JP6977702B2 - Method for improving iron loss of grain-oriented electrical steel sheets and its equipment - Google Patents

Description

The present invention relates to a method of forming a linear groove on the surface of a grain-oriented electrical steel sheet to improve iron loss, and in particular, a method of forming a linear groove on the surface of a grain-oriented electrical steel sheet by utilizing etching. The present invention relates to a method for improving an iron loss, which can improve the iron loss by forming a linear groove having a uniform shape while suppressing deterioration of the hysteresis loss due to the formation of the linear groove. The present invention also relates to an iron loss improving device suitable for carrying out the above method.

Electrical steel sheets with excellent magnetic characteristics are mainly used as materials for iron cores of transformers, and in order to improve the energy efficiency of transformers, it is required to reduce the iron loss. Methods for reducing the iron loss of grain-oriented electrical steel sheets include a method of highly aligning secondary recrystallized grains in the steel sheet in the Goss direction (sharpening), a method of increasing film tension, and a method of thinning the steel sheet. In addition, a method by surface processing of a steel sheet is known.

The iron loss reduction technology by surface processing of steel sheet introduces non-uniform strain such as linear strain to the surface of steel sheet by a physical method, and subdivides the width of the magnetic domain to reduce iron loss. One of them is a method of forming a groove on the surface of a finished and annealed steel sheet by using a tooth mold roll. According to this method, the magnetic domain on the surface of the steel sheet can be subdivided by forming the groove, and the iron loss of the steel sheet can be reduced. Further, it is known that even when heat treatment such as strain removal annealing is performed after groove formation, the introduced groove does not disappear, so that the iron loss reduction effect is maintained. However, in this method, the groove shape tends to be uneven due to the heavy wear of the tooth mold roll, and the roll is heated to a high temperature or lubricated in order to suppress the wear of the tooth mold roll. There was a problem that it was necessary and the manufacturing cost increased.

Therefore, a method of forming a linear groove on the surface of a steel sheet by etching has been developed without using a mechanical means such as a tooth mold roll. Specifically, a resist ink is applied to the surface of the steel sheet before the forsterite film is formed in a predetermined pattern to form a resist, and then the portion where the resist is not formed is subjected to a method such as electrolytic etching. By selectively etching the steel sheet, grooves are formed on the surface of the steel sheet. In this method, since there is almost no mechanical wear of the device, maintenance is easier than in the method using a tooth mold roll.

By the way, it is known that the magnetic properties of a steel sheet in which such a linear groove is formed are greatly affected by the shape of the linear groove. Specific shape elements include the depth and width of the groove, and forming a narrow and deep groove is suitable for improving iron loss. Besides that, it is known that detailed shapes such as the curvature between the side surface portion and the bottom surface portion in the groove cross section affect the iron loss. Therefore, if the shape of the resist that functions as an etching mask varies when the linear groove is formed by the above-mentioned etching method, the groove shape also varies, and as a result, the magnetic characteristics of the steel sheet vary. .. Therefore, in a method of forming a linear groove by etching, a technique has been proposed in which the coating accuracy of the resist is improved and the variation in the magnetic characteristics of the steel sheet is suppressed.

For example, Patent Document 1 proposes a technique for forming a linear groove having a uniform shape by controlling the temperature of a resist ink and a steel plate to be constant when applying a resist. By keeping the temperature constant, the variation in the viscosity of the resist ink is suppressed, and as a result, the variation in the groove shape is suppressed.

Patent Document 2 proposes a technique for controlling conditions such as the viscosity of the resist ink used and the mesh pattern of the gravure roll in a specific range when the resist is applied by gravure offset printing. As a result, it is possible to suppress the generation of halftone dots caused by the gravure cells formed on the surface of the gravure roll and improve the accuracy of the resist pattern.
It is possible to improve the accuracy of the resist pattern to some extent by adopting the methods as in Patent Documents 1 and 2, but there is still room for improvement.

Here, Patent Document 3 describes forming a resist pattern using a laser in order to avoid a problem in gravure offset printing. That is, after the resist is uniformly applied to the entire surface of the steel sheet, the resist is instantly evaporated or sublimated by irradiating the portion corresponding to the etching position, which does not require coating, with a laser, and the resist of the irradiated portion is selectively selected. It is removed. With such a method, the shape of the portion from which the resist is removed is not affected by the variation of the gravure cell and the like, so that a linear groove having a uniform shape can be formed.

Japanese Unexamined Patent Publication No. 11-279646 Japanese Unexamined Patent Publication No. 07-032575 WO2017-07908 Gazette

If the method proposed in Patent Document 3 is used, the shape accuracy of the resist is significantly improved. Further, in this method, by using a laser device having a small beam diameter, it is possible to form a narrow and deep groove. As described above, by improving the shape accuracy of the resist and realizing the formation of narrow and deep grooves, it is possible to significantly improve the iron loss characteristics.

In this technique, the key to increasing productivity is to increase the beam scanning speed as much as possible. However, when the scanning speed is increased, a high-power laser irradiation device is required to secure the energy required for stripping the resist. Increasing the output of these lasers and reducing the diameter of the beam are contradictory parameters, and it is extremely difficult to achieve both. A single-mode fiber laser having a small beam diameter and a high energy density has a relatively high advantage from this point of view.

However, as a result of the studies by the inventors, it has been found that there is still room for improvement in the groove width even if a relatively superior single-mode fiber laser is applied in the technique described in Patent Document 3. That is, while the resist width peeled off by the laser is very narrow, the groove width after electrolytic etching is not as narrow as expected, and the effect of improving iron loss has not been maximized. rice field. In other words, even the highly superior single-mode fiber laser did not produce the expected results.

The present invention has been made in view of the above circumstances, and proposes a method capable of obtaining the maximum iron loss improving effect when forming a linear groove based on a resist pattern formed by using a laser. The purpose is to do. Another object of the present invention is to provide an apparatus suitable for carrying out the above method.

