JPS60245769A - Grain-oriented silicon steel sheet having low iron loss and its production - Google Patents

Abstract

PURPOSE:To improve the grain size and arrangement of secondary recrystallization and to obtain a grain-oriented silicon steel sheet having a low iron loss by subjecting a hot rolled silicic steel sheet to cold rolling including intermediate annealing and coating an accelerator for development of secondary recrystallization thereon after decarburization and primary recrystallization annealing then subjecting the steel sheet to finish annealing. CONSTITUTION:The hot-rolled silicic steel sheet is subjected to cold rolling including intermediate annealing to a final sheet thickness and is then subjected to decarburization and primary recrystallization annealing. The accelerator for development of secondary recrystallization such as SrO powder is discretely stuck to the surface of such steel sheet. A separating agent for annealing consisting essentially of MgO is then coated thereon and the steel sheet is subjected to final finish annealing and finish coating. The grain-oriented silicon steel sheet of which the grain size distribution of the secondary recrystallization grains is made into the duplex grain size distribution consisting of 40- 80% number ratio of crystal grains having 1.0-2.5mm. grain size and >=15% number ratio of the crystal grains having 5.0-10.0 grain size and which has the low iron loss is thus obtd. Such silicon steel sheet has the exceptionally outstanding iron loss characteristic without having the deteriorated magnetic flux density.

Description

Detailed Description of the Invention Technical Field The technical content described in this specification regarding a grain-oriented silicon steel sheet with low core loss and its manufacturing method is to improve the grain size and distribution of secondary recrystallized grains after final annealing. By adjusting this, it is possible to improve the iron loss characteristics without reducing the magnetic flux density of the product.

BACKGROUND TECHNOLOGY Grain-oriented silicon steel sheets are mainly used as cores for transformers and other electrical equipment, and their magnetization properties are excellent.
In particular, low iron loss (represented by W1~150) is required.

For this purpose, firstly, the secondary recrystallized grains in the steel sheet should be <OO1
＞It is necessary to highly align grain orientation in the rolling direction,
Secondly, it is necessary to reduce as much as possible the impurities and precipitates present in the final steel product. The iron loss value of grain-oriented silicon steel sheets manufactured under these considerations has been improved over the years through many improvement efforts, and recently, the value of W17150 has increased to 1 for products made of 0.80 silk plate thickness. .05
A product with a low core loss of W/'Kg has been obtained.

However, as a result of the energy crisis that occurred a few years ago, the trend toward using electrical equipment with lower power loss became even stronger, and grain-oriented silicon steel sheets with even lower core loss were required as core materials for these devices. It has become.

Conventional technology and its problems By the way, methods to reduce the iron loss of grain-oriented silicon steel sheets include increasing the Si content, reducing the thickness of the product plate, making the secondary recrystallized grains finer, and reducing the impurity content. , and (110)[001] oriented secondary recrystallized grains to a higher degree of alignment.Although metallurgical methods are generally known, these methods are no longer compatible with current production methods. It has reached its limit and it is extremely difficult to make any further improvements, and even if some improvement is recognized, the effectiveness of iron loss improvement is small compared to the efforts made.

For example, in a method of highly aligning secondary recrystallized grains in the (110)[001] orientation, if the degree of accumulation in the (110)[001] direction is increased as much as possible, the magnetic flux density (magnetization Although the maximum magnetic flux density B1o at a force of 1000 A/m improved, the iron loss deteriorated because the secondary recrystallized grains gradually became coarser.

By the way, various studies have been conducted on the optimum grain size of secondary recrystallized grains for iron loss, and it has been found that reducing the grain size to the order of the average grain size l is effective, however, if it is made smaller than that, It is known that iron loss actually deteriorates.

As a technique for refining secondary recrystallized grains, for example, in Japanese Patent Publication No. 54-28647,
? A method has been proposed in which the secondary recrystallized grains are substantially refined by forming a recrystallization blocking region and inhibiting the growth of secondary recrystallized grains in the blocking region. Furthermore, Japanese Patent Application Laid-Open No. 54-71028 discloses that the primary recrystallization texture is controlled by cold rolling using grooved rolls. , a method for refining secondary recrystallized grains is disclosed.

