JP2022022490A - Grain oriented electrical steel sheet - Google Patents

Abstract

To further reduce noise without impairing the core loss reduction effect of a grain oriented electrical steel sheet obtained by controlling the shape of a linear groove formed for subdividing a magnetic domain and the Ra value of surface roughness on the bottom and side surfaces of the groove within a fixed range.SOLUTION: A grain oriented electrical steel sheet includes a steel sheet including, by mass%, at least Si:2.50-4.50% and Mn:0.01-0.15 and the remainder consisting of Fe and impurities, having a linear groove extended in a direction forming an angle of 0-30° to a rolling rectangular direction and formed at an interval of 1-20 mm and having a steel sheet surface. A depth D of the groove is 10-50 μm; a groove width W is 20-200 μm; a Ra value of the surface roughness of the groove bottom surface is more than 5.0 μm:; the MnS of the groove bottom surface is not subjected to the substitution of Cu, etc. to a sulfide and the coating of Cu, etc.; and the Ra value of the surface roughness of the groove side surface is 0.1-5.0 μm.SELECTED DRAWING: Figure 1

Description

The present invention relates to grain-oriented electrical steel sheets.

The grain-oriented electrical steel sheet generally contains about 2% by mass to 5% by mass of Si as a steel sheet component, and the orientation of the crystal grains of the steel sheet is highly integrated in the {110} <001> orientation called the Goss orientation. It is a steel plate. The grain-oriented electrical steel sheet has excellent magnetic characteristics and is used, for example, as an iron core material for a static induction device such as a transformer.

In such grain-oriented electrical steel sheets, various technological developments have been made in order to improve the magnetic characteristics. In particular, with the recent demand for energy saving, further reduction of iron loss is required for grain-oriented electrical steel sheets. In order to reduce the iron loss of the grain-oriented electrical steel sheet, it is effective to increase the degree of integration in the Goss direction with respect to the orientation of the crystal grains of the steel sheet to improve the magnetic flux density and reduce the hysteresis loss.

The grain-oriented electrical steel sheet used as the base material of the winding transformer is required to have low iron loss and at the same time further low noise. In electrical steel sheets, magnetic domain subdivision is performed to reduce iron loss, but in winding transformers, strain removal and annealing is performed in the manufacturing process, so heat-resistant magnetic domain subdivision technology is required when performing magnetic domain subdivision. be.

As a heat-resistant magnetic domain control subdivision method, there is a method of forming periodic grooves in a steel sheet. For example, in Patent Document 1, the N content in the forsterite film formed after final finish annealing is suppressed to 3.0% by mass or less, and magnetic domain subdivision treatment by laser irradiation is performed. It is disclosed that the iron loss of the grain-oriented electrical steel sheet is reduced. In addition, by controlling the amount of Al and Ti in the forsterite film to suppress fluctuations in the composition of each forsterite, and making the standard deviation of the forsterite particle size 1.0 times or less the average particle size, iron loss It is disclosed that the improvement effect is further improved.

In Patent Document 2, linear scratches having an interval of 5 mm or less, a width of 1 mm or less, a depth of 0.3 to 5.0 μm in Ra value and a Rmax value of 10 μm or less are formed on the surface of the steel sheet before or after decarburization annealing. It is described that by applying the coating, a grain-oriented electrical steel sheet having extremely excellent iron loss and excellent film adhesion can be obtained.

Patent Document 3 describes a grain-oriented electrical steel sheet having a steel sheet surface extending in a direction intersecting the rolling direction and having a groove formed in which a groove depth direction is a plate thickness direction. The formed groove has an asymmetric shape with respect to the groove width center in the groove width direction. The average depth of the groove having such a cross-sectional shape, the arithmetic average height Ra of the roughness curve forming the contour of the groove bottom region, and the average length RSm of the roughness curve element forming the contour of the groove bottom region are calculated. It is disclosed that the iron loss reduction effect can be obtained by setting the specific range.

Patent Documents 1 to 3 have proposed various magnetic domain subdivision techniques for obtaining the effect of reducing iron loss in the case of magnetic domain subdivision, but have not proposed any noise reduction.

Japanese Unexamined Patent Publication No. 2012-31512 Japanese Unexamined Patent Publication No. 1-189429 International Publication No. 2016/171130

The grain-oriented electrical steel sheet used as the base material of the winding transformer is required to have lower noise as well as lower iron loss. The heat-resistant magnetic domain subdivision is generally performed by forming a linear groove, but at present, a sufficient noise reduction effect has not been obtained.
When the surface roughness of the linear groove formed for the subdivision of the magnetic domain is large, the domain wall area changes due to the domain wall movement, and the domain wall moves more slowly due to the greater pinning effect than when there is no groove. Become. At this time, on the side surface of the groove, the leakage of magnetic flux is reduced due to the large surface roughness, and the effect of reducing iron loss is greatly reduced. On the other hand, when the surface roughness is large on the bottom surface of the groove, the reduction of magnetic flux leakage is small, and the effect on the iron loss reduction effect is small.

