JP2008150697A - Production method of magnetic steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic steel sheet which comprises a secondary recrystallized grain and has a regular cubic orientation with a high magnetic permeability (magnetic flux density), both in the rolling direction and the direction perpendicular thereto. <P>SOLUTION: In a production method of the magnetic steel sheet, the amount of Al added to steel is 0.001-0.009%, which has been reduced compared to that in conventional methods; the amounts of Se, S, O and N are each reduced to ≤30 ppm; an Sn content in the steel is controlled to 0.01-0.20%; an average temperature-rising rate is controlled to ≥20°C/s between 500-750°C for decarburization and recrystallization annealing, and final finish annealing is subsequently carried out. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing an electrical steel sheet that is excellent in magnetic properties in the rolling direction and the direction perpendicular to the rolling direction, which is suitable as a core material for motors and generators.

It is known that the magnetic properties of an electrical steel sheet are affected by the crystal orientation, and in order to obtain excellent magnetic properties, the easy magnetization axis <001> needs to be parallel to the steel sheet surface.
By the way, the conventional electrical steel sheet is a non-oriented electrical steel sheet or secondary recrystallization in which a general cold-rolled steel sheet, a low-grade product obtained by decarburizing the steel sheet, or Si is added to further reduce impurities by reducing impurities. It is divided into a unidirectional electrical steel sheet that is preferentially grown in the {110} <001> orientation and a bi-directional electrical steel sheet that is developed in the {100} <001> orientation. However, conventional non-oriented electrical steel sheets have poor texture development, and the number of crystal grains whose <001> axes are parallel in the steel sheet surface is small, so that good magnetic properties have not been obtained.

  The unidirectional electrical steel sheet made of crystal grains accumulated in the {110} <001> orientation (Goth orientation), which is most commonly used as a core material for transformers, is highly integrated in the rolling direction. Therefore, it exhibits excellent magnetic properties when magnetized in the rolling direction. However, since the <111> axis, which is the most difficult to magnetize, is included in the plane, the magnetic properties are extremely poor when magnetized in this direction. Therefore, it is effective for applications where the magnetic properties in one direction are good like a transformer, but good magnetic properties are required in all directions in the plane like iron core materials for motors and generators. In this case, good magnetic properties cannot be obtained even if a unidirectional electrical steel sheet is used.

  If an electrical steel sheet having a structure with {100} as the rolling surface can be produced for these electrical steel sheets, there are many <100> axes in the rolling surface and no <111> axes in the surface. Therefore, it is very advantageous. In particular, a {100} <uvw> structure in which the direction of the <001> axis is random on the rolled surface has no magnetic property anisotropy in the surface and is ideal as a material for a motor. Therefore, techniques for developing {100} structures have been tried for a long time.

For example, in a method for producing a non-oriented electrical steel sheet, a method in which the reduction ratio of cold rolling is 85% or more, preferably 90% or more, and annealing is performed at 700 to 1200 ° C. for a period of 1 minute to 1 hour is disclosed in Patent Document 1 is disclosed. However, in this method, although the {100} structure develops after rolling, the {111} structure also develops when recrystallized, so that good magnetic properties cannot be obtained.
Japanese Patent Publication No.51-942

Patent Document 2 discloses a method of developing a {100} structure by controlling the cooling rate in the phase transformation from the γ phase to the α phase during recrystallization after cold rolling. However, since this method is premised on causing a γ transformation during recrystallization, the amount of Si that stabilizes the α phase cannot be increased. For example, when C and Mn are not included, the γ transformation does not occur when the Si content is about 2% or more, and in this case, this technique cannot be applied. Thus, this method can be said to be a disadvantageous method in which it is not possible to use an effective Si increase for reducing iron loss.
Japanese Patent Publication No.57-14411

Furthermore, in Patent Document 3, steel having a component containing C: 0.006 to 0.020% is cold-rolled, heated to 900 to 1100 ° C. and recrystallized, and then decarburized and annealed at a temperature of 900 ° C. or less. Technology is disclosed. According to Example 1, the magnetic properties obtained by this technique are only about 1.66 to 1.68 T in average value of the magnetic flux density B _{50 in} the rolling direction and in the direction perpendicular to the rolling direction. The degree of integration is considered low.
As described above, the conventional technique for improving the manufacturing method of the non-oriented electrical steel sheet cannot obtain a {100} structure with a high degree of integration, and therefore the improvement in magnetic properties is insufficient.
JP-A-5-5126

