DE102023121470A1 - Process for producing a raw magnet - Google Patents

Abstract

The invention relates to a method for producing a raw magnet (1), wherein- a magnetic starting material (3) is mixed with a binder (5), whereby a mixture (7) of the magnetic starting material (3) and the binder (5) is obtained, whereby- the mixture (7) is filled layer by layer into a negative mold (19), whereby a raw mold (9) having a plurality of layers (17) is produced layer by layer from the mixture (7), whereby- an external magnetic field is applied to at least one layer (17) of the raw mold (9), whereby- the raw mold (9) is sintered, whereby the raw magnet (1) is obtained.

Description

The invention relates to a method for producing a raw magnet.

Permanent magnets made from raw magnets from the rare earth group are used in a wide range of technical applications and are characterized by a particularly high energy product. Neodymium-iron-boron magnets in particular have an energy product of up to 400 kJ/m ³ .

Known methods for producing a permanent magnet include producing, in particular pressing, a raw form and then sintering the raw form. The disadvantage of these methods is that only simple magnet shapes, in particular cylinders or cuboids, and/or simple magnetizations, in particular axial magnetization, can be realized. A magnet shape and/or magnetization adapted to a specific requirement is therefore not possible.

To create complex magnet shapes and/or complex magnetizations, methods are known in which at least two magnetized magnets are connected to one another. The disadvantage is that these methods are very complicated and time-consuming due to the mutual attraction of the magnets. In addition, the magnets can be damaged and a worker can be injured, particularly in the form of crush injuries, if the magnets collide with one another in an uncontrolled manner due to their mutual attraction.

In addition, it is difficult to mechanically fix a magnet containing at least one rare earth element in an assembly using form-fitting. The reasons for this include the simple shape of the magnet and the fact that threads and holes cannot be produced using press sintering. Machining the magnet is also difficult because it is extremely brittle and should be avoided in order to use raw materials efficiently.

There are known methods for fixing magnets, especially in an assembly, in which the magnets are glued into the assembly or are covered with an impregnating resin or are molded around. The disadvantage of this is that assembly is very complex and that the glue and/or the impregnating resin can cause corrosion of the magnet.

The invention is therefore based on the object of creating a method for producing a raw magnet, in particular for producing a permanent magnet, wherein the disadvantages mentioned, in particular with regard to the permanent magnet to be produced, are at least partially eliminated, preferably avoided.

The object is achieved by providing the present technical teaching, in particular the teaching of the independent claims as well as the embodiments disclosed in the dependent claims and the description.

The object is achieved in particular by providing a method for producing a raw magnet, wherein a magnetic starting material is mixed with a binder, whereby a mixture of the magnetic starting material and the binder is obtained. The mixture is filled layer by layer into a negative mold, whereby a raw mold having a plurality of layers is produced from the mixture layer by layer. An external magnetic field is applied to at least one layer of the raw mold. The raw mold is then sintered, whereby the raw magnet is obtained.

The method is advantageously suitable for producing permanent magnets, which are obtained after magnetizing the raw magnets, with a complex magnet shape and/or a complex magnetization. The permanent magnet produced preferably has a magnet shape and/or magnetization which can be adapted to a specific requirement. Furthermore, little or no post-processing of the raw magnet is required.

Advantageously, dipoles of the magnetic starting material are aligned in a parallel orientation - at least within one layer - by means of the externally applied magnetic field during the production of the raw form.

In one embodiment, the mixture comprises the magnetic starting material and the binder. Alternatively, the mixture consists of the magnetic starting material and the binder.

In particular, the mixture has a temperature of 30 °C to 250 °C, preferably 50 °C to 100 °C, during the layer-by-layer production of the raw form. In one embodiment, the temperature of the mixture is selected such that the mixture is flowable and in particular has a viscosity of 10 mPa to 100,000 mPa.

In one embodiment, the externally applied magnetic field is controlled by a switchable electric magnet and/or a permanent magnet.

In one embodiment, the atmosphere in which the raw form is produced layer by layer has a pressure of 900 mbar absolute to 1100 mbar absolute or normal pressure under standard conditions, in particular approximately 1013 mbar absolute. In particular, the raw form is produced layer by layer under a prevailing ambient pressure.

In particular, the raw form is produced in a currently prevailing atmosphere, in particular the earth's atmosphere, especially in air.

In the context of the present technical teaching, the earth's atmosphere, in particular air, is understood to mean in particular a gas mixture which comprises nitrogen, in particular with a volume fraction of approximately 78%, and oxygen, in particular with a volume fraction of approximately 21%. In addition, the gas mixture comprises argon, in particular with a volume fraction of approximately 1%, and carbon dioxide, in particular with a volume fraction of approximately 0.04%.

In one embodiment, a powdered magnetic starting material is used for the process, which is formed on the basis of a newly melted alloy, in particular in the form of a cast block or in the form of melt-spun material or in the form of strip-cast material. Alternatively or additionally, recycled magnetic material and/or contaminated recycled magnetic material is used for the process. Material obtained by recycling can be alloyed with at least one rare earth element, preferably in powder form, to improve its properties.

The magnetic starting material can be in a pure form or in a hydrogenated form. The US patent application US 2013/0263699 A1 and the German patent DE 198 43 883 C1 describe a process called hydrogen decrepitation (HD) to produce a hydrogenated form of the magnetic starting material by means of hydrogen-induced decomposition.

In one embodiment, the magnetic starting material is mechanically comminuted, in particular by grinding, to a particle size of 1 µm to 200 µm, preferably 2 µm to 15 µm, in order to obtain the powdered magnetic starting material.

In one embodiment, the magnetic starting material is not partially or completely dehydrated after grinding and/or before mixing with the binder, but is in a hydrated state. In particular, the magnetic starting material is mixed with the binder in a hydrated state after grinding.

Advantageously, it is possible in a simple manner using the method to produce a Halbach array, in particular a one-sided Halbach array or a two-sided Halbach array, as a raw magnet in a first embodiment. Alternatively, it is possible in a simple manner using the method to produce a multi-pole raw magnet in a second embodiment.

According to a further development of the invention, it is provided that the raw form is produced layer by layer using a method selected from a group consisting of ink-jet printing, filament printing, screen printing and casting, in particular injection molding. Advantageously, this makes it possible to produce the raw form layer by layer in a simple manner.

According to a further development of the invention, it is provided that a material which comprises particles of an R _x T _y B alloy is used as the magnetic starting material. In one embodiment, a material which consists of particles of an R _x T _y B alloy is used as the magnetic starting material. In particular, a material which comprises particles of an Nd _x Fe _y B alloy or consists of particles of an Nd _x Fe _y B alloy is used as the magnetic starting material.

In one embodiment, a material which has particles of an R _x T _y B alloy and particles of a rare earth-rich phase is used as the magnetic starting material. In particular, the magnetic starting material consists of a mixture of particles of an R _x T _y B alloy and particles of a rare earth-rich phase. In one embodiment, a material which has particles of an Nd _x Fe _y B alloy and particles of a neodymium-rich phase or consists of such particles is used as the magnetic starting material. In particular, the magnetic starting material has a mixture of particles of an Nd _x Fe _y B alloy and particles of a neodymium-rich phase or consists of such a mixture. In particular, the particles of the rare earth-rich phase have at least one element selected from a group consisting of neodymium, cerium, lanthanum, dysprosium, terbium, praseodymium, and a combination of at least two of the preceding elements.

