JP2746631B2 - High magnetic flux density oriented silicon steel sheet with excellent iron loss characteristics and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a high magnetic flux density oriented silicon steel sheet having excellent iron loss characteristics and a method for producing the same, and more particularly to an effective subdivision of a secondary particle size. It is intended to advantageously improve the iron loss characteristics without lowering the magnetic flux density.

(Prior art) Grain-oriented silicon steel sheets are used as soft magnetic materials as core materials for transformers and generators. Magnetic properties such as magnetic flux density and iron loss must be good. In addition, it is necessary to form a surface coating with few defects. Materials with excellent magnetic properties are the product crystal grains (hereinafter referred to as 2).
(Referred to as the next grain) must be highly aligned with the (110) [001] orientation called the Goss orientation, thereby realizing an improvement in magnetic flux density.

As such a crystal orientation control technique, for example, Japanese Patent Publication No. 33-4710 and Japanese Patent Publication No. 40-15644 disclose that Al is contained in the material and the reduction rate of the final cold rolling is 81 to 95%. A technique for precipitating AlN by annealing before final cold rolling with a lower rate, and Japanese Patent Publication No. 46-23820 discloses that the cooling rate in this annealing before final cold rolling is from a temperature range of 750 to 950 ° C.
A technique for rapidly cooling to 400 ° C. in 2 to 200 seconds is disclosed.

The magnetic flux density has been improved by the above-mentioned techniques, and at present, those having characteristics of about 96% of the theoretical value have been industrially manufactured. Accordingly, iron loss has been improved, but there are two problems here.

The first point is that as the magnetic flux density increases, the secondary particle size of the product increases, and the desired effect of improving iron loss cannot be obtained.

Second, when the product thickness is reduced in order to improve iron loss, secondary recrystallization becomes difficult, and the orientation of secondary grains cannot be aligned with the Goss orientation. This leads to deterioration.

As a workaround for the first problem, Japanese Patent Publication No. Sho 50-26493 discloses a technique of keeping the inter-pass temperature of cold rolling at a predetermined temperature and aging it. It was difficult to completely control the particle size of the particles, and it was not only extremely complicated in actual operation but also helpless to the second problem.

A technique for avoiding the second problem is disclosed in
No. 197819, 0.03 to 0.5 wt% of Cu (hereinafter simply referred to as%) and Sn of 0.03 to 0.5% are added to the material, the finishing front temperature in hot rolling is 1150 to 1250 ° C, and the finishing rear surface temperature is 950. ~ 105
A technique has been proposed for producing a low core loss, high magnetic flux density directional silicon steel sheet having a sheet thickness of 0.30 mm or less by controlling the winding temperature to a temperature range of 500 to 600 ° C. while keeping the temperature at 0 ° C. . The inclusion of Cu in steel containing Al has been known for a long time as disclosed in the above-mentioned Japanese Patent Publication No. 33-4710, and the point of this technique is to regulate the conditions of the hot rolling process. Thus, precipitation of AlN during hot rolling is suppressed, and Sn is positively precipitated at grain boundaries.

However, in the above technique, Sn precipitates at the grain boundary, which causes the steel to become brittle, breaks in the subsequent rolling, or causes a surface defect of a scale-like pattern, and that the pickling property is not good. Therefore, even after rolling, part of the oxide layer remains on the steel sheet surface, causing decarburization failure during decarburization annealing, deteriorating magnetic properties,
In some cases, barbed defects were generated on the surface, and stability was lacking.

(Problems to be Solved by the Invention) The present invention advantageously solves the above-mentioned problems, and aims to stabilize the magnetic flux density in a high-flux-density silicon steel sheet having a thickness of 0.30 mm or less. It is an object of the present invention to propose a high magnetic flux density directional silicon steel sheet having excellent iron loss characteristics in which the secondary particle diameter is reduced and iron loss is effectively reduced, together with its advantageous production method.

