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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
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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
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  • C21D8/0221—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
  • C21D8/0226—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
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  • C21D8/0221—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
  • C21D8/0236—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
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  • C21D8/0247—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
  • C21D8/0263—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following 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
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0247—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
  • C21D8/0273—Final recrystallisation annealing
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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
  • C21D8/1216—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
  • C21D8/1238—Flattening; Dressing; Flexing
• • C—CHEMISTRY; METALLURGY
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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
• • C—CHEMISTRY; METALLURGY
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  • 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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  • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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  • 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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  • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
• • C—CHEMISTRY; METALLURGY
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  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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• • C—CHEMISTRY; METALLURGY
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  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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  • 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
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  • 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
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/20—Recycling

Definitions

• the present disclosure relates to a method for manufacturing a grain-oriented electrical steel sheet and a hot-rolled steel sheet for a grain-oriented electrical steel sheet.
• Grain-oriented electrical steel sheets are mainly used as materials for cores inside transformers. In order to improve the energy efficiency of transformers, there is a demand for low iron loss in grain-oriented electrical steel sheets.
• Methods for reducing iron loss in grain-oriented electrical steel sheets include methods such as increasing the resistivity of the steel sheet, increasing the coating tension, and thinning the steel sheet, as well as methods such as surface processing of the steel sheet, and ⁇ 110 ⁇ ⁇ 001> orientation (hereinafter referred to as Goss orientation) by sharpening the crystal orientation.
• Goss orientation the index of sharpening of the crystal orientation
• Patent Document 1 discloses a method using AlN and MnS
• Patent Document 2 discloses a method using MnS and MnSe, respectively. It has been put to practical use.
• Patent Document 4 discloses that the primary recrystallized structure contains many crystal grains of ⁇ 554 ⁇ 225> orientation and crystal grains of ⁇ 411] ⁇ 148> orientation, thereby increasing the Goss orientation after secondary recrystallization. It has been shown that the concentration in the
• An object of the present disclosure is to control the texture of the primary recrystallized plate to a high degree while actively using the inhibitor, so that the magnetism is superior to the conventional technology.
• An object of the present invention is to provide a method for producing a grain-oriented electrical steel sheet that exhibits properties.
• the present inventors have made intensive studies to solve the above problems. As a result, the present inventors have found that in order to form a texture that is preferable for obtaining good magnetic properties in the primary recrystallized sheet, not only the crystal grain size before cold rolling is coarsened, but also the It was found that it is important to increase the existence frequency of grains with low strain before rolling. In addition, in order to increase the existence frequency of crystal grains with low strain before cold rolling, among the rough rolling conditions of hot rolling, heavy rolling in the temperature range where the ⁇ phase fraction is maximum and the number of passes was found to be important.
• the present inventors have developed the present disclosure based on the finding that it is possible to create a strong primary recrystallization texture, and as a result, an extremely high magnetic flux density can be obtained after secondary recrystallization annealing.
• the present disclosure is based on the above findings. That is, the gist configuration of the present disclosure is as follows.
• the steel slab is subjected to rough rolling including two or more passes of rolling at a temperature of (the temperature at which the ⁇ phase fraction is maximized ⁇ 20° C.) or higher, and a plate thickness true strain ⁇ t of 0.50 or higher. to make a rough rolled plate
• the rough rolled sheet is subjected to finish rolling at a rolling end temperature of 900 ° C. or higher to obtain a hot rolled sheet
• the hot-rolled sheet is cooled at a cooling rate of 70 ° C./s or more for 1 second or more, Winding the hot-rolled sheet after cooling at a winding temperature of 600 ° C.
• the hot-rolled sheet is rolled at a soaking temperature of 750° C. or more (1080-5Y)° C. or less, where Y (%) is the recrystallization rate of the thickness center layer of the hot-rolled sheet after winding.
• a hot-rolled annealed sheet is obtained by performing soaking hot-rolled sheet annealing, Next, the hot-rolled and annealed sheet is cold-rolled once or twice or more with intermediate annealing to obtain a cold-rolled sheet having a final thickness, Next, the cold-rolled sheet is subjected to primary recrystallization annealing to obtain a primary recrystallization annealing sheet, Next, a method for producing a grain-oriented electrical steel sheet, wherein the primary recrystallization annealing sheet is subjected to secondary recrystallization annealing to obtain a grain-oriented electrical steel sheet.
• the plate thickness true strain ⁇ t is calculated by the following equation (1).
• ⁇ t -ln (thickness after rolling/thickness before rolling) (1)
• the component composition further includes Sb: 0.005 to 0.500 mass% and Sn: 0.005 to 0.500 mass%
• Sb 0.005 to 0.500 mass%
• Sn 0.005 to 0.500 mass%
• the component composition further includes Ni: 0.01 to 1.50 mass%, Cr: 0.005 to 0.50 mass%, Cu: 0.03 to 0.50 mass%, P: 0.005 to 0.500 mass%, As: 0.0005 to 0.050 mass%, Bi: 0.005 to 0.500 mass%, Mo: 0.005 to 0.100 mass%, B: 0.0002 to 0.0025 mass%, Te: 0.0005 to 0.0100 mass%, Zr: 0.001 to 0.010 mass%, Nb: 0.001 to 0.010 mass%, V: 0.001 to 0.010 mass% and Ta: 0.001 to 0.010 mass%
• the rough rolling includes rolling for one pass or more at (the temperature at which the ⁇ phase fraction is maximized -20°C) or higher (the temperature at which the ⁇ phase fraction is maximized +50°C) or less, and the above [1 ] to [3].
