EP4593040A1 - Method for producing soft magnetic core - Google Patents

Abstract

In a method for producing a soft magnetic core, at least one amorphous or semi-crystalline strip (3) made of a metallic alloy is wound around a winding axis, and the amorphous or semi-crystalline strip (3) is then introduced into a holding device (1). In addition, a pressing device (4) then exerts a mechanical compressive force on the wound amorphous or semi-crystalline strip (3), during which an electric current flows through the amorphous or semi-crystalline strip (3), which is heated by the electric current flow, and/or during which the amorphous or semi-crystalline strip (3) is heated by inductive heating, and/or during which the amorphous or semi-crystalline strip (3) is heated indirectly by means of a heating coil spaced apart from the amorphous or semi-crystalline strip (3), such that nanocrystalline grains are formed in the amorphous or semi-crystalline strip (3).

Description

The present invention relates to a method and a device for producing a soft magnetic core.

Soft magnetic materials are used in electrical machines to amplify and direct the magnetic flux. Unlike hard magnetic materials or permanent magnets, they are characterized by their easy remagnetization. The coercive field strength is crucial here, as it indicates the magnetic field strength at which by which a previously magnetized material is demagnetized. The lower the coercive field strength, the lower the magnetic reversal losses in the low-frequency range. At frequencies above 1 kHz, however, eddy current losses dominate, which depend on factors such as the specific electrical resistance of the material and the layer thickness of the soft magnetic material. To achieve a high power density of the component, the soft magnetic material used should also exhibit a high saturation polarization.

With the discovery of the so-called Finemet alloy (Fe-Si-B-Cu-Nb), a new group of soft magnetic materials was introduced: nanocrystalline alloys. These alloys are initially produced as thin amorphous ribbons using a rapid solidification process. They are then wound into toroidal cores. Heat treatment above the crystallization temperature results in the formation of nanometer-sized grains within an amorphous matrix. Due to this unique structure, nanocrystalline soft magnets exhibit one of the lowest coercive field strengths of all soft magnetic materials. However, the saturation polarization is reduced due to the non-ferromagnetic alloying elements, which are necessary for glass formation and to inhibit grain growth.

Therefore, research has intensified in recent years to identify glass-forming materials with a significantly higher proportion of ferromagnetic elements. These are intended to combine low coercive field strength with high magnetic saturation polarization in order to increase magnetic performance and thus minimize component size.

However, it has been shown that the absence of ferromagnetic alloying elements, which hinder grain growth, requires a significant reduction in the duration of the thermal influence during heat treatment. This means that a high heating rate is essential for the formation of nanocrystalline grains. However, heat treatment with a heating rate in the range of several Kelvin per second is not possible in a conventional furnace.

A further challenge is the rough surface of the strips (> 2 µm), which results in a fill factor of only about 80% for the toroidal cores. However, since the fill factor directly influences the power density, a reduced fill factor leads to a reduced power density of the resulting soft magnetic core.

To solve these problems, US 11,352,677 B2 A process for producing a soft magnetic material with both a high saturation polarization and a low coercive field strength, in which the amorphous ribbons are clamped between preheated copper blocks and heated at a heating rate of at least 10 K/s. However, the disadvantage of this process is that the throughput is very low due to the batch operation, making it suitable only for laboratory applications.

The present invention is therefore based on the object of proposing a method and a device for producing a soft magnetic core with a low coercive field strength, which can be used in an industrial environment.

This object is achieved according to the invention by a method for producing a soft magnetic core according to claim 1 and a device for producing a soft magnetic core according to claim 11. Advantageous embodiments and further developments are described in the dependent claims.

In a method for producing a soft magnetic core, at least one amorphous or semi-crystalline strip made of a metallic alloy is wound around a winding axis and then introduced into a holding device. Furthermore, a mechanical compressive force is exerted on the wound amorphous or semi-crystalline strip via a pressing device, wherein during the exertion of the compressive force, an electric current flows through the amorphous or semi-crystalline strip and the latter is heated by the electric current flow, so that nanocrystalline grains are formed in the amorphous or semi-crystalline strip. Alternatively or additionally, during the exertion of the compressive force The amorphous or semi-crystalline strip can be heated by inductive heating. In a further embodiment, it is alternatively or additionally possible to heat the amorphous or semi-crystalline strip indirectly while the compressive force is being applied, using a heating coil spaced apart from the amorphous or semi-crystalline strip.

