JPH08269557A - Production of mirror-finished grain-oriented silicon steel sheet reduced in iron loss - Google Patents

Abstract

PURPOSE: To produce a grain-oriented silicon steel sheet excellent in iron loss characteristic at a low cost. CONSTITUTION: The grain-oriented silicon steel sheet is produced by applying hot rolling to a slab having a composition consisting of, by weight ratio, 0.8-4.8% Si, 0.012-0.05% Al, <=0.01% N, and the balance Fe with inevitable impurities, further applying cold rolling to the resulting sheet once or two or more times interposing process annealing between the cold rollings, and subjecting the resulting sheet to decarburizing annealing and to finish annealing. At this time, decarburizing annealing is executed in an atmospheric gas having a degree of oxidation of forming no Fe oxides and, after the application of alumina as a separation agent at annealing, finish annealing is executed. After grooves are formed in the steel sheet by chemical or thermal means, a tension film is formed on it to increase the number of active magnetic domain walls of the grain oriented silicon steel sheet, by which iron loss can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a grain-oriented electrical steel sheet mainly used as an iron core of a transformer or other electric equipment. In particular, the present invention discloses a manufacturing method for achieving an improvement in iron loss characteristics at low cost by effectively introducing a mirroring means for the surface and a magnetic domain subdividing means.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are used as magnetic iron cores in many electric devices. The grain-oriented electrical steel sheet is Si
Of 0.8 to 4.8% and the crystal grain orientation of the product is {11
It is a steel plate highly integrated in the 0} <001> direction. The magnetic properties are required to have a high magnetic flux density (represented by a B ₈ value) and low iron loss (represented by a W17 / 50 value). In particular, recently, there is an increasing demand for reduction of power loss from the viewpoint of energy saving.

In response to this demand, a technique for subdividing magnetic domains has been developed as a means for reducing the iron loss of grain-oriented electrical steel sheets. For example, Japanese Patent Laid-Open No. 58-26405 discloses a method of irradiating a steel sheet after finish annealing with a laser beam to subdivide magnetic domains to reduce iron loss. However, since the reduction of iron loss by this method is caused by the strain introduced by laser irradiation, it cannot be used for a wound core transformer that requires strain relief annealing after forming into a transformer.

As an improved technique, for example, JP-A-61-161
No. 117284, after finishing annealing, a part of the surface glass layer of the grain-oriented electrical steel sheet is removed by laser irradiation or the like, and the steel sheet base iron is melted with an acid such as hydrochloric acid or nitric acid to form a groove, and then tension is applied. A method of subdividing magnetic domains by forming a film and embedding a tension film having a coefficient of thermal expansion smaller than that of base iron in the groove is disclosed. However, in this method, in order to form a groove on the surface of the steel sheet, it is necessary to add a step of partially removing the glass coating such as laser irradiation and a step of dissolving the base iron by pickling etc. The cost will be high. .

On the other hand, when the movement of the magnetic domains of the steel sheet subjected to the magnetic domain refining treatment by such a method is observed in detail, statically some of the subdivided magnetic domains do not move. Do you get it. In order to further reduce the iron loss value of the grain-oriented electrical steel sheet, it is necessary to introduce a technology (magnetic domain activation technology) that eliminates factors that obstruct the movement of magnetic domains, in addition to the magnetic domain subdivision technology by the above method. .

For that purpose, it is effective to remove the glass coating on the surface of the steel sheet, which is a major factor that hinders the movement of magnetic domains, to make the surface mirror-finished. As a means for this, a method of removing the glass coating by pickling or the like after finish annealing and then performing chemical polishing or electrolytic polishing to make the surface mirror-finished is disclosed in, for example, JP-A-64-83620.

However, although chemical polishing, electrolytic polishing and the like can process a small sample material at the laboratory level, in order to perform it on an industrial scale, concentration control of the chemical solution,
There are major problems in terms of temperature control, provision of pollution prevention equipment, and the like, and the addition of such steps further increases the manufacturing cost, so that it has not yet been put to practical use.

[0008]

DISCLOSURE OF THE INVENTION According to the present invention, after finishing annealing, a part of the surface glass layer of a grain-oriented electrical steel sheet is removed by laser irradiation or the like, and the steel sheet base iron is melted using an acid such as hydrochloric acid or nitric acid. The method of forming a groove by forming a groove and then forming a tension coating is high in cost, and in order to maximize the effect of this magnetic domain refining treatment and obtain a large low iron loss value. Simultaneously solves the problem that the cost is increased because it is necessary to perform a surface treatment such as chemical polishing. That is, the present invention discloses a method for producing a grain-oriented electrical steel sheet which does not deteriorate in magnetic properties even when subjected to strain relief annealing and has better iron loss properties than conventional products at low cost.

