阅读说明：本技术 无方向性电磁钢板 (Non-oriented electromagnetic steel sheet ) 是由 宫本幸乃 财前善彰 尾田善彦 于 2020-04-13 设计创作，主要内容包括：本发明提供一种兼具低高频铁损与高磁通密度的无方向性电磁钢板。一种无方向性电磁钢板,包含内层部和设置在上述内层部两侧的表层部,且上述表层部和上述内层部具有特定的成分组成；上述无方向性电磁钢板的板厚t为0.01～0.35mm,定义为上述表层部的合计厚度：t-(1)与上述t的比率的复层比t-(1)/t为0.10～0.70,定义为上述表层部的Si含量：[Si]-(1)与上述内层部的Si含量：[Si]-(0)之差([Si]-(1)-[Si]-(0))的ΔSi为1.0～4.5质量％,且定义为板厚中心位置(t/2)的Mn含量：[Mn]-(0)与上述无方向性电磁钢板的从表面到深度(1/10)t的位置的区域内的平均Mn含量：[Mn]-(1)之差([Mn]-(0)-[Mn]-(1))的ΔMn为0.01～0.40质量％。(The invention provides a non-oriented electromagnetic steel sheet having both low and high frequency iron loss and high magnetic flux density. A non-oriented electrical steel sheet comprising an inner layer portion and surface layer portions provided on both sides of the inner layer portion, the surface layer portions and the inner layer portion having a specific composition; the thickness t of the non-oriented electrical steel sheet is 0.01 to 0.35mm, and is defined as the total thickness of the surface layer portion: t is t 1 A multilayer ratio t to the above ratio t 1 A/t of 0.10 to 0.70, defined as the above-mentioned surface layerSi content of the portion: [ Si ]] 1 Si content in the inner layer portion: [ Si ]] 0 Difference ([ Si ]] 1 ‑[Si] 0 ) Δ Si of 1.0 to 4.5 mass%, and defined as the Mn content at the center position (t/2) of the sheet thickness: [ Mn ]] 0 Average Mn content in a region from the surface to the depth (1/10) t of the non-oriented magnetic steel sheet: [ Mn ]] 1 Difference of ([ Mn ]] 0 ‑[Mn] 1 ) The delta Mn of (A) is 0.01 to 0.40 mass%.)

1. A non-oriented electrical steel sheet comprising an inner layer portion and surface layer portions provided on both sides of the inner layer portion,

the surface layer part has the following composition: contains, in mass%, Si: 2.5-7.0%, Mn: 0.50% or less, and is selected from the group consisting of P: 0.010% -0.100%, Sn: 0.001% -0.10% and Sb: 0.001-0.10% of 1 or more species, the remainder being composed of Fe and unavoidable impurities;

the inner layer part has the following composition: contains, in mass%, Si: 1.5-5.0%, Mn: 0.01% -0.50%, and is selected from the group consisting of P: 0.010% -0.100%, Sn: 0.001% -0.10% and Sb: 0.001-0.10% of 1 or more species, the remainder being composed of Fe and unavoidable impurities;

the non-oriented electromagnetic steel sheet has a sheet thickness t of 0.01 to 0.35mm,

is defined as the total thickness t of the surface layer part₁A multilayer ratio t of the ratio to t₁The/t is 0.10 to 0.70,

is defined as the Si content [ Si ] of the surface layer portion]₁And the Si content [ Si ] of the inner layer portion]₀Difference of [ Si ]]₁-[Si]₀Has a.DELTA.Si of 1.0 to 4.5 mass%, and

defined as the Mn content [ Mn ] of the center position (t/2) of the sheet thickness]₀And an average Mn content [ Mn ] in a region from the surface of the non-oriented magnetic steel sheet to a position of depth (1/10) t]₁Difference of [ Mn ]]₀-[Mn]₁The delta Mn of (A) is 0.01 to 0.40 mass%.

2. The non-oriented electrical steel sheet according to claim 1, wherein Δ Mn is 0.05 to 0.40 mass%.

3. The non-oriented electrical steel sheet according to claim 1 or 2, wherein the depth from the surface of the non-oriented electrical steel sheet is a sheet thickness1/4 of the azimuthal distribution function of the face₂The cross-section of 45 DEG has a texture in which the ratio {100}/{111} of the {100} plane concentration to the {111} plane concentration is 0.55 to 0.90.

Technical Field

The present invention relates to a non-oriented electrical steel sheet, and more particularly to a non-oriented electrical steel sheet having both low high-frequency iron loss and high magnetic flux density.

Background

From the viewpoint of downsizing and high efficiency, motors for hybrid electric vehicles and vacuum cleaners are driven in a high frequency range of 400Hz to 2 kHz. Therefore, a non-oriented electrical steel sheet used as a core material of such a motor is desired to have a low high-frequency iron loss and a high magnetic flux density.

In order to reduce the high-frequency core loss, it is effective to increase the intrinsic resistance. Therefore, a high Si steel in which the inherent resistance is increased by increasing the amount of Si has been developed. However, since Si is a nonmagnetic element, there is a problem that saturation magnetization decreases with an increase in the amount of Si.

Therefore, as a method of achieving both the reduction of the high-frequency iron loss and the high magnetic flux density, an Si-gradient magnetic material has been developed which controls the Si concentration gradient in the thickness direction of the electrical steel sheet. For example, patent document 1 proposes an electrical steel sheet having a Si concentration gradient in the sheet thickness direction, and the Si concentration on the surface of the steel sheet is higher than the Si concentration in the sheet thickness center portion of the steel sheet. Specifically, in the above-mentioned electromagnetic steel sheet, the Si concentration in the center portion of the sheet thickness is 3.4% or more, and surface layer portions having an Si concentration of 5 to 8 mass% are provided on both surfaces of the steel sheet. The thickness of the surface layer portion is set to be 10% or more of the plate thickness.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 11-293422

Disclosure of Invention

However, the conventional Si gradient magnetic material proposed in patent document 1 has the following problems: when used as an iron core material for an electric device having a maximum frequency of several kHz, the iron loss is not sufficiently reduced because the hysteresis loss is high.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a non-oriented electrical steel sheet having both low iron loss and high magnetic flux density in a high frequency region such as a frequency of 400Hz to 2 kHz.

As a result of intensive studies on a method for solving the above problems, the present inventors have found that in order to reduce the iron loss in a high frequency region such as a frequency of 400Hz to 2kHz, it is important to reduce the stress caused by the difference in magnetostriction between the surface layer portion and the inner layer portion of the steel sheet, the difference in lattice constant, and the like. The present invention has been completed based on the above-described findings, and the gist thereof is as follows.

