METHOD FOR PRODUCING A STARTING MATERIAL FOR THE PRODUCTION OF RARE EARTH MAGNETS

Description

[0001] The present invention relates to a method for producing a starting material for the production of a rare-earth magnet according to the features of claim 1. State of the art

[0002] A permanent magnet is a piece of a magnetizable material, such as iron, cobalt, or nickel, that retains a static magnetic field without requiring an electric current, unlike electromagnets. A permanent magnet can be created by applying a magnetic field to a ferromagnetic material.

[0003] The term "rare-earth magnet" refers to a group of permanent magnets consisting primarily of ferrous metals (iron, cobalt, less commonly nickel) and rare-earth metals (especially neodymium, samarium, praseodymium, dysprosium, terbium, and gadolinium). Rare-earth magnets are characterized by their high magnetic remanence density and, consequently, their high magnetic energy density.

[0004] To produce a starting material required for the manufacture of permanent magnets, in particular Nd-Fe-B (neodymium-iron-Bohr) magnets, it is known in the art to produce rare-earth metal alloys into a powdered intermediate product, for example in the form of coarse or fine powder. Conventional comminution techniques are generally suitable for the production of powdered intermediate products.

[0005] For coarse comminution or for the production of coarse powder with a particle size of approximately 100 µm to 300 µm, mechanical comminution plants and / or hydrogen technology are used, for example.

[0006] For fine grinding or the production of fine powders with a particle size of approximately 0.1 µm to 20 µm, grinding systems for fine grinding, such as fluidized bed jet mills or similar grinding systems, are used, which are operated under a protective gas atmosphere. The protective gas used is usually nitrogen or argon.

[0007] Since rare earth metals are a limited resource, in addition to rare earth metal alloys used to produce raw materials for rare earth magnets, scrap magnets are also becoming increasingly important for this purpose. These scrap magnets are used, for example, in motors, electronic waste, or similar products and are no longer needed, or no longer fully meet their required properties and / or performance standards. Therefore, the use of scrap magnets is also referred to as a recycled material.

[0008] Unlike rare earth metal alloys, a used magnet or such recycled material has a higher concentration of unwanted impurities. These impurities are mostly non-metallic, such as oxygen, nitrogen, and carbon, which are trapped within the material and / or absorbed due to reactions with the environment, previous manufacturing processes, or similar factors.

[0009] This means that the raw materials for the production of rare-earth magnets, obtained through the comminution process from old magnets or recycled material, also contain undesirable impurities such as oxygen, nitrogen, carbon, and their compounds. These impurities significantly impair the properties of the rare-earth magnets produced from the raw material, for example, with regard to the achievable magnetic strength (remanence) and opposing field stability. The impurities also contribute to significantly poor corrosion resistance, for example, in wet and humid conditions.

[0010] In order to reduce unwanted impurities and to produce a rare earth magnet with desired properties, it is therefore known in the prior art to combine powders made from scrap magnets with alloys comprising powders made from rare earth metals.

[0011] WO 2014 / 205002 A2 discloses a process for recycling scrap magnets to produce rare-earth magnets, in particular Nd-Fe-B magnets. This process involves numerous steps, beginning with pretreatment of the scrap magnet to be recycled, such as demagnetization and temperature treatment (heating and cooling). Following this preparation, the pretreated scrap magnet is ground into a powder and then mixed with a rare-earth metal powder to form a homogeneous mixture, which constitutes the starting material for the production of rare-earth magnets.

[0012] Since the production of a starting material for manufacturing rare-earth magnets with the desired properties requires not only scrap magnets but also an alloy containing rare-earth metals, the process described in the WO publication for producing starting materials for rare-earth magnets is costly. Furthermore, this process again relies on rare-earth metal alloys, which are generally scarce and expensive.

[0013] EP 2 273 513 A1 discloses a process for manufacturing an RTB sintered magnet. The EP provides a metal alloy as a starting material, which can then be coarsely pulverized by adding hydrogen. The pulverized material is fed to a classifier, which separates a coarse fraction from a fine fraction and then repeatedly grinds the coarse fraction until a desired particle size is achieved.