• the first average cooling rate v1 from the soaking temperature to 800 ° C. is less than 40 ° C./s, and the second average cooling rate v from 800 ° C. to 650 ° C.
• the recrystallization rate Y is 20% or more, and skin-pass rolling is performed at an elongation rate of 0.1% or more after the finish rolling is completed and before the hot-rolled sheet annealing, from the above [1] to [7]. ]
• C 0.005 to 0.085 mass%, Si: 2.00 to 4.50 mass%, Mn: 0.03 to 1.00 mass%, sol. Al: 0.008 mass% or more and less than 0.030 mass% and N: 0.004 to 0.009 mass% and further At least one of S: 0.0005 to 0.02 mass% and Se: 0.0005 to 0.02 mass%, with the balance being Fe and unavoidable impurities,
• the component composition further includes Sb: 0.005 to 0.500 mass% and Sn: 0.005 to 0.50 mass%
• Sb 0.005 to 0.500 mass%
• Sn 0.005 to 0.50 mass%
• the component composition further includes Ni: 0.01 to 1.50 mass%, Cr: 0.03 to 0.50 mass%, Cu: 0.03 to 0.50 mass%, P: 0.005 to 0.500 mass%, As: 0.0005 to 0.050 mass%, Bi: 0.005 to 0.500 mass%, Mo: 0.005 to 0.100 mass%, B: 0.0002 to 0.0025 mass%, Te: 0.0005 to 0.0100 mass%, Zr: 0.001 to 0.010 mass%, Nb: 0.001 to 0.010 mass%, V: 0.001 to 0.010 mass% and Ta: 0.001 to 0.010 mass%
• a method for producing a grain-oriented electrical steel sheet that exhibits excellent magnetic properties compared to conventional techniques by highly controlling the texture of the primary recrystallized sheet while actively using an inhibitor is provided. can do.
• the inventors first investigated whether it is effective to coarsen the grain size before cold rolling in order to form a preferable texture for improving the magnetic properties of the primary recrystallized sheet of the grain-oriented electrical steel sheet. In order to verify this, the crystal structure of the hot-rolled sheet was carefully observed.
• Rough rolling consisting of 1-pass rolling at .4 was performed to obtain a rough rolled sheet.
• the rough-rolled sheet was finish-rolled at a final rolling temperature of 1050° C. to obtain a hot-rolled sheet having a thickness of 2.5 mm.
• the steel sheet was cooled at a cooling rate of 80°C/s for 5 seconds, and then coiled at a coiling temperature of 520°C.
• the hot-rolled sheet was subjected to hot-rolled sheet annealing at 1020° C. for 60 seconds to obtain a hot-rolled annealed sheet.
• the hot-rolled and annealed sheet is subjected to primary cold rolling to an intermediate sheet thickness of 2.0 mm, further subjected to intermediate annealing at 1120° C. for 80 seconds, and then subjected to secondary cold rolling to obtain a final sheet thickness of 0.22 mm. cold-rolled sheet.
• the cold-rolled sheet was subjected to primary recrystallization annealing by a known method to obtain a primary recrystallization annealing sheet, and then secondary recrystallization annealing was applied to the primary recrystallization annealing sheet to obtain a grain-oriented electrical steel sheet.
• the crystal grains elongated in the rolling direction are caused by residual strain.
• the crystal grains elongated in the rolling direction are defined as crystal grains having a ratio of the diameter in the rolling direction to the diameter in the sheet thickness direction of 2.0 or more.
• the recrystallization rate Y of the sheet thickness center layer which will be described later, was 5%. Further, as a result of observing the microstructure of the L-section of the hot-rolled and annealed sheet, many crystal grains elongated in the rolling direction were observed.
• B8 means the magnetic flux density of the sample when the sample is magnetized in the rolling direction with a magnetizing force of 800 A/m.
• a steel slab having the same chemical composition as above was made into a steel slab.
• the steel slab was slab heated to 1310°C.
• the steel slab was then subjected to one pass rolling at 1220°C with thickness true strain ⁇ t 0.5, one pass rolling at 1180°C with thickness true strain ⁇ t 0.4 and 1140°C thickness true strain ⁇ t 0 Rough rolling consisting of one-pass rolling at No. 5 was performed to obtain a rough rolled sheet.
• the rough-rolled sheet was finish-rolled at a final rolling temperature of 1050° C. to obtain a hot-rolled sheet having a thickness of 2.5 mm.
• the hot-rolled sheet was cooled at a cooling rate of 80°C/s for 5 seconds 1s after finishing rolling, and then coiled at a coiling temperature of 520°C. Then, the hot-rolled sheet was subjected to hot-rolled sheet annealing at 1020° C. for 60 seconds to obtain a hot-rolled annealed sheet. Next, the hot-rolled and annealed sheet is subjected to primary cold rolling to an intermediate sheet thickness of 1.8 mm, further subjected to intermediate annealing at 1120° C. for 80 seconds, and then subjected to secondary cold rolling to obtain a final sheet thickness of 0.22 mm. cold-rolled sheet.