(Means for Solving the Problems) As a result of intensive studies to solve the above-mentioned problems, the inventors have found that the secondary grain size after finish annealing is made fine by including Ge in steel. The present inventors have found that the present invention can be made, and after adding various ideas based on this finding, have completed the present invention.

That is, the present invention relates to Si: 2.5% or more, 4.0% or less, Mn:
0.04% or more, 0.15% or less, Ge: 0.005% or more, 0.20% or less,
And sometimes Mo: 0.005 to 0.20%, Cu: 0.01
~ 0.3%, Sb: 0.005 ~ 0.20%, Sn: 0.010 ~ 0.025% and
P: contains at least one selected from 0.010 to 010%, with the balance being Fe and trace amounts of unavoidable elements.
It is a high magnetic flux density directional silicon steel sheet having an excellent iron loss characteristic having a secondary grain size of 3 to 7 mm and a thickness of 0.10 to 0.30 mm.

Further, the present invention, C: 0.02-0.090%, Si: 2.5-4.0%,
Mn: 0.04 to 0.15%, sol Al: 0.010 to 0.050% and N: 0.00
0.005 to 0.20% for steel materials whose basic component is 40 to 0.0120%
% Of a silicon steel slab to which Ge has been added in the range of 0.1%, hot-rolled, and then subjected to a first cold rolling to an intermediate sheet thickness. ℃ rapidly cooled to 7 ° C / s or more at a cooling rate of 7 ° C / s or more, and then subjected to a second cold rolling under the condition of a reduction rate of 75 to 90% to finish a final cold rolled sheet with a thickness of 0.10 to 0.30 mm. After that, primary recrystallization annealing also serves as decarburization, then an annealing separator containing MgO as a main component is applied, and then high-temperature finish annealing is performed. This is a method for producing a silicon nitride steel sheet.

Hereinafter, the experimental results on which the present invention is based will be described.

C: 0.066%, Si: 3.25%, S: 0.025%, sol Al: 0.025% and N: 0.008%, the balance being substantially Fe-free molten steel, Ge-free and 0.001-0.50 A total of 10 steel ingots with various amounts added in the range of% were cast.

After heating these steel ingots to 1200 ° C., they were subjected to slab rolling, and then to 1420 ° C. and hot-rolled to obtain 2.3 mm thick hot-rolled sheets. After pickling, these were subjected to a first cold rolling to an intermediate plate thickness of 1.50 mm, then annealed in N ₂ at 1100 ° C. for 3 minutes, and quenched in hot water at 80 ° C. ( Average cooling rate: 40 ° C / s). Next, after secondary cold rolling to a final thickness of 0.23 mm, decarburizing annealing was performed at 850 ° C. for 5 minutes in wet H ₂ . Thereafter, an annealing separator mainly composed of MgO was applied, followed by finish annealing in H ₂ at 1200 ° C. for 20 hours.

FIG. 1 shows the results obtained by examining the magnetic properties and the average secondary particle size of the product sheet thus obtained.

As is clear from the figure, Ge is contained in the directional silicon steel material.
Is contained in the range of 0.005 to 0.20%,
In the product plate, the secondary particle size is reduced, and a remarkable reduction in iron loss is brought about. Moreover, there is no deterioration of the magnetic flux density.

When the cause of such a reduction in secondary particle size was investigated, as shown in FIG. 2, the (110) strength of the texture of the surface layer of the decarburized / primary recrystallized plate of the experimental material was remarkably high. It was found to be increasing. It was also found that, among the AlN precipitation sizes of the decarburized / primary recrystallized plate, the precipitation frequency of extremely small precipitates of 50 ° or less was increasing. The fact that the fine precipitates of AlN are increasing in this way means that the suppressing power is strengthened, and therefore, even if the thickness of the steel sheet is reduced, the magnetic flux density can be prevented from lowering. it is conceivable that. Also, an increase in the (110) intensity means an increase in the frequency of nucleation in the secondary recrystallization.
It is considered that the generation frequency of the secondary particles increased, and the secondary particle size was reduced.

