Method and plant for the production of a starting material for the production of rare earth magnets

Abstract

A method and a plant for the production of a powdery starting material, which is provided for the manufacture of rare earth magnets, are disclosed. First of all, at least one magnetic material, which is comminuted into a powdery intermediate product with a possibly increased concentration of impurities, and/or at least one alloy including rare earth metal are provided, which includes a low concentration of impurities. A classification of the powdery intermediate product to at least one criterion takes place subsequently, wherein, for the classification of the powdery intermediate product with the increased concentration of impurities, at least one dynamic classifier is provided, which divides the powdery intermediate product with impurities into at least two fractions based on the at least one criterion, wherein at least a high concentration of impurities accumulates in a first fraction and no impurities or at least a lower concentration of impurities than in the case of the first fraction accumulate in a second fraction, and wherein the fraction without impurities or with a low concentration of impurities forms the starting material for the manufacture of rare earth magnets.

Claims

1. A method for the production of a powdery starting material, which is provided for the manufacture of rare earth magnets, comprising the following steps: providing at least one magnetic material and/or at least one alloy comprising rare earth metal, which includes a low concentration of impurities, comminuting the provided at least one magnetic material and/or the provided at least one alloy including rare earth metal, wherein a powdery intermediate product is created from the at least one magnetic material and/or from the at least one alloy including rare earth metal, the intermediate product can contain an increased concentration of impurities than the provided at least one magnetic material and/or than the provided at least one alloy including rare earth metal, classifying the powdery intermediate product according to at least one criterion, wherein, for the classification of the powdery intermediate product, at least one dynamic classifier divides the powdery intermediate product into at least two fractions so that impurities are sorted out into a first fraction having at least a first concentration of impurities accumulated therein and a second fraction having no impurities or at least a second concentration of impurities accumulated therein, the second concentration being lower than the first concentration, and the first fraction with the first concentration of impurities is formed by a first particle size, and the second fraction with no impurities or with the second concentration of impurities is formed by a second particle size that is larger than the first particle size of the first fraction, wherein the classifying step is performed such that the first concentration of impurities is provided between 0.02 and 10.0 percent by weight and the second concentration of impurities is provided less than 1.0 percent by weight; wherein the step of classifying is performed without comminuting the second fraction, wherein the second fraction forms the starting material for the manufacture of rare earth magnets.

2. The method according to claim 1, in which the at least one criterion is defined by the particle size, particle density or the like.

3. The method according to claim 1, in which the second concentration of impurities of the second fraction is decreased by at least one-fourth relative to the first fraction by classifying the powdery intermediate product into the at least two fractions.

4. The method according to claim 1, in which the at least one magnetic material and/or the at least one alloy comprising rare earth metal is comminuted in such a way that the produced powdery intermediate product is a coarse powder or a fine powder.

5. The method according to claim 1, in which the at least one dynamic classifier process takes place by means of the dynamic classifier on the coarse powder or on the fine powder.

6. The method according to claim 3, in which the at least one magnetic material and/or the at least one alloy comprising rare earth metal is comminuted in such a way that the produced powdery intermediate product is a coarse powder or a fine powder.

7. The method according to claim 4, in which the at least one dynamic classifier process takes place by means of the dynamic classifier on the coarse powder or on the fine powder.

8. The method according to claim 1, in which at least a protective gas is supplied to the at least one dynamic classifier, so that the powdery intermediate product is divided into the at least two fractions under protective gas atmosphere.

9. The method according to claim 1, in which, temporally before or during the comminution, at least one excipient in solid, liquid or gaseous state is supplied to the provided at least one magnetic material and/or to the provided at least one alloy comprising rare earth metal.

10. The method according to claim 3, in which the second concentration of impurities of the second fraction is decreased by at least three-fourths relative to the first fraction by classifying the powdery intermediate product into the at least two fractions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention and the advantages thereof will be described in more detail below on the basis of the enclosed Figures. The size ratios of the individual elements to one another in the Figures do not always correspond to the actual size ratios, because some shapes are illustrated in a simplified manner and other shapes are illustrated in an enlarged manner in comparison with other elements for better visualization.

