JP7385098B2 - Grain-oriented electrical steel sheet with good iron loss and its manufacturing method - Google Patents

Description

The present invention relates to a grain-oriented electrical steel sheet subjected to magnetic domain refining treatment using grooves, and in particular, by specifying the groove depth, a grain-oriented electrical steel sheet with sufficiently high magnetic flux density after groove formation and low iron loss. , and its manufacturing method.

Unidirectional electrical steel sheets are required to reduce iron loss from the viewpoint of energy conservation. Particularly for wound core transformers, Patent Document 1 discloses a means for maintaining the magnetic domain refining effect even after strain relief annealing by artificially introducing grooves. This method involves introducing grooves into a steel plate using a mechanical means such as a toothed roll to refine the magnetic domains.

In addition to the above-mentioned mechanical means, there are etching methods disclosed in Patent Document 2 and Patent Document 3, but both introduce grooves and maintain the magnetic domain refining effect even after strain relief annealing. It is a technique similar to mechanical means in that it exerts its effects.

Japanese Patent Application Publication No. 1-252726 Japanese Unexamined Patent Publication No. 179105/1983 Japanese Patent Application Publication No. 4-88121

In grain-oriented electrical steel sheets, it is known that core loss can be reduced by forming grooves in a direction intersecting the rolling direction to control magnetic domains.

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

While investigating the relationship between the groove depth and magnetic properties of various materials, the present inventor found that the relationship between the groove depth and the iron loss improvement effect was determined by the optimum value of the groove depth, which changes according to the excited magnetic flux density. It was discovered that there is. For example, in a specific test material, the optimum value of the groove depth under 1.7T excitation was about 30 μm, whereas the optimum value of the groove depth under 1.5T excitation exceeded 35 μm.

Based on these findings, the present inventor came up with the idea of determining the optimal value of the depth of the grooves formed for magnetic domain control in relation to the magnetic properties of the steel sheet, particularly the magnetic flux density. In addition to the depth of the grooves, the arrangement of the grooves (the interval between the grooves and the angle between the grooves and the rolling direction of the steel plate) is determined based on the magnetic flux density B8 (T) when the steel plate is excited at 800 (A/m). We succeeded in optimizing the relationship.

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

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]
A groove having a chemical composition in which Si: 2.00 to 7.00% is contained in mass %, the balance being Fe and impurities, and the direction intersecting the rolling direction and the groove depth direction is the plate thickness direction. A steel plate having regular intervals,
The magnetic flux density when the steel plate is excited at 800 (A/m) is defined as B8(T), B8(T) of the steel plate with the groove removed is defined as B8n(T), and the depth of the groove is d (μm), the interval between the grooves is p (mm), and the angle between the grooves and the direction perpendicular to the rolling direction is defined as θ (°). Grain-oriented electrical steel sheet with a 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
It is.
[2]
A method for producing a grain-oriented electrical steel sheet having a casting process, a hot rolling process, a cold rolling process, a decarburization annealing process, and a finish annealing process, the method comprising: a direction intersecting the rolling direction and a groove depth after the cold rolling process; Including a groove forming process in which grooves are formed at regular intervals with the horizontal direction being the plate thickness direction,
The magnetic flux density when the steel plate is excited at 800 (A/m) is defined as B8 (T), and the depth d (μm) of the groove is determined by the target B8 (T) for the grooved material and the target B8 (T) for the non-grooved material. A method for manufacturing a grain-oriented electrical steel sheet, characterized in that it is determined from B8 (T).
[3]
The target B8(T) of the grooved material is defined as B8m(T), the B8(T) of the non-grooved material is defined as B8n(T), the interval between the grooves is p (mm), and the groove is rolled. The groove depth d (μm) formed in the groove forming step is calculated according to the following formula (2), where the angle formed with the perpendicular direction is defined as θ (°), and the groove width The method for producing grain-oriented electrical steel sheet according to item [2], in which W is 20 to 100 μm

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

According to the present invention, when forming grooves in a product sheet of grain-oriented electrical steel sheet (grain-oriented electrical steel sheet on which a tension coating is formed) to control magnetic domains, the magnetic flux density after 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 arranging experimental values of the amount of decrease in magnetic flux density with respect to groove depth d. FIG. 2 is a chart arranging the magnetic flux density B8 before groove formation and the magnetic flux density reduction amount ΔB8 due to groove formation.

