JPH1161358A - Electric steel sheet excellent in blanking and magnetic property in rolling direction and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electric steel sheet excellent in blanking and magnetic properties in the rolling direction by forming texture accumulated in the Goss azimuth without utilizing secondary recrystallization. SOLUTION: This electric steel sheet has the composition consisting of <=0.003 wt.% C, 0.1-4.5 wt.% Si and the balance Fe essentially and the normal grain whose average crystal grain size is 0.1-5.0 mm and in which the deviation of the <001> axis of the 110} <001> azimuth to the parallel axial line in the rolling direction is within ±15 deg. by a rotational angle is >=80% of the entire crystal grain. The manufacturing method is that, after executing hot rough- rolling of a steel slab containing <=0.003 wt.% C and 0.1-4.5 wt.% Si, hot finish- rolling is executed under the conditions that draft (one pass) is >=30%, rolling completed temp. is 600-800 deg.C and to the thickness of the hot rolled sheet of <=1.5 mm, as necessary, after annealing the hot rolled sheet, executing two or more times of cold rolling or the like including annealing after pickling and making the sheet into the final thickness, finish annealing is executed and, next, an insulated film is imparted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic steel sheet used for an AC magnetic core and having excellent punching properties and magnetic properties in a rolling direction, and a method for producing the same.

[0002]

2. Description of the Related Art It is desirable for an electromagnetic steel sheet to have excellent electromagnetic characteristics in the direction of magnetization during use, and the characteristics greatly depend on the texture. The preferred texture differs depending on the type of use, that is, which direction of the steel sheet is used as the magnetization direction. When only one direction parallel to the rolling is the magnetization direction, as in some transformers, the rolling direction Is optimal, such that the crystal orientation of <001> is <001>. Electromagnetic steel sheets in which such crystal orientations are preferentially grown to improve the electromagnetic properties in the rolling direction are widely manufactured and sold as so-called grain-oriented electromagnetic steel sheets.

[0003] The texture along with the crystal orientation in the rolling direction,
It is defined by the crystal orientation in the direction of the axis perpendicular to the rolling plane. The current grain-oriented electrical steel sheet has a surface parallel to the rolling surface of $ 1.
10}, which is called a {110} <001> direction or a Goss direction.

A grain-oriented electrical steel sheet having a Goss orientation is made of Fe-Si.
Rolling and annealing are repeated several times on a material containing about 0.03-0.10% of C in the basic component system and about 0.01-0.05% of MnS or AlN as an inhibitor component. In general, a method of manufacturing by abnormal growth, that is, secondary recrystallization is used.

In this method, C is contained in steel because it is indispensable for the ultimate development of Goss orientation. However, in order to improve iron loss characteristics, C is usually added before secondary recrystallization. Requires a process of decarburization.

Inhibitors are added for the purpose of suppressing the growth of normal grains prior to the secondary recrystallization in order to preferentially abnormally grow crystal grains having a Goss orientation during secondary recrystallization. However, if remaining in the product steel sheet, it has an adverse effect on the electromagnetic characteristics, so that it must be finally removed by annealing.

[0007] As described above, the conventional manufacturing method employs an extremely complicated and costly process in order to secure electromagnetic characteristics, and has a serious problem from the viewpoint of industrial productivity.

[0008] Above all, the biggest cause of deterioration in productivity is that high-temperature and long-time purification annealing is required after secondary recrystallization in order to remove the inhibitor. For this reason,
If a texture that is strongly integrated in the Goss orientation can be obtained without adding an inhibitor, the industrial significance is enormous,
No such technique is known.

[0009] Another cause of the deterioration of productivity is the addition of C. C is also an essential component for accumulating the Goss orientation in the normal manufacturing process, so it is necessary to perform decarburizing annealing before secondary recrystallization, which is disadvantageous in terms of manufacturing time and cost. It is. However, a technique for omitting C is not known.

When an electromagnetic steel sheet is used for a small transformer core, punchability is required. Electrical steel sheets are broadly classified into `` non-oriented '' and `` oriented ''. Generally, non-oriented electrical steel sheets have a fine grain size and good punching properties, while grain-oriented electrical steel sheets are rolled. Although the electromagnetic characteristics in the direction are excellent, there is a problem in terms of punchability.

