JPH0673509A - Grain oriented silicon steel sheet excellent in magnetic property and its production - Google Patents

Abstract

PURPOSE:To produce a grain oriented silicon steel sheet excellent in magnetic properties by forming a silicon steel sheet having a specific composition consisting of Si, C, Al, N, Mn, S, and Fe so that primary recrystallized grains after decarburizing annealing become respectively specified grain size and coefficient of variation. CONSTITUTION:A slab of a silicon steel which has a composition consisting of, by weight, 2.5-4.0% Si, 0.03-0.10% C, 0.010-0.065% acid soluble Al, 0.0010-0.0150% N, 0.02-0.30% Mn, 0.005-0.040% S, and the balance Fe with inevitable impurities and further containing, if necessary, <=0.4% of one or more elements among Sn, Cu, Sb, and Se is heated up to >=1300 deg.C, hot-rolled, annealed, and subjected to final cold rolling at >=80%. Resulting sheet is subjected to decarburizing annealing and to final finish annealing. At this time, the average diameter of primary recrystallized grains after decarburizing annealing and the coefficient of variation of diameter are regulated to 6-11mum and <=0.5, respectively. Further, final finish annealing is done in a state of a coil of >=300nm inside diameter, and the average diameter of the primary recrystallized grains is increased by 5-30% just before the initiation of the secondary recrystallization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, which is used as an iron core of a transformer or the like.

[0002]

2. Description of the Related Art Unidirectional magnetic steel sheets are mainly used as iron core materials for transformers and other electrical equipment, and are required to have excellent magnetic characteristics such as excitation characteristics and iron loss characteristics. The magnetic field strength is 800A as a numerical value showing the excitation characteristics.
The magnetic flux density B _{8 at} / m is usually used.

The numerical value representing the iron loss characteristic is 1 when magnetized to 1.7 Tesler (T) at a frequency of 50 Hz.
Iron loss W _17/50 per kg is used. The magnetic flux density is the most dominant factor of the iron loss characteristics, and generally speaking, the higher the magnetic flux density, the better the iron loss characteristics. Generally, when the magnetic flux density is increased, the secondary recrystallized grains become large, which may result in poor iron loss characteristics. On the other hand, by controlling the magnetic domains, the iron loss characteristics can be improved regardless of the grain size of the secondary recrystallized grains.

This unidirectional electrical steel sheet undergoes secondary recrystallization in the final finishing annealing step to develop a so-called Goss structure having {110} axis on the steel sheet surface and <001> axis in the rolling direction. Being manufactured. In order to obtain good magnetic properties, it is necessary to highly align <001>, which is the easy magnetization axis, in the rolling direction.

A representative technique for manufacturing such a high magnetic flux density grain-oriented electrical steel sheet is Satoshi Taguchi et al.
0-15644 and Japanese Patent Publication Sho 51
There is a method described in JP-A-13469. MnS and AlN are used in the former, and MnS, MnSe and Sb are used in the latter.
Etc. are used as main inhibitors. Therefore, in the current technology, it is essential to properly control the size, morphology and dispersion state of the precipitates that function as these inhibitors.

[0006] The unidirectional electrical steel sheet is a functional material, and its main purpose is to improve the magnetic properties, but industrially, it is necessary to have a stable manufacturing technique. is there. From such a viewpoint, the present inventors have developed a technique for predicting and controlling the characteristics of an end product with an intermediate product (Japanese Patent Application No. 1-1778, etc.).

[0007]

DISCLOSURE OF THE INVENTION The present invention is directed to a process for producing a grain-oriented electrical steel sheet which requires a long period of time to pass through a series of steps such as hot rolling, annealing and cold rolling from the steelmaking stage to become a product. ,
It gives a quantitative evaluation standard for the problem that the characteristics of the final product are difficult to predict from the intermediate product and its control is not easy,
It provides a product with excellent magnetic properties obtained by that technique.

[0008]

The subject matter of the present invention is as follows. (1) In the unidirectional electrical steel sheet containing Si: 2.5 to 4.0% by weight ratio, the Al amount of the steel sheet with the insulating film removed and the surface coating is Al (WG) (% )
When the Al amount of the steel sheet after removing the surface coating is Al (WOG) (%) in weight ratio, Al (WG) -Al (WOG) ≧ 0.0050%, and the average of the product sheets Crystal diameter (circle equivalent diameter) is 1.5
The average value of the ratio l _R / l _T between the maximum length l _R of the crystal grains in the rolling direction and the maximum length l _{T in} the direction perpendicular to the rolling direction is 1.0 to 3.5, and the average diameter is With respect to the crystal orientation of the center of gravity in the crystal grain of more than 5 mm, the orientation dispersion of 0.5 to 5 degrees exists in the crystal grain, and the magnetic flux density of the product is B ₈
A grain-oriented electrical steel sheet with ≧ 1.88T.