(2) FIG. 1 clarifies individual steps for the implementation of an embodiment of a method according to the invention.

(3) FIG. 2 shows the concentration of impurities of the powdery intermediate product after a coarse grinding and in each case after two classifier processes in a tabular comparison.

DETAILED DESCRIPTION

(4) Identical reference numerals are used for elements of the invention, which are identical or which have identical effects. For better visualization, only reference numerals, which are required for the description of the respective Figure, are furthermore illustrated in the individual Figures. The illustrated embodiments only represent examples for how the method according to the invention and the plant according to the invention can be embodied and do not represent a conclusive limitation.

(5) FIG. 1 shows individual method steps for the production of a starting material AM for the manufacture of rare earth magnets, based on at least one magnetic material M.

(6) In a first step, at least one magnetic material M is provided. The at least one magnetic material M is preferably old magnets, in particular Nd—Fe—B old magnets, which were used in motors or in old electrical appliances or the like. Such old magnets generally comprise low, in particular an unwanted, but unavoidable and non-negligible concentration of impurities, which are contained in the respective magnetic material M and/or are enclosed in the respective material. These impurities are preferably oxygen, carbon, nitrogen, and/or the compounds thereof. The low concentration of impurities in the provided at least one magnetic material and/or in the provided at least one alloy comprising rare earth metal preferably lies between at least 0.01 percent by weight and maximally 1.5 percent by weight. For example, the concentration of impurities of oxygen can in particular be between 0.1 percent by weight and 1.0 percent by weight, of nitrogen between 0.01 percent by weight and 0.1 percent by weight, and of carbon between 0.01 percent by weight and 0.15 percent by weight.

(7) In a next step, the provided at least one magnetic material M is comminuted, wherein a powdery intermediate product ZP, which may also contain an increased concentration of impurities than the provided at least one magnetic material M, is created from the at least one magnetic material M. The increased concentration of impurities in the powdery intermediate product preferably lies between at least 0.01 percent by weight and maximally 2.0 percent by weight. For example, the concentration of impurities of oxygen can in particular be between 0.1 percent by weight and 1.2 percent by weight, of nitrogen between 0.01 percent by weight and 0.15 percent by weight, and of carbon between 0.01 percent by weight and 0.20 percent by weight.

(8) By means of the comminution of the at least one magnetic material M, the latter generally absorbs additional impurities, such as oxygen, carbon, nitrogen, and/or the compounds thereof from the environment, which causes an increase of the concentration of impurities in the powdery intermediate product ZP as compared to the provided at least one magnetic material M. Oxygen is in particular increasingly absorbed, because the at least one magnetic material is stirred up by means of the comminution and is thrown around inside the comminution apparatus.

(9) The comminution of the at least one magnetic material M thereby takes place in such a way that a coarse powder or fine powder is produced, which forms the powdery intermediate product ZP.

(10) A comminution process by means of a mechanical comminution plant or the use of hydrogen, which causes an embrittlement of the at least one magnetic material M and thus a break-up of the at least one magnetic material M into coarse-grained powdery intermediate product, is optionally suitable for the production of a coarse powder. With the use of hydrogen, the powdery intermediate product ZP also has, in addition to impurities, such as oxygen, carbon, nitrogen, and/or the compounds thereof, an increased concentration of impurities of hydrogen and/or hydrogen-containing compounds.

(11) A plurality of comminution processes, in particular a plurality of grinding processes and/or a fine grinding of the at least one magnetic material M can be carried out for the production of fine-grained powdery intermediate product ZP, wherein an increased concentration of unwanted impurities, such as oxygen, carbon, nitrogen, and/or the compounds thereof, is then usually present in the powdery intermediate product ZP.