On the other hand, a method for producing a so-called bidirectional electrical steel sheet that develops a {100} <001> structure by secondary recrystallization has long been studied.
For example, in Patent Document 4, after cold rolling in one direction, cold rolling is further performed in a direction crossing the cold rolling direction, and short time annealing and high temperature annealing at 900 to 1300 ° C. are performed. , {100} <001> oriented grains are secondarily recrystallized using an inhibitor, and Patent Document 5 discloses cold rolling at a rolling reduction of 50 to 90% in a direction perpendicular to the hot rolling direction. Next, after annealing for the purpose of primary recrystallization, final finishing annealing for the purpose of secondary recrystallization and purification is performed, and {100 "<001> oriented grains are subjected to secondary recrystallization using AlN. Each method of crystallization is disclosed. However, none of these methods is a realistic method for producing a cube-structure steel sheet because it requires a process that requires an increase in production cost such as cross rolling and special final finish annealing.
Japanese Patent Publication No. 35-2657 JP-A-4-362132

On the other hand, Patent Document 6 contains Al: 0.0010 to 0.012 mass% as a steel component, Se, S, O, and N are each 30 ppm or less, and the average particle size before final rolling is 100 μm or more. Thus, a technique for obtaining a {100} <001> structure developed to a preferable level is disclosed. In this technique, a steel sheet with a {100} <001> neighborhood structure can be obtained at a very low cost compared to the conventional manufacturing method. However, controlling the average grain size before rolling to 100 μm or more has the effect of component fluctuations. Since it is difficult to receive, a product excellent in magnetic properties in the direction perpendicular to the rolling cannot always be obtained, leading to a decrease in product yield. In addition, there has been a problem of deterioration in rollability accompanying an increase in the average particle size before rolling.
JP 2000-309859 A

  The present invention was developed in view of the above-mentioned present situation, and based on the technique of Patent Document 6, secondary recrystallized grains having a positive cube orientation having a high permeability (magnetic flux density) in the direction perpendicular to the rolling direction as well as the rolling direction. An object of the present invention is to propose a method capable of stably producing a magnetic steel sheet having high productivity.

Here, as a material for the core of a motor or generator, the rolling direction of the magnetic flux density B ₅₀ is more than 1.80T, perpendicular to the rolling direction of the magnetic flux density B ₅₀ is desirably not less than 1.75 T.
The object of the present invention is to establish a method for stably and inexpensively producing such materials. In addition, the azimuth having such characteristics and having an azimuth close to {100} <001> (within an azimuth difference of 20 ° or less) is generically referred to as a “normal cube azimuth” in the present invention.

Now, in order to solve the above-mentioned problems, the inventors have conducted extensive research on the additive elements in steel and the recrystallization annealing method. As a result, the amount of Al added to the steel has been reduced more than before, and Se, In the method for producing a magnetic steel sheet having a high magnetic flux density in the rolling direction and the direction perpendicular to the rolling by reducing S, O, N, an appropriate amount of Sn is added to the steel, and at 500 to 750 ° C. in decarburization / recrystallization annealing. By increasing the rate of temperature rise in the temperature range of 20 ° C./s or higher, a positive cube structure can be obtained stably after final finish annealing even if the average crystal grain size before the final cold rolling is less than 100 μm. I got new knowledge that I can do it.
The present invention is based on the above findings.

That is, the gist configuration of the present invention is as follows.
1. In mass%, C: 0.003-0.080%, Si: 2.0-8.0%, Mn: 0.005-3.0%, Al: 0.0010-0.0090% and Sn: 0.01-0.20%, and S, Se, O, N Steel slabs, each reduced to 30ppm or less, with the balance being Fe and inevitable impurities, hot-rolled, if necessary, and then hot-rolled sheet annealing, or once or two or more times with intermediate annealing In the manufacturing method of electrical steel sheet, which consists of a series of processes in which cold rolling is performed to finish to the final plate thickness, followed by decarburization and recrystallization annealing, and if necessary, an annealing separator is applied and then final finishing annealing is performed. ,
A method for producing an electrical steel sheet, wherein an average rate of temperature increase between 500 and 750 ° C. in the decarburization / recrystallization annealing is set to 20 ° C./s or more.

2. In the method 1, the annealing temperature before the final cold rolling is set to 900 ° C. or higher and lower than 1000 ° C.

3. In the above 1 or 2, the steel slab is one type selected from Sb: 0.005 to 0.50%, Cu: 0.01 to 0.50%, Mo: 0.005 to 0.50%, and Cr: 0.01 to 1.0% by mass%. The manufacturing method of the electrical steel sheet characterized by including 2 or more types.