(2) By weight ratio, Si: 2.5 to 4.0.
%, C: 0.03 to 0.10%, acid-soluble Al: 0.0
10 to 0.065%, N: 0.0010 to 0.0150
%, Mn: 0.02-0.30%, S: 0.005-
A silicon steel hot-rolled steel sheet containing 0.040% and the balance of Fe and unavoidable impurities is annealed by hot-rolled steel sheet if necessary, and then includes final cold rolling with a rolling reduction of 80% or more, and if necessary. The average diameter of the primary recrystallized grains of the steel sheet after decarburization annealing in the method of manufacturing a unidirectional electrical steel sheet by performing cold rolling one or more times with intermediate annealing between them, followed by decarburization annealing and final finishing annealing. Is 6 to 11 μm, the coefficient of variation of the diameter of the primary recrystallized grains is 0.5 or less, and immediately before the start of secondary recrystallization of the final finish annealing performed in a coil shape with an inner diameter of 300 mm or more,
(1) The method for producing a unidirectional electrical steel sheet according to (1), wherein the average diameter of the primary recrystallized grains is increased by 5 to 30% with respect to the average diameter of the steel sheet after decarburization annealing.

(3) 0.4% or less Sn, C in the slab
The method for producing a steel sheet according to (2), which contains one or more of u, Sb, and Se.

[0011]

The unidirectional electrical steel sheet targeted by the present invention is
Molten steel obtained by a conventional steelmaking method is cast by a continuous casting method or an ingot making method, and if necessary, a slab may be sandwiched between slabs, followed by hot rolling to a hot rolled sheet, and then this The hot-rolled sheet is annealed if necessary, and then the rolling reduction is 8
It is manufactured by including 0% or more of final cold rolling, and if necessary, performing one or more cold rollings with intermediate annealing, decarburizing annealing, and final finishing annealing in this order.

The inventors of the present invention have extensively studied a method of predicting and controlling the properties of an intermediate product to a final product in the production process of grain-oriented electrical steel sheets. As a result, the material after decarburization annealing and before final finishing annealing is A new finding was obtained that the change in the crystal structure of Fe and the change in the crystal structure until the start of secondary recrystallization during final finish annealing greatly affect the magnetic properties of the product, and the change is related to the decrease in the Al content in steel. It was

A detailed description will be given below based on experimental results. Figure 1
In addition, the average diameter d of the primary recrystallized plate obtained by image analysis of the crystal structure (total thickness in the plate thickness direction) of the steel plate after decarburization annealing (hereinafter referred to as decarburization annealed plate) observed with an optical microscope.
(Circle equivalent diameter) and diameter variation coefficient σ ^* (standard deviation of crystal diameter distribution standardized by average diameter d of primary recrystallized grains)
Shows the effect of on the magnetic flux density (B ₈ value) of the product.

In this case, the weight ratio of Si: 3.0-3.
4%, C: 0.068 to 0.090%, acid-soluble Al:
0.014-0.032%, N: 0.0071-0.0
090%, Mn: 0.071 to 0.086%, S: 0.
A silicon steel slab of 024 to 0.030% and the balance of Fe and unavoidable impurities is heated to 1300 to 1400 ° C. for 1 hour and hot-rolled to a hot-rolled sheet having a thickness of 2.3 mm.
(1) The hot-rolled sheet was annealed at 980 ° C., cold-rolled to a thickness of 1.6 mm, then subjected to intermediate annealing at 1100 ° C., and then cold-rolled at a rolling reduction of about 86%, 0.22 mm thick cold rolled sheet, (2) cold rolled this hot rolled sheet to 1.6 mm thick,
Then, after subjecting to an intermediate annealing at 1100 ° C., a reduction rate of about 86
% To obtain a 0.22 mm-thick cold-rolled sheet. (3) This hot-rolled sheet is annealed at 1100 ° C., and then cold-rolled at a reduction rate of about 90%. 0.22mm thick cold rolled sheet,
The final cold-rolled sheet having a thickness of 0.22 mm was obtained by the three types of processes.

