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 material, which is provided for the manufacture of rare earth magnets. First of all, at least one magnetic or magnetizable raw material, respectively, is provided and is comminuted into a powdery intermediate product, which includes powder particles including corners and edges, by means of conventional comminuting methods. The sharp-edged powder particles are chamfered subsequently. The optimized powdery product including the chamfered powder particles is used 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 or magnetizable raw material; comminuting the at least one magnetic or magnetizable raw material, to create a powdery intermediate product, wherein the powdery intermediate product contains powder particles that have corners and/or edges; and chamfering the powder particles of the powdery intermediate product such that the corners and/or edges thereof are reduced or abraded to be rounded, thereby forming a powdery product, which contains chamfered powder particles; wherein the method further comprises: using the powdery product as a first starting material to manufacture first rare earth magnets; or classifying the powdery product, such that abrasion fractions created in response to the chamfering are removed and a fraction including the chamfered powder particles is used as a second starting material to manufacture second rare earth magnets; wherein an average particle size of the chamfered powder particles of the powdery product and the powder particles of the powdery intermediate product is between approximately 2 μm and 10 μm.

2. The method according to claim 1, wherein the reducing and/or abrading process is performed by means of an abrading device, in which the powder particles of the powdery intermediate product are moved in such a way that the powder particles of the powdery intermediate product rub against each other.

3. The method according to claim 1, wherein the reducing and/or abrading process is carried out by using a protective gas.

4. The method according to claim 2, wherein the abrading device includes a receiving chamber, into which the powder particles of the powdery intermediate product are filled and are moved in such a way that they rub against each other, wherein between 50% and 99% of the receiving chamber is filled with powdery intermediate product.

5. The method according to claim 4, wherein the remaining space inside the receiving chamber is filled by protective gas.

6. The method according to claim 3, wherein the chamfering of the powder particles of the powdery intermediate product is carried out at a gas pressure between 0.25 bar and 1.00 bar.

7. The method according to claim 1, wherein the first rare earth magnets produced by using the powdery product have an increased magnetic value or a higher magnetic energy density as compared to rare earth magnets which are produced by using a powdery intermediate product.

8. The method according to claim 1, wherein the second rare earth magnets produced by using the fraction including the chamfered powder particles have an increased magnetic value or a higher magnetic energy density as compared to rare earth magnets which are produced by using a powdery intermediate product.

9. The method according to claim 2, wherein the abrading process is carried out by using a protective gas.

10. The method according to claim 4, wherein the powdery intermediate product fills at least 80% of the receiving chamber.

11. The method according to claim 1, wherein the chamfering is performed without further comminution.

12. The method according to claim 1, wherein the average particle size of the chamfered powder particles of the powdery product and the powder particles of the powdery intermediate product is between approximately 3 μm and 5 μm.

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, for better visualization, some shapes are illustrated in a simplified manner and other shapes are illustrated in an enlarged manner in comparison with other elements.

(2) FIG. 1 shows a scanning electron microscopic recording of a conventionally produced rare earth magnetic powder.

(3) FIG. 2 shows individual particles of a conventionally produced rare earth magnetic powder illustrated schematically in an exemplary manner.

(4) FIG. 3 shows a scanning electron microscopic recording of an optimized starting material for the production of rare earth magnets.

(5) FIG. 4 shows individual particles of the optimized starting material illustrated schematically in an exemplary manner.

(6) FIG. 5 shows individual method steps for the production of an optimized rare earth magnetic powder for the manufacture of rare earth magnets, based on at least one magnetic or magnetizable raw material, respectively.

(7) FIG. 6 shows, schematically, a plant for the production of a powdery starting material, which is provided for the manufacture of rare earth magnets.

DETAILED DESCRIPTION

(8) 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 device according to the invention or the method according to the invention can be embodied and do not represent a conclusive limitation.