  According to the present invention, the normal cube structure is appropriately set at the time of final finishing annealing without necessarily setting the annealing temperature before the final cold rolling to a high temperature of 1000 ° C. or higher and setting the grain size before the final cold rolling to an average grain size of 100 μm or more. As a result, it is possible to stably produce an electromagnetic steel sheet having a high magnetic flux density in the direction perpendicular to the rolling direction, not to mention the rolling direction, under a high production yield and a low production cost.

Hereinafter, experimental results that led to the present invention will be described. In addition, unless otherwise indicated, "%" display regarding the component composition of a steel plate shall mean mass% (mass%).
Experiment 1
In order to clarify the effects of the additive elements, steel ingots with the components shown in Table 1 were melted and heated to 1150 ° C, then hot rolled into a hot-rolled sheet with a thickness of 2.2 mm, and then 950 ° C and 1050 ° C. After performing hot-rolled sheet annealing for 30 seconds, cold rolling at a temperature of 200 ° C. to a final thickness of 0.30 mm, followed by recrystallization annealing at 850 ° C. for 15 seconds. Here, the temperature increase rate (between 500 and 750 ° C.) of the recrystallization annealing was set to 15 ° C./s or 25 ° C./s. Next, after applying an annealing separator, after final finishing annealing at 900 ° C for 30 hours, a specimen (30 mm x 280 mm) in the rolling direction and in the direction perpendicular to the rolling direction is cut out, and the rolling direction and rolling are performed by the Epstein test method. The perpendicular magnetic properties were measured.
The obtained results are also shown in Table 1.

As shown in the table, when Sn is not added, the magnetic flux density B _{50 in the} direction perpendicular to the rolling does not exceed 1.80 T unless the hot-rolled sheet annealing temperature is raised to 1050 ° C. Whereas no structure is obtained, Sn is added and the rate of temperature increase in recrystallization annealing is set to 25 ° C./s, so that the B _{50 in the} direction perpendicular to the rolling direction is also obtained when the hot-rolled sheet annealing temperature is 950 ° C. Has reached a level exceeding 1.80 T, and it has been found that a positive cube structure can be obtained stably regardless of the hot-rolled sheet annealing temperature.

Here, the average particle diameter of the ingot 1 and the ingot 2 after hot-rolled sheet annealing was 65 μm when the hot-rolled sheet annealing temperature was 950 ° C. and 110 μm when the temperature was 1050 ° C.
Therefore, in the steel ingot 2 to which Sn was added, it can be said that the crystal grains having the positive cube orientation were stably recrystallized even when the average grain size before the final cold rolling was less than 100 μm.
Thus, by adding Sn and further increasing the heating rate of recrystallization annealing to 25 ° C./s, a steel sheet with a normal cube orientation can be obtained even when the grain size before the final cold rolling is less than 100 μm. Therefore, it becomes possible to prevent cracks and the like in the final cold rolling, and it is possible to stably produce with good yield.

  In addition, an appropriate amount of Sn is added to the steel, the temperature increase rate of recrystallization annealing is set to 25 ° C / s, and the annealing before final cold rolling is set to 1050 ° C, so that the average particle size before cold rolling is reduced to 110 µm. In the case of coarsening, excellent characteristics reaching 1.86 T at an average magnetic flux density (L + C + 2D) / 4 are obtained.

Experiment 2
Next, an experiment was conducted to clarify the appropriate range of Sn.
Steel containing C: 0.004%, Si: 2.5%, Mn: 0.10%, O: 0.0010%, N: 0.0010%, Al: 0.0020%, S: 0.0010%, Se ≦ 0.0003% and Sn: 0 to 0.5% The ingot is melted, heated to 1150 ° C, hot rolled to a hot rolled sheet of 2.2mm thickness, then annealed at 950 ° C for 30 seconds, then cold rolled at a temperature of 200 ° C to 0.30mm After the final plate thickness was reached, recrystallization annealing was performed at 850 ° C. for 15 seconds. Here, the heating rate (between 500 and 750 ° C.) of the recrystallization annealing was set to 25 ° C./s.
Next, after applying an annealing separator, after final finishing annealing at 900 ° C for 30 hours, a specimen (30 mm x 280 mm) in the rolling direction and in the direction perpendicular to the rolling direction is cut out, and the rolling direction and rolling are performed by the Epstein test method. The perpendicular magnetic properties were measured.
The obtained results are shown in FIG.

As shown in the figure, when the Sn addition amount is 0.01 to 0.20%, the target characteristics of the rolling direction B ₅₀ ≧ 1.80 T and the perpendicular direction B ₅₀ ≧ 1.75 T are obtained, and the Sn addition amount is 0.01 A range of ~ 0.20% was found to be appropriate.

