阅读说明：本技术 一种高温度稳定性烧结稀土永磁材料及其制备方法 (High-temperature-stability sintered rare earth permanent magnet material and preparation method thereof ) 是由 董生智 李栋 徐吉元 韩瑞 陈红升 李冬丽 周鸣鸽 李卫 于 2020-06-22 设计创作，主要内容包括：本发明属于稀土永磁材料技术领域,涉及一种高温度稳定性烧结稀土永磁材料。所述永磁材料的化学式通式按质量百分比为LRE<Sub>a</Sub>HRE<Sub>b</Sub>Co<Sub>c</Sub>B<Sub>d</Sub>TM<Sub>e</Sub>Fe<Sub>100-a-b-c-d-e</Sub>,其中：10≤a≤35,0<b≤25,28≤a+b≤36,1≤c≤35,0.8≤d≤1.5,0<e≤3；LRE为轻稀土Pr、Nd、La、Ce、Y中的一种或多种稀土元素,且LRE中必包含Pr或Nd,HRE为重稀土Gd、Tb、Dy、Ho中的一种或多种稀土元素,TM为Cu、Al、Cr、Nb、Zr、Ga、Ti、Mn、Zn、V、Mo中的两种以上的组合,且TM中必包含Cu或Al,该永磁材料的微观组织具有多种成分偏析。本发明通过优化永磁材料晶界相与晶界的结构,使获得的永磁材料在呈现较高的室温综合磁性能以及较高的居里温度的同时,还具有优异的温度稳定性与较高的使用温度。(The invention belongs to the technical field of rare earth permanent magnet materials, and relates to a high-temperature stable sintered rare earth permanent magnet material. The general formula of the permanent magnet material is LRE according to mass percent a HRE b Co c B d TM e Fe 100‑a‑b‑c‑d‑e Wherein: a is more than or equal to 10 and less than or equal to 35 and 0<b≤25，28≤a+b≤36，1≤c≤35，0.8≤d≤1.5，0<e is less than or equal to 3; the LRE is one or more rare earth elements of light rare earth Pr, Nd, La, Ce and Y, the LRE must contain Pr or Nd, the HRE is one or more rare earth elements of heavy rare earth Gd, Tb, Dy and Ho, the TM is the combination of more than two of Cu, Al, Cr, Nb, Zr, Ga, Ti, Mn, Zn, V and Mo, the TM must contain Cu or Al, and the microstructure of the permanent magnet material has multi-component segregation. The invention optimizes the structure of the grain boundary phase and the grain boundary of the permanent magnetic material, so that the obtained permanent magnetic material has higher room temperature comprehensive magnetic performance and higher performanceThe curie temperature is high, and the temperature stability is excellent and the use temperature is high.)

1. A high-temperature stable sintered rare earth permanent magnet material is characterized in that: the general formula of the permanent magnetic material is LRE according to weight percentage_aHRE_bCo_cB_dTM_eFe_{100-a-b-c-d-e}Wherein a is more than or equal to 10 and less than or equal to 35 and 0<b≤25，28≤a+b≤36，1≤c≤35，0.8≤d≤1.5，0<e is less than or equal to 3; LRE is one or more rare earth elements of light rare earth Pr, Nd, La, Ce and Y, LRE must contain Pr or Nd, HRE is one or more rare earth elements of heavy rare earth Gd, Tb, Dy and Ho, TM is the combination of more than two of Cu, Al, Cr, Nb, Zr, Ga, Ti, Mn, Zn, V and Mo, and TM must contain Cu or Al;

the microstructure of the high-temperature-stability sintered rare earth permanent magnet material comprises a main phase and a grain boundary phase, wherein the main phase is a main phase crystal grain with a structure of RE (Fe, Co): B ═ 2:14:1, and a cobalt-containing amorphous structure exists in the grain boundary phase; wherein the microstructure of the permanent magnetic material has the following composition segregation:

first segregation: the iron content in the main phase is higher than that in the grain boundary phase;

second segregation: the total content of light rare earth in the main phase is lower than that in the grain boundary phase;

third segregation: a cobalt-poor area with the cobalt content lower than that in the main phase grains and a cobalt-rich area with the cobalt content higher than that in the main phase grains exist in the grain boundary phase;

fourth segregation: the average cobalt content in the grain boundary phase is higher than the average cobalt content in the main phase.

