Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/008—Heat treatment of ferrous alloys containing Si
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
  • C21D1/76—Adjusting the composition of the atmosphere
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1216—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the working step(s) being of interest
  • C21D8/1233—Cold rolling
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1216—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the working step(s) being of interest
  • C21D8/1238—Flattening; Dressing; Flexing
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1244—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest
  • C21D8/125—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest with application of tension
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1244—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest
  • C21D8/1272—Final recrystallisation annealing
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
  • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
  • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
  • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
  • H01F1/147—Alloys characterised by their composition
  • H01F1/14766—Fe-Si based alloys
  • H01F1/14775—Fe-Si based alloys in the form of sheets
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
  • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
  • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
  • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
  • H01F1/16—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of sheets

Definitions

• the invention relates to a method for producing a non-grain-oriented electrical steel strip.
• Non-grain-oriented electrical steel is required in many electrical engineering applications and is well known in practice.
• NGO Non Grain Oriented
• the non-grain-oriented metallic electrical steel is used to influence the course of electromagnetic fields.
• Typical applications for such steels are rotors and stators in electric motors and electric generators.
• non-grain-oriented metallic flat products in particular non-grain-oriented electrical steel, are required which combine comparatively low core losses at comparatively high frequencies with a comparatively high magnetic polarization and induction as well as comparatively high permeability, in particular in the relevant ranges of the magnetic field strength, namely at comparatively low magnetic field strength.
• the invention is based on the object of providing alternatives to known electrical strips or sheets which, with regard to their magnetic properties on the one hand and their mechanical properties on the other hand, are in a constant or higher degree, but also allows for a design in small thicknesses.
• the invention is solved by a method for producing a non-grain-oriented electrical steel strip having the features of claim 1.
• the final annealing is carried out in a continuous furnace.
• a strip tension acting on the strip is adjusted depending on a predetermined magnetic property which the resulting non-grain-oriented electrical strip should have.
• the electrical steel strip of greater thickness can be produced using a conventional production route via a continuous casting plant or via thin slab production.
• a steel melt with a suitable specification for example of the type mentioned at the beginning, is melted into a starting material and cast into a starting material, which in conventional production can be a slab or a thin slab.
• the raw material produced in this way can then be heated to a raw material temperature of, for example, between 1100 and 1300 degrees Celsius. If necessary, the raw material is reheated or kept at the respective target temperature using the casting heat.
• the pre-material heated in this way can then be hot-rolled into a hot strip with a thickness of, for example, between 1 mm and 3 mm, preferably between 1.5 mm and 2.5 mm.
• Hot rolling begins, for example, in a manner known per se, at a hot rolling initial temperature in the finishing stage of 900 to 1150 degrees Celsius and ends, for example, with a hot rolling final temperature of 700 to 920 degrees Celsius, in particular 780 to 850 degrees Celsius.
• the hot strip obtained can then be cooled to a coiling temperature and coiled into a coil.
• the coiling temperature is ideally chosen so that problems are avoided during the subsequent cold rolling.
• the coiling temperature is, for example, at most 700 degrees Celsius, preferably 550 to 700 degrees Celsius.
• step (A) can be transferred directly, i.e. immediately afterwards, to step (B) of the process according to the invention.
• step (A') hot strip annealing is carried out at a temperature of 700 to 800 degrees Celsius, preferably at a temperature of 720 to 1000 degrees Celsius, depending on the process used, for example batch annealing or continuous annealing.
• the specific infeed belt tension is at most 3 N/mm 2 , preferably at most 2 N/mm 2 , particularly preferably at most 1.7 N/mm 2
• the specific outfeed belt tension is at most 3 N/mm 2 , preferably at most 2 N/mm 2 , particularly preferably at most 1.7 N/mm 2
• the sum of the infeed belt tension and the outfeed belt tension can be considered, in which case the sum of the amount of specific infeed belt tension and the amount of specific outfeed belt tension should be at most 6 N/mm 2 , preferably at most 4 N/mm 2 , particularly preferably at most 3.4 N/mm 2 .
• all three conditions are met simultaneously.
• the specific belt tension is the result of the quotient of the belt tension, which is a force with the unit N, and the cross-section of the belt.
