JP2861787B2 - Non-oriented electrical steel sheet with low iron loss and method of manufacturing the same - Google Patents

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 widely used as an iron core of electric equipment, and more particularly to a non-oriented electrical steel sheet suitable for a rotating machine and a small transformer 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 In recent years, there has been an increase in the use of high-frequency electrical equipment for high efficiency and miniaturization, and there has been an increasing demand for electrical steel sheets having low iron loss in high-frequency areas. ing.

[0003] In general, iron loss can be expressed as the sum of a hysteresis loss proportional to the first power of frequency and an eddy current loss proportional to the square of frequency. Therefore, in the high frequency range, the ratio of the eddy current loss, which is proportional to the square of the frequency, to the iron loss increases, and reduction of the eddy current is extremely important for reducing the iron loss. It is known that in order to reduce the eddy current, it is effective to reduce the plate thickness and increase the electric resistance. In other words, the increase in the electromagnetic resistance of the steel sheet due to the reduction in thickness and the addition of alloy elements is a great guideline for the development of high-frequency electromagnetic steel sheets.

Japanese Patent Application Laid-Open No. 62-103321 discloses a method for producing a high silicon steel sheet containing about 6.5% of Si.
When Si is added to iron, the magnetostriction becomes almost zero at an addition amount of about 6.5%, so that the hysteresis loss is significantly reduced. Also, high Si addition is advantageous in reducing eddy current loss since the electrical resistance increases. Therefore, the high-silicon steel sheet of about 6.5% Si can reduce both the iron loss factors of hysteresis loss and eddy current loss at the same time, and has a better iron loss than other high alloy steels having the same electric 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, special equipment and conditions are required to process the iron core on the user side of the steel sheet. Will be very limited.

[0006] JP-A-62-196354 and JP-A-62-196354
Japanese Patent Publication No. 196358 discloses that Si contains 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 not less than 20.0% contains one or more selected from two or more.

[0007] In the steel sheets of these inventions as well, when about 6.5% of Si 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. In these inventions, the molten metal quenching method is considered to be the main production method, and the thickness is limited to a very thin plate having a thickness of 0.30 mm or less. For this reason, the use is inevitably limited.

[0008]

SUMMARY OF THE INVENTION The present invention eliminates the limitations on the thickness of the conventional manufacturing method as described above and the limitations on the use thereof, and furthermore, the cold workability, punching workability and magnetic properties of the product steel sheet. This was done to improve the characteristics.

An object of the present invention is to reduce iron loss in a high-frequency range and to have excellent average magnetic properties in the entire circumferential direction of the sheet thickness or average magnetic properties in a direction perpendicular to the rolling direction, and furthermore, to a core such as punching and cutting. To provide a non-oriented electrical steel sheet that is easy to process, and a method of manufacturing them using a general hot rolling and cold rolling process that can easily produce products of various thicknesses. is there.

[0010]

The gist of the present invention is as follows.
(1) Non-oriented electrical steel sheets and (2) and (3).

(1) By weight%, Si: less than 1.5%, Al: 2.5%
-6.0% and Mn: 1.0-3.0%, and satisfy the following formula, and the balance substantially consists of Fe and unavoidable impurities, and the crystal grain size R (μm) has a low iron loss satisfying the following formula. 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) After hot rolling a steel slab which substantially satisfies the chemical composition and formula described in the above (1), and the remainder substantially consists of Fe and unavoidable impurities, two cold working steps including intermediate annealing are performed. The first and second rollings are finished to a product thickness with both the rolling reductions of 40 to 80%, and then annealed to make the crystal grain size R (μm) satisfy the above formula. Manufacturing method of electrical steel sheet.

(3) After hot rolling a steel slab which satisfies the chemical composition and formula described in the above (1) and the remainder substantially consists of Fe and unavoidable impurities, it is annealed at 650 to 1000 ° C. , And the first time of two cold rollings sandwiching intermediate annealing,
A method for producing a non-oriented electrical steel sheet having a low iron loss and a crystal grain size R (μm) in a range satisfying the above formula, after finishing the product sheet thickness with both reduction ratios being both 40 to 80%. .

The method (2) is intended for a non-oriented electrical steel sheet for a rotating machine iron core, and it is important that the average magnetic properties in all thickness directions are excellent. The evaluation of the magnetic properties is performed using a ring test piece. (3) above
Is intended for small transformer cores (EI cores), and it is important that the average magnetic properties in the rolling direction and the direction perpendicular to the rolling direction are important. Perform using

[0016]

[Function] As described above, the high silicon content steel of about 6.5% Si
Although 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 a punching process.

