阅读说明：本技术 高性能烧结钐钴磁体的制备方法 (Preparation method of high-performance sintered samarium-cobalt magnet ) 是由 宋奎奎 于 2019-12-02 设计创作，主要内容包括：本发明公开了一种高性能烧结钐钴磁体的制备方法,包括：1)按照如下重量百分比配制钐钴合金原料：Sm：20～25％、Fe：12～25％、Zr：2～4％、Cu：3～8％、余量为Co；将配制好的钐钴合金原料在惰性气氛下熔炼、浇铸得到合金铸锭；2)将合金铸锭在氮气的保护下依次经过机械破碎、中破碎、气流磨制备合金粉末；3)向合金粉末中加入润滑剂,混粉,制得合金磁粉；4)将合金磁粉在氮气的保护下进行称料,再在敞开压机中取向成型,然后再进行冷等静压压制,制备出生坯；5)将生坯烧结进行致密化处理,然后冷却进行固溶处理,并快速风冷至室温,然后升温保温冷却保温,并风冷至室温,得到烧结钐钴磁体。本发明克服了磁体的稀土挥发和氧化难题,减小了废气的排放,得到的磁体剩磁高均匀性较好。(The invention discloses a preparation method of a high-performance sintered samarium-cobalt magnet, which comprises the following steps: 1) samarium cobalt alloy raw materials are prepared according to the following weight percentages: sm: 20-25%, Fe: 12-25%, Zr: 2-4%, Cu: 3-8% and the balance of Co; smelting and casting the prepared samarium-cobalt alloy raw material in an inert atmosphere to obtain an alloy ingot; 2) preparing alloy powder by sequentially carrying out mechanical crushing, intermediate crushing and airflow grinding on the alloy cast ingot under the protection of nitrogen; 3) adding a lubricant into the alloy powder, and mixing the powder to obtain alloy magnetic powder; 4) weighing the alloy magnetic powder under the protection of nitrogen, then performing orientation forming in an open press, and then performing cold isostatic pressing to prepare a green body; 5) and sintering the green body to carry out densification treatment, then cooling to carry out solution treatment, rapidly cooling to room temperature, then heating, preserving heat, cooling and preserving heat, and cooling to room temperature to obtain the sintered samarium-cobalt magnet. The invention overcomes the problems of rare earth volatilization and oxidation of the magnet, reduces the emission of waste gas, and obtains the magnet with high residual magnetism and good uniformity.)

1. A preparation method of a high-performance sintered samarium-cobalt magnet is characterized by comprising the following steps:

1) samarium cobalt alloy raw materials are prepared according to the following weight percentages: sm: 20-25%, Fe: 12-25%, Zr: 2-4%, Cu: 3-8% and the balance of Co;

smelting and casting the prepared samarium-cobalt alloy raw material in an inert atmosphere to obtain an alloy ingot;

2) preparing alloy powder by sequentially carrying out mechanical crushing, intermediate crushing and airflow grinding on the alloy cast ingot under the protection of nitrogen;

3) adding a lubricant with the total weight of 0.2-0.5 per mill into the alloy powder, and mixing for 0.5-3 hours to obtain alloy magnetic powder;

4) weighing the alloy magnetic powder under the protection of nitrogen, then performing orientation molding in an open press, wherein the magnetic field intensity of the orientation molding is 1.2-2T, and then performing cold isostatic pressing, wherein the cold isostatic pressing pressure is 450-500 MPa, so as to prepare a green body;

5) heating the green body to 1160-1190 ℃, sintering for 0.5-2 h for densification, cooling to 1130-1160 ℃, performing solid solution treatment for 1-4 h, rapidly air-cooling to room temperature, heating to 800-900 ℃, preserving heat for 5-40 h, cooling to 400 ℃, preserving heat for 1-20 h, and air-cooling to room temperature to obtain the sintered samarium-cobalt magnet.

2. The method of making a high performance sintered samarium cobalt magnet of claim 1 wherein in step 1) the samarium cobalt alloy starting material is melted and cast under argon.

3. The method of making a high performance sintered samarium cobalt magnet of claim 1 wherein the size of the alloy powder after crushing in step 2) is 2 to 4 μm.

