JP2000104144A - Silicon steel sheet excellent in magnetic property in l orientation and c orientation and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon steel sheet excellent in magnetic properties in the L orientation and in the C orientation by optimizing the steel compsn. and the texture thereof and to provide a method for industrially and inexpensively producing it. SOLUTION: The silicon steel sheet has a texture in which the integrated intensity in the 100}<001> orientation and in the (011)[100] orientation respectively lie in the range of >=2.0 times and in the range of 2.0 to 10.0 times that of the random structure. Moreover, as for the method for producing this steel sheet, a steel slab is subjected to hot rough rolling to form a desired steel structure, immediately after that, it is subjected to hot finish rolling under prescribed conditions, then, as it is, or after its structure is formed into the recrystallized one by hot rolled sheet annealing as necessary, the steel sheet is pickled and is subsequently subjected to cold rolling and annealing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for an AC magnetic core and has two directions of a rolling direction (hereinafter, referred to as "L direction") and a direction perpendicular thereto (hereinafter, referred to as "C direction"). The present invention relates to an electromagnetic steel sheet having excellent magnetic properties and a method for manufacturing the same.

[0002]

2. Description of the Related Art Iron core materials for transformers and motors are required to have high magnetic flux density and low iron loss in order to increase the efficiency and miniaturization of these devices. As a magnetic alloy to be provided for this type of iron core material, an Fe-Si alloy is known, and is widely used as a non-oriented electrical steel sheet.In order to improve the magnetic properties of this steel sheet, the texture is improved. Various attempts have been made.

Among them, the (011) [100] direction,
That is, by enriching crystal grains in the Goss orientation, iron loss is reduced, and in particular, magnetic flux density is increased.
No. 54-110121. Usually, the Goss orientation improves the magnetic properties in the L direction, and consequently the average magnetic properties including the C direction.

[0004] However, since the magnetic properties in the C direction are only improved to some extent, there is naturally a limit in improving the average magnetic properties.

[0005] On the other hand, it is known that the {100} <001> orientation, that is, the cubic orientation on the plane, improves the magnetic properties in two directions, L direction and C direction, simultaneously.

However, in order to obtain a structure which is accumulated only in the cubic orientation on the surface, a high-temperature intermediate annealing method described in JP-B-46-23814 and a method described in JP-A-5-271883 are disclosed. Direction rolling method, quenching ribbon method described in JP-A-5-306438, γ → α transformation method associated with decarburization described in JP-A-1-108345, etc. In addition, it is presumed that a long process is required and the cost is high, so that industrial utility cannot be established.

Further, as means for improving the magnetic characteristics, a crystal grain having an orientation for improving the magnetic characteristics is promoted,
In addition, it is useful to suppress crystal grains in an orientation that degrades magnetic properties. As crystal grains having an orientation that deteriorates magnetic properties, there are crystal grains having a <111> // ND (direction perpendicular to the steel sheet surface) orientation, and it is desirable to suppress the generation of crystal grains having such an orientation. Except for the case where special and expensive means are used, it has been difficult to reduce the crystal grains in the <111> // ND orientation in the conventional methods for producing non-oriented electrical steel sheets.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electromagnetic steel sheet having excellent magnetic properties in the L and C directions by optimizing the steel composition and texture, and to use the steel sheet industrially. Another object of the present invention is to provide a manufacturing method for manufacturing at low cost.

[0009]

The present inventors have conducted extensive research on means for practically improving the magnetic properties of non-oriented electrical steel sheets, and as a result, have found that the rolling reduction in one pass in hot rolling can be sufficiently reduced. It has been found that when set to a large value, the degree of integration in the cubic orientation on the surface increases, and this was proposed in Japanese Patent Application No. 9-244216.

The research was further advanced to select a practical texture and to carefully study a manufacturing method that can apply the current manufacturing process of the magnetic steel sheet. By increasing the degree of integration, and more preferably, simultaneously suppressing the degree of integration in the <111> // ND orientation, a practical electrical steel sheet having extremely excellent average magnetic properties in the L and C directions is obtained. Was found to be.

[0011] In order to form such a texture, a manufacturing method to which the current manufacturing process of magnetic steel sheets can be applied has been established.

The above-mentioned electrical steel sheet and its manufacturing method were obtained based on the following findings by examining in detail the relationship between the finish hot rolling conditions and the microstructure and texture.

That is, it has been known that when rolling coarse grains, non-uniform deformation zones within grains are likely to be formed, and recrystallization within grains is promoted in the subsequent recrystallization process. ,
The present inventors have found that if the relationship between the strain rate and the rolling reduction and the amount of Si satisfies a certain relationship, non-uniform deformation structures such as intragranular shear bands are reduced, and in the subsequent recrystallization process, It has been found that recrystallization is suppressed and recrystallization from grain boundaries is promoted.

Further, the recrystallized grains on the grain boundaries of the steel sheet rolled under such conditions have a high frequency of (015) [100] oriented grains. It was also found that (001) [100] increases later, and that the <111> // ND orientation tends to decrease, and (015) for exhibiting excellent magnetic properties.
The present invention has been realized by clarifying the required amount of the [100] direction.

The (015) [100] oriented grains undergo {001} <10 through cold rolling and recrystallization annealing.
0> has already been disclosed in known literature (Taoka et al .: Iron and Steel, 54 (1968) 162.).

However, industrially (015) [10
0] were completely unknown about the composition, production method, and the effect of (015) [100] grains on the final magnetic properties and texture. For this reason, the present inventors have found a new technique for expressing and controlling (015) [100] grains.