The present inventors have studied in detail a 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 with iron cores. did. As a result, the following findings were found.

In a steel sheet whose electric resistance has been increased by adding a proper amount of Si, Mn, and Al, a good iron loss equivalent to that of a steel sheet whose electric resistance has been increased by adding about 6.5% of Si alone can be obtained. .

Furthermore, the punching workability is superior to the case where only Si is added.

By controlling the crystal grain size to be optimal according to the excitation frequency used, good iron loss can be obtained.

By recrystallizing the steel sheet by hot-rolled sheet annealing, it is possible to improve the average iron loss in the direction perpendicular to the rolling direction. In this case, the non-oriented electrical steel sheet is suitable for a small transformer core.

Cold rolling is performed twice with intermediate annealing therebetween.
In any rolling, setting the rolling reduction 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 material steel, the crystal grain size of the product magnetic steel sheet and the manufacturing method are limited as described above will be described. % Means% by weight.

(1) Chemical composition of the product electrical steel sheet or its material steel: Si: less than 1.5% As the content of Si increases, the electrical resistance of the steel sheet increases and the eddy current loss decreases, resulting in a reduction in iron loss. It has the effect of reducing. However, when the Si content is 1.5% or more, cracks tend to occur during cold rolling and punching. Therefore, the Si content is set to less than 1.5%. Desirable lower limit is 0.1
%.

Mn: 1.0 to 3.0% Mn is effective in increasing the electric resistance of the steel sheet, similarly to Si, and aggressive addition is effective from the viewpoint of reducing iron loss.
In addition, by adding the Al together with an appropriate amount of Al, extremely good iron loss can be obtained in a high frequency range.
In order to obtain these effects, it is necessary to contain 1.0% or more. On the other hand, if the content exceeds 3.0%, the strength becomes too high to make cold rolling difficult. Therefore, the upper limit is set to 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 an electrical steel sheet having excellent average properties in the entire thickness direction in the high frequency range.

One of the reasons why the addition of Al improves the average iron loss in the entire thickness direction is considered to be due to the formation of a texture containing a large number of {100} planes. Al content
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. If it is less than 2.5%, the electric resistance is too low and the iron loss in a high frequency range cannot be reduced.

However, the fact that the combined addition of Mn and Al is extremely effective in improving iron loss cannot be explained solely from the above two reasons, and it is necessary to consider the influence of the magnetic domain structure on the eddy current loss. That is, it is considered that the addition of these two elements in appropriate amounts may cause a magnetic domain structure advantageous for eddy current loss in a high frequency range.

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 set to 6.0%.

Si + Al + 1/2 · Mn: 5.5% or more When Si, Al and Mn are added, the electric resistance of the steel sheet is increased as described above, so that an extremely good iron loss can be obtained in a 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 a high frequency range.
The reason why the coefficient of Mn is 1/2 is that the effect of Mn on the increase in electric 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 has an adverse effect on iron loss, so is preferably not more than 0.010%, more preferably not more than 0.005%. This is because C remaining in the product stage generates carbides, which hinders domain wall movement and increases iron loss.

[0032] S combines with Mn to form MnS, which, like carbides, hinders domain wall movement and causes iron loss. Therefore, the iron loss is improved as the S content is lower,
It is desirable that the content be 6% or less, more specifically 0.003% or less.

Since P makes the steel sheet brittle, it is desirable that the content be 0.020% or less.

Since N combines with Al to form AlN and hinders the movement of the domain wall, it is necessary to lower N.
It is desirable to make the following.

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

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

The coefficient of f in the expression 500 and -20 and +20
Is obtained from the experimental results.

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

In general, the optimum crystal grain size is determined by a balance between eddy current loss and hysteresis loss. That is, as the crystal grain size increases, the area of the crystal grain boundary that hinders the domain wall movement decreases, so that the hysteresis loss decreases. It is considered that the reason why the optimum grain size decreases as the excitation frequency increases is that the moving speed of the domain wall increases with an increase in the frequency, and the ratio of eddy current loss to iron loss increases.

However, the crystal grain size is (500 × f ^−1/3 +20)
When the value exceeds 大 き く, 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 of the hysteresis loss. As a result, the total iron loss including the eddy current loss and the hysteresis loss increases.

On the other hand, when the crystal grain size is smaller than (500 × f ^−1/3 −20), the increase in the hysteresis loss exceeds the reduction in 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 steps and conditions of the present invention will be described. The raw steel slab has the above composition. This can be done either by converting molten steel that has been melted in a converter or electric furnace and then subjected to treatment such as vacuum degassing, if necessary, to a slab by continuous casting, or to ingot and slab rolling. Good.