4. The method of making a high performance sintered samarium cobalt magnet of claim 1 wherein the orientation forming magnetic field strength in step 4) is 2.0T and the cold isostatic pressure is 500 MPa.

5. The method of making a high performance sintered samarium cobalt magnet of claim 1, wherein the rate of the last cooling in step 5) is controlled to be 0.5 to 1 ℃/min to obtain a sintered samarium cobalt magnet.

6. A high-performance sintered samarium cobalt magnet obtained by the process of any one of claims 1 to 5.

Technical Field

The present invention relates to a magnetic material. More specifically, the invention relates to a method for preparing a high-performance sintered samarium-cobalt magnet.

Background

Precipitation hardening type Sm₂Co₁₇The sintered permanent magnet is favored by researchers due to excellent high-temperature magnetic property, lower temperature coefficient and good oxidation resistance and corrosion resistance. Sm due to unique excellent performance₂Co₁₇Sintered permanent magnets of the type are used in various high-precision motors. The permanent magnet motor has the advantages of high torque, high power density and high efficiency, is widely applied to various fields of military industry and aerospace, but has high-temperature-resistant working capacity and electromagnetic property under strong impact vibration of permanent magnet materialsThe samarium cobalt permanent magnet has the characteristics of high Curie temperature, difficult field loss and the like, and is concerned about in the fields of military industry and aerospace.

The magnetic performance index of samarium cobalt mainly comprises remanence B_rIntrinsic coercive force H_cjMaximum magnetic energy product (BH)_maxAnd samarium cobalt squareness (knee point field H_k) And the like. The heat treatment process of sintered samarium cobalt mainly comprises sintering densification, solution treatment, isothermal aging and graded cooling or slow cooling heat treatment, wherein the purpose of sintering is to ensure that the magnet has higher remanence, and the solution treatment and the aging heat treatment are key processes for ensuring that the magnet has high coercivity. The residual magnetism of the magnet can be improved by increasing the sintering temperature or the holding time, however, the high sintering temperature can cause a large amount of volatilization and oxidation of rare earth, meanwhile, the higher sintering temperature can promote the precipitation of a zirconium-rich phase and the abnormal growth of crystal grains, and as a result, the performance of the magnet is deteriorated, and although the patent CN201910064865 discloses a preparation method of sintered samarium cobalt, the sintering time is still longer (150 minutes), and the long-time sintering molding can still cause the volatilization and oxidation of rare earth. The performance and oxygen content of the magnet can be controlled by reducing the oxygen element entering in the preparation process, for example, in patent CN109148139A, the oxygen entering is reduced by filling argon gas with ultrahigh pressure (above 900 MPa) in the sintering process, so as to optimize the performance of the magnet, however, this method will cause excessive waste and use of argon gas, and sintering under ultrahigh pressure has high requirements for the safety and usability of the sintering equipment, which is not favorable for industrial production. Therefore, a preparation technology of the sintered samarium cobalt, which can meet the requirements of the existing equipment, is convenient for industrial mass production and is relatively green and environment-friendly, is urgently needed.

Disclosure of Invention

An object of the present invention is to solve at least the above problems and to provide at least the advantages described later.

The invention also aims to provide a preparation method of the high-performance sintered samarium cobalt magnet, which prepares the magnetic powder with uniform and fine powder by optimizing the air flow milling process, prepares a green body under the action of isostatic pressing of ultrahigh pressure after the magnetic powder is oriented and molded, and then obtains a densified blank by sintering the green body at a lower temperature for a shorter time.

To achieve these objects and other advantages in accordance with the purpose of the invention, there is provided a method of manufacturing a high-performance sintered samarium cobalt magnet, comprising:

1) samarium cobalt alloy raw materials are prepared according to the following weight percentages: sm: 20-25%, Fe: 12-25%, Zr: 2-4%, Cu: 3-8% and the balance of Co;

smelting and casting the prepared samarium-cobalt alloy raw material in an inert atmosphere to obtain an alloy ingot;

2) preparing alloy powder by sequentially carrying out mechanical crushing, intermediate crushing and airflow grinding on the alloy cast ingot under the protection of nitrogen;

3) adding a lubricant with the total weight of 0.2-0.5 per mill into the alloy powder, and mixing for 0.5-3 hours to obtain alloy magnetic powder;