Next, to investigate the cause of the (110) increase,
Examination of the structure of the steel sheet after the intermediate annealing revealed that extremely fine carbides were densely precipitated, as shown in the example of FIG. 3A in which 0.032% Ge was added.
In comparison with this, the frequency of precipitation of fine carbides is much lower in FIG. 3 (b) where Ge is not added.

From the above, the addition of Ge promotes the fine precipitation of carbides after intermediate annealing, increases the (110) strength of the steel sheet surface layer after decarburization and primary recrystallization annealing, and at the same time, the core of secondary recrystallization. It is presumed that the secondary particle diameter became fine as a result of the increase in the generation frequency.

The components of the silicon steel sheet material used in the present invention are as follows.

That is, C: 0.02-0.090%, Si: 2.5-4.0%, Mn: 0.04
~ 0.15%, sol Al: 0.010-0.040% and N: 0.0040-0.0
Ge is contained in a steel material containing 120% as a basic component in a range of 0.005 to 0.20%. Furthermore, in order to reinforce the suppressing force, conventionally known S and / or Se: 0.010
~ 0.040%, Sb and / or Mo: 0.005 ~ 0.20%, Cu: 0.
01-0.3%, P: 0.010-0.10%, and Sn: 0.010-0.025
% May be added.

Hereinafter, the reason why the silicon steel material is limited to the above range in the present invention will be described.

C is an element useful for improving the hot-rolled structure by utilizing transformation, and requires 0.02% or more. However, if it exceeds 0.090%, poor decarburization will be caused by decarburization annealing in the subsequent process. Not preferred.

Si is a major element that increases electric resistance and reduces iron loss, and requires at least 2.5%. If it exceeds 4.0%, cold rolling becomes difficult, which is not preferable.

sol Al and N are the basic elements of this component system.
Precipitates as N and acts as an inhibitor, but s
ol Al ranges from 0.010 to 0.050%, and N ranges from 0.0040 to 0.050%.
Outside the range of 120%, secondary recrystallization becomes unstable.

Mn not only effectively contributes to the improvement of hot workability of steel, but also contains MnS or MnS when S or Se is mixed.
e forms a precipitate such as e and also functions as an inhibitor, so that the content is in the range of 0.04 to 0.15%.

The greatest feature of the present invention is to add Ge to the above components, and by adding Ge to the steel material, AlN and carbide in the steel become dispersed and precipitated very finely, which is more preferable. The primary recrystallization structure of a thin steel plate is improved. However, Ge is 0.00
If it is less than 5%, this effect is small, while if it exceeds 0.20%, the precipitation of carbides is reduced and the suppression effect is weakened.
Must be contained in the range of ~ 0.20%.

The object of the present invention is realized by using the above-mentioned steel material component, but in addition to the above, the following elements can be added as reinforcement of the suppressing force. That is, S, Se, Sb, Mo, Cu, P, Sn, and the like may be added as a suppressing force reinforcing element.

Both S and Se are useful elements as inhibitors, and both have the same effect, but if the content is less than 0.010%, a sufficient inhibitory effect cannot be expected, while 0.040%
If the content exceeds the above range, coarsening of MnS or the like, poor purification, deterioration of surface properties, etc. will be caused. Therefore, it is preferable to add MnS in the range of 0.010 to 0.040% either alone or in combination.

Sb has the effect of segregating at the grain boundaries to increase the suppression power, and Mo has the effect of sharpening the nuclei of secondary grains to the Goss orientation, all of which have an effect in the range of 0.005 to 0.20%. Is remarkable.

Cu, like Mn, is an element that combines with S and Se to form precipitates and enhance the suppression effect, and the effect is 0.01 to 0.3%.
In the range.

P, like Sb, has the effect of segregating at the grain boundaries to increase the suppressing power, and the effect is remarkable in the range of 0.010 to 0.10%.

