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  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/26—Methods of annealing
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  • C21D6/00—Heat treatment of ferrous alloys
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  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1216—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties characterised by the working steps
  • C21D8/1222—Hot rolling
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  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1216—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties characterised by the working steps
  • C21D8/1233—Cold rolling
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  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1244—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties characterised by the heat treatment
  • C21D8/1272—Final recrystallisation annealing
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  • 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
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  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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  • 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%
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  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
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  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
• • C—CHEMISTRY; METALLURGY
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  • C22C—ALLOYS
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  • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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  • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
• • 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
  • C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
• • C—CHEMISTRY; METALLURGY
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  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
• • C—CHEMISTRY; METALLURGY
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  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
• • C—CHEMISTRY; METALLURGY
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  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
• • C—CHEMISTRY; METALLURGY
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  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
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  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
• • 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
• • 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
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F3/00—Cores, Yokes, or armatures
  • H01F3/02—Cores, Yokes, or armatures made from sheets
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
  • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
  • H01F41/0206—Manufacturing of magnetic cores by mechanical means
  • H01F41/0233—Manufacturing of magnetic circuits made from sheets
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K15/00—Processes or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines
  • H02K15/02—Processes or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines of stator or rotor bodies
• • 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
  • C21D2201/00—Treatment for obtaining particular effects
  • C21D2201/05—Grain orientation
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/60—Other road transportation technologies with climate change mitigation effect
  • Y02T10/64—Electric machine technologies in electromobility

Definitions

• the present invention relates to a non-oriented electrical steel sheet, a manufacturing method thereof, and a motor core using the non-oriented electrical steel sheet.
• a motor core is divided into a stator core and a rotor core.
• a large centrifugal force acts on the rotor core of an HEV drive motor due to its large outer diameter.
• the rotor core has a very narrow portion (width: 1 to 2 mm) called a rotor core bridge portion due to its structure, and this portion is in a particularly high stress state during motor operation.
• the electromagnetic steel sheets used for the rotor core must have excellent fatigue properties.
• the magnetic steel sheet used for the stator core desirably has high magnetic flux density and low core loss in order to achieve miniaturization and high output of the motor.
• the properties required for the magnetic steel sheets used in motor cores are that the magnetic steel sheets for rotor cores should have excellent fatigue properties, and the magnetic steel sheets for stator cores should have high magnetic flux density and low iron loss. is.
• the properties required for the rotor core and stator core are significantly different.
• the rotor core material and the stator core material are simultaneously obtained by punching from the same material steel plate, and then the respective steel plates are laminated to assemble the rotor core or the stator core. is desirable.
• Patent Document 1 discloses manufacturing a high-strength non-oriented electrical steel sheet and punching the steel sheet into a rotor core material.
• a technique for manufacturing a high-strength rotor core and a low-iron-loss stator core from the same material is disclosed, in which a stator core material is sampled and layered to assemble the rotor core and the stator core, and then strain relief annealing is performed only on the stator core.
• the yield stress is improved by using a high-strength non-oriented electrical steel sheet, but the punching fatigue strength, which is the most important characteristic, is not necessarily improved.
• the punching fatigue strength is the fatigue strength in the case where the end face is not processed such as polishing after punching.
• the technique disclosed in Patent Document 1 has a problem in that the iron loss value after stress relief annealing cannot necessarily stably achieve the level required in industry.
• the present invention has been made in view of the above-mentioned problems of the prior art, and its object is to provide a high-strength non-oriented electrical steel sheet having good fatigue properties suitable for rotor cores and an excellent magnetic steel sheet suitable for stator cores.
• the object is to provide a non-oriented electrical steel sheet having properties (low core loss) and to propose a method for manufacturing the non-oriented electrical steel sheet at low cost.
• the present inventors have made intensive studies to solve the above problems, and found that a non-oriented electrical steel sheet with high punching fatigue strength can be obtained by controlling the grain size distribution, and that the non-oriented electrical steel sheet can be strained.
• the present inventors have found that excellent low iron loss can be stably achieved when grains are grown by pre-annealing (heat treatment). Furthermore, it was found that the crystal grain size distribution can be controlled by optimizing the conditions in the final pass of cold rolling.
• the present invention has been made based on such findings, and has the following configurations.
• a non-oriented electrical steel sheet in % by mass, C: 0.01% or less, Si: 2.0% or more and 5.0% or less, Mn: 0.05% or more and 5.00% or less, P: 0.1% or less, S: 0.01% or less, Al: 3.0% or less and N: 0.0050% or less, Si + Al is 4.5% or more, and the balance is Fe and inevitable impurities,
• the average crystal grain size X1 is 50 ⁇ m or less
• the standard deviation S1 of the crystal grain size distribution is expressed by the following formula ( 1 ): S1 / X1 ⁇ 0.75 ( 1 ) and a skewness ⁇ 1 of grain size distribution of 2.00 or less.
