RU2805665C1 - Method for producing anisotropic electrical steel sheet - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: production of sheets of anisotropic electrical steel. A method for producing an anisotropic electrical steel sheet includes the process of heating a slab containing, by wt.%: C – 0.01 or more and 0.10 or less, Si – 2.5 or more and 4.5 or less, Mn – 0.01 or more and 0.50 or less, the total amount of one or more of S, Se and Te – 0.001 or more and 0.050 or less, acid-soluble Al – greater than 0 and 0.05 or less, and N – greater than 0 and 0.015 or less, optionally one or more elements selected from the group containing Cu – 0-1.0, Sn – 0-1.0, Ni – 0-1.0, Cr – 0-1.0, Sb – 0-1.0, and Bi – 0-1.0, with the remainder of iron and impurities, hot rolling it and, if necessary, annealing to obtain a hot-rolled steel sheet or annealed hot-rolled steel sheet, a process of cold rolling a hot-rolled steel sheet or an annealed hot-rolled sheet to obtain a cold-rolled steel sheet, an annealing process of a cold-rolled steel sheet to obtain a primary recrystallized annealed sheet, a process of coating the surface of the sheet with an annealing separator including MgO, and then finishing annealing it to produce a finishing annealed sheet, the process of covering the finishing annealed sheet with an insulating coating and then annealing it to smooth it. At least one steel sheet of hot-rolled, hot-rolled annealed, cold-rolled primary recrystallized annealed sheet is processed by shot peening and solution contacting. In shot peening, the average particle size of the shot is 0.1 mm or more and 5.0 mm or less, and its velocity is 10 m/s or more and 150 m/s or less. The solution contains one or more of the: elements Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni, has a total element concentration of 0.00001% or more and 1.0000% or less, and a pH value of 1.5 or more and less than 7 and has a solution temperature of 15°C or more and 100°C or less, and the time for which the steel sheet is immersed in the solution is 5 s or more and 200 s or less.

EFFECT: increased magnetic flux density.

4 cl, 3 tbl, 4 ex

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

[0001]

The present invention relates to a method for producing anisotropic electrical steel sheet.

PREREQUISITES FOR CREATION OF THE INVENTION

[0002]

The anisotropic electrical steel sheet is a steel sheet containing 2-5 mass% Si and having crystal grains highly aligned to the {110}<001> orientation, called the Goss orientation. Anisotropic electrical steel sheet has excellent magnetic properties and is used, for example, as the core material of transformers and other stationary induction devices, etc.

[0003]

For such anisotropic electrical steel sheet, various methods have been developed to improve the magnetic characteristics. In particular, along with the need for energy saving, in recent years there has been a demand for additional reduction of magnetic losses in a sheet of anisotropic electrical steel. To reduce losses in an anisotropic electrical steel sheet core, it is effective to increase the integration degree of the crystal grain orientation of the steel sheet to the Goss orientation to improve the magnetic flux density and reduce the hysteresis loss.

[0004]

Here, in the production of anisotropic electrical steel sheet, crystal orientation is controlled using a catastrophic grain growth phenomenon called "secondary recrystallization". However, in order to suitably control crystal orientations by secondary recrystallization, it is important to improve the thermal stability of microinclusions in steel, called “inhibitors.”

[0005]

For example, mention may be made of a method of completely dissolving inhibitors during heating of a steel slab before hot rolling, and then finely releasing them during hot rolling and subsequent annealing. In particular, the method illustrated in the following Patent Document 1 of using MnS and AlN as inhibitors and rolling with a reduction greater than 80% in the final cold rolling process, or the method illustrated in the following Patent Document 2 of using MnS and MnSe as inhibitors and performing cold rolling twice.

[0006]

In addition, Patent Documents 3 and 4 disclose a technology for controlling the annealing conditions and pickling conditions of a hot-rolled sheet for producing an anisotropic electrical steel sheet having excellent coating properties. In addition, Patent Document 5 discloses a technology for controlling pickling conditions, additional annealing separator conditions, and finishing annealing conditions for producing anisotropic electrical steel having excellent coating properties. Patent Document 6 discloses a technology for controlling carbides by heat treatment before cold rolling to produce an anisotropic electrical steel sheet having excellent magnetic characteristics. In addition, Patent Document 7 discloses a technology for controlling a temperature raising process during primary recrystallization annealing and introducing micro-strains during the temperature raising process, thereby producing an anisotropic electrical steel having excellent magnetic characteristics.

[0007]

In addition, the following Patent Document 8 discloses a technology for controlling the thermal profile in a primary recrystallization annealing temperature raising process for producing an anisotropic electrical steel sheet having reduced core loss along the entire length of the coil. In addition, the following Patent Document 9 discloses a technology for strictly controlling the average crystal grain size after secondary recrystallization and the deviation angle from the ideal orientation for reducing loss in an anisotropic electrical steel sheet core.