That is, in order to obtain excellent electromagnetic characteristics in a grain-oriented electrical steel sheet, crystal grains aligned in the Goss orientation are abnormally grown by secondary recrystallization to form giant crystal grains (average crystal grain size).
(10 mm or more) must be formed, but these giant crystal grains deteriorate the punchability.

When the prior art is evaluated from the viewpoint of obtaining a Goss orientation without generating giant grains due to secondary recrystallization,
Actually, in the manufacturing process of the grain-oriented electrical steel sheet, crystal grains having a {110} <001> orientation exist to some extent near the surface layer of the hot-rolled steel sheet, and the subsequent steps such as cold rolling and decarburizing annealing are performed. Will increase the relative abundance of that orientation,
It is hardly possible to obtain good electromagnetic characteristics as it is.

That is, ｛1 at the stage before such secondary recrystallization
The integrated strength in the 10 ° <001> orientation is at most about 5 times the ratio with the random orientation obtained from the orientation distribution function of the texture, and is not over the entire thickness.

On the other hand, even in the category of non-oriented electrical steel sheets, attempts have been made to improve the electromagnetic properties in the rolling direction by controlling the texture.

That is, Japanese Patent Application Laid-Open No. 54-110121 discloses that a cold-rolled steel sheet is rapidly heated to transform α → γ, and then slowly cooled to transform γ → α, thereby reducing $ 11
It is described that the degree of integration of the 0 ° plane increases. However, the degree of integration was at most about five times that of the random orientation.

[0016] Also, in the literature (Min. Takashima et al .: "Materials and Processes", Vol. 5 (1992), p. 1921), by adding a small amount of Sb, the {110} <001> Is described as increasing. However, this has only recovered from the originally small orientation at most to the existing ratio in the case of the random orientation, and is far from the texture accumulated in the original Goss orientation.

Similarly, the literature (H. Shimanaka et al .: "Energy
Efficient Electrical Steels '' TMS-AIME (1980) p.1
93) and the method of adding skin pass rolling after intermediate annealing described in the literature (Morio Shiozaki et al .: “Materials and Processes”, Vol. 5 (1992), p. 1923). Does not provide sufficient accumulation in the Goss orientation. Moreover, all of these methods have the disadvantage that the steps are complicated and the production cost is increased.

[0018]

SUMMARY OF THE INVENTION The present invention does not require C in hot rolling, and {110} over the entire sheet thickness.
By forming a texture accumulated in the <001> orientation and using this material, the inhibitor component is not particularly required,
In addition, it is not necessary to grow crystal grains abnormally by secondary recrystallization. By growing normal grains, the grain size of the crystal grains can be appropriately controlled, and the punching property can be accumulated in the {110} <001> direction. An object of the present invention is to provide an electrical steel sheet having excellent magnetic properties in the rolling direction and a method for producing the same.

[0019]

Means for Solving the Problems The above-mentioned problem, that is, C is 0.
At 005% or less, a texture integrated in the {110} <001> orientation is formed by hot rolling without using secondary recrystallization, and {110} <001> orientation without using secondary recrystallization. In order to solve the problem of accumulating grains, the inventors conducted intensive research.

In the grain-oriented electrical steel sheet manufactured by using ordinary secondary recrystallization, goss grains are present only in the vicinity of the surface layer of the sheet surface in the hot rolling stage, and are not present in the central part of the sheet thickness. Therefore, secondary recrystallization had to be used to accumulate Goss grains in the final stage.

For this reason, in the hot rolling stage, the inventors of the present invention have found that if the integrated strength in the {110} <001> orientation is increased over the entire thickness of the sheet, and especially if the strength is sufficiently increased even in the center of the sheet thickness, $ 11 without using next recrystallization
As a result of repeated studies based on the idea that 0 ° <001> orientation grains can be accumulated, the following findings were obtained.

That is, in the hot finish rolling, the rolling end temperature and the rolling reduction in one pass are controlled, and under the condition that the rolling is performed at a lower temperature and stronger in one pass than that employed in the normal process.
By performing hot finish rolling to a thickness of 1.5 mm or less, it is possible to form a texture integrated in the {110} <001> orientation after hot rolling. Furthermore, by using this material, secondary recrystallization is used. The present inventors have found that {110} <001> orientation grains can be highly integrated without performing the present invention, and have completed the present invention.