In the context of the present technical teaching, R stands for a rare earth element, T for at least one element selected from a group consisting of iron and cobalt, and B for the element boron. In particular, the elements iron and cobalt partially or completely substitute for one another such that either only iron or only cobalt or any iron-cobalt mixture is present. In one embodiment, the rare earth element is neodymium. In one embodiment, the R _x T _y B alloy additionally comprises a further element, preferably a metal, in particular a transition metal, selected from a group consisting of aluminum, copper, zirconium, gallium, hafnium, and niobium, preferably in trace amounts.

In one embodiment, the magnetic starting material comprises particles of a Nd ₂ Fe ₁₄ B alloy or consists of particles of a Nd ₂ Fe ₁₄ B alloy.

In one embodiment, the rare earth-rich phase, in particular the neodymium-rich phase, comprises at least one rare earth element, in particular neodymium, or a chemical compound of this rare earth element, in particular neodymium. In addition, the rare earth-rich phase, in particular the neodymium-rich phase, can contain at least one further element of the R _x T _y B alloy, in particular the Nd _x Fe _y B alloy. Alternatively or additionally, the at least one rare earth element, in particular neodymium, is present in a hydrogenated form. In one embodiment, the neodymium-rich phase comprises NdH ₂ and/or NdH _2.7 or consists of NdH ₂ and/or NdH _2.7 . Alternatively, it is possible that the rare earth-rich phase, in particular the neodymium-rich phase, consists of at least one rare earth element, in particular neodymium, or of a chemical compound of this rare earth element, in particular neodymium.

Without being bound to theory, the rare earth-rich phase in the structure of the raw magnet and in particular in the structure of the permanent magnet obtained from the raw magnet forms a phase that is located at grain boundaries of the structure.

According to a further development of the invention, it is provided that the binder comprises at least one polymer selected from a group consisting of polyethylene glycol, polyvinyl acetate, polyvinyl alcohol, polybutyl acrylate, polybutyl methacrylate, polyvinylpyrrolidone, polymethyl methacrylate, polyvinyl butyral, paraffin wax, and a combination of at least two of the preceding polymers. In one embodiment, a polymer selected from a group consisting of polyethylene glycol, polyvinyl acetate, polyvinyl alcohol, polybutyl acrylate, polybutyl methacrylate, polyvinylpyrrolidone, polymethyl methacrylate, polyvinyl butyral, paraffin wax, and a combination of at least two of the preceding polymers is used as the binder. The binder advantageously facilitates alignment of the particles of the magnetic starting material.

In one embodiment, paraffin wax is used as a binder. As a thermoplastic, paraffin wax is particularly suitable for producing the raw mold.

According to a further development of the invention, the magnetic starting material and the binder are additionally mixed with a solvent to form the mixture. A mixture with solvent is advantageously flowable at a lower temperature than a mixture without solvent.

In one embodiment, the mixture comprises the magnetic starting material, the binder and the solvent. Alternatively, the mixture consists of the magnetic starting material, the binder and the solvent. In particular, during the layer-by-layer production of the raw form, the mixture has a temperature of room temperature, in particular 15 °C to 25 °C, to 50 °C. In one embodiment, the temperature of the mixture is selected such that the mixture is flowable and in particular has a viscosity of 10 mPa to 100,000 mPa.

According to a development of the invention, it is provided that the solvent comprises at least one compound selected from a group consisting of an alcohol, in particular ethanol, methanol, and isopropanol, a ketone, in particular acetone, an ester, in particular ethyl acetate, an aromatic compound, in particular benzene, toluene, xylene, an alkane, in particular n-hexane, n-heptane, cyclohexane, an organic solvent, and a combination of at least two of the preceding compounds. In one embodiment, a compound selected from a group consisting of an alcohol, in particular ethanol, methanol, and isopropanol, a ketone, in particular acetone, an ester, in particular ethyl acetate, an aromatic compound, in particular benzene, toluene, xylene, an alkane, in particular n-hexane, n-heptane, cyclohexane, an organic solvent, and a combination of at least two of the preceding compounds is used as the solvent.

According to a further development of the invention, it is provided that the magnetic starting material and the binder are additionally coated with at least one Surfactant can be mixed into the mixture. Surfactants advantageously support a more homogeneous dispersion of the particles of the magnetic starting material in the mixture. In particular, surfactants wet a surface of the particles of the magnetic starting material and improve wetting of the particles in the mixture. In addition, surfactants act in particular as a spacer between two particles of the magnetic starting material, so that agglomeration of these is at least partially prevented.

In one embodiment, the mixture comprises the magnetic starting material, the binder and the at least one surfactant. Alternatively, the mixture consists of the magnetic starting material, the binder and the at least one surfactant.

In a further embodiment, the mixture comprises the magnetic starting material, the binder, the solvent and the at least one surfactant. Alternatively, the mixture consists of the magnetic starting material, the binder, the solvent and the at least one surfactant.

In particular, the surfactant is a compound selected from a group consisting of an anionic surfactant, a cationic surfactant, a nonionic surfactant, an amphoteric surfactant, a fatty acid, in particular stearic acid, a salt of a fatty acid, in particular sodium stearate, polysorbate 20, polysorbate 40, polysorbate 60, polysorbate 65, and polysorbate 80.

According to a further development of the invention, the mass fraction of the magnetic starting material in the mixture is from 70% to 95%, preferably from 85% to 92%. Alternatively or additionally, the mass fraction of the binder in the mixture is from 1% to 15%, in particular from 8% to 10%. Alternatively or additionally, the mass fraction of the solvent in the mixture is from 4% to 25%, in particular 4% to 8%. Alternatively or additionally, the mass fraction of the at least one surfactant in the mixture is from 0.03% to 2.4%.

In one embodiment, a quotient of the mass fraction of the binder and the mass fraction of the solvent is from 1.5 to 2.5, in particular from 1.75 to 2.25, in particular from 1.9 to 2.1, in particular 2.

In a first embodiment, the mixture consists of the magnetic starting material and the binder. The mass fraction of the magnetic starting material is 85% to 92% and the mass fraction of the binder is 8% to 15%.

In a second embodiment, the mixture consists of the magnetic starting material, the binder and the solvent. The mass fraction of the magnetic starting material is from 77% to 88%, the mass fraction of the binder is from 8% to 15% and the mass fraction of the solvent is from 4% to 8%. In particular, the mass fraction of the at least one surfactant is from 0.03% to 2.4%.

In particular, the mass fractions and the temperature of the mixture are selected such that the mixture is flowable and in particular has a viscosity of 10 mPa to 100,000 mPa.

According to a further development of the invention, it is provided that the layers of the raw form are produced with a predetermined layer thickness of 5 µm to 1 mm, in particular of 50 µm to 100 µm.

In particular, a volume of the mixture is calculated in advance from the predetermined layer thickness and a layer area determined orthogonal to the layer thickness, which volume is then filled into the negative mold to form a layer with the predetermined layer thickness.

According to a further development of the invention, it is provided that the raw form is produced in an atmosphere that has at least one inert gas, in particular helium, argon, and nitrogen. Alternatively, the raw form is produced in an atmosphere that has an inert gas mixture of at least two inert gases. Alternatively, the raw form is produced in an atmosphere that consists of at least one inert gas, in particular helium, argon, and nitrogen. Alternatively, the raw form is produced in an atmosphere that consists of an inert gas mixture.

