HIGHLY THERMOSTABLE RARE-EARTH PERMANENT MAGNETIC MATERIAL, PREPARATION METHOD THEREOF AND MAGNET CONTAINING THE SAME

Abstract

Provided are a highly thermostable rare-earth permanent magnetic material, a preparation method thereof and a magnet containing the same. A composition of the rare-earth permanent magnetic material by an atomic percentage is as follows: SM.sub.xR.sub.aFe.sub.100-x-y-z-aM.sub.yN.sub.z, wherein R is at least one of Zr and Hf, M is at least one of Co, Ti, Nb, Cr, V, Mo, Si, Ga, Ni, Mn and Al, x+a is 7-10%, a is 0-1.5%, y is 0-5% and z is 10-14%.

Claims

1. A rare-earth permanent magnetic material, a composition of the rare-earth permanent magnetic material by an atomic percentage being as follows:
SM.sub.xR.sub.aFe.sub.100.sub.x-y-z-aM.sub.yN.sub.z wherein R is at least one of Zr and Hf, M is at least one of Co, Ti, Nb, Cr, V, Mo, Si, Ga, Ni, Mn and Al, x+a is 7-10%, a is 0-1.5%, y is 0-5%, and z is 10-14%.

2. The rare-earth permanent magnetic material as claimed in claim 1, wherein the rare-earth permanent magnetic material comprises a TbCu.sub.7 phase, a Th.sub.2Zn.sub.17 phase and a soft magnetic phase -Fe.

3. A preparation method of the rare-earth permanent magnetic material as claimed in claim 1, comprising the following steps: (1) performing master alloy smelting on Sm, R, Fe, and M; (2) quick-quenching a master alloy obtained in the step (1) to prepare a quick-quenched ribbon; (3) performing a crystallization treatment on the quick-quenched ribbon obtained in the step (2); and (4) nitriding a permanent magnetic material crystallized in the step (3) to obtain the rare-earth permanent magnetic material.

4. The preparation method as claimed in claim 3, wherein the smelting in the step (1) is performed by means of an intermediate frequency or an electric arc; and an ingot obtained by the smelting is preliminarily crushed into millimeter-level ingot blocks.

5. The preparation method as claimed in claim 3, wherein the quick-quenching in the step (2) is as follows: putting the master alloy into a quartz tube having a nozzle; and smelting into an alloy liquid via induction smelting, and spraying to a rotary water-cooling copper mould via the nozzle to obtain the quick-quenched ribbon; and a wheel speed in the quick-quenching is 20-80 m/s.

6. The preparation method as claimed in claim 3, wherein the crystallization treatment in the step (3) is as follows: after wrapping the quick-quenched ribbon, performing a heat treatment and then a quenching treatment.

7. The preparation method as claimed in claim 3, wherein the nitriding in the step (4) is performed in a nitriding furnace.

8. A magnet, comprising the rare-earth permanent magnetic material as claimed in claim 1.

9. The magnet as claimed in claim 8, wherein the magnet is formed by bonding the rare-earth permanent magnetic material and an adhesive, the magnet prepared with the following method: mixing the rare-earth permanent magnetic material with an epoxy resin to obtain a mixture, adding a lubricant to the mixture, then performing a treatment to obtain a bonded magnet, and at last thermocuring the bonded magnet.

10. The magnet as claimed in claim 9, wherein a proportion of the rare-earth permanent magnetic material to the epoxy resin by weight is 100:1-10.

11. The preparation method as claimed in claim 4, wherein the quick-quenching in the step (2) is as follows: putting the master alloy into a quartz tube having a nozzle, smelting into an alloy liquid via induction smelting, and spraying to a rotary water-cooling copper mould via the nozzle to obtain the quick-quenched ribbon.

12. The preparation method as claimed in claim 4, wherein the crystallization treatment in the step (3) is as follows: after wrapping the quick-quenched ribbon, performing a heat treatment and then a quenching treatment.

