JP2021155833A - Manufacturing method of grain-oriented electrical steel sheet - Google Patents

Abstract

To provide a manufacturing method of grain-oriented electrical steel sheet that can stably obtain excellent coating characteristics.SOLUTION: The manufacturing method of grain-oriented electrical steel sheet includes hot-rolling of a slab containing C of 0.01 to 0.10%, Si of 2.0 to 5.0%, Mn of 0.01 to 1.0% and Cr of 0.01 to 0.2% and further containing an inhibitor-forming component, cold-rolling, decarburization annealing that also serves as primary recrystallization annealing, coating of an annealing separator on a surface of the steel sheet, and finish annealing thereafter. A method of generating at a frequency of 80% or more grain boundaries having a misorientation angle of 15 to 45° on an outermost layer of the steel sheet after decarburization annealing, is to apply, for example, any one or more means consisting of a work roll with a diameter of 600 mm or less used in finishing hot rolling, a friction coefficient in the finishing hot rolling of 0.40 or more, and oxygen potential of an atmosphere of intermediate annealing PH2O/PH2 set to be range of 0.10 to 0.25.SELECTED DRAWING: Figure 1

Description

The present invention relates mainly to a method for manufacturing grain-oriented electrical steel sheets used for iron cores of transformers and rotating equipment, and particularly to a method for manufacturing grain-oriented electrical steel sheets having excellent coating characteristics.

Electrical steel sheets are soft magnetic materials mainly used for iron cores of transformers and rotating equipment, and are required to have high magnetic flux density and low iron loss as magnetic characteristics. In such a directional electromagnetic steel plate, a steel slab containing an inhibitor necessary for causing secondary recrystallization, for example, a component forming MnS, MnSe, AlN, etc., is hot-rolled, and if necessary, hot-rolled sheet is annealed. Then, it is cold-rolled once or cold-rolled two or more times with intermediate annealing in between to obtain a cold-rolled plate with the final plate thickness, then decarburized and annealed, annealed separator is applied to the surface of the steel plate, and then secondary. Manufactured by subjecting finish annealing to recrystallize.

By the way, except for special cases such as mirroring, a film mainly composed of _{forsterite (Mg 2} SiO _{4) is generally formed on the surface of the grain-oriented electrical steel sheet.} It is known that this forsterite coating not only imparts electrical insulation to the surface of the steel sheet, but also contributes to reduction of iron loss by applying tensile stress to the surface of the steel sheet due to its low thermal expansion. Further, the forsterite film is formed by finish annealing, and its forming behavior has a great influence on the production of inhibitors such as MnS, MnSe and AlN, that is, secondary recrystallization. Furthermore, the forsterite film absorbs unnecessary inhibitor-forming components after the completion of secondary recrystallization and purifies the steel sheet, thereby contributing to the improvement of magnetic properties.

Therefore, forming a defect-free, uniform, and excellently adherent forsterite film is extremely important in producing a grain-oriented electrical steel sheet having excellent magnetic properties. Generally, the forsterite film is formed by the following steps. First, a cold-rolled sheet whose final thickness is obtained by cold rolling is decarburized and annealed at a temperature of 700 to 900 ° C., which also serves as primary recrystallization annealing, in a wet hydrogen atmosphere. In this step, during the subsequent finish annealing, a primary recrystallized structure is formed so that an appropriate secondary recrystallized structure can be obtained, and at the same time, C is reduced to 0.003 mass% or less in order to prevent magnetic aging of the product plate. It is decarburized until it becomes, and an oxide film mainly composed _{of SiO 2 is formed on the surface layer of the steel sheet.} Then, after applying an annealing separator mainly composed of MgO to the surface of the steel sheet, it is annealed at a temperature of 1000 to 1200 ° C. in a reducing or non-oxidizing atmosphere in the finish annealing, and forsterite is subjected to the following reaction. A film is formed.
2MgO + SiO ₂ → Mg ₂ SiO ₄

