JP6880814B2 - Electrical steel sheet and its manufacturing method - Google Patents

Description

The present invention relates to an electromagnetic steel sheet having an increased magnetic flux density, which is suitable for applications such as magnetic cores of motors, generators, and transformers, and which can contribute to miniaturization and high efficiency of these magnetic cores, and a method for manufacturing the same.

Motors and generators are required to have high efficiency as a measure against global warming. Therefore, magnetic steel sheets used for magnetic cores of motors, generators, etc. are required to have high magnetic flux density and low iron loss. In order to increase the magnetic flux density of the magnetic steel sheet, it is sufficient to develop the <100> orientation in the plate surface, which is the axial direction in which iron is easily magnetized. For iron loss, measures are taken to increase the content concentration of solid solution elements such as Si, Al, and Mn.

Patent Document 1 discloses a non-oriented electrical steel sheet having a ground iron having a specific oxide layer and a specific tension-applied insulating coating formed on the surface of the ground iron. According to Patent Document 1, a specific oxide layer contributes to improving the adhesion between the bare metal and the tension-applying type insulating film.

International release WO2011 / 102328

From the viewpoint of improving the magnetic flux density and reducing the iron loss, the present inventors are studying an electromagnetic steel sheet in which Mn is contained in a high concentration to enhance the accumulation of {100} <011> orientations.
However, it has been found that the adhesiveness of the insulating film may be lowered in the steel sheet containing Mn at a high concentration even if the technique as in Patent Document 1 is applied.
One reason for this is that Mn is contained in a high concentration, but in the {100} <011> orientation, the crystal plane that becomes the surface of the steel sheet becomes a low exponential plane, and the oxidation formed on it. It was also considered that the bondability with the film and the insulating film was lowered.

The present invention has been made in view of the above circumstances, and in a steel grade having a relatively high Mn content and a strongly developed {100} surface, it has excellent adhesion to an insulating film, has a low iron loss, and has a low iron loss. Provided is an electromagnetic steel sheet having excellent magnetic characteristics.

As a result of diligent studies, the present inventors have formed an oxide layer containing a high concentration of Mn on the surface layer of an electromagnetic steel plate having a specific composition, so that the oxide layer has excellent adhesion to an insulating film. We have obtained the finding that this is the case, and have completed the present invention.

That is, in the electromagnetic steel plate according to the present invention, Si is 2.0% by mass or more and 4.5% by mass or less, Mn is 2.5% by mass or more and 5.0% by mass or less, Al is 0.0355% by mass or less, and Sn. And Sb are 0.50% by mass or less, C is 0.0040% by mass or less, N is 0.0040% by mass or less, S is 0.020% by mass or less, P is 0.5% by mass or less, and Cr is 20% by mass or less, Ni is 10% by mass or less, Cu is 0.2% by mass or less, B is 0.01% by mass or less, Ti is 0.0020% by mass or less, Nb is 0.0020% by mass or less, Mo is It is an α-γ transformation system consisting of 0.0020% by mass or less, Ca of 0.050% by mass or less, Mg of 0.050% by mass or less, rare earth elements of 0.050% by mass or less, the balance Fe and unavoidable impurities. An electromagnetic steel plate having an oxide layer containing Mn on a mother steel plate.
_{The maximum concentration D 1} (mass%) of Mn in the oxide layer _{and the maximum concentration D 2} (mass%) of Si in the oxide layer satisfy the following formula (1).
Equation (1) (D ₁ / D ₂ ) ≧ 1.50
It is characterized in that the ratio of strength to random in the {100} <011> orientation at the surface position of the mother steel plate is 15 or more.

In one embodiment of the electromagnetic steel sheet of the present invention, when the concentration of Mn at the position where the thickness of the mother steel sheet is 1/2 is D ₀ (mass%), a low Mn region satisfying the following formula (2) exists. To do.
Equation (2) (D _x / D ₀ ) <0.92
(In the formula (2), D _x represents the concentration of Mn at a point on a straight line passing through the D _{0 measurement point and perpendicular to the mother steel plate.)}

In one embodiment of the electrical steel sheet of the present invention, the thickness of the low Mn region is 3 to 25 μm.

In one embodiment of the electromagnetic steel sheet of the present invention, the Al content in the mother steel sheet is less than 0.03% by mass.

One embodiment of the electrical steel sheet of the present invention further has an insulating film on the oxide layer.

The method for manufacturing an electromagnetic steel sheet according to the present invention is a method for producing the electrical steel sheet according to the present invention.
Si is 2.0% by mass or more and 4.5% by mass or less, Mn is 2.5% by mass or more and 5.0% by mass or less, Al is 0.0355% by mass or less, and Sn and Sb are 0.50% by mass in total. Hereinafter, C is 0.0040% by mass or less, N is 0.0040% by mass or less, S is 0.020% by mass or less, P is 0.5% by mass or less, Cr is 20% by mass or less, and Ni is 10% by mass. Hereinafter, Cu is 0.2% by mass or less, B is 0.01% by mass or less, Ti is 0.0020% by mass or less, Nb is 0.0020% by mass or less, Mo is 0.0020% by mass or less, and Ca is 0. .050 mass% or less, Mg 0.050 mass% or less, rare earth element 0.050 mass% or less, balance Fe and unavoidable impurities , hot rolling using ingot, which is an α-γ transformation system, as a hot-rolled plate. It has a step, a cold rolling step of using the hot-rolled plate as a cold-rolled plate, an oxidation step of forming an oxide layer on the cold-rolled plate, and a finish annealing step.
The oxidation step may be included in the temperature raising step in the finish annealing step.
The oxidation step is a step of holding the cold rolled plate at a temperature of 400 ° C. to 800 ° C. for 5 seconds or more and 15 seconds or less in an atmosphere having a dew point temperature of 0 ° C. or higher and 80 ° C. or lower.
When the oxidation step is included in the temperature raising process in the finishing annealing step, the cooling rate from the maximum reached temperature in the temperature lowering process is 3 ° C./s or more and 600 ° C./s or less. ..

One embodiment of the method for manufacturing electrical steel sheets of the present invention includes a step of performing shot blasting after the hot rolling step and before the cold rolling step.

According to the present invention, it is possible to provide an electromagnetic steel sheet having excellent adhesion to an insulating film, low iron loss, and excellent magnetic properties.

FIG. 1 is a schematic view showing an example of a cross section of an electromagnetic steel sheet according to the present invention. FIG. 2 is a graph showing an example of the element distribution measurement results in the depth direction of the steel sheet by glow discharge emission spectroscopy (GDS).

Hereinafter, the electromagnetic steel sheet according to the present invention and its manufacturing method will be described in detail in order.
It should be noted that the terms such as "parallel", "vertical", and "same" and the values of length and angle used in the present specification to specify the shape and geometric conditions and their degrees are strict. Without being bound by meaning, we will interpret it including the range in which similar functions can be expected.
Further, in the present invention, "ppm" represents a mass ratio unless otherwise specified.

[Electromagnetic steel sheet]
The electromagnetic steel sheet according to the present invention contains Si in an amount of 2.0% by mass or more and 4.5% by mass or less and Mn in an amount of 2.5% by mass or more and 5.0% by mass or less, and is placed on a mother steel sheet containing Fe as a main component. , An electromagnetic steel sheet having an oxide layer containing Mn,
_{The maximum concentration D 1} (mass%) of Mn in the oxide layer _{and the maximum concentration D 2} (mass%) of Si in the oxide layer satisfy the following formula (1).
Equation (1) (D ₁ / D ₂ ) ≧ 1.50

The electromagnetic steel sheet of the present invention has excellent adhesion to an insulating film, low iron loss, and excellent magnetic properties because Mn is present in the oxide layer at a high concentration of Mn at a specific value or more with respect to Si.
Hereinafter, the oxide layer satisfying the formula (1) in the present invention may be referred to as a “high Mn oxide layer”.