13. The preparation method as claimed in claim 5, wherein the crystallization treatment in the step (3) is as follows: after wrapping the quick-quenched ribbon, performing a heat treatment and then a quenching treatment.

14. The rare-earth permanent magnetic material as claimed in claim 2, wherein the content of the TbCu.sub.7 phase in the rare-earth permanent magnetic material is 50% or more, the content of the Th.sub.2Zn.sub.17 phase in the rare-earth permanent magnetic material is 0-50%, excluding 0, and the content of the soft magnetic phase -Fe in the rare-earth permanent magnetic material is 0-5%, excluding 0.

15. The rare-earth permanent magnetic material as claimed in claim 2, wherein the rare-earth permanent magnetic material is composed of crystal grains having an average size of 10 nm to 1 m.

16. The preparation method as claimed in claim 6, wherein the heat treatment is performed in a tubular resistance furnace and in an argon atmosphere.

17. The preparation method as claimed in claim 6, wherein a temperature of the heat treatment is 700-900 C. and a time is 5 min or more.

18. The preparation method as claimed in claim 7, wherein the nitriding is performed in a high-purity nitrogen atmosphere at 1-2 atm.

19. The preparation method as claimed in claim 7, wherein a temperature of the nitriding is 350-600 C. and a time is for 12 h or more.

20. The magnet as claimed in claim 10, wherein an added amount of the lubricant is 0.2-1 wt %.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0057] To understand the present application easily, the embodiments listed by the present application are set forth hereinafter. A person skilled in the art should know that the embodiments are only for a further understanding of the present application, rather than specific limits to the present application.

[0058] It is to be noted that the embodiments of the present application and the characteristics of the embodiments may be combined with each other if there is no conflict. The present application will be described below with reference to the embodiments in detail.

[0059] It is to be noted that terms herein are only intended to describe the specific embodiments, but not limit the exemplary embodiments of the present application. As described here, unless otherwise explicitly specified by the context, any singular form also includes a plural form. Additionally, it is to be understood that when terms contain and/or include are used in the description, it refers to that there exists a characteristic, a step, a device, a component and/or their combinations.

[0060] The present application provides a rare-earth permanent magnetic material; a composition of the rare-earth permanent magnetic material by an atomic percentage is as follows:

SM.sub.xR.sub.aFe.sub.100-x-y-z-aM.sub.yN.sub.z

[0061] Wherein R is at least one of Zr and Hf, M is at least one of Co, Ti, Nb, Cr, V, Mo,

[0062] Si, Ga, Ni, Mn and Al, x+a is 7-10%, a is 0-1.5%, y is 0-5% and z is 10-14%. The above ranges all include an endpoint value, and N is a nitrogen element.

[0063] In the present application, the content of the rare-earth element Sm has a great influence on a phase structure of the quick-quenched SmFe alloy ribbon. It is easy to form the soft magnetic phase when the Sm content is below 7 at % and to form a samarium-enriched phase when the Sm content is 10 at % or more, all of which are not beneficial to preparing the quick-quenched alloy having 95% or more of the main phase of the TbCu.sub.7 structure. Moreover, the Zr or the Hf may substitute the Sm element and the substituted amount is below 1.5 at %. With the substitution of the M element to the Fe element, the Sm/Fe proportion to form the TbCu.sub.7 may be expanded. The Sm content in the present application is 7-10 at % preferably.

[0064] The magnetic property Hcj of the rare-earth permanent magnetic material provided by the present application reaches to 10kOe or more and the magnetic energy product Bh is 14 MGOe or more. The irreversible flux loss of a magnet prepared from the rare-earth permanent magnetic material of the present application is less than 5% (the thermostability is characterized by means of the irreversible flux loss of a bonded magnet, by exposing for 2 h in the air at 120 C.).

