WO2012172624A1 - Manufacturing method for unidirectional electromagnetic steel sheet - Google Patents

Abstract

The present invention has the following steps: a final annealing step (S07) for annealing in a batch furnace a steel sheet (ferrite) wound into a coil, and forming a glass coating on the surface of the steel sheet (ferrite); an insulating film forming step (S08) for, after the final annealing step (S07), forming an insulating film on top of the glass coating; and a laser irradiation step (S09) for irradiating the insulating film from above with a laser beam, and for controlling the magnetic domain. In the laser irradiation step (S09), a laser beam is shone onto a surface facing the radial exterior side of the coil at the time of the final annealing step (S07).

Description

Manufacturing method of unidirectional electrical steel sheet

The present invention relates to a method for producing a unidirectional electrical steel sheet in which a glass film and an insulating film are formed on the surface of a steel plate, and the magnetic domain is controlled by laser irradiation.

The above-mentioned unidirectional electrical steel sheet is used as a material constituting an iron core of electrical equipment such as a transformer and a rotating machine. Such a unidirectional electrical steel sheet is required to reduce energy loss (iron loss) when magnetized. Iron loss is classified into eddy current loss and hysteresis loss. Furthermore, eddy current loss is classified into classical eddy current loss and abnormal eddy current loss.

Here, in order to reduce the classic eddy current loss, a thin unidirectional electrical steel sheet having an insulating film formed on the plate surface is provided. As a unidirectional electrical steel sheet on which an insulating film is formed, for example, as shown in Patent Document 1, a glass film is formed on the surface of a steel plate, and a two-layer structure in which an insulating film is further formed on the glass film. Structures have been proposed.

Further, in order to suppress abnormal eddy current loss, for example, as shown in Patent Documents 2 and 3, a laser beam is condensed and irradiated from above the insulating film, and is scanned in the substantially width direction of the electromagnetic steel sheet. A magnetic domain control method has been proposed in which magnetic domains are subdivided by providing regions having residual strain periodically in the direction.

The above-mentioned unidirectional electrical steel sheet is, for example, a silicon steel slab as a raw material, a hot rolling process → an annealing process → a cold rolling process → a decarburizing annealing process → a final finish annealing process → an insulating film forming process → a laser irradiation process, It is manufactured by the procedure. Here, in the annealing before the final finish annealing step, an oxide layer mainly composed of silica (SiO ₂ ) is formed on the surface of the steel plate iron.
Moreover, in the final finishing annealing process, it heat-processes using a batch type furnace in the state which wound steel plate iron in the shape of a coil. For this reason, in order to prevent seizure of the steel sheet steel in the final finishing annealing process, an annealing separator mainly composed of magnesia (MgO) is applied to the surface of the steel sheet steel before the final finishing annealing process.
In the final finish annealing step, the above glass film is formed by the reaction between the oxide layer mainly composed of silica and the annealing separator mainly composed of magnesia.

By the way, in the laser irradiation process, an insulating film is formed on the glass film, and a magnetic beam is controlled by irradiating a laser beam on the insulating film. Here, wrinkles may occur in the insulating film and the glass film due to the irradiation of the laser beam. Here, wrinkles refers to film damage such as defect peeling, lifting, alteration, and discoloration of these films, which can be recognized by visual inspection or visual inspection under a microscope. In particular, when wrinkles occur in the glass film, the steel plate steel is exposed to the outside and rust is generated. For this reason, when wrinkles occurred in the glass film, it was necessary to apply the insulating film again.

Moreover, in a unidirectional electrical steel sheet, since many heat processing are implemented, in the longitudinal direction (rolling direction) and width direction of a steel plate base iron, the interface structure and thickness of a glass film or an insulating film may vary. is there. Therefore, even if the laser irradiation conditions are adjusted, it may be difficult to reliably suppress the generation of wrinkles in the glass film over the entire steel plate.

Under such circumstances, there has been a demand for a method for producing a unidirectional electrical steel sheet that can suppress generation of wrinkles in a glass film due to laser irradiation and can provide a high-quality unidirectional electrical steel sheet. .