The electromagnetic steel sheet of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing an example of a cross section of an electromagnetic steel sheet according to the present invention. Further, FIG. 2 is a graph showing an example of the element distribution measurement results in the depth direction of the steel sheet by glow discharge emission spectroscopic analysis (GDS).
As shown in the example of FIG. 1, the electromagnetic steel sheet 10 of the present invention has at least a mother steel sheet 1 and an oxide layer 2 on the mother steel sheet, and further, an insulating film (not shown) on the oxide layer 2. May have.
In the present invention, the steel plate surface 3 refers to the surface of the oxide layer 2, and when it has an insulating film, the interface between the oxide layer 2 and the insulating film is defined as the steel sheet surface. In the present invention, one steel plate surface 3 is arbitrarily set to a distance of 0, and a distance x (μm) is set in the direction perpendicular to the steel plate surface. At this time, on the other steel plate surface, the "distance from the steel plate surface" becomes the same value as the plate thickness t (μm) of the steel plate.
In the present invention, the oxide layer 2 is defined as a region where the oxygen concentration exceeds 0.5% by mass from the steel sheet surface 3. In the example of FIG. 2, the oxide layer is in the range of 0 to α from the surface of the steel sheet.

In the magnetic steel sheet of the present invention, the maximum concentration D _{1 (mass%) of Mn and the maximum concentration D 2} (mass%) of Si in the oxide layer _{are (D 1} / D _{2) in the region of the oxide layer 2.} ) ≧ 1.50.
Hereinafter, each configuration of the electromagnetic steel sheet will be described in detail.

<Oxidized layer>
In the present invention, the oxide layer may be formed independently of the mother steel sheet by depositing or spraying a composition for an oxide layer on the mother steel sheet, which will be described later, and is formed by oxidizing the surface of the mother steel sheet. You may.
In the present invention, the oxide layer contains at least Mn, and the maximum concentration D ₁ (mass%) of Mn in the oxide layer and the maximum concentration D ₂ (mass%) of Si in the oxide layer are expressed by the following formula (1). ) Satisfies.
Equation (1) (D ₁ / D ₂ ) ≧ 1.50

The reason why the oxide layer having such a composition has a favorable effect on the film adhesion is not clear, but it is considered as follows. In the electromagnetic steel sheet of the present invention, it will be described later that oxidation in which Mn and Si compete with each other occurs in the finish annealing during the manufacturing process, but the oxide layer having a high Si concentration has a lower deformability than the oxide layer having a high Mn concentration, and Si. It is considered that when an oxide layer having a high concentration is formed, film peeling is likely to occur from this as a starting point. By preferably setting the above ratio to 1.55 or more, more preferably 1.60 or more, the adhesion to the insulating film is excellent.
Although detailed studies have not been conducted on the optimum morphology of Mn and Si in the oxide layer, generally, Mn oxide, Si oxide, and Fe are added to form a composite oxide of these. , It is possible to obtain a high Mn oxide layer as in the present invention.

<Composition of mother steel sheet>
In the electromagnetic steel sheet of the present invention, the mother steel sheet contains Si in an amount of 2.0% by mass or more and 4.5% by mass or less and Mn in an amount of 2.5% by mass or more and 5.0% by mass or less, and does not impair the effects of the present invention. It has a chemical composition containing Fe (iron) as a main component, which may contain other elements in the range.
In the present invention, the main component means a component showing the highest ratio, and usually has an element content of 50% by mass or more.

In the present invention, the mother steel sheet is a base material of the electromagnetic steel sheet. The above chemical composition is the composition of the steel components constituting the mother steel sheet, and if the oxide layer on the surface and the measurement sample have an insulating film, it is necessary to measure after removing the insulating film.
As a method for removing the oxide layer and the insulating film of the electromagnetic steel sheet, for example, there are the following methods. First, the electromagnetic steel sheet having an oxide layer or the insulating film, NaOH: _10% by mass ₊ H 2 O: 90 wt% aqueous sodium hydroxide for 15 minutes at 80 ° C., immersion. Then, _{it is immersed in a sulfuric acid aqueous solution of H 2} SO ₄ : 10% by mass + H ₂ O: 90% by mass at 80 ° C. for 3 minutes. Thereafter, _HNO 3: 10 _{wt% +} H 2 O: by the 90 wt% nitric acid aqueous solution, 1 minute weak at room temperature, washed immersed in. Finally, dry with a warm air blower for a little less than 1 minute. As a result, a mother steel sheet from which the oxide layer and the insulating film described later have been removed can be obtained. Further, the surface layer of the mother steel sheet may have a low Mn region, which will be described later, but the steel component shall be measured as a value including the low Mn region.

In the electromagnetic steel sheet of the present invention, an oxide layer in which the content of Si is suppressed and Mn is contained in a relatively high concentration is formed on the surface of the mother steel sheet having the above components. As a result, the steel sheet exhibits a feature of being excellent in adhesion to an insulating film described later.

(Si: 2.0% by mass or more and 4.5% by mass or less)
In the electromagnetic steel sheet of the present invention, the Si content is 2.0% by mass or more and 4.5% by mass or less. When the Si content is 2.0% by mass or more, the electric resistance of the steel sheet is increased and the iron loss can be reduced. Further, when the Si content is 4.5% by mass or less, it is possible to prevent the steel sheet from cracking during cold rolling. Further, when the oxide layer is formed by the production method of oxidizing the mother steel sheet, which will be described later, it is possible to suppress the concentration of Si in the oxide layer and obtain a preferable oxide layer.

(Mn: 2.5% by mass or more and 5.0% by mass or less)
In the electromagnetic steel sheet of the present invention, the Mn content is 2.5% by mass or more and 5.0% by mass or less. Mn is an element that is generally effective in increasing the electrical resistance of steel sheets and reducing iron loss.
The lower limit of the amount of Mn is set in consideration of the viewpoint of ensuring the film adhesion, which is an object of the present invention. That is, if the Mn content is 2.5% by mass or less, film adhesion can be ensured without applying the technique of the present application, and thus the present invention is excluded. Further, when the oxide layer is formed by the production method of oxidizing the mother steel sheet described later, the Mn concentration in the oxide layer can be increased, and a preferable oxide layer can be obtained. Further, when the Mn content is 5.0% by mass or less, it is possible to suppress a decrease in the saturation magnetic flux density. The upper limit was set in consideration of cracks in the steel material due to the manufacturing process.
Further, if the Mn concentration is within this range, the magnetic flux density can be increased by assuming that the crystal orientations of the steel sheets are strongly integrated in the {100} <011> orientations by the manufacturing method described later.
It is preferably 2.8% or more, more preferably 3.0% or more, still more preferably 3.5% or more.

(Al: less than 3.0% by mass)
In the present invention, the mother steel sheet may contain Al. The Al content is preferably less than 3.0% by mass. When the Al content is 3.0 mass or more, the rollability is lowered and the productivity is hindered, and the saturation magnetic flux density of the steel sheet is lowered, so that it is difficult to obtain a high magnetic flux density even if the crystal orientation is controlled. There is a risk of becoming. Further, when the oxide layer is formed by the manufacturing method of oxidizing the mother steel sheet described later, the concentration of Al in the oxide layer on the surface of the steel sheet is suppressed by setting the Al content to less than 0.03% by mass. And a preferable oxide layer can be obtained. It is preferably 0.02% by mass or less, more preferably 0.01% by mass or less. The content may be 0 (zero).