• the belt tension is for belt transport of Steel strip is a quantity known to the expert, and its measurement and monitoring is a common professional measure when operating strip mills. The measurement can be carried out, for example, using a commercially available force transducer, also known as a strain gauge, with a measuring amplifier.
• the specific strip tension is a measure of the tension state on the strip.
• the electrical steel strip is transported with an infeed roller stand positioned in front of the continuous furnace as viewed in the direction of strip transport with the infeed belt train and with an outfeed roller stand positioned after the continuous furnace as viewed in the direction of strip transport with the outfeed belt train.
• the preferred magnetic property is a predetermined maximum loss, i.e. maximum remagnetization loss, at a specified frequency and a specified polarization.
• the predetermined magnetic property can be a predetermined polarization at a specified control level. Both values have the advantage that they are values that are usually considered for sections of electrical steel strip and can therefore be determined without any special effort.
• the core losses can be understood, for example, in the sense of DIN EN 60404-2:2009-01: Magnetic materials - Part 2: Method for determining the magnetic properties of electrical steel strip and sheet using an Epstein frame.
• the formula symbol P(1.0T;50Hz) symbolizes core losses in watts per kilogram, in short: W/kg, in an alternating electromagnetic field with 50 Hz core frequency and 1.0 T magnetic flux density in the material.
• P(1.0T;400Hz) or P(1.0T;2000Hz) or another suitable value can be considered.
• P is a thickness-dependent parameter, it applies to the measured sample as it is, where, for example, the thickness of the sample can be between 0.200 mm and 0.300 mm.
• the magnetic polarization can be considered at a given field strength and frequency, also referred to collectively as the modulation:
• the formula symbol J100;50Hz denotes, for example, a magnetic polarization at a magnetic field strength of 100 A/m in an alternating electromagnetic field with 50 Hz.
• Methods for determining polarization and field strength are known to those skilled in the art, for example by means of an Epstein frame for determining the polarization, in particular in accordance with DIN EN 60404-2:2009-01: Magnetic materials - Part 2: Method for determining the magnetic properties of electrical steel strip and sheet using an Epstein frame.
• the polarization applies in particular to the measured sample as it is present according to the invention, wherein the thickness of the sample is advantageously between 0.200 mm and 0.300 mm.
• At least three samples are produced, with the following steps being carried out for each sample, preferably with identical production parameters: (A) Producing a hot-rolled, optionally hot-strip annealed, for example non-grain-oriented, electrical strip; (B) cold rolling the electrical strip provided in step (A) to a thickness of between 0.150 mm and 0.400 mm, preferably between 0.200 mm and 0.330 mm; (C) final annealing and cooling the cold strip obtained in step (B) to obtain the non-grain-oriented electrical strip.
• a sample is produced with a low strip tension during final annealing, and a sample is produced with a high strip tension during final annealing, and a sample is produced with an average strip tension lying between the low strip tension and the high strip tension.
• each of the samples apart from only the strip tension or tensions, corresponds in alloy composition and in the production process to the process provided for producing the electrical strip to be produced according to the invention.
• adjusting the belt tension acting on the belt is to be understood as adjusting the sum of the amount of specific infeed belt tension and the amount of specific outfeed belt tension, and a high belt tension is between 10 and 20 N/mm 2 , and a small belt tension is between 1 and 8 N/mm 2 , and the medium belt tension is a value that lies between the high belt tension and the small belt tension. It is not excluded that more than three values of the belt tension are considered.
• adjusting the belt tension acting on the belt is to be understood as adjusting a specific infeed belt tension, and a high belt tension is between 4 and 8 N/mm 2 , and a small belt tension is between 1 and 3 N/mm 2 , and the medium belt tension is a value that lies between the respective selected value for the high belt tension and the small belt tension. It is not excluded that more than three values of the belt tension are considered.
• step (iii) can be carried out, for example, on the basis of a relationship between the magnetic property and the specific strip tension obtained by means of linear regression fitting. This consideration does not follow a closed scientific theory, but rather the obvious observation that in the relevant strip tension ranges the magnetic quantities considered show an approximately linear relationship to one another.
• the selection of the strip tension acting on the strip can be carried out, for example, by selecting the highest strip tension with which the specified magnetic property is achieved, less a safety tolerance of, for example, 0.1% or 1% or 5% or 10% of the nominal value (for example in the case of magnetic loss) of the magnetic property or plus a safety tolerance of, for example, 0.1% or 1% or 5% or 10% of the nominal value (for example in the case of magnetic polarization) of the magnetic property.
