JPH09228006A - Nonoriented silicon steel sheet excellent in magnetic property and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a nonoriented silicon steel sheet low in the content of Si and excellent in magnetic properties and to provide a method for producing the same. SOLUTION: This nonoriented silicon steel sheet excellent in magnetic properties has a compsn. contg. <=0.01% C, 0.01 to 1.0% Si, 0.01 to 1.0% Mn, <=0.15% P, <=0.035% S, 0.008 to 0.02% tot.O (total oxygen in the steel) and <0.002% sol.Al, also satisfying Mn/S>=10, in which the compositional weight ratios of three kinds of oxide inclusions of MnO, SiO2 and Al2 O3 present in the steel are regulated to MnO/SiO2 <=0.43, 0.1<=Al2 O3 /SiO2 <=1.0 and SiO2 /(SiO2 +MnO+Al2 O3 )<0.75, and the balance Fe with inevitable impurities. As for the method for producing the same, the content of C in molten steel is regulated to <=0.01% and O (oxygen) to <=0.02% by vacuum treatment, thereafter, Al is added thereto in the range so as to regulated the content of sol.Al to <0.002% to deoxidize the same, and next, Si and Mn are added thereto to regulate into required compsns., by which the chemical compsn. of the steel and oxide inclusions in the steel are regulated.

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 excellent magnetic properties, which is widely used as an iron core of electric equipment, and a method for producing the same. For non-oriented electrical steel sheets, the steel sheet manufacturer performs finish annealing after cold rolling, and the user side does not particularly anneal the full process material used for the iron core and the user side punches. There is a semi-processed material manufactured on the premise that it is annealed after working, but the present invention is applied to any of these cases.

[0002]

2. Description of the Related Art Magnetic steel sheets used for iron cores of electric appliances include non-oriented electrical steel sheets and grain-oriented electrical steel sheets, which are non-oriented as compared with grain-oriented electrical steel sheets mainly used for power transformers. Magnetic electrical steel sheets are widely used in general-purpose motors, small motors and small transformers. Some electric devices, such as generators, convert rotational energy into electrical energy, and devices such as transformers change into a form that is easy to use by raising or lowering the voltage, or motors that rotate electrical energy. There are other things that can be converted into mechanical energy. In equipment that performs such energy conversion, it is necessary to suppress wasteful loss of energy such as heat generation as low as possible, and the iron core used for it has low loss and high efficiency, that is, low iron loss and high magnetic flux density. Required.

Iron loss of electromagnetic steel sheets is divided into eddy current loss and hysteresis loss. Since the eddy current loss decreases as the electric resistance increases, in order to obtain a non-oriented electrical steel sheet with low iron loss, Si is usually contained in a large amount, which has the effect of increasing the electric resistance. However, the addition of Si tends to lower the magnetic flux density, and the addition of Si not only raises the cost, but also causes problems such as hardening the steel and increasing the deformation resistance of rolling.

On the other hand, in the case of a non-oriented electrical steel sheet, the hysteresis loss decreases as the crystal grain size of the steel sheet increases if the chemical composition such as Si is the same. However, the eddy current loss tends to increase as the crystal grain size increases, and thus it is said that there is an optimum crystal grain size at which the iron loss becomes the minimum value. However, the optimum grain size is considerably larger than the recrystallized grain size obtained by annealing after cold rolling of several tens% or more in general, and in order to reduce iron loss, the grain size after annealing is reduced. Various measures are usually taken to make the diameter as large as possible.

In a non-oriented electrical steel sheet having a low Si content level, in order to make crystal grain growth during annealing as easy as possible, fine precipitates that inhibit grain growth can be reduced. For example, in the invention disclosed in JP-A-63-195217,
l.Al is limited to 0.001 to 0.005% (weight%: "weight" is omitted hereinafter) to reduce the amount of fine AlN produced,
On the contrary, as in the invention of JP-A-61-119652, Al is replaced by 0.15
It is known to increase the content of AlN precipitates to about 0.60% to coarsen AlN precipitates and reduce the effect. Also, S is M
Since it becomes a precipitate such as nS and hinders grain growth, it is generally kept as low as possible.