For the purposes of this document, "soft magnetic" refers to any metallic alloy with a coercive field strength of less than 1 kA/m. Furthermore, "semi-crystalline" refers to any ribbon that already contains partially nanocrystalline grains, with a concentration of nanocrystalline grains of < 50 vol. Furthermore, "nanocrystalline" refers to an average grain diameter of less than or equal to 100 nm. Furthermore, a "ribbon" is defined as a flat and elongated strip, i.e., a length and width are greater than a thickness; preferably, the thickness of the ribbon is a maximum of 10 percent of the length and/or width. Furthermore, the heating of the amorphous or semi-crystalline ribbon is referred to below as heat treatment, and the application of the compressive force is referred to as compaction. This means that the compaction and heat treatment of the amorphous or semi-crystalline ribbon take place simultaneously, i.e., in parallel, in the process described above. Heating can be achieved directly by an electric current flowing through the strip, which enables high heating rates and is therefore advantageous for alloys with high saturation polarization. If lower heating rates are sufficient, inductive heating can also be used, in which no direct electric current flows through the strip, or indirect heating can be achieved by a heating coil, typically also carrying an electric current, which is spaced from the amorphous or semi-crystalline strip and thus not in direct, i.e., immediate contact with it.

Furthermore, it can be provided that the pressing device and the amorphous or semi-crystalline strip are introduced into the holding device.

By heating the amorphous or semi-crystalline ribbon by a direct electric current flow through the ribbon, the heating rate is in a range of up to 1000 K/min, resulting in an alloy with a medium Grain diameters in a range from 10 nm to 100 nm can be produced. The heating rate is preferably in a range from 100 K/min to 1000 K/min. In particular, the average grain diameter is in a range from 10 nm to 40 nm. The average grain diameter is particularly preferably in a range from 15 nm to 25 nm.

Furthermore, this process can be used to produce alloys with a magnetic saturation polarization in a range from 1 T to 2.2 T, particularly in a range from 1 T to 2 T. At the same time, the fill factor of the soft magnetic cores is controlled by precisely adjusting the mechanical compressive force. The pressure-induced buckling and viscous flow of the amorphous or semi-crystalline ribbons under additional temperature influence increases the fill factor, allowing soft magnetic cores to be produced with a fill factor in a range from 70 vol.% to 95 vol.% of the total volume of the magnetic core. "Buckling" refers to any permanent change in the shape of the windings of the amorphous or semi-crystalline ribbon that represents a deviation from the original shape or form of the winding. Increasing the maximum fill factor also directly increases the magnetic power density of the soft magnetic core. Compaction preferably takes place in a pressure range of < 1 GPa, particularly preferably < 100 MPa.

Furthermore, it can be provided that the metallic alloy is formed from Fe-B-X, in particular from Fe-Si-B-Cu or Fe-Si-B-P-Cu-(C) or Fe-Si-B-Mn. Here, X can comprise the elements Si and/or Co and/or Cu and/or P and/or Mn and/or Nb.

The variety of possible metallic alloys that can be used in the presented process makes it possible to cover a broad spectrum of applications. Furthermore, the process can be flexibly adapted to a wide variety of application tasks.

In addition, the mechanical compressive force can be applied axially along the winding axis of the amorphous or semi-crystalline ribbon.

Due to the axial application of the mechanical compressive force, the wound amorphous or semi-crystalline ribbon can easily buckle and flow viscously, thereby achieving improved compaction of the amorphous or semi-crystalline ribbon. Furthermore, the mechanical compressive force can act on both sides of the amorphous or semi-crystalline ribbon along the winding axis. The improved compaction can further increase the fill factor. Furthermore, compared to conventional soft magnetic cores, the axially acting mechanical compressive force induces a preferred magnetic direction that is aligned parallel to the winding axis of the soft magnetic core. The preferred magnetic direction can be determined by aligning the atoms in a preferred direction during heat treatment. This can introduce magnetic uniaxial anisotropy into the material.

