JP2001316729A - Method for manufacturing non-oriented electrical steel sheet with low iron loss and high magnetic flux density - Google Patents

Abstract

PROBLEM TO BE SOLVED: To propose a manufacturing method for giving excellent magnetic flux density and iron loss to a non-oriented electrical steel sheet, which surpasses the magnetic properties obtained by the prior art. SOLUTION: Si: 1.5 to 4.0 mass% and Mn: 0.005
Hot rolling is performed on a steel slab containing 1.51.50 mass%, then hot-rolled sheet annealing is performed, and then cold rolling is performed once or twice or more with intermediate annealing to finish to a final sheet thickness. A method for producing a non-oriented electrical steel sheet, comprising performing recrystallization annealing and applying an insulating coating as necessary, wherein the Al content in the steel slab is 0.017 mass% or less and the N content is 0.0030% or less.
mass% or less and the average grain size after hot-rolled sheet annealing is controlled to 0.050 to 0.40 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a non-oriented electrical steel sheet mainly used for a core material of electric equipment.

[0002]

2. Description of the Related Art In recent years, with the worldwide movement to save energy such as electric power, there has been a strong demand for higher efficiency of electric equipment. Also, from the viewpoint of reducing the size of electric devices, there is an increasing demand for reducing the size of iron core materials.

In order to increase the efficiency of the electric equipment and reduce the size of the iron core material, it is effective to improve the magnetic properties of the magnetic steel sheet used as the material of the iron core. Here, in the field of conventional non-oriented electrical steel sheets, in order to reduce eddy current loss by increasing electric resistance as a means for reducing iron loss among magnetic properties, in particular, Si, Al and Mn are used. Techniques for increasing the content of have been generally used. However, this method has an essential problem that a reduction in magnetic flux density cannot be avoided.

On the other hand, in addition to simply increasing the content of Si, Al, and the like, it is also necessary to reduce C and S at the same time, or to add B as described in JP-A-58-15143. It is also a generally known method to increase the alloy component, such as adding Ni as described in JP-A-3-281758. With the method of adding these alloy components, although the iron loss is mainly improved, the effect of improving the magnetic flux density is small and not satisfactory. Furthermore, since the hardness of the steel sheet increases with the addition of the alloy and the workability deteriorates, the versatility of processing this non-oriented electrical steel sheet for use in electrical equipment is poor, and its use is extremely limited. Had become.

[0005] In addition, several methods have been proposed to improve the magnetic characteristics by improving the degree of integration of the crystal orientation of the product plate, that is, the texture, by changing the manufacturing process. For example, Japanese Patent Publication No. 58-181822 discloses that Si:
4.0 mass% and Al: 200 for steel containing 0.3-2.0 mass%
Warm rolling within the temperature range of ~ 500 ° C, {100} <UV
W> How to develop an organization
No. 422 discloses that Si: 1.5 to 4.0 mass% and Al:
After hot rolling of steel containing 0.1-2.0 mass%, {100} microstructure is developed by a combination of hot-rolled sheet annealing at 1000 ° C or more and 1200 ° C or less and rolling reduction of 80-90%. Methods are disclosed, respectively.

However, the effect of improving the magnetic properties by these methods has not been satisfactory yet, and there remains problems in workability and recyclability. That is,
If a certain amount of Al is contained in steel, the hardness of the steel sheet increases first, impairing the workability, and also damages the electrodes of the electric furnace when recycling core materials or scrapping at the customer , To develop the problem.

However, the improvement of the magnetic characteristics by these methods is small. For example, in Example 2 in JP-B-58-191922, Si: 3.40mass%, Al : 0.60mass% in magnetic flux density B ₅₀ of products of steel with thickness 0.35mm component system containing 1.70
T, iron loss is about 2.1 W / kg at W15 / ₅₀ , Tokuhei 3-2944
No. 22 discloses Si: 3.0 mass%, Al: 0.30 mass% and M
n: magnetic flux density B ₅₀ of products of steel with thickness 0.50mm component system containing 0.20mass% 1.71T, iron loss at W _15/50 2.5 W / kg
The value of the degree.

Other proposals have been made to improve the manufacturing process, but in all cases, the achievement of low iron loss was insufficient and the magnetic flux density was low.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to propose a manufacturing method for imparting an excellent magnetic flux density and iron loss to a non-oriented electrical steel sheet, which surpasses the magnetic properties obtained by the prior art. And

[0010]

Means for Solving the Problems The inventors of the present invention have intensively studied the problems in the prior art in order to simultaneously achieve a low iron loss and a high magnetic flux density, and have developed a new method for producing a non-oriented electrical steel sheet. I came to. That is, the gist configuration of the present invention is as follows.

