Sheet metal for manufacturing an electromagnetic component, in particular a stator or rotor core, and method for manufacturing an electromagnetic component

Abstract

To provide a sheet metal for manufacturing an electromagnetic component, in particular a stator core or a rotor cores, which is coated with an adhesive of a heat-activated adhesive.SOLUTION: An adhesive includes 60 pts.wt. of epoxy resin in a solid resin form, 0.5 to 15 pts.wt. of latent hardener, and 1 to 15 pts.wt. of latent accelerator. Furthermore, the present invention relates to a method of manufacturing an electromagnetic component.SELECTED DRAWING: Figure 2a

Description

[Technical field]

[0001] The present invention relates to a sheet metal for manufacturing an electromagnetic component, in particular a stator or rotor core. The present invention also relates to a method for manufacturing an electromagnetic component, in particular a stator or rotor core for an electric machine, in particular an electric motor. [Background technology]

[0002] The mode of operation of electric machines, such as electric motors, has been known for a long time. The importance of electric motors continues to grow, especially in light of their increasing use in personal passenger transport, known by the buzzword "electric vehicle". The substantial components of all electric motors are a stator and a rotor, the term "stator" meaning the stationary part of the motor and the term "rotor" meaning the moving part of the motor.

[0003] One challenge in providing electric motors is to increase the efficiency of the electric motor, e.g., the delivered power per volume and / or the efficiency factor, as part of an economically rational effort.

[0004] One concept for providing efficient electric motors is to manufacture the stator and / or rotor, or parts of the stator and / or rotor, as so-called stator or rotor cores. In this case, said components are assembled from individual so-called lamellae, as sheet metal cores, also known as lamella cores. The term "lamella" means a shaped part removed from an electrical steel sheet or strip, for example by punching. A lamella core consists of a number of thin lamellae, which are stacked together and are partly or preferably completely electrically insulated from one another. For such purposes, the use of so-called electrical insulating varnishes, which fall into the so-called insulating classes, is known in practice, for example.

[0005] The manufacture of such sheet metal cores always includes the steps of manufacturing the lamellae and interconnecting them. The connection is preferably established in such a way that after the connection the lamellae are partially, preferably completely, electrically insulated from one another, which preferably means that two adjacent lamellae are not electrically interconnected.

[0006] The individual lamellae can be produced, for example, by punching. The connection of the punched lamellae to form the sheet metal core can be achieved by various known methods, for example by screwing, applying clips, welding or punch stacking. However, due to the mechanical actions occurring during the connection process, each of these production methods known to the skilled person is accompanied by a negative effect on the electromagnetic properties of the finished sheet metal core, which prevail after the connection. In particular, the mechanical stresses that are unavoidable in the connections produced according to the prior art can, at least to some extent, negatively affect the magnetic properties and the path of the magnetic field lines in the sheet metal core, with a direct negative effect on the efficiency of the electric motors produced therefrom, for example. The electrical connection between two or more lamellae that occurs in some connection processes, such as stamped stacking or welding, results in additional losses.

[0007] A convenient option to reduce the adverse effects of mechanical influences on the lamellae and at the same time achieve good insulation between them is to use adhesives as a connecting means. These adhesive systems also have insulating properties similar to those of electrical insulating varnishes.

[0008] A procedure known to the skilled person is the use of so-called baking varnish. The use of baking varnish for gluing punched magnetic steel sheets is described, for example, in DE 38 29 068 C1. One procedure for using baking varnish is the coating of sheet metal, in particular sheet metal strips, followed by punching out individual lamellae from the sheet metal, positioning the individual lamellae in alignment with one another, and then heat-treating the resulting sheet stack for a defined period of time and at a defined temperature. In many cases, the lamellae are pressed against one another during the heat treatment, for example by applying a force on the end faces, preferably with a uniform surface force, in the axial direction of the sheet metal core, towards the inside of the sheet metal core. Typical reaction temperatures are 150 to 250 degrees Celsius, and typical times for the baking varnish to react are 30 to 150 minutes, followed by a cooling phase, although the exact parameters naturally depend on the particular baking varnish used and the particular geometry present, since the core temperature, for example set on the part, affects the course of the baking varnish process. Good electromagnetic properties of the stator and / or rotor cores can generally be achieved using this procedure. However, it is immediately apparent that the use of baking varnish is not suitable, or at least not optimal, for continuous mass production due to the time required for the procedure. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] German Patent No. 3829068 Summary of the Invention [Problem to be solved by the invention]

[0010] Against the background of the described arrangement, the object of the invention is to create the prerequisites for the efficient production of sheet metal cores, i.e. in particular stator cores or rotor cores, in a mechanized production environment.

[0011] Furthermore, in view of the desire for ever greater efficiency, it is an object of the present invention to provide electromagnetic components and electric machines with improved conversion of electromagnetic energy into mechanical energy. [Means for solving the problem]

[0012] This object is achieved by a sheet metal for manufacturing electrical components, in particular stator cores or rotor cores.

[0013] The term "sheet metal" generally refers to rolled products made of metallic material, including light gauge or thick gauge metal sheets, as well as products made of metal strip, metal strip or metal sheet, such as soft magnetic material, steel strip or electric steel strip. Other methods of producing sheet metal can optionally be used.

[0014] The sheet metal is covered with an adhesive cover of heat activated adhesive. The adhesive includes: 60 parts by weight of an epoxy resin based on its solid resin form, 0.5 to 15 parts by weight of a latent hardener; 1 to 15 parts by weight of a latent accelerator.

[0015] The adhesive preferably contains 1 to 10 parts by weight of the latent hardener, and particularly preferably 2 to 5 parts by weight of the latent hardener.

[0016] The term "latent hardener" means a substance that is used to harden epoxy resins, but that must be activated for hardening, especially by supplying chemical and / or thermal energy. Latent hardeners are added to the adhesive as solids, for example in powder form.

[0017] The term "latent accelerator" refers to a substance that accelerates the curing of the epoxy resin by the latent hardener. The attribute "latent" associated with the accelerator is related to the fact that the accelerator must also be pre-activated by chemical and / or thermal energy in order to perform its function. Latent accelerators are added to the adhesive as solids, for example in powder form.