[0014] WO 2014 / 154517 A1 discloses a process for separating rare earth metal particles from a mixture containing rare earth metals. To form a particle mixture containing rare earth metal particles, the mixture containing rare earth metals is first comminuted. Subsequently, at least one step is taken to demagnetize the rare earth metal particles in the particle mixture, followed by the separation of the demagnetized rare earth metal particles from the particle mixture. The demagnetization and subsequent magnetization of the rare earth metal particles, as well as the separation of the demagnetized rare earth metal particles, require numerous complex process steps, which have proven to be disadvantageous and costly in the prior art and in practice.

[0015] WO 2014 / 033004 A1 discloses a process for recovering neodymium oxide from a feedstock mixture, in particular scrap metal. After pre-crushing the feedstock mixture to be recycled, a hydrometallurgical digestion is carried out with the addition of acid, while the volumetric flow rate of hydrogen released is simultaneously determined. To increase the neodymium concentration of a neodymium-containing fraction, a classification of parts of the feedstock mixture can be carried out before the hydrometallurgical digestion, thereby separating smaller, relatively isotropic Nd-Fe-B fragments from larger particles present in the feedstock mixture. Optionally, at least one magnetic separation can also be carried out to separate all ferromagnetic and ferrimagnetic materials.

[0016] However, the solution disclosed in the WO application has proven to be disadvantageous in that it requires the addition of acid and / or other liquids / chemicals and / or salts or the like, as well as the application of heat, which has made the process laborious, complicated and costly. Description

[0017] The invention is based on the objective of providing a method for producing a starting material for the manufacture of rare-earth magnets, by which the impurities present in the powdered intermediate product are at least largely reduced and / or eliminated in a simple manner, and by which an optimized starting material for the production of improved rare-earth magnets is provided. Simultaneously, the method for producing a powdered starting material for the manufacture of rare-earth magnets is to be optimized. Furthermore, a system for producing a starting material for the manufacture of rare-earth magnets is provided, by means of which the method for producing a starting material for the manufacture of a rare-earth magnet can be carried out in a simple manner.

[0018] The problem is solved by a method with the features in claim 1. Further advantageous embodiments and developments of the invention are specified in the respective dependent claims.

[0019] To solve the aforementioned problems, the invention proposes a method for producing a powdered starting material intended for the manufacture of rare-earth magnets.

[0020] In a first step, at least one magnetic material and / or at least one rare-earth metal alloy is provided, each containing a small, particularly undesirable, but unavoidable and not negligible, concentration of impurities. The at least one magnetic material is preferably a scrap magnet(s) that was / were used, for example, in motors and / or waste electrical and electronic equipment (WEEE) and is no longer usable for further use. Preferably, the at least one magnetic material or scrap magnet is an Nd-Fe-B (neodymium-iron-Bohr) magnet.The impurities can include, for example, oxygen, carbon, and / or nitrogen, compounds containing oxygen, carbon, and / or nitrogen, or similar impurities present in the materials provided. Common impurities are formed by compounds of oxygen, carbon, and / or nitrogen with neodymium. For example, in sintered magnets, oxygen is usually bound in the form of neodymium oxide (Nd₂O₃), nitrogen in the form of neodymium nitride (NNd), and carbon in the form of neodymium carbide (NdₓCy). Furthermore, oxygen-nitrogen-containing impurities can be present, for example, in the form of neodymium(III) nitrate (Nd(NO₃)₃). Impurities from hydrogen, hydrogen-containing compounds, or similar substances are also conceivable.The low concentration of impurities in the provided magnetic material and / or in the provided alloy comprising at least one rare earth metal can be between at least 0.01 percent by weight and at most 1.5 percent by weight.

[0021] The concentration of impurities of oxygen in the powdered intermediate product is in particular between 0.1 wt% and 1.2 wt%, the impurity of nitrogen is in particular between 0.01 wt% and 0.15 wt% and that of carbon is in particular between 0.01 wt% and 0.20 wt%.