1. A non-oriented electrical steel sheet comprising an inner layer portion and surface layer portions provided on both sides of the inner layer portion,

the surface layer portion has the following composition: contains, in mass%, Si: 2.5-7.0%, Mn: 0.50% or less, and is selected from the group consisting of P: 0.010% -0.100%, Sn: 0.001% -0.10% and Sb: 0.001-0.10% of 1 or more species, the remainder being composed of Fe and unavoidable impurities;

the inner layer part has the following composition: contains, in mass%, Si: 1.5-5.0%, Mn: 0.01% -0.50%, and is selected from the group consisting of P: 0.010% -0.100%, Sn: 0.001% -0.10% and Sb: 0.001-0.10% of 1 or more species, the remainder being composed of Fe and unavoidable impurities;

the thickness t of the non-oriented electromagnetic steel sheet is 0.01 to 0.35mm,

is defined as the total thickness of the surface layer portion: t is t₁A multilayer ratio t to the above ratio t₁The/t is 0.10 to 0.70,

si content defined as the surface layer portion: [ Si ]]₁Si content in the inner layer portion: [ Si ]]₀Difference ([ Si ]]₁-[Si]₀) Has a.DELTA.Si of 1.0 to 4.5 mass%, and

mn content defined as the center position (t/2) of the sheet thickness: [ Mn ]]₀And the average Mn content in a region from the surface of the non-oriented magnetic steel sheet to the depth (1/10) t: [ Mn ]]₁Difference of ([ Mn ]]₀-[Mn]₁) The delta Mn of (A) is 0.01 to 0.40 mass%.

2. The non-oriented electrical steel sheet according to claim 1, wherein Δ Mn is 0.05 to 0.40 mass%.

3. The non-oriented electrical steel sheet according to claim 1 or 2, wherein φ is an orientation distribution function of a plane 1/4 having a depth of a sheet thickness from a surface of the non-oriented electrical steel sheet₂The cross-section of 45 DEG has a texture in which the ratio {100}/{111} of the {100} plane concentration to the {111} plane concentration is 0.55 to 0.90.

According to the present invention, a non-oriented electrical steel sheet having both low and high frequency iron loss and high magnetic flux density can be provided.

Drawings

Fig. 1 is a schematic view showing the structure of a non-oriented electrical steel sheet according to an embodiment of the present invention.

Fig. 2 is a schematic view showing an example of Si content distribution in the plate thickness direction of a non-oriented electrical steel sheet.

FIG. 3 shows the difference (. DELTA.Si) between the Si contents at the surface layer portion and the center of the plate and the iron loss (W)_10/400) A graph of the correlation of (1).

Fig. 4 is a graph showing an example of the concentration distribution of Si and Mn in the plate thickness direction.

FIG. 5 shows the difference in Mn content (Δ Mn) between the surface layer portion and the center of the sheet thickness and the iron loss (W)_10/400) A graph of the correlation of (1).

FIG. 6 shows the total thickness t of the surface layer portion₁Thickness t of non-oriented electromagnetic steel sheetThe ratio of the multilayer to the iron loss (W)_10/400) A graph of the correlation of (1).

Detailed Description

The method for carrying out the present invention will be specifically described below. The following description shows examples of preferred embodiments of the present invention, but the present invention is not limited to these examples.

[ non-oriented Electrical Steel sheet ]

Fig. 1 is a schematic view showing the structure of a non-oriented electrical steel sheet according to an embodiment of the present invention. Fig. 2 is a schematic view showing an example of Si content distribution in the plate thickness direction of a non-oriented electrical steel sheet. In fig. 2, the vertical axis represents the position in the plate thickness direction, 0 represents one surface of the non-oriented magnetic steel plate, and t represents the other surface of the non-oriented magnetic steel plate.

As shown in fig. 1, a non-oriented electrical steel sheet 1 (hereinafter, may be simply referred to as "steel sheet") according to the present invention includes an inner portion 10 and surface portions 20 provided on both sides of the inner portion 10, and the Si content of the surface portions 20 is different from that of the inner portion 10. The Si content may be continuously changed in the thickness direction of the steel sheet (fig. 2 (a)) or may be changed in stages (fig. 2 (b)). When the Si content is changed stepwise, the Si content can be changed in any of 2 or more steps. In the following description, the "surface layer portion" refers to a surface layer portion provided on both surfaces of a non-oriented electrical steel sheet. Therefore, in the present invention, both the 1 st surface layer portion provided on one surface and the 2 nd surface layer portion provided on the other surface of the non-oriented electrical steel sheet satisfy the following conditions.

Here, a portion having an Si content equal to or higher than the average Si content of the total thickness of the non-oriented electrical steel sheet is defined as a "surface portion", and a portion having an Si content smaller than the average Si content of the total thickness of the non-oriented electrical steel sheet is defined as an "inner portion". When a non-oriented electrical steel sheet is produced by coating 2 kinds of steel materials (a high Si material and a low Si material) having different Si contents as described later, a portion made of the high Si material is generally a surface layer portion, and a portion made of the low Si material is an inner layer portion. In this case, the amount of Si in the surface layer portion is substantially constant, and the amount of Si in the inner layer portion is also substantially constant.

[ composition of ingredients ]

First, the composition of the surface portion and the inner portion will be described. In the following description, "%" indicating the content of each element represents "% by mass" unless otherwise specified.

[ composition of the surface layer part ]

First, the composition of the surface layer will be described. In the present invention, both the 1 st surface layer portion provided on one surface and the 2 nd surface layer portion provided on the other surface of the non-oriented electrical steel sheet have the following composition. In general, the composition of the 1 st surface layer portion and the composition of the 2 nd surface layer portion may be the same, but they may be different. Here, the content of the element in the surface layer portion means an average content of the element in 1 surface layer portion.

Si：2.5～7.0％

Si is an element having the effects of increasing the electrical resistance of the steel sheet and reducing eddy current loss. If the Si content in the surface layer portion ([ Si ]]₁) Less than 2.5%, eddy current loss cannot be effectively reduced. Therefore, the Si content in the surface layer portion is 2.5% or more, preferably 3.0% or more, and more preferably more than 3.5%. On the other hand, if the Si content in the surface layer portion exceeds 7.0%, the magnetic flux density decreases due to the decrease in saturation magnetization, and the manufacturability decreases. Therefore, the Si content in the surface layer portion is 7.0% or less, preferably 6.5% or less, and more preferably 6.0% or less. As described above, the Si content in the surface layer portion of 2.5% to 7.0% means that the average Si content in the 1 st surface layer portion is 2.5% to 7.0%, and the average Si content in the 2 nd surface layer portion is 2.5% to 7.0%. The Si content of the 1 st surface layer portion and the Si content of the 2 nd surface layer portion may be the same or different. The same applies to other elements.

