EP3008221A1

EP3008221A1 - Magnetic material, use thereof, and method for producing same

Info

Publication number: EP3008221A1
Application number: EP14728593.6A
Authority: EP
Inventors: Arne Huber; Jürgen OBERLE; Lars BOMMER; Friederike KÖPPEN; Gerhard Schneider; Dagmar GOLL; Roman KARIMI; Ralf Löffler; Roland Stein
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2013-06-13
Filing date: 2014-06-10
Publication date: 2016-04-20
Anticipated expiration: 2034-06-10
Also published as: CN105555980A; US20160148734A1; DE102013009940A1; WO2014198708A1; EP3008221B1; JP2016528717A

Abstract

The invention relates to a magnetic material which contains at least one transition metal (TM), at least one rare earth metal (RE), and titanium. The content of the transition metal equals 74 to 94 at%, the content of the rare earth metal equals 2 to 20 at%, and the content of titanium equals 7 to 9 at%, in each case based on the total mass of the magnetic material, and the transition metal comprises cobalt.

Description

description

title

Magnetic material, its use and process for its preparation. State of the art

The present invention relates to a magnetic material, its use, as well as a method for producing the magnetic material.

Due to the recent increase in the use of electric motors, not least in the automotive industry, the need for high-performance magnetic

Materials, and in particular permanent magnets, have risen sharply in recent years. Suitable magnetic materials include those with hard magnetic phases, which are characterized by a high remanent magnetization, a large coercive field and a large energy product. Due to the high power density of these magnetic materials, they are particularly well suited for use in space-reduced devices. High-performance, permanently stable and at the same time cost-intensive magnetic materials are therefore key components of electromobility. As particularly powerful, so having a large energy product, magnetic materials have proven that at least one rare earth metal such as neodymium (Nd), praseodymium (Pr) and samarium (Sm), and at least one transition metal such as iron (Fe) or cobalt (Co) include. Often, such materials to optimize the microstructure and thus the intrinsic magnetic properties with interstitial additives, such as boron (B), carbon (C), nitrogen (N) or hydrogen (H), added. As a particularly powerful magnetic

Material has turned out to be Nd ₂ Fe ₁₄ B. Due to its limited chemical, mechanical and thermal long-term stability, however, a complete replacement of the conventional ferrites by Nd ₂ Fei ₄ B has not yet taken place. Another disadvantage of Nd ₂ Fe ₁ B are its high raw material and

Production costs. In addition, the availability of rare earth metals in such highly limited, whereby the production quantities of magnets based on highly rare earth metal-containing magnetic materials, such as just Nd ₂ Fei ₄ B, are severely limited.

Disclosure of the invention

The magnetic material according to the invention is characterized

excellent magnetic properties, and thus a high remanent magnetization, a high coercive force, as well as a large energy product. Its mechanical, magnetic, and thermal stability is high, which makes it suitable for use in heavy-duty, so for example, moving

Devices, such as motor vehicles and mobile electronic devices, predestined. By using at least one transition metal (TM), at least one rare earth element (RE) and titanium, the content of

Transition metal 74 to 94 atom%, the content of rare earth metal (RE) 2 to 20 atom% and the content of titanium 3 to 15 atom%, in each case based on

Total mass of the magnetic material is, and wherein the

Transition metal cobalt, a highly efficient magnetic material is obtained, which is characterized by particularly good mechanical properties, and in particular by excellent magnetic characteristics. Due to the specific content of titanium, on the one hand, the lattice structure of the magnetic material is stabilized and, on the other hand, the development of the anisotropy is promoted. It has also been found that cobalt, especially in the o.g. Combination with titanium makes a significant contribution to improving the magnetic characteristics of the magnetic material according to the invention. In particular, by combining a transition metal, a

Rare earth metal and titanium with cobalt the anisotropy constant and

Saturation polarization increased. This means that through the

Element combination essential to the invention both the strength of the magnetic material and its demagnetization, so its