(Sn + Sb: 0.50% by mass or less)
It is known that the contents of Sn and Sb are generally controlled for the purpose of improving the texture, suppressing oxidation, nitriding, and carburizing during production, and particularly improving the high frequency characteristics. , May be contained in the range of 0.50% by mass or less in total. If it exceeds this value, the rollability is lowered and the productivity is hindered. However, when the oxide layer of the present invention is formed by a production method for oxidizing a mother steel sheet, which will be described later, oxidation control is important, but since Sn and Sb have a relatively strong influence on the oxidation behavior, this production method is used. When adopting it, it is necessary to pay attention to the content. When the content is high, surface oxidation is excessively suppressed, and it becomes difficult to form an oxide layer useful in the present invention. Therefore, it is preferable to keep the total content of Sn and Sb at 0.30% by mass or less. It is more preferably 0.10% or less, still more preferably 0.03% or less. The content may be 0 (zero).

In the electromagnetic steel sheet of the present invention, the mother steel sheet may further contain other elements as long as the effects of the present invention are not impaired. Examples of the elements that may be contained include C, N, S, P, Cr, Ni, Cu, B, Ti, Nb, Mo, Ca, Mg, rare earth elements (REM) and the like. Hereinafter, these elements, which have a relatively strong influence on the effects of the present invention, will be described.

(C: 0.0040% by mass or less)
C may form carbides and deteriorate the magnetic properties in a high magnetic field. Further, when magnetic aging occurs, the magnetic characteristics in a high magnetic field also deteriorate, so it is preferable to reduce the C content. Therefore, the C content is preferably 0.0040% by mass or less.
From the viewpoint of manufacturing cost, it is advantageous to reduce the C content by degassing equipment (for example, RH vacuum degassing equipment) at the molten steel stage, and if the C content is 0.0030% by mass or less, the magnetic aging is suppressed. The effect is great. Since the electromagnetic steel sheet according to the present invention does not use non-metal precipitates such as carbides as the main means for increasing the strength, there is no merit of intentionally containing C, and it is preferable that the C content is low. Therefore, the C content is preferably 0.0020% by mass or less, and more preferably 0.0015% by mass or less. By using a technique such as electrodeposition, it is possible to reduce the content to 0.0001% by mass or less, which is below the limit of chemical analysis, and the C content may be 0%. On the other hand, considering the industrial cost, the lower limit is 0.0003%.

(N: 0.0040% by mass or less)
Like C, N deteriorates the magnetic properties in a high magnetic field due to the formation of nitrides and magnetic aging. Therefore, the N content is preferably 0.0040% by mass or less. The N content is preferably low in order to avoid deterioration of the magnetic properties in a high magnetic field, and if it is 0.0027% by mass or less, the adverse effects on the magnetic properties in a high magnetic field due to magnetic aging and the formation of nitrides are sufficiently avoided. it can. The N content is even more preferably 0.0022% by mass or less, and even more preferably 0.0015% by mass or less. By using a technique such as electrodeposition, it is possible to reduce the content to 0.0001% by mass or less, which is below the limit of chemical analysis, and the N content may be 0% by mass. On the other hand, considering the industrial cost, the lower limit is 0.0003% by mass.

(S: 0.020% by mass or less)
Since S may form sulfides and deteriorate the magnetic properties in a high magnetic field, the S content is preferably low. The S content is preferably 0.020% by mass or less, more preferably 0.0040% by mass or less, even more preferably 0.0020% by mass or less, and most preferably 0.0010% by mass or less. Is. The S content may be 0% by mass.

(P: 0.5% by mass or less)
The content of P is controlled for the purpose of adjusting the strength, nitriding during production, and suppressing carburizing, and further, when segregated at the grain boundaries before cold rolling, the texture is improved and the magnetic flux density is improved. It is known that it can be contained in an amount of 0.001% by mass or more. In a general practical steelmaking method, impurities may be contained in an amount of about 0.002% by mass or more. On the other hand, excessive addition makes the steel embrittlement and lowers cold ductility and workability of the product. Therefore, the P content is preferably 0.5% by mass or less, more preferably 0.3% by mass or less. Is.

(Cr: 20% by mass or less)
The content of Cr is controlled for the purpose of adjusting strength, corrosion resistance, and controlling oxidation behavior during manufacturing, and it is known that it particularly improves high-frequency characteristics, and it is possible to contain Cr in an amount of 0.001% by mass or more. Is. In a practical steelmaking method in which scrap or the like is mixed, impurities may be contained in an amount of about 0.01% by mass or more. On the other hand, excessive addition increases the addition cost and lowers the magnetic properties, so the Cr content is preferably 20% by mass or less, and more preferably 5% by mass or less.

(Ni: 10% by mass or less)
The content of Ni is controlled for the purpose of adjusting strength, corrosion resistance, and controlling oxidation behavior during manufacturing, and it is also known to improve high-frequency characteristics in particular, and it is possible to contain Ni in an amount of 0.001% by mass or more. Is. In a practical steelmaking method in which scrap or the like is mixed, impurities may be contained in an amount of about 0.01% by mass or more. On the other hand, excessive addition increases the addition cost and lowers the magnetic properties, so the Ni content is preferably 10% by mass or less, more preferably 3% by mass or less.

(Cu: 0.2% by mass or less)
Cu, as a solid solution element, significantly reduces the saturation magnetic flux density Bs of the mother steel sheet. A decrease in the saturation magnetic flux density Bs leads to a decrease in magnetic characteristics. Therefore, it is not necessary to intentionally contain Cu in the mother steel sheet of the electromagnetic steel sheet according to the present invention unless there is a special purpose. In a practical steelmaking method in which scrap or the like is mixed, impurities may be contained in an amount of about 0.01% by mass or more. Therefore, the Cu content is preferably 0.2% by mass or less, and more preferably 0.15% by mass or less. On the other hand, it is also known that the strength can be increased by Cu precipitation, and the mother steel sheet of the electromagnetic steel sheet according to the present invention can be appropriately used according to a known technique.

(B: 0.01% by mass or less)
It is known that the content of B is controlled for the purpose of suppressing nitriding and carburizing during production, and in particular, it forms a composite oxide containing oxides and nitrides to improve magnetic properties. It can be contained in an amount of 0.0001% by mass or more. On the other hand, excessive addition makes the steel brittle and lowers the magnetic properties. Therefore, the B content is preferably 0.01% by mass or less, and more preferably 0.005% by mass or less.

(Ti: 0.0020% by mass or less)
It is known that the content of Ti is controlled for the purpose of adjusting the strength due to the precipitate, and in particular, it forms a composite oxide containing oxides and sulfides to improve the magnetic properties, and is 0.0001. It can be contained in an amount of% by mass or more. In a practical steelmaking method in which scrap or the like is mixed, impurities may be contained in an amount of about 0.0002% by mass or more. On the other hand, since these precipitates may hinder the movement of the domain wall and significantly deteriorate the magnetic properties, the Ti content is preferably 0.0020% by mass or less, and more preferably 0.0015% by mass or less. Is.

(Nb: 0.0020% by mass or less)
Nb does not need to be intentionally contained because precipitates such as NbC effectively increase the strength, but these precipitates hinder the movement of the domain wall and significantly deteriorate the magnetic properties in a high magnetic field. Therefore, the Nb content is preferably 0.0020% by mass or less, and more preferably 0.0010% by mass or less. In a practical steelmaking method in which scrap or the like is mixed, impurities may be contained in an amount of about 0.0002% by mass or more.

(Mo: 0.0020% by mass or less)
It is known that the content of Mo is controlled for the purpose of suppressing nitriding and carburizing during production, and in particular, it forms a composite oxide containing oxides and carbides to improve magnetic properties. It can be contained in an amount of .0001% by mass or more. On the other hand, since these precipitates may hinder the movement of the domain wall and significantly deteriorate the magnetic properties in a high magnetic field, the Mo content is preferably 0.0020% by mass or less, and more preferably 0. It is 0015 mass% or less.