In addition to such fine precipitates of nitrides and sulfides, oxide-based inclusions are known to inhibit the growth of crystal grains. For example, in the above-mentioned JP-A-63-195217, C: 0.015% or less, Si: 0.1-1.0%, sol.
Al: 0.001 to 0.005%, Mn: 1.5% or less, S: 0.0
In a non-oriented electrical steel sheet containing 08% or less, N: 0.0050% or less, tot.O (total oxygen in steel): 0.02% or less, three kinds of interposition of SiO ₂ , MnO, and Al ₂ O ₃ in the steel. If the ratio of the weight of MnO to the total weight of the product is 15% or less,
The invention proposes that the low melting point inclusions that hinder the crystal grain growth are eliminated, the average grain size after annealing increases, and the magnetic properties improve. Also, the inclusions S in the steel have exactly the same chemical composition except that sol.Al is 0.0005 or more and less than 0.0010%.
M based on the total weight of three kinds of iO ₂ , MnO, and Al ₂ O ₃
The weight ratio of nO is 15% or less, and the weight ratio of SiO ₂ is
The invention of an electrical steel sheet in which the grain growth property is improved to 75% or more and which is similar to the above is also disclosed in JP-A-7-150248.

The reason why the oxide-based inclusions inhibit the growth of crystal grains is that in the above invention, when the weight ratio of MnO exceeds 15% and the weight ratio of SiO ₂ becomes less than 75%, This is because the softening point is lowered and the inclusions are stretched during rolling, which hinders the crystal grain growth during annealing. If the composition ratio of oxide inclusions in the steel is changed, the inclusions become spherical, and if so, the effect of suppressing crystal grain growth is small, so grain growth is said to be improved. However, as a method for reducing the weight ratio of MnO to 15% or less,
In these inventions, a large amount of Fe-
A Mn alloy is added to enhance the deoxidation of molten steel by Mn. In such a non-oriented electrical steel sheet having a low Si content and containing almost no other alloying elements, it is strongly desired to make the cost as low as possible, but MnO is generated due to deoxidation and a large amount is produced. Consuming Mn of causes an increase in cost. Further, if the ratio of SiO ₂ inclusions is increased to 75% or more, nozzle clogging during continuous casting is likely to occur, which deteriorates the punching workability for converting the steel sheet into the iron core of electrical equipment, and further It is easy to cause defects.

[0008]

SUMMARY OF THE INVENTION The present invention focuses on the fact that the morphology of oxide inclusions in steel affects the improvement of magnetic properties, and by changing the composition ratio, not only the magnetic properties but also the magnetic properties are improved. It is an object of the present invention to provide a non-oriented electrical steel sheet having a low Si content, which is improved in the manufacturing cost, appearance, and punching workability, and a manufacturing method thereof.

[0009]

DISCLOSURE OF THE INVENTION The inventors of the present invention are directed to a pure iron-based non-oriented electrical steel sheet containing Si of 1.0% or less and Mn of 1.0% or less, which is manufactured by a method of extremely reducing carbon in a molten steel stage. , We found that the magnetic composition often had inferior magnetic properties even though there was no abnormality in the chemical composition, and we investigated the cause and countermeasures. First, samples having greatly different magnetic properties were extracted from steel sheets manufactured under almost the same composition and under the same manufacturing conditions, and the metallographic structure and manufacturing process conditions were investigated in detail. As a result, the samples with poor magnetic properties showed poor crystal grain growth. Further investigation further suggested that the cause was that the dispersed state of oxide inclusions hinders the crystal grain growth. That is, the low-melting-point oxide spread by hot rolling is finely crushed by cold rolling and dispersed in a point sequence, which hinders the grain boundary migration during annealing and inhibits the growth of crystal grains. . As a result of investigating the composition of these oxide-based inclusions, it was found that the MnO ratio tends to be high when the grain growth is extremely inhibited.

Then, the conditions for vacuum treatment of molten steel, which is mainly used for decarburization, and the method of adding a deoxidizing agent are changed, and the composition of these oxide-based inclusions is changed with particular intention to obtain various steels. The effects of inclusions on the magnetic properties were investigated by melting, rolling, annealing, etc.

In this case, although the oxide-based inclusions are intended to be rendered harmless by changing their composition, the smaller the total amount, the better the magnetic properties and the crystal grain growth property. O should be as low as possible. Normal,
Al, which is added for the purpose of deoxidizing, changes the form of oxides in steel, but cannot decrease tot.O.
When sol.Al comes to exist, fine AlN is deposited and hinders crystal grain growth. Therefore, since decarburization in vacuum treatment is also a powerful deoxidizing method, detoxification of molten steel by utilizing decarburizing reaction in vacuum is performed as much as possible to reduce tot.O, and then sol.Al. Is 0.0
Al was added so as not to exceed 02% to perform complementary deoxidation, and then Si, Mn, etc. were added to adjust to a desired chemical composition.

