JP2020143314A - Directional electromagnetic steel plate having good iron loss and producing method thereof - Google Patents

Abstract

To provide a directional electromagnetic steel plate, in which grooves for a purpose of magnetic domain control are formed on the surface of the steel plate, which has a sufficiently high magnetic flux density after the groove formation, and has low iron loss.SOLUTION: There is provided a steel plate, which has a chemical composition of Si:2.00 to 7.00% of mass% and Fe and impurities as balances, and has grooves with a constant interval, which is a direction intersecting the rolling direction and whose plate a groove depth direction is a thickness direction. When the magnetic field density when the steel sheet is excited at 800(A/m) is defined at B8 (T), B8 (T) is defined as B8n(T) in a case where the grooves are removed from the steel plate, the groove depth is defined at d (μm), the interval between the grooves is defined at p (mm), and an angel and the angle between the grooves and the direction perpendicular to rolling is defined at θ (°), the directional electromagnetic steel plate satisfies the following formula (1) and has a groove width W of 20 to 100 μm: (1) B8n+{0.1428+0.0032*d-(0.0722+0.0024*d)*B8n}*(3/p)*e^(-qθ)≥1.87 (provided that B8n≥1.90(T), 0≤θ≤30°, 2≤p≤30, and q=0.075).SELECTED DRAWING: Figure 2

Description

The present invention relates to a grain-oriented electrical steel sheet that is subjected to magnetic domain subdivision processing by grooves. In particular, by defining the groove depth, the magnetic flux density after groove formation is sufficiently high and the grain-oriented electrical steel sheet has low iron loss. , And its manufacturing method.

One-way electrical steel sheets are required to reduce iron loss from the viewpoint of energy saving. In particular, for wound iron core transformers, Patent Document 1 discloses a means for maintaining the magnetic domain subdivision effect even after strain removal annealing by artificially introducing a groove. In this method, a groove is introduced into the steel sheet by a mechanical means such as a tooth profile roll to subdivide the magnetic domain.

In addition to the above mechanical means, there are techniques disclosed in Patent Documents 2 and 3 as means by etching, but in each case, a groove is introduced to obtain a magnetic domain subdivision effect even after strain removal annealing. It is a technology similar to mechanical means in that it is exerted.

Japanese Unexamined Patent Publication No. 1-252726 Japanese Unexamined Patent Publication No. 62-179105 Japanese Unexamined Patent Publication No. 4-88121

It is known that in grain-oriented electrical steel sheets, iron loss is reduced by forming grooves in a direction intersecting the rolling direction and controlling magnetic domains.

Magnetic domain control by groove formation has the advantage of improving iron loss (reducing iron loss) by forming grooves, but on the other hand, there is a problem that the magnetic flux density decreases due to the presence of grooves. Practically, it is adjusted within an allowable range of decrease in magnetic flux density, but a clear design guideline has not been established, and it cannot be said that the optimum formation conditions have been selected.

The present inventor investigated the relationship between the groove depth and the magnetic properties of various materials, and found that the relationship between the groove depth and the iron loss improving effect is the optimum value of the groove depth that changes according to the magnetic flux density to be excited. Was found to exist. For example, in a specific test material, the optimum value of the groove depth at 1.7 T excitation was about 30 μm, while the optimum value of the groove depth at 1.5 T excitation exceeded 35 μm.

From these findings, the present inventor has come up with the idea of determining the optimum value of the groove depth formed for magnetic domain control in relation to the magnetic characteristics of the steel sheet, particularly the magnetic flux density. Then, not only the depth of the groove but also the arrangement of the grooves (the distance between the grooves and the angle formed by the groove and the rolling direction of the steel sheet) are set to the magnetic flux density B8 (T) when the steel sheet is excited at 800 (A / m). Succeeded in optimizing in relation to.

The present invention has been achieved based on the above findings. In a grain-oriented electrical steel sheet in which grooves are formed on the surface of the steel sheet for the purpose of controlling magnetic domains, the magnetic flux density after the groove formation is sufficiently high and low iron. Direction of loss The purpose is to obtain electrical steel sheets.

ただし、
0≦θ≦30°
2≦p≦30
q=0.075
である。
[４]
前記溝形成工程が、前記冷間圧延工程後かつ前記脱炭焼鈍工程前であることを特徴とする項目[２]または[３]に記載の方向性電磁鋼板の製造方法。
[５]
前記溝形成工程が、張力被膜形成工程後であることを特徴とする項目[２]または[３]に記載の方向性電磁鋼板の製造方法。 The present invention provides the following aspects.
[1]
Grooves containing Si: 2.00 to 7.00% by mass, having a chemical composition in which the balance is Fe and impurities, and having a direction intersecting the rolling direction and a groove depth direction being the plate thickness direction. It is a steel plate held at regular intervals and
The magnetic flux density when the steel sheet is excited at 800 (A / m) is defined as B8 (T), the B8 (T) of the steel sheet from which the grooves are removed is defined as B8n (T), and the depth of the grooves is defined as B8n (T). When defined as d (μm), the distance between the grooves is defined as p (mm), and the angle formed by the grooves in the direction perpendicular to rolling is defined as θ (°), the following equation (1) is satisfied, and the groove Directional electromagnetic steel sheet with width W of 20 to 100 μm
B8n + {0.1428 + 0.0032 * d- (0.0722 + 0.0024 * d) * B8n} * (3 / p) * e ^ (-qθ) ≧ 1.87… (1)
However, B8n ≥ 1.90 (T)
0 ≤ θ ≤ 30 °
2 ≤ p ≤ 30
q = 0.075
Is.
[2]
A method for manufacturing a directional electromagnetic steel plate having a casting process, a hot rolling process, a cold rolling process, a decarburization annealing process, and a finish annealing process. After the cold rolling process, the direction intersects the rolling direction and the groove depth. Including a groove forming step of forming grooves whose vertical direction is the thickness direction at regular intervals.
The magnetic flux density when the steel sheet is excited at 800 (A / m) is defined as B8 (T), and the groove depth d (μm) is defined as the target B8 (T) of the groove forming material and the groove unformed material. A method for manufacturing a directional electromagnetic steel sheet, which comprises determining from B8 (T).
[3]
The target B8 (T) of the groove forming material is defined as B8m (T), the B8 (T) of the ungrooved material is defined as B8n (T), the interval between the grooves is p (mm), and the grooves are rolled. When the angle formed in the perpendicular direction is defined as θ (°), the groove depth d (μm) formed in the groove forming step is calculated according to the following equation (2), and the width of the groove is characterized. The method for manufacturing a directional electromagnetic steel sheet according to item [2], wherein W is 20 to 100 μm.