• the component composition is further mass %, The non-oriented electrical steel sheet according to [1] above, containing Co: 0.0005% or more and 0.0050% or less.
• the component composition is further mass %, The non-oriented electrical steel sheet according to [1] or [2] above, containing Cr: 0.05% or more and 5.00% or less.
• the component composition is further mass %, Ca: 0.001% or more and 0.100% or less,
• the component composition is further mass %, The non-oriented electrical steel sheet according to any one of [1] to [4] above, containing any one or two of Sn: 0.001% or more and 0.200% or less and Sb: 0.001% or more and 0.200% or less.
• the component composition is further mass %, Cu: 0% or more and 0.5% or less, Ni: 0% or more and 0.5% or less, Ti: 0% or more and 0.005% or less, Nb: 0% or more and 0.005% or less, V: 0% or more and 0.010% or less, Ta: 0% or more and 0.002% or less, B: 0% or more and 0.002% or less, Ga: 0% or more and 0.005% or less, Pb: 0% or more and 0.002% or less, Zn: 0% or more and 0.005% or less, Mo: 0% or more and 0.05% or less, W: 0% or more and 0.05% or less,
• the non-oriented electrical steel sheet according to any one of [1] to [5] above, containing one or more of Ge: 0% or more and 0.05% or less and As: 0% or more and 0.05% or less.
• a non-oriented electrical steel sheet Having the component composition according to any one of [1] to [6], Regarding the grains in the steel sheet, the average grain size X2 is 80 ⁇ m or more , and the standard deviation S2 of the grain size distribution is expressed by the following formula ( 2 ): S2/X2 ⁇ 0.75 ( 2 ) and a skewness ⁇ 2 of grain size distribution of 1.50 or less.
• the pickled hot-rolled sheet has a final pass entrance temperature T1 of 50 °C or higher, a final pass rolling reduction r of 15% or higher, and a final pass strain rate ⁇ m of 100 s -1 or higher and 1000 s.
• the cold - rolled sheet is heated to an annealing temperature T2 of 700°C or higher and 850°C or lower under the condition that the average heating rate V1 from 500°C to 700°C is 10°C/s or more, and then cooled to
• a method for manufacturing a non-oriented electrical steel sheet comprising:
• a method for producing the non-oriented electrical steel sheet described in [7] above, wherein the non-oriented electrical steel sheet described in any one of [1] to [6] is A method for manufacturing a non-oriented electrical steel sheet , comprising a heat treatment step of heating at a heat treatment temperature T3 of.
• non-oriented electrical steel sheet having good fatigue properties suitable for rotor cores and a non-oriented electrical steel sheet having excellent magnetic properties (low iron loss) suitable for stator cores.
• these non-oriented electrical steel sheets can be provided from the same steel sheet. Therefore, by using the non-oriented electrical steel sheet of the present invention, a high-performance motor core can be provided at low cost with good material yield.
• the non-oriented electrical steel sheet of the present invention can also be suitably used for small-sized, high-output motors.
• the non-oriented electrical steel sheets of the present invention include a first non-oriented electrical steel sheet suitable mainly for rotor cores and a second non-oriented electrical steel sheet mainly suitable for stator cores.
• the preferred chemical composition is common to the first non-oriented electrical steel sheet and the second non-oriented electrical steel sheet.
• C 0.01% or less C is a harmful element that forms carbides during use of the motor, causes magnetic aging, and deteriorates iron loss characteristics.
• the C content in the steel sheet should be 0.01% or less.
• the C content is 0.004% or less.
• the C content is preferably 0.0001% or more because the steel sheet with excessively reduced C content is very expensive.
• Si 2.0% to 5.0%
• Si has the effect of increasing the specific resistance of steel and reducing iron loss, and also has the effect of increasing the strength of steel through solid-solution strengthening.
• the Si content should be 2.0% or more.
• the Si content if the Si content exceeds 5.0%, the saturation magnetic flux density decreases and the magnetic flux density remarkably decreases, so the upper limit of the Si content is set to 5.0%. Therefore, the Si content should be in the range of 2.0% or more and 5.0% or less.
• the Si content is preferably 2.5% or more and 5.0% or less, more preferably 3.0% or more and 5.0% or less.
• Mn 0.05% to 5.00%
• Mn is an element useful for increasing the specific resistance and strength of steel. In order to obtain such effects, the Mn content must be 0.05% or more. On the other hand, when the Mn content exceeds 5.00%, the precipitation of MnC may be promoted and the magnetic properties may be degraded, so the upper limit of the Mn content was made 5.00%. Therefore, the Mn content should be 0.05% or more and 5.00% or less.