Mn: less than 0.50%

When the Mn content exceeds 0.50%, magnetostriction increases, magnetic permeability decreases, iron loss increases, and cost increases. Therefore, the Mn content is set to 0.50% or less. On the other hand, from the above viewpoint, the lower the Mn content, the better, and therefore, the lower limit of the Mn content is not particularly limited, and may be 0%.

The composition of the surface layer further contains a component selected from the group consisting of P: 0.010% -0.100%, Sn: 0.001% -0.10% and Sb: 0.001-0.10% of 1 or more than 2.

P：0.010～0.100％

By adding P, the texture is greatly improved, the magnetic flux density is increased, and the hysteresis loss can be reduced. In the case where P is added, the content of P is set to 0.010% or more in order to obtain the above-described effects. On the other hand, if the P content exceeds 0.100%, the effect is saturated, and the productivity is also degraded. Therefore, the P content is set to 0.100% or less.

Sn：0.001～0.10％

By adding Sn as in P, the texture is greatly improved, the magnetic flux density is increased, and the hysteresis loss can be reduced. In the case where Sn is added, the Sn content is set to 0.001% or more in order to obtain the above-described effects. On the other hand, if the Sn content exceeds 0.10%, the effect is saturated, and this leads to a reduction in the productivity and an increase in the cost. Therefore, the Sn content is set to 0.10% or less.

Sb：0.001～0.10％

Like P and Sn, addition of Sn greatly improves the texture, increases the magnetic flux density, and reduces the hysteresis loss. In the case where Sb is added, the Sb content is set to 0.001% or more in order to obtain the above effects. On the other hand, if the Sb content exceeds 0.10%, the effect is saturated, and this leads to a decrease in the productivity and an increase in the cost. Therefore, the Sb content is 0.10% or less.

In one embodiment of the present invention, the surface layer portion has a composition containing the element, and the remainder is composed of Fe and unavoidable impurities.

In another embodiment of the present invention, the composition of the surface layer portion may further optionally contain the following elements.

C: 0.0090% or less

C is a grain boundary strengthening element, and the elongation of the steel sheet can be improved by containing C. Therefore, C may be contained arbitrarily. However, when C is contained in a large amount, carbide precipitates by aging, resulting in an increase in iron loss. Therefore, when C is contained, the C content is set to 0.0090% or less. On the other hand, the lower limit of the C content is not particularly limited, and may be 0%. However, from the viewpoint of enhancing the effect of adding C, the C content is preferably 0.0015% or more.

S: 0.0050% or less

S is an element which forms sulfides such as MnS and inhibits grain growth. Therefore, by adding S, an increase in eddy current loss due to grain growth in annealing at high temperatures of 1000 ℃. However, if the S content exceeds 0.0050%, solid-solution Mn decreases due to the reaction between S and Mn, and the Mn distribution in the sheet thickness direction varies, so that there is a possibility that the iron loss cannot be efficiently reduced. Therefore, when S is added, the S content is 0.0050% or less. On the other hand, the lower limit of the S content is not particularly limited, and may be 0%. However, from the viewpoint of further reducing the eddy current loss, the S content is preferably 0.0010% or more.

Al: less than 0.10%

Al is an element that forms a nitride and suppresses grain growth. Therefore, by adding Al, an increase in eddy current loss due to grain growth in annealing at high temperatures of 1000 ℃. However, if the Al content exceeds 0.10%, nitrides are excessively formed, and as a result, hysteresis loss increases. Therefore, when Al is added, the Al content is set to 0.10% or less. On the other hand, the lower limit of the Al content is not particularly limited, and may be 0%. However, from the viewpoint of further reducing the eddy current loss, the Al content is preferably 0.0030% or more.

Ti, Nb, V, Zr: less than 0.030%

Ti, Nb, V and Zr are elements that form nitrides or carbides, inhibiting grain growth. Therefore, by adding at least 1 kind selected from Ti, Nb, V, and Zr, it is possible to suppress an increase in eddy current loss due to grain growth in annealing at high temperatures of 1000 ℃. However, if the content of each of these elements exceeds 0.030%, nitrides and/or carbides are excessively formed, and as a result, hysteresis loss increases. Therefore, when these elements are added, the content of each element is 0.030% or less. On the other hand, the lower limit of the content of these elements is not particularly limited, and may be 0%. However, from the viewpoint of further reducing the eddy current loss, the content of each element to be added is preferably 0.0020% or more.

Therefore, the surface layer portion of the non-oriented electrical steel sheet according to one embodiment of the present invention may have the following composition: contains, in mass%, Si: 2.5-7.0%, Mn: 0.50% or less, and is selected from the group consisting of P: 0.010% -0.100%, Sn: 0.001% -0.10% and Sb: 0.001-0.10% of 1 or more than 2 species, C: 0-0.0090%, S: 0-0.0050%, Al: 0 to 0.10%, and at least 1 selected from Ti, Nb, V and Zr: 0 to 0.030% each, and the balance of Fe and inevitable impurities.

[ composition of the inner layer ]

Next, the composition of the inner part will be explained. Here, the content of the element in the inner layer refers to an average content of the element on the inner side of the plate thickness at the boundary between the surface layer and the inner layer, which is determined as a position of the average value of the Si amount.

Si：1.5～5.0％

Si is an element having the effects of increasing the electrical resistance of the steel sheet and reducing eddy current loss. If the Si content in the inner layer portion ([ Si ]]₀) Less than 1.5%, the eddy current loss increases. Therefore, the Si content in the inner layer portion is set to 1.5% or more. On the other hand, if the Si content in the inner layer portion exceeds 5.0%, there arises a problem such as core cracking when a motor core (motor core) produced using a non-oriented electrical steel sheet is pressed. Therefore, the Si content in the inner layer portion is 5.0% or less, preferably 4.0% or less.