However,
0 ≤ θ ≤ 30 °
2 ≤ p ≤ 30
q = 0.075
Is.
[4]
The method for producing a grain-oriented electrical steel sheet according to item [2] or [3], wherein the groove forming step is after the cold rolling step and before the decarburization annealing step.
[5]
The method for manufacturing a grain-oriented electrical steel sheet according to item [2] or [3], wherein the groove forming step is after the tension film forming step.

According to the present invention, when a groove is formed in a product plate of a grain-oriented electrical steel sheet (a grain-oriented electrical steel sheet having a tension film formed) to control a magnetic domain, the magnetic flux density after the groove formation is sufficiently high and the iron loss is low. A grain-oriented electrical steel sheet can be obtained.

FIG. 1 is a chart in which experimental values of the amount of decrease in magnetic flux density with respect to the groove depth d are arranged. FIG. 2 is a chart in which the magnetic flux density B8 before groove formation and the amount of decrease in magnetic flux density ΔB8 due to groove formation are arranged.

The directional electromagnetic steel sheet according to one aspect of the present invention has a chemical composition containing Si: 2.00 to 7.00% in mass% and the balance being Fe and impurities, and has a steel sheet rolling direction on the surface of the steel sheet. Magnetic zone control is performed by having grooves at regular intervals in which the intersecting direction and the groove depth direction are the plate thickness direction.
The groove depth d (μm) according to one aspect of the present invention satisfies the following equation (1).
B8n + {0.1428 + 0.0032 * d- (0.0722 + 0.0024 * d) * B8n} * (3 / p) * e ^ (-qθ) ≧ 1.87… (1)
Here, B8n (T) is the magnetic flux density when the steel sheet from which the grooves have been removed is excited at 800 (A / m). Further, θ is an angle (°) at which the groove intersects the rolling perpendicular direction, and θ = 0 (°) when the groove is orthogonal to the rolling direction (in the width direction of the steel sheet). p is the groove spacing (mm) and q is the coefficient, satisfying the following.
2 ≤ p ≤ 30
q = 0.075
The groove forms a reflux magnetic domain extending in the groove direction, and the 180 ° magnetic domain that existed before the formation of the groove is subdivided, which has the effect of reducing iron loss. In this respect, the direction of the groove is preferably a direction orthogonal to the rolling direction of the steel sheet, but the direction of the groove may be inclined to some extent in the rolling direction, and θ should be selected between 0 and 30 °. Can be done.
Here, q is defined as follows. First, a large number of samples in which B8 before groove formation was between 1.90T and 1.96T were prepared, and a groove with d = 15 μm was formed in this sample. However, θ was set to 0 to 30 °. After straining and annealing the sample after forming these grooves, B8 was measured again, and this was defined as B8 m (θ). Further, after removing the grooves of these samples, removing strain and annealing, B8 was measured again to obtain B8n (θ).
ΔB8 (θ) = B8n (θ) -B8m (θ). In addition, it is shown that it is a function of θ that (θ) is attached to each.
Next, ΔB8 (θ) normalized by ΔB8 (0) was plotted against θ, and this plot was fitted with e ^ (-qθ) so that it became 1 at θ = 0 to determine q. Where q was 0.075.
The groove depth d should satisfy equation (1), but the groove width W can be selected from 20 μm to 100 μm. Here, the width W of the groove is the average width of the cross section observed at an angle forming 90 ° with the groove formation direction, and for the definition of the average width, the area occupied by the cross-sectional shape of the groove is divided by the maximum depth of the groove. It is a value. For example, if the shape of the groove cross section is rectangular, the width of the groove on the steel plate surface is W as it is, and if the shape of the groove cross section is triangular, 1/2 of the width of the groove on the steel plate surface is W.
Here, if W is too small, the iron loss reduction effect by magnetic domain control cannot be obtained, and if W is too large, it becomes difficult to avoid a decrease in B8 even if the groove depth is controlled by the present invention. Therefore, W should be between 20 μm and 100 μm.

An electromagnetic steel sheet having a groove depth d defined by the equation (1) will be described.
As described above, the magnetic domain control method by groove formation has a problem that the magnetic flux density decreases due to the presence of the groove, and in addition, the amount of decrease in the magnetic flux density due to the groove formation may vary. Therefore, in practical operation, the groove depth is determined with a sufficient margin up to the shipping standard value.