This forsterite film is a ceramic film in which fine forsterite crystals having a particle size of 1 to 2 μm are accumulated, and as described above, an oxide film formed during decarburization annealing is formed as one of the raw materials. Will be done. Therefore, the type, amount, distribution, etc. of this oxide film have a great influence on the nucleation and grain growth behavior of forsterite, and by extension, the uniformity and adhesion of the forsterite film. Therefore, it is extremely important to optimize the physical properties of the oxide film formed on the surface layer of the steel sheet during decarburization annealing in order to form a forsterite film having excellent film characteristics.

Conventionally, as a technique for improving the uniformity and adhesion of a forsterite film, for example, Patent Document 1 states that during decarburization annealing, grain boundaries having an orientation difference angle of less than 15 ° or 45 ° or more are formed on the outermost layer of a steel sheet. , A method of generating 40% or more at that frequency has been proposed. Further, in Patent Document 2, 0.1 to 1.0 mass% of Cr is added to the steel slab, and spinel-type Cr oxide is generated in the oxide film formed on the surface layer of the steel sheet during decarburization annealing. A method has been proposed to make it. This spinel-type Cr oxide reacts with MgO according to the following formula during finish annealing.
MgO + FeCr ₂ O ₄ → Mg _1-x Fe _x O + Mg _1-x Fe _x Cr ₂ O ₄
According to Patent Document 2, this Mg _1-x Fe _x O promotes the formation of forsterite. Further, the spinel-type Cr oxide is formed slightly inside the surface of the steel sheet, and has the effect of improving the coating properties by promoting the formation of forsterite at this position.

Japanese Unexamined Patent Publication No. 2001-200317 Japanese Unexamined Patent Publication No. 2000-355717

However, in the technique described in the above-mentioned prior art, although a certain effect of improving the film characteristics is recognized, there is a problem that there are still some cases in which the film characteristics are not improved and the magnetic characteristics are not improved.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to propose a method for manufacturing a grain-oriented electrical steel sheet capable of stably obtaining excellent coating properties. ..

In order to solve the above problems, the inventors are keenly paying attention to the influence of the directional difference angle of the grain boundary of the outermost layer of the steel sheet after decarburization annealing on the formation of the oxide film and, by extension, on the characteristics of the forsterite film. After repeated examinations. As a result, when the intergranular frequency having the above-mentioned directional difference angle is in the range, the intergranular oxidation is promoted, and a spinel-type Cr oxide is generated slightly inside the surface of the steel sheet, and as a result, the coating characteristics are remarkably improved. The present invention has been completed.

Based on the above findings, the present invention has C: 0.01 to 0.10 mass%, Si: 2.0 to 5.0 mass%, Mn: 0.01 to 1.0 mass% and Cr: 0.01 to 0.2 mass. A steel slab containing%, further containing any one of the following groups A to C as an inhibitor-forming component, and having a component composition in which the balance is Fe and unavoidable impurities, is hot-rolled. Then, it is cold-rolled once or cold-rolled two or more times with an intermediate annealing in between to obtain a cold-rolled plate with the final plate thickness, decarburized and annealed, which also serves as primary recrystallization annealing, and an annealing separator is applied to the surface of the steel plate. In the method for producing a directional electromagnetic steel sheet, which consists of a series of steps of coating and then finish annealing, grain boundaries having an orientation difference angle of 15 to 45 ° are formed at a frequency of 80% or more on the outermost surface layer of the steel sheet after decarburization annealing. We propose a method for manufacturing a directional electromagnetic steel sheet, which is characterized in that it is produced.
Description-Group A; At least one selected from S: 0.002 to 0.03 mass% and Se: 0.002 to 0.003 mass%-Group B: Al: 0.005 to 0.04 mass% and N : 0.003 to 0.012 mass%
Group C; at least one selected from S: 0.002 to 0.03 mass% and Se: 0.002 to 0.003 mass%, Al: 0.005 to 0.04 mass% and N: 0.003. ~ 0.012 mass%