Incidentally, in the case of a component steel having a high alloying element content and difficult to recrystallize, recrystallization does not sufficiently proceed by ordinary hot rough rolling, and unrecrystallized grains tend to increase. Although such advanced grains are coarse grains, due to hot rolling at high temperature, the vicinity of grain boundaries is locally recrystallized. , (015)
It was also newly found that the development of the [100] orientation grains was not promoted.

By the way, {100} <001> is the most convenient orientation for improving the magnetic properties in the L and C directions, and (011) [100] is the most convenient orientation for improving the magnetic properties in the L direction.
The 11 >> // ND orientation is the orientation that minimizes the in-plane magnetic properties.

In the prior art, both {100} <001> -oriented grains and (011) [100] -oriented grains could not be obtained with a high degree of integration.

Based on the above findings, the present inventors made various trials of steel sheets integrated in these two orientations and evaluated the performance. As a result, by controlling the accumulation strength of the crystal grains in these two orientations, the L direction was increased. And found that the magnetic characteristics in the C direction can be dramatically improved, thereby completing the present invention.

Further, they have found that it is possible to manufacture a steel sheet in which the accumulation strength of these two orientations is maintained and the accumulation strength of the <111> // ND orientation grains is suppressed at the same time. By controlling these three orientations, it is possible to produce a steel sheet. It has also been found that the magnetic properties in the C direction can be further improved.

That is, the gist of the present invention is as follows.
The first invention provides a {100} <001> direction and (011)
An electromagnetic steel sheet having a texture whose accumulated strength in the [100] orientation is 2.0 times or more and 2.0 to 10.0 times that of a random structure, respectively.

The magnetic steel sheet further comprises <111> ///
The average accumulation intensity in the ND direction is 2.0
It is preferable to have a texture that is in the range of not more than twice.

The magnetic steel sheet preferably contains Si: 4.0 wt% or less. In order to further improve iron loss by increasing the electric resistance of the steel, P: 0.30 wt% is further required.
Below, Al: 2.0 wt% or less, Mn: 2.0 wt% or less, Cr: 10.0
wt% or less, Mo: 2.0 wt% or less, W: 2.0 wt% or less, Cu:
2.0 wt% or less, Ni: 2.0 wt% or less, Co: 1.0 wt% or less, preferably contains at least one kind. Further, when it is necessary to further suppress the generation of fine particles, Ti: 0.20 wt% or less, V: 0.20 wt% or less, Nb: 0.20 wt
%, Zr: 0.20 wt% or less, Ta: 0.50 wt% or less, As: 0.
20 wt% or less, Sb: 0.20 wt% or less, Sn: 0.20 wt% or less,
C: 0.050 wt% or less, S: 0.050 wt% or less, B: 0.010
It is more preferable to contain at least one of wt% or less, N: 0.010 wt% or less, and O: 0.010 wt% or less.

In addition, the magnetic steel sheet has a Si content of 1.0
wt% to 4.0 wt% or less, and / or
It is preferable to have a component composition that satisfies the following formula (1) and does not generate an austenite phase.

Note 1 f = (1.5 [S i] +2 [P] +2.5 [Al] + [Cr] + [Mo] + [W]) − (30 [C] +30 [N] +0 .5 [Mn] +0.5 [Cu] + [N i]) ≧ 2.5-(a) where f is a non-transformation index, and [] means wt%.

[0027] The second invention is the method for manufacturing an electromagnetic steel sheet, wherein the steel slab is hot rough-rolled, and the following 2 (1):
Immediately after performing the hot finish rolling under the conditions described in the following 2 (2) and (3), the steel structure was changed to the steel structure shown in (2), and then pickled after the recrystallized structure was obtained as it was or as needed by hot rolled sheet annealing. Thereafter, cold rolling and annealing are performed, and this is a method for producing an electrical steel sheet having excellent magnetic properties in the L and C directions.

Note 2 (1) The volume fraction of equiaxed ferrite grains is 80% or more, and the average grain size of equiaxed ferrite grains is 300 μm or more and the grain size is
The volume fraction of equiaxed ferrite grains of 100 μm or less is 20% or less. (2) The steel sheet temperature at the time of entering the finish rolling mill is set to a temperature range of not more than Ar ₁ transformation point and not more than 900 ° C and not less than 500 ° C for a steel having a component composition which generates an austenite phase, and a component composition which does not generate an austenite phase. 900 for steel having
Temperature range below 500 ° C. (3) Assuming that the rolling reduction in each rolling stand of the finishing mill is R (%) and the thickness reduction strain rate is Z (s ⁻¹ ), the ratio of the reduction thickness rate (Z) to the reduction rate (R) ( Z /
R) satisfies the following inequality relationship of (b) in 3 according to the Si content (wt%).

Note 3 Z / R ≧ 0.51−0.04 [S i] (b) where Z = ln (t ₀ / t) / [｛(d / 2) × cos ⁻¹ ((dt ₀ + t) / d)｝ /
{V × 1000/60}], R = (1-t / t ₀ ) × 100, [Si] means wt% of Si element, t ₀ and t are the entrance side of each rolling stand and The thickness of the sheet at the exit side (mm), d is the outer diameter of the work roll at each stand (mm), and V is the speed at which the steel sheet is transported at the exit side of each stand (m /
Minutes).