(Ca: 0.050% by mass or less)
Ca is known to form a composite oxide containing an oxide and a sulfide to improve magnetic properties, and can be contained in an amount of 0.0001% by mass or more. On the other hand, these precipitates may hinder the movement of the domain wall and significantly deteriorate the magnetic properties in a high magnetic field. Therefore, the Ca content is preferably 0.050% by mass or less, and more preferably 0. It is 010% by mass or less.

(Mg: 0.050% by mass or less)
Mg is known to form a composite oxide containing an oxide and a sulfide to improve magnetic properties, and can be contained in an amount of 0.0001% by mass or more. On the other hand, since these precipitates may hinder the movement of the domain wall and significantly deteriorate the magnetic properties in a high magnetic field, the Mg content is preferably 0.050% by mass or less, and more preferably 0. It is 010% by mass or less.

(REM: 0.050% by mass or less)
REM is known to form a composite oxide containing an oxide and a sulfide to improve magnetic properties, and can contain 0.0001% by mass or more. On the other hand, since these precipitates may hinder the movement of the domain wall and significantly deteriorate the magnetic properties in a high magnetic field, the REM content is preferably 0.050% by mass or less, preferably 0.010. It is less than mass%.

Further, in the present invention, the mother steel sheet preferably has a chemical composition satisfying the α-γ transformation system. The α-γ transformation system is a component system having an A3 point, the α phase being the main phase below the A3 point, and the γ phase being the main phase at the A3 point or more. Since the mother steel sheet has a chemical composition that satisfies the α-γ transformation system, it is possible to manufacture an excellent non-directional electromagnetic steel sheet having a ratio of random strength to random strength in the {100} <011> orientation of the mother steel sheet of 30 or more. Become.
Since the electromagnetic steel sheet of the present invention has an oxide layer containing a high concentration of Mn on the surface of the steel sheet as described above, a steel material having a crystal orientation of a low exponential plane {100} <011> and formed on the steel material. The effect of lowering the bondability with the insulating film is also suppressed, and the adhesion with the insulating film is excellent.

In the present invention, the temperature of the steel sheet at the A3 point, that is, the temperature at which the γ phase starts to appear from the α phase is referred to as T1 (° C.), and the temperature at which the γ phase becomes a single phase is referred to as T2 (° C.).
The T1 of the mother steel sheet is not particularly limited, but it is preferably kept in the range of 600 ° C. or higher and 1100 ° C. or lower from the viewpoint of improving the ratio of strength to random in the {100} <011> orientation.
The T2 of the mother steel sheet is not particularly limited, but it is usually preferable that the mother steel sheet has a chemical composition such that T2-T1> 0 and T2-T1 ≧ 10.
The A3 point can be measured by utilizing the difference in the coefficient of thermal expansion between the α phase and the γ phase. Specifically, the coefficient of thermal expansion is measured while heating the target steel, and the inflection point of the coefficient of thermal expansion is set to point A3.
By using an α-γ transformation type ingot containing the above elements, the movement speed of grain boundaries is significantly slowed down, so that the hot-rolled plate obtained in the hot rolling process can maintain the processed austenite during cooling while maintaining the processed austenite. The strain is not released and is transformed into a ferrite phase. By cold-rolling and annealing this hot-rolled plate, the {100} <011> orientations are strongly integrated, which is convenient for the magnetic characteristics.

(Inevitable impurities)
In the electromagnetic steel sheet of the present invention, the mother steel sheet may contain various elements (unavoidable impurities) that are inevitably mixed as long as the effects of the present invention are not impaired.

The content ratio of each element in the base steel sheet can be measured by, for example, inductively coupled plasma mass spectrometry (ICP-MS method). Specifically, first, an electromagnetic steel sheet to be measured is prepared. A part of the electrical steel sheet is cut into pieces and weighed, and this is used as a measurement sample. The measurement sample is dissolved in an acid to prepare an acid solution, the residue is collected from a filter paper and separately melted in an alkali or the like, and the melt is extracted with an acid to form a solution. By mixing the solution and the acid solution and diluting it if necessary, an ICP-MS measurement solution can be obtained.

<Low Mn region>
The electromagnetic steel sheet of the present invention preferably has a low Mn region satisfying the following formula (2) when the concentration of Mn at the position where the thickness of the mother steel sheet is 1/2 is D _{0 (mass%).} ..
Equation (2) (D _x / D ₀ ) <0.92
(In the formula (2), D _x represents the concentration of Mn at a point on a straight line passing through the D _{0 measurement point and perpendicular to the mother steel plate.)}

The low Mn region will be described with reference to FIGS. 1 and 2. In the electromagnetic steel sheet 10 of the present invention, the low Mn region 4 is formed on the surface layer adjacent to the oxide layer 2 in the steel sheet 1. In the present invention, the low Mn region 4 is a region in which the oxygen concentration is 0.5% by mass or less and the Mn concentration is less than 92% of _{D 0.} In the example of FIG. 2, the region from the terminal α on the plate thickness center side of the oxide layer 2 to β where the Mn concentration is 92% of Do is defined as the low Mn region.
_{The reason why the Mn concentration D 0} at the position where the thickness of the mother steel sheet is 1/2 is used as a reference is that Mn has a constant concentration at the center of the plate thickness as shown in FIG.

The low Mn region is a region formed by enriching Mn in the oxide layer when it is formed by oxidizing the surface of the mother steel sheet. Since the mother steel sheet and the oxide layer are integrally formed in the electromagnetic steel sheet having such a low Mn region, the adhesion between the mother steel sheet and the oxide layer is excellent.
When (D _x / D ₀ ) is 0.92 or more, the Mn concentration in the essential oxide layer becomes insufficient, and the effect of improving the film adhesion becomes small. Further, since the low Mn region is also a region lacking Mn for increasing the electric resistance and reducing the iron loss, if this ratio becomes too small, the adverse effect on the iron loss becomes large. Further, since the effect of improving the film adhesion due to the concentration of Mn on the oxide layer is saturated, the lower limit is preferably about 0.70. When it is preferably 0.75 or more, more preferably 0.80 or more, it is possible to obtain a sufficient effect of improving film adhesion with almost no concern about adverse effects on iron loss.

Further, when the electromagnetic steel sheet of the present invention forms the low Mn region, the thickness of the region satisfying the formula (2) is preferably 3 to 25 μm.
If it is less than 3 μm, the Mn concentration in the essential oxide layer becomes insufficient, and the effect of improving the film adhesion becomes small. Further, the low Mn region is also a region lacking Mn for increasing the electric resistance and reducing the iron loss. Although it depends on the degree of decrease in Mn concentration, the target should be about 1/10 of the plate thickness so that it stays at 25 μm or less.

These concentrations can be evaluated by investigating the emission intensity profile from the surface of the steel sheet by glow discharge emission surface analysis (GDS). The absolute value of the concentration can be specified by the calibration curve of the emission intensity of GDS and the element content of the material in which the content of each element is changed.
For GDS, for example, GDA750 manufactured by Rigaku is used for analysis at an anode diameter of 4 mm and a pressure of 3 hPa. The optimum sputter time varies depending on the thickness required for measurement, but if the steel sheet is at the time when the oxide layer is formed on the surface of the mother steel sheet, it is generally possible to analyze the mother steel sheet in 200 seconds. In addition, it is not necessary to continuously dig in the depth direction from the outermost surface of the measurement sample by sputtering GDS, but by removing an appropriate thickness by polishing separately and analyzing the outermost surface concentration of the sample after removal. It is also possible to obtain the elemental concentration at a specific depth position of the original steel sheet.