The cold rolled sheet was decarburized and annealed in the temperature range of 820 to 900 ° C. (25% N ₂ + 75% H ₂ , dew point 58 to 68).
C) was applied. The average diameter of the primary recrystallized grains of this decarburized annealed plate and the coefficient of variation of the diameter were measured using an optical microscope and image analysis.

Then, an annealing separator containing MgO as a main component is applied to the steel sheet to form a coil shape (5 tons) having an inner diameter of 400 mm and in an annealing atmosphere containing 0 to 100% of N ₂ (the balance is H ₂ ). Then, the temperature was raised to 1200 ° C. at a heating rate of 15 ° C./Hr, and a final finishing annealing was carried out at 1200 ° C. for 20 hours in an H ₂ annealing atmosphere.

After that, it was cut into SST size, made into a flat plate shape, subjected to strain relief annealing at 850 ° C. for 4 hours, and subjected to magnetic measurement.

As is apparent from FIG. 1, the average diameter d of primary recrystallized grains (decarburized and annealed plate) is 6 to 11 μm, and the variation coefficient of the diameter of primary recrystallized grains is 0.5 or less only. , B ₈ ≧ 1.88T, and a product having good magnetic properties was obtained.

However, even within this range, there were cases where B ₈ <1.88 T, so the cause was examined in detail. The results of this examination will be described below.

In the experiment shown in FIG. 1, the average diameter d of the primary recrystallized grains of the decarburized and annealed plate in the experiment shown in FIG.
And grain growth rate until the secondary recrystallization starting just before the final annealing after decarburization annealing in the same material variation coefficient of the diameter of the primary recrystallized grains sigma ^* was 0.5 or less [Delta] d / d ((two Difference between the average diameter of the primary recrystallized grains immediately before the next recrystallization and in the decarburized annealed plate) / (average diameter of the primary recrystallized grains in the decarburized annealed plate)
(%) And the magnetic flux density (B ₈ ) are shown.

In this case, the steel sheet was drawn out from the annealing furnace when the furnace temperature during the temperature rising process of the final finishing annealing performed again was 1100 ° C. (sheet temperature 901 to 1080 ° C. (calculated value)). In this sample, the low temperature part has a primary recrystallization structure and the high temperature part has a secondary recrystallization structure.

By observing this crystal structure, the portion having the primary recrystallization structure in the vicinity of the portion where the grain penetrating the plate thickness (secondary recrystallized grain) was set to the state immediately before the secondary recrystallization (start). Call.

As is clear from FIG. 2, the grain growth ratio Δd from the decarburization annealing to immediately before the start of secondary recrystallization in the final finish annealing.
In all cases where / d is 5 to 30%, B ₈ ≧ 1.88T
Good magnetic properties were obtained.

The reason why the relationships shown in FIGS. 1 and 2 are established is not necessarily clear, but the present inventors presume as follows. The average diameter of the primary recrystallized grains is an amount inversely proportional to the total grain boundary area (per unit volume), and these grain boundary energies serve as a driving force for grain growth of the secondary recrystallized grains.

When this driving force is low, secondary recrystallization occurs from a low temperature, and when this driving force is high, the temperature at which secondary recrystallization occurs becomes high, and in extreme cases, secondary recrystallization does not occur. . On the other hand, the larger the coefficient of variation of the diameter, the more the mixed particles are in the mixed particle state, and the mixed particle in the mixed particle state becomes more prominent as the particle grows. There is a tendency.

When the primary recrystallization structure is in a mixed grain state,
The probability that coarse grains of other orientations are adjacent to {110} <001> oriented grains increases, and the possibility that {110} <001> oriented grains grow and secondary recrystallized grains can be prevented is increased. It will be. Therefore, the mixed grain state (state in which the variation coefficient of the diameter is large) is disadvantageous for the generation of secondary recrystallized grains.

On the other hand, by high temperature slab heating as in the present invention,
In the manufacturing process in which AlN and MnS are completely solid-solved and AlN and MnS are finely precipitated by hot rolling, hot-rolled sheet annealing, etc., grain size of grain boundary migration is increased by increasing inhibitor strength during secondary recrystallization. Increase the field character dependence, {110}
In order to secondary recrystallize only the oriented grains highly accumulated in the <001> orientation, the inhibitor during decarburization annealing becomes inevitably strong, and the adjustment of the primary recrystallized grain size is a short time annealing. Carbon annealing alone is not enough.

