JPH09157748A - Low iron loss, high magnetic flux density unidirectional electrical steel sheet manufacturing method - Google Patents

Abstract

(57) An object of the present invention is to provide a method for producing a low iron loss, high magnetic flux density unidirectional electrical steel sheet by a magnetic domain control effect that does not disappear even if strain relief annealing is performed. In a known method for producing a unidirectional electrical steel sheet, a linear groove is formed on the surface of the steel sheet before annealing between hot rolling and final cold rolling, and an oxide is formed on the groove bottom portion by subsequent annealing,
This oxide is embedded in the steel sheet by subsequent cold rolling.
Then, this linear oxide is used as a final product in a rolling direction of 60 to 9
It is characterized in that the depth in the steel sheet is 3 μm or more and 30 μm or less, the width is 10 μm or more and 100 μm or less, and the interval in the rolling direction is 1 mm or more and 10 mm or less at an angle of 0 °. According to the present invention, a magnetic domain control effect that does not disappear even when strain relief annealing is performed makes it possible to relatively easily and inexpensively manufacture a grain-oriented electrical steel sheet having low iron loss and high magnetic flux density characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a low iron loss and a high magnetic flux density which has a magnetic domain control effect that does not disappear even if strain relief annealing is performed by linearly introducing an oxide near the surface of a steel sheet. The present invention relates to a method for manufacturing a grain-oriented electrical steel sheet.

[0002]

2. Description of the Related Art Unidirectional electrical steel sheets are used as iron core materials for electrical equipment such as transformers, and must have good magnetic excitation characteristics and iron loss characteristics. Moreover, in recent years, the market demand for low iron loss materials with particularly low energy loss has been increasing.

A steel sheet having a high magnetic flux density has a low iron loss and a small iron core, and is a very important development target.
This unidirectional electrical steel sheet having a high magnetic flux density has a {110} <001> orientation (goss orientation) by finish annealing a steel sheet that has been made a final sheet thickness from a hot rolled sheet by appropriate cold rolling and annealing. It is obtained by so-called secondary recrystallization in which secondary recrystallized grains are selectively grown.

In the secondary recrystallization, fine precipitates such as MnS, AlN, MnSe and Cu ₂ are contained in the steel sheet before the secondary recrystallization.
This is achieved by the presence of S, BN, (Al, Si) N, etc., or the presence of grain boundary segregation type elements such as Sn, Sb. These precipitates and grain boundary segregation type elements are described in J.
B. May and Turnbull (Trans. Met. Soc. AIME 212 (19
58) As described in P769 / 781), the growth of primary recrystallized grains other than the {110} <001> orientation is suppressed in the finish annealing step, and the {110} <001> oriented grains are selectively grown. With function.

Such a grain growth suppressing effect is generally called an inhibitor effect. Therefore, the priority issue of research and development in this field is to use any kind of precipitates or grain boundary segregation type to stabilize the secondary recrystallization, and increase the existence ratio of accurate {110} <001> oriented grains. In order to achieve their proper existence. Particularly, recently, in the method using one kind of precipitate, {11
Since there is a limit to the control of the altitude of the 0} <001> direction, by clarifying the advantages and disadvantages of each precipitate,
The development of a technique that can organically combine several precipitates to stably manufacture a product having a higher magnetic flux density and at a lower cost is underway.

At present, there are three kinds of typical industrially produced grain-oriented electrical steel sheets, each of which has advantages and disadvantages. The first technique is a two-time cold rolling process using MnS disclosed in Japanese Patent Publication No. 30-3651 by MF Littmann. The obtained secondary recrystallized grains are stably developed, but have a high magnetic flux density. I can't get it.

The second technique is Taguchi et al.
This is a process in which the final cold rolling using AlN + MnS disclosed in Japanese Patent No. 5644 is performed at a high pressure reduction rate of 80% or more, and a high magnetic flux density can be obtained, but strict control of manufacturing conditions is required in industrial production. . The third technique is the Mn disclosed in Japanese Patent Publication No. 51-13469.
This is a process of manufacturing silicon steel containing S (and / or MnSe) + Sb by two cold rolling steps, and a relatively high magnetic flux density is obtained, but harmful and expensive elements such as Sb and Se are used. In addition, since it is a double cold rolling method, the manufacturing cost is high.