In the present invention, the heat transfer coefficient of the precipitate on the surface of the steel plate is deviated from the specific heat and the heat transfer coefficient of the base iron by performing a pickling treatment using a special pickling solution before the groove formation. Then, it is an object to promote the unevenness of the groove bottom surface due to the difference in heat transfer at the time of groove formation by laser irradiation, and to obtain the noise reduction effect without impairing the iron loss reduction effect.

The present invention has been made in view of the above problems. By controlling the Ra value of the shape of the linear groove formed for magnetic domain subdivision and the surface roughness of the groove bottom surface and the groove side surface within a certain range, the iron loss of the obtained grain-oriented electrical steel sheet is reduced. At the same time, the purpose is to realize further noise reduction.

The gist of the present invention is mass%, containing at least Si: 2.50 to 4.50%, Mn: 0.01 to 0.15%, the balance being Fe and impurities, and 0 to 0 to the direction perpendicular to the rolling direction. A directional electromagnetic steel plate having a steel plate surface having linear grooves extending in a direction forming an angle of 30 ° formed at intervals of 1 to 20 mm, wherein the groove depth D is 10 to 10 to. It is 50 μm, the groove width W is 20 to 200 μm, the Ra value of the surface roughness of the groove bottom surface is more than 5.0 μm, and the MnS of the groove bottom surface is Cu, Hg, Ag, Pb, Cd, Co, Zn. And one selected from the group consisting of Ni without substitution with one or more sulfides selected from the group consisting of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni. Alternatively, it is a directional electromagnetic steel sheet that is not coated with two or more kinds and has a Ra value of the surface roughness of the groove side surface of 0.1 to 5.0 μm.
Hereinafter, in the present specification, "one or more selected from the group consisting of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni" is simply referred to as "Cu and the like", and "Cu, etc." One or more sulfides selected from the group consisting of Hg, Ag, Pb, Cd, Co, Zn and Ni "are simply referred to as" sulfides such as Cu ".

According to the present invention, the groove formed by the laser irradiation makes the bottom surface of the groove uneven, so that the pinning effect of the domain wall is increased and the noise is reduced while maintaining the iron loss reducing effect.

FIG. 1 is a cross-sectional view of a groove portion of a grain-oriented electrical steel sheet of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail. Unless otherwise specified, the notation "A to B" for the numerical values A and B means "A or more and B or less". When a unit is attached only to the numerical value B in such a notation, the unit shall be applied to the numerical value A as well.

[Component composition of steel sheet]
First, the composition of the steel sheet used for the grain-oriented electrical steel sheet according to the invention will be described.
In the following, unless otherwise specified, the notation "%" means "mass%". Further, the balance of the steel sheet other than the elements described below is Fe and impurities.

The components of the steel sheet used in the grain-oriented electrical steel sheet according to the present invention have a preferable component composition for controlling the crystal orientation to a Goss texture integrated in the {110} <001> orientation, and at least Si: 2. It contains 50 to 4.50% and Mn: 0.01 to 0.15%.

(Si: 2.50-4.50%)
The content of Si (silicon) is 2.50 to 4.50%. Si reduces the eddy current loss, which is one of the causes of iron loss, by increasing the electric resistance of the steel sheet. When the Si content is less than 2.50%, it becomes difficult to sufficiently suppress the eddy current loss of the final grain-oriented electrical steel sheet, which is not preferable. When the Si content is more than 4.50%, the workability of the grain-oriented electrical steel sheet is deteriorated, which is not preferable. Therefore, the Si content is 2.50 to 4.50%, preferably 2.70 to 4.00%.

(Mn: 0.01-0.15%)
The content of Mn (manganese) is 0.01 to 0.15%. Mn forms MnS, MnSe and the like, which are inhibitors that influence secondary recrystallization. When the Mn content is less than 0.01%, the absolute amounts of MnS and MnSe that cause secondary recrystallization are insufficient, which is not preferable. When the Mn content is more than 0.15%, it is not preferable because it becomes difficult to dissolve Mn during slab heating. Further, when the Mn content is more than 0.15%, the precipitation sizes of the inhibitors MnS and MnSe tend to be coarse, and the optimum size distribution as an inhibitor is impaired, which is not preferable. Therefore, the Mn content is 0.01 to 0.15%, preferably 0.03 to 0.13%.

Components other than Si and Mn can be components contained in ordinary grain-oriented electrical steel sheets.
For example, as components other than Si and Mn, C: ~ 0.085% or less, acid-soluble Al: ~ 0.065% or less, N: ~ 0.012% or less, Cr: ~ 0.3% in mass%. Below, Cu: ~ 0.4% or less, P: ~ 0.5% or less, Sn: ~ 0.3% or less, Sb: ~ 0.3% or less, Ni: ~ 1% or less, S: ~ 0. It can contain 015% or less, Se: ~ 0.015% or less, and Bi: ~ 0.02% or less.

The rest of the steel sheet other than the above components is Fe and impurities. Here, the impurity element refers to a component contained in the raw material or a component mixed in the manufacturing process and not intentionally contained in the steel sheet.