<{100} <011> X-ray random intensity ratio>
In the present invention, the crystal orientation and the crystal plane are generally described with respect to the surface of the steel sheet, which is used to express the orientation of the crystal in the steel sheet and the crystal plane and texture to be measured. That is, the crystal orientation is the orientation perpendicular to the surface of the steel sheet, and the crystal plane is the plane parallel to the surface of the steel sheet. Further, it is expressed by applying the extinction rule in the X-ray measurement of the crystal plane due to the crystal structure of the body-centered cubic which is the α phase of Fe. For example, {100} is used for the crystal orientation, and {200} is used for the crystal plane and texture, but these represent information on the same crystal grains.
The electromagnetic steel plate of the present invention can increase the X-ray random intensity ratio of {100} <011> on the plate surface to obtain a high magnetic flux density in the 45 ° direction with respect to the rolling direction. When the X-ray random intensity ratio is 30 or more, a sufficiently high magnetic flux density can be obtained in the 45 ° direction with respect to the rolling direction, and more preferably 60 or more. Further, the upper limit of the X-ray random intensity ratio is not particularly limited, but since the effect of increasing the magnetic flux density is saturated, an X-ray random intensity of 200 or less is usually sufficient.
The X-ray random intensity ratio of the α-Fe phase of {100} <011> is based on the pole diagrams of {200}, {110}, {310}, and {211} of the α-Fe phase measured by X-ray diffraction. It can be obtained from the crystal orientation distribution function (ODF) that represents a three-dimensional texture calculated by the series expansion method.
The random intensity ratio is the X-ray intensity of the standard sample and the test material that do not accumulate in a specific orientation under the same conditions, and the X-ray intensity of the obtained test material is the X-ray intensity of the standard sample. It is the value divided by the intensity. The measurement may be performed on the outermost surface of the sample, or may be performed at an arbitrary plate thickness position. At that time, the measurement surface is finished by chemical polishing or the like so as to be smooth.

The thickness of the electromagnetic steel sheet of the present invention may be appropriately adjusted according to the intended use and is not particularly limited, but is usually 0.010 mm or more and 0.50 mm or less, and 0.015 mm from the viewpoint of manufacturing. More preferably 0.50 mm or less. From the viewpoint of the balance between magnetic characteristics and productivity, 0.015 mm or more and 0.35 mm or less is preferable.

The electromagnetic steel sheet of the present invention may further have an insulating film on the surface of the steel sheet. In the present invention, since the oxide layer has excellent adhesion to the insulating film, it is an electromagnetic steel sheet in which the insulating film is less likely to peel off even during punching.
It should be noted that the present invention covers not only "electrical steel sheets having an insulating film" but also "electrical steel sheets not having an insulating film". If it is an "electromagnetic steel sheet having an insulating film", it has an effect that the film adhesion is good in that state, and even if it is an "electromagnetic steel sheet without an insulating film", after that. This is because if an insulating film is formed and used, good film adhesion, which is the effect of the present invention, can be obtained.

In the present invention, the insulating film is not particularly limited, and can be appropriately selected and used from known ones according to the intended use, and may be either an organic film or an inorganic film. Examples of the organic film include polyamine resin, acrylic resin, acrylic styrene resin, alkyd resin, polyester resin, silicone resin, fluororesin, polyolefin resin, styrene resin, vinyl acetate resin, epoxy resin, phenol resin, urethane resin, and melamine. Examples include resin. Examples of the inorganic film include a phosphate film, an aluminum phosphate film, and an organic-inorganic composite film containing the above resin.
The thickness of the insulating film is not particularly limited, but the film thickness per side is preferably 0.05 μm or more and 2 μm or less. If it is less than 0.05 μm, sufficient insulation cannot be ensured, and if it exceeds 2 μm, the space factor when laminated as a core becomes low, and the motor efficiency decreases.

The method for forming the insulating film is not particularly limited. For example, a composition for forming an insulating film in which the above resin or an inorganic substance is dissolved in a solvent is prepared, and the composition for forming the insulating film is uniformly applied to the surface of the steel sheet by a known method. An insulating film can be formed by applying to.

<Use of electrical steel sheet>
The electromagnetic steel sheet of the present invention is a non-oriented electrical steel sheet having excellent adhesion of an insulating film. In general, peeling of an insulating film often causes a problem in punching workability. Therefore, the electrical steel sheet of the present invention is particularly suitable for applications in which it is punched into an arbitrary shape. For example, servo motors and stepping motors used in electrical equipment, compressors in electrical equipment, motors used in industrial applications, electric vehicles, hybrid cars, drive motors for trains, generators and iron cores used in various applications, chokes. Any of conventionally known applications in which an electromagnetic steel plate is used, such as a coil, a reactor, and a current sensor, can be suitably applied.

[Manufacturing method of electrical steel sheet]

<First manufacturing method>
As one of the methods for producing an electromagnetic steel sheet of the present invention, there is a method of first producing a grain steel sheet and then forming an oxide layer on the surface of the grain steel sheet.
In this case, the method for producing the mother steel sheet is not particularly limited, and Si is contained in an amount of 2.0% by mass or more and 4.5% by mass or less, Mn is contained in an amount of 2.5% by mass or more and 5.0% by mass or less, and Fe is the main component. After the molten steel is cast into an ingot, it can be manufactured through processes such as hot rolling, hot rolling sheet annealing, pickling, cold rolling, and finish annealing. Examples of general manufacturing conditions include the following. In casting, slabs of about 150 to 300 mm are produced by continuous casting. Hot rolling is heated to about 1000 to 1300 ° C. and rolled to about 1 to 4 mm at a finishing temperature of about 900 ° C. In many cases, hot-rolled sheet annealing is not carried out, but if it is carried out, it will be treated at about 850 to 1200 ° C for several seconds to several minutes for continuous annealing, and for several minutes to several hours at about 600 to 950 ° C for box annealing. Become. The pickled steel sheet is cold-rolled to a thickness of about 0.1 to 0.5 mm at a reduction rate of about 70 to 95%. Finish annealing is finally carried out, but in general, recrystallization is completed by heat treatment at about 750 to 1200 ° C. for several seconds to several minutes by continuous annealing. The cold rolling and recrystallization may be repeated in two or more times so that the total cold rolling reduction rate is as described above. In this way, a mother steel sheet having a steel structure favorable for magnetic properties is produced.

(Method of forming the oxide layer)
In the first production method, the oxide layer may be formed on the surface of the mother steel sheet produced by the above method so that the Mn and Si concentrations are controlled so as to satisfy the above formula (1).
Common methods include processes such as thin film deposition and thermal spraying. Alternatively, a method in which Mn or Si is plated and then heated in an oxygen-presence atmosphere to oxidize Mn or Si on the surface is also possible. Further, a so-called enamel-like process in which an oxide powder containing Mn or Si is applied to the surface of the steel sheet and the oxide powder is melted by heating to form an oxide film on the surface of the steel sheet is also possible.
The present invention also covers electrical steel sheets on which the oxide layer defined by the present invention is formed by these processes. However, although these methods are very direct and simple, it is difficult to incorporate these processes into a process that is continuously manufactured at high speed like electrical steel sheets, and the manufacturing cost may be very high. There is.