A grain-oriented electrical steel sheet according to one embodiment of the present invention has a chemical composition in which the steel sheet surface contains Si: 2.00 to 7.00%, and the balance is Fe and impurities, and the steel sheet surface has a direction in which the steel sheet is rolled. Magnetic domain control is performed by having grooves at regular intervals in which the intersecting directions and the groove depth direction are in the plate thickness direction.
The depth d (μm) of the groove according to one embodiment of the present invention satisfies the following formula (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 plate from which the grooves have been removed is excited at 800 (A/m). Further, θ is the angle (°) at which the groove intersects the direction perpendicular to the rolling direction, and when the groove is perpendicular to the rolling direction (in the width direction of the steel plate), θ=0 (°). p is the groove spacing (mm), and q is a coefficient, which satisfies the following.
2≦p≦30
q=0.075
The grooves form reflux magnetic domains extending in the direction of the grooves, and the 180° magnetic domains that existed before the grooves were formed are subdivided, which has the effect of lowering iron loss. In this regard, the direction of the groove is preferably perpendicular to the rolling direction of the steel plate, but the direction of the groove may be inclined to the rolling direction to some extent, and θ should be selected between 0 and 30 degrees. Can be done.
Here, q was determined as follows. First, a large number of samples whose B8 before groove formation was between 1.90T and 1.96T were prepared, and grooves of d=15 μm were formed on them. However, θ was set from 0 to 30°. After these grooved samples were annealed to remove strain, B8 was measured again, and this was defined as B8m(θ). Furthermore, after removing the grooves of these samples and annealing them to remove strain, B8 was measured again and found to be B8n(θ).
ΔB8(θ)=B8n(θ)−B8m(θ). Note that the addition of (θ) to each indicates that it is a function of θ.
Next, ΔB8(θ) normalized by ΔB8(0) was plotted against θ, and q was determined by fitting this plot with e^(-qθ) so that it becomes 1 when θ=0. Here q was 0.075.
The depth d of the groove should satisfy equation (1), but the width W of the groove can be selected between 20 μm and 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 forming direction, and the definition of the average width is the area occupied by the cross-sectional shape of the groove divided by the maximum depth of the groove. For example, if the cross-sectional shape of the groove is rectangular, the width of the groove on the surface of the steel plate is W as is, and if the cross-section of the groove is triangular, W is 1/2 of the width of the groove on the steel plate surface.
Here, if W is too small, it will not be possible to obtain the iron loss reduction effect by magnetic domain control, and if W is too large, it will be 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 formula (1) will be explained.
As described above, the magnetic domain control method using groove formation has the problem that the magnetic flux density decreases due to the presence of the groove, and in addition, the amount of decrease in magnetic flux density due to groove formation may vary. Therefore, in practical operation, the depth of the groove is determined with a sufficient margin up to the shipping standard value.

Generally, shipping standards for magnetic flux density are determined depending on the product grade. Here, explanation 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 plate is excited at 800 (A/m). Note that in this specification, B8(T) of the steel plate from which the grooves have been removed may be referred to as B8n(T). As a means of removing the grooves, the surface of the steel plate is completely removed in the thickness direction down to the bottom of the grooves by grinding or pickling. Furthermore, if distortion due to grinding remains, distortion relief annealing is performed. The heat treatment conditions for the strain relief annealing are usually normally used. For example, it is preferable to heat the material to 800°C, hold it for 2 hours, and then cool it to 300°C or less over a period of 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 non-oxidizing, and may be, for example, 75% by volume hydrogen and the balance nitrogen.
When removing the grooves, the thickness of the steel plate to be removed should be limited to about several tens of μm so as not to significantly reduce the thickness of the steel plate. This is because the magnetic properties may change if the thickness of the steel plate is significantly reduced. If you pay attention to these points, it can be assumed that properties such as iron loss and magnetic flux density change due to the presence of grooves, so the steel plate from which the grooves have been removed will be substantially equivalent to the steel plate before the grooves were formed. It can be treated as having characteristics (iron loss, magnetic flux density, etc.).
In addition, in this specification, B8 of the non-grooved material (electromagnetic steel sheet from which the formed grooves have been removed or the electromagnetic steel sheet before forming the grooves) is referred to as B8n, and B8 of the groove-formed material (the electromagnetic steel sheet after forming the grooves) The target B8 of steel plate) is sometimes referred to as B8m.