• the Mn content is preferably 0.1% or more and preferably 3.0% or less.
• P 0.1% or less
• P is a useful element used for adjusting the strength (hardness) of steel.
• the P content exceeds 0.1%, the toughness decreases and cracks are likely to occur during working, so the P content is made 0.1% or less.
• the lower limit of the P content is not specified, it is preferable that the P content is 0.001% or more because a steel sheet with an excessively reduced P content is very expensive.
• the P content is preferably 0.003% or more and preferably 0.08% or less.
• S 0.01% or less S is an element that forms fine precipitates and adversely affects iron loss characteristics. In particular, if the S content exceeds 0.01%, the adverse effects become noticeable, so the S content is made 0.01% or less.
• the S content is preferably 0.0001% or more because the steel sheet with excessively reduced S is very expensive.
• the S content is preferably 0.0003% or more, preferably 0.0080% or less, and more preferably 0.005% or less.
• Al 3.0% or less
• Al is a useful element that has the effect of increasing the specific resistance of steel and reducing iron loss.
• the Al content is preferably 0.005% or more.
• the Al content is more preferably 0.010% or more, still more preferably 0.015% or more.
• the Al content exceeds 3.0%, nitridation of the surface of the steel sheet may be promoted and the magnetic properties may be degraded, so the upper limit of the Al content was made 3.0%.
• the Al content is preferably 2.0% or less.
• N is an element that forms fine precipitates and adversely affects iron loss characteristics. In particular, if the N content exceeds 0.0050%, the adverse effect becomes remarkable, so the N content is made 0.0050% or less.
• the N content is preferably 0.0030% or less. Although the lower limit of the N content is not specified, it is preferable that the N content is 0.0005% or more because steel sheets with excessively reduced N are very expensive.
• the N content is preferably 0.0008% or more and preferably 0.0030% or less.
• Si + Al 4.5% or more
• the balance other than the above components is Fe and unavoidable impurities.
• the composition of the electrical steel sheet of another embodiment may contain, in addition to the above components (elements), a predetermined amount of one or more selected from the elements described later, depending on the required properties. can be done.
• Co 0.0005% to 0.0050%
• Co has the effect of reinforcing the effect of reducing the skewness of the grain size distribution of the annealed sheet by appropriately controlling Si + Al and cold rolling conditions. That is, by adding a small amount of Co, the skewness of the grain size distribution can be stably reduced. In order to obtain such effects, the Co content should be 0.0005% or more. On the other hand, if the content of Co exceeds 0.0050%, the effect saturates and unnecessarily increases the cost. Therefore, the above component composition preferably further contains Co: 0.0005% or more and 0.0050% or less.
• the above component composition preferably further contains Cr: 0.05% or more and 5.00% or less.
• Ca 0.001% to 0.100%
• Ca is an element that fixes S as a sulfide and contributes to the reduction of iron loss.
• the Ca content should be 0.001% or more.
• the upper limit of the Ca content is set to 0.100%.
• Mg 0.001% to 0.100%
• Mg is an element that fixes S as a sulfide and contributes to the reduction of iron loss. In order to obtain such effects, the Mg content should be 0.001% or more. On the other hand, when the content of Mg exceeds 0.100%, the effect saturates and the cost is unnecessarily increased.
• REM 0.001% to 0.100% REM is a group of elements that fix S as sulfides and contribute to the reduction of iron loss. In order to obtain such effects, the REM content should be 0.001% or more. On the other hand, when the content of REM exceeds 0.100%, the effect saturates and the cost unnecessarily increases.
• the above component composition further contains one or more of Ca: 0.001% to 0.100%, Mg: 0.001% to 0.100%, and REM: 0.001% to 0.100%. is preferred.
• Sn 0.001% or more and 0.200% or less
• Sn is an element that is effective in improving the magnetic flux density and reducing iron loss by improving the texture.
• the Sn content should be 0.001% or more.
• the Sn content exceeds 0.200%, the effect saturates and unnecessarily increases the cost.
• Sb 0.001% or more and 0.200% or less
• Sb is an element that is effective in improving the magnetic flux density and reducing iron loss by improving the texture.
• the Sb content should be 0.001% or more.
• the content of Sb exceeds 0.200%, the effect saturates, and the cost unnecessarily increases.
• the above component composition preferably further contains one or two of Sn: 0.001% or more and 0.200% or less and Sb: 0.001% or more and 0.200% or less.
• Cu 0% to 0.5%
• Cu is an element that improves the toughness of steel and can be added as appropriate. However, when the Cu content exceeds 0.5%, the effect saturates, so when Cu is added, the upper limit of the Cu content is set at 0.5%.
