JPH07228953A - Nonoriented silicon steel sheet reduced in iron loss and its production - Google Patents

Abstract

PURPOSE:To produce a silicon steel sheet reduced in iron loss in a high frequency region by preparing a nonoriented silicon steel sheet containing Si, Al, and Mn under specific conditions and having specific crystalline grain size. CONSTITUTION:A slab of steel, which has a composition consisting of, by weight, <1.5% Si, 2.5-6.0% Al, 1.0-3.0% Mn, and the balance essentially Fe with inevitable impurities and satisfying inequality I, is prepared. This steel slab is hot-rolled, subjected to hot rolled plate annealing at 650-1000 deg.C, and finished to product sheet thickness by means of two-time cold rolling, while process-annealed between cold rolling stages, by regulating the drafts in the first and the second cold rolling to 40-80%, respectively. Then annealing is done. By the above procedure, crystalline grain size R (mum) [where (f) is excitation frequency (Hz)] is regulated to a figure in the range satisfying inequality II. By this method, the nonoriented silicon steel sheet, excellent in average magnetic properties in the entire-peripheral direction of sheet thickness or average magnetic properties in a rolling direction and in a direction perpendicular to the rolling direction, can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-oriented electrical steel sheet having a low iron loss, which is widely used as an iron core for electric equipment, and is particularly suitable for iron cores for rotating machines and small transformers used in a high frequency range. The present invention relates to a grain-oriented electrical steel sheet and a method for manufacturing the same.

[0002]

2. Description of the Related Art Recent electric appliances tend to be used in a high frequency range for the purpose of high efficiency and miniaturization, and there is an increasing demand for magnetic steel sheets having a low iron loss in the high frequency range. ing.

Iron loss can be generally expressed as the sum of a hysteresis loss proportional to the frequency squared and an eddy current loss proportional to the frequency squared. Therefore, in the high frequency range, the ratio of the eddy current loss proportional to the square of the frequency to the iron loss is high, and reduction of the eddy current is extremely important for reducing the iron loss. It is known that reducing the plate thickness and increasing the electrical resistance are effective for reducing the eddy current. In other words, increasing the electromagnetic resistance of the steel sheet due to thinning and addition of alloying elements is a major guideline for the development of electromagnetic steel sheets for high frequencies.

Japanese Unexamined Patent Publication (Kokai) No. 62-103321 discloses a method for producing a high silicon steel sheet containing about 6.5% Si.
When Si is added to iron, the magnetostriction becomes almost 0 at an addition amount of around 6.5%, so that the hysteresis loss becomes extremely low. Further, addition of a high amount of Si increases the electric resistance, which is also advantageous in reducing eddy current loss. Therefore, in a high silicon steel sheet with around 6.5% Si, both iron loss factors such as hysteresis loss and eddy current loss can be reduced at the same time, so it is better than other high alloy steels with similar electrical resistance. Is believed to be obtained.

However, the high silicon steel sheet as shown in the present invention is extremely brittle, and even if it can be manufactured, the user of the steel sheet needs special equipment and conditions to process it into an iron core. Will be very limited.

JP-A-62-196354 and JP-A-62-196354
In 196358, the content of Si is 2.5 to 7.0%, and W:
0.05-3.0%, Mo: 0.05-3.0%, Ti: 0.05-3.0%,
Mn: 0.1-11.5%, Ni: 0.1-20.0%, Co: 0.5-20.0
%, Cr: 0.1 to 10.0% and Al: 0.5 to 13.0%, a high alloy soft magnetic steel sheet containing one or more selected from the range of not more than 20.0%.

Also in the steel sheets of these inventions, when Si of about 6.5% is contained, the iron loss becomes good, but the punching property naturally becomes poor. On the other hand, when Si is replaced with another alloy component, good iron loss cannot be obtained. Further, in these inventions, the melt quenching method is considered to be the main manufacturing method, and the plate thickness is limited to an extremely thin plate thickness of 0.30 mm or less. For this reason, the application is inevitably limited.

[0008]

DISCLOSURE OF THE INVENTION The present invention solves the restrictions on the plate thickness in the conventional manufacturing method as described above and the limitation of applications due to the restrictions, and further, the cold workability, the punching workability and the magnetic property of the product steel sheet. This was done to improve the characteristics.