(1) Si: 1.5 to 4.0 mass% and Mn: 0.00
Hot rolling is performed on a steel slab containing 5 to 1.50 mass%,
Next, after performing hot-rolled sheet annealing, the sheet is subjected to one or two or more times of cold rolling sandwiching intermediate annealing to finish to a final sheet thickness,
Thereafter, recrystallization annealing is performed, and if necessary, an insulating coating is applied. In the method for manufacturing a non-oriented electrical steel sheet, the Al content in the steel slab is 0.017 mass% or less and the N content is 0.00
A method for producing a non-oriented electrical steel sheet having a low iron loss and a high magnetic flux density, wherein the non-oriented electrical steel sheet has a low iron loss and a high magnetic flux density, while being adjusted to 30 mass% or less and controlling the average grain size after the hot-rolled sheet annealing to 0.050 to 0.40 mm.

(2) In the above (1), the amounts of B, O, S, Ti, V, Zr, Nb, and Ta contained in the steel slab are each 20
A method for producing a non-oriented electrical steel sheet having a low iron loss and a high magnetic flux density, characterized in that the steel sheet has a core loss of not more than ppm.

(3) In the above (1) or (2), the recrystallization annealing is carried out at a rate of 100 ° C./h in a temperature range of 700 ° C. or more.
A method for producing a non-oriented electrical steel sheet having a low iron loss and a high magnetic flux density, characterized by reaching a temperature range of 750 ° C or more and 1200 ° C or less.

(4) In the above (1) or (2), the recrystallization annealing is performed at a rate of 2 ° C./s in a temperature range of 500 to 700 ° C.
After raising the temperature to 700 ° C or higher to complete the recrystallization, cooling to a temperature range of 700 ° C or lower, and again raising the heating rate in the temperature range of 700 ° C or higher to 100 ° C / h or lower, 750 ° C or higher
A method for producing a non-oriented electrical steel sheet having a low iron loss and a high magnetic flux density, characterized by reaching a temperature range of 1200 ° C or lower.

(5) In any one of the above (1) to (4), the steel slab further comprises Cr: 0.01 to 1.50 mass%, Ni:
0.01 to 3.50 mass%, Cu: 0.01 to 0.50 mass%, Sb: 0.
005 to 0.50 mass%, Sn: 0.005 to 0.50 mass% and P:
A method for producing a non-oriented electrical steel sheet having low iron loss and high magnetic flux density, characterized by containing at least one of 0.005 to 0.5 mass%.

The present inventors have made intensive studies to overcome the limitations of the conventional technology for improving the magnetic properties of the conventional high Si non-oriented electrical steel sheet, and as a result, have found that the Al content and the N content in the material can be reduced. By controlling the crystal grain size after annealing of the hot-rolled sheet and the hot-rolled sheet in an appropriate range, it has been newly found that the orientation of the crystal constituting the steel sheet can be appropriately controlled to greatly improve the magnetic properties. In addition, as a result of further study on recrystallization annealing conditions, particularly advantageous conditions were newly found. Hereinafter, regarding the experimental results that led to the present invention,
It will be described in detail.

First, regarding the effects of hot-rolled sheet annealing and the amount of Al,
An experiment was performed. That is, C: 0.0025 mass%, Si:
3.3 mass%, Mn: 0.07 mass%, Sb: 0.04 mass%, A
l: B containing 0.20 mass% and N: 0.0020 mass%
O, S, Ti, V, Zr, Nb and Ta contents are each 20ppm
A steel ingot (Steel A) having the following reduced composition and C: 0.002
6 mass%, Si: 3.3 mass%, Mn: 0.07 mass%, Sb:
0.04 mass%, Al: 0.0040 mass% and N: 0.0020 ma
Ingot (Steel B) containing ss%, and the content of each of B, O, S, Ti, V, Zr, Nb and Ta reduced to 20 ppm or less (steel B), and C: 0.0030 mass%, Si: 3.3 mass%, M
n: 0.07 mass%, Sb: 0.04 mass%, Al: 0.0040 mas
s% and N: 0.0040 mass%, B, O, Ti,
Ingots (steel C) having a component composition in which the contents of V, Zr, Nb, and Ta were each reduced to 20 ppm or less were produced. These ingots were then heated to 1050 ° C and hot-rolled to 2.5 mm
Finished thick. Thereafter, hot-rolled sheet annealing was performed under various conditions, and after measuring the crystal grain size after the hot-rolled sheet annealing, the annealed steel sheet was further pickled and cold-rolled at a temperature of 200 ° C. Finished to a thickness of 0.35mm. After this cold rolling, these steel sheets were heated at a heating rate of 500 to 700 ° C. at a rate of 10 ° C./s, and recrystallized and annealed at 1000 ° C. for 10 seconds to obtain product sheets. Samples were cut out from these product sheets in parallel with the rolling direction and at right angles to the rolling direction, and the JIS C
The magnetic flux density and iron loss were measured according to 2550, and the average magnetic flux density and iron loss were determined.