Generally, the shipping standard of magnetic flux density is set according to the product grade. Here, the description will be given using the following shipping standards for magnetic flux density.
B8 ≧ 1.87 (T)… <1>
B8 is the magnetic flux density when the steel sheet is excited at 800 (A / m). In the present specification, B8 (T) of the steel sheet from which the grooves have been removed may be referred to as B8n (T). As a means for removing the groove, the surface of the steel sheet is completely removed to the bottom of the groove in the plate thickness direction by grinding or pickling. Further, if the strain due to grinding remains, strain relief annealing is performed. The heat treatment conditions for strain removal annealing are usually sufficient. For example, it is preferable to heat to 800 ° C., retain for 2 hours, and then cool to 300 ° C. or lower for 15 hours or more. The heating rate is not particularly limited as long as the overshoot is within several tens of degrees Celsius. The atmosphere needs to be a non-oxidizing atmosphere, for example, 75% by volume of hydrogen and residual nitrogen may be used.
When removing the grooves, the thickness of the steel sheet to be removed should be limited to about several tens of μm so that the thickness of the steel sheet is not significantly reduced. This is because the magnetic characteristics may change if the thickness of the steel sheet is greatly reduced. If you pay attention to these points, it can be considered that the characteristics such as iron loss and magnetic flux density change depending on the existence of grooves. Therefore, the steel sheet from which the grooves have been removed is substantially equivalent to the steel sheet before the grooves are formed. It can be treated as having characteristics (iron loss, magnetic flux density, etc.).
Further, in the present specification, B8 of the non-grooved material (electrical steel sheet from which the formed groove is removed or electrical steel sheet before forming the groove) is referred to as B8n, and the groove-forming material (electromagnetic steel after forming the groove) is referred to as B8n. The target B8 of (steel plate) is sometimes called B8m.

As an example of the conventional practical operation, the groove depth d (μm) is determined as follows.
FIG. 1 is a chart in which experimental values of the amount of decrease in magnetic flux density with respect to the groove depth d when θ is 0 ° and p = 3 mm are arranged. The groove depth d can be determined based on such empirical data.
When the average magnetic flux density B8n before groove formation is about 1.905T, ΔB8 (decrease in magnetic flux density B8) is allowed up to 0.035T (1.905-1.87 = 0.035) in order to satisfy the condition of Eq. <1>. You should be able to. Based on the chart of FIG. 1, the depth of the groove where ΔB8 is 0.035T is approximately more than 25 μm.

However, in reality, the amount of decrease in magnetic flux density due to groove formation varies widely, and the amount of decrease in B8 (ΔB8) is not constant even if the same groove depth is processed. For this reason, 0.035T is not adopted as the upper limit of ΔB8, and the groove depth is determined by taking a margin of about 0.01T with respect to Eq. <1>. As a result, 0.025T was adopted as ΔB8, and the groove depth was set to about 20 μm based on FIG.

The groove depth determined in consideration of the above margin is not preferable from the viewpoint of improving iron loss. As described above, in the magnetic domain control by groove formation, there is an optimum groove depth in consideration of only the magnetic characteristics. That is, by optimizing the groove depth, better iron loss should be obtained.

Further, as described above, the optimum groove depth is related to the magnetic flux density to be excited, and generally, the optimum groove depth is smaller as the exciting magnetic flux density is higher. In other words, the higher the magnetic flux density to be excited, the greater the effect of improving iron loss per unit depth by groove formation tends to be. As a result, in the material showing B8 higher than the condition of <1>, the effect of obtaining a better iron loss can be obtained more remarkably by forming a deeper groove.

The present inventors consider that it is necessary to clarify the cause or the actual condition of the variation in the amount of decrease in the magnetic flux density due to the groove in order to optimize the groove depth and obtain a good iron loss. As a result, it was found that the amount of decrease in magnetic flux density due to the groove depends on B8n (B8 of the ungrooved material (steel plate before forming the groove) or the steel plate having the groove removed). FIG. 2 is an example of this.

FIG. 2 shows the magnetic flux density B8n of the ungrooved material (steel plate before forming the groove) or the steel plate from which the groove has been removed, and the amount of decrease in magnetic flux density ΔB8 due to the grooves of θ = 0 °, p = 3 mm, and W = 50 μm. This is an example of the chart shown, and is grouped by the groove depth d. By repeating the example of FIG. 2 and the tests with various materials, it was confirmed that the higher the magnetic flux density B8n is, the larger the decrease in magnetic flux density ΔB8 due to the groove is at the same groove depth.

Further, ΔB8 with respect to the magnetic flux density B8 n of the ungrooved material (steel plate before forming the groove) or the steel plate from which the groove has been removed differs depending on the groove depth d by repeating the test of the example of FIG. 2 and various materials. It was confirmed that. In general, it was confirmed that the larger the groove depth d, the larger ΔB8.

Based on the above findings, the present inventors have established a relational expression between the amount of decrease in magnetic flux density ΔB8 due to the groove and the magnetic flux density B8n of the ungrooved material (steel plate before forming the groove) or the steel plate from which the groove has been removed. I came up with the idea of formulating as follows.
ΔB8 = a × B8n + b… <2>
a = h × d + i… <3>
b = j × d + k… <4>

In the above equations <2> to <4>, h, i, j, and k are linear regressions of groove depth d based on the example of FIG. 2 and the data obtained by repeating the tests with various materials. Can be determined from. In that case, <3> and <4> are rewritten to the following <5> and <6>.
a = 0.0024 * d + 0.0722… <5>
b = -0.0032 * d-0.1428… <6>

Assuming that the magnetic flux density of the groove forming material (the electromagnetic steel sheet after forming the groove, which is the object of the present invention) is B8 _m , ΔB8 is given by the following equation <7>.
ΔB8 = B8n-B8 _m … <7>
By substituting <5> to <7> into the equation <2>, the following equation <8> for obtaining d for obtaining B8 _m specified by the present invention can be obtained.

According to the formula <8>, the magnetic flux density B8n of the non-grooved material (the electrical steel sheet before forming the groove) or the magnetic steel sheet from which the groove has been removed and the magnetic flux density B8 of the grain-forming material (the electrical steel sheet after forming the groove) The relationship between _m and the optimum groove depth d can be determined. That is, it is possible to obtain a magnetic domain control directional electromagnetic steel sheet in which a groove having an optimum depth is formed from the viewpoint of high magnetic flux density after groove formation and low iron loss.