[0018] The above-mentioned compositions relate to mixtures of components present as solids in specific parts by weight, which in dispersion and / or solution with a suitable liquid form an adhesive mixture that becomes an adhesive capable of forming an adhesive cover. In a usable state, i.e. in a form suitable for coating, the adhesive with the specific components is preferably present as a dispersion of the above-mentioned composition in a dispersion medium, in particular as an aqueous dispersion.

[0019] The sheet metal is provided with an adhesive cover made of a thermally activated adhesive, so that the adhesive-covered sheet metal is used as a preliminary product for a flexibly adaptable manufacturing process of electromagnetic components, in particular stator or rotor cores. Since the adhesive must first be thermally activated, the adhesive function can be performed at any desired time or in any desired method step after the lamellae have been removed from the sheet metal, for example by punching. Within a short period of time after activation, the lamellae must be brought together (optionally, preferably under partial or full surface pressure in a press and / or a subsequent compression process) so that they are glued together during a chemical hardening reaction. This is the only way to create defect-free, delamination-free, geometrically accurate and mechanically stable cores.

[0020] With the adhesive composition according to the invention, the sheet metal has a surface with a short activation time, for example 0.5 to 1 second, and a short curing time of only a few seconds. These properties go hand in hand with a relatively high heat resistance and a relatively high insulating and aging capacity. [Brief description of the drawings]

[0021] [Figure 1a]FIG. 1a shows the shear value test results for samples stored at room temperature. [Figure 1b] FIG. 1b shows the shear value test results for samples stored at 40° C. [Figure 2a] FIG. 2a shows an example of a method for manufacturing a sheet metal core for an electric motor. [Figure 2b] FIG. 2b shows a manufacturing process similar to the known baking varnish process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The epoxy resins present in the adhesives used in accordance with the present invention comprise one or more epoxy resin components having two or more epoxy groups, at least one of which preferably has a softening point above 50 degrees Celsius.

[0023] The epoxy resin may be an aliphatic, cycloaliphatic or aromatic epoxy resin. Aliphatic epoxy resins include components bearing both an aliphatic group and at least two epoxy resin groups.

[0024] Examples of aliphatic epoxy resins can be butanediol diglycidyl ether, hexanediol diglycidyl ether, dimethylpentane dioxide, butadiene dioxide, diethylene glycol diglycidyl ether.

[0025] Examples of cycloaliphatic epoxy resins include 3-cyclohexenylmethyl-3-cyclohexylcarboxylate diepoxide, 3,4-epoxycyclohexylalkyl-3',4'-epoxycyclohexanecarboxylate, 3,4-epoxy-6-methylcyclohexylmethyl-3',4'-epoxy-o-methylcyclohexanecarboxylate, vinylcyclohexane dioxide, bis(3,4-epoxycyclohexylmethyl)adipate, dicyclopentadiene dioxide, and 1,2-epoxy-6-(2,3-epoxypropoxy)hexahydro-4,7-methanoindane.

[0026] Examples of aromatic epoxy resins include bisphenol A epoxy resin, bisphenol F epoxy resin, phenol novolac epoxy resin, cresol novolac epoxy resin, biphenyl epoxy resin, biphenol epoxy resin, 4,4'-biphenolline epoxy resin, divinylbenzene dioxide, 2-glycidylphenyl glycidyl ether, and tetraglycidylmethylene dianiline.

[0027] In a preferred embodiment of the present invention, the epoxy resin is a bisphenol A epoxy resin.

[0028] The latent hardener used is preferably a substance or mixture of substances that enters into a hardening reaction with the epoxy resin of the adhesive at temperatures in the range of 80 degrees Celsius to 200 degrees Celsius.

[0029] The curing agent may include dicyandiamide, aziridine derivatives, triazine derivatives, imidazolines, imidazoles, o-tolylbiguanides, cyclic amidines, organic hexafluoroantimonate or hexafluorophosphate compounds or BF3 amine complexes. The compounds may be used individually or in combination.

[0030] Examples include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole. dazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl- s-2,4-diamino-6-[2"methylimidazolyl-(1')]-ethyl-s-triazine, 2-phenylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, (1-dodecyl-2-methyl-3-benzyl)imidazolium chloride, 2-methylimidazoline, 2-phenylimidazoline, 2,4-diamino-6-vinyl 1,3,5-triazine, 2,4-diamino-6-vinyl-1,3,5-triazine isocyanine acid adduct, 2,4-diamino-6-methacryloyloxyethyl-1,3,5-triazine, 2,4-diamino-6-methacryloyloxyethyl-1,3,5-triazine isocyanine acid adduct, 1,3,5-triazine, 2,4-diamino-6-methyl-1,3,5-triazine, 2,4-diamino-6-nonyl-1,3,5-triazine, 2,4-diamino-6-phenyl-1 3,5-triazine, 2,4-dimethoxy-6-methyl-1,3,5-triazine, 2,4-dimethoxy-6-phenyl-1,3,5-triazine, 2-amino-4,6-dimethyl-1,3,5-triazine, 2-amino-4-dimethylamino-6-methyl-1,3,5-triazine, 2-amino-4-ethoxy-6-methyl-1,3,5-triazine, 2-amino-4-ethyl-6-methoxy-1,3,5-triazine, 2-amino-4-methoxy-6-methyl-1,3,5-triazine, 2-amino-4-methyl-6-phenyl-1,3,5-triazine, 2-chloro-4,6-dimethoxy-1,3,5-triazine, 2-ethylamino-4-methoxy-6-methyl-1,3,5-triazine, and 1-o-tolylbiguanide.

[0031] In a preferred embodiment of the invention, the accelerator comprises a urea derivative and / or an imidazole.

[0032] The adhesive composition according to the present invention may also contain further ingredients.

[0033] In a preferred embodiment of the present invention, the curing agent comprises dicyandiamide, imidazole, BF3 amine complex, or a combination thereof.

[0034] In one embodiment, the adhesive may comprise from 1 to 10 parts by weight of latent accelerator, preferably from 1 to 5 parts by weight of latent accelerator, particularly preferably from 2 to 5 parts by weight of latent accelerator, very particularly preferably from 2 to 4 parts by weight of latent accelerator.

[0035] In another preferred embodiment, the adhesive further comprises 0.2 to 8 parts by weight, preferably 0.2 to 4 parts by weight, of an absorbing additive. The absorbing additive which may be provided according to this further concept is selected from the group of lamp blacks and / or the group of water-soluble dyes.