In the context of the present technical teaching, an inert gas refers in particular to a gas that is at least inert to the substances used - in particular the magnetic starting material, the binder and the solvent - at least on a time scale of the process. Inert gases include in particular nitrogen, noble gases - in particular helium, neon, argon, krypton, xenon and radon - and sulphur hexafluoride.

In particular, the blank is produced in a helium atmosphere. Alternatively, the blank is produced in an argon atmosphere. Alternatively, the blank is produced in a nitrogen atmosphere. Alternatively, the blank is produced in an argon-helium atmosphere. Alternatively, the blank is produced in an argon-nitrogen atmosphere. Alternatively, the blank is produced in a helium-nitrogen atmosphere. Alternatively, the raw form is produced in an argon-helium-nitrogen atmosphere. In particular, the atmosphere selected from the helium atmosphere, the argon atmosphere, the nitrogen atmosphere, the argon-helium atmosphere, the argon-nitrogen atmosphere, the helium-nitrogen atmosphere, and the argon-helium-nitrogen atmosphere has a pressure of 900 mbar absolute to 1100 mbar absolute or normal pressure under standard conditions, in particular approximately 1013 mbar absolute.

In the context of the present technical teaching, a helium atmosphere is understood in particular to mean a gas which consists of pure helium and optionally impurities with a total volume fraction of no more than 5%.

In the context of the present technical teaching, an argon atmosphere is understood in particular to mean a gas which consists of pure argon and optionally impurities with a total volume fraction of no more than 5%.

In the context of the present technical teaching, a nitrogen atmosphere is understood in particular to mean a gas which consists of pure nitrogen and optionally impurities with a total volume fraction of no more than 5%.

In the context of the present technical teaching, an argon-helium atmosphere is understood in particular to mean a gas which consists of pure argon, pure helium and optionally impurities with a total volume fraction of no more than 5%.

In the context of the present technical teaching, an argon-nitrogen atmosphere is understood in particular to mean a gas which consists of pure argon, pure nitrogen and optionally impurities with a total volume fraction of no more than 5%.

In the context of the present technical teaching, a helium-nitrogen atmosphere is understood in particular to mean a gas which consists of pure helium, pure nitrogen and optionally impurities with a total volume fraction of no more than 5%.

In the context of the present technical teaching, an argon-helium-nitrogen atmosphere is understood in particular to mean a gas which consists of pure argon, pure helium, pure nitrogen and optionally impurities with a total volume fraction of no more than 5%.

According to a further development of the invention, it is provided that the external magnetic field is generated by a magnetization device. In one embodiment, the magnetization device has at least one magnetization unit. This advantageously makes it possible to produce a raw magnet with a complex magnetization, in particular with a magnetization that is formed differently in layers.

In a first embodiment, the magnetization device has an arm extension with a magnetization unit, wherein the magnetization unit is arranged on the arm extension so as to be rotatable about at least one axis. To apply the external magnetic field to the raw mold, the arm extension is arranged over at least one layer of the raw mold. In one embodiment, the layer surface of the at least one layer is larger than a planar extent of the magnetization unit, so that the at least one layer is only partially exposed to the external magnetic field. In this case, the at least one layer can be treated in a grid-like manner using the magnetization unit. Optionally, the magnetization unit is rotated relative to the arm extension between the treatment of individual grid fields of a grid of the at least one layer, so that different grid fields of the at least one layer are exposed to different magnetic field orientations of the magnetization unit. Furthermore, in another embodiment, at least one layer surface of the raw mold can be smaller than a planar extent of the magnetization unit.

In a second embodiment, the magnetization device has an arm extension with a plurality of magnetization units, wherein at least one magnetization unit of the plurality of magnetization units is arranged on the arm extension so as to be rotatable about at least one axis. To apply the external magnetic field to the raw form, the arm extension is arranged over at least one layer of the raw form. In one embodiment, the layer surface of the at least one layer is larger than a planar extent of the plurality of magnetization units, so that the at least one layer is only partially exposed to the external magnetic field. In this case, the at least one layer can be treated in a grid-like manner using the plurality of magnetization units. Optionally, at least one magnetization unit of the plurality of magnetization units is rotated relative to the arm extension between the treatment of individual grid fields of a grid of the at least one layer, so that different grid fields of the at least one layer are exposed to different magnetic field orientations of the magnetization units. Alternatively, the magnetization units can be aligned such that at least two magnetization units have different magnetic field alignments during a treatment step of the at least one layer. Furthermore, in another embodiment, at least one layer surface of the raw form can be smaller than a planar extent of the plurality of magnetization units.

In a third embodiment, the magnetization device is designed as a roller, wherein the roller in particular has a plurality of magnetization units. In one embodiment, the magnetization units are arranged in a tangential or radial direction. In particular, the magnetization units are arranged such that at least two magnetization units have different magnetic field orientations. During the treatment of the at least one layer, the magnetization device designed as a roller is rolled over the at least one layer.

In particular, the magnetization device designed as a roller has exactly one magnetization unit. To realize complex magnetizations of the raw form, the roller is rolled on at least two layers of the raw form in different directions. The at least two layers therefore have different orientations of the particles of the magnetic starting material.

According to a development of the invention, it is provided that a first layer of the mixture is first filled into the negative mold. During or after the production of the first layer, a first external magnetic field is at least partially applied to the first layer. The first layer is then dried. A second layer of the mixture is then filled into the negative mold on top of the first dried layer. The second layer is then dried. Optionally, a second external magnetic field is at least partially applied to the second layer before the second layer is dried. The particles of the magnetic starting material are advantageously fixed in the raw mold during drying, so that a magnetic alignment of the particles can no longer change after drying.

In one embodiment, the first layer is dried for a drying time of 15 seconds to 2 minutes, preferably 1 minute. Alternatively or additionally, the second layer is dried for a drying time of 15 seconds to 2 minutes, preferably 1 minute.

In particular, the drying time is selected depending on the layer thickness and the layer area, whereby the drying time increases with increasing layer thickness, and whereby the drying time can decrease with increasing layer area.

In one embodiment, the first external magnetic field has a complex first field geometry, in particular the first external magnetic field is generated in a grid-like manner by means of the magnetization device or by means of the roller. Alternatively or additionally, the second external magnetic field has a complex second field geometry, in particular the second external magnetic field is generated in a grid-like manner by means of the magnetization device or by means of the roller. In particular, the first external magnetic field and the second external magnetic field are identical or different.

In particular, a third layer of the mixture is filled into the negative mold on top of the second dried layer. The third layer is then dried. Optionally, a third external magnetic field is applied to at least part of the third layer before the third layer is dried. In particular, the procedure is repeated for a plurality of layers.

According to a further development of the invention, it is provided that at least one layer of the plurality of layers is dried by means of a blower, infrared radiation, and/or under reduced pressure or vacuum.

In the context of the present technical teaching, drying with reduced pressure is referred to as drying by means of partial pressure. In particular, the terms "reduced pressure" and "partial pressure" are to be understood as synonymous with one another in the context of the present technical teaching. In the context of the present technical teaching, a reduced pressure is understood to mean an atmosphere which has a pressure of 1 mbar absolute to 900 mbar absolute, in particular of 10 mbar absolute to 900 mbar absolute.

In the context of the present technical teaching, a vacuum is understood to be an atmosphere which has a pressure of less than 1 mbar absolute.

According to a further development of the invention, it is provided that the negative mold is produced layer by layer and in time alternating with the layer-by-layer production of the raw mold. Alternatively, the negative mold is produced before the layer-by-layer production of the raw mold. In particular, the negative mold is produced layer by layer before the layer-by-layer production of the raw mold.

