阅读说明：本技术 高膝点矫顽力烧结钐钴磁体的制备方法 (Preparation method of high-knee-point coercive force sintered samarium-cobalt magnet ) 是由 宋奎奎 于 2019-09-27 设计创作，主要内容包括：本发明公开了一种高膝点矫顽力烧结钐钴磁体的制备方法,包括1)铸锭的制备；2)制粉；3)混粉；4)磁场成型、等静压；5)磁场热处理。本发明在外界强磁场下对生坯进行烧结和时效处理,优化钐钴磁体内部的微结构,细化磁体的磁畴,制备的磁体膝点矫顽力和取向度得到很大的改善,解决了钐钴磁体取向度差的瓶颈问题,制备工艺简单,具有较好的经济效益,适合产业化。(The invention discloses a preparation method of a high-knee-point coercive force sintered samarium cobalt magnet, which comprises the following steps of 1) preparing an ingot; 2) milling; 3) mixing the powder; 4) magnetic field forming and isostatic pressing; 5) and (4) performing magnetic field heat treatment. According to the invention, the green body is sintered and aged under an external strong magnetic field, the microstructure inside the samarium cobalt magnet is optimized, the magnetic domain of the magnet is refined, the knee point coercive force and the orientation degree of the prepared magnet are greatly improved, the bottleneck problem of poor orientation degree of the samarium cobalt magnet is solved, the preparation process is simple, and the method has good economic benefit and is suitable for industrialization.)

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

1) samarium cobalt alloy raw materials are prepared according to the following weight percentages: sm: 24-29%, Fe: 10-25%, Zr: 2-6%, Cu: 2-8% 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) directly weighing the alloy magnetic powder in the air, then carrying out orientation molding in an open press, wherein the magnetic field intensity of the orientation molding is 1.4-2T, and then carrying out cold isostatic pressing, wherein the cold isostatic pressing pressure is 200-300 MPa, so as to prepare a green body;

5) heating the green body to 1190-1220 ℃, sintering for 0.5-2 h for densification, then cooling to 1150-1190 ℃, performing solid solution treatment for 2-8 h, and rapidly cooling to room temperature by air; and then heating to 800-900 ℃, preserving heat for 5-40 h, cooling to 400 ℃, preserving heat for 1-20 h, air-cooling to room temperature, and carrying out the whole heat treatment process under a magnetic field with the magnetic field intensity of 3-10T to obtain the sintered samarium-cobalt magnet.

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

3. The method of making a high-knee-point coercivity sintered samarium cobalt magnet of claim 1, wherein the alloy powder size after crushing in step 2) is 3 to 6 μm.

4. The method of making a high-knee-point coercivity sintered samarium cobalt magnet of claim 1, wherein the orientation shaping magnetic field strength in step 4) is 2.0T and the cold isostatic pressure is 300 MPa.

5. The method for preparing a high-knee-point coercivity sintered samarium cobalt magnet of claim 1, characterized in that after densification in step 5), heating to 1190-1220 ℃ for sintering for 0.5-2 h for densification, then cooling to 1150-1190 ℃ for solution treatment for 2-8 h, and rapidly air-cooling to room temperature; and then heating to 800-900 ℃, preserving heat for 5-40 h, cooling to 520 ℃ at the speed of 0.5-1 ℃/min, preserving heat for 2-5 h, cooling to 400 ℃ at the speed of 0.5-1 ℃/min, preserving heat for 1-20 h, air-cooling to room temperature, and carrying out the whole heat treatment process under the magnetic field with the magnetic field intensity of 3-10T to obtain the sintered samarium-cobalt magnet.

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

Technical Field

The present invention relates to a magnetic material. More specifically, the invention relates to a preparation method of a high-knee-point coercive force sintered samarium-cobalt magnet.

Background

The second generation 2:17 type samarium cobalt permanent magnet material is widely applied to instruments such as aerospace, military tanks, instruments and meters and the like due to higher high-temperature magnetic property, lower temperature coefficient and extremely strong corrosion resistanceOn the device, the magnetic performance index of samarium cobalt mainly has remanence B_rIntrinsic coercive force H_cjMaximum magnetic energy product (BH)_maxHowever, the squareness of samarium cobalt (knee point coercivity H)_k) The samarium cobalt magnet is one of main indexes for measuring the uniformity of the magnet, the size of the samarium cobalt magnet directly determines the high-temperature magnetic loss characteristic of the material, and whether a country can prepare the samarium cobalt magnet with excellent performance directly determines the strength of military force, so that the intensive research on the aspect is very necessary.

