JPH11158590A - Silicon steel sheet excellent in magnetic property and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a steel sheet excellent in magnetic properties by allowing it to have a compsn. contg. a specified amt. of P, and the balance substantial Fe and a texture in which the integrated intensity in the 100}<001> orientation and the 100}<011> orientation are respectively regulated to specified times or above of that of the random structure. SOLUTION: The steel sheet is the one having a compsn. contg., by weight, 0.2 to 1.2% P, and the balance substantial Fe and having a texture in which the integrated intensity in the 100}<001> orientation and the 100}<011> orientation is regulated to three times or above of that of the random structure. It is also preferable that the compsn. is the one contg. 0.2 to 1.2% P, furthermore contg. one or >= two kinds selected from Si, Al and Mn by 0.1 to 5.0% in total, and the balance substantial Fe. The steel slab is subjected to hot rough rolling and is next subjected to hot finish rolling under the conditions of >=50% draft (one pass) and 750 to 1050 deg.C rolling finishing temp., and the obtd. hot rolled sheet is annealed in the temp. range of <=700 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic steel sheet which is advantageously used as an iron core material of a transformer or an electric motor.

[0002]

2. Description of the Related Art Iron core materials for transformers and electric 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 an electromagnetic steel sheet to be used for this type of iron core material, a silicon steel sheet containing 7 wt% or less of Si has been exclusively used because it has excellent characteristics that satisfy the above requirements.

Here, when Si is contained, iron loss is reduced, but magnetic flux density is lowered. When the magnetic flux density is low, the exciting current becomes large, so that the copper loss caused by the iron core winding increases. Therefore, in order to avoid this increase in copper loss, development of a technique for increasing the magnetic permeability as much as possible to increase the magnetic flux density in a constant magnetic field has been promoted. However, this type of improvement is limited since the material-specific saturation magnetic flux density does not increase.

On the other hand, some alloying elements other than Si are superior to Si in magnetic properties, mechanical properties, and particularly any of the workability and alloy cost, but there is no overall advantage over Si. That was the general view. However, the present inventors have conducted intensive studies on the application of alloying elements other than Si to electrical steel sheets, and found that the Fe-P-based composition can provide properties superior to silicon steel as electrical steel sheets. A proposal was made in Japanese Patent Application Laid-Open No. 9-41101. Here, having a high saturation magnetic flux density,
A new electromagnetic steel composition has been established that can significantly improve the other properties remaining when one of iron loss and magnetic flux density is at the same level as compared with conventional materials.

[0005] It is desirable that the magnetic steel sheet has a texture such that the electromagnetic properties in the magnetization direction during use are excellent. The preferred texture depends on the form of use,
When the magnetization direction is isotropic in the plane as in a rotating machine, the direction of the rolling surface is {100}, and the direction <001> of the easy axis is randomly distributed in the plane. What
A so-called random cubic texture is most desirable. In addition,
This texture can be defined as one in which the orientation of the rolling surface is {100} and the orientation in the rolling direction (RD) is accumulated in both <001> and <011>. If such a texture can be obtained, the average magnetic flux density in all directions in the plane is further improved. Therefore, obtaining a random cubic texture in the Fe-P-based magnetic steel sheet is extremely significant.

[0006] In order to obtain such a texture, various methods have been proposed mainly for silicon steel. For example, Japanese Unexamined Patent Publication (Kokai) No. 2-133523 discloses a method combining cold rolling and annealing with ultra-quenching of molten metal,
Utilization of a method combining cold rolling under high pressure and decarburizing annealing described in JP-A-48-19767 and annealing of a cold-rolled sheet described in JP-A-7-278666 and subsequent rapid cooling That is the method that was done.

[0007]

However, among the above-mentioned methods, the super-quenching method has a problem that the production cost is high because a special cooling roll is required. In addition, the method combining cold rolling under high pressure and decarburization annealing is disadvantageous in that it requires complicated steps and is mainly limited to special thin steel sheets of 0.30 mm or less. Further, the annealing and quenching methods can easily make the magnetic properties in the plate surface uniform, but do not lead to obtaining a particularly high magnetic flux density.