(9) FIG. 1 shows a scanning electron microscopic recording of a conventionally produced rare earth magnetic powder and FIG. 2 shows individual particles 2 of such a conventionally produced rare earth magnetic powder 1 illustrated schematically in an exemplary manner. The production of the rare earth magnetic powder 1 takes place, for example, by grinding of a corresponding raw material. The magnetic or magnetizable raw material, respectively, can be alloys comprising ferromagnetic metals, for example, iron, nickel, cobalt, in particular an alloy of neodymium, iron and boron (NdFeB), or old magnets or mixtures of rare earth alloys and old magnets. The magnetic or magnetizable raw material, respectively, is thereby ground for example, in fluidized bed jet mills or similar grinding plants in such a way that a fine rare earth magnetic powder 1 is created, in the case of which the average particle size (d50-value) of the powder particles 2 lies between 2 μm and 10 μm, preferably between 3 μm and 5 μm.

(10) As can be seen clearly in FIGS. 1 and 2, this rare earth magnetic powder 1 contains powder particles 2 comprising sharp corners 3 and edges 4. If this conventionally produced rare earth magnetic powder 1 is now used for the magnet production, magnets 5 are created (see FIG. 5), the magnetic values or magnetic energy densities of which, respectively, lie significantly below the theoretically calculated values.

(11) FIG. 3 shows a scanning electron microscopic recording of a second optimized starting material AM2 for the production of rare earth magnets 20—see also the figure description of FIG. 5 for this purpose—and FIG. 4 shows individual particles 12, 12a, 12b of the second optimized starting material AM 2 illustrated schematically in an exemplary manner.

(12) The second optimized starting material AM2 is, in particular produced by means of a method, as it will be described in detail below in connection with FIG. 5. The second optimized starting material AM2 contains, in particular powder particles 12, which, compared to the powder particles 2 of the rare earth magnetic powder 1, only have a significantly reduced number of rounded off corners 13 and rounded off edges 14, in particular slightly rounded and/or rounded off powder particles 12a or rounded powder particles 12b, respectively.

(13) FIG. 5 shows individual method steps for the production of an optimized starting material AM1, AM2, in particular of an optimized rare earth magnetic powder 10 or of a rare earth magnetic powder, which is further optimized by means of additional classification, for the manufacture of rare earth magnets 19, 20, based on at least one magnetic or magnetizable raw material M, respectively. FIG. 6 shows, schematically, a plant 25 for the production of a powdery starting material AM2, which is provided for the manufacture of rare earth magnets 20.

(14) In a first method step, at least one magnetic or magnetizable raw material M, respectively, is provided. The at least one magnetic or magnetizable raw material M, respectively, is preferably rare earth alloys and/or old magnets, in particular Nd—Fe—B alloys and/or Nd—Fe—B old magnets.

(15) In a next method step, the provided at least one magnetic or magnetizable raw material M, respectively, is comminuted, wherein a powdery intermediate product ZP, in particular a rare earth magnetic powder 1 comprising powder particles 2 comprising corners 3 and edges 4 according to FIGS. 1 and 2, is created from the at least one magnetic or magnetizable raw material M, respectively.

(16) The comminution takes place by means of a comminution apparatus 30, for example, by means of conventionally known comminution techniques. A first coarse comminution for the production of coarse powder with a particle size of approximately 100 μm to 300 μm can take place, for example, by using mechanical comminution plants, such as mills 31, and/or by using hydrogen technology. Grinding plants for the fine grinding, such as, for example, fluidized bed jet mills 32 or similar grinding plants, which are operated, in particular under protective gas S, are used for the fine grinding or for the production of fine powder, respectively, with a particle size of approximately 0.1 μm to 20 μm. The used protective gas is typically nitrogen or argon. A rare earth magnetic powder 1 produced in this way is used, for example, for the production of conventional rare earth magnets 5. In a further method step, this rare earth magnetic powder 1 is now filled into an abrading device 40 under protective gas S and is then moved in this abrading device 40 under protective gas S for a defined period of time. The powder particles 2 of the rare earth magnetic powder 1 are thereby swirled around inside the abrading device 40. The defined period of time for this method step preferably lies between 0.5 hours and 3 hours, in particular at approximately one hour.