In the method for producing a directional electromagnetic steel sheet of the present invention, the method of forming grain boundaries having an orientation difference angle of 15 to 45 ° on the outermost layer of the steel sheet after decarburization annealing at a frequency of 80% or more is the method of hot rolling. and 600mm below the work roll diameter in the finishing rolling, and 0.40 or more friction coefficient in finish rolling of the hot rolling, and, 0.10 to oxygen potential _P H2O _{/ P H2} atmosphere in the intermediate annealing It is characterized in that it is a means of any one or more of the range of 0.25.

Further, in the steel slab used for producing the directional electromagnetic steel plate of the present invention, in addition to the above component composition, B: 0.0002 to 0.0025 mass%, P: 0.005 to 0.08 mass%, Ti: 0.001 to 0.01 mass%, Ni: 0.01 to 1.5 mass%, Cu: 0.01 to 0.5 mass%, Nb: 0.002 to 0.08 mass%, Mo: 0.005 to 0. It is characterized by containing at least one selected from 1 mass%, Sn: 0.005 to 0.5 mass%, Sb: 0.005 to 0.5 mass% and Bi: 0.002 to 0.08 mass%. do.

According to the present invention, during decarburization annealing, a spinel-type Cr oxide is formed slightly inside the surface of the steel sheet by forming grain boundaries having a specific orientation difference angle on the outermost layer of the steel sheet at a predetermined frequency or more. Since it is generated, it becomes possible to more stably manufacture a directional electromagnetic steel sheet having excellent coating characteristics.

It is a graph which shows the influence which the grain boundary frequency of the orientation difference angle of 15 to 45 ° in the outermost layer of a steel sheet has on the Cr concentration distribution in the thickness direction of a steel sheet after decarburization annealing.

First, the experiment that triggered the development of the present invention will be described.
It contains C: 0.03 mass%, Si: 3.2 mass%, Mn: 0.06 mass%, Cr: 0.05 mass%, and further contains S: 0.003 mass% as an inhibitor-forming component, and the balance is Fe. A steel slab having a component composition composed of unavoidable impurities was heated to a temperature of 1380 ° C. for 30 minutes and then hot-rolled to obtain a hot-rolled plate. At this time, the work roll diameter of the final stand for finish rolling was variously changed, and the coefficient of friction between the work roll of the stand and the steel plate was set to 0.35. Then, the hot-rolled sheet th one cold rolled to a cold-rolled sheet of the intermediate plate thickness 1.7 mm, under a humid hydrogen atmosphere at _P H2O _{/ P H2} atmosphere 0.30, of 1050 ° C. × 1min After intermediate annealing, it is cold-rolled for the second time to obtain a cold-rolled plate with a final plate thickness of 0.23 mm, and then primary recrystallization at 840 ° C. × 2 min under a wet hydrogen atmosphere with _PH2O / _{PH2 of 0.30.} Decarburization annealing was performed, which also served as annealing.

Next, the directional difference angle of each grain boundary of the outermost layer of the steel sheet after decarburization annealing obtained as described above was measured by electron backscatter diffraction (EBSP). Here, the outermost layer of the steel sheet means a range from the surface of the steel sheet to 5 μm, and the angle of rotation of the grain boundaries is necessary for superimposing the directions of adjacent grains across the grain boundaries. The minimum rotation angle.

_{Next, an annealing separator containing MgO as the main component and 2.0 mass% of TiO 2} was applied to the surface of the steel sheet after decarburization and annealing, and then held at a temperature of 850 ° C. for 50 hours for secondary recrystallization. After performing finish annealing in a hydrogen atmosphere at a temperature of 1200 ° C. for 5 hours for purification treatment, the surface of the steel sheet after finish annealing was coated with an insulating coating mainly composed of magnesium phosphate and colloidal silica.