As an example of conventional practical operation, the depth d (μm) of the groove is determined as follows.
FIG. 1 is a chart arranging experimental values of the amount of decrease in magnetic flux density with respect to groove depth d when θ is 0° and p=3 mm. Based on such empirical data, the groove depth d can be determined.
If 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 formula <1>. It should be possible. Based on the chart in FIG. 1, the depth of the groove at which ΔB8 is 0.035T is approximately over 25 μm.

However, in reality, the amount of decrease in magnetic flux density due to groove formation varies widely, and even if the same groove depth is processed, the amount of decrease in B8 (ΔB8) is not constant. For this reason, 0.035T is not adopted as the upper limit value of ΔB8, but the groove depth is determined by taking a margin of about 0.01T with respect to formula <1>. As a result, 0.025T was adopted as ΔB8, and the depth of the groove 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 iron loss improvement. This is because, as described above, in magnetic domain control by groove formation, there is an optimum groove depth that takes only the magnetic properties into consideration. In other words, better iron loss should be obtained by optimizing the groove depth.

Further, as described above, the optimal groove depth has a relationship with the exciting magnetic flux density, and generally speaking, the higher the exciting magnetic flux density, the smaller the optimal groove depth. In other words, the higher the magnetic flux density to be excited, the greater the iron loss improvement effect per unit depth by groove formation tends to be. As a result, in the case of a material exhibiting B8 higher than the condition <1>, the effect of obtaining better iron loss by forming deeper grooves can be more significantly obtained.

The present inventors believe that in order to optimize the groove depth and obtain good iron loss, it is necessary to clarify the cause or actual state of the variation in the amount of decrease in magnetic flux density due to grooves, and have conducted extensive studies. As a result, it was found that the amount of decrease in magnetic flux density due to grooves was dependent on B8n (B8 of the non-grooved material (steel plate before grooves were formed) or the steel plate with grooves removed). FIG. 2 is an example of this.

Figure 2 shows the magnetic flux density B8n of a material without grooves (a steel plate before forming grooves) or a steel plate with grooves removed, and the magnetic flux density decrease ΔB8 due to grooves with θ=0°, p=3mm, and W=50μm. This is an example of a chart, which is divided into groups by groove depth d. By repeating the example in FIG. 2 and tests with various materials, it was confirmed that at the same groove depth, the higher the magnetic flux density B8n, the greater the magnetic flux density drop ΔB8 due to the groove.

In addition, by repeating the example in Fig. 2 and tests with various materials, we found that ΔB8 for the magnetic flux density B8 n of a material without grooves (a steel plate before forming grooves) or a steel plate with grooves removed differs depending on the groove depth d. This was confirmed. In general, it was confirmed that the larger the groove depth d, the larger ΔB8.

Based on the above findings, the present inventors developed a relational expression between the magnetic flux density reduction amount ΔB8 due to grooves and the magnetic flux density B8n of a material without grooves (a steel plate before forming grooves) or a steel plate with grooves removed. I came up with the idea of arranging it 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 determined by linear regression of groove depth d based on the example in Figure 2 and data obtained from repeated tests with various materials. It can be determined from In that case, <3> and <4> will be rewritten as <5> and <6> below.
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 electrical steel sheet after forming the grooves, which is the subject of the present invention) is B8 _m , ΔB8 is expressed by the following formula <7>.
ΔB8=B8n-B8 _m …<7>
By substituting <5> to <7> into equation <2>, the following equation <8> can be obtained to obtain d to obtain B8 _m defined by the present invention.