The object of the present invention is to provide a low iron loss in a high frequency range and an excellent average magnetic property in the entire circumferential direction of the plate thickness or in a direction perpendicular to the rolling direction, and further to an iron core such as punch cutting. To provide a non-oriented electrical steel sheet that is easy to process and a method for manufacturing them by using a process that undergoes general hot rolling and cold rolling that allows products of various thicknesses to be easily manufactured separately. is there.

[0010]

The summary of the present invention is as follows.
The non-oriented electrical steel sheet of (1) and its manufacturing method of (2) and (3).

(1) wt%, Si: less than 1.5%, Al: 2.5
-6.0% and Mn: 1.0-3.0%, satisfying the following formula, the balance substantially consisting of Fe and inevitable impurities, and having a crystal grain size R (μm) satisfying the following formula: low iron loss Non-oriented electrical steel sheet.

[Si (%) + Al (%) + 1/2 · Mn (%)] ≧ 5.5% (500 × f ^−1/3 −20) ≦ R ≦ (500 × f ^{− 1/3} +20) ···, where f represents the excitation frequency (Hz).

(2) A steel slab satisfying the chemical composition and formula described in (1) above, the balance consisting essentially of Fe and unavoidable impurities, is hot-rolled and then subjected to two cold-rolling steps with intermediate annealing. Non-directionality with low iron loss, with the grain size R (μm) within the range satisfying the above formula, after finishing the product sheet thickness by setting both the first and second rolling reductions to 40 to 80% Manufacturing method of electrical steel sheet.

(3) A steel slab satisfying the chemical composition and formula described in (1) above, the balance consisting essentially of Fe and unavoidable impurities, is hot-rolled and then annealed at 650 to 1000 ° C. The first cold rolling between the first and second intermediate rollings.
Method for producing non-oriented electrical steel sheet with low iron loss in which the grain size R (μm) is within a range that satisfies the above formula after finishing the product sheet thickness with the second reduction rate of both 40 to 80% .

The manufacturing method of the above (2) is intended for non-oriented electrical steel sheets for iron cores of rotating machines, and since it is important that the average magnetic properties in the entire thickness direction are excellent, The magnetic properties are evaluated using a ring test piece. Above (3)
The manufacturing method of is intended for small transformer cores (EI cores), and it is important to have excellent average magnetic properties in the rolling direction and the direction perpendicular to the rolling direction. Perform using.

[0016]

[Operation] As mentioned above, the high silicon content steel of around 6.5% Si is
Although it is advantageous for iron loss in the high frequency range, it is extremely brittle and easily cracks during cold rolling. Even if cold rolling can be performed without cracking, extremely special conditions are required when a user performs a working operation on an iron core such as punching.

The inventors of the present invention have studied in detail the method for producing a non-oriented electrical steel sheet which has good ductility during cold rolling, has good iron loss equivalent to that of high silicon steel, and is easy to work on an iron core. did. As a result, the following findings were found.

In the steel sheet whose electric resistance is increased by adding a proper amount of Si, Mn, and Al, the same good iron loss as that of the steel sheet whose electric resistance is increased by adding 6.5% Si alone is obtained. .

Moreover, the punching workability is superior to the case of adding Si alone.

A good iron loss can be obtained by controlling the crystal grain size to be optimum according to the excitation frequency used.

By recrystallizing the steel sheet by hot-rolled sheet annealing, improvement of the average iron loss in the rolling direction and the direction perpendicular to the rolling direction can be obtained. In this case, the non-oriented electrical steel sheet is suitable for a small transformer core.

Cold rolling is performed twice with an intermediate annealing between them,
In any rolling, setting the reduction rate to 40 to 80% is effective for improving iron loss.

Next, the reasons why the chemical composition of the magnetic steel sheet of the present invention or its raw material steel, the crystal grain size of the product magnetic steel sheet, and the manufacturing method are limited as described above will be explained. % Means% by weight.

(1) Chemical composition of product electromagnetic steel sheet or its material steel Si: less than 1.5% As Si content increases, the electrical resistance of the steel sheet increases and eddy current loss decreases, resulting in iron loss. Has the effect of reducing. However, if the Si content is 1.5% or more, cracks are likely to occur during cold rolling and punching. Therefore, the Si content is set to less than 1.5%. The preferred lower limit is 0.1
%.