• the cold-rolled sheet is subjected to primary recrystallization annealing by the same method as described above to obtain a primary recrystallization annealing sheet, and then the primary recrystallization annealing sheet is subjected to secondary recrystallization annealing to obtain a grain-oriented electrical steel sheet. did.
• the present inventors have found that the rough rolling process of hot rolling has a strong effect on the microstructure of the hot-rolled sheet. Furthermore, the present inventors have found that by appropriately controlling the microstructure of the hot-rolled sheet, the structure elongated in the rolling direction in the intermediate-annealed sheet disappears, and the magnetic flux density of the grain-oriented electrical steel sheet after secondary recrystallization annealing I got the idea that it would be higher. In the method of actively using an inhibitor, the slab heating temperature is high and the crystal grains after heating are large, so recrystallization is less likely to occur during hot rolling. For this reason, the present inventors believe that the method of positively using an inhibitor is effective in controlling the structure of the hot-rolled sheet by optimizing the rough rolling conditions, and have found the present disclosure. rice field.
• the present inventors thought that if the microstructure of the hot-rolled sheet could be appropriately controlled, it would be possible to newly determine an appropriate hot-rolled sheet annealing temperature in a method in which an inhibitor is actively used. .
• a steel material with the balance being Fe and unavoidable impurities (C: 0.065 mass%, Si: 3.40 mass%, Mn: 0.060 mass%, sol. Al: 0.017 mass%, N: 0.007 mass%, Se : 0.006 mass%, Sb: 0.035 mass%) is melted to form a steel slab, then the steel slab is slab-heated to 1330 ° C. and one-pass rolling at 1200 ° C. with a sheet thickness true strain ⁇ t of 0.6 , 1-pass rolling at a thickness true strain ⁇ t of 0.5 at 1150° C., and 1-pass rolling at a thickness true strain ⁇ t of 0.4 at 1100° C.
• hot-rolled sheet A a steel slab having the same chemical composition as above is heated to 1310 ° C., 1-pass rolling at 1220 ° C. with a plate thickness true strain of 0.6, 1180 ° C. with a plate thickness true strain of 0.3. and 1-pass rolling at 1100° C.
• Hot-rolled sheet B Hot-rolled sheet A and hot-rolled sheet B were hot-rolled and annealed under four conditions: 900°C for 60 seconds, 950°C for 60 seconds, 1000°C for 60 seconds, and 1050°C for 60 seconds. made into a board.
• the hot-rolled and annealed sheet is subjected to primary cold rolling to an intermediate sheet thickness of 1.8 mm, further subjected to intermediate annealing at 1120° C. for 80 seconds, and then subjected to secondary cold rolling to obtain a final sheet thickness of 0.22 mm. cold-rolled sheet.
• the cold-rolled sheet was subjected to primary recrystallization annealing by a known method to obtain a primary recrystallization annealing sheet, and then secondary recrystallization annealing was applied to the primary recrystallization annealing sheet to obtain a grain-oriented electrical steel sheet.
• Table 1 shows the magnetic flux density B8 of the grain-oriented electrical steel sheets using the hot - rolled sheets A and B.
• the hot-rolled sheet annealing temperature at which the magnetic flux density of the grain-oriented electrical steel sheet was maximized was 900 to 950 ° C.
• the hot-rolled sheet annealing temperature at which the magnetic flux density of the grain-oriented electrical steel sheet was maximized was 1050°C.
• the present inventors came to the idea that a higher magnetic flux density could be obtained by appropriately determining the hot-rolled sheet annealing according to the microstructure of the hot-rolled sheet.
• the inventors conducted the following experiment in order to investigate in more detail the effect of rough rolling on the recrystallization rate Y of the hot-rolled sheet.
• the steel sheet was cooled at a cooling rate of 80°C/s for 5s, and then coiled at a coiling temperature of 500 to 550°C.
• the microstructure of the L-section of the hot-rolled sheet after winding was observed, and the recrystallization rate Y was evaluated.
• a method for evaluating the recrystallization rate Y will be described later. Table 2 shows the results.
• the present inventors have estimated the following tendencies (i) to (iii).
• the steel slab is subjected to rough rolling including at least two passes of rolling at a temperature of ( ⁇ 20 ° C. where the ⁇ phase fraction is maximized) and a plate thickness true strain ⁇ t of 0.50 or more. If applied, a high recrystallization rate Y of 15% or more can be obtained in the hot-rolled sheet.
• the temperature at which the ⁇ -phase fraction is maximized is found to be 1150° C. by equilibrium calculation in advance.
• Rough rolling in hot rolling is performed at a temperature not less than (the temperature at which the ⁇ phase fraction is maximized -20°C) and not more than (the temperature at which the ⁇ phase fraction is maximized +50°C) at least
• a higher recrystallization rate Y (18% or more in the above results) can be obtained.
• the present inventors conducted experiments in which the soaking temperature for subsequent hot-rolled sheet annealing was changed by several levels for each hot-rolled sheet having a different recrystallization rate Y.