In one embodiment, the negative mold consists of at least two partial negative molds, wherein the individual partial negative molds are manufactured individually and wherein the negative mold is manufactured by joining, in particular reversible joining, the at least two partial negative molds. Advantageously, it is possible in a simple manner to separate the partial negative molds from one another again after the raw mold has been manufactured and thus to shape the raw mold.

In a further embodiment, a first negative mold layer of the negative mold is first produced. The first layer of the mixture is then filled into the negative mold. In particular, the volume of the mixture for the first layer is calculated from a layer height of the first negative mold layer and its layer area. After the first layer has been exposed to the first magnetic field and the first layer has dried, a second negative mold layer of the negative mold is produced and - in particular directly during production - joined to the first negative mold layer. The second layer of the mixture is then filled into the negative mold.

According to a further development of the invention, it is provided that the negative mold is made from a polymer. In particular, the negative mold has a polymer or consists of a polymer. This advantageously makes it possible to produce the negative mold in a simple and cost-effective manner. It is also advantageously possible to produce the negative mold from a polymer layer by layer and in time, alternating with the layer-by-layer production of the raw mold. In this case, a layer of the negative mold and a layer of the raw mold are produced alternately. Furthermore, when produced from a polymer, the negative mold can have complex geometries, in particular with undercuts.

In particular, the polymer is selected from a group consisting of paraffin wax, epoxy resin, polyurethane, silicone, polylactide, polypropylene, acrylonitrile-butadiene-styrene, methacrylate, polyethylene, polyethylene glycol, polyvinyl alcohol and polyvinyl acetate. Advantageously, with a negative mold made of silicone, it is easy to press the raw mold out of the negative mold after production and thus to shape the raw mold.

In one embodiment, the negative mold is made from polyethylene glycol, polyvinyl alcohol or polyvinyl acetate. In particular, the negative mold has at least one polymer selected from a group consisting of polyethylene glycol, polyvinyl alcohol, polyvinyl acetate, and a combination of at least two of the previous polymers. Alternatively, the negative mold consists of at least one polymer selected from a group consisting of polyethylene glycol, polyvinyl alcohol, polyvinyl acetate, and a combination of at least two of the previous polymers.

Alternatively, the negative mold is made from a ceramic. In particular, the negative mold has a ceramic or consists of a ceramic. Advantageously, the negative mold made from the ceramic is reusable. Furthermore, it is advantageously possible to debinder and sinter the raw mold in the negative mold made from ceramic.

In particular, the ceramic is selected from a group consisting of aluminum oxide, zirconium oxide, and yttrium oxide.

In one embodiment, the negative mold comprises the binder or consists of the binder.

According to a further development of the invention, it is provided that the negative mold is produced by means of a method selected from a group consisting of ink-jet printing, filament printing, screen printing, stereolithography, layer lamination, casting, in particular injection molding, machining, forming, in particular thermoforming, and plastic 3D printing.

According to a further development of the invention, it is provided that the raw mold is formed from the negative mold before sintering.

In one embodiment, the raw mold is formed by breaking the negative mold down into partial negative molds. Alternatively, the raw mold is formed by pressing it out of the negative mold. Alternatively, the raw mold is formed by thermally decomposing the negative mold. Alternatively or additionally, the raw mold is formed by chemically decomposing the negative mold. Alternatively or additionally, the negative mold is melted, thereby forming the raw mold.

In one embodiment, the negative mold is melted at a temperature of 50 °C to 130 °C, in particular from 60 °C to 100 °C.

In a particularly preferred embodiment, the raw form is formed by thermal decomposition of the negative form in an atmosphere that contains hydrogen and/or at least one inert gas, in particular helium, argon, and nitrogen. Alternatively, the raw form is formed by thermal decomposition of the negative form in an atmosphere that consists of hydrogen and/or at least one inert gas, in particular helium, argon, and nitrogen. Alternatively or additionally, the forming is carried out at a pressure from 10 mbar absolute to 1100 mbar absolute. Alternatively or additionally, the raw form is formed at a forming temperature of 250 °C to 750 °C.

According to a further development of the invention, the raw form is debindered before sintering. Alternatively or additionally, the raw form is debindered after being removed from the negative mold.

In particular, the raw form is at least partially, in particular completely, debindered. In one embodiment, the binder is at least partially, in particular completely, removed from the raw form during debinding.

In one embodiment, the debinding is carried out as solvent debinding - in particular as solvent extraction - wherein the raw form is completely debinding by means of a debinding solvent.

In a further embodiment, the debinding is carried out as thermal debinding, whereby the raw form is completely debindered by means of heating - in particular when heating the raw form during sintering.

In a further embodiment, the raw form is pre-debindered by means of solvent debinding - in particular solvent extraction - whereby the raw form is partially debindered by means of the debinding solvent. The remaining binder is then completely removed by means of thermal debinding - in particular when heating the raw form during sintering.

In a further embodiment, the binder in the raw form is chemically split by means of a chemical reaction. The split binder is then completely removed from the raw form by means of thermal debinding.

In one embodiment, at least one non-polar organic solvent selected from a group consisting of n-heptane, n-hexane, and cyclohexane is used as the debinding solvent, in particular for pre-debinding. Alternatively or additionally, at least one polar organic solvent selected from a group consisting of acetone, isopropanol, and ethanol is used as the debinding solvent, in particular for pre-debinding. Alternatively or additionally, at least one acid selected from a group consisting of nitric acid, acetic acid, and oxalic acid is used as the debinding solvent, in particular for pre-debinding.

In one embodiment of the solvent debinding, the raw form is treated with the debinding solvent for a predetermined duration, at a predetermined pressure and at a predetermined temperature. In one embodiment, the predetermined temperature is from a lower temperature limit to 10 °C less than a boiling temperature of the debinding solvent at the predetermined pressure. The lower temperature limit can be 15 °C to 30 °C, in particular 25 °C. Alternatively or additionally, the predetermined pressure is from 900 mbar absolute to 1100 mbar absolute, or the predetermined pressure is in particular almost identical, in particular identical, to the normal pressure under standard conditions, in particular approximately 1013 mbar absolute. In particular, the solvent debinding is carried out under a currently prevailing ambient pressure. Alternatively or additionally, the predetermined duration is from 1 hour to 72 hours.

In one embodiment of the thermal debinding, the binder is at least partially, in particular completely, removed from the raw form in an atmosphere that contains or consists of hydrogen and/or at least one inert gas, in particular argon, helium, or nitrogen. In particular, the binder is at least partially, in particular completely, removed from the raw form in a hydrogen atmosphere or a hydrogen inert gas atmosphere at a pressure of 50 mbar absolute to 1100 mbar absolute, in particular at normal pressure under standard conditions, in particular at approximately 1013 mbar absolute. The raw form is heated to a temperature of 350 °C to 650 °C at a heating rate of 0.1 K/min to 10 K/min. Optionally, a holding stage is provided during the heating of the raw form at at least one predetermined temperature, in particular holding stages are provided at a plurality of predetermined temperatures, the temperature being maintained in the at least one holding stage for a predetermined period, in particular from 30 minutes to 300 minutes. In particular, a temperature of 600 °C is maintained for a duration of 180 minutes in a holding stage. Thus, pure heating without holding stages takes from 35 minutes to 6500 minutes, particularly depending on the heating rate and the temperature to which the raw mold is heated. The duration of the complete process for removing the binder from the raw mold in one embodiment results from the selected heating rate, the temperature to which the raw mold is heated, and a number and respective duration of the holding stages.

