WO2020149347A1 - 方向性電磁鋼板の製造方法 - Google Patents
方向性電磁鋼板の製造方法 Download PDFInfo
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- 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
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- C21D2201/00—Treatment for obtaining particular effects
- C21D2201/05—Grain orientation
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- Y02P10/20—Recycling
Definitions
- the present invention relates to a method for manufacturing a grain-oriented electrical steel sheet having excellent magnetic properties, which is suitable as an iron core material for a transformer.
- the present application claims priority based on Japanese Patent Application No. 2019-5083 filed in Japan on January 16, 2019, the content of which is incorporated herein.
- Oriented electrical steel sheets are mainly used for transformers.
- the transformer is continuously excited for a long period of time from being installed to being discarded, and continues to generate energy loss.Therefore, energy loss when magnetized by alternating current, that is, iron loss, It is the main indicator that determines performance.
- a grain-oriented electrical steel sheet contains 7 mass% or less of Si and has a texture controlled so that the crystal orientation of each crystal grain matches the ⁇ 110 ⁇ 001> orientation called the Goss orientation. It has a base material steel plate and an insulating coating for imparting insulation to the base material steel plate.
- applying tension to the base steel sheet is an effective method for reducing iron loss.
- it is effective to form a coating film made of a material having a smaller thermal expansion coefficient than the base material steel plate on the surface of the base material steel plate at a high temperature.
- the forsterite coating produced by the reaction of the oxide present on the surface of the base steel sheet with the annealing separator can give tension to the base steel sheet. Since there are irregularities at the interface between the forsterite-based coating and the base steel sheet, the forsterite-based coating also functions as an intermediate coating that enhances the adhesion between the insulating coating and the base steel sheet due to the anchor effect due to this irregularity. To do.
- Patent Document 1 for forming an insulating coating by baking a coating liquid mainly containing colloidal silica and phosphate has a large effect of applying tension to the base steel sheet and is effective in reducing iron loss.
- a general method for producing a grain-oriented electrical steel sheet is to apply an insulating coating mainly containing phosphate while leaving the forsterite coating film generated in the finish annealing step.
- an insulating coating capable of giving not only an insulating property to the base steel sheet but also a tension is referred to as a tension insulating coating.
- Patent Documents 2 to 5 by controlling the dew point of the atmosphere of decarburization annealing and using alumina as an annealing separator, the surface of the base steel sheet without forming a forsterite coating film in finish annealing.
- a technique for smoothing is disclosed.
- Patent Document 6 by using an annealing separating agent containing 5% by weight or more and 30% by weight or less of magnesia with respect to the total weight of alumina and magnesia as an annealing separating agent, forsterite is formed on the surface of the base steel sheet.
- an annealing separating agent containing 5% by weight or more and 30% by weight or less of magnesia with respect to the total weight of alumina and magnesia as an annealing separating agent, forsterite is formed on the surface of the base steel sheet.
- the present invention has been made in view of the above circumstances, and an object thereof is to reduce the core loss of the grain-oriented electrical steel sheet in which the forsterite-based coating does not exist between the base material steel sheet and the tension insulating coating as compared with the conventional one. ..
- the present inventors obtained a sufficient iron loss improving effect when producing a grain-oriented electrical steel sheet in which there is no forsterite coating between the base material steel sheet and the tension insulating coating.
- An intensive study was conducted on the cause of the failure.
- a large number of needle-shaped inclusions were present in the surface layer region of the base material steel sheet.
- the present inventors presumed that the needle-shaped inclusions are the cause of hindering the movement of the domain wall, that is, the cause of adversely affecting iron loss.
- the present invention has been made based on the above findings, and the gist thereof is as follows.
- a method of manufacturing a grain-oriented electrical steel sheet according to an aspect of the present invention includes a step of obtaining a hot-rolled sheet by hot rolling a slab, and an annealing by performing hot-rolled sheet annealing on the hot-rolled sheet.
- the decarburizing annealed plate has a step of applying an annealing separating agent containing alumina as a main component, and a step of applying a finish annealing to the decarburizing annealed sheet coated with the annealing separating agent, wherein the annealing separating agent is 28 to 50% by mass of MgO, and the coating amount of the annealing separator is 6.0 to 14.0 g/m 2 per side of the decarburized and annealed plate.
- the alumina may have a BET specific surface area of 3.0 to 10.0 m 2 /g.
- the slab has a chemical composition of, in mass%, C: 0.085% or less, Si: 0.80 to 7 0.00%, Mn: 0.05 to 1.00%, acid-soluble Al: 0.010 to 0.065%, S: 0.01% or less, N: 0.004% to 0.012%, B: 0.0005 to 0.0080%, P: 0 to 0.50%, Ni: 0 to 1.00%, Sn: 0 to 0.30%, Sb: 0 to 0.30%, Cu: 0 to 0 40%, Cr:0 to 0.30%, Bi:0 to 0.01%, and the balance may be Fe and impurities.