• the cold-rolled sheet was subjected to primary recrystallization annealing by a known method to obtain a primary recrystallization annealing sheet, and then secondary recrystallization annealing was applied to the primary recrystallization annealing sheet to obtain a grain-oriented electrical steel sheet.
• the magnetic flux density B8 of the obtained grain - oriented electrical steel sheets was evaluated by the Epstein test described later. Table 3 shows the soaking temperature for hot-rolled sheet annealing and the magnetic flux density B8 of the obtained grain-oriented electrical steel sheet.
• C 0.005 to 0.085 mass% If C is less than 0.005 mass%, the grain boundary strengthening effect of C is lost, cracks occur in the slab, and production is hindered. In addition, non-uniform deformation, which is preferable for improving magnetic properties and is caused by strain aging during rolling, is suppressed. On the other hand, when the amount of C exceeds 0.085 mass%, it becomes difficult to reduce the amount of C to 0.005 mass% or less at which magnetic aging does not occur in the primary recrystallization annealing. Therefore, C should be in the range of 0.005 to 0.085 mass%.
• the amount of C is preferably 0.010 mass% or more, more preferably 0.030 mass% or more. Also, the amount of C is preferably 0.080 mass% or less, more preferably 0.070 mass% or less.
• Si 2.00 to 4.50 mass%
• Si is an important element for increasing the resistivity of the steel sheet and reducing iron loss. Addition of less than 2.00 mass% of Si cannot sufficiently exhibit these effects. On the other hand, when the amount of Si exceeds 4.50 mass%, the brittleness of the steel sheet increases, making rolling difficult. Therefore, Si should be in the range of 2.00 to 4.50 mass%.
• the amount of Si is preferably 2.50 mass% or more, more preferably 3.0 mass% or more.
• the Si content is preferably 4.50 mass% or less, more preferably 4.0 mass% or less.
• Mn 0.03-1.00 mass%
• Mn is an element necessary for improving the hot workability of steel. A Mn content of less than 0.03 mass% is not sufficient to obtain the above effect. On the other hand, when the Mn amount exceeds 1.00 mass%, the magnetic flux density of the product sheet is lowered. Therefore, Mn should be in the range of 0.03 to 1.00 mass%.
• the amount of Mn is preferably 0.05 mass% or more, more preferably 0.06 mass% or more.
• the amount of Mn is preferably 0.20 mass% or less, more preferably 0.15 mass% or less.
• Acid-soluble Al (sol. Al): 0.008 mass% or more and less than 0.030 mass% Al plays a role as an inhibitor and is an important element for secondary recrystallization of Goss-oriented grains, and exhibits its effect. 0.008 mass% or more is required to On the other hand, if it is added excessively, grain growth is excessively suppressed and secondary recrystallization of Goss-oriented grains is prevented.In addition, a dense oxide film is formed on the surface, making it difficult to control the amount of nitriding during nitriding. or inhibit decarburization, so sol. Al is suppressed to less than 0.030 mass%.
• the amount of Al is preferably 0.010 mass% or more, more preferably 0.013 mass% or more.
• the Al content is preferably 0.022 mass% or less, more preferably 0.025 mass% or less.
• N 0.004 to 0.009 mass% Like Al, N plays a role as an inhibitor and is an important element for secondary recrystallization of Goss-oriented grains. On the other hand, since N may cause defects such as blisters during slab heating, it is suppressed to 0.009 mass% or less. In addition, N binds to Al and precipitates as AlN, and since Al and N are bound at an atomic weight ratio of 1:1, N having an atomic weight ratio of 1 or more to Al, that is, sol. Al mass% content: [% sol. Al], (14.00/26.98) ⁇ [% sol. Al], even if it is contained in a range that deviates excessively, the effect of the inhibitor cannot be exhibited sufficiently.
• the amount of N is set to 0.009 mass% or less.
• the amount of N is (14.00/26.98) x [% Sol. Al]-0.002 mass% or more.
• the amount of N is (14.00/26.98) ⁇ [% Sol. Al] + 0.002 mass% or less condition is satisfied.
• S 0.0005 to 0.02 mass%
• Se at least one of 0.0005 to 0.02 mass% S and Se combine with Mn to form an inhibitor, but one selected from S and Se
• the absolute amount of the inhibitor is insufficient, resulting in insufficient suppression of normal grain growth.
• the content of one or two selected from S and Se exceeds 0.02 mass%, deS and Se are incomplete in secondary recrystallization annealing, resulting in deterioration of iron loss. cause. Therefore, one or two selected from S and Se should be in the range of 0.0005 to 0.02 mass%, respectively.
• the content of one or two selected from S and Se is preferably 0.001 mass% or more, more preferably 0.002 mass% or more.
• the content of one or two selected from S and Se is preferably in the range of 0.01 mass% or less, more preferably 0.008 mass% or less.
• the remainder of the steel slab composition other than the above components is Fe and unavoidable impurities.
• the component composition may further contain one or more selected from the group consisting of Sb: 0.005 to 0.500 mass% and Sn: 0.005 to 0.50 mass%.
• Sb 0.005 to 0.500 mass%
• Sb is an element necessary as an inhibitor to enhance the selective growth of Goss-oriented grains, and is added in an amount of 0.005 mass % to obtain that effect. On the other hand, when excessively added, the rollability is impaired and production is hindered, so the upper limit is made 0.500 mass%.