[0009]

In order to solve the above problems, the present invention performs decarburization annealing in an atmosphere gas having an oxidation degree that does not form Fe-based oxide, and then applies alumina as an annealing separating agent. By making the surface of the steel sheet after finish annealing mirror-like, chemically or thermally forming grooves in the steel sheet and then forming a tension film to increase the number of active domain walls, thereby performing strain relief annealing. The present invention also provides a grain-oriented electrical steel sheet that does not deteriorate in characteristics and has lower iron loss than conventional products. Further, since there is no additional step as compared with the conventional manufacturing step, the manufacturing cost does not substantially increase.

[0010]

The present invention will be described in detail below. As a basic manufacturing method, a manufacturing method using (Al, Si) N as a main inhibitor by Komatsu et al. (For example, Japanese Patent Publication No. 62-452).
No. 85), or AlN and MnS by Taguchi, Sakakura, etc.
A production method using as a main inhibitor (for example, Japanese Patent Publication No.
No. 0-15644) may be applied.

Si is an important element for increasing the electric resistance and reducing the iron loss. If the content exceeds 4.8%, the material tends to crack during cold rolling, making rolling impossible. on the other hand,
If the amount of Si is reduced, α → γ transformation occurs during finish annealing, and the crystal orientation is impaired. Therefore, the lower limit is 0.8%, which does not affect the crystal orientation during finish annealing.

Acid-soluble Al is an essential element for binding N and functioning as AlN or (Al, Si) N as an inhibitor. Higher magnetic flux density 0.012
˜0.050% is the limited range. N is 0.0 during steelmaking
If 1% or more is added, voids in the steel sheet called blisters are generated, so 0.01% is made the upper limit.

Mn and S precipitate as MnS and serve as an inhibitor. When Mn is less than 0.02% and S is less than 0.005%, a predetermined amount of effective MnS inhibitor cannot be secured. Further, if Mn is more than 0.3% and S is more than 0.04%, solution treatment during heating of the slab becomes insufficient, and secondary recrystallization is not stably performed. Therefore, Mn: 0.02-0.3%, S: 0.005
~ 0.04%. B, Bi, Se, Pb, Sn, Ti and the like can be added as other inhibitor constituent elements.

The molten steel having the above components is formed into a hot rolled sheet by a usual process. A production method using (Al, Si) N as a main inhibitor by Komatsu et al. (For example, Japanese Patent Publication No. 62-452).
No. 85), from the viewpoint of securing the temperature during hot rolling, 1
100 ° C or higher, and 1280 without complete solution of AlN
Hot rolling is performed after heating at a temperature of ℃ or less. Further, a production method using AlN and MnS as main inhibitors by Taguchi, Sakakura, etc. (see, for example, Japanese Patent Publication No. 40-15644).
In Japanese Patent Laid-Open Publication No. 2003), hot rolling may be performed after heating at a temperature of 1300 ° C. or higher for complete solution treatment.

The hot rolled sheet is cold-rolled immediately or after being annealed for a short time. Annealing is performed in the temperature range of 750 to 1200 ° C. for 30 seconds to 30 minutes, and this annealing is effective to enhance the magnetic properties of the product. It is advisable to decide whether to accept or reject the product considering the characteristic level and cost of the desired product. Cold rolling
Basically, as disclosed in Japanese Patent Publication No. 40-15644, the final cold rolling reduction may be 80% or more.

The material after cold rolling is 750 to 900 ° C. in a wet hydrogen atmosphere in order to remove carbon contained in steel.
Decarburization annealing is performed in the temperature range of. In this decarburization annealing, F
One of the points of the present invention is to perform annealing at an oxidation degree that does not form an e-based oxide (Fe ₂ SiO ₄ , FeO, etc.) and apply alumina as an annealing separator. For example, in the temperature range of 800 to 850 ° C. where decarburization annealing is usually performed, the degree of oxidation of the atmospheric gas (PH ₂ O / PH ₂ )
By adjusting to <0.15, generation of Fe-based oxide can be suppressed. However, if the degree of oxidation is lowered too much, the decarburization rate becomes slow, which is not preferable from an industrial viewpoint. Taking both of these into consideration, it is preferable to anneal in the range of the degree of oxidation of atmospheric gas (PH ₂ O / PH ₂ ): 0.01 to 0.15.