Therefore, it is necessary to adjust the primary recrystallized grain size by finish annealing which is annealing for a long time. When adjusting this primary recrystallized grain size, if the decarburized annealed plate has already had a mixed grain structure (state with a large variation coefficient of diameter),
Along with the grain growth, the tendency of mixed grains increases and secondary recrystallization is less likely to occur, which is not preferable.

Then, while the coefficient of variation of the diameter is controlled to a low value as in the present invention, grain growth is caused during the final annealing, and the average diameter is set within a predetermined range immediately before secondary recrystallization. It is possible to control the secondary recrystallization temperature and the driving force for grain growth of the secondary recrystallized grains within a preferable range.

Therefore, the average diameter of the decarburized annealed sheet, the coefficient of variation of the diameter, the change rate of the average diameter from after decarburization annealing to immediately before the start of secondary recrystallization in the final finish annealing, and the secondary recrystallization orientation {110 } <001> It is assumed that the degree of integration (magnetic flux density B _{8 of the} product) has a strong correlation.

Various studies were conducted on the cause of the grain growth immediately before the secondary recrystallization. The materials of the present invention are AlN and Mn.
S is used as an inhibitor, and the decomposition of AlN and MnS is considered to be related to the oxidation phenomenon in the surface layer.

Particularly, in the case of AlN, it is considered that deoxidation proceeds by being oxidized to form Al ₂ O ₃ . Therefore, it is presumed that Al removal is an important controlling factor for grain growth.

Therefore, in the experiment shown in FIG. 1, the average diameter d of the primary recrystallized grains of the decarburized annealed sheet is 6 to 11 μm.
And the coefficient of variation σ ^* of the diameter of the primary recrystallized grains is 0.5
Below, the grain growth rate Δd / d (%) shown in FIG.
= 5 to 30% of the material, after the final annealing, it was made into a flat plate shape, and the Al amount of the steel sheet with the surface coating of the sample subjected to strain relief annealing was Al (WG) (%) by weight, and this surface coating Al (WO
G) (%), all samples had Al (WG) -Al (WOG) ≧ 0.0050% as shown in FIG.

This shows that Al was concentrated in the surface coating during the final finish annealing.
It is related to the possibility that the grain growth of the primary recrystallized grains occurs before the secondary recrystallization due to the fact that l is concentrated in the film from the steel, the amount of AlN in the steel is reduced, and the inhibitor is weakened. , Al being concentrated in the surface coating is considered to be a necessary condition for obtaining good magnetic properties.

On the other hand, the average crystal grain size of the product plate is one of the controlling factors of the iron loss characteristics, and the average diameter (circle equivalent diameter) of the crystal grains of the material shown in FIG. 3 is measured by using an image analyzer. Then, as shown in FIG. 4, the average diameter is 1.5 to 10 mm.
Met. The smaller this average diameter, the better the iron loss,
This range is preferable for improving the magnetic flux density. Further, as in the present invention, a secondary recrystallization is produced in a coil shape,
Then, as a flat plate, in the case of a product, in the flat plate shape, in the rolling direction, orientation dispersion of secondary recrystallization occurs,
This affects the magnetic flux density and iron loss of the product.

Therefore, this azimuth dispersion is determined by the ECP method (Ele
ctron Channeling Pattern). For the evaluation of orientation dispersion, the difference between the orientation of the center of gravity of each secondary recrystallized grain having a diameter of 5 mm or more and the orientation at the point in the grain farthest from the center of gravity of the grain in the rolling direction was used as the quantile dispersion.
This quantile dispersion was 0.5 to 5 degrees as shown in FIG. This quantile dispersion is necessary for magnetic domain control using a laser or the like and for magnetic domain subdivision by film tension.

In addition, as the colonies are likely to exist in the primary recrystallization texture in the rolling direction and the secondary recrystallized grains grow in the coil direction in the rolling direction, the orientation grains in the corresponding orientation relationship decrease. For example, the maximum length l _{R in} the rolling direction of the secondary recrystallized grains of the product and the maximum length l in the direction perpendicular to the rolling direction
The ratio of _T deviates from 1.

