Process for producing a raw magnet

Abstract

The invention relates to a process for producing a raw magnet (1), wherein – a magnetic starting material (3) is mixed with a binder (5) to obtain a mixture (7) of the magnetic starting material (3) and the binder (5), wherein – a blank form (9) is produced from the mixture (7), wherein – the blank form (9) is treated with a dispersion (11) including at least one dispersant and a disperse phase, where at least one first substance (15) selected from the dispersant and the disperse phase includes an alloying addition for the raw magnet (1), to obtain a treated blank form (13), wherein – the treated blank form (13) is sintered to obtain the raw magnet (1).

Description

[0001] MIMplus Technologies GmbH & Co. KG

[0002] DESCRIPTION

[0003] Process for producing a raw magnet

[0004] The invention relates to a method for producing a raw magnet.

[0005] Permanent magnets made from raw magnets from the rare earth group are used in a wide variety 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 / m² 3 on.

[0006] Particularly in industrial applications, permanent magnets must have the highest possible coercive field strength. The coercive field strength indicates how strong an opposing magnetic field to which the permanent magnet is exposed can be to prevent permanent damage to the permanent magnet.

[0007] Permanent magnets from the rare earth group, especially neodymium-iron-boron magnets, exhibit a temperature-dependent coercive field strength, with the coercive field strength decreasing with increasing temperature. Therefore, permanent magnets with a high coercive field strength are preferred in industrial applications, especially those where high temperatures can occur, especially in electric motors.

[0008] A first possibility for increasing the coercive field strength is to alloy at least one additional rare earth element, especially at least one "heavy" rare earth element, such as dysprosium and / or terbium. The disadvantage is that these elements are very expensive and also reduce the remanence of the permanent magnet.

[0009] A second possibility for increasing the coercive field strength relative to a comparable permanent magnet is to produce a microstructure with a finer grain than that of the comparable permanent magnet. Such a microstructure can be achieved, in particular, by using a starting powder with a finer grain than the starting powder of the comparable permanent magnet. The disadvantage of this is that such a finer-grained powder, especially with a grain size < 5 pm, is both very difficult to produce and very difficult to process, particularly since the finer-grained powder is easily oxidized and thus rendered unusable.

[0010] A third option for increasing coercive field strength is suitable heat treatment, especially for permanent magnets produced by sintering. The disadvantage of this is that it only allows for a very limited increase in coercive field strength.

[0011] A grain boundary diffusion process can also be used. This involves coating sintered blanks with a dispersion of active substances either directly after the sintering process, after a grinding or wire-cutting process, or after a post-treatment process with acids to remove surface contaminants. These active substances contain at least one heavy rare earth element, which diffuses into the permanent magnet along the grain boundaries during a subsequent heat treatment process. The disadvantage of this process is that the diffusion process is slow, and therefore only permanent magnets with a wall thickness of 5 mm or less can be treated economically.

[0012] In addition, a powder blending process can be used. This involves mixing different powders to produce the raw forms for NdFeB permanent magnets. These powders have different proportions of heavy rare earth elements and different particle sizes. During sintering of the raw forms, the heavy rare earth elements accumulate near the grain boundary. A disadvantage of such powder blending processes is that the different powders tend to agglomerate due to van der Waals forces and / or magnetic attraction. This makes mixing challenging and can lead to local inhomogeneities. This makes it difficult to optimally utilize the heavy rare earth elements.

[0013] 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 aforementioned disadvantages, particularly with regard to the permanent magnet to be produced, are at least partially remedied, preferably avoided. This object is achieved by providing the present technical teaching, in particular the teaching of the independent claims and the embodiments disclosed in the dependent claims and the description.

[0014] 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, resulting in a mixture of the magnetic starting material and the binder. A raw form is then produced from the mixture. Furthermore, the raw form is treated with a dispersion comprising at least one dispersant and a disperse phase, resulting in a treated raw form. At least one first substance, selected from the dispersant and the disperse phase, comprises an alloying additive for the raw magnet. The treated raw form is then sintered, resulting in the raw magnet.

[0015] Advantageously, the method makes it possible to introduce the first substance, in particular the alloying additive, into the raw form in an economical and evenly distributed manner. The economical introduction of the first substance, in particular the alloying additive, reduces the cost of the raw magnet in the case of expensive and rare alloying additives. Furthermore, the magnetic properties of the raw magnet, in particular the coercive field strength, are advantageously improved, in particular increased, compared to conventionally manufactured magnets. Furthermore, the method makes it possible to treat raw forms with a wall thickness of up to 40 mm. Advantageously, the first substance, in particular the alloying additive, diffuses between particles of the magnetic starting material, in particular along grain boundaries between the particles, into the raw form.In addition, it is advantageously possible for the first substance, in particular the alloying additive, to diffuse into the particles of the magnetic starting material, whereby the coercive field strength also increases, particularly in the case of heavy rare earth elements as the alloying additive.