Accordingly, the present invention provides an assembly having a high degree of integration of {100} <001> and {100} <011> orientations in a hot rolling step without requiring complicated processes and at low cost. An object of the present invention is to propose a magnetic steel sheet having a structure together with its advantageous manufacturing method.

[0009]

Means for Solving the Problems The inventors have conducted intensive studies in order to obtain a magnetic steel sheet having a random cubic texture formed by hot rolling and having enhanced magnetic properties in two directions, especially magnetic flux density. , P as the main alloying element, and further controlling the rolling temperature and the rolling reduction in the hot finish rolling to achieve a higher temperature and a higher rolling reduction condition than those conventionally used in the ordinary process. We have found that it is extremely effective in achieving this. The present invention is based on the above findings.

That is, the gist of the present invention is as follows. 1. P: 0.2 to 1.2 wt%, the balance being substantially Fe composition, {100} <001> orientation and {10
An electromagnetic steel sheet having excellent magnetic properties, characterized by having a texture whose integrated strength in the 0 ° <011> direction is at least three times that of a random structure.

2. P: 0.2 to 1.2 wt%
One, two or more selected from i, Al and Mn are contained in a total amount of 0.1 to 5.0 wt%, and the balance substantially becomes Fe, and the {100} <001> orientation and {100} <
011> An electrical steel sheet having excellent magnetic properties, characterized by having a texture in which the integrated strength in each direction is at least three times that of a random texture.

3. P: Hot rough rolling is performed on a steel slab having a composition containing 0.2 to 1.2 wt%, and then a rolling reduction (1
Pass): 50% or more and rolling end temperature: after hot finish rolling under the condition of 750 to 1050 ° C, the obtained hot rolled sheet is annealed at a temperature range of 700 ° C or less. A method for manufacturing electrical steel sheets with excellent properties.

4. P: 0.2 to 1.2 wt%
A steel slab having a composition containing a total of 0.1 to 5.0 wt% of one or more selected from i, Al and Mn,
After performing hot rough rolling, and then performing hot finish rolling under the conditions of a rolling reduction (1 pass): 50% or more and a rolling end temperature: 750 to 1050 ° C, the obtained hot rolled sheet is 700 ° C or less. A method for producing an electrical steel sheet having excellent magnetic properties, characterized by annealing in a temperature range of 1.

5. 3. The method for producing an electrical steel sheet having excellent magnetic properties according to the above item 3 or 4, wherein after the hot finish rolling, cold rolling with a rolling reduction of less than 40% and then annealing are performed.

According to the present invention, in a magnetic steel sheet containing P, {100} <001> and {100} <001>
Since it has a texture whose orientation integrated strength is more than three times that of the random structure, it is possible to provide a steel sheet with excellent electromagnetic properties only by hot rolling or without using a special method, Cost reduction. Here, when the iron loss is low, the magnetic steel sheet also has a low magnetic flux density, and generally has poor average characteristics in all directions in the sheet plane. On the other hand, the electrical steel sheet according to the present invention has the same non-oriented electrical steel sheet as the ordinary non-oriented electrical steel sheet by providing such a degree of integration as shown in an experimental example described later. in silicon steel sheets is equal to or less core loss, and significantly higher flux density, in particular at an average for all orientations of the plate surface, W _15/50 is B ₅₀ or more 1.70T at 2 to 3.5 W / kg, the W _{15/5 0} is 3.5 ~6W / kg
B ₅₀ can be ensured more than 1.76T at.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, experimental results which led to the present invention will be described. In a small vacuum melting furnace,
P: 0.56 wt%, C: 0.003 wt%, Si: 0.01 wt%, Mn: 0.
Composition containing 03 wt% and Al: 0.05 wt%, that is, P
And the remainder was melted with a 50 kg ingot having a composition of Fe and impurities, and rolled to a plate thickness of 5 mm by hot rough rolling. After heating this steel sheet at 1100 ° C for 30 minutes, the roll diameter is 700mmφ
Was rolled at a peripheral speed of 800 m / min, a rolling reduction of 80%, and a rolling end temperature of 950 ° C. to obtain a hot-rolled sheet having a thickness of 0.7 mm.