For the material shown in FIG. 3, this ratio l _R / l
The average value of _T was 1.0 to 3.5 as shown in FIG. In order to reduce this value to less than 1.0, it is necessary to use a method involving cost increase such as applying local strain at a few mm interval in the direction perpendicular to the rolling before finish annealing, which is not preferable.
If it exceeds 5, the magnetic flux density when formed into a flat plate is significantly reduced, which is not preferable.

Next, the reasons for limiting the constituent features of the present invention will be described. The weight ratio of the components of the slab, which is the starting material of the present invention, is Si: 2.5 to 4.0% and C: 0.03.
~ 0.10%, acid-soluble Al: 0.010-0.065
%, N: 0.0010 to 0.0150%, Mn: 0.0
2 to 0.30%, S: 0.005 to 0.040% must be contained.

If Si exceeds 4.0%, embrittlement becomes severe and cold rolling becomes difficult, which is not preferable. On the other hand, 2.5%
If it is less than 1, the electric resistance is low and it is difficult to obtain good iron loss characteristics.

If C is less than 0.03%, the γ amount before decarburization annealing becomes extremely small, and the metal structure after decarburization annealing becomes unsuitable. On the other hand, if it exceeds 0.10%, decarburization becomes poor, which is not preferable.

The acid-soluble Al, N is a basic component for obtaining the main inhibitor AlN essential for obtaining a high magnetic flux density in the present invention, and if it deviates from the above range, the secondary recrystallization becomes unstable. Al is 0.010 to 0.06
5% and N are 0.0010 to 0.0150%.

Mn and S are elements necessary for forming the inhibitor MnS. If the content of Mn and S deviates from the above range, secondary recrystallization becomes unstable. Therefore, Mn is 0.02 to 0.30% and S
Is set to 0.005 to 0.040%.

Further, Sn and C which are the constituent elements of the inhibitor
Containing 0.4% or less of each of one or more of u, Sb, and Se is preferable in the technique of controlling primary recrystallized grain growth as in the present invention. If it exceeds 0.4%, grain growth is significantly suppressed, which is not preferable.

The slab is heated at a temperature of 1300 ° C. or higher for hot rolling. If the slab heating temperature is lower than 1300 ° C., the solid solution of AlN and MnS becomes insufficient and the secondary recrystallization becomes unstable, which is not preferable. Hot rolling is performed by a usual method.

Such hot-rolled sheet is annealed by hot-rolled sheet if necessary, and then includes final cold rolling with a rolling reduction of 80% or more, and if necessary, one or more cold-rolling steps with intermediate annealing are performed. Next, it is premised on a step of sequentially performing decarburization annealing and final finishing annealing. If the final cold rolling reduction is less than 80%, it is difficult to obtain a high magnetic flux density, which is not preferable.

The average diameter of the primary recrystallized grains of the steel sheet after decarburization annealing is set to 6 to 11 μm, the variation coefficient of the diameter of the primary recrystallized grains is set to 0.5 or less, until just before the start of secondary recrystallization of the final annealing. First, it is necessary to make the average diameter of the primary recrystallized grains 5 to 30% larger than the average diameter of the steel sheet after decarburization annealing.

As shown in FIGS. 1 and 2, good magnetic characteristics of B ₈ ≧ 1.88 T can be stably obtained by controlling within the above range. Means for controlling the average diameter of the primary recrystallized grains, the coefficient of variation, and the grain growth behavior during final finish annealing within the above range are not particularly limited.

Component range of inhibitor constituent elements, heat cycle of hot-rolled sheet annealing, heat cycle of decarburizing annealing, atmosphere gas, kind and amount of additive to annealing separator, heat cycle of final annealing, atmosphere gas, etc. The above values can be controlled within the required range by the combination of.

The final finish annealing is performed in a coil shape having an inner diameter of 300 mm or more. If the diameter is less than 300 mm, secondary recrystallization in a coil shape is performed, and the intragranular orientation dispersion of the secondary recrystallization orientation for flattening and using as a product becomes too large, which is not preferable. The upper limit of the inner diameter of the coil is not particularly limited, but if it is 10000 mm or more, the annealing furnace becomes too large and the controllability of the annealing furnace deteriorates, which is not preferable.

After the final finish annealing, magnetic properties are further improved by performing magnetic domain control using an insulating coating that gives tension or a laser.