[0016] In particular, the dispersion consists of at least one dispersing agent and the disperse phase.

[0017] In particular, the at least one first substance is the alloying additive. In particular, the at least one first substance consists of the alloying additive.

[0018] The first substance of the dispersion or the alloying additive is in particular selected from a group consisting of a rare earth element, in particular a heavy rare earth element, in particular dysprosium, terbium, holmium, and a light rare earth element, in particular praseodymium, neodymium, an oxide of a rare earth element, a hydride of a rare earth element, a nitride of a rare earth element, a carbide of a rare earth element, a halide of a rare earth element, a copper-rare earth element compound, an aluminum-rare earth element compound, a zirconium-rare earth element compound, a gallium-rare earth element compound, an R x T y B alloy with a heavy rare earth element, a dysprosium-cobalt compound, a dysprosium-terbium-cobalt compound, and a terbium-cobalt compound.

[0019] The process is advantageously suitable for a powdered magnetic starting material formed from a newly melted alloy, in particular in the form of a cast ingot or in the form of melt-spun material. Alternatively or additionally, the process is suitable for recycled magnetic material and / or for contaminated recycled magnetic material. In addition, material obtained through recycling is preferably alloyed with at least one rare earth element, preferably in powder form, to improve its properties.

[0020] The magnetic starting material is present, in particular, in a pure form or in a hydrogenated form. US patent application US 2013 / 0263699 A1 and German patent DE 198 43 883 CI describe a process called hydrogen decrepitation (HD) for producing a hydrogenated form of the magnetic starting material by means of hydrogen-induced decay.

[0021] Preferably, the magnetic starting material is mechanically comminuted, in particular by grinding, to a particle size of 1 pm to 200 pm in order to obtain the powdered magnetic starting material.

[0022] Preferably, the magnetic starting material is not partially or completely dehydrated after milling 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 milling.

[0023] In one embodiment of the process, the mixture has a volume fraction of at least

[0024] 45% to a maximum of 75% of the magnetic starting material and a volume fraction of at least 25% to a maximum of 55% of the binder. The binder preferably contains at least one organic binder component.

[0025] In one embodiment, the binder comprises at least two, in particular at least three, binder components. In particular, a first binder component of the at least two binder components is a base polymer, wherein the base polymer is in particular soluble in a solvent used for pre-debinding and / or is decomposable by an acid used for pre-debinding. Furthermore, a second binder component of the at least two binder components is a backbone polymer, wherein the backbone polymer is in particular not or only very poorly soluble in the solvent used for pre-debinding and / or is not decomposable by the acid used for pre-debinding. In particular, the backbone polymer has a solubility in the solvent of less than 1 g / liter. In addition, the backbone polymer preferably does not swell in the solvent used for pre-debinding.The framework polymer thus advantageously stabilizes the raw mold until the raw mold is sintered. In particular, the binder comprises another base polymer, another framework polymer, and / or a dispersant as a third binder component.

[0026] In particular, the binder comprises at least one substance selected from a group consisting of polyoxymethylene, polypropylene, paraffin wax, polyethylene, and polyamide. Polyoxymethylene, polypropylene, paraffin wax, polyethylene, and polyamide are advantageously thermoplastics and are therefore suitable for producing the blank mold. Furthermore, the at least one substance selected from a group consisting of polyoxymethylene, polypropylene, paraffin wax, polyethylene, and polyamide facilitates the alignment of the particles of the magnetic starting material.

[0027] In particular, the binder consists of at least one substance selected from a group consisting of polyoxymethylene, polypropylene, paraffin wax, polyethylene and polyamide, and at least one backbone polymer.

[0028] In particular, polyethylene, in particular LDPE, is used as the at least one backbone polymer. Alternatively or additionally, a wax, in particular paraffin wax, is used as the base polymer. Alternatively or additionally, a surfactant, in particular stearic acid, is used as the dispersant. In particular, at least one non-polar organic solvent selected from a group consisting of n-heptane, n-hexane, and cyclohexane is used for the pre-debinding. Alternatively or additionally, at least one polar organic solvent selected from a group consisting of acetone, isopropanol, and ethanol is used for the pre-debinding. Alternatively or additionally, at least one acid selected from a group consisting of nitric acid, acetic acid, and oxalic acid is used for the pre-debinding.