Sn, like Sb, is an element that segregates at the grain boundaries and enhances the inhibitory power. However, if it is less than 0.010%, the effect of its addition is poor, while if it exceeds 0.025%, the magnetic properties and surface properties described above become unstable. Therefore, it is set to 0.010 to 0.025%.

In each of the above components, C, S, Se, N, Al, P, etc. perform their respective functions, C is mainly used in decarburizing annealing, and S, Se, N, Al, P, etc. are used in the latter half of finishing annealing. Is removed during the purification annealing of the steel, only a trace amount of impurities remains in the base iron of the product.

 Next, the manufacturing method of the present invention will be described.

The silicon steel material having the above-mentioned components can be produced by any conventionally known melting method, ingot-making method, or ingot-making method. Next, this silicon steel material is rolled into a hot-rolled coil by ordinary hot rolling. The hot-rolled coil is subjected to a norma annealing as necessary in a known manner.
A final thickness of 0.10 to 0.30 mm is obtained by performing two cold rolling operations with intermediate annealing at 00 to 1200 ° C for 0.5 to 10 minutes. Here, the final sheet thickness was limited to the range of 0.10 to 0.30 mm because the sheet thickness was 0.30
For those larger than 0.1 mm, the technology of the present invention does not need to be particularly applied, while for those smaller than 0.10 mm,
This is because it is difficult to obtain a good product even by the technique of the present invention.

The first and second distributions of the rolling reduction in the cold rolling process are sufficient by the techniques disclosed in, for example, Japanese Patent Publication Nos. 40-15644 and 46-23820. Here, the second rolling reduction requires a strong rolling as is known in the rolling of silicon steel containing Al, but in the component system of the present invention, it is 75 to 90%, which is the conventional preferable range. The preferred range has shifted to a slightly lower rolling reduction side than 95%.

In the method of the present invention, it is advantageous to control the cooling rate in the intermediate annealing. Conventionally, cooling of silicon steel containing Al during annealing is described, for example, in Japanese Patent Publication No. 46-2382.
As described in Japanese Patent Publication No. 0, rapid cooling is considered to be good. This is related to the precipitation of AlN during cooling, which is extremely important for magnetic properties.
It is pointed out that it is necessary to perform delicate control depending on the material components. These technologies are roughly classified into those which require controlled cooling to rapidly cool to around 500 ° C. (including the blackening point) (JP-B-46-23820, JP-A-51-63314, JP-A-51-63314,
62-180015) and a technique that requires rapid cooling while controlling to room temperature (Japanese Patent Publication No. 59-48934).

However, even in the former technique, the cooling rate below the temperature of about 500 ° C. is not related to the precipitation of AlN, and the actual cooling process is performed by cooling with hot water or water quenching, and is substantially adopted. The difference between the two was not clear.

The present inventors have conducted intensive studies on this point, and found that, in a material containing Al and Ge, at least 5% was used to prevent coarse precipitation of AlN and carbide.
It is advantageous to quench at a rate of 7 ° C./s or more up to 00 ° C. More preferably, the temperature range that requires substantial quenching is from 750 ° C. to 250 ° C., and this range is the average cooling rate. : 7
Cooling at ℃ 25 ° C./s, and even more suitably, the temperature range of 750-250 ° C. is quenched at an average cooling rate of 7-25 ° C./s as described above,
It has been found that it is preferable to set the cooling rate to 4 ° C./s or lower at a slow cooling rate to 4 ° C.

Here, the average cooling rate in the range of 750 ° C to 250 ° C is 7 ° C / s
If it is less than the above, coarse precipitation of AlN and carbides may occur, while if it exceeds 25 ° C./s, the precipitation amount of AlN and carbides may be insufficient. Therefore, the preferable average cooling rate in this temperature range is 7 ° C./s to 25 ° C./s, which is characterized by a point that the average cooling rate is smaller than that of the material not containing Ge. Is also advantageous for industrial production.