After subjecting the hot-rolled sheet to annealing at 600 ° C. for 2 hours, the texture was examined. As a result, {100} <0
01> The degree of accumulation in the direction is 5.2 times that of the random organization,
In addition, the degree of accumulation in the {100} <011> direction was 4.3 times higher than that of the random structure, and both were higher. Furthermore, in order to easily evaluate the average magnetic properties in all directions of the plate surface, a ring-shaped sample having an outer diameter of 35 mm and an inner diameter of 25 mm was cut out, and the magnetic properties were measured.The iron loss was _{W15 / 50} . 6.6 W /
kg and magnetic flux density and 1.79 T at B _50, hot-rolled steel sheet without excellent properties so far were obtained.

Here, the degree of integration of a specific orientation indicates how much the frequency of existence of crystal grains having that orientation is relative to a structure having a completely random orientation distribution.
It can be determined as follows. That is, the central portion of the plate thickness parallel to the plate surface of the steel plate sample is polished, and the polished surface is subjected to the (110), (200) and
Measure the incomplete pole figure of (211) as numerical data. This measurement data is described in H. J. Bunge's “Texture Analys
It is converted into a three-dimensional azimuth distribution function using the series expansion method described in "Is Materials Science". If this distribution function is a perfect random distribution, the frequency of occurrence in any azimuth will be 1 To determine the degree of integration of a particular orientation that has been normalized, the orientation, here {100} <
The value of the distribution function in the <001> or {100} <011> direction may be adopted. This value is correctly a multiple of the degree of integration for the random distribution. In addition, the steel plate having the same composition rolled under the condition of the rolling end temperature: 700 ° C. was similarly examined, and it was found that {100} <001> and {10}.
It has been found that the degree of integration in the 0 ° <011> direction has decreased.

Further, the hot-rolled sheet obtained by the hot rolling at a rolling end temperature of 950 ° C. is cold-rolled to a thickness of 0.5 mm (reduction ratio:
29%), and annealed at 850 ° C. for 1 minute. After examining the texture and magnetic properties, {100} <001
> And {100} <011> orientations are 5.0 times and 4.6 times that of the random structure, respectively, and the degree of accumulation at the hot-rolled sheet stage is almost maintained. 4.8W / kg at _15/50, flux density is B ₅₀ 1.80 T
As compared with the conventional non-oriented electrical steel sheet having the same iron loss, an electrical steel sheet having a remarkably high magnetic flux density was obtained as a result of evaluation using a ring sample. On the other hand, when the rolling end temperature in the hot rolling was 700 ° C., the degree of integration in the {100} <001> and {100} <011> orientations in the cold-rolled sheet both decreased.

The present invention is based on the above experimental facts, and the hot rolling conditions become important in addition to the component composition. That is, a suitable texture can be obtained only when the temperature of the steel sheet at the end of hot rolling is sufficiently high and the rolling reduction is also sufficiently high. Furthermore, by performing cold rolling at an appropriate draft, this texture is strengthened. Although the reason for this has not been completely elucidated, in hot rolling, in recrystallization during rolling deformation under specific conditions, crystal grains having {100} planes parallel to the rolling plane appear preferentially It is thought to be. In addition, regarding the maintenance of the texture during cold rolling and annealing, according to conventional knowledge, it has been considered that the texture is destroyed by the reduction during cold and the degree of accumulation is reduced, but here the degree of accumulation is maintained. And the magnetic properties have been improved. This is thought to be related to the special texture of the hot-rolled sheet, but has not yet been clearly explained.

Now, the reasons for limiting various conditions in the present invention will be described. First, regarding the component composition, P has the effect of increasing the specific resistance and reducing the slip current loss. That is, although the magnetic flux density slightly decreases as the amount of P added increases, when P and Si are compared at the same specific resistance level, P is advantageous in that the decrease in magnetic flux density is smaller than that of Si. Here, if the content of P is less than 0.2 wt%, the above effect is not sufficiently exhibited, while if it exceeds 1.2 wt%, Fe ₃ P and the like mainly precipitate along the grain boundaries, so that the magnetic flux density sharply increases. And iron loss increases, and workability also deteriorates. Therefore, the P content was limited to the range of 0.2 to 1.2 wt%.