Coercive force, and thus the power density of the magnetic material can be improved. Furthermore, this can effectively reduce the content of rare earth metal, which lowers the raw material costs of the magnetic material according to the invention and ensures a high availability of the raw materials. Thus supply shortages can be prevented and a limitation of the production quantities avoided. In addition, the addition of cobalt Temperature of the magnetic material significantly raised, causing the

Application of the magnetic material promotes especially where very high temperatures occur, such as in electric motors and generators. Consequently, the use of the magnetic material according to the invention opens up many possible applications, even in low-price products, without having a detrimental effect on their qualitative properties.

The dependent claims show preferred developments of the invention.

According to an advantageous embodiment of the invention that includes

Transition metal cobalt at a content of 1 atomic% to less than 50

Atom%, preferably 3 to 30 atom% and in particular 8 to 20 atom%, based on the Gesamtgeha! T in atom% of transition metal. This achieves an optimum compromise between very good magnetic properties and a moderate cost structure of the magnetic material. Further advantageously, the transition metal contains at least one of: iron

(Fe), nickel (Ni) and manganese (Mn) or mixtures thereof, wherein the

Main portion is preferably iron. The transition metals mentioned here form with rare earth metals, titanium and cobalt particularly stable lattice structures and contribute more to the expression of the desired advantageous magnetic properties, ie in particular to saturation and increase of the magnetic

Anisotropy of the material according to the invention, in. Furthermore, their availability in the market is high with relatively low raw material costs, which significantly reduces the material costs of the magnetic material according to the invention. The preferred use of Fe among these metals is for its health and environmental safety and, moreover, for its compared to

Ni and Mn once again significantly reduced raw material costs.

A further advantageous development provides that the rare earth metal is selected from the group consisting of: neodymium (Nd), lanthanum (La), cerium (Ce), dysprosium (Dy), praseodymium (Pr), samarium (Sm), promethium ( Pm), yttrium (Y), scandium (Sc), gadolinium (Gd), holmium (Ho) and erbium (Er) and preferably Ce and / or La. The listed rare earth metals Nd, La, Ce, Dy, Pr, Sm, Pm, Y, Sc, Gd, Ho and Er, have been found to be particularly compatible with the other components essential to the invention, and promote in turn, the formation of permanently stable crystal lattice structures with high

Anisotropy, whereby the magnetic properties of the magnetic material according to the invention are improved. Due to the particularly high availability and relatively low raw material costs, the use of the elements La and Ce is particularly advantageous.

Further advantageously, the content of transition metal is 79 to 89 atomic%, preferably 82 to 86 atomic%, and / or the content of rare earth metal 5 to 11 atomic%, preferably 7 to 9 atomic% and / or the content of titanium 5 to 11 atom %, preferably 7 to 9 atom%, in each case based on the total mass of the magnetic material. This improves the power density and the mechanical properties of the magnetic material according to the invention. In particular, the remanent magnetization and the coercive field strength of the magnetic material according to the invention are thus maximized with a reduced content of rare earth metal, and thus an optimized cost structure.

According to a further advantageous development, the structure of

Tetragonal RE (TM, Ti) _12t magnetic material according to the invention which has a positive effect on the formation of anisotropic phases of the magnetic material according to the invention due to the advantageous electron structure and electron configuration, as well as the spin and orbit moments of the atoms.

Further according to the invention, a permanent magnet is described which comprises a magnetic material as described above. The material according to the invention is preferably present in the permanent magnet according to the invention as a hard magnetic phase. The permanent magnet according to the invention, in addition to the magnetic material according to the invention further magnetic or non-magnetic phases, but can also only from the

consist of magnetic material according to the invention. For example, the permanent magnet may be sintered or plastic bonded in the conventional sense.