FIGS. 1 and 2 show the relationship between the grain size after hot-rolled sheet annealing and the magnetic flux density and iron loss of a product sheet. As shown in FIGS. 1 and 2, in the case of steel A containing 0.20 mass% of Al, the influence of the crystal grain size after hot-rolled sheet annealing on the magnetic flux density and iron loss is small, and With a particle size of about 0.10 mm, a slight improvement in magnetic properties was observed.

On the other hand, in steel B in which both the Al content and the N content were reduced, both the magnetic flux density and the iron loss were significantly improved when the grain size after the hot-rolled sheet annealing was in the range of 0.050 to 0.40 mm. In steel C in which only the amount of Al was reduced, the improvement in magnetic flux density was recognized as in steel B, but the iron loss deteriorated when the grain size after hot-rolled sheet annealing was 0.10 mm or more. Showed the worst iron loss value.

Therefore, in order to clarify the reason why excellent iron loss was obtained in steel B, the crystal grain size of each product sheet was examined. The result of this investigation is shown in FIG. As shown in FIG. 3, in the case of steel A containing 0.20 mass% of Al, the influence of the crystal grain size after hot-rolled sheet annealing on the product sheet crystal grain size is small.
On the other hand, in steel B in which both the Al content and the N content were reduced, the crystal grain size of the product sheet significantly increased when the grain size after annealing of the hot-rolled sheet was in the range of 0.050 to 0.40 mm. In addition, steel C with only reduced Al content
In Table 2, the grain size of the product sheet tended to decrease when the grain size after the hot-rolled sheet annealing was 0.10 mm or more. From the above, it was found that in steel B, the grain size of the product sheet increased in the range of 0.050 to 0.40 mm after annealing of the hot-rolled sheet, and this contributed to the improvement of iron loss.

In order to elucidate the reason why excellent magnetic flux density was obtained in steel B, the crystal grain strength of each product plate was determined by X-ray diffraction using {100} plane strength and {111}.
｝ Surface strength was investigated. FIG. 4 shows the relationship between the grain size after hot-rolled sheet annealing and the {100} plane strength of the product sheet, and FIG. 5 shows the relationship between the crystal grain size after hot-rolled sheet annealing and the {111} plane strength of the product sheet. Shown respectively. As shown in FIG. 4 and FIG.
% Steel A has a small effect on the crystal grain orientation of the product sheet after the hot-rolled sheet annealing. On the other hand, in steel B in which both the Al content and the N content are reduced, and in steel C in which only the Al content is reduced, the {100} surface strength increases when the grain size after hot-rolled sheet annealing is in the range of 0.050 to 0.40 mm, {111} Surface strength decreased. That is, in steel B and steel C, the magnetic flux density was improved by increasing the {100} strength, which has good magnetization properties, and decreasing the {111} strength, which was poor in magnetization properties, in the crystal orientation of the product sheet. all right.

Further, the results of a more detailed study of the relationship between the Al content and the N content will be described. C: 0.0020 mass%, Si: 3.0 mass%, Mn: 0.10 mass
% And Sb: 0.03 mass%, and further ingots in which the contents of Al and N were variously changed were melted. The contents of B, O, S, Ti, V, Zr, Nb, and Ta in these ingots were each reduced to 30 ppm or less. These steel souls
Thereafter, it was heated to 1100 ° C. and finished to a thickness of 2.4 mm by hot rolling. Next, hot-rolled sheet annealing was performed at 1100 ° C. × 2 minutes. The crystal grain size after the hot-rolled sheet annealing was in the range of 0.20 to 0.40 mm. Further, the annealed steel sheet was pickled and cold rolled at a temperature of 200 ° C. to a final thickness of 0.35 mm. After this cold rolling, these steel sheets were subjected to recrystallization annealing at 950 ° C. × 20 seconds to obtain product sheets. From the product sheet thus obtained, samples were cut out in parallel with the rolling direction and at right angles to the rolling direction, and the magnetic flux density and iron loss were measured in accordance with JIS C2550, and the average magnetic flux density and iron loss were measured. I asked.

FIG. 6 shows the relationship between the magnetic flux density and the Al content and the N content. As the Al content becomes 0.017 mass% or less, the magnetic flux density B ₅₀ increases to 1.7 T or more. Has a small effect on the amount of N. FIG. 7 shows iron loss
The relationship between the Al content and the N content is shown.
When the content becomes 7 mass% or less, the iron loss increases, and the N content becomes 0.00
It can be seen that when the content is reduced to 30 mass% or less, the improvement effect is particularly large.