As a result, the ratio of the weight of SiO _{2 to} the total weight of three kinds of SiO ₂ , MnO and Al ₂ O ₃ is set to 75% or more as in the invention of Japanese Patent Application Laid-Open No. 7-150248 mentioned above. , It was clarified that the magnetic properties were further improved when it was made less than 75%. In addition, the above-mentioned
In the invention of 63-195217, since the ratio of the amount of MnO decreases, Mn is added before the vacuum treatment at the time of tapping the converter to perform deoxidation. On the other hand, if deoxidation is performed as much as possible by vacuum treatment that does not produce deoxidation products in steel, the amount of oxide-based non-metallic inclusions in the steel is significantly reduced, but the composition of inclusions changes with it. Therefore, it is considered that the magnetic properties became more suitable and the improvement effect became larger.

Based on the above knowledge, not only the magnetic properties but also the influence on the occurrence of surface flaws and punchability, and the workability during manufacturing are investigated, and the limit of the composition of the preferable oxide inclusions is investigated. The present invention has been completed by clarifying the above and considering the conditions during manufacturing. The gist of the present invention is as follows.

(1) C: ≦ 0.01% by weight, Si: 0.01
~ 1.0%, Mn: 0.01 ~ 1.0%, P: ≤ 0.15%, S: ≤
0.035%, tot.O (total oxygen in steel): 0.008-0.02%,
sol.Al: <0.002% and Mn (%) / S (%) ≧
10, the composition weight of three oxide inclusions of MnO, SiO ₂ and Al ₂ O ₃ which are present in the steel (hereinafter, such composition ratio (%) is omitted). The ratio is MnO / SiO ₂ ≦ 0.43 ······ 0.1 ≦ Al ₂ O ₃ / SiO ₂ ≦ 1.0 ・ ・ ・SiO ₂ / (SiO ₂ + MnO + Al ₂ O ₃ ) <0.75, and the balance being Fe and unavoidable impurities, which is a non-oriented electrical steel sheet with excellent magnetic properties.

(2) After adjusting C in molten steel to 0.01% or less and O (oxygen) to 0.02% or less by vacuum treatment, sol.
Controlling the chemical composition of steel and oxide-based inclusions in steel by adding Al in a range of less than 0.002% to deoxidize it, and then adding Si and Mn to adjust the required composition. The method for manufacturing a non-oriented electrical steel sheet according to claim 1.

The slab obtained by adjusting the components and oxide-based inclusions may be made into a magnetic steel sheet by processes such as hot rolling, cold rolling and annealing under normal conditions. If desired to further improve the magnetic properties, it may be annealed before cold rolling, if necessary, the present invention, the production cost as low as possible to obtain a non-oriented electrical steel sheet of sufficient performance This is one of the goals, and it is desirable to eliminate extra steps as much as possible.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The reasons for limiting each factor and condition in implementing the present invention will be described below.

(1) C C is an element that deteriorates the magnetic properties, so the smaller it is, the better it is in the product steel sheet.

However, at the stage of decarburization or deoxygenation of molten steel by vacuum treatment, if C in molten steel becomes less than 0.001%, tot.
%, It cannot be reduced to below%, so some residual is unavoidable. The limit is 0.010% or less so that no significant adverse effect appears.

(2) Si As the content of Si increases, the electric resistance of steel increases, which is effective in reducing iron loss. However, on the other hand, as the content increases, the magnetic flux density decreases, so in order to secure a sufficient magnetic flux density, the upper limit of the content is 1.0%. Also, sol.Al
Of less than 0.002% does not increase the amount of MnO, the deoxidizing effect of Si is important, and at least 0.05% or more is required for this purpose. Therefore, Si
Content range of 0.05 to 1.0%.

(3) Mn In the present invention, the content of Mn is adjusted mainly for the purpose of suppressing cracking during hot rolling due to the presence of S, that is, hot embrittlement, and reducing grain growth inhibition. In order to obtain this effect, it is essential that the Mn / S content be at least 10 or more. Mn increases electric resistance and is therefore significant in reducing iron loss, but its effect is smaller than that of Si, and the effect of suppressing the harmful effect of S is saturated even if the content is increased, resulting in an increase in cost. The upper limit is 1.0%.