Further, for the purpose of assisting the function of P, one or more selected from Si, Al and Mn, which increase the specific resistance, may be contained in a total amount of 0.1 to 5.0 wt%. it can. That is, if the total of one or two or more of these is less than 0.1 wt%, the effect of addition does not appear and does not exceed the range of impurities, so the lower limit is 0.1 wt%. Meanwhile, 5.
If it exceeds 0 wt%, the magnetic flux density decreases and the workability also deteriorates, so the upper limit is 5.0 wt%.

On the other hand, C and O have magnetic properties,
From the viewpoint of subsequent cold rolling and punching properties,
It is preferable to suppress the content to 0.01 wt% or less.

Next, the texture will be described. The present invention relates to {100} <001> and {100} <011.
> It is characterized by a structure that accumulates in the orientation, and in order to fully utilize this effect as an electrical steel sheet product, it is important that the degree of accumulation be at least three times that of a random structure.

Next, the manufacturing conditions will be described. First, as for the rolling end temperature in hot rolling, if it is less than 750 ° C., the integrated strength of the {100} <001> and {100} <011> orientations is less than three times that of the random structure, while it exceeds 1050 ° C. In addition to the time limitation from the feeding of the heating furnace to the rolling, the heating at a high temperature is required and the cost rises. Therefore, the rolling end temperature is limited to the range of 750 to 1,050 ° C. If the rolling reduction of the hot rolling is less than 50%, sufficient strain required for recrystallization having a suitable texture cannot be imparted. Therefore, the rolling reduction is set to 50% or more.

Further, {100} <001> and {1}
In order to increase the degree of integration in both directions of 00 <011> in a well-balanced manner, it is advantageous to perform hot-rolled sheet annealing. When the annealing temperature exceeds 700 ° C., particularly, {100} <0
11> The degree of integration in the orientation is weakened, and the magnetic properties in the direction in the rolling plane and inclined at 45 ° to the rolling direction are deteriorated. As a result, the average magnetic properties in all directions in the rolling plane are deteriorated. Therefore, the annealing temperature of the hot rolled sheet is set to 700 ° C. or less.

Here, it is usual in the production on an industrial scale that the hot-rolled sheet after hot rolling is wound on a coil, but when this winding is carried out, it depends on the winding temperature. Annealing. Therefore, when the coil winding temperature is high, the hot-rolled sheet annealing is performed at a high temperature.When the hot-rolled sheet is wound around the coil, the winding temperature is the same as the annealing temperature described above. It must be below 700 ° C. In addition, if an effect equivalent to annealing can be obtained in this winding step, it is needless to say that it is not necessary to newly provide an annealing step for the hot-rolled sheet.

Further, when performing cold rolling and then annealing after the above hot finish rolling, the rolling reduction in the cold rolling is
If it is at least 40%, the random cubic structure obtained at the stage of hot-rolled sheet changes, and the in-plane isotropic property is lost. Therefore, cold rolling is performed at a rolling reduction of less than 40%.

[0029]

Example 1 In a small vacuum melting furnace, a 50 kg steel ingot having each component composition shown in Table 1 was melted. In Table 1, steels (C), (D) and (E) are the component compositions according to the present invention, steel (D) is P alone, and steels (C) and (E) are Si, Al and
This is an example in which Mn is added. Steels (A) and (B) are comparative examples of the composition of ordinary silicon steel sheets. In addition, steel (F)
This is an example in which the added amounts of Si, Al and Mn are out of the range of the present invention.

Next, these ingots were heated to 1150 ° C., and then subjected to hot rough rolling to obtain plates having a thickness of 1.3 to 4.0 mm. This board,
After heating to 1100 ° C, the rolling end temperature is controlled at 600 to 950 ° C, and at a rolling speed of 800m / min, it is finished to 0.8mm in one pass (rolling reduction: 40 to 80%), and then at 600 ° C for 2 hours. Annealed.

