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US20180355454A1 - Method for producing non-oriented electrical steel sheet - Google Patents

Method for producing non-oriented electrical steel sheet Download PDF

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US20180355454A1
US20180355454A1 US15/781,920 US201615781920A US2018355454A1 US 20180355454 A1 US20180355454 A1 US 20180355454A1 US 201615781920 A US201615781920 A US 201615781920A US 2018355454 A1 US2018355454 A1 US 2018355454A1
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mass
heating
steel sheet
oriented electrical
induction heating
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Tomoyuki Okubo
Yoshiaki Zaizen
Yoshihiko Oda
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JFE Steel Corp
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JFE Steel Corp
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    • 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
    • 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
    • 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
    • C21D1/34—Methods of heating
    • C21D1/42—Induction heating
    • 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
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • 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
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • 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
    • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
    • 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
    • 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
    • C21D8/1222—Hot 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
    • C21D8/1233—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
    • C21D8/1244—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
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
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    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • 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
    • C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
    • 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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C2202/00—Physical properties
    • C22C2202/02—Magnetic
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Definitions

  • This invention relates to a method for producing a non-oriented electrical steel sheet, and more particularly to a method for producing a non-oriented electrical steel sheet having a high magnetic flux density.
  • the magnetic flux density in the non-oriented electrical steel sheet In order to increase the magnetic flux density in the non-oriented electrical steel sheet, it is known effective to improve a texture of a product sheet, or decrease grains of ⁇ 111 ⁇ orientation and/or increase grains of ⁇ 110 ⁇ or ⁇ 100 ⁇ orientation.
  • the magnetic flux density is increased by increasing a crystal grain size before a cold rolling or optimizing a cold rolling reduction to improve the texture.
  • a method of increasing a heating rate in recrystallization annealing As another means for controlling the texture of the product sheet is mentioned a method of increasing a heating rate in recrystallization annealing.
  • This method is often used in the production of grain-oriented electrical steel sheets, which is based on the fact that an iron loss is improved by increasing a heating rate in decarburization annealing (primary recrystallization annealing) to increase grains of ⁇ 110 ⁇ orientation in the steel sheet after the decarburization annealing and refining secondary recrystallized grains of the steel sheet after finish annealing (for example, see Patent Document 1).
  • Patent Document 1 JP-A-H01-290716
  • Patent Document 2 JP-A-H02-011728
  • Patent Document 3 JP-A-2011-256437
  • Patent Document 4 JP-A-2012-132070
  • Patent Document 5 JP-A-2013-010982
  • Patent Document 1 relates to the grain-oriented electrical steel sheet and cannot be applied to a non-oriented electrical steel sheet as it is.
  • Patent Document 3 utilizes an induction heating, but the effect of stably increasing the magnetic flux density cannot be obtained by this technique as a result of the inventors' verification. Also, this technique is required to conduct cooling and reheating after the rapid heating, so that there is a problem that the production cost and equipment cost become higher.
  • aspects of the invention are made in view of the above problems inherent to the conventional techniques, and an object thereof is to propose a method for producing a non-oriented electrical steel sheet which is capable of stably attaining a higher magnetic flux density even when the heating in the finish annealing is a rapid heating by an induction heating.
  • the inventors have made various studies focusing on heating conditions in the finish annealing, especially conditions of an induction heating and a radiation heating to solve the above task. As a result, it has been found out that it is effective for increasing the magnetic flux density by performing the heating in the finish annealing two stages of performing an induction heating and subsequently a radiation heating, conducting the induction heating up to not lower than 720° C. at an average heating rate of not less than 50° C./sec between 600° C. and 700° C., and setting a time from the end of the induction heating to the start of the radiation heating to not more than 8 seconds.