The present inventors investigated the cause and countermeasures regarding the fact that the resist width peeled off by the laser is very narrow, while the groove width after electrolytic etching is not as narrow as expected. , The following (a) to (f) have been obtained.
(A) The region where the resist is peeled off is limited to the region where the laser beam intensity is equal to or higher than a certain threshold value.
(B) Even in the region where the resist is not peeled off, there is a portion damaged by the laser beam, and the film thickness is reduced in this portion as compared with the non-irradiated portion (there is a resist film thickness reduction portion). The amount of this film thickness decrease is proportional to the energy density.
(C) In the resist film thickness reduction portion, the resist resistance deteriorates, dielectric breakdown occurs during electrolytic etching, and grooves are formed (grooves expand). This decrease in resist film thickness was the reason why the groove with the narrow width as expected was not obtained.
(D) When the laser beam in the area where the film thickness is reduced is cut by a slit, the interface between the resist peeling portion and the resist portion becomes steep, and the resist film thickness reduction portion that causes dielectric breakdown during electrolytic etching is reduced. , It is possible to prevent unintended groove formation (groove expansion).
(E) Further, the slit shape is such that the slit width on the laser beam exit side is larger than the slit width on the laser beam entry side, so that the beam quality due to diffused reflection of the laser light on the slit side surface when passing through the slit is obtained. It becomes possible to suppress deterioration.
(F) When the beam width (length in the traveling direction of the steel sheet) of the surface of the steel sheet is 0.08 mm or less, particularly excellent magnetic characteristics can be obtained. On the other hand, if it is smaller than 0.01 mm, the magnetic characteristics tend to deteriorate.

Based on the above findings, a detailed study was conducted on the conditions for removing the resist by laser irradiation, and the present invention was completed.
That is, the gist structure of the present invention is as follows.
1. 1. A resist forming process for forming a resist on the surface of grain-oriented electrical steel sheets,
A laser irradiation step in which a laser is irradiated in a direction crossing the rolling direction of the directional electromagnetic steel plate to remove the resist of the irradiated portion of the laser, at intervals in the rolling direction of the directional electromagnetic steel plate. When,
It has an etching step of etching a resist-removed portion of the grain-oriented electrical steel sheet to form a linear groove.
The laser irradiation in the laser irradiation step is a method for improving iron loss of a grain-oriented electrical steel sheet, which is performed through a slit of a slit plate that partially cuts the laser beam.

2. 2. The method for improving iron loss of a grain-oriented electrical steel sheet according to 1 above, wherein the slit has a larger opening width on the laser beam exit side than the opening width on the laser beam entry side in the slit plate.

3. 3. The method for improving iron loss of grain-oriented electrical steel sheets according to 1 or 2 above, wherein the laser in the laser irradiation step is a single-mode fiber laser.

4. The direction according to any one of 1 to 3 above, wherein in the laser irradiation step, the maximum beam width of the surface of the grain-oriented electrical steel sheet in a direction orthogonal to the scanning direction of the laser is 0.01 mm or more and 0.08 mm or less. How to improve iron loss of electrical steel sheets.

5. A resist forming portion that forms a resist on the surface of the grain-oriented electrical steel sheet along the sheet-passing line of the grain-oriented electrical steel sheet, and the surface of the grain-oriented electrical steel sheet on which the grain is formed is irradiated with a laser to partially irradiate the resist. The laser irradiation part to be specifically removed and the etching part to etch the resist removing part of the grain-oriented electrical steel sheet are arranged in order in the plate-passing direction of the grain-oriented electrical steel sheet, and the laser irradiation section collects laser. An iron loss improving device for grain-oriented electrical steel sheets provided with a slit plate that partially cuts laser light between the portion and the surface of the grain-oriented electrical steel sheet.

6. The iron loss improving device for grain-oriented electrical steel sheets according to 5 above, wherein the slit plate has a slit in which the opening width on the laser beam exit side is larger than the opening width on the laser beam entry side.

7. The laser irradiation unit is the iron loss improving device for grain-oriented electrical steel sheets according to 5 or 6, which has a laser irradiation device for a single-mode fiber laser.

8. The laser irradiation unit has 1 to 3 laser irradiation devices having a maximum beam width of 0.01 mm or more and 0.08 mm or less in a direction orthogonal to the scanning direction of the laser on the surface of the grain-oriented electrical steel sheet. The iron loss improving device for grain-oriented electrical steel sheets described in any of the above.

9. In order to produce a grain-oriented electrical steel sheet by hot-rolling and then cold-rolling the material for grain-oriented electrical steel, the surface of the steel sheet is described in any of 1 to 4 at the stage after the cold rolling. A method for manufacturing a grain-oriented electrical steel sheet that forms a linear groove using the method for improving iron loss.

According to the present invention, when forming a linear groove on the surface of a grain-oriented electrical steel sheet by using etching, a narrow and deep linear groove can be formed in a uniform shape, so that the magnetic domain is subdivided by forming the groove. It becomes possible to enjoy the maximum effect, and a grain-oriented electrical steel sheet having very excellent iron loss characteristics can be obtained. In particular, when a high-power single-mode fiber laser is used, high-speed resist stripping processing becomes possible, and both high productivity and low iron loss can be achieved.

It is a figure which shows the procedure of laser irradiation. It is a figure which shows the relationship between the beam profile and the resist peeling width Rt in the cross section along the traveling direction Y of a steel sheet. It is a figure which shows the relationship between the thickness (coating thickness) of a resist film, and a beam profile. It is a figure which shows the relationship between the width and depth of a groove, and the thickness (coating thickness) of a resist film. It is a figure which shows the arrangement of a slit plate. It is a figure which shows the relationship between a beam width and a resist peeling width. It is a figure which shows the relationship between the film thickness of a resist film and a beam profile. It is a graph which shows the influence of the distance between a steel plate-slit plate on the difference between a beam width and a resist peeling width. It is a graph which shows the influence of the thickness of a slit plate on the difference between a beam width and a resist peeling width. It is a figure which shows the opening shape of a slit. It is a graph which shows the influence of the thickness of a slit plate on the difference between a beam width and a resist peeling width. It is a figure which shows the irradiation form of a laser. It is a figure which shows the irradiation form of a laser. It is a figure which shows the irradiation form of a laser. It is a figure which shows the irradiation form of a laser. It is a graph which shows the relationship between iron loss and groove width.