(17) The receiving chamber of the abrading device 40 is thereby not completely filled with rare earth magnetic powder 1. The receiving chamber is preferably filled in such a way that the rare earth magnetic powder 1 fills between 50% and 99% of the grinding chamber. The receiving chamber is, in particular filled in such a way that the rare earth magnetic powder 1 fills at least 80% of the receiving chamber. The remaining 20% of the grinding chamber are filled by protective gas S.

(18) The rare earth magnetic powder 1 is vigorously swirled around in the abrading device 40, whereby the corners 3 and edges 4 of the powder particles 2 are abraded among one another on one another by means of mutual rubbing of the powder particles 2. An optimized rare earth magnetic powder 10 with chamfered powder particles 12 according to FIGS. 3 and 4 is created thereby. In particular, no further grinding of the rare earth magnetic powder 1 takes place in the abrading device 40, so that no new sharp corners 3 and breaking edges 4 can be created.

(19) The abrading device 40 is preferably operated at a low gas pressure, for example, at a gas pressure of between 0.25 bar and 1.00 bar. The gas pressure thereby has to, in particular be adapted in such a way that even though the intermediate product ZP or rare earth magnetic powder 1, respectively, can be swirled around in the abrading device 40, so that the powder particles 2 rub against each other, whereby the corners 3 and edges 4 are abraded, and chamfered powder particles 12 according to FIGS. 3 and 4 are formed. The energy of the powder particles 2 and 12, however, must thereby not be sufficient for a further grinding. The conventionally produced rare earth magnetic powder 1 is preferably treated in the abrading device 40 until only rounded powder particles 12b according to FIG. 4 are present for the most part.

(20) An optimized rare earth magnetic powder 10, which can now already be used as first starting material AM1 for the production of first optimized rare earth magnets 19, is created by means of the chamfering. However, in addition to the chamfered powder particles 12—see also FIGS. 3 and 4—the optimized rare earth magnetic powder 10 also contains very fine abrasion portions F, which represent, in particular the abrasion of the corners 3 and edges 4 of the powder particles 2 of the rare earth magnetic powder 1. These very fine abrasion portions F are removed in an optional method step, in order to produce a further optimized second starting material AM2 for the production of second further optimized rare earth magnets 20. The very fine abrasion portions F are preferably removed, in that the first optimized rare earth magnetic powder 10 is subsequently classified in a separation apparatus 50, for example, a quickly rotating, dynamic classifier 51, so that the second starting material AM2 for the production of second further optimized rare earth magnets 20 only still contains chamfered powder particles 12.

(21) Experiments have shown that first optimized rare earth magnets 19, and in particular second further optimized rare earth magnets 20 have magnetic values or magnetic energy densities, respectively, which are higher than the magnetic values or magnetic energy densities, respectively, of rare earth magnets 5, which are made of a conventionally produced rare earth magnetic powder 1. The second rare earth magnets 20 of a second optimized starting material AM2, in particular have a magnetic value or a value of the magnetic energy density, respectively, which comes markedly close to a theoretically calculated optimal value.

(22) The embodiments, examples and alternatives of the preceding paragraphs, the claims and the Figures, including their different views or respective individual features, can be used independently of one another or in any combination. Features, which are described in combination with an embodiment, can used for all embodiments, provided that the features are not incompatible.

(23) When reference is also generally made to “schematic” illustrations and views in connection with the Figures, this does in no way suggest that the figure illustrations and the descriptions thereof are to be of minor importance with regard to the disclosure of the invention. The person of skill in the art is absolutely able to gather sufficient information from the illustrations, which are drawn in a schematic and abstract manner, which make it easier for him to understand the invention, without impacting his understanding in any way for instance from the drawn size ratios of the powder particles or other drawn elements, which might possibly not be exactly true to scale. The Figures thus make it possible to the person of skill in the art as reader to derive a better understanding for the ideas of the invention worded in a general and/or abstract manner in the claims as well as in the general part of the description, by means of the concretely described implementations of the method according to the invention and the concretely described mode of operation of the device according to the invention.

(24) 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.