JPH07331333A - Grain oriented silicon steel sheet excellent in iron loss characteristic and its production - Google Patents

Abstract

PURPOSE:To provide superior iron loss characteristic free from deterioration even after coiling annealing by forming many linear grooves in the surface of a steel sheet in a direction intersecting a rolling direction and then forming a low Si region, lower in Si content than a material, at least in one face among the bottom face and both side faces of each groove, over a prescribed depth or above. CONSTITUTION:The linear grooves to be formed in the surface of a steel sheet are constituted so that they have 30-30mum width, 10-7mum depth, and 1-30mm spacing between grooves and the angle of intersection with a rolling direction is regulated to <=30 deg. with respect to the direction perpendicular to the rolling direction. At least per face of each linear groove, a low Si region having Si content lower than that of a material by >=0.3wt.% is formed over a depth of >=50mum. It is preferable to form this low Si region by forming linear grooves by electrolytic etching, applying a water slurry of fine CaCO3 powder to the grooves, drying them, and then performing annealing at >=800 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grain-oriented electrical steel sheet having excellent iron loss characteristics and suitable for use as an iron core material for transformers and other electrical equipment, and a method for producing the same.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are mainly used as iron cores for transformers and other electrical equipment, and are required to have excellent magnetic properties, and especially low iron loss. This iron loss is
It can be roughly expressed by the sum of the hysteresis loss and the eddy current loss, and the hysteresis loss can be obtained by using the inhibitor having a strong suppressing force to change the crystal orientation to the Goss orientation, that is, (11
0) It has been drastically reduced by highly accumulating in the [001] direction and reducing the impurity element that causes generation of a pinning factor when the domain wall moves when magnetized. On the other hand, regarding eddy current loss, increasing the Si content to increase electrical resistance, thinning the steel plate thickness, and forming a coating on the surface of the steel plate base metal with a coefficient of thermal expansion different from that of the base iron The reduction has been achieved by applying tension to iron and reducing the magnetic domain width by refining the crystal grains.

More recently, due to the reduction of eddy current loss,
As a technique for further reducing iron loss, there has been proposed a method of irradiating a laser beam (Japanese Patent Publication No. 57-2252) or a plasma flame (Japanese Patent Publication No. 62-96617) in a direction perpendicular to the rolling direction of the steel sheet. It was These methods subdivide the magnetic domains by introducing fine thermal strains in a linear or spot form on the steel plate surface,
The magnetic domain is subdivided to reduce the iron loss. However, these methods cannot be used as a material for wound cores that require stress relief annealing after irradiation because the iron loss reduction effect disappears when heat treatment at high temperature is performed after magnetic domain refinement. It was

Therefore, various methods utilizing groove formation in a steel sheet have been developed as a magnetic domain refining technique capable of withstanding strain relief annealing. As such a technique, for example, there is a method of locally forming a groove in a steel sheet after finish annealing, that is, after secondary recrystallization, and subdividing a magnetic domain by the demagnetizing effect thereof. Mechanical processing (Japanese Patent Publication No. 50-356)
79) or laser light irradiation to locally remove the insulating coating and the underlying coating, followed by electrolytic matching.
63-76819) method has been proposed. In addition,
In JP 62-53579, a method of subdividing a magnetic domain by achieving groove formation and recrystallization by performing stress relief annealing after stamping with a tooth profile roll is further disclosed in JP-A-59-197520. Respectively disclose a method of forming a groove in a steel sheet before finish annealing.

[0005]

Although the groove forming technique as described above makes it possible to maintain the magnetic domain refining effect even after the strain relief annealing, the iron loss can be reduced by the above-mentioned laser beam or plasma flame. However, it is not sufficient compared with the method of irradiating the same, and further reduction of iron loss has been desired. The present invention advantageously responds to the above-mentioned demands, and an object thereof is to propose a novel technique that can stably realize further lower iron loss in the technique of reducing iron loss by forming a groove.