Mn：0.01～0.50％

Mn is an element having an effect of suppressing red hot brittleness during hot rolling in the production process of a non-oriented electrical steel sheet. Even in the case of siliconizing, the Mn content in the inner layer portion is substantially the same as the slab stage amount, and therefore, in order to obtain the above-described effects, the Mn content in the inner layer portion is set to 0.01% or more. On the other hand, if the Mn content exceeds 0.50%, the magnetostriction increases, the magnetic permeability decreases, and the iron loss increases, and the cost increases. Therefore, the Mn content is set to 0.50% or less.

The inner layer further contains a component selected from the group consisting of P: 0.010% -0.100%, Sn: 0.001% -0.10% and Sb: 0.001-0.10% of 1 or more than 2.

P：0.010～0.100％

By adding P, the texture is greatly improved, the magnetic flux density is increased, and the hysteresis loss can be reduced. In the case where P is added, the content of P is set to 0.010% or more in order to obtain the above-described effects. On the other hand, if the P content exceeds 0.100%, the effect is saturated, and the productivity is also degraded. Therefore, the P content is set to 0.100% or less. The P content in the inner layer portion may be the same as or different from the P content in the surface layer portion.

Sn：0.001～0.10％

Like P, by adding Sn, the texture is greatly improved, the magnetic flux density is increased, and the hysteresis loss can be reduced. In the case where Sn is added, the Sn content is set to 0.001% or more in order to obtain the above-described effects. On the other hand, if the Sn content exceeds 0.10%, the effect is saturated, and this leads to a reduction in the productivity and an increase in the cost. Therefore, the Sn content is set to 0.10% or less. The Sn content in the inner layer may be the same as or different from the Sn content in the surface layer.

Sb：0.001～0.10％

Like P and Sn, the addition of Sn greatly improves the texture, increases the magnetic flux density, and reduces the hysteresis loss. In the case where Sb is added, the Sb content is set to 0.001% or more in order to obtain the above effects. On the other hand, if the Sb content exceeds 0.10%, the effect is saturated, and this leads to a decrease in the productivity and an increase in the cost. Therefore, the Sb content is 0.10% or less. The Sb content in the inner layer portion may be the same as or different from that in the surface layer portion.

In one embodiment of the present invention, the inner layer portion has a composition containing the element, and the remainder is composed of Fe and unavoidable impurities.

In another embodiment of the present invention, the composition of the inner layer may further optionally contain the following elements.

C: 0.0090% or less

C is a grain boundary strengthening element, and the elongation of the steel sheet can be improved by containing C. Therefore, C may be contained arbitrarily. However, when C is contained in a large amount, carbide precipitates by aging, resulting in an increase in iron loss. Therefore, when C is contained, the C content is set to 0.0090% or less. On the other hand, the lower limit of the C content is not particularly limited, and may be 0%. However, from the viewpoint of enhancing the effect of adding C, the C content is preferably 0.0015% or more.

S: 0.0050% or less

S is an element which forms sulfides such as MnS and inhibits grain growth. Therefore, by adding S, an increase in eddy current loss due to grain growth in annealing at high temperatures of 1000 ℃. However, if the S content exceeds 0.0050%, solid-solution Mn decreases due to the reaction between S and Mn, and the Mn distribution in the sheet thickness direction varies, so that there is a possibility that the iron loss cannot be efficiently reduced. Therefore, when S is added, the S content is 0.0050% or less. On the other hand, the lower limit of the S content is not particularly limited, and may be 0%. However, from the viewpoint of further reducing the eddy current loss, the S content is preferably 0.0010% or more.

Al: less than 0.10%

Al is an element that forms a nitride and suppresses grain growth. Therefore, by adding Al, an increase in eddy current loss due to grain growth in annealing at high temperatures of 1000 ℃. However, if the Al content exceeds 0.10%, nitrides are excessively formed, and as a result, hysteresis loss is increased. Therefore, when Al is added, the Al content is set to 0.10% or less. On the other hand, the lower limit of the Al content is not particularly limited, and may be 0%. However, from the viewpoint of further reducing the eddy current loss, the Al content is preferably 0.0030% or more.

Ti, Nb, V, Zr: less than 0.030%

Ti, Nb, V and Zr are elements that form nitrides or carbides, inhibiting grain growth. Therefore, by adding at least 1 kind selected from Ti, Nb, V, and Zr, it is possible to suppress an increase in eddy current loss due to grain growth in annealing at high temperatures of 1000 ℃. However, if the content of each of these elements exceeds 0.030%, nitrides and/or carbides are excessively formed, and as a result, hysteresis loss increases. Therefore, when these elements are added, the content of each element is 0.030% or less. On the other hand, the lower limit of the content of these elements is not particularly limited, and may be 0%. However, from the viewpoint of further reducing the eddy current loss, the content of each element to be added is preferably 0.0020% or more.

Therefore, the inner layer portion of the non-oriented electrical steel sheet according to one embodiment of the present invention may have the following composition: contains, in mass%, Si: 1.5-5.0%, Mn: 0.01% -0.50%, and is selected from the group consisting of P: 0.010% -0.100%, Sn: 0.001% -0.10% and Sb: 0.001-0.10% of 1 or more than 2, C: 0-0.0090%, S: 0-0.0050%, Al: 0 to 0.10%, and at least 1 selected from Ti, Nb, V and Zr: 0 to 0.030% each, and the balance of Fe and inevitable impurities.

[ sheet thickness ]

t：0.01～0.35mm

Thickness of non-oriented electrical steel sheet: when t is less than 0.01mm, cold rolling and annealing in the production of the non-oriented electrical steel sheet become difficult, and the cost significantly increases. Therefore, t is 0.01mm or more, preferably 0.05mm or more. On the other hand, when t exceeds 0.35mm, the eddy current loss increases and the total iron loss increases. Therefore, t is 0.35mm or less, preferably 0.30mm or less.

[ difference in Si content ]

In the present invention, the Si content [ Si ] defined as the surface layer portion]₁And Si content in the inner layer [ Si ]]₀Difference ([ Si ]]₁-[Si]₀) The content of [ Delta ] Si is 1.0 to 4.5 mass%. The reason for this will be explained below.

In order to examine the influence of the difference in Si content (Δ Si) between the surface portion and the inner portion on the magnetic properties, non-oriented electrical steel sheets having various Δ Si were produced in the following order, and the magnetic properties thereof were evaluated.