(12) Due to the fact that, if possible, no or a low concentration of impurities should be present in the respective starting material AM for the provision of a starting material AM for the manufacture of a rare earth magnet, these impurities have to be separated from the powdery intermediate product ZP. For this purpose, a classification of the powdery intermediate product ZP to at least one criterion takes place in a next step, wherein the concentration of impurities can possibly increase further due to the classification. A high increase of oxygen preferably takes place, because the powdery intermediate product ZP is stirred up as part of the classification. The at least one criterion can comprise the particle size, the particle density or the like, wherein in the case of the method according to the invention, a classification of the powdery intermediate product ZP preferably takes place according to the particle size.

(13) The classification of the powdery intermediate product ZP takes place by means of at least one dynamic classifier, which divides the produced powdery intermediate product into at least two fractions F.sub.1, F.sub.2 based on the at least one criterion, in particular based on the particle size, wherein at least a high concentration of impurities accumulates in a first fraction F.sub.1 and no impurities or at least a lower concentration of impurities than in the first fraction F.sub.1 accumulates in a second fraction F.sub.2. The first fraction F.sub.1 with a high concentration of impurities is preferably formed by a small particle size and the second fraction F.sub.2 without impurities or with a lower concentration than in the case of the first fraction F.sub.1 is formed by a larger particle size of the classified powdery intermediate product ZP. The concentration of impurities in the first fraction preferably lies between at least 0.02 percent by weight and maximally 10.0 percent by weight. The concentration of impurities of oxygen, for example, can in particular be between 0.5 percent by weight and 8.0 percent by weight, of nitrogen between 0.05 percent by weight and 0.35 percent by weight, and of carbon between 0.05 percent by weight and 0.35 percent by weight.

(14) The concentration of impurities in the second fraction is preferably 0.00 percent by weight, maximally 1.0 percent by weight. The concentration of impurities in the second fraction of oxygen can in particular be 0.01 percent by weight or less than maximally 0.2 percent by weight, of nitrogen 0.01 percent by weight or less than maximally 0.05 percent by weight, and of carbon 0.01 percent by weight or less than maximally 0.05 percent by weight.

(15) Due to the fact that no impurities or only a lower concentration of impurities than in the case of the first fraction F.sub.1 with the smaller particle size accumulates in the second fraction F.sub.2 with the larger particle size, the material separated in the second fraction F.sub.2 forms the starting material AM for the manufacture of rare earth magnets. In contrast, the first fraction F.sub.1 with the smaller particle size and the higher concentration of impurities is not of interest for the manufacture of a rare earth magnet and is not used further or is sorted out, respectively.

(16) Even though further impurities, such as oxygen, nitrogen, carbon, and/or the compounds thereof, are absorbed by means of the classification of the powdery intermediate product ZP, these additionally absorbed impurities and the impurities, which are already present, are separated out and sorted out via the classification into the at least two fractions F.sub.1, F.sub.2, so that a second fraction F.sub.2 without impurities or with a low concentration of impurities is created.

(17) If the second fraction F.sub.2 comprises a concentration of impurities, which is still too high, after the first classification by means of the dynamic classifier, further dynamic classifier processes can be carried out by means of the dynamic classifier any number of times and/or repeatedly, so that a starting material AM can be produced and provided for the manufacture of rare earth magnets without or with a concentration of impurities, which is as low as possible. The first fraction F.sub.1 with the high concentration of impurities as compared to the second fraction F.sub.2 is in each case sorted out for the further classifier processes, while the second fraction F.sub.2 in each case serves for the further classification into at least two further fractions.

(18) To avoid unwanted reactions of the powdery intermediate product ZP with the environment and/or the like, at least one protective gas can be supplied to the dynamic classifier, so that the powdery intermediate product ZP is divided into at least two fractions F.sub.1, F.sub.2 under protective gas atmosphere.

(19) At least one excipient in solid, liquid or gaseous state can optionally be supplied to the at least one magnetic material M. The at least one excipient can be, for example, zinc stearate, isopropanol or the like, which places itself around the individual particles of the respective material like a coating and thus decreases the absorption of impurities during the comminution of the at least one magnetic material M into a powdery intermediate product ZP.