Preferably, the steel slab contains Si: 4.0 wt% or less. The term "equiaxed ferrite grains" as used herein means ferrite grains whose ratio of the major axis to the minor axis is 2 or less.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the reasons for limiting the texture of the present invention will be described. In order to simultaneously improve the magnetic properties in the L direction and the C direction, the integrated intensity in the {100} <001> direction and (011) [100] direction should be 2.0 times or more and 2.0 times or more that of the random structure, respectively.
The present inventor has found that it is necessary to set the average integrated intensity in the range of 10.0 times or less, and more preferably, the average integrated intensity in the <111> // ND direction to 2.0 times or less of that of the random structure. Found them.

The experimental results will be described. In a small vacuum melting furnace, a 50 kg ingot having a composition containing 2.1 wt% of Si was melted and hot-rolled to a thickness of 3.5 mm. After heating this steel sheet at 1150 ° C for 30 minutes, the rolling reduction was 35
% Hot pass rolling was performed in two passes, followed by air cooling to produce a hot rolled sheet having a thickness of 1.5 mm. At this time, steel sheets having different textures after finish annealing were manufactured by changing the hot rolling temperature and the rolling speed in various ways. In each of the steel sheets, 100% of the ferrite grains before hot finish rolling were equiaxed grains, the average fephite grain size was 1000 µm, and the volume fraction of grains having a size of 100 µm or less was 1% or less. Thereafter, the hot-rolled sheet was annealed at 1000 ° C. for 1 minute, cold-rolled after pickling to a final sheet thickness of 0.5 mm, and then subjected to finish annealing at 900 ° C. for 30 seconds. Table 1 shows the results of evaluating the texture and magnetic properties of the steel sheet manufactured in this manner.

[0033]

[Table 1]

From the results in Table 1, it can be seen that the integrated strengths of the {100} <001> orientation and the (011) [100] orientation are 2.0 times or more and 2.0 times or more that of the random structure, respectively.
The steels G to J and L to Q of the present invention, which are not more than 10.0 times, have a lower L strength than the comparative steels A to F in which the integrated strength in at least one of these directions is smaller than the proper range of the present invention.
It can be seen that the magnetic properties in the directions C and C, that is, the average magnetic properties in the LC direction are excellent.

Further, the comparative steel K having the (011) [100] orientation in which the integrated strength is larger than the proper range of the present invention has excellent properties in the L direction, but has poor magnetic properties in the C direction. It can be seen that the LC average characteristics have not been improved.

Further, if the integrated strength in the <111> // ND orientation is set to 2.0 times or less that of the random structure, the LC average characteristics can be further improved. It is clear from the comparison of the magnetic properties with G.

Next, the reasons for limiting the steel composition components of the present invention will be described. Si: 4.0 wt% or less Si has the effect of increasing the specific resistance and reducing the eddy current loss, and is an effective additive element in the present invention. However, when the Si content exceeds 4.0%, the decrease in magnetic east density increases and the workability decreases. Therefore, the Si content is 4.0wt
% Is preferable. Further, when it is necessary to further increase the specific resistance and the texture, it is more preferable to set the Si content to be more than 1.0 wt%.

The Si content in the steel is further limited by the relationship between the rolling reduction during finishing hot rolling and the strain rate in order to obtain a favorable texture for the magnetic properties in relation to the manufacturing conditions of the electrical steel sheet. However, this point will be described later.

In the present invention, the component compositions in the steel sheet and the steel slab are not particularly limited in both the electrical steel sheet (the first invention) and the method for producing the same (the second invention). Within the range, further, as other components, P: 0.30 wt% or less, Al: 2.0 wt% or less, Mn: 2.0 wt% or less, Cr: 10.0 wt% or less, Mo: 2.0 wt% or less.
%, W: 2.0 wt% or less, Cu: 2.0 wt% or less, Ni: 2.
One or more selected from 0 wt% or less and Co: 1.0 wt% or less can be contained.

P: 0.30 wt% or less P has the effect of increasing the specific resistance and reducing the eddy current loss. However, if the P content exceeds 0.30% by weight, the processability decreases. Therefore, the P content is preferably in the range of 0.30% by weight or less.

Al: 2.0 wt% or less, Mn: 2.0 wt% or less Both Al and Mn are effective as deoxidizing agents for steel and have the effect of increasing the specific resistance and reducing the eddy current loss. But Al and Mn
If the content of each exceeds 2.0 wt%, the magnetic flux density and workability are greatly reduced. Therefore, the content of Al and Mn is preferably in the range of 2.0 wt% or less.

Cr: 10.0 wt% or less Cr has the effect of increasing the specific resistance and reducing the eddy current loss. However, if the Cr content exceeds 10.0 wt%, the magnetic flux density and workability are greatly reduced. Therefore, the Cr content is 1
The range of 0.0 wt% or less is preferable.

Mo: 2.0 wt% or less, W: 2.0 wt% or less, C
u: 2.0 wt% or less Mo, W and Cu all have the effect of increasing the specific resistance and reducing the eddy current loss. However, each of these contents is 2.0
If the content exceeds wt%, the magnetic flux density and workability are greatly reduced. Therefore, the contents of Mo, W and Cu are preferably in the range of 2.0 wt% or less.

Ni: 2.0 wt% or less Ni has the effect of increasing the specific resistance and reducing the eddy current loss. However, when the Ni content exceeds 2.0 wt%, the magnetic flux density is greatly reduced. Therefore, the Ni content is preferably in the range of 2.0 wt% or less.