Furthermore, the amorphous or semi-crystalline strip can be wound on a winding device, in particular a mandrel.

Among other things, the use of a winding device allows for the production of soft magnetic cores with various geometries. Furthermore, the winding device prevents the amorphous or semi-crystalline strip from breaking off in the radial direction perpendicular to the winding axis. Toroidal cores can be produced by simply winding or coiling the strips onto a mandrel. By cutting the toroidal cores, application-specific C, E, or U cores are also possible.

In addition, the amorphous or semi-crystalline tape can be coated with an electrically insulating layer before winding.

By applying an additional insulation layer prior to compaction, e.g., through sol-gel dip coating or thermal oxidation, the formation of contact points between the strip windings can be prevented. This prevents eddy currents, which increase energy losses, in later applications. The coating does not impede the flow of electrical current that heats the amorphous or semi-crystalline strip, since the insulation layer is parallel to the electrical current flow. Furthermore, the formation of an insulating layer between the windings of the amorphous or semi-crystalline strip increases the strength of the strip winding. This facilitates subsequent separation using wire sawing or waterjet cutting to produce cut strip cores. Applying the insulating layer can also enable the compaction of rapidly solidified strips made of brittle crystalline alloys such as Fe-6.5Si and Sendust alloy, typically comprising 85 wt.% (mass percent) iron, 9 wt.% silicon, and 6 wt.% aluminum. The electrically insulating layer can be applied to one or both sides.

In addition, the process can be carried out under vacuum or under a protective gas atmosphere.

By performing the process under vacuum or a protective gas atmosphere, oxidation of the amorphous or semi-crystalline ribbon can be prevented, thus altering the magnetic properties of the soft magnetic core. This process variant is therefore particularly advantageous when high purity of the magnetic cores is required. Alternatively, the process can also be performed under atmospheric conditions, i.e., in particular under standard conditions at 101325 Pa = 1.01325 bar = 1 atm in air.

In addition, after no mechanical compressive force is exerted on the band and no electrical current flows through the band, a fluid can flow around the band and/or the band can be formed from the holding device and the pressing device.

This makes it possible to cool the strip more quickly after heat treatment and compaction, significantly reducing the process time. Flowing a fluid around the strip is particularly advantageous when the process takes place under vacuum. In this case, the flow of a fluid can also be understood as "flooding the process chamber" with a fluid. Additionally, the force-applying electrodes can be water-cooled, allowing the cooling rate to be further increased.

In addition, the temperature of the amorphous or semi-crystalline ribbon can be controlled by a thermocouple and/or a pyrometer. The thermocouple continuously measures the temperature, and these measured values are processed via a connected control and regulation circuit. This makes it possible to adjust the temperature profiles, i.e., specific heating rates of the amorphous or semi-crystalline ribbon, or to keep the temperature constant over a longer period of time, i.e., to integrate hold times into the process.

It can also be provided that the shape of a hysteresis curve of the material of the amorphous or semi-crystalline ribbon, and thus of the ribbon itself, can be adjusted by the mechanical compressive force. This advantageously enables easy adjustment of certain magnetic properties, and the amorphous or semi-crystalline ribbon can be manufactured according to the desired properties.

A device for producing a soft magnetic core comprises a holding device configured to receive at least one amorphous or semi-crystalline strip made of a metallic alloy and wound around a winding axis. A pressing device configured to exert a mechanical compressive force on the wound amorphous or semi-crystalline strip is also provided. Furthermore, a current/voltage source ensures that an electrical current flows through the amorphous or semi-crystalline strip, so that nanocrystalline grains form in the amorphous or semi-crystalline strip. Alternatively or in addition to the direct current flow through the amorphous or semi-crystalline strip, an inductive heating device may also be provided, which is configured to heat the amorphous or semi-crystalline strip by inductive heating, so that nanocrystalline grains form in the amorphous or semi-crystalline strip. Alternatively or in addition to the two alternatives mentioned, the device can also have a heating coil spaced apart from the amorphous or semi-crystalline ribbon, which is designed to indirectly heat the amorphous or semi-crystalline ribbon so that nanocrystalline grains form in the amorphous or semi-crystalline ribbon. For this purpose, an electric current can flow through the heating coil.