However, all of these methods are methods that simply bring the secondary recrystallized grains of the entire steel sheet closer to the above-mentioned optimal grain size of about 1fi, and therefore, these methods
Even if it were possible to achieve finer recrystallized grains, the decrease in magnetic flux density due to grain refinement could not be avoided, and this sometimes led to a deterioration of iron loss itself. .

In addition, research has been conducted on the appropriate grain size of grain-oriented silicon steel product sheets, such as JP-A No. 59-288.
Publication No. 22 discloses that after completing secondary recrystallization, a part of the surface of the steel sheet is subjected to processing strain, and then annealed again, so that the area to which processing strain has been applied has a size of approximately 200μ or less (sheet thickness). 0.
A method for obtaining a grain-oriented silicon steel sheet with low iron loss by arranging recrystallized grains (in the case of 40 m or less) is disclosed.

However, with the above method, in addition to the disadvantage of complicating the process, the fine grains of about 200 μm or less that recrystallize due to the introduction of processing strain are essentially primary recrystallized grains. is the preferred orientation (110)
There remained a problem in that the deviation from (001) was large and a decrease in magnetic flux density was unavoidable.

The invention with the object of the invention advantageously solves the above problem and ea
The purpose of this paper is to propose a grain-oriented silicon steel sheet and a method for producing the same that realizes an advantageous improvement in iron loss characteristics without reducing the east density.

Introduction to the Invention This invention was newly developed after extensive research into the relationship between magnetic properties and crystal grain size in order to solve the above problems. It is based on new knowledge that the intended purpose can be advantageously achieved by adding ingenuity to the method.

The structure of the invention, that is, the present invention has a particle size distribution of secondary recrystallized grains of a silicon-containing steel sheet that has undergone final finish annealing.
A mixed grain distribution in which the number ratio of crystal grains with 0 to 2.5 heads is 40 to 80%, -10,000 grain size 75.0 to 10.0 m +7) The number ratio of crystal grains is 15% or more This is a grain-oriented silicon steel sheet with low iron loss.

In addition, this invention provides a hot rolled sheet obtained by hot rolling a silicon-containing steel slab, which is cold rolled once or twice with intermediate annealing to achieve the final thickness, and then decarburized.・A method for producing grain-oriented silicon steel sheets, which consists of a series of steps of performing primary recrystallization annealing, applying an annealing separator mainly composed of KMgO to the surface of the steel sheet in b, and then performing final annealing and top coating treatment. After decarburization and primary recrystallization annealing, a secondary recrystallization promoter is discretely attached to the surface of the steel sheet before application of an annealing separator, thereby changing the particle size distribution of secondary recrystallized grains to: 1. Directional silicon with low iron loss, characterized in that the number ratio of θ~2.5u is 40-80%, and the number ratio of crystal grains with grain size 5.0-10.0 is 15% or more This is a method for manufacturing steel plates.

In this invention, particle size 1. The formation region of crystal grains of θ ~ 2.5 dew is a continuous or discontinuous band-shaped region that is oriented almost perpendicular to the rolling direction of the steel sheet and whose width is 1.0 to 4.0 mm. Particularly advantageous are repetition intervals of 5 to 155 m in the rolling direction.

This invention will be specifically explained below based on the experimental results that led to this invention.

Now, in the manufacturing process of grain-oriented silicon steel sheet, the final sheet thickness is 1
c Cold rolled steel sheets are usually subjected to decarburization annealing to remove harmful carbon. By such annealing, the steel sheet is decarburized and recrystallized at the same time, so it is called a decarburized and primary recrystallization annealed sheet. Further, the recrystallized grains obtained at this time are composed of various types and orientations and are called normal grains or primary recrystallized grains. Then, in the subsequent secondary recrystallization annealing, (110) (
Grains of about 0.013 million grow preferentially and explosively, and thus all grains in the steel sheet become (110) [OOX]
The grains will be in this direction or in a similar direction. Such abnormal grain growth phenomenon is called secondary recrystallization, which means that normal rice grains, that is, primary recrystallized grains, are recrystallized. In this secondary recrystallization, in order to preferentially grow grains close to the (110)COOL:] orientation, it is necessary to suppress the growth of grains in other orientations, and for this purpose a component called an inhibitor is used. Added to steel. Currently, such inhibitors include various sulfides, selenides, nitrides, carbides, and KB, 8
b, Te, etc. are known.