First, a catalyst having a composition containing Si: 2.0%, Mn: 0.10%, Sn: 0.04% and the balance of Fe and inevitable impurities, and hot rolling the steel slab to obtain a hot-rolled steel sheet. The hot-rolled steel sheet was subjected to hot-rolled sheet annealing at 950 ℃ × 30s, and then cold-rolled to have a sheet thickness t: 0.20mm cold rolled steel sheet. Thereafter, in SiCl₄The cold-rolled steel sheet was subjected to siliconizing treatment in an atmosphere at 1200 ℃ and then diffusion treatment in a nitrogen atmosphere at 1200 ℃ to be cooled at 10 ℃/s, thereby obtaining a non-oriented electrical steel sheet. The composition of the surface layer portion of the obtained non-oriented electrical steel sheet was the same for both surfaces.

From the obtained non-oriented electrical steel sheet, test pieces each having a width of 30mm and a length of 180mm were collected, and subjected to an Epstein (Epstein) test to evaluate magnetic properties. In the epstein test, an L-direction test piece taken so that the longitudinal direction of the test piece becomes the rolling direction (L direction) and a C-direction test piece taken so that the longitudinal direction of the test piece becomes the rolling orthogonal direction (C direction) are used in equal amounts, and the average value of the magnetic properties in the L direction and the C direction is evaluated.

FIG. 3 shows the difference ([ Si ] in Si content between the surface layer portion and the inner layer portion]₁-[Si]₀) Δ Si (mass%) of (A) and iron loss W at 1.0T and 400Hz_10/400(W/kg). From the results, it is understood that when Δ Si is 1.0 mass% to 4.5 mass%, the iron loss is greatly reduced. This is considered to be based on the following reason. That is, when the Si amount in the surface layer portion is higher than that in the inner layer portion, the magnetic permeability of the surface layer portion becomes higher than that of the inner layer portion. As a result, the magnetic flux is concentrated in the surface layer portion, and the eddy current loss is reduced. However, if Δ Si is too large, the difference in lattice constant and the difference in magnetostriction between the surface layer portion and the inner layer portion increase. As a result, stress applied when magnetizing the steel sheet increases, and hysteresis loss increases. For the above reasons, Δ Si is set to 1.0 to 4.5 mass% in the present application. Δ Si is preferably 1.5 mass% or more. Further, Δ Si is preferably 4.0 mass% or less.

[ difference in Mn content ]

In the present invention, will be defined asMn content [ Mn ] in the center position (t/2) of the sheet thickness]₀And the average Mn content [ Mn ] in the region from the surface of the non-oriented magnetic steel sheet to the depth (1/10) t]₁Difference of ([ Mn ]]₀-[Mn]₁) The Delta Mn of (A) is 0.01 to 0.4 mass%. Here, [ Mn ]]₁The concentration distribution of Mn in the plate thickness direction of the non-oriented electrical steel sheet is obtained by an Electron Probe Microanalyzer (EPMA), and calculated from the obtained concentration distribution. The reason why Δ Mn is within the above range will be described below.

The present inventors have made studies to achieve further reduction in iron loss of a non-oriented electrical steel sheet, and as a result, have found that variation occurs in iron loss of a non-oriented electrical steel sheet produced by a siliconizing method. The reason for this is examined, and it is found that the average Mn content of the surface portion (region from the surface to the depth (1/10) t) of the non-oriented electrical steel sheet is smaller than the Mn content of the center position of the sheet thickness, and that the difference in Mn content between the surface portion and the center position of the sheet thickness differs depending on the non-oriented electrical steel sheet.

The reason why the Mn content in the surface portion is reduced is considered to be that the atmosphere during the siliconizing treatment contains chlorine gas. That is, the atmosphere of the siliconizing treatment contains chlorine gas originally contained in the raw material gas and chlorine gas generated by the reaction of silicon tetrachloride used in the siliconizing treatment and Fe in the steel. It is considered that the chlorine gas reacts with Mn present in the surface layer of the steel sheet to form MnCl₂And volatilizes to thereby lower the Mn content of the surface portion.

Therefore, in order to examine the influence of the difference (Δ Mn) in the Mn content between the surface portion and the center position of the sheet thickness on the magnetic properties, non-oriented electrical steel sheets having various Δ Mn were produced in the following order, and the magnetic properties thereof were evaluated.

First, a catalyst having a composition containing Si: 2.5%, Mn: 0.50%, Sn: a steel slab having a composition consisting of 0.04% and the balance of Fe and inevitable impurities is hot-rolled to obtain a hot-rolled steel sheet. The hot-rolled steel sheet was subjected to hot-rolled sheet annealing at 950 ℃ × 30s, and then cold-rolled to have a sheet thickness t: 0.20mm cold rolled steel sheet. Thereafter, in SiCl₄The cold-rolled steel sheet is siliconized in an atmosphere at various temperatures, and then,the resulting film was subjected to diffusion treatment in a nitrogen atmosphere at 1200 ℃ and cooled at 10 ℃/s to obtain a non-oriented electrical steel sheet. The Si content in the surface layer portion of the obtained non-oriented electrical steel sheet was 4.0%, and the difference Δ Si between the Si contents in the inner layer portion and the surface layer portion was 1.5%. The surface layer portion has the same composition on both sides.

As an example, fig. 4 shows the concentration distribution of Si and Mn in a non-oriented electrical steel sheet having Δ Mn of 0.10% and Δ Si of 1.5%. The above concentration distribution was measured by an Electron Probe Microanalyzer (EPMA). As is clear from fig. 4, the obtained non-oriented electrical steel sheet had a surface portion with a lower Mn content than the center of the sheet thickness. This tendency is also observed in other non-oriented electrical steel sheets.

Next, test pieces having a width of 30mm and a length of 180mm were collected from the obtained non-oriented electrical steel sheet, and subjected to an epstein test to evaluate magnetic properties. In the epstein test, an L-direction test piece taken so that the longitudinal direction of the test piece becomes the rolling direction (L direction) and a C-direction test piece taken so that the longitudinal direction of the test piece becomes the rolling orthogonal direction (C direction) are used in equal amounts, and the average value of the magnetic properties in the L direction and the C direction is evaluated.

FIG. 5 shows the core loss W at 1.0T and 400Hz and Δ Mn_10/400(W/kg). Here,. DELTA.Mn is defined as the Mn content [ Mn ] of the plate thickness center position (t/2)]₀And an average Mn content [ Mn ] in an inner region of 10% or less of depth t from the surface of the non-oriented electrical steel sheet]₁Difference of ([ Mn ]]₀-[Mn]₁)。

From the results shown in fig. 5, it is understood that when Δ Mn is 0.01 to 0.40 mass%, the iron loss is greatly reduced. This is considered to be based on the following reason. That is, when the Mn content in the surface portion is lower than the sheet thickness center position, the magnetic permeability of the surface portion becomes higher than the sheet thickness center position. As a result, the magnetic flux is concentrated in the surface layer portion, and the eddy current loss is reduced. However, if Δ Mn is too large, the difference in lattice constant between the surface portion and the center position of the sheet thickness increases. As a result, stress generated in the steel sheet increases, and hysteresis loss increases. For the above reasons, in the present application, Δ Mn is set to 0.01 to 0.40 mass%. Δ Mn is preferably 0.05 mass% or more. Further, Δ Mn is preferably 0.35 mass% or less.