Further, the above three kinds of techniques have the following problems in common. That is, in any of the above techniques, the slab heating temperature prior to hot rolling as a technique for controlling the precipitate finely and uniformly is shown in the first technique at 1260 ° C. or higher, and in the second technique as disclosed in JP-A-48-51852. Depending on the amount of Si as the material, 1350 ° C. in the case of 3% Si, 1230 ° C. or more in the third technique as shown in JP-A-51-20716, and 1320 ° C. in the embodiment in which a high magnetic flux density is obtained. By making the temperature extremely high, coarsely existing precipitates are once solid-dissolved, and then precipitated during hot rolling or heat treatment. Increasing the slab heating temperature lowers the production efficiency due to an increase in energy used during heating, a decrease in yield due to the generation of slag, and an increase in the frequency of repairs of the heating furnace.
As disclosed in Japanese Patent No. 41526, there is a problem that a continuous casting slab cannot be used because a linear secondary recrystallization defect occurs.

However, what is more important than the above cost problem is to take measures such as increasing the amount of Si and reducing the product thickness in order to improve iron loss. The number of occurrences of iron is increased, and it is difficult to hope for the improvement of iron loss in the future with the technology based on the high temperature slab heating method. On the other hand, in the technique disclosed in Japanese Examined Patent Publication No. 61-60896, by reducing S in the steel, secondary recrystallization is extremely stable, and a high Si thin product is made possible. However, this technique has a problem in the stability of the magnetic flux density in factory production on a mass production scale, and an improved technique disclosed in, for example, Japanese Patent Laid-Open No. 62-40315 has been proposed.
Until now, it has not been completely resolved.

As described above, the orientation of the secondary recrystallized grains is {11
0} <001> and further thinning of high Si
Although the iron loss has been improved, on the other hand, in order to further improve the iron loss, as disclosed in, for example, Japanese Patent Publication No. 57-2252, magnetic domain control is performed by introducing strain near the surface of the steel sheet by laser treatment or the like. Technology is being developed. Moreover, recently, improved magnetic domain control technology has begun to be developed, in which the effect does not disappear even if strain relief annealing is performed. As this method, for example, as disclosed in JP-A-4-88121, a method of introducing a groove space near the surface of a steel sheet,
For example, as disclosed in Japanese Patent Application Laid-Open No. 60-103124, a method has been devised in which a foreign material such as an oxide having a composition different from that of the steel sheet is introduced near the surface of the steel sheet. However, these methods still have problems such as too high cost and difficulty in accurately introducing foreign matter into the steel sheet.

[0011]

DISCLOSURE OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION As described above, there is provided a manufacturing method for imparting excellent magnetic properties inexpensively and stably to a grain-oriented electrical steel sheet which has been conventionally costly or difficult to manufacture. It is an object of the present invention.

[0012]

As a result of repeated studies to solve the above problems, the inventors of the present invention have formed linear grooves on the surface of a steel sheet before final cold rolling, and then oxidize the sheet surface by annealing. By further cold rolling and introducing an oxide near the plate surface, it has a magnetic domain control effect that does not disappear even if strain relief annealing is performed,
We have found a method for manufacturing an inexpensive, low iron loss, high magnetic flux density grain-oriented electrical steel sheet.

That is, the gist of the present invention is C by weight.
: 0.03 to 0.10%, Si: 2.5 to
4.5%, Mn: 0.02-0.15%, S
: 0.01-0.05%, acid-soluble Al: 0.01-
0.04%, N: 0.003 to 0.015%, and optionally Sb: 0.01 to 0.15% and Se:
0.01 to 0.15% of one or two kinds, and the balance F
Using a slab consisting of e and unavoidable impurities as a raw material, after hot rolling and precipitation annealing, one cold rolling at a final cold rolling reduction of 50% or more or two or more cold rolling including intermediate annealing is performed, and further decarburization annealing is performed. In the method for producing a unidirectional electrical steel sheet for finish annealing, a linear groove is formed on the surface of the steel sheet under the condition of the following formula (1) before annealing between hot rolling and final cold rolling, and an oxide is formed by subsequent annealing. Formed at the bottom of the groove, the final product has a linear oxide with a depth of 3 μm or more and 30 μm or less and a width of 10 μm.
It is a method for manufacturing a low iron loss, high magnetic flux density unidirectional electrical steel sheet, characterized in that the distance in the rolling direction is 1 mm or more and 10 mm or less. tan α = (t ₁ / t ₀ ) × tan β (1) where α is the angle between the linear groove and the direction perpendicular to the cold rolling direction immediately after the groove is formed β: After the final cold rolling , Angle formed by the direction perpendicular to the cold rolling direction and the linear groove 0 ° ≦ β ≦ 30 ° t ₀ : plate thickness immediately after groove formation t ₁ : plate thickness after final cold rolling