As described above, in a high-grade non-oriented electrical steel sheet having a high Si content, a method of increasing the specific electric resistance by adding Al has been adopted in order to improve iron loss. This method also has the effect of agglomerating and coarsening AlN, which is a precipitate in steel, which suppresses the growth of crystal grains, thereby promoting the growth of crystal grains. In order to obtain these effects, it is necessary to ensure that the content of Al is a certain amount or more.
Is regulated to an amount exceeding at least 0.1 mass%, and is usually about 0.4 to 1.0 mass%. However, the results obtained by the above experiments of the inventors show that, by setting the Al content much lower than the range of the prior art, the texture is most preferably developed, so that the magnetic flux density is improved and the N content is further improved. It is a new finding that, by also reducing the grain size, the grain growth in the product sheet is also improved, and the iron loss is greatly improved.

Although the reason why a good texture is developed by reducing the content of Al in the raw material component is not always clear, the present inventors have linked the effect of suppressing the grain boundary migration of impurities, I think as follows. In other words, by reducing Al, it approaches a crystal lattice arrangement state closer to pure iron, so that the difference in the original moving speed of the grain boundaries depending on the grain boundary structure becomes apparent, and the grain growth accompanying recrystallization During the process, only some grain boundaries move preferentially,
It is considered that the growth of many magnetically disadvantageous crystal grains such as {111}, {554}, and {321} is suppressed and grain growth occurs in the direction of increasing {100} strength, which is considered to have improved magnetic properties. .

Further, only the Al content is reduced and the N content is reduced to 0.0030 ma.
If it is not reduced to ss% or less, Al is reduced to about 0.1%, which is equivalent to that of the conventional technology.
The iron loss value was inferior to that of steel containing 20 mass%. In this case, it was observed that AlN dissolved in solid during the soaking of the hot-rolled sheet, and finer AlN was precipitated during the cooling of the hot-rolled sheet. It is presumed that as a result of the AlN precipitate suppressing grain growth during recrystallization annealing, the crystal grain size of the product sheet did not increase and iron loss deteriorated. On the other hand, the amount of N is 0.0030mass%
When the content is reduced below, it is considered that AlN precipitates are reduced and good grain growth is ensured even during recrystallization annealing. As a result, iron loss increases with an increase in magnetic flux density.

As described above, in the method of improving the magnetic properties by improving the texture without adding a large amount of Al, since the amount of Al is reduced, the recyclability of the material is improved, and the addition amount of the alloy element is reduced. Therefore, the saturation magnetic flux density can be increased. At the same time, when the addition amount of the alloy element is reduced,
Since the increase in hardness of the steel sheet is suppressed, the workability of the product is ensured, and the advantage that application to general-purpose electrical products is promoted is also obtained.

Next, as a requirement for further improving the iron loss and the magnetic flux density, an experiment on recrystallization annealing conditions was performed. That is, Si: 2.0 mass% and Mn: 0.13 mass%
, And the Al content is 0.0030 mass% and the N content is 0.0015 ma.
Steel ingot reduced to ss% (steel D), Si: 3.6 mass%, Mn: 0.
Contains 13 mass%, Sb: 0.06 mass%, and has an Al content of 0.0040 ma
A steel ingot (steel E) in which the ss% and the N content were reduced to 0.0011 mass% was smelted, respectively. These ingots are then
It was heated to 00 ° C and hot-rolled to a thickness of 2.5 mm. Thereafter, hot-rolled sheet annealing is performed at 1000 ° C for 1 minute, the annealed steel sheet is pickled, and cold-rolled at a temperature of 200 ° C to obtain a final sheet thickness of 0.
Finished to 35mm. After this cold rolling, samples were obtained from the obtained coils, and recrystallization annealing was separately performed by the following three methods to obtain product sheets.

[Annealing 1] Heating rate: average temperature 30 ° C./s between normal temperature and 500 ° C., 500-70
15 ° C / s on average between 0 ° C, 8 ° C / s on average between 700 and 900 ° C
s, soaking 900 ° C x 10 seconds Cooling rate: average 10 ° C / s from soaking to normal temperature Annealing atmosphere: 50% hydrogen, 50% nitrogen, dew point -30 ° C [annealing 2] Heating rate: between normal temperature and 500 ° C 100 ℃ / h on average, 500 ~
50 ° C / h between 900 ° C, soaking at 900 ° C for 10 hours, cooling rate: 100 ° C / h average from soaking to normal temperature Atmosphere: Ar dew point -30 ° C [Annealing 3] After annealing 1, annealing 2 was performed. Do.

Samples were cut from these product sheets in parallel with the rolling direction and perpendicular to the rolling direction, and the magnetic flux density and iron loss were measured in accordance with JIS C2550, and the average magnetic flux density and iron loss were measured. I asked.