By the way, among the components added as inhibitors, S and Se
If , N, etc. remain in the final product, it will have a significant negative effect on the magnetic properties, so following the secondary recrystallization treatment, 120%
Annealing is performed in a H2 atmosphere at a high temperature of about 0° C. to remove the above-mentioned residual impurities from the steel. Such annealing is therefore called purification annealing.

Furthermore, since secondary recrystallization annealing and purification annealing are usually performed continuously, they are sometimes collectively referred to as final finish annealing.

Now, the grain size of the primary recrystallized grains of the decarburized and primary recrystallized annealed plate is:
Usually, it is about zOμm, but if the suppressing effect of the above-mentioned inhibitor is insufficient in the subsequent secondary recrystallization annealing, the normal grains will grow, resulting in the expected 1. 'C Secondary recrystallization may occur, and as a result, the steel plate after final annealing will be composed of so-called normal grains of up to several hundred sizes, and the magnetic properties of the product will deteriorate significantly. become.

In order to quantitatively understand the above-mentioned situation, the inventors developed a grain-oriented silicon steel sheet containing 84% by weight of Sl (hereinafter simply expressed as %) by variously changing the manufacturing conditions. The crystal grain size of a product with a thickness of 0.80 mm was intentionally changed, and the relationship between the average grain size of the obtained crystal grains and magnetic properties (ω flux density Blo and iron loss W17150) was investigated. The results are shown in Figure 1a.

Indicated by bKO mark.

As is clear from Fig. 1, as the average grain size increases, the BI3 value simply increases, but the iron loss value W1715
gradually decreases, reaches a minimum value at particle sizes of 1 to 811111, and then tends to increase again. Therefore, in terms of iron loss, in terms of average particle size, as is known from the past,
The optimum value is 8 troubles.

By the way, according to Fig. 1, both the BI3 value and the W1?150 value change rapidly in the average grain size range of 0.5 to 1.0 mm, but this phenomenon is caused by the change in the crystal grains that make up the steel sheet. The results show that, with an average grain size of 0.5 to 1.0, normal grains are predominant on the finer grain side, while secondary recrystallized grains are predominant on the coarser grain side. That is, the average particle size is 1.
At temperatures above Om, the appearance of secondary recrystallized grains causes the (1
The degree of integration in the 1O) [001] direction increases, leading to a rapid increase in the BI3 value and a rapid reduction in iron loss.

Next, the inventors investigated the grain size distribution and arrangement of crystal grains in a steel sheet. The experiment was carried out in 8.2 listed above.
%S1-containing grain-oriented silicon steel sheet, and one was carried out locally on the product sheet indicated by the circle in FIG. By applying strain and then reannealing, recrystallized grains with an average grain size of approximately 0.1 square meters are arranged on the surface of the steel sheet in a direction perpendicular to the rolling direction, and this arrangement is repeated in the rolling direction. The test was repeated at a pitch of 12 m. The obtained results are shown in FIG. 1 by the symbol Δ. Another method is to attach fine SrO powder to the surface of the decarburized and primary recrystallized annealed plate, thereby changing the secondary recrystallization structure of the product plate to a grain size of 1.0 to 2.5.
A region consisting of a group of secondary recrystallized grains with a size of g+m was provided. This region is a strip-shaped region having a contraction length of 8 m and continuous or discontinuously extending in a direction perpendicular to the rolling direction, and has a repeating pitch of 12 frames in the rolling direction. The obtained results are shown in FIG. 1 with a mark ◎. By attaching fine SrO powder to the surface of the decarburized/primary recrystallized annealed plate, the product plate has a grain size of 1. The reason why fine secondary recrystallized grains of θ~2.5 mm are formed is that the appearance of secondary recrystallized grains is accelerated in the areas to which such SrO powder is attached during secondary recrystallization annealing, and the growth of the secondary recrystallized grains is accelerated. This is thought to be because the speed is not high, so as a result, fine secondary recrystallized grains remain in the steel sheet. -The reason why the growth rate of secondary recrystallized grains is slow is presumed to be because their orientation is slightly deviated from the (110)COOL) orientation.