According to a further development of the invention, the raw form is sintered in a vacuum. Alternatively, the raw form is sintered in an atmosphere containing at least one process gas, selected from a group consisting of argon and helium. Alternatively, the green form is sintered in an atmosphere consisting of at least one process gas selected from a group consisting of argon and helium.

In particular, the raw form is sintered in a helium atmosphere. Alternatively, the raw form is sintered in an argon atmosphere. Alternatively, the raw form is sintered in an argon-helium atmosphere. In particular, the atmosphere, selected from the helium atmosphere, the argon atmosphere and the argon-helium atmosphere, has a pressure of 1·10 ^-6 mbar absolute to 1300 mbar, in particular of 1·10 ^-3 mbar absolute to 1300 mbar absolute.

In particular, the raw form is sintered at a sintering temperature of 950 °C to 1200 °C, preferably 1000 °C to 1100 °C.

In one embodiment, during sintering, the treated raw form is heated from room temperature or a debinding temperature to the sintering temperature at a heating rate of 0.1 K/min to 10 K/min. Optionally, a holding stage is provided at at least one predetermined intermediate temperature during the heating of the treated raw form, in particular holding stages are provided at a plurality of predetermined intermediate temperatures, the temperature in the at least one holding stage being kept constant for a predetermined period, in particular from 30 minutes to 1200 minutes. In particular, the at least one intermediate temperature is from 450 °C to 900 °C, preferably from 700 °C to 800 °C.

According to a further development of the invention, it is provided that the raw magnet is magnetized after sintering in a magnetization device by means of a magnetization magnetic field with a magnetic field strength of 1 Tesla to 6 Tesla, preferably 2.5 Tesla to 3 Tesla, whereby a permanent magnet is obtained. In one embodiment, the magnetization magnetic field in the magnetization device is applied to the raw magnet as a pulse, in particular as a short-term pulse. The method is in particular a method for producing a permanent magnet.

According to a further development of the invention, it is provided that the magnetization magnetic field which is generated by means of the magnetization device is analogous to the magnetic field externally applied to the raw form.

In the context of the present technical teaching, the fact that the magnetization magnetic field is analogous to the externally applied magnetic field means that the two magnetic fields differ only by a shrinkage factor that occurs during sintering, in particular from 10% to 25%; in particular, the magnetization magnetic field is smaller than the externally applied magnetic field by the shrinkage factor. In particular, the magnet segments with constant magnetic orientation also differ by the shrinkage factor.

The invention also includes a raw magnet, in particular a permanent magnet, which is produced by means of a method according to the invention or by means of a method according to one or more of the previously described embodiments.

The invention further includes a use of such a raw magnet, in particular such a permanent magnet, in a device selected from a group consisting of an electric motor, a loudspeaker, a microphone, a generator, a hard disk drive, and a sensor.

The invention also includes a device selected from a group consisting of an electric motor, a loudspeaker, a microphone, a generator, a hard disk drive, and a sensor, wherein the device has a permanent magnet which is created by means of a method according to the invention or a method according to one or more of the previously described embodiments.

• 1 ein Flussdiagramm eines Ausführungsbeispiels eines Verfahrens zur Herstellung eines Rohmagneten,
• 2 ein Flussdiagramm eines ersten Ausführungsbeispiels zur schichtweisen Herstellung einer Rohform des Rohmagneten,
• 3 ein Flussdiagramm eines zweiten Ausführungsbeispiels zur schichtweisen Herstellung der Rohform des Rohmagneten,
• 4 eine schematische Darstellung eines ersten Ausführungsbeispiels einer Magnetisierungsvorrichtung,
• 5 eine schematische Darstellung eines zweiten Ausführungsbeispiels der Magnetisierungsvorrichtung,
• 6 eine schematische Darstellung eines dritten Ausführungsbeispiels der Magnetisierungsvorrichtung,
• 7 eine schematische Darstellung eines Halbach-Array als Rohmagnet, und
• 8 eine schematische Darstellung eines Ausführungsbeispiels eines mehrpoligen Rohmagneten.

The invention is explained in more detail below with reference to the drawing, in which:

• 1 a flow chart of an embodiment of a method for producing a raw magnet,
• 2 a flow chart of a first embodiment for the layer-by-layer production of a raw form of the raw magnet,
• 3 a flow chart of a second embodiment for the layer-by-layer production of the raw form of the raw magnet,
• 4 a schematic representation of a first embodiment of a magnetization device,
• 5 a schematic representation of a second embodiment of the magnetization device,
• 6 a schematic representation of a third embodiment of the magnetization device,
• 7 a schematic representation of a Halbach array as a raw magnet, and
• 8 a schematic representation of an embodiment of a multipole raw magnet.

1 shows a flow chart of an embodiment of a method for producing a raw magnet 1.

In a first step a), a magnetic starting material 3 is mixed with a binder 5, whereby a mixture 7 of the magnetic starting material 3 and the binder 5 is obtained.

In a preferred embodiment, in the first step a), the magnetic starting material 3 is mixed with the binder 5 and a solvent 11, whereby the mixture 7 of the magnetic starting material 3, the binder 5 and the solvent 11 is obtained. Alternatively, in the first step a), the magnetic starting material 3 is mixed with the binder 5 and at least one surfactant 12, whereby the mixture 7 of the magnetic starting material 3, the binder 5 and the at least one surfactant 12 is obtained. Alternatively, in the first step a), the magnetic starting material 3 is mixed with the binder 5, the solvent 11 and the at least one surfactant 12, whereby the mixture 7 of the magnetic starting material 3, the binder 5, the solvent 11 and the at least one surfactant 12 is obtained.

In particular, the mixture 7 comprises the magnetic starting material 3 and the binder 5. Alternatively, the mixture 7 consists of the magnetic starting material 3 and the binder 5. Alternatively, the mixture 7 comprises the magnetic starting material 3, the binder 5 and the solvent 11. Alternatively, the mixture 7 consists of the magnetic starting material 3, the binder 5 and the solvent 11. Alternatively, the mixture 7 comprises the magnetic starting material 3, the binder 5 and the at least one surfactant 12. Alternatively, the mixture 7 consists of the magnetic starting material 3, the binder 5 and the at least one surfactant 12. Alternatively, the mixture 7 comprises the magnetic starting material 3, the binder 5, the solvent 11 and the at least one surfactant 12. Alternatively, the mixture 7 consists of the magnetic starting material 3, the binder 5, the solvent 11 and the at least one surfactant 12. Alternatively or additionally, the mixture 7 has a temperature of room temperature, in particular from 15 °C to 30 °C, to 200 °C during layer-by-layer production of a raw form 9. Alternatively or additionally, the mass fraction of the magnetic starting material 3 in the mixture 7 is from 70% to 95%, in particular from 85% to 92%. Alternatively or additionally, the mass fraction of the binder 5 in the mixture 7 is from 1% to 15%, in particular from 8% to 10%. Alternatively or additionally, the mass fraction of the solvent 11 in the mixture 7 is from 4% to 25%, in particular 4% to 8%. Alternatively or additionally, the mass fraction of the at least one surfactant 12 in the mixture 7 is from 0.03% to 2.4%. Alternatively or additionally, a quotient of the mass fraction of the binder 5 and the mass fraction of the solvent 11 is from 1.5 to 2.5, in particular from 1.75 to 2.25, preferably from 1.9 to 2.1, in particular 2. In particular, the temperature of the mixture 7 and/or the mass fractions of the mixture 7 are selected such that the mixture 7 is flowable and preferably has a viscosity of 10 mPa to 100,000 mPa.