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
As described above, as one method of magnetic domain control technology in which the effect does not disappear even if strain relief annealing is performed, for example, Japanese Patent Laid-Open No. 60-10
As disclosed in Japanese Patent No. 3124, there has been devised a method of introducing a foreign substance such as an oxide having a composition different from that of the steel sheet to the vicinity of the surface of the steel sheet. However, these methods
For example, in order to apply foreign substances such as oxides on the surface of the steel sheet in a linear shape with a width of 1 mm and a repeat interval of 2 mm, or to bury it in the steel sheet with precision by cold rolling, high productivity and low cost are assumed. There are considerable problems in industrialization.

On the other hand, in the case of the present invention, the introduction of linear grooves is not so difficult as mechanical or etching techniques, and has already been industrialized since the final cold rolling. Further, the introduction of the oxide into the groove is based on the oxidation inside the groove by annealing and the burying effect of the oxide by the subsequent cold rolling, which can be easily performed industrially. The effect of embedding by the cold rolling further promotes the magnetic domain control effect. Moreover, since an oxide consisting of the same element as that formed during decarburization annealing is formed inside the groove by annealing after the introduction of the linear groove, the product plate becomes a part of the glass coating on the surface of the base metal, so the steel plate surface Not only the magnetic domain subdivision effect due to the formation of the groove space in the groove, but also the effect of improving the film adhesion is provided.

The present inventors examined the appropriate conditions for introducing an oxide near the surface of the steel sheet and obtained the following results. Before annealing between hot rolling and final cold rolling, a linear groove is formed on the steel sheet surface under the following conditions, then an oxide is formed at the groove bottom by annealing, and this oxide is embedded in the steel sheet by subsequent cold rolling. . At this time, the direction of the linear groove introduced on the surface of the steel sheet is the final product, that is, the angle (β) formed by the linear groove and the direction perpendicular to the cold rolling direction after the final cold rolling is 0 ° to 30 °. The magnetic properties were good under the conditions. Therefore, the angle α required for forming the groove is set within the range of the following formula (1) in consideration of plastic deformation due to cold rolling. tan α = (t ₁ / t ₀ ) × tan β (1) where α is the angle between the linear groove and the direction perpendicular to the cold rolling direction immediately after the groove is formed β: After the final cold rolling , Angle formed by the direction perpendicular to the cold rolling direction and the linear groove 0 ° ≦ β ≦ 30 ° t ₀ : plate thickness immediately after groove formation t ₁ : plate thickness after final cold rolling

Further, the depth of the linear oxide in the embedded final product in the steel is 3 μm or more and 30 μm or less, and the width is 10 μm.
The magnetic properties were good when m or more and 100 μm or less and the distance in the rolling direction was 1 mm or more and 10 mm or less. Further, the reason that the width of the oxide in the final product is limited to 10 μm or more is that the width of the groove formation, which is relatively easy industrially, is the lower limit. The method of forming such an oxide is not particularly limited, but a method of adjusting the annealing time before cold rolling and the degree of oxidation of the atmosphere is industrially advantageous. In this case, the linear oxide does not necessarily have to be continuous, and similar effects can be obtained even if the interval is 2 mm or less narrower than the magnetic domain width.

Next, the reason why the steel composition and manufacturing conditions are limited as described above in the present invention will be described in detail. C is γ
The lower limit is set to 0.03% so that the phases are appropriately generated and the fine dispersion of the precipitate is good, and the upper limit is set to 0.10% unless the decarburization becomes difficult. Si has a lower limit of 2.5% in order to improve iron loss, but if it is too much, it easily cracks during cold rolling and becomes difficult to work, so the upper limit is made 4.5%.