[0022] In a next step, the provided at least one magnetic material and / or the provided alloy comprising at least one rare earth metal is ground into a powder, resulting in a powdered intermediate product which may contain a higher concentration of impurities than the provided at least one magnetic material and / or the provided alloy comprising at least one rare earth metal. The increased concentration of impurities in the powdered intermediate product is preferably between at least 0.01% and at most 2.0% by weight.

[0023] By grinding the at least one magnetic material and / or the alloy comprising at least one rare earth metal, impurities such as oxygen, carbon, nitrogen and / or hydrogen or corresponding oxygen-, carbon-, nitrogen- and / or hydrogen-containing compounds etc. can be additionally absorbed by the material to be ground from the environment, which causes an increase in the concentration of impurities in the powdered intermediate product compared to the provided at least one magnetic material and / or the alloy comprising at least one rare earth metal.

[0024] In a further step, the powdered intermediate product is classified according to at least one criterion, wherein at least one dynamic classifier is provided for the classification of the powdered intermediate product with impurities, which divides the powdered 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 first fraction accumulates in a second fraction.Although classifying the powdered intermediate may lead to an overall increase in the concentration of impurities, classifying it into at least two fractions allows the proportion of impurities to be separated in such a way that the proportion of absorbed impurities and the other impurities absorbed in the respective powdered intermediate can be sorted out via the at least two fractions.

[0025] The concentration of impurities in the first fraction is between at least 0.02% by weight and at most 10.0% by weight. According to one embodiment, for example, the concentration of impurities can be, in particular, between 0.5% and 8.0% by weight of oxygen, in particular between 0.05% and 0.35% by weight of nitrogen, and in particular between 0.05% and 0.35% by weight of carbon.

[0026] The concentration of impurities in the second fraction is a maximum of 1.0 wt%. According to one embodiment, for example, the proportion of impurities in the second fraction can be greater than 0.01 wt% or less than a maximum of 0.2 wt% for oxygen, greater than 0.01 wt% or less than a maximum of 0.05 wt% for nitrogen, and greater than 0.01 wt% or less than a maximum of 0.05 wt% for carbon.

[0027] The fraction, especially the second fraction, without impurities or with a low concentration of impurities forms the starting material for the manufacture and / or production of rare earth magnets.

[0028] The classification of the powdered intermediate product into at least two fractions by the dynamic classifier can also be referred to as a dynamic classifier process.

[0029] It may be stipulated that at least one criterion is defined by the physical property of particle size or the like. Alternatively, any further criteria, such as particle density, may be suitable for classifying the powdered intermediate product into at least two fractions.

[0030] According to preferred embodiments of the invention, the first fraction with a high concentration of impurities is formed by a small particle size and the second fraction without impurities or with a low concentration of impurities is formed by a larger particle size than in the first fraction.

[0031] Furthermore, the powdered intermediate product, in particular the second fraction free of impurities or with a low concentration of impurities, can be classified multiple times by the dynamic classifier and separated into at least two fractions. In this way, the impurities present in the powdered intermediate product can be successively sorted out and thus reduced via the at least two fractions, in order to provide a starting material for the production of rare-earth magnets that is free of impurities or has the lowest possible concentration of impurities. The repeated classifying processes also result in a homogeneous material, for example, with regard to particle size. Classification by the dynamic classifier can be repeated as often as desired, thereby producing a starting material for the production of rare-earth magnets that is at least largely homogeneous.

[0032] It may be possible to reduce the concentration of impurities in the second fraction compared to the first fraction by at least one quarter to at least three-quarters or more by classifying the powdered intermediate into at least two fractions. Alternatively, the impurities may be completely separated from the second fraction.

[0033] Depending on the embodiment of the invention, the at least one magnetic material and / or the alloy comprising at least one rare-earth metal may be comminuted in such a way that the resulting powdered intermediate product is either a coarse powder or a fine powder. In this respect, a distinction can be made between coarse grinding and fine grinding.