<Second manufacturing method>
As another method for producing the electromagnetic steel sheet of the present invention, there is a method of forming an oxide layer by oxidizing the surface of the mother steel sheet. That is, the method for producing an electromagnetic steel sheet according to the present invention contains Si in an amount of 2.0% by mass or more and 4.5% by mass or less, Mn in an amount of 2.5% by mass or more and 5.0% by mass or less, and Fe as a main component. It has a hot rolling step of using the ingot as a hot-rolled plate, a cold rolling step of using the hot-rolled plate as a cold-rolled plate, an oxidation step of forming an oxide layer on the cold-rolled plate, and a finishing annealing step. And
The oxidation step may be included in the temperature raising step in the finish annealing step.
The oxidation step is a step of holding the cold rolled plate at a temperature of 400 ° C. to 800 ° C. for 5 seconds or more and 15 seconds or less in an atmosphere having a dew point temperature of 0 ° C. or higher and 80 ° C. or lower.
According to the manufacturing method, an electromagnetic steel sheet having an oxide layer satisfying the above formula (1) can be continuously manufactured at high speed, and the productivity can be excellent and the manufacturing cost can be suppressed.

This method is effective for oxidizing a mother steel sheet or a steel sheet in the manufacturing process of the mother steel sheet to form an oxide layer in which elements (Si and Mn) derived from the steel sheet are concentrated, so-called internal oxide layer, directly under the surface of the mother steel sheet. Acts on.
Simply thinking, the concentration ratio of Mn and Si in the oxide layer seems to be determined by the concentration ratio of Mn and Si contained in the mother steel sheet, and it seems that simply oxidizing the steel sheet is sufficient. However, the oxide layer suitable for the insulating film characteristics, which is the object of the present invention, is not formed only by controlling the components of Mn and Si of the mother steel sheet. Of course, if the Mn / Si ratio of the mother steel sheet is increased, the (D ₁ / D ₂ ) specified in the present application also increases, but in order to form the oxide layer necessary for ensuring the adhesion of the insulating film, the mother steel sheet must be formed under the following conditions. It is important to oxidize the steel sheet.
In order to obtain the oxide layer required for the present invention, the temperature of 400 ° C. to 800 ° C. is maintained for 5 seconds or more and 15 seconds or less in an atmosphere where the dew point temperature is 0 ° C. or higher and 80 ° C. or lower in the initial process of oxidizing the mother steel sheet. Is preferable.
The reason for this is not clear, but it is considered that the cause is the difference in the oxidation behavior of Si and Mn, which are essential elements for ensuring the magnetic properties in the steel of the present invention. Both of these elements are more easily oxidized than Fe, and when the mother steel sheet is oxidized, it becomes concentrated in it, but Si has a stronger oxidation tendency and the diffusion rate in the Fe phase is higher for Si. When it is rapidly oxidized at a high temperature or a low dew point, Si is preferentially concentrated in the oxide layer, and Mn concentration is less likely to occur. In addition, external oxidation, which will be described later, is likely to occur, and it is unlikely to be in a preferable state in the present invention. By performing oxidation while maintaining the above dew point and time in the above temperature range at the initial stage of oxidation, Mn thickening occurs to the extent necessary, which is effective in improving the adhesion of the insulating film (D ₁ / D). ₂ ) An oxide layer having a range is formed. These ranges were obtained experimentally, but we hope that detailed phenomena will be elucidated in the future.
Industrially, it is advantageous in terms of cost and productivity to perform this oxidation treatment in the heating process of finish annealing. Alternatively, it may be carried out as a separate step before or after the finish annealing, separately from the finish annealing. In this case as well, since the annealing furnace generally used in the production of electrical steel sheets can be used as it is, adverse effects on cost and productivity are tolerable.
It should be noted that an external oxide layer may be formed on the surface side of the internal oxide layer depending on the composition of the steel sheet and the oxidation conditions. This external oxide layer is a dense oxide layer, and it is difficult to contain Mn at a high concentration, which is not preferable for the adhesion of the insulating film. Therefore, it is preferable to carry out the above-mentioned oxidation under conditions that do not cause external oxidation. This condition cannot be unequivocally limited because it changes depending on the composition of the steel sheet, but in general, those skilled in the art who perform heat treatment of various steel sheets while considering the oxidation of the steel sheet can set appropriate conditions. It's not difficult. Of course, it is easy to determine appropriate conditions if heat treatment is performed in the laboratory in advance and the oxidation status is investigated.
Further, when the external oxide layer is formed, the steel sheet of the present invention exerts the effect of the present invention by removing the external oxide layer by pickling or grinding until the oxide layer satisfying the requirements of the present invention becomes a surface. Can be obtained.
Hereinafter, each step of the second production method will be described with reference to preferable specific examples, but the step is not limited to the following, and a known method can be appropriately adopted.

(Hot rolling process)
A hot-rolled plate is obtained by hot-rolling an ingot containing 2.0% by mass or more and 4.5% by mass or less of Si and 2.5% by mass or more and 5.0% or less of Mn and containing Fe as a main component. It is a process. Specifically, for example, molten steel having the above composition is solidified into steel pieces having a thickness of 50 mm or more by casting, and then rough rolling and finish rolling are performed in a hot rolling step. The rolling temperature at the time of finish rolling is not particularly limited, but it is preferable for productivity to be 800 ° C. or higher and 1100 ° C. or lower. When the ingot has an α-γ transformation type chemical composition, it is more preferable that the rolling temperature at the time of finish rolling is 800 ° C. or higher and T2 or lower. By setting the value to T2 or less, the moving speed of the grain boundaries is suppressed, the processed austenite is maintained, and the {100} <011> of the electrical steel sheet obtained after cold rolling and finish annealing can be highly integrated. When the rolling temperature is above T2, the processed austenite is maintained by then cooling the hot-rolled sheet above T2 at a cooling rate of 200 ° C./sec or more to 250 ° C. or less within 3 seconds. Can be done.
The thickness of the hot-rolled plate is not particularly limited, but is usually 1 mm or more and 4 mm or less, and 2 mm or more and 3 mm or less is preferable from the viewpoint of productivity.

(Cold rolling process)
The cold rolling step is not particularly limited, and the cold rolling step in the conventionally known method for manufacturing electrical steel sheets can be appropriately adopted. For example, in the cold rolling step, one cold rolling or two or more cold rollings sandwiching intermediate annealing can be performed to obtain a cold rolled plate. One-time cold rolling means that the rolling mill is passed through the rolling mill once or multiple times without performing intermediate annealing in the middle to finish the rolling mill to a desired thickness. Further, the intermediate annealing is an annealing step performed after the intermediate plate thickness is increased by passing the plate through the rolling mill once or multiple times. After the intermediate annealing, the rolling mill is passed through the plate once or multiple times. Finish to the desired plate thickness. The cold rolling of two or more times including the intermediate annealing means the cold rolling in which the intermediate annealing is carried out once or more.
The intermediate annealing conditions are not particularly limited, and for example, appropriate conditions may be selected such as carrying out in a temperature range of 750 to 1200 ° C. for 30 seconds to 10 minutes.
In the present invention, setting the total cold rolling reduction ratio to 88% or more increases the {100} <011> orientation of the obtained electrical steel sheet, and has a high magnetic flux density and low iron loss in a high frequency region. It is preferable from the viewpoint that an electromagnetic steel sheet having higher strength can be obtained, and it is more preferable that the total cold rolling reduction ratio is 90% or more. Here, "total" means the plate thickness at the time when cold rolling is started after hot rolling, and the plate at the time when finish annealing is performed after one or more cold rolling steps. It means that it is a rolling rate calculated from the thickness.
In the present invention, the plate thickness of the cold-rolled plate may be appropriately selected within a range satisfying the cold rolling reduction rate, and is not particularly limited, but is preferably 0.1 mm or more and 0.5 mm or less, and 0.15 mm or more. It is more preferably 0.40 mm or less.