• the adjustment of the belt tension acting on the belt is preferably carried out, as already mentioned above by way of example, by adjusting the sum of the amount of specific infeed belt tension and the amount of specific outfeed belt tension.
• the strip tension acting on the strip is adjusted as a function of a predetermined magnetic property of the non-grain-oriented electrical steel strip obtained by using value pairs of magnetic properties - strip tension as a reference, the value pairs of magnetic properties - strip tension being determined by the samples described above with steps (i) to (iii).
• the samples preferably correspond completely in terms of alloy composition and production process to the electrical steel strip to be produced according to the invention, with the exception of strip tensions that vary during the final annealing when producing the samples.
• the strip tension is set in such a way that a predetermined magnetic property that is desired for the finished strip is obtained according to the value pairs Magnetic property - strip tension or, for example, minus a safety tolerance of, for example, 0.1% or 1% or 5% or 10% of the nominal value (for example in the case of magnetic loss) of the magnetic property or plus a safety tolerance of, for example, 0.1% or 1% or 5% or 10% of the nominal value (for example in the case of magnetic polarization) of the magnetic property, is just achieved, alternatively: is just not achieved.
• a magnetic property corresponding to the predetermined magnetic property is assigned to a
• the strip tension to be set for the final annealing is assigned to the strip tension, and this strip tension is then set for the final annealing.
• a characteristic curve derived from the value pairs is used for the adjustment, which has been obtained from the value pairs, for example, by means of linear regression or by means of spline interpolation. It can therefore preferably be provided that a strip tension acting on the strip during the final annealing is adjusted in such a way that a predetermined magnetic property of the non-grain-oriented electrical strip obtained is obtained, and that the aim of obtaining a magnetic property in a predetermined manner is achieved by inferring the strip tension to be adjusted during the final annealing from empirically found value pairs of magnetic property - strip tension or from a characteristic curve derived from the empirically found value pairs, starting from a predetermined magnetic property.
• the process is adjusted such that the annealing temperature is maintained for a period of 10 to 90 seconds.
• the cold strip is cooled to room temperature, whereby the cooling of the cold strip is preferably carried out to room temperature with a cooling rate of maximum 25 K/s This means that a cooling rate of 25 K/s is not exceeded during the entire cooling process.
• Controlled cooling is used in particular to prevent the formation of undesirable residual stresses in the electrical steel strip, which have detrimental properties on the magnetic behavior of the strip.
• both conditions are met cumulatively.
• the cold rolling in step (B) is preferably carried out to a thickness of the cold strip between 0.230 mm and 0.265 mm, preferably to a thickness between 0.235 mm and 0.255 mm.
• Hot-rolled electrical steel strip with the following composition was cold-rolled to a final thickness of 0.30 mm and then finally annealed: Composition, each in weight percent, balance Fe and unavoidable impurities: carbon 0.0021 silicon 3.27 manganese 0.13 phosphorus 0.011 sulfur 0.0005 aluminum 0.755 chrome 0.028 copper 0.009 niobium 0.001 molybdenum 0.001 Nitrogen 0.0016 titanium 0.0028 Vanadium 0.001 nickel 0.015 boron 0.0003 tin 0.002 magnesium 0.0024 arsenic 0.003 calcium 0.0004 The final annealing was carried out in the continuous furnace with the following parameters: Final thickness mm Furnace annealing temperature °C Hydrogen content in atmosphere % Glow time in the high glow range s 0.30 960-1000 60-80 40
• the magnetic properties for the strip samples obtained are determined.
• the core losses P were determined using an Epstein frame in accordance with DIN EN 60404-2:2019-05: "Magnetic materials - Part 2: Method for determining the magnetic properties of electrical strip and sheet using an Epstein frame”. Electrical sheets were cut into longitudinal and transverse strips and measured as a mixed sample in the Epstein frame.
• Table 1 shows that there is a continuous relationship between the magnetic properties and the inlet and/or outlet belt tensions.
• the table obtained can be used as a reference for later repetitions, whereby the newly acquired knowledge of a reproducible relationship between strip tension and magnetic properties is used to adjust the strip tension based on the desired magnetic properties, whereby the strip tension is preferably maximized for given desired magnetic properties.

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• 2022
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