4) weighing the alloy magnetic powder under the protection of nitrogen, then performing orientation molding in an open press, wherein the magnetic field intensity of the orientation molding is 1.2-2T, and then performing cold isostatic pressing, wherein the cold isostatic pressing pressure is 450-500 MPa, so as to prepare a green body;

5) heating the green body to 1160-1190 ℃, sintering for 0.5-2 h for densification, cooling to 1130-1160 ℃, performing solid solution treatment for 1-4 h, rapidly air-cooling to room temperature, heating to 800-900 ℃, preserving heat for 5-40 h, cooling to 400 ℃, preserving heat for 1-20 h, and air-cooling to room temperature to obtain the sintered samarium-cobalt magnet.

Preferably, the samarium cobalt alloy raw material in the step 1) is smelted and cast under the protection of argon.

Preferably, the granularity of the alloy powder crushed in the step 2) is 2-4 μm.

Preferably, the orientation molding magnetic field intensity in the step 4) is 2.0T, and the cold isostatic pressure is 500 MPa.

Preferably, the last cooling speed in the step 5) is controlled to be 0.5-1 ℃/min, and the sintered samarium-cobalt magnet is obtained.

The high-performance sintered samarium-cobalt magnet prepared by the preparation method.

The invention at least comprises the following beneficial effects:

the sintering process is a process of liquefying and flowing rare earth in samarium cobalt magnetic powder and rotating and phagocytizing particles, the magnetic powder with small powder granularity and good uniformity is prepared by optimizing a crushing process, then a green body is prepared in isostatic pressing equipment with high pressure after the magnetic powder is subjected to orientation molding, and then the green body is subjected to heat treatment at a lower temperature to obtain the high-density magnet, so that the problems of rare earth volatilization and oxidation are solved, the economic benefit is better, the sintering process is suitable for industrialization, the residual magnetism and the oxygen content of the magnet are better than those reported in the patent CN201910064865 with the same mark.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.

Detailed Description

The present invention is further described in detail below with reference to examples to enable those skilled in the art to practice the invention with reference to the description.

It will be understood that terms such as "having," "including," and "comprising," as used herein, do not preclude the presence or addition of one or more other elements or groups thereof.

It is to be noted that the experimental methods described in the following embodiments are all conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified.

< example 1>

The preparation method of the high-performance sintered samarium-cobalt magnet comprises the following steps:

1) preparing an ingot:

samarium cobalt alloy raw materials are prepared according to the following weight percentages: 24.6 percent of Sm, 20.1 percent of Fe, 2.4 percent of Zr, 4.6 percent of Cu and the balance of Co;

smelting and casting the prepared samarium cobalt alloy raw material in a pure argon atmosphere, wherein the smelting is carried out in a medium-frequency smelting furnace, and the casting is carried out in a cold water copper cooling mold to obtain an alloy ingot with the thickness of about 10 mm;

2) milling:

sequentially carrying out mechanical crushing, medium crushing and airflow grinding on the alloy cast ingot under the protection of nitrogen to prepare alloy powder with the average particle size of 3.45 microns;

3) mixing powder:

adding a lubricant with the total weight of 0.33 per mill into the alloy powder, and mixing for 2.2 hours to obtain alloy magnetic powder in order to ensure uniform mixing;

4) magnetic field forming, isostatic pressing:

weighing the mixed alloy magnetic powder under the protection of nitrogen, then carrying out orientation molding in a press, wherein the magnetic field intensity of the orientation molding is 2.0T, then carrying out cold isostatic pressing, and the cold isostatic pressing pressure is 450MPa to prepare a green body;

5) sintering solid solution and aging treatment:

heating the green body to 1168 ℃ and sintering for 1h for densification, cooling to 1136 ℃ for 4h for solution treatment, and quickly cooling to room temperature by air; and then heating to 830 ℃, keeping the temperature for 25h, cooling to 400 ℃ at the speed of 0.73 ℃/min, keeping the temperature for 10h, and cooling to room temperature by air to obtain the sintered samarium-cobalt magnet.