For each of the hot-rolled steel sheets thus obtained, X
(110), (200), and (211) pole figures were obtained by line analysis, and three-dimensional azimuth analysis was performed using the series expansion method described above to obtain three-dimensional azimuth distribution density. In addition, outer diameter 35mm and inner diameter 25mm
Perform magnetic measurement with the sample cut out in a ring shape of
Iron loss value W _15/50 at 1.5T excitation and 5000A /
It was determined magnetic flux density B ₅₀ in the case of m. Table 2 shows the obtained results.

[0032]

[Table 1]

[0033]

[Table 2]

Nos. 1 to 3 are comparative examples using ordinary silicon steel sheet compositions. As can be seen from a comparison between Nos. 1 and 2, generally, the iron loss decreases as the alloy addition amount increases. The magnetic flux density also decreases. Next, No. 3 is a comparative example which conforms to the rolling conditions of the present invention but has a composition generally in accordance with conventional silicon steel. No. 3 shows that {100} <001> and {1}
It can be seen that the integrated strength in the 00 ° <011> orientation was increased, and as a result, the magnetic flux density of the ring-shaped sample was particularly improved with respect to Nos. 1 and 2.

On the other hand, No. 4 and No. 5 which are in the same rolling conditions as No. 3 and which conform to the composition range of the present invention.
It is noteworthy that, in the magnetic flux density of the ring-shaped sample, a higher magnetic flux density can be obtained as compared with No. 3 having the same iron loss value. That is, compared with the steel sheet No. 3 of the conventional composition obtained under the rolling conditions of the present invention, the steel sheets Nos. 4 and 5 according to the rolling conditions and the composition of the present invention have an average iron loss in all directions in the sheet plane. Excellent characteristics with a low and extremely high magnetic flux density can be obtained. This is the same for Nos. 6 and 8 according to the present invention.

No. 10 is an invention example containing Si and Al in addition to P. In this case, too, the comparative example No. 1
The magnetic flux density is much higher at the same iron loss level as compared with.

On the other hand, the compositions of Nos. 7 and 9 are within the scope of the invention, but the rolling conditions are out of the scope of the invention.
The characteristics are almost the same as those of No. 3. In No. 11, since the total amount of Si, Al and Mn exceeds the scope of the invention, the level of the conventional magnetic properties cannot be exceeded.

Embodiment 2 Next, an embodiment relating to the rolling reduction of cold rolling will be described. 50kg of the composition of steel (C) shown in Table 1 in a small vacuum melting furnace
The steel ingot was melted, heated to 1150 ° C., and then subjected to hot rough rolling to obtain a plate having a thickness of 2 to 3 mm. After heating this plate to 1100 ° C, the rolling end temperature was controlled at 950 ° C, and the rolling speed was 800 m / min, and the rolling speed was 0.6 to 1.0 mm in one pass (rolling reduction: 65 to 70%).
Finished. Thereafter, the scale on the surface of the hot-rolled sheet is removed by shot blasting, and annealed at 650 ° C. for 2 hours in an atmosphere of 35% hydrogen and 65% nitrogen.
After cold rolling to a thickness of 0.5 mm at 17 to 50%, annealing was performed at 850 ° C. for 1 minute in an atmosphere of 35% hydrogen and 65% nitrogen.

For each of the cold rolled steel sheets thus obtained, X
(110), (200), and (211) pole figures were obtained by line analysis, and three-dimensional azimuth analysis was performed using the series expansion method described above to obtain three-dimensional azimuth distribution density. In addition, outer diameter 35mm and inner diameter 25mm
Perform magnetic measurement with the sample cut out in a ring shape of
Iron loss value at 1.5T excitation; W _15/50 and excitation magnetic field: 50
Magnetic flux density at 00 A / m; _B50 was determined. Table 3 shows the obtained results.

[0040]

[Table 3]

Nos. 12 and 13 are examples in which the rolling reduction of the cold rolling is within the applicable range, the integrated strength of the {100} <001> and {100} <011> directions is high, and The average magnetic flux density in the direction is extremely high.

On the other hand, in No. 14, since the rolling reduction of the cold rolling is excessive, the degree of integration in the {100} <001> direction is high, but the degree of integration in the {100} <011> direction is It is not so large and the magnetic flux density is slightly lower.