[0036] The term absorbing additive means a substance that absorbs thermal radiation, which is particularly associated with the advantage of allowing a more efficient use of methods in which thermal activation of the adhesive is carried out by irradiation with electromagnetic radiation, in particular with light in the infrared wavelength range, preferably in the near infrared wavelength range.

[0037] The adhesive preferably includes one or more insulating additives known to those skilled in the art, the term "insulating additive" referring to an additive specifically provided to increase the electrical resistance of the adhesive. The insulating additive may be included in the adhesive in an amount of 1 to 10 parts by weight, preferably 1 to 5 parts by weight.

[0038] The latent accelerator contained in the adhesive preferably consists of at least 50% by weight, more preferably at least 90% by weight, and even more preferably entirely, of urea derivatives.

[0039] Particularly preferably, the urea derivative is N,N-dimethylurea or N,N'-dimethylurea, or preferably a bifunctional urea derivative having two urea groups as functional groups, very particularly preferably 4,4'-methylene-bis-(phenyldimethylurea), or a mixture of some of the above.

[0040] The latent accelerator contained in the adhesive preferably consists of at least 50% by weight, more preferably at least 90% by weight, even more preferably at least 98% by weight, and most preferably entirely, 4,4'-methylene-bis-(phenyldimethylurea).

[0041] Alternatively, urea derivatives are used according to the invention in which at least one, preferably two, particularly preferably three hydrogen atoms are substituted, independently of one another, by alkyl and / or phenyl groups, which in turn may be further substituted. The alkyl groups are preferably methyl, ethyl, propyl or butyl, preferably methyl. The phenyl groups are phenyl or deeply substituted, preferably in the 4-position and also preferably as a coul 1 of the above alkyl. In a further alternative, within the meaning of the invention, bifunctional urea derivatives are indicated as the above derivatives having two functional groups. The point of the group is a group of atoms that largely determines the material properties, in particular the reaction behavior of the compound towards functional group reactions. Furthermore, the urea derivatives used according to the invention do not contain halogens. Alternatively, the urea derivatives used according to the invention have two urea derivatives as functional groups. As a result, the epoxy resins can be advantageously cured without the presence of dicyanamide as a crosslinking agent.

[0042] Alternatively, asymmetrically substituted ureas may also be used in conjunction or exclusively as urea derivatives.

[0043] In a further alternative, a mixture of two, three or more of the foregoing is used.

[0044] The following urea derivatives are available:

[0045] [ka]

[0046] (wherein R is hydrogen or a group shown below,

[0047] [ka]

[0048] During the ceremony, n is 0 or 1, preferably 1; X is O or S, preferably O; R 1 , R 2 and R 3 each represents a hydrogen atom, a halogen atom, a nitro group, a substituted or unsubstituted alkyl group, an alkoxyl group, an aryl group, or an aryloxyl group, R 4 is an alkyl, alkenyl, cycloalkyl, cycloalkenyl or aralkyl group optionally substituted with halogen, hydroxyl or cyano, preferably methyl, ethyl, propyl or butyl, particularly preferably methyl, R 5 is R 4 or an alkoxy group, or R 5 is R 4 may form a heterocycle together with or N,N-dimethyl-N'-(3,4-dichlorophenyl)urea or N,N-dimethyl-N'-(3-chloro-4-methylphenyl)urea or N,N-dimethyl-N'-(3-chloro-4-methoxyphenyl)urea or N,N-dimethyl-N'(3-chloro-4-ethylphenyl)urea or N,N-dimethyl-N'-(4-methyl-3-nitrophenyl)urea or N-(N'-3,4-dichlorophenylcarbamoyl)morpholine or N,N-dimethyl-N'(3-chloro-4-methylphenyl)thiourea, may be provided, and the urea derivative is preferably 4,4'-methylene-bis-(phenyldimethylurea).

[0049] Alternatively, the urea derivative is a mixture of two, three or more of the above. Such mixtures preferably contain at least 10%, 25%, preferably 50%, 60%, 70%, 80% or 90% of 4,4'-methylene-bis-(phenyldimethylurea). The advantages of these urea derivatives are due to GB 1293142A, and the inventors have found that such derivatives can be excellently used in the manufacture of electromagnetic components.

[0050] The urea derivative may also be a mixture of two or more of the aforementioned urea derivatives.

[0051] The average particle size (arithmetic mean) of the urea derivative is preferably between 1 micrometer and 30 micrometers.

[0052] The adhesive cover can be applied to the sheet metal on one or both sides. When the adhesive cover is applied to both sides, the thickness of the cover can be the same, but different thicknesses can also be provided.

[0053] Application of the adhesive to the sheet metal can be carried out by known methods, in particular coil coating (roll-to-roll).

[0054] The preferred thickness of the adhesive cover, i.e. the thickness of the coating on one side in the case of a single-sided adhesive, or the total thickness of the adhesive covers on both sides in the case of a double-sided adhesive coating, is between 1 micrometer and 20 micrometers, preferably between 2 micrometers and 10 micrometers. A total thickness between 4 and 8 micrometers is particularly preferred.

[0055] The adhesive coating of sheet metal, which is carried out on one side, is easier to manufacture in terms of the device. The adhesive coating of sheet metal on both sides has the advantage that then, when the individual lamellae made of sheet metal are superimposed, the adhesive surface is placed on the adhesive surface, which improves the adhesion and therefore achieves a higher mechanical stability of the electromagnetic components. This has been confirmed by tests and is shown below.

[0056] The first partial coating on the first sheet metal surface and the second partial coating on the second sheet metal surface with the second thickness are particularly preferably adapted to one another in such a way that the first thickness is at least 1.5 times, preferably twice, the thickness of the second coating. In such a configuration, the risk of adhesion gaps is almost negligible, since the first thickness is responsible for the excellent insulation, and the thinner of the two, i.e. the second partial coating applied with the second thickness, substantially helps to create excellent adhesion.

[0057] Very particularly preferred are double-sided covers, with a total thickness of both covers between 4 and 6 micrometers. As the produced examples show, such low coating thicknesses are possible with the adhesives used according to the invention or according to the developments of the invention, due to their high reactivity. Known baking varnish adhesives usually require a thickness of the cover of more than 6 micrometers (for example, 5 μm on each side for baking varnish on both sides). This results in the advantage that components, in particular stators or rotors, can be produced from sheet metal according to the invention or their developments, with a significantly higher iron filling than components produced by the baking varnish method. The advantage is that the efficiency of the electric machine with the components is somewhat higher. However, adhesive coatings of between 1 and 20 micrometers in total, preferably between 2 and 8 micrometers, can be provided.