The slab is subjected to hot rolling, but the conditions are not particularly limited.

However, it is desirable that the heating temperature be 1100 to
1250 ° C, 700-950 ° C at finishing temperature.

(A) Annealing of hot rolled sheet Annealing of hot rolled sheet is performed as necessary according to the magnetic properties of the product. By recrystallizing the hot-rolled sheet by hot-rolled sheet annealing, it is possible to particularly improve iron loss in the direction perpendicular to the rolling direction. This is because the hot-rolled sheet undergoes recrystallization and grain growth to have a {110} <001> -oriented texture during annealing after cold rolling.

Annealing can be performed by a box annealing method or a continuous annealing method, but the annealing temperature is in the range of 650 to 1000 ° C. If the annealing temperature is lower than 650 ° C., recrystallization of the hot-rolled sheet does not sufficiently proceed, 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 tend 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 a very important requirement in the present invention. In order to obtain a good iron loss, it is necessary to set both the rolling reductions of the two cold rollings including the intermediate annealing to 40 to 80%.

The hot-rolled sheet as it is or after the hot-rolled sheet annealing is performed, the cold rolling is performed twice with the intermediate annealing therebetween, and the rolling reduction at this time is optimized within the range of 40 to 80%. If not, even after performing the appropriate annealing described later after the second cold rolling, a texture advantageous to iron loss will not be obtained.

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

The method and conditions of the intermediate annealing are not particularly limited, but any of a box annealing method and a continuous annealing method can be used, and the temperature is desirably soaked at 650 to 1000 ° C.

(C) Annealing after Cold Rolling In order to obtain a 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 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 crystal grain size after annealing satisfies the above equation. Desirable conditions at this time are, in the case of box annealing, a temperature range of 650 to 950 ° C., a time range of 10 minutes to 48 hours,
More preferably, respectively, 700-900 ℃, 30 minutes ~
24 hours range. For continuous annealing, the temperature is 700 to 10
The temperature is in the range of 10 seconds to 5 minutes at 00 ° C, more preferably in the range of 750 to 950 ° C and 30 seconds to 2 minutes, respectively.

[0054]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Among the examples shown below, Examples 1-4 are non-oriented electrical steel sheets for small transformers and Examples 5-8 are 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 50 kg ingots.
These test steels have a high alloy composition except for G and have almost the same electric resistance. Table 1 shows the electrical resistance of the test steels.
Except for the three elements shown in Table 1, in all steel types C: 0.00
30% or less, P: 0.015% or less, S: 0.0020% or less, N:
It was 0.0030% or less, and the other elements were also at unavoidable impurity levels.

After each ingot was heated to 1130 ° C., it was hot-rolled at a finishing temperature of 830 ° C. to form a 2.3 mm thick hot rolled sheet.
Next, after hot-rolled sheet annealing at 800 ° C for 1 hour,
The first cold rolling was performed to a thickness of 0.80 mm (rolling reduction: 65
%). Steel types C, D, E, F and G could be rolled to the target plate thickness, but steel types A and B could not be rolled due to cracking. Therefore, for the steel types A and B, the test pieces were heated to 300 ° C. and subjected to warm rolling to obtain the target sheet thickness.

After the first cold-rolled plate was subjected to intermediate annealing at 880 ° C. for 1 minute, the steel types A and B were heated to 300 ° C.
Then, each of the steel types C, D, E, F and G was subjected to the second cold rolling at room temperature to finish to a thickness of 0.35 mm (reduction rate: 56%).

After the second cold-rolled sheet was annealed at 870 ° C. for 1 minute with uniform heat, a test piece (30 mm width, 280 mm length: seam, half width) was prepared by punching. However, steel types A and B were cracked from the end faces. Therefore, steel types A and B were processed into the above-described magnetic measurement test pieces by electric discharge machining.

These magnetic test pieces were subjected to strain relief annealing at 750 ° C. for 2 hours. Then, at an excitation frequency of 1 kHz
Iron loss was measured by an audio 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 range of the optimum crystal grain size at an excitation frequency of 1 kHz (30 to 70 μm)
Was within. Table 1 also shows whether or not cracking occurred (×) or not (○) in cold rolling and punching of each steel type.

[0061]

[Table 1]

[0062] The steel types C and D of the present invention exhibit extremely good workability without cracking during cold rolling and punching, and have high iron loss, which is conventionally known to be good. It can be seen that it is as good as steel type A corresponding to silicon steel. Further, steel type E having a higher Si than the steel type of the present invention, steel type F having a lower Mn, and (Si + Al + 1 /
Steel type G with low 2 · Mn) has good workability but inferior 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 those in Example 1 for all steel types.
Was at a similar level.