In a first embodiment, the mass fraction of the magnetic starting material 3 is from 85% to 92% and the mass fraction of the binder 5 is from 8% to 15%.

In a second embodiment, the mass fraction of the magnetic starting material 3 is from 77% to 88%, the mass fraction of the binder 5 is from 8% to 15% and the mass fraction of the solvent 11 is from 4% to 8%. In particular, the mass fraction of the at least one surfactant 12 is from 0.03% to 2.4%.

In particular, a material which comprises particles of an R _x T _y B alloy is used as the magnetic starting material 3. In one embodiment, a material which consists of particles of an R _x T _y B alloy is used as the magnetic starting material 3. In particular, a material which comprises particles of an Nd _x Fe _y B alloy or consists of particles of an Nd _x Fe _y B alloy is used as the magnetic starting material 3.

In particular, the binder 5 comprises at least one polymer selected from a group consisting of polyethylene glycol, polyvinyl acetate, polyvinyl alcohol, polybutyl acrylate, polybutyl methacrylate, polyvinylpyrrolidone, polymethyl methacrylate, polyvinyl butyral, paraffin wax, and a combination of at least two of the preceding polymers. In one embodiment, a polymer selected from a group consisting of polyethylene glycol, polyvinyl acetate, polyvinyl alcohol, polybutyl acrylate, polybutyl methacrylate, polyvinylpyrrolidone, polymethyl methacrylate, polyvinyl butyral, paraffin wax, and a combination of at least two of the preceding polymers is used as the binder 5. Paraffin wax is particularly preferably used as the binder.

In particular, the solvent 11 comprises at least one compound selected from a Group consisting of an alcohol, in particular ethanol, methanol, and isopropanol, a ketone, in particular acetone, an ester, in particular ethyl acetate, an aromatic compound, in particular benzene, toluene, xylene, an alkane, in particular n-hexane, n-heptane, cyclohexane, an organic solvent, and a combination of at least two of the preceding compounds. In one embodiment, a compound selected from a group consisting of an alcohol, in particular ethanol, methanol, and isopropanol, a ketone, in particular acetone, an ester, in particular ethyl acetate, an aromatic compound, in particular benzene, toluene, xylene, an alkane, in particular n-hexane, n-heptane, cyclohexane, an organic solvent, and a combination of at least two of the preceding compounds is used as the solvent 11.

In particular, the at least one surfactant 12 is a compound selected from a group consisting of an anionic surfactant, a cationic surfactant, a nonionic surfactant, an amphoteric surfactant, a fatty acid, in particular stearic acid, a salt of a fatty acid, in particular sodium stearate, polysorbate 20, polysorbate 40, polysorbate 60, polysorbate 65, and polysorbate 80.

In a second step b), the mixture 7 is filled layer by layer into a negative mold 19, wherein the raw mold 9 having a plurality of layers 17 is produced layer by layer from the mixture 7. An external magnetic field is applied to at least one layer 17 of the raw mold 9.

Preferably, the atmosphere in which the raw form 9 is produced layer by layer has a pressure of 900 mbar absolute to 1100 mbar absolute, or normal pressure under standard conditions, in particular approximately 1013 mbar absolute. In particular, the raw form 9 is produced layer by layer under a currently prevailing ambient pressure. Alternatively or additionally, the raw form 9 is produced in an atmosphere which has at least one inert gas, in particular helium, argon, and nitrogen. Alternatively, the raw form 9 is produced in an atmosphere which has an inert gas mixture of at least two inert gases. Alternatively, the raw form 9 is produced in an atmosphere which consists of at least one inert gas, in particular helium, argon, and nitrogen. Alternatively, the raw form 9 is produced in an atmosphere which consists of an inert gas mixture.

In one embodiment, the raw mold 9 is produced layer by layer by means of a process selected from a group consisting of ink-jet printing, filament printing, screen printing, and casting, in particular injection molding.

In particular, the layers 17 of the blank 9 with a layer thickness 37 - shown in 7 - from 5 µm to 1 mm, in particular from 50 µm to 100 µm. In this case, a volume of the mixture 7 is calculated in particular from the layer thickness 37 and a layer area measured orthogonal to the layer thickness 37, which is then filled into the negative mold 19 to form a layer 17 with the layer thickness 37.

In a third step c), the raw form 9 is sintered, whereby the raw magnet 1 is obtained. In particular, the raw form 9 is sintered in a vacuum. Alternatively, the raw form 9 is sintered in an atmosphere which has at least one process gas selected from a group consisting of argon and helium. Alternatively, the raw form 9 is sintered in an atmosphere which consists of at least one process gas selected from a group consisting of argon and helium. The atmosphere has a pressure in particular of 1·10 ^-6 mbar absolute to 1300 mbar absolute, in particular of 1·10 ^-3 mbar absolute to 1300 mbar absolute. Alternatively or additionally, the raw form 9 is sintered at a sintering temperature of 950 °C to 1200 °C, in particular of 1000 °C to 1100 °C.

In one embodiment, the externally applied magnetic field is generated by a switchable electromagnet and/or a permanent magnet. In particular, the externally applied magnetic field is generated by means of a magnetization device 23 - shown in the 4 to 6 - generated.

In an optional fourth step d), the raw mold 9 - in particular before sintering in the third step c) - or the raw magnet 1 - in particular after sintering in the third step c) - is formed from the negative mold 19.

In one embodiment, the raw mold 9 or the raw magnet 1 is formed by dismantling the negative mold 19 into partial negative molds. Alternatively, the raw mold 9 is formed by pressing it out of the negative mold 19. Alternatively, the raw mold 9 is formed by thermally decomposing the negative mold 19. Alternatively, the raw mold 9 is formed by chemically decomposing the negative mold 19.

In one embodiment, the raw form 9 is formed by thermal decomposition of the negative form 19 in an atmosphere that contains hydrogen and/or at least one inert gas, in particular helium, argon, and nitrogen. Alternatively, the raw form 9 is formed by thermal decomposition of the Negative mold 19 is formed in an atmosphere consisting of hydrogen and/or at least one inert gas, in particular helium, argon and nitrogen. Alternatively or additionally, the forming is carried out at a pressure of 10 mbar absolute to 1100 mbar absolute. Alternatively or additionally, the raw mold 9 is formed at a forming temperature of 250 °C to 750 °C.

In an optional fifth step e), the raw mold 9 is debindered - in particular before sintering in the third step c). In particular, the fifth step e) is carried out after the fourth step d), so that the raw mold 9 is debindered after being removed from the negative mold 19. Alternatively, the fourth step d) and the fifth step e) are carried out simultaneously. Alternatively, the fourth step d) is carried out after the fifth step e), in particular when the raw magnet 1 is removed from the mold after sintering in the third step c).

In one embodiment, the raw form 9 is at least partially, in particular completely, debindered. During debinding, the binder 5 is at least partially, in particular completely, removed from the raw form 9. In one embodiment, the debinding is carried out as solvent debinding - in particular as solvent extraction. Alternatively, the debinding is carried out as thermal debinding, wherein the raw form 9 is completely debindered by heating. Alternatively, the raw form 9 is pre-debindered by solvent debinding - in particular solvent extraction - wherein the raw form 9 is partially debindered by means of the debinding solvent. The remaining binder 5 is then completely removed by means of thermal debinding. Alternatively, the binder 5 in the raw form 9 is chemically split by means of a chemical reaction. The split binder 5 is then completely removed from the raw form 9 by means of thermal debinding.