More specifically, when a groove having an optimum groove depth d is formed in a groove-unformed material having a magnetic flux density of B8n (an electromagnetic steel sheet before forming the groove), the groove-forming material (invented steel sheet, The magnetic flux density B8 _m of the magnetic steel sheet after forming the groove) satisfies the equation <8>, and the steel sheet has a magnetic domain control direction in which a groove having an optimum depth is formed from the viewpoint of magnetic flux density and low iron loss. It becomes a grain-oriented electrical steel sheet.

Further, by modifying the equation <8>, it is possible to derive the equation <9> for obtaining the magnetic flux density B8 _m of the groove forming material with d as a variable.
B8 _m = (0.9278-0.0024 * d) * B8n + 0.0032 * d + 0.1428… <9>
The present invention targets an electromagnetic steel sheet having a sufficiently high magnetic flux density, and defines the magnetic flux density B8 _m of the electromagnetic steel sheet (electrical steel sheet having a groove) according to the present invention as B8 _m ≥ 1.87. The upper limit of B8m is not particularly limited, and the upper limit of B8m may be 1.93 (T). Therefore, the electromagnetic steel sheet according to the present invention satisfies the following formula <10>.
(0.9278-0.0024 * d) * B8n + 0.0032 * d + 0.1428 ≧ 1.87… <10>
The range of B8n to which the above formula can be applied is not particularly limited, but it is conceivable that the optimization of the groove depth by the above formula may deviate in the material having extremely low B8n or extremely high B8n. Considering this, the lower limit of B8n may be 1.90 (T) or less, but may be 1.91 (T) as the target of the applicable range of B8n. Further, the upper limit value of B8n may be 1.95 (T) or more, but may be 1.94 (T).

Furthermore, as a result of examining the effects of the groove angle θ (°) and the groove pitch p (mm), it was clarified that the <11> equation should be used in the range of 0 ° ≤ θ ≤ 30 °.
B8n + {0.1428 + 0.0032 * d- (0.0722 + 0.0024 * d) * B8n} * (3 / p) * e ^ (-qθ) ≧ 1.87… <11>
However,
B8n ≧ 1.90 (T)
2 ≤ p ≤ 30
q = 0.075
Is.
The reason why p is limited to between 2 mm and 30 mm here is that if it is less than 2 mm, the iron loss will worsen due to groove formation, and if it exceeds 30 mm, the iron loss improvement effect due to groove formation will not be sufficiently obtained. is there.

In the specification of the present application, iron loss is evaluated by W17 / 50 (W / kg). The smaller the iron loss, the more preferable, and the iron loss of the electromagnetic steel sheet according to the present invention may be 0.84 or less, more preferably 0.78 or less, still more preferably 0.75 or less when the plate thickness is 0.23 mm, for example. It may be.

The chemical composition of an electromagnetic steel sheet, which is one aspect of the present invention, will be described.
The grain-oriented electrical steel sheet according to the present invention contains Si: 2.00% to 7.00% in terms of mass fraction as a chemical composition, and the balance is Fe and impurities.

The above chemical composition is a preferable chemical composition for controlling the crystal orientation to be accumulated in the {110} <001> orientation.

Further, the grain-oriented electrical steel sheet according to the present invention may contain a known arbitrary element instead of a part of Fe for the purpose of improving magnetic properties. Examples of the optional element contained in place of a part of Fe include the following elements. Each numerical value means an upper limit value when those elements are contained as arbitrary elements.
By mass%
C: 0.005% or less Mn: 1.00% or less,
S and Se: 0.015 or less in total,
Al: 0.065 or less,
N: 0.005% or less Cu: 0.40% or less,
Bi: 0.010% or less,
B: 0.080% or less,
P: 0.50% or less,
Ti: 0.015% or less,
Sn: 0.10% or less,
Sb: 0.10% or less,
Cr: 0.30% or less,
Ni: 1.00% or less,
One or more of Nb, V, Mo, Ta, and W: 0.030% or less in total.
Since these arbitrary elements may be contained according to a known purpose, it is not necessary to set a lower limit value for the content of the arbitrary element, and the lower limit value may be 0%.

The impurity is not limited to the optional elements exemplified above, but means an element that does not impair the effect of the present invention even if it is contained. Not limited to the case of intentional addition, it also includes ore as a raw material, scrap, or an element unavoidably mixed from the manufacturing environment when the steel sheet is industrially manufactured. The upper limit of the total content of impurities is about 5%.

It should be noted that grain-oriented electrical steel sheets generally undergo decarburization annealing and purification annealing during secondary recrystallization, resulting in a relatively large change in chemical composition (decrease in content). is there. Depending on the element, it is reduced to 50 ppm or less, and if purified annealing is sufficiently performed, it may reach a level that cannot be detected by general analysis (1 ppm or less).
It should be added that the above-mentioned chemical composition of the grain-oriented electrical steel sheet according to the present invention is the chemical composition in the final product and is different from the composition of the slab described later which is also the starting material.

The chemical composition of the grain-oriented electrical steel sheet according to the present invention may be measured by a general method for analyzing steel. For example, the chemical composition of the grain-oriented electrical steel sheet may be measured using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Specifically, a 35 mm square test piece collected from a grain-oriented electrical steel sheet is measured with an ICPS-8100 or the like (measuring device) manufactured by Shimadzu Corporation under conditions based on a calibration curve prepared in advance to obtain a chemical composition. Be identified. C and S may be measured by using the combustion-infrared absorption method, and N may be measured by using the inert gas melting-thermal conductivity method.

On the surface of the grain-oriented electrical steel sheet according to the present invention, a film generally provided on the grain-oriented electrical steel sheet may be formed. These are called, for example, a glass coating, an insulating coating, a tension coating, and the like.