Co: 1.0 wt% or less Co has the effect of increasing the specific resistance and reducing the eddy current loss. However, when the Co content exceeds 1.0 wt%, the magnetic flux density decreases and the cost increases remarkably. Therefore, the Co content is 1.0
The range of wt% or less is preferable.

When it is necessary to further suppress the generation of fine grains, the content of Ti is set to 0.20 wt% or less, and the content of V is set to 0.
20 wt% or less, Nb: 0.20 wt% or less, Zr: 0.20 wt% or less, T
a: 0.50 wt% or less, As: 0.20 wt% or less, Sb: 0.20 wt% or less, Sn: 0.20 wt% or less, C: 0.050 wt% or less, S: 0.05
More preferably, it contains at least one selected from 0 wt% or less, B: 0.010 wt% or less, N: 0.010 wt% or less, and O: 0.010 wt% or less.

Ti: 0.20 wt% or less, V: 0.20 wt% or less, N
b: 0.20 wt% or less, Zr: 0.20 wt% or less, Ta: 0.50 wt% or less Ti, V, Nb, Zr, and Ta are all combined with C and N to form a fine M (C, N) (however, M Means Ti, V, Nb, Zr or Ta). Such precipitates suppress recrystallization between passes of the finish rolling mill, and effectively act on maintenance of coarse grains before hot finish rolling, which is one of the essential features of the invention in the production method of the present invention. . However, T
If the contents of i, V, Nb, and Zr exceed 0.20 wt%, or the Ta content exceeds 0.50 wt%, the magnetic properties tend to deteriorate due to the domain wall movement suppressing action in the final product, the magnetic steel sheet. Therefore, it is more preferable that the upper limit of each content of Ti, V, Nb, and Zr be 0.20 wt%, and the upper limit of the Ta content be 0.50 wt%.

As: 0.20 wt% or less, Sb: 0.20 wt% or less, S
n: 0.20 wt% or less As, Sb, and Sn all segregate at the grain boundaries to suppress recrystallization between passes of the finishing mill, and heat, which is one of the essential features of the invention in the manufacturing method of the present invention, is specified. Effectively works to maintain coarse grains before finish rolling. However, A
If the content of each of s, Sb and Sn exceeds 0.20 wt%, the magnetic properties tend to be degraded due to the action of suppressing magnetic domain wall movement in the final product of the magnetic steel sheet. Therefore, the upper limit of each of these contents is 0.20 wt%. Is more preferable.

C: 0.050 wt% or less C segregates at crystal grain boundaries or forms carbides, suppresses recrystallization between passes of a finish rolling mill, and is an essential feature of the invention in the production method of the present invention. One of them is effective in maintaining coarse grains before hot finish rolling. However, if the C content exceeds 0.050 wt%, the magnetic properties of the magnetic steel sheet, which is the final product, tend to be degraded due to the action of suppressing magnetic domain wall movement. Therefore, the upper limit of the C content is more preferably 0.050 wt%. .

S: 0.050 wt% or less S forms MnS and suppresses recrystallization between passes of a finish rolling mill. Before hot finish rolling, which is one of the essential features of the invention in the manufacturing method of the present invention, Effectively acts to maintain coarse grains. However, if the S content exceeds 0.050 wt%, the magnetic properties of the magnetic steel sheet as the final product tend to deteriorate due to the action of suppressing magnetic domain wall movement. Therefore, the upper limit of the S content is more preferably 0.050 wt%. It is.

B: not more than 0.010 wt% B segregates at the crystal grain boundary or forms nitride, suppresses recrystallization between passes of the finish rolling mill, and is essential for the manufacturing method of the present invention. Effectively acts to maintain coarse grains before hot finish rolling. However, if the B content exceeds 0.010 wt%, the magnetic properties of the magnetic steel sheet as the final product tend to deteriorate due to the action of suppressing magnetic domain wall movement. Therefore, the upper limit of the B content is more preferably set to 0.010 wt%. It is.

N: not more than 0.010 wt% N forms nitrides, suppresses recrystallization between passes of a finish rolling mill, and performs hot finish rolling which is one of the essential features of the invention in the production method of the present invention. Effectively maintains the previous coarse grains. However, the N content is 0.010 wt%
Is exceeded, the magnetic properties of the magnetic steel sheet as the final product tend to deteriorate due to the domain wall movement suppressing action.
More preferably, the upper limit of the content is 0.010 wt%.

O: 0.010 wt% or less O forms an oxide, suppresses recrystallization between passes of a finish rolling mill, and performs hot finish rolling which is one of the essential features of the invention in the production method of the present invention. Effectively maintains the previous coarse grains. However, the O content is 0.010 wt%
Is exceeded, the magnetic properties of the magnetic steel sheet, which is the final product, tend to deteriorate due to the domain wall movement suppressing action.
More preferably, the upper limit of the content is 0.010 wt%.

Further, the magnetic steel sheet of the present invention is preferably made of a steel having a single phase of ferrite even in a heating region before hot rolling, that is, a steel having a component composition that does not cause phase transformation.
That is, when the content of the ferrite forming element is small,
Austenite phase is formed at high temperature, ferrite transformation occurs before hot finish rolling, and crystal grains are easily refined,
Accordingly, it is difficult to reduce the average ferrite grain size before hot finish rolling to coarse grains of 200 μm or more, and there is a possibility that the effect of improving magnetic properties may not be sufficiently obtained.

Incidentally, as the composition conditions for obtaining the non-transformed steel, it is necessary to satisfy the following equation (1).