- FIG. 3 is a phase diagram of a ternary system of Al 2 O 3 —MgO—SiO 2 . It is a figure which shows the relationship between the amount of MgO of an annealing separator, and the number of mullite. It is a figure which shows the relationship between the amount of MgO of an annealing separator, and iron loss ( W17/50 ). It is a figure which shows the relationship between the annealing separation agent application amount per one surface, and the number of mullites.
- a method for manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention includes a hot rolling step, a hot rolled sheet annealing step, a cold rolling step, and a decarburizing annealing step. And an annealing separator application step and a final annealing step.
- the hot rolling step is a step of hot rolling a slab having a predetermined chemical composition to obtain a hot rolled sheet.
- the hot rolled sheet annealing step is a step of obtaining an annealed hot rolled sheet by performing hot rolled sheet annealing on the hot rolled sheet.
- the cold rolling step is a step of obtaining a cold rolled sheet by cold rolling the annealed hot rolled sheet.
- the decarburization annealing step is a step of obtaining a decarburized annealed sheet by subjecting the cold rolled sheet to decarburization annealing.
- the annealing separating agent applying step is a step of applying an annealing separating agent containing alumina as a main component to the decarburized annealing plate.
- the finish annealing step is a step of performing finish annealing on the decarburized annealed plate coated with the annealing separator.
- the annealing separator having alumina as a main component contains 28 to 50% by mass of MgO.
- the coating amount of the annealing separator is 6.0 to 14.0 g/m 2 per side of the decarburized and annealed plate.
- the present inventors have found that one of the reasons why the iron loss cannot be sufficiently reduced is that the magnetic properties are adversely affected during finish annealing. I thought that it might be due to the formation of inclusions that affect Therefore, the present inventors took a sample from a grain-oriented electrical steel sheet having a large iron loss (inferior) so that a cross section (C cross section) orthogonal to the rolling direction of the base steel sheet was exposed, and the sample cross section was taken. It was observed with an optical microscope.
- the surface layer region of the base steel sheet appearing in the C section more specifically, from the base steel sheet surface to the inner side of the base steel sheet in the thickness direction of the base steel sheet. It was found that a large number of needle-shaped inclusions were present in a region having a length of 10 ⁇ m. Furthermore, it was found that these needle-like inclusions were mullite (3Al 2 O 3 .2SiO 2 ).
- decarburization annealing is performed before finish annealing for the purpose of removing C (carbon) contained in the cold rolled sheet.
- C contained in the cold rolled sheet is removed, and at the same time, an oxide film of SiO 2 is formed on the surface of the cold rolled sheet.
- a steel sheet obtained by such decarburization annealing, that is, a cold rolled sheet from which C is removed and an SiO 2 oxide film is formed on the surface is called a decarburization annealed sheet.
- the decarburization annealed sheet having an SiO 2 oxide film is used as an annealing separation agent containing alumina as a main component. Apply. Then, the decarburization annealing plate coated with the annealing separator is subjected to finish annealing.
- mullite is a composite oxide of alumina (Al 2 O 3 ) and SiO 2 , it is generated due to insufficient removal of SiO 2 formed by decarburization annealing during finish annealing. It is thought that it survived.
- SiO 2 formed by decarburization annealing is adsorbed and removed by alumina having a high BET specific surface area during finish annealing, and is removed by washing and removing the annealing separator. Therefore, the reason why the SiO 2 formed by decarburization annealing is not sufficiently removed is considered to be the insufficient amount of the annealing separator applied.
- the inventors of the present invention have the technical concept of suppressing the formation of mullite by adjusting the component composition and the coating amount of the annealing separator, and can suppress the formation of mullite.
- the amount was carefully studied. As a result, they have found that mullite formation can be suppressed by adding MgO to the annealing separator containing alumina as a main component at a specific ratio and controlling the coating amount of the annealing separator within a specific range.
- FIG. 1 shows a ternary phase diagram of Al 2 O 3 (alumina)-MgO-SiO 2 .
- alumina Al 2 O 3
- MgO alumina
- FIG. 1 shows a ternary phase diagram of Al 2 O 3 (alumina)-MgO-SiO 2 .
- the present inventors have found that the amount of MgO added to the annealing separator having alumina as a main component and the number of mullites generated in the surface layer region of the base steel sheet (steel sheet obtained after finishing annealing of a decarburized annealed sheet). I investigated the relationship with.
- a decarburized annealed plate having a plate thickness of 0.23 mm was used, and an annealing separator containing alumina as a main component was added to the decarburized annealed plate in a range of 0 to 80% by mass of MgO added.
- the coating amount was 8.0 g/m 2 per side.
- the decarburized annealed sheet is subjected to finish annealing, and the forsterite coating is not present on the surface of the base steel sheet (steel sheet obtained after finishing annealed the decarburized annealed sheet).
- a steel plate was obtained.
- the finish annealing was carried out by stacking decarburized annealing plates coated with an annealing separator.
- a 20 mm square test piece was sampled, and a cross section (C cross section) orthogonal to the rolling direction of the test piece was cut with a diamond. Polished with a buff. Then, using an optical microscope, the test piece was observed at a magnification of 1000 times, and had a length of 10 ⁇ m from the steel plate surface toward the inside of the base metal plate in the plate thickness direction of the base metal plate, and The number of needle-like inclusions having a length of 1 ⁇ m or more existing in a region (observation region) having a length of 20 mm in the plate width direction was measured. Needle-like inclusions were defined as inclusions having a maximum major axis/maximum minor axis of 10 times or more.