The average cooling rate from 250 ° C. to 150 ° C. is particularly important. If the average cooling rate is large, the reason is not clear, but secondary grains may be locally coarsened and iron loss may be deteriorated. Therefore, it is particularly advantageous that the average cooling rate in this temperature range is 4 ° C./s or less.

In the present invention, in the cold rolling step,
The technique of performing aging treatment among a plurality of passes disclosed in Japanese Patent Publication No. 846 and Japanese Patent Publication No. 54-29182 is not particularly necessary, but since it has a slight stabilizing effect on magnetic characteristics, it is not necessary to prevent this application. Absent.

The cold-rolled sheet rolled to the final thickness is then 750
Carbide annealing at ~ 900 ° C for about 0.5-10min. At this time,
In the case of performing the above-described cooling control in the above-described intermediate annealing, further improving the magnetic properties can be expected by rapidly heating the temperature to 10 ° C./s or more.

An annealing separator containing MgO as a main component is applied to the surface of the steel sheet after the decarburizing annealing to prevent the steel sheet from burning during the final annealing and to form a surface forsterite film.

Here, as the above-mentioned annealing separating agent, JP-B-51-12451.
It is more preferable that TiO ₂ is added as disclosed in Japanese Patent Application Laid-Open No. H10-260, 1988.

The final annealing is performed in a mixed gas atmosphere of H ₂ or H ₂ , N ₂ , Ar or the like at 1100 ° C. or more for 5 hours or more. During the secondary recrystallization, a mixed gas atmosphere of H ₂ and N ₂ is particularly preferable. It is desirable that

Further, a known inorganic coating mainly composed of magnesium phosphate, aluminum phosphate, calcium phosphate, etc., which has both insulating properties and imparts tension, is formed on the surface of the steel sheet after the finish annealing, while also performing flattening annealing. Can also.

(Action) The product thus obtained is characterized in that the crystal grain size is extremely small in the secondary particle size as compared with the conventional product. That is, while the conventional average secondary particle size is about 10 to 20 mm, that of the present invention is only 3 to 7 mm. Moreover, since there is no decrease in the crystal orientation, an excellent oriented silicon steel sheet having a high magnetic flux density and an extremely low iron loss can be obtained. Further, it has excellent surface properties and stability of magnetic properties, and has the advantage of easy manufacture.

(Example) Example 1 C: 0.062%, Si: 3.26%, Mn: 0.075%, Se: 0.010%, S:
A slab containing 0.015%, sol Al: 0.025%, N: 0.008%, Sb: 0.020% and Ge: 0.045%, with the balance being substantially Fe, was heated at 1380 ° C for 3 hours, and then heated. By hot rolling, a hot-rolled sheet having a thickness of 2.2 mm was obtained. Then, the hot-rolled sheet was annealed at 1150 ° C. for 30 seconds in N ₂ , pickled, and then subjected to a first cold rolling to obtain a cold-rolled sheet having an intermediate sheet thickness of 1.40 mm.

The cold-rolled sheet was then divided into six parts and subjected to intermediate annealing at 1050 ° C. for 2 minutes in N _2. At this time, the average cooling rate from 750 ° C. to 250 ° C. and the average cooling rate from 250 ° C. to 150 ° C. Was adjusted using the mist cooling, gas cooling and hot water cooling methods so that the speed was as shown in Table 1. An example of the cooling curve at this time is shown in FIG.

All of these steel sheets were cold rolled for the second time,
Thickness: 0.20 mm (rolling reduction: about 86%) as a cold-rolled sheet, followed humidity 850 ° C. in H _2, then subjected to decarburization annealing for 2 minutes, by applying a separating agent composed mainly of MgO From (N ₂ : 50% -H ₂ : 50
%) From 850 ° C at a rate of 7 ° C / h in an atmosphere of 1%.
Raise the temperature to 150 ° C, then switch to H ₂ from 1150 ° C to 1200
After raising the temperature to 15 ° C / h at 15 ° C / hour, holding at 1200 ° C for 10 hours, 700
After cooling to ° C., the mixture was switched to N ₂ and cooled. Thereafter, the unreacted separating agent was removed, and the tension coating was baked to obtain a product.