First, the width of the resist peeled off by the laser is very narrow, while the width of the groove after electrolytic etching is not as narrow as expected. The results of experiments conducted on the cause will be described.
That is, as shown in FIG. 1, the laser irradiation device 2 is orthogonal to the rolling direction while passing a directional electromagnetic steel plate (hereinafter, also simply referred to as a steel plate) 1 having a resist coating R formed on its surface in the direction of arrow Y. Laser irradiation performed by scanning in the direction X was repeated at intervals of 5 mm in the rolling direction (arrow Y direction). Here, the resist portion removed by laser irradiation is defined as the resist peeling width Rt, and the length of the laser beam on the surface of the steel plate 1 in the Y direction is defined as the beam width Bt. The laser irradiation was performed by a single mode fiber laser with an output of 1.5 kW by a polygon mirror method at a speed of 150 m / s, a scanning width of 350 mm, and a scanning interval of 5 mm.

FIG. 2 shows the relationship between the beam profile and the resist peeling width Rt in the cross section of the steel sheet along the traveling direction Y of the above laser irradiation. The beam profile is displayed as an index with the maximum value of beam energy as 1 for the results measured using a commercially available CCD camera type fixed beam profiler. The beam diameter was set at a position where the intensity was 0.135 times the maximum intensity. In this laser irradiation, the beam width Bt and the beam diameter are the same, but as shown in FIG. 2, when the beam diameter (beam width Bt) and the resist peeling width Rt do not match and the irradiation energy is small, the irradiation energy is small. It was found that there was a part where the resist film was not peeled off even in the area irradiated with the laser beam.

Next, FIG. 3 shows the results of investigating the relationship between the thickness of the resist film (coating thickness) and the beam profile. The coating thickness is expressed as an index in which the maximum coating thickness (thickness of the laser irradiation non-affected portion where peeling does not occur) is 1 for the result derived from the SEM image. From FIG. 3, it was found that the film thickness was reduced due to the influence of laser irradiation even in the portion where the resist was not peeled off.

Further, the sample from which the resist was peeled off was subjected to electrolytic etching treatment, and the relationship between the width and depth of the groove and the thickness of the resist film (coating thickness) was investigated. The groove depth was measured using a laser microscope, and the film thickness was indexed in the same manner as in FIG. As shown in FIG. 4, the width from which the resist was peeled off was very narrow, 0.06 mm, but the groove width formed by electrolytic etching was doubled to 0.12 mm. .. From the results shown in FIGS. 2 to 4, the reason why the groove width was not narrowed as expected was that there was a film thickness reduction portion (thin film portion) of the resist film around the resist peeling portion, and the resist resistant portion was present in the thin film portion. It is presumed that the property deteriorated and dielectric breakdown occurred during electrolytic etching.

That is, the fact that the groove width did not narrow as expected means that the resist resistance deteriorates in the portion (thin film portion) where the film thickness is reduced even if the beam energy is weak and the resist film is not peeled off. It is presumed that this is due to the fact that there is. Therefore, a slit plate 3 as shown in FIG. 5 was installed on the steel plate with the intention of covering the region corresponding to the thin film portion with respect to the laser beam. The slit plate 3 has a slit 4 extending along the entire width of the steel plate 1 with an opening width of 0.07 mm. With the slit plate 3 installed, laser irradiation was performed under the above-mentioned conditions, and the relationship between the beam width and the resist peeling width, and the relationship between the film thickness of the resist film and the beam profile were investigated. The results are shown in FIGS. 6 and 7.

As shown in FIG. 6, the difference between the beam width and the resist peeling width is about 0.01 mm. Regarding the film thickness, as shown in FIG. 7, the resist film thickness reduction portion (thin film portion) at the boundary portion is a very narrow region, and the peeled portion steeply reaches a steady film thickness. confirmed. It is presumed that the beam width and the resist peeling width did not completely match because the laser beams interfered with each other when passing through the slit and the beam quality (convergence) deteriorated.

Next, the sample from which the resist was peeled off was subjected to electrolytic etching treatment, and the relationship between the groove width and the resist film thickness was investigated. As a result, the width from which the resist was peeled off was 0.06 mm, while the groove width after electrolytic etching was 0.07 mm, which was significantly narrower than when the slit was not used. Table 1 shows the iron loss evaluation results of the steel sheet after the electrolytic etching treatment. From the table, it can be seen that the sample that realized the groove narrowing by using the slit realized the low iron loss. Further, when the slit is not used, the iron loss is not further reduced even if the groove depth is deeper than 20 μm, whereas when the slit is used, the iron loss is reduced as the groove becomes deeper. You can see that. _{Here, the iron loss W 17/50} at a magnetic flux density of 1.7 T and an excitation frequency of 50 Hz was evaluated by a single plate magnetic tester in accordance with JIS C 2556. Samples used herein, with magnetic measured before grooving, B ₈ were used as the 1.94T. Furthermore, the groove depths of the samples with and without slits were adjusted to be the same by adjusting the processing time of electrolytic etching.

Next, in order to minimize the beam interference when passing through the slit, the effects of the distance between the steel plate and the slit plate and the slit thickness on the difference between the beam width and the resist peeling width were investigated. First, FIG. 8 shows the influence of the distance between the steel plate and the slit plate on the difference between the beam width and the resist peeling width. As shown in the figure, when the distance between the steel plate and the slit plate exceeds 10000 μm, there is no significant difference in the difference between the beam width and the resist peeling width, and when it is 10000 μm or less, the smaller the distance, the smaller the difference (interference is suppressed). ) Tendency was observed. From the above results, it can be seen that it is more preferable that the distance between the steel plate and the slit plate is 10000 μm or less. However, even if it exceeds 10000 μm, it is significantly improved compared to the case where there is no slit plate intervention, so even if the slit plate is installed at a position where the distance from the steel plate exceeds 10000 μm, a corresponding effect can be expected.

