JP6870381B2 - 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 electric motors, generators, and transformers, and which can contribute to miniaturization and high efficiency of these magnetic cores, and a method for manufacturing the same.

High efficiency is required for motors and generators to prevent global warming. Therefore, electrical steel sheets used for magnetic cores of motors, generators, and the like are required to have high magnetic flux density and low iron loss, and in particular, low iron loss in a high frequency region is strongly required. In order to increase the magnetic flux density of the magnetic steel sheet, it is sufficient to contain more crystal grains having the <100> direction in the plate surface, which is the axial direction in which iron is easily magnetized.

The non-oriented electrical steel sheet may be used after being punched into a desired shape depending on the application. If the crystal grain size and hardness of the steel sheet are insufficient, sagging and burrs may occur during punching.
For example, Patent Document 1 discloses a specific non-oriented electrical steel sheet containing a specific amount of Mn as a non-oriented electrical steel sheet having excellent punching property. In Patent Document 1, Mn is added for various purposes, and one of them is punching property.
However, it has been pointed out that even if Mn is contained, the punching property may not be sufficiently improved, and further improvement in punching property is required.
Further, regarding punching property in particular, Patent Documents 2 and 3 mainly control mechanical properties such as hardness and yield stress, and Patent Document 4 controls crystal grain size related to strength. Is mainly done. In addition, Patent Document 5 shows that the {011} orientation is preferable as the crystal orientation, and Patent Document 6 examines the influence of grain boundary strength.

Japanese Unexamined Patent Publication No. 2003-213385 Japanese Unexamined Patent Publication No. 2005-60737 Japanese Unexamined Patent Publication No. 2005-105407 Japanese Unexamined Patent Publication No. 2014-122405 Japanese Unexamined Patent Publication No. 2012-36474 Japanese Unexamined Patent Publication No. 2014-40622

In the Mn-containing steel, demanganese (decrease in manganese concentration in the steel) occurs during annealing, and the hardness near the surface layer of the steel sheet tends to decrease. Therefore, the effect of improving punching property by adding Mn is sufficient. It was found that it may not be exhibited in the above.

The present invention has been made in view of the above circumstances, and provides a non-oriented electrical steel sheet having excellent punching property.

As a result of diligent studies, the present inventors have obtained the finding that demanganese is suppressed by using a specific element, and have completed the present invention.

That is, in the non-directional 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, and Sn and Sb are 0 in total. .80% by mass or less, Al 0.1070% by mass or less, C 0.0040% by mass or less, N 0.0040% by mass or less, S 0.020% by mass or less, P 0.5% by mass or less , 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 0.0020% by mass or less, Ca is 0.050% by mass or less, Mg is 0.050% by mass or less, rare earth element is 0.050% by mass or less, and the balance is Fe and unavoidable impurities. A Mn-containing oxide layer is provided on the mother steel plate, which is a system.
The thickness of the oxide layer is 0.02 μm or more and 3.0 μm or less.
When the concentration of Mn at the position where the thickness of the mother steel sheet is 1/2 is D ₀ (mass%), the following formula (2) is satisfied for the entire region of the mother steel sheet in the plate thickness direction.
Equation (2) (D _x / D ₀ ) ≧ 0.98
(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 base steel plate.)}
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 9 or more.

In one embodiment of the electrical steel sheet of the present invention, 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 have the following formula (1). Fulfill.
Equation (1) (D ₁ / D ₂ ) <1.50

In one embodiment of the electromagnetic steel sheet of the present invention, the total content of Sn and Sb in the mother steel sheet is 0.05% by mass or more and 0.80% by mass or less .

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

The method for manufacturing a non-oriented electrical steel sheet according to the present invention is the method for producing the above-mentioned non-oriented electrical steel sheet.
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, Sn and Sb are 0.80% by mass or less in total, and Al is 0.1070% by mass. 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 2 seconds or more and 10 seconds or less in an atmosphere having a dew point temperature of −60 ° C. or higher and 5 ° C. or lower.