After each ingot was heated to 1100 ° C., it was hot-rolled at a finishing temperature of 810 ° C. to form a hot-rolled sheet having a thickness of 2.3 mm.
Next, after performing a hot-rolled sheet annealing at a temperature shown in Table 2 for 1 minute, a first cold rolling was performed under the conditions of the rolling reduction and the sheet thickness shown in Table 2. However, in test No. 1, no hot-rolled sheet annealing was performed.
Next, after performing an intermediate annealing at 770 ° C. for 1 hour, a second cold rolling was performed at a rolling reduction shown in Table 2 to obtain a thickness of 0.23 mm, and further annealing at 880 ° C. for 1 minute. did.

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

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

[0067]

[Table 2]

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

However, a test in which hot-rolled sheet annealing was not performed
No.1 and test N where the hot-rolled sheet annealing temperature was lower than the range of the present invention
In 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, cracks occurred during cold rolling, and subsequent experiments could not be performed.

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

(Example 3) Si: 1.44%, Mn:
1.84%, Al: 4.04% composition steel, vacuum melted, 50kg
Ingot. The contents other than Si, Mn and Al were at the same level as in Example 1 in all steel types.

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

Then, after performing an intermediate annealing at 750 ° C. for 1 hour, a second cold rolling was performed at room temperature to finish to a thickness of 0.35 mm (reduction rate: 56%). After that, the same Epstein test piece as in Example 1 was collected, and then at 700 to 900 ° C. for 30 minutes.
The soaking was performed for 1 minute, and the crystal grain size and the magnetism at an excitation frequency of 1 kHz were measured.

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

Example 4 In a high frequency furnace, Si: 1.07%, Mn:
1.28%, Al: 4.47% composition steel is vacuum melted and 50kg
Ingot. The contents other than Si, Mn and Al were at the same level as in Example 1 in all steel types.

After each ingot was heated to 1150 ° C., it was hot-rolled at a finishing temperature of 840 ° C. to form a 2.3 mm thick hot rolled sheet.
Next, after hot-rolled sheet annealing at 880 ° C for 1 minute,
The first cold rolling was performed at room temperature to reduce the thickness to 0.70 mm (reduction rate: 70%).

Then, after performing an intermediate annealing at 840 ° C. for 1 minute soaking, a second cold rolling was performed at room temperature to finish to a thickness of 0.35 mm (rolling reduction: 50%). After that, the same Epstein test piece as in Example 1 was collected,
Annealing for 400 minutes, crystal grain size and excitation frequency 400Hz
Of the magnetism was measured.

FIG. 2 shows the crystal grain size and the iron loss (W
_13/400 ). As shown in the figure, when the crystal grain size is within the range of the optimum crystal grain size (48 to 88 μm) at the excitation frequency of 400 Hz, it is understood that 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 50 kg ingots.
These test steels have a high alloy composition having almost the same electric resistance except N. Table 3 shows the electrical 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.

After each ingot was heated to 1170 ° C., it was hot-rolled at a finishing temperature of 800 ° C. to form a 2.3 mm thick hot rolled sheet.
Next, the first cold rolling was performed to reduce the thickness to 0.80 mm (reduction ratio: 65%).

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

After the first cold-rolled sheet was subjected to soaking at 900 ° C. for 1 minute, the steel types H and I were heated to 300 ° C.
Then, the steel types J, K, L, M, and N were each subjected to the second cold rolling at room temperature to finish to a thickness of 0.35 mm (a reduction ratio: 56%).

After the second cold-rolled sheet was annealed at 850 ° C. for 1 minute soak, a ring-shaped magnetic measurement specimen (inner diameter 33 mm, outer diameter 45 mm) was prepared by punching. However, steel types H and I were cracked from the end faces and cracked. Therefore, steel types H and I were processed into the above-described magnetic measurement test pieces by electric discharge machining.

These magnetic test pieces were subjected to strain relief annealing at 750 ° C. for 2 hours. Thereafter, 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 an excitation frequency of 1 kHz (30 to 70 μm)
Was within. Table 3 also shows the occurrence of cracks (×) and no (○) in each steel type during cold rolling and punching.

[0086]

[Table 3]

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

Example 6 A test 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 those in Example 1 for all steel types.
Was at a similar level.