The product obtained by the above-mentioned technique has a weight ratio of S
i: 2.5 to 4.0% is contained. This is inevitably determined from the above steel composition. Also, the insulating coating was removed, and the Al amount of the steel sheet with surface coating was expressed as
(WG) (%) and the Al amount of the steel sheet when this surface coating is also removed is Al (WOG) (%), as shown in FIG. 3, Al (WG) -Al (WOG) ≧ 0.005
It must be 0%.

This is because the above-mentioned manufacturing method removes A during the final finish annealing.
This is because the basic technique is the grain growth of the primary recrystallized grains by l, and the use of this technique enables a high magnetic flux density. Al (WG) -Al (WO
The upper limit of G) is not particularly limited, but when judged from the upper limit of acid-soluble Al in the production method and the amount of non-acid-soluble Al in a normal slab (0.001%), 0.0
66%. The reason that the coating is removed here is to remove the influence of Al which may be contained as a coating component.

On the other hand, the average crystal diameter of the product sheet is 1.5 to 10 mm as shown in FIG. 4, and the maximum length l _R of the crystal grains in the rolling direction and the maximum length l _{T in} the direction perpendicular to the rolling direction are obtained. Ratio l _R
The average value of each sample of / l _T is 1.0 as shown in FIG.
.About.3.5, and there is an orientation dispersion of 0.5 to 5 degrees as shown in FIG. 5 with respect to the crystal orientation of the center of gravity in the crystal grains with an average diameter of more than 5 mm (a total of 90). .

The characteristics shown in FIGS. 4, 5, and 6 are characteristic characteristics of the product obtained by the manufacturing method of the present application. As described above, good magnetic characteristics are obtained unless these ranges are observed. I can't get it. As shown in Fig. 2, the magnetic flux density of the product is B ₈ ≧
Must be 1.88T.

[0056]

【Example】

Example 1 By weight ratio, Si: 3.26%, C: 0.081%, acid-soluble Al: 0.026%, N: 0.0079%, Mn:
1. A 250 mm thick slab containing 0.077% and S: 0.024% was held at 1350 ° C. for 1 hour and then hot rolled.
A hot rolled sheet having a thickness of 3 mm was used.

The hot-rolled sheet was annealed at 1120 ° C. for 30 seconds and then at 900 ° C. for 30 seconds to be rapidly cooled, followed by cold rolling to a thickness of 0.285 mm at a rolling reduction of about 88%. 8
Decarburization annealing (25% N ₂ +75 held at 40 ° C for 150 seconds)
% H ₂ in an atmosphere gas having a dew point of 63 ° C.). Using an optical microscope and an image analyzer, the average diameter d of the primary recrystallized grains of this decarburized annealed plate and the coefficient of variation σ ^{* of the} diameter were measured.

An annealing separator containing MgO as a main component was applied to the decarburized annealed plate to form a 5-ton coil having a coil inner diameter of 600 mm, and the temperature was raised to 1200 ° C. at 15 ° C./Hr.
Final finishing annealing was carried out at 20 ° C. for 20 hours. The annealing atmosphere during the holding of the final finish annealing at 1200 ° C. was 10
0% H ₂ and 15% N ₂ + 85% atmosphere gas during temperature rise
% H ₂ .

Further, after applying an annealing separator to a 5 ton coil prepared under the same process conditions and the same components as the above 5 ton coil, the temperature was raised at 15 ° C./Hr under the above atmosphere conditions, and the furnace temperature was 1100 ° C. (plate At a temperature of 921 to 1092 ° C (calculated value), the steel sheet was pulled out from the annealing furnace, and the primary recrystallized structure in the vicinity of the secondary recrystallized grains was investigated using an optical microscope and an image analyzer, and the average of the primary recrystallized grains was examined. The diameter was measured.

Table 1 shows the characteristic amounts of the decarburized annealed sheet obtained under these conditions, the steel sheet immediately before secondary recrystallization, and the steel sheet after the final finish annealing. The magnetic measurement, the average diameter of the secondary recrystallized grains, the average aspect ratio, the orientation measurement, and the Al amount measurement were performed after the strain relief annealing in which the sample was made into SST size after the final finish annealing and was kept flat at 850 ° C. for 4 hours. .

[0061]

[Table 1]

Example 2 By weight ratio, Si: 3.30%, C: 0.079%, acid-soluble Al: 0.025%, N: 0.0080%, Mn:
0.080%, S: 0.023%, and
(A) no addition, (B) Sn: 0.15% addition, (C)
Cu: 0.07% added, (D) Sn: 0.12%, C
u: 0.06% addition, (E) Sb: 0.03% addition,
(F) Se: 6 kinds of slabs with a thickness of 250 mm added with 0.03 are held at 1350 ° C. for 1 hour and then hot rolled to 2.3 mm
A thick hot rolled sheet was used.