[ ratio of layers ]

To the total thickness t of the surface layer part₁The ratio (t) of the thickness (t) of the non-oriented magnetic steel sheet to the thickness (t) of the non-oriented magnetic steel sheet₁The influence of/t) (hereinafter, sometimes referred to as "lamination ratio") on magnetic properties was examined, and non-oriented electrical steel sheets having various lamination ratios of 0.05 to 0.8 were produced in the following order, and their magnetic properties were evaluated. Here, the "total thickness of the surface layer portions" refers to the sum of the thicknesses of the surface layer portions provided on both sides of the non-oriented electrical steel sheet.

First, a catalyst having a composition containing Si: 2.0%, Mn: 0.18%, Sn: a steel slab having a composition consisting of 0.04% and the balance of Fe and inevitable impurities is hot-rolled to obtain a hot-rolled steel sheet. The hot-rolled steel sheet was subjected to hot-rolled sheet annealing at 950 ℃ × 30s, and then cold-rolled to have a sheet thickness t: 0.20mm cold rolled steel sheet. Thereafter, in SiCl₄The cold-rolled steel sheet was subjected to siliconizing treatment at 1280 ℃ in an atmosphere, and then subjected to diffusion treatment in a nitrogen atmosphere at 1200 ℃ to be cooled at 10 ℃/s, thereby obtaining a non-oriented electrical steel sheet.

The surface layer portion of the obtained non-oriented electrical steel sheet had an Si content of 4.0%, Δ Si of 2.0%, and Δ Mn of 0.10. The surface layer portion has the same composition on both sides. By controlling diffusion treatment time and SiCl₄The flow rate of the gas controls the Δ Si and the multilayer ratio. For example, if the diffusion processing time is shortened, Δ Si increases. In addition, if SiCl is added₄The flow rate of the gas increases the multilayer ratio.

Next, test pieces having a width of 30mm and a length of 180mm were collected from the obtained non-oriented electrical steel sheet, and subjected to an epstein test to evaluate magnetic properties. In the epstein test, an L-direction test piece taken so that the longitudinal direction of the test piece becomes the rolling direction (L direction) and a C-direction test piece taken so that the longitudinal direction of the test piece becomes the rolling orthogonal direction (C direction) are used in equal amounts, and the average value of the magnetic properties in the L direction and the C direction is evaluated.

FIG. 6 shows the multilayer ratio t₁Core loss W at/T and 1.0T, 400Hz_10/400(W/kg). From the results, it is found that the iron loss is significantly reduced when the multilayer ratio is 0.10 to 0.70. This reduction in iron loss is considered to be caused by the following reasons. First, when the multilayer ratio is less than 0.10, the ratio of the surface layer portion having a high resistance is low, and thus the eddy current concentrated in the surface layer portion cannot be effectively reduced. On the other hand, when the multilayer ratio is higher than 0.70, the difference in the magnetic permeability between the surface layer portion and the inner layer portion is small, and therefore, the magnetic flux penetrates into the inner layer portion, and eddy current loss also occurs from the inner layer portion. Therefore, the iron loss can be reduced by setting the multilayer ratio to 0.10 to 0.70. For the above reasons, in the present application, the multilayer ratio is set to 0.10 to 0.70. The multilayer ratio is preferably 0.20 or more. The multilayer ratio is preferably 0.60 or less.

[ texture ]

Addition of an appropriate amount of at least 1 of P, Sn and Sb as segregation elements increases the {100} planes of the non-oriented electrical steel sheet and decreases the {111} planes, thereby facilitating magnetization in the plane of the non-oriented electrical steel sheet. As a result, the magnetic flux density is increased and the hysteresis loss is further reduced. Therefore, from the viewpoint of further improving the magnetic properties, the ratio {100}/{111} of the {100} plane concentration to the {111} plane concentration is preferably 0.55 or more. Further, if {100}/{111} is excessively large, the workability of the core may be deteriorated. Therefore, from the viewpoint of improving workability, {100}/{111} is preferably 0.90 or less. Here, {100}/{111} is defined as: orientation Distribution Function (ODF) phi of 1/4 plane with depth of plate thickness from surface of non-oriented magnetic steel plate₂The ratio of the {100} plane concentration to the {111} plane concentration in the 45 ° cross section {100}/{111 }.

[ production method ]

The non-oriented electrical steel sheet of the present invention is not particularly limited, and can be produced by any method. Hereinafter, an example of the method for producing a non-oriented electrical steel sheet according to the present invention will be described.

(siliconizing diffusion treatment method)

In one embodiment of the present invention, the non-oriented electrical steel sheet may be produced by a siliconizing diffusion treatment. Specifically, first, a steel sheet having a composition containing Si, Mn, and 1 or more selected from P, Sn and Sb, with the remainder consisting of Fe and unavoidable impurities, is subjected to a siliconizing treatment. In the siliconizing treatment, Si is deposited on the surface of the steel sheet by, for example, a chemical vapor deposition method (CVD method). In the siliconizing treatment by the CVD method, an Si-containing gas such as silicon tetrachloride is used as an Si source. The siliconizing treatment is carried out at a predetermined siliconizing treatment temperature for a predetermined siliconizing treatment time. The steel sheet used in the siliconizing treatment may be a normal steel sheet having a substantially uniform composition in the thickness direction.

After the siliconizing treatment, the supply of the Si-containing gas was stopped, and the diffusion treatment was performed in a nitrogen atmosphere. In the diffusion treatment, the siliconized steel sheet may be kept at a predetermined diffusion treatment temperature for a predetermined diffusion treatment time. By the diffusion treatment, Si deposited on the surface of the steel sheet diffuses into the steel sheet.

By performing the above siliconizing diffusion treatment, the Si content in the surface layer portion of the steel sheet can be increased. The non-oriented electrical steel sheet obtained by the siliconizing diffusion treatment has, for example, a Si content distribution as shown in fig. 2 (a).