Note 1 f = (1.5 [S i] +2 [P] +2.5 [Al] + [Cr] + [Mo] + [W]) − (30 [C] +30 [N] +0 .5 [Mn] +0.5 [Cu] + [N i]) ≧ 2.5-(a) where f is a non-transformation index, and [] means wt%.

Next, the manufacturing conditions of the present invention will be described. (I) Before hot finish rolling In the production method of the present invention, before hot finish rolling,
The volume fraction of equiaxed ferrite grains is 80% or more, and the average grain size of equiaxed ferrite grains is 300 μm or more and the grain size is 100 μm.
It is essential that the volume fraction of equiaxed ferrite grains of m or less be 20% or less.

That is, the grain boundaries of unrecrystallized grains have undergone local recrystallization after hot rough rolling, and the formation of (015) [100] oriented grains from the grain boundaries after hot finish rolling. Does not contribute to Therefore, it is necessary that the volume fraction of equiaxed ferrite grains recrystallized after hot rough rolling is 80% or more. Further, the larger the equiaxed ferrite average grain size before hot finish rolling, the larger the (015) [10] after hot rolling or annealing.
0] Orientation grains increase, and accompanying this, an increase in (011) [100] orientation grains after cold rolling and finish annealing, and furthermore,
This is because it leads to the suppression of <111> // ND orientation, and as a result, the texture after finish annealing is improved and the magnetic properties are improved. Therefore, it is necessary that the average particle diameter of the ferrite be 300 μm or more.

Further, the average particle diameter of the ferrite is 300 μm.
Even with the above, when fine grains are mixed, (0)
15) The suppression of the growth of [100] -oriented grains deteriorates the magnetic properties. Therefore, it is important to suppress the volume fraction of fine grains at the same time. For that purpose, it is necessary to limit the volume fraction of recrystallized ferrite grains of 100 μm or less to 20% or less.

The above effect becomes more remarkable as the ferrite grain size increases, and the production of <111> // ND orientation grains from grain boundaries decreases during the recrystallization process after hot finish rolling. The texture and magnetic properties of are further improved.
In addition, when the ferrite grain size is large, recrystallization after hot rolling is suppressed, so that the reduction of the coarse grain effect due to the fine recrystallization between rolling stands is suppressed, which further leads to improvement in magnetic properties. For this purpose, the average ferrite grain size is set to 650
It is desirable that the thickness be at least μm. That is, when the average ferrite grain size is 650 μm or more, the texture and magnetic properties are synergistically improved.

(II) During hot finishing rolling (i) Temperature of steel sheet when entering hot finishing rolling mill: For steel having a component composition that causes phase transformation, it is below the Ar ₁ transformation point and below 900 ° C. and above 500 ° C. For steels with a component composition that does not cause phase transformation, the temperature range should be 900 ° C or lower and 500 ° C or higher.To make the most of the effect of coarse grains before hot finish rolling, It is important to suppress the miniaturization due to recrystallization in rolling, and for that purpose, it is effective to perform rolling at a low temperature. Therefore, the upper limit of the finish hot rolling temperature is set to be below the Ar ₁ transformation point and below 900 ° C for steels having a component composition that generates the austenite phase (phase transformation), and the component that does not produce the austenite phase (phase transformation). 900 ° C for steel with composition
It must be:

That is, for steel having a component composition that causes a phase transformation, rolling in the two-phase region or the austenite region loses its effect due to the subsequent transformation. Phase region, that is, Ar
_This is because the temperature needs to be lower than _one transformation point. Furthermore, in the production method of the present invention, in order to maintain coarse grains before hot finish rolling, which is an essential feature of the invention, in all the stands of finish rolling, miniaturization due to recrystallization during finish rolling is suppressed. Is essential, and for that,
It is effective to roll in the low temperature range as much as possible, with an upper limit of 90
Set to 0 ° C.

Further, the lower limit of the finishing hot rolling temperature of any steel is such that rolling at a low temperature range of less than 500 ° C. increases the amount of accumulated strain and deteriorates the recrystallization texture. ° C.

(Ii) The ratio of the thickness reduction strain rate Z to the rolling reduction R at each rolling stand satisfies the relationship of the following inequality of (b) 3: 3 Z / R ≧ 0.51−0.04 [S i] − --- (b)

The present inventors have found that when the rolling speed, that is, the thickness-reducing strain rate Z is high, uneven deformation within grains is suppressed, recrystallization from grain boundaries is promoted, and the thickness-reducing strain rate is reduced. When Z, the reduction ratio R, and the amount of Si satisfy a certain relational expression, the frequency of existence of (015) [100] oriented grains is high in the recrystallized grains from the grain boundary, and (015) [10
0] Orientation grains are # 1 by cold rolling and finish annealing.
It has been found that this leads to the growth of 00｝ <001> and leads to the suppression of the <111> // ND orientation grains, thereby dramatically improving the magnetic properties.

The thickness reduction strain rate Z, rolling reduction R and Si
The experiment which found the relational expression of quantity is described. In a small vacuum melting furnace, a 50 kg steel ingot having a composition containing 0.5%, 1.0, 1.5, 2.1, and 3.2 wt% of Si was melted and hot-rolled to a thickness of 10 mm. Further, in order to make the thickness of the hot-rolled sheet 1.5 mm (constant), the sheet thickness before hot rolling was adjusted by mechanical cutting according to the hot-rolling conditions. This steel sheet was heated at 1150 ° C. for 30 minutes, subjected to one pass hot finishing rolling at 850 ° C., and then air-cooled to produce a hot-rolled sheet having a thickness of 1.5 mm. At this time, the rolling reduction R and the thickness reduction rate Z were variously changed. The average grain size of the phephite immediately before the hot finish rolling was 1000 μm. Thereafter, the hot-rolled sheet is subjected to hot-rolled sheet annealing in a ferrite single-phase region between 850 to 1000 ° C. depending on the component system, and cold-rolled after pickling to a final sheet thickness of 0.5 mm. Finish annealing was performed at 1000 ° C. for 30 seconds.