Next, (1) this hot rolled sheet was annealed at 950 ° C., then cold rolled to a thickness of 1.6 mm, and then 1
After performing an intermediate annealing at 100 ° C, cold rolling is performed at a reduction rate of about 86% to obtain a cold rolled sheet having a thickness of 0.22 mm. (2) This hot rolled sheet is cold rolled to 1.6 mm, and then 1100 After the intermediate annealing at ℃, it is cold rolled at a rolling reduction of about 86% to make a 0.22 mm thick cold rolled sheet. (3) After this hot rolled sheet is annealed at 1100 ° C , Cold rolled with a reduction rate of about 90%, 0.22mm
0.22 in 3 kinds of process, which is to make thick cold rolled sheet
The final cold-rolled sheet with a thickness of mm was used.

This final cold-rolled sheet was processed under the conditions described in Example 1 until the final finish annealing. In this case, the decarburization annealed sheet, the primary recrystallized structure immediately before the secondary recrystallization, and the characteristic amount of the steel sheet after the final finish annealing (magnetic content measurement) were examined in the same manner as in Example 1. The results are shown in Table 2.

[0065]

[Table 2]

[0066]

[Table 3]

[0067]

INDUSTRIAL APPLICABILITY According to the present invention, the average diameter of the primary recrystallized grains of the steel sheet after decarburization annealing, the coefficient of variation of the diameter, and the primary recrystallization just before the start of secondary recrystallization of the final finish annealing and after the decarburization annealing are performed. By controlling the ratio of the average diameter of the crystal grains (grain growth ratio), the unidirectional electrical steel sheet having excellent magnetic properties can be finally annealed in a coil shape and stably manufactured.
Furthermore, by adding one or more of Sn, Cu, Sb, and Se, it is possible to stably produce a grain-oriented electrical steel sheet having even more excellent magnetic properties. Therefore, these technologies have industrial significance. It is extremely large.

The product obtained according to the present invention has an Al concentration in the surface coating and has an average crystal diameter of secondary recrystallized grains.
The average value of the ratio of the maximum length in the rolling direction and the maximum length in the direction perpendicular to the rolling direction, and the outstanding magnetic properties with remarkable features in the orientation dispersion in the crystal grains with an average diameter of more than 5 mm.

[Brief description of drawings]

FIG. 1 is a chart showing the influence of the average diameter of primary recrystallized grains and the coefficient of variation of the diameter on the magnetic flux density of a product in a decarburized annealed plate.

FIG. 2 is a table showing the relationship between the grain growth rate and the magnetic flux density of the product after decarburization annealing and immediately before the start of secondary recrystallization in final annealing.

FIG. 3A of the steel sheet with surface coating of the sample after final finish annealing
It is a chart showing the frequency of the difference between the amount of Al (Al (WG)) and the amount of Al (Al (WOG)) of the steel sheet when this surface coating is also removed.

FIG. 4 is a chart showing the frequency of the average diameter of the secondary recrystallized grains of the product.

FIG. 5 is a chart showing the frequency of orientation dispersion in secondary recrystallized grains of a product.

FIG. 6 is a chart showing the frequency of the in-sample average value of the ratio of the maximum length l _R in the rolling direction and the maximum length l _{T in} the direction perpendicular to the rolling of the secondary recrystallized grains of the product.

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[Procedure amendment]

[Submission date] August 28, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

[0008]

The subject matter of the present invention is as follows. (1) In the unidirectional electrical steel sheet containing Si: 2.5 to 4.0% by weight ratio, the Al amount of the steel sheet with the insulating film removed and the surface coating is Al (WG) (% )
When the Al amount of the steel sheet after removing the surface coating is Al (WOG) (%) in weight ratio, Al (WG) -Al (WOG) ≧ 0.0050%, and the average of the product sheets Crystal diameter (circle equivalent diameter) is 1.5
The average value of the ratio l _R / l _T between the maximum length l _{R in} the rolling direction of the crystal grains and the maximum length l _{T in} the direction perpendicular to the rolling direction is 1.0 to 3.5, and the diameter is 5 mm. The orientation dispersion of 0.5 to 5 degrees with respect to the crystal orientation of the center of gravity in the super crystal grain exists in the crystal grain, and the magnetic flux density of the product is B ₈ ≧
1.88T unidirectional electrical steel sheet.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0054