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

More specifically, when grooves with the optimum groove depth d are formed in an ungrooved material (an electrical steel sheet before forming grooves) with a magnetic flux density of B8n, the grooved material (invented steel sheet, The magnetic flux density B8 _m of the electromagnetic steel sheet (after forming the grooves) satisfies the formula <8>, and the steel sheet has a magnetic domain control direction in which grooves of optimal depth are formed from the viewpoint of magnetic flux density and low core loss. It becomes a magnetic electrical steel sheet.

Furthermore, by modifying equation <8>, equation <9> can be derived to obtain the magnetic flux density B8 _m of the groove forming material using 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 (electromagnetic steel sheet having grooves) as B8 _m ≧1.87. Note that the upper limit of B8m is not particularly limited, and the upper limit of B8m may be 1.93 (T). Therefore, the electrical 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>
Note that the range of B8n to which the above formula can be applied is not particularly limited, but it is conceivable that optimization of the groove depth by the above formula may be deviated in materials where B8n is extremely low or extremely high. Considering this, as a target for the applicable range of B8n, the lower limit of B8n may be set to 1.90(T) or less, or may be set to 1.91(T). Further, the upper limit value of B8n may be 1.95(T) or more, or may be 1.94(T).

Furthermore, as a result of examining the influence of the groove angle θ (°) and the groove pitch p (mm), it became clear that formula <11> 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
It is.
The reason why p is limited to between 2 mm and 30 mm is because 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 by groove formation will not be sufficiently obtained. be.

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

The chemical composition of the electrical steel sheet that is one embodiment of the present invention will be explained.
The grain-oriented electrical steel sheet according to the present invention contains, as a chemical composition, Si: 2.00% to 7.00% in mass fraction, and the remainder is Fe and impurities.

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

Further, the grain-oriented electrical steel sheet according to the present invention may contain a known arbitrary element in place of a part of Fe for the purpose of improving magnetic properties. Examples of optional elements contained in place of a part of Fe include the following elements. Each numerical value means the upper limit when those elements are contained as optional elements.
In 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.
These arbitrary elements may be contained according to known purposes, so there is no need to set a lower limit for the content of the arbitrary elements, and the lower limit may be 0%.

Note that impurities are not limited to the above-mentioned arbitrary elements, but also mean elements that do not impair the effects of the present invention even if they are contained. It is not limited to cases where it is added intentionally, but also includes elements that are unavoidably mixed in from ores used as raw materials, scraps, or the manufacturing environment when industrially manufacturing steel sheets. The estimated 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, which causes a relatively large change in chemical composition (reduction in content). be. Depending on the element, the content may be reduced to 50 ppm or less, and if purification annealing is performed sufficiently, it may even reach a level that cannot be detected by general analysis (1 ppm or less).
It should be noted that the above chemical composition of the grain-oriented electrical steel sheet according to the present invention is the chemical composition of the final product, and is different from the composition of the later-described slab, which is also the starting material.

The chemical components of the grain-oriented electrical steel sheet according to the present invention may be measured by a general steel analysis method. For example, the chemical composition of a grain-oriented electrical steel sheet may be measured using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Specifically, a 35 mm square test piece taken from a grain-oriented electrical steel sheet is measured using a Shimadzu ICPS-8100 (measuring device) under conditions based on a pre-prepared calibration curve to determine the chemical composition. be identified. Note that C and S may be measured using a combustion-infrared absorption method, and N may be measured using an inert gas melting-thermal conductivity method.

A coating generally provided on grain-oriented electrical steel sheets may be formed on the surface of the grain-oriented electrical steel sheet according to the present invention. These are called, for example, glass coatings, insulation coatings, tension coatings, and the like.