• the Cu content is more preferably 0.01% or more and more preferably 0.1% or less. Note that the Cu content may be 0%.
• Ni 0% or more and 0.5% or less
• Ni is an element that improves the toughness of steel and can be added as appropriate. However, when the Ni content exceeds 0.5%, the effect saturates, so when Ni is added, the upper limit of the Ni content is set to 0.5%. When Ni is added, the Ni content is more preferably 0.01% or more and more preferably 0.1% or less. Note that the Ni content may be 0%.
• Ti 0% to 0.005%
• Ti forms fine carbonitrides and increases the strength of the steel sheet by precipitation strengthening, thereby improving the punching fatigue strength, so it can be added as appropriate.
• the content of Ti exceeds 0.005%, it deteriorates the grain growth in the heat treatment process and causes an increase in core loss. Therefore, when adding Ti, the upper limit of the Ti content is set to 0.005%.
• Ti content is more preferably 0.002% or less. Note that the Ti content may be 0%.
• Nb 0% or more and 0.005% or less Nb forms fine carbonitrides and increases the steel sheet strength by precipitation strengthening, thereby improving the punching fatigue strength. Therefore, it can be added as appropriate.
• the content of Nb exceeds 0.005%, it deteriorates the grain growth in the heat treatment process and causes an increase in iron loss. Therefore, when Nb is added, the upper limit of the Nb content is set to 0.005%.
• the Nb content is more preferably 0.002% or less. Note that the Nb content may be 0%.
• V 0% or more and 0.010% or less V forms fine carbonitrides and increases the strength of the steel sheet by precipitation strengthening, thereby improving the punching fatigue strength, so it can be added as appropriate.
• the content of V exceeds 0.010%, it deteriorates the grain growth in the heat treatment process and causes an increase in iron loss. Therefore, when V is added, the upper limit of the V content is set to 0.010%.
• the V content is more preferably 0.005% or less. Note that the V content may be 0%.
• Ta 0% or more and 0.002% or less Ta forms fine carbonitrides and increases the strength of the steel sheet by precipitation strengthening, thereby improving the punching fatigue strength, so it can be added as appropriate.
• the content of Ta exceeds 0.002%, it deteriorates the grain growth in the heat treatment process and causes an increase in iron loss. Therefore, when Ta is added, the upper limit of the Ta content is set to 0.0020%. Ta content is more preferably 0.001% or less. Note that the Ta content may be 0%.
• B 0% or more and 0.002% or less B can be added as appropriate in order to improve the punching fatigue strength by forming fine nitrides and increasing the strength of the steel sheet through precipitation strengthening.
• the content of B exceeds 0.002%, the grain growth in the heat treatment process is deteriorated, resulting in an increase in iron loss. Therefore, when B is added, the upper limit of the B content is set to 0.002%.
• the B content is more preferably 0.001% or less. Note that the B content may be 0%.
• Ga 0% or more and 0.005% or less Ga forms fine nitrides and increases the strength of the steel sheet by precipitation strengthening, thereby improving the punching fatigue strength, so it can be added as appropriate.
• the content of Ga exceeds 0.005%, it deteriorates the grain growth in the heat treatment process and causes an increase in iron loss. Therefore, when Ga is added, the upper limit of the Ga content is set to 0.005%.
• Ga content is more preferably 0.002% or less. Note that the Ga content may be 0%.
• Pb 0% or more and 0.002% or less Pb forms fine Pb particles and improves the punching fatigue strength by increasing the strength of the steel sheet through precipitation strengthening, so it can be added as appropriate.
• the content of Pb exceeds 0.002%, it deteriorates the grain growth property in the heat treatment process and causes an increase in core loss. Therefore, when Pb is added, the upper limit of the Pb content is set to 0.002%.
• the Pb content is more preferably 0.001% or less. Note that the Pb content may be 0%.
• Zn 0% or more and 0.005% or less
• Zn is an element that increases fine inclusions and increases core loss. In particular, when the content exceeds 0.005%, the adverse effects become noticeable. Therefore, even when Zn is added, the Zn content is in the range of 0% or more and 0.005% or less. The Zn content is more preferably 0.003% or less. Note that the Zn content may be 0%.
• Mo 0% or more and 0.05% or less Mo forms fine carbides and increases the strength of the steel sheet by precipitation strengthening, thereby improving the punching fatigue strength, so it can be added as appropriate.
• the content of Mo exceeds 0.05%, it deteriorates the grain growth in the heat treatment process and causes an increase in iron loss. Therefore, when Mo is added, the upper limit of the Mo content is set to 0.05%.
• Mo content is more preferably 0.02% or less. Note that the Mo content may be 0%.