After each ingot was heated to 1150 ° C., a hot-rolled sheet having a thickness of 2.3 mm was formed by hot rolling at a finishing temperature of 810 ° C.
Next, the first cold rolling was performed under the conditions of the rolling reduction and the sheet thickness shown in Table 4. Next, after performing an intermediate annealing at 780 ° C. for 1 hour soaking, a second cold rolling was performed at a rolling reduction shown in Table 4.
It was finished to a thickness of 0.23 mm and further annealed at 890 ° C. for 1 minute.

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

The crystal grain size after annealing was 45 to 65 μm.
And the optimal crystal grain size range at the excitation frequency of 1 kHz (30
7070 μm).

[0092]

[Table 4]

In Tests Nos. 11 and 12, which are the methods of the present invention, it can be seen that there is no occurrence of cracks in cold rolling or punching, extremely good workability, and good iron loss. However, the first and second cold rolling reduction rates are:
In Test Nos. 9, 10, and 13 higher or lower than the range of the present invention, iron loss is inferior.

(Example 7) Si: 1.21%, Mn:
1.24%, Al: 4.41% of test steel is vacuum melted and 50kg
Ingot. The contents other than Si, Mn and Al were at the same content levels as in Example 1 in all steel types.

After each ingot was heated to 1150 ° C., a hot-rolled sheet having a thickness of 2.5 mm was formed by hot rolling at a finishing temperature of 810 ° C.
Next, the first cold rolling was performed at room temperature to reduce the thickness to 0.80 mm (reduction rate: 68%).

Next, after performing an intermediate annealing at 700 ° C. for 5 hours soaking, a second cold rolling was performed at room temperature to finish to a thickness of 0.35 mm (rolling reduction: 56%). Then, the same ring-shaped magnetism test specimen as in Example 5 was sampled by punching, and then annealed at 700-1100 ° 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 the iron loss (W
_{13 / 1k} ). As shown in the figure, 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 if the thickness is within 70 μm).

Example 8 In a high frequency furnace, Si: 1.03%, Mn:
Sample steel of 1.33%, Al: 4.27% composition is vacuum melted and 50kg
Ingot. The contents other than Si, Mn and Al were at the same level as in Example 1 in all steel types.

After each ingot was heated to 1120 ° C., it was hot-rolled at a finishing temperature of 820 ° C. to form a hot-rolled sheet having a thickness of 2.3 mm.
Next, the first cold rolling was performed at room temperature to reduce the thickness to 0.70 mm (reduction rate: 70%).

Next, after performing an intermediate annealing at 740 ° C. for 1 hour soaking, a second cold rolling was performed at room temperature to finish to a thickness of 0.35 mm (rolling reduction: 50%). Then, the same ring-shaped magnetism test specimen as in Example 5 was sampled by punching, and then annealed at 700-1100 ° C. for 30 seconds to measure the crystal grain size and magnetism at an excitation frequency of 400 Hz. did.

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

[0102]

The non-oriented electrical steel sheet of the present invention is excellent in cold workability and average magnetic properties in the high frequency range in the direction perpendicular to the rolling direction and in the direction perpendicular to the rolling direction or in the entire thickness direction. No special equipment and conditions are required for the method of manufacturing the steel sheet and the method of punching the steel sheet.

[Brief description of the drawings]

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

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

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

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

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-223445 (JP, A) JP-A-4-341539 (JP, A) JP-A-4-224624 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) C22C 38/00-38/60 C21D 8 / 12,9 / 46 501 H01F 1/16

Claims (3)

(57) [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 being substantially composed of Fe and unavoidable impurities, and having a low iron loss having a crystal grain size R (μm) satisfying the following formula. Grain-oriented electrical steel sheets. [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) By weight%, Si: less than 1.5%, Al: 2.5-6.
0% and Mn: 1.0 to 3.0%, and the following formula is satisfied, and the rest is substantially cold-rolled twice by hot rolling a steel slab consisting essentially of Fe and unavoidable impurities, followed by intermediate annealing. In the first and second times, the reduction rate is 40 to 80% for both products, and the product is finished to a thickness, annealing is performed, and the crystal grain size R (μm) falls within a range satisfying 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) where f represents the excitation frequency (Hz). (3) By weight%, Si: less than 1.5%, Al: 2.5-6.
0% and Mn: 1.0 to 3.0%, and the following formula is satisfied. The remainder is substantially hot-rolled from a steel slab substantially composed of Fe and unavoidable impurities. After the first and second cold rolling with intermediate annealing, the first and second rolling reductions are both 40-80% and finished to product thickness, and then annealing is performed. 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) where f represents the excitation frequency (Hz).