(4) P P is one of the impurities that are inevitably mixed in the steel, but in the case of non-oriented electrical steel sheet, the effect of increasing electrical resistance and hardness to improve punchability Therefore, it is added positively. However, since it tends to embrittle steel, its content should be at most 0.15%.

(5) Since S S deteriorates the magnetic properties, the smaller the content, the better. However, it has the effect of improving the punchability and machinability of the steel sheet, so it is added if necessary, but even in that case the content is up to 0.035%. As described above, if Mn / S is set to 10 or more, magnetic property deterioration and hot brittleness can be reduced, but if the content exceeds this, the effect becomes remarkable.

When the magnetic characteristics are emphasized, the content is preferably 0.006% or less. However, when punching property and machinability are strongly desired, 0.015 to 0.035% is preferable.

(6) Al Al is added as a deoxidizing agent for molten steel to obtain a sound cast piece. Although a part of the deoxidized product floats by the addition, the balance forms oxide inclusions, and the excess Al is sol.A.
It remains in the steel as l. sol.Al easily forms fine precipitates of AlN, and if the amount increases, it becomes an obstacle to crystal grain growth and domain wall movement. Therefore, the sol.Al amount is less than 0.002%.

By reducing sol.Al, N
Although the formation of AlN fine precipitates can be suppressed even if a large amount of Si is contained, the presence of Si and Mn poses a risk of generating Si—Mn—N-based fine precipitates. Therefore, N should be as small as possible, preferably 0.005% or less.

(7) tot.O (total oxygen) The amount of tot.O in steel is set to 0.008 to 0.02%. This is based on the following results.

C: 0.003 to 0.005%, Si: 0.2 to 0.3
%, Mn: 0.2 to 0.3%, sol.Al: <0.002%
Steel with various tot.O contents was melted in the laboratory by changing the ultimate vacuum, hot-rolled, cold-rolled and annealed to form a 0.5 mm thick steel plate, and then JIS-C- The magnetic properties were investigated by the Epstein test method specified in 2550.

FIG. 1 shows the results of measuring the _iron loss value (W _15/50 ) with respect to the oxygen content of these steel sheets.

As is clear from this result, the amount of tot.O is
If it is less than 0.008% or exceeds 0.02%, the iron loss value is bad. It is considered that when the content exceeds 0.02%, the amount of inclusions increases and the magnetic properties deteriorate. It is not clear why it becomes worse at less than 0.008%, but since the crystal grain size of the steel sheet is not large, the dispersed state of inclusions changes due to too little O content, which hinders crystal grain growth during annealing. I was wondering if I did. In addition, in production in an actual factory, in order to reduce the tot.O to 0.008% or less while controlling the amount to be well below the upper limit of C of 0.010%, the limit of the capacity of the exhaust equipment for molten steel vacuum processing and It is practically difficult because it causes a large increase in cost, such as selection of expensive refractory materials in consideration of oxygen supply and the like.

(8) If the composition tot. O of the oxide-based inclusions is reduced and Al is not used as much as possible, the main composition of the oxide-based inclusions is MnO and Si.
It is estimated to be O ₂ . Therefore, in a laboratory-made electromagnetic steel sheet with the above composition range, the weight composition ratio of MnO to SiO _{2 in} inclusions was taken, and the relationship with iron loss was examined, and the results shown in Fig. 2 were obtained. Was given. That is, MnO
Good magnetic properties can be obtained by setting / SiO ₂ to 3/7 or less, or 0.43 or less. This is because when the ratio of MnO is decreased, the softening point of inclusions rises, expansion of inclusions due to hot rolling and crushing due to cold rolling are suppressed,
This is probably because the crystal grain growth was promoted.

If it is preferable to decrease the ratio of MnO, the amount of A with respect to the amount of Si when tot.
It seems that the amount of l used should be carefully considered. Therefore, the relationship between the oxide inclusions and the ratio of Al ₂ O ₃ to SiO ₂ was investigated. As a result, Al ₂ O ₃ / SiO ₂
It was found that the magnetic properties were good in the range of 0.1 to 1.0. If the Al ₂ O ₃ ratio exceeds 1.0, the magnetic properties deteriorate.
Precipitation is the main cause. The reason why it is not good if it is less than 0.1 is not clear, but it is considered that it may be due to the formation of Si—Mn—N type fine precipitates which adversely affect the grain growth property and the magnetic properties.