[0029] In one embodiment, the binder comprises polyethylene, in particular LDPE, as the backbone polymer, wax, in particular paraffin wax, as the base polymer, and a surfactant, in particular stearic acid, as the dispersant. Furthermore, a non-polar organic solvent, in particular n-heptane, is used for pre-debinding.

[0030] In particular, a colloidal dispersion is used as the dispersion.

[0031] In particular, a stable dispersion is used. In the context of the present technical teaching, a stable dispersion is characterized by the fact that the disperse phase, in particular the alloy additive for the raw magnet, settles very slowly in the Earth's gravitational field, in particular only after at least one hour, or does not settle at all.

[0032] In one embodiment, the raw form is treated with the dispersion at least twice, in particular more than twice. Alternatively, the raw form is first treated at least once with a first dispersion and then at least once with a second dispersion, wherein the first dispersion and the second dispersion are different from one another. In particular, the first dispersion comprises a first alloying additive and the second dispersion comprises a second alloying additive, wherein the first alloying additive and the second alloying additive are different from one another. Alternatively or additionally, the treated raw form is treated with a further substance, in particular a liquid, in particular before sintering. In particular, the raw form is treated in a plurality of treatment steps with a plurality of - in particular different - dispersions and / or a plurality of - in particular different - further substances.

[0033] In particular, blanks with a wall thickness of 0.4 mm to a maximum of 10 mm are produced and treated with the dispersion. In particular, the blank magnet is magnetized using a magnetic field, in particular using a magnetic pulse, to produce a permanent magnet. The magnetic field, in particular the magnetic pulse, preferably has a magnetic flux density of at least 2 Tesla, particularly preferably at least 3 Tesla. In particular, the method, including this step, is a method for producing a permanent magnet.

[0034] According to a further development of the invention, it is provided that a material is used as the magnetic starting material which contains particles of an R x T y B alloy. Preferably, the magnetic starting material used is a material consisting of particles of an R x T yB alloy. In particular, a material containing particles of a Nd x Fe y B alloy or from particles of a Nd x Fe y B alloy.

[0035] Preferably, the magnetic starting material used is a material which contains particles of an R x T y B alloy and particles of a rare earth-rich phase. In particular, the magnetic starting material preferably consists of a mixture of particles of an R x T y B alloy and particles of a rare earth-rich phase. Preferably, the magnetic starting material used is a material which comprises particles of a NdxFeyB alloy and particles of a neodymium-rich phase or consists of such particles. In particular, the magnetic starting material preferably comprises a mixture of particles of a Nd x Fe yB alloy and particles of a neodymium-rich phase or consists of such a mixture.

[0036] 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 each other such that either only iron or only cobalt or any iron-cobalt mixture is present. Preferably, the rare earth element is neodymium. In a preferred embodiment, the R x T y B alloy additionally contains 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 traces.

[0037] Preferably, the magnetic starting material comprises particles of a Nd2Fei4B alloy or consists of particles of a Nd2Fei4B alloy. Preferably, 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, preferably contains at least one further element of the R x T y B alloy, especially Nd x Fe yB alloy. Alternatively or additionally, the at least one rare earth element, in particular neodymium, is present in a hydrogenated form. The neodymium-rich phase preferably comprises NdFe and / or NdEhj or consists of NdEE and / or NdFE. Alternatively, in a preferred embodiment, 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.

[0038] The rare earth-rich phase preferably forms a phase in the structure of the raw magnet and, in particular, in the structure of the permanent magnet obtained from the raw magnet, which is located at grain boundaries of the structure.

[0039] According to a further development of the invention, an external magnetic field is applied to the blank during its production. Alternatively or additionally, an external magnetic field is applied to the blank after its production. Advantageously, dipoles of the magnetic starting material are aligned in a parallel orientation by means of the externally applied magnetic field during and / or after the production of the blank.

[0040] Preferably, the magnetic field is applied to the blank before treating the blank with the dispersion.

[0041] Preferably, the externally applied magnetic field is generated by a switchable electromagnet and / or a permanent magnet.

[0042] In one embodiment, the blank is produced in the externally applied magnetic field. Advantageously, the particles of the magnetic starting material from which the blank is produced align themselves according to the externally applied magnetic field during the production of the blank. Preferably, the magnetic starting material of the blank is hard magnetic. In particular, the external magnetic field is applied to the blank only during the production of the blank. In particular, the external magnetic field is not applied to the blank after the production of the blank.