Due to the subdivision of magnetic domains, grooves are formed on the surface of the steel sheet extending in a direction intersecting the rolling direction and having a groove depth direction in the plate thickness direction. The groove may be provided so as to intersect the rolling direction, and the groove extending direction and the rolling direction do not necessarily have to be orthogonal to each other, but form an angle of 0 to 30 ° with the rolling perpendicular direction. It is provided in the direction. Further, the groove does not necessarily have a linear shape when viewed from the plate thickness direction (when the groove is viewed in a plane), and may have an arcuate shape. The following groove shape is measured by removing the insulating film from the final product by pickling or the like.

The grooves are formed on the surface of the steel sheet at intervals of 1 to 20 mm. If the groove spacing is less than 1 mm, the magnetic domain subdivision effect is saturated and the eddy current loss reduction effect can hardly be obtained, but the hysteresis loss increases due to the strain, so that the iron loss increases, which is not preferable. If it exceeds 20 mm, the effect of subdividing the magnetic domain decreases, so that the effect of improving iron loss is insufficient, which is not preferable. A preferred groove spacing is 2-10 mm.

FIG. 1 is a cross-sectional view of a groove portion of an electromagnetic steel sheet of the present invention. In this figure, the groove portion has a shape close to a trapezoid, but the groove shape may be a bow shape. In one embodiment of the electrical steel sheet of the present invention, the depth D of the groove is in the range of 10 μm to 50 μm. When the depth D is less than 10 μm, the amount of magnetic poles generated from the side surface of the groove is small, and a sufficient iron loss reduction effect cannot be obtained. When the depth D exceeds 50 μm, the magnetic domain is subdivided, but the decrease in magnetic flux density due to groove formation becomes large, and a sufficient iron loss reduction effect cannot be obtained. The preferred depth is 15 μm to 30 μm.

(Measurement of groove depth D)
The method for measuring "depth D" according to the present invention is as follows.
Select any one location of the electromagnetic steel plate, and the deeper of the maximum depths of the two groove portions (A) and (B) separated by any 3 mm shown in the groove cross-sectional view of FIG. 1 is the deeper. The measurement was performed using a laser microscope (a 3D laser microscope using a confocal optical system with pinholes) with the shallow side as the depth d'. The depth D is the average value of these values.

The "width W of the groove portion" referred to in the present invention is a portion indicated by w, w'in FIG. 1. The width W of the groove portion is in the range of 20 μm to 200 μm. When the width W is less than 20 μm, the magnetic flux leaking from the groove side surface enters the groove side surface on the opposite side, the amount of magnetic poles generated is reduced, and a sufficient iron loss reduction effect cannot be obtained. When the width W exceeds 200 μm, the iron loss reducing effect is saturated, the laser power required for forming the groove is increased, and the manufacturing cost is only increased. The preferred width W is 30 to 100 mm.

(Measurement of groove width W)
The method for measuring the "groove width W" according to the present invention is as follows.
Of the width in which the groove depths of the two groove portions (A) and (B) separated by an arbitrary 3 mm are halved, as shown in the groove cross-sectional view of FIG. The measurement was performed using a laser microscope (3D laser microscope using a confocal optical system with pinholes) with the wide side as w and the narrow side as w'. The groove width W is an average value of these values.

The "surface roughness Ra value of the groove bottom surface and the groove side surface" as used in the present invention is the arithmetic mean height Ra of the roughness curve of the groove bottom surface and the groove side surface between the two points (A) and (B) in FIG. It is a value. The definition of the arithmetic mean height Ra of the roughness curve follows the Japanese Industrial Standards JIS B 0601 (2013).
The "groove bottom surface" means the portion where the bottom depth of the groove is the deepest. "Groove side surface" means a side surface portion where the depth is half of the maximum groove depth in the groove cross section.

In the grain-oriented electrical steel sheet of the present invention, Ra on the bottom surface of the groove is more than 5.0 μm, preferably 6.0 μm or more. The upper limit is 10.0 μm or less, preferably 8.0 μm or less. This is because if Ra is less than 5.0 μm, the noise reduction effect cannot be obtained. When Ra exceeds 10.0 μm, the effect of increasing the hysteresis loss becomes large, and a grain-oriented electrical steel sheet having low noise and low iron loss cannot be obtained. Further, in the grain-oriented electrical steel sheet of the present invention, MnS on the bottom surface of the groove is not replaced with a sulfide such as Cu, or is not coated with Cu or the like. Here, "MnS on the bottom surface of the groove is not replaced with sulfide such as Cu or coated with Cu" means that the substitution rate of MnS being replaced with sulfide such as Cu is 0% and MnS. Means that the coverage rate covered with Cu or the like is 0%.