In the present invention, it is preferable to have a step of performing shot blasting after the hot rolling step and before the cold rolling step from the viewpoint that the oxide layer can be brought into a suitable oxidation state. In the present invention, shot blasting is a processing method in which fine sand or particles made of steel, cast iron, etc. are sprayed onto the surface of a metal material to finish the surface.
The reason why an oxide layer in a suitable oxidized state can be obtained by performing shot blasting is not clear, but by adding a special strain to the surface layer of a steel sheet by shot blasting, in finish annealing after cold rolling. This is considered to be because very fine recrystallized grains are formed on the surface layer of the steel sheet when the steel sheet is recrystallized. It is known that internal oxidation occurs when oxygen invades the inside of the steel sheet due to the diffusion of oxygen at the grain boundaries along the grain boundaries. Since this eventually suppresses external oxidation, it is considered that the formed oxide layer becomes a suitable form for the present invention.
The conditions for shot blasting are not particularly limited, and can be appropriately selected from known methods adopted for steel sheets. For example, a method in which a ceramic spherical material having an average diameter of 0.1 to 0.7 mm is made to collide with an air pressure of 0.35 MPa from a position 50 to 200 mm away from the hot-rolled plate is a preferable example.

The purpose of shot blasting is to introduce strain into the surface layer, but the amount of strain introduced is greatly affected by the type of steel and the like. In addition, the degree of effect varies considerably depending on the oxidation conditions after cold rolling, which will be described later. For this reason, the conditions for shot blasting are not specified. The effect on the present invention can be recognized, for example, by the change in hardness of the surface layer of the steel sheet before and after shot blasting, and it can be said that this is more suitable for evaluating the change in the phenomenon. Specifically, the surface layer is given a strain of 15 or more, further 25 or more, to the extent that the hardness increases, with a Vickers hardness of 15 or more at a load of 50 g measured in accordance with the Vickers hardness test described in JIS Z 2244. It is preferable to do so.
Although the effect was explained here by shot blasting, the method is not limited as long as it is possible to apply additional strain to the surface layer of the steel sheet before cold rolling, and a light reduction such as skin pass is applied. It is also possible.

(Oxidation process)
The present invention is characterized by having an oxidation step of forming an oxide layer on the surface of the cold rolled plate obtained in the cold rolling step. The oxidation step may be included in the temperature raising process in the finish annealing step described later, or may be a step independently performed after the cold rolling step and before the finish annealing step described later.

(A) When the oxidation step is included in the temperature raising process in the finish annealing step The cold-rolled plate obtained by the cold-rolling step is decarburized and annealed by a known method as necessary. After that, finish annealing including an oxidation step is performed.
In this case, the finish annealing may control the temperature raising process so that the time required to reach 400 ° C. to 800 ° C. is 5 seconds or more and 15 seconds or less in an atmosphere where the dew point temperature is 0 ° C. or higher and 80 ° C. or lower.
For the conditions other than the above in the finish annealing step, a conventionally known method can be appropriately adopted. For example, the maximum temperature reached for finish annealing can be set to 800 ° C. or higher and 1200 ° C. or lower, and when the steel sheet is an α-γ transformation system, it can be set to less than T1 to set {100} <011>. It is preferable for high integration. The holding time of the final finish annealing temperature is not particularly limited, and can be appropriately set in the range of, for example, 10 seconds or more and 240 hours or less. When the maximum temperature reached is 800 ° C. or higher, the atmosphere in the temperature range of 800 ° C. or higher is preferably a dew point temperature of less than 0 ° C. from the viewpoint of not promoting oxidation.
The cooling rate after finish annealing is not particularly limited, but when the steel sheet is an α-γ transformation system, the maximum temperature reached is over T1 in order to avoid adverse effects on the magnetic properties due to strain generation due to transformation. In some cases, the cooling rate V1 up to T1 is preferably 3 ° C./s or more and 600 ° C./s or less, and when the maximum temperature reached is T1 or more, it is from T1. When the maximum temperature is less than T1. It is preferable that the cooling rate from the maximum temperature reached to 400 ° C. is less than V1.

(B) When the oxidation step is a step independently held after the cold rolling step and before the finish annealing step The cold rolled plate obtained by the cold rolling step is decarburized and annealed by a known method, if necessary. After annealing and annealing, the cold-rolled sheet is held at a temperature of 400 ° C. to 800 ° C. for 5 seconds or more and 15 seconds or less in an atmosphere of a dew point temperature of 0 ° C. or higher and 80 ° C. or lower to form an oxide layer. The temperature change between 400 ° C. and 800 ° C. is arbitrary and is not specified.
If the oxidation step is independent, then finish annealing is performed by a known method. In this case, the finish annealing step is not particularly limited, but since the oxide layer has already been formed, it is preferable to perform the finish annealing in an atmosphere where the dew point temperature is less than 0 ° C. in the entire process including the temperature raising process. The conditions other than the above in the finish annealing step can be the same as those in the finish annealing described in (A) above.

The above-mentioned oxidation step is a preferable condition for forming an oxide layer preferable for the present invention in the initial state of oxidation of the mother steel sheet. Since oxidation itself does not occur below 400 ° C., it is not necessary to consider the contribution to the effect of the invention. Above 800 ° C., oxidation occurs rapidly and oxidation of Si is prioritized, so that it is difficult to form an oxide layer having a composition preferable for the present invention. If the dew point temperature is less than 0 ° C, a sufficient internal oxide layer is not formed in the above temperature range, and if it exceeds 80 ° C, an external oxide layer is likely to be formed in the initial process, and even if internal oxidation occurs, the internal oxide layer is formed. It becomes too thick and adversely affects the magnetic characteristics. A more preferable temperature range to be controlled is 350 to 750 ° C., and a more preferable dew point temperature is 10 to 40 ° C.
Further, even if a suitable initial oxidation occurs in a temperature range of 800 ° C. or lower, if the oxidation further progresses in a high temperature range of more than 800 ° C. thereafter, the oxide layer deviates from the suitable range, and thus exceeds 800 ° C. When the heat treatment is performed, the dew point temperature of the atmosphere should be less than 0 ° C. A more preferable dew point temperature is −15 ° C. or lower, further preferably −30 ° C. or lower.
Further, it is a preferable form that the initial oxidation is completed by the time the temperature reaches 750 ° C. and the dew point temperature of the atmosphere of 750 ° C. or higher is set to less than 0 ° C.
The holding time in the temperature range of 400 to 800 ° C. and the atmosphere is 5 to 15 seconds.
If it is less than 5 seconds, the time for forming an oxide layer suitable for the invention is insufficient, and if it exceeds 15 seconds, the superiority of Mn oxidation in internal oxidation is lost and the effect is saturated. The holding time specified here is the holding time in the above temperature range, in other words, the time of staying in the above temperature range, and it is not necessary to hold at a constant temperature (so-called retention). If it is carried out before the general finish annealing, the heating process may be used as this process.

(Crystal orientation control)
Among the mother steel sheets having the components of the present invention, it is an α-γ transformation system, containing 2.0% by mass or more and 4.5% by mass or less of Si and 2.5% by mass or more and 5.0% by mass or less of Mn. When Al is less than 0.03% by mass, it is possible to produce a {100} <011> orientation to random intensity ratio of 30 or more. Since the α-γ transformation type steel ingot having such a composition has a significantly slower grain boundary movement speed, the hot-rolled plate obtained in the hot rolling process is strained while the processed austenite is maintained during cooling. It tends to be transformed into a ferrite phase without being released. By cold-rolling and annealing this hot-rolled plate, the {100} <011> orientations are strongly integrated, and it is possible to impart very good magnetic characteristics. For example, in the manufacturing process of the mother steel sheet, as described above, in the hot rolling process, the processed austenite phase is maintained to complete the hot rolling, the recrystallization rate of the hot rolled steel sheet is controlled, and the reduction during cold rolling is performed. By setting the ratio to 88% or more and performing finish annealing in the α single-phase region, a steel sheet having a {100} <011> orientation to random strength ratio of 30 or more can be produced.