Now, as is clear from the results shown in Figure 1, in the example (△ mark) in which recrystallized grains with a size of about 100 μm are arranged on the steel plate surface according to the conventional method, it is true that the average grain size is about 7 to 20 μm. Although a large iron loss reduction effect was seen in the range, the value was only about the same as that of the product with the optimum grain size marked with ○, while on the other hand, the magnetic flux density (BI3 value) showed a considerable decrease. .

On the other hand, the one in which a band-shaped region consisting of fine secondary recrystallization groups of 1.0 to 2.5 m is arranged (◎ mark) has an extremely large iron loss improvement effect, and the result is even better than the conventional best value. was obtained, and there was almost no decrease in magnetic flux density (B10 value) as shown in the figure.

In other words, by arranging secondary recrystallized grains with different grain sizes alternately in the rolling direction, a grain-oriented silicon steel sheet with lower iron loss than before can be obtained without deteriorating the magnetic flux density. It turned out that it was possible. The reason why this does not cause deterioration of magnetic flux density is that although the crystal grains that make up the steel sheet are fine, they are secondary recrystallized grains, so the deviation from the (110) [0013 orientation is small. It is believed that there is.

FIGS. 2a and 2b show the frequency distribution of crystal grain size and the coarse weave of Mac I2, respectively, for the product marked with ◎ in No. 11M, which has an average grain size of 8.98 m. In the region marked A in Figure 2 (width 8 squares), the number of crystal grains of 1.0 to L'5so+ accounts for approximately 90%, while the other region marked B (width 9 squares) In this case, the number of crystal grains having a grain size of 5.0 to 7.5% accounted for about 60%.

In addition, when areas A and B are not distinguished, the particle size is 1.0 to 2.
The number ratio of 5 dragon crystal grains is approximately 60%, 5.0 to 7.5
That of the III grains was about 17%.

On the other hand, when we conducted a similar investigation on our product, which has an average grain size of 3.89 among the conventional materials marked with a circle in Figure 1, the frequency distribution of the crystal grain size is shown in Figure 8. As shown above, crystal grains with a grain size of 2.5 to 5.0 t are the largest number, accounting for about 70% of the total, and as the grains become finer than this, the grains become coarser. The numbers tended to decrease accordingly.

In this way, in the conventional product, the particle size distribution of the secondary recrystallized grains exhibits a regular distribution, whereas in the product according to the present invention, the particle size distribution of the secondary recrystallized grains exhibits a mixed distribution. has major characteristics.

Now, to explain how to calculate the crystal grain size and average grain size, in Figures 2 and 8, both crystal grains are
Since they are secondary recrystallized grains, in products with a plate thickness of 0.81) m, the crystal grains penetrate through the plate thickness. Therefore, it is sufficient to calculate only one side of the steel plate. now,
If the area of one crystal grain is S mB, the crystal grain diameter Dm can be calculated as D=zJ. Next, the average grain size of the polycrystalline grains is calculated by taking the total area as 8- and the crystal grains contained therein.

Note that the method for calculating the particle size distribution within the area shown in Figure 2 is that particles completely contained in areas A and B are classified into areas A and B, respectively.
On the other hand, grains spanning regions A and B were counted as belonging to the region with the larger area among the eight areas of the grain divided into two by the boundary line.

Next, regarding the iron loss improvement effect, the particle size distribution of the secondary recrystallized grains is a mixed grain type, and the secondary recrystallized groups with a grain size of 1.0 to 2.5 grains are arranged in a band shape. So, in order to find out which one is more essential, we conducted the experiment described below.

'That is, when applying fine SrO powder to the surface of the decarburized and primary recrystallization annealed plate to obtain fine grains, the SrO
The powder was scattered in spots, and the subsequent treatment was carried out in the same manner as in the previous example to obtain a product. The frequency distribution and macrostructure of the secondary recrystallized grains of the obtained product are shown in FIGS. 4a and 4b, respectively.

As is clear from Figure 4, this product plate has a grain size of 1.
Regions of secondary recrystallized grains of 0 to 2.5 m are scattered in spots,
Regarding the particle size distribution, the number of particles with a diameter of 1.0 to 2.5 mm is the largest at about 64%, while the number of particles with a diameter of 5.0 to 7.5mm is the second largest at about 20%, and All others are 1
0% or less, and a mixed grain type product almost the same as the example shown in FIG. 2 above was obtained.