One embodiment of the method for producing an electromagnetic steel sheet of the present invention includes a step of setting the surface roughness Ra of the steel sheet to less than 0.3 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 punching property.

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 on a mother steel sheet containing Fe as a main component. , An electromagnetic steel sheet having an oxide layer containing Mn,
The thickness of the oxide layer is 0.02 μm or more and 3.0 μm or less.

Since the thickness of the oxide layer of the electromagnetic steel sheet of the present invention is 0.02 μm or more and 3.0 μm or less, the hardness near the surface of the steel sheet does not decrease, and the punching property is excellent.
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 sheet 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.

The electromagnetic steel sheet of the present invention has an area of the oxide layer 2 of 0.02 μm or more and 3.0 μm or less, so that the hardness near the surface of the steel sheet does not decrease and the punching property is excellent.
Hereinafter, each configuration of the electromagnetic steel sheet will be described in detail.

<Oxidized layer>
In the present invention, the oxide layer is a layer containing at least Mn and is formed on a mother steel sheet described later with a thickness of 0.02 μm or more and 3.0 μm or less.
By suppressing the internal oxidation of the steel sheet, the thickness of the oxide layer can be realized to be 3.0 μm or less. In a steel sheet containing a relatively high concentration of Mn, which is the subject of the present invention, internal oxidation tends to be accompanied by preferential oxidation of Mn. Therefore, when internal oxidation occurs, the Mn concentration immediately below the internal oxide layer is lowered. It will be accompanied. In such a region where the Mn concentration has decreased, the hardness decreases, which causes a decrease in punching property. The electromagnetic steel sheet of the present invention suppresses internal oxidation as much as possible to form an externally oxidized oxide layer as much as possible even when an oxide layer is formed, thereby suppressing a decrease in hardness and having good punching property. It becomes a steel plate.
As the oxidation progresses and the oxide layer becomes thicker, the oxidation becomes an internal oxidation type and becomes an oxide layer unfavorable for the present invention. 3.0 μm is set as this limit thickness. It is preferably 2.0 μm or less, more preferably 1.0 μm or less.
When a dense oxide layer having a suitable composition in the present invention is formed with a thickness of 0.02 μm or more, the effect of improving the punching property can be seen in the oxide layer itself. Since it is possible to obtain such an effect of improving punching property, the thickness of the oxide layer is preferably 0.05 μm or more.

Further, in the present invention, the composition of the external oxidation type oxide layer in which internal oxidation is suppressed as described above (hereinafter, may be simply referred to as an external oxide layer) depends on the composition of the mother steel sheet, but the oxidation is described above. It is preferable that the maximum concentration D _{1 (mass%) of Mn in the 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 reason why the oxide layer having such a composition suppresses internal oxidation is not clear, but it is considered as follows. In the electromagnetic steel sheet of the present invention, oxidation in which Mn and Si compete with each other occurs during finish annealing during the manufacturing process, but the oxide layer having a high Si concentration has a denser structure than the oxide layer having a high Mn concentration. When formed as an external oxide layer on the surface of the steel sheet, it is considered that the supply of oxygen to the inside of the steel sheet is suppressed, and as a result, the effect of suppressing the internal oxidation in which Mn is preferentially oxidized is produced. When the above ratio is preferably less than 1.2, more preferably less than 1.0, still more preferably less than 0.8, the oxidation of Mn is suppressed and the formation of the low Mn region described later is sufficiently suppressed. This is a preferred form.
The characteristics of the oxidation behavior according to the invention will be described later in the production method, particularly in relation to the roughness adjustment before finish annealing and the initial oxidation in annealing.
Although a detailed study on the optimum form of the contained element in the oxide layer of the present invention has not been carried out, considering the composition of the mother steel sheet of the present invention, Mn oxide, Si oxide, and Fe are added to these. It is formed of an oxide composed of a composite oxide.
It should be noted that when an oxide layer unfavorable for the present invention is formed, the oxide layer is acidified together with the low Mn region described later until a region having a composition similar to that of the central layer of the mother steel sheet becomes the surface. If it is removed by washing or grinding, it is possible to obtain a steel sheet that does not have a low Mn region that causes a decrease in punching property for the time being. The externally oxidized oxide layer formed with a dense and appropriate thickness specified in the present invention itself hardens the surface of the steel sheet, and has a favorable effect on punching property. That is, as described above, the steel sheet in which the oxide layer is removed together with the low Mn region described later by pickling or grinding can certainly avoid the deterioration of the punching property due to the low Mn region, but obtains better punching property. It is not possible.
As described above, a method that does not involve a change in the composition of the mother steel sheet on the surface of the steel sheet in which the oxide layer is removed together with the low Mn region described later by pickling or grinding, for example, vapor deposition or spraying, or Mn or Si. After plating, this is heated in an oxygen-presence atmosphere to oxidize Mn and Si on the surface, and further, an oxide powder containing Mn and Si is applied to the surface of the steel sheet, and the oxide is heated by heating. It is possible to obtain a steel sheet conforming to the present invention by forming a suitable oxide layer shown in the present invention by a process such as a so-called hollow, in which powder is melted to form an oxide film on the surface of the steel sheet. , It is possible to obtain the effect of the present invention. However, these methods are not practical because of the large increase in production cost.