The results obtained by examining the magnetic properties and the average secondary particle size of the product thus obtained are also shown in Table 1.

As is clear from the table, although good magnetic properties were obtained regardless of the cooling conditions,
The average cooling rate up to 7 to 25 ° C / s and from 250 ° C to 150 ° C
Particularly good values are obtained when the average cooling rate to 4 ° C is 4 ° C / s or less.

Example 2 C: 0.055%, Si: 3.20%, Mn: 0.080%, Se: 0.024%, C
A slab containing u: 0.03%, sol Al: 0.018%, N: 0.0082%, Mo: 0.012% and Ge: 0.040%, with the balance being substantially Fe, the temperature is raised to 1420 ° C, and then heat By cold rolling,
A 2.5 mm thick hot rolled sheet was used. This hot-rolled sheet was pickled, cold-rolled for the first time to an intermediate sheet thickness of 1.20 mm, heated in N ₂ at 1000 ° C. for 2 minutes, and mist-cooled as shown in FIG. After performing the cooling treatment of the curve C, the second cold rolling was performed to obtain a final thickness of 0.18 mm. At this time, aging treatment was performed at 300 ° C. for 1 minute for each rolling pass.

Then, the cold-rolled plate was divided into 6 parts, each of which was
Decarburization annealing was performed at 0 ° C for 2 minutes.
The heating rate up to 800 ° C. was changed as fk in Table 2.

Then, after applying a separating agent mainly composed of MgO, (N ₂ :
25% -H ₂ : 75%) in an atmosphere at a rate of 9 ° C./h
After the temperature was raised to 150 ° C., the atmosphere was switched to an H ₂ atmosphere, kept at 1200 ° C. for 15 hours, cooled to 400 ° C., and further switched to N ₂ for cooling. Thereafter, the unreacted separating agent was removed, and the tension coating was baked to obtain a product.

The results obtained by examining the magnetic properties and the average secondary particle size of the product sheet thus obtained are also shown in Table 2.

As is clear from the table, particularly good magnetic properties were obtained when the temperature rise rate of the decarburization / first recrystallization annealing was 10 ° C./s or more.

Example 3 Silicon steel material slabs having various compositions shown in Table 3 were used.
A and B are heated at 1250 ° C for 2 hours, and others (C to I) are heated at 1400 ° C for 1 hour and then hot-rolled.
A 2.5 mm thick hot rolled sheet was used. After pickling these hot rolled sheets, 1
In the first cold rolling, an intermediate sheet thickness of 1.35 mm was obtained, and then 1100 ° C
After 2 minutes of annealing at 80 ° C., the sample was put in hot water at 80 ° C. and cooled along the cooling curve shown in FIG. Next, after the second cold rolling to a final thickness of 0.23 mm, 86 mm in wet H ₂
After decarburizing annealing at 0 ° C for 3 minutes, applying a separating agent mainly composed of MgO, the temperature is raised to 800 ° C in a N ₂ atmosphere, and 800 ° C
Up to 1200 ° C at a rate of 5 ° C / h (N ₂ : 20% -H ₂ : 80
%), Then switched the atmosphere to H ₂ at 1200 ° C., kept at 1200 ° C. for 5 hours, cooled to 600 ° C., switched to N ₂ gas, and cooled to room temperature. . Thereafter, after removing the unreacted separating agent, the tension coating was baked to obtain a product.

Table 4 shows the results obtained by examining the magnetic properties, average secondary particle size, and surface defect rate of the product sheet thus obtained.

Table 5 shows the analysis results of the components in the steel of the obtained product.
Shown in In addition to the listed components, trace amounts of C, Al, S, Se, N, and the like were present as impurity components in iron, but these were reduced to levels at which there was no problem with magnetism.