The magnetic properties and coating properties (uniformity and adhesion) of the product board thus obtained were investigated. The uniformity of the coating film is determined by visually observing the appearance of the coating film, and the adhesion of the coating film is the minimum diameter at which the coating film does not peel off when the steel plate after finish annealing is wound around a round bar having a different diameter. (Hereinafter, the above diameter is also referred to as "bending peeling diameter").

The results of the above measurements are shown in Table 1. From this table, it was found that a glossy, uniform, and excellently adherent forsterite film can be obtained when the frequency of grain boundaries having an orientation difference angle of 15 to 45 ° is 80% or more. On the other hand, when the frequency of the grain boundaries was less than 80%, only a film having low gloss, non-uniformity, and poor adhesion was obtained.

The above result seems to contradict the result of Patent Document 1, but in this experiment, since Cr is added to the steel slab, the effect of adding Cr on the coating characteristics of the orientation difference angle of the grain boundaries is exerted. Is considered to have changed. However, even if Cr is added, the method described in Patent Document 2 shows a certain effect of improving the film characteristics, but the characteristics still vary, and there are some cases where the magnetic characteristics are not improved.

Next, in order to investigate the effect of the addition of Cr, the relationship between the grain boundary frequency of the directional difference angle of 15 to 45 ° on the outermost layer of the steel sheet and the Cr concentration distribution in the thickness direction from the surface of the steel sheet was investigated by a glow discharge emission analyzer ( The measurement was performed using GDS), and the result is shown in FIG. From this figure, when the grain boundary frequency of the orientation difference angle of 15 to 45 ° was 80% or more, a Cr peak was observed slightly inside the surface of the steel sheet. That is, it was found that when the frequency of the grain boundaries was 80% or more, a large amount of spinel-type Cr oxide was generated slightly inside the surface of the steel sheet.

The inventors consider the cause as follows.
Grain boundaries with an orientation difference angle of 15 to 45 ° are high-energy grain boundaries and serve as a high-speed diffusion path for elements. Therefore, when the frequency of grain boundaries is high, grain boundary diffusion becomes dominant rather than body diffusion. Further, in a general decarburized annealing atmosphere, Cr causes internal oxidation. Therefore, when the frequency of the grain boundaries is 80% or more, it is presumed that as a result of the internal oxidation of Cr being promoted by the diffusion of oxygen grain boundaries, spinel-type Cr oxide was generated slightly inside the surface of the steel sheet. Will be done.

Further, as in Patent Document 2, the fact that a forsterite film having excellent coating characteristics was obtained when the grain boundary frequency of the outermost layer of the steel sheet was 15 to 45 ° and the grain boundary frequency was 80% or more was obtained on the surface of the steel sheet. It is considered that this is because the formation of spinel-type Cr oxide was slightly inward, and as a result, the formation of forsterite was promoted at this position. However, according to the results of this experiment, the above effect is obtained only by forming a grain boundary frequency of 15 to 45 ° with an orientation difference angle of 80% or more on the outermost layer of the steel sheet during decarburization annealing, as compared with the surface of the steel sheet. A spinel-type Cr oxide can be formed slightly inside, and a stable can be obtained. The grain boundary frequency at which the orientation difference angle of the steel sheet resurface layer after decarburization annealing is 15 to 45 ° is preferably 85% or more, more preferably 90% or more.
The present invention has been developed based on the above-mentioned novel findings.

Next, the method for manufacturing the grain-oriented electrical steel sheet of the present invention will be described. First, the component composition of the steel material (slab) used for producing the grain-oriented electrical steel sheet of the present invention will be described.
C: 0.01-0.1 mass%
C is an important component for improving the primary recrystallization texture, but the above effect cannot be sufficiently obtained unless the content is less than 0.01 mass%. On the other hand, if it exceeds 0.1 mass%, it becomes difficult to reduce C to 0.003 mass% or less, which does not cause magnetic aging due to decarburization annealing. In addition, since oxygen is consumed for decarburization, the amount of oxygen is reduced, which may lead to deterioration of film characteristics. Therefore, C is limited to the range of 0.01 to 0.1 mass%. It is preferably in the range of 0.02 to 0.08 mass%.