- the iron loss W 17/50 of the test pieces of different levels having different amounts of MgO of the annealing separator was measured.
- the average of the measured values at 10 points was defined as the iron loss W 17/50 of the test piece.
- FIG. 2 is a diagram showing the relationship between the amount of MgO in the annealing separator and the number of mullite.
- FIG. 3 is a diagram showing the relationship between the amount of MgO in the annealing separator and the iron loss (W 17/50 ).
- mullite is not generated when the MgO content of the annealing separator is 28 mass% or more.
- the MgO amount of the annealing separator is 28% by mass or more, the iron loss is less than 1.00 W/kg, and the iron loss improving effect is obtained. It can be seen that when the amount of MgO exceeds 50% by mass, the iron loss becomes 1.00 W/kg or more, which is inferior.
- the surface of the steel sheet obtained was analyzed by XRD.
- forsterite was detected at a level of 54% by mass or more of MgO, and that the XRD peak height of forsterite increased as the amount of MgO increased. From this, it is considered that when the amount of MgO of the annealing separator exceeds 50 mass %, mullite is not generated (see FIG. 2), but on the other hand, forsterite is generated and the iron loss characteristics are deteriorated.
- a decarburized annealing plate having a plate thickness of 0.23 mm was coated with an annealing separator containing alumina as a main component and containing 45% by mass of MgO.
- the applied amount of the annealing separator was changed in the range of 5.0 to 15.0 g/m 2 per side.
- a plurality of decarburized annealed plates coated with an annealing separator and dried were stacked and finish annealed to produce a grain-oriented electrical steel sheet.
- a 20 mm square test piece was sampled, and a cross section (C cross section) orthogonal to the rolling direction of the test piece was cut with a diamond. Polished with a buff. Then, using an optical microscope, the test piece was observed at a magnification of 1000 times, and had a length of 10 ⁇ m from the steel plate surface toward the inside of the base metal plate in the plate thickness direction of the base metal plate, and The number of needle-like inclusions having a length of 1 ⁇ m or more existing in a region (observation region) having a length of 20 mm in the plate width direction was measured.
- FIG. 4 is a diagram showing the relationship between the amount of annealing separator applied per one surface and the number of mullite. From FIG. 4, it is understood that when the amount of the annealing separating agent applied per one surface is less than 6.0 g/m 2 , "acicular inclusions (mullite) having a length of 1 ⁇ m or more" are generated.
- mullite According to the ternary phase diagram of Al 2 O 3 —MgO—SiO 2 shown in FIG. 1, if MgO is present in a proportion of 50 mol% (28% by mass) or more with respect to alumina, mullite is not formed. Mullite should not be generated when the amount of MgO added is 45% by mass. However, as shown in FIG. 4, when the amount of the annealing separating agent containing 45% by mass of MgO applied on one surface was less than 6.0 g/m 2 , “acicular inclusions (mullite) having a length of 1 ⁇ m or more” were obtained. Is generated. The reason for this is considered as follows.
- the coating amount of the annealing separator exceeds 14.0 g/m 2 , the coating effect is saturated and the manufacturing cost increases, so the coating amount of the annealing separator is set to 14.0 g/m 2 or less.
- the inventors of the present invention have controlled the MgO addition amount of the annealing separating agent containing alumina as the main component and the coating amount of the annealing separating agent to be within the specific ranges, so that the surface layer of the base steel sheet of the grain-oriented electrical steel sheet. It has been found that it is possible to suppress the formation of acicular inclusions (mullite) in the region, and thereby reduce the iron loss of the grain-oriented electrical steel sheet. Based on the above-described research results by the present inventors, the present manufacturing method is characterized by satisfying the following two manufacturing conditions. (Condition 1) The annealing separator containing alumina as a main component contains 28 to 50% by mass of MgO. (Condition 2) The coating amount of the annealing separator is 6.0 to 14.0 g/m 2 per side of the decarburized and annealed plate.
- ⁇ MgO content of annealing separator 28 to 50% by mass>
- the amount of MgO in the annealing separator is 28% by mass or more. It is preferably 32% by mass or more, and more preferably 35% by mass or more.
- the amount of MgO in the annealing separator is 50% by mass or less. It is preferably 48% by mass or less, more preferably 45% by mass or less.
- ⁇ Adhesion amount per unit area of one side after application/drying of the annealing separator (application amount of the annealing separator per one side of the decarburized annealed plate): 6.0 to 14.0 g/m 2 >
- the coating amount of the annealing separator containing 45% by mass of MgO per one surface is less than 6.0 g/m 2 , "acicular inclusions (mullite) having a length of 1 ⁇ m or more" are formed.
- the amount of adhesion of the annealing separating agent per unit area on one side after coating and drying is 6.0 g/m 2 or more. It is preferably 7.0 g/m 2 or more, more preferably 8.0 g/m 2 or more.