However, these coatings are not essential elements of the grain-oriented electrical steel sheet according to the present invention. The above chemical composition of the grain-oriented electrical steel sheet according to the present invention is the composition of the steel component that is the base material of the grain-oriented electrical steel sheet with a coating, and is measured after removing the surface insulation coating by grinding etc. shall be taken as a thing.

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

The steps and quantitative conditions in each step shown below are examples adopted to demonstrate the feasibility of implementing the present invention, and the present invention is not limited to these steps and quantitative values. The method for manufacturing a grain-oriented electrical steel sheet according to the present invention may employ various conditions as long as the purpose of the present invention is achieved without departing from the gist of the present invention.

(Casting process)
In the casting process, a slab is prepared. An example of a method for manufacturing a slab is as follows. Manufacture (melting) molten steel. Manufacture slabs using molten steel. The slab may be manufactured by continuous casting. An ingot may be manufactured using molten steel, and the ingot may be subjected to blooming rolling to manufacture 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 between 220 mm and 280 mm. As the slab, a so-called thin slab having a thickness of 10 mm to 70 mm may be used. When using a thin slab, rough rolling before finish rolling can be omitted in the hot process.

As the chemical composition of the slab, the chemical composition of a 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 effective element for controlling the primary recrystallized structure in the manufacturing process, if the content in the final product is excessive, it will adversely affect the magnetic properties. Therefore, the C content is 0.085% or less. A preferable upper limit of the C content is 0.075%. C is mainly removed in the decarburization annealing process described below, and becomes 0.005% or less after the final annealing process. When C is included, the lower limit of the C content may be more than 0%, and may be 0.001%, considering productivity in industrial production.

Si: 2.00% to 7.00%
Silicon (Si) increases the electrical resistance of grain-oriented electrical steel sheets and reduces core loss. If the Si content is less than 2.00%, γ transformation occurs during final 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%, cold workability decreases and cracks are likely to occur during cold rolling. The lower limit of the Si content is preferably 2.50%, more preferably 3.00%. A preferable upper limit of the Si content is 4.50%, more preferably 4.00%.

Mn: 0.05% to 1.00%
Manganese (Mn) combines with S or Se to produce MnS or MnSe, which functions as an inhibitor. When Mn is included, secondary recrystallization is stabilized when the Mn content is within the range of 0.05% to 1.00%. When a part of the inhibitor function is performed by nitride, the strength of MnS or MnSe as an 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, secondary recrystallization is stabilized when the total content of S and Se is 0.003% to 0.035%. When a part of the inhibitor function is performed by nitride, the strength of MnS or MnSe as an inhibitor is controlled to be weak. Therefore, a preferable upper limit of the total S and Se content is 0.025%, more preferably 0.010%. When S and Se remain after final annealing, they form a compound and deteriorate iron loss. Therefore, it is preferable to reduce S and Se as much as possible by purification during final 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 either S or Se, and neither S nor Se The content of either one may be 0.003% to 0.035% in total, or the slab may contain both S and Se, and the content of S and Se may be 0.003% to 0 in total. It may be .035%.

Al: 0.010% to 0.065%
Aluminum (Al) combines with N to precipitate as (Al, Si)N, and functions as an inhibitor. When containing Al, when the Al content is within the range of 0.010% to 0.065%, AlN as an inhibitor formed by nitriding described below expands the secondary recrystallization temperature range, In particular, secondary recrystallization is stabilized at high temperatures. Therefore, the Al content is 0.010% to 0.065%. A preferable lower limit of the Al content is 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) combines with Al and functions as an inhibitor. Since N can be contained by nitriding during the manufacturing process, no lower limit is specified. On the other hand, when N is included, if the N content exceeds 0.012%, blisters, which are a type of defect, are likely to occur in the steel sheet. A preferable upper limit of the N content is 0.010%, more preferably 0.009%. N is purified in the final annealing process, and may be 0.005% or less after the final annealing process.