Now, let's take a look at the eight types of frequency distributions shown in Figures 2 to 4 above, as well as the magnetic properties of the product sheets with macrostructures.
The results were as shown in 31 below.

Table 1 As is clear from Table 1, even when fine secondary recrystallization groups are scattered in spots, they are still not as good as the example shown in Figure 2, in which they are distributed in a band shape in the direction perpendicular to the rolling direction. However, it was found that it has a considerable effect on low iron loss.

Regarding the improvement of iron loss without deterioration of magnetic flux density, the essential factor is not the arrangement of fine secondary recrystallized groups, but the particle size distribution has a great meaning. For example, as shown in Figure 2. It was quickly determined that it was important to use a more mixed grain type as shown in Figure 4.

- Now, regarding the ingredients of the grain-oriented silicon steel sheet in this invention, it is essential to contain Sl, but if the amount is less than 2.0%, the iron loss will deteriorate significantly, while if the amount is less than 2.0%, the iron loss will be significantly deteriorated.
If it exceeds S, cold workability is likely to deteriorate.
The i content is preferably 2.0 to 4.0%. As for the other components (b), any conventionally known components can be used as long as they are normally used as components of grain-oriented silicon steel sheets.

゛The thickness of the steel plate is preferably about 0.15 to 0.5 fins. This is because if it is less than 0.15 m, secondary recrystallization is difficult, whereas if it exceeds 0.5 fl, the effect of improving iron loss is poor and it is not funny.

Further, the crystal grains constituting the steel plate need to be secondary recrystallized grains whose tl has a grain size of 1.0i or more and whose deviation from the (110)[001] orientation is small.

If the particle size is less than 1.0 (110) (Q 01 )
This is because the deviation from the orientation is large, and in extreme cases, normal grains may remain, seriously impairing the magnetic flux density of the steel sheet and ultimately the iron loss.

Here, the grain size distribution of the crystal grains constituting the steel sheet is a mixed grain type, that is, the solid number ratio is 1.
40-80% secondary recrystallized grains with a grain size of 0-2.6 m
Preferably 60-70% crab meat, 5.0-10.0
It is required that the secondary recrystallization grain force of the grain size of m is -16% or more.

This is because if the number ratio of secondary recrystallized grains with a grain size of 1.0 to 2.5H is less than 40%, the iron loss reduction effect is poor;
%, or when the number ratio of crystal grains with a grain size of 5.0 to 10.0 mm is less than 15% (well, the number ratio on the coarse grain side becomes small and the magnetic flux density is poor. This is because it invites

It is preferable that the number of dead crystal grains having a grain size exceeding 2.5 fins and less than 5.0 m+a is smaller than that of crystal grains having a diameter of 5.0 = 10.011 II.

By creating a mixed grain type particle size distribution in this way,
This makes it possible to reduce iron loss without reducing the magnetic flux density of the product, and rounding to create a mixed grain type secondary recrystallization structure requires decarburization and primary recrystallization annealing. What is necessary is to attach to the plate something that will stand up to the secondary recrystallization annealing and promote the development of secondary recrystallization.In addition to SrO powder, such a secondary recrystallization promoter can be used. , Mo OB
and SnO.

SnOs powder is particularly advantageously suited.

The reason why these agents promote the development of secondary recrystallization is that during secondary recrystallization annealing, these agents change the form of the 5tO2 rice grains dispersed in the isthmus of the surface layer of the steel plate. This is because the time (referred to as latent time) during which the secondary recrystallized grains appear is shortened. With these drugs,
Since the growth rate of secondary recrystallized grains that appeared early is smaller than the growth rate of normal secondary recrystallized grains, the result is 1.0
It remains on the steel plate as fine grains of ~2.5 m. It is presumed that the reason for this slow growth rate is that the orientation is slightly deviated from the (110)[001] orientation.

The area to which such a secondary recrystallization promoter is attached accelerates the onset of secondary recrystallization, resulting in secondary recrystallized grains of about 1.0 to 2.5 mm in the steel sheet after the final thickness. , while 2
The areas where the next recrystallization promoter is not attached are mainly 5.0 to 10.
Since 0*i+ crystal grains are developed, the desired mixed grain type secondary recrystallized structure is obtained.