The phase structure of the 2:17 type samarium cobalt magnet is mainly Sm2Co17R main phase, SmCo5H cell wall phase and zirconium-rich Z phase, and the coercive force of the magnet is from the pinning of the cell wall of SmCo5H relative to the domain wall. For a samarium cobalt magnet, the magnetic domain (the orientation direction is vertical to an observation surface) on the surface of the samarium cobalt magnet is mainly a labyrinth domain, the magnetic domain (the orientation direction is parallel to the observation surface) inside the magnet is mainly a sheet domain, the research result shows that the sheet domain is dependent on the state of a cell structure and the distribution of Cu element on the cell wall, the smaller the size of the magnetic domain is, the more the positions of the domain walls are, the more pinning positions are, the better the performance of the magnet is, the formation of the cell structure and the redistribution of the Cu element occur in the aging stage of the samarium cobalt, and the samarium cobalt magnet prepared by the traditional process has poor squareness (H, Co, Mn_k15kOe, where H_k/H_cj40%) and the main reason is that no suitable way is found for regulating the cell structure and element distribution of samarium cobalt, and research results show that the crystal grain size of samarium cobalt is large, generally 50-100 μm, and the mismatching degree between the crystal grains can directly influence the orientation degree of samarium cobalt material, thereby influencing the squareness of the magnet, while the size and the form of the crystal grains of samarium cobalt material are completely dependent on sintering and solid solution stages, and the traditional heat treatment mode only overcomes the energy barrier of element diffusion, but can not regulate the element distribution directionally.

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.

It is yet another object of the present invention to provide a method of making a high knee point coercivity sintered samarium cobalt magnet which is effective by magnetic field heat treatmentThe microstructure of the samarium cobalt material is regulated and controlled, the size of the magnetic domain of the prepared samarium cobalt magnet is small and the distribution is uniform, and meanwhile, the knee point coercive force H of the magnet_kThe method is greatly improved from 14kOe to 20kOe, and the method is simple in process and suitable for industrial production.

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

1) samarium cobalt alloy raw materials are prepared according to the following weight percentages: sm: 24-29%, Fe: 10-25%, Zr: 2-6%, Cu: 2-8% 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) directly weighing the alloy magnetic powder in the air, then carrying out orientation molding in an open press, wherein the magnetic field intensity of the orientation molding is 1.4-2T, and then carrying out cold isostatic pressing, wherein the cold isostatic pressing pressure is 200-300 MPa, so as to prepare a green body;

5) heating the green body to 1190-1220 ℃, sintering for 0.5-2 h for densification, then cooling to 1150-1190 ℃, performing solid solution treatment for 2-8 h, and rapidly cooling to room temperature by air; and then heating to 800-900 ℃, preserving heat for 5-40 h, cooling to 400 ℃, preserving heat for 1-20 h, air-cooling to room temperature, and carrying out the whole heat treatment process under a magnetic field with the magnetic field intensity of 3-10T 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 3-6 μm.

Preferably, the orientation molding magnetic field intensity in the step 4) is 2.0T, and the cold isostatic pressure is 300 MPa.

Preferably, after densification treatment in the step 5), heating to 1190-1220 ℃, sintering for 0.5-2 h for densification treatment, then cooling to 1150-1190 ℃, performing solid solution treatment for 2-8 h, and rapidly air-cooling to room temperature; and then heating to 800-900 ℃, preserving heat for 5-40 h, cooling to 520 ℃ at the speed of 0.5-1 ℃/min, preserving heat for 2-5 h, cooling to 400 ℃ at the speed of 0.5-1 ℃/min, preserving heat for 1-20 h, air-cooling to room temperature, and carrying out the whole heat treatment process under the magnetic field with the magnetic field intensity of 3-10T to obtain the sintered samarium-cobalt magnet.

The sintered samarium cobalt magnet obtained by the preparation method.

The invention at least comprises the following beneficial effects:

according to the invention, the green body is sintered and aged under an external strong magnetic field, the microstructure inside the samarium cobalt magnet is optimized, the magnetic domain of the magnet is refined, the knee point coercive force and the orientation degree of the prepared magnet are greatly improved, the bottleneck problem of poor orientation degree of the samarium cobalt magnet is solved, the preparation process is simple, and the method has good economic benefit and is suitable for industrialization.