The remainder of the chemical composition of the slab consists of Fe and impurities. In addition, "impurities" as used herein are unavoidable components contained in raw materials or components mixed in during the manufacturing process when slabs are manufactured industrially, and which substantially affect the effects of the present invention. means an element that does not give

The chemical composition of the slab may contain known arbitrary elements in place of a portion of Fe, in order to solve manufacturing problems, strengthen the inhibitor function through compound formation, and consider the effect on magnetic properties. . Examples of optional elements contained in place of a part of Fe include the following elements. Each numerical value means the upper limit when those elements are contained as optional elements.
In 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.
These arbitrary elements may be contained according to known purposes, so there is no need to set a lower limit for the content of the arbitrary elements, and the lower limit 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 plate. In the hot rolling process, for example, the silicon steel material (slab) heated in the heating process is roughly rolled, and then finish rolled to a predetermined thickness, for example, 1.8 mm to 3.5 mm. Use steel plate. After finish rolling, the hot rolled steel sheet may be rolled up at a predetermined temperature.

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

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

(cold rolling process)
In the cold rolling process, the hot rolled steel plate obtained in the hot rolling process or the annealed steel plate obtained in the hot rolled plate annealing process is cold rolled once or multiple times (through annealing (intermediate annealing)). This is a process 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, at a total cold rolling rate of 80% to 95%) (two or more times).

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

(Nitriding treatment)
The manufacturing method according to one embodiment of the present invention may include a nitriding step. The nitriding treatment is a process that is performed as necessary to adjust the strength of the inhibitor in secondary recrystallization. The nitriding treatment increases the amount of nitrogen in the steel sheet by about 40 ppm to 200 ppm between the start of decarburization treatment and the start of secondary recrystallization in final annealing. Examples of the nitriding treatment include annealing in an atmosphere containing a gas with nitriding ability such as ammonia, and finish annealing of a decarburized annealed steel sheet coated with an annealing separator containing a powder with nitriding ability such as MnN. etc. are exemplified.

(Annealing separator application process)
The annealing separator application process is a process of applying an annealing separator to a decarburized annealed steel plate, and is a process that is performed as necessary. As the annealing separator, for example, an annealing separator containing MgO as a main component can be used. The decarburized and annealed steel sheet coated with the annealing separator is wound up into a coil and is finish annealed in the next finish annealing step.

(Final annealing process)
The final annealing step is a step in which a decarburized annealed steel sheet or a decarburized annealed steel sheet coated with an annealing separator is subjected to final annealing to cause secondary recrystallization. In this step, by proceeding with secondary recrystallization while suppressing the growth of primary recrystallized grains with an inhibitor, {100}<001> oriented grains grow preferentially, and the magnetic flux density is dramatically improved.

(Tension film formation process)
A coating solution (e.g., containing phosphoric acid or phosphates, chromic acid or chromate anhydride, and colloidal silica) is applied to a steel plate and baked (e.g., at 350°C to 1150°C for 5 seconds). 300 seconds) to form a tension coating.

(Groove formation process)
For the purpose of magnetic domain control (magnetic domain refining), grain-oriented electrical steel sheets are made with local grooves using known methods such as laser, electron beam, plasma, mechanical methods, and etching in the post-cold rolling process. It is formed. Generally, grooves with a depth of approximately several μm to several tens of μm extend in a direction that makes an angle of 0 to 50 degrees with the direction perpendicular to the rolling direction, and at regular intervals of approximately several mm to several tens of mm. is formed. The depth d (mm) of the groove in one embodiment of the present invention will be described later. Further, in one aspect of the present invention, the grooves may extend in a direction forming an angle of 0 to 30 degrees with the direction perpendicular to the rolling direction, and be formed at regular intervals of about 2 mm to 30 mm. Here, "constant" means that the actual spacing between each groove is within ±10% of the prescribed value with respect to the spacing prescribed above. Further, the groove width is preferably from 20 μm to 100 μm. Note that the groove width refers to the average dimension in a cross section perpendicular to the groove forming direction.
The grooves may be formed at any timing, such as immediately after cold rolling and before decarburization annealing, after decarburization annealing, after final annealing, or after the formation of a tension film.
In the present invention, the depth of the grooves to be formed is defined in relation to the magnetic flux density of the electromagnetic steel sheet with and without grooves.