Steel having good magnetic properties but having difficulty in production or use of the product cannot be applied to mass production.
Examining the effect of the composition of oxide inclusions from such a viewpoint, an increase in Al ₂ O ₃ tends to cause nozzle clogging at the time of casting, increasing the surface defects of the steel sheet, and further punching and cutting electromagnetic steel sheets. It tends to shorten the tool life when doing. However, limiting tot.O, and Al ₂
If the O ₃ / SiO ₂ is limited to a range of 1.0 or less, such a problem disappears.

Even if the ratio of MnO or Al ₂ O ₃ to SiO ₂ is regulated as described above, if almost all the composition of oxide inclusions is changed to SiO ₂ , the magnetic properties will be slightly inferior. Not only that, but it shortens the tool life and deteriorates punchability. The reason for deteriorating the magnetic properties seems to be the difference in the effect due to the morphological change of inclusions. It is presumed that hard SiO ₂ itself has an influence on the tool life, and it was considered that oxide inclusions in which MnO, Al ₂ O _{3 and the} like are mixed to some extent are preferable. Such a range is a SiO ₂ ratio, that is, SiO ₂ / (SiO ₂ + Mn
O + Al ₂ O ₃ ) is less than 0.75.

The above Si in the oxide inclusions
The compositional limits of O ₂ , MnO and Al ₂ O ₃ are summarized above and in the equation. Further, when the range of the present invention is displayed, the range surrounded by the thick line shown in FIG. 3 is displayed.

However, the composition of the individual oxide-based inclusions present in the actual steel sheet is not the same but varies with the steel sheets obtained from the same cast piece. However, if 80% or more of all oxide-based inclusions present in the steel sheet fall within this composition range, a non-oriented electrical steel sheet with good magnetic properties is obtained. That is, the composition of the oxide inclusions may be substantially within the composition range defined here.

(9) Method for deoxidizing molten steel To make the amount of tot.O 0.008 to 0.02%, C under reduced pressure is used.
The ultimate vacuum and the vacuum treatment time are controlled by utilizing the deoxidation caused by the generation of O so that the C in the molten steel becomes 0.002 to 0.005%. The ultimate vacuum is preferably 0.01 atm, but
Even if the pressure is about 05 atm, the required to
It can be lowered to the t.O range. Then add Al, then S
It is preferable to add i and Mn to adjust the steel composition. Prior to vacuum treatment of molten steel or during vacuum treatment, addition of Al for the purpose of deoxidation heating is avoided as much as possible.

This is because if Al is added before the completion of deoxidation by vacuum treatment, not only tot.O does not fall within the target range, but also the composition of inclusions becomes large in Al ₂ O _3. is there. If Al is added after the vacuum treatment,
The inclusion can contain an appropriate amount of Al ₂ O ₃ to suppress an increase in the ratio of SiO ₂ and satisfy the formula.

Si or Mn may be added before the vacuum treatment or during the vacuum treatment depending on the purpose of heating or the target composition, but the formula is satisfied and the composition of the oxide-based inclusions is shown in FIG. In order to make it within the scope of the invention, it is preferable to add Al.

It is important that C in the molten steel be present to some extent or more in the molten steel in order to control tot.O within the target range of the present invention. However, in the manufacturing process for making the cast slab into the final electrical steel sheet, decarburization due to the atmosphere may occur in the annealing step, for example, and this may be reduced, so the lower limit of the C content is not particularly restricted as the chemical composition of the electrical steel sheet. .

In the manufacturing process for finishing the cast slab into the final electromagnetic steel sheet, desirable conditions for obtaining better magnetic properties are as follows. That is, it is preferable that the slab heating temperature in hot rolling is 1200 ° C or lower, the finishing temperature is 860 to 950 ° C, and the coiling temperature is 600 to 700 ° C. The reason why the slab heating temperature is set to 1200 ° C. or lower is that it can be improved by lowering the slab heating temperature, especially when the content of S, which tends to deteriorate the magnetic properties, is large. However, since the finishing temperature cannot be secured, there is a limit to the decrease in heating temperature. The finishing temperature of 860 ° C or higher is desirable because the characteristics can be improved by combining it with the winding temperature of 600 to 700 ° C. It is considered that this is because recrystallization is sufficiently performed in the wound state. 950
Finishing temperatures above ℃ are difficult to achieve by heating slabs below 1200 ℃, and in addition, surface defects increase and the product appearance deteriorates.

