Preparation method of high-performance rapid-quenching samarium-iron-nitrogen magnetic powder

Abstract

The invention provides a preparation method of high-performance rapid-quenching samarium-iron-nitrogen magnetic powder, and belongs to the technical field of magnetic materials, and the preparation method comprises the following steps: A1, weighing according to 2-3% excess Sm, and smelting and rapidly hardening samarium powder and iron powder in a small smelting and rapid-quenching device to obtain primary alloy powder; a2, cooling the primary alloy powder, uniformly mixing the cooled primary alloy powder with metal samarium powder, and carrying out smelting and rapid hardening again to obtain secondary alloy magnetic powder; a3, the secondary alloy powder is subjected to HDDR treatment, and modified alloy powder is obtained; and A4, the modified alloy powder is subjected to nitriding treatment, and the high-performance rapid-quenching samarium-iron-nitrogen magnetic powder uniform in structure is obtained. According to the invention, through loss of metal samarium in a primary alloy powder stage and alloy component segregation caused by density difference of a molten pool in smelting, metal samarium complementation in secondary smelting is increased, and the phenomenon of nonuniform magnetic performance of magnetic powder particles caused by alloy component segregation is effectively restrained; and the prepared magnetic material has relatively high coercive force, magnetic performance and uniformity.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetic materials, and in particular relates to a method for preparing high-performance rapidly quenched samarium iron nitrogen magnetic powder. Background Art

[0002] SmFeN materials have high Curie temperature and good corrosion resistance. They can be used for a long time in a humid environment and are widely used in the preparation of micro motor magnetic strips and functional magnetic materials. With the lightweight and high performance of household appliances, instrumentation, aerospace and new energy vehicles, there is an urgent need to develop high-performance and cost-effective SmFeN materials.

[0003] In existing industrial production, it is usually necessary to carry out smelting and rapid solidification treatment under the protection of inert gas, obtain fine powder with specific crushing equipment, and slowly cool after high-temperature nitriding to obtain samarium iron nitrogen magnetic powder. However, due to the active chemical properties of samarium elements, in the preparation process of samarium iron nitrogen materials, during smelting and rapid solidification, due to the high vapor pressure of samarium and the melting point of 1074℃, which is significantly lower than 1538℃ of iron, it will preferentially volatilize at the high melting temperature of 1600-1700℃. Metal samarium will be easily lost, and insufficient vacuum or too long smelting time during smelting will lead to samarium loss. Although the total samarium loss rate has been reduced from 15-20% to 3-5% after the existing technology optimizes the process, such as through liquid nitrogen crushing, dynamic argon protection, etc., the density difference in the molten pool will still cause the composition segregation in the smelted alloy liquid, resulting in the appearance of samarium-poor phase and samarium-rich phase. Because in the subsequent cooling, the rapid quenching cooling roller requires the molten pool alloy liquid level to be extremely stable before it can throw out continuous strips. In order to ensure the stability of the cooling strips, mechanical or electric current stirring cannot be used. The difference in component density under the static state of the molten pool liquid level causes the composition segregation of the alloy strips flowing out to the cooling roller, which will lead to low magnetic properties and extremely uneven performance of the finished magnetic powder. It makes it difficult for the final magnetic powder to achieve high magnetic properties and consistency. In current production practice, magnetic separators are generally used to classify and screen magnetic powders into high, medium and low performance types, resulting in a waste of rare earth resources and energy, and reducing production efficiency. Summary of the invention

[0004] In order to solve the problems existing in the background technology, the present invention provides a method for preparing high-performance rapid-quenching samarium iron nitrogen magnetic powder, which can effectively suppress the samarium loss and component segregation problems of the samarium iron nitrogen material during the preparation process, and effectively improve the production efficiency, and prepare a samarium iron nitrogen magnetic powder with high coercive force and uniform magnetic properties.

[0005] In order to achieve the above object, the present invention provides the following technical solutions: A method for preparing high-performance rapid-quenching samarium iron nitrogen magnetic powder comprises the following steps: A1. Sm2Fe 17Based on the components, weigh according to the excess of 2-3% Sm, melt, quench and solidify samarium powder and iron powder in a small melting and quenching device under vacuum and argon filling conditions, and crush to a particle size of 30-400 mesh to obtain a primary alloy powder; A2, mixing the primary alloy powder and the metal samarium powder and stirring them evenly, subjecting the mixture to a smelting, rapid quenching and rapid solidification treatment in a small smelting and rapid quenching device under vacuum and argon filling conditions, and crushing the mixture into particles of 60-200 mesh to obtain a secondary modified alloy powder; A3, subjecting the secondary modified alloy powder to HDDR treatment, crushing it to a particle size of 100-400 mesh, and subjecting it to aging treatment to obtain modified alloy powder; A4. Place the modified alloy powder in a high-temperature nitriding furnace for 4-12 hours, and then rapidly cool it to room temperature in vacuum within 1 hour to obtain high-performance rapidly quenched samarium iron nitrogen magnetic powder with uniform structure.