In the grain-oriented electrical steel sheet of the present invention, Ra on the side surface of the groove is 0.1 to 5.0 μm, preferably 0.1 to 3.0 μm, and more preferably 0.1 to 1.0 μm. When Ra is less than 0.1 μm, there is no problem with the magnetic characteristics, but it is difficult to realize in terms of manufacturing technology. When Ra exceeds 5.0 μm, the pinning effect of the domain wall becomes large, the hysteresis loss increases, and a sufficient iron loss reducing effect cannot be obtained.

In the grain-oriented electrical steel sheet of the present invention, MnS on the bottom surface of the groove is not replaced with sulfide such as Cu or coated with Cu or the like, Ra on the bottom surface of the groove is more than 5.0 μm, and the surface of the side surface of the groove is formed. The reason why both low iron loss and low noise are achieved by setting the roughness Ra to the range of 0.1 to 5.0 μm is that the iron loss reduction effect can be obtained by controlling the surface roughness Ra of the groove side surface. This is probably because the noise reduction effect is obtained by controlling the surface roughness Ra of the bottom surface of the groove.

(Measuring method of surface roughness Ra of groove bottom surface and groove side surface)
Each Ra was measured using a laser microscope (3D laser microscope using a confocal optical system with pinholes). Select any one place of the electrical steel sheet, and set the points d and d'of the maximum depths of the two groove portions (A) and (B) separated by any 3 mm as shown in the groove cross-sectional view of FIG. The unevenness of the bottom surface of the groove of the connected straight line is defined as the surface roughness Ra of the bottom surface of the groove of the present invention. Further, among the points (d / 2, d'/ 2) that are half the depths of the maximum depths d and d'of both grooves, the points on the same side with the maximum depth in between are connected. Ra and Ra'of the unevenness of the groove side surface of a straight line are derived, and the average value of these values is defined as Ra on the groove side surface.

[Manufacturing method of grain-oriented electrical steel sheet]
The manufacturing process of the directional electromagnetic steel sheet of the present invention will be described separately by dividing it into a process for obtaining a cold-rolled steel sheet and a subsequent magnetic domain control process.

[Process from slab to obtaining cold-rolled steel sheet]
By mass%, hot rolling is performed on a slab containing at least Si: 2.50% to 4.50% and Mn: 0.01% to 0.15%, the balance of which is Fe and impurities. Obtain a rolled steel plate.
Next, the pickled steel plate is pickled to obtain a pickled plate, or the hot-rolled steel plate is annealed to obtain a hot-rolled annealed plate, and then the hot-rolled steel plate is acidified. A pickling plate is obtained by washing. The pickling solution used here contains one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni (also referred to as "Cu etc.") and has a concentration of each element. The total is 0.0001 to 0.1000% or less, and the pH is -1 or more and 5 or less. The liquid temperature of the pickling solution is 15 ° C. to 100 ° C., and the time for the steel sheet to be immersed in the pickling solution is 5 seconds or more and 200 seconds or less. A pickling plate is obtained by this pickling step, and the pickling plate is cold-rolled to obtain a cold-rolled steel sheet.

[Slab component composition]
The component of the slab used for manufacturing the grain-oriented electrical steel sheet according to the present invention contains at least Si: 2.50 to 4.50% and Mn: 0.01 to 0.15%.

The content of Si (silicon) is 2.5 to 4.5%. Si reduces the eddy current loss, which is one of the causes of iron loss, by increasing the electric resistance of the steel sheet. When the Si content is less than 2.5%, it becomes difficult to sufficiently suppress the eddy current loss of the final grain-oriented electrical steel sheet, which is not preferable. When the Si content is more than 4.5%, the workability of the grain-oriented electrical steel sheet is deteriorated, which is not preferable. Therefore, the Si content is 2.5% to 4.5%, preferably 2.7 to 4.0%.

The content of Mn (manganese) is 0.01 to 0.15%. Mn forms MnS, MnSe and the like, which are inhibitors that influence secondary recrystallization. When the Mn content is less than 0.01%, the absolute amounts of MnS and MnSe that cause secondary recrystallization are insufficient, which is not preferable. When the Mn content is more than 0.15%, it is not preferable because it becomes difficult to dissolve Mn during slab heating. Further, when the Mn content is more than 0.15%, the precipitation sizes of the inhibitors MnS and MnSe tend to be coarse, and the optimum size distribution as an inhibitor is impaired, which is not preferable. Therefore, the Mn content is 0.01 to 0.15%, preferably 0.03 to 0.13%.

The components other than Si and Mn can be the following components.
For example, as components other than Si and Mn, C: 0.020 to 0.100%, total of one or two of S and Se: 0.001 to 0.050%, acid-soluble Al, in terms of mass%. : 0.010 to 0.050%, N: 0.002 to 0.015%, Cr: ~ 0.300% or less, Cu: ~ 0.400% or less, P: ~ 0.500% or less, Sn: ~ 0.300% or less, Sb: ~ 0.300% or less, Ni: ~ 1.000% or less, S: ~ 0.015% or less, Se: ~ 0.015% or less, Bi: ~ 0.020% It can contain:

The content of C (carbon) is 0.02 to 0.10%. C has various roles, but when the C content is less than 0.02%, the crystal grain size becomes excessively large when the slab is heated, resulting in iron loss of the final grain-oriented electrical steel sheet. It is not preferable because it increases the value. When the C content is more than 0.10%, the decarburization time becomes long and the manufacturing cost increases during decarburization after cold rolling, which is not preferable. Further, when the C content is more than 0.10%, decarburization tends to be incomplete, which may cause magnetic aging in the final grain-oriented electrical steel sheet, which is not preferable. Therefore, the content of C is 0.02 to 0.10%, preferably 0.05 to 0.09%.