[0042]

【Example】

[Example 1] The chemical composition is shown in Table 1, and tot.O is 0.02%.
The target is to:
After adding O after 0.02% or less of Si, Si and Mn
16 types of steels with different composition adjustment methods, such as those with adjusted content, those with Al added before or during vacuum treatment, those with Si and Mn added before or during vacuum treatment, etc. The slab was melted. These slabs at 1180 ℃
Finishing temperature 870 ~ 890 ℃, winding temperature 660 ~ 680
After hot rolling to 2.0 mm at 2.0 ° C, descaling and cold rolling to finish to 0.5 mm thickness, annealing at 850 ° C for 1 min soaking, and surface insulation coating similar to ordinary non-oriented electrical steel sheets. I did it.

[0043]

[Table 1]

The obtained steel sheet was subjected to analysis of the composition of inclusions in the steel, measurement of magnetic properties, and punchability evaluation test. The inclusion composition was analyzed by the energy dispersive X-ray analysis method, and the magnetic properties were measured based on the Epstein test method specified in JIS-C-2550, and the iron loss (W _15/50 ) and magnetic flux density (B ₅₀ ) Was asked. Regarding punchability, the corner R part with clearances of 5%, 8% and 10%.
Using an SKD-11 mold capable of punching 3 types of 12 mm 20 mm square blanks at the same time, punching was performed 200 times / min with emulsion lubrication, and judgment was made by relative evaluation of burr generation.

Table 2 also shows these results. Also,
The composition ratio of oxide inclusions in these steels is shown in FIG.

[0046]

[Table 2]

Steel A to which Al is added after the tot.O is sufficiently lower than 0.02% by vacuum treatment of molten steel and the chemical composition and oxide-based inclusion composition fall within the range defined by the present invention F shows excellent magnetic properties and punchability.

On the other hand, before vacuum treatment, Si or Al
In the steels G, H and I added with, the ratio of SiO ₂ or Al ₂ O _{3 in} the inclusions is out of the range defined by the present invention, resulting in poor punchability. In Steels J and K, the amount of C in the molten steel during vacuum treatment was slightly high, tot.O was below the range defined by the present invention, and the MnO ratio in the inclusions was too high, resulting in poor magnetic properties. It is considered that this is because the number of fine oxide inclusions increased. Steel L is also for heating the molten steel A
The addition of 1 also increased the ratio of sol.Al and Al ₂ O ₃ , resulting in not only poor magnetic properties but also poor punchability. Steels M to P are Si, Mn, and
P, S, etc. are out of the ranges defined in the present invention, and the magnetic properties or punchability are not improved.

[0049]

INDUSTRIAL APPLICABILITY According to the present invention, by controlling the composition of oxide inclusions in steel, magnetic properties of low iron loss and high magnetic flux density can be obtained without using expensive alloying elements or special manufacturing processes. It provides an excellent low-Si non-oriented electrical steel sheet, which is extremely significant in practical use.

[Brief description of drawings]

[Figure 1] Total oxygen (tot.O) content in steel and iron loss (W
It is a figure which shows the relationship with _15/50 ).

FIG. 2 shows oxide inclusions MnO / SiO _{2 in} steel,
It is a figure which shows the relationship with the iron loss ( _{W15 / 50} ) of a steel plate.

FIG. 3 is a diagram showing an example of the composition ratio of oxide-based inclusions in steel in the case of the steel of the present invention range and Example 1.

Claims (2)

[Claims] 1. By weight%, C: ≦ 0.01%, Si: 0.01-
1.0%, Mn: 0.01 to 1.0%, P: ≤ 0.15%, S: ≤ 0.
035%, tot.O (total oxygen in steel): 0.008-0.02%, so
l.Al: <0.002% and Mn / S ≧ 10, and MnO, SiO ₂ and Al ₂ O ₃ which are present in the steel.
The composition weight ratio of the three oxide inclusions of MnO / SiO ₂ ≦ 0.43 ····· 0.1 ≦ Al ₂ O ₃ / SiO ₂ ≦ 1.0 · _{············ SiO 2 / (SiO 2 +} MnO + Al 2 O 3) < 0.75 ..., the balance in the magnetic properties, which is a Fe and unavoidable impurities Excellent non-oriented electrical steel sheet. 2. C content in molten steel is 0.01% by weight by vacuum treatment.
% Or less and O (oxygen) to 0.02% or less, then sol.
It is characterized in that the chemical composition of the steel and the oxide-based inclusions in the steel are controlled by adding Al and deoxidizing it in the range where l is less than 0.002%, and then adding Si and Mn. The method for manufacturing a non-oriented electrical steel sheet according to claim 1.