[0006] Furthermore, the small-scale smelting and quenching device comprises a continuous feeding overflow crucible and a cold cutting roller, which continuously feed materials at one end and continuously overflow materials at the other end. The cold cutting roller is placed at the overflow port of the crucible. The feeding port and the overflow port of the continuous feeding overflow crucible adopt a double-end sealing structure. An annular argon nozzle with a pressure of 0.2-0.5MPa is arranged on the periphery of the overflow port and the cooling roller interface to form an inert gas barrier. The outer diameter of the continuous feeding overflow crucible is: diameter 80-300mm, height: 100-300mm.

[0007] Furthermore, the feed port of the continuous feeding overflow crucible is located at the top of the crucible for continuously adding raw materials. Dynamic sealing is used to accommodate continuous feeding. The feed port uses a double gate valve or a rotary air lock valve to achieve synchronization of feeding and sealing. The overflow port is located at the bottom of the crucible to control the stable outflow of the melt and form a uniform liquid film to prevent gas backflow. The discharge port maintains the local atmosphere through gas protection or mechanical sealing to prevent gas disturbance in the cooling roller area, thereby realizing a double-end sealing structure for the feed port and overflow port of the continuous feeding overflow crucible. ‌‌ Furthermore, in step A1, the smelting rapid quenching and rapid solidification treatment process is as follows: under vacuum and then argon filling conditions, the mixture of samarium powder and iron powder is placed in a small smelting rapid quenching device and heated to 1600-1700°C, a uniform melt is continuously obtained by continuously feeding at one end and continuously overflowing at the other end, and the melt is placed on the surface of a cooling roller rotating at a speed of 20-30m / s for cooling for ≥10 5 The cooling rate of K / s is fast solidification. Affected by factors such as vacuum degree, the smelting, rapid quenching and rapid solidification treatment is carried out in a single material warehouse batch of ≤500 kg.

[0008] Furthermore, in step A1, the crushing method is physical crushing by air jet mill or vacuum crusher, the crushing temperature is 120-140° C., and the pressure is 0.06-0.1 MPa.

[0009] Furthermore, in step A2, the proportion of the metal samarium powder added is calculated by mass balance to record the raw material input amount and the product mass, and the total loss rate is calculated by the difference method, wherein the difference method calculation formula is: total loss rate = (1-Sm mass in finished magnetic powder / Sm mass of raw material) × 100%, and the accuracy control range is ±0.5%.

[0010] Furthermore, in step A3, the specific process of HDDR treatment is: heating from room temperature to 750-850°C under vacuum conditions, disproportionation in a hydrogen atmosphere of 0.04-0.6 MPa for 1.5-2.5 hours, slowly heating to 900-950°C, and vacuum dehydrogenation for 1-2 hours.

[0011] Furthermore, in step A3, the specific process of aging treatment is: first heating to 650-700°C, keeping warm for 30-60 minutes, and then vacuum cooling to 200-220°C, keeping warm for 2-3 hours.

[0012] Furthermore, in step A4, the nitrogen pressure of the high temperature nitridation treatment is: heating from room temperature to 500-600° C. under the condition of 0.1-1.5 MPa.

[0013] This application has the following beneficial effects: 1. The present invention provides a method for preparing high-performance rapid-quenching SmFeN magnetic powder, which increases the metal samarium supplement in the secondary smelting and weighs the magnetic powder particles in proportion to the Sm excess of 2-3% by the loss of metal samarium in the primary alloy powder stage and the alloy component segregation caused by the density difference of the molten pool during smelting, effectively curbs the uneven magnetic properties of the magnetic powder particles caused by the segregation of the alloy components, effectively suppresses the uneven magnetic properties of the SmFeN material in the preparation process, and makes the prepared magnetic material have higher coercive force and magnetic property uniformity.