[0043] In a further embodiment, the external magnetic field is applied to the blank mold after the blank mold has been produced. In particular, the external magnetic field is applied to the blank mold only after the blank mold has been produced. In particular, the external magnetic field is not applied to the blank mold during the blank mold's production.

[0044] In a further embodiment, the external magnetic field is applied to the blank during and after the production of the blank.

[0045] Preferably, the blank mold is heated to a softening temperature of the mixture while the external magnetic field is applied.

[0046] According to a further development of the invention, the raw mold is pre-debindered before treatment with the dispersion. Alternatively or additionally, the raw mold is pre-debindered during treatment with the dispersion. Alternatively or additionally, the treated raw mold is debindered before sintering. In particular, soluble binder components are dissolved out of the raw mold during pre-debindering, whereby the raw mold advantageously has an at least partially open-pored surface, in particular is completely open-pored. In particular, a porosity of the raw mold of at least 30 vol%, preferably at least 40 vol%, preferably at least 50 vol%, particularly preferably at least 55 vol% to at most 60 vol% is obtained. Advantageously, the backbone polymer of the binder remains in the raw mold after pre-debindering. The backbone polymer advantageously increases the mechanical stability of the raw mold.

[0047] The at least partially open-pored surface and / or the open-pored structure of the raw form advantageously enables rapid and uniform penetration of the dispersion, in particular of the first substance, in particular of the alloying additive, into the raw form. Furthermore, it is advantageously possible for the dispersion, in particular of the first substance, in particular of the alloying additive, to diffuse freely in the raw form during an optional subsequent heat treatment.

[0048] In particular, pre-debinding is performed as a solvent debinding process. If the dispersion treatment is carried out after pre-debinding, the raw form has an open-pore structure, and the dispersion can easily penetrate into the pore channels of the raw form.

[0049] If the pre-debinding is carried out simultaneously with the treatment with the dispersion, soluble organic binder components are dissolved out of the raw form, while at the same time the first substance, in particular the alloying additive, diffuses into the pore channels of the raw form.

[0050] In a preferred embodiment of the process, the binder is at least partially removed from the raw mold by means of a particularly organic solvent, in particular by means of solvent extraction, or another chemical process. Alternatively or additionally, a residual portion of the binder is removed from the treated raw mold by means of thermal decomposition, in particular directly before sintering. Alternatively, a residual portion of the binder is removed from the treated raw mold by means of thermal decomposition during sintering.

[0051] In an alternative embodiment, the raw form is treated with the dispersion, in particular coated, before the raw form is pre-debindered and / or debindered.

[0052] According to a further development of the invention, it is provided that the raw form is pre-debindered for a predetermined period of time, at a predetermined pressure and at a predetermined temperature.

[0053] In particular, the predetermined temperature is at least as high as room temperature, in particular 25°C, in particular the predetermined temperature is at least 30°C. Alternatively or additionally, the predetermined temperature is at most so high that the predetermined temperature is at least 10°C lower than a boiling point of the solvent used in the pre-debinding at the predetermined pressure.

[0054] In particular, the predetermined pressure is at least 50 mbar below ambient pressure to at most 50 mbar above ambient pressure, preferably the predetermined pressure is almost identical, in particular identical, to the ambient pressure.

[0055] In particular, the predetermined duration is at least 1 hour and at most 72 hours. According to a further development of the invention, the treated blank form is dried before sintering.

[0056] In one embodiment, the blank form is dried after the first treatment with the dispersion and / or after the treatment with the first dispersion. In particular, the blank form is dried before the blank form is treated a second time with the dispersion and / or with the second dispersion.

[0057] In a further embodiment, the treated raw form is dried before the treated raw form is treated with the further substance.

[0058] According to a further development of the invention, a suspension or an aerosol is used as the dispersion. A second substance of the dispersion, selected from the dispersant and the dispersed phase, is in particular selected from a group consisting of a solvent, air, nitrogen, argon, and helium.The first substance of the dispersion is selected from a group consisting of a rare earth element, in particular a heavy rare earth element, in particular dysprosium, terbium, holmium, and a light rare earth element, in particular praseodymium, neodymium, an oxide of a rare earth element, a hydride of a rare earth element, a nitride of a rare earth element, a carbide of a rare earth element, a halide of a rare earth element, a copper-rare earth element compound, an aluminum-rare earth element compound, a zirconium-rare earth element compound, a gallium-rare earth element compound, an R. x T y B alloy with a heavy rare earth element, a dysprosium-cobalt compound, a dysprosium-terbium-cobalt compound, and a terbium-cobalt compound.