FIG. 8 shows the relationship between recrystallization annealing conditions and magnetic properties. First, regarding the iron loss, the steel loss of all steels after annealing 2 and annealing 3 is better than that of annealing 1. In particular, the iron loss of the steel E to which Sb is added is good. On the other hand, regarding the magnetic flux density, in steel E to which Al and Sb are added, annealing 2 and annealing 3 are improved as compared with annealing 1, but in steel D not containing Sb, the improvement is small.

FIG. 9 shows the relationship between the grain size after recrystallization annealing and the recrystallization annealing conditions. As shown in FIG. 8, the maximum temperature reached in each annealing condition was the same as 950 ° C., but in annealing 2 in which the temperature was gradually increased compared with annealing 1 in which the temperature was rapidly increased, the grain growth was slightly increased. The annealing 3 in which the rapid heating was performed and then the gradual heating was performed increased the grain growth more remarkably than the annealings 1 and 2.

Here, in the case of annealing 2, the temperature reached is the same as in annealing 1 which is a rapid temperature rise, but the soaking time is different, so that it is considered that grain growth has progressed. Regarding Annealing 3, although the difference from Annealing 2 is small, the grain size is significantly increased as compared with Annealing 2. When Annealing 2 and Annealing 3 are compared, in Annealing 3, it is considered that recrystallization nuclei have been generated by the rapid rapid temperature annealing in the first half, and the heating rate at the time of recrystallization nucleus generation is different. It is presumed that the difference in recrystallization texture based on the difference in texture formation process due to the different heating rates during nucleation greatly changed the subsequent grain growth behavior, but the essential mechanism is Not clear.

Further, when the addition element of the material was examined, it was found that the addition of Ni improves the magnetic flux density of the product. It is presumed that the fact that Ni is a ferromagnetic element contributes to the improvement of the magnetic flux density for some reason, but the reason is not clear. Also, Sn,
It was also confirmed that iron loss was improved by adding Cu, P and Cr. Probably, it is presumed that the iron loss is reduced by increasing the electric resistance.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The reasons for limiting the constituent elements of the present invention will be described below. That is, as a component of the magnetic steel sheet of the present invention, it is necessary to increase the electrical resistance by containing Si to reduce iron loss.
1.5 mass% or more of Si is required. On the other hand, if the content exceeds 4.0 mass%, the magnetic flux density decreases and the secondary workability of the product significantly deteriorates.
Limit to mass%.

Mn is a component necessary for improving the hot workability, but the effect is poor if it is less than 0.005 mass%.
On the other hand, when the saturation magnetic flux density exceeds 1.50 mass%, the saturation magnetic flux density decreases.

In order to realize good magnetic properties,
Reduce the amount of Al in the steel sheet to 0.017 mass% or less, preferably 0.005 mass%
% Or less, and the N content is 0.0030 mass% or less, preferably 0.1% or less.
It is important to reduce it to 0020 mass% or less. That is, when the Al content exceeds 0.017 mass%, the texture of the product plate is deteriorated, the magnetic flux density is reduced, and the N content is 0.0003 mass%.
If it exceeds 0 mass%, fine AlN precipitates are formed after hot-rolled sheet annealing, and the growth of crystal grains during recrystallization annealing is suppressed, so that iron loss is greatly deteriorated.

Further, in order to obtain good iron loss, it is preferable that the contents of B, O, S, Ti, V, Zr, Nb and Ta as molten steel components are each 20 ppm or less.

C is preferably reduced to 0.0050 mass% or less in order to suppress magnetic aging deterioration and sufficiently exhibit the effect of improving the texture by lowering Al. The reduction of C may be 0.0050 mass% or less in the molten steel stage, or may be 0.0050 mass% or less in the molten steel stage even if it exceeds 0.0050 mass% by decarburization treatment in the middle of the process. C content in steel sheet during crystal annealing is 50ppm
It is important that:

Next, in the present invention, control of the crystal orientation is essential. That is, in order to obtain good magnetic properties,
It is important to control the grain size after hot-rolled sheet annealing to a range of 0.050 to 0.40 mm. If the grain size after the hot-rolled sheet annealing is out of the above range, the texture of the product sheet is degraded and the magnetic flux density is reduced. Here, the grain size after hot-rolled sheet annealing is calculated as a circle equivalent diameter by measuring the number of crystal grains in the cross-sectional structure. In order to obtain a statistically significant grain size,
It is preferable that the number of measured crystal grains is 200 or more.