In an optional seventh step f), the raw magnet 1 is magnetized after sintering in a magnetization device by means of a magnetization magnetic field with a magnetic field strength of 1 Tesla to 6 Tesla, preferably 2.5 Tesla to 3 Tesla, whereby a permanent magnet 21 is obtained. In particular, the magnetization magnetic field which is generated by means of the magnetization device is selected analogously to the magnetic field externally applied to the raw form 9.

2 and 3 show flow charts of a first and second embodiment for the layer-by-layer production of the raw form 9 of the raw magnet 1.

In one embodiment, the negative mold 19 is produced in the first second step b1) or the fifth second step b5) by means of a method selected from a group consisting of ink-jet printing, filament printing, screen printing, stereolithography, layer lamination, casting, in particular injection molding, machining, forming, in particular thermoforming, and plastic 3D printing.

In a second step b2), a first layer 17.1 of the mixture 7 is first filled into the negative mold 19 - in particular into a first negative mold layer 15.1 of the negative mold 19.

In a third second step b3), a first external magnetic field is at least partially applied to the first layer 17.1. In particular, the second second step b2) and the third second step b3) are carried out simultaneously. Alternatively, the third second step b3) is carried out after the second second step b2).

In a fourth second step b4), the first layer 17.1 is dried.

If all layers 17 of the raw form 9 have been created, the production of the raw form 9 is completed. Otherwise, the second steps b1) to b4) or b2) to b4) are carried out again.

In particular, in the second second step b2), a second layer 17.2 of the mixture 7 is filled into the negative mold 19 - in particular into a second negative mold layer 15.2 of the negative mold 19 - on top of the first dried layer 17.1. Optionally, in the third second step b3), a second external magnetic field is at least partially applied to the second layer 17.2. Furthermore, in the fourth second step b4), the second layer 17.2 is dried.

In one embodiment, at least one layer 17 of the plurality of layers 17 of the raw form 9 is dried in the fourth second step b4) for a drying time of 15 seconds to 2 minutes, in particular 1 minute. In particular, the drying time is selected depending on the layer thickness 37 and the layer area, wherein the drying time increases with increasing layer thickness 37 and/or the drying time can decrease with decreasing layer thickness 37. In particular, in the fourth second step b4), the at least one layer 17 of the plurality of layers 17 of the raw form 9 is dried by means of a blower, infrared radiation, and/or under reduced pressure or vacuum.

In particular, the negative form 19 is formed in a first second step b1) or a fifth second step b5) is made from a polymer. In particular, the negative mold 19 has a polymer or consists of a polymer. In particular, the polymer is selected from a group consisting of paraffin wax, epoxy resin, polyurethane, silicone, polylactide, polypropylene, acrylonitrile-butadiene-styrene, methacrylate, polyethylene, polyethylene glycol, polyvinyl alcohol and polyvinyl acetate. Preferably, the negative mold 19 is made from polyethylene glycol, polyvinyl alcohol or polyvinyl acetate. Alternatively, the negative mold 19 has at least one polymer selected from a group consisting of polyethylene glycol, polyvinyl alcohol, polyvinyl acetate and a combination of the previous polymers. Alternatively, the negative mold 19 consists of at least one polymer selected from a group consisting of polyethylene glycol, polyvinyl alcohol, polyvinyl acetate and a combination of the previous polymers. Alternatively, the negative mold 19 is made from a ceramic. In particular, the negative mold 19 has a ceramic or consists of a ceramic. In particular, the ceramic is selected from a group consisting of aluminum oxide, zirconium oxide and yttrium oxide.

In 2 In the first second step b1), the negative mold 19 is produced layer by layer and alternating in time with the layer-by-layer production of the raw mold 9.

In particular, before the production of the first layer 17.1 of the raw mold 9, the first negative mold layer 15.1 of the negative mold 19 is produced. Then, in the second second step b2), the first layer 17.1 of the mixture 7 is filled into the negative mold 19. In particular, the volume of the mixture 7 for the first layer 17.1 is calculated from the layer height of the first negative mold layer 15.1 and the layer area. After the third second step b3) and the fourth second step b4), the second negative mold layer 15.2 of the negative mold 19 is produced. Then, in the second second step b2), the second layer 17.2 of the mixture 7 is filled into the negative mold 19.

In 3 in the fifth second step b5), the negative mold 19 is produced before the layer-by-layer production of the raw mold 9. In one embodiment, the negative mold 19 is produced layer-by-layer. Alternatively or additionally, the negative mold 19 consists of at least two, preferably a plurality of partial negative molds, wherein individual partial negative molds are produced individually and wherein the negative mold 19 is produced by joining, in particular reversibly joining, the at least two partial negative molds, in particular the plurality of partial negative molds.

4 , 5 and 6 show schematic representations of a first, second and third embodiment of the magnetization device 23.

The magnetization device 23 is shown in connection with the blank mold 9, which is arranged in the negative mold 19. The magnetization device 23 and the blank mold 9 are shown in a plan view of a layer 17 of the blank mold, wherein the layer thickness 37 is orthogonal to the plane of the drawing and the layer surface lies in an x-y plane.

The layer 17 of the raw form 9 is divided into a grid with a plurality of grid fields 29, wherein at least one grid field 29, in particular a plurality of grid fields 29, is assigned an orientation of the particles of the magnetic starting material 3, which result from the application of the external magnetic field to the grid field 29, by means of an arrow 31.

For a clearer presentation, only three grid fields 29 and three arrows 31 are provided with reference symbols.

In 4 the magnetization device 23 has an arm extension 25 with a magnetization unit 27, wherein the magnetization unit 27 is arranged in the arm extension 25 so as to be rotatable about at least one axis. To apply the external magnetic field to the raw mold 9, the arm extension 25 is arranged and in particular displaced over the layer 17 of the raw mold 9. In particular, a planar extent of the magnetization unit 27 is smaller than the layer surface of the layer 17, so that the at least one layer is only partially exposed to the external magnetic field. In one embodiment, the layer 17 is treated in a grid-like manner by means of the magnetization unit 27. In particular, the magnetization unit 27 is rotated relative to the arm extension 25 between the treatment of individual grid fields 29 of the layer 17, so that different grid fields 29 of the layer 17 are exposed to different magnetic field orientations of the magnetization unit 27.

In particular, eight grid fields 29 have an alignment of the particles of the magnetic starting material 3, with a total of five different alignments being realized. Furthermore, a majority of grid fields 29 have no alignment of the particles of the magnetic starting material 3, since these grid fields 29 have not been and/or have not yet been treated by means of the magnetization device 23, in particular have not been subjected to an external magnetic field.

In 5 the magnetization device 23 has the arm extension 25 with a plurality of magnetization units 27, wherein at least one magnetization unit 27 of the plurality of magnetization units 27 is arranged in the arm extension 25 so as to be rotatable about at least one axis. Analogous to 4 To apply the external magnetic field to the raw form 9, the arm extension 25 is arranged over the layer 17 of the raw form 9. In particular, a planar extent of the plurality of magnetization units 27 is smaller than the layer surface of the layer 17, so that the layer 17 is only partially exposed to the external magnetic field. In one embodiment, the layer 17 is treated in a grid-like manner by means of the plurality of magnetization units 27. In particular, at least one magnetization unit 27 of the plurality of magnetization units 27 is rotated relative to the arm extension 25 between the treatment of individual grid fields 29 of the layer 17, so that different grid fields 29 of the layer 17 are exposed to different magnetic field orientations of the magnetization units 27.