[0006]

Means for Solving the Problems Now, as a result of intensive experiments and studies for reducing the iron loss of grain-oriented electrical steel sheets, the inventors have found that in grain-oriented electrical steel sheets having linear grooves on the surface,
It was found that iron loss can be significantly reduced by reducing the Si content in the vicinity of the linear groove as compared with the steel material. The present invention builds on the above findings.

That is, according to the present invention, a large number of linear grooves extending in a direction intersecting the rolling direction are formed on the surface of a steel sheet, and at least one of the bottom surface and both side surfaces of the linear groove has a Si surface. It is a grain-oriented electrical steel sheet with excellent iron loss characteristics, characterized in that a low Si region whose content is 0.3 wt% or more lower than that of the material is formed over a depth of 50 μm or more.

In the present invention, the silicon-containing slab is hot-rolled, and then cold-rolled once or twice or more with an intermediate anneal to obtain a final product sheet thickness, followed by decarburizing-annealing. In a method for producing a grain-oriented electrical steel sheet comprising a series of steps for applying finish annealing, a steel sheet that has undergone final cold rolling is formed with a number of linear grooves in a direction intersecting the rolling direction, and after final finish annealing, After attaching calcium carbonate to at least one of the three surfaces of the bottom surface and both side surfaces of the linear groove,
A method for producing a grain-oriented electrical steel sheet having excellent iron loss characteristics, which is characterized by annealing at a temperature of 800 ° C or higher.

In the present invention, the linear groove formed on the surface of the steel sheet has a width of 30 to 300 μm, a depth of 10 to 70 μm,
It is preferable that the groove interval is 1 to 30 mm, and the angle of intersection with the rolling direction is within 30 ° with respect to the direction perpendicular to the rolling direction.

The present invention will be described in detail below. First, the experimental results that are the basis of the present invention will be described. A steel slab containing a small amount of Mn, Se and Al as inhibitor forming elements was subjected to hot rolling according to a conventional method and then cold rolling twice with intermediate annealing interposed therebetween to obtain a final cold rolled sheet having a thickness of 0.23 mm. Then, a resist ink was applied to the cold rolled plate to mask it, leaving a non-coated portion corresponding to the linear groove shape. Here, the shape of the non-coating part has a width parallel to the plate width direction: 20
A straight line of 0 μm was used. Such a straight non-coated portion,
It was left with an interval of 3 mm in the rolling direction. Next, a linear groove having a depth of 20 μm was formed by electrolytic etching using a NaCl bath. Then, after removing the resist agent, decarburization annealing and finish annealing were performed, and a slurry in which CaCO ₃ fine powder was suspended in water was applied to the groove portion and then dried, and then 700 to 11
Annealing was performed at various temperatures in the range of 00 ° C. Then, a tension coating was applied and baked, and then strain relief annealing was performed at 850 ° C. for 3 hours.

For comparison, a steel plate not subjected to linear groove forming treatment on the final cold-rolled steel plate, width: 200 μm, depth:
Decarburization annealing, finish annealing and strain relief annealing were applied to a steel sheet having linear grooves parallel to the sheet width direction of 20 μm and groove interval: 3 mm under the same conditions as above.

From each of the steel plates thus obtained, Epstein test pieces were cut out so that the longitudinal direction thereof coincided with the rolling direction, and the measurement results of the respective magnetic properties are shown in FIG. Apply CaCO ₃ as shown in Figure 1 and
When annealed at a temperature of 00 ° C. or higher, the iron loss is remarkably reduced as compared with the conventional material in which only the groove is formed as well as the case without the groove. In addition, the Si content around the groove of the steel plate
An investigation by EPMA revealed that the amount of Si was reduced in a strip-shaped region with a width of about 160 μm on both sides of the groove (thus a depth of about 160 μm on both sides).