Further, FIG. 9 shows the influence of the thickness of the slit plate on the difference between the beam width and the resist peeling width. As shown in the figure, the difference between the beam width and the resist peeling width remained at almost the same level in the region where the slit plate thickness was larger than 7,000 μm, which was smaller than that without the slit plate intervention. On the other hand, below 7,000 μm, the smaller the thickness, the smaller the difference. Therefore, it is more preferable that the slit plate thickness is 7,000 μm or less.

Here, it is presumed that the thinner the slit plate thickness, the smaller the difference between the beam width and the resist peeling width, because the repeated reflection of the beam on the side surface of the slit is suppressed. Based on this result, it was examined to incline the side surface as a means of suppressing the reflection on the side surface. That is, the slit shape shown as slit A in FIG. 10 and having the same opening width on the laser beam entry side and the opening width on the laser beam exit side used in the above-mentioned experiment and the laser beam entry side shown as slit B in the same figure. The effect of the slit shape in which the opening width on the laser beam exit side is larger than the opening width of the laser beam was investigated. The same experimental result by the slit B is shown in FIG. 11 by comparing the result with the data of FIG. 9 shown above. It was found that, in contrast to the slit A used in the evaluations so far, in the slit B, the increase in the difference between the beam width and the resist peeling width due to the increase in the thickness of the slit plate is significantly suppressed.

Based on the above results, a method for carrying out the present invention will be specifically described. The following description shows a preferred embodiment of the present invention, and the present invention is not limited to the following description. In addition, each term used in the present specification shall be defined as follows unless otherwise specified.
"Resist removing part": A part where the resist is removed by laser irradiation in the laser irradiation process and the surface of the grain-oriented electrical steel sheet is exposed.
"Scanning length L": The length in one scan per laser irradiation device.
"Scanning speed v": The scanning speed of the laser irradiated in the laser irradiation step on the surface of the steel sheet, which is defined by the following equation.
v = L / t (t is the time required to scan the scan length L)
"Output P": The output of the laser irradiated in the laser irradiation process.
"Line speed _VL ": The moving speed of the steel plate conveyed in the processing device. Also called board speed. When the speed differs depending on the position in the processing device, the speed at the position where the laser is irradiated is used. Unless otherwise specified, the steel sheet is conveyed in the rolling direction in the processing apparatus.
"Spacing of linear grooves": Spacing of linear grooves formed on the surface of a steel sheet in the rolling direction. It is equal to the spacing in the rolling direction of the resist removing portions formed in the laser irradiation step.

In the method of the present invention, the following steps (1) to (4) are sequentially applied to the grain-oriented electrical steel sheet.
(1) Resist forming process,
(2) Laser irradiation step (3) Etching step (4) Resist removing step In addition, after the above (2) laser irradiation step and before the above (3) etching step, an imaging step for monitoring the resist peeling status is provided. Is preferable. Since the groove shape mainly changes depending on the resist peeling status, monitoring of the resist peeling status can be replaced by monitoring the groove width. However, since the groove shape is affected by other than resist peeling, it is more preferable to directly monitor the resist peeling state before groove formation.

[Directional magnetic steel sheet]
In the present invention, a grain-oriented electrical steel sheet is used as a base material. It should be noted that a steel sheet in the middle of the manufacturing process of the grain-oriented electrical steel sheet, for example, a steel sheet that has undergone a cold rolling process may be used. As the grain-oriented electrical steel sheet, any one can be used without particular limitation, but from the viewpoint of reducing iron loss, it is preferable to use one containing Si in the range of 2.0 to 8.0% by mass, and in addition, it is passed through. From the viewpoint of plate properties, it is more preferable to use one containing Si in the range of 2.5 to 4.5% by mass.

The composition of components other than Si, which is suitable as a grain-oriented electrical steel sheet, is as follows. Of course, the composition is not limited to the following, and any electromagnetic steel sheet can be surely improved in iron loss before application by the application of the present invention.

Mn: 0.005 to 1.0% by mass
Mn is an element effective for improving hot workability, but if it is less than 0.005% by mass, the above effect cannot be obtained, while if it exceeds 1.0% by mass, the magnetic flux density will decrease. Therefore, Mn is preferably in the range of 0.005 to 1.0% by mass. More preferably, it is in the range of 0.01 to 0.2% by mass.

Ni: 0.03 to 1.50% by mass, Sn: 0.01 to 1.50% by mass, Sb: 0.005 to 1.50% by mass, Cu: 0.03 to 3.0% by mass, P: 0.03 to 0.50% by mass, Mo: 0.005 to 0.10% by mass and Cr: One or more selected from 0.03 to 1.50% by mass

Further, the grain-oriented electrical steel sheet of the present invention is further selected from Ni, Sn, Sb, Cu, P, Mo and Cr in addition to Si and Mn described above for the purpose of improving magnetic properties. Species or two or more species may be optionally contained within the above range.
Ni is an element useful for improving the hot-rolled plate structure and improving the magnetic properties. However, if it is less than 0.03% by mass, the above effect is small, while if it exceeds 1.50% by mass, the secondary recrystallization becomes unstable and the magnetic characteristics deteriorate. Further, Sn, Sb, Cu, P, Mo and Cr are elements useful for improving the magnetic properties, but all of them have a small effect of improving the magnetic properties below the above lower limit value, while the above upper limit values are set. If it exceeds, the development of secondary recrystallized grains will be inhibited, so it is preferable to contain each in the above range.

The steel material (steel slab, etc.) used for manufacturing the grain-oriented electrical steel sheet of the present invention contains the following components in addition to the above components.
C: 0.01 to 0.08% by mass
C is an element necessary for improving the texture during primary recrystallization, and is preferably contained in an amount of 0.01% by mass or more in order to obtain the effect. On the other hand, when C exceeds 0.08% by mass, it becomes difficult to reduce it to 0.0050% by mass or less where magnetic aging does not occur by decarburization annealing. Therefore, C is preferably in the range of 0.01 to 0.08% by mass. More preferably, it is in the range of 0.03 to 0.07% by mass.