2. The high temperature stable sintered rare earth permanent magnetic material of claim 1, wherein: a is more than or equal to 18 and less than or equal to 30, b is more than or equal to 3 and less than or equal to 11, a + b is more than or equal to 29 and less than or equal to 33, c is more than or equal to 5 and less than or equal to 15, d is more than or equal to 0.93 and less than or equal to 1.05, and e is more than or equal to 0.4.

3. The high temperature stable sintered rare earth permanent magnetic material of claim 1, wherein: the first segregation is greater than 30%; the second segregation is greater than 80%; in the third segregation, the cobalt content in the cobalt-poor region is 3-15% lower than that in the main phase crystal grains, and the cobalt content in the cobalt-rich region is 5-50% higher than that in the main phase crystal grains; the fourth segregation is 3% -30%.

4. The high temperature stable sintered rare earth permanent magnetic material of claim 1, wherein: the cobalt-rich area in the grain boundary phase is wider than the area occupied by the cobalt-poor area, and the volume ratio of the cobalt-rich area to the cobalt-poor area is more than 55: 45.

5. The high temperature stable sintered rare earth permanent magnetic material of claim 1, wherein: the high temperature stability sintered rare earth permanent magnetic material has the following remanence temperature coefficient: the temperature is-0.08%/DEG C to-0.001%/DEG C at 20-120 ℃; intrinsic coercivity temperature coefficient: the temperature of 20-120 ℃ is-0.6 to-0.3%/DEG C.

6. The high temperature stable sintered rare earth permanent magnetic material of claim 1, wherein: the density of the high-temperature-stability sintered rare earth permanent magnet material is 7.5-8.0 g/cm³。

7. The high temperature stable sintered rare earth permanent magnetic material of claim 1, wherein: the average size of the main phase crystal grains is 1-10 μm.

8. The high temperature stable sintered rare earth permanent magnetic material of claim 1, wherein: the Curie temperature of the high-temperature-stability sintered rare earth permanent magnet material is 350-700 ℃; the maximum service temperature is greater than 120 ℃.

9. The high temperature stable sintered rare earth permanent magnetic material of claim 1, wherein: when the length-diameter ratio of the high-temperature-stability sintered rare earth permanent magnet material cylinder sample is 1, the irreversible magnetic flux loss after heat preservation at 100 ℃ for 24 hours is less than 3%.

10. The high temperature stable sintered rare earth permanent magnetic material of claim 1, wherein: the high-temperature-stability sintered rare earth permanent magnet material is prepared by the process steps of smelting, hydrogen crushing, jet milling, magnetic field orientation forming, sintering, quick cooling and tempering.

11. A method of preparing a high temperature stable sintered rare earth permanent magnetic material as claimed in any of claims 1 to 10, characterized in that: the preparation method comprises the following steps:

(1) preparing raw materials: according to the chemical formula LRE of the rare earth permanent magnet material in percentage by mass_aHRE_bCo_cB_dTM_eFe_{100-a-b-c-d-e}Preparing raw materials, wherein: a is more than or equal to 10 and less than or equal to 35 and 0<b≤25，28≤a+b≤36，1≤c≤35，0.8≤d≤1.5，0<e is less than or equal to 3; LRE is one or more rare earth elements of light rare earth Pr, Nd, La, Ce and Y, and LRE must contain Pr or Nd, HRE is one or more rare earth elements of heavy rare earth Gd, Tb, Dy and Ho, TM is the combination of more than two of Cu, Al, Cr, Nb, Zr, Ga, Ti, Mn, Zn, V and Mo, and Cu or Al must be contained;

(2) preparing a quick-setting tablet: putting the raw materials into a crucible of a rapid hardening furnace, carrying out vacuum induction melting under the protection of argon, keeping the temperature of 1200-1600 ℃ after the raw materials are fully melted, pouring alloy liquid onto a water-cooling rotary copper roller, and preparing a rapid hardening sheet with the average thickness of 0.2-0.4 mm;