Si: 2.0-5.0 mass%
Si is an essential component for increasing the specific resistance of steel and reducing eddy current loss, but the above effect cannot be sufficiently obtained unless the content is less than 2.0 mass%. On the other hand, if it exceeds 5.0 mass%, the cold ductility is significantly impaired. Therefore, Si is limited to the range of 2.0 to 5.0 mass%. It is preferably in the range of 2.5 to 4.5 mass%.

Mn: 0.01 to 1.0 mass%
Like Si, Mn has the effect of increasing the specific resistance of steel and reducing eddy current loss. Further, although it is an important component for improving heat ductility, the above effect cannot be sufficiently obtained unless the content is less than 0.01 mass%. On the other hand, if it exceeds 1.0 mass%, γ transformation is induced and the magnetic properties are deteriorated. Therefore, Mn is set in the range of 0.01 to 1.0 mass%. It is preferably in the range of 0.01 to 0.50 mass%.

Cr: 0.01-0.2 mass%
Cr is an important component in the present invention, and by adding it to a steel slab, spinel-type Cr oxide can be generated in an oxide film formed on the surface layer of a steel sheet during decarburization annealing. However, if the content is less than 0.01 mass%, the above effect cannot be sufficiently obtained, while if it exceeds 0.2 mass%, heterogeneous oxidation is promoted and the film characteristics are rather deteriorated. Therefore, Cr is set in the range of 0.01 to 0.2 mass%. It is preferably in the range of 0.01 to 0.1 mass%.

Further, the steel material used for producing the grain-oriented electrical steel sheet of the present invention needs to contain a component forming an inhibitor for expressing secondary recrystallization in addition to the above components.
The inhibitor-forming component varies depending on the type of inhibitor. For example, when MnS and / or MnSe is used as the inhibitor, in addition to the above-mentioned Mn, S: 0.002 to 0.03 mass% and Se: 0. It is necessary to contain at least one selected from 002 to 0.003 mass%. When AlN is used as an inhibitor, it is necessary to contain Al: 0.005 to 0.04 mass% and N: 0.003 to 0.012 mass%. As the inhibitor, AlN may be used together with MnS and / or MnSe. In that case, at least 1 selected from S: 0.002 to 0.03 mass% and Se: 0.002 to 0.003 mass%. It is necessary to contain the seed and Al: 0.005 to 0.04 mass% and N: 0.003 to 0.012 mass%.

Further, in the steel material used for producing the directional electromagnetic steel plate of the present invention, the balance other than the above components is substantially Fe and unavoidable impurities, but for the purpose of improving the magnetic properties, in addition to the above components, further , B: 0.0002 to 0.0025 mass%, P: 0.005 to 0.08 mass%, Ti: 0.001 to 0.01 mass%, Ni: 0.01 to 1.5 mass%, Cu: 0.01 ~ 0.5 mass%, Nb: 0.002 to 0.08 mass%, Mo: 0.005 to 0.1 mass%, Sn: 0.005 to 0.5 mass%, Sb: 0.005 to 0.5 mass%, And Bi: at least one selected from 0.002 to 0.08 mass% may be appropriately contained.

Next, the method for manufacturing the grain-oriented electrical steel sheet of the present invention will be described.
First, the steel material (slab) of the grain-oriented electrical steel sheet of the present invention is formed by a conventional continuous casting method or a conventional method after melting a steel having a component composition suitable for the present invention by a commonly known refining process. It can be produced by the ingot-lump rolling method.

