JPH08269554A - 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 characteristics 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 plate once or two or more times interposing process annealing between cold rollings, and then subjecting the resulting sheet to decarburizing annealing and to finish annealing. At this time, decauburizing 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. Then, after mechanical local stress is applied to the steel sheet to form grooves, a tension film is formed to increase the number of active magnetic domain walls of the grain oriented silicon steel sheet, thereby, the 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
Japanese Laid-Open Patent Publication No. 117218 discloses a method in which after finishing annealing, a work strain is applied by, for example, a gear-shaped roll to form fine grains to subdivide magnetic domains. However, in this method, since it is necessary to crush the surface ceramics layer of the grain-oriented electrical steel sheet by the gear type roll, the gear roll is largely worn, which causes a problem in manufacturing cost.

On the other hand, when the movement of the magnetic domains of the steel sheet subjected to the magnetic domain subdivision processing was observed in detail, it was found that some of the statically subdivided magnetic domains did not move. In order to further reduce the iron loss value of grain-oriented electrical steel sheet, a technology to eliminate the factors that obstruct the movement of the magnetic domain together with the magnetic domain subdivision technology by the above method (magnetic domain activation technology)
Need to be introduced.

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, methods such as chemical polishing and electrolytic polishing can process a small amount of material at the laboratory level, but for industrial scale, chemical solution concentration control, temperature control,
There is a big problem in terms of providing pollution prevention equipment, etc., and the addition of such a step increases the manufacturing cost, so that it has not yet been put to practical use.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a low iron loss value can be obtained by forming a fine grain by applying processing strain with a gear type roll or the like, but the gear roll is worn out and the manufacturing cost is high. The problem is that the cost increases when surface treatment such as pickling and chemical polishing is performed in order to maximize the effect of this magnetic domain refinement treatment and obtain a significantly low iron loss value. The point is solved at the same time. That is, it discloses a method for manufacturing an inexpensive grain-oriented electrical steel sheet in which magnetic properties are not deteriorated even when strain relief annealing is performed and iron loss properties are significantly improved.

[0008]

In order to solve the above-mentioned problems, the present invention performs decarburization annealing in an atmosphere gas having an oxidation degree that does not form Fe-based oxides, and uses alumina as an annealing separator. By applying, the surface of the steel sheet after finish annealing is mirror-finished, a local stress is mechanically applied to the steel sheet to form a groove after forming a groove, and the number of active domain walls is increased to remove strain. It is intended to provide a grain-oriented electrical steel sheet that does not deteriorate in characteristics even when subjected to annealing and has a 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.

[0009]

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 bonding with 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 is basically carried out by the above Japanese Patent Publication No. 40-
As disclosed in Japanese Patent No. 15644, the final cold rolling reduction may be 80% or more. The material after cold rolling is in a wet hydrogen atmosphere to remove carbon contained in steel,
Decarburization annealing is performed in the temperature range of 750 to 900 ° C.

In this decarburization annealing, one of the points of the present invention is to perform annealing at an oxidation degree that does not form Fe-based oxides (Fe ₂ SiO ₄ , FeO, etc.) and apply alumina as an annealing separator. is there. For example, in the temperature range of 800 to 850 ° C. in which decarburization annealing is usually performed, the Fe-based oxide is generated by adjusting the degree of oxidation of the atmospheric gas (PH ₂ O / PH ₂ ) <0.15. 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. Considering both of them, in the temperature range of 750 to 900 ° C., the degree of oxidation of atmospheric gas (PH ₂ O / PH ₂ ): 0.0
It is preferable to anneal in the range of 1 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 annealed sheets, alumina is dry-coated as an annealing separator 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 the secondary recrystallization is completed, 110% 100% hydrogen is used to purify impurities such as nitrides and smooth the surface.
Anneal at a temperature of 0 ° C. or higher. After finishing annealing, mechanical stress is applied to the steel sheet to form grooves and then a tension film is formed to increase the number of active domain walls in a manner that is not affected by strain relief annealing. This is an important point of the invention.

The finished annealed plate having a plate thickness of 0.23 mm and the above-mentioned method of the present invention was subjected to gear rolling to form grooves having a width of 20 μm and a depth of 10 μm at intervals of 5 mm.
Then, a coating solution containing colloidal silica and phosphate as a main component was applied, and a tension coating was formed by baking at 850 ° C. for 2 minutes, and then strain relief annealing was performed at 800 ° C. for 4 hours.

FIG. 1 shows magnetic domain micrographs of the conventional product (a) and the product (b) produced by the method of the present invention, and FIG. 2 shows the domain wall moving speed of both products under an alternating magnetic field. FIG. 3 shows the relationship between the magnetic flux density (B ₈ value) of the product and the iron loss (W17 / 50). FIG. 4 shows an iron loss deterioration margin due to wear of the gear roll.