Experiment 3
Subsequently, an experiment was performed to obtain an appropriate range of the temperature increase rate of recrystallization annealing.
Contains C: 0.004%, Si: 2.5%, Mn: 0.10%, O: 0.0010%, N: 0.0010%, Al: 0.0020%, S: 0.0010%, Se ≦ 0.0003% and Sn: 0.02% or 0% The steel ingot is melted, heated to 1150 ° C, hot-rolled into a 2.2mm thick hot-rolled sheet, then annealed at 950 ° C for 30 seconds, then cold-rolled at a temperature of 200 ° C to 0.30 After the final thickness of mn was reached, recrystallization annealing was performed at 850 ° C. for 15 seconds. Here, the temperature increase rate (between 500 and 750 ° C.) of the recrystallization annealing was variously changed between 5 and 70 ° C./s.
Next, after applying an annealing separator, after final finishing annealing at 1900 ° C for 30 hours, specimens (30mm x 280mm) in the rolling direction and in the direction perpendicular to the rolling direction are cut out, and the rolling direction and rolling are performed by the Epstein test method. The perpendicular magnetic properties were measured.
The change of B _{50 in} the direction perpendicular to the rolling is shown in FIG. The B ₅₀ in the rolling direction was 1.80 T or more in the entire range.

As shown in FIG. 2, when the recrystallization annealing is performed on the Sn-containing material, the temperature increase rate in the temperature range of _{500 to} 750 ° C. is set to 20 ° C./s or more, so that the rolling direction B ₅₀ ≧ 1.80T. And the target characteristic of the perpendicular direction of rolling B ₅₀ ≧ 1.75 was obtained. In addition, when the rate of temperature rise is 25 ° C / s or more, particularly excellent characteristics such as a perpendicular direction of rolling B ₅₀ ≧ 1.80T have been obtained. B ₅₀ is improved more than 1.83T.

Action

According to the present invention, 0.01 to 0.20% of Sn is contained as a steel component, and the temperature increase rate between 500 to 750 ° C. during recrystallization annealing is set to 20 ° C./s or more, so that the grain size before the final cold rolling becomes 100 μm. Even if it is less, a texture accumulated in the positive cube can be obtained after secondary recrystallization.
Although the reason for this has not been clearly clarified yet, the inventors speculate as follows.

  When trying to obtain a positive cube structure by secondary recrystallization, it is necessary to suppress the growth of competing Goss orientation structures as secondary recrystallized grains. For this purpose, the inventors have come up with the idea that the intensity of the orientation in the vicinity of {111} <112> where the Goss orientation and the grain boundary energy are the highest should be reduced.

  By the way, in the conventional method for producing a unidirectional electrical steel sheet having Goss orientation, a method of increasing the temperature raising rate of recrystallization annealing is used for the purpose of increasing the primary recrystallized grains of {110} orientation including Goss orientation. It was sometimes done. However, if this action works strongly, the growth of the Goss orientation increases, which inhibits the development of the regular cube structure.

  On the other hand, since the {111} strength in the primary recrystallized structure decreases due to an increase in the rate of temperature increase during recrystallization annealing, in the present invention, the decrease in {111} strength due to the increase in the rate of temperature increase indicates the growth of the normal cube structure. It is thought that it contributed effectively to improvement. However, in actuality, as shown in FIG. 2, the increase in the temperature increase rate of recrystallization annealing did not lead to the development of positive cubes by secondary recrystallization. The reason for this is considered that the normal cube orientation did not undergo secondary recrystallization only by reducing the {111} strength while the {100} strength of the primary recrystallized structure was insufficient.

  On the other hand, it is presumed that by adding an appropriate amount of Sn, the {100} strength in the primary recrystallized structure increases and the positive cube orientation by secondary recrystallization is easily grown. The mechanism of primary recrystallized structure improvement by Sn addition is not clear, but the nature of the grain boundary changes due to the segregation of Sn in the steel to the grain boundary before rolling, and the {111} orientation from the grain boundary As a result of suppressing the formation of, it is considered that the same effect as that when the grain diameter before cold rolling becomes coarse was brought about. However, as shown in Table 1, the Sn addition is also effective for improving the magnetic properties in the direction perpendicular to the rolling when the annealing temperature before the final cold rolling is low and the crystal grain size is less than 100 μm. It does n’t come.

  The present invention, as described above, is a special effect obtained by simultaneously eliminating the inhibition factor of the development of the positive cube structure by increasing the temperature increase rate of recrystallization annealing and increasing the good orientation by adding Sn. If one of these is missing, a normal cube structure cannot be obtained after secondary recrystallization under the condition that the grain size before the final cold rolling is less than 100 μm.