Mn: 1.0 to 3.0% Mn is effective in increasing the electric resistance of the steel sheet as in the case of Si, and positive addition is effective from the viewpoint of reducing iron loss.
Further, by adding a combination with an appropriate amount of Al, it is possible to obtain extremely good iron loss in the high frequency range.
To obtain these effects, it is necessary to contain 1.0% or more. On the other hand, if it exceeds 3.0%, the strength will increase excessively, making cold rolling difficult, so the upper limit was made 3.0%.

Al: 2.5 to 6.0% By adding Al together with an appropriate amount of Mn as described above, it is possible to obtain a magnetic steel sheet having excellent average characteristics in the entire thickness circumferential direction in the high frequency range.

One of the reasons why the addition of Al improves the average iron loss in the circumferential direction of the plate thickness is considered to be that a texture containing many {100} planes is formed. Al content is
If it is less than 2.5%, the above effect is small. Another reason is that the addition of Al has a remarkable effect of increasing the electric resistance, and if it is less than 2.5%, the electric resistance is too low to reduce the iron loss in the high frequency range.

However, the fact that the combined addition of Mn and Al is extremely effective for improving the iron loss cannot be explained only from the above two reasons, and the influence of the magnetic domain structure on the eddy current loss must be taken into consideration. That is, it is considered that the addition of appropriate amounts of these two elements causes a magnetic domain structure advantageous for eddy current loss in the high frequency region.

On the other hand, if the Al content exceeds 6.0%, cracks are likely to occur during cold rolling or punching, so the upper limit was made 6.0%.

Si + Al + 1 / 2.Mn: 5.5% or more When Si, Al, and Mn are added, the electrical resistance of the steel sheet is increased as described above, so that extremely good iron loss can be obtained in the high frequency range. . Such an effect of improving iron loss cannot be obtained when Si + Al + 1/2 · Mn is less than 5.5%. That is, if it is less than 5.5%, the electric resistance is too low to reduce the iron loss in the high frequency range.
The reason why the coefficient of Mn is 1/2 is that the effect of Mn on the increase in electrical resistance is half that of Si and Al.

Except for the above three elements, it is desirable to keep the steel slab as low as possible. For example, C adversely affects iron loss, so 0.010% or less, more specifically 0.005% or less, is desirable. This is because C remaining in the product stage forms carbides, which impedes domain wall movement and increases iron loss.

S combines with Mn to form MnS, which becomes an obstacle to the movement of the domain wall similarly to the carbide, and causes the deterioration of iron loss. Therefore, the lower the S content, the better the iron loss.
6% or less, more preferably 0.003% or less is desirable.

Since P makes the steel sheet brittle, 0.020% or less is desirable.

N is combined with Al to form AlN and becomes an obstacle to the movement of the domain wall. Therefore, it is necessary to reduce N to 0.0060%.
The following is desirable.

From the viewpoint of preventing cracking, B is 0.0020%.
It does not prevent inclusion in the following range.

(2) Crystal Grain Size As described above, it was found that the product steel sheet has the optimum crystal grain size R (μm) for iron loss, and the relationship is expressed by the following equation. However, f is the excitation frequency (Hz).

(500 × f ^−1/3 −20) ≦ R ≦ (500 × f ^−1/3 +20) · That is, the optimum crystal grain size R is basically inversely proportional to the cube root of the excitation frequency f.

The coefficients of f in the equation 500 and -20 and +20
Is obtained from the experimental result.

An optimum iron loss can be obtained by controlling the crystal grain size R so as to satisfy the above formula. The reason for this is considered as follows.

Generally, the optimum crystal grain size is determined by the balance between the eddy current loss and the hysteresis loss. That is, as the crystal grain size increases, the area of the crystal grain boundary, which hinders the domain wall movement, decreases, so that the hysteresis loss decreases. It is considered that the optimum grain size decreases as the excitation frequency increases because the moving speed of the domain wall increases and the ratio of the eddy current loss to the iron loss increases as the frequency increases.