• W 0% or more and 0.05% or less W can be added as appropriate in order to improve the punching fatigue strength by forming fine carbides and increasing the strength of the steel sheet through precipitation strengthening.
• the content of W exceeds 0.05%, it deteriorates the grain growth in the heat treatment process and causes an increase in iron loss. Therefore, when W is added, the upper limit of the W content is set to 0.05%.
• the W content is more preferably 0.02% or less. Note that the W content may be 0%.
• Ge 0% or more and 0.05% or less Ge is an element effective in improving magnetic flux density and reducing iron loss by improving the texture, so it can be added as appropriate.
• the Ge content exceeds 0.05%, the effect saturates, so when Ge is added, the upper limit of the Ge content is made 0.05% or less.
• the Ge content is more preferably 0.002% or more and more preferably 0.01% or less. Note that the Ge content may be 0%.
• As 0% or more and 0.05% or less As is an element effective in improving magnetic flux density and reducing iron loss by improving the texture, so it can be added as appropriate.
• As content exceeds 0.05%, the effect saturates, so when adding As, the upper limit of the As content is made 0.05% or less.
• the As content is more preferably 0.002% or more and more preferably 0.01% or less. Note that the As content may be 0%.
• the balance other than the above components is Fe and unavoidable impurities.
• Such a first non-oriented electrical steel sheet is a material particularly suitable for rotor cores.
• the punching fatigue strength can satisfy the value required for rotor materials of motors applied to HEVs or EVs (hereinafter referred to as HEV/EV motors).
• HEV/EV motors the value required for rotor materials of motors applied to HEVs or EVs
• the average crystal grain size X1 was set to 50 ⁇ m or less.
• the value required for the rotor material is 430 MPa or more.
• the lower limit of the average grain size X 1 is not particularly specified, but if the grain size is excessively fine, the ductility of the steel sheet decreases and processing becomes difficult, so the average grain size X 1 is 1 ⁇ m or more. is preferably
• the grain size distribution skewness ⁇ 1 is 2.00 or less , the punching fatigue limit satisfies the above value required for HEV/EV motor rotor materials, and after strain relief annealing, Low core loss can be achieved. Therefore, in the first non-oriented electrical steel sheet, the skewness ⁇ 1 of the grain size distribution is set to 2.00 or less .
• the skewness ⁇ 1 of grain size distribution in the first non-oriented electrical steel sheet is preferably 1.50 or less.
• the lower limit of the skewness ⁇ 1 does not need to be specified in particular, but it is usually 0 or more even when manufactured by making full use of the technique of the present invention.
• the skewness ⁇ 1 can be obtained according to the procedure described in Examples below.
• the first non-oriented electrical steel sheet having the above-described microstructure (state of crystal grains) can become the second non-oriented electrical steel sheet when subjected to heat treatment for grain growth, as described later. Therefore, next, the microstructure (state of crystal grains) in the second non-oriented electrical steel sheet of the present invention will be described.
• Such a second non-oriented electrical steel sheet is a particularly suitable material for the stator core.
• the core loss of non-oriented electrical steel sheets varies depending on the average grain size.
• the average crystal grain size X2 was set to 80 ⁇ m or more . This makes it possible to achieve the target iron loss characteristic (W 10/400 ⁇ 11.0 (W/kg)).
• the standard deviation S2 of the crystal grain size distribution is calculated by the following formula in order to indicate the above-mentioned target value required for the stator material of the HEV/EV motor. (2): S2/X2 ⁇ 0.75 ( 2 ) It was decided to satisfy In addition, the second non-oriented electrical steel sheet has the standard deviation S2 of the grain size distribution of the following formula ( 2 ′): S2/X2 ⁇ 0.70 ( 2 ') is preferably satisfied.
• the inventors have found that excellent low core loss can be achieved by controlling the skewness of the grain size distribution. Such an effect can be obtained by simultaneously controlling the skewness of the grain size distribution and the standard deviation S2 of the grain size distribution described above.
• the large skewness of the grain size distribution means that the grain size distribution has a long tail on the coarse grain side, and there is a high probability that grains that are considerably coarser than the average grain size are present. means that Such crystal grains induce an increase in eddy current loss and deteriorate the iron loss characteristics of the steel sheet as a whole.
• the skewness ⁇ 2 of the grain size distribution is set to 1.50 or less.
• the grain size distribution skewness ⁇ 2 of the second non-oriented electrical steel sheet is preferably 1.20 or less, more preferably 1.00 or less.
• the lower limit of the skewness ⁇ 2 does not have to be specified, but it is usually 0 or more even when the method of the present invention is used for production.
• the skewness ⁇ 2 can be obtained according to the procedure described in Examples below.