The conditions in the examples described below are one-condition examples adopted for confirming the feasibility and effect of the present invention, and the present invention is not limited to this one-condition example. The present invention can adopt various conditions as long as the gist of the present invention is not deviated and the object of the present invention is achieved.

(Example: Manufacturing of electrical steel sheet)
Ingots adjusted to the composition shown in Steel Types A to K in Table 1 are cast in a vacuum melting furnace. Using the obtained ingot, an electromagnetic steel sheet is manufactured according to Tables 2 and 3. Specifically, the ingot is hot-rolled at the finish rolling temperatures shown in Tables 2 to 3 to obtain hot-rolled plates having a thickness of 2.1 to 3.2 mm, respectively. The hot-rolled plate thus obtained was shot-blasted (excluding samples Nos. 11-23, 37-44, and 47) without annealing the hot-rolled plate, and then cold-rolled to be performed in Table 2. -A cold rolled plate having the thickness shown in Table 3 is used. The cold rolled plate is then oxidized. In the table, the process "A" is a step in which the oxidation step is included in the temperature raising process in the finish annealing step, and the process "B" is a step in which the oxidation step is independently held after the cold rolling step and before the finish annealing step. Indicates the case where. In the case of the process "A", the "dew point temperature" in the table indicates the atmosphere in the temperature raising step of the finish annealing, and the "holding time" indicates the time from 400 ° C. to 800 ° C. Further, in the case of the process "B", the oxidation step is performed with the maximum temperature reached at 750 ° C., the "dew point temperature" in the table indicates the atmosphere in the oxidation step, and the "holding time" is from 400 ° C. including the cooling process. It shows the holding time in the temperature range of 750 ° C. Then, finish annealing is performed under the temperature conditions shown in Tables 2 to 3 to obtain an electromagnetic steel sheet.

Each of the obtained electromagnetic steel sheets is measured by glow discharge emission spectroscopy (GDS), and the element distribution measurement results in the depth direction of the steel sheet are graphed _{to obtain D 1} , D ₂ , D _x , and D ₀ , respectively. Further, the thickness t of the low Mn region and the minimum value Dxmin of Dx are calculated.
In this embodiment, a sample cut out so that the rolling direction and the direction of 45 ° are the magnetization directions is used in a magnetic field of 5000 A / m in accordance with the magnetic steel sheet single plate magnetic property test method described in JIS C 2556. The magnetic flux density B50 is measured. As for the iron loss, the iron loss W10 / 800 is measured when the maximum magnetic flux density is 1.0 T and the frequency is 800 Hz.
The random intensity ratio of {100} <011> is measured by X-ray diffraction on a plane parallel to the rolling plane at 1 / 5t position from the surface layer of the obtained electromagnetic steel plate, and is obtained from the crystal orientation distribution function.
The film adhesion is evaluated by a bending test. Wrap the product plate around a round bar of φ20 mm, and determine the area ratio of the peeled part. A pass (○) is given when the peeled area ratio is 10% or less. The results are shown in Tables 4-5.

[Summary of results]
As shown in Tables 4 to 5, on a mother steel sheet containing 2.0% by mass or more and 4.5% by mass or less of Si and 2.5% by mass or more and 5.0% by mass or less of Mn and containing Fe as a main component. In addition, in an electromagnetic steel sheet having an oxide layer containing Mn, the maximum concentration D ₁ (mass%) of Mn in the oxide layer and the maximum concentration D ₂ (mass%) of Si in the oxide layer are (mass%). It was clarified that the electrical steel sheets of Examples 1 to 30 satisfying the relationship of D ₁ / D _{2) ≧ 1.50 are excellent in film adhesion.}

1 Base steel sheet 2 Oxidized layer 3 Steel sheet surface 4 Low Mn region 10 Electromagnetic steel sheet

Claims (7)

Si is 2.0% by mass or more and 4.5% by mass or less, Mn is 2.5% by mass or more and 5.0% by mass or less, Al is 0.0355% by mass or less, and Sn and Sb are 0.50% by mass in total. Hereinafter, C is 0.0040% by mass or less, N is 0.0040% by mass or less, S is 0.020% by mass or less, P is 0.5% by mass or less, Cr is 20% by mass or less, and Ni is 10% by mass. Hereinafter, Cu is 0.2% by mass or less, B is 0.01% by mass or less, Ti is 0.0020% by mass or less, Nb is 0.0020% by mass or less, Mo is 0.0020% by mass or less, and Ca is 0. .050 mass% or less, Mg 0.050 mass% or less, rare earth element 0.050 mass% or less, balance Fe and unavoidable impurities , Mn-containing oxidation on the mother steel plate which is an α-γ transformation system An electromagnetic steel plate with a layer
_{The maximum concentration D 1} (mass%) of Mn in the oxide layer _{and the maximum concentration D 2} (mass%) of Si in the oxide layer satisfy the following formula (1).
Equation (1) (D ₁ / D ₂ ) ≧ 1.50
An electromagnetic steel sheet having a ratio of random strength to random strength in {100} <011> orientation at the surface position of the mother steel sheet of 15 or more. The electromagnetic steel sheet according to claim 1, wherein a low Mn region satisfying the following formula (2) exists when the concentration of Mn at the position where the thickness of the mother steel sheet is 1/2 is D _{0 (mass%).}
Equation (2) (D _x / D ₀ ) <0.92
(In the formula (2), D _x represents the concentration of Mn at a point on a straight line passing through the D _{0 measurement point and perpendicular to the mother steel plate.)} The electromagnetic steel sheet according to claim 2, wherein the thickness of the low Mn region is 3 to 25 μm. The electromagnetic steel sheet according to any one of claims 1 to 3, wherein the content of Al in the mother steel sheet is less than 0.03% by mass. The electromagnetic steel sheet according to any one of claims 1 to 4, further comprising an insulating film on the oxide layer. The method for manufacturing an electromagnetic steel sheet according to claim 1.
Si is 2.0% by mass or more and 4.5% by mass or less, Mn is 2.5% by mass or more and 5.0% by mass or less, Al is 0.0355% by mass or less, and Sn and Sb are 0.50% by mass in total. Hereinafter, C is 0.0040% by mass or less, N is 0.0040% by mass or less, S is 0.020% by mass or less, P is 0.5% by mass or less, Cr is 20% by mass or less, and Ni is 10% by mass. Hereinafter, Cu is 0.2% by mass or less, B is 0.01% by mass or less, Ti is 0.0020% by mass or less, Nb is 0.0020% by mass or less, Mo is 0.0020% by mass or less, and Ca is 0. Hot rolling using an α-γ transformation system ingot as a hot-rolled plate, consisting of .050% by mass or less, Mg of 0.050% by mass or less, rare earth elements of 0.050% by mass or less, balance Fe and unavoidable impurities. It has a step, a cold rolling step of using the hot-rolled plate as a cold-rolled plate, an oxidation step of forming an oxide layer on the cold-rolled plate, and a finish annealing step.
The oxidation step may be included in the temperature raising step in the finish annealing step.
The oxidation step is a step of holding the cold rolled plate at a temperature of 400 ° C. to 800 ° C. for 5 seconds or more and 15 seconds or less in an atmosphere having a dew point temperature of 0 ° C. or higher and 80 ° C. or lower.
When the oxidation step is included in the temperature raising process in the finishing annealing step, the cooling rate from the maximum temperature reached in the temperature lowering process is 3 ° C./s or more and 600 ° C./s or less. , Manufacturing method of electrical steel sheet. The method for manufacturing an electromagnetic steel sheet according to claim 6, further comprising a step of performing shot blasting after the hot rolling step and before the cold rolling step.

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