On the other hand, the Mn content in the surface layer portion of the steel sheet is reduced by the above siliconizing treatment. The reason is considered to be that: as described above, Mn present in the surface layer portion of the steel sheet reacts with chlorine from the gas used for the siliconizing treatment to volatilize. Further, Mn is diffused from the inner layer portion to the surface layer portion by performing diffusion treatment after the Mn content in the surface layer portion is reduced by siliconizing treatment.

The above siliconizing diffusion treatment can be basically carried out according to a conventional method. In this case, the amount of Si deposited, the treatment temperature, and the treatment time in the siliconizing treatment and the diffusion treatment may be controlled so that the Si content, Δ Si, Δ Mn, and the multilayer ratio in the surface layer portion of the finally obtained non-oriented electrical steel sheet become desired values.

From the viewpoint of shortening the treatment time, the above siliconizing treatment may be performed at a siliconizing treatment temperature of 1250 ℃ or higher. However, when the siliconizing temperature is 1250 ℃ or higher, the siliconizing is performed at a temperature close to the melting point of the steel sheet, and therefore the steel sheet may melt and break. Therefore, from the viewpoint of preventing the steel sheet from breaking, it is preferable to set the siliconizing treatment temperature to less than 1250 ℃. On the other hand, when the siliconizing treatment temperature is too low, the productivity is lowered. Therefore, from the viewpoint of improving productivity, the siliconizing treatment temperature is preferably set to 1000 ℃.

In the production conditions of the non-oriented electrical steel sheet of the present invention, the diffusion rate of Si is higher than the diffusion rate of Mn. This is because the diffusion coefficient of Si is larger than that of Mn, and the concentration gradient of Si in the thickness direction is also larger than that of Mn. Therefore, the diffusion treatment temperature and the diffusion treatment time may be adjusted so that a desired Δ Si to multilayer ratio can be obtained. In this case, if the diffusion treatment temperature is too low, the productivity is lowered. Therefore, from the viewpoint of improving productivity, the diffusion treatment temperature is preferably 880 ℃ or higher. On the other hand, when the diffusion treatment temperature is too close to the melting point of the steel sheet, the steel sheet may melt and break. Therefore, from the viewpoint of preventing the fracture of the steel sheet, the diffusion treatment temperature is preferably less than 1250 ℃.

On the other hand, even in the cooling process after the end of the diffusion treatment, the diffusion of the element occurs in a relatively high temperature region. In particular, in the non-oriented electrical steel sheet of the present invention, it is necessary to control the Mn content and Δ Mn to be in the range of 1-bit or more lower than the Si content and Δ Si, and therefore, in order to obtain a desired Δ Mn, it is important to control the cooling rate after the diffusion treatment.

Specifically, in the cooling process after the diffusion treatment, the cooling rate in the temperature range from the diffusion treatment temperature to 880 ℃ is set to 10 ℃/s or more. If the cooling rate is less than 10 ℃/s, the time for which the steel sheet stays in the high temperature region during cooling becomes long, and thus Mn diffuses significantly from the inner layer portion to the surface layer portion. As a result, it is difficult to secure the desired Δ Mn. In particular, in the case where the siliconizing treatment is performed at a relatively low siliconizing treatment temperature of less than 1250 ℃, the cooling rate from the diffusion treatment temperature to 880 ℃ is set to 17 ℃/s or more in order to achieve a desired Δ Mn and suppress Mn removal at the surface layer portion in the siliconizing treatment. On the other hand, if the cooling rate is too high, cooling strain may be generated, and as a result, hysteresis loss may increase. Therefore, from the viewpoint of suppressing an increase in hysteresis loss due to cooling strain, the cooling rate from the diffusion treatment temperature to 880 ℃ is preferably set to 30 ℃/s or less.

[ coating method ]

In addition, as another production method, a method of coating a steel material having a different Si content and Mn content is exemplified. The composition of the steel material can be adjusted by, for example, blowing materials different in composition in a converter and degassing the molten steel.

The coating method is not particularly limited, and for example, billets having different Si contents and Mn contents may be prepared, and the billet for the surface layer portion may be bonded to both surfaces of the billet for the inner layer portion at a thickness such that the final multilayer ratio becomes a desired value, and then rolled. The rolling may be performed by, for example, 1 or 2 or more types selected from hot rolling, warm rolling, and cold rolling. In general, a combination of hot rolling and subsequent warm rolling, or a combination of hot rolling and subsequent cold rolling is preferable. The hot rolled sheet annealing is preferably performed after the above hot rolling. The warm rolling and the cold rolling may be performed 2 or more times with intermediate annealing interposed therebetween. The finishing temperature and the winding temperature in the hot rolling are not particularly limited, and may be determined by a conventional method. The final annealing is performed after the rolling. The non-oriented electrical steel sheet obtained by coating the steel materials having different Si contents has, for example, a Si content distribution as shown in fig. 2 (b).

Examples

In order to confirm the effects of the present invention, non-oriented electrical steel sheets were produced in the following procedure, and their magnetic properties were evaluated.

First, slabs having the composition shown in table 1 were prepared. The composition of the billet is adjusted by degassing after blowing in a converter. As described later, the composition of the non-oriented electrical steel sheet finally obtained at the center of the sheet thickness is the same as that of the steel slab used.

Next, the slab was heated at 1140 ℃ for 1hr, and then hot-rolled to obtain a hot-rolled steel sheet having a thickness of 2 mm. The hot rolling finishing temperature in the hot rolling was set to 800 ℃. The hot-rolled steel sheet was coiled at a coiling temperature of 610 ℃ and then annealed at 900 ℃x30 s. And then acid pickling and cold rolling are performed.

Then, the cold-rolled steel sheet is subjected to a siliconizing diffusion treatment to obtain a non-oriented electrical steel sheet. In the above siliconizing diffusion treatment, firstly, SiCl is added₄In the atmosphere, the siliconizing treatment was performed for the siliconizing treatment time and at the siliconizing treatment temperature shown in table 1. Then, in N₂Diffusion treatment was performed at a diffusion treatment temperature of 1200 ℃ in an atmosphere, and then cooling was performed. The average cooling rate in the temperature region from the diffusion treatment temperature to 880 ℃ in the above cooling is shown in table 1.