• the Sb content is preferably 0.010 mass% or more, more preferably 0.015 mass% or more. Also, the Sb content is preferably 0.20 mass% or less, more preferably 0.10 mass% or less.
• Sn 0.005 to 0.500 mass%
• Sn is an element necessary to enhance the selective growth of Goss-oriented grains as an inhibitor, and is added in an amount of 0.005 mass % to obtain that effect.
• the upper limit is made 0.500 mass% in order to improve the rollability.
• the Sn content is preferably 0.010 mass% or more, more preferably 0.015 mass% or more. Also, the Sn content is preferably 0.20 mass% or less, more preferably 0.10 mass% or less.
• Ni 0.01 to 1.50 mass%, Cr: 0.005 to 0.50 mass%, Cu: 0.03 to 0.50 mass%, P: 0.005-0.500 mass%, As: 0.0005-0.05 mass%, Bi: 0.005-0.500 mass%, Mo: 0.005-0.100 mass%, B: 0.0002- 0.0025 mass%, Te: 0.0005 to 0.0100 mass%, Zr: 0.001 to 0.010 mass%, Nb: 0.001 to 0.010 mass%, V: 0.001 to 0.010 mass% and Ta : 1 or 2 or more selected from 0.001 to 0.010 mass%.
• the amount added is more preferably 0.01 mass % or more. Further, when Cr is added, the amount added is more preferably 0.1 mass % or less in order to keep the magnetic flux density B8 within a more suitable range.
• the ⁇ phase fraction can be increased.
• the amount added is more preferably 0.5 mass % or less in order to further reduce manufacturing costs and prevent embrittlement of steel.
• a steel material having the chemical composition described above is melted by a conventional refining process, and then a steel slab is formed by a conventional ingot-slabbing-rolling method or continuous casting method.
• a thin steel slab with a thickness of 100 mm or less may be produced by direct casting.
• the steel slab is slab-heated to a temperature higher than the ⁇ -phase precipitation temperature and 1380° C. or lower, and subjected to hot rolling.
• the ⁇ -phase precipitation temperature may be estimated in advance using equilibrium calculation software such as Thermo-Calc (Thermo-Calc Software AB), or may be verified experimentally.
• TCFE7 TCS Steel and Fe-alloys Database v7.0 is used as the database. Only elements available in this database are used for calculations. If the ⁇ phase precipitates during reheating, C concentrates in the ⁇ phase, the structure becomes uneven, and a high magnetic flux density cannot be obtained. Also, if the slab is heated above 1380° C., the ferrite grain size before hot rolling becomes excessively large, the recrystallization rate becomes low, and a high magnetic flux density cannot be obtained after the final annealing.
• the temperature of slab heating is preferably 1360° C. or less. The slab heating temperature is based on the surface temperature of the steel slab.
• the slab-heated steel slab is subjected to two or more passes of rolling with a sheet thickness true strain ⁇ t of 0.50 or more at a temperature of ( ⁇ 20 ° C. where the ⁇ phase fraction is maximized) or more. It is rolled to obtain a rough rolled sheet.
• the plate thickness true strain ⁇ t is more preferably 0.60 or more.
• the upper limit of the plate thickness true strain ⁇ t is not particularly limited, it is preferably 0.80 or less.
• Rough rolling preferably includes one or more passes of rolling at (the temperature at which the ⁇ phase fraction maximizes ⁇ 20° C.) or higher (the temperature at which the ⁇ phase fraction maximizes +50° C.) or lower.
• the rolling at a temperature of -20°C at which the ⁇ phase fraction is maximized and not higher than (+50°C at which the ⁇ phase fraction is maximized a large amount of hard ⁇ phase is dispersed. Therefore, the introduction of strain into the ferrite is promoted, the recrystallization driving force can be increased, the microstructure before finish rolling can be refined, and the magnetic flux density B8 can be further improved.
• the rough rolling includes one or more passes of rolling at (the temperature at which the ⁇ phase fraction becomes maximum ⁇ 15° C.) or higher. Further, more preferably, the rough rolling includes one or more passes of rolling at (the temperature at which the ⁇ phase fraction is maximized + 40°C) or less.
• the rolling temperature for rough rolling is based on the surface temperature of the steel sheet.
• the number of passes for rough rolling is four in total.
• the number of passes for rough rolling is four in total.
• the finishing temperature of finish rolling is set to 900°C or higher.
• the finish rolling end temperature is the average temperature of the surface of the steel sheet at the coil front end and the coil tail end. This is because if the finishing temperature of the finish rolling is lower than 900° C., the inhibitor precipitates during the finish rolling, and the inhibitor of the hot-rolled sheet becomes excessively coarse. Since the finer the inhibitor is, the more advantageous it is for the Goss orientation selective growth during the secondary recrystallization annealing, it is preferable that the inhibitor is finely precipitated at the stage of the hot-rolled sheet.
• the finish rolling finish temperature is preferably 950° C. or higher. Although the upper limit of the finishing temperature of finish rolling is not particularly limited, it is preferably 1000° C. or less in order to prevent coarse precipitation of inhibitors after rolling.