That is, in the present invention, the increase in the temperature increase rate of recrystallization annealing having two actions of increasing the Goss strength in the primary recrystallized structure and suppressing the {111} orientation is combined with the increase in {100} strength by Sn addition. Thus, it is considered that the effect of the latter (reduction in {111} orientation) is successfully extracted with respect to the effect of the former (increase in {110} orientation), which is disadvantageous for the development of the normal cube structure.
Further, in the method of the present invention, when the crystal grain size before rolling is 100 μm or more, it is presumed that a further excellent orientation integration degree is realized in synergy with the above effect.

  Here, as a method for producing a bi-directional electrical steel sheet having a normal cube orientation, Japanese Patent Application Laid-Open No. 5-287384 discloses an average temperature increase rate from 200 ° C. to 800 ° C. after cold rolling at 10 ° C./min (0.17 ° C. / s), the technology is disclosed, but this technology is an acid-soluble Al: 0.010 to 0.050%, N: 0.0120% or less in a component system containing a large amount of inhibitor component compared to the present invention, This is a technique for developing a positive cube structure after secondary recrystallization by a technique of rolling in the direction perpendicular to the rolling. Therefore, it can be said that the technical content is fundamentally different from the present invention in which the amount of Al and N can be reduced and a steel sheet having a normal cube structure can be obtained at low cost without rolling in the direction perpendicular to the rolling. The preferred range of the average rate of temperature increase in recrystallization annealing with this technique is 0.17 ° C / s or more, which is a range that includes almost the entire range of temperature increase rate of general recrystallization annealing. It is considered that most of the control of the primary recrystallization structure advantageous to the development is borne by the content of the inhibitor and rolling in the direction perpendicular to the rolling.

  In addition, JP 2000-309859 A discloses a method of containing Sn or the like in steel in a technique for setting the grain size before the final cold rolling to 100 μm or more, but the special effect by adding Sn is disclosed. Is not shown at all. The reason is that the effect of the temperature rising rate in the recrystallization annealing found in the present invention is not combined.

The reasons for limiting the constituent requirements of the present invention will be described below.
First, the reason why the component composition of the steel slab is limited to the above range in the present invention will be described.

Si: 2.0-8.0%
In the production of electrical steel sheets, Si must be contained in the range of 2.0 to 8.0% as an essential component of the material. This is because if the content is less than 2.0%, a satisfactory reduction in iron loss cannot be expected, while if it exceeds 8.0%, the workability deteriorates.

C: 0.003-0.080%
C promotes local deformation within the crystal grains and promotes the development of a positive cube structure, thereby effectively contributing to improving magnetic properties. However, if the content is less than 0.003%, the effect of forming {100} <001> grains is reduced, leading to a decrease in magnetic flux density. On the other hand, if it exceeds 0.080%, it is difficult to remove by decarburization annealing. In addition, the C content was limited to a range of 0.003 to 0.080% in order to cause partial γ transformation during hot-rolled sheet annealing and excessively refine the coarse grain size before cold rolling of 100 μm or more.

Mn: 0.005-3.0%
Mn is an element useful for improving hot workability. However, if the content is less than 0.005%, its effect is poor, while if it exceeds 3.0%, secondary recrystallization becomes difficult. It was limited to the range of 0.005 to 3.0%.

Al: 0.0010 to 0.0090%
By limiting the content of Al to a range of 0.0010 to 0.0090%, which is less than that of the conventional Al, it is possible to appropriately develop positive cube grains during finish annealing. Here, if the amount of Al is less than 0.0010%, the degree of integration of the positive cube orientation is reduced and a good magnetic flux density cannot be obtained. On the other hand, if it exceeds 0.0090%, the degree of integration of the positive cube orientation is also reduced. However, the Goss direction is increased and the magnetic properties in the direction perpendicular to the rolling are deteriorated. Therefore, the Al content is limited to the range of 0.0010 to 0.0090%.

Sn: 0.01-0.20%
By adding Sn, the abundance ratio of the {100} orientation in the primary recrystallization structure after recrystallization annealing increases, and secondary recrystallization in the positive cube orientation can be promoted. However, since the growth of the Goth orientation cannot be suppressed only by increasing the {100} orientation, the effect of promoting the secondary recrystallization in the positive cube orientation is exhibited by using it together with the increase in the heating rate of recrystallization annealing. Here, if the Sn content is less than 0.01%, the above effect is not exerted and the magnetic characteristics become poor. On the other hand, if it exceeds 0.20%, the secondary recrystallization is adversely affected and the magnetic characteristics are still deteriorated. In order to cause deterioration, the Sn content was limited to a range of 0.01 to 0.20%.