[0059] If a heavy rare earth element is used as an alloying additive, especially as the first element, the coercive field strength increases, as the heavy rare earth element accumulates at the grain boundary during sintering. Alternatively or additionally, the heavy rare earth element diffuses into the particles of the magnetic starting material, which also increases the coercive field strength.

[0060] If a copper compound, in particular a copper-rare earth element compound, in particular an alloy, or an aluminum compound, in particular an aluminum-rare earth element compound, in particular an alloy, is used as an alloying additive, in particular as the first substance, a layer thickness of the rare earth-rich phase increases, in particular during sintering, and thus the coercive field strength increases in particular.

[0061] If a zirconium compound, in particular a zirconium-rare earth element compound, in particular alloy, is used as an alloying additive, in particular as the first substance, grain growth is advantageously reduced and / or prevented, in particular during sintering.

[0062] If a gallium compound, in particular a gallium-rare earth element compound, in particular alloy, is used as an alloying additive, in particular as the first substance, the rare earth-rich phase has an amorphous structure, in particular after sintering, which advantageously increases the coercive field strength.

[0063] According to a further development of the invention, it is provided that a compound selected from a group consisting of cyclohexane, n-hexane, n-heptane, paraffin oil, acetone, isopropanol, ethanol, and an organic solvent is used as the solvent.

[0064] In particular, a non-polar, especially organic solvent is used as the solvent.

[0065] According to a further development of the invention, the dispersion comprises the first substance as particles with a particle size of at least 0.001 pm to at most 30 pm. Alternatively or additionally, the volume fraction of the first substance in the dispersion is at least 1% to at most 70%.

[0066] In particular, the first substance is present at the beginning of the process in particle form with a particle size of at least 0.001 pm to at most 30 pm. Alternatively, the first substance is processed by means of a milling process—in particular as a sub-step of the process—to produce the particles with a particle size of at least 0.001 pm to at most 30 pm. Preferably, the milling process is carried out using a device selected from a group consisting of a jet mill, a ball mill, and an attritor mill.

[0067] According to a further development of the invention, the raw form is treated with the dispersion by a method selected from a group consisting of spraying, in particular using a spray gun; coating, in particular using a brush and / or a roller; dipping; printing, in particular pad printing and / or screen printing; and slot die coating. Advantageously, the raw form, which has been pre-debindered and is thus particularly open-pored, is infiltrated with the dispersion.

[0068] In one embodiment, the blank mold is immersed in the dispersion such that it is completely surrounded by the dispersion. In particular, the dispersion comprises the alloying additive and a solvent. In particular, the dispersion consists of the alloying additive and a solvent. In particular, the blank mold is immersed in the dispersion, in particular, encased in the dispersion, for a period of at least 1 second to a maximum of 24 hours.

[0069] In a further embodiment, the blank form is coated with the dispersion, in particular an entire surface of the blank form is coated with the dispersion. In particular, the blank form is sprayed and / or painted with the dispersion. In particular, the dispersion comprises the alloying additive and at least one gas selected from a group consisting of air and an inert gas, in particular nitrogen, argon, and helium. In particular, the dispersion consists of the alloying additive and at least one gas selected from a group consisting of air and an inert gas, in particular nitrogen, argon, and helium. In particular, the blank form is sprayed with the dispersion for a duration of at least 1 second to at most 30 seconds.

[0070] According to a further development of the invention, it is provided that the raw form is produced by means of a method selected from a group consisting of injection molding, in particular metal powder injection molding, additive manufacturing, extrusion, and wet pressing.

[0071] In one embodiment of the method, the blank mold is produced by injection molding a mixture comprising the magnetic starting material and the binder, in particular an organic one. Alternatively, the blank mold is produced by injection molding a mixture consisting of the magnetic starting material and the binder, in particular an organic one.

[0072] In a further embodiment of the process, the blank is produced by wet pressing a magnetic starting material. During wet pressing, an organic solvent, preferably a volatile non-polar and / or polar organic solvent, is used as a binder. The volatile non-polar and / or polar organic solvent is selected from a group consisting of an alcohol, an acyclic alkane, a cyclic alkane, a ketone, and a mixture of volatile organic substances that can serve as solvents. Ethanol or isopropanol is preferably used as the alcohol. Cyclohexane is preferably used as the cyclic alkane. Acetone is preferably used as the ketone. The mixture of volatile organic substances is preferably selected from a group consisting of petroleum, white spirit, and light petroleum. Furthermore, the blank is preferably dried before sintering.