  • one aspect of the invention proposes a method for producing a non-oriented electrical steel sheet by hot rolling a steel slab having a chemical composition comprising C: not more than 0.005 mass %, Si: not more than 5.0 mass %, Mn: not more than 3.0 mass %, P: not more than 0.2 mass %, S: not more than 0.005 mass %, Al: not more than 3.0 mass %, N: not more than 0.005 mass %, Ni: not more than 3.0 mass %, Cr: not more than 5.0 mass %, Ti: not more than 0.005 mass %, Nb: not more than 0.005 mass %, B: not more than 0.005 mass %, 0: not more than 0.005 mass % and the remainder being Fe and inevitable impurities and subjecting the sheet to a cold rolling after a hot band annealing or without a hot band annealing and then to a finish annealing, characterized in that heating in the finish annealing is conducted in two
  • the steel slab used in the method for producing a non-oriented electrical steel sheet according to aspects of the invention is characterized by containing one or two selected from Sn: 0.005-0.20 mass % and Sb: 0.005-0.20 mass % in addition to the above chemical composition.
  • the steel slab used in the method for producing a non-oriented electrical steel sheet according to aspects of the invention is characterized by containing one or two or more selected from Ca: 0.0001-0.010 mass %, Mg: 0.0001-0.010 mass % and REM: 0.0001-0.010 mass % in addition to the above chemical composition.
  • the method for producing a non-oriented electrical steel sheet according to aspects of the invention is characterized in that a ferrite grain size of a steel sheet structure before a final cold rolling in the cold rolling is set to not more than 70 ⁇ m.
  • FIG. 1 is a diagram showing a heating pattern at 200° C./sec.
  • FIG. 2 is a graph showing an influence of an achieving temperature by an induction heating (end temperature) upon a magnetic flux density B 50 when a time from an end of an induction heating to a start of a radiation heating is set to 2 seconds.
  • FIG. 3 is a graph showing an influence of a time from an end of an induction heating to a start of a radiation heating upon a magnetic flux density B 50 when an achieving temperature by an induction heating is 740° C.
  • the hot rolled sheet is pickled and cold rolled to form a cold rolled sheet having a final sheet thickness of 0.5 mm, which is then subjected to a finish annealing (recrystallization annealing) under various heating conditions.
  • the finish annealing is conducted in two stages of heating in a solenoid type induction heating furnace and subsequently heating in an electric furnace (radiation heating furnace), wherein an average heating rate between 600° C. and 700° C. is set to two levels of 20° C./sec and 200° C./sec.
  • an atmosphere is a dry nitrogen atmosphere.
  • a heating pattern at 200° C./sec is shown in FIG. 1 .
  • test specimens of 280 mm ⁇ 30 mm in a rolling direction and a widthwise direction as a longitudinal direction to measure a magnetic flux density B 50 by an Epstein test in accordance with JIS C2550-1 (2011) and evaluate magnetic properties thereof.
  • FIG. 2 shows an influence of an achieving temperature by an induction heating (end temperature) upon the magnetic flux density B 50 when a time from an end of the induction heating to a start of a radiation heating (transition time) is set to 2 seconds.
  • the magnetic flux density is largely increased by setting the achieving temperature to not lower than 720° C.
  • FIG. 3 shows an influence of a time from the end of the induction heating to the start of the radiation heating (transition time) upon the magnetic flux density B 50 when the achieving temperature by the induction heating is 740° C.
  • the magnetic flux density is increased by setting the transition time to not more than 8 seconds.
  • a grain-oriented electrical steel sheet is produced by using a raw material (slab) containing a large amount of a hard second phase such as carbide, inhibitor or the like in its ferrite structure to stably develop a secondary recrystallization.
  • a raw material such as carbide, inhibitor or the like
  • a steel sheet obtained from the raw material containing such a second phase is subjected to cold rolling, local crystal rotation is caused in a ferrite around the second phase, which is easily rendered in a nucleating site for recrystallization.
  • C is a harmful element causing magnetic aging to form a carbide deteriorating an iron loss property in the product sheet.
  • C is limited to not more than 0.0050 mass %. Preferably, it is not more than 0.0030 mass %.