The method is designed to be carried out with the described device, i.e. the device is suitable for carrying out the described method.

Embodiments of the invention are illustrated in the drawings and are described below with reference to Figures 1 and 2 described. Recurring features are provided with identical reference symbols.

• Fig. 1 eine schematische Darstellung einer Haltevorrichtung sowie einer Aufwicklungsvorrichtung mit einem gewickelten amorphen Band in einer Draufsicht und
• Fig. 2 eine schematische Zeichnung einer Vorrichtung zur Herstellung eines weichmagnetischen Kerns in einer frontalen Ansicht.

They show:

• Fig. 1 a schematic representation of a holding device and a winding device with a wound amorphous ribbon in a plan view and
• Fig. 2 a schematic drawing of a device for producing a soft magnetic core in a frontal view.

Fig. 1 depicts an amorphous strip 3 wound around a winding device 2, wherein the wound amorphous strip 3 is additionally placed in a holding device 1. Alternatively, the amorphous strip 3 can also be semi-crystalline. Here, the amorphous strip 3 is wound up until the outer diameter of the strip winding matches the outer diameter of a pressing device 4 (not shown here). The amorphous strip 3 is then cut off. Alternatively, the amorphous strip 3 can also be wound up and cut off in such a way that it does not abut the holding device 1. The amorphous strip 3 can therefore also be pressed if the outer diameter of the amorphous strip 3 is smaller than that of the pressing device 4. In this exemplary embodiment, the winding device 2 is designed as a mandrel. In this case, the mandrel prevents, among other things, the amorphous strip 3 from breaking out in the radial direction, i.e. perpendicular to the winding axis of the amorphous strip 3, during compaction.

Fig. 2 represents an amorphous band 3 wound in the holding device 1 around the winding device 2 during compaction. This means that in this embodiment, it is wound on both sides along the winding axis of the amorphous A mechanical compressive force is applied to the wound amorphous strip 3 by a pressing device 4. In this embodiment, the pressing device 4 is designed as an upper punch and lower punch, so that two-sided pressing occurs. Alternatively, it is also possible to apply the mechanical compressive force only on one side by a pressing device 4, for example, only by an upper punch or only by a lower punch. Furthermore, a current/voltage source 6 is connected to the punches in such a way that a current can flow through the amorphous strip. This is possible because the punches are designed to be in direct contact with the amorphous strip 3.

Thus, compaction and heat treatment can be summarized under the FAST/SPS process (FAST: "Field Assisted Sintering Technique", SPS: "Spark Plasma Sintering"). The FAST/SPS process is a uniaxial pressing process for metallic and ceramic powders under the influence of pressure and temperature. The pressure is typically less than 100 MPa, so graphite can be selected as the material for the pressing tool (corresponding here to pressing device 4). To enable higher pressures, hot-work tool steels, TZM alloys (typically comprising molybdenum, 0.50% titanium, 0.08% zirconium, and 0.01-0.04% carbon), or ceramic materials are also used for the tool. The temperature used depends on the material and can reach up to 2500 °C. The heating of the sample material and the compression tool is based on Joule heating, with a pulsed direct current flowing through the sample material and the compression tool. Due to the direct heating of the sample material, high heating rates of up to 1000 K/min can be achieved. This high heating rate enables the creation of special microstructures, especially for very small grains. This allows for short process cycles of less than one hour. This distinguishes FAST/SPS from conventional hot pressing, where compaction can take several hours.

In this embodiment, the pressing device 4 comprises two annular punches, allowing the production of toroidal cores with an outer diameter of 30 mm and an inner diameter of 20 mm. The inner diameter is determined by the diameter of the mandrel.

