WO2024094823A1

WO2024094823A1 - Process for producing a raw magnet

Info

Publication number: WO2024094823A1
Application number: PCT/EP2023/080615
Authority: WO
Inventors: Johannes MAURATH
Original assignee: Mimplus Technologies Gmbh & Co. Kg
Priority date: 2022-11-04
Filing date: 2023-11-02
Publication date: 2024-05-10
Also published as: DE102022129227A1

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

MIMplus Technologies GmbH & Co. KG

DESCRIPTION

Process for producing a raw magnet

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 .

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 in order to prevent permanent damage to the permanent magnet.

Permanent magnets from the rare earth group, especially neodymium-iron-boron magnets, have a temperature-dependent coercive field strength, with the coercive field strength decreasing as the temperature increases. Permanent magnets with a high coercive field strength are therefore preferred for industrial applications, especially in applications where high temperatures can occur, especially in electric motors.

A first possibility for increasing the coercive field strength is to add at least one additional rare earth element, in particular at least one "heavy" rare earth element, such as dysprosium and/or terbium. The disadvantage of this is that these elements are very expensive and at the same time reduce the remanence of the permanent magnet.

A second possibility for increasing the coercive field strength in relation to a comparable permanent magnet is to produce a structure that is finer-grained than the comparable permanent magnet. Such a structure can be realized in particular by using a starting powder that is finer-grained than a Starting powder of the comparable permanent magnet. The disadvantage is that such a fine-grained powder, especially with a grain size < 5 pm, is on the one hand very difficult to produce in terms of process technology and on the other hand very difficult to process, especially since the fine-grained powder easily oxidizes and thus becomes unusable.

A third possibility for increasing the coercive field strength is a suitable heat treatment, especially for permanent magnets that are produced by sintering. The disadvantage of this is that the coercive field strength can only be increased to a very limited extent.

A grain boundary diffusion process can also be used. Sintered raw forms are coated 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 contamination. 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 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.

In addition, a powder mixing process, known as powder blending, can be used. In this process, different powders are mixed together to produce the raw forms for NdFeB permanent magnets. The 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 in the area of the grain boundary. The disadvantage of such powder mixing processes is that the different powders tend to agglomerate due to Van der Waals forces and/or magnetic attraction, which is why mixing is difficult and local inhomogeneities can arise. This makes it difficult to make optimal use of the heavy rare earth elements.

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. A raw form is then produced from the mixture. The raw form is further treated with a dispersion which has at least one dispersant and a disperse phase, whereby a treated raw form is obtained. At least one first substance, selected from the dispersant and the disperse phase, has an alloy additive for the raw magnet. The treated raw form is then sintered, whereby the raw magnet is obtained.

Advantageously, the method makes it possible to introduce the first substance, in particular the alloy additive, into the raw form in an economical and evenly distributed manner. The economical introduction of the first substance, in particular the alloy additive, reduces the cost of the raw magnet in the case of expensive and rare alloy additives. In addition, 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 alloy additive, diffuses into the raw form between particles of the magnetic starting material, in particular along grain boundaries between the particles. In addition, it is advantageously possible for the first substance, in particular the alloy additive, to diffuse into the particles of the magnetic starting material, whereby the coercive field strength also increases, in particular in the case of heavy rare earth elements as the alloy additive.

In particular, the dispersion consists of at least one dispersant and the disperse phase.

In particular, the at least one first substance is the alloy additive. In particular, the at least one first substance consists of the alloy additive.

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, 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.

The method is advantageously suitable for a powdered magnetic starting material 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. Alternatively or additionally, the method is suitable for recycled magnetic material and/or for contaminated recycled magnetic material. In addition, material which is obtained by recycling is preferably alloyed with at least one rare earth element, preferably in powder form, to improve its properties.

The magnetic starting material is in particular present in a pure form or in a hydrogenated form. The US patent application US 2013/0263699 Al and the 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.

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.

Preferably, 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.