Next, the steel material (slab) is reheated to a temperature of 1250 ° C. or higher and then hot-rolled to obtain a hot-rolled plate having a predetermined plate thickness. If the reheating temperature of the slab is less than 1250 ° C., the added inhibitor-forming component does not sufficiently dissolve in the steel. The preferred slab heating temperature is 1300 ° C. or higher. As a means for heating the slab, a commonly known means such as a gas furnace, an induction heating furnace, and an energizing furnace can be used.

The reheated slab is then subjected to hot rolling. The rolling temperature in hot rolling may be carried out under generally known conditions, and there is no particular limitation. However, in order to generate grain boundaries with an orientation difference angle of 15 to 45 ° at a frequency of 80% or more on the outermost layer of the steel sheet after decarburization annealing, which is a feature of the present invention, a work roll during hot rolling is used. It is important to control the shear stress on the steel sheet by varying the diameter and / or coefficient of friction.

Specifically, the work roll at the final stand of hot finish rolling may be 600 mm or less, and / or the friction coefficient between the work roll and the steel plate at the final stand of hot finish rolling may be 0.40 or more. is important. By satisfying the above conditions, a fine structure is formed on the surface layer of the steel sheet of the hot-rolled sheet, and the number of recrystallized nuclei in the decarburization annealing increases. It is possible to generate a grain boundary of ° with a frequency of 80% or more.

Next, the hot-rolled plate after the hot-rolling is annealed by hot-rolling plate in order to completely recrystallize the hot-rolled structure, if necessary. The temperature of this hot-rolled plate annealing is preferably in the range of 950 to 1200 ° C. Below 950 ° C, the hot-rolled structure may not be completely recrystallized. On the other hand, if the temperature exceeds 1200 ° C., the crystal grain size after annealing on the hot-rolled plate becomes coarse, and it becomes difficult to obtain a sized primary recrystallized structure. More preferably, it is in the range of 1000 to 1100 ° C.

Next, the hot-rolled plate after the hot-rolling or hot-rolling plate annealing is made into a cold-rolled plate having a final plate thickness by one cold rolling or two or more cold rollings sandwiching intermediate annealing. The cold rolling conditions may be carried out according to a conventional method, and there is no particular limitation.

However, when cold rolling is performed two or more times, in order to generate grain boundaries with a displacement angle of 15 to 45 ° more frequently on the outermost layer of the steel sheet after decarburization annealing, it is necessary to perform cold rolling. it is important to control the oxidation potential _P H2O _{/ P H2} atmosphere in the intermediate annealing carried out.

Specifically, the oxygen potential _P H2O _{/ P H2} atmosphere in the intermediate annealing in the range of 0.10 to 0.25 is important. By satisfying the above conditions, surface decarburization during intermediate annealing is suppressed, that is, precipitation of carbides is promoted, which increases recrystallization nuclei during decarburization annealing. Therefore, the outermost layer of the steel sheet after decarburization annealing. In addition, it is possible to generate grain boundaries having an orientation difference angle of 15 to 45 ° at a frequency of 80% or more.

Next, the cold-rolled plate having the final plate thickness is subjected to decarburization annealing that also serves as primary recrystallization annealing. The decarburization annealing, in order to ensure the decarburizing oxygen potential _P H2O _{/ P H2} annealing atmosphere under a humid atmosphere in the range of 0.25 to 0.55, carried out in a temperature range of 800 to 900 ° C. Is desirable. By this annealing, C in the steel sheet is reduced to 0.003 mass% or less, and at the same time, grain boundaries with an orientation difference angle of 15 to 45 ° are generated at a frequency of 80% or more on the outermost layer of the steel sheet after decarburization annealing. Can be made to.

Next, the steel sheet after the primary recrystallization annealing is subjected to finish annealing for expressing secondary recrystallization and purification treatment after applying an annealing separator mainly containing MgO to the surface of the steel sheet and drying it. By this finish annealing, Al, N, S and Se in the steel sheet are at the impurity level, specifically, Al: 0.004 mass% or less, N: 0.003 mass% or less, S: 0.002 mass% or less and Se. : Reduced to 0.002 mass% or less.