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.

Drawings

FIG. 1 is a schematic process flow diagram of the present invention;

fig. 2 is a schematic view of typical magnetic domain structures (a) with magnetic field heat treatment and (b) without magnetic field heat treatment of two samples according to the present invention, in which the observation planes are parallel to the c-axis.

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.

A method for preparing a high-knee-point coercivity sintered samarium cobalt magnet, as shown in FIG. 1, comprises:

1) preparing an ingot:

samarium cobalt alloy raw materials are prepared according to the following weight percentages: sm: 24-29%, Fe: 10-25%, Zr: 2-6%, Cu: 2-8% and the balance of Co;

smelting and casting the prepared samarium cobalt alloy raw material in an inert atmosphere (comprehensive cost and effect, preferably under the protection of argon, aiming at effectively preventing volatilization of Sm and oxidation of cast ingots), wherein the smelting is carried out in a medium-frequency smelting furnace, and the casting is carried out in a cold water copper mold of a disc to obtain alloy cast ingots 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 3-6 mu m;

3) mixing powder:

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 ensure uniform mixing to obtain alloy magnetic powder;

the purpose of adding the lubricant is to reduce the friction force among the magnetic powder in the magnetic field forming process, so that the magnetic powder is easier to rotate in the orientation forming process, and the size of the orientation field can be reduced after the lubricant is added, so that the electric energy is saved, and the production cost is further saved.

4) Magnetic field forming, isostatic pressing:

directly weighing the alloy magnetic powder in the air, then carrying out orientation molding in an open press, wherein the magnetic field intensity of the orientation molding is 1.4-2T, and then carrying out cold isostatic pressing, wherein the cold isostatic pressing pressure is 200-300 MPa, so as to prepare a green body;

5) magnetic field heat treatment:

heating the green body to 1190-1220 ℃, sintering for 0.5-2 h for densification, then cooling to 1150-1190 ℃, performing solid solution treatment for 2-8 h, and rapidly cooling to room temperature by air; and then heating to 800-900 ℃, preserving heat for 5-40 h, cooling to 400 ℃, preserving heat for 1-20 h, air-cooling to room temperature, and carrying out the whole heat treatment process under a magnetic field with the magnetic field intensity of 3-10T to obtain the sintered samarium-cobalt magnet.

< example 1>

The preparation method of the high-knee-point coercive force sintered samarium cobalt magnet comprises the following steps:

1) preparation of ingot

The cast ingot consists of the following components: 28.2 percent of Sm, 20.6 percent of Fe, 2.4 percent of Zr, 5.6 percent of Cu and the balance of Co;

the preparation method of the alloy ingot comprises the following steps: preparing samarium cobalt alloy raw materials; smelting and casting the prepared raw materials in high-purity helium gas, smelting in an intermediate frequency smelting furnace, and then casting in a cold water copper mould to prepare an alloy ingot with the average thickness of about 10 mm;

2) powder making

Mechanically crushing the cast ingot under the protection of nitrogen, crushing the cast ingot in the middle, and preparing the average grain size of the alloy powder by airflow milling to be 3.48 mu m;

3) mixed powder

Adding a lubricant with the total weight of 0.35 per mill into the alloy powder, and controlling the time for 3 hours to prepare alloy magnetic powder in order to ensure uniform mixing;

4) magnetic field shaping, isostatic pressing

Directly weighing the mixed alloy magnetic powder in the air, carrying out orientation molding in an open press under a 2T magnetic field, and then carrying out cold isostatic pressing at 300MPa to obtain a green body;

5) magnetic field heat treatment

Heating the green body to 1198 ℃, sintering for 1h for densification treatment, then cooling to 1173 ℃, performing solid solution treatment for 6h, and rapidly cooling to room temperature by air; and then heating to 830 ℃, keeping the temperature for 20h, cooling to 520 ℃ at the speed of 0.65 ℃/min, keeping the temperature for 4h, cooling to 400 ℃ at the speed of 0.78 ℃/min, keeping the temperature for 10h, and cooling to room temperature by air to obtain the samarium-cobalt magnet, wherein the whole heat treatment process is carried out in a strong magnetic field of 8T.