[0034] The comminution of the at least one magnetic material and / or the alloy comprising at least one rare earth metal, in particular into a coarse powder, can be carried out by one or more grinding processes of a mechanical grinding plant or with the aid of hydrogen technology, whereby the addition of hydrogen can cause embrittlement of the at least one magnetic material and / or the alloy comprising at least one rare earth metal.

[0035] If coarse grinding is carried out and the resulting powdered intermediate is therefore a coarse powder, classification by the dynamic classifier can be performed on this coarse-grained, powdered intermediate, which can then be divided into at least two fractions according to at least one criterion. It may be possible to subject the fraction free of impurities or with a low concentration of impurities to further comminution after classification, so that a fine powder is produced and made available as the starting material for the manufacture of the rare-earth magnet.Alternatively, the coarse powder can be used as starting material for the production of the rare earth magnet immediately after classification by the dynamic classifier into at least two fractions, with the fraction without impurities or with the lower concentration of impurities being used as starting material for the production of the rare earth magnet.

[0036] Optionally, fine grinding can be carried out after coarse grinding by one or more grinding processes of a mechanical grinding plant, so that a fine-grained powdered intermediate product is produced from the previously provided alloy comprising at least one magnetic material and / or at least one rare earth metal, which is then classified by the dynamic classifier into at least two fractions according to at least one criterion.

[0037] It may be provided that at least one dynamic classifier is supplied with protective gas, so that the powdered intermediate product is separated into at least two fractions under a protective gas atmosphere. The protective gas used can be, for example, helium, argon, nitrogen, or similar protective gases.

[0038] In addition, at least one auxiliary material in solid, liquid, or gaseous state can be added to the at least one provided magnetic material and / or the alloy comprising at least one rare-earth metal before or during comminution. The at least one auxiliary material can, for example, comprise zinc stearate, isopropanol, or the like.

[0039] The at least one auxiliary substance can contribute to ensuring that, during the comminution of the provided at least one magnetic material and / or the provided alloy comprising at least one rare earth metal, no or fewer impurities are absorbed by the at least one magnetic material and / or the provided alloy comprising at least one rare earth metal, so that the concentration of impurities does not increase or only increases significantly compared to the provided at least one magnetic material and / or the provided alloy comprising at least one rare earth metal. The at least one auxiliary substance can coat the individual particles of the respective material, so that the concentration of impurities in the powdered intermediate product does not increase or only increases slightly.

[0040] Furthermore, a plant for producing a powdered starting material intended for the manufacture of rare-earth magnets is described, which plant is specifically designed to carry out a process according to claim 1. The plant comprises at least one comminution device, which produces a powdered intermediate product by comminution of at least one magnetic material and / or at least one rare-earth metal alloy. The at least one comminution device may be a mechanical comminution machine, each of which can produce a powdered intermediate product with an increased concentration of impurities.Alternatively, the comminution device can be a device which, with the aid of hydrogen technology, can produce the provided alloy comprising at least one magnetic material and / or at least one rare earth metal into a powdered intermediate product.

[0041] The plant further comprises at least one separation device designed to classify the powdered intermediate product according to at least one criterion. This separation device may be a dynamic classifier capable of separating the powdered intermediate product containing impurities into at least two fractions based on the at least one criterion. The first fraction contains a high concentration of impurities, and the second fraction contains no impurities or a lower concentration of impurities than the first fraction. The second fraction, free of impurities or with a low concentration of impurities, forms the starting material for the production of rare-earth magnets.

[0042] At least one criterion for classifying the powdered intermediate may include the particle size, particle density, or similar characteristics of the powdered intermediate.

[0043] According to one embodiment of the system, the at least one separation device can comprise at least one dynamic classifier integrated into the system. Alternatively, the at least one separation device can comprise at least one dynamic classifier designed as a separate component from the system, to which the powdered intermediate product to be classified is fed.

[0044] Furthermore, it may be provided that at least one protective gas is supplied to the dynamic classifier, so that the classification based on at least one criterion takes place under a protective gas atmosphere. The protective gas used could be, for example, helium, argon, nitrogen, or similar protective gases.