Comparing (a) and (b) of FIG. 1, the magnetic domain refining effect of the product (b) according to the method of the present invention is statically observed as in the conventional material (a). As shown in FIG. 2, the magnetic domain wall movement behavior under an alternating magnetic field shows that almost all the magnetic domain walls of the product according to the method of the present invention are moving. On the other hand, in the conventional product, some domain walls cannot move at all due to the pinning effect of the glass coating. Due to such a difference in the actual number of active domain walls, a difference of 10 to 20% occurs as the iron loss value as shown in FIG.

Further, FIG. 4 shows an iron loss deterioration margin due to wear of the gear roll. In the method of the present invention, since there is no ceramic coating on the surface of the steel sheet after finish annealing as in the conventional case, the gear roll It can be seen that the life is extended by 5 times or more. Thus, according to the method of the present invention, compared with the conventional method,
Iron loss is 10 to 20 without adding new manufacturing process
%, And the life of the gear roll is extended 5 times or more.

The grooves formed in the steel sheet are at right angles to the rolling direction or within a range of 45 degrees from the right angles, and the intervals are 2 to.
10 mm is preferable from the viewpoint of reducing iron loss. The shape of the groove may be continuous, discontinuous, or dot-shaped. The width and depth of the groove are preferably 10 to 300 μm and 5 to 50 μm, respectively, from the viewpoint of reducing iron loss. If the width of the groove is narrowed, it tends to become a starting point of bending when performing bending with a small radius of curvature. If the width of the groove is widened, the magnetic flux density will decrease. Similarly, if the depth of the groove is too deep, the magnetic flux density will decrease.

As the tension film, for example, JP-A-48-3 is used.
A coating liquid mainly composed of colloidal silica and aluminum phosphate according to Japanese Patent No. 9338, JP-A-50-79.
No. 442, a coating liquid containing colloidal silica and magnesium phosphate as a main component, or JP-A-6-65.
The method of baking an alumina sol and a coating liquid containing boric acid as main components according to Japanese Patent No. 754 may be adopted.

[0028]

【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 oxidized in a mixed gas of nitrogen and hydrogen to a degree of oxidation (A: method of the present invention) of 0.06, and (B: conventional method).
It was annealed at 0.48 at a temperature of 830 ° C for 100 seconds for primary recrystallization.
Then, by annealing in an ammonia atmosphere, the amount of nitrogen was increased to 0.025% to strengthen the inhibitor.

These steel sheets were then subjected to (A: method of the present invention).
Alumina (Al ₂ O ₃ ) and (B: conventional method) magnesia (MgO) were applied as a water slurry, and then finish annealing was performed. A groove having a width of 50 μm and a depth of 15 μm was formed on each of the samples by a gear roll in a direction of 10 ° from the direction perpendicular to the rolling direction, and then a coating liquid containing colloidal silica and phosphate as a main component was applied. It was baked at 850 ° C for 2 minutes. After measuring the magnetic properties of these samples, 800 ° C
Then, strain relief annealing was performed for 4 hours. The magnetic properties of the obtained product are shown in Table 1.

[0031]

[Table 1]

(Example 2) The sample after the finish annealing of Example 1 was 30 μm wide and 10 μm deep in the direction perpendicular to the rolling direction.
After forming the groove of the tooth mold by pressing,
Apply a coating liquid consisting mainly of sol and boric acid
Baking at 870 ° C for 2 minutes. 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.

[0033]

[Table 2]

(Example 3) Si: 3.3% by weight, M
n: 0.1%, C: 0.05%, S: 0.007%, acid-soluble A
l: 0.03%, N: 0.008%, Sn: 0.05%, the balance is 1150 of a silicon steel slab consisting essentially of Fe and inevitable impurities.
After heating at ℃, hot rolled to a plate thickness of 2.3 mm. The hot rolled sheet was annealed at 1100 ° C. for 2 minutes and then cold rolled to a final sheet thickness of 0.30 mm.

This cold-rolled sheet was oxidized in a mixed gas of nitrogen and hydrogen to a degree of oxidation (A: method of the present invention) of 0.06, and (B: conventional method).
It was annealed at 0.44 at a temperature of 830 ° C for 150 seconds for primary recrystallization.
Then, by annealing in an ammonia atmosphere, the amount of nitrogen was increased to 0.025% to strengthen the inhibitor.

These steel sheets were then subjected to (A: method of the present invention).
Alumina (Al ₂ O ₃ ) and (B: conventional method) magnesia (MgO) were applied as a water slurry, and then finish annealing was performed. A groove having a width of 50 μm and a depth of 15 μm was formed on each of the samples by a gear roll in a direction of 10 ° from the direction perpendicular to the rolling direction, and then a coating liquid containing colloidal silica and phosphate as a main component was applied. It was baked at 850 ° C for 2 minutes. After measuring the magnetic properties of these samples, 800 ° C
Then, strain relief annealing was performed for 4 hours. Table 3 shows the magnetic properties of the obtained product.