Further, the non-oriented electrical steel sheet of example No.47 was produced by a cladding method instead of the siliconizing treatment. Specifically, a surface layer portion billet having a composition shown in table 1 as No.47a and an inner layer portion billet having a composition concentration shown in table 47b were prepared. The surface layer portion billet and the inner layer portion billet were both rough-rolled to a thickness of a final multilayer ratio of 0.25. Next, the surface layer portion billet is welded to both surfaces of the inner layer portion billet to produce a clad slab. The above welding is performed in vacuum using an electron beam. Thereafter, the coated slab was heated at 1140 ℃ for 1hr, and then hot-rolled to obtain a hot-rolled steel sheet having a thickness of 2 mm. The hot rolling finishing temperature in the hot rolling was set to 800 ℃. The hot-rolled steel sheet was coiled at a coiling temperature of 610 ℃ and then annealed at 900 ℃x30 s. Then, pickling and cold rolling were performed to make the thickness 0.20 mm. In N₂：H₂80: the cold-rolled steel sheet was subjected to finish annealing at 1100 ℃ for 30 seconds in an atmosphere of 20 ℃ to obtain a non-oriented electrical steel sheet.

(amount of Si)

The obtained non-oriented electrical steel sheet was embedded in a carbon mold, and the Si content distribution in the cross section in the sheet thickness direction was measured with an Electron Probe microanalyzer (Electron Probe Micro Analyzer). An average value of the Si content in the total thickness of the steel sheet is calculated, and a portion having a higher Si concentration than the average value is defined as a surface layer portion, and a portion having a lower Si concentration than the average value is defined as an inner layer portion. From the obtained results, the average Si content [ Si ] of the surface layer portion was obtained]₁And Si content in the inner layer [ Si ]]₀. The content of Si in the inner layer [ Si ]]₀The Si content is the same as that of the raw material before siliconizing treatment. From the [ Si ] obtained]₁And [ Si]₀To calculate a definition of ([ Si ]]₁-[Si]₀) Δ Si of (a). In the measurement using EPMA, the Si content is calculated from the strength by performing measurement based on the measurement result of the steel slab before siliconizing, the Si content of which is known.

(amount of Mn)

The measurement using EPMA was performed in the same procedure as the measurement of Δ Si described above, and the Mn content distribution in the cross section in the sheet thickness direction was obtained. From the obtained results, the following values were calculated.

Average Mn content of the surface layer portion

Average Mn content of inner layer portion

Mn content at the center of the sheet thickness (t/2): [ Mn ]]₀

Average Mn content in a region from the steel sheet surface to the position of depth (1/10) t: [ Mn ]]₁

By the [ Mn ] obtained]₁And [ Mn]₀The value was calculated as ([ Mn)]₁-[Mn]₀) Δ Mn of (a). Mn content [ Mn ] in the center of the sheet thickness]₀The Mn content of the steel plate blank before siliconizing treatment is the same as that of the steel plate blank before siliconizing treatment. As described above, the surface layer portion and the inner layer portion are defined as a portion (surface layer portion) having an Si concentration higher than the average Si content of the total sheet thickness and a portion (inner layer portion) having an Si concentration lower than the average Si content.

The measured Si content and Mn content of the non-oriented electrical steel sheet after the siliconizing treatment are shown in table 2. Note that, with respect to elements other than Si and Mn, the concentration does not change by the siliconizing treatment. That is, the contents of elements other than Si and Mn in the surface layer portion and the inner layer portion of the obtained non-oriented electrical steel sheet are the same as the contents in the steel slab used.

The thickness t of the finally obtained non-oriented electrical steel sheet is defined as the total thickness t of the front and back surfaces of the surface portion determined by the above-mentioned Si distribution₁A multilayer ratio t to the above ratio t₁The value of/t is shown in Table 2.

(magnetic Properties)

Next, the obtained non-oriented electrical steel sheet was measured for magnetic properties. The above measurement was carried out in accordance with JIS C2550-1 using a 25cm Epstein circle. As the magnetic properties, the iron loss W at 1.0T and 400Hz was measured_10/400(W/kg), 1.0T, and core loss W at 1kHz_10/1k(W/kg), 1.0T, and an iron loss W at 2kHz_10/2k(W/kg) and a magnetic flux density B at a magnetic field strength of 5000A/m₅₀. The measurement results are shown in Table 3.

The magnetic properties required for the non-oriented electrical steel sheet vary depending on the sheet thickness and the Si content. Therefore, when the iron loss at each frequency satisfies the conditions specified by the following expressions (1) to (3), it is determined that the iron loss at the frequency is good.

W_10/400≤19-0.3/t-0.6[Si]…(1)

W_10/1k≤55-0.4/t-2[Si]…(2)

W_10/2k≤140-0.9/t-5[Si]…(3)

Here, the first and second liquid crystal display panels are,

t: the thickness of the board,

t₁: total thickness of surface layer part

[ Si ]: average Si content of the total sheet thickness

The frequency range in which the iron loss is required to be low differs depending on the use conditions of the motor, but in the present invention, the high-frequency iron loss of the final non-oriented electrical steel sheet is also evaluated based on the following criteria.

When the conditions of the above formulas (1) to (3) are not satisfied: general no (x)

When the conditions of the above equations (1) and (2) are satisfied: good (∘)

When the conditions of the above equations (1) to (3) are satisfied: excellent (verygood)

(texture)

In order to examine the texture of the obtained non-oriented electrical steel sheet, the orientation distribution function φ of the 1/4 plane having a depth of the sheet thickness from the surface of the non-oriented electrical steel sheet was measured₂The ratio of the {100} plane concentration to the {111} plane concentration in the 45 ° cross section {100}/{111 }. Specifically, the grain-oriented electrical steel sheet was chemically polished from the surface to a sheet thickness of 1/4, and subjected to ODF (Orientation Distribution Function) analysis using X-rays. The measurement results are also shown in Table 1.

As is clear from the results shown in table 1, the non-oriented electrical steel sheet satisfying the conditions of the present invention has excellent magnetic properties. Specifically, the iron loss was evaluated as good (. largecircle.) or excellent (. circleincircle.), and the magnetic flux density B was evaluated as₅₀Is 1.59T or more. In comparative example 6, the steel sheet was broken during annealing during the production, and the subsequent evaluation was not possible. In comparative examples 34 to 36, the steel sheet broke during cold rolling, and therefore, the following evaluation was not possible.

[ Table 1]

TABLE 1

Cooling rate in temperature range from diffusion treatment temperature (1200 ℃) to 880 ℃

[ Table 2]

TABLE 2

[ Table 3]

TABLE 3

Description of the symbols

1 non-oriented electromagnetic steel sheet

10 inner layer part

20 surface layer part