[0013]

The linear groove introduced on the surface of the steel sheet forms a free magnetic pole when the electromagnetic steel sheet is magnetized, and the magnetic domain width is reduced so as to reduce the magnetic energy generated by this magnetic pole.
As a result, it is known that abnormal eddy current loss is reduced. However, since the magnetic flux lines tend to bypass the lower part of the linear groove to prevent the magnetic pole from being generated, the effect of reducing the eddy current loss is reduced accordingly. This detour of the magnetic flux lines occurs against the magnetic anisotropy of the grain-oriented silicon steel sheet. Therefore, by strengthening the magnetic anisotropy around the linear grooves, the magnetic domain subdivision by the detour of the magnetic flux lines is performed. It is possible to suppress a decrease in the effect. Here, in the Fe-Si alloy, the smaller the Si content, the larger the magnetocrystalline anisotropy constant, so if the Si content around the groove is reduced, it is possible to effectively prevent the detour of the magnetic flux line, As a result, the magnetic domain subdivision effect can be enhanced.

As a distribution form of the region containing a small amount of Si, at least one of the regions directly below the linear groove or adjacent to both side surfaces of the linear groove, that is, at least one of the three surfaces of the bottom surface and both side surfaces of the linear groove is used. Any strip-shaped region may be used. Here, the width (depth on each surface) of the strip-shaped area is 50μ.
If the width is less than m, the rotation of magnetization is likely to occur, so the width of the low Si region must be 50 μm or more. However, this low
If the Si region width is too large, the magnetic resistivity of the steel sheet will decrease, which will rather lead to deterioration of iron loss.
It is preferably not more than μm.

Further, the Si reduction amount in this strip region is
It should be 0.3 wt% or more than the Si content of the material. This is because if the Si reduction amount is less than 0.3 wt%, the effect of enhancing the magnetic anisotropy is small, and it is not possible to effectively suppress the detour of the linear groove below the magnetic flux line to improve the iron loss. is there.

It is more preferable that the strip-shaped region is continuously formed in the plate width direction along the linear groove, but it is not always necessary to be continuous, and it is intermittent like a broken line. It may be. Further, the crystal grain orientation of this band-shaped region is the same as that of the periphery thereof, that is, it is desirable that the low Si region is formed in the same crystal grain,
Grain boundaries or fine crystal grains may be present in this region.

Regarding the shape of the linear groove, width: 30 to 300 μ
It is preferable that m is m, depth is 10 to 70 μm, groove interval is 1 to 30 mm, and angle of intersection with the rolling direction is within 30 ° with respect to the direction perpendicular to the rolling direction. This is because when the groove width is less than 30 μm and the groove depth is less than 10 μm,
This is because the amount of magnetic poles generated is small, so a sufficient domain refinement effect cannot be obtained, while when the groove width exceeds 300 μm and the groove depth exceeds 70 μm, the magnetic flux density is significantly reduced. . Further, if the groove spacing is less than 1 mm, the magnetic flux density is remarkably reduced, while if it exceeds 30 mm, the magnetic domain refining effect is reduced and the iron loss is not sufficiently reduced. Further, if the direction of the linear groove deviates from the range of ± 30 ° with respect to the direction perpendicular to the rolling direction, the effect of domain refinement will be sharply reduced, and the effect of reducing iron loss will be significantly deteriorated.

The linear grooves may be formed at any stage before and after the final finish annealing as long as they are after the final cold rolling. Examples of the method of forming the groove include a method of locally performing an etching treatment, a method of scribing with a cutting tool, a method of rolling with a protruding roll, and the like, but the most preferable method is immediately after final cold rolling, resist-electrolysis. It is a method of forming grooves in a steel sheet by an electrochemical method such as etching or a chemical method such as etching.

Next, a low Si region is formed around the linear groove. As such a method, the linear groove portion is formed after the finish annealing.
The method of applying CaCO ₃ and annealing at a temperature of 800 ° C. or higher is advantageously suitable. If the annealing temperature is lower than 800 ° C., as shown in FIG. 1, a low Si region cannot be formed sufficiently in the peripheral region of the groove, and a satisfactory domain refinement effect cannot be obtained. Annealing temperature is 800 ℃ or higher (preferably 11
It is necessary to set the temperature below 00 ° C).