The advantageous effects, advantages and developments described for the magnetic material according to the invention also find application to the permanent magnet according to the invention. Also according to the invention, a process for producing a magnetic material is described, said process being characterized by the steps of mixing at least one transition metal (TM), at least one

Rare earth metal (RE) and titanium, wherein the content of transition metal is 74 to 94 atom%, the content of rare earth metal is 2 to 20 atom% and the content of titanium is 3 to 15 atom%, based on the total mass of the magnetic material, and wherein the transition metal comprises cobalt and the melting of the resulting mixture is characterized. By the

The inventive method is a simple and inexpensive way a magnetic material with high power density, excellent remanent magnetization and coercive field strength, and large

Provided energy product, which also has a very good mechanical stability.

The melting of the mixture of the elements essential to the invention can be carried out, for example, in an electric arc or in a vacuum oven. This procedure ensures that all elements are complete

be melted without causing oxidation of the material, so that a homogeneous crystal structure is formed, which not only the mechanical stability of the forming magnetic material advantageously influenced, but also significantly characterizes the desired magnetic properties.

The advantageous properties, effects and developments described for the magnetic material according to the invention are also applicable to the method according to the invention for producing such a magnetic material. It should also be noted that the above-described magnetic

Material can be produced by the method according to the invention.

According to a further advantageous embodiment, in a step subsequent to the melting, a heat treatment is carried out at a temperature between 500 ° C and 1500 ° C, preferably between 700 ° C and 1100 ° C, for a period of 10 minutes to 2 weeks and preferably for 5 to 2 days. By this heat treatment, preferably under

Protective gas atmosphere, and in particular under argon, is carried out, the full formation of the magnetic material, preferably as a hard magnetic phase, favored. According to a further advantageous embodiment of the method according to the invention, the mixture obtained is ground after melting or after heat treatment in a subsequent step and / or subjected to nitridation. Milling the resulting mixture promotes its further processability, for example, to a sintered magnetic material. By nitriding, the magnetic properties of the material, and in particular its anisotropy, can be improved. Particularly advantageously, the resulting mixture is first ground and then nitrided, since in this way a uniform nitridation can be achieved even in the finest grain, whereby the magnetic

Properties of the resulting material are particularly improved.

The present invention also relates to a plastic-bonded magnet containing a magnetic material as described above or a magnetic material produced by the above-described method. The magnetic material can also be produced by means of rapid solidification (melt spinning).

Further according to the invention, the use of a as above

designed magnetic material, preferably in wind turbines, cars, commercial vehicles, starters, electric motors, speakers and microelectromechanical systems described. Due to the outstanding magnetic

Characteristics of the magnetic material according to the invention, as well as its excellent stability, and thus also its advantageous usability in space-reduced applications and applications under high

Temperatures, the use in the devices mentioned is of particular advantage.

In accordance with the invention, an electric machine is described, in particular a generator, motor vehicle, starter, electric motor, loudspeaker or microelectromechanical system which comprises the magnetic material according to the invention or at least one permanent magnet or a magnetic material according to the invention

has been prepared according to the invention contains. The electric machine has very good magnetic properties and high thermal stability with a moderate cost structure. The magnetic material according to the invention, as well as the

Advantages described according to the invention, advantageous effects and preferred developments are also applied to the

plastic-bonded magnet and the inventive electrical

Machine.

Short description of the drawing (s)

Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings. In the drawing is:

Figure 1 is a light micrograph of a section of the

magnetic material according to an advantageous

Training in polarized light,

FIG. 2 shows a light-microscopic photograph of a section of a cerium,

Iron- and titanium-containing magnetic material in the

polarized light, Figure 3 is a diagram in which the saturation polarization J _s of

magnetic materials of Figures 1 and 2 are applied at different temperatures,

Figure 4 is a diagram showing a first example of a

Heat treatment according to an advantageous embodiment of

Invention represents

5 shows a diagram in which the saturation polarization Js of a

magnetic material is applied according to a first advantageous embodiment of the invention against the cobalt content and