The gist configuration of the present invention is as follows. 1. C: 0.005 wt% or less, Si: 0.1 to 4.5 wt%, the balance is substantially composed of Fe, and the average crystal grain size is
Within the range of 0.1 to 5.0 mm, the deviation of the <001> axis of the {110} <001> orientation with respect to the axis parallel to the rolling direction is within ± 15 ° of the rotation angle, and more than 80% of the normal grains are the whole grains. An electromagnetic steel sheet having excellent punching properties and magnetic properties in the rolling direction.

2. C: 0.005 wt% or less, Si: 0.1 to 4.5
The steel slab containing wt% and the balance substantially consisting of Fe is subjected to hot rough rolling, hot finish rolling, and then, if necessary, hot rolled sheet annealing. After performing cold rolling or warm rolling twice or more including intermediate annealing to the final sheet thickness, performing finish annealing, and then applying an insulating film to manufacture an electromagnetic steel sheet, hot finishing rolling,
Rolling reduction (1 pass): 30% or more and rolling end temperature: 600 ~
A method for producing a magnetic steel sheet having excellent punching properties and magnetic properties in a rolling direction, characterized in that the hot-rolled sheet thickness is set to 1.5 mm or less at 800 ° C.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below. In a small vacuum melting furnace, Si: 3.12wt
%, C: 0.003 wt%, Mn: 0.01 wt%, and Al: 0.005 wt%. A 50 kg steel ingot was melted, and hot-rolled to a thickness of 5 mm for sizing. At 1100 ℃
After heating for 30 minutes, using a rolling mill with a roll diameter of 700 mmφ, the peripheral speed is 800 m / min., The rolling reduction (1 pass) is 84%, and the rolling end temperature is
Hot finish rolling was performed at 750 ° C to produce a 0.8 mm thick steel sheet. As a result of examining the texture and magnetic properties of this steel sheet, the integrated strength in the {110} <001> orientation was found to be that of a random structure. 28 times higher than that of W _15/50
And 1.705T in 2.3 W / kg, at B _50, it was obtained steel sheet having excellent magnetic properties not ever.

Further, based on this finding, as a result of conducting a more detailed study, it has been found that, under the condition that the Si-containing steel is subjected to a strong pressure reduction in one pass at a lower temperature than that employed in the ordinary process, the steel is 1.
By hot finishing rolling to a thickness of 5 mm or less, the degree of integration in the {110} <001> orientation of the hot-rolled sheet is remarkably improved. Furthermore, by using this material, secondary recrystallization is performed. It has been found that {110} <001> orientation grains can be highly accumulated without using, and the present invention has been completed. In the present invention, the integrated strength in the {110} <001> orientation in the hot rolling stage is:
It has also been found that it depends only on the hot finish rolling conditions described above and hardly depends on other manufacturing conditions.

Hereinafter, the reasons for limiting the steel composition, the steel structure, and the manufacturing conditions of the present invention will be described.

(1) Steel composition (a) C: 0.005 wt% or less C is an indispensable additional element when a grain-oriented electrical steel sheet is manufactured by a conventional manufacturing method because a Goss orientation eventually develops. However, in the present invention, C is an unnecessary component,
Since the decarburization step before the secondary recrystallization performed in the normal step does not need to be dared to be performed, it is preferable that the decarburization step is smaller, and therefore, 0.00
5 wt% or less.

(B) Si: 0.1-4.5 wt% Si has the effect of increasing the specific resistance and reducing the eddy current loss, and is an essential component in the present invention. However, 0.1wt%
When the amount is less than 4.5 wt%, the effect is not sufficiently exhibited. When the amount exceeds 4.5 wt%, not only the magnetic flux density is largely reduced but also the punching property is deteriorated. Therefore, the content of Si is set in the range of 0.1 to 4.5 wt.

(C) In the present invention, components other than C and Si are not particularly limited, but various known third elements can be appropriately added depending on the use. For example, Al and Mn are components having an effect of increasing the specific resistance similarly to Si and can be added. However, if the addition amount of Al and Mn exceeds 2.0 wt%, the cost increases. Therefore, it is preferable to add each of them within the range of 2.0 wt% or less.