However, if the crystal grain size is (500 × f ^-1/3 +20)
If it exceeds, the magnetic domain width increases, and the moving speed of the domain wall also increases, so that the eddy current loss increases and exceeds the reduction amount of the hysteresis loss. As a result, total iron loss including eddy current loss and hysteresis loss increases.

On the other hand, when the crystal grain size is smaller than (500 × f ^−1/3 −20), the increase of the hysteresis loss exceeds the reduction of the eddy current loss, and the eddy current loss and the hysteresis loss are combined. Total iron loss increases.

(3) Manufacturing Method Next, the manufacturing process and conditions of the present invention will be described. The raw steel slab has the above composition. This is either melted in a converter, an electric furnace, etc., and if necessary melted steel that has been subjected to vacuum degassing, etc., made into a slab by continuous casting, or slab-rolled as an ingot. Good.

The slab is hot-rolled, but there is no particular restriction on the conditions.

However, it is preferable that the heating temperature is 1100 to
The temperature is 1250 ℃, and the finishing temperature is 700-950 ℃.

(A) Annealing of hot-rolled sheet Annealing of hot-rolled sheet is carried out if necessary according to the magnetic characteristics of the product. By recrystallizing the hot-rolled sheet by annealing the hot-rolled sheet, the iron loss in the rolling direction and the direction perpendicular thereto can be improved. This is because the hot-rolled sheet is recrystallized and grain-grown to form a texture oriented in {110} <001> during annealing after cold rolling.

The annealing can be performed by a box annealing method or a continuous annealing method, but the annealing temperature is set in the range of 650 to 1000 ° C. If the annealing temperature is less than 650 ° C, recrystallization of the hot rolled sheet does not proceed sufficiently and the effect of annealing cannot be obtained. On the other hand, if the temperature exceeds 1000 ° C., the crystal grains become too coarse and cracks are likely to occur during cold rolling.

In the case of box annealing, 650 to 900 ° C. is preferable, and in the case of continuous annealing, 750 to 1000 ° C. is preferable.

(B) Cold Rolling Cold rolling conditions are extremely important requirements in the present invention. In order to obtain a good iron loss, it is necessary to set the rolling reductions of the two cold rollings with the intermediate annealing to 40 to 80%.

[0050] The hot-rolled sheet as it is, or after the hot-rolled sheet is annealed, cold rolling is performed twice with intermediate annealing sandwiched, and the reduction ratios at this time are both optimized within the range of 40 to 80%. If not done, even if appropriate annealing described later is performed after the second cold rolling, the texture does not become advantageous for iron loss.

Cold rolling may be performed at room temperature, but warm rolling may be performed from the viewpoint of preventing cracking. The temperature for warm rolling is preferably 300 ° C or lower. This is because if the temperature exceeds 300 ° C, it becomes difficult to control the shape of rolling and the rolling oil becomes special.

The method and conditions of the intermediate annealing are not particularly limited, but either a box annealing method or a continuous annealing method is possible, and it is desirable that the temperature is soaked at 650 to 1000 ° C.

(C) Annealing after cold rolling In order to obtain the desired good iron loss in the product steel sheet, the steel sheet finished to a predetermined thickness by two cold rollings is annealed and recrystallized. And cause grain growth. The annealing method in this case may be either box annealing or continuous annealing, but the annealing conditions are selected so that the grain size after annealing satisfies the above formula. In this case, in the case of box annealing, it is desirable that the temperature is 650 to 950 ℃, the time is 10 minutes to 48 hours.
More desirable is 700-900 ℃, 30 minutes-
The range is 24 hours. In the case of continuous annealing, the temperature is 700 to 10
The temperature is 00 ° C., the time is 10 seconds to 5 minutes, more preferably 750 to 950 ° C., and the time is 30 seconds to 2 minutes, respectively.

[0054]

EXAMPLES Among the examples shown below, Examples 1 to 4 are non-oriented electrical steel sheets intended for small transformers and Examples 5 to 8 are intended for rotary machines.

Example 1 Seven kinds of test steels having the compositions shown in Table 1 were vacuum-melted in a high frequency furnace to obtain a 50 kg ingot.
These test steels are of high alloy composition except for G, which have almost the same electric resistance. Table 1 shows the electric resistance of the test steel.
C: 0.00 for all steel types except the three elements shown in Table 1.
30% or less, P: 0.015% or less, S: 0.0020% or less, N:
It was 0.0030% or less, and other elements were inevitable impurity levels.