- the coating amount of the annealing separator exceeds 14.0 g/m 2 , the coating effect is saturated and the manufacturing cost increases, so the coating amount of the annealing separator is set to 14.0 g/m 2 or less. It is preferably 13.0 g/m 2 or less, more preferably 12.0 g/m 2 or less.
- ⁇ Molten steel having a specified chemical composition is cast by a normal method to obtain a silicon steel slab.
- the chemical composition of the silicon steel slab is not limited to a specific composition as long as the magnetic properties and mechanical properties required for the grain-oriented electrical steel sheet can be obtained, but an example of the chemical composition of the silicon steel slab is as follows. is there.
- a silicon steel slab has a chemical composition, in mass %, C: 0.085% or less, Si: 0.80 to 7.00%, Mn: 0.05 to 1.00%, acid-soluble Al:0. 0.010 to 0.065%, N: 0.004 to 0.012%, S: 0.01% or less, and B: 0.0005 to 0.0080%.
- C 0.085% or less C is an element effective in controlling the primary recrystallization structure, but has an adverse effect on the magnetic properties, and is an element removed by decarburization annealing before finish annealing. If the C content exceeds 0.085%, the decarburization annealing time becomes long and the productivity decreases, so the C content is set to 0.085% or less.
- the C content is preferably 0.070% or less, more preferably 0.050% or less.
- the lower limit of the amount of C includes 0%, but if the amount of C is reduced to less than 0.0001%, the manufacturing cost increases significantly. Therefore, 0.0001% is the practical lower limit of the amount of C in practical steel sheets. .. In the grain-oriented electrical steel sheet, the C content is usually reduced to about 0.001% or less by decarburization annealing.
- Si 0.80 to 7.00% Si is an element that increases the electrical resistance of the steel sheet and improves the iron loss characteristics. If the Si content is less than 0.80%, ⁇ -transformation occurs during finish annealing and the crystal orientation of the steel sheet is impaired, so the Si content is set to 0.80% or more.
- the amount of Si is preferably 1.50% or more, more preferably 2.50% or more.
- the Si content should be 7.00% or less.
- the Si amount is preferably 5.50% or less, more preferably 4.50% or less.
- Mn 0.05-1.00% Mn is an element that prevents cracking during hot rolling and forms MnS that functions as an inhibitor by combining with S and/or Se. If the Mn content is less than 0.05%, the effect of addition is not sufficiently exhibited, so the Mn content is set to 0.05% or more.
- the amount of Mn is preferably 0.07% or more, more preferably 0.09% or more.
- the Mn content exceeds 1.00%, the precipitation dispersion of MnS becomes non-uniform, the required secondary recrystallization structure cannot be obtained, and the magnetic flux density decreases, so the Mn content is 1.00% or less.
- the amount of Mn is preferably 0.80% or less, more preferably 0.06% or less.
- Acid soluble Al 0.010-0.065% Acid-soluble Al is an element that combines with N to produce (Al,Si)N that functions as an inhibitor. If the amount of acid-soluble Al is less than 0.010%, the effect of addition is not sufficiently expressed and secondary recrystallization does not proceed sufficiently, so the amount of acid-soluble Al is set to 0.010% or more. The amount of acid-soluble Al is preferably 0.015% or more, more preferably 0.020% or more.
- the soluble Al content is 0.065% or less.
- the amount of acid-soluble Al is preferably 0.050% or less, more preferably 0.040% or less.
- N 0.004 to 0.012% N is an element that combines with Al to form AlN that functions as an inhibitor, but is also an element that forms blisters (holes) in the steel sheet during cold rolling. If the N content is less than 0.004%, the formation of AlN is insufficient, so the N content is set to 0.004% or more.
- the amount of N is preferably 0.006% or more, more preferably 0.007% or more.
- the N content exceeds 0.012%, blisters (holes) may be generated in the steel sheet during cold rolling, so the N content should be 0.012% or less.
- the amount of N is preferably 0.010% or less, more preferably 0.009% or less.
- S 0.01% or less S is an element that combines with Mn to form MnS that functions as an inhibitor.
- the amount of S exceeds 0.01%, the precipitation and dispersion of MnS becomes non-uniform after purification, the desired secondary recrystallization structure cannot be obtained, the magnetic flux density is lowered, and the hysteresis loss is deteriorated, or MnS is purified after purification. Remain, and the hysteresis loss deteriorates.
- the lower limit is not particularly set, but the S content is preferably 0.003% or more.
- the S amount is more preferably 0.007% or more.
- B 0.0005 to 0.0080% B is an element that combines with N and forms a complex precipitate with MnS to form BN that functions as an inhibitor.
- the amount of B is preferably 0.0010% or more, more preferably 0.0015% or more.
- the amount of B is preferably 0.0060% or less, more preferably 0.0040% or less.
- the balance other than the above elements is Fe and impurities.
- Impurities are elements that are inevitably mixed from the steel raw material and/or in the steelmaking process, and are elements that are allowed within the range that does not impair the properties of the grain-oriented electrical steel sheet.
- the silicon steel slab does not hinder the magnetic properties of the grain-oriented electrical steel sheet and can enhance other properties, so that Cr: 0.30% or less, Cu: 0.40% or less, P: 0.50%.