The total content of S (sulfur) and Se (selenium) is 0.001 to 0.050%. S and Se form an inhibitor together with Mn described above. Both S and Se may be contained in the slab, but at least one of them may be contained in the slab. If the total content of S and Se is out of the above range, a sufficient inhibitory effect cannot be obtained, which is not preferable. Therefore, the total content of S and Se is 0.001 to 0.050%, preferably 0.001 to 0.040%.

The content of acid-soluble Al (acid-soluble aluminum) is 0.01 to 0.05%. The acid-soluble Al constitutes an inhibitor necessary for producing a grain-oriented electrical steel sheet having a high magnetic flux density. When the content of the acid-soluble Al is less than 0.01%, the acid-soluble Al is insufficient in quantity and the inhibitor strength is insufficient, which is not preferable. When the content of the acid-soluble Al is more than 0.05%, AlN precipitated as an inhibitor becomes coarse and the inhibitor strength is lowered, which is not preferable. Therefore, the content of acid-soluble Al is 0.01 to 0.05%, preferably 0.01 to 0.04%.

The content of N (nitrogen) is 0.002 to 0.015%. N forms the inhibitor AlN together with the acid-soluble Al described above. If the content of N is out of the above range, a sufficient inhibitory effect cannot be obtained, which is not preferable. Therefore, the content of N is 0.002 to 0.015%, preferably 0.002 to 0.012%.

Further, in addition to the above-mentioned elements, the slab used for producing the directional electromagnetic steel plate according to the present embodiment has Cu: 0. 4% or less, P: 0.5% or less, Sn: 0.3% or less, Sb: 0.3% or less, Ni: 1.0% or less, S: 0.015% or less, Se: 0.015% Hereinafter, one or more selected from the group consisting of Bi: 0.02% or less may be contained. In the slab according to one embodiment, the Cr content may be 0.02% or more, the Bi content may be 0.0005% or more, and the Sb content may be 0.005 in mass%. % Or more, Se content may be 0.001% or more, and Mo content may be 0.005% or more.

A slab is formed by casting molten steel adjusted to the composition of the components described above. The method of casting the slab is not particularly limited. Further, in research and development, even if a steel ingot is formed in a vacuum melting furnace or the like, the same effect as that in the case where a slab is formed can be confirmed for the above components.

[Process for making hot-rolled steel sheet]
The cast slab is heated at a predetermined temperature, and the heated slab is hot-rolled and processed into a hot-rolled steel sheet. The thickness of the hot-rolled steel sheet after processing may be, for example, 1.8 mm to 3.5 mm. When the thickness of the hot-rolled steel sheet is less than 1.8 mm, the temperature of the steel sheet after hot rolling becomes low and the amount of AlN deposited in the steel sheet increases, resulting in unstable secondary recrystallization, resulting in instability. It is not preferable for a grain-oriented electrical steel sheet having a target thickness of 0.23 mm or less because the magnetic properties are deteriorated. When the thickness of the hot-rolled steel sheet exceeds 3.5 mm, the rolling load in the cold rolling process becomes large, which is not preferable.

[Annealing process]
A normal hot-rolled sheet is annealed to obtain a hot-rolled annealed plate, and then the hot-rolled and annealed plate is subjected to a cold-rolling step.

[Process for making cold-rolled steel sheet]
After pickling the hot-rolled steel sheet, it is processed into a cold-rolled steel sheet by rolling it by one cold rolling or multiple cold rolling with intermediate annealing sandwiched between them.
Further, the steel sheet may be heat-treated at about 300 ° C. or lower between the cold rolling passes, between the rolling roll stands, or during rolling. In such a case, the magnetic properties of the final grain-oriented electrical steel sheet can be improved. The hot-rolled steel sheet may be rolled by cold rolling three or more times, but in order to increase the manufacturing cost, the hot-rolled steel sheet is cold-rolled once or twice. It is preferable to roll by rolling. When the cold rolling is performed by reverse rolling such as Zendimia mill, the number of passes in each cold rolling is not particularly limited, but from the viewpoint of manufacturing cost, 9 times or less is preferable.
The process from slab to obtaining cold-rolled steel sheet has been described above.

Subsequently, decarburization annealing is performed. The cold-rolled steel sheet is heat-treated (that is, decarburized and annealed) under predetermined temperature conditions (for example, heating at 700 to 900 ° C. for 1 to 3 minutes). When the decarburization annealing treatment is carried out, carbon is reduced to a predetermined amount or less in the cold-rolled steel sheet, and a primary recrystallization structure is formed. Further, in decarburization annealing, an oxide layer containing silica (SiO ₂ ) as a main component is formed on the surface of the cold-rolled steel sheet.