[0045] Furthermore, at least one auxiliary substance in solid, liquid or gaseous state can be supplied to the at least one comminution device in order to suppress undesirable reactions of the produced powdered intermediate product with the environment, at least to a large extent.

[0046] The impurities could be non-metallic substances such as oxygen, carbon, and nitrogen, and / or their compounds. Furthermore, impurities such as hydrogen, its compounds, or similar substances would also be conceivable.

[0047] With regard to all the aforementioned aspects and embodiments of the inventive process for producing a powdered starting material intended for the manufacture of rare-earth magnets, it should be noted here that these aspects and characteristics can equally be part of, or applied to, the apparatus for producing a powdered starting material intended for the manufacture of rare-earth magnets. Therefore, whenever the above description refers to specific aspects and embodiments of the process for producing a powdered starting material intended for the manufacture of rare-earth magnets, these aspects and embodiments should be read as referring to the apparatus and understood in that manner.

[0048] The following exemplary embodiments of the invention and its advantages will be explained in more detail with reference to the accompanying figures. The relative sizes of the individual elements in the figures do not always correspond to the actual relative sizes, as some shapes are simplified and others are enlarged for better illustration. Figure 1 illustrates individual steps for implementing an embodiment of a method according to the invention. Figure 2 shows the concentrations of impurities in the powdered intermediate product after coarse grinding and after two classifying processes in a tabular comparison.

[0049] Identical reference numerals are used for identical or equivalently functioning elements of the invention. Furthermore, for the sake of clarity, only those reference numerals necessary for describing the respective figure are shown in the individual figures. The illustrated embodiments merely represent examples of how the method according to the invention and the system suitable for carrying out the method may be configured and do not constitute an exhaustive limitation.

[0050] Figure 1 shows individual process steps for the production of a starting material AM for the manufacture of rare earth magnets, based on at least one magnetic material M.

[0051] In a first step, at least one magnetic material M is provided. This at least one magnetic material M is preferably a scrap magnet, in particular an Nd-Fe-B scrap magnet, which was used in motors, waste electrical and electronic equipment (WEEE), or the like. Such scrap magnets typically contain a small, in particular an unintentional, but unavoidable and not negligible, concentration of impurities, which are contained in and / or trapped within the respective magnetic material M. These impurities are preferably oxygen, carbon, nitrogen, and / or their compounds. The small concentration of impurities in the provided at least one magnetic material and / or in the provided alloy comprising at least one rare-earth metal is preferably between at least 0.01 percent by weight and at most 1.5 percent by weight.In particular, the concentration of impurities can range from 0.1% by weight to 1.0% by weight of oxygen, from 0.01% by weight to 0.1% by weight of nitrogen, and from 0.01% by weight to 0.15% by weight of carbon.

[0052] In a next step, the provided at least one magnetic material M is comminuted, yielding a powdered intermediate product ZP, which may contain a higher concentration of impurities than the provided at least one magnetic material M. The increased concentration of impurities in the powdered intermediate product is preferably between at least 0.01% and at most 2.0% by weight. In particular, for example, the concentration of impurities may be between 0.1% and 1.2% by weight of oxygen, between 0.01% and 0.15% by weight of nitrogen, and between 0.01% and 0.20% by weight of carbon.

[0053] During the comminution of the at least one magnetic material M, it typically absorbs additional impurities from the environment, such as oxygen, carbon, nitrogen, and / or their compounds. This results in an increase in the concentration of impurities in the powdered intermediate product ZP compared to the initial at least one magnetic material M. In particular, increased oxygen uptake occurs because the comminution process agitates the at least one magnetic material, causing it to be flung around within the comminution device.

[0054] The comminution of the at least one magnetic material M is carried out in such a way that a coarse powder or fine powder is produced, which forms the powdery intermediate product ZP.

[0055] To produce a coarse powder, either a comminution process using a mechanical comminution plant or the use of hydrogen is suitable. Hydrogen causes the embrittlement of the at least one magnetic material M, leading to its disintegration into a coarse-grained, powdery intermediate product. Due to the use of hydrogen, the powdery intermediate product ZP exhibits not only impurities such as oxygen, carbon, nitrogen, and / or their compounds, but also an increased concentration of hydrogen and / or hydrogen-containing compounds.