The shape of the pressing dies, i.e., the shape of the pressing device, can be round or oval for ring-shaped geometries, or square with rounded edges, allowing the production of toroidal cores, C-, E-, and U-shaped cores. The pressing dies can have a hole in the center. The mandrel provided for this purpose fits into this cavity. This mandrel, together with the holding device 1, which fits on the outside of the dies, prevents the amorphous strip 3 from subsequently breaking out in the radial direction during compaction. This means that the holding device 1 is arranged outside the pressing device 4, which has a cavity in the center to which the winding device 2 is complementary. This means that the winding device 2 can be guided into the cavity of the pressing device. Furthermore, the outer diameter of the wound amorphous strip 3 exactly corresponds to the outer diameter of the pressing device 4.

For the production of rectangular geometries for I-cores or circular segments, no mandrel, i.e., no winding device 2, is necessary. The material and geometry of the device are adapted to the soft magnetic core to be produced and the pressing conditions. Temperature control is achieved via a thermocouple 5 in a hole in the holding device 1, so that the temperature is measured near the amorphous strip 3. Alternatively, the thermocouple 5 can also be placed in a hole in one of the pressing dies.

Furthermore, in the present case, an amorphous strip 3 is used which has been coated on both sides. This means that the flat sides of the amorphous strip 3 are coated. Alternatively, it is also possible to coat only one flat side of the amorphous strip 3, i.e., to form a one-sided coating. The coating can be applied using any method in which at least one flat side of the amorphous strip 3 is completely and continuously covered. In particular, the coating can be produced by thermal oxidation or sol-gel dip coating in order to prevent an induced electrical current flow between the windings in the application. This additional insulation layer, applied before compaction, can prevent the formation of contact points between the strip windings. Thus, This prevents eddy currents, which increase energy losses, in subsequent applications. The coating does not impede the flow of electrical current used to heat the winding, as the insulation layer is parallel to the electrical current flow. Furthermore, the formation of a separating layer between the windings increases the strength of the strip winding.

In addition, rapidly solidified ribbons made of crystalline alloys, such as Fe-6.5Si and Sendust alloy, typically comprising 85 wt.% iron, 8-10 wt.% silicon, and 5-7 wt.% aluminum, can be compacted due to their insulation properties. These alloys have so far only been used as powders in dust cores. Due to their higher electrical resistance and lack of magnetostriction, both alloys are particularly suitable for high frequencies and noise-sensitive applications.

The process sequence described in this exemplary embodiment can therefore be summarized as follows: The coated, rapidly solidified amorphous strip 3 is wound onto the mandrel. The strip 3 is cut when the outer diameter of the strip winding matches the outer diameter of the pressing device 4 comprising an upper and a lower pressing die. The upper and lower pressing dies are then pushed onto the mandrel. The device is fully prepared when the holding device 1 is pushed over one of the pressing dies onto the winding, thus preventing radial breakage. Furthermore, in this exemplary embodiment, the device is located in a vacuum-sealed process chamber.

The wound amorphous strip 3 is then compacted, for example, at 25 MPa and a heating rate of 100 K/min until it reaches 400 °C. A fill factor of 90 vol.% is achieved. The wound amorphous strip 3 is then heat-treated at 520 °C for one hour, with the measurable maximum permeability being 550,000 and the magnetic saturation being above 1 T. This also makes it possible to incorporate application-specific holding times during the heat treatment. This can improve the strength of the coated strips. By switching off the current flow and thus stopping the heating of the amorphous strip 3, the originally amorphous strip 3, which becomes nanocrystalline after heating, cools down. Faster cooling is possible by flooding the process chamber to atmospheric pressure and removing the wound amorphous strip 3 from the device, ie, from the pressing device 4, the winding device 2, and the holding device 1.

This process, with its high heating rate of up to 1000 K/min, allows the production of nanocrystalline alloys with a high iron content and average grain diameters of less than 30 nm. These alloys exhibit a significantly higher magnetic saturation of up to 2.2 T than commercially available Fe-Si-B-Cu-Nb alloys with 1.2 T.