Subsequently, an annealing separator is applied. In this step, an annealing separator containing magnesia (MgO) as a main component is applied to the surface of the cold-rolled steel sheet (the surface of the oxide layer).
Subsequently, the cold-rolled steel sheet coated with the annealing separator, which is subjected to finish annealing, is heat-treated (that is, finish annealing) under predetermined temperature conditions (for example, conditions of heating at 1100-1300 ° C. for 20 to 24 hours). Processing) is carried out. When the finish annealing treatment is carried out, secondary recrystallization occurs in the cold-rolled steel sheet and the cold-rolled steel sheet is purified. As a result, a cold-rolled steel sheet having the above-mentioned chemical composition of the steel sheet and whose crystal orientation is controlled so that the axis of easy magnetization of the crystal grains and the rolling direction X coincide with each other can be obtained.

Further, when the finish annealing treatment as described above is carried out, the oxide layer containing silica as a main component reacts with the annealing separator containing magnesia as a main component, and forsterite (Mg) is formed on the surface of the steel sheet. ₂ A glass film containing a composite oxide such as SiO ₄ ) is formed. In the finish annealing process, the finish annealing treatment is performed with the steel sheet wound in a coil shape. By forming a glass film on the surface of the steel sheet during the finish annealing treatment, it is possible to prevent seizure from occurring on the coiled steel sheet.

[Pickling process]
Subsequently, the finished annealed plate is pickled.

The pickling solution contains one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni, and the total concentration of each element is 0.0001 to 0.1000%. , The pH is -1 or more and 5 or less. The liquid temperature of the pickling solution is 15 ° C. or higher and 100 ° C. or lower, and the time for the steel sheet to be immersed in the pickling solution is 5 seconds or longer and 200 seconds or shorter.

When the total concentration of one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni in the pickling solution is less than 0.0001%, the effect of inhibitor control in the plate thickness direction is effective. It is not preferable because it is insufficient. When the total concentration of one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni in the pickling solution is more than 0.1000%, the effect of improving magnetism is saturated. In addition, it is not preferable because the cost of the pickling solution increases. Therefore, the total concentration of one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni in the pickling solution is 0.0001 to 0.1000%.

If the pH of the pickling solution is less than -1, the acidity becomes too strong and it becomes difficult to handle the pickling solution, which is not preferable. When the pH of the pickling solution is more than 5, the effect of the inhibitor control in the plate thickness direction by the pickling treatment becomes insufficient, which is not preferable. Therefore, the pH of the pickling solution is -1 or more and 5 or less.

When the liquid temperature of the pickling solution is less than 15 ° C., the effect of inhibitor control in the plate thickness direction by the pickling treatment becomes insufficient, which is not preferable. If the temperature of the pickling solution exceeds 100 ° C., it becomes difficult to handle the pickling solution, which is not preferable. Therefore, the liquid temperature of the pickling solution is 15 ° C. or higher and 100 ° C. or lower.

When the time for the steel sheet to be immersed in the pickling solution in the pickling treatment is less than 5 seconds, the effect of the pickling treatment on the inhibitor control in the plate thickness direction is insufficient, which is not preferable. If the time for the steel sheet to be immersed in the pickling solution in the pickling treatment is more than 200 seconds, the equipment becomes long, which is not preferable. Therefore, in the pickling treatment, the time for the steel sheet to be immersed in the pickling solution is 5 seconds or more and 200 seconds or less.

When the finished annealed sheet is pickled under the above-mentioned conditions, MnS, which is a precipitate in the steel, is replaced with a sulfide such as Cu on the surface layer of the steel sheet, or is coated with Cu or the like. , The heat transfer coefficient of the surface layer of the steel sheet containing the precipitate becomes constant. Here, "substitution" means that the Mn portion of MnS originally formed is replaced with Cu or the like derived from a pickling solution, and MnS is replaced with a sulfide such as Cu, and is "coated". "" Means that Cu or the like derived from the pickling solution is newly deposited around the originally formed MnS. Since such a phenomenon in the present invention is not affected by the method of depositing Cu or the like, either the phenomenon of substitution of Cu or the like with a sulfide or the phenomenon of coating of Cu or the like may occur during the pickling treatment. As a result, the heat transfer effect such as laser irradiation can be made constant on the surface layer of the steel sheet. Under the above-mentioned conditions, pickling only homogenizes the heat transfer coefficient of the surface layer, so that Ra on the side surface of the groove near the surface layer is reduced. On the other hand, the Mn portion of MnS, which is a precipitate near the bottom surface of the groove away from the surface layer, is not replaced with the metal being pickled and is not coated. Therefore, the heat transfer coefficient is not made uniform, and Ra on the bottom surface of the groove is not reduced as compared with the side surface of the groove. Therefore, if MnS is not sufficiently replaced with a sulfide such as Cu by pickling, or if it is not coated with Cu or the like, the heat transfer coefficient of the surface layer of the steel sheet varies widely, and Ra on both the bottom surface and the side surface of the groove becomes large. On the other hand, even if the pickling time and the pickling liquid concentration are set to a certain level or higher, the effect of stabilizing the heat transfer coefficient is saturated, and the effect of stabilizing the heat transfer coefficient in the depth direction cannot be obtained. There is no reduction, and Ra at the bottom of the groove does not change. Further, the pickling conditions here vary depending on the depth of the groove to be formed, and it is better that the deeper the groove to be formed, the longer the pickling time, the higher the concentration of the pickling solution, or the lower the pH. Iron loss characteristics can be obtained.