- Cr 0.30% or less
- Cu 0.40% or less
- P 0.50%.
- Ni 1.00% or less
- Sn 0.30% or less
- Sb 0.30% or less
- Bi 0.01% or less
- the lower limit is 0 because these elements do not have to be contained.
- a hot rolled sheet is obtained by hot rolling a slab having the above chemical composition.
- the hot rolling conditions are not particularly limited, and ordinary conditions can be used.
- the hot rolled sheet obtained by the hot rolling process is wound into a coil.
- the slab Before subjecting the slab to hot rolling, the slab may be heated to a temperature higher than 1300° C. in order to sufficiently incorporate the inhibitor components of MnS and AlN. Further, from the viewpoint of productivity and manufacturing cost, the slab may be heated to about 1250° C. on the assumption that the inhibitor is enhanced by the nitriding treatment in the subsequent step.
- the coil-shaped hot-rolled sheet is rewound into a strip-shaped hot-rolled sheet, and then the strip-shaped hot-rolled sheet is annealed to obtain an annealed hot-rolled sheet.
- the hot rolled sheet annealing conditions are not particularly limited, and ordinary conditions can be used.
- the annealed hot rolled sheet is subjected to cold rolling once or twice or more to obtain a cold rolled sheet having a final sheet thickness.
- the cold rolled sheet may be obtained by subjecting the annealed hot rolled sheet to cold rolling two or more times with intermediate annealing.
- the crystal structure is homogenized.
- Cold rolling conditions are not particularly limited, and ordinary conditions can be used.
- a decarburized annealed sheet is obtained by subjecting the cold rolled sheet to decarburization annealing.
- the cold rolled sheet is heat-treated in wet hydrogen to reduce the amount of C in the cold rolled sheet to an amount that does not deteriorate due to magnetic aging in the product steel sheet, Allow crystals to form and prepare for the next secondary recrystallization.
- the decarburization annealing conditions are not particularly limited, and ordinary conditions can be used.
- An oxide film of SiO 2 is formed on the surface of the decarburized and annealed plate obtained by the decarburization and annealing step.
- the decarburizing and annealing sheet is annealed in an ammonia atmosphere so that AlN that functions as an inhibitor is contained in the decarburizing and annealing sheet. To generate.
- alumina Al 2 O 3
- alumina is the main component of the decarburized annealed sheet for the purpose of removing SiO 2 existing on the surface of the decarburized annealed sheet and preventing seizure in the final annealing step.
- Apply annealing separator The annealing separator containing alumina as a main component contains 28 to 50% by mass of MgO, and the coating amount of the annealing separator is 6.0 to 14.0 g/m 2 per side of the decarburized annealed plate. is there.
- the decarburized annealed plate coated with the annealing separator is wound into a coil after the annealing separator is dried.
- the MgO content (addition amount) of the annealing separator containing alumina as the main component is controlled to 28 to 50% by mass, and the amount of the annealing separator applied is 6.0 per surface of the decarburized annealing plate.
- acicular inclusions (mullite) are generated in the surface layer region of the decarburized annealed plate during the final annealing of the decarburized annealed plate in the subsequent finish annealing step. Can be suppressed.
- the iron loss W 17/50 of the final product can be reduced to a low value of less than 1.00 W/kg.
- the BET specific surface area of alumina which is the main component of the annealing separator, can be controlled to 3.0 to 10.0 m 2 /g. preferable.
- the BET specific surface area of alumina is preferably 3.0 m 2 /g or more. It is more preferably 5.0 m 2 /g or more.
- the BET specific surface area of alumina is preferably 10.0 m 2 /g or less. It is more preferably 8.0 m 2 /g or less.
- the coil-shaped decarburized annealing plate coated with the annealing separator is subjected to finish annealing to obtain the base material steel sheet of the final product (oriented electrical steel sheet).
- the secondary annealing is performed on the decarburized annealed sheet by performing the finish annealing at a temperature of 1100° C. or higher.
- the finish annealing conditions are not particularly limited, and ordinary conditions can be used.
- the decarburization annealed plate after the completion of secondary recrystallization may be subjected to purification annealing so that the precipitate used as an inhibitor is rendered harmless.
- the MgO content of the annealed separator is controlled to 28 to 50% by mass, and the applied amount of the annealed separator is the decarburized annealed plate. Since it is controlled to 6.0 to 14.0 g/m 2 per one surface of Al, it is possible to suppress Al from reacting with SiO 2 remaining on the surface of the decarburized annealed plate. Further, as a result, it is possible to suppress the formation of needle-like inclusions (mullite) in the surface layer region of the decarburized and annealed plate during the finish annealing. Further, since the MgO content of the annealing separator is limited to 50% by mass or less, it is possible to suppress the formation of a forsterite coating film on the surface of the decarburized annealed plate during the final annealing.