Table 2 shows the results of the evaluation of the texture and the magnetic properties of the steel sheet thus manufactured.
The results in Table 2 are further plotted and arranged in terms of the average values of iron loss and magnetic flux density in the LC direction.
Shown in In FIG. 1, "●" indicates a steel sheet manufactured according to the manufacturing method of the present invention, and "○" indicates a steel sheet manufactured under manufacturing conditions outside the proper range of the present invention.

[0068]

[Table 2]

As described above, the magnetic characteristics are divided into superior and inferior at the boundary line in FIG. Further, as is clear from Table 2 and FIG. 1, (015) after hot finish rolling and annealing
It can be seen that the integrated strength and magnetic properties of the [100] oriented grains vary greatly depending on the amount of Si, the rolling reduction, and the strain rate.

The larger the ratio of the strain rate to the rolling reduction, the smaller the non-uniform deformation in the grains during hot rolling, the more easily recrystallization occurs from the grain boundaries, and the more the amount of Si becomes. Closely related to behavior.

The inventors of the present invention have analyzed these relationships in various ways. As shown in FIG. 2, the present inventors explained the relationship between the ratio Z / R of the thickness reduction strain rate Z to the rolling reduction R and the Si content. Clarified what can be done.

In FIG. 2, based on the conditions shown in Table 2, in FIG. 1, those exhibiting good magnetic properties are indicated by “●”, and those having poor magnetic properties are indicated by “○”. Accordingly, in the manufacturing method of the present invention, the boundary line shown in FIG. 2 as a condition for exhibiting good magnetic properties, that is, the rolling reduction R and the thickness reduction strain rate Z and the Si amount in each rolling stand of the finish rolling mill, Satisfying the inequality relation of (b) in 3) above is regarded as an essential matter for specifying the invention.

(III) A structure that has been substantially recrystallized before cold rolling. The present invention relates to a texture formed by recrystallization after hot rolling, particularly (015) [100] grains. It develops into a characteristic texture after cold rolling and finish annealing. Therefore, it is an essential requirement that the structure before cold rolling is recrystallized. As a means for recrystallization, either self-annealing after hot rolling or reheating annealing may be used. It is sufficient that the volume fraction of the recrystallized grains is 60% or more.

(IV) Other Production Conditions The production method of the present invention needs to satisfy the conditions described in the above (I) to (III). In addition, the production conditions are limited to the following. Is more preferable.

(I) Slab heating temperature: in the range of 1100 to 1500 ° C. In slab heating, the higher the heating temperature, the coarser the crystal grains during heating, and the larger the crystal grains before hot finish rolling. Therefore, it is effective to increase the slab heating temperature to improve the magnetic properties. Therefore, the slab heating temperature is desirably 1100 ° C. or higher. However, an excessively high temperature causes a problem such as a decrease in yield due to an increase in scale.
It is preferably set to 00 ° C.

(Ii) Heating or keeping temperature before hot finish rolling: temperature range of 1000 ° C. or more In this invention, in order to obtain coarse grains before hot finish rolling, after hot rough rolling, hot finish rolling is performed. Before setting the temperature of the steel sheet at the time of entering the machine to the above-mentioned appropriate temperature, it is more preferable to heat or keep the temperature at 1000 ° C. or more to coarsen the crystal grains. In addition, the steel which becomes the austenite phase during this heating undergoes ferrite transformation during subsequent cooling. However, since the initial austenite grain size is large, it is also effective in increasing the ferrite grain size when entering a finish rolling mill.

(Iii) Reduction rate in cold rolling: 50 to 85% When the structure formed by hot rolling is cold-rolled, if the rolling is excessively reduced by cold rolling, the <111> // ND orientation Therefore, the upper limit of the rolling reduction in cold rolling is 85
% Is desirable. Further, if the rolling reduction is too small, the positive Cube decreases, so that the cold rolling reduction is desirably 50% or more.

(Iv) (015) [1]
00] Orientation accumulation strength: a range of 3.0 times or more of that of the random structure When the density of the (015) [100] orientation grains in the steel sheet before cold rolling increases, the positive Cube ( <111> // N
The D direction is reduced, and the magnetic properties are improved. For this reason, it is more preferable that the integrated strength of the (015) [100] orientation in the steel sheet before cold rolling is set to be 3.0 times or more that of the random structure.

The above is only an example of the embodiment of the present invention, and various changes can be made within the scope of the claims.

[0080]

EXAMPLES The steels shown in Tables 3 and 4 were melted in a converter and continuously cast into slabs having a thickness of 200 mm. Slabs 1-5
It consists of a basic composition whose Si content is within the preferred range of the present invention. The slab 6 has a Si content outside the preferred range of the present invention, and the slabs 30 and 31 have a Si content within the preferred range (Si: 4 wt% or less) of the present invention, but have a further preferred range (Si : More than 1.0 wt% and less than 4.0 wt%). The slabs 7 to 19 have a composition to which a second element is added for the purpose of improving the iron loss value by increasing the electric resistance. Slab 14
Nos. To 17 are those in which the addition amount of at least one second element exceeds the preferred range of the present invention. Slabs 18 and 19 were obtained by examining the effect of the non-transformation index f. The slabs 20 to 29 have a composition to which an element for forming grain boundary segregation or precipitate is added.
Slabs 21, 25 and 28 are those in which these elements deviate from the preferred range of the present invention, and are comparative examples to slabs 20, 24 and 27, respectively. Table 4 also shows the non-transformation index f.