Analogous to 4 In particular, eight grid fields 29 have an alignment of the particles of the magnetic starting material 3, with a total of five different alignments being realized. Furthermore, a majority of grid fields 29 have no alignment of the particles of the magnetic starting material 3, since these grid fields 29 have not been and/or have not yet been treated by means of the magnetization device 23, in particular have not been subjected to an external magnetic field.

In 6 the magnetization device 23 is designed as a roller 33, wherein the roller 33 in particular has a plurality of magnetization units 27. In particular, the magnetization units 27 are arranged such that at least two magnetization units 27 have different magnetic field orientations 35. During the treatment of the layer 17, the magnetization device 23 designed as a roller 33 is rolled over the layer 17 - in particular in the x-direction.

7 shows a schematic representation of a Halbach array as a raw magnet 9 in an xz-plane, with the layer thickness 37 aligned in the z-direction.

The raw mold 9 is arranged in the negative mold 19 and furthermore the magnetization device 23 is arranged on a third layer 17.3 of the raw mold 9.

The raw form 9 has three layers 17 in the z-direction and each layer 17 is divided into a plurality of grid fields 29, wherein an external magnetic field was applied to the plurality of grid fields 29 of the first layer 17.1 and the third layer 17.3 in order to align the particles of the magnetic starting material 3. The alignment of the particles of the magnetic starting material 3 is shown by means of the arrows 31. The second layer 17.2 was not subjected to an external magnetic field during the production of the raw form 9.

For a clearer presentation, only three grid fields 29 and three arrows 31 are provided with reference symbols.

8 shows a schematic representation of an embodiment of a multi-pole raw magnet 9 in a plan view - in particular the xy plane - and a side view - in particular the xz plane.

Analogous to the 4 to 7 the raw magnet 9 is divided into a plurality of grid fields 29, wherein in a plurality of grid fields 29 the particles of the magnetic starting material 3 have an orientation which is shown by means of the arrows 31.

For a clearer presentation, only three grid fields 29 and three arrows 31 are provided with reference symbols.

In the top view in 8 a) the alignments of the grid fields 29 are designed such that the raw magnet 9 has a south pole at the top and bottom in the y-direction and a north pole at the left and right in the x-direction.

In the side view in 8 b) the four layers 17 of the raw magnet 9 are shown. The alignment of the grid fields 29 is designed such that the first layer 17.1 and the third layer 17.3 each have a south pole on the left and right in the x-direction. Furthermore, the alignment of the grid fields 29 is designed such that the second layer 17.2 and a fourth layer 17.4 each have a north pole on the left and right in the x-direction.

The arrows 31 in the first layer 17.1 and the third layer 17.3, which are shown in the positive x-direction in the second and fourth grid fields 29, are orthogonal to the drawing plane and point into the drawing plane. The arrows 31 in the second layer 17.2 and the fourth layer 17.4, which are shown in the positive x-direction in the second and fourth grid fields 29, are orthogonal to the drawing plane and point out of the drawing plane.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• US 2013/0263699 A1 [0019]
• DE 198 43 883 C1 [0019]

Claims (15)

Method for producing a raw magnet (1), wherein - a magnetic starting material (3) is mixed with a binder (5), whereby a mixture (7) of the magnetic starting material (3) and the binder (5) is obtained, whereby - the mixture (7) is filled layer by layer into a negative mold (19), whereby a raw mold (9) having a plurality of layers (17) is produced layer by layer from the mixture (7), whereby - an external magnetic field is applied to at least one layer (17) of the raw mold (9), whereby - the raw mold (9) is sintered, whereby the raw magnet (1) is obtained. procedure according to claim 1 , wherein a material comprising particles of an R _x T _y B alloy is used as the magnetic starting material (3). Method according to one of the preceding claims, wherein as the binder (5) a polymer selected from a group consisting of polyethylene glycol, polyvinyl acetate, polyvinyl alcohol, polybutyl acrylate, polybutyl methacrylate, polyvinyl pyrrolidone, polymethyl methacrylate, polyvinyl butyral, paraffin wax, and a combination of at least two of the preceding polymers is used. Method according to one of the preceding claims, wherein the magnetic starting material (3) and the binder (5) are additionally mixed with a solvent (11) to form the mixture (7). Method according to one of the preceding claims, wherein as the solvent (11) a compound selected from a group consisting of an alcohol, in particular ethanol, methanol, and isopropanol, a ketone, in particular acetone, an ester, in particular ethyl acetate, an aromatic compound, in particular benzene, toluene, xylene, an alkane, in particular n-hexane, n-heptane, cyclohexane, an organic solvent, and a combination of at least two of the preceding compounds is used. Method according to one of the preceding claims, wherein in the mixture (7) the mass fraction - of the magnetic starting material (3) is from 70% to 95%, and/or - of the binder (5) is from 1% to 10%, and/or - of the solvent (11) is from 4% to 25%, and/or - of at least one surfactant (12) is from 0.03% to 2.4%. Method according to one of the preceding claims, wherein the layers (17) of the raw form (9) are produced with a layer thickness (37) of 5 µm to 1 mm, preferably of 50 µm to 100 µm. Method according to one of the preceding claims, wherein the external magnetic field is generated by a magnetization device (23), wherein the magnetization device (23) preferably has at least one magnetization unit (27). Method according to one of the preceding claims, wherein - a first layer (17.1) of the mixture (7) is filled into the negative mold (19), wherein - a first external magnetic field is applied at least partially to the first layer (17.1), wherein - the first layer (17.1) is dried, wherein - a second layer (17.2) of the mixture (7) is filled into the negative mold (19) onto the first dried layer (17.1), wherein - the second layer (17.2) is dried, wherein - preferably before the drying of the second layer (17.2), a second external magnetic field is applied at least partially to the second layer (17.2). Method according to one of the preceding claims, wherein at least one layer (17) of the plurality of layers (17) is dried by means of a blower, infrared radiation, and/or under reduced pressure or vacuum. Method according to one of the preceding claims, wherein the negative mold (19) a) is produced before the layer-by-layer production of the raw mold (9), or b) is produced layer-by-layer and in time alternating with the layer-by-layer production of the raw mold (9). Method according to one of the preceding claims, wherein the negative mold (19) is made of a polymer, in particular paraffin wax, epoxy resin, polyurethane, silicone, polylactide, polypropylene, acrylonitrile-butadiene-styrene, methacrylate, polyethylene, polyethylene glycol, polyvinyl alcohol and polyvinyl acetate, or a ceramic, in particular aluminum oxide, zirconium oxide and yttrium oxide. Method according to one of the preceding claims, wherein the negative mold (19) is produced by means of a method selected from a group consisting of ink-jet printing, filament printing, screen printing, stereolithography, layer lamination, casting, in particular injection molding, machining, forming, in particular thermoforming, and plastic 3D printing. Method according to one of the preceding claims, wherein the raw mold (9) is formed from the negative mold (19) before sintering, in particular by means of thermal and/or chemical decomposition of the negative mold (19). Method according to one of the preceding claims, wherein the raw mold (9) is debindered before sintering and in particular after removal from the negative mold (19).

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