Next, the rate of temperature rise at 700 ° C. or more during recrystallization annealing is gradually reduced to 100 ° C./h or less to reach a temperature range of 750 ° C. to 1200 ° C., thereby promoting grain growth. This is effective for improving magnetic characteristics. That is, if the heating rate at 700 ° C or more exceeds 100 ° C / h,
The rate of temperature increase is 100
C./h or less is preferable. Although the lower limit of the heating rate is not particularly defined, if the heating rate is less than 1 ° C./h, the annealing time is too long, which is economically disadvantageous. On the other hand, if the temperature reached by recrystallization annealing is less than 750 ° C, grain growth will be insufficient and magnetic properties will deteriorate, and if it exceeds 1200 ° C, surface oxidation will progress and iron loss will deteriorate, so recrystallization will occur. The ultimate temperature of annealing is preferably 750 ° C or more and 1200 ° C or less. Although there is no particular limitation on the soaking time, it is effective to promote grain growth for a long time within an economically acceptable range in order to obtain good iron loss.

Further, in order to remarkably promote grain growth and improve magnetic properties, in the first half of recrystallization annealing, 500 to
The rate of temperature rise between 700 ° C is 70 ° C
Raise the temperature to 0 ° C or higher to complete the recrystallization.
Cool to the following temperature, and increase the heating rate above 700 ° C again.
It is effective to reach a temperature of 750 ° C to 1200 ° C at a rate of 100 ° C / h or less.

That is, 500 at the time of temperature rise in the first half of recrystallization annealing.
If the heating rate between 700 ° C. and 700 ° C. is less than 2 ° C./s, the effect of accelerating the grain growth in the latter half annealing becomes small.
C./s or higher is preferred. Similarly, when the temperature in the first half of the recrystallization annealing is less than 750 ° C and exceeds 1200 ° C, the effect of promoting the grain growth in the second half of annealing becomes small, so the temperature reached during the first half of the recrystallization annealing is 750 to 1200 ° C. It is desirable to do. In the latter half of recrystallization annealing,
When the temperature exceeds 100 ° C./h, the effect of improving the texture is reduced.
100 ° C./h or less. If the temperature reached in the latter half of the recrystallization annealing is lower than 750 ° C, the grain growth will be insufficient and the magnetic properties will deteriorate, and if it exceeds 1200 ° C, the surface oxidation will progress and iron loss will deteriorate. It is preferable that the temperature reached in the second half of annealing is 750 ° C or more and 1200 ° C or less. Although the soaking time in the latter half of the recrystallization annealing is not particularly defined, it is effective to promote grain growth as long as possible within an economically acceptable range in order to obtain good iron loss.

Here, the rate of temperature rise up to 500 ° C. does not have a significant effect on the recrystallization behavior, and thus does not need to be particularly restricted. The cooling conditions do not need to be particularly restricted in terms of magnetic properties, but are economically at 60 ° C./min.
Rates in the range of 10 ° C./h are advantageous.

Further, in order to improve the magnetic flux density,
Ni can be added. If the addition amount of Ni is less than 0.01 mass%, the amount of improvement in magnetic properties becomes small, while
If the content exceeds ss%, the texture is insufficiently developed and the magnetic properties are deteriorated. Therefore, the addition amount is set to 0.01 to 3.50 mass%. Similarly, in order to improve iron loss, Sn: 0.01 to 0.50 mass%,
Cu: 0.01 to 0.50 mass%, P: 0.005 to 0.50 mass%, Cr:
It is also effective to add 0.01 to 1.50 mass%. When the addition amount is less than this range, there is no effect of improving iron loss, and when the addition amount is large, the saturation magnetic flux density decreases.

By the way, molten steel having the above-mentioned components is
The slab may be formed by a normal ordinary ingot making method or a continuous casting method, or a thin slab having a thickness of 100 mm or less may be produced by a direct casting method. Next, the slab is heated and hot-rolled by a usual method, but may be hot-rolled immediately after casting without heating. In the case of a thin slab, hot rolling may be performed, or hot rolling may be omitted and the process may proceed to the subsequent steps. Subsequently, hot-rolled sheet annealing is performed, and if necessary, one or more times of cold rolling sandwiching intermediate annealing is performed, then continuous annealing is performed, and an insulating coating is applied as necessary. Finally, in order to improve the iron loss of the laminated steel sheet, an insulating coating is applied to the steel sheet surface. For this purpose, a multilayer film composed of two or more kinds of films may be used, or a resin or the like may be mixed. A coated coating may be applied.

[0047]

EXAMPLES Example 1 C: 0.0033 mass%, Si: 3.33 mass%, Mn: 0.13 mass%,
Al: 0.0030 mass%, N: 0.0020 mass%, Sb: 0.03 mass%
And a steel slab having a component composition in which the contents of B, O, S, Ti, V, Zr, Nb and Ta were reduced to 20 ppm or less, respectively, was produced by continuous casting. The slab is heated at 1220 ° C for 50
It was heated for 2.3 minutes and finished by hot rolling to a thickness of 2.3 mm. Next, hot-rolled sheet annealing was performed under the conditions shown in Table 1, and the average particle size after hot-rolled sheet annealing was measured. Thereafter, the steel sheet was pickled to remove scale, and then cold-rolled at a temperature of 220 ° C. to finish to a final thickness of 0.35 mm. Then, in a hydrogen atmosphere 1000 ℃ × 30
After recrystallization annealing for 2 seconds, a semi-organic coating solution was applied and baked at 300 ° C. to obtain a product.