A production method using (Al, Si) N as a main inhibitor for this decarburized annealed sheet (see, for example, Japanese Examined Patent Publication No. 62-4).
No. 5285), a nitriding treatment is performed. The method of this nitriding treatment is not particularly limited, and there is a method of performing it in an atmosphere gas having a nitriding ability such as ammonia. Quantitatively, 0.005% or more, preferably, the total nitrogen content may be nitrided by Al equivalent or more in the steel.

When laminating these decarburized and annealed sheets, alumina is dry-coated as an annealing and separating agent by a water slurry or an electrostatic coating method. In the case of coating with a water slurry, it is preferable to employ the method disclosed in, for example, Japanese Patent Application No. 5-211602.

This laminated plate is finish annealed to carry out secondary recrystallization and purification of nitride. Secondary recrystallization is described in JP-A-2-2.
As disclosed in Japanese Patent No. 58929, it is effective to increase the magnetic flux density by carrying out at a predetermined temperature by means such as holding at a constant temperature. After completing the secondary recrystallization, in order to purify impurities such as nitride and smooth the surface, 10
Anneal with 0% hydrogen at a temperature of 1100 ° C. or higher.

After finishing annealing, it is an important point of the present invention to increase the number of active domain walls by forming grooves on the steel sheet chemically or thermally and then forming a tension film. That is, (A) the method of the present invention having a plate thickness of 0.23 mm,
And (B) the steel sheet after finish annealing produced by the conventional method,
(A) The present invention is as it is, (B) In the conventional method, after irradiating a laser to remove a part of the glass coating, a width of 50 μm and a depth of 5 mm are linearly formed in the direction perpendicular to the rolling direction by a photoetching method. After forming the groove of 20 μm, a coating liquid containing colloidal silica and phosphate as main components was applied and baked at 850 ° C. to form a tension film. Then, strain relief annealing was performed at 800 ° C. for 4 hours. In Table 1,
The iron loss characteristics of a conventional product and a product manufactured by the method of the present invention are shown. As shown in Table 1, it can be seen that the iron loss value varies by about 20% due to the difference in the number of active domain walls.

[0021]

[Table 1]

As the method for forming the groove, any of the above-mentioned photo-etching method as a chemical method and irradiation with laser, infrared ray, electron beam or the like as a thermal method may be used. Further, the groove direction is preferably at right angles to the rolling direction or within a range of 45 degrees from the right angle, and the interval is preferably 2 to 10 mm from the viewpoint of reducing iron loss. The shape of the groove may be continuous, discontinuous linear or dotted, and the width is 10 to 10
A range of 0 μm and a depth of 10 μm or more and 50 μm or less is desirable from the viewpoint of magnetic properties.

After that, a tension film is formed. As the tension film, for example, a coating liquid containing mainly colloidal silica and aluminum phosphate according to JP-A-48-39338, and a coating containing mainly colloidal silica and magnesium phosphate according to JP-A-50-79442. A method of baking a solution or a coating solution containing alumina sol and boric acid as main components according to JP-A-6-65754 may be adopted.

[0024]

【Example】

(Example 1) Si: 3.3%, Mn: 0.1% by weight,
C: 0.05%, S: 0.007%, acid-soluble Al: 0.03%,
A silicon steel slab consisting of N: 0.008%, Sn: 0.05%, and the balance substantially Fe and unavoidable impurities was heated at 1150 ° C. and then hot rolled to a plate thickness of 2.3 mm. This hot rolled sheet is 1.8mm
Cold-rolled and annealed at 1100 ℃ for 2 minutes, final thickness 0.23mm
Cold rolled.

This cold-rolled sheet was annealed at a temperature of 830 ° C. for 100 seconds in a mixed gas of nitrogen and hydrogen with an oxidation degree of 0.06 to perform primary recrystallization. Then, by annealing in an ammonia atmosphere, the amount of nitrogen was increased to 0.025% to strengthen the inhibitor. This steel sheet was coated with alumina (Al ₂ O ₃ ) as a water slurry and then subjected to finish annealing.

A portion of these samples was irradiated with a laser and
Grooves having a width of 60 μm and a depth of 25 μm were formed at intervals of mm in the direction perpendicular to the rolling direction. After that, apply a coating liquid containing colloidal silica and phosphate as the main components.
Baking for 2 minutes at 50 ° C. After measuring the magnetic properties of these samples, strain relief annealing was further performed at 800 ° C. for 4 hours.
The magnetic properties of the obtained product are shown in Table 2.