[0081]

[Table 3]

[0082]

[Table 4]

Next, these slabs were reheated, and hot finish rolling was performed after hot rough rolling. Table 5 shows heating conditions, conditions before and after hot finish rolling, and conditions during cold rolling, and cold rolling conditions. In addition, the sheet thickness of the hot rough rolling and the hot finish rolling was set such that the sheet thickness of the cold-rolled sheet was 0.50 mm. Further, normalization after hot rolling was performed in a single phase region of ferrite at 850 to 1000 ° C depending on the component system, and finish annealing after cold rolling was performed at 850 to 1000 ° C.

For the steel having a composition that produces an austenite phase together with the respective production conditions, the A _r1 transformation point (° C.), the volume fraction of equiaxed ferrite just before hot finish rolling (%), and the average ferrite grain size (μm) Table 5 shows the volume fraction of the grain size of 100 μm or less and the integrated strength of the (015) [100] orientation before cold rolling, and {100} <0 after finish annealing.
01> orientation, (011) [100] orientation, and <111
Table 6 shows the evaluation results of the average integration strength and magnetic properties of the ND orientation.

[0085]

[Table 5]

[0086]

[Table 6]

The results of improving the magnetic characteristics according to the present invention will be described below with reference to Tables 5 and 6. Here, the present invention also includes a specific resistance increasing component for improving iron loss. Therefore, the effects of the present invention in Tables 5 and 6 were comprehensively determined based on the balance between iron loss and magnetic flux density.

From these tables, it can be seen from the comparison of Invention Steels 1 to 5 that if the Si content is within the preferred range of the present invention, good texture and magnetic properties can be obtained. Also,
Invention steels 1, 2, 44 and 45 having a Si content of 1 wt% or less;
Comparison with Inventive Steels 3 to 5 in which the amount exceeds 1 wt% shows that the effect of the present invention is further exhibited when the Si amount exceeds 1 wt%. Furthermore, the comparative steel 6 in which the amount of Si is larger than the preferred range of the present invention (4.2 wt%) has deteriorated magnetic properties, and the intended effect of the present invention has not been obtained.

The steels 7 and 8 and the steels 24 and 25 were manufactured by using the slabs having the same composition by the conventional manufacturing method and the manufacturing method of the present invention. It can be seen that the steel has much better magnetic properties than the steel sheet manufactured by the conventional method.

Further, invention steel 8 and invention steels 21 to 24, 26 and 27
It can be seen from the comparison with that that even if a second element such as Al or Mn is added to improve iron loss, excellent texture and magnetic properties can be obtained. Invention steels 8, 21 to 24, 26 and 27 and comparative steels 28 to
From a comparison with No. 31, it can be seen that when the second elements such as Al and Mn for iron loss improvement deviate from the preferred ranges of the present invention, the texture and magnetic properties are reduced, and the effects of the present invention are exhibited. I understand.

Invention steels 34, 36-38, 40, 41 and 43 containing segregation and precipitate forming elements within the preferred range of the present invention.
It can be seen that excellent magnetic properties were obtained in the same manner as in Invention Steel 8. On the other hand, from the comparison of invention steels 8, 34, 36 to 38, 40, 41 and 43 with invention steels 35, 39 and 42 in which segregation and precipitate forming elements deviate from the preferred range of the present invention, the latter is considered to be the former. It can be seen that the effect of improving the magnetic characteristics is small in comparison.

From the comparison between Invention Steels 1 to 5 and Comparison between Invention Steel 8 and Invention Steels 32 and 33, it is clear that the effect of the present invention is exhibited more strongly in a non-transformed steel which is not transformed into austenite at a high temperature. I understand.

From the comparison between Invention Steel 8 and Invention Steel 10, when the slab heating temperature is lower than the preferred range of the present invention, the grain size before hot finish rolling becomes smaller, and the effect of the present invention becomes smaller. I understand.

From the comparison between Invention Steel 8 and Invention Steel 11, the adoption of the heating / heating step before hot finish rolling increases the grain size before hot rolling even when the slab heating temperature is low. It turns out that it is fully exhibited.

From a comparison of Invention Steel 8 with Comparative Steels 12 and 13 having a hot finish rolling temperature higher than the proper range of the present invention,
In the latter, it can be seen that the effect of the present invention is not exhibited because the coarse grain effect disappears due to recrystallization between passes during hot finish rolling.

The comparative steels 15 and 16 had a grain size before hot finish rolling outside the proper range of the present invention due to a change in the hot rough rolling conditions. It can be seen that the effects of the present invention are not exhibited when the ferrite grains before the hot rolling do not satisfy the conditions of the present invention.

Comparison of invention steels 8, 9, 11 with invention steels 10, 14 having a grain size before hot finish rolling outside the preferred range (650 μm or more) of the present invention shows that in the latter case, It can be seen that the effect of the present invention is reduced.

From a comparison between inventive steel 8 and comparative steels 17 and 18 having a Z / R value outside the range of the present invention, in the latter case,
It can be seen that the texture deteriorates and the effect of the present invention is not exhibited.