From the product sheet thus obtained, samples were cut out in parallel to the rolling direction and at right angles to the rolling direction, and the magnetic flux density and iron loss were measured in accordance with JIS C2550. Iron loss was determined. As shown in Table 1, the measurement results show that the steel sheet having a grain size after annealing of the hot-rolled sheet in the range of 0.05 to 0.40 mm has excellent magnetic properties.

[0049]

[Table 1]

Example 2 C: 0.0020 mass%, Si: 2.04 mass%, Mn: 0.05 mass%,
Al: 0.013 mass% and 0.0015 mass% of N, and the content of B, O, S, Ti, V, Zr, Nb and Ta is 20 respectively.
A steel slab having a component composition reduced to less than ppm was manufactured by continuous casting. This slab was heated at 1100 ° C. for 30 minutes and finished to a 2.8 mm thickness by hot rolling. Next, hot-rolled sheet annealing was performed for 10 minutes.
Performed at 50 ° C. for 30 seconds. The average particle size after annealing of the hot-rolled sheet was 0.15 mm. Next, the steel sheet was pickled to remove scale, and then cold-rolled at a temperature of 180 ° C. to a final thickness of 0.35 mm. Then, in a hydrogen atmosphere, Table 2
The temperature is raised at the rate shown in
After recrystallization annealing, a semi-organic coating solution was applied and baked at 300 ° C. to obtain a product.

From the product sheet thus obtained, samples were cut out in parallel with the rolling direction and at right angles to the rolling direction, and the magnetic flux density and iron loss were measured in accordance with JIS C2550. Iron loss was determined. As shown in Table 2, the rate of temperature increase from normal temperature to 700 ° C. during recrystallization annealing was set to 200 ° C./h.
Assuming that the average heating rate at 0 ° C. or higher is 1 ° C. to 100 ° C./h,
It can be seen that by reaching a temperature of 750 ° C. or more and 1200 ° C. or less, a product having particularly good magnetic properties can be obtained.

[0052]

[Table 2]

Example 3 C: 0.0019 mass%, Si: 3.43 mass%, Mn: 0.03 mass%,
Al: 0.0030 mass%, N: 0.0015 mass%, Sb: 0.05 mass%
And a steel slab having a component composition in which the contents of B, O, S, Ti, V, Zr, Nb, and Ta were each reduced to 20 ppm or less was produced by continuous casting. This slab is heated at 1150 ° C for 30
And heated to a thickness of 2.8 mm by hot rolling. Next, hot-rolled sheet annealing was performed at 1120 ° C. for 10 seconds. The average particle size after annealing of the hot-rolled sheet was 0.32 mm. Next, the steel sheet was pickled to remove the scale, and then finished by cold rolling at room temperature to 1.6 mm. Intermediate annealing was performed at 1000 ° C. for 60 seconds, and then cold rolling was performed at room temperature to finish to a thickness of 0.20 mm. Thereafter, primary recrystallization annealing was performed in an Ar atmosphere according to the conditions shown in Table 3,
After cooling to a temperature of 0 ° C. or lower, the product was subsequently subjected to secondary recrystallization annealing to obtain a product.

From the product sheet thus obtained, samples were cut out in parallel with the rolling direction and at right angles to the rolling direction, and the magnetic flux density and iron loss were measured in accordance with JIS C2550. Iron loss was determined. As shown in Table 3, the measurement results are as follows: the primary annealing in recrystallization annealing is performed at a temperature of 500 to 700 ° C. at 2 ° C./s or more, and the subsequent secondary annealing is performed at a temperature increasing rate of 700 ° C. or more at 1 ° C. to 100 ° C. It is understood that a product having particularly good magnetic properties can be obtained by reaching a temperature of 750 ° C. or more and 1200 ° C. or less as ° C./h.

[0055]

[Table 3]

Example 4 Steel slabs having the components shown in Table 4 were produced by continuous casting.
This slab is heated at 1220 ° C for 50 minutes and hot-rolled to 1.8 mm
Finished thick. Next, hot-rolled sheet annealing was performed under the conditions shown in Table 1, and the average particle size after hot-rolled sheet annealing was measured. Thereafter, the steel sheet was pickled to remove scale, and then cold-rolled to a final thickness of 0.50 mm. Next, recrystallization annealing was performed at 1020 ° C. for 30 seconds in a hydrogen atmosphere, and a semi-organic coating solution was applied and baked at 300 ° C. to obtain a product.