However, these coatings are not essential elements of the grain-oriented electrical steel sheet according to the present invention. The above-mentioned chemical composition of the grain-oriented electrical steel sheet according to the present invention is the composition of the steel component which is the base material of the grain-oriented electrical steel sheet having a coating film, and is measured after removing the insulating coating on the surface by grinding or the like. It shall be.

Next, one aspect of the method for manufacturing a grain-oriented electrical steel sheet according to the present invention will be described. The method for producing a directional electromagnetic steel sheet according to the present invention includes a casting step, a hot rolling step, a cold rolling step, a decarburization annealing step, and a finish annealing step, and a direction intersecting the rolling direction after the cold rolling step. In addition, it includes a step of forming grooves having a groove depth direction in the plate thickness direction at regular intervals.
The groove depth d (μm) is determined from the groove forming material B8 (T) and the groove non-forming material B8 (T). Here, B8 (T) is the magnetic flux density when the steel sheet is excited at 800 (A / m).

The steps shown below and the quantitative conditions in each step are examples adopted to show the feasibility of the present invention, and the present invention is not limited to these steps and quantitative values. The method for producing a grain-oriented electrical steel sheet according to the present invention does not deviate from the gist of the present invention, and various conditions can be adopted as long as the object of the present invention is achieved.

(Casting process)
In the casting process, slabs are prepared. An example of a slab manufacturing method is as follows. Manufacture (melt) molten steel. Manufacture slabs using molten steel. The slab may be manufactured by a continuous casting method. An ingot may be produced using molten steel, and the ingot may be block-rolled to produce a slab. The thickness of the slab is not particularly limited. The thickness of the slab is, for example, 150 mm to 350 mm. The thickness of the slab is preferably 220 mm to 280 mm. As the slab, a so-called thin slab having a thickness of 10 mm to 70 mm may be used. When a thin slab is used, rough rolling before finish rolling can be omitted in the hot process.

As the chemical composition of the slab, the chemical composition of the slab used in the production of general grain-oriented electrical steel sheets can be used. The chemical composition of the slab contains, for example, the following elements:

C: 0.085% or less,
Although C is an element effective in controlling the primary recrystallization structure in the manufacturing process, if the content in the final product is excessive, it adversely affects the magnetic properties. Therefore, the C content is 0.085% or less. The preferred upper limit of the C content is 0.075%. C is mainly removed in the decarburization annealing step described later, and becomes 0.005% or less after the finish annealing step. When C is contained, the lower limit of the C content may be more than 0% or 0.001% in consideration of productivity in industrial production.

Si: 2.00% to 7.00%
Silicon (Si) increases the electrical resistance of grain-oriented electrical steel sheets and reduces iron loss. If the Si content is less than 2.00%, γ transformation occurs during finish annealing, and the crystal orientation of the grain-oriented electrical steel sheet is impaired. On the other hand, if the Si content exceeds 7.00%, the cold workability is lowered and cracks are likely to occur during cold rolling. The preferred lower limit of the Si content is 2.50%, more preferably 3.00%. The preferred upper limit of the Si content is 4.50%, more preferably 4.00%.

Mn: 0.05% to 1.00%
Manganese (Mn) binds to S or Se to produce MnS or MnSe and functions as an inhibitor. When Mn is contained, the secondary recrystallization is stable when the Mn content is in the range of 0.05% to 1.00%. When a part of the function of the inhibitor is carried out by the nitride, the MnS or MnSe intensity as the inhibitor is controlled to be weak. Therefore, the preferable upper limit of the Mn content is 0.50%, and more preferably 0.20%.

S and Se: 0.003% to 0.035% in total
Sulfur (S) and selenium (Se) combine with Mn to produce MnS or MnSe, which functions as an inhibitor. When at least one of S and Se is contained, the secondary recrystallization is stable when the total content of S and Se is 0.003% to 0.035%. When a part of the function of the inhibitor is carried out by the nitride, the strength of MnS or MnSe as the inhibitor is controlled to be weak. Therefore, the preferable upper limit of the total S and Se contents is 0.025%, and more preferably 0.010%. When S and Se remain after finish annealing, they form compounds and deteriorate iron loss. Therefore, it is preferable to reduce S and Se as much as possible by purifying during finish annealing.

Here, "the total content of S and Se is 0.003% to 0.035%" means that the chemical composition of the slab contains only one of S and Se, and either S or Se. The total content of one of them may be 0.003% to 0.035%, or the slab contains both S and Se, and the total content of S and Se is 0.003% to 0. It may be .035%.

Al: 0.010% to 0.065%
Aluminum (Al) binds to N and precipitates as (Al, Si) N, and functions as an inhibitor. When Al is contained, when the Al content is in the range of 0.010% to 0.065%, AlN as an inhibitor formed by nitriding described later expands the secondary recrystallization temperature range. In particular, secondary recrystallization is stable in the high temperature range. Therefore, the Al content is 0.010% to 0.065%. The lower limit of the Al content is preferably 0.020%, more preferably 0.025%. From the viewpoint of stability of secondary recrystallization, the preferable upper limit of the Al content is 0.040%, more preferably 0.030%.

N: 0.012% or less Nitrogen (N) binds to Al and functions as an inhibitor. Since N can be contained by nitriding in the middle of the manufacturing process, the lower limit is not specified. On the other hand, when N is contained, if the N content exceeds 0.012%, blister, which is a kind of defect, is likely to occur in the steel sheet. The preferred upper limit of the N content is 0.010%, more preferably 0.009%. N is purified in the finish annealing step and may be 0.005% or less after the finish annealing step.

The rest of the chemical composition of the slab consists of Fe and impurities. It should be noted that the "impurities" referred to here are unavoidably mixed from the components contained in the raw materials or the components mixed in the manufacturing process when the slab is industrially manufactured, and substantially affects the effect of the present invention. Means an element that does not give.