[0014] 2. In order to accurately supplement the samarium metal in the secondary smelting, the preparation of the rapid quenching samarium iron nitrogen magnetic powder adopts a continuous feeding overflow crucible small smelting and rapid quenching equipment with one end of the silo continuously feeding the crucible and the other end continuously overflowing. The overflow design can achieve the stability of the alloy liquid level relative to the cooling roller during the smelting process, reduce the fluctuation of the alloy strip size, and improve the uniformity of the alloy; the small-sized crucible has a small molten pool volume and a short heating time, which avoids the long waiting time for the alloy liquid to overflow caused by heating a large amount of raw materials, reduces the loss of samarium elements due to high temperature volatilization, and reduces the equipment volume. Small, double-end sealing structure with good sealing performance, using high-purity industrial argon gas at 1.1 atmospheres, dynamic argon positive pressure protection can reduce the oxidation loss of samarium during the smelting process, and the overflow crucible can be continuously fed by the silo. The small smelting equipment can shorten the smelting time and reduce waste generation. The raw material cost per unit mass of magnetic powder is reduced by 15-20%, and it is suitable for large-scale production scenarios. The single silo batch is ≤500 kg. Combined with the external segmented vacuum feeding system, the silo can be replenished regularly and continuous production can be carried out without stopping. DETAILED DESCRIPTION

[0015] The present application is further described in detail below with reference to the embodiments.

[0016] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available. Example 1

[0017] A method for preparing high-performance rapid-quenching samarium iron nitrogen magnetic powder comprises the following steps: 1. Sm2Fe 17 Based on the components, weigh according to the excess of 2% Sm, melt and quench the samarium powder and iron powder in a small melting and quenching device under vacuum and argon filling conditions, and crush them using a hydrogen gas jet mill at a crushing temperature of 130°C and a pressure of 0.08Mpa to a particle size of 200 meshes to obtain a primary alloy powder; A2. Calculate the total samarium loss rate by the difference method, mix the primary alloy powder and the calculated samarium metal powder, stir them evenly, and perform smelting, quenching and solidification treatment on the mixture again in a small smelting and quenching device under vacuum and argon filling conditions, and crush them using a hydrogen gas jet mill at a crushing temperature of 130° C. and a pressure of 0.08 MPa to a particle size of 100 mesh, to obtain a secondary alloy powder; A3. The secondary modified alloy powder was subjected to HDDR treatment, heated from room temperature to 800°C under vacuum conditions, disproportionated in a 0.05MPa hydrogen atmosphere for 2h, then slowly heated to 900°C, and vacuum dehydrogenated for 1.5h. The powder was crushed to a particle size of 200 mesh, and subjected to aging treatment, first heated to 650°C, kept warm for 40min, then vacuum cooled to 220°C, and kept warm for 2h to obtain the modified alloy powder; A4. Place the modified alloy powder in a high-temperature nitriding furnace, heat it from room temperature to 500℃ under 0.2MPa conditions for high-temperature nitriding treatment for 8 hours, and then quickly cool it to room temperature in vacuum within 1 hour to obtain high-performance rapid-quenching samarium iron nitrogen magnetic powder with uniform structure.

[0018] In step A1, the smelting, rapid quenching and rapid solidification treatment process is as follows: under vacuum and argon filling conditions, the mixture of samarium powder and iron powder is placed in a continuous feeding overflow crucible with an outer diameter of 200 mm and a height of 186 mm and heated to 1600° C., and a uniform melt is continuously obtained by continuously feeding at one end and continuously overflowing at the other end, and the melt is placed on the surface of a cooling roller rotating at a speed of 25 m / s for cooling, and the mixture is heated to 10 5 K / s cooling rate for rapid solidification.

[0019] Comparative Example 2

[0020] A method for preparing high-performance rapid-quenching samarium iron nitrogen magnetic powder comprises the following steps: A1. Sm2Fe 17 Based on the components, weigh according to the excess of 2% Sm, melt and quench the samarium powder and iron powder in a small melting and quenching device under vacuum and argon filling conditions, and crush them using a hydrogen gas jet mill at a crushing temperature of 130°C and a pressure of 0.08Mpa to a particle size of 100 mesh to obtain alloy powder; A2. The alloy powder was subjected to HDDR treatment, and the temperature was raised from room temperature to 800°C under vacuum conditions, and the powder was disproportionated in a hydrogen atmosphere of 0.05MPa for 2h, and then slowly raised to 900°C and vacuum dehydrogenated for 1.5h. The powder was crushed to a particle size of 200 mesh, and then subjected to aging treatment, first heated to 650°C, kept warm for 40min, and then vacuum cooled to 220°C, and kept warm for 2h to obtain the modified alloy powder; A3. Place the modified alloy powder in a high-temperature nitriding furnace, heat it from room temperature to 500°C at 1MPa for 8 hours, and then quickly cool it to room temperature in vacuum within 1 hour to obtain rapidly quenched samarium iron nitrogen magnetic powder.