[Step of forming a linear groove on the surface of a steel sheet]
In the subsequent laser irradiation step, the surface of the steel sheet on which the glass film is formed (only one side) is irradiated with a laser to roll a plurality of grooves extending in a direction intersecting the rolling direction on the surface of the steel sheet. It is formed at intervals of 1 to 20 mm along the direction.

In the laser irradiation step, the laser irradiation device irradiates the surface of the steel plate with laser light by rotationally driving the polygon mirror, and scans the laser light in a direction forming an angle of 0 to 30 ° with the rolling perpendicular direction.

Simultaneously with the irradiation of the laser beam, an assist gas such as air or an inert gas is sprayed onto the portion of the steel sheet irradiated with the laser beam. The inert gas is, for example, nitrogen, argon or the like. The assist gas plays a role of removing molten or evaporated components from the steel sheet by laser irradiation. By spraying the assist gas, the laser beam reaches the steel sheet without being hindered by the melted or evaporated components, so that the grooves are stably formed.

As the laser light source, a high-power laser generally used for industrial purposes such as a fiber laser, a YAG laser, a semiconductor laser, or a CO ₂ laser can be used. Further, a pulse laser or a continuous wave laser may be used as a laser light source as long as the groove can be stably formed. As the laser light, it is preferable to use a single-mode laser having high light-collecting property and suitable for forming grooves.

As the irradiation conditions of the laser light, for example, the laser output is 200 W to 3000 W, and the focused spot diameter in the rolling direction of the laser light (that is, the diameter including 86% of the laser output, hereinafter abbreviated as 86% diameter) is 10 μm to 200 μm. It is preferable to set the focused spot diameter (86% diameter) in the plate width direction of the laser beam to 10 μm to 1000 μm and the laser scanning speed to 5 m / s to 50 m / s. These laser irradiation conditions are appropriately adjusted so that a groove depth D of 10 to 50 μm can be obtained.

In the final insulating film forming step, an insulating coating liquid containing, for example, colloidal silica and phosphate is applied over the glass film onto the surface of the steel sheet in which the grooves are formed by the above laser irradiation. Then, the heat treatment is carried out under a predetermined temperature condition (for example, 840 to 920 ° C.), and finally, the grain-formed steel sheet, the glass film and the insulating steel sheet according to the present invention are provided. Is obtained.

With respect to the groove shape formed on the obtained grain-oriented electrical steel sheet, the groove depth D, the groove width W, and the surface roughness Ra of the groove bottom surface and the groove side surface were measured by using the above-mentioned measuring methods.

Hereinafter, the grain-oriented electrical steel sheet of the present invention will be described more specifically with reference to examples. It should be noted that the examples shown below are merely examples of the grain-oriented electrical steel sheets according to the present embodiment, and the grain-oriented electrical steel sheets according to the present embodiment are not limited to the examples shown below.

By mass fraction, Si: 3.0%, C: 0.08%, acid-soluble Al: 0.05%, N: 0.01%, Mn: 0.12%, Cr: 0.05%, Cu : 0.04%, P: 0.01%, Sn: 0.02%, Sb: 0.01%, Ni: 0.005%, S: 0.007%, Se: 0.001%. Then, hot rolling was carried out on the slab having a chemical component whose balance was Fe and impurities, and a hot-rolled steel plate having a thickness of 2.3 mm was obtained.

Subsequently, the hot-rolled steel sheet was annealed under the temperature condition of heating at 1000 ° C. for 1 minute.
After the annealing treatment, cold rolling was carried out to obtain a cold-rolled steel sheet having a thickness of 0.23 mm. Subsequently, the cold-rolled steel sheet was subjected to decarburization-annealing treatment under a temperature condition of heating at 800 ° C. for 2 minutes, and then an annealed separator containing magnesia (MgO) as a main component was cold-rolled. It was applied to the surface of the steel plate.

Subsequently, the cold-rolled steel sheet coated with the annealing separator was subjected to finish annealing under the temperature condition of heating at 1200 ° C. for 20 hours. As a result, a steel sheet having the above-mentioned chemical composition and having a crystal orientation controlled so that the axis of easy magnetization of the crystal grains and the rolling direction coincide with each other was obtained, and a steel sheet having a glass film formed on the surface was obtained.