(2) Steel Structure The electrical steel sheet of the present invention does not have a structure in which grains are grown by a mechanism that causes abnormal growth by secondary recrystallization as in the conventional manufacturing method. Its main feature is that it has a structure grown by appropriately controlling the diameter, the {110} <001> orientation and the proportion of normal grains having this orientation. This makes it possible to achieve both magnetic properties and punching properties, which have been considered difficult for steel sheets.

(A) Average crystal grain size: in the range of 0.1 to 5.0 mm If the average crystal grain size of the crystal grains is less than 0.1 mm, the internal hysteresis loss of the iron loss increases and the iron loss remarkably deteriorates. That is, if it exceeds 5 mm, the punching property is deteriorated. Accordingly, the average crystal grain size of the crystal grains is in the range of 0.1 to 5.0 mm.

(B) # 11 with respect to an axis parallel to the rolling direction
The deviation of the <001> axis in the 0 ° <001> direction is ±
In terms of the {110} <001> orientation and the proportion of normal grains having this orientation, the normal grains within 15 ° are 80% or more of the entire crystal grains. {110} <001> with respect to the axis parallel to the rolling direction. Misalignment of <001> axis in azimuth is 15
If it is larger than 0 ° C, the magnetic flux density is extremely deteriorated, and the ratio of the normal grains in which the deviation is within ± 15 ° in the rotation angle to the whole crystal grains is less than 80% by volume percentage. , The magnetic flux density deteriorates. Therefore, the magnetic steel sheet of the present invention has {110} <001 with respect to the axis parallel to the rolling direction.
The normal grains in which the deviation of the <001> axis in the orientation is within ± 15 ° in the rotation angle are limited to those in which 80% or more of the entire crystal grains are present.

(3) Manufacturing Conditions Next, the reasons for limiting the manufacturing method of the present invention will be described. (A) Hot finishing rolling conditions (a) Rolling end temperature: 600 to 800 ° C Figure 1 shows a vacuum small melting furnace with Si: 3.12 wt%, C: 0.00
A steel ingot consisting of 3 wt%, Mn: 0.01 wt%, and Al: 0.005 wt% was subjected to a final one-pass reduction of 60% and a finished plate thickness of 1.0.
mm hot finish rolling was performed at various rolling end temperatures to produce various steel sheets.
It shows the relationship between the integration strength in the 0 ° <001> direction and the rolling end temperature.

From FIG. 1, it can be seen from FIG. 1 that if the rolling end temperature exceeds 800 ° C., the accumulation of the {110} <001> orientation becomes weak, and if it is lower than 600 ° C., the rolling load increases extremely and it becomes difficult to roll. . Therefore, the rolling end temperature was set at 600 to 800 ° C.

(B) Rolling reduction (1 pass): 30% or more FIG. 2 shows a steel ingot having the above composition, at a rolling end temperature of 700 ° C., and a rolling reduction in the final 1 pass changed in the range of 10 to 80%. Various types of hot-rolled steel sheets with a finished sheet thickness of 1.0 mm were manufactured, and the relationship between the accumulation strength in the {110} <001> direction at the center of the sheet thickness and the rolling reduction in the final pass was shown. It is a thing.

From FIG. 2, if the rolling reduction in one pass is less than 30%, the accumulation in the {110} <001> orientation becomes weak, and the magnetic properties and orientation accumulation in the final product are deteriorated. The rolling reduction in one pass in rolling was 30% or more.

(C) Hot-rolled sheet thickness: 1.5 mm or less FIG. 3 shows that the steel ingot having the above composition has a rolling reduction of 80 in the last single pass.
%, Rolling end temperature: hot rolling under the condition of 700 ° C,
Various steel sheets having a thickness of 0.8 to 3.0 mm are manufactured, and the relationship between the integrated strength in the {110} <001> direction at the center of the thickness of each steel sheet and the finished sheet thickness is shown.

From FIG. 3, if the thickness of the hot-rolled sheet is larger than 1.5 mm, the accumulation in the {110} <001> orientation becomes weak, so the thickness of the hot-rolled sheet is set to 1.5 mm or less.