(20) FIG. 2 shows the concentration after a coarse grinding of a magnetic material as well as after two classifier processes of an exemplary embodiment of the invention in a schematic manner and in a tabular overview.

(21) In the case of the exemplary embodiment at hand, a coarse powder was created from a magnetic material M, in particular from an Nd—Fe—B old magnet, with the help of the hydrogen technology, wherein the supplied hydrogen penetrates into the provided Nd—Fe—B old magnet, so that the latter breaks up into a coarse powder with a fineness of zero to approximately 300-3000 μm. The produced coarse powder is thus the powdery intermediate product ZP.

(22) The produced coarse-grained powdery intermediate product ZP comprises impurities, such as oxygen and/or oxygen-containing compounds with, for example, 0.8 percent by weight of oxygen, carbon and/or carbon-containing compounds with, for example, 0.07 percent by weight of carbon as well as nitrogen and/or nitrogen-containing compounds with, for example, 0.06 percent by weight of nitrogen.

(23) To decrease the concentration of impurities in the powdery intermediate product ZP of the comminuted Nd—Fe—B old magnet, the powdery intermediate product ZP is classified to at least one criterion, in particular to its particle size. At least one dynamic classifier, which divides the powdery intermediate product ZP comprising the oxygen-, carbon-, and nitrogen-containing impurities into at least two fractions F.sub.1-1 (not illustrated), F.sub.2-1, based on the particle size, is provided for the classification.

(24) The at least two fractions F.sub.1-1, F.sub.2-1 differ in that at least a high concentration of impurities accumulates in a first fraction F.sub.1-1 with a small particle size, and at least a lower concentration of impurities than in the case of the first fraction F.sub.1-1 accumulates in a second fraction F.sub.2-1 with a larger particle size.

(25) After a first classifier process, the percentage of oxygen has thus decreased to 0.4 percent by weight, of carbon to 0.05 percent by weight, and of nitrogen to 0.04 percent by weight, wherein this information is the concentration of impurities in the second fraction F.sub.2-1 with the larger particle size. The concentration of impurities could thus be decreased by at least one-fourth and by half by means of the first classifier process in the second fraction F.sub.2-1.

(26) Due to the fact that the first fraction F.sub.1-1 with the smaller particle size is characterized by a concentration of impurities, which is significantly higher as compared to the second fraction F.sub.2-1, and is thus not relevant for the manufacture of rare earth magnets, said first fraction F.sub.1-1 will not be discussed in more detail. It is also important to mention at this point that hydrogen impurities, which result from the coarse grinding, will not be discussed in more detail.

(27) Due to the fact that a starting material AM with or without a lower concentration of impurities is desirable, if possible, a second classifier process of the previously separated second fraction F.sub.2-1 takes place so as to thus further decrease the concentration of impurities.

(28) The material of the preciously separated second fraction F.sub.2-1 is divided into at least two fractions F.sub.1-2 (not illustrated), F.sub.2-2 based on the particle size by means of another classification by means of at least one dynamic classifier, wherein at least a high concentration of impurities accumulates in a first fraction F.sub.1-2 with a small particle size, and no impurities or at least a lower concentration of impurities than in the case of the first fraction F.sub.1-2 accumulate in a second fraction F.sub.2-2 with a large particle size. The second classifier process thus contributes to the fact that the percentage of oxygen is decreased to 0.2 percent by weight, of carbon to 0.02 percent by weight, and of nitrogen to 0.02 percent by weight in the second fraction F.sub.2-2 in each case. The concentration of impurities could thus be decreased by at least one-fourth and by half by means of the second classifier process.

(29) To further decrease the concentration of impurities, classifier processes can be performed any number of times, so as to subsequently embody a fraction without impurities or with a lower concentration of impurities, which represents the starting material AM for the manufacture of rare earth magnets.

(30) The invention has been described with reference to a preferred embodiment. It is conceivable for a person of skill in the art, however, that modifications or changes can be made to the invention, without thereby leaving the scope of protection of the following claims.