(3) hydrogen breaking: crushing the quick-setting tablets obtained in the step (2) by using a hydrogen crushing furnace to obtain hydrogen crushed powder with the granularity of less than 1 mm;

(4) and (3) jet milling: in the protection of nitrogen, crushing hydrogen powder into magnetic powder with the average particle size of 1-4 mu m;

(5) profiling: the magnetic powder is subjected to orientation pressing forming in a magnetic field press with the temperature of more than 1.8T to obtain a neodymium iron boron blank, and then isostatic pressing treatment is carried out to obtain the neodymium iron boron blank with the density of 3-6 g/cm³The green compact of (a);

(6) and (3) sintering: sintering the pressed green body under a vacuum condition, wherein the sintering temperature is 1000-1200 ℃, and the sintering time is 2-6 h;

(7) tempering: performing primary tempering at 800-980 ℃ for 2-4 hours, and rapidly reducing the temperature of the blank to below 600 ℃ at a speed of not less than 5 ℃ per second after the primary tempering is finished; and then performing secondary tempering at 400-650 ℃ for 2-6 h to obtain a sintered rare earth permanent magnet material blank.

12. The method for preparing a high temperature stable sintered rare earth permanent magnetic material according to claim 11, wherein: in the step (3), hydrogen is absorbed at room temperature under 0.1-0.5 MPa, and then dehydrogenation treatment is carried out, wherein the dehydrogenation temperature is 500-650 ℃, and the time is 2-6 hours.

13. The method for preparing a high temperature stable sintered rare earth permanent magnetic material according to claim 11, wherein: in the step (4), the oxygen content of the magnetic powder is controlled to be 10-200 ppm.

Technical Field

The invention belongs to the technical field of rare earth permanent magnet materials, and particularly relates to a high-temperature-stability sintered rare earth permanent magnet material and a preparation method thereof.

Background

Since the advent of Nd-Fe-B magnets in 1984, the use of sintered Nd-Fe-B magnets has rapidly expanded into a variety of fields. The maximum energy product of Nd-Fe-B rare-earth permanent-magnet material is highest among the permanent-magnet materials known at present, and is a creditable "magnetic king". Because of its excellent room temperature magnetic property and lower production cost, it is the most widely used permanent magnetic material at present. But its curie temperature is relatively low (generally not exceeding 360 ℃); the temperature stability is relatively poor (the temperature coefficient of remanence is between-0.09 and-0.12%/DEG C); and the coating is easy to oxidize and corrode and is difficult to meet the requirements of a plurality of high-temperature fields. In order to better meet the requirements of core control devices in the fields of electric automobiles, wind power generation, nuclear energy application, aerospace and the like on the performance stability, reliability and high heat-resistant indexes of rare earth permanent magnet materials, the main factors and action rules influencing the thermal stability of the magnet are researched, and the method has important academic significance and practical value.

The magnetic property and the stability are two important aspects of the technical advancement of the permanent magnet material, the magnetic property of the permanent magnet material is mainly evaluated by parameters such as remanence, coercive force, maximum magnetic energy product and the like, and the stability of the permanent magnet material is mainly evaluated by temperature stability and time stability. The temperature stability mainly includes two aspects: the first is the maximum service temperature (maximum holding temperature of open-circuit magnetic flux irreversible loss less than or equal to 5% for a cylindrical sample with an aspect ratio of 0.7). If the maximum use temperature is too low, the range of application is greatly limited. The second is the temperature coefficient. Some fields require that the magnetic performance of the magnet is substantially maintained when the ambient temperature changes, although the ambient temperature is not so high.

At present, the common method for improving the service temperature of the neodymium iron boron magnet is to add heavy rare earth elements, and the principle is to greatly improve the coercive force of the magnet, so that the magnet can still keep strong enough demagnetization resistance at higher service temperature.

In the existing preparation of high-temperature-stability sintered rare earth permanent magnet materials, only the change of components is emphasized, and the control on the microstructure of the materials is often ignored. For example, in chinese patent application No. 201710243774.0, a 'high temperature stability permanent magnetic material and its application' are disclosed, which improve the temperature stability by adjusting the element content, but do not actively regulate the microstructure of the material.