[0073] According to a further development of the invention, the treated blank form is sintered in a vacuum. Alternatively, the treated blank form is sintered in an atmosphere comprising at least one process gas selected from a group consisting of argon and helium. Alternatively, the treated blank form is sintered in an atmosphere comprising at least one process gas selected from a group consisting of argon and helium. Advantageously, during sintering, the particles of the magnetic starting material, in particular the R x T y B particles, alloyed with the alloying additive, and the magnetic properties of the raw magnet, especially the coercive field strength, consequently increase.

[0074] In the context of the present technical teaching, a vacuum is understood to be an atmosphere which has a pressure of less than 1 - 10' 3 mbar absolute.

[0075] In particular, the blank is sintered in a helium atmosphere. Alternatively, the blank is sintered in an argon atmosphere. Alternatively, the blank 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 at least 1 10' 3 mbar to a maximum of 200 mbar above ambient pressure. In the context of the present technical teaching, a helium atmosphere is understood in particular to mean a gas consisting of pure helium and impurities of a maximum of 5 vol.%.

[0076] In the context of the present technical teaching, an argon atmosphere is understood in particular to mean a gas consisting of pure argon and impurities of a maximum of 5 vol.%.

[0077] In the context of the present technical teaching, an argon-helium atmosphere is understood in particular to mean a gas consisting of pure argon, pure helium, and impurities of no more than 5 vol. In particular, the raw form is sintered at a sintering temperature of at least 950 °C to at most 1200 °C, preferably of at least 1000 °C to at most 1100 °C.

[0078] In one embodiment, during sintering, the treated blank is heated from room temperature or a debinding temperature to the sintering temperature at a heating rate of at least 0.1 K / min to at most 10 K / min. During heating of the treated blank, a holding stage is preferably provided at at least one predetermined intermediate temperature, in particular holding stages are installed at a plurality of predetermined intermediate temperatures, wherein the temperature in the at least one holding stage is kept constant for a predetermined duration, preferably from at least 30 minutes to at most 1200 minutes. In particular, the at least one intermediate temperature is from at least 450 °C to at most 900 °C, preferably from at least 700 °C to at most 800 °C. Advantageously, in the at least one holding stage, the particles of the magnetic starting material, in particular the R x T yB particles, pre-alloyed with the alloying additive. In one embodiment of the process, the holding stages improve the diffusion of the alloying additive along the grain boundaries or the surface of the magnetic starting material into the interior of the blank.

[0079] The invention also includes a raw magnet - in particular a permanent magnet obtained after magnetization of the raw 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.

[0080] The invention further includes a use of 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.

[0081] 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.

[0082] The invention is explained in more detail below with reference to the drawings, in which: Fig. 1 shows a flow diagram of an embodiment of a method for producing a raw magnet, and

[0083] Fig. 2 is a schematic representation of the embodiment for producing the raw magnet.

[0084] Figure 1 shows a flow chart of an embodiment of a method for producing a raw magnet 1.

[0085] 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.

[0086] In particular, a material is used as the magnetic starting material 3 which contains particles of an R x T y B alloy. Alternatively, a material consisting of particles of an R x T y B alloy. Alternatively, a material containing particles of a Nd x Fe y B alloy or particles of a Nd x Fe y B alloy.

[0087] Preferably, the mixture 7 has a volume fraction of at least 40% to at most 75% of the magnetic starting material 3 and a volume fraction of at least 25% to at most 55% of the binder 5. The binder 5 preferably has at least one organic binder component.

[0088] In a second step b), a blank mold 9 is produced from the mixture 7. In particular, the blank mold 9 is produced by a process selected from a group consisting of injection molding, in particular metal powder injection molding, additive manufacturing, extrusion, and wet pressing.

[0089] In particular, an external magnetic field is applied to the raw mold 9 in the second step b), in particular during the production of the raw mold 9.

[0090] In a third step c), the raw form 9 is treated with a dispersion 11 comprising at least one dispersant and a disperse phase, thereby obtaining a treated raw form 13. Alternatively, in the third step c), the raw form 9 is treated with a dispersion 11 comprising at least one dispersant and the disperse phase, thereby obtaining the treated raw form 13.

[0091] At least one first substance 15, selected from the dispersant and the disperse phase, comprises an alloying additive for the raw magnet 1. In particular, the at least one first substance 15, selected from the dispersant and the disperse phase, consists of the alloying additive.