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

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

In one embodiment, the binder has 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 framework polymer, wherein the framework 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 framework polymer has a solubility in the solvent that is less than 1 g/liter. In addition, the framework polymer preferably does not swell in the solvent used for pre-debinding. As a result, the framework polymer advantageously stabilizes the raw form until the raw form is sintered. In particular, the binder has a further base polymer, a further framework polymer, and/or a dispersant as a third binder component.

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 alignment of the particles of the magnetic starting material.

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.

In particular, polyethylene, in particular LDPE, is used as the at least one framework 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.

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

In particular, a colloidal dispersion is used as the dispersion.

In particular, a stable dispersion is used. In the context of the present technical teaching, a stable dispersion is characterized in that the disperse phase, in particular the alloy additive for the raw magnet, sediments very slowly in the earth's gravitational field, in particular only after at least one hour, or not at all.

In one embodiment, the raw form is treated at least twice, in particular more than twice, with the dispersion. 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 has a first alloy additive and the second dispersion has a second alloy additive, wherein the first alloy additive and the second alloy 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.

In particular, blank shapes with a wall thickness of 0.4 mm to a maximum of 10 mm are produced and treated with the dispersion. In particular, the raw magnet is magnetized by means of a magnetic field, in particular by means of a magnetic pulse, whereby a permanent magnet is obtained. Preferably, the magnetic field, in particular the magnetic pulse, 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.

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. Preferably, a material which consists of particles of an R _x T _y B alloy is used as the magnetic starting material. In particular, preferably, 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.

Preferably, a material is used as the magnetic starting material which has 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, a material is used as the magnetic starting material which has particles of an Nd x Fe y B alloy and particles of a neodymium-rich phase or consists of such particles. In particular, the magnetic starting material preferably 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 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. The rare earth element is preferably neodymium. In a preferred 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.

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, 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. Preferably, the neodymium-rich phase comprises NdFE and/or NdEhj or consists of NdEE and/or NdFE. Alternatively, in a preferred embodiment, it is possible for the rare earth-rich phase, in particular the neodymium-rich phase, to consist of at least one rare earth element, in particular neodymium, or of a chemical compound of this rare earth element, in particular neodymium.

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.

According to a further development of the invention, an external magnetic field is applied to the raw mold during the production of the raw mold. Alternatively or additionally, an external magnetic field is applied to the raw mold after the production of the raw mold. Dipoles of the magnetic starting material are advantageously aligned in a parallel orientation by means of the externally applied magnetic field during production and/or after the production of the raw mold.

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

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

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 while the blank is being produced. Preferably, the magnetic starting material of the blank is hard magnetic. In particular, the blank is only applied to the blank during the production of the blank. external magnetic field is applied. In particular, the external magnetic field is not applied to the blank mold after the blank mold has been manufactured.

In a further embodiment, the external magnetic field is applied to the raw mold after the raw mold has been produced. In particular, the external magnetic field is only applied to the raw mold after the raw mold has been produced. In particular, the external magnetic field is not applied to the raw mold during the production of the raw mold.

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

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

According to a development of the invention, it is provided that the raw form is pre-debindered before treatment with the dispersion. Alternatively or additionally, the raw form is pre-debindered during treatment with the dispersion. Alternatively or additionally, the treated raw form is debindered before sintering. In particular, during the pre-debindering, soluble binder components are dissolved out of the raw form, whereby the raw form advantageously has an at least partially open-pored surface, in particular is completely open-pored. In particular, a porosity of the raw form 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 framework polymer of the binder remains in the raw form after the pre-debindering. The framework polymer advantageously increases the mechanical stability of the raw form.

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 alloy additive, into the raw form. Furthermore, it is advantageously possible for the dispersion, in particular of the first substance, in particular of the alloy additive, to diffuse freely in the raw form during an optional subsequent heat treatment.