[0065] The present application further provides a preparation method of the rare-earth permanent magnetic material, including the following steps:

[0066] (1) performing master alloy smelting on Sm, R, Fe and M;

[0067] (2) quick-quenching a master alloy obtained in the step (1) to prepare a quick-quenched ribbon;

[0068] (3) performing a crystallization treatment on the quick-quenched ribbon obtained in the step (2); and

[0069] (4) nitriding a permanent magnetic material crystallized in the step (3) to obtain the rare-earth permanent magnetic material.

[0070] In the above preparation process, the critical step is the crystallization treatment on the quick-quenched ribbon in the step (3). The quick-quenched Sm Fe alloy contains a TbCu.sub.7 type SmFe.sub.9phase, a few soft magnetic phase -Fe and an amorphous phase, and there are vacancies and defects remained due to rapid cooling in the structure, so by virtue of the crystallization heat treatment, the amorphous structure is changed into a crystal structure on one hand, and on the other hand, the homogeneity of the microstructure is improved. In the crystallization heat treatment at a relatively low temperature, while the TbCu.sub.7 type structure is formed, a few soft magnetic phase -Fe is produced. The crystal grains in the structure are relatively small, so the remanence and the magnetic energy product of the samarium-iron-nitrogen magnetic powder are relatively high, but the coercivity still is relatively low.

[0071] It is found by the inventors that, under the experimental conditions, when the temperature of the crystallization heat treatment is relatively low and the time is relatively short, less TbCu.sub.7 type metastable phase in the alloy is transformed into a Th.sub.2Zn.sub.17 type oblique hexagonal phase. On the contrary, when the temperature is raised and the treatment time is increased, more TbCu.sub.7 type metastable phase is transformed into the Th.sub.2Zn.sub.17 type oblique hexagonal phase, but meanwhile, the proportion of the soft magnetic phase -Fe is increased. After the magnetic powder is used for preparing a bonded magnet, the irreversible flux loss of the samarium-iron-nitrogen magnet is reduced. By adjusting the temperature and the time for the crystallization heat treatment of the quick-quenched SmFe to improve the proportion of the Th.sub.2Zn.sub.17 type structure in the TbCu.sub.7 type SmFe alloy, the highly thermostable samarium-iron-nitrogen magnetic material can be obtained.

[0072] In the present application, the main phase of the material is the TbCu.sub.7 type structure, the intrinsic magnetic property of the samarium-iron-nitrogen magnetic powder having the structure is higher than the quick-quenched NdFeB magnetic powder, and the corrosion resistance is also better than other magnetic powder. The samarium iron in the TbCu.sub.7 type structure is of a metastable phase and its formation requires strict component control and process condition control as well as a quick cooling manner. However, in preparation, there also have compounds with other structures, such as ThMn.sub.12 or Th.sub.2Ni.sub.17 or Th.sub.2Zn.sub.17 structure. The samarium-iron alloy prepared by melt quick quenching is of a Th.sub.2Zn.sub.17 structure in general, the size of the magnetic powder having such structure needs to reach to a micron level and the relatively good magnetic property is obtained by orienting compression in a magnetic field. Generally, the remanence and the magnetic energy product of the quick-quenched magnetic powder having the Th.sub.2Zn.sub.17 structure are quite low, and even are less than 8 MGOe, but the coercivity H.sub.cj may be up to 20 kOe or more. The samarium iron having the TbCu.sub.7 structure is of the metastable phase and may be transformed into the Th.sub.2Zn.sub.17 structure via a certain crystallization heat treatment and nitrizing treatment, and meanwhile, the soft magnetic phase -Fe is also produced. As a result, there are excessive stable Th.sub.2Zn.sub.17 structures due to the overhigh temperature of the heat treatment and therefore the magnetic property is greatly reduced. According to the present application, by optimizing the crystallization process, adjusting the contents of the Th.sub.2Zn.sub.17 structure phase and the -Fe soft magnetic phase in the alloy, and specifying that the content of the -Fe soft magnetic phase is less than 5% and that of the Th.sub.2Zn.sub.17 structure phase is 1% or more, the TbCu.sub.7 structure phase is the main phase and its content is 50% or more, the preferable temperature of the crystallization heat treatment is 700-900 C.