(B) Other Manufacturing Conditions According to the present invention, the integrated strength in the {110} <001> orientation in the hot rolling stage depends only on the hot finish rolling conditions,
It has already been mentioned above that it hardly depends on other manufacturing conditions. Therefore, annealing, pickling, cold rolling or warm rolling, and the conditions for forming the insulating film are not particularly limited,
It can be performed within the range normally performed. As an example, a hot-rolled sheet is annealed at 1000 ° C. for 2 minutes, pickled, cold-rolled at a reduction of 70%, and subjected to finish annealing at 850 ° C. for 3 minutes to form an insulating film. .

[0041]

EXAMPLE Next, an electrical steel sheet was manufactured using the manufacturing method of the present invention, and its performance was evaluated.・ Example 1 Fe-2.0% Si (steel type A) and Fe-3.3 in a small vacuum melting furnace
% Si (steel type B) 50kg each of two ingots composed of different compositions, then heated at 1150 ° C and hot-rolled to 1.4 ~
8.0mm thick plates, each plate was heated at 1100 ℃,
The rolling end temperature is controlled to 550 to 850 ° C and the thickness is 1.0mm in one pass at a rolling speed of 800m / min.
For 5 minutes. Further, it is pickled and then cold-rolled to a thickness of 0.35 mm.
Annealed for a minute. EBSD (Electron
Back Scattering Diffraction) was used to measure the orientation of crystal grains, and the percentage of {110} <001> oriented grains was determined. The results were plotted as a relationship between the rolling end temperature in finish rolling and the 1-pass rolling reduction. As shown in FIG.

The circles “○” and “●” in the figure indicate steel type A.
And triangles “△” and “▲” indicate steel type B, and white circles “○” and “△” indicate the <001> axis of {110} <001> orientation with respect to an axis parallel to the rolling direction. When the normal grains whose deviation is within ± 15 ° in the rotation angle are 80% or more of the whole crystal grains, the black marks “●” and “▲” indicate that the normal grains are less than 80% of the whole crystal grains. This is the case where

From the results shown in FIG. 4, it can be seen that both the steel types A and B have a finish rolling temperature of 600 to 800 ° C. and
When the rolling reduction in the pass is 30% or more, <001> of the {110} <001> direction with respect to the axis parallel to the rolling direction is <001.
> The normal grains whose axis deviation was within ± 15 ° in the rotation angle were 80% or more of the whole crystal grains.

Example 2 In a small vacuum melting furnace, a steel ingot 10 having a composition of Fe-3.2% Si was used.
Dissolve 0kg, then heat at 1150 ° C and hot rough rolling
The plate was 1.4 to 8.0 mm thick. The plate was heated at 1100 ° C and the rolling temperature was controlled at 600, 650, 750 and 850 ° C,
Finishing to a thickness of 1.0mm in one pass at a rolling speed of 0m / min.
Thereafter, annealing was performed at a temperature of 1000 ° C. for 2 minutes. Further, it was pickled, then finished by cold rolling to a sheet thickness of 0.35 mm, and further annealed at a temperature of 950 ° C. for 2 minutes. For each of these steel sheets, the orientation of the crystal grains was measured by EBSD, and {110} <00
1> together determine the existence ratio of oriented grains, with magnetic measurements, the maximum magnetic flux density 1.7 tesla (T), iron loss value per 1kg for Frequency 50Hz: W _17/50 and, magnetizing force 800 A /
It was determined B _8; flux density by m. Furthermore, the cross section of the steel sheet was observed with an optical microscope to determine the average crystal grain size. Table 1 shows the results.

[0045]

[Table 1]

Nos. 1, 5, 7, and 10 are examples in which the rolling reduction of hot rolling is low, and No. 11 is an example in which the rolling temperature of hot rolling is high. The deviation of the <001> axis of the {110} <001> direction with respect to the parallel axis is ±
In this example, the ratio of crystal grains within 15 ° is less than 80%, the crystal grain size is small, and the magnetic properties are deteriorated. Others are examples of the present invention, and the ratio is 80% or more in each case, and the magnetic properties are excellent.