In particular, the pre-debinding is carried out as solvent debinding. If the treatment with the dispersion is carried out after the pre-debinding, the raw form has an open-pore structure and the dispersion can easily enter the pore channels of the raw form.

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 alloy additive, diffuses into the pore channels of the raw form.

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

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.

According to a further development of the invention, it is provided that the raw mold is pre-debindered for a predetermined period of time, with a predetermined pressure and with a predetermined temperature.

In particular, the predetermined temperature is at least as high as the 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 less than a boiling point of the solvent used in the pre-debinding at the predetermined pressure.

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.

In particular, the predetermined duration is at least 1 hour and at most 72 hours. According to a further development of the invention, it is provided that the treated raw form is dried before sintering.

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

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

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 disperse 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.

If a heavy rare earth element is used as an alloy additive, especially as the first substance, 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.

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

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

If a gallium compound, in particular a gallium-rare earth element compound, in particular alloy, is used as an alloy 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.

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.

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

According to a further development of the invention, it is provided that 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, a volume fraction of the first substance in the dispersion is at least 1% to at most 70%.

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 grinding process - in particular as a sub-step of the process - in order to produce the particles with a particle size of at least 0.001 pm to at most 30 pm. Preferably, the grinding process is carried out by means of a device selected from a group consisting of a jet mill, a ball mill and an attritor mill.

According to a further development of the invention, it is provided that the raw form is treated with the dispersion 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. Advantageously, the pre-debindered and thus particularly open-pored raw form is infiltrated with the dispersion.

In one embodiment, the raw form is immersed in the dispersion such that the raw form is completely surrounded by the dispersion. In particular, the dispersion comprises the alloy additive and a solvent. In particular, the dispersion consists of the alloy additive and a solvent. In particular, the raw form is immersed in the dispersion for a period of at least 1 second to a maximum of 24 hours, in particular surrounded by the dispersion.

In a further embodiment, the raw form is coated with the dispersion, in particular an entire surface of the raw form is coated with the dispersion. In particular, the raw form is sprayed and/or coated with the dispersion. In particular, the dispersion comprises the alloy 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 alloy 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 raw form is sprayed with the dispersion for a period of at least 1 second to a maximum of 30 seconds.

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.

In one embodiment of the method, the raw form is produced by injection molding a mixture which comprises the magnetic starting material and the in particular organic binder. Alternatively, the raw form is produced by injection molding a mixture which consists of the magnetic starting material and the in particular organic binder.

In a further embodiment of the method, the blank form is produced by wet pressing a magnetic starting material. In 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 raw form is preferably dried before sintering.

According to a development of the invention, it is provided that the treated raw form is sintered in a vacuum. Alternatively, the treated raw form is sintered in an atmosphere which has at least one process gas selected from a group consisting of argon and helium. Alternatively, the treated raw form is sintered in an atmosphere which consists of 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, are alloyed with the alloy additive, and the magnetic properties of the raw magnet, in particular the coercive field strength, are consequently increased.

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.

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 at least 1 10' ³ mbar to at most 200 mbar above ambient pressure. In the context of the present technical teaching, a helium atmosphere is understood in particular to mean a gas that consists of pure helium and impurities of at most 5 vol.%.

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 impurities of at most 5 vol.%.

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 impurities of at most 5 vol.%. In particular, the raw form is sintered at a sintering temperature of at least 950 °C to at most 1200 °C, preferably at least 1000 °C to at most 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 at least 0.1 K/min to at most 10 K/min. During heating of the treated raw form, 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, the temperature in the at least one holding stage being kept constant for a predetermined period, 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 _y B particles, are pre-alloyed with the alloy additive. In one embodiment of the process, the holding steps improve the diffusion of the alloy addition along the grain boundaries or the surface of the magnetic starting material into the interior of the blank.

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.

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.

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.

The invention is explained in more detail below with reference to the drawing. Fig. 1 is a flow chart of an embodiment of a method for producing a raw magnet, and

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

Figure 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 particular, a material which comprises particles of an R _x T _y B alloy is used as the magnetic starting material 3. Alternatively, a material which consists of particles of an R _x T _y B alloy is used as the magnetic starting material 3. Alternatively, 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.