The chemical composition of the slab may contain a known arbitrary element instead of a part of Fe in consideration of the enhancement of the inhibitor function by compound formation and the influence on the magnetic properties in addition to solving the manufacturing problem. .. Examples of the optional element contained in place of a part of Fe include the following elements. Each numerical value means an upper limit value when those elements are contained as arbitrary elements.
By mass%
Cu: 0.40% or less,
Bi: 0.010% or less,
B: 0.080% or less,
P: 0.50% or less,
Ti: 0.015% or less,
Sn: 0.10% or less,
Sb: 0.10% or less,
Cr: 0.30% or less,
Ni: 1.00% or less,
One or more of Nb, V, Mo, Ta, and W: 0.030% or less in total.
Since these arbitrary elements may be contained according to a known purpose, it is not necessary to set a lower limit value for the content of the arbitrary element, and the lower limit value may be 0%.

(Hot rolling process)
The hot rolling step is a step of hot rolling a slab heated to a predetermined temperature (for example, 1100 ° C. to 1400 ° C.) to obtain a hot rolled steel sheet. In the hot rolling step, for example, the silicon steel material (slab) heated in the heating step is roughly rolled and then finished rolled to have a predetermined thickness, for example, 1.8 mm to 3.5 mm. Use a steel plate. After the finish rolling is completed, the hot-rolled steel sheet may be wound at a predetermined temperature.

When the MnS strength as an inhibitor is not so required, the slab heating temperature is preferably 1100 ° C. to 1280 ° C. in consideration of productivity.

(Hot rolled plate annealing process)
The production method according to one aspect of the present invention may include a hot-rolled plate annealing step. The hot-rolled sheet annealing step is a step of annealing the hot-rolled steel sheet obtained in the hot-rolling step under predetermined temperature conditions (for example, 750 ° C. to 1200 ° C. for 30 seconds to 10 minutes) to obtain an annealed steel sheet. ..
The hot-rolled plate annealing step is a step of finally controlling the morphology of precipitates such as AlN in the high-temperature slab heating process, and the conditions can be adjusted so that the precipitates are uniformly and finely deposited.

(Cold rolling process)
In the cold rolling step, the hot rolled steel sheet obtained in the hot rolling step or the annealed steel sheet obtained in the hot rolled sheet annealing step is subjected to one cold rolling or annealing (intermediate annealing) a plurality of times ( This is a step of obtaining a cold-rolled steel sheet having a thickness of, for example, 0.10 mm to 0.50 mm by cold rolling (for example, 80% to 95% in total cold rolling ratio) by cold rolling (twice or more).

(Decarburization annealing process)
In the decarburization annealing step, the cold-rolled steel sheet obtained in the cold rolling step is decarburized and annealed (for example, at 700 ° C. to 900 ° C. for 1 minute to 3 minutes) to obtain a decarburized annealed steel sheet in which primary recrystallization has occurred. It is a process. By decarburizing and annealing the cold-rolled steel sheet, C contained in the cold-rolled steel sheet is removed. Decarburization annealing is preferably performed in a moist atmosphere in order to remove "C" contained in the cold-rolled steel sheet.

(Nitriding treatment)
The production method according to one aspect of the present invention may include a nitriding treatment step. The nitriding treatment is a step carried out as necessary in order to adjust the strength of the inhibitor in the secondary recrystallization. The nitriding treatment increases the amount of nitrogen in the steel sheet by about 40 ppm to 200 ppm from the start of the decarburization treatment to the start of secondary recrystallization in finish annealing. The nitriding treatment includes, for example, a treatment of annealing in an atmosphere containing a nitriding gas such as ammonia, and a treatment of finishing and annealing a decarburized annealed steel sheet coated with an annealing separator containing a nitriding powder such as MnN. Etc. are exemplified.

(Annealing separator application process)
The annealing separator coating step is a step of applying an annealing separator to a decarburized annealed steel sheet, and is a step to be carried out as necessary. As the annealing separator, for example, an annealing separator containing MgO as a main component can be used. The decarburized annealed steel sheet after applying the annealing separating agent is subjected to finish annealing in the next finish annealing step in a coiled state.

(Finish annealing process)
The finish annealing step is a step of subjecting a decarburized annealed steel sheet and a decarburized annealed steel sheet coated with an annealing separator to finish annealing to generate secondary recrystallization. In this step, the {100} <001> oriented grains are preferentially grown and the magnetic flux density is dramatically improved by advancing the secondary recrystallization in a state where the growth of the primary recrystallized grains is suppressed by the inhibitor.

(Tension film forming process)
A coating solution (eg, a coating solution containing phosphoric acid or phosphate, chromic anhydride or chromate, and colloidal silica) is applied to the steel sheet and baked (for example, at 350 ° C to 1150 ° C for 5 seconds). A tension film may be formed for ~ 300 seconds).

(Groove formation process)
For the purpose of magnetic domain control (magnetic domain subdivision), the directional electromagnetic steel plate has local grooves in the process after cold rolling by known methods such as laser, electron beam, plasma, mechanical method, and etching. It is formed. In general, grooves with a depth of about several μm to several tens of μm are stretched in a direction forming an angle of 0 to 50 ° with the rolling perpendicular direction, and have a constant interval between about several mm and several tens of mm. Is formed by. The groove depth d (mm) in one aspect of the present invention will be described later. Further, in one aspect of the present invention, the grooves may be stretched in a direction forming an angle of 0 to 30 ° with the direction perpendicular to rolling, and may be formed at regular intervals between about 2 mm and 30 mm. Here, constant means that the actual spacing between the grooves is within ± 10% of the specified value with respect to the spacing specified above. The groove width is preferably 20 μm to 100 μm. The groove width refers to the average dimension in the cross section perpendicular to the groove forming direction.
The timing of forming the groove includes immediately after cold rolling and before decarburization annealing, after decarburization annealing, after finish annealing, after forming a tension film, and the like, and the groove may be formed at any timing.
The present invention defines the depth of the groove to be formed in relation to the magnetic flux density of the magnetic steel sheet in the state where the groove is formed and the state where the groove is not formed.