JP 2007-119821 A Special table 2003-500541 gazette Japanese Patent Publication No. 06-019112

A method for producing a unidirectional electrical steel sheet according to the present invention includes a steel sheet base iron, a glass coating formed on the surface of the steel plate base, and an insulating coating formed on the glass coating. A method for producing a steel sheet, comprising: annealing in a batch furnace in a state where the steel sheet steel is wound in a coil shape, and forming a glass film on the surface of the steel sheet steel; and the final finishing process. After the annealing step, an insulating coating forming step for forming an insulating coating on the glass coating, and a laser irradiation step for performing magnetic domain control by irradiating a laser beam on the insulating coating, the laser irradiation In the process, a laser beam is irradiated onto the surface facing the radially outer side of the coil in the final finish annealing process.

In the final finish annealing process, heat treatment is performed in a batch furnace in a state where the steel sheet steel is wound in a coil shape, and the surface facing the radially outer side and the surface facing the radially inner side of the coiled steel sheet steel A glass film is formed. And in an insulating film formation process, an insulating film is formed on a glass film in the state which unwound the steel plate iron wound by coil shape, and was extended in plate shape. Further, in the laser irradiation step, the plate surface is irradiated with a laser beam in a state where the steel plate base iron on which the glass film and the insulating film are formed is extended in a plate shape.

Here, when the steel sheet steel wound in a coil shape is unwound and stretched into a plate shape, a compressive stress acts on the glass film formed on the surface facing the outer side in the radial direction of the coil, and the coil Tensile stress acts on the glass film formed on the surface facing the inner side in the radial direction. Further, the glass film is weak against tensile stress but strong against compressive stress.
Therefore, in the laser irradiation process, generation of wrinkles in the glass film is suppressed by irradiating the laser film to the surface facing the radial outside of the coil in the final finish annealing process, that is, the glass film on which the compressive stress is applied. It becomes possible to do. Thereby, it is not necessary to form an insulating film again after the laser irradiation step, and the production efficiency of the unidirectional electrical steel sheet can be greatly improved.

According to the present invention in which the laser beam is focused and irradiated on the surface facing the radially outer side of the coil in the final finishing annealing process in which the adhesion between the main body of the steel plate (ground iron) and the glass coating has not deteriorated, It is possible to reliably suppress the occurrence of the above and provide a high-quality unidirectional electrical steel sheet.

It is a section explanatory view of the unidirectional electrical steel plate manufactured by the manufacturing method of the unidirectional electrical steel plate which is an embodiment of the present invention. It is a flowchart of the manufacturing method of the unidirectional electrical steel plate which is embodiment of this invention. It is a schematic explanatory drawing of the decarburization annealing process and annealing separation agent application | coating process in FIG. It is a schematic explanatory drawing of the final finish annealing process in FIG. It is a schematic explanatory drawing of the insulating film formation process in FIG. It is a schematic explanatory drawing of the laser irradiation process in FIG. It is a figure which shows the evaluation result of the example of this invention. It is a figure which shows the evaluation result of a comparative example.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

A unidirectional electrical steel sheet 10 shown in FIG. 1 includes a steel sheet steel 11 (ground metal), a glass film 12 formed on the surface of the steel sheet steel 11, and an insulating film 13 formed on the glass film 12. It is equipped with.
The steel plate base iron 11 (base iron) is made of an iron alloy containing Si. In the present embodiment, Si: 2.5% by mass to 4.0% by mass, C: 0.02% by mass to 0.10% by mass, Mn: 0.05% by mass to 0.20% by mass, Acid-soluble Al: 0.020% by mass or more and 0.040% by mass or less, N: 0.002% by mass or more and 0.012% by mass or less, S: 0.001% by mass or more and 0.010% by mass or less, P: 0 0.01 mass% or more and 0.04 mass% or less, and the balance is Fe and inevitable impurities.
Moreover, the thickness of the steel plate base iron 11 (base iron) is generally 0.15 mm or more and 0.35 mm or less.