<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 mother steel sheet as the measurement sample has an oxide layer or an insulating film on the surface, it is necessary to measure after removing the oxide layer or 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 an insulating coating, 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.

Since the electromagnetic steel sheet of the present invention has a thickness of less than 3.0 μm even when an oxide layer is formed on the surface of the mother steel sheet having the above components, the transfer of Mn to the oxide layer is suppressed and the mother steel sheet is suppressed. The overall hardness is maintained. As a result, the electromagnetic steel sheet of the present invention is characterized by being excellent in punching property.

(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, in the present invention, Si is an important element for preferentially oxidizing to form an external oxide layer having a high Si composition that inhibits the progress of internal oxidation. 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.

(Mn: 2.5% by mass or more and 5.0% by mass or less)
In the electromagnetic steel sheet of the present invention, the content ratio of Mn 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.
By setting the Mn content to 2.5% by mass or more, an electromagnetic steel sheet in which iron loss is suppressed can be obtained. Further, when the Mn content is 5.0% by mass or less, not only the decrease in the saturation magnetic flux density can be suppressed, but also it is effective to make the oxide layer have a high Si composition. Furthermore, 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 3.1% or more, more preferably 3.6% or more, still more preferably 4.1% or more.

(Al: less than 0.1% by mass)
Al is generally added in non-oriented electrical steel sheets to increase the electrical resistance of the steel sheets and reduce iron loss. At the same time, Al is known as a strong oxidizing element, and its content should be noted in the mother steel sheet of the present invention. When the Al content is high, it becomes difficult to control the oxide layer, which is a feature of the present invention, to an appropriate thickness and composition. Although the oxide layer containing a high concentration of Al is an external oxidation type, the effect of suppressing internal oxidation that should be avoided in the present invention is not great. Therefore, Al is preferably less than 0.10% by mass. It is preferably 0.03% by mass or less, more preferably 0.01% by mass or less. The content may be 0 (zero).

(Sn + Sb: 0.05% by mass or more and 0.80% 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. However, if the total amount exceeds 0.80% by mass, the rollability is lowered and there is an increasing concern that the productivity is hindered. In the present invention, it is preferable that the steel sheet contains at least 0.05% by mass in total of one or more elements selected from Sn and Sb. Both Sn and Sb tend to segregate on the surface layer of the steel sheet during annealing. As a result, the progress of internal oxidation can be suppressed, and even when oxidized, it can be limited to external oxidation. As a result, the decrease of Mn directly under the oxide layer is suppressed, which effectively works to improve the punching property. It is preferably 0.10% or more, more preferably 0.30% or more.