[0073] According to the present application, it is also specified that the samarium-iron-nitrogen magnetic material is 10-40 m in an average thickness and consists of nanocrystals having the average size of 10-200 nm. As the thickness of the quick-quenched samarium-iron alloy is associated with the preparation method, the TbCu.sub.7 structure needs a large cooling speed and the overquick cooling speed is not beneficial to the formation of the ribbon, the thickness of the prepared samarium-iron alloy is at the specified appropriate thickness. The grain size of the magnetic powder directly affects the magnetic property, the alloy with small and uniform grains has relatively high coercivity and the thermostability of the magnetic powder also can be improved. Generally, the magnetic powder having the grain size kept between 10 nm and 1 m can obtain the relatively good magnetic property. To enable the magnetic powder to keep the relatively good coercivity and improve the thermostability, the grain size of the magnetic powder is preferably 10-200 nm.

Embodiments 1-15

[0074] The preparation method includes the following steps:

[0075] (1) after mixing metals listed in each embodiment according to a proportion in

[0076] Table 1, putting into an induction smelting furnace, and smelting under Ar gas protection to obtain an alloy ingot;

[0077] (2) after roughly crushing the alloy ingot, putting into a quick quenching furnace, wherein the protective gas is an Ar gas, the spray pressure is 80 kPa, the nozzle diameter is 0.8 and the speed of a water cooling roller is 20-80 m/s; and quickly quenching to obtain flaky alloy powder;

[0078] (3) after performing a heat treatment on the alloy under the Ar gas protection, performing a nitriding treatment under a N.sub.2 gas at 1 atm to obtain nitride magnetic powder, wherein the conditions for the heat treatment and the nitriding treatment in crystallization are referred to Table 2; and

[0079] (4) detecting a phase proportion and a magnetic property of the nitride magnetic powder.

TABLE-US-00001 TABLE 1 Embodiment Component 1 Sm.sub.8.5Zr.sub.1.2Fe.sub.77.7Si.sub.1.0 N.sub.11.6 2 Sm.sub.8.5Zr.sub.1.2Fe.sub.76.9Al.sub.1.0 N.sub.12.4 3 Sm.sub.8.5Zr.sub.1.2Fe.sub.79.2Mn.sub.1.0 N.sub.10.1 4 Sm.sub.8.5Zr.sub.1.2Fe.sub.72.3Co.sub.4.5 N.sub.13.5 5 Sm.sub.8.5Zr.sub.1.2Fe.sub.73.3Co.sub.4.5 N.sub.12.5 6 Sm.sub.8.5Hf.sub.1.2Fe.sub.74.3Co.sub.4.5 N.sub.11.5 7 Sm.sub.8.5Zr.sub.1.2Fe.sub.82.8Co.sub.4.5Nb.sub.1.2 N.sub.1.8 8 Sm.sub.8.5Zr.sub.1.2Fe.sub.73.4Co.sub.4.5Ti.sub.1.2 N.sub.11.2 9 Sm.sub.8.5Zr.sub.1.2Fe.sub.73.8Co.sub.4.5Mo.sub.1.2 N.sub.10.8 10 Sm.sub.8.5Hf.sub.1.2Fe.sub.73.7Ni.sub.4.5 N.sub.12.1 11 Sm.sub.8.5Zr.sub.1.2Fe.sub.77.6Ga.sub.0.3 N.sub.12.4 12 Sm.sub.8.5Zr.sub.1.2Fe.sub.75.8V.sub.1.5 N.sub.13 13 Sm.sub.8.5Zr.sub.1.2Fe.sub.75.3Nb.sub.1.5 N.sub.13.5 14 Sm.sub.8.5Zr.sub.1.2Fe.sub.78.3Cr.sub.1.5 N.sub.10.5 15 Sm.sub.8.5Zr.sub.1.2Fe.sub.74.9Cr.sub.1.5 N.sub.13.9