FIG. 6 shows a diagram in which the Curie temperature Tc of a

magnetic material is applied according to a first advantageous embodiment of the invention against the cobalt content. Embodiments of the invention

FIG. 1 shows a photomicrograph of a section of the

Inventive magnetic material 10 according to an advantageous development in polarized light. The material 10 according to the invention has the following composition: Fe ₆ Co 2 .6 Ce ₈ , o Ti ₈ .o and is preferably present with a predominantly tetragonal Ce (Fe / Co, Ti) ₁₂ (ThMn ₁₂ ) structure. The

Composition was determined by EDX (energy dispersive

X-ray spectroscopy) and the crystal structure determined by X-ray spectroscopy.

The magnetic material 10 according to the invention was obtained by mixing and melting the individual elements in the electric arc furnace. By

Temperature treatment at 1050 ° C for 230 hours under argon, formed a hard magnetic phase.

The magnetic material 10 according to the invention from FIG. 1 is therefore in the form of a hard magnetic phase, which can be recognized by the so-called Kerr pattern, ie a rosette-like or striated pattern depending on the viewing angle, which indicates the presence of a strong hard magnetic phase

Ce (Fe / Co, Ti) ₂ displays. The terminal domains are relatively broad, which is reflected in a high anisotropy constant K1 of about 3.0 MJ / m ³ . The

Anisotropy constant K1 can be determined as described in the following literature: R. Bodenberger, A. Hubert, Phys. Stat. Sol. (a) 44, K7-K11 (1977). The magnetic material 10 according to the invention is thus characterized by a large energy product, a high Curie temperature, a high coercitive field strength, high remanent magnetization, and good, due to the homogeneous crystal structure, mechanical properties.

FIG. 2 shows a photomicrograph of a section of a cerium, iron and titanium-containing magnetic material 20. The magnetic material 20 has the following composition: Fe ₈ 4 _{, 2} Ce _8,7 Ti _7,1 and preferably lies with a predominantly tetragonal Ce (Fe , Ti) ₁₂ structure. The composition was determined by EDX (energy dispersive X-ray spectroscopy) and the crystal structure by X-ray spectroscopy. The magnetic material 20 was also obtained by mixing and melting the individual elements in the arc furnace. By thermal treatment at 1050 ° C for 230 hours under argon, a hard magnetic phase formed.

Magnetic material 20 also exhibits a Kerr pattern, but the termination domains are significantly narrower compared to the magnetic material of the present invention. This manifests itself in a lower

Anisotropiekonstante of about 2.5 MJ / m ³ and thus poorer magnetic characteristics. In addition, due to the absence of cobalt, the thermal stability of the magnetic material 20 is low.

Figure 3 is a graph plotting the saturation polarization J _{s of} the magnetic materials of Figures 1 and 2 at different temperatures. It can clearly be seen that the saturation polarization of the magnetic material 10 according to the invention increases compared with the non-inventive material 20 by the addition of cobalt, whereby the temperature stability is improved. Accordingly, the Curie temperature also increases with the addition of cobalt, which is especially important for applications where high temperatures prevail, such as in an electric motor.

FIG. 4 is a diagram illustrating a first example of a heat treatment according to an advantageous embodiment of the invention. As already stated, by a, for example, the melting of the elements essential to the invention to a magnetic material

subsequent heat treatment, advantageously under inert gas, the complete expression of a hard magnetic phase ensured. In a first step, the molten material after cooling within about 5 hours in a vacuum oven heated to 1050 ° C, held for about 235 hours at about 1050 ° C, then cooled to room temperature (about 20 ° C) within about 5 hours , As a result, a magnetic material having excellent magnetic properties, that is, a magnetic material having a fully-developed hard magnetic phase composed particularly of hard magnetic grains, is further formed, which is further excellent in mechanical and thermal stability. FIGS. 5 and 6 show diagrams in which, on the one hand, the

Saturation polarization Js in Tesla of the magnetic material according to the invention is plotted against the cobalt content in atomic percent (At.%) And the Curie temperature Tc in ° C against the cobalt content in atomic percent. The magnetic material had the following composition: 8 at.% Ti, 8 at.% Ce, Fe and Co, with Fe serving as a balance and varying the amount of Co. The magnetic material was produced by mixing the respective elements and melting them in the arc.