[0058] In a further alternative, an insulating varnish layer is disposed between the sheet metal and the adhesive layer and / or only the insulating varnish is disposed on the side opposite the adhesive layer.

[0059] The sheet metal is particularly preferably designed as or separated from non-oriented electrical steel strip, also called NO electrical steel, which in addition to Fe and unavoidable impurities contains the following elements (all data in % by weight): 0.1~3.50Si, 0.01 to 1.60 Al, 0.07~0.65 Mn, Optionally, P is up to 0.25. Of course, the sum of all alloying elements and impurities equals 100% by weight.

[0060] The following conditions are particularly preferred (all data in % by weight): 2.3~3.40 Si, 0.3~1.1 Al, 0.07~0.250 Mn, Optionally, up to 0.030 P, balance Fe and unavoidable impurities. Of course, the sum of all alloying elements and impurities equals 100% by weight.

[0061] The non-oriented electrical steel strip or sheet preferably has a specific core loss determined according to DIN EN60404-2 of P1.0; 50 Hz in the range of 0.7-7 W / kg and P1.5; 50 Hz in the range of 1.8-15 W / kg, and / or polarization in J2500 in the range of 1.45T-1.71T and J5000 in the range of 1.6T-1.8T.

[0062] In a more preferred embodiment the non-oriented electrical steel strip or sheet has a specific core loss at 50 Hz of P1.0; 0.8-3.5 W / kg and P1.5; 1.9-8.0 W / kg and / or polarization at J2500 in the range of 1.47T-1.71T and J5000 in the range of 1.58T-1.80T, determined according to DIN EN60404-2.

[0063] In a further preferred embodiment the non-oriented electrical steel strip or sheet has a specific core loss at 50 Hz of P1.0; 1.0-1.5 W / kg and P1.5; 2.2-3.3 W / kg and / or polarization at J2500 in the range of 1.47T-1.57T and J5000 in the range of 1.58T-1.65T, determined according to DIN EN60404-2.

[0064] The non-oriented electrical steel strip or sheet preferably has a specific core loss at 400Hz of P1.0; in the range of 8-120 W / kg and P1.5; in the range of 18-360 W / kg and / or a polarization at J2500 in the range of 1.45T to 1.75T, J5000 in the range of 1.45T to 1.85T and J10,000 in the range of 1.50 to 1.95T, determined according to DIN EN60404-2.

[0065] In a further preferred embodiment the material has a specific core loss, determined according to DIN EN60404-2, of P1.0; at 400 Hz in the range of 10-25 W / kg and P1.5; at 400 Hz in the range of 25-49 W / kg, and / or a polarization, determined according to DIN EN60404-2, of J2500 in the range of 1.45T to 1.75T, of J5000 in the range of 1.45T to 1.85T and of J10,000 in the range of 1.50 to 1.95T.

[0066] The non-oriented electrical steel strip or sheet preferably has, under standard normal conditions, a longitudinal yield point of 190 to 610 MPa and an ultimate tensile strength of 310 to 740 MPa and a minimum elongation at break A80 of 6 to 48%, measured according to DIN EN ISO 6892-1, and a hardness Hv5 of 100 to 250.

[0067] In a particularly preferred embodiment, the material has a longitudinal yield strength at room temperature of 310 to 600 MPa, an ultimate tensile strength of 400 to 640 MPa, an elongation at break A80, measured according to DIN EN ISO 6892-1, of 7 to 32% and a hardness Hv5 of 130 to 250.

[0068] This material preferably has an anisotropy at 400 Hz in the range of P1.0; 5-17%.

[0069] Alternatively, a sheet metal can be provided made of a soft magnetic material having the following alloy composition: Iron, consisting of iron plus unavoidable impurities (all data in % by weight): 0.1 to 4.0 Si, Al from 0.01 to 2.60, Mn 0.07-3.0; optionally P up to 0.5, optionally B up to 0.015, optionally up to 0.2 Sb, optionally up to 0.01% Zn, optionally up to 5 Cr, optionally up to 5 Ni, Optionally, V up to 0.25, optionally up to 0.5 Sn, optionally As up to 0.01, optionally up to 0.3 Nb, optionally up to 0.5 W, optionally Zr up to 0.85; optionally up to 0.2 Mo, optionally Cu up to 1.0; optionally up to 0.5 Ti, Optionally, C up to 0.5, optionally Ce up to 0.01.

[0070] Sheet metal having a thickness between 0.05 and 2.5 mm, in particular electromagnetic steel strip, is suitable and preferably used, the thickness being preferably between 0.1 and 1.0 mm, with a thickness of 0.15-0.4 mm being particularly preferred.

[0071] Alternatively, the sheet metal can be a multi-layer composite (sandwich) consisting of a sheet metal layer, for example consisting of one of the electrical strips mentioned above, and one or more additional layers, for example with an acoustic damping functional layer (for example Bondal E). Furthermore, the sheet metal can also be covered on one or both sides with an acoustic damping functional layer (for example Semibondal E), so that the described adhesive system connects directly to the acoustic damping functional layer (for example chemical-based acrylate). It is known in the art that epoxy resin systems have good compatibility.

[0072] Alternatively, the sheet metal can have an acoustically attenuating functional layer on one side and an adhesive layer used in accordance with the present invention on the opposite sheet metal side.

[0073] Tests have shown that the provision of the sheet metal in an excellent manner according to the invention or one of its further developments allows the joining of sheet metal lamellae to be carried out with the highest reactivity of the adhesive and, moreover, has the advantage of providing a suitable method for the production of sheet metal cores even in linear production processes with a large number of parts at once. The above tests are shown below as examples.

[0074] In the case of the sheet metal provided according to the invention, a particularly advantageous production of sheet metal cores for electric motors is possible, since, according to the knowledge of the developers, for the first time a starting material prepared for further processing is provided, which can be used with high economic efficiency both in-line, i.e. continuous processing, and off-line, i.e. based on baking varnish bonding.