[0056] To produce a fine-grained powdered intermediate product ZP, several comminution processes, in particular several grinding processes and / or fine grinding of the at least one magnetic material M, can be carried out, whereby the powdered intermediate product ZP usually contains an increased concentration of undesirable impurities, such as oxygen, carbon, nitrogen and / or their compounds.

[0057] Since the starting material AM for manufacturing a rare-earth magnet should ideally contain no or only a very low concentration of impurities, these impurities must be removed from the powdered intermediate product ZP. In a subsequent step, the powdered intermediate product ZP is classified according to at least one criterion, whereby the concentration of impurities may potentially increase further as a result of the classification process. Preferably, there is an increased increase in oxygen concentration, since the powdered intermediate product ZP is agitated during classification. The at least one criterion can include particle size, particle density, or the like, with the powdered intermediate product ZP preferably being classified according to particle size in the process according to the invention.

[0058] The classification of the powdered intermediate ZP is carried out by at least one dynamic classifier, which divides the produced powdered intermediate into at least two fractions F1 and F2 based on at least one criterion, in particular particle size. A first fraction F1 contains at least a high concentration of impurities, while a second fraction F2 contains no impurities or at least a lower concentration of impurities than the first fraction F1. Preferably, the first fraction F1 with a high concentration of impurities is formed by a small particle size, and the second fraction F2 without impurities or with a lower concentration than the first fraction F1 is formed by a larger particle size of the classified powdered intermediate ZP.The concentration of impurities in the first fraction is between a minimum of 0.02% by weight and a maximum of 10.0% by weight. Specifically, for example, the concentration of impurities can range from 0.5% to 8.0% by weight of oxygen, from 0.05% to 0.35% by weight of nitrogen, and from 0.05% to 0.35% by weight of carbon.

[0059] The concentration of impurities in the second fraction is a maximum of 1.0 wt%. In particular, the concentration of impurities in the second fraction can be greater than 0.01 wt% or less than a maximum of 0.2 wt% for oxygen, greater than 0.01 wt% or less than a maximum of 0.05 wt% for nitrogen, and greater than 0.01 wt% or less than a maximum of 0.05 wt% for carbon.

[0060] Since the second fraction, F2, with its larger particle size, accumulates no impurities or only a low concentration of impurities compared to the first fraction, F1, with its smaller particle size, the material separated in the second fraction, F2, forms the starting material, AM, for the production of rare-earth magnets. In contrast, the first fraction, F1, with its smaller particle size and higher concentration of impurities, is unsuitable for the production of a rare-earth magnet and is therefore discarded or not used further.

[0061] Although further impurities, such as oxygen, nitrogen, carbon and / or their compounds, are absorbed during the classification of the powdered intermediate product ZP, these additionally absorbed impurities and the already existing impurities are separated and sorted out into at least two fractions F 1 , F 2 via the classification process, so that a second fraction F 2 is produced without impurities or with a low concentration of impurities.

[0062] If the second fraction F2 still contains an excessively high concentration of impurities after the first classification by the dynamic classifier, further dynamic classifying processes can be carried out as often and / or multiple times as necessary, so that a starting material AM for the production of rare-earth magnets can be produced and made available with no or the lowest possible concentration of impurities. In each subsequent classifying process, the first fraction F1 with the high concentration of impurities is sorted out compared to the second fraction F2, while the second fraction F2 is used for further classification into at least two additional fractions.

[0063] To avoid undesirable reactions of the powdered 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 powdered intermediate product ZP is separated into at least two fractions F 1 , F 2 under a protective gas atmosphere.

[0064] Optionally, at least one auxiliary substance in solid, liquid, or gaseous state can be added to the at least one magnetic material M. This at least one auxiliary substance can be, for example, zinc stearate, isopropanol, or the like, which forms a coating around the individual particles of the respective material, thereby reducing the absorption of impurities during the comminution of the at least one magnetic material M into a powdered intermediate product ZP.