Example 3 In a small vacuum melting furnace, Fe-3.4% Si (steel type 1), Fe4.8% Si
(Steel type 2) Dissolve 50kg of steel ingot composed of
The plate was heated at 50 ° C. and hot-rolled into a plate having a thickness of 5 mm. This plate was heated at 1100 ° C, the rolling temperature was controlled at 750, and 800
The sheet was finished to a thickness of 1.0 mm in one pass at a rolling speed of m / min. and annealed at a temperature of 1000 ° C. for 2 minutes. Further, pickling was performed, and then: cold rolling was performed to finish the sheet to a thickness of 0.35 mm. Further, in order to change the grain size of the crystal grains, the temperature and time were changed, and recrystallization and grain growth annealing were performed. For each of these steel sheets were measured the orientation of the crystal grains in EBSD, together determine the existence ratio of the {110} <001> oriented grains, with magnetic measurements, W _17/50
And I was asked to B _8. Furthermore, the cross section of the steel sheet was observed with an optical microscope to determine the average crystal grain size. In addition, punchability was also evaluated. Table 2 shows the results.
Incidentally, the punching property in Table 2 is “O” when the punching property is good,
Poor cases are indicated by "x".

[0048]

[Table 2]

From the results shown in Table 2, Nos. 1 to 4 are _applicable examples of the present invention, and all of the _iron loss value W _17/50 , the magnetic flux density B _8, and the punching property are good. No. 7 and 8 are comparative examples where high Si content, in particular deteriorates magnetic flux density B _8,
Further, this is an example in which the punching property is also deteriorated. Nos. 5 and 6 are comparative examples when the average crystal grain size is larger than 5 mm,
In particular, the punchability is deteriorated. In addition, with respect to No. 6, it can be seen that the magnetic flux density B ₈ is considerably deteriorated due to excessive grain growth.

[0050]

According to the present invention, accumulation in (110) <110> oriented grains, which was not feasible without using secondary recrystallization in the conventional method for manufacturing a grain-oriented electrical steel sheet, is described. It can be performed without using secondary recrystallization, and by properly controlling the grain size of normal grains, it is possible to improve the punchability, which tends to be inferior in conventional grain-oriented electrical steel sheets. it can. Further, in the present invention, the steps of decarburizing annealing, secondary recrystallization annealing, and purification annealing, which are essential steps in the prior art, can be omitted, so that significant cost reduction, shortening of manufacturing time, and energy saving can be achieved. As described above, according to the present invention, it has become possible to inexpensively obtain an electromagnetic steel sheet having good punching properties and excellent magnetic properties in the rolling direction.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the integrated strength in the (110) <110> orientation and the rolling end temperature at the center position of a thickness.

FIG. 2 is a diagram showing the relationship between the integrated strength in the (110) <110> direction and the rolling reduction in one pass at the plate thickness center position.

FIG. 3 is a diagram showing the relationship between the integrated strength in the (110) <110> orientation and the hot-rolled sheet thickness at the sheet thickness center position.

FIG. 4 is a diagram in which the result of obtaining the abundance ratio of (110) <110> orientation grains is plotted as a relationship between a rolling end temperature in finish rolling and a rolling reduction in one pass.

Claims (2)

[Claims] C: 0.005 wt% or less, Si: 0.1 to 4.5 wt%
%, And the balance is substantially composed of Fe. The average crystal grain size is in the range of 0.1 to 5.0 mm, and the deviation of the <001> axis in the {110} <001> direction with respect to the axis parallel to the rolling direction. Of normal grains within ± 15 ° of rotation angle
%, Characterized in that it has excellent punching properties and magnetic properties in the rolling direction. 2. C: 0.005 wt% or less, Si: 0.1 to 4.5 wt%
%, With the balance substantially consisting of Fe, after hot rough rolling, hot finishing rolling, and then, if necessary, hot-rolled sheet annealing, and once or halfway after pickling. After performing cold rolling or warm rolling two or more times including annealing to obtain a final sheet thickness, performing finish annealing, and then applying an insulating film to manufacture an electromagnetic steel sheet, hot finish rolling is performed by reducing The rate (1 pass): 30% or more and the rolling end temperature: 600 to 800 ° C, and the hot-rolled sheet thickness is reduced to 1.5 mm or less. Excellent manufacturing method of electrical steel sheet.