  • Si not more than 5.0 mass %
  • Si has an effect of increasing a specific resistance of steel to reduce an iron loss and thus is preferable to be added in an amount of not less than 0.1 mass %. Preferably, it is not less than 1.0 mass %. However, an addition exceeding 5.0 mass % causes hardening of the steel and makes rolling difficult, so that the upper limit of Si is set to 5.0 mass %. A preferable upper limit is 4.0 mass %. Moreover, Si reduces the iron loss but also decreases the magnetic flux density, and thus when the magnetic flux density is considered to be important, it is preferably not more than 3.0 mass %.
  • Mn has not only an effect of increasing a specific resistance of steel to reduce an iron loss but also an effect of preventing hot brittleness, so that it is preferable to be added in an amount of not less than 0.05 mass %. More preferably, it is not less than 0.1 mass %. However, an addition exceeding 3.0 mass % causes precipitation of a carbonitride and rather deteriorates the iron loss property, so that an upper limit of Mn is 3.0 mass %. A preferable upper limit is 1.0 mass %. Moreover, an addition exceeding 2.0 mass % largely decreases the magnetic flux density similarly to Si, so that when the magnetic flux density is considered to be important, it is preferably not more than 2.0 mass %.
  • P is an element used for controlling a hardness (punchability) of steel. When it is added in an amount exceeding 0.2 mass %, however, steel is embrittled to make rolling difficult, so that the upper limit of P is set to 0.2 mass %. It is preferably not more than 0.1 mass %, more preferably not more than 0.04 mass %.
  • Al has an effect of increasing a specific resistance of steel to reduce an iron loss similarly to Si. When it exceeds 3.0 mass %, however, steel is hardened to make rolling difficult, and thus the upper limit is set to 3.0 mass %.
  • Al is preferably not more than 0.01 mass %. More preferably, it is not more than 0.003 mass %.
  • Al preferably falls within a range of 0.1 to 3.0 mass %. More preferably, it falls in a range of 0.1 to 2.0 mass %.
  • Ni not more than 3.0 mass %
  • Ni is an element effective for adjusting the strength of steel and increasing the magnetic flux density.
  • Ni is an expensive element, and an addition exceeding 3.0 mass % brings about the increase of raw material cost, so that the upper limit is set to 3.0 mass %. It is preferably not more than 1.0 mass %, more preferably not more than 0.5 mass %.
  • Cr has an effect of increasing a specific resistance of steel to reduce an iron loss.
  • an addition exceeding 5.0 mass % brings about precipitation of carbonitride and adversely deteriorates the iron loss property, so that the upper limit of Cr is set to 5.0 mass %. It is preferably not more than 2.0 mass %, more preferably not more than 1.0 mass %.
  • S, N, Ti, Nb, B and O are harmful elements forming fine precipitates of carbide, nitride, sulfide, boride, oxide and so on to deteriorate the iron loss property.
  • the upper limit of the each element is 0.005 mass %.
  • Ti, Nb and B may be intentionally added for fixing nitrogen, but the amount is necessary to be within the above range even in this case.
  • the non-oriented electrical steel sheet according to aspects of the invention can contain the following ingredients in addition to the aforementioned ingredients.
  • each element is preferable to be added in an amount of not less than 0.005 mass %. However, when each element is added in an amount exceeding 0.20 mass %, the above effect is saturated. Therefore, each addition amount of Sn and Sb is preferable to fall within a range of 0.005 to 0.20 mass %. More preferably, it is a range of 0.01 to 0.1 mass %.
  • Ca, Mg and REM have an effect of forming and fixing stable sulfides and/or selenides with S and/or Se to improve the grain growth.
  • each element is preferable to be added in an amount of not less than 0.0001 mass %.
  • the upper limit is preferably set to 0.010 mass %. More preferably, it falls within a range of 0.0010 to 0.0050 mass %.
  • a steel adjusted to have the aforementioned chemical composition is melted by a well-known refining process such as a converter-vacuum degassing treatment or the like and then shaped into a steel material (slab) by a well-known method such as continuous casting method or the like.