Further, the following components are impurities used as a precipitation dispersed phase for secondary recrystallization, and must be contained in appropriate amounts for effective action. That is, Mn:
0.02-0.15%, S: 0.01-0.05%, acid-soluble Al: 0.01-0.04%, N: 0.003-
0.015%, Sb: 0.01 to 0.15%, Se:
By appropriately combining two or more kinds of 0.01 to 0.15%, it is possible to obtain secondary recrystallization having a high degree of Goss orientation grain integration. In addition, at least one of Cu and Sn may be added so as to be 1.0% or less for the purpose of strengthening the inhibitor.

The cast slab is then hot rolled and then 950
After annealing at ˜1200 ° C. for 30 seconds to 30 minutes, a final cold rolling reduction of 80% or more is performed once or two or more times of cold rolling including intermediate annealing is performed, and a final plate having a thickness of 200 μm or less is obtained. Be thick. After that, decarburization annealing is performed in a wet hydrogen atmosphere, and if necessary, nitriding treatment is performed. Further, an annealing separator such as MgO is applied, and 1100 is used for secondary recrystallization and purification.
A thin unidirectional electrical steel sheet having a high magnetic flux density is manufactured by performing finish annealing at ℃ or higher.

[0021]

Next, an embodiment of the present invention will be described. [Example 1] Molten steel containing the composition of the steel material A shown in Table 1 was cast. Next, this steel ingot was heated at 1350 ° C. for 1 hour and then hot rolled to obtain a hot rolled sheet having a thickness of 2.1 mm. Mechanically linear grooves were formed on the surface of this hot rolled plate at the angles shown in Table 2. Then, this hot-rolled sheet was annealed at 1100 ° C. for 5 minutes in an atmosphere containing 5% of O _{2 in} N ₂ to form an oxide at the bottom of the groove, and subsequently cold-rolled to a thickness of 0.23 mm,
During this time, the oxide was embedded in the steel sheet. Next, this cold rolled sheet was annealed at 830 ° C. for 2 minutes in an atmosphere of wet hydrogen and nitrogen for decarburization, further coated with MgO powder, and then 1200 ° C. ×
High temperature annealing was performed in a hydrogen gas atmosphere for 20 hours.

As a result, the depth of the linear oxide in the final product embedded near the surface of the steel sheet was 12 μm, and the width was 60 μm.
m, the distance in the rolling direction was 4 mm. As shown in Table 2, in the case of the conditions of the present invention, the results of magnetic measurement of this product plate showed that the iron loss characteristics superior to those of the comparative material were obtained. Further, FIG. 1 shows the relationship between the angle β formed by the linear grooves (the angle formed by the linear groove and the direction perpendicular to the rolling direction) and the iron loss. As is clear from the figure, it is found that the angle β formed by the linear groove is preferably 30 ° or less.

[0023]

[Table 1]

[0024]

[Table 2]

Example 2 Molten steel containing the composition of the steel material B shown in Table 1 was cast. Next, this steel ingot was heated at 1150 ° C. for 1 hour and then hot rolled to obtain a hot rolled sheet having a thickness of 2.1 mm. A laser was applied to the surface of this hot-rolled sheet at a right angle to the rolling direction to form linear grooves. Then, this hot-rolled sheet was annealed at 1100 ° C. for 5 minutes in an atmosphere containing O _{2 in} N ₂ at 0 to 10% to form an oxide at the bottom of the groove, and subsequently cold-rolled to a thickness of 0.23 mm, during which The oxide was embedded in the steel plate. Next, this cold-rolled sheet was decarburized and annealed at 830 ° C. for 2 minutes in an atmosphere of wet hydrogen and nitrogen, and then 1% of ammonia was added.
Nitrogen treatment was performed at 750 ° C. for 30 seconds in an atmosphere containing hydrogen and nitrogen to adjust the amount of nitrogen in the steel sheet to 200 ppm. And M
After applying the gO powder, high temperature annealing was performed in a hydrogen gas atmosphere at 1200 ° C. for 20 hours.

As a result, the depth of the linear oxide in the final product embedded near the surface of the steel sheet was as shown in Table 3. The width was 80 μm, and the interval in the rolling direction was 5 mm. As shown in Table 3, in the case of the conditions of the present invention, the result of magnetic measurement of this product plate showed that the iron loss characteristics superior to those of the comparative material were obtained.