[0092] In particular, in step c) the raw form 9 is treated with the dispersion 11 by a method selected from a group consisting of spraying, in particular by means of a spray gun, coating, in particular by means of a brush and / or a roller, dipping, printing, in particular pad printing and / or screen printing, and slot die coating.

[0093] In particular, a colloidal and / or stable dispersion is used as dispersion 11.

[0094] In particular, a suspension or an aerosol is used as dispersion 11.

[0095] In particular, the first substance 15 of the dispersion 11 is selected from a group consisting of a rare earth element, in particular a heavy rare earth element, in particular dysprosium, terbium, holmium, and a light rare earth element, in particular praseodymium, neodymium, an oxide of a rare earth element, a hydride of a rare earth element, a nitride of a rare earth element, a carbide of a rare earth element, a halide of a rare earth element, a copper-rare earth element compound, an aluminum-rare earth element compound, a zirconium-rare earth element compound, a gallium-rare earth element compound, an R x T yB alloy with a heavy rare earth element, a dysprosium-cobalt compound, a dysprosium-terbium-cobalt compound, and a terbium-cobalt compound. Alternatively or additionally, the dispersion 11 comprises the first substance 15 as particles with a particle size of at least 0.001 pm to at most 30 pm. Alternatively or additionally, the volume fraction of the first substance 15 in the dispersion 11 is at least 1% to at most 70%.

[0096] In particular, a second substance 17 of the dispersion 11, selected from the dispersant and the dispersed phase, is selected from a group consisting of a solvent, air, nitrogen, argon, and helium. In particular, a compound selected from a group consisting of cyclohexane, n-hexane, n-heptane, liquid paraffin, acetone, isopropanol, ethanol, and an organic solvent is used as the solvent.

[0097] In particular, the raw mold 9 is pre-debindered in the third step c), especially during treatment with the dispersion 11. In particular, the raw mold 9 is pre-debindered for a predetermined duration, at a predetermined pressure, and at a predetermined temperature.

[0098] Optionally, the third step c) is performed at least twice, in particular multiple times. Thus, the raw form 9 is treated at least twice, in particular multiple times, with the dispersion 11 and / or with different dispersions 11, in particular a first dispersion and a second dispersion. In particular, the first dispersion comprises a first substance and the second dispersion comprises a second substance, wherein the first substance and the second substance are different.

[0099] In a fourth step d), the treated blank 13 is sintered, yielding the raw magnet 1. In particular, the treated blank 13 is sintered in a vacuum. Alternatively, the treated blank 13 is sintered in an atmosphere containing at least one process gas selected from a group consisting of argon and helium.

[0100] In an optional manufacturing step carried out after the fourth step d), the raw magnet is magnetized using a magnetic field, in particular a magnetic pulse, to produce a permanent magnet. The magnetic field, in particular the magnetic pulse, preferably has a magnetic flux density of at least 2 Tesla, particularly preferably at least 3 Tesla.

[0101] In an optional fifth step e), after the second step b), in particular after the production of the raw mold 9, and before the third step c), in particular from the treatment of the raw mold 9 with the dispersion 11, an external magnetic field is applied to the raw mold 9.

[0102] In an optional first sixth step (f1), the raw form 9 is pre-debindered after the second step (b), in particular after the production of the raw form 9, and before the third step (c), in particular before treatment with the dispersion 11. Preferably, the first sixth step (f1) is carried out after the fifth step (e). However, it is also possible to carry out the first sixth step (f1) before or simultaneously with the fifth step (e).

[0103] In an optional second sixth step f2), the treated raw form 13 is debindered, in particular thermally debindered, before the fourth step d), in particular before sintering.

[0104] In an optional first seventh step gl), the treated blank 13 is dried before the fourth step d), in particular before sintering.

[0105] In an optional second seventh step g2), the treated raw form 13 is dried before a renewed third step c), in particular before a renewed treatment with the dispersion 11 and / or a treatment with a further dispersion 11.

[0106] Figure 2 shows a schematic representation of the embodiment for producing the raw magnet 1.

[0107] Identical and functionally identical elements are provided with the same reference symbols in all figures, so that reference is made to the preceding description in each case.

[0108] In Figure 2 a), the mixture 7 is made of the magnetic starting material 3, preferably of an RxTyB alloy, in particular of an Nd x Fe yB alloy, and the particularly organic binder 5. The blank form 9 is produced from the mixture 7 by means of a process, preferably selected from a group consisting of injection molding, additive manufacturing, extrusion, and wet pressing.