Each ingot was heated to 1130 ° C. and then hot-rolled at a finishing temperature of 830 ° C. to obtain a hot-rolled sheet having a thickness of 2.3 mm.
Next, after soaking the hot-rolled sheet for 1 hour at 800 ℃,
The first cold rolling was performed to a thickness of 0.80 mm (reduction ratio: 65
%). Steel types C, D, E, F, and G were able to be rolled to the target plate thickness, but steel types A and B were cracked and could not be rolled. Therefore, for the steel types A and B, the test pieces were heated to 300 ° C. and warm-rolled to obtain the target plate thickness.

The first cold-rolled sheet was soaked and intermediately annealed at 880 ° C. for 1 minute, and then the steel types A and B were heated to 300 ° C.
Then, the steel types C, D, E, F, and G were each cold-rolled at room temperature for the second time and finished to a thickness of 0.35 mm (reduction ratio: 56%).

The second cold-rolled sheet was subjected to soaking annealing at 870 ° C. for 1 minute, and then punched to prepare an Epstein magnetism test piece (width 30 mm, length 280 mm: seam, half-split). However, the steel types A and B had cracks from the end faces and were cracked. Then, about the steel types A and B, it processed into the said magnetic measurement test piece by electrical discharge machining.

These magnetic measurement test pieces were subjected to strain relief annealing at 750 ° C. for 2 hours. After that, at excitation frequency 1 kHz
The iron loss was measured by the audio frequency iron loss test specified in JIS C2550, and the results shown in Table 1 were obtained.

The crystal grain size after annealing is 40 to 60 μm, and the optimum crystal grain size range at the excitation frequency of 1 kHz (30 to 70 μm)
It was inside. Table 1 also shows whether or not cracks occurred (x) and no (o) during cold rolling and punching of each steel type.

[0061]

[Table 1]

The steel grades C and D of the present invention show extremely good workability without cracking during cold rolling or punching, and have been known to have good iron loss. It can be seen that it is as good as steel type A corresponding to silicon steel. Further, the steel grade E having a higher Si than the steel grade of the present invention, the steel grade F having a lower Mn, and the same (Si + Al + 1 /
Steel type G with a low 2 · Mn) has good workability but poor iron loss.

(Example 2) A test steel having the composition shown in Table 2 was vacuum-melted in a high frequency furnace to obtain a 50 kg ingot. The contents other than the three elements shown in Table 2 are the same as in Example 1 in all steel types.
It was the same level as.

Each ingot was heated to 1100 ° C. and then hot-rolled at a finishing temperature of 810 ° C. to obtain a hot-rolled sheet having a thickness of 2.3 mm.
Next, after hot-rolled sheet annealing was carried out for 1 minute at the temperature shown in Table 2, the first cold rolling was performed under the rolling reduction and sheet thickness conditions shown in Table 2. However, test No. 1 is without hot-rolled sheet annealing.
Then, after an intermediate soaking for 1 hour at 770 ° C, a second cold rolling was performed at the rolling reduction shown in Table 2 to finish the thickness to 0.23 mm, and further annealing for 1 minute at 880 ° C. did.

After that, an Epstein test piece similar to that in Example 1 was sampled by punching, subjected to strain relief annealing at 770 ° C. for 5 minutes, and then iron loss was measured in the same manner as in Example 1.

Table 2 also shows the magnetic measurement results. The crystal grain size after annealing is 45 to 65 μm, and the excitation frequency is
It was within the range of the optimum crystal grain size (30 to 70 μm) at 1 kHz.

[0067]

[Table 2]

In Test Nos. 5 and 6 which are the methods of the present invention, it can be seen that there is no cracking in cold rolling or punching, that is, very good workability is exhibited and that iron loss is also good.

However, a test in which hot-rolled sheet annealing was not carried out
Test N with No. 1 and hot-rolled sheet annealing temperature lower than the range of the present invention
At o.2, iron loss is inferior. In test No. 8 in which the hot-rolled sheet annealing temperature was higher than the range of the present invention, cracking occurred during cold rolling, and subsequent experiments could not be performed.