• the finish rolling end temperature is based on the temperature of the surface of the steel sheet.
• the hot-rolled sheet is cooled for 1 second or more at a cooling rate of 70 ° C./s or more within 2 seconds after the end of finish rolling, and the hot-rolled sheet after cooling is rolled.
• the hot rolling process is completed by coiling at a coiling temperature of 600°C or less.
• the hot-rolled sheet is cooled within 1 second after finishing rolling.
• the cooling time is preferably set to 2 seconds or more.
• the upper limit of the cooling time is not particularly limited, it is preferably 8 seconds or less.
• the cooling rate is preferably 80° C./s or higher.
• the upper limit of the cooling rate is not particularly limited, it is more preferably 300° C./s or less.
• the cooling rate is based on the surface temperature of the steel sheet.
• the lower limit of the winding temperature is not particularly limited, it is preferably 450° C. or higher.
• the winding temperature is 600° C. or lower.
• the coiling temperature is the average value of the steel sheet surface temperature at the leading edge of the hot-rolled sheet and the steel sheet surface temperature at the trailing edge of the strip.
• skin-pass rolling may be performed after finish rolling and before hot-rolled sheet annealing.
• Skin pass rolling can force the shape of the steel sheet.
• the elongation rate of skin pass rolling is preferably 0.05% or more.
• strain to the hot-rolled sheet with an elongation rate of skin-pass rolling of 0.05% or more the size of ferrite grains is increased in the subsequent hot-rolled sheet annealing step, and the texture of the primary recrystallized sheet is made more preferable. It is possible to further increase the magnetic flux density B8 of the grain - oriented electrical steel sheet through making the material.
• the introduction of strain by skin-pass rolling is less effective unless the recrystallization ratio Y of the hot-rolled sheet is 20% or more. It is more preferable to set the elongation rate of the skin pass rolling to 0.1% or more. It is more preferable to set the elongation rate of the skin pass rolling to 10% or less.
• the hot-rolled sheet after the finish rolling or the hot-rolled sheet obtained by the skin pass rolling is subjected to hot-rolled sheet annealing.
• the point of the present disclosure is to appropriately precipitate the inhibitor according to the recrystallization rate Y of the hot-rolled sheet.
• the soaking temperature for hot-rolled sheet annealing is 750° C. or higher. This is because if the soaking temperature is less than 750° C., the amount of diffusion of the inhibitor-forming element such as Al is insufficient, and the inhibitor is not sufficiently precipitated.
• a soaking temperature of 750° C. or higher and as low as possible is preferable for inhibitor precipitation.
• the upper limit of the soaking temperature is determined according to the recrystallization rate Y (%) of the hot-rolled sheet, specifically (1080-5Y)° C. or less. That is, when the recrystallization rate Y of the hot-rolled sheet is high, the soaking temperature is set to a lower temperature so that more inhibitors can be precipitated.
• the hot-rolled sheet is annealed at a higher soaking temperature in order to prioritize the removal of strain in the ferrite structure.
• the soaking temperature for hot-rolled sheet annealing is more preferably 800° C. or higher. Further, the soaking temperature for hot-rolled sheet annealing is more preferably set to (1080° C.-5.5Y)° C. or less. The soaking temperature for hot-rolled sheet annealing is based on the surface temperature of the steel sheet.
• the recrystallization rate Y of the sheet thickness center layer of the hot-rolled sheet is obtained as follows.
• the microstructure of the L-section of the hot-rolled sheet is measured by the SEM-EBSD method (scanning electron microscope-electron back scattering diffraction).
• the L section of the hot-rolled sheet is polished to form an observation surface. Measurement is performed from the 1/5 thickness depth position of the observation surface (the layer that is 20% inside in the thickness direction from one side of the steel sheet) to the 4/5 thickness depth position (80% inside the thickness direction from the above one side)
• the area up to the layer in which the The measurement area in the rolling direction is preferably 1 mm or more and is as large as possible. Step size is 1.5 ⁇ m.
• the obtained data is analyzed by software such as OIM Analysis (v9), and kernel average misorientation (KAM) map analysis is performed.
• the point for calculating the KAM value is the second closest point.
• the KAM value reflects local crystal orientation changes due to dislocations in the structure, and is thought to have a good correlation with microscopic strain. shows a low value of
• the recrystallization rate Y is defined as the area ratio of the region where the KAM value is 0.4 or less in the region from the depth position of 1/4 of the plate thickness to the depth position of 3/4 of the plate thickness.
• the plate thickness range to be measured is extremely important. Generally, in the hot rolling process, the surface side of the steel sheet receives a large shear strain.
• the recrystallization rate of the hot-rolled sheet exhibits a higher value on the surface layer side of the sheet thickness.
• the KAM value is When the area ratio of the region having a thickness of 0.4 or less was calculated, it was 50%.
• the recrystallization rate Y of the hot-rolled sheet is preferably 15% or more, more preferably 18% or more, still more preferably 20% or more, and most preferably 24% or more. .
• the hot-rolled annealed sheet is cold-rolled two or more times with intermediate annealing to obtain a cold-rolled sheet having a final thickness.