The magnetic performance of the prepared sintered samarium cobalt magnet is as follows:remanence B_r11.72kGs magnetic product (BH)_max32.75MGOe, intrinsic coercivity H_cj> 25kOe, knee point coercivity H_k＝19.38kOe。

< example 2>

The preparation method of the high-knee-point coercive force sintered samarium cobalt magnet comprises the following steps:

1) preparation of ingot

The cast ingot consists of the following components: 27.4 percent of Sm, 17.2 percent of Fe, 2.8 percent of Zr, 5.8 percent of Cu and the balance of Co;

the preparation method of the alloy ingot comprises the following steps: preparing samarium cobalt alloy raw materials; smelting and casting the prepared raw materials in high-purity argon, smelting in an intermediate frequency smelting furnace, and then casting in a cold water copper mold to prepare an alloy ingot a with the average thickness of about 10 mm;

2) powder making

Mechanically crushing the cast ingot under the protection of nitrogen, crushing the cast ingot in the middle, and preparing the average grain size of the alloy powder by airflow milling to be 4.13 mu m;

3) mixed powder

Adding a lubricant with the total weight of 0.30 per mill into the alloy powder, and controlling the time for 2.5 hours to prepare alloy magnetic powder in order to ensure uniform mixing;

4) magnetic field shaping, isostatic pressing

Directly weighing the mixed alloy magnetic powder in the air, carrying out orientation forming in an open press under a 1.8T magnetic field, and then carrying out cold isostatic pressing at 280MPa to obtain a green body;

5) magnetic field heat treatment

Heating the green body to 1203 ℃, sintering for 1.5h for densification treatment, then cooling to 1180 ℃, performing solid solution treatment for 5h, and quickly cooling to room temperature by air; and then heating to 850 ℃, keeping the temperature for 15h, cooling to 520 ℃ at the speed of 0.75 ℃/min, keeping the temperature for 3h, cooling to 400 ℃ at the speed of 0.88 ℃/min, keeping the temperature for 6h, and cooling to room temperature by air to obtain the samarium-cobalt magnet, wherein the whole heat treatment process is carried out in a strong magnetic field of 6T.

The magnetic performance of the prepared sintered samarium cobalt magnet is as follows: remanenceB_r11.32kGs magnetic product (BH)_max30.42MGOe, intrinsic coercivity H_cj> 25kOe, knee point coercivity H_k＝21.43kOe。

< example 3>

The preparation method of the high-knee-point coercive force sintered samarium cobalt magnet comprises the following steps:

1) preparation of ingot

The cast ingot consists of the following components: 26.1 percent of Sm, 15.4 percent of Fe, 3.1 percent of Zr, 6.4 percent of Cu and the balance of Co;

the preparation method of the alloy ingot comprises the following steps: preparing samarium cobalt alloy raw materials; smelting and casting the prepared raw materials in high-purity argon, smelting in an intermediate frequency smelting furnace, and then casting in a cold water copper mold to prepare an alloy ingot with the average thickness of about 10 mm;

2) powder making

Mechanically crushing the cast ingot under the protection of nitrogen, crushing the cast ingot in the medium, and preparing the alloy powder by airflow milling, wherein the average particle size of the alloy powder is 4.47

μm；

3) Mixed powder

Adding a lubricant with the total weight of 0.24 per mill into the alloy powder, and controlling the time for 2 hours to prepare alloy magnetic powder in order to ensure uniform mixing;

4) magnetic field shaping, isostatic pressing

Directly weighing the mixed alloy magnetic powder in the air, carrying out orientation molding in an open press under a 1.6T magnetic field, and then carrying out cold isostatic pressing at 260MPa to obtain a green body;

5) magnetic field heat treatment

Heating the green body to 1208 ℃, sintering for 1.5h for densification, then cooling to 1185 ℃, performing solid solution treatment for 4h, and rapidly cooling to room temperature by air; and then heating to 860 ℃, keeping the temperature for 12h, cooling to 520 ℃ at the speed of 0.85 ℃/min, keeping the temperature for 2.5h, then cooling to 400 ℃ at the speed of 0.78 ℃/min, keeping the temperature for 5h, and cooling to room temperature by air to obtain the samarium-cobalt magnet, wherein the whole heat treatment process is carried out in a 5T high-intensity magnetic field.