Se, S, O, N: 30ppm or less each
All of Se, S, O and N remarkably inhibit the expression of the normal cube structure, and are difficult to remove in the subsequent process, so all of them need to be reduced to 30 ppm or less, preferably 20 ppm or less in the molten steel component.

  As described above, the essential component and the suppressing component have been described. In addition, in the present invention, one or more selected from Sb, Cu, Mo, and Cr are appropriately included for the purpose of improving iron loss. be able to. However, these addition amounts are preferably Sb: 0.005 to 0.50%, Cu: 0.01 to 0.50%, Mo: 0.005 to 0.50%, and Cr: 0.01 to 1.0%, respectively. When the amount of each additive is less than the lower limit, the effect of improving iron loss is poor. On the other hand, when the amount exceeds the upper limit, the development of the normal cube structure is inhibited.

Next, preferred production conditions for the grain-oriented electrical steel sheet of the present invention will be described.
The molten steel adjusted to the above preferred component composition is made into a slab by a normal ingot-making method or a continuous casting method. Further, a thin cast piece having a thickness of 100 mm or less may be manufactured by a direct casting method.
The slab is heated by a normal method and then subjected to hot rolling. However, the slab may be immediately subjected to hot rolling without being heated after casting. In the case of a thin slab, hot rolling may be performed, or the hot rolling may be omitted and the subsequent process may be performed as it is.

Next, after performing hot-rolled sheet annealing as necessary, finish it to the final sheet thickness by cold rolling at least once with one or two intermediate sandwiches, and after decarburization and primary recrystallization annealing, as necessary After applying the annealing separator, the final cube annealing is performed to develop a normal cube structure.
Thereafter, an insulating coating is applied as necessary.

In the present invention, in the above manufacturing process, the average temperature increase rate between 500 and 750 ° C. in recrystallization annealing is 20 ° C./s or more, preferably 25 ° C./s or more, more preferably 40 ° C./s or more. Is essential. When this rate of temperature rise is less than 20 ° C./s, the presence ratio of {111} <112> structure, which is advantageous for the growth of Goth orientation in the primary recrystallized structure, becomes high, and the cube orientation is changed by secondary recrystallization. It will not develop. On the other hand, by setting the average temperature increase rate between 500 and 750 ° C. in recrystallization annealing to 20 ° C./s or more, the abundance ratio of {111} <112> orientation decreases, and the increase of {100} orientation due to Sn addition By achieving at the same time, the positive cube orientation is secondarily recrystallized. As a result, the magnetic flux density B ₅₀ in the rolling direction exceeds 1.80 T, and the magnetic flux density in the direction perpendicular to the rolling is 1.75 T or more. Furthermore, by setting the average heating rate to 25 ° C./s or more, B _{50 in the} direction perpendicular to the rolling also becomes 1.80 T or more.

  The reason why the temperature range for controlled heating is set to 500 to 750 ° C is that the nuclei of recrystallized grains are generated in this temperature range, so the effect on the texture is strong, and the heating rate in this temperature range is set appropriately. This is because it is possible to reduce the {111} <112> orientation by controlling.

  Further, in the present invention, it is not necessary to coarsen the crystal grain size before the final cold rolling to 100 μm or more as in the prior art by the above-mentioned measures, so that the occurrence of cracks in the subsequent cold rolling is prevented. Can do. However, from the viewpoint of ensuring the frequency of {100} structure formation from within the crystal grains, the grain size before the final cold rolling is preferably 60 μm or more. From this point of view, when trying to produce a steel sheet having a normal cube structure with good productivity, in order to set the average grain size before the final cold rolling to 60 to 100 μm, the annealing temperature before the final cold rolling is 900. It should be higher than 1000 ℃ and lower than 1000 ℃.

  On the other hand, when trying to obtain a positive cube structure with a higher degree of integration, it is desirable to make the crystal grain size before the final cold rolling as coarse as possible within the range allowed by manufacturing restrictions such as cold rolling properties. For this purpose, annealing at a temperature of 1000 ° C. or higher before the final cold rolling to increase the grain size before rolling to 100 μm or more is useful for improving the magnetic properties. Furthermore, sandwiching the intermediate annealing between cold rolling is also useful for stabilizing the magnetic properties.

  Further, the final sheet thickness is finished by the final cold rolling, and the reduction ratio at that time is preferably about 70 to 90% in order to develop the normal cube structure. Further, by setting the temperature of at least one pass of the final cold rolling to 100 to 350 ° C., the positive cube structure can be further developed and the magnetic properties can be improved. If the rolling temperature is less than 100 ° C., the effect of improving the structure is hardly sufficient. On the other hand, if the rolling temperature exceeds 350 ° C., the rollability deteriorates due to the rolling load variation due to dynamic strain aging.