• the motor core of the present invention is the first non-oriented electrical steel sheet, that is, the average grain size X 1 is 50 ⁇ m or less, the standard deviation S 1 satisfies [S 1 /X 1 ⁇ 0.75], and the distortion
• the rotor core which is a laminate of non-oriented electrical steel sheets with ⁇ 1 of 2.00 or less, and the above-mentioned second non-oriented electrical steel sheet, that is, the average crystal grain size X2 of which is 80 ⁇ m or more , and the standard deviation S2 satisfies [S 2 /X 2 ⁇ 0.75] and a stator core, which is a laminate of non-oriented electrical steel sheets having a skewness ⁇ 2 of 1.50 or less. Since the rotor core has high punching fatigue strength and the stator core has excellent magnetic properties, the motor core can easily achieve miniaturization and high output.
• the method for manufacturing the non-oriented electrical steel sheet of the present invention will be described. Schematically, it is a method in which a steel material having the above chemical composition is used as a starting material, and a hot rolling process, an optional hot-rolled sheet annealing process, a pickling process, a cold rolling process, and an annealing process are sequentially performed. , the first non-oriented electrical steel sheet of the present invention described above can be obtained. Moreover, the above-described second non-oriented electrical steel sheet of the present invention can be obtained by heat-treating the first non-oriented electrical steel sheet.
• other conditions are not particularly limited as long as the chemical composition of the steel material, the conditions of the cold rolling process, the conditions of the annealing process, and the conditions of the heat treatment process are within predetermined ranges.
• the method for manufacturing the motor core is not particularly limited, and a generally known method can be used.
• the steel material is not particularly limited as long as it has the chemical composition described above for the non-oriented electrical steel sheet.
• a method for melting the steel material is not particularly limited, and a known melting method using a converter or an electric furnace can be employed. From issues such as productivity, it is preferable to make a slab (steel material) by a continuous casting method after melting. good.
• a hot-rolling process is a process of obtaining a hot-rolled sheet by subjecting a steel material having the above chemical composition to hot-rolling.
• the hot-rolling process is not particularly limited as long as it is a process in which a steel material having the above composition is heated and hot-rolled to obtain a hot-rolled sheet having a predetermined size. Applicable.
• a steel material is heated to a temperature of 1000°C or more and 1200°C or less, and the heated steel material is subjected to hot rolling at a finish rolling delivery temperature of 800°C or more and 950°C or less.
• appropriate post-rolling cooling for example, the temperature range of 450 ° C to 950 ° C is cooled at an average cooling rate of 20 ° C / s to 100 ° C / s
• a hot-rolling process of coiling at a coiling temperature of 400° C. or higher and 700° C. or lower to obtain a hot-rolled sheet having a predetermined size and shape can be mentioned.
• the hot-rolled sheet annealing step is a step of annealing the hot-rolled sheet by heating and maintaining the hot-rolled sheet at a high temperature.
• the hot-rolled sheet annealing process is not particularly limited, and a common hot-rolled sheet annealing process can be applied. Note that this hot-rolled sheet annealing step is not essential and can be omitted.
• the pickling step is a step of pickling the hot-rolled sheet after the hot-rolling step or any hot-rolled sheet annealing step.
• the pickling process is not particularly limited as long as it can be pickled to the extent that the steel plate after pickling can be cold-rolled.
• a conventional pickling process using hydrochloric acid or sulfuric acid can be applied.
• the pickling process may be performed continuously in the same line as the hot-rolled sheet annealing process, or may be performed in a separate line.
• the cold rolling step is a step of cold rolling the pickled hot-rolled sheet (pickled sheet). More specifically, in the cold rolling process, the pickled hot-rolled sheet is subjected to a final pass entry temperature T1 of 50 °C or higher, a final pass rolling reduction r of 15% or higher, and a final pass strain of 15% or higher. Cold rolling is performed at a speed ⁇ m of 100 s ⁇ 1 or more and 1000 s ⁇ 1 or less to obtain a cold rolled sheet. In the cold rolling process, as long as the above cold rolling conditions are satisfied, the cold rolled sheet having a predetermined size may be obtained by cold rolling twice or more with intermediate annealing as necessary. Well, the conditions for the intermediate annealing in this case are not particularly limited, and conventional intermediate annealing can be applied.
• the final pass entrance temperature T1 shall be 50 °C or higher.
• the reason why the final pass entrance temperature T1 is set to 50 °C or more is to set the skewness ⁇ 1 of the crystal grain size distribution in the obtained first non-oriented electrical steel sheet to 2.00 or less and form the desired steel sheet structure. be.
• the final pass entry temperature T1 is less than 50°C, the strain distribution of the cold-rolled sheet is biased, and the grain growth selectivity is emphasized in the subsequent annealing process. skewness increases.