In a further embodiment, inductive heating can also be used as an alternative to direct heating by means of an electric current flowing through the strip 3. In a further embodiment, the strip 3 can also be heated indirectly by a heating coil through which an electric current flows and, for example, surrounds the strip 3. It is also possible to combine the three aforementioned methods for heating the strip 3, or at least two of these methods.

As mentioned above, the geometry of the soft magnetic cores can be determined by the shape of the pressing device 4 and the shape of the winding device 2. Toroidal cores can be produced by simply winding the amorphous strip 3 onto a mandrel. By cutting the toroidal cores, suitable C-, E-, or U-shaped cores are also possible. By cutting the strip into pieces and laminating it in the device, I-shaped cores can also be produced.

The fill factor can be controlled by adjusting the mechanical pressure. The pressure-induced buckling and viscous flow of the amorphous ribbons 3 under the additional influence of temperature increases the fill factor. Cores with a lower fill factor in the conventional range of 70 to 80% are more suitable for high-frequency applications up to 100 kHz.

Cores manufactured under high compression pressure with increased fill factors are more suitable for lower frequencies up to 20 kHz. However, they exhibit a higher magnetic power density than conventional nanocrystalline cores. Furthermore, adjusting the mechanical pressure can also influence the shape of the hysteresis loop, meaning that, in particular, the permeability and remanence can be adjusted to a certain extent.

Applications for the nanocrystalline components produced in this way, with high magnetic saturation polarization and low losses, arise in the power supply and electromobility sectors. The former includes power transformers, common-mode chokes, storage chokes, and magnetic amplifiers. A transformer is an electrical device capable of transforming alternating current from one voltage level to another in order to convert an input voltage into a higher or lower output voltage. It typically consists of two tightly wound coils arranged around a common magnetic core. This core can be either block-shaped or ring-shaped. Requirements for the soft magnetic material are high magnetic saturation to enable the transformer to be as small as possible, very high permeability, and low core losses to achieve high efficiency. Since the nanocrystalline strip, with thicknesses of about 20 µm, is significantly thinner than conventional electrical steel sheets (d > 200 µm), the eddy current losses, which depend quadratically on the thickness, are drastically reduced at frequencies above 1 kHz, so that a significant increase in efficiency can be expected.

A common-mode choke is an electrical component used in circuits to reduce interference and noise. It consists of two identical inductors wound in opposite directions. By using a common-mode choke, the common-mode noise that occurs when two signals at the same potential level change can be minimized. The choke blocks the common-mode noise and allows only the differential signal to pass. This allows for better signal quality. Due to a higher fill factor and higher magnetic polarization, the compacted windings of the Amorphous Band 3 cores made from more advanced alloy systems only saturate at higher field strengths than conventional toroidal cores. Therefore, they only become unusable at higher field strengths, distinguishing them from conventional cores when used as common-mode chokes.

A magnetic storage choke consists of a magnetic core and a winding. When a current flows through the winding, it creates a magnetic field around the core. This magnetic field stores a certain amount of energy. When the current in the winding is switched off, the energy stored in the magnetic field is released again in the form of an electric current flow in the winding. This process thus enables energy to be stored and released again. The magnetic storage choke is often used in power supplies and other electronic devices to reduce interference and ensure a stable power supply. Due to the higher power density with similar losses, the compact windings manufactured using the described process are also preferable to conventional toroidal cores in this area.

A magnetic amplifier, also known as a magnetic amplifier ring or magnetic amplifier core, is used to improve the efficiency and performance of electrical transformers or coils. It is made of a core material with high magnetic permeability, typically ferrite or iron. The magnetic amplifier works by concentrating the magnetic field and increasing the magnetic flux. When a coil is wound around the magnetic amplifier and a current flows through the coil, this current creates a magnetic field. The magnetic field is passed through the magnetic amplifier core, which amplifies the magnetic flux and transfers magnetic energy more efficiently. By using a magnetic amplifier, the efficiency of transformers and coils can be improved because less energy is lost and better magnetic coupling is achieved. This results in improved performance and reduced energy loss in electrical circuits.