[0065] Figure 2The figure shows schematically and in a tabular overview the concentration after coarse grinding of a magnetic material and after two classifier processes of an embodiment of the inventive method.

[0066] In the present embodiment, a coarse powder was produced from a magnetic material M, in particular from an Nd-Fe-B scrap magnet, using hydrogen technology. The supplied hydrogen penetrates the provided Nd-Fe-B scrap magnet, causing it to disintegrate into a coarse powder with a fineness ranging from zero to approximately 300–3000 µm. The resulting coarse powder is thus the powdered intermediate product ZP.

[0067] The produced coarse-grained, powdered intermediate product ZP includes impurities such as oxygen and / or oxygen-containing compounds with, for example, 0.8% by weight oxygen, carbon and / or carbon-containing compounds with, for example, 0.07% by weight carbon, and nitrogen and / or nitrogen-containing compounds with, for example, 0.06% by weight nitrogen.

[0068] To reduce the concentration of impurities in the powdered intermediate product ZP of the comminuted Nd-Fe-B waste magnet, the powdered intermediate product ZP is classified according to at least one criterion, in particular its particle size. For this classification, at least one dynamic classifier is provided, which separates the powdered intermediate product ZP containing oxygen, carbon, and nitrogen impurities into at least two fractions, F1-1 (not shown) and F2-1, based on particle size.

[0069] The at least two fractions F 1-1 , F 2-1 differ in that in a first fraction F 1-1 with a small particle size, at least a high concentration of impurities accumulates, and in a second fraction F 2-1 with a larger particle size, at least a lower concentration of impurities accumulates than in the first fraction F 1-1.

[0070] Following an initial classifying process, the proportion of oxygen decreased to 0.4% by weight, carbon to 0.05% by weight, and nitrogen to 0.04% by weight. These figures represent the concentration of impurities in the second fraction, F 2-1, which has a larger particle size. The concentration of impurities in the second fraction, F 2-1, was thus reduced by at least a quarter and by half through this initial classifying process.

[0071] Since the first fraction, F 1-1, with its smaller particle size, is characterized by a significantly higher concentration of impurities compared to the second fraction, F 2-1, and is therefore not relevant for the production of rare-earth magnets, it will not be discussed further. It should also be noted that hydrogen impurities resulting from the coarse grinding process will not be discussed further.

[0072] Since a starting material AM with as few or no impurities as possible is desirable for the production of rare earth magnets, a second classifying process is carried out on the previously separated second fraction F 2-1 in order to further reduce the concentration of impurities.

[0073] By reclassification using at least one dynamic classifier, the material of the previously separated second fraction F 2-1 is divided into at least two fractions, F 1-2 (not shown) and F 2-2, based on particle size. In the first fraction, F 1-2, with its small particle size, at least a high concentration of impurities accumulates, while in the second fraction, F 2-2, with its large particle size, no impurities accumulate, or at least a lower concentration of impurities than in the first fraction, F 1-2. Thus, the second classifier process reduces the oxygen content in the second fraction, F 2-2, to 0.2 wt%, the carbon content to 0.02 wt%, and the nitrogen content to 0.02 wt%. The concentration of impurities was therefore reduced by at least a quarter and by half through the second classifier process.

[0074] To further reduce the concentration of impurities, classifier processes can be carried out as often as desired to subsequently form a fraction without impurities or with a low concentration of impurities, which represents the starting material AM for the production of rare earth magnets.