The recrystallization annealing after the final cold rolling is preferably performed in a temperature range of 750 to 950 ° C. At this time, when the amount of material C is large, it is preferably carried out in a wet hydrogen atmosphere, and the amount of C is preferably reduced to 50 ppm or less at which magnetic aging does not occur. You may use together the technique which increases Si amount by the siliconization method after final cold rolling or after decarburization annealing. The finish annealing is preferably in the temperature range of 850 to 1050 ° C. When the temperature is lower than 850 ° C. or higher than 1050 ° C., the progress of secondary recrystallization is inhibited. And in order to complete secondary recrystallization, it is desirable to hold | maintain in this temperature range for 30 hours or more.
Moreover, when using it, laminating | stacking a steel plate, in order to improve an iron loss, it is effective to give an insulating coating to the steel plate surface. For this purpose, a multilayer film composed of two or more kinds of coatings may be used. Furthermore, you may give the coating which mixed resin etc. according to a use. In particular, an insulating coating mainly composed of a phosphate that imparts tension is effective in reducing iron loss and noise.

Example 1
Steel slabs having the following two types of compositions A and B were heated at 1150 ° C. for 30 minutes and then finished to a thickness of 2.2 mm by hot rolling.
(A) C: 0.010%, Si: 2.8%, Mn: 0.15%, Al: 0.0050%, Se: 2ppm, S: 10ppm, O: 10ppm, N: 10ppm.
(B) C: 0.010%, Si: 2.8%, Mn: 0.15%, Al: 0.0050%, Se: 2ppm, S: 10ppm, O: 10ppm, N: 10ppm, Sn: 0.06%.
Next, after performing hot-rolled sheet annealing under the conditions shown in Table 2, after pickling treatment, the final heat of 0.30 mm was obtained by cold rolling for 6 passes under the condition that the temperature immediately after rolling was 200 ° C due to the heat generated by rolling. Finished to plate thickness. Thereafter, recrystallization annealing was performed in an atmosphere of hydrogen: 75%, nitrogen: 25%, dew point: 50 ° C, 930 ° C, soaking time: 30 seconds, and C in the steel was reduced to 10 ppm. In this recrystallization annealing, as shown in Table 2, the average heating rate between 500 and 750 ° C. was variously changed between 10 and 60 ° C./s.

Next, a final finish annealing was performed in a nitrogen atmosphere at 950 ° C. for 35 hours. Then, after performing flattening annealing which hold | maintains at 900 degreeC for 30 second, the coating liquid which mixed aluminum dichromate, emulsion resin, and ethylene glycol was apply | coated, and it baked at 300 degreeC, and was set as the product.
From the product plate thus obtained, Epstein specimens in the rolling direction and the direction perpendicular to the rolling direction were cut out, and the magnetic flux density B ₅₀ was measured in each direction.
The obtained results are also shown in Table 2.

In Table 2, Nos. 1 to 10 and Nos. 11 to 20 are results obtained by treating the material A, which is a comparative steel, and the material B, which is a compatible steel, under the same conditions. As is clear from the comparison between the two groups, in each case, B _{50 in the} direction perpendicular to the rolling direction is improved by adding Sn.
In particular, in the material B to which Sn is added, even when the hot-rolled sheet annealing temperature is 900 ° C. or higher and lower than 1000 ° C., by increasing the temperature increase rate of recrystallization annealing (decarburization annealing) to 20 ° C./s or more, rolling direction of B ₅₀ or more 1.80T, perpendicular to the rolling direction of B ₅₀ is positive cube tissue obtained than 1.75 T. Further, when the material B to which Sn is added has a hot-rolled sheet annealing temperature of 1050 ° C. and a recrystallization annealing temperature increase rate of 20 ° C./s or more, B _{50 in the} direction perpendicular to the rolling is 1.84 T. Excellent characteristics exceeding the above are obtained.