[0021] In step A1, the smelting, rapid quenching and rapid solidification treatment process is as follows: under vacuum and argon filling conditions, the mixture of samarium powder and iron powder is placed in a continuous feeding overflow crucible with an outer diameter of 148 mm and a height of 186 mm and heated to 1600° C., and a uniform melt is continuously obtained by continuously feeding at one end and continuously overflowing at the other end, and the melt is placed in a cooling roller rotating at a speed of 25 m / s for cooling, and the mixture is heated to 10 5 K / s cooling rate for rapid solidification.

[0022] Comparative Example 3

[0023] A method for preparing high-performance rapid-quenching samarium iron nitrogen magnetic powder comprises the following steps: A1. Sm2Fe17 Based on the components, the samarium powder and iron powder were weighed according to the chemical formula ratio, and the samarium powder and iron powder were melted, quenched and solidified in a melting device under vacuum and argon filling conditions. The melting time was 1 hour, and the powder was crushed by a hydrogen gas jet mill at a crushing temperature of 130°C and a pressure of 0.08Mpa to a particle size of 200 mesh to obtain alloy powder; A2. The alloy powder was subjected to HDDR treatment, the temperature was raised from room temperature to 800°C under vacuum conditions, disproportionated in a hydrogen atmosphere of 0.05MPa for 2h, slowly raised to 900°C, vacuum dehydrogenated for 1.5h, crushed to a particle size of 200 mesh, and subjected to aging treatment, first heated to 650°C, kept warm for 40min, then vacuum cooled to 220°C, and kept warm for 2h to obtain modified alloy powder; A3. Place the modified alloy powder in a high-temperature nitriding furnace, heat it from room temperature to 500°C at 1MPa for 8 hours, and then quickly cool it to room temperature in vacuum within 1 hour to obtain rapidly quenched samarium iron nitrogen magnetic powder.

[0024] Proven results The performance tests were conducted on the samarium iron nitrogen magnetic powders obtained in Example 1 and Comparative Examples 2 and 3, respectively, and the test steps are as follows: 1. Screening of magnetic properties of magnetic powders: 10 kg of the magnetic powders obtained in the above examples and comparative examples were taken and screened by magnetic separators to obtain magnetic powders of three categories of performance, high, medium and low. The magnetic powders of three categories of performance, high, medium and low selected by the examples and comparative examples were divided into 9 parts and weighed separately; 2. Preparation of test sample columns: 98 grams of each of the 9 samples were mixed evenly according to the ratio of 98 parts of samarium iron nitrogen magnetic powder, 1.5 parts of binder and 0.5 parts of auxiliary agent, and then the mixture was put into a press to be pressed and molded, and the molding pressure was 1.0 GPA. After the pressing was completed, a magnet was obtained, and the coercive force Hcj and the corresponding magnetic property BHmax of the magnet were tested. The effect is shown in Table 1:

[0025] Results Analysis By analyzing Example 1 and Comparative Examples 2-3 and summarizing Table 1, it can be seen that the samarium iron nitrogen magnetic powder material prepared by the method for preparing high-performance rapid quenching samarium iron nitrogen magnetic powder provided by the present invention has a high coercive force, the magnet coercive force can reach 14.1KOe, the magnetic properties are evenly distributed and the performance is excellent, and it has a high preparation yield and greatly reduces the unit mass raw material cost waste rate. The specific analysis is as follows: Compared with Example 1, Comparative Example 2 does not use the secondary smelting + difference method to calculate the total samarium loss rate. Although 2% excess Sm is weighed in the early stage, the total samarium loss is not supplemented by secondary smelting, resulting in a larger samarium-iron mass balance error than that of Example 1. The magnetic properties of the magnetic powder particles caused by the segregation of alloy components are seriously uneven, and the coercive force of the obtained magnet is significantly reduced.

[0026] Compared with Example 1, Comparative Example 3 adopts ordinary rapid quenching smelting, hydrogen cracking, and nitriding methods, and adopts an ordinary smelting pool, which not only increases the time of a single smelting, but also is not conducive to the control and accounting of raw material input, resulting in a high waste rate of raw material cost per unit mass, and fails to make up for the total samarium loss in smelting. The uneven magnetic properties of the magnetic powder particles caused by the segregation of alloy components are more serious, and the coercive force and magnetic properties of the obtained magnet are significantly reduced.