[0075] In addition to this particularly advantageous combination of properties, it has surprisingly been found that the sheet metals provided according to the invention are also stable over time. This means that, in particular in combination with the possibility of in-line production of the sheet metal cores, the sheet metals provided according to the invention fulfil the basic requirements for integration into typical production processes in the automotive industry due to their long-term stability, since on the one hand they allow long-term storage for up to at least several weeks, and also, due to their temperature stability, processing in the sense of just-in-time deliveries, which are usually carried out even in mid-summer on unreinforced trucks, which must be able to withstand temperatures of at least 40 degrees Celsius for long periods of time.

[0076] Another advantage of the sheet metals provided according to the invention is that they are mechanically stable, i.e. the adhesive remains dimensionally stable when pressed, in particular compared to the adhesives previously used from the baked varnish method mentioned at the beginning.

[0077] The bond is temperature stable, as the following examples show: In contrast to conventional baking varnish systems, so-called squeezing out of the adhesive system during pressing does not occur or only occurs to a very small extent.

[0078] The targeted combination of sheet metals offers a combination of properties previously unknown, particularly in the automotive industry, in the further development of specially selected sheet metals and specially selected adhesive compositions for use in electric vehicles, i.e. sheet metal cores and electromagnetic components in large scale industry, which offers previously unknown flexibility to those skilled in the art entrusted with the implementation of the invention.

[0079] Advantages such as electromagnetic, mechanical and thermal machine design, the possibility to choose different sheet metals, increased freedom of construction of the lamella design, and advantages regarding possible component tolerances and media and / or thermal guidance are conceivable. Further advantages are also in terms of component and machine manufacturing (e.g. when dealing with compact and solid parts) and machining. Further advantages in electric machines with one of the sheet metals according to the invention or one of its developments are higher performance and efficiency, smaller required installation space, better geometric properties (e.g. especially at constant surface pressure, which can be achieved by recompression against stops, with the advantage of better dimensional stability of the electromagnetic components), and, depending on the design, acoustic advantages.

[0080] Another aspect of the invention relates to a method for manufacturing an electromagnetic component, in particular a sheet metal core for an electric machine, preferably an electric motor, can be provided as the electromagnetic component, the sheet metal core being preferably either a stator core or a rotor core, i.e. it is a stator or part of a stator or a rotor or part of a rotor.

[0081] The method comprises the following steps: A) In a first step, a sheet metal according to the invention or one of its developments is provided. The sheet metal can be, for example, an electromagnetic steel strip or a printed circuit board separated from a sheet metal strip. B) The sheet metal is conveyed through an in-line system having at least the following stations: a punching tool, a means for outputting infrared rays, and an extrusion punch.

[0082] The term "in-line system" means that several processing stations, i.e. at least the ones mentioned above, are arranged in a predetermined sequence and the sheet metal, e.g. electrical steel strip, fed into the in-line system is automatically and sequentially processed at the predetermined stations.

[0083] A punching tool is a tool with which one, preferably two or more, for example four, lamellae are punched out of the sheet metal. In step C), the lamellae are preferably punched out using a punching tool such that a number of connecting webs, for example three connecting webs, remain between the associated punched lamellae and the sheet metal originally transported in the in-line system and the punched lamellae are still an integral part of the sheet metal. This is used to allow the lamellae to be further transported together with the sheet metal, in particular the metal strip, via the in-line system.

[0084] In the above context, the term "lamella" refers to a shaped part obtained by cutting it out of sheet metal, in particular a shaped part obtained by punching.

[0085] In a preferred alternative, an electromagnetic component, preferably a rotor core, is manufactured by a conventional stacking process, for example stamp stacking, and a further electromagnetic component, preferably a stator core for the same electric machine as the conventionally manufactured stator core, is manufactured using the method according to the invention described above. This can be done, for example, in a combined manner or sequentially. A stress relief anneal or a recrystallization anneal, optionally further coating steps, an activation step and / or an inspection step can preferably be carried out before packaging. An activation step in this context means the activation of the adhesive used.

[0086] The means for emitting infrared radiation can in particular be designed as a NIR emitter, ie a lamp designed to emit electromagnetic radiation in the NIR wavelength spectrum, ie with wavelengths between 780 nm and 3 μm.

[0087] In a preferred method, the molded parts are irradiated in the near infrared wavelength range, preferably 0.8 to 1.2 micrometers are used, particularly preferably with near infrared radiation of wavelengths between 0.85 and 0.9 micrometers, the maximum value of the luminous power being achieved. Activation (irradiation) takes place only in the areas of the covered surface that are available (active) for bonding. The remaining areas are blocked by screens in order to activate only the required areas. The separation of the individual sheet metal cores when the entire height is reached is carried out by overactivating the individual lamellae, so that they are no longer reactive and therefore no longer bond.

[0088] Furthermore, as mentioned above, the in-line system has an extrusion punch which, by applying a force perpendicular to the sheet metal surface, sequentially separates the lamellae, which are still connected to the sheet metal, in particular to the metal strip, by one or more webs, by separating the one or more webs from the sheet metal, and then, preferably in the same process step, conveys the lamellae to a receiving device arranged below the sheet metal, where they are collected.

[0089] In the in-line system, the shaped part designed as an electrical component, in particular a stator lamella or rotor lamella, is punched out of the sheet metal provided in step A) with a punching tool. One web or several, in particular three webs, preferably have a sufficient connection to the sheet metal for further transport of the shaped part.

[0090] D) The adhesive coating of the moulding formed in step C) is then irradiated with infrared radiation by means of a means for outputting infrared radiation in order to activate the adhesive coating, in other words, a temperature sufficient for activation is brought to the sheet metal and especially the adhesive by irradiation for a period of between 0.5 and 1 second with an emitted power of between 5 and 10 kilowatts, where an activation temperature of between 100 degrees Celsius and 250 degrees Celsius is sufficient for the adhesive.

[0091] The molded parts are extruded with an ejection punch and, preferably in the same movement, are introduced into a receiving device in which a positioning area is arranged, which is used to position and / or angulate the molded parts entering the positioning area with respect to the molded parts already present there, so that finally a stack of molded parts is obtained which is aligned and provided with an activated adhesive.