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 depth d (μm) of the groove may satisfy the following formula (2).

Here, B8(T) is the magnetic flux density when the steel plate is excited at 800 (A/m), B8n is the magnetic flux density B8 of the non-grooved material or the steel plate from which the grooves have been removed, and B8m is the magnetic flux density of the grooved material. The magnetic flux density is B8.
According to this equation (2), the magnetic flux density B8n of the non-grooved material (electromagnetic steel sheet before forming grooves) or the electromagnetic steel sheet (material) with grooves removed, and the magnetic flux density B8n of the grooved material (electromagnetic steel sheet after forming grooves) From the magnetic flux density B8 _m of the steel plate), the depth d of the groove to obtain B8 _m defined by the present invention can be determined. In other words, by forming a groove with a groove depth d that satisfies formula (2), B8 _m of the groove forming material (electromagnetic steel sheet after forming the groove) can be obtained. In addition, iron loss can be reduced if the steel plate has a groove depth d that satisfies equation (2). 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, or may be 1.91 (T). Further, the upper limit value of B8n may be 1.95(T) or more, or may be 1.94(T).

The present invention will be explained using the following examples. However, the present invention should not be interpreted as being limited to this example.

A grain-oriented electrical steel sheet (with a chemical composition of 2.00 to 7.00% Si content, the balance being Fe and impurities) with a thickness of 0.23 mm and which has a tension coating formed thereon is produced by a conventional method. Several types were prepared. The B8n of the electromagnetic steel sheet before groove formation was 1.90 to 1.96 (T). Grooves with a width of 50 μm were introduced into each electromagnetic steel sheet substantially parallel to the sheet width direction at intervals of 5 mm using a gear roll. At this time, the pressure applied to the gear roll was changed to control the groove depth d to be the various depths listed in Table 1. B8k (T) and iron loss W17/50 (W/kg) after groove formation were measured for the sample after groove formation. The measurement results are shown in Table 1.
For evaluation <1> in Table 1, those whose B8k(T) after groove formation satisfies the following formula are marked as "O", and those that do not meet are marked as "-". “〇” means that the decrease in magnetic flux density due to groove formation is small.
B8k(T)≧1.87(T)
In addition, for evaluation <2> in Table 1, iron loss W17/50 (W/kg) is ``-'' if it is over 0.84, ``〇'' if it is 0.84 or less, and ``〇'' if it is 0.78 or less. Those with a score of 0.72 or less were marked with a "◎" and those with a score of 0.72 or less were marked with a "☆."
According to the present invention, it is possible to obtain an electromagnetic steel sheet in which the decrease in magnetic flux density due to groove formation is small and the iron loss is low.

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 (with a chemical composition of 2.00 to 7.00% Si content, the balance being Fe and impurities) with a thickness of 0.23 mm and which has a tension coating formed thereon is produced by a conventional method. Several types were prepared. The electromagnetic steel sheet had a B8na of 1.90 to 1.91 (T) before groove formation. Grooves with a width of 50 μm were introduced into each electromagnetic steel sheet substantially parallel to the sheet width direction at intervals of 5 mm using a gear roll. The depth d of the groove 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 introducing the grooves, the pressure applied to the gear roll was varied so that the determined groove depth d was achieved. The reproduction test was repeated 100 times under the same conditions. B8ka (T) and iron loss W17/50 (W/kg) after groove formation were measured for the sample after groove formation. Table 2 shows the average value of B8ka (T) and the results of yields with iron loss W17/50 of 0.8 (W/kg) or less. Here, when the yield was 95% or more, it was marked as ○, and when it was less than 95%, it was marked as -. Note that the comparative example is the result of forming grooves using a conventional method using FIG.
According to the present invention, an electromagnetic steel sheet with a small decrease in magnetic flux density due to groove formation and a low core loss can be obtained at a high yield.