By the way, in the mixed grain type mentioned above, 1.0 to 2.5
If the secondary recrystallized grain group of tx is repeatedly distributed in a band-like manner in a direction perpendicular to the rolling direction, a further effect in reducing iron loss can be obtained. At this time, the particle size is 1.0~L5m
The width of the band-like region of the crystal grain group is preferably 1.0 to 4.0 m+a, and the repeating interval is preferably 5 to 15 m+m.

The surface of the steel plate is forsterite (M, 9
It has a glass film made of a S x O4), and may further have an overcoating film thereon if necessary due to requirements such as interlayer resistance. The top coating film includes not only a normal insulating film but also a type of coating film that applies tension to the steel plate.

Examples Example I A silicon steel material containing 8.2% Si was made into a cold-rolled steel plate with a thickness of 0.80 m according to a conventional method, and then decarburized and 1
After the second recrystallization annealing, the steel plate is divided into two parts, one of which is coated with an annealing separator containing MgO as the main component, and final finish annealing consisting of a second recrystallization annealing and a purification annealing at 1200°C for 5 hours is carried out. This was used as a comparative example. In the other method, SrO powder with an average particle size of 500A is repeatedly deposited on the surface of a steel plate in a band shape in a direction perpendicular to the rolling direction with a deposition width of 2 mm, and at an interval of 7 fi in the rolling direction, and then an annealing separator is applied. After coating on top of this, final finish annealing was performed in the same manner as in the comparative example to produce a product.

As a result, in the latter example, fine secondary recrystallized grains with a grain size of 1.0 to 2.5 mm appeared in a band shape in the area to which the SrO powder was attached, whereas in the comparative example, fine secondary recrystallized grains with a grain size of 2.5 mm appeared.
5-5. Owm had the most secondary recrystallized grains. The results of measuring these particle size distributions are as shown in Figure 5.
The comparative example showed a regular grain distribution, but the example showed a mixed grain distribution, and the number ratio of crystal grains with a grain size of 1.0 to 2.5 m+a was 72.8%, while 5.0 to 10. The number ratio of Om particle size was 15.6%.

And these magnetic properties are as follows: Example force 1B = 1.9
i T ; W17150 = 0.985 W/kl
? In contrast to Tearuno 0, the comparative example has B1o=1. QO8T ; W 1
? 150 = 1.078 W/kl? Met.

Example 2 A silicon steel material containing 8.2% Si was made into a cold-rolled steel plate with a thickness of 0.28 m according to a conventional method, and then decarburized and 1
When performing the next recrystallization annealing and then applying an annealing separator, MoOB powder with an average particle size of 101 ooo'h was sprinkled on the surface of the steel plate in spots of 8u in diameter before application, and then the annealing separator was applied.

Then, secondary recrystallization annealing was performed to 1200"c.

Purification annealing was performed for 5 hours.

For comparison, only an annealing separator containing MgO as the main component was applied according to a conventional method, and secondary recrystallization annealing was performed at 1200".
A comparative example was then subjected to purification annealing for 5 hours.

As a result, in the example, a group of fine secondary recrystallized grains of 1.0 to 2.5 grains appeared in spots in the area where the M2O3 powder was attached, but in the comparative example, a group of fine secondary recrystallized grains of 1.0 to 2.5 grains appeared in spots. 5
．． The largest number of secondary recrystallized grains was 0 m.

As shown in Figure 6, the results of measuring these particle size distributions showed that the comparative examples had a regular particle distribution, but the examples showed a mixed particle distribution, with particle sizes ranging from 1.0 to 2.5. The number ratio is 71.
4%; 5. The number ratio of particles with a diameter of θ ~ 10.0 fl is 19
．． It was 7%.

These magnetic properties are B□ in Example. = 1.885 T; W 1?150 =
9 to 0.856 W/, while the comparative example has B1o
= ],,889 T.

W 1? /ltO=0.937 W/kl? Met.