- Needle-like inclusions are not formed in the surface layer region of the base material steel sheet (decarburization annealed sheet after finish annealing) obtained by the above manufacturing method, and the surface of the base material steel sheet is not formed. Has no forsterite coating. That is, according to the present manufacturing method, it is possible to obtain a base material steel sheet in which two factors that hinder the movement of the domain wall are eliminated. Therefore, by forming the tension insulating coating on the surface of the base steel sheet after the finish annealing step, a grain-oriented electrical steel sheet having no forsterite coating between the base steel sheet and the tension insulating coating was obtained as the final product. In this case, it is possible to obtain a grain-oriented electrical steel sheet having a lower iron loss than the conventional one.
- the condition in the example is one condition example adopted for confirming the feasibility and effect of the present invention, and the present invention is based on this one condition example. It is not limited.
- the present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.
- Example 1 The slabs having the component compositions shown in Table 1 were heated to 1100° C. and subjected to hot rolling to obtain a hot-rolled sheet having a plate thickness of 2.60 mm, and the hot-rolled sheet was annealed at 1100° C. It was subjected to multiple times of cold rolling with annealing sandwiched, and wound as a cold-rolled sheet having a final sheet thickness of 0.23 mm.
- the cold-rolled sheet is unwound, decarburized and annealed at 820° C. in a humid atmosphere of hydrogen 75%, nitrogen 25% and dew point 40° C., and then nitriding annealed for the purpose of forming an inhibitor AlN in the decarburized and annealed sheet.
- aqueous slurry of an annealing separating agent containing alumina having a BET specific surface area of 3.0 to 10.0 m 2 /g as a main component and containing MgO in an amount of 0 to 80% by mass was applied to the surface of the decarburized annealed plate per one side.
- the coating amount was varied in the range of 5.0 to 15.0 g/m 2 , and the coating was wound into a coil.
- the coil-shaped decarburized annealed plate coated and dried with the above annealing separator was subjected to finish annealing at 1200°C for 20 hours. From the base material steel sheet obtained after finish annealing, the excess annealing separator is washed off with water to obtain a base material steel sheet of a grain-oriented electrical steel sheet that has no forsterite coating and has a specular gloss and that has completed secondary recrystallization. It was
- a 20 mm square test piece was sampled from the outermost peripheral portion in the width direction of the thus obtained coiled grain-oriented electrical steel sheet (base steel sheet).
- a cross section (C cross section) orthogonal to the rolling direction of the test piece was polished with a diamond buff.
- a cross section of one side (20 mm) of the test piece was observed with an optical microscope (1000 times), and needle-like interpositions with a length of 1 ⁇ m or more present in an observation region having a length in the plate thickness direction of 10 ⁇ m and a length in the plate width direction of 20 mm. The number of items was measured. Further, the iron loss W 17/50 of the test piece was measured according to JIS C 2550. The results are shown in Table 2.
- the amount of MgO in the annealing separator was controlled in the range of 28% by mass to 50% by mass, and the amount of the annealing separator applied was 6.0 to 14.
- the iron loss W 17/50 is less than 1.00 W/kg.
- the coating amount of the annealing separator was controlled to be in the range of 6.0 to 14.0 g/m 2 per surface, but the amount of MgO of the annealing separator was 28. Since the content was less than mass %, a plurality of needle-like inclusions (mullite) having a length of 1 ⁇ m or more were present in the observation region of the base steel sheet, and the iron loss W 17/50 increased to more than 1.00 W/kg.
- mullite needle-like inclusions
- the coating amount of the annealing separator is controlled to be in the range of 6.0 to 14.0 g/m 2 per surface, but the amount of MgO of the annealing separator is more than 50% by mass.
- the iron loss W 17/50 exceeds 1.00 W/kg. Rose.
- the amount of MgO of the annealing separator is 28% by mass or more, but since the amount of the annealing separator applied is less than 6.0 g/m 2 per side, the observation area of the base steel sheet has a length of 1 ⁇ m. A plurality of the above needle-shaped inclusions (mullite) were present, and the iron loss W 17/50 increased to over 1.00 W/kg.
- the amount of MgO of the annealing separator is controlled in the range of 28% by mass to 50% by mass, but since the amount of the annealing separator applied is less than 6.0 g/m 2 per side, A plurality of needle-shaped inclusions (mullite) having a length of 1 ⁇ m or more existed in the observation region of the base steel sheet, and the iron loss W 17/50 increased to more than 1.00 W/kg.
- Example 2 Steel No. shown in Table 1
- the slab having the composition of A5 was heated to 1100° C. and subjected to hot rolling to obtain a hot-rolled sheet having a plate thickness of 2.60 mm.
- the hot-rolled sheet was annealed at 1100° C., and then subjected to intermediate annealing. It was subjected to a plurality of cold rolling operations to be sandwiched and wound as a cold rolled sheet having a final sheet thickness of 0.23 mm.
- the cold-rolled sheet is unwound, subjected to decarburization annealing at 820° C. in a humid atmosphere of hydrogen 75%, nitrogen 25% and dew point 40° C., and then subjected to nitriding annealing for the purpose of forming inhibitor AlN in the decarburized annealed sheet. did.