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, these precipitates may hinder the movement of the domain wall and significantly deteriorate the magnetic properties in a high magnetic field. Therefore, 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 suppresses the decrease in Mn on the surface layer of the steel sheet as described above, the crystal orientation may not be a preferable orientation for punching property in a steel material having a {100} <011> orientation. However, it is possible to compensate for the factor of lowering the punching property due to the crystal orientation and to secure the good punching property.

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 sample for measurement 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>
In 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%), the following formula (2) is applied to the entire region in the thickness direction of the mother steel sheet. Satisfaction is preferable from the viewpoint of punching property.
Equation (2) (D _x / D ₀ ) ≧ 0.98
(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 base steel plate.)}
In the present invention, in the mother steel sheet, a region that does not satisfy the formula (2), that is, a region where (D _x / D ₀ ) <0.98 is defined as a “low Mn region”.

When the internal oxidation of the steel sheet occurs, the oxide formed by the internal oxidation is formed by preferentially oxidizing Mn in the steel, so that the Mn contained in the region adjacent to the oxide layer of the mother steel sheet is the oxide layer. Move to. When this internal oxidation is remarkable, the Mn concentration in the region immediately below the oxide layer decreases beyond the limit of the formula (2) to become a “low Mn region”. When the low Mn region is formed, the hardness is lowered, so that the punching property is lowered. The above formula (2) shows that even if there is a portion where the Mn concentration is reduced, if the reduction rate is within 2%, the reduction in punching property does not pose a practical problem. In the present invention, it is shown that the punching property is excellent by satisfying the above formula (2) in the entire region of the mother steel sheet in the plate thickness direction.
_{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.

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 0.10 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 the 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 punching property, which is the effect of the present invention, can be obtained.

In the present invention, the insulating coating is not particularly limited, and can be appropriately selected and used from known coatings according to the intended use, and may be either an organic coating or an inorganic coating. Examples of the organic coating include polyamine resins, acrylic resins, acrylic styrene resins, alkyd resins, polyester resins, silicone resins, fluororesins, polyolefin resins, styrene resins, vinyl acetate resins, epoxy resins, phenol resins, urethane resins, and melamines. Examples include resin. Examples of the inorganic coating include a phosphate-based coating, an aluminum phosphate-based coating, and an organic-inorganic composite coating containing the above-mentioned resin.
The thickness of the insulating coating 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 decreases, and the motor efficiency decreases.

The method for forming the insulating film is not particularly limited, but 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 the insulating film often causes a problem in punching property. 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 the 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]
The method for producing an electromagnetic steel sheet according to the present invention is 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% by mass or less of Mn and containing Fe as a main component. It has a hot rolling step of using the hot rolled plate, a cold rolling step of using the hot rolled plate as a cold rolled plate, an oxidizing step of forming an oxide layer on the cold rolled plate, and a finishing 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 2 seconds or more and 10 seconds or less in an atmosphere having a dew point temperature of −60 ° C. or higher and 5 ° C. or lower.

According to the above-mentioned production method of the present invention, it is possible to produce an electromagnetic steel sheet having an oxide layer thickness of less than 3.0 μm by suppressing internal oxidation during finish annealing, and the obtained electromagnetic steel sheet has punching properties. Are better.