A grain-oriented electrical steel sheet (having a chemical composition of 3.20% Si content and the balance being Fe and impurities) having a thickness of 0.23 mm and having a tension coating formed thereon was prepared by a conventional method. The B8n of the electromagnetic steel sheet before groove formation was 1.90 (T). Grooves were introduced into each electromagnetic steel sheet approximately parallel to the sheet width direction at intervals of 5 mm using a gear roll. At this time, the groove depth d was adjusted to approximately 20 μm by changing the pressure applied to the gear roll.
The groove widths W were controlled to be various as shown in Table 3. B8k (T) and iron loss W17/50 (W/kg) after groove formation were measured for the sample after groove formation. The measurement results are shown in Table 3.
For evaluation <1> in Table 3, those whose B8k(T) after groove formation satisfies the following formula are marked as "O", and those that do not meet are marked as "-". “〇” means that the decrease in magnetic flux density due to groove formation is small.
B8k(T)≧1.87(T)
In addition, for evaluation <2> in Table 3, iron loss W17/50 (W/kg) is "-" if it is over 0.84, "○" if it is 0.84 or less, and "〇" if it is 0.78 or less. Those with a score of 0.72 or less were marked with a "◎" and those with a score of 0.72 or less were marked with a "☆."
According to the present invention, it is possible to obtain an electromagnetic steel sheet in which the decrease in magnetic flux density due to groove formation is small and the iron loss is low.

A grain-oriented electrical steel sheet (having a chemical composition of 3.20% Si content and the balance being Fe and impurities) having a thickness of 0.23 mm and having a tension coating formed thereon was prepared by a conventional method. The B8n of the electromagnetic steel sheet before groove formation was 1.90 (T). Grooves were introduced into each electromagnetic steel sheet approximately parallel to the width direction of the sheet at intervals of 1.5 to 40 mm using a gear roll. At this time, the pressure applied to the gear roll was controlled to adjust the groove depth d to approximately 20 μm.
The groove spacing p was controlled to be various as shown in Table 4. B8k (T) and iron loss W17/50 (W/kg) after groove formation were measured for the sample after groove formation. The measurement results are shown in Table 4.
For evaluation <1> in Table 4, those whose B8k(T) after groove formation satisfies the following formula are marked as "O", and those that do not meet are marked as "-". “〇” means that the decrease in magnetic flux density due to groove formation is small.
B8k(T)≧1.87(T)
In addition, for evaluation <2> in Table 4, iron loss W17/50 (W/kg) is ``-'' if it is over 0.84, ``〇'' if it is 0.84 or less, and ``○'' if it is 0.78 or less. Those with a score of 0.72 or less were marked with a "◎" and those with a score of 0.72 or less were marked with a "☆."
According to the present invention, it is possible to obtain an electromagnetic steel sheet in which the decrease in magnetic flux density due to groove formation is small and the iron loss is low.

Claims (1)

A chemical that includes a casting process, a hot rolling process, a cold rolling process, a decarburization annealing process, and a final annealing process, and contains Si: 2.00 to 7.00% by mass %, and the balance is Fe and impurities. A method for producing a grain-oriented electrical steel sheet having a composition, comprising a groove forming step of forming grooves at regular intervals in a direction intersecting the rolling direction and with the groove depth direction in the sheet thickness direction after the cold rolling step,
The groove forming step is after the tension coating forming step,
The magnetic flux density when the steel plate is excited at 800 (A/m) is defined as B8 (T),
The target B8(T) of the grooved material is defined as B8m(T), the B8(T) of the non-grooved material is defined as B8n(T), the interval between the grooves is p (mm), and the groove is rolled. The groove depth d (μm) formed in the groove forming step is calculated according to the following formula (2), where the angle formed with the perpendicular direction is defined as θ (°), and the groove width A method for producing a grain-oriented electrical steel sheet in which W is 20 to 100 μm.
here
B8n≧1.90(T), B8m≧1.87(T)
0≦θ≦30°
2≦p≦30
q=0.075.

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