The glass film 12 is made of a composite oxide such as forsterite (Mg ₂ SiO ₄ ), spinel (MgAl ₂ O ₄ ), and cordierite (Mg ₂ Al ₄ Si ₅ O ₁₆ ). The thickness of the glass coating 12 is about 1 μm.

The insulating film 13 is, for example, (JP-A-48-39338, JP-B-53-28375) a coating liquid mainly composed of colloidal silica and phosphate (magnesium phosphate, aluminum phosphate, etc.) (JP-A-6-65754, JP-A-6-65555) The coating liquid is a mixture of alumina sol and boric acid. In this embodiment, the insulating film 13 is shown for aluminum phosphate, colloidal silica, and chromic anhydride (Japanese Patent Publication No. 53-28375). The insulating film 13 has a thickness of about 2 μm.

And in this unidirectional electrical steel sheet 10, residual strain is given to a linear region substantially orthogonal to the rolling direction by irradiating the insulating film 13 with a laser beam. The linear region to which the residual strain is applied is formed in a predetermined cycle in the rolling direction, and in a region sandwiched between two linear regions and magnetized in the rolling direction, a direction substantially orthogonal to the rolling direction. Subdivide the magnetic domain width.

Next, the manufacturing method of the unidirectional electrical steel sheet which is this embodiment is demonstrated.
As shown in the flowchart of FIG. 2, the method for producing a unidirectional electrical steel sheet according to the present embodiment includes a casting step S01, a hot rolling step S02, an annealing step S03, a cold rolling step S04, It has a carbon annealing step S05, an annealing separator coating step S06, a final finish annealing step S07, an insulating film forming step S08, and a laser irradiation step S09.

In the casting step S01, the molten steel prepared to the above composition is supplied to a continuous casting machine, and the ingot is continuously produced.
In the hot rolling step S02, the obtained ingot is heated to a predetermined temperature (for example, 1150 to 1400 ° C.) to perform hot rolling. Thereby, for example, a hot rolled material having a thickness of 1.8 to 3.5 mm is produced.

In the annealing step S03, heat treatment is performed on the hot-rolled material under conditions of, for example, 750 to 1200 ° C. × 30 seconds to 10 minutes.
In the cold rolling step S04, the surface of the hot rolled material after the annealing step S03 is pickled and then cold rolling is performed. Thereby, for example, a cold rolled material having a thickness of 0.15 to 0.35 mm is produced.

In the decarburization annealing step S05, the cold-rolled material is heat-treated, for example, under conditions of 700 to 900 ° C. × 1 to 3 minutes. Here, in the decarburization annealing step S05, as shown in FIG. 3, the cold rolled material wound up in a coil shape is drawn out in a plate shape, and heat treatment is performed while running in the furnace 21. Thereby, the steel plate iron 11 is produced. Further, as shown in FIG. 3, an oxide layer 15 mainly composed of silica (SiO ₂ ) is formed on the surface of the steel plate 11 by the decarburization annealing step S05.
In the annealing separator application step S06, an annealing separator 16 mainly composed of magnesia (MgO) is applied on the oxide layer 15 as shown in the enlarged cross-sectional view of the steel plate surrounded by circles in FIG.

In the final finish annealing step S07, as shown in FIG. 4, the steel plate 11 coated with the annealing separator 16 is wound in a coil shape and charged into the batch furnace 22 to perform heat treatment. . The heat treatment condition in the final finish annealing step S07 is 1100 to 1300 ° C. × 20 to 24 hours. In this final finish annealing step S07, the oxide layer 15 mainly composed of silica reacts with the annealing separator 16 mainly composed of magnesia, and as shown in the enlarged cross-sectional view of the steel sheet surrounded by circles in FIG. A glass film 12 made of forsterite (Mg ₂ SiO ₄ ) is formed on the surface of the base iron 11.