[0027]

[Table 3]

Example 3 Molten steel containing the composition of the steel material C shown in Table 1 was cast. Next, this steel ingot was heated at 1350 ° C. for 1 hour and then hot rolled to obtain a hot rolled sheet having a thickness of 2.1 mm. The surface of the hot-rolled sheet after pickling is applied by printing with a resist having a linear non-application area at right angles to the rolling direction,
After drying and forming a linear groove by etching, the resist was removed. Then, this hot-rolled sheet was annealed at 1100 ° C. and 1050 ° C. for 5 minutes in an atmosphere containing 2% of O _{2 in} N ₂ to form an oxide at the bottom of the groove, and subsequently cold-rolled to a thickness of 0.23 mm, During this time, the oxide was embedded in the steel sheet. Next, this cold rolled sheet was decarburized and annealed at 830 ° C. for 2 minutes in a wet hydrogen and nitrogen atmosphere, further coated with MgO powder, and then annealed at 1200 ° C. for 20 hours at a high temperature in a hydrogen gas atmosphere.

As a result, the spacing in the rolling direction of the linear oxide in the final product embedded near the surface of the steel sheet was as shown in Table 4. The depth was 7 μm and the width was 90 μm. As shown in Table 4, in the case of the conditions of the present invention, the results of magnetic measurement of this product plate showed that the iron loss characteristics superior to those of the comparative material were obtained.

[0030]

[Table 4]

[0031]

According to the present invention, in the method for producing a grain-oriented electrical steel sheet containing a known inhibitor element in a slab, after linear groove formation on the surface of the steel sheet before final cold rolling, the sheet surface is annealed. By oxidizing and further cold rolling to introduce an oxide near the plate surface, it has a magnetic domain control effect that does not disappear even if strain relief annealing is performed, and it is possible to obtain low iron loss and high magnetic flux density characteristics at low cost. it can.

[Brief description of the drawings]

FIG. 1 shows the relationship between the magnetic properties and the angle of the linear oxide near the plate surface in the cold rolling direction in the vicinity of the plate surface in a thin material having a plate thickness of 0.23 mm.

Claims (3)

[Claims] 1. By weight, C: 0.03 to 0.10%, Si: 2.5 to 4.5%, Mn: 0.02 to 0.15%, S: 0.01 to 0.05. %, Acid-soluble Al: 0.01 to 0.04%, N: 0.003 to 0.015%, and a slab containing the balance Fe and unavoidable impurities as a raw material. After hot rolling and precipitation annealing, final cooling is performed. In a method for producing a unidirectional electrical steel sheet, wherein cold rolling is performed once or twice or more including intermediate annealing with a rolling reduction of 50% or more, and further decarburization annealing and finish annealing are performed. Before the annealing of, the linear groove is formed on the surface of the steel sheet under the condition of the following formula (1), and the oxide is formed at the groove bottom portion by the subsequent annealing, and the depth of this linear oxide in the steel sheet in the final product is Is 3 μm or more and 30 μm or less, the width is 10 μm or more and 100 μm or less, and the interval in the rolling direction is 1 mm or more,
A method for manufacturing a low iron loss, high magnetic flux density unidirectional electrical steel sheet, which is characterized by having a thickness of 10 mm or less. tan α = (t ₁ / t ₀ ) × tan β (1) where α is the angle between the linear groove and the direction perpendicular to the cold rolling direction immediately after the groove is formed β: After the final cold rolling , Angle formed by the direction perpendicular to the cold rolling direction and the linear groove 0 ° ≦ β ≦ 30 ° t ₀ : plate thickness immediately after groove formation t ₁ : plate thickness after final cold rolling 2. The method for producing a low iron loss, high magnetic flux density unidirectional electrical steel sheet according to claim 1, wherein the final cold rolling reduction of the material is 80% or more. 3. A molten steel component, by weight, C: 0.03 to 0.10%, Si: 2.5 to 4.5%, Mn: 0.02 to 0.15%, acid-soluble Al: 0. 0.01 to 0.04%, N: 0.003 to 0.015%, and Sb: 0.
01-0.15% and S, Se: 0.01-0.05
% Is contained at least 1 type, Claim 1 characterized by the above-mentioned.
A method for producing the described low iron loss, high magnetic flux density unidirectional electrical steel sheet.