A comparison of Invention Steel 8 with Invention Steels 19 and 20 whose rolling reductions are out of the preferred range of the present invention in the cold rolling shows that in the latter case, the texture deteriorates and the effect of the present invention is reduced. Is smaller.

[0100]

The electrical steel sheet of the present invention can achieve much better magnetic properties than conventional electrical steel sheets by optimizing the steel composition and texture. Further, according to the method for manufacturing an electrical steel sheet of the present invention, a high magnetic flux density electrical steel sheet having excellent magnetic properties in both the L direction and the C direction, which has been difficult to realize by the conventional manufacturing method, is produced by a special cold rolling. And it can be manufactured industrially and at low cost without relying on an annealing step.

[Brief description of the drawings]

FIG. 1 shows the data of Table 1 for the iron loss and the magnetic flux density L.
It is the figure plotted by the average value of C direction.

FIG. 2 is a diagram showing the relationship between the ratio Z / R of the thickness reduction strain rate Z to the rolling reduction R in each rolling stand of the finishing mill and the Si content for the data in Table 1.

Continued on the front page (72) Inventor Shigeaki Takagi 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside Kawasaki Steel Research Institute (72) Inventor Takako Yamashita 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Co., Ltd. Inside the company technology laboratory

Claims (9)

[Claims] 1. The {100} <001> direction and (01)
1) The L direction and the C direction have a texture in which the integrated strength in the [100] direction is 2.0 times or more and 2.0 to 10.0 times that of the random structure, respectively.
Electrical steel sheet with excellent magnetic properties in different directions. 2. The magnetic steel sheet according to claim 1, further comprising a texture whose average integrated strength in the <111> // ND orientation is 2.0 times or less of that of the random structure. Electrical steel sheet. 3. The magnetic steel sheet according to claim 1, wherein the steel sheet contains 4.0 wt% or less of Si. 4. The electrical steel sheet according to claim 1, further comprising: P: 0.30 wt% or less, Al: 2.0 wt% or less, Mn: 2.
0 wt% or less, Cr: 10.0 wt% or less, Mo: 2.0 wt% or less,
W: 2.0 wt% or less, Cu: 2.0 wt% or less, Ni: 2.0 wt% or less, Co: 1.0 wt% or less. 5. The magnetic steel sheet according to claim 1, further comprising: Ti: 0.20 wt% or less, V: 0.20 wt% or less, Nb: 0.
20 wt% or less, Zr: 0.20 wt% or less, Ta: 0.50 wt% or less, A
s: 0.20 wt% or less, Sb: 0.20 wt% or less, Sn: 0.20 wt% or less, C: 0.050 wt% or less, S: 0.050 wt% or less, B: 0.
An electrical steel sheet comprising at least one selected from the group consisting of 010 wt% or less, N: 0.010 wt% or less, and O: 0.010 wt% or less. 6. The electrical steel sheet according to claim 1, wherein the Si content is in the range of more than 1.0 wt% and less than 4.0 wt%. 7. The electrical steel sheet according to claim 1, wherein the electrical steel sheet satisfies the following formula (1) and has a component composition that does not generate an austenite phase. Note 1 f = (1.5 [S i] +2 [P] +2.5 [Al] + [Cr] + [Mo] + [W]) − (30 [C] +30 [N] +0.5 [ [Mn] +0.5 [Cu] + [N i]) ≧ 2.5 ---- (a) where f is a non-transformation index and [] means wt%. 8. A method for producing an electromagnetic steel sheet, comprising: subjecting a steel slab to hot rough rolling to obtain a steel structure shown in the following item (1), and immediately showing the steel structure shown in the following items (2) and (3). After performing hot finish rolling under the conditions, as it is, or as needed, after recrystallizing by hot-rolled sheet annealing, pickling is performed, and then cold rolling and annealing are performed. A method for manufacturing electrical steel sheets with excellent properties. Note 2 (1) The volume fraction of equiaxed ferrite grains is 80% or more, and the average grain size of equiaxed ferrite grains is 300 µm or more and the grain size is
The volume fraction of equiaxed ferrite grains of 100 μm or less should be 20% or less. (2) The steel sheet temperature at the time of entering the finish rolling mill is set to a temperature range of not more than Ar ₁ transformation point and not more than 900 ° C and not less than 500 ° C for a steel having an austenitic phase, and a component composition which does not generate an austenitic phase. 900 for steel having
Temperature range below 500 ℃ and below 500 ℃. (3) Assuming that the rolling reduction in each rolling stand of the finishing mill is R (%) and the thickness reduction rate is Z (s ⁻¹ ), the ratio of the thickness reduction rate (Z) to the reduction rate (R) ( Z /
R) satisfies the following inequality relationship of (b) in 3 according to the Si content (wt%). Note 3 Z / R ≧ 0.51-0.04 [S i] ---- (b) where Z = ln (t ₀ / t) / [｛(d / 2) × cos ⁻¹ ((dt ₀ + t) / d)｝ /
{V × 1000/60}], R = (1-t / t ₀ ) × 100, [Si] means wt% of Si element, t ₀ and t are the entry side of each rolling stand and The thickness at the delivery side (mm), d is the outer diameter (m
m) and V are the conveying speed of the steel sheet at the exit side of each stand (m / min)
And 9. The method for producing an electromagnetic steel sheet according to claim 8, wherein the steel slab contains Si: 4.0 wt% or less.