In detail, Figure 5 can be seen two curves that were recorded at different temperatures (300 K and 400 K). Both curves show that the saturation polarization Js increases with increasing cobalt content. It can also be seen that the saturation polarization no longer decreases so much at the higher temperature (400 K).

The curve in FIG. 6 shows that the Curie temperature Tc increases with increasing cobalt content. This allows the magnetic material to be used particularly well in high temperature applications.

Claims

claims

1. A magnetic material containing at least one transition metal (TM), at least one rare earth element (RE) and titanium, wherein the content of transition metal 74 to 94 atom%, the content of rare earth metal 2 to 20 atom% and the content of titanium 7 to 9 atom %, in each case based on the total mass of the magnetic material, and wherein the transition metal comprises cobalt.

2. Magnetic material according to claim 1, wherein the transition metal cobalt containing from 1 atom% to less than 50 atom%, preferably 3 to 30 atom%, in particular 8 to 20 atom%, based on the total content in atomic% of transition metal, includes.

3. Magnetic material according to claim 1 or 2, characterized in that the transition metal contains at least one of: Fe, Ni and Mn or mixtures thereof, preferably Fe.

4. Magnetic material according to one of the preceding claims,

characterized in that the rare earth metal is selected from the group consisting of: Nd, La, Ce, Dy, Pr, Sm, Pm, Y, Sc, Gd, Ho, Er and mixtures thereof, and preferably Ce and / or La.

5. Magnetic material according to one of the preceding claims,

characterized in that the content of transition metal 79 to 89 atom%, preferably 82 to 86 atom%, and / or the content of

Rare earth metal 5 to 11 atom%, preferably 7 to 9 atom%, in each case based on the total mass of the magnetic material.

6. Magnetic material according to one of the preceding claims,

characterized in that the structure of the magnetic material is tetragonal RE (TM, Ti) i ₂ having a ThMn ₁₂ structure. Permanent magnet comprising at least one magnetic material according to one of claims 1 to 6.

A method of producing a magnetic material

Mixing at least one transition metal (TM), at least one rare earth element (RE) and titanium, wherein the content of transition metal is 74 to 94 atom%, the content of rare earth metal is 2 to 20 atom% and the content of titanium is 7 to 9 atom%, respectively based on the

Total mass of the magnetic material, and wherein the transition metal comprises cobalt and

- Melting of the resulting mixture until a homogeneous mixture is formed.

A method according to claim 8, characterized in that in a step subsequent to the melting, a heat treatment at a temperature between 500 ° C and 1500 ° C, preferably between 700 ° C and 1 00 ° C for a period of 10 min up to 2 Weeks and preferably for 5 to 12 days.

Method according to one of claims 8 or 9, characterized in that the obtained mixture is ground in a further step and / or subjected to a nitridation.

Plastic-bonded magnet, containing

- A magnetic material according to any one of claims 1 to 6 or

- A produced according to one of claims 8 to 10 magnetic material or

- A magnetic material according to any one of claims 1 to 6, which has been prepared via rapid solidification.

Use of a magnetic material according to any one of claims 1 to 6 or at least one permanent magnet according to claim 7, in

Wind turbines, cars, commercial vehicles, starters, electric motors, loudspeakers and microelectromechanical systems. 13. Electrical machine, in particular generator, motor vehicle, starter, electric motor, loudspeaker or microelectromechanical system, comprising a magnetic material according to one of claims 1 to 6 or containing at least one permanent magnet according to claim 7.