[Correction method] Change

[Correction content]

On the other hand, the average crystal diameter of the product sheet is 1.5 to 10 mm as shown in FIG. 4, and the maximum length l _R of the crystal grains in the rolling direction and the maximum length l _{T in} the direction perpendicular to the rolling direction are obtained. Ratio l _R
The average value of each sample of / l _T is 1.0 as shown in FIG.
.About.3.5, and there is an orientation dispersion of 0.5 to 5 degrees as shown in FIG. 5 with respect to the crystal orientation of the center of gravity in the crystal grains with a diameter of more than 5 mm (90 in total) in each sample.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0061

[Correction method] Change

[Correction content]

[0061]

[Table 1]

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0065

[Correction method] Change

[Correction content]

[0065]

[Table 2]

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0066

[Correction method] Change

[Correction content]

[0066]

[Table 3]

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0068

[Correction method] Change

[Correction content]

The product obtained according to the present invention has an Al concentration in the surface coating and has an average crystal diameter of secondary recrystallized grains.
It has excellent magnetic properties, with remarkable features in the average value of the ratio of the maximum length in the rolling direction and the maximum length in the direction perpendicular to the rolling direction, and the azimuth dispersion within the crystal grains with a diameter of more than 5 mm.

[Procedure amendment]

[Submission date] November 11, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0037

[Correction method] Change

[Correction content]

Further, as the colonies are likely to exist in the primary recrystallization texture in the rolling direction and the secondary recrystallized grains grow in the coil direction in the rolling direction, the orientation grains in the corresponding orientation relationship decrease. For this reason, the ratio of the maximum length l _{R in} the rolling direction of the secondary recrystallized grains of the product and the maximum length l _{T in} the direction perpendicular to the rolling direction deviates from 1.

Claims (3)

[Claims] 1. In a unidirectional electrical steel sheet containing Si: 2.5 to 4.0% by weight, the insulating coating is removed, and the Al content of the steel sheet with a surface coating is expressed by Al (W
G) (%), and the Al content of the steel sheet after removal of this surface coating is also Al (WOG) (%) in weight ratio Al (WG) -Al (WOG) ≧ 0.0050% , The average crystal diameter of the product plate (circle equivalent diameter) is 1.5
The average value of the ratio l _R / l _T between the maximum length l _R of the crystal grains in the rolling direction and the maximum length l _{T in} the direction perpendicular to the rolling direction is 1.0 to 3.5, and the average diameter is With respect to the crystal orientation of the center of gravity in the crystal grain of more than 5 mm, the orientation dispersion of 0.5 to 5 degrees exists in the crystal grain, and the magnetic flux density of the product is B ₈
A grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that ≧ 1.88T. 2. By weight ratio, Si: 2.5-4.0%, C: 0.03-0.10%, acid-soluble Al: 0.010-0.065%, N: 0.0010-0. 0.0150%, Mn: 0.02 to 0.30%, S: 0.005 to 0.040%, 1 balance of the silicon steel slab consisting of Fe and unavoidable impurities
It is heated at a temperature of 300 ° C or higher, hot-rolled, and then the hot-rolled sheet is annealed, if necessary, and finally cold-rolled at a reduction rate of 80% or more, and if necessary, intermediate In the method of producing a unidirectional electrical steel sheet by performing cold rolling one or more times with annealing between them, followed by decarburization annealing and final finishing annealing, the average diameter of the primary recrystallized grains of the steel sheet after decarburization annealing (circle Equivalent diameter) is 6 to 11 μm, the coefficient of variation of the diameter of the primary recrystallized grains is 0.5 or less, and immediately before the start of secondary recrystallization of the final finish annealing performed in a coil shape with an inner diameter of 300 mm or more,
A method for producing a unidirectional electrical steel sheet having excellent magnetic properties, characterized in that the average diameter of primary recrystallized grains is made 5 to 30% larger than the average diameter of the steel sheet after decarburization annealing. 3. A silicon steel slab containing 0.4% or less Sn,
3. The method for producing a grain-oriented electrical steel sheet having excellent magnetic properties according to claim 2, which contains one or more of Cu, Sb, and Se.