[0075] The invention has been described with reference to a preferred embodiment. However, it is conceivable to a person skilled in the art that modifications or alterations of the invention can be made without departing from the scope of protection of the following claims. Reference symbol list

[0076] M magnetic material ZP powder intermediate F 1 , F 1-1 , F 1-2 first fraction F 2 , F 2-1 , F 2-2 second fraction AM starting material

Claims

1. A method used to produce a powdered starting material (AM) provided for the manufacture of rare earth magnets, the method comprising the following steps: - supplying at least one magnetic material (M) and / or at least one alloy comprising rare earth metal, which magnetic material (M) or which alloy comprise a low concentration of impurities, - comminuting the supplied at least one magnetic material (M) and / or the supplied at least one alloy comprising rare earth metal, wherein a powdered intermediate product (ZP) forms from the at least one magnetic material (M) and / or from the at least one alloy comprising rare earth metal, - classifying the powdered intermediate product (ZP) according to at least one criterion, wherein at least one dynamic classifier is provided for the classification of the powdered intermediate product (ZP), which dynamic classifier divides the powdered intermediate product (ZP) with impurities into at least two fractions (F1, F2) on the basis of the at least one criterion, - wherein at least a high concentration of impurities accumulates in a first fraction (F1) and no impurities or at least a lower concentration of impurities than in the first fraction (F1) accumulates in a second fraction (F2), and wherein the first fraction (F1) is formed with a high concentration of impurities by a small particle size and the second fraction (F2) is formed without impurities or with a low concentration of impurities by a larger particle size than that in the first fraction (F1), - and wherein the fraction without impurities or with a low concentration of impurities forms the starting material (AM) for the production of rare earth magnets, - wherein a concentration of impurities of oxygen in the powdered intermediate product is, in particular, between 0.1 per cent by weight and 1.2 per cent by weight, a concentration of impurities of nitrogen is, in particular, between 0.01 per cent by weight and 0.15 per cent by weight, and a concentration of impurities of carbon is, in particular, between 0.01 per cent by weight and 0.20 per cent by weight, - wherein the concentration of impurities in the first fraction is between at least 0.02 per cent by weight and at most 10.0 per cent by weight, and - wherein the concentration of impurities in the second fraction is a maximum of 1.0 per cent by weight.

2. The method according to claim 1, in which the second fraction (F2) without impurities or with a low concentration of impurities is classified several times by the dynamic classifier and is in each case divided into at least two fractions (F1, F2).

3. The method according to claim 1 or claim 2, in which the concentration of impurities in the second fraction (F2) is reduced relative to the first fraction (F1) by at least one quarter to at least three quarters or more, or optionally completely, by classifying the powdered intermediate product (ZP) into the at least two fractions (F1, F2).

4. The method according to one of the claims 1 to 3, in which the at least one magnetic material (M) and / or the at least one alloy comprising rare earth metal is comminuted in such a manner that the powdered intermediate product (ZP) produced is a coarse powder or a fine powder.

5. The method according to one of the claims 1 to 4, in which the at least one dynamic classification process is carried out by the dynamic classifier on the coarse powder or on the fine powder.

6. The method according to one of the previous claims, in which the concentration of impurities of oxygen in the first fraction (F1) is between 0.5 per cent by weight and 8.0 per cent by weight, the concentration of impurities of nitrogen is between 0.05 per cent by weight and 0.35 per cent by weight, and the concentration of impurities of carbon is between 0.05 per cent by weight and 0.35 per cent by weight.

7. The method according to one of the previous claims, in which the proportion of impurities of oxygen in the second fraction (F2) is greater than 0.01 per cent by weight or less than 0.2 per cent by weight, the proportion of impurities of nitrogen is greater than 0.01 per cent by weight or less than 0.05 per cent by weight, and the proportion of impurities of carbon is greater than 0.01 per cent by weight or less than 0.05 per cent by weight.

8. The method according to claim 7, wherein the comminution of the at least one magnetic material (M) and / or of the at least one alloy comprising rare earth metal is carried out by one grinding operation or by a plurality of grinding operations performed by a mechanical grinding system or with the aid of hydrogen technology.

9. The method according to one of the previous claims, in which at least one inert gas is supplied to the at least one dynamic classifier such that the powdered intermediate product (ZP) is divided into at least two fractions (F1, F2) under an inert gas atmosphere.

10. The method according to one of the previous claims, in which at least one auxiliary material in a solid, liquid, or gaseous state is fed to the supplied at least one magnetic material (M) and / or to the supplied at least one alloy comprising rare earth metal temporally before or during the comminution.