  • a reheating temperature of the slab prior to the hot rolling, a finish rolling end temperature in the hot rolling, a coiling temperature and so on are not particularly limited. However, it is preferable that the reheating temperature falls within a range of 1000° C. to 1200° C. and the finish rolling end temperature falls within a range of 700° C. to 900° C. and the coiling temperature falls within in a range of 600° C. to 800° C. from a viewpoint of ensuring the magnetic properties and productivity.
  • the steel sheet after the hot rolling (hot rolled sheet) is subjected to a hot band annealing, if required, and one cold rolling or two or more cold rollings interposing an intermediate annealing therebetween to form a cold rolled sheet having a final sheet thickness.
  • a ferrite grain size of the steel sheet structure before the final cold rolling is preferably controlled to not more than 70 ⁇ m, more preferably not more than 50 ⁇ min order to enhance the effect of aspects of the invention.
  • the above ferrite grain size is an average grain size obtained by measuring grain sizes in a cross-sectional texture of the steel sheet in the thickness direction through an intercept method.
  • the inventors have considered the reason why the application of aspects of the invention is preferable when the ferrite grain size of the steel sheet structure before the final cold rolling is not more than 70 ⁇ m as follows. Since recrystallized grains having a ⁇ 111 ⁇ orientation are produced from the vicinity of the grain boundary of the steel sheet structure before the final cold rolling in the finish annealing, when the ferrite grain size of the structure before the final cold rolling is small, ⁇ 111 ⁇ recrystallized grains are increased in the structure after the cold rolling and recrystallization. Thus, it is considered that an effect of decreasing ⁇ 111 ⁇ grains by the rapid heating becomes remarkable.
  • the hot band annealing or intermediate annealing In order to render the ferrite grain size before the final cold rolling in not more than 70 ⁇ m, it is preferable to omit the hot band annealing or intermediate annealing, and when such a treatment is conducted, it is preferable to decrease the annealing temperature as much as possible. From a viewpoint of preventing ridging, however, it is preferable that the recrystallization ratio of the steel sheet before the final cold rolling is controlled to not less than 80%. Moreover, there is a merit that a reduction of the production cost can be attained by decreasing the temperature in the hot band annealing or intermediate annealing or by omitting the hot band annealing or intermediate annealing.
  • the cold rolled sheet having a given final sheet thickness is subjected to a finish annealing.
  • the heating in the finish annealing is performed in two stages of conducting an induction heating and then a radiation heating.
  • the induction heating is of solenoid type. It is because the solenoid type has a merit that a heating efficiency is high and a uniformity of the temperature in the widthwise direction is excellent.
  • the induction heating is used in a preceding stage of the heating process in the finish annealing.
  • the more preferable heating rate is not less than 100° C./sec.
  • the upper limit of the heating rate is not particularly limited, but is preferably set to not more than 1000° C./sec from a viewpoint of reducing the equipment cost.
  • an average heating rate in a temperature range of lower than 600° C. is not particularly defined, but is preferably set to not less than 1° C./sec, preferably not less than 10° C./sec from a viewpoint of the productivity.
  • the induction heating may be conducted by dividing into plural segments. Also, in order to reduce the equipment cost for the induction heating, the steel sheet is preheated by a radiation heating before the induction heating and then the induction heating may be applied only to a temperature range of the rapid heating. In this case, the upper limit of the preheating temperature is preferable to be set to not higher than 500° C. from a viewpoint of recovery prevention.
  • an achieving temperature by the induction heating (end temperature) is necessary to be not lower than 720° C. Preferably, it is not lower than 735° C. Moreover, the heating efficiency violently drops in the vicinity of a Curie point of the material in the solenoid type induction heating, so that the induction heating furnace is desirably designed so as to heat by a large power in the vicinity of the Curie temperature.
  • the upper limit of the achieving temperature by the induction heating is not particularly limited, but is desirable to be about 780° C. from a viewpoint of suppressing the equipment cost.
  • a time from the end of the induction heating to the start of the radiation heating is necessary to be not more than 8 seconds. It is preferably not more than 5 seconds, more preferably not more than 3 seconds.