• the soaking temperature for the intermediate annealing is preferably in the range of 900 to 1200°C. If the soaking temperature is 900° C. or higher, the recrystallized grains after the intermediate annealing can be suitably prevented from becoming too fine, and further, the reduction of the Goss nuclei in the primary recrystallized structure can be suitably prevented, thereby improving the grain-oriented electrical steel sheet. Magnetic properties are further improved. In addition, if the soaking temperature is 1200° C. or less, the crystal grains are not excessively coarsened, and a more preferable primary recrystallized structure with uniform grains can be obtained.
• the soaking temperature for intermediate annealing is based on the surface temperature of the steel sheet.
• the hot - rolled sheet after soaking is subjected to a first average cooling rate v from the soaking temperature to 800 ° C. 1 is less than 40°C/s, and the second average cooling rate v2 from 800°C to 650°C is preferably v1 or more.
• a first average cooling rate v from the soaking temperature to 800 ° C. 1 is less than 40°C/s
• the second average cooling rate v2 from 800°C to 650°C is preferably v1 or more.
• a first average cooling rate v from the soaking temperature to 800 ° C. 1 is less than 40°C/s
• the second average cooling rate v2 from 800°C to 650°C is preferably v1 or more.
• cooling at a cooling rate of 50 ° C./s or more for 2 Cooling for seconds or longer is preferred. More preferably, cooling is performed for 3 seconds or more at a cooling rate of 50°C/s or more in a temperature range of 400°C or less.
• Cold rolling may be either tandem rolling (unidirectional rolling) or reverse rolling, and known warm rolling technology or interpass aging technology may be used.
• the final thickness of the cold-rolled sheet is preferably 0.15 mm or more from the viewpoint of reducing the rolling load.
• the upper limit of the final thickness of the grain-oriented electrical steel sheet is not particularly limited, it is preferably 0.30 mm.
• the cold-rolled sheet with the final thickness is then subjected to primary recrystallization annealing.
• the annealing temperature in this primary recrystallization annealing is preferably in the range of 800 to 900 ° C. from the viewpoint of speeding up the decarburization reaction when decarburization annealing is also used, and the atmosphere is a humid atmosphere. is preferred.
• decarburization annealing may be performed separately from the primary recrystallization annealing.
• the annealing temperature of the primary recrystallization annealing is based on the surface temperature of the steel sheet.
• the primary recrystallization annealing sheet is subjected to secondary recrystallization annealing to obtain a grain-oriented electrical steel sheet.
• an annealing separator mainly composed of MgO is applied to the surface (one side or both sides) of the primary recrystallization annealed sheet, and after drying, the secondary It is preferable to apply recrystallization annealing.
• "mainly composed of MgO” refers to containing 80% or more by mass of MgO with respect to the entire annealing separator.
• a secondary recrystallized structure highly integrated in the Goss orientation is developed, and the forsterite coating is formed on the steel sheet surface. can be formed.
• the annealing separating agent is not applied, or secondary recrystallization annealing is performed using an annealing separating agent mainly composed of silica, alumina, or the like. preferably applied.
• mainly composed of silica, alumina, or the like means that 80% or more by mass of silica, alumina, or the like is contained in the entire annealing separator.
• the forsterite coating is not formed, it is also effective to apply the annealing separator by electrostatic application that does not bring in moisture.
• a known heat-resistant inorganic material sheet may be used instead of the annealing separator. Heat-resistant inorganic material sheets include, for example, silica, alumina, and mica.
• the secondary recrystallization annealing when forming a forsterite film, the secondary recrystallization is developed and completed by holding at around 800 to 1050 ° C. for 20 hours or more, and then up to a temperature of 1100 ° C. or higher. It is preferable to raise the temperature. It is more preferable to further raise the temperature to about 1200° C. when the iron loss property is emphasized and the purification treatment is performed.
• the annealing can be completed by raising the temperature up to 800 to 1050° C. because the secondary recrystallization should be completed.
• the annealing temperature of the secondary recrystallization annealing is based on the temperature of the steel sheet surface. Alternatively, when it is difficult to directly measure the temperature of the steel sheet surface, the temperature of the steel sheet surface estimated from the furnace temperature or the like may be used as the annealing temperature for the secondary recrystallization annealing.
• the secondary recrystallization annealing sheet (grain-oriented electrical steel sheet) after secondary recrystallization annealing may be washed with water, brushed, pickled, or the like to remove unreacted annealing separating agent adhering to the surface of the steel sheet. Further, the secondary recrystallization annealed sheet may be further subjected to flattening annealing. Since the secondary recrystallization annealing is usually performed in a coil state, the coil tends to curl. This curl may degrade iron loss characteristics. By performing flattening annealing, the shape can be corrected and the iron loss can be further reduced.
• an insulating coating when steel sheets are laminated and used, it is effective to form an insulating coating on the surface of the steel sheets before, during, or after the flattening annealing.
• a tension imparting coating that imparts tension to the steel sheet as the insulating coating.
• an inorganic substance is vapor-deposited on the steel sheet surface layer by physical vapor deposition or chemical vapor deposition, and an insulating coating is applied thereon. can be employed. According to these methods, it is possible to form an insulating coating which is excellent in coating adhesion and has a remarkably large effect of reducing iron loss.