This method works effectively to control the state of initial oxidation of the mother steel sheet or the steel sheet in the manufacturing process of the mother steel sheet to form an oxide layer preferable for the present invention, that is, an external oxide layer having a high Si composition.
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 that brings about a favorable effect on the punching 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 lowered, the (D 1} / D ₂ ) specified in the present application is also lowered, but if the influence of the composition of the mother steel sheet is excluded, in order to form a preferable oxide layer, the following It is important to oxidize the mother steel sheet under the above conditions.
In order to obtain an oxide layer having a thickness of less than 3.0 μm required for the present invention, in the initial process of oxidizing the mother steel sheet, the temperature of 400 ° C. to 800 ° C. is set to 2 at a dew point temperature of -60 ° C. or higher and 5 ° C. or lower. It is preferable to hold for 2 seconds or more and 10 seconds or less. By forming the oxide layer under the condition that the oxidation does not proceed easily in this way, the thickness of the oxide layer can be controlled to less than 3.0 μm.
Further, by performing oxidation under such conditions, an oxide layer having a range _{(D 1} / D _{2) effective for improving punching property is formed.}
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. Basically, Si has a stronger oxidation tendency and Si has a faster diffusion rate in the Fe phase, but this advantage is lost when simply oxidized at high temperature or high dew point. Therefore, a considerable amount of Mn is concentrated in the oxide layer. In addition, internal oxidation 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, an external oxide layer having a high Si composition in which Si is preferentially oxidized is formed, which is effective for improving punching performance. An oxide layer having a range of (D ₁ / D _{2) 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.
Hereinafter, each step of the above-mentioned 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% by mass 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 preferably 800 ° C. or higher and 1100 ° C. or lower from the viewpoint of productivity. 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 to 250 ° C. or less at a cooling rate of 200 ° C./sec or more 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 that the surface roughness Ra of the steel sheet subjected to the oxidation step described later is less than 0.30 from the viewpoint that the oxide layer can be in a suitable oxidation state. More preferably, it is 0.1 or less. The reason for this is not clear, but the smooth surface that reacts with the atmosphere during finish annealing allows the oxidation reaction to proceed stably in the micro region, that is, the difference in oxidation behavior between the micro convex and concave parts. It is considered that this is eliminated and a dense and uniform external oxide layer is formed. In the present invention, since it is necessary to control the oxide layer having a thickness of several μm, preferably submicron, on the surface, it is considered that the influence of the surface roughness at the time of finish annealing is detected. In addition, the formation of such a dense external oxide layer also suppresses internal oxidation, which is a form to be avoided in the present invention.
The surface roughness may be controlled by adjusting the roughness of the rolling roll used in cold rolling, which is generally a means for adjusting the roughness of the steel plate, particularly the roughness of the rolling roll of the final stand. After cold rolling, it is also possible to perform pickling, polishing, etc. to smooth the surface.

(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 subjected to decarburization annealing and nitriding annealing 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 rise process so that the time from 400 ° C. to 800 ° C. is 2 seconds or more and 10 seconds or less in an atmosphere of dew point temperature of -60 ° C. or higher and 5 ° 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 a temperature range of less than T1 {100} <011. > Is preferable from the viewpoint of 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 if the maximum temperature reached is T1 or more, it is from T1. If the maximum temperature is less than T1. The cooling rate from the maximum temperature reached to 400 ° C. is preferably 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 2 seconds or more and 10 seconds or less in an atmosphere of a dew point temperature of −60 ° C. or higher and 5 ° C. or lower to form an oxide layer. The temperature change between 400 ° C. and 800 ° C. is arbitrary and is not particularly 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 tends to be in the internal oxidation type, and it is difficult for the external oxide layer to form an oxide layer having a composition preferable to the present invention. If the dew point temperature is less than −60 ° C., the oxide layer itself is hardly formed, and the above-mentioned effect of improving punching property by the oxide layer cannot be obtained. If the temperature exceeds 5 ° C., an internal oxide layer is likely to be formed in the initial process, the superiority of Si oxidation is lost even in external oxidation, and it becomes difficult to obtain an oxide layer suitable for the present invention. The more preferable temperature range to be controlled is 350 to 750 ° C., and the more preferable dew point temperature is more than −30 ° C. and less than 0 ° C.
Further, even if 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 800 ° C. or higher. When the heat treatment is performed, the dew point temperature of the atmosphere should be less than -20 ° C. A more preferable dew point temperature is −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 −20 ° C. In the steel of the present invention, by performing the above-mentioned low dew point and short-time treatment, a dense external oxide layer having an appropriate composition is formed on the surface of the steel sheet, and as a result, the formation of a low Mn region due to internal oxidation is suppressed. To. As a result, it is presumed that the obtained steel sheet can more easily satisfy the above formula (2) and becomes a steel sheet having excellent punching property.
The holding time in the temperature range of 400 to 800 ° C. and the atmosphere is 0.2 to 10 seconds.
If it is less than 0.2 seconds, the time for forming an oxide layer suitable for the invention is insufficient, and if it exceeds 10 seconds, the superiority of Si oxidation in external oxidation is lost, which hinders the formation of an oxide layer having a preferable composition. Not only will the effect be 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 M in Table 1 are cast in a vacuum melting furnace. Using the obtained ingot, an electromagnetic steel sheet is manufactured according to Table 2. Specifically, the ingot is hot-rolled at the finish rolling temperatures shown in Table 2 to obtain hot-rolled plates having a thickness of 2.2 to 2.9 mm, respectively. The surface roughness Ra of the obtained hot-rolled plate is calculated based on the arithmetic mean roughness defined in JIS B 0601. The obtained hot-rolled plate is cold-rolled without being annealed to obtain a cold-rolled plate having the thicknesses shown in Tables 2 and 3. 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. The holding time in the temperature range of 750 ° C. is shown. Then, finish annealing is performed under the temperature conditions shown in Table 2 to obtain an electromagnetic steel sheet.

