method of obtaining the abnormal score of the first temperature data according to the first temperature data included in the cooling initial temperature sequence, and obtaining the copper roller speed adjustment coefficient of the second temperature data according to the abnormal scores of all the first temperature data included in the cooling initial temperature sequence and the copper roller cooling rate matching degree of the second temperature data is as follows: Using an anomaly detection algorithm on the first temperature data in the cooling initial temperature sequence to obtain anomaly scores of all first temperature data; Record the difference between the abnormal score of the first temperature data and the average of the abnormal scores of all the first temperature data included in the cooling initial temperature sequence as the abnormal score difference of the first temperature data; Recording the abnormal score difference of the first temperature data in the cooling initial temperature sequence at the same time as the acquisition time of the second temperature data as the first abnormal score difference of the second temperature data; The ratio of the abnormal score difference of the second temperature data to the matching degree of the copper roller cooling rate is recorded as the copper roller speed adjustment coefficient of the second temperature data.

9. The method for preparing high temperature sintered NdFeB magnets based on copper roller speed control according to claim 8, characterized in that: The method of obtaining the upward floating probability and the downward floating probability of the second temperature data includes: The number of the first second temperature data to the first level temperature data in the cooling completion temperature sequence that is within the upper floating range of the metal liquid cooling completion temperature is recorded as the upper floating number of the first level temperature data; The ratio of the upward floating quantity of the first-level temperature data to the first quantity of the first-level temperature data is recorded as the upward floating probability of the first-level temperature data.

10. The method for preparing high temperature sintered NdFeB magnets based on copper roller speed control according to claim 1, characterized in that: The copper roller speed is obtained according to the copper roller speed adjustment sequence and the copper roller speed adjustment coefficient, the copper roller speed is controlled, and the rapid solidification casting is completed. Then, the obtained NdFeB alloy sheet is subjected to hydrogen crushing, air flow grinding, magnetic field pressing, sintering, heat treatment and performance testing respectively to obtain a high-performance high-temperature resistant sintered NdFeB magnet. The specific method includes: The copper roller speed adjustment sequence is input into the neural network to obtain the copper roller speed control ratio value, wherein the neural network uses the BP neural network and the optimization algorithm uses the SGD algorithm; The copper roller speed control ratio value of the temperature data and the copper roller speed adjustment coefficient are input into the PID controller to obtain the speed of the copper roller; The rotation speed of the copper roller is obtained as the actual rotation speed of the copper roller to realize the control of the rotation speed of the copper roller, complete the rapid solidification casting, and obtain the NdFeB alloy sheet; The obtained NdFeB alloy flakes are subjected to hydrogen crushing and then dehydrogenation treatment; The hydrogen-crushed product is then ground into a NdFeB alloy powder of a predetermined size using argon gas in a jet mill; The NdFeB alloy powder of a preset size is subjected to magnetic field pressing, wherein the magnetic field pressing includes two stages, namely, forming and isostatic pressing, to obtain a green body; After pressing and forming, the green body is sintered. The sintering process includes two steps: heating and heat preservation. After sintering, it is quickly cooled. The green body obtained after the rapid cooling treatment is subjected to heat treatment to obtain a high temperature resistant sintered NdFeB magnet; The performance test of high temperature sintered NdFeB magnets includes magnetic properties, microstructure observation of rapid solidification casting strip, micro-region composition and fracture morphology analysis, particle size distribution measurement and magnet average grain size measurement, to obtain a comprehensive evaluation of the performance of high temperature sintered NdFeB magnets; According to the comprehensive evaluation of the performance of high temperature resistant sintered NdFeB magnets, high performance high temperature resistant sintered NdFeB magnets are obtained.

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