[0092] The positioning area is, for example, a cylindrical tube, which is below the conveying surface of the molded parts so that after extrusion, the molded parts fall by gravity into the existing stack of molded parts. The alignment of the molded parts is carried out through a positioning area designed, for example, as a cylindrical hollow tube with a side cross section which substantially corresponds to the cross section of the molded parts and is aligned in the intended positioning.

[0093] Steps C) to E) are repeated as necessary until the desired number of formed parts are in the positioning area to form a stack of formed parts. The punching tool and the extrusion punch are particularly preferably part of the same press, which has the advantage that the punching and extrusion processes are highly synchronized.

[0094] The means for outputting infrared radiation particularly preferably has at least one upper lamp arranged between the punching tool and the extrusion punch and directed towards the punching direction on the first sheet metal surface and at least one lower lamp arranged on the opposite side of the sheet metal where the punching tool is arranged and directed towards the punching direction or has both at least one upper lamp and at least one lower lamp. The alignment of the lamps on the lamella surface does not necessarily have to be at a right angle, but can also be performed at another angle.

[0095] In particular, when upper and lower ramps are present, activation of the adhesive is possible in a particularly suitable manner on both the first and the opposite second sheet metal side, with the advantageous result that excellent adhesion between the sheet metals can be expected.

[0096] According to a particularly preferred development of the method, after positioning the last molded part with the desired number of molded parts, the resulting sheet metal core is subsequently compressed. The compression step is carried out by compressing the sheet metal core in the axial direction of the sheet metal core with a uniform surface pressure on the end faces in the axial direction of the sheet metal core. By means of compression, an adhesive bond is generated particularly well between the individual molded parts, which contributes to the service life of the sheet metal core. The downstream compression step is preferably carried out in a downstream compression station outside the press. However, alternatively, the compression step can also be carried out, preferably partially or completely, by the pressure of the extrusion punch in the punching tool.

[0097] Steps C) to E) are preferably carried out at a stroke speed of at least 80 per minute, preferably at least 100 per minute, particularly preferably at least 120 per minute, and / or at a stroke speed of up to 1000 per minute, preferably up to 300 per minute, particularly preferably up to 220 per minute. This means that a number of molded parts corresponding to the stroke speed is introduced into the positioning area within one minute.

[0098] Another method provides that after providing one or more sheets, preferably magnetic steel strips, several shaped parts from the sheet provided in step A) are punched out in step B) on a punching tool. Afterwards, a registration and / or angular alignment superposition of the shaped parts is performed and these shaped parts are pressed in a separate station, which can be designed for example as an oven, and heated for a given time, for a given time or to a temperature in a given temperature range. This procedure is very similar to the procedure known from the baking varnish method described at the beginning, but differs in the starting material used, specifically one of the materials mentioned at the beginning. Only with the material mentioned at the beginning can a long storage time be achieved on the one hand and at the same time the provision of a sheet core with a certain number of finished sheet packages per one be achieved. As a result, a good use of this method in mass production can be expected.

[0099] The predefined time is preferably between 10 and 60 minutes, particularly preferably between 10 and 40 minutes. In the case of the first-mentioned sheet metal used according to the invention, this time is entirely sufficient to obtain the finished sheet metal core. The predefined temperature is particularly preferably between 100 and 200 degrees Celsius, in particular between 100 and 150 degrees Celsius. For example, in laboratory tests, samples have been successfully produced at a predefined temperature of 120 degrees Celsius and a predefined duration of 30 minutes. This example also shows one of the advantages of the method according to the invention compared to the conventional baking varnish method, where both higher temperatures and longer times are common, for example annealing at 190 degrees Celsius for 60 minutes. The reason is that it is now possible to provide the sheet metal with a significantly more reactive adhesive than previously used adhesives. The main influence on the actually required joining parameters (time / pressure and temperature) depends in particular on the given geometry, since for example the core temperature set on the component affects the course of the joining method.

[0100] The edges of the sheet metal cores can be cleaned according to the method for manufacturing said cores in order to remove adhesive residues on the edges or sides of the sheet metal cores. Cleaning can be carried out chemically and / or mechanically.

[0101] To increase the strength of the adhesive layer, provision can be made for disposing inorganic and / or organic fibers within the adhesive cover. EXAMPLES

[0102] Working Example Examples of sheet metal according to the invention and its advantageous behavior with respect to the method according to the invention are the results of tests carried out. The following sample was created: Printed circuit board made from electrical steel strip M800-50A (according to EN 10027-1) with material code 1.0816 (according to EN 10027-2), thickness 0.5 mm, length x width: 200 x 150 mm. Samples 0, 1, 2, and 3 were made. Samples 0, 1, and 2 are comparative samples, which are covered with an adhesive not according to the invention. Sample 3 is a sample according to the present invention. The samples produced were printed circuit boards of the type described above, covered with adhesive using an application roller according to the following parameters:

[0103] [Table 1]

[0104] Layer thickness Sample 0: 1st surface: 6 μm, 2nd surface: 0 μm, Sample 1: 1st surface: 6 μm, 2nd surface: 0 μm, Sample 2: 1st surface: 4 μm, 2nd surface: 2 μm, Sample 3: 1st side: 4 μm, 2nd side 2 μm.

[0105] Multiple specimens were made from each sample type. To test long-term stability, 18 sandwich structures were made from two identical samples.

[0106] Two samples of the same type are placed on a plate with a surface area of ​​200 mm × 200 mm and a surface pressure of 3 N / mm 2 The adhesive was bonded using a plate press and the adhesive was activated in an oven by heating to 120°C and holding at 120°C for 30 minutes. Eight samples were then placed in an oven and stored at 40°C. Every week samples were taken and subjected to a shear value test (according to DIN EN 1465). Additionally, a shear value test was performed every week on the samples stored at room temperature. The test results are shown in Figures 1a and 1b.

[0107] The results show that at room temperature the composition used according to the invention has better shear values ​​than the reference samples Sample 0, Sample 1 and Sample 2. Sample 0 tested after 6 weeks had a significant decrease in shear value and after 8 weeks Sample 0 had a shear value of 0.

[0108] After one week at the latest, the shear value of reference sample 0 is 0, meaning that this sample is not storage stable at 40°C. After two weeks, samples 1 and 2 have a shear value of 7.0 N / mm 2 The good shear values ​​above 0.05% remained almost unchanged but began to deteriorate significantly after 3 weeks of storage.