• the final pass entrance temperature T1 is preferably 55°C or higher, more preferably 60°C or higher. Although the upper limit of the final pass entrance temperature T1 is not particularly limited, the final pass entrance temperature T1 is preferably 300° C. or less from the viewpoint of seizure of the steel sheet to the rolls.
• the rolling reduction r of the final pass shall be 15% or more.
• the reason why the rolling reduction r of the final pass is set to 15% or more is to obtain the effects of a series of cold rolling controls and form a desired steel sheet structure. If the rolling reduction r of the final pass is less than 15%, the rolling reduction is too low, making it difficult to control the structure after annealing. On the other hand, when the rolling reduction r of the final pass is 15% or more, the effect of a series of cold rolling control is exhibited. As a result, a desired steel sheet structure is obtained.
• the draft r of the final pass is preferably 20% or more.
• the upper limit of the rolling reduction ratio r of the final pass is not particularly limited, an excessively high rolling reduction ratio requires a large capacity of the apparatus and makes it difficult to control the shape of the cold-rolled sheet. Usually less than 50%.
• the strain rate ⁇ m of the final pass is less than 100 s ⁇ 1 , the strain distribution of the cold-rolled sheet is biased, and the grain growth selectivity is emphasized in the subsequent annealing process, so the grain size of the annealed sheet The skewness of the distribution increases. The reason for this is not clear, but the inventors believe that a low strain rate reduces the flow stress, which makes it easier for strain to concentrate on crystal grains with easily deformable crystal orientations, and uneven deformation is likely to occur. I'm guessing. On the other hand, when the strain rate ⁇ m of the final pass exceeds 1000 s ⁇ 1 , the flow stress increases excessively, and brittle fracture tends to occur during rolling.
• the final pass strain rate ⁇ m is preferably 150 s ⁇ 1 or more and preferably 800 s ⁇ 1 or less.
• v R is the peripheral velocity of the roll (mm/s)
• R' is the radius of the roll (mm)
• h1 is the plate thickness at the entrance side of the roll (mm)
• r is the rolling reduction (%).
• the annealing step is a step of annealing the cold-rolled sheet that has undergone the cold-rolling step. More specifically, in the annealing step, the cold-rolled sheet that has undergone the cold rolling step is annealed at 700°C or higher and 850°C or lower under the condition that the average temperature increase rate V1 from 500°C to 700°C is 10°C/s or higher. After heating to temperature T2, it is cooled to obtain a cold - rolled annealed sheet (first non-oriented electrical steel sheet).
• an insulating coating can be applied to the surface.
• the method of coating and the type of coating are not particularly limited, and a conventional insulating coating process can be applied.
• the average heating rate V1 from 500°C to 700°C is set to 10°C/s or more.
• the reason why the average heating rate V1 is set to 10°C/s or more is that the standard deviation S1 of the grain size distribution in the obtained non-oriented electrical steel sheet satisfies the above formula ( 1 ), and the desired steel sheet structure This is to form
• the average heating rate V1 is less than 10° C./s, excessive recovery reduces the frequency of recrystallization nuclei formation and increases the location dependence of the number of recrystallization nuclei.
• the standard deviation S1 of the crystal grain size distribution becomes large, and the above formula ( 1 ) is no longer satisfied.
• the average heating rate V1 is 10° C./s or more, the frequency of recrystallization nuclei is high and the location dependence of the number of recrystallization nuclei is small. As a result, the standard deviation S1 of the crystal grain size distribution becomes small, and the above formula ( 1 ) is satisfied.
• the average heating rate V1 from 500°C to 700°C is preferably 20°C/s or more, more preferably 50°C/s or more.
• the upper limit of the average temperature increase rate V1 is not particularly limited, but if the temperature increase rate is excessively high, temperature unevenness is likely to occur, so the average temperature increase rate V1 is preferably 500°C/s or less. .
• the annealing temperature T2 is 700° C or higher and 850°C or lower.
• the reason for setting the annealing temperature T2 to 700° C or higher and 850°C or lower is as follows. When the annealing temperature T2 is less than 700° C., grain growth is suppressed, so the location dependence of the number of recrystallized nuclei is emphasized, resulting in a structure with initial non-uniformity. Therefore, the standard deviation S1 of the crystal grain size distribution becomes large.
• the annealing temperature T2 is 700° C or higher, sufficient grain growth occurs, the standard deviation S1 of the grain size distribution satisfies the above formula ( 1 ), and the desired steel sheet structure is obtained. can get.
• the annealing temperature T2 is preferably 750°C or higher.
• the annealing temperature T2 is higher than 850°C, recrystallized grains grow excessively and the average grain size X1 cannot be 50 ⁇ m or less. Therefore, the annealing temperature T2 should be 850°C or lower .