Especially in electromobility, disc-shaped axial flux motors are Particularly advantageous in the aviation and motorsport sectors due to their higher torque-to-power ratio and low weight. Unlike radial flux motors, the magnetic flux in axial flux motors is not radial, but axial to the axis of rotation. The stator is arranged between two rotors equipped with permanent magnets. It consists of coils containing soft magnetic core materials for flux conduction. The electric current flowing through the coils creates a magnetic field, which is amplified by the soft magnetic core material. This creates magnetic poles at the ends of the coils.

These induced poles of the stator interact with the poles of the rotor's permanent magnets. By carefully controlling the electric current in the coils, the magnetic poles in the soft magnets are magnetized in such a way that the rotors are set in motion by their interaction with the poles of the hard magnets they contain. The increased strength and higher conductivity of the soft magnetic cores manufactured here can improve the performance of these motors.

Claims (11)

Method for producing a soft magnetic core, in which at least one amorphous or semi-crystalline band (3) which is made of a metallic alloy, is wound around a winding axis and then the amorphous or semi-crystalline ribbon (3) is introduced into a holding device (1) and then a mechanical pressure force is exerted on the wound amorphous or semi-crystalline strip (3) by a pressing device (4), wherein an electric current flows through the amorphous or semi-crystalline ribbon (3) and the amorphous or semi-crystalline ribbon (3) is heated by the electric current flow and/or during which the amorphous or semi-crystalline ribbon (3) is heated by inductive heating and/or during which the amorphous or semi-crystalline ribbon (3) is heated indirectly by means of a heating coil spaced apart from the amorphous or semi-crystalline ribbon (3), so that nanocrystalline grains are formed in the amorphous or semi-crystalline ribbon (3). Method for producing a soft magnetic core according to claim 1, characterized in that the metallic alloy is formed from Fe-BX, in particular from Fe-Si-B-Cu or Fe-Si-BP-Cu-(C) or Fe-Si-B-Mn. A method for producing a soft magnetic core according to claim 2, characterized in that X comprises the elements Si and/or Co and/or Cu and/or P and/or Mn and/or Nb. Method for producing a soft magnetic core according to one of the preceding claims, characterized in that the compressive force is applied axially along the winding axis of the amorphous or semi-crystalline strip (3). Method for producing a soft magnetic core according to one of the preceding claims, characterized in that the amorphous or semi-crystalline strip (3) is wound on a winding device (2), in particular a mandrel. Method for producing a soft magnetic core according to one of the preceding claims, characterized in that the amorphous or semi-crystalline strip (3) is coated with an electrically insulating layer on at least one side, preferably on both sides, before winding. Method for producing a soft magnetic core according to one of the preceding claims, characterized in that the method is carried out under vacuum or under a protective gas atmosphere. Method for producing a soft magnetic core according to one of the preceding claims, characterized in that the strip (3) is flowed around by a fluid after no more compressive force is exerted on the strip (3) and no more electric current flows through the strip (3) and/or the strip (3) is formed from the holding device (1) and the pressing device (4). Method for producing a soft magnetic core according to one of the preceding claims, characterized in that the temperature of the amorphous or semi-crystalline strip (3) is controlled by a thermocouple (5). Method for producing a soft magnetic core according to one of the preceding claims, characterized in that a shape of a hysteresis curve of the amorphous or semi-crystalline band (3) is adjusted by the mechanical compressive force. Apparatus for producing a soft magnetic core comprising: a holding device (1) which is designed to receive at least one amorphous or semi-crystalline strip (3) which is made of a metallic alloy and wound around a winding axis, a pressing device (4) which is designed to exert a mechanical compressive force on the wound amorphous or semi-crystalline strip (3) and a current/voltage source (6) which is designed to conduct electrical current through the amorphous or semi-crystalline band (3) so that nanocrystalline grains form in the amorphous or semi-crystalline band (3), and/or an inductive heating device designed to heat the amorphous or semi-crystalline strip (3) by inductive heating, and/or a heating coil spaced from the amorphous or semi-crystalline band (3) which is designed to heat the amorphous or semi-crystalline band (3) indirectly, so that nanocrystalline grains form in the amorphous or semi-crystalline band (3).