In the test Nos. 3, 4, and 7 in which the first and second cold rolling reductions are higher or lower than the range of the present invention,
Iron loss is inferior even if both the chemical composition and the annealing conditions of the hot rolled sheet are within the scope of the present invention.

(Example 3) Si: 1.44%, Mn: in a high frequency furnace
1.84%, Al: 4.04% of the sample steel is vacuum-melted, 50kg
It was an ingot. The contents other than Si, Mn, and Al were at the same level as in Example 1 for all steel types.

Each ingot was heated to 1130 ° C. and then hot-rolled at a finishing temperature of 800 ° C. to obtain a hot-rolled sheet having a thickness of 2.5 mm.
Next, after soaking the hot rolled sheet for 1 hour at 780 ° C,
The first cold rolling was performed at room temperature to a thickness of 0.80 mm (reduction ratio: 68%).

Then, after carrying out an intermediate anneal of soaking at 750 ° C. for 1 hour, a second cold rolling was carried out at room temperature to finish to a thickness of 0.35 mm (reduction ratio: 56%). After that, the same Epstein test piece as in Example 1 was sampled, and then at 700 to 900 ° C.
Annealing was performed for soaking for minutes, and the crystal grain size and magnetism at an excitation frequency of 1 kHz were measured.

FIG. 1 shows the crystal grain size and iron loss (W
_{13 / 1k} ) and FIG. As shown in the figure, the crystal grain size is in the range of the optimum crystal grain size at the excitation frequency of 1 kHz (30
It can be seen that good iron loss can be obtained when the thickness is within 70 μm).

(Example 4) Si: 1.07%, Mn: in a high frequency furnace
1.28%, Al: 4.47% composition of the sample steel is vacuum melted, 50kg
It was an ingot. The contents other than Si, Mn, and Al were at the same level as in Example 1 for all steel types.

Each ingot was heated to 1150 ° C. and then hot-rolled at a finishing temperature of 840 ° C. to obtain a hot-rolled sheet having a thickness of 2.3 mm.
Next, after soaking the hot rolled sheet for 1 minute at 880 ° C,
The first cold rolling was performed at room temperature to a thickness of 0.70 mm (reduction ratio: 70%).

Then, after soaking intermediate anneal at 840 ° C. for 1 minute, a second cold rolling was performed at room temperature to finish to 0.35 mm thickness (reduction ratio: 50%). After that, the same Epstein test piece as in Example 1 was sampled, and then 30 minutes at 750 to 950 ° C.
Annealing for soaking for minutes, crystal grain size and excitation frequency 400Hz
The magnetic field was measured at.

FIG. 2 shows the crystal grain size and iron loss (W
_13/400 ). As shown in the figure, if the crystal grain size is within the optimum crystal grain size range (48 to 88 μm) at the excitation frequency of 400 Hz, good iron loss can be obtained.

Example 5 Seven kinds of test steels having the compositions shown in Table 3 were vacuum-melted in a high frequency furnace to obtain a 50 kg ingot.
These test steels have a high alloy composition having almost the same electric resistance except N. Table 3 shows the electric resistance of the test steel.
The contents other than the three elements shown in Table 3 were at the same level as in Example 1 in all steel types.

Each ingot was heated to 1170 ° C. and then hot-rolled at a finishing temperature of 800 ° C. to obtain a hot-rolled sheet having a thickness of 2.3 mm.
Next, the first cold rolling was performed to a thickness of 0.80 mm (reduction ratio: 65%).

Steel types J, K, L, M and N were able to be rolled to a target plate thickness, but steel types H and I were cracked and could not be rolled. Therefore, for steel types H and I, the test pieces were heated to 300 ° C and warm-rolled to obtain the target plate thickness (reduction ratio: 65
%).

After the first cold rolling sheet was subjected to soaking and intermediate annealing at 900 ° C. for 1 minute, the steel types H and I were 300 ° C.
With respect to the steel types J, K, L, M and N, the second cold rolling was performed at room temperature to finish the thickness to 0.35 mm (reduction ratio: 56%).