The means for forming the low Si region is C
It is not limited to the coating and baking method of aCO ₃ , but the following methods are also applicable. After reducing the amount of Si in the material in advance and forming linear grooves,
A method of applying Si treatment to a region other than the adjacent region of the linear groove. After the linear grooves are formed, a method of heating only the region near the linear grooves in a strong oxidizing atmosphere to oxidize and desiliconize.

The application of the present invention is not particularly limited, and any conventionally known magnetic steel sheet can be applied. The preferred composition is as follows. C: 0.01 to 0.10 wt% (hereinafter simply referred to as "%") C is an element useful not only for uniform refinement of the structure during hot rolling and cold rolling but also for development of Goss orientation, and at least 0.01%. However, if the content exceeds 0.10%, the Goss orientation will be disturbed, so 0.01 to 0.10%
It is preferably about the same.

Si: 2.0 to 4.5% Si increases the resistivity of the steel sheet and effectively contributes to the reduction of iron loss, but if it exceeds 4.5%, the cold rolling property is impaired, while 2.0%
If it does not satisfy the requirement, not only the specific resistance decreases, but also the crystal orientation is randomized by α-γ transformation during the finish annealing performed for secondary recrystallization and blunting, and a sufficient iron loss reduction effect is obtained. Therefore, the amount of Si is preferably set to about 2.0 to 4.5%.

Mn: 0.02 to 0.12% Mn requires at least about 0.02% to prevent hot embrittlement, but if it is too much, the magnetic properties deteriorate, so the upper limit is preferably set to about 0.12%. .

The inhibitors added to suppress the grain growth of crystal grains having an orientation other than the Goss orientation and effectively grow the Goss orientation include MnS, MnSe-based and AlN-based inhibitors.・ MnS, MnSe system; at least 1 selected from Se and S
Species: 0.005 to 0.06% Se and S are all effective elements as inhibitors, and at least about 0.005% is required from the viewpoint of securing inhibitory power, but if it exceeds 0.06%, the effect is rather impaired. In either case of single addition or complex addition, the content is preferably about 0.005 to 0.06%. AlN system; Al: 0.005 to 0.10%, N: 0.004 to 0.015% The range of Al and N is also set to the above range for the same reason as in the case of the above MnS and MnSe systems. Here, the above-mentioned MnS, MnSe system and AlN system can be used together.

In addition to S, Se, and Al described above, Cu, Sn, Cr, Ge, Sb, Mo, Te, and
Bi and P etc. can be used. Here, the preferred addition ranges of the above components are Cu, Sn, Cr: 0.01 to 0, respectively.
15%, Ge, Sb, Mo, Te, Bi: 0.005 to 0.1%, P: 0.01
.About.0.2%, and each of these inhibitors can be used alone or in combination.

[0026]

【Example】

Example 1 A silicon steel slab containing trace amounts of Al, Mn, Se and Sb as inhibitor forming elements was subjected to hot rolling according to a conventional method and then cold rolling twice with intermediate annealing sandwiched between them to obtain a final cold 0.23 mm thickness. It was a rolled sheet. Then, a resist ink was applied to the cold rolled plate to mask it, leaving a non-coated portion corresponding to the linear groove shape. Here, the shape of the non-coated portion was a straight line having a width of 200 μm extending in the plate width direction. Such a linear non-coated portion was left at a distance of 3 mm in the rolling direction. Next, a linear groove having a depth of 20 μm was formed by electrolytic etching using a NaCl bath. Next, after removing the resist agent, decarburization annealing and finish annealing were performed, and then a slurry in which CaCO ₃ powder was suspended in water was applied to the groove portion, dried, and baked. Annealed in.

For comparison, a steel plate not subjected to the linear groove forming treatment on the final cold-rolled sheet, width: 200 μm, depth:
For the steel plate after removing the resist agent, which has a linear groove parallel to the plate width direction of 20 μm and a rolling direction interval of 3 mm,
Similarly, after decarburizing and finishing annealing,
Strain relief annealing was performed at ℃ for 3 hours.