Each of the obtained electromagnetic steel sheets is measured by glow discharge emission spectroscopy (GDS), the element distribution measurement results in the depth direction of the steel sheet are graphed, and D ₁ , D ₂ , D _x , and D ₀ are obtained, respectively. The minimum value Dxmin of the thickness t and Dx of the Mn region is calculated.
In this embodiment, in a sample cut out so that the rolling direction and the direction of 45 ° are the magnetization directions, the magnetic flux in a magnetic field of 5000 A / m is based on the magnetic steel sheet single plate magnetic property test method described in JIS C 2556. The density B50 is measured. Further, as 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.
To evaluate the punching property, the obtained electromagnetic steel sheet was punched into a circle of 50 mmφ with a clearance of 12%, and the burr height of the end face was repeatedly measured 5 times (n = 5) for each steel sheet, and the average burr height was measured. If it is less than 1/20 t with respect to the plate thickness t of the electromagnetic steel sheet, that is, if the value obtained by dividing the average burr height by the plate thickness t is less than 0.05, it is evaluated that the punching property is excellent.
The results are shown in Table 3.

From the results in Table 3, Mn is contained 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. It was confirmed that the electrical steel sheet having an oxide layer containing the above-mentioned oxide layer, in which the thickness of the oxide layer is 0.02 μm or more and 3.0 μm or less, is excellent in punching property.

1 Base steel sheet 2 Oxidized layer 3 Steel sheet surface 10 Electromagnetic steel sheet

Claims (6)

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, Sn and Sb are 0.80% by mass or less in total, and Al is 0.1070% by mass. 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 Has layers and
The thickness of the oxide layer is 0.02 μm or more and 3.0 μm or less.
When the concentration of Mn at the position where the thickness of the mother steel sheet is 1/2 is D ₀ (mass%), the following formula (2) is satisfied for the entire region of the mother steel sheet in the plate thickness direction.
Equation (2) (D _x / D ₀ ) ≧ 0.98
(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 base steel plate.)}
A non-oriented electrical 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 9 or more. The non-directionality according to claim 1 _{, wherein 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). Electromagnetic steel plate.
Equation (1) (D ₁ / D ₂ ) <1.50 The non-oriented electrical steel sheet according to claim 1 or 2, wherein the total content of Sn and Sb in the mother steel sheet is 0.05% by mass or more and 0.80% by mass or less. The non-oriented electrical steel sheet according to any one of claims 1 to 3, further comprising an insulating film on the oxide layer. The method for manufacturing a non-oriented electrical 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, Sn and Sb are 0.80% by mass or less in total, and Al is 0.1070% by mass. 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 2 seconds or more and 10 seconds or less in an atmosphere having a dew point temperature of −60 ° C. or higher and 5 ° C. or lower. Manufacturing method of grain-oriented electrical steel sheet. The method for producing a non-directional electromagnetic steel sheet according to claim 5, further comprising a step of setting the surface roughness Ra of the steel sheet to less than 0.30 after the hot rolling step and before the cold rolling step.

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