Example 8 A silicon steel material containing 8.0% Si was made into a cold-rolled steel plate with a thickness of 0.8 (1 m) according to a conventional method, and then decarburized and
When performing primary recrystallization annealing and then applying an annealing separator, SnO powder was sprinkled on the surface of the steel sheet in spots with a diameter of Z, and then the annealing separator was applied.

Then, secondary recrystallization annealing was performed at 1200°C.

Purification annealing was performed for 5 hours.

For comparison, only an annealing separator containing MgO as the main component was applied according to a conventional method, followed by secondary recrystallization annealing and then 1200
A comparative example was obtained by performing purification annealing at ℃ for 5 hours.

As a result, in the example, a group of fine secondary recrystallized grains of 1.0 to 2.5 grains appeared in spots in the area to which the SnO powder was attached, but in the comparative example, a group of fine secondary recrystallized grains of 1.0 to 2.5 grains appeared in spots. 5
．． The number of secondary recrystallized grains was the largest.

When the number ratio of particle size distribution was calculated, in the example, 1
．． The number ratio of particles with a diameter of 0 to 2.5 m was 68.0%:5.
0-10. The number ratio of Omtt particle size was 16.8%. On the other hand, in the comparative example, the -number ratio is 9.
8%; 18.5%, and the number ratio of particle sizes of 2.5 to 5.0 was 65%.

These magnetic properties of the example are Blo=1.915 T; Wl! +150 =
0.997 W/#, whereas the comparative example is Bl
o = 1.920 T ; W 1?150 = x, 0
It was & at 62 W/.

Effects of the Invention Thus, according to the present invention, it is possible to obtain a grain-oriented silicon steel sheet with much better iron loss characteristics than the conventional one without deteriorating the magnetic flux density.

[Brief explanation of the drawing]

Figure 1 a and b are the average particle size and B□, respectively. Oyohi W
1 'Graph showing the relationship with I/60, Figure Z a,
b is a schematic diagram showing the grain size distribution and macrostructure of a grain-oriented silicon steel sheet according to the present invention, FIGS. 8a and b are schematic diagrams of the grain size distribution and macrostructure of a conventional grain-oriented silicon steel sheet, respectively; Figures 4a and 4b are schematic diagrams showing the particle size distribution and macrostructure of other embodiments of the present invention, and Figures 5 and 6 compare the particle size distributions of the present invention and conventional examples, respectively. This is a graph shown as follows. Figure 2 (a) (b) Figure 3 (a) 0.5 10 2.5 50 75 10 15 Ayu Shokinin (Kayacho (b) Figure 4 (a) (tj) Figure 5 6 Figure Zhao Yisheki (haiku hat)

Claims (1)

[Claims] 1. Regarding the grain size distribution of secondary recrystallized grains of a silicon-containing steel sheet that has undergone final finish annealing, the number ratio of crystal grains with a grain size of 1.0 to 2.5 m is 40 to 80%, On the other hand, the particle size is 5.0-10. O
A grain-oriented silicon steel sheet with low iron loss characterized by having a mixed grain distribution in which the number ratio of m+ crystal grains is 15% or more. L Grain size: The formation region of crystal grains with a grain size of 1.0 to 2.5W is a continuous or discontinuous band-like region oriented almost perpendicular to the rolling direction of the steel sheet, and the width of the band-like region is 1.5W.
The grain-oriented silicon steel sheet according to claim 1, wherein the rolling direction is 0 = 4.0 m and the repetition interval in the rolling direction is in the range of 5 to 15 mm. & Hot-rolled sheets obtained by hot-rolling silicon-containing steel slabs are cold-rolled once or twice with intermediate annealing to reach the final thickness, and then decarburized and primary re-rolled. In a method for manufacturing a grain-oriented silicon steel sheet, which consists of a series of steps of crystal annealing, then applying an annealing separator mainly composed of M, 90 to the surface of the steel sheet, and then final annealing and top coating treatment. By discretely attaching a secondary recrystallization promoter to the surface of the steel sheet after charcoal/primary recrystallization annealing and before applying an annealing separator, the particle size distribution of secondary recrystallization grains can be adjusted to a particle size of 1, θ.
~2.5 particles ratio is 40~80%, particle size is 5.0~1
0. A method for producing a grain-oriented silicon steel sheet with low iron loss, characterized in that the number ratio of Ohm crystal grains is 16% or more.