[0109] Figure 2 b) shows the raw form 9 after pre-debinding, in particular the at least partial removal of the organic binder 5. In particular, during pre-debinding, soluble binder components of the binder 5 are dissolved out of the raw form 9, whereby the raw form 9 has an at least partially open-pored surface, in particular is completely open-pored. In particular, a framework polymer 19 of the binder 5 remains in the raw form 9 after pre-debinding.

[0110] For clarity, only one particle of the magnetic starting material 3 is provided with a reference symbol. Figure 2 c) shows the raw form 9 during treatment with the dispersion 11. In particular, the raw form 9 in Figure 2 c) is infiltrated with the dispersion 11, so that the dispersion 11 penetrates the pores of the raw form 9.

[0111] For a clearer illustration, only one particle of the magnetic starting material 3 and only one framework polymer 19 are provided with a reference symbol.

[0112] Figure 2 d) shows the treated raw form 13, particularly after drying of the treated raw form 13. The first substance 15 is embedded in particle form between the particles of the magnetic starting material 3 and the framework polymer 19.

[0113] Figure 2 e) shows the raw magnet 1 after sintering. The particles of the magnetic starting material 3 are deposited into grains 21, in particular R x T y B grains, together. The

[0114] Grains 21 are each enclosed in particular by the first substance 15.

Claims

CLAIMS 1. 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 - a raw form (9) is produced from the mixture (7), wherein - the raw form (9) is treated with a dispersion (11) comprising at least one dispersing agent and a disperse phase, wherein at least one first substance (15) selected from the dispersing agent and the disperse phase comprises an alloying additive for the raw magnet (1), whereby a treated raw form (13) is obtained, wherein - the treated raw form (13) is sintered to obtain the raw magnet (1).

2. The method according to claim 1, wherein as the magnetic starting material (3) a material is used which contains particles of an R x T yB alloy and preferably particles of a rare earth rich phase.

3. Method according to one of the preceding claims, wherein an external magnetic field is applied to the raw mold (9) during and / or after the production of the raw mold (9).

4. Method according to one of the preceding claims, wherein - the raw form (9) is pre-debindered before and / or during treatment with the dispersion (11), and / or - the treated raw form (13) is debound before sintering.

5. Method according to one of the preceding claims, wherein the blank form (9) is pre-debindered for a predetermined duration, at a predetermined pressure and at a predetermined temperature.

6. Method according to one of the preceding claims, wherein the treated blank form (13) is dried before sintering.

7. Method according to one of the preceding claims, wherein - a suspension or an aerosol is used as the dispersion (11), wherein - a second substance (17) of the dispersion (11), selected from the dispersing agent and the disperse phase, is selected from a group consisting of a solvent, air, nitrogen, argon, and helium, wherein - the first substance (15) is selected from a group consisting of a rare earth element, in particular a heavy rare earth element, in particular dysprosium, terbium, holmium, and a light rare earth element, in particular praseodymium, neodymium, an oxide of a rare earth element, a hydride of a rare earth element, a nitride of a rare earth element, a carbide of a rare earth element, a halide of a rare earth element, a copper-rare earth element compound, an aluminum-rare earth element compound, a zirconium-rare earth element compound, a gallium-rare earth element compound, an R x T y B- Alloy with a heavy rare earth element, a dysprosium-cobalt compound, a dysprosium-terbium-cobalt compound, and a terbium-cobalt compound.

8. A process according to any one of the preceding claims, wherein the solvent used is a compound selected from a group consisting of cyclohexane, n-hexane, n-heptane, liquid paraffin, acetone, isopropanol, ethanol, and an organic solvent.

9. Method according to one of the preceding claims, wherein - the dispersion (11) comprises the first substance (15) as particles with a particle size of at least 0.001 pm to at most 30 pm, and / or a volume fraction of the first substance (15) in the dispersion (11) is at least 1% to at most 70%. Method according to one of the preceding claims, wherein the blank form (9) is treated with the dispersion (11) by a method selected from a group consisting of spraying, in particular by means of a spray gun, coating, in particular by means of a brush and / or a roller, dipping, printing, in particular pad printing and / or screen printing, and slot die coating. Method according to one of the preceding claims, wherein the blank form (9) is produced by means of a method selected from a group consisting of injection molding, additive manufacturing, extrusion, and wet pressing. Method according to one of the preceding claims, wherein the treated blank form (13) is produced in a vacuum or in an atmosphere containing at least one process gas selected from a group consisting of argon and helium.

Images