• the grain-oriented electrical steel sheet in order to further reduce iron loss, it is preferable to subject the grain-oriented electrical steel sheet to magnetic domain refining treatment.
• a method of magnetic domain refining treatment a method of forming grooves on the surface (front or back) of a grain-oriented electrical steel sheet (final product sheet), plasma irradiation, laser irradiation, electron beam irradiation, etc., causes thermal strain in a linear or point manner.
• a known magnetic domain refining treatment method such as a method of introducing impact strain, a method of etching the surface of a cold-rolled sheet that has been cold-rolled to the final thickness or a steel sheet surface in an intermediate process to form grooves, can be used. .
• the manufacturing conditions other than the conditions described above can be according to the usual method.
• a grain - oriented electrical steel sheet having a magnetic flux density B8 of 1.940 T or more can be manufactured.
• the magnetic flux density B8 is measured according to the Epstein method described in JIS C2550 by cutting an Epstein test piece from the grain-oriented electrical steel sheet.
• the hot-rolled steel sheet for grain-oriented electrical steel sheets of the present disclosure will be described.
• the inhibitor is actively used, and the texture of the primary recrystallized sheet is also highly controlled, so that the grain-oriented electrical steel sheet exhibits excellent magnetic properties compared to the conventional technology.
• An electromagnetic steel sheet can be provided.
• the hot-rolled steel sheet for grain-oriented electrical steel sheet is 750° C. or more and (1080-5Y)° C.
• a hot-rolled annealed sheet is obtained by performing hot-rolled sheet annealing at a soaking temperature of Next, the hot-rolled and annealed sheet is cold-rolled once or twice or more with intermediate annealing to obtain a cold-rolled sheet having a final thickness, Next, the cold-rolled sheet is subjected to primary recrystallization annealing to obtain a primary recrystallization annealing sheet, Then, the primary recrystallization annealing sheet is subjected to secondary recrystallization annealing to obtain a grain-oriented electrical steel sheet having excellent magnetic properties.
• the conditions for hot-rolled sheet annealing, cold rolling, primary recrystallization annealing, and secondary recrystallization annealing are the same as the conditions described above, so descriptions thereof are omitted here.
• a method for manufacturing a hot-rolled steel sheet for a grain-oriented electrical steel sheet includes heating a steel slab having the above-described chemical composition to a temperature above the ⁇ -phase precipitation temperature and 1380° C. or less, Then, the steel slab is subjected to rough rolling including two or more passes of rolling at a temperature of (the temperature at which the ⁇ phase fraction becomes maximum ⁇ 20 ° C.) or higher, and a plate thickness true strain ⁇ t of 0.50 or higher. to make a rough rolled plate, Next, the rough rolled sheet is subjected to finish rolling at a rolling end temperature of 900 ° C.
• the hot-rolled sheet is cooled at a cooling rate of 70 ° C./s or more for 1 second or more,
• the hot-rolled steel sheet after cooling may be coiled at a coiling temperature of 600° C. or less to obtain a hot-rolled steel sheet for grain-oriented electrical steel sheets.
• the conditions for slab heating, rough rolling, finish rolling, cooling, and coiling are the same as the conditions described above, so descriptions thereof are omitted here.
• the recrystallization rate Y of the hot-rolled steel sheet for grain-oriented electrical steel sheet is preferably 18% or more, more preferably 20% or more, and most preferably 24% or more.
• the steel slab is slab-heated under the conditions shown in Table 5, the steel slab is subjected to rough rolling to obtain a rough-rolled sheet, the rough-rolled sheet is subjected to finish rolling to obtain a hot-rolled sheet, and after completion of finish rolling, 1.5
• the hot-rolled sheet was cooled within seconds, the hot-rolled sheet after cooling was wound up, and the hot-rolled sheet was subjected to hot-rolled sheet annealing to obtain a hot-rolled annealed sheet.
• the ⁇ -phase precipitation temperature and the temperature at which the ⁇ -phase fraction is maximized are determined by Thermo-Calc ver. Calculated according to 2017b.
• condition (1) of rough rolling in Table 5 is defined as "at a temperature of (the temperature at which the ⁇ phase fraction is maximized -20 ° C.) or higher, the introduced sheet thickness true strain ⁇ t is 0.50 or higher.
• the rolling of 2 or more passes is defined as ".
• the condition (2) is defined as “one or more passes of rolling at (the temperature at which the ⁇ phase fraction is maximized ⁇ 20° C.) or higher (the temperature at which the ⁇ phase fraction is maximized +50° C.)”.
• condition (3) is that "the total number of rough rolling passes is 4". In Table 5, ⁇ indicates that these conditions are satisfied, and x indicates that they do not.
• the end of finish rolling was the average value of the steel sheet surface temperature at the tip of the strip and the steel sheet surface temperature at the tail end of the strip.
• the plate thickness after hot rolling was 2.4 to 2.5 mm in all examples.
• the sheets were pickled to remove scale, and then cold-rolled to a sheet thickness of 1.9 mm.
• intermediate annealing was performed at a temperature of 1050° C. to 1120° C. for 100 seconds. Then, it was cold rolled to a plate thickness of 0.22 mm.
• primary recrystallization annealing was performed at 860° C.

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