Disclosure of Invention

Aiming at the technical problems, the invention aims to provide a high-temperature-stability sintered rare earth permanent magnet material and a preparation method thereof, and solves the problems of low use temperature, poor temperature stability and the like of a sintered neodymium-iron-boron magnet. In the invention, the heavy rare earth element, the cobalt element and the trace element are jointly added to effectively regulate and control the magnetic moment and the microstructure of the material, optimize the structure of a grain boundary phase and a grain boundary of the sintered rare earth permanent magnet material, form a cobalt-containing amorphous grain boundary phase (see the attached figure 2 of the specification), and obtain the sintered rare earth permanent magnet material with high temperature stability.

In order to achieve the purpose, the invention provides the following technical scheme:

a high-temp stable sintered permanent-magnet RE material with the general chemical formula of LRE_aHRE_bCo_cB_dTM_eFe_{100-a-b-c-d-e}Wherein a is more than or equal to 10 and less than or equal to 35 and 0<b≤25，28≤a+b≤36，1≤c≤35，0.8≤d≤1.5，0<e≤3; LRE is one or more rare earth elements of light rare earth Pr, Nd, La, Ce and Y, LRE must contain Pr or Nd, HRE is one or more rare earth elements of heavy rare earth Gd, Tb, Dy and Ho, TM is the combination of more than two of Cu, Al, Cr, Nb, Zr, Ga, Ti, Mn, Zn, V and Mo, and TM must contain Cu or Al;

the microstructure of the high-temperature-stability sintered rare earth permanent magnet material comprises a main phase and a grain boundary phase, wherein the main phase is a main phase crystal grain with a structure of RE (Fe, Co): B ═ 2:14:1, and a cobalt-containing amorphous structure exists in the grain boundary phase; wherein the microstructure of the permanent magnetic material has the following composition segregation:

first segregation: the iron content in the main phase is higher than that in the grain boundary phase;

second segregation: the total content of light rare earth in the main phase is lower than that in the grain boundary phase;

third segregation: a cobalt-poor area with the cobalt content lower than that in the main phase grains and a cobalt-rich area with the cobalt content higher than that in the main phase grains exist in the grain boundary phase;

fourth segregation: the average cobalt content in the grain boundary phase is higher than the average cobalt content in the main phase.

18≤a≤30，3<b≤11，29≤a+b≤33，5≤c≤15，0.93≤d≤1.05，0.4<e≤1.6。

The first segregation is greater than 30%; the second segregation is greater than 80%; in the third segregation, the cobalt content in the cobalt-poor region is 3-15% lower than that in the main phase crystal grains, and the cobalt content in the cobalt-rich region is 5-50% higher than that in the main phase crystal grains; the fourth segregation is 3% -30%.

The cobalt-rich area in the grain boundary phase is wider than the area occupied by the cobalt-poor area, and the volume ratio of the cobalt-rich area to the cobalt-poor area is more than 55: 45.

The high temperature stability sintered rare earth permanent magnetic material has the following remanence temperature coefficient: the temperature is-0.08%/DEG C to-0.001%/DEG C at 20-120 ℃; intrinsic coercivity temperature coefficient: the temperature of 20-120 ℃ is-0.6 to-0.3%/DEG C.

The density of the high-temperature-stability sintered rare earth permanent magnet material is 7.5-8.0 g/cm³；

The average size of the main phase crystal grains is 1-10 μm.

The Curie temperature of the high-temperature-stability sintered rare earth permanent magnet material is 350-700 ℃; the maximum service temperature is greater than 120 ℃.

When the length-diameter ratio of the high-temperature-stability sintered rare earth permanent magnet material cylinder sample is 1, the irreversible magnetic flux loss after heat preservation at 100 ℃ for 24 hours is less than 3%.

The high-temperature-stability sintered rare earth permanent magnet material is prepared by the process steps of smelting, hydrogen crushing, jet milling, magnetic field orientation forming, sintering, quick cooling and tempering.