Next, the steel sheet after finish annealing is subjected to washing with water, brushing, pickling, etc. in order to remove the unreacted annealing separator remaining on the surface of the steel sheet, and then flattened for shape correction and improvement of iron loss characteristics. It is preferable to perform annealing.

When steel sheets (product plates) are laminated and used, an insulating film may be applied to the surface of the steel sheets during or before and after the flattening annealing in order to ensure the insulating property between the steel sheets. preferable. Further, in order to further reduce the iron loss, it is desirable to apply a tension-applying type insulating film that applies tensile tension to the steel sheet. Further, in order to further enhance the iron loss reduction effect, an insulating film is formed via a binder, or an inorganic layer is formed on the surface of the steel sheet by a physical vapor deposition method or a chemical vapor deposition method, and then the insulating film is formed. It is preferable to improve the adhesion of the film.

Further, in order to further reduce iron loss, grooves are formed on the surface of the steel sheet in any of the steps after the cold rolling, the surface of the steel sheet after finish annealing is irradiated with an electron beam or a laser beam, or the surface of the steel sheet is subjected to. Magnetic domain subdivision processing may be performed by mechanically introducing a strain region.

A steel slab having various component compositions shown in Table 2 was heated to a temperature of 1380 ° C. for 30 minutes and then hot-rolled to obtain a hot-rolled plate having a plate thickness of 2.4 mm. At this time, the diameter of the work roll of the final stand for finish rolling and the coefficient of friction between the work roll of the stand and the steel plate were variously changed. Then, the hot rolled plate rolled first cold, the cold-rolled sheet of the intermediate plate thickness 1.7 mm, in a humidified atmosphere with an adjusted oxidation potential _P H2O _{/ P H2} in 0.30, 1050 ° C. × 60s After intermediate annealing, the first cold rolling was performed to obtain a cold rolled plate having a final plate thickness of 0.23 mm. Next, the cold-rolled sheet is _{decarburized and annealed in a wet hydrogen atmosphere having a PH2O} / _PH2 of 0.30, which also serves as a primary recrystallization annealing at 840 ° C. × 120 s, and then the outermost surface layer of the steel sheet after the decarburization annealing. The orientation difference angle of each grain boundary was measured by electron backscatter diffraction (EBSP).
_{Next, an annealing separator containing MgO as a main component and TiO 2} added in an amount of 2.0 mass% was applied to the surface of the steel sheet after decarburization and annealing, dried, and then secondary recrystallized under the condition of holding at a temperature of 850 ° C. for 50 hr. After the above-mentioned finish annealing, the surface of the steel sheet after finish annealing is subjected to finish annealing by holding it at a temperature of 1150 ° C. for 5 hours in a hydrogen atmosphere for 5 hours, and then an insulating coating mainly composed of magnesium phosphate and colloidal silica is applied to the surface of the steel sheet after finish annealing. Was given.

The magnetic properties and coating properties (uniformity and adhesion) of the product board thus obtained were investigated, and the results are also shown in Table 2. The uniformity was evaluated by visually observing the appearance of the film, and the film adhesion was evaluated by the bending peel diameter. From Table 2, it can be seen that by applying the present invention, a forsterite coating having excellent coating characteristics can be obtained.