[0037]

[Table 3]

(Example 4) Si: 3.3% by weight, M
n: 0.1%, C: 0.05%, S: 0.007%, acid-soluble A
l: 0.03%, N: 0.008%, Sn: 0.05%, the balance is 1150 of a silicon steel slab consisting essentially of Fe and inevitable impurities.
After heating at ℃, it was hot rolled to a plate thickness of 1.8 mm. The hot rolled sheet was cold rolled to 1.4 mm, annealed at 1100 ° C. for 2 minutes, and then cold rolled to a final sheet thickness of 0.15 mm.

This cold-rolled sheet was oxidized in a mixed gas of nitrogen and hydrogen to a degree of oxidation (A: method of the present invention) of 0.06, and (B: conventional method).
It was annealed at a temperature of 830 ° C. for 0.4 seconds at 0.44 to perform primary recrystallization. Then, by annealing in an ammonia atmosphere, the amount of nitrogen was increased to 0.025% to strengthen the inhibitor.

These steel sheets were then subjected to (A: method of the present invention).
Alumina (Al ₂ O ₃ ) and (B: conventional method) magnesia (MgO) were applied as a water slurry, and then finish annealing was performed. A groove having a width of 50 μm and a depth of 15 μm was formed on each of these samples by a gear roll in a direction of 10 degrees from the direction perpendicular to the rolling direction, and then a coating liquid containing colloidal silica and phosphate as a main component was applied. It was baked at 850 ° C for 2 minutes. After measuring the magnetic properties of these samples, 800 ° C
Then, strain relief annealing was performed for 4 hours. Table 4 shows the magnetic properties of the obtained product.

[0041]

[Table 4]

(Example 5) 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 oxidized in a mixed gas of nitrogen and hydrogen to a degree of oxidation (A: method of the present invention) of 0.1, and (B: conventional method).
It was annealed at a temperature of 850 ° C. for 0.4 seconds at 0.44 to perform primary recrystallization.
These steel sheets were then subjected to (A: Inventive method) alumina (A
l ₂ O ₃ ) and (B: conventional method) magnesia (MgO)
Was applied with a water slurry and then subjected to finish annealing.

A width of 50 μm and a depth of 15 μm were applied to these samples by a gear roll in a direction 10 ° from the direction perpendicular to the rolling direction.
After forming the groove, a coating liquid 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 performed at 00 ° C. for 4 hours. Table 5 shows the magnetic properties of the obtained products.

[0045]

[Table 5]

[0046]

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.

[Brief description of drawings]

FIG. 1 is a photomicrograph showing the state of magnetic domains in a conventional product (a) and a grain-oriented electrical steel sheet (b) produced by the method of the present invention.

FIG. 2 is a diagram showing domain wall moving speeds of a conventional product and a grain-oriented electrical steel sheet produced by the method of the present invention under an alternating magnetic field.

[Fig. 3] Product magnetic flux density (B ₈ value) and iron loss (W17 / 5)
Chart of relationship 0).

FIG. 4 is a chart of an iron loss deterioration margin due to wear of a gear roll.

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[Procedure amendment]

[Submission date] March 30, 1995

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

FIG.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yozo Suga 20-1 Shintomi, Futtsu City Shin-Nippon Steel Co., Ltd. Technical Development Division (72) Inventor Takashi Mogi 1-1 Hibatacho, Tobata-ku, Kitakyushu Inside the Yawata Works

Claims (3)

[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 silicon steel slab of 1100 ° C. or higher and 1280 ° C. or lower, it is hot-rolled, and is subjected to decarburization annealing / nitriding treatment to a final sheet 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. Mirror surface direction of low iron loss characterized by increasing the number of active magnetic domain walls by forming a tension film after forming a groove by mechanically applying a local stress to the steel plate surface of For manufacturing high-performance electrical steel sheet 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 is made by heating a silicon steel slab consisting essentially of Fe and unavoidable impurities to 1300 ° C. or higher, and then hot rolling it 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 made into a mirror surface state, and mechanical stress is applied to the steel sheet to form a groove after forming a groove, thereby increasing the number of active domain walls. Low iron loss characterized by increasing Method for producing a mirror-oriented electrical steel sheet. 3. A method of forming a groove by mechanically applying a local stress, wherein the groove formed on the steel sheet is at right angles to the rolling direction or within a range of 45 degrees from the right angle, and the interval is 1 to 20 mm in the rolling direction. The width is 10 to 300 μm, and the depth is 5 μm or more and 50 μm or less, the method for producing a mirror-oriented electrical steel sheet with low iron loss according to claim 1 or 2.