Prepared sintered samarium cobaltThe magnetic performance of the magnet is as follows: remanence B_r10.83kGs magnetic product (BH)_max27.41MGOe, intrinsic coercivity H_cj> 25kOe, knee point coercivity H_k＝22.16kOe。

< example 4>

The preparation method of the high-knee-point coercive force sintered samarium cobalt magnet comprises the following steps:

1) preparation of ingot

The cast ingot consists of the following components: 25.4 percent of Sm, 12.6 percent of Fe, 2.7 percent of Zr, 6.5 percent of Cu and the balance of Co;

the preparation method of the alloy ingot comprises the following steps: preparing samarium cobalt alloy raw materials; smelting and casting the prepared raw materials in high-purity helium gas, smelting in an intermediate frequency smelting furnace, and then casting in a cold water copper mold to prepare an alloy ingot a with the average thickness of about 10 mm;

2) powder making

Mechanically crushing the cast ingot under the protection of nitrogen, crushing the cast ingot in the medium, and preparing the alloy powder by airflow milling, wherein the average particle size of the alloy powder is 5.13

μm；

3) Mixed powder

Adding lubricant with the total weight of 0.30 per mill into the alloy powder, and controlling the time for 2.5 hours to obtain alloy magnetic powder in order to ensure uniform mixing;

4) magnetic field shaping, isostatic pressing

Directly weighing the mixed alloy magnetic powder in the air, carrying out orientation molding in an open press under a 1.5T magnetic field, and then carrying out cold isostatic pressing at 250MPa to obtain a green body;

5) magnetic field heat treatment

Heating the green body to 1212 ℃ for sintering for 1.5h for densification treatment, then cooling to 1185 ℃ for solid solution treatment for 4h, and rapidly cooling to room temperature by air; and then heating to 830 ℃, keeping the temperature for 10 hours, cooling to 400 ℃ at the speed of 0.75 ℃/min, keeping the temperature for 4 hours, and cooling to room temperature by air to obtain the samarium-cobalt magnet, wherein the whole heat treatment process is carried out in a 5T strong magnetic field.

Prepared sintered samarium cobalt magnet magnetismCan be as follows: remanence B_r10.56kGs magnetic product (BH)_max24.63MGOe, intrinsic coercivity H_cj> 25kOe, knee point coercivity H_k＝21.38kOe。

< comparative example 1>

The preparation method of the high-knee-point coercive force sintered samarium cobalt magnet is the same as that of the example 1, except that no magnetic field is added in the step 5).

< comparative example 2>

The preparation method of the high-knee-point coercive force sintered samarium cobalt magnet is the same as that of the example 2, except that no magnetic field is added in the step 5).

< comparative example 3>

The preparation method of the high-knee-point coercive force sintered samarium cobalt magnet is the same as that of the example 3, except that no magnetic field is added in the step 5).

< comparative example 4>

The preparation method of the high-knee-point coercive force sintered samarium cobalt magnet is the same as that of the example 4, except that no magnetic field is added in the step 5).

In order to verify the preparation method of the high-knee-point coercivity sintered samarium cobalt magnet disclosed by the invention, the performance indexes of examples 1-4 and comparative examples 1-4 are respectively listed in the following table 1. It can be seen that the present invention provides a method for preparing a high knee point coercivity sintered samarium cobalt magnet (high remanence, high knee point coercivity), the magnetic domains in the magnet become uniform and fine after magnetic field heat treatment (see fig. 2), the observation surfaces of the two samples of example 1 and comparative example 1 are parallel to the typical magnetic domain structure of the c-axis (a) magnetic field heat treatment and (b) no magnetic field heat treatment; the observed area was 80 μm × 80 μm, and it can be seen that the remanence B of the magnet of example 1 was relative to that of comparative example 1_rKnee point coercive force H_kA significant improvement is obtained.

TABLE 1

	Br(kGs)	Hcj(kOe)	(BH)max(MGOe)	Hk(kOe)
					Example 1	11.72	>25	32.75	19.38
Example 2	11.32	>25	30.42	21.43
					Example 3	10.83	>25	27.41	22.16
Example 4	10.56	>25	24.63	21.38
					Comparative example 1	11.65	>25	31.78	9.92
Comparative example 2	11.25	>25	29.51	11.86
					Comparative example 3	10.72	>25	26.47	12.07
Comparative example 4	10.38	>25	23.38	12.39

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.