A steel slab having various component compositions shown in Table 3 was heated to a temperature of 1380 ° C. for 30 minutes and then hot-rolled to obtain a hot-rolled plate having a plate thickness of 2.4 mm. At this time, the work roll diameter of the final stand for finish rolling was set to 650 mm, and the friction coefficient between the work roll of the stand and the steel plate was set to 0.35. Next, the hot-rolled plate was cold-rolled for the first time to obtain a cold-rolled plate having an intermediate plate thickness of 1.7 mm, and then in a moist atmosphere having various oxygen potentials shown in Table 3, the temperature was 1050 ° C. × 60 s. After intermediate annealing, the first cold rolling was performed to obtain a cold rolled plate having a final plate thickness of 0.23 mm. Next, the cold-rolled sheet is _{decarburized and annealed in a moist hydrogen atmosphere having an oxygen potential PH2O} / _PH2 of 0.30, which also serves as primary recrystallization annealing at 840 ° C. × 120 s, and then the steel sheet after decarburization annealing. The orientation difference angle of each grain boundary on the outermost layer was measured by electron backscatter diffraction (EBSP).
_{Next, an annealing separator containing MgO as a main component and TiO 2} added in an amount of 2.0 mass% was applied to the surface of the steel sheet after decarburization and annealing, dried, and then secondary recrystallized under the condition of holding at a temperature of 850 ° C. for 50 hr. After the finish annealing is performed by maintaining the temperature at 1150 ° C. for 5 hours in a hydrogen atmosphere for purification treatment, the surface of the steel sheet after the finish annealing is coated with an insulating coating mainly composed of magnesium phosphate and colloidal silica. provided.

The magnetic properties and coating properties (uniformity and adhesion) of the product board thus obtained were investigated, and the results are also shown in Table 3. The uniformity was evaluated by visually observing the appearance of the film, and the film adhesion was evaluated by the bending peel diameter. From Table 3, it can be seen that by applying the present invention, a forsterite coating having excellent coating characteristics can be obtained.

Claims (3)

It contains C: 0.01 to 0.10 mass%, Si: 2.0 to 5.0 mass%, Mn: 0.01 to 1.0 mass% and Cr: 0.01 to 0.2 mass%, and further contains an inhibitor. A steel slab containing any one of the following groups A to C as a forming component and having a component composition in which the balance is Fe and unavoidable impurities is hot-rolled and then cold-rolled once. Alternatively, cold-rolled two or more times with intermediate annealing in between to obtain a cold-rolled plate with the final thickness, decarburization annealing that also serves as primary recrystallization annealing, applying an annealing separator to the surface of the steel plate, and then finishing annealing. In the method for producing a directional electromagnetic steel sheet comprising the above steps, a grain boundary having an orientation difference angle of 15 to 45 ° is generated at a frequency of 80% or more on the outermost surface layer of the steel sheet after decarburization annealing. Manufacturing method of sex electromagnetic steel sheet.
Description-Group A; At least one selected from S: 0.002 to 0.03 mass% and Se: 0.002 to 0.003 mass%-Group B: Al: 0.005 to 0.04 mass% and N : 0.003 to 0.012 mass%
Group C; at least one selected from S: 0.002 to 0.03 mass% and Se: 0.002 to 0.003 mass%, Al: 0.005 to 0.04 mass% and N: 0.003. ~ 0.012 mass% The method of forming grain boundaries with an orientation difference angle of 15 to 45 ° on the outermost layer of the steel sheet after decarburization annealing at a frequency of 80% or more is to set the work roll diameter in the finish rolling of the hot rolling to 600 mm or less. the coefficient of friction at finish rolling in the hot rolling to 0.40 or more, and, the oxygen potential _P H2O _{/ P H2} atmosphere in the intermediate annealing in the range of 0.10 to 0.25, of The method for manufacturing a directional electromagnetic steel sheet according to claim 1, wherein the means is any one or more. In addition to the above component composition, the steel slab further contains B: 0.0002 to 0.0025 mass%, P: 0.005 to 0.08 mass%, Ti: 0.001 to 0.01 mass%, Ni: 0. 01 to 1.5 mass%, Cu: 0.01 to 0.5 mass%, Nb: 0.002 to 0.08 mass%, Mo: 0.005 to 0.1 mass%, Sn: 0.005 to 0.5 mass% , Sb: 0.005 to 0.5 mass% and Bi: 0.002 to 0.08 mass%. Manufacturing method.

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