Al, N, S and Se
The contents of these components differ depending on whether or not Inhibita is used to cause secondary recrystallization.
When an inhibita is used to cause secondary recrystallization, for example, when an AlN-based inhibita is used, Al and N are contained in the range of Al: 0.01 to 0.065% by mass and N: 0.005 to 0.012% by mass, respectively. Further, when using an MnS / MnSe-based inhibitor, it is preferable to contain Se and / or S in the range of S: 0.005 to 0.03% by mass and Se: 0.005 to 0.03% by mass, respectively. Moreover, you may use both Inhibita together.

On the other hand, when the inhibitor is not used to generate secondary recrystallization, Al, N, S and Se, which are the inhibitor-forming components, are Al: 0.0100% by mass or less, N: 0.0050% by mass or less, S: It is preferable to reduce to 0.0050% by mass or less and Se: 0.0050% by mass or less.

The rest other than the above components are Fe and unavoidable impurities. Since C is decarburized by primary recrystallization annealing and Al, N, S and Se are purified by final finish annealing, these components in the steel sheet (product plate) after final finish annealing are unavoidable impurities. The content is reduced to a degree. Specifically, C: 0.005% by mass or less, S: 0.005% by mass or less, N: 0.005% by mass or less, Al: 0.010% by mass or less, Se: 0.005% by mass or less.

If a film is formed on the surface of the grain-oriented electrical steel sheet, etching may be hindered depending on the type of the film. Therefore, a film that is insoluble or sparingly soluble in the etching solution (electrolyte solution), such as a forsterite film or a tension-applying film, is not formed on the surface of the steel sheet, and the resist described later is applied directly to the surface of the steel sheet. It is preferable to be done.

[Resist forming process]
A resist is formed on the surface of the steel sheet prior to laser irradiation. The resist functions as an etching resist for preventing the steel sheet from being etched in the etching process described later. As the resist, any material can be used as long as it can prevent etching of the steel sheet, but it is preferable to use a resist containing a thermosetting resin as a main component. As the thermosetting resin, for example, at least one selected from the group consisting of an alkyd-based resin, an epoxy-based resin, and a melamine-based resin can be used. UV curability and electron beam curability as used in the semiconductor field are not always necessary. Further, in terms of suppressing ink dripping, it is better that the viscosity of the resin is high. In order to keep the viscosity of the resist high, the temperature of the resist to be applied is preferably 40 ° C. or lower. On the other hand, the lower limit of the temperature of the resist is not particularly limited, but is preferably 20 ° C. or higher. Further, although there is a problem in terms of equipment that the size of the apparatus becomes large, usually, an insulating film formed on the surface layer of the magnetic steel sheet may be used as the resist. In this case, the coating may be performed according to the prior art. The same is true for drying.

The method for forming the resist on the surface of the steel sheet is not particularly limited, and any method can be used, but it is preferably performed by roll coating. Above all, it is preferable to use a gravure printing method using a gravure roll, and it is more preferable to use a gravure offset printing method using an offset roll. In the present specification, the gravure printing method refers to a printing method using a gravure roll in general, and includes a gravure offset printing method. When the gravure printing method is used, it is preferable to install a doctor blade above the gravure roll to make the amount of ink on the gravure roll uniform in order to keep the film thickness constant.

The resist forming pattern in the present invention is not particularly limited and may be any pattern as long as it can finally form a desired linear groove, but in the present invention, the resist is formed by laser irradiation. It is preferable to form a resist on the entire surface of the steel sheet in order to partially remove it.

The basis weight (coating amount) of the resist liquid is preferably ^{1.0 to 10.0 g / m 2.} If the grain size is ^{less than 1.0 g / m 2} , the resist resistance will be insufficient and insulation breakdown may occur during electrolytic etching, preventing the steel plate on the resist-coated part from being etched. It is preferably 1.0 g / m ^{2 or more.} In addition, by setting the amount of grain to 10.0 g / m ² or less, the amount of resist removed in the laser irradiation step is reduced, and the vaporized resist adheres to the optical system of the laser irradiation device, resulting in laser properties. Fluctuations can be suppressed. The basis weight of the resist liquid is a value before and after laser peeling, and is derived from the sample weight difference before and after the resist coating and the coating area.

After applying the resist, the resist is dried prior to the next laser irradiation step. The drying method is not particularly limited, and for example, hot air drying, vacuum drying, or the like can be used. In the case of hot air drying, the drying temperature is preferably 180 to 300 ° C. In the case of vacuum drying, the pressure is preferably 10 Pa or less, and the drying time is preferably 5 seconds or more.

[Laser irradiation process]
Next, irradiation is performed while scanning the laser in a direction crossing the rolling direction of the grain-oriented electrical steel sheet coated with resist. By this laser irradiation, the resist in the portion irradiated with the laser is locally heated and vaporized, and as a result, an exposed resist removing portion is formed on the surface of the steel sheet. The steel plate portion exposed in the resist removing portion is selectively etched in the etching step described later to form a linear groove. The dimensions of the linear grooves formed by etching affect the final magnetic properties of the grain-oriented electrical steel sheet, and are preferably narrower and deeper. In order to form a narrow and deep groove, it is preferable that the pattern of the etching resist, that is, the dimension of the resist removing portion is narrower in width. Further, even if a narrow resist removing portion is formed in appearance, if a resist film thickness reducing portion exists around the peeling portion, dielectric breakdown occurs during electrolytic etching in the resist film thickness reducing portion, and a groove is formed. The narrow groove as expected cannot be obtained. Therefore, it is preferable that the resist film thickness reduction portion around the peeled portion is as small as possible.

It is preferable that the scanning of the laser is performed linearly. Further, the scanning direction of the laser may be a direction that crosses the rolling direction, but from the viewpoint of enhancing the effect of reducing iron loss, the angle of the laser scanning direction with respect to the width direction of the steel plate is preferably 40 ° or less. , It is more preferable to scan the laser in the width direction of the steel plate (direction perpendicular to the rolling direction). The laser scanning in the laser irradiation step is periodically performed in the rolling direction of the grain-oriented electrical steel sheet. In other words, the laser scanning is repeated so that the resist removing portions are formed at regular intervals in the rolling direction. The distance between the resist removing portions in the rolling direction (hereinafter referred to as “resist removing portion spacing”) is preferably 2 mm or more and 10 mm or less. Since the spacing of the linear grooves formed by etching in the rolling direction (hereinafter referred to as "spacing of the linear grooves") is equal to the spacing of the resist removing portions, the spacing of the resist removing portions should be within the above range. Therefore, the spacing between the linear grooves can be set in a suitable range, and the magnetic characteristics of the grain-oriented electrical steel sheet can be further improved.