Example 2
Steel slabs having the following five compositions of C to G were heated at 1150 ° C. for 30 minutes, and then finished to 2.5 mm thickness by hot rolling.
(C) C: 0.0020%, Si: 3.0%, Mn: 0.10%, Al: 0.0040%, Se: 2ppm, S: 10ppm, O: 10ppm, N: 10ppm
(D) C: 0.0020%, Si: 3.0%, Mn: 0.10%, Al: 0.0040%, Se: 2ppm, S: 10ppm, O: 10ppm, N: 10ppm, Sn: 0.12%
(E) C: 0.0020%, Si: 3.0%, Mn: 0.05%, Al: 0.0040%, Se: 1ppm, S: 10ppm, O: 10ppm, N: 10ppm, Sn: 0.05%, Sb: 0.02%
(F) C: 0.0020%, Si: 3.0%, Mn: 0.05%, Al: 0.0040%, Se: 1ppm, S: 10ppm, O: 10ppm, N: 10ppm, Sn: 0.05%, Cu: 0.05%, Mo : 0.1%
(G) C: 0.0020%, Si: 3.0%, Mn: 0.05%, Al: 0.0040%, Se: 1ppm, S: 10ppm, O: 10ppm, N: 10ppm, Sn: 0.05%, Cr: 0.1%

  Next, after pickling the obtained hot-rolled sheet, it was rolled to 1.5 mm by cold rolling at 200 ° C. and 4 passes, and then subjected to intermediate annealing that was held at 950 ° C. for 30 seconds in a nitrogen atmosphere. After that, it was finished to a final thickness of 0.35mm by cold rolling at 150 ° C for 4 passes. Thereafter, recrystallization annealing was performed in an atmosphere of hydrogen: 75%, nitrogen: 25%, holding temperature: 930 ° C., soaking time: 30 seconds. In this recrystallization annealing, as shown in Table 3, the average heating rate between 500 and 750 ° C. was variously changed between 10 and 60 ° C./s.

Next, a final finish annealing was performed in a nitrogen atmosphere at 950 ° C. for 35 hours. Then, after performing flattening annealing which hold | maintains at 900 degreeC for 30 second, the coating liquid which mixed aluminum dichromate, emulsion resin, and ethylene glycol was apply | coated, and it baked at 300 degreeC, and was set as the product.
From the product plate thus obtained, Epstein specimens in the rolling direction and the direction perpendicular to the rolling direction were cut out, and the magnetic flux density B ₅₀ was measured in each direction.
The results obtained are also shown in Table 3.

As shown in the table, in the material D to which Sn is added, the intermediate annealing temperature is 950 ° C, which is relatively low, by increasing the rate of temperature increase in recrystallization annealing (decarburization annealing) to 20 ° C / s or more. Even in this case, a normal cube structure in which the B ₅₀ in the rolling direction is 1.80 T or more and the B _{50 in the} direction perpendicular to the rolling is 1.75 T or more is obtained. This is the same for the raw materials E to G, and with the addition of an appropriate amount of Sn, the temperature increase rate of recrystallization annealing (decarburization annealing) is set to 20 ° C./s or more, so that the intermediate annealing temperature is relatively 950 ° C. Even in the case of a low temperature, a positive cube structure is obtained in which the B ₅₀ in the rolling direction is 1.80 T or more and the B _{50 in the} direction perpendicular to the rolling is 1.75 T or more.
Further, in the material B to which Sn is added, when the hot-rolled sheet annealing temperature is set to 1050 ° C. and the recrystallization annealing temperature rise rate is set to 20 ° C./s or more, B _{50 in the} direction perpendicular to the rolling is 1.84T. Excellent characteristics that exceed it are obtained.

It is a diagram showing the relationship between the Sn addition amount and the B ₅₀ Product plate in the steel. Is a diagram showing the relationship between heating rate of recrystallization annealing and (inter 500 to 750 ° C.) and B ₅₀ of the product sheet.

Claims (3)

In mass%, C: 0.003-0.080%, Si: 2.0-8.0%, Mn: 0.005-3.0%, Al: 0.0010-0.0090% and Sn: 0.01-0.20%, and S, Se, O, N Steel slabs, each reduced to 30ppm or less, with the balance being Fe and inevitable impurities, hot-rolled, if necessary, and then hot-rolled sheet annealing, or once or two or more times with intermediate annealing In the manufacturing method of electrical steel sheet, which consists of a series of processes in which cold rolling is performed to finish to the final plate thickness, followed by decarburization and recrystallization annealing, and if necessary, an annealing separator is applied and then final finishing annealing is performed. ,
A method for producing an electrical steel sheet, wherein an average rate of temperature increase between 500 and 750 ° C. in the decarburization / recrystallization annealing is set to 20 ° C./s or more.   The method for manufacturing an electrical steel sheet according to claim 1, wherein an annealing temperature before final cold rolling is set to 900 ° C or higher and lower than 1000 ° C.   3. The steel slab according to claim 1, wherein the steel slab is further selected by mass% from Sb: 0.005 to 0.50%, Cu: 0.01 to 0.50%, Mo: 0.005 to 0.50%, and Cr: 0.01 to 1.0%. Or the manufacturing method of the electrical steel sheet characterized by containing 2 or more types.

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