In the insulating film forming step S08, as shown in FIG. 5, the steel sheet steel 11 wound in a coil shape is unwound, stretched into a plate shape and conveyed, and the glass film formed on both surfaces of the steel sheet metal 11 An insulating agent 13 is formed on the insulating layer 13 by applying and baking on the insulating layer 12. The steel plate base 11 on which the insulating film 13 is formed is wound up in a coil shape.

In the laser irradiation step S09, as shown in FIG. 6, the steel sheet steel 11 wound in a coil shape is unwound, stretched into a plate shape, and conveyed, and a laser beam is collected toward one surface of the steel sheet steel 11. Light and irradiate and scan in the approximate width direction of the electromagnetic steel sheet. Thereby, the linear distortion substantially orthogonal to the rolling direction is imparted to the surface of the steel plate 11 at intervals set in advance in the rolling direction. At this time, in the final finishing step S07, the laser irradiation device 23 is arranged so as to irradiate the laser beam onto the surface facing the radially outer side of the coil when charged in the batch furnace 22. The light source and type of the laser are not particularly limited as long as they are laser light sources that are usually used for magnetic domain control by laser irradiation. In the present embodiment, an example using a YAG laser is shown in the laser irradiation step S09.

In this way, the glass coating 12 and the insulating coating 13 are formed on the surface of the steel plate base 11, and the unidirectional electrical steel plate 10 whose magnetic domain is controlled by laser irradiation is manufactured.

According to the method for manufacturing a unidirectional electrical steel sheet according to the present embodiment configured as described above, the steel sheet base iron 11 coated with the annealing separator 16 is wound in a coil shape in the final finish annealing step S07. Since the heat treatment is performed by charging the batch-type furnace 22 in a heated state, the glass coating 12 is respectively provided on the surface facing the radially outer side and the surface facing the radially inner side of the coiled steel plate iron 11. It is formed.

In the laser irradiation step S09, the steel sheet steel 11 wound in a coil shape is unwound and stretched into a plate shape and conveyed, and the radial direction of the coil charged in the batch furnace 22 in the final finishing step S07. A laser beam is applied to the surface facing outward.

Here, when the steel sheet steel 11 wound in a coil shape is unwound and stretched into a plate shape, a compressive stress acts on the glass film 12 formed on the surface facing the radially outer side of the coil. Tensile stress acts on the glass coating 12 formed on the surface facing the radial inner side of the coil.

In this embodiment, in the laser irradiation step S09, the laser beam is irradiated onto the surface on which the glass film 12 on which the compressive stress is applied is formed. The glass film 12 is weak against tensile stress but strong against compressive stress. Thereby, it is suppressed that a flaw generate | occur | produces in the glass membrane | film | coat 12, and it can prevent that the steel plate steel 11 is exposed outside.

Therefore, it is not necessary to form the insulating film 13 again after the laser irradiation step S09. Moreover, it becomes possible to suppress generation | occurrence | production of the flaw in the glass film 12 reliably, without restrict | limiting the laser irradiation conditions in laser irradiation process S09 more than necessary. Therefore, the production efficiency of the unidirectional electrical steel sheet 10 can be greatly improved.
Moreover, the high-quality unidirectional electrical steel sheet 10 with less generation of wrinkles in the glass coating 12 can be provided.

Next, a confirmation experiment conducted to confirm the effect of the present invention will be described.
First, Si: 3.0% by mass, C: 0.05% by mass, Mn: 0.1% by mass, acid-soluble Al: 0.02% by mass, N: 0.01% by mass, S: 0.01% by mass %, P; 0.02 mass%, and a slab having a composition of the balance being Fe and inevitable impurities was prepared.
The slab was hot rolled at 1280 ° C. to produce a hot rolled material having a thickness of 2.3 mm.

Next, heat treatment was performed on the hot-rolled material under conditions of 1000 ° C. × 1 minute. After the heat treatment, the steel sheet was pickled and then cold rolled to produce a cold rolled material having a thickness of 0.23 mm.
The cold-rolled material was decarburized and annealed under conditions of 800 ° C. × 2 minutes. And the annealing separation material which has a magnesia as a main component was apply | coated to both surfaces of the cold-rolled material after decarburization annealing.