The type of laser is determined from the viewpoint of iron loss characteristics and productivity. From the viewpoint of iron loss characteristics, a narrow groove width is advantageous, so it is preferable to use a laser device having high light-collecting property to narrow the resist peeling width. On the other hand, from the viewpoint of productivity, it is required to perform laser scanning at high speed. When laser scanning is performed at high speed, it is preferable to use a laser device having a higher output in order to secure the energy density required for peeling. In order to achieve both the beam focusing property and the laser output, it is preferable to use a single mode fiber laser as the type of laser. However, when a slit plate as in the present invention is installed, the superiority of the single-mode fiber laser is reduced, so that another type of laser can be adopted. From the viewpoint of speeding up, the laser scanning described above is preferably performed by rotationally driving a mirror such as a galvano mirror or a polygon mirror.

Any number of laser irradiation devices (irradiation sources) can be used for the laser irradiation, but it is preferable to use 1 to 3 irradiation devices. If there are more than three irradiation devices, the time required for maintenance will increase and productivity will decrease.

Since most of the commonly used steel plates have a width of about 1 m, it is difficult to uniformly irradiate the laser over the entire plate width if there is only one irradiation device, and the beam properties are made uniform. It becomes necessary to increase the beam diameter. Therefore, it is more preferable to use two or more laser irradiation devices. When a plurality of laser irradiation devices are used, it is not necessary that the laser irradiated from each irradiation device is scanned over the entire width of the steel sheet, and the sum of the scanning ranges of each irradiation device may cover the entire width of the steel sheet. ..

Here, at the boundary portion generated by the use of the plurality of laser irradiation devices, when the lap portion is generated as shown in FIG. 12A, the steel plate is etched more than necessary, which causes iron loss and deterioration of the magnetic flux density. On the other hand, even if a gap (discontinuous portion) is generated as shown in FIG. 12B, the iron loss still deteriorates. Therefore, as shown in FIG. 12C, it is preferable that the groove is continuously formed as a result of matching the end and the start of the irradiation laser among the plurality of laser irradiation devices. Ideally, it is preferably completely continuous as shown in FIG. 12C. Further, as shown in FIG. 12D, if the lap portions shown in FIG. 12A are not separated and the lap portions overlap to form a continuous groove, the deterioration of iron loss is small and the improvement margin of iron loss is guaranteed. Therefore, it is suitable.

In the above-mentioned laser irradiation, in order to suppress contamination of the apparatus by the resist vaporized by the laser irradiation, it is preferable to collect the resist vaporized by the dust collector by blowing air or suctioning. However, in order to prevent the steel sheet from vibrating and being out of focus, the air volume for blowing or sucking the laser irradiation treatment tank ^{is preferably 100 m 3} / min or less. The lower limit of the air volume is not particularly limited, ^{but is preferably 10 m 3} / min or more.

The resist removal state in the above-mentioned laser irradiation is determined by the irradiation energy per unit scan. Since the required irradiation energy differs depending on the type of resist film, it is preferable to irradiate the resist film to be adopted in advance with different irradiation energies and investigate and determine the conditions under which the peeled portion is satisfactorily formed. The scanning speed v of the laser irradiation device is not particularly limited, but a higher scanning speed v is advantageous in terms of productivity because _{the line speed VL of the steel sheet can be increased.} Further, the minimum required output P of the laser is derived from the irradiation energy E and the scanning speed v required for the adopted resist film at P = vE.

Further, from the viewpoint of iron loss, it is preferable that the width of the resist removing portion is smaller. Even if the output of the laser is adjusted so that the resist peeling width is smaller than the laser beam diameter, the unpeeled part is also damaged by the laser irradiation, and the insulation is broken during the electrolytic etching in the next process. You can't make a narrow groove. Therefore, in order to form a narrow groove, it is necessary to limit the range of irradiating the resist film with a laser having a small beam diameter.
Here, FIG. 13 shows the results of investigating the relationship between the iron loss and the groove width using a sample (plate thickness 0.27 mm) having a magnetic flux density B _{8 before groove formation of 1.92 T.} The groove depth was adjusted to a constant 25 μm by adjusting the electrolytic etching time. The narrower the groove width, the more the iron loss tends to improve, and especially when the groove width is 0.08 mm or less, the improvement tendency of the iron loss becomes remarkable. On the other hand, when it becomes 0.01 mm or less, the improvement of iron loss is saturated. From the above, it can be seen that it is preferable to set the laser beam diameter to 0.01 to 0.08 mm in order to obtain a suitable iron loss improving effect. However, it is very difficult to achieve both high output and high light collection property, and the laser device is very expensive. Therefore, there is a high hurdle in its introduction from the viewpoint of cost.

Therefore, in the present invention, by introducing the slit plate as shown in FIG. 2, it is possible to reduce the beam width in the traveling direction of the steel plate reaching the surface of the steel plate even with a relatively inexpensive laser device. If the slit plate is interposed in the laser irradiation process according to this method, the laser beam is not irradiated on the steel plate except for the region passing through the slit of the slit plate. Therefore, since the resist film is not damaged in the region other than the resist peeling portion (groove forming portion), the groove is formed only in the resist peeling portion. Therefore, when a slit is applied, in order to obtain a more preferable groove width (0.01 to 0.08 mm) for the iron loss characteristic, the beam width on the steel sheet with respect to the traveling direction of the steel sheet should be set to 0.01 mm to 0.08 mm. It will be good. The slit width varies depending on the installation distance from the steel plate, but the resist peeling width may be set to a desired width. The closer to the steel plate, the smaller the difference between the slit width and the resist width, and the farther away from the steel plate, the larger the slit width.