[0109] In both cases, the shear value of sample 2, whose surface is covered on both sides, is higher than the shear value of sample 1, whose surface is covered on one side.

[0110] In particular, Sample 3 was found to have the best shelf stability with good shear values ​​even after 4 weeks of storage at 40 degrees Celsius. The only sample available was a printed circuit board sandwich with good shear values ​​even after 4 weeks of storage at 40 degrees Celsius. At the time of filing, testing was still pending.

[0111] Additionally, tests were performed on the completed sandwiches, heating them to the test temperature and then holding them for a short period of time before testing the shear value.

[0112] [Table 2]

[0113] The results show that both Sample 2 and Sample 3 can withstand high temperatures up to 200°C for a certain period of time without losing mechanical stability. In particular, the shear value of Sample 3 was found to be significantly higher than that of the comparative Sample 2.

[0114] When a temperature test was carried out using sample 0 as the standard, after heating to 150°C, the resistance was approximately 0.90N / mm 2 It has been shown that shear values ​​of 0.01 to 0.01 mm were obtained. It has therefore been found, based on sample 3, that the sheet metal according to the invention is suitable for the manufacture of more temperature-stable sheet metal cores compared to the known sheet metals.

[0115] An example of a first embodiment of a method for manufacturing sheet metal cores for electric motors is shown in Fig. 2a. Sheet metal, already covered with plastic material, is provided, in particular as non-oriented magnetic steel strip 1. It is conveyed in an in-line system. In a first station, by means of several extrusion punches 4, shaped parts 2 designed as rotor or stator lamellae are extruded. In a subsequent station, the shaped parts are illuminated by means designed as NIR emitters for outputting infrared radiation 5, and the resulting heating activates the adhesive cover of the shaped parts. The shaped parts are then extruded by means of an extrusion punch 6 and collected in a positioning area to form a stack 3 in a position orientation and / or angular manner. Finally, in a compression station, compression by a compression ram 7 takes place until the adhesive hardens and the finished sheet metal core can be removed.

[0116] Figure 2b shows a manufacturing process similar to the known baking varnish process. The method of Figure 2b differs from that of Figure 2a in particular in that the molded part 2 is extruded and the stack 3 is formed before the adhesive coating is activated. The adhesive is only finally activated in an oven 8 at a temperature of, for example, between 100 and 200 degrees Celsius, while the sample is compressed by a stamp 7.

Claims

1. A sheet metal for manufacturing an electromagnetic component, in particular a stator core or a rotor core, said sheet metal being covered with a heat-activated adhesive, said adhesive comprising: 60 parts by weight of epoxy resin in solid resin form, Latent hardener 0.5 to 15 parts by weight, Latent accelerator: 1 to 15 parts by weight Including, the adhesive coating is applied to both sides of the sheet metal and has a thickness between 2 μm and 8 μm, said thickness being the total thickness of the adhesive coating on both sides; The sheet metal, wherein the adhesive coating comprises a first partial coating on a first sheet metal surface having a first thickness and a second sheet metal surface having a second thickness, the first thickness being at least 1.5 times the second thickness.

2. The sheet metal according to claim 1, characterized in that the adhesive contains 1 to 10 parts by weight of a latent hardener, preferably 2 to 5 parts by weight of a latent hardener.

3. The metal plate according to claim 1 or 2, characterized in that the epoxy resin is a bisphenol A type epoxy resin.

4. The latent curing agent is dicyandiamide, imidazole, BF 3 The sheet metal according to any one of claims 1 to 3, characterized in that it comprises an amine complex or a combination thereof.

5. 5. The sheet metal according to claim 1, wherein the adhesive contains 1 to 10 parts by weight of a latent accelerator, preferably 1 to 5 parts by weight of a latent accelerator, particularly preferably 2 to 5 parts by weight of a latent accelerator.

6. 6. The sheet metal according to claim 1, wherein the adhesive further comprises 0.2 to 8 parts by weight of an absorbent additive selected from the group of lamp black and / or water-soluble dyes.

7. The sheet metal according to any one of claims 1 to 6, characterized in that the latent accelerator comprises a urea derivative.

8. 8. The sheet metal according to claim 7, characterized in that the urea derivative is N,N-dimethylurea or N,N'-dimethylurea, or a bifunctional urea derivative, preferably having two urea groups as functional groups, particularly preferably 4,4'-methylene-bis-(phenyldimethylurea), or a mixture of a plurality of the above.

9. 9. The sheet metal according to claim 7 or 8, characterized in that as the urea derivative, an asymmetrically substituted urea is used in addition or exclusively.

10. The urea derivative is 【Chemistry 1】 where R is hydrogen or the following group: 【Chemistry 2】 During the ceremony, n is 0 or 1, preferably 1; X is O or S, preferably O; R 1 , R 2 and R 3 each represents a hydrogen atom, a halogen atom, a nitro group, a substituted or unsubstituted alkyl group, an alkoxyl group, an aryl group, or an aryloxyl group, R 4 represents an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group, or an aralkyl group, which is optionally substituted with a halogen, a hydroxyl group, or a cyano group, and is preferably methyl, ethyl, propyl, or butyl, and particularly preferably methyl; R 5 is R 4 or an alkoxyl group, or R 5 is arbitrarily R 4 and or N,N-dimethyl-N'-(3,4-dichlorophenyl)urea, or N,N-dimethyl-N'-(3-chloro-4-methylphenyl)urea, or N,N-dimethyl-N'-(3-chloro-4-methoxyphenyl)urea, or N,N-dimethyl-N'-(3-chloro-4-ethylphenyl)urea, or N,N-dimethyl-N'-(4-methyl-3-nitrophenyl)urea, or N-(N'-3,4-dichlorophenylcarbamoyl)morpholine, or N,N-dimethyl-N'(3-chloro-4-methylphenyl)thiourea, The urea derivative is preferably 4,4'-methylene-bis-(phenyldimethylurea), Or a mixture of two, three or more of these, according to any one of claims 7 to 9.

11. The sheet metal according to any one of claims 7 to 10, wherein the particles of the urea derivative have an average particle size of 1 μm to 30 μm.

12. The sheet metal according to any one of the preceding claims, characterized in that the adhesive coating has a total thickness of between 4 μm and 6 μm.