The cold rolled material coated with the annealing separator was wound into a coil and charged into a batch furnace, and final finish annealing was performed at 1200 ° C. for 20 hours. Thereby, the steel plate iron with a glass film formed on the surface was produced.
Next, an insulating material made of aluminum phosphate was applied and baked (850 ° C. × 1 minute) on the glass film to form an insulating film.

And the laser beam was irradiated with respect to the steel plate iron in which the insulating film and the glass film were formed, and the distortion was provided to the surface of the steel plate iron. The laser beam irradiation conditions at this time were an output of 200 W, a substantially elliptical condensing spot shape dl (diameter in the rolling direction) × dc (diameter in the width direction) = 100 μm × 4000 μm, a scanning speed Vc = 16 m / s, and a pitch of 4 mm. did.

In the example of the present invention, the laser beam was applied to the surface facing the radially outer side of the coil during the final finish annealing.
In the comparative example, a laser beam was applied to the surface facing the radially inner side of the coil during the final finish annealing.

The thus obtained unidirectional electrical steel sheet as an example of the present invention and the unidirectional electrical steel sheet as a comparative example were subjected to a salt spray test and evaluated with a rust rating. The rust score was evaluated in the following five stages according to the rust generation rate (visual and image processing) of the laser irradiated portion according to JIS K2246 5.34 wetness test method.
Rating 5 Pass, no rusting, and laser irradiation cannot be visually confirmed. It cannot be confirmed with a microscope.
Score 4 Pass, no rusting, and the laser irradiated part is confirmed with a microscope. It cannot be confirmed visually.
Rating 3 Pass, no rusting, and laser irradiation can be visually confirmed. (The insulation film may be altered or damaged, but the glass film is healthy and the insulation is maintained.)
Score 2 Fail, rust occurred, visually confirmed rust discretely.
Score 1 Fail, rust generated, visually confirmed rust continuously.
If the score is 4 or more, there is no need to re-apply the insulating film. The evaluation results are shown in FIGS.

According to the example of the present invention, as shown in FIG. 7, the rust score is 4 and 5, and it is confirmed that no flaws are generated in the glass film.
On the other hand, in the comparative example, as shown in FIG. It is judged that the glass film is wrinkled in many places, and the steel plate steel is exposed.
In addition, in the other glass coatings and insulating coatings other than the above-described embodiments, the surface of the glass coating on which the glass coating on which the compressive stress is applied is similarly irradiated to the surface of the glass coating. It was confirmed that the generation of soot was suppressed. Further, the generation of wrinkles was examined using a fiber laser or the like as the laser light to be irradiated, and similar results were obtained as a tendency.
From the above, according to the example of the present invention, it was confirmed that generation of wrinkles in the glass film can be suppressed even under the same laser irradiation conditions.

According to the present invention, a high-quality unidirectional electrical steel sheet in which generation of wrinkles in a glass film is suppressed by irradiating a laser beam onto a surface on which a glass film on which compressive stress is applied is formed. Can be provided.

DESCRIPTION OF SYMBOLS 10 Unidirectional electrical steel sheet 11 Steel plate base metal 12 Glass film 13 Insulation film S07 Final finishing annealing process S09 Laser irradiation process

Claims (1)

A method for producing a unidirectional electrical steel sheet having a steel sheet ground iron, a glass film formed on the surface of the steel sheet steel, and an insulating film formed on the glass film,
Annealing in a batch furnace in a state where the steel plate iron is wound in a coil shape, and a final finish annealing step for forming a glass film on the surface of the steel plate iron,
After the final finish annealing step, an insulating film forming step of forming an insulating film on the glass film,
A laser irradiation step of irradiating a laser beam from above the insulating film and performing magnetic domain control,
In the said laser irradiation process, the laser beam is irradiated to the surface which faces the radial direction outer side of the coil in the said last finish annealing process, The manufacturing method of the unidirectional electrical steel sheet characterized by the above-mentioned.

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