Scattering of laser light when passing through a slit causes deterioration of laser quality such as an increase in the arrival beam width and a decrease in the arrival beam intensity. An increase in the reach beam width causes the iron loss improvement effect to not be enjoyed to the maximum, and a decrease in the reach beam intensity requires an increase in the initial output by the amount of the decrease in the middle, which is a higher cost high-power laser beam. It is disadvantageous in terms of cost reduction because it is necessary to adopt. It is preferable to make the slit plate thinner because the thinner the slit plate is, the more it is suppressed. It is preferably 7,000 μm or less. However, a certain thickness is required to ensure the rigidity of the slit plate. Therefore, in order to prevent the quality of the laser beam from deteriorating due to the thickness of the slit plate, it is effective to make the slit shape larger than the slit width on the entry side and the slit width on the exit side as described above. It is possible to suppress the interference of light. Further, the distance between the slit plate and the steel plate also has an effect, and is more preferably 10000 μm or less.

[Etching process]
After the laser irradiation step is completed, etching is performed to form a linear groove on the surface of the steel sheet. As the method used for etching, any method can be used as long as the steel sheet can be etched, but it is preferable to use at least one of chemical etching and electrolytic etching. From the viewpoint of controlling the etching amount, it is more preferable to use electrolytic etching. In the case of chemical etching, for example, an aqueous solution containing at least one selected from the group consisting of _{FeCl 3} , HNO ₃ , HCl, and H ₂ SO _{4 can be used as the etching solution.} Further, in the case of electrolytic etching, for example, an aqueous solution containing at least one selected from the group consisting of _{NaCl, KCl, CaCl 2} and NaNO _{3 can be used as the etching solution (electrolyte solution).}

Further, when performing etching, it is preferable to stir the etching solution. By stirring the etching solution, it is possible to eliminate the bias in the temperature and concentration of the electrolytic solution in the etching tank and perform etching more uniformly. Further, the etching efficiency can be improved by increasing the flow rate of the electrolytic solution in the tank. The method for performing the stirring is not particularly limited, but for example, mechanical stirring, stirring by circulating the etching solution, or the like can be used. When mechanically stirring, it is preferable to use a resin-made stirring member in consideration of resistance to the etching solution. In the case of stirring by circulation, for example, an etching solution ejection port can be provided in the etching tank, and the etching solution can be ejected from the etching solution by using a pump or the like.

When the etching is performed by electrolytic etching, the steel sheet can be energized by any method. For example, a radial cell type or horizontal cell type etching tank is used to energize by direct energization or indirect energization. It can be carried out. The electrolysis conditions may be appropriately adjusted according to the steel sheet to be treated, the electrolytic solution to be used, and the like, and for example, the current density can be adjusted within the range of 1 ^{to 100 A / dm 2.}
The shape of the linear groove formed by etching can be adjusted by the shape of the laser beam and the etching conditions, but from the viewpoint of the magnetic characteristics of the grain-oriented electrical steel sheet, the width of the linear groove is 10 μm or more and 80 μm or less, and the depth is 10 μm. It is preferably 40 μm or less.

[Iron loss improvement device]
As a device for forming a groove in a steel sheet in accordance with the present invention to improve iron loss, a device having any configuration is not particularly limited as long as each of the above steps can be performed. Can be carried out using. However, from the viewpoint of productivity, it is preferable to use a continuous processing device capable of continuously processing the grain-oriented electrical steel sheet supplied as a coil.

The continuous processing apparatus includes a payout portion that dispenses a directional electromagnetic steel plate wound in a coil shape, a welded portion that joins coils to each other, a resist coating portion that applies a resist to the surface of the directional electromagnetic steel plate, and the above. A resist forming part consisting of a drying part that dries the resist applied to the surface of the directional electromagnetic steel plate, and a laser irradiation part that partially removes the resist by irradiating the surface of the directional electromagnetic steel plate on which the resist is formed with a laser. , The etching part that etches the directional electromagnetic steel plate in the portion where the resist has been removed, the resist removing part that removes the resist from the surface of the directional electromagnetic steel plate, the cutting part that cuts the directional electromagnetic steel plate, and the directionality. It is preferable that the winding portions for winding the electromagnetic steel plate are arranged in this order.

Further, it is preferable to provide an image pickup image section for monitoring the resist peeling state after the laser irradiation section and in front of the etching section. That is, in the present invention, there is a demerit that the quality of the laser tends to deteriorate as the laser passes through the slit. This demerit can be reduced by the slit shape and accurate installation, but as the operation continues, the slit installation condition deteriorates due to disturbance factors, the laser quality deteriorates more than acceptable, and the beam width on the steel plate surface becomes the laser. It cannot be ruled out that the peeling width becomes larger than the permissible amount, and even the unpeeled portion of the resist may be damaged by laser irradiation, resulting in an increase in the groove width. Alternatively, from the viewpoint of iron loss, a continuous groove that is ideally completely continuous and that at least one part overlaps is preferable. In order to realize this continuous groove with a plurality of laser devices, it is important to synchronize all the laser devices. In many cases, the timing of each laser irradiation also gradually shifts over time due to deterioration of laser device parts and the like. In such a situation, it is effective to install an image pickup image section for monitoring the resist peeling state after the laser irradiation section in order to detect an abnormality as soon as possible. More preferably, it is more preferable to construct a logic that can automatically perform synchronization correction and the like by feeding back the image diagnosis result, because the setting can be corrected without stopping the line.

Further, it is more preferable to provide a looper for keeping the plate passing speed in the laser irradiation unit constant. That is, if the plate passing speed decreases at a part of the line during the welding or the like, the plate passing speed is reduced to the plate passing speed in the laser irradiation portion, and the irradiation energy temporarily increases, resulting in the obtained groove width. May fluctuate and the iron loss characteristics of grain-oriented electrical steel sheets may vary. However, by installing a looper for keeping the plate passing speed constant, it is possible to suppress fluctuations in the plate passing speed in the laser irradiation section and prevent variations in the magnetic characteristics of the grain-oriented electrical steel sheet. Specifically, it is preferable to install the looper between the welded portion and the resist coated portion, and between the resist removing portion and the cutting portion.