13. The sheet metal of claim 1, wherein the first thickness is twice the second thickness.

14. The metal sheet according to any one of claims 1 to 13, characterized in that an insulating varnish layer is arranged between the metal sheet and the adhesive coating and / or that only insulating varnish is arranged on the side opposite the adhesive coating.

15. 15. Sheet metal according to any one of the preceding claims, characterised in that the sheet metal is an electric steel strip, in particular a non-crystallised electric steel strip, or is separated from a non-crystallised electric steel strip.

16. In addition to Fe and unavoidable impurities, Si from 0.1 to 3.50, Al from 0.01 to 1.60, Mn between 0.07 and 0.65, optionally P up to 0.25; (all data given in % by weight); Preferably, in addition to Fe and unavoidable impurities, Si from 2.3 to 3.40, Al from 0.3 to 1.1, Mn from 0.07 to 0.250; optionally P up to 0.030; (all data in % by weight), The metal sheet of claim 15.

17. The sheet metal is a soft magnetic metallic material, for example containing, in addition to Fe and unavoidable impurities, the following components (all data in % by weight): Si from 0.1 to 4.0, Al from 0.01 to 2.60, Mn of 0.07 to 3.0, optionally P up to 0.5; optionally B up to 0.015; optionally up to 0.2 Sb; optionally up to 0.01 Zn, optionally up to 5 Cr, optionally up to 5 Ni; optionally a V of up to 0.25; optionally up to 0.5 Sn; optionally As up to 0.01; optionally up to 0.3 Nb; optionally W up to 0.5; optionally up to 0.85 Zr; optionally Mo up to 0.2; optionally Cu up to 1.0; optionally up to 0.5 Ti, optionally C up to 0.5; optionally up to 0.01 Ce, The metal sheet according to any one of claims 1 to 16, characterized in that it consists of

18. The sheet metal according to any one of claims 15 to 17, wherein the sheet metal has a thickness of 0.05 mm to 2.5 mm, preferably 0.15 mm to 0.4 mm.

19. The sheet metal according to any one of claims 15 to 18, wherein the sheet metal is a sandwich or is covered on one or both sides with an acoustically damping functional layer.

20. The metal sheet according to any one of claims 14 to 18, wherein one or both sides of the metal sheet are covered with an acoustically damping functional layer having an acrylate as a chemical base, and the adhesive coating is directly connected to the acoustically damping functional layer.

21. 21. The sheet metal according to any one of claims 14 to 20, wherein the sheet metal is a non-oriented electrical strip with specific core losses P1.0; in the range of 0.7-7 W / kg at 50 Hz, P1.5; in the range of 1.8-15 W / kg at 50 Hz, and / or with polarization in J2500 in the range of 1.45 T to 1.71 T and J5000 in the range of 1.6 T to 1.8 T, preferably with specific core losses P1.0; in the range of 1.0-1.5 W / kg at 50 Hz, P1.5; in the range of 2.2-3.3 W / kg at 50 Hz, and / or with polarization in J2500 in the range of 1.47 T to 1.57 T and J5000 in the range of 1.58 T to 1.65 T.

22. The sheet metal according to any one of claims 14 to 21, having a longitudinal yield strength at room temperature of 310 to 600 MPa, an ultimate tensile strength of 400 to 640 MPa, and an elongation at break A80 of 7 to 32%.

23. A method for manufacturing an electromagnetic component, in particular a sheet metal core for an electric machine, the sheet metal core being preferably either a stator core or a rotor core, comprising the following steps: A) providing a sheet metal with an adhesive coating or a plurality of sheet metals with an adhesive coating according to any one of claims 1 to 22, B) transporting the sheet metal to an in-line system including a punching tool, a means for outputting infrared light, and an extrusion punch; C) punching out a moulding designed as a stator lamella or rotor lamella from the sheet metal provided in step A with a punching tool; D) applying infrared light by a means for outputting infrared light to activate the adhesive coating of the molded part formed in step C; D) extruding the molded article using an extrusion punch; E) positioning the molded part in the positioning area in alignment and / or angular alignment; F) repeating steps C) through E) until the desired number of molded articles is collected in the positioning area; Including, at least one upper lamp which is directed in the punching direction onto the surface of the first moulded part, - at least one lower lamp is provided which irradiates the surface of the second part opposite the punching tool against the punching direction, method.

24. 24. The method of claim 23, characterized in that the manufacturing of the part is performed in an in-line process, the punching tool and the extrusion punch being part of the same press.

25. 25. The method according to claim 23, characterized in that after the last molded part of the desired number of molded parts has been positioned, the part obtained by the compression step downstream of step F is finally compressed with uniform surface pressure.

26. A method according to any one of claims 23 to 25, characterised in that steps C to E are carried out at a stroke speed of at least 80 / min, preferably between 120 / min and 300 / min.

27. A method for manufacturing an electromagnetic component, in particular a sheet metal core for an electric machine, the sheet metal core being preferably either a stator core or a rotor core, comprising the following steps: A) providing a sheet metal with an adhesive coating or a plurality of sheet metals with an adhesive coating according to any one of claims 1 to 22, B) punching a number of lamellae, in particular shaped parts designed as stator or rotor lamellae, from the sheet metal provided in step A with a punching tool; C) overlapping the molded parts with registration and / or angle alignment; D) pressing the overlapping molded parts; E) heating the overlapped molded parts at a predetermined temperature for a predetermined time; F) an optional step, after positioning the last molded part of the desired number of molded parts, of compressing the part obtained by the compression step downstream of step E with a uniform surface pressure at the ends in a direction perpendicular to the surface of the molded part; The method includes:

28. 28. A method according to claim 27, characterized in that said predetermined time is between 10 and 60 minutes, preferably between 10 and 40 minutes.

29. A method according to any of claims 27 or 28, wherein the predetermined temperature is between 100°C and 200°C, preferably between 100°C and 150°C.

30. A sheet metal core for an electrical component or machine comprising a plurality of mouldings of sheet metal according to any one of claims 1 to 22.

31. 31. The sheet metal core according to claim 30, designed as a stator core or as a rotor core.

32. 32. An electric machine, in particular an electric motor, having a stator core and / or a rotor core according to claim 31.

33. 33. The electric machine of claim 32 designed as an electric motor for a car, a truck, an electric two-wheeler, a small electric vehicle, an aircraft or a drone.

34. An electric machine comprising an electric component according to claim 30.

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