< example 2>

The preparation method of the ultrahigh-performance sintered samarium-cobalt magnet comprises the following steps:

1) preparing an ingot:

samarium cobalt alloy raw materials are prepared according to the following weight percentages: 23.7 percent of Sm, 18.1 percent of Fe, 2.7 percent of Zr, 5.5 percent of Cu and the balance of Co;

smelting and casting the prepared samarium cobalt alloy raw material in a pure argon atmosphere, wherein the smelting is carried out in a medium-frequency smelting furnace, and the casting is carried out in a cold water copper cooling mold to obtain an alloy ingot with the thickness of about 10 mm;

2) milling:

preparing alloy powder with the average particle size of 3.1 mu m from the alloy cast ingot by mechanical crushing, medium crushing and airflow grinding in sequence under the protection of nitrogen;

3) mixing powder:

adding a lubricant with the total weight of 0.25 per mill into the alloy powder, and mixing for 1.8 hours to obtain alloy magnetic powder in order to ensure uniform mixing;

4) magnetic field forming, isostatic pressing:

weighing the mixed alloy magnetic powder under the protection of nitrogen, then carrying out orientation molding in a press, wherein the magnetic field intensity of the orientation molding is 1.8T, then carrying out cold isostatic pressing, and the cold isostatic pressing pressure is 500MPa to prepare a green body;

5) sintering solid solution and aging treatment:

heating the green body to 1176 ℃ at low temperature, sintering for 0.8h for densification, cooling to 1145 ℃ for 3h for solid solution treatment, and rapidly cooling to room temperature by air; and then heating to 850 ℃, keeping the temperature for 18h, cooling to 400 ℃ at the speed of 0.80 ℃/min, keeping the temperature for 6h, and cooling to room temperature by air to obtain the sintered samarium-cobalt magnet.

< example 3>

The preparation method of the high-performance sintered samarium-cobalt magnet comprises the following steps:

1) preparing an ingot:

samarium cobalt alloy raw materials are prepared according to the following weight percentages: 22.4 percent of Sm, 15.3 percent of Fe, 3.0 percent of Zr, 6.2 percent of Cu and the balance of Co;

smelting and casting the prepared samarium cobalt alloy raw material in a pure argon atmosphere, wherein the smelting is carried out in a medium-frequency smelting furnace, and the casting is carried out in a cold water copper cooling mold to obtain an alloy ingot with the thickness of about 10 mm;

2) milling:

preparing alloy powder with the average particle size of 2.55 microns by sequentially carrying out mechanical crushing, medium crushing and airflow grinding on the alloy cast ingot under the protection of nitrogen;

3) mixing powder:

adding a lubricant with the total weight of 0.4 per mill into the alloy powder, and mixing for 3 hours to obtain alloy magnetic powder in order to ensure uniform mixing;

4) magnetic field forming, isostatic pressing:

weighing the mixed alloy magnetic powder under the protection of nitrogen, performing orientation molding in an open press with the orientation molding magnetic field intensity of 1.5T, and then performing cold isostatic pressing with the cold isostatic pressure of 450MPa to prepare a green body;

5) sintering solid solution and aging treatment:

heating the green body to 1180 ℃ at low temperature, sintering for 0.6h for densification, cooling to 1156 ℃ for solid solution treatment for 2.5h, and quickly cooling to room temperature by air; and then heating to 870 ℃, preserving heat for 14h, cooling to 400 ℃ at the speed of 0.93 ℃/min, preserving heat for 5h, and cooling to room temperature by air to obtain the sintered samarium-cobalt magnet.

< example 4>

The preparation method of the high-performance sintered samarium-cobalt magnet comprises the following steps:

1) preparing an ingot:

samarium cobalt alloy raw materials are prepared according to the following weight percentages: 21.7 percent of Sm, 13.2 percent of Fe, 3.4 percent of Zr, 7.3 percent of Cu and the balance of Co;

smelting and casting the prepared samarium cobalt alloy raw material in a pure argon atmosphere, wherein the smelting is carried out in a medium-frequency smelting furnace, and the casting is carried out in a cold water copper cooling mold to obtain an alloy ingot with the thickness of about 10 mm;

2) milling:

preparing alloy powder with the average particle size of 2.25 mu m from the alloy cast ingot by mechanical crushing, medium crushing and airflow grinding in sequence under the protection of nitrogen;