  • a high-temperature radiation heating furnace is desirable to be arranged apart from the induction heating equipment from a viewpoint of protecting the induction heating equipment. It is difficult to satisfy the above conditions unless these equipment is designed intentionally.
  • the steel sheet temperature is not decreased to not higher than 700° C. from the end of the induction heating to the start of the radiation heating from a viewpoint of promoting recrystallization of ⁇ 110 ⁇ orientation grains or ⁇ 100 ⁇ orientation grains by the rapid heating.
  • a condition can be easily attained by threading a dummy coil or the like in an annealing furnace to increase a furnace wall temperature between an induction heating furnace and a radiation heating furnace before the application of aspects of the invention.
  • the heating rate by the radiation heating is preferable to be not less than 5° C./sec from a viewpoint of promoting the recrystallization.
  • Such a condition can be easily fulfilled by using a usual radiation heating furnace. More preferably, it is not less than 10° C./sec.
  • the “radiation heating” in accordance with aspects of the invention means a system for heating the steel sheet by radiation from a heating element such as a radiant tube, an electric heater or the like, and a heating system of heating only by radiation from the furnace wall is excluded.
  • a heating method not using the heating element such as a radiant tube, an electric heater or the like may be used, but it is, not realistic considering the industrial productivity.
  • a soaking temperature after being heated by the radiation heating falls within a range of 740° C. to 1100° C. and a soaking time falls within a range of 1 to 600 seconds.
  • the soaking temperature is lower than 740° C., the good iron loss property cannot be obtained, and when the soaking times is less than 1 second, the control of the soaking temperature during the operation is difficult.
  • the soaking temperature exceeds 1100° C., pick-up defects are frequently caused, and when the soaking time exceeds 600 seconds, the decrease of the productivity is caused. More preferably, the soaking temperature falls within 900° C. to 1050° C., and the soaking time falls within 5 to 120 seconds.
  • An atmosphere in the finish annealing is preferable to be a non-oxidizing atmosphere or a reduced atmosphere.
  • the steel sheet after the finish annealing is coated with an insulation coating, if necessary, to form a product sheet.
  • an insulation coating may be used any one of a known organic, inorganic or organic-inorganic mixed coating according to the purpose.
  • Each of steel slabs having various chemical compositions shown in Table 1 is reheated at 1100° C. for 30 minutes and hot rolled at a finish rolling end temperature of 760° C. to form a hot rolled sheet having a sheet thickness of 2.2 mm, which is coiled at a temperature of 650° C. Then, the hot rolled sheet is pickled after or without a hot band annealing for holding at a different soaking temperature for 30 seconds and cold rolled to form a cold rolled sheet having a final sheet thickness of 0.5 mm. In this case, recrystallization ratios of all the steel sheets before the final cold rolling are 100%.
  • the cold rolled sheet is subjected to a finish annealing with a continuous annealing facility made from a combination of a solenoid type induction heating furnace and a radiant tube type radiation heating furnace at 950° C. for 10 seconds.
  • a continuous annealing facility made from a combination of a solenoid type induction heating furnace and a radiant tube type radiation heating furnace at 950° C. for 10 seconds.
  • an output power and a line speed are adjusted to control an achieving temperature in the induction heating furnace and a time up to the start of the radiation annealing.
  • the temperature drop from the end of the induction heating to the start of the radiation heating is within 10° C.
  • an atmosphere in the induction heating furnace is a dry nitrogen

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Electromagnetism (AREA)
  • Manufacturing & Machinery (AREA)
  • Manufacturing Of Steel Electrode Plates (AREA)
  • Soft Magnetic Materials (AREA)
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JP2015240390A JP6406522B2 (ja) 2015-12-09 2015-12-09 無方向性電磁鋼板の製造方法
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CA3006620C (en) 2021-06-08
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BR112018010370B1 (pt) 2021-12-14
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CN108368561A (zh) 2018-08-03
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EP3388537A4 (en) 2018-12-05

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