[0027]

[Table 2]

(Embodiment 2) Infrared rays are focused on a part of the sample after the finish annealing of Embodiment 1 in a direction perpendicular to the rolling direction to obtain a width of 8
After forming a groove with a depth of 0 μm and a depth of 20 μm, apply a coating liquid containing alumina sol and boric acid as main components.
Baking at 70 ° C for 2 minutes. After measuring the magnetic properties of these samples, strain relief annealing was further performed at 800 ° C. for 4 hours.
Table 3 shows the magnetic properties of the obtained product.

[0029]

[Table 3]

(Example 3) Si: 3.1% by weight, M
n: 0.07%, C: 0.07%, S: 0.025%, acid-soluble A
l: 0.026%, N: 0.008%, Sn: 0.1%, the balance is a silicon steel slab consisting essentially of Fe and unavoidable impurities 13
After heating at 50 ° C, hot rolling was performed to a plate thickness of 2.3 mm. The hot rolled sheet was pickled, cold rolled to 1.8 mm, annealed at 1100 ° C. for 2 minutes, and then cold rolled to a final sheet thickness of 0.23 mm.

This cold-rolled sheet was annealed at a temperature of 850 ° C. for 100 seconds in a mixed gas of nitrogen and hydrogen with an oxidation degree of 0.1 for primary recrystallization. These steel sheets were then treated with alumina (Al ₂ O
₃ ) was applied with a water slurry and then subjected to finish annealing.

These samples were photoetched at a width of 40 μm and a depth of 25 at intervals of 4 mm in the direction perpendicular to the rolling direction.
A μm groove was formed. Then, a coating solution containing colloidal silica and phosphate as main components was applied and baked at 850 ° C. for 2 minutes. After measuring the magnetic properties of these samples, strain relief annealing was further performed at 800 ° C. for 4 hours. Table 4 shows the magnetic properties of the obtained product.

[0033]

[Table 4]

[0034]

According to the present invention, it is possible to manufacture a grain-oriented electrical steel sheet in which magnetic properties are not deteriorated by strain relief annealing and which has significantly better iron loss properties than conventional ones without increasing the cost.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hisawa Kitakawa 1-1, Tobata-cho, Tobata-ku, Kitakyushu City Inside the Hachiman Works, Nippon Steel Corporation (72) Inventor, Koji Yamazaki 1-1, Hibata-cho, Tobata-ku, Kitakyushu Inside Nippon Steel Co., Ltd. Yawata Works

Claims (2)

[Claims] 1. By weight ratio, Si: 0.8 to 4.8%, acid-soluble Al: 0.012 to 0.05%, N ≤ 0.01%, the balance being substantially Fe and unavoidable impurities. After heating the above silicon steel slab at 1100 ° C. or more and 1280 ° C. or less, hot rolling it, and performing decarburization annealing / nitriding treatment to obtain the final plate thickness by one or two or more cold rollings with intermediate annealing. In the method for producing a grain-oriented electrical steel sheet subjected to finish annealing, after decarburization annealing is performed in an atmosphere gas having an oxidation degree that does not form Fe-based oxides, after applying finish-annealing by applying alumina as an annealing separator. Of the mirror-oriented magnetic steel sheet having a low iron loss, characterized in that the number of active domain walls is increased by forming a tension coating after chemically or thermally forming grooves on the steel sheet surface of Production method. 2. By weight ratio, Si: 0.8-4.8%, acid-soluble Al: 0.012-0.05%, N ≦ 0.01%, Mn: 0.02-0.3% , S: 0.005 to 0.040%, the balance being heated at 1300 ° C. or higher to a silicon steel slab substantially consisting of Fe and unavoidable impurities, and then hot-rolled, once or twice or more with intermediate annealing. In a method for producing a grain-oriented electrical steel sheet, which is cold rolled to a final thickness, and then subjected to decarburization annealing and finish annealing, decarburizing annealing is performed in an atmosphere gas with an oxidation degree that does not form Fe-based oxide, and then annealed. By applying alumina as a separating agent, the surface of the steel sheet after finish annealing is mirror-finished, and the number of active domain walls is increased by forming a tension coating after chemically or thermally forming grooves on the steel sheet. Characteristic mirror surface with low iron loss Method of manufacturing oriented electrical steel sheet.