As is clear from the table, good magnetic properties are obtained only when an appropriate amount of Ge according to the present invention is contained.

(Effects of the Invention) Thus, according to the present invention, even for a thin plate having a thickness of 0.30 mm or less, it is possible to stably obtain a grain-oriented silicon steel sheet having excellent magnetic properties, particularly magnetic flux density and iron loss properties. is there.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the Ge content and B ₈ , W _17/50 and average secondary particle size. FIG. 2 is a graph showing the Ge content and the texture of the decarburized / primary recrystallized plate surface layer. Graph showing the relationship between the (110) strength and the frequency of precipitation of fine AlN, and FIGS. 3a and 3b are metal structures showing the difference in the precipitation state of fine carbides in steel after intermediate annealing depending on the presence or absence of Ge. Photo, Fig. 4 is an example of cooling curve after intermediate annealing, hot water cooling at 80 ° C (a), mist cooling (c), (c '), gas cooling (e)
It is.

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Yoshiaki Iida 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Corporation Research and Development Headquarters (72) Inventor Kazuo Sadayo 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Shikisha Technology Research Division

Claims (5)

(57) [Claims] (1) Si: 2.5 wt% or more, 4.0 wt% or less, Mn: 0.04 wt% or more, 0.15 wt% or less, Ge: 0.005 wt% or more, 0.20 wt% or less, with the balance Fe and trace amounts Consisting of unavoidable elements,
A high magnetic flux density oriented silicon steel sheet having an average secondary grain size of 3 to 7 mm and a sheet thickness of 0.10 to 0.30 mm and excellent iron loss properties. 2. The composition contains: Si: 2.5 wt% or more, 4.0 wt% or less, Mn: 0.04 wt% or more, 0.15 wt% or less, Ge: 0.005 wt% or more, 0.20 wt% or less, and Mo: 0.005 to 0.20wt%, Cu: 0.01 ~ 0.3wt%, Sb: 0.005 ~ 0.20wt%, Sn: 0.010 ~ 0.025wt% and P: 0.010 ~ 0.10wt%, at least one selected from the group consisting of Fe and trace amounts Unavoidable element, average secondary particle size is 3 ~ 7m
High magnetic flux density directional silicon steel sheet with excellent iron loss characteristics, with a thickness of 0.10 to 0.30 mm. 3. The basic components are as follows: C: 0.02 to 0.090 wt%, Si: 2.5 to 4.0 wt%, Mn: 0.04 to 0.15 wt%, sol Al: 0.010 to 0.050 wt% and N: 0.0040 to 0.0120 wt%. A silicon steel slab with Ge added to a steel material in the range of 0.005 to 0.20 wt% is hot-rolled and then subjected to the first cold rolling to obtain an intermediate sheet thickness, and then at 1000 to 1200 ° C and 0.5 to After 10 minutes of intermediate annealing, the steel sheet is rapidly cooled to at least 500 ° C. at a cooling rate of 7 ° C./s or more, and then subjected to a second cold rolling under the condition of a reduction ratio of 75 to 90% to obtain a sheet thickness of 0.10 to 0.30. After finishing the final cold-rolled sheet of mm, it is subjected to primary recrystallization annealing also serving as decarburization, and thereafter, an annealing separator containing MgO as a main component is applied, followed by high-temperature finish annealing. Manufacturing method of high magnetic flux density oriented silicon steel sheet with excellent iron loss characteristics. 4. The cooling rate after the intermediate annealing is from 750 ° C. to 250 ° C.
4. The method according to claim 3, wherein the average cooling rate is 7 to 25 [deg.] C./s over the temperature range up to. 5. The cooling rate after the intermediate annealing is from 750 ° C. to 250 ° C.
4. The production method according to claim 3, wherein the average cooling rate is 7 to 25 [deg.] C./s until 250 [deg.] C., and the average cooling rate is 4 [deg.] C./s or less from 250 [deg.] C.