A preparation method of a high-temperature stable sintered rare earth permanent magnet material comprises the following steps:

(1) preparing raw materials: according to the chemical formula LRE of the rare earth permanent magnet material in percentage by mass_aHRE_bCo_cB_dTM_eFe_{100-a-b-c-d-e}Preparing raw materials, wherein: a is more than or equal to 10 and less than or equal to 35 and 0<b≤25，28≤a+b≤36，1≤c≤35，0.8≤d≤1.5，0<e is less than or equal to 3; LRE is one or more rare earth elements of light rare earth Pr, Nd, La, Ce and Y, and LRE must contain Pr or Nd, HRE is one or more rare earth elements of heavy rare earth Gd, Tb, Dy and Ho, TM is the combination of more than two of Cu, Al, Cr, Nb, Zr, Ga, Ti, Mn, Zn, V and Mo, and Cu or Al must be contained;

(2) preparing a quick-setting tablet: putting the raw materials into a crucible of a rapid hardening furnace, carrying out vacuum induction melting under the protection of argon, keeping the temperature of 1200-1600 ℃ after the raw materials are fully melted, pouring alloy liquid onto a water-cooling rotary copper roller, and preparing a rapid hardening sheet with the average thickness of 0.2-0.4 mm;

(3) hydrogen breaking: crushing the quick-setting tablets obtained in the step (2) by using a hydrogen crushing furnace to obtain hydrogen crushed powder with the granularity of less than 1 mm;

(4) and (3) jet milling: in the protection of nitrogen, crushing hydrogen powder into magnetic powder with the average particle size of 1-4 mu m;

(5) profiling: the magnetic powder is subjected to orientation pressing forming in a magnetic field press with the temperature of more than 1.8T to obtain a neodymium iron boron blank, and then isostatic pressing treatment is carried out to obtain the neodymium iron boron blank with the density of 3-6 g/cm³The green compact of (a);

(6) and (3) sintering: sintering the pressed green body under a vacuum condition, wherein the sintering temperature is 1000-1200 ℃, and the sintering time is 2-6 h;

(7) tempering: performing primary tempering at 800-980 ℃ for 2-4 hours, and rapidly reducing the temperature of the blank to below 600 ℃ at a speed of not less than 5 ℃ per second after the primary tempering is finished; and then performing secondary tempering at 400-650 ℃ for 2-6 h to obtain a sintered rare earth permanent magnet material blank.

In the step (3), hydrogen is absorbed at room temperature under 0.1-0.5 MPa, and then dehydrogenation treatment is carried out, wherein the dehydrogenation temperature is 500-650 ℃, and the time is 2-6 hours.

In the step (4), the oxygen content of the magnetic powder is controlled to be 10-200 ppm.

Compared with the prior art, the invention has the beneficial effects that:

the invention provides a high-temperature stable sintered rare earth permanent magnet material, which effectively regulates and controls the magnetic moment and microstructure of the material by jointly adding heavy rare earth elements, cobalt elements and trace elements, optimizes the structure of a grain boundary phase and a grain boundary of the sintered rare earth permanent magnet material, and forms a cobalt-containing grain boundary phase and segregation of various components by controlling the component proportion of the material and the cooling speed after sintering and tempering, particularly after the sintering and tempering are finished, thereby obtaining the high-temperature stable sintered rare earth permanent magnet material with excellent comprehensive performance, which is optimized in magnetic performance, thermal stability and mechanical performance.

Drawings

FIG. 1 is a schematic diagram of SEM micro-region morphology and components of a high-temperature-stability sintered rare earth permanent magnet material of the invention;

FIG. 2 is an HR-TEM micro-area morphology and Fourier transform of a main phase and a cobalt-rich grain boundary phase of the high temperature stability sintered rare earth permanent magnet material of the present invention;

fig. 3 is a graph of demagnetization curves at different temperatures for a typical high temperature stability sintered rare earth permanent magnet material.

Detailed Description

The following further describes embodiments of the present invention with reference to the drawings. It should be noted, however, that the following examples are for illustrative purposes only, and the scope of the present invention is not limited to the following examples.