3) mixing powder:

adding a lubricant with the total weight of 0.42 per mill into the alloy powder, and mixing for 3 hours to obtain alloy magnetic powder in order to ensure uniform mixing;

4) magnetic field forming, isostatic pressing:

weighing the mixed alloy magnetic powder under the protection of nitrogen, then carrying out orientation molding in a press, wherein the magnetic field intensity of the orientation molding is 1.4T, then carrying out cold isostatic pressing, and the cold isostatic pressing pressure is 500MPa to prepare a green body;

5) sintering solid solution and aging treatment:

heating the green body to 1188 ℃, sintering for 0.5h for densification, cooling to 1155 ℃, performing solid solution treatment for 2.5h, and rapidly cooling to room temperature by air; and then heating to 885 ℃, preserving heat for 10h, cooling to 400 ℃ at the speed of 0.74 ℃/min, preserving heat for 2h, and air-cooling to room temperature to obtain the sintered samarium-cobalt magnet.

< comparative example 1>

The preparation method of the high-performance sintered samarium cobalt magnet is the same as that in example 1 except that in step 4), cold isostatic pressing is performed after orientation forming, and the cold isostatic pressing pressure is 200MPa, so that a green body is prepared.

< comparative example 2>

The preparation method of the high-performance sintered samarium cobalt magnet is the same as that in example 2, except that in step 4), after orientation forming, cold isostatic pressing is carried out, the cold isostatic pressing pressure is 200MPa, a green body is prepared, in step 5), the sintering temperature is 1210 ℃, heat preservation is carried out for 2 hours, and other processes are not changed.

< comparative example 3>

The preparation method of the high-performance sintered samarium cobalt magnet is the same as that in example 3, except that in step 4), after orientation forming, cold isostatic pressing is carried out, and a green body is prepared, wherein the cold isostatic pressing pressure is 100 MPa; and 5), keeping the sintering temperature at 1215 ℃ for 0.6h, and keeping other processes unchanged.

< comparative example 4>

The preparation method of the high-performance sintered samarium cobalt magnet is the same as that of the example 4, except that in the step 5), the sintering temperature is 1188 ℃, the sintering time is 0.2h, and other processes are not changed.

In order to verify the preparation method of the high-performance sintered samarium cobalt in the patent of the invention, the performance indexes of examples 1 to 4 and comparative examples 1 to 4 are respectively listed in the following table 1. Comparing the properties of comparative example 1 and example 1, it can be seen that if the isostatic pressure is a conventional pressure, then at low temperature sintering, although the oxygen content of the final magnet is controlled, the remanence and density of the magnet are both less than in the examples; from the performance results of comparative example 2 and example 2, it can be seen that under the conventional isostatic pressure, a higher sintering temperature is required to densify the magnet (the density and remanence of comparative example 2 and example 2 are comparable), however, the high sintering temperature causes the oxygen content of the magnet to be too high (about 2920ppm), and the high oxygen content deteriorates the texture of the magnet, and further deteriorates the uniform performance of the magnet; as can be seen from the performance results of comparative example 3 and example 3, if the pressure of isostatic pressing is too low, the density and performance of the produced magnet are not comparable to those of example 3 even at a high sintering temperature, and the oxygen content in the magnet is also increased; combining the performance results of comparative example 4 and example 4, it is clear that even under the same high isostatic pressure conditions, if the holding time is too short, no excellent performance can be achieved. The invention provides a preparation method of a high-performance sintered samarium-cobalt magnet, which is characterized in that after a green body is subjected to isostatic pressing under ultrahigh pressure (450-500 MPa) and is sintered at low temperature for a proper time, the density and the remanence of the final magnet are obviously improved, and the oxygen content in a sample is greatly improved.

TABLE 1

The number of apparatuses and the scale of the process described herein are intended to simplify the description of the present invention. Applications, modifications and variations of the present invention will be apparent to those skilled in the art.

While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable to various fields of endeavor for which the invention may be embodied with additional modifications as would be readily apparent to those skilled in the art, and the invention is therefore not limited to the details given herein and to the examples shown and described without departing from the generic concept as defined by the claims and their equivalents.