Embodiment 3 Here, an embodiment relating to hot rolled sheet annealing will be described. In a small vacuum melting furnace, a 50 kg steel ingot having the composition of steel (C) shown in Table 1 was melted, and the steel ingot was heated to 1150 ° C. and then hot-rolled into a 2.0 mm thick plate. After heating this plate to 1100 ° C,
The rolling end temperature was controlled at 950 ° C., and the roll was finished to 0.7 mm in one pass at a rolling speed of 800 m / min (reduction rate: 65%) to obtain a finished hot rolled sheet. A shot is applied to the surface of the hot-rolled sheet to reduce the scale, and the scale is removed in an atmosphere of 35% hydrogen and 65% nitrogen.
After annealing at 0 to 900 ° C. for 2 hours, it was cold-rolled to 0.5 mm at a reduction of 29%, and annealed at 850 ° C. for 1 minute in an atmosphere of 35% hydrogen and 65% nitrogen.

For each of the magnetic steel sheets thus obtained, X
(110), (200), and (211) pole figures were obtained by line analysis, and three-dimensional azimuth analysis was performed using the series expansion method described above to obtain three-dimensional azimuth distribution density. In addition, outer diameter 35mm and inner diameter 25mm
Perform magnetic measurement with the sample cut out in a ring shape of
_Iron loss W _15/50 at 1.5 T excitation and 5000 A /
It was determined magnetic flux density B ₅₀ in the case of m. Table 4 shows the obtained results.

[0045]

[Table 4]

Nos. 15 to 17 are examples in which the hot-rolled sheet annealing temperature is suitable, and {100} <001> and {100}.
<011> The integrated strength in both directions is high, and in particular, the average magnetic flux density in all directions in the plate surface is extremely high.

On the other hand, in Nos. 18 and 19, since the annealing temperature of the hot-rolled sheet was too high, the degree of integration in the {100} <001> direction was high, but the degree of integration in the {100} <011> direction was high. Is reduced, and as a result, the magnetic flux density of the ring sample is slightly reduced.

[0048]

According to the present invention, a high magnetic flux density electromagnetic steel sheet whose magnetization direction is in-plane non-direction, that is, highly integrated in a random cubic structure, which cannot be realized by the conventional manufacturing method, can be used. It can be provided inexpensively as it is during cold rolling and without resorting to a special cold rolling or annealing step.

Claims (5)

[Claims] 1. P: 0.2 to 1.2 wt%, with the balance substantially consisting of Fe, and the {100} <001> orientation and the {100} <011> orientation are both random. An electrical steel sheet having excellent magnetic properties, characterized by having a texture that is at least three times that of the texture. 2. P: contains 0.2 to 1.2 wt%, and further contains Si,
One or two or more selected from Al and Mn are contained in a total amount of 0.1 to 5.0 wt%, and the remainder substantially has a Fe composition, and has {100} <001> orientation and {100} <01.
1> An electrical steel sheet having excellent magnetic properties, characterized by having a texture whose accumulated strength in each direction is at least three times that of a random texture. 3. A steel slab having a composition containing P: 0.2 to 1.2 wt% is subjected to hot rough rolling, and then a reduction ratio (1 pass): 50% or more and a rolling end temperature: 750 to 1050 ° C. After hot finishing rolling under the conditions, the resulting hot rolled sheet
A method for producing an electrical steel sheet having excellent magnetic properties, characterized by annealing at a temperature of 700 ° C or lower. 4. A composition containing P: 0.2 to 1.2 wt%, further comprising Si,
A steel slab having a composition containing a total of 0.1 to 5.0 wt% of one or more selected from Al and Mn is subjected to hot rough rolling, and then a reduction (1 pass): 50% or more and Rolling end temperature: After finishing hot rolling under the condition of 750 to 1050 ° C, the obtained hot rolled sheet is annealed in a temperature range of 700 ° C or less. Production method. 5. The method for producing an electrical steel sheet having excellent magnetic properties according to claim 3 or 4, wherein after the hot finishing rolling, cold rolling and annealing are performed at a rolling reduction of less than 40%.