- the coil-shaped decarburized annealed plate coated and dried with the above annealing separator was subjected to finish annealing at 1200°C for 20 hours. From the base material steel sheet obtained after finish annealing, the excess annealing separator is washed off with water to obtain a base material steel sheet of a grain-oriented electrical steel sheet that has no forsterite coating and has specular gloss and that has completed secondary recrystallization. It was
- a 20 mm square test piece was sampled from the outermost peripheral portion in the width direction of the thus obtained coiled grain-oriented electrical steel sheet (base steel sheet).
- a cross section (C cross section) orthogonal to the rolling direction of the test piece was polished with a diamond buff.
- a cross section of one side (20 mm) of the test piece was observed with an optical microscope (1000 times), and needle-like interpositions with a length of 1 ⁇ m or more present in an observation region having a length in the plate thickness direction of 10 ⁇ m and a length in the plate width direction of 20 mm. The number of items was measured. Further, the iron loss W 17/50 of the test piece was measured according to JIS C 2550. The results are shown in Table 3.
- the amount of the annealing separator applied was in the range of 6.0 to 14.0 g/m 2 per side. It is understood that the iron loss W 17/50 can be greatly reduced by controlling and further controlling the BET specific surface area of alumina, which is the main component of the annealing separator, to 3.0 to 10.0 m 2 /g. It is considered that this is because needle-like inclusions were not generated and the amount of SiO 2 adsorbed by alumina was increased.
- the present invention it is possible to reduce the iron loss of the grain-oriented electrical steel sheet in which the forsterite-based coating is not present between the base steel sheet and the tension insulating coating as compared with the conventional one. Therefore, the present invention is highly applicable in the electromagnetic steel sheet manufacturing industry and the electromagnetic steel sheet utilizing industry.
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Abstract
Description
本願は、2019年1月16日に、日本に出願された特願2019-5083号に基づき優先権を主張し、その内容をここに援用する。
本発明者らは、この針状介在物が磁壁の移動を妨げる原因、つまり鉄損に悪影響を及ぼす原因だと推測した。本発明者らがさらなる研究を行った結果、焼鈍分離剤の成分と塗布量を特定の条件下で制御することにより、母材鋼板の表層領域において針状介在物の生成を抑制でき、母材鋼板と張力絶縁被膜との間にフォルステライト系被膜が存在しない方向性電磁鋼板の鉄損を従来よりも低減できることを見出した。
熱間圧延工程は、所定の化学組成を有するスラブに熱間圧延を施すことにより熱延板を得る工程である。熱延板焼鈍工程は、熱延板に熱延板焼鈍を施すことにより焼鈍熱延板を得る工程である。冷間圧延工程は、焼鈍熱延板に冷間圧延を施すことにより冷延板を得る工程である。脱炭焼鈍工程は、冷延板に脱炭焼鈍を施すことにより脱炭焼鈍板を得る工程である。焼鈍分離剤塗布工程は、脱炭焼鈍板にアルミナを主成分とする焼鈍分離剤を塗布する工程である。仕上げ焼鈍工程は、焼鈍分離剤が塗布された脱炭焼鈍板に仕上げ焼鈍を施す工程である。
各工程の詳細については後述するが、本製造方法において、最終製品である方向性電磁鋼板の母材鋼板の表層領域に針状介在物が生成されるのを抑制するために、以下の2つの製造条件を満たしていることが特徴である。
(条件1)アルミナを主成分とする焼鈍分離剤は、28~50質量%のMgOを含有する。