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.

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

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

In a third step c), the raw form 9 is treated with a dispersion 11 which comprises at least one dispersant and a disperse phase, whereby a treated raw form 13 is obtained. Alternatively, in the third step c), the raw form 9 is treated with a dispersion 11 which consisting of at least one dispersant and the disperse phase, whereby the treated raw form 13 is obtained.

At least one first substance 15, selected from the dispersant and the disperse phase, comprises an alloy 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 alloy additive.

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.

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

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

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 _y B 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 has the first substance 15 as particles with a particle size of at least 0.001 pm to at most 30 pm. Alternatively or additionally, a volume fraction of the first substance 15 in the dispersion 11 is at least 1% to at most 70%.

In particular, a second substance 17 of the dispersion 11, selected from the dispersant and the disperse 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, paraffin oil, acetone, isopropanol, ethanol, and an organic solvent is used as the solvent.

In particular, the raw form 9 is pre-debindered in the third step c), in particular during the treatment with the dispersion 11. In particular, the raw form 9 is pre-debindered for a predetermined period of time, at a predetermined pressure and at a predetermined temperature.

Optionally, the third step c) is carried out at least twice, in particular several times. The raw form 9 is thus treated at least twice, in particular several 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 has a first first substance and the second dispersion has a second first substance, wherein the first first substance and the second first substance are different.

In a fourth step d), the treated raw form 13 is sintered, whereby the raw magnet 1 is obtained. In particular, the treated raw form 13 is sintered in a vacuum. Alternatively, the treated raw form 13 is sintered in an atmosphere which comprises at least one process gas selected from a group consisting of argon and helium.

In an optional manufacturing step carried out after the fourth step d), the raw magnet is magnetized by means of a magnetic field, in particular by means of a magnetic pulse, whereby a permanent magnet is obtained. Preferably, the magnetic field, in particular the magnetic pulse, has a magnetic flux density of at least 2 Tesla, particularly preferably at least 3 Tesla.

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 the treatment of the raw mold 9 with the dispersion 11, an external magnetic field is applied to the raw mold 9.

In an optional first sixth step fl), 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 the treatment with the dispersion 11. Preferably, the first sixth step fl) is carried out after the fifth step e). However, it is also possible to carry out the first sixth step fl) before or simultaneously with the fifth step e).

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.

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

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.

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

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

Figure 2 a) shows the mixture 7 of the magnetic starting material 3, preferably of an RxTyB alloy, in particular of an Nd _x Fe _y B alloy, and the in particular 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.

Figure 2 b) shows the raw form 9 after the preliminary debinding, in particular the at least partial removal of the organic binder 5. In particular, during the preliminary 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, after the preliminary debinding, a framework polymer 19 of the binder 5 remains in the raw form 9.

For a clearer illustration, 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 into the pores of the raw form 9.

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.

Figure 2 d) shows the treated raw form 13, in particular after drying 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.

Figure 2 e) shows the raw magnet 1 after sintering. The particles of the magnetic starting material 3 are aggregated to form grains 21, in particular R _x T _y B grains.

Grains 21 are each particularly enclosed by the first substance 15.

Claims

EXPECTATIONS

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), whereby

- the raw form (9) is treated with a dispersion (11) which comprises at least one dispersant and a disperse phase, wherein at least one first substance (15) selected from the dispersant and the disperse phase comprises an alloy 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 comprises particles of an R _x T _y B 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 blank mold (9) during and/or after the production of the blank 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 blank (13) is debound before sintering.

5. Method according to one of the preceding claims, wherein the blank mold (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 (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),

- a second substance (17) of the dispersion (11), selected from the dispersant 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, paraffin oil, 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 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. Method according to one of the preceding claims, wherein the raw 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 raw 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, is sintered.