• the annealing temperature T2 is preferably 825 °C or less.
• the steel is heated to the annealing temperature T2 and then cooled.
• This cooling is preferably performed at a cooling rate of 50° C./s or less from the viewpoint of preventing uneven cooling.
• the heat treatment step is a step of heat-treating the cold-rolled annealed sheet (first non-oriented electrical steel sheet) that has undergone the annealing step. More specifically, in the heat treatment step, the cold-rolled annealed sheet (first non - oriented electrical steel sheet) that has undergone the annealing step is heated to a heat treatment temperature T3 of 750°C or higher and 900°C or lower. A heat-treated sheet (second non-oriented electrical steel sheet) can be obtained by cooling after heating.
• the heat treatment process is usually applied to the stator core formed by laminating the non-oriented electrical steel sheets, the same effect can be obtained even when the heat treatment process is applied to the non-oriented electrical steel sheets before lamination.
• Heat treatment temperature T3 750°C or higher and 900°C or lower
• the heat treatment temperature T3 is set at 750°C or higher and 900°C or lower.
• the reason for setting the heat treatment temperature T3 to 750° C. or higher and 900° C. or lower is as follows. If the heat treatment temperature T3 is less than 750°C , the grain growth becomes insufficient, and the average grain size X2 of the obtained second non-oriented electrical steel sheet cannot be 80 ⁇ m or more. Therefore , the heat treatment temperature T3 is set at 750°C or higher.
• the heat treatment temperature T3 is preferably 775°C or higher.
• the heat treatment temperature T3 is set to 900° C. or less.
• the heat treatment temperature T3 is preferably 875° C. or lower.
• the microstructure of the second non-oriented electrical steel sheet that is, the average grain size X2 is 80 ⁇ m or more , and the standard deviation S2 is [S2/ X2 ⁇ 0.75 ] and has a strain degree ⁇ 2 of 1.50 or less. This structural change is affected by the microstructure of the steel sheet before the heat treatment process.
• the steel sheet before the heat treatment process must have a standard
• the deviation S 1 must satisfy [S 1 /X 1 ⁇ 0.75] and the skewness ⁇ 1 must be 2.00 or less.
• a hot-rolled sheet with a thickness of 2.0 mm was obtained by subjecting the obtained slab to hot rolling.
• the obtained hot-rolled sheet was subjected to hot-rolled sheet annealing and pickling by a known method, and then cold-rolled to the sheet thickness shown in Table 2 to obtain a cold-rolled sheet.
• the obtained cold-rolled sheet was annealed under the conditions shown in Table 2 and then coated by a known method to obtain a cold-rolled annealed sheet (first non-oriented electrical steel sheet).
• a rotor core formed by laminating cold-rolled annealed sheets (first non-oriented electrical steel sheets) and a stator core formed by laminating heat-treated sheets (second non-oriented electrical steel sheets) are combined using a known method.
• first non-oriented electrical steel sheets first non-oriented electrical steel sheets
• second non-oriented electrical steel sheets second non-oriented electrical steel sheets
• ⁇ Evaluation> (Observation of microstructure) Specimens for structure observation were taken from the obtained cold-rolled annealed sheets and heat-treated sheets. Next, the thickness of the sampled test piece was reduced by chemical polishing so that the position corresponding to 1/4 of the thickness of the rolled surface (ND surface) became the observation surface, and the surface was mirror-finished. Electron backscatter diffraction (EBSD) measurements were performed on the mirrored observation plane to obtain local orientation data. At this time, the step size: 2 ⁇ m and the measurement area: 4 mm 2 or more were set for the cold-rolled annealed sheet, and the step size: 10 ⁇ m and the measurement area: 100 mm 2 or more were set for the heat-treated sheet.
• EBSD Electron backscatter diffraction
• the width of the measurement area was appropriately adjusted so that the number of crystal grains in the subsequent analysis was 5000 or more.
• the measurement may be performed by scanning the entire area once, or by combining the results of multiple scans using the Combo Scan function.
• Analysis software: OIM Analysis 8 was used to analyze the obtained local orientation data.
• the grain boundaries are defined as follows: Grain Tolerance Angle of 5°, Minimum Grain Size of 2, Minimum Anti Grain Size of 2, Multiple Rows Requirement and Anti-Grain Multiple Rows Requirement.
• Grain Size Diameter in microns
• X i grain size from Grain File Type 2
• Average grain sizes X 1 and X 2 , standard deviations S 1 and S 2 , and skewnesses ⁇ 1 and ⁇ 2 were calculated for all grain information obtained. The following formulas were used for the calculation.
• n is the number of crystal grains
• Xi is each crystal grain size data ( i : 1, 2, . . . , n).

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