ここで、Ｂ８（T）は鋼板を８００(Ａ/ｍ)で励磁した場合の磁束密度であり、Ｂ８ｎは溝未形成材または溝を除去した鋼板の磁束密度Ｂ８であり、Ｂ８ｍは溝形成材の磁束密度Ｂ８である。
この式(2)によれば、溝未形成材（溝を形成する前の電磁鋼板）または溝を除去した電磁鋼板（素材）の磁束密度B8n、および溝形成材（溝を形成した後の電磁鋼板）の磁束密度B8_mから、本発明が規定するB8_mを得るための溝の深さdを求めることができる。言い換えると、式(2)を満たす溝の深さｄの溝を形成することにより、溝形成材（溝を形成した後の電磁鋼板）のB8_mを得ることができる。また、(2)式を満たす溝の深さｄを有する鋼板であれば、鉄損を小さくすることができる。溝形成材のB8_mは、1.93≧B8_m≧1.87であってもよい。また、溝未形成材のB8nの下限値は、1.90(T)以下を採用してもよいが、1.91(T)としてもよい。また、B8nの上限値は、1.95(T)以上を採用してもよいが、1.94(T)としてもよい。 According to one aspect of the present invention, the groove depth d (μm) may satisfy the following equation (2).

Here, B8 (T) is the magnetic flux density when the steel sheet is excited at 800 (A / m), B8n is the magnetic flux density B8 of the ungrooved material or the steel sheet from which the grooves are removed, and B8m is the groove-forming material. The magnetic flux density of B8.
According to this equation (2), the magnetic flux density B8n of the non-grooved material (electrical steel sheet before forming the groove) or the magnetic steel sheet (material) from which the groove is removed, and the groove forming material (electromagnetic steel after forming the groove). From the magnetic flux density B8 _m of the steel sheet), the groove depth d for obtaining B8 _m specified by the present invention can be obtained. In other words, by forming a groove having a groove depth d satisfying the equation (2), B8 _m of the groove forming material (electrical steel sheet after forming the groove) can be obtained. Further, if the steel sheet has a groove depth d satisfying the equation (2), the iron loss can be reduced. The B8 _{m of the} groove forming material may be 1.93 ≧ B8 _m ≧ 1.87. Further, the lower limit value of B8n of the non-grooved material may be 1.90 (T) or less, but may be 1.91 (T). Further, the upper limit value of B8n may be 1.95 (T) or more, but may be 1.94 (T).

The present invention will be described with reference to the following examples. However, the present invention should not be construed as being limited to this example.

A grain-oriented electrical steel sheet (Si content 2.00 to 7.00%, having a chemical composition in which the balance is Fe and impurities) having a thickness of 0.23 mm and having a tension film formed by a usual method. I prepared several types. The B8n of the electromagnetic steel sheet before groove formation was 1.90 to 1.96 (T). Grooves having a width of 50 μm were introduced into each electromagnetic steel sheet by gear rolls at intervals of 5 mm substantially parallel to the plate width direction. At this time, the pressure applied to the gear roll was changed to control the groove depth d so as to have various depths shown in Table 1. For the sample after groove formation, B8k (T) and iron loss W17 / 50 (W / kg) after groove formation were measured. The measurement results are shown in Table 1.
In the evaluation <1> in Table 1, those in which B8k (T) after groove formation satisfied the following formula were designated as “◯”, and those in which the following formula was not satisfied were designated as “−”. “○” means that the decrease in magnetic flux density due to groove formation is small.
B8k (T) ≥ 1.87 (T)
In addition, the evaluation <2> in Table 1 shows that the iron loss W17 / 50 (W / kg) is "-" for those with an iron loss of more than 0.84, "○" for those with an iron loss of 0.84 or less, and 0.78 or less. Those with a value of 0.72 or less were designated as "◎", and those with a value of 0.72 or less were designated as "☆".
According to the present invention, an electromagnetic steel sheet having a small decrease in magnetic flux density due to groove formation and low iron loss can be obtained.

ただし、θ＝０°、p=５ｍｍである。
溝を導入する際に、決定した溝深さｄとなるように、歯車ロールに付与する圧力を変化させた。同一の条件で１００回の再現試験を繰り返した。溝形成後の試料について、溝形成後のＢ８ｋａ（Ｔ）および鉄損Ｗ１７/５０（Ｗ/ｋｇ）を測定した。Ｂ８ｋａ（Ｔ）の平均値および、鉄損Ｗ１７/５０が０．８（Ｗ/ｋｇ）以下の収率の結果を表２に示す。ここで、収率が９５％以上であった場合に○、９５％未満であった場合に−とした。なお、比較例は図１を用いて従来通りの方法で溝を形成した結果である。
本発明によれば、溝形成による磁束密度の低下が小さく、低鉄損の電磁鋼板が、高収率で得られる。 A grain-oriented electrical steel sheet (Si content 2.00 to 7.00%, having a chemical composition in which the balance is Fe and impurities) having a thickness of 0.23 mm and having a tension film formed by a usual method. I prepared several types. The B8na of the electromagnetic steel sheet before groove formation was 1.90 to 1.91 (T). Grooves having a width of 50 μm were introduced into each electromagnetic steel sheet by gear rolls at intervals of 5 mm substantially parallel to the plate width direction. The groove depth d introduced in the example of the present invention was determined by setting B8ma (T) after groove formation and substituting it into the following formula together with B8na before groove formation.