Epstein test pieces were cut from each of the thus obtained steel sheets after stress relief annealing so that the longitudinal direction thereof coincided with the rolling direction, and the measurement results of the respective magnetic properties are shown in Table 1.

[0029]

[Table 1]

As is clear from Table 1, when CaCO ₃ is applied to the linear groove portion according to the present invention and annealed at 800 ° C. or higher, iron loss is significantly reduced as compared with the comparative material.

Example 2 A silicon steel slab containing a small amount of Al, Mn, Se and Sb as inhibitor forming elements was subjected to hot rolling according to a conventional method and then cold rolling twice with intermediate annealing interposed therebetween to obtain a thickness of 0.23 mm. Cold-rolled sheet. Then, a resist ink was applied to the cold rolled plate to mask it, leaving a non-coated portion corresponding to the linear groove shape. Here, the shape of the non-coated portion was a straight line having a width of 200 μm and extending at an angle of 10 ° with respect to the plate width direction. Such linear non-coated portions were left at intervals of 3 mm. Then Na
After forming a linear groove having a depth of 25 μm by electrolytic etching using a Cl bath, the resist agent was removed, and then decarburization annealing and finish annealing were performed. After that, YAG in the linear groove
After irradiating a laser to remove the coating formed in the linear groove, a slurry in which CaCO ₃ powder was suspended in water was applied and annealed.

For comparison, a steel plate not subjected to linear groove forming treatment on the final cold-rolled plate, width: 200 μm, depth:
A linear groove extending linearly at 25 μm, an interval of 3 mm, and an angle of 10 ° with respect to the plate width direction was formed, and after removing the resist agent, the steel plate on which the YAG laser was irradiated was linearly decarburized and annealed. After finishing annealing, a tension coating was applied and baked, and then strain relief annealing was performed at 800 ° C for 3 hours.

Epstein test pieces were cut from each of the thus obtained steel sheets after stress relief annealing so that the longitudinal direction thereof coincided with the rolling direction, and the measurement results of the respective magnetic properties are shown in Table 2.

[0034]

[Table 2]

As is clear from Table 2, the steel sheet obtained according to the present invention has significantly reduced iron loss as compared with the comparative material.

[0036]

As described above, according to the present invention, it is possible to stably obtain a grain-oriented electrical steel sheet having excellent iron loss characteristics, which is not deteriorated by strain relief annealing, and is particularly suitable for transformer core applications. Serve and play a great effect.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between annealing temperature and iron loss.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Keiji Sato, 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Technical Research Division, Kawasaki Steel Co., Ltd. (72) Kazuhiro Suzuki, 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba (72) Inventor Michio Komatsubara, 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Kawasaki Steel Co., Ltd.

Claims (3)

[Claims] 1. A steel sheet surface having a large number of linear grooves extending in a direction intersecting the rolling direction, and at least one of the bottom surface and both side surfaces of the linear groove has a Si content. Depth of low Si region 0.3 wt% lower than that of material: 50
A grain-oriented electrical steel sheet with excellent iron loss characteristics, characterized by being formed over μm. 2. The linear groove according to claim 1, wherein the width is 30 to
300 μm, depth: 10 to 70 μm, groove interval: 1 to 30 mm, crossing angle with rolling direction: grain oriented electrical steel sheet with excellent iron loss characteristics within 30 ° with respect to the direction perpendicular to the rolling direction. 3. A silicon-containing steel slab is hot-rolled,
In the method for producing a grain-oriented electrical steel sheet, which comprises a series of steps in which a final product sheet thickness is obtained by performing cold rolling once or twice or more with an intermediate annealing between them, followed by decarburization annealing and final finishing annealing. A large number of linear grooves are formed on the rolled steel plate in a direction intersecting with the rolling direction, and after final finishing annealing, calcium carbonate is adhered to at least one of the bottom surface and both side surfaces of the linear groove. A method for producing a grain-oriented electrical steel sheet with excellent iron loss characteristics, which comprises annealing at a temperature of 800 ° C or higher.