The second cold-rolled sheet was annealed at 850 ° C. for 1 minute to obtain a ring-shaped magnetic test piece (inner diameter 33 mm, outer diameter 45 mm) by punching. However, the steel types H and I had cracks from the end faces and cracked. Therefore, for the steel types H and I, the above magnetic measurement test pieces were processed by electrical discharge machining.

These magnetic measurement test pieces were subjected to strain relief annealing at 750 ° C. for 2 hours. Then, the iron loss was measured at an excitation frequency of 1 kHz and the results shown in Table 3 were obtained.

The crystal grain size after annealing is 40 to 60 μm, and the range of the optimum crystal grain size at the excitation frequency of 1 kHz (30 to 70 μm)
It was inside. Table 3 also shows whether or not cracks occurred (x) and no (o) during cold rolling and punching of each steel type.

[0086]

[Table 3]

The steel grades J and K of the present invention show extremely good workability without cracking during cold rolling or punching, and have been known to have good iron loss as well. It can be seen that it is as good as the steel type H corresponding to silicon steel. Further, a steel type L having a higher Si than the steel type of the present invention, a steel type M having a lower Mn, and a similar (Si + Al + 1 /
Steel type N with a low 2 · Mn) has good workability but poor iron loss.

Example 6 A sample steel having the composition shown in Table 4 was vacuum-melted in a high frequency furnace to obtain a 50 kg ingot. The contents other than the three elements shown in Table 4 are the same as in Example 1 in all steel types.
It was the same level as.

Each ingot was heated to 1150 ° C. and then hot-rolled at a finishing temperature of 810 ° C. to obtain a hot-rolled sheet having a thickness of 2.3 mm.
Next, the first cold rolling was performed under the rolling reduction and plate thickness conditions shown in Table 4. Then, after carrying out an intermediate annealing of soaking at 780 ° C. for 1 hour, by the second cold rolling at the rolling reduction shown in Table 4,
It was finished to have a thickness of 0.23 mm and further subjected to soaking annealing at 890 ° C for 1 minute.

Thereafter, a ring-shaped magnetic measurement test piece similar to that of Example 5 was sampled by punching, strain relief annealing was performed at 750 ° C. for 10 minutes, and then the iron loss was measured by the same method as in Example 5. . Table 4 also shows the magnetic measurement results.

The crystal grain size after annealing is 45 to 65 μm in all cases.
And the range of the optimum crystal grain size at the excitation frequency of 1 kHz (30
Within ~ 70 μm).

[0092]

[Table 4]

In Test Nos. 11 and 12 which are the methods of the present invention, it is understood that no cracking occurs in cold rolling or punching, that is, very good workability is exhibited, and that iron loss is also good. However, the first and second cold rolling reduction rates are
In Test Nos. 9, 10 and 13 which are higher or lower than the range of the present invention, the iron loss is inferior.

(Example 7) Si: 1.21%, Mn: in a high frequency furnace
1.24%, Al: 4.41% of the sample steel is vacuum-melted, 50kg
It was an ingot. The contents other than Si, Mn, and Al were the same as those in Example 1 for all steel types.

Each ingot was heated to 1150 ° C. and then hot-rolled at a finishing temperature of 810 ° C. to obtain a hot-rolled sheet having a thickness of 2.5 mm.
Next, the first cold rolling was performed at room temperature to a thickness of 0.80 mm (reduction ratio: 68%).

Then, after an intermediate annealing of soaking at 700 ° C. for 5 hours, a second cold rolling was performed at room temperature to finish the thickness to 0.35 mm (reduction ratio: 56%). After that, a ring-shaped magnetic measurement test piece similar to that of Example 5 was sampled by punching, and soaking was annealed at 700 to 1100 ° C. for 30 seconds to measure the crystal grain size and magnetism at an excitation frequency of 1 kHz. did.

FIG. 3 shows the crystal grain size and iron loss (W
_{13 / 1k} ) and FIG. As shown in the figure, the crystal grain size is in the range of the optimum crystal grain size at the excitation frequency of 1 kHz (30
It can be seen that good iron loss can be obtained when the thickness is within 70 μm).

(Example 8) Si: 1.03%, Mn: in a high frequency furnace
Vacuum-melted a sample steel with a composition of 1.33%, Al: 4.27%, 50kg
It was an ingot. The contents other than Si, Mn, and Al were at the same level as in Example 1 for all steel types.