However, θ = 0 ° and p = 5 mm.
When the groove was introduced, the pressure applied to the gear roll was changed so as to have the determined groove depth d. The reproduction test was repeated 100 times under the same conditions. For the sample after groove formation, B8ka (T) and iron loss W17 / 50 (W / kg) after groove formation were measured. Table 2 shows the average value of B8ka (T) and the result of the yield of iron loss W17 / 50 of 0.8 (W / kg) or less. Here, when the yield was 95% or more, it was evaluated as ◯, and when it was less than 95%, it was evaluated as −. The comparative example is the result of forming the groove by the conventional method using FIG.
According to the present invention, an electromagnetic steel sheet having a small decrease in magnetic flux density due to groove formation and a low iron loss can be obtained in a high yield.

A grain-oriented electrical steel sheet having a thickness of 0.23 mm (Si content: 3.20%, the balance having a chemical composition of Fe and impurities) produced by a usual method and having a tension film formed was prepared. The B8n of the electromagnetic steel sheet before groove formation was 1.90 (T). Grooves were introduced into each electrical steel sheet by gear rolls at intervals of 5 mm substantially parallel to the plate width direction. At this time, the pressure applied to the gear roll was changed to adjust the groove depth d to approximately 20 μm.
It was controlled so as to have various groove widths W shown in Table 3. For the sample after groove formation, B8k (T) and iron loss W17 / 50 (W / kg) after groove formation were measured. The measurement results are shown in Table 3.
In the evaluation <1> of Table 3, those in which B8k (T) after groove formation satisfied the following formula were designated as “◯”, and those in which the following formula was not satisfied were designated as “−”. “○” means that the decrease in magnetic flux density due to groove formation is small.
B8k (T) ≥ 1.87 (T)
In addition, the evaluation <2> in Table 3 shows that the iron loss W17 / 50 (W / kg) is "-" for those with an iron loss of more than 0.84, "○" for those with an iron loss of 0.84 or less, and 0.78 or less. Those with a value of 0.72 or less were designated as "◎", and those with a value of 0.72 or less were designated as "☆".
According to the present invention, an electromagnetic steel sheet having a small decrease in magnetic flux density due to groove formation and low iron loss can be obtained.

A grain-oriented electrical steel sheet having a thickness of 0.23 mm (Si content: 3.20%, the balance having a chemical composition of Fe and impurities) produced by a usual method and having a tension film formed was prepared. The B8n of the electromagnetic steel sheet before groove formation was 1.90 (T). Grooves were introduced into each electrical steel sheet by gear rolls at intervals of 1.5 to 40 mm substantially parallel to the plate width direction. At this time, the pressure applied to the gear roll was controlled to adjust the groove depth d to approximately 20 μm.
It was controlled so as to have various groove spacings p shown in Table 4. For the sample after groove formation, B8k (T) and iron loss W17 / 50 (W / kg) after groove formation were measured. The measurement results are shown in Table 4.
In the evaluation <1> in Table 4, those in which B8k (T) after groove formation satisfied the following formula were designated as “◯”, and those in which the following formula was not satisfied were designated as “−”. “○” means that the decrease in magnetic flux density due to groove formation is small.
B8k (T) ≥ 1.87 (T)
In addition, the evaluation <2> in Table 4 shows that the iron loss W17 / 50 (W / kg) is "-" for those with an iron loss of more than 0.84, "○" for those with an iron loss of 0.84 or less, and 0.78 or less. Those with a value of 0.72 or less were designated as "◎", and those with a value of 0.72 or less were designated as "☆".
According to the present invention, an electromagnetic steel sheet having a small decrease in magnetic flux density due to groove formation and low iron loss can be obtained.

Claims (5)

Grooves containing Si: 2.00 to 7.00% by mass, having a chemical composition in which the balance is Fe and impurities, and having a direction intersecting the rolling direction and a groove depth direction being the plate thickness direction. It is a steel plate held at regular intervals and
The magnetic flux density when the steel sheet is excited at 800 (A / m) is defined as B8 (T), the B8 (T) of the steel sheet from which the grooves are removed is defined as B8n (T), and the depth of the grooves is defined as B8n (T). When defined as d (μm), the distance between the grooves is defined as p (mm), and the angle formed by the grooves in the direction perpendicular to rolling is defined as θ (°), the following equation (1) is satisfied, and the groove Directional electromagnetic steel sheet with width W of 20 to 100 μm

B8n + {0.1428 + 0.0032 * d- (0.0722 + 0.0024 * d) * B8n} * (3 / p) * e ^ (-qθ) ≧ 1.87… (1)

However, B8n ≥ 1.90 (T)
0 ≤ θ ≤ 30 °
2 ≤ p ≤ 30
q = 0.075. A method for manufacturing a directional electromagnetic steel plate having a casting process, a hot rolling process, a cold rolling process, a decarburization annealing process, and a finish annealing process, in a direction intersecting the rolling direction and a groove depth after the cold rolling process. Includes a groove forming step of forming grooves whose direction is the thickness direction at regular intervals.
The magnetic flux density when the steel sheet is excited at 800 (A / m) is defined as B8 (T), and the groove depth d (μm) is defined as the groove forming material B8 (T) and the groove unformed material B8. A method for manufacturing a grain-oriented electrical steel sheet, which is characterized by determining from (T). B8 (T) of the groove forming material is defined as B8m (T), B8 (T) of the ungrooved material is defined as B8n (T), the interval between the grooves is p (mm), and the grooves are at right angles to rolling. When the angle formed with the direction is defined as θ (°), the groove depth d (μm) formed in the groove forming step is calculated according to the following equation (2), and the groove width W The method for manufacturing a directional electromagnetic steel sheet according to claim 2, wherein the thickness is 20 to 100 μm.

here
0 ≤ θ ≤ 30 °
2 ≤ p ≤ 30
q = 0.075. The method for producing a grain-oriented electrical steel sheet according to claim 2 or 3, wherein the groove forming step is after the cold rolling step and before the decarburization annealing step. The method for manufacturing a grain-oriented electrical steel sheet according to claim 2 or 3, wherein the groove forming step is after the tension film forming step.

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