The surface of the finished annealed sheet was pickled under the pickling solution and pickling conditions shown in Table 1, and then cold-rolled to obtain a cold-rolled steel sheet having a thickness of 0.23 mm. Subsequently, the cold-rolled steel sheet was subjected to decarburization-annealing treatment under a temperature condition of heating at 800 ° C. for 2 minutes, and then an annealed separator containing magnesia (MgO) as a main component was cold-rolled. It was applied to the surface of the steel plate.

Table 1 shows the components, concentration, pH value, and immersion time of the pickling solution used.

Subsequently, the surface of the steel sheet was irradiated with a laser to form a plurality of grooves extending in a direction intersecting the rolling direction on the surface of the steel sheet at predetermined intervals along the rolling direction.

The laser light irradiation conditions are such that the laser output is in the range of 200 W to 3000 W and the focused spot diameter (86% diameter) in the rolling direction of the laser light is in the range of 10 μm to 500 μm so that the desired groove depth D can be obtained. The focused spot diameter (86% diameter) in the plate width direction of the laser beam is in the range of 10 μm to 1000 μm, the laser scanning speed is in the range of 5 m / s to 50 m / s, and the laser scanning pitch (interval PL) is 1 mm. Adjusted to a range of ~ 20 mm.

As described above, the grooved steel sheet is coated with an insulating coating liquid containing colloidal silica and phosphate from above the glass film, and then heated at 850 ° C. for 1 minute under the temperature condition. The heat treatment was carried out, and finally, a directional electromagnetic steel sheet having a grooved steel sheet, a glass film and an insulating film was obtained.

As a comparative example, the result of pickling using a pickling solution outside the scope of the present invention as a pickling solution is shown.

With respect to the formed groove shape, the groove depth D, the groove width W, and the surface roughness Ra of the groove bottom surface and the groove side surface were measured by using the above-mentioned measuring method.
For noise measurement, a sample having a width of 100 mm and a length of 500 mm is taken from each grain-oriented electrical steel sheet. The length direction of the sample corresponds to the rolling direction RD, and the width direction corresponds to the plate width direction TD.
The magnetostriction of the sample is measured by the AC magnetostriction measuring method using a magnetostriction measuring device. The magnetostriction measuring device is a device including a laser Doppler vibration meter, an exciting coil, an exciting power supply, a magnetic flux detection coil, an amplifier, and an oscilloscope.
Specifically, an AC magnetic field is applied to the sample so that the maximum magnetic flux density is 1.7 T and the frequency is 50 Hz in the rolling direction. The change in sample length due to expansion and contraction of the magnetic domain is measured with a laser Doppler vibrometer to obtain a magnetostrictive signal. The obtained magnetostrictive signal is Fourier analyzed to obtain the amplitude Cn of each frequency component fn (n is a natural number of 1 or more) of the magnetostrictive signal. The noise characteristic (dB) represented by the following equation is obtained by using the A correction coefficient αn of each frequency component fn.
Noise characteristics = 20 x Log (√ (Σ (ρc x 2π x fn x αn x Cn / √2) 2) / Pe0)
Here, ρc is an intrinsic acoustic resistance, and ρc = 400. Pe0 is the minimum audible sound pressure, and Pe0 = 2 × 10-5 (Pa) is used. As the A correction coefficient αn, the values shown in Table 2 of JIS C 1509-1 (2005) are used. Σ is 10 points in 100 Hz increments from the frequency component 100 to 1000 Hz.
Table 2 shows the measurement results together with the pickling conditions, iron loss W17 / 50 and noise (dB).

In addition, SEM-EDS measurement is performed on the groove cross section and element mapping is performed. If the mapping of Mn and S does not overlap, it does not exist as MnS and is replaced with sulfide such as CuS or coated with Cu or the like. We evaluated the presence or absence of the heat transfer constant effect on the side surface of the groove and the bottom of the groove. In the table, ○ indicates that there was a heat transfer stabilizing effect, and × indicates that there was no heat transfer stabilizing effect.

From this result, by performing the pickling treatment of the example (invention example), the Ra value of the surface roughness of the groove bottom surface and the groove side surface is controlled within a certain range, and the iron loss and noise are higher than those of the comparative example. It can be seen that it is further reduced.

Claims (1)

By mass%, it contains at least Si: 2.50 to 4.50% and Mn: 0.01 to 0.15%, and the balance is Fe and impurities, forming an angle of 0 to 30 ° with the direction perpendicular to rolling. A directional electromagnetic steel plate comprising a steel plate having a steel plate surface in which linear grooves extending in the direction are formed at intervals of 1 to 20 mm.
The groove depth D is 10 to 50 μm.
The groove width W is 20 to 200 μm, and the groove width W is 20 to 200 μm.
The Ra value of the surface roughness of the groove bottom surface is more than 5.0 μm, and the MnS of the groove bottom surface is one or more selected from the group consisting of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni. Is not substituted with sulfide, or is not coated with one or more selected from the group consisting of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni, and said groove. A directional electromagnetic steel plate having a Ra value of the surface roughness of the side surface of 0.1 to 5.0 μm.

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