Each ingot was heated to 1120 ° C. and then hot-rolled at a finishing temperature of 820 ° C. to obtain a hot-rolled sheet having a thickness of 2.3 mm.
Next, the first cold rolling was performed at room temperature to a thickness of 0.70 mm (reduction ratio: 70%).

Next, after soaking at 740 ° C. for 1 hour in an intermediate anneal, cold rolling was performed a second time at room temperature to finish the product to a thickness of 0.35 mm (reduction ratio: 50%). After that, a ring-shaped magnetic measurement test piece similar to that of Example 5 was sampled by punching, and soaking was annealed at 700 to 1100 ° C. for 30 seconds to measure the crystal grain size and the magnetism at an excitation frequency of 400 Hz. did.

FIG. 4 shows the crystal grain size and iron loss (W
_13/400 ). As shown in the figure, if the crystal grain size is within the optimum crystal grain size range (48 to 88 μm) at the excitation frequency of 400 Hz, good iron loss can be obtained.

[0102]

INDUSTRIAL APPLICABILITY The non-oriented electrical steel sheet of the present invention is excellent in cold workability and in the high frequency range, the average magnetic characteristics in the rolling direction and the direction perpendicular thereto, or the average magnetic characteristics in the entire thickness direction. The method for manufacturing the steel sheet and the method for punching the steel sheet do not require special equipment and conditions.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a relationship between crystal grain size and iron loss (W _{13 / 1k} ) in a non-oriented electrical steel sheet for a small transformer.

FIG. 2 is a diagram showing an example of a relationship between crystal grain size and iron loss (W _13/400 ).

FIG. 3 is a diagram showing an example of a relationship between a crystal grain size and a core loss (W _{13 / 1k} ) in a non-oriented electrical steel sheet for a rotating machine.

FIG. 4 is a diagram showing an example of a relationship between crystal grain size and iron loss (W _13/400 ).

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Claims (3)

[Claims] 1. By weight%, Si: less than 1.5%, Al: 2.5-6.
0% and Mn: 1.0 to 3.0%, satisfying the following formula, the balance consisting essentially of Fe and inevitable impurities, and having a crystal grain size R (μm) satisfying the following formula: Grain-oriented electrical steel sheet. [Si (%) + Al (%) + 1/2 ・ Mn (%)] ≧ 5.5% ・ ・ ・ ・ ・ (500 × f ^-1/3 -20) ≤ R ≤ (500 × f ^-1/3 +20) ... However, f represents the excitation frequency (Hz). 2. Si: less than 1.5% by weight, Al: 2.5-6.
A steel slab containing 0% and Mn: 1.0 to 3.0% and satisfying the following formula, and the balance consisting essentially of Fe and unavoidable impurities, is hot-rolled, and then cold-rolled twice with intermediate annealing. The first and second reductions are both 40 to 80%, and after finishing the product sheet thickness, annealing is performed, and the crystal grain size R (μm) is in the range that satisfies the following formula. Steel plate manufacturing method. [Si (%) + Al (%) + 1/2 ・ Mn (%)] ≧ 5.5% ・ ・ ・ ・ ・ (500 × f ^-1/3 -20) ≤ R ≤ (500 × f ^-1/3 +20) ... However, f represents the excitation frequency (Hz). 3. By weight%, Si: less than 1.5%, Al: 2.5-6.
After hot rolling a steel slab containing 0% and Mn: 1.0 to 3.0% and satisfying the following formula, and the balance consisting essentially of Fe and unavoidable impurities, hot-rolled sheet annealing is performed at 650 to 1000 ° C. After being applied, the cold rolling is performed twice with intermediate annealing sandwiched between the first and second reductions of 40 to 80% to finish the product sheet thickness and then annealed. The crystal grain size R (μm) is as follows. A method for producing a non-oriented electrical steel sheet having a low iron loss within a range satisfying the formula. [Si (%) + Al (%) + 1/2 ・ Mn (%)] ≧ 5.5% ・ ・ ・ ・ ・ (500 × f ^-1/3 -20) ≤ R ≤ (500 × f ^-1/3 +20) ... However, f represents the excitation frequency (Hz).