[0027] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0028] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing high-performance rapid-quenching samarium iron nitrogen magnetic powder, characterized in that: The preparation method comprises the following steps: A1. Sm2Fe 17 Based on the components, weigh according to the excess of 2-3% Sm, melt, quench and solidify samarium powder and iron powder in a small melting and quenching device under vacuum and then argon filling conditions, and crush to a particle size of 30-400 mesh after cooling to obtain a primary alloy powder; A2, the primary alloy powder and the samarium metal powder are mixed and stirred evenly, and the mixture is again subjected to a smelting, rapid quenching and rapid solidification treatment in a small smelting and rapid quenching device under vacuum and then argon filling conditions, and crushed to a particle size of 60-200 mesh to obtain a secondary modified alloy powder; A3, subjecting the secondary modified alloy powder to HDDR treatment, crushing it to a particle size of 100-400 mesh, and subjecting it to aging treatment to obtain modified alloy powder; A4. Place the modified alloy powder in a high-temperature nitriding furnace for 4-12 hours, and then rapidly cool it to room temperature in vacuum within 1 hour to obtain high-performance rapidly quenched samarium iron nitrogen magnetic powder with uniform structure.

2. The method for preparing high-performance rapid-quenching samarium iron nitrogen magnetic powder according to claim 1, characterized in that: In step A1, the small-scale smelting and quenching device is a continuous feeding overflow crucible and a cold cutting roller with continuous feeding at one end and continuous overflow at the other end. The cold cutting roller is placed at the overflow port of the crucible. The feeding port and the overflow port of the continuous feeding overflow crucible adopt a double-end sealing structure. An annular argon nozzle with a pressure of 0.2-0.5MPa is arranged on the periphery of the overflow port and the cooling roller interface to form an inert gas barrier. The outer diameter of the continuous feeding overflow crucible is: diameter 80-300mm, height: 100-300mm.

3. The method for preparing high-performance rapid-quenching samarium iron nitrogen magnetic powder according to claim 1, characterized in that: In step A1, the smelting, rapid quenching and rapid solidification treatment process is as follows: under vacuum and argon filling conditions, the mixture of samarium powder and iron powder is placed in a small smelting and rapid quenching device and heated to 1600-1700°C, a uniform melt is continuously obtained by continuously feeding the heating crucible at one end and continuously overflowing the other end, and the melt is placed on the surface of a cooling roller rotating at a speed of 20-30 m / s for cooling for ≥10 5 The cooling rate of K / s is fast solidification, and the smelting, rapid quenching and rapid solidification treatment single material warehouse batch is ≤500 kg.

4. The method for preparing high-performance rapid-quenching samarium iron nitrogen magnetic powder according to claim 1, characterized in that: In step A1, the crushing method is physical crushing by air jet mill or vacuum crusher, the crushing temperature is 120-140° C., and the pressure is 0.06-0.1 MPa.

5. The method for preparing high-performance rapid-quenching samarium iron nitrogen magnetic powder according to claim 1, characterized in that: In step A2, the proportion of the metal samarium powder added is calculated by mass balance to record the raw material input amount and the product mass, and the total loss rate is calculated by the difference method, wherein the difference method calculation formula is: total loss rate = (1-Sm mass in finished magnetic powder / Sm mass of raw material) × 100%, and the accuracy control range is ±0.5%.

6. The method for preparing high-performance rapid-quenching samarium iron nitrogen magnetic powder according to claim 1, characterized in that: In step A3, the specific process of HDDR treatment is: heating from room temperature to 750-850° C. under vacuum conditions, disproportionation in a hydrogen atmosphere of 0.04-0.6 MPa for 1.5-2.5 h, slowly heating to 900-950° C., and vacuum dehydrogenation for 1-2 h.

7. The method for preparing high-performance rapid-quenching samarium iron nitrogen magnetic powder according to claim 1, characterized in that: In step A3, the specific process of aging treatment is: first heating to 650-700°C, keeping warm for 30-60 minutes, and then vacuum cooling to 200-300°C, keeping warm for 2-3 hours.

8. The method for preparing high-performance rapid-quenching samarium iron nitrogen magnetic powder according to claim 1, characterized in that: In step A4, the nitrogen pressure of the high temperature nitridation treatment is: heating from room temperature to 500-600° C. under the condition of 0.1-1.5 MPa.

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