Next, the present invention will be specifically described based on Examples. The following examples show a suitable example of the present invention, and the present invention is not limited to the above examples. The embodiments of the present invention can be appropriately modified to the extent suitable for the gist of the present invention, and all of them are included in the technical scope of the present invention.

In order to evaluate the influence of the laser irradiation condition, a linear groove was formed on the surface of the grain-oriented electrical steel sheet under a plurality of conditions. As the directional electromagnetic steel plate, C: 0.07% by mass, Si: 3.1% by mass, Mn: 0.05% by mass, Al: 0.025% by mass, N: 0.012% by mass, S: 0.005% by mass and Se: 0.01% by mass. The steel slab having the composition of the above was hot-rolled according to a conventional method and then cold-rolled to obtain a 0.20 mm cold-rolled plate. Then, the resist was uniformly applied to the entire surface of the steel sheet by the gravure offset printing method. The basis weight of the resist was 4.5 g / m ² .

After applying the resist, it was dried at 300 ° C. and 60 s, and then the laser was irradiated while scanning the laser irradiation device linearly in the width direction of the steel sheet under the conditions shown in Table 2. The laser scanning was periodically performed at intervals of 5.0 mm in the rolling direction. In this experiment, three single-mode fiber laser irradiation devices were installed side by side in the width direction of the steel plate, and a coil having a width of 1200 mm was irradiated. After the laser irradiation was completed, the surface of the steel sheet was observed, and the resist removal width (peeling length with respect to the traveling direction of the steel sheet) in the laser irradiation section was measured. The measurement results are also shown in Table 2. Here, the synchronization timing of the laser apparatus was set under a plurality of conditions, and a sample having a plurality of continuous / discontinuous peeling modes was prepared.

Subsequently, each sample was subjected to electrolytic etching to form a linear groove. A 25% NaCl aqueous solution was used as the electrolytic solution, and the current density was adjusted in advance so that a desired linear groove (width / depth) was formed. The electrolytic conditions were an electrolytic solution temperature: 20 ° C., a current density: 4 to 24 A / dm ² , and an energization time: 2 min. After the etching was completed, the resist remaining on the front and back surfaces of the steel sheet was removed with an aqueous NaOH solution. The temperature of the aqueous NaOH solution was maintained at 50-70 ° C. Then, water washing and surface washing were performed.

Then, decarburization annealing, final finish annealing and tension film formation were performed for all the samples under the same conditions, and then the iron loss W _17/50 and the width and depth of the linear groove were measured. The measurement results are also shown in Table 3. After final finishing annealing, C, Al, N, S and Se were reduced to the extent of unavoidable impurities.

As can be seen from the results shown in Table 3, those adopting the manufacturing method within the scope of the present invention have a narrower groove width than those outside the scope of the present invention, and as a result, good iron loss characteristics are obtained. You can see that it has been done. Further, in the sample including the laser irradiation end portion, the sample in which the groove was continuously formed showed good characteristics even within the scope of the present invention.

Claims (9)

A resist forming process for forming a resist on the surface of grain-oriented electrical steel sheets,
A laser irradiation step in which a laser is irradiated in a direction crossing the rolling direction of the directional electromagnetic steel plate to remove the resist of the irradiated portion of the laser, at intervals in the rolling direction of the directional electromagnetic steel plate. When,
It has an etching step of etching a resist-removed portion of the grain-oriented electrical steel sheet to form a linear groove.
The laser irradiation in the laser irradiation step is a method for improving iron loss of a grain-oriented electrical steel sheet, which is performed through a slit of a slit plate that partially cuts the laser beam. The method for improving iron loss of a grain-oriented electrical steel sheet according to claim 1, wherein the slit has a larger opening width on the laser beam exit side than the opening width on the laser beam entry side in the slit plate. The method for improving iron loss of grain-oriented electrical steel sheets according to claim 1 or 2, wherein the laser in the laser irradiation step is a single-mode fiber laser. The method according to any one of claims 1 to 3, wherein in the laser irradiation step, the maximum beam width of the surface of the grain-oriented electrical steel sheet in a direction orthogonal to the scanning direction of the laser is 0.01 mm or more and 0.08 mm or less. The method for improving iron loss of the described grain-oriented electrical steel sheet. A resist forming portion that forms a resist on the surface of the grain-oriented electrical steel sheet along the sheet-passing line of the grain-oriented electrical steel sheet, and the surface of the grain-oriented electrical steel sheet on which the grain is formed is irradiated with a laser to partially irradiate the resist. The laser irradiation part to be specifically removed and the etching part to etch the resist removing part of the grain-oriented electrical steel sheet are arranged in order in the plate-passing direction of the grain-oriented electrical steel sheet, and the laser irradiation section collects laser. An iron loss improving device for grain-oriented electrical steel sheets provided with a slit plate that partially cuts laser light between the portion and the surface of the grain-oriented electrical steel sheet. The iron loss improving device for grain-oriented electrical steel sheets according to claim 5, wherein the slit plate has a slit in which the opening width on the laser beam exit side is larger than the opening width on the laser beam entry side. The iron loss improving device for grain-oriented electrical steel sheets according to claim 5 or 6, wherein the laser irradiation unit has a laser irradiation device for a single-mode fiber laser. From claim 5, the laser irradiation unit has 1 to 3 laser irradiation devices having a maximum beam width of 0.01 mm or more and 0.08 mm or less in a direction orthogonal to the scanning direction of the laser on the surface of the grain-oriented electrical steel sheet. The iron loss improving device for grain-oriented electrical steel sheets according to any one of 7. In manufacturing a grain-oriented electrical steel sheet by hot-rolling and then cold-rolling the material for grain-oriented electrical steel, at the stage after the cold rolling, the surface of the steel sheet is subjected to any of claims 1 to 4. A method for manufacturing a grain-oriented electrical steel sheet that forms a linear groove using the described iron loss improving method.

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