(条件2)焼鈍分離剤の塗布量は、脱炭焼鈍板の片面当たり6.0~14.0g/m2である。
(y)仕上げ焼鈍中、AlN(インヒビター)の分解で生成したAlが、焼鈍分離剤のAl成分に加わり、焼鈍分離剤におけるMgOの比率が相対的に低下し、焼鈍分離剤の成分組成が、ムライト生成域に移行する(図1参照)。
上記のような本発明者らによる研究結果に基づき、本製造方法では、以下の2つの製造条件を満たしていることを特徴としている。
(条件1)アルミナを主成分とする焼鈍分離剤は、28~50質量%のMgOを含有する。
(条件2)焼鈍分離剤の塗布量は、脱炭焼鈍板の片面当たり6.0~14.0g/m2である。
図2に示すように、焼鈍分離剤のMgO量が28質量%以上であると、ムライトが生成せず、かつ、図3に示すように、鉄損W17/50が1.00W/kg未満と優位である。そのため、焼鈍分離剤のMgO量は28質量%以上とする。好ましくは32質量%以上、より好ましくは35%質量以上である。
図4に示すように、MgOを45質量%含む焼鈍分離剤の片面当たりの塗布量が6.0g/m2未満であると、“長さ1μm以上の針状介在物(ムライト)”が生成するので、焼鈍分離剤の塗布・乾燥後の片面単位面積当たりの付着量(脱炭焼鈍板の片面当たりの焼鈍分離剤の塗布量)は6.0g/m2以上とする。好ましくは7.0g/m2以上、より好ましくは8.0g/m2以上である。
Cは、一次再結晶組織の制御に有効な元素であるが、磁気特性に悪影響を及ぼすので、仕上げ焼鈍前に脱炭焼鈍で除去する元素である。C量が0.085%を超えると、脱炭焼鈍時間が長くなり、生産性が低下するので、C量は0.085%以下とする。C量は好ましくは0.070%以下、より好ましくは0.050%以下である。
Siは、鋼板の電気抵抗を高めて、鉄損特性を改善する元素である。Si量が0.80%未満では、仕上げ焼鈍時にγ変態が生じ、鋼板の結晶方位が損なわれるので、Si量は0.80%以上とする。Si量は好ましくは1.50%以上、より好ましくは2.50%以上である。
Mnは、熱間圧延時の割れを防止するとともに、S及び/又はSeと結合して、インヒビターとして機能するMnSを形成する元素である。Mn量が0.05%未満では、添加効果が十分に発現しないので、Mn量は0.05%以上とする。Mn量は好ましくは0.07%以上、より好ましくは0.09%以上である。
酸可溶性Alは、Nと結合して、インヒビターとして機能する(Al、Si)Nを生成する元素である。酸可溶性Al量が0.010%未満では、添加効果が十分に発現せず、二次再結晶が十分に進行しないので、酸可溶性Al量は0.010%以上とする。酸可溶性Al量は好ましくは0.015%以上、より好ましくは0.020%以上である。
Nは、Alと結合して、インヒビターとして機能するAlNを形成する元素であるが、一方で、冷間圧延時、鋼板中にブリスター(空孔)を形成する元素でもある。N量が0.004%未満では、AlNの形成が不十分となるので、N量は0.004%以上とする。N量は好ましくは0.006%以上、より好ましくは0.007%以上である。
Sは、Mnと結合して、インヒビターとして機能するMnSを形成する元素である。
Bは、Nと結合し、MnSと複合析出して、インヒビターとして機能するBNを形成する元素である。
表1に示す成分組成のスラブを1100℃に加熱して熱間圧延に供し、板厚2.60mmの熱延板とし、該熱延板に1100℃で熱延板焼鈍を施した後、中間焼鈍を挟む複数回の冷間圧延に供し、最終板厚0.23mmの冷延板として巻き取った。
比較例b4及びb5では、焼鈍分離剤の塗布量が片面当たり6.0~14.0g/m2の範囲に制御されているが、焼鈍分離剤のMgO量が50質量%超である。この場合、母材鋼板の観察領域に長さ1μm以上の針状介在物(ムライト)は存在しないが、フォルステライトが生成され、その結果、鉄損W17/50が1.00W/kg超に上昇した。
比較例b6では、焼鈍分離剤のMgO量は28質量%以上であるが、焼鈍分離剤の塗布量が片面当たり6.0g/m2未満であるので、母材鋼板の観察領域に長さ1μm以上の針状介在物(ムライト)が複数存在し、鉄損W17/50は1.00W/kg超に上昇した。
比較例b7~b15では、焼鈍分離剤のMgO量は28質量%~50質量%の範囲に制御されているが、焼鈍分離剤の塗布量が片面当たり6.0g/m2未満であるので、母材鋼板の観察領域に長さ1μm以上の針状介在物(ムライト)が複数存在し、鉄損W17/50は1.00W/kg超に上昇した。
表1に示す鋼No.A5の成分組成のスラブを1100℃に加熱して熱間圧延に供し、板厚2.60mmの熱延板とし、該熱延板に1100℃で熱延板焼鈍を施した後、中間焼鈍を挟む複数回の冷間圧延に供し、最終板厚0.23mmの冷延板として巻き取った。
Claims (3)
- スラブに熱間圧延を施すことにより熱延板を得る工程と、
前記熱延板に熱延板焼鈍を施すことにより焼鈍熱延板を得る工程と、
前記焼鈍熱延板に冷間圧延を施すことにより冷延板を得る工程と、
前記冷延板に脱炭焼鈍を施すことにより脱炭焼鈍板を得る工程と、
前記脱炭焼鈍板にアルミナを主成分とする焼鈍分離剤を塗布する工程と、
前記焼鈍分離剤が塗布された前記脱炭焼鈍板に仕上げ焼鈍を施す工程と
を有し、
前記焼鈍分離剤は、28~50質量%のMgOを含有し、
前記焼鈍分離剤の塗布量は、前記脱炭焼鈍板の片面当たり6.0~14.0g/m2であることを特徴とする方向性電磁鋼板の製造方法。 - 前記アルミナのBET比表面積が3.0~10.0m2/gであることを特徴とする請求項1に記載の方向性電磁鋼板の製造方法。
- 前記スラブは、化学組成として、質量%で、
C:0.085%以下、
Si:0.80~7.00%、
Mn:0.05~1.00%、
酸可溶性Al:0.010~0.065%、
S:0.01%以下、
N:0.004%~0.012%、
B:0.0005~0.0080%、
P:0~0.50%、
Ni:0~1.00%、
Sn:0~0.30%、
Sb:0~0.30%、
Cu:0~0.40%、
Cr:0~0.30%、
Bi:0~0.01%、
を含有し、残部がFe及び不純物からなる
ことを特徴とする請求項1又は2に記載の方向性電磁鋼板の製造方法。
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WO2022250162A1 (ja) * | 2021-05-28 | 2022-12-01 | Jfeスチール株式会社 | 方向性電磁鋼板の製造方法 |
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