TABLE-US-00002 TABLE 2 Pro- Pro- portion portion of of Pro- TbCu.sub.7 Th.sub.2Zn.sub.17 portion Embod- Crystallization Nitriding type type of -Fe iment heat treatment treatment phase phase phase 1 7000 C.*90 min 3500 C.*24 h 98.7 1.3 2 7250 C.*80 min 3800 C.*24 h 97.3 1.4 1.3 3 7500 C.*70 min 4000 C.*24 h 96.2 2.1 1.7 4 7750 C.*60 min 4100 C.*24 h 92.4 5.5 2.1 5 8000 C.*50 min 4200 C.*24 h 91.5 6.1 2.4 6 8250 C.*40 min 4600 C.*24 h 87.6 9.1 3.3 7 8500 C.*30 min 4500 C.*20 h 84.4 11.7 3.9 8 8750 C.*20 min 4400 C.*24 h 78.5 16.6 4.9 9 9000 C.*10 min 4300 C.*24 h 52.4 38.4 9.2 10 7750 C.*70 min 4700 C.*24 h 91.7 6.0 2.3 11 8000 C.*60 min 5100 C.*16 h 89.2 7.9 2.9 12 8250 C.*50 min 5000 C.*24 h 84.2 12.3 3.5 13 8500 C.*40 min 4000 C.*30 h 65.3 29.8 4.9 14 8750 C.*30 min 4500 C.*24 h 51.2 44.4 4.4 15 9000 C.*20 min 6000 C.*12 h 50.0 45.1 4.9

[0080] Performance test

[0081] The performance test is performed on the permanent magnetic material obtained in the embodiments 1-15 and the test results are referred to Table 3 hereinafter.

TABLE-US-00003 TABLE 3 Embodiment Br/kGs Hcj/kOe (BH)m/MGOe 2 h@120 FL % 1 9.1 9.5 16.2 6.1 2 9.7 9.8 16.5 4.9 3 9.3 10.3 16.2 3.8 4 9.2 10.9 15.3 3.4 5 8.9 11.2 15.4 3.2 6 8.6 12.1 14.5 3.2 7 8.3 13.0 14.2 3.4 8 8.5 12.5 14.2 3.4 9 7.9 11.8 12.9 5.7 10 8.9 11.4 15.8 3.3 11 8.6 11.6 15.1 3.6 12 8.5 11.3 14.0 3.5 13 8.4 12.6 14.1 4.5 14 8.3 12.1 13.4 4.3 15 7.8 10.9 12.2 5.1 2 h/FL % is the irreversible flux loss with exposure for 2 h in the air at 120 C.

[0082] The high thermostability of the magnetic powder prepared in the embodiments is characterized by the irreversible flux loss of the bonded magnet and by exposing the bonded magnet for 2 h in the air at 25-120 C.

[0083] It may be seen from the Table 2 that the proportions of the TbCu.sub.7 type phase, the Th.sub.2Zn.sub.17 type phase and the -Fe phase in the embodiment 1 and the embodiment 9 are not within the preferable ranges of the claims, so the performance is slightly poor. The irreversible flux loss of the magnetic powder prepared in the rest embodiments basically is less than 5%, the magnetic property Hcj substantially is up to 10 kOe or more, and the magnetic energy product BH is up to 12 MGOe or more.

[0084] Obviously, the above embodiments are examples only intended to illustrate the present application clearly, rather than limits to the embodiments. A person having ordinary skill in the art further can make changes or modifications in other different forms on the basis of above description. Here, there is no necessity and no need to give an example for all embodiments one by one. And any obvious change or modification hereto shall all fall within the protection scope of the present application.