From the product sheet thus obtained, samples were cut out in parallel with the rolling direction and at right angles to the rolling direction, and the magnetic flux density and iron loss were measured in accordance with JIS C2550. Iron loss was determined. As shown in Table 4, the Al content was 0.017 ma.
It can be seen that a product having excellent magnetic properties is obtained in a component system in which the ss% or less and the N content are 0.0030 mass% or less and the particle diameter after annealing of the hot-rolled sheet is in the range of 0.05 to 0.40 mm.

[0058]

[Table 4]

[0059]

According to the present invention, it is possible to obtain a non-oriented electrical steel sheet having excellent magnetic flux density and iron loss, which surpasses the magnetic properties obtained by the prior art.

[Brief description of the drawings]

1 is a diagram showing the relationship between the average particle diameter and the magnetic flux density B ₅₀ after the hot rolled sheet annealing.

FIG. 2 is a view showing the relationship between the average grain size after hot-rolled sheet annealing and iron loss W _15/50 .

FIG. 3 is a diagram showing a relationship between an average particle size after annealing of a hot-rolled sheet and an average particle size of a product sheet.

Fig. 4 Average grain size after annealing of hot rolled sheet and (1
FIG. 10 is a diagram showing a relationship with surface strength.

FIG. 5 shows the average grain size of annealed hot rolled sheet and (11
It is a figure which shows the relationship with 1) surface strength.

6 is a diagram showing the relationship between the Al and N contents and magnetic flux density B ₅₀ of the material.

FIG. 7 is a diagram showing the relationship between the amounts of Al and N of a material and iron loss W _15/50 .

FIG. 8 is a graph showing the relationship between finish annealing conditions and product sheet magnetic properties.

FIG. 9 is a graph showing the relationship between finish annealing conditions and product sheet grain size.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22C 38/60 C22C 38/60 (72) Inventor Yuka Komori 1-chome Mizushima Kawasaki-dori Kurashiki City, Okayama Prefecture (M) Kawasaki Steel Corporation Mizushima Works (72) Inventor Masaki Kono 1-chome, Mizushima Kawasaki-dori, Kurashiki City, Okayama Pref. EA02 HA01 HA03 KA01 5E041 AA02 AA19 CA02 HB07 HB11 NN01 NN18

Claims (5)

[Claims] 1. Si: 1.5 to 4.0 mass% and Mn: 0.005
Hot rolling is performed on a steel slab containing 1.51.50 mass%, then hot-rolled sheet annealing is performed, and then cold rolling is performed once or twice or more with intermediate annealing to finish to a final sheet thickness. A method for producing a non-oriented electrical steel sheet, comprising performing recrystallization annealing and applying an insulating coating as necessary, wherein the Al content in the steel slab is 0.017 mass% or less and the N content is 0.0030% or less.
A method for producing a non-oriented electrical steel sheet having a low iron loss and a high magnetic flux density, wherein the non-oriented electrical steel sheet has a low iron loss and a high average magnetic flux density. 2. The steel slab according to claim 1, wherein the amounts of B, O, S, Ti, V, Zr, Nb and Ta are each 20.
A method for producing a non-oriented electrical steel sheet having a low iron loss and a high magnetic flux density, characterized in that the steel sheet has a core loss of not more than ppm. 3. The recrystallization annealing according to claim 1, wherein the recrystallization annealing is performed at a temperature rising rate of 100 ° C./h or less in a temperature range of 700 ° C. or more to reach a temperature range of 750 ° C. or more and 1200 ° C. or less. A method for producing a non-oriented electrical steel sheet having a low iron loss and a high magnetic flux density. 4. The recrystallization annealing according to claim 1, wherein the recrystallization annealing is performed at a temperature rising rate of 2 ° C./s or more in a temperature range of 500 to 700 ° C. to 700 ° C. or more to complete recrystallization. Later, 70
Cool to a temperature range of 0 ° C or lower, and again set the heating rate in a temperature range of 700 ° C or higher to 100 ° C / h or less and 750 ° C to 1200 ° C.
A method for producing a non-oriented electrical steel sheet having a low iron loss and a high magnetic flux density, characterized by reaching the following temperature range. 5. The method according to claim 1, wherein
Steel slab further contains Cr: 0.01-1.50 mass%, Ni: 0.01
~ 3.50mass%, Cu: 0.01 ~ 0.50mass%, Sb: 0.005 ~
0.50 mass%, Sn: 0.005 to 0.50 mass% and P: 0.005
A method for producing a non-oriented electrical steel sheet having a low iron loss and a high magnetic flux density, characterized by containing at least one of 0.5 to 0.5 mass%.