LIST OF REFERENCES CITED

PATENT LITERATURE

[0008]

[Patent Document 1] Japanese Examined Published Patent Application No. 40-15644b

[Patent Document 2] Japanese Examined Published Patent Application No. 51-13469

[Patent Document 3] Japanese Unexamined Published Patent Application No. 2019-99827

[Patent Document 4] Japanese Unexamined Published Patent Application No. 2003-193141

[Patent Document 5] Japanese Unexamined Published Patent Application No. 2014-196559

[Patent Document 6] Japanese Unexamined Published Patent Application No. 2016-156068

[Patent Document 7] Japanese Unexamined Published Patent Application No. 6-212274

[Patent Document 8] WO2014/049770

[Patent Document 9] Japanese Unexamined Published Patent Application No. 7-268567

SUMMARY OF THE INVENTION

TECHNICAL PROBLEM

[0009]

Along with increasing global regulation of transformer efficiency, the need to reduce losses in anisotropic electrical steel sheet core has increased significantly. On the other hand, transformers are important equipment that support social infrastructure in the long term, so continuous stable operation is important. For this reason, greater reliability is required from the anisotropic electrical steel sheet that forms the main elements, contributing to more stable operation of transformers. In particular, the uniform appearance of the anisotropic electrical steel sheet without uneven color, etc. has become an important element in gaining the trust of users.

[0010]

The above-mentioned Patent Documents 3 to 5 disclose a technology for creating a difference in the concentration of Mn or Cu at the surface of a steel sheet and at the center of the sheet thickness to improve the adhesion of a coating film. However, the technology of creating a concentration of a certain component on the surface of a steel sheet is a technology aimed only at improving the characteristics of the coating. The technology to consistently achieve superior magnetic performance has not been studied.

[0011]

The above-mentioned Patent Document 6 promotes the transition from cementite to graphite by heat treatment before cold rolling to improve the texture obtained during subsequent primary recrystallization. However, the process of temperature rise during primary recrystallization annealing and etching are based on traditional methods and have not been studied anew.

[0012]

In addition, as disclosed in the above-mentioned Patent Document 7, it is confirmed that the magnetic performance of the anisotropic electrical steel sheet is greatly influenced by rapidly increasing the temperature to 700°C or higher at a rate of 100°C/s or more during the temperature raising process of primary recrystallization annealing and the introduction of microstrains with a nominal value of 0.1% or more during this rapid heating. In addition, in the above-mentioned Patent Document 8, it is confirmed that the magnetic characteristics of the anisotropic electrical steel sheet are significantly affected by rapidly increasing the temperature to 500-600°C at a rate of 100°C/s or more during the temperature raising process of primary recrystallization annealing. The above-mentioned Patent Document 9 discloses setting the temperature to 850°C at a rate of 300°C/s or 450°C/s in the process of raising the temperature in the primary recrystallization annealing.

[0013]

However, the above-mentioned Patent Documents 7 to 9 have not studied in detail how the magnetic characteristics of an anisotropic electrical steel sheet are affected by changing inhibitors in the thickness direction of the steel sheet.

[0014]

Accordingly, the present invention has been made in view of the above-described problem. It is an object of the present invention to provide a new and improved method for producing anisotropic electrical steel sheet capable of producing anisotropic electrical steel sheet with high magnetic flux density and excellent magnetic characteristics.

SOLUTION

[0015]

To solve the above problem, in accordance with one aspect of the present invention

A method for producing an anisotropic electrical steel sheet is proposed, containing

a process for heating and hot rolling a slab containing, in mass%, C 0.01% or more and 0.10% or less, Si: 2.5% or more and 4.5% or less, Mn: 0.01 % or more and 0.50% or less, the total amount of one or more of S, Se and Te: 0.001% or more and 0.050% or less, acid-soluble Al: more than 0% and 0.05% or less, and N: more than 0% and 0.015% or less, with a residue of iron and impurities, to obtain a hot-rolled steel sheet or annealing a hot-rolled steel sheet to obtain an annealed hot-rolled steel sheet,

cold rolling process of hot-rolled steel sheet or annealed hot-rolled sheet to obtain cold-rolled steel sheet,

annealing process of cold rolled steel sheet for primary recrystallization to obtain primary recrystallized annealed sheet,

the process of coating the surface of a primary recrystallized annealed sheet with an annealing separator including MgO, and then finishing annealing it to obtain a finish annealed sheet,

wherein at least one steel sheet of hot-rolled steel sheet, annealed hot-rolled sheet, cold-rolled steel sheet and primary recrystallized annealed sheet is shot peened and also solution contact processed, and

the process of covering a finished annealed sheet with an insulating coating and then annealing it to level it,

wherein in shot blasting the average particle size of the shot is 0.1 mm or more and 5.0 mm or less, and their speed is 10 m/s or more and 150 m/s or less,

wherein the solution contains one or more of the elements Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni, has a total element concentration of 0.00001% or more and 1.0000% or less, a pH value of -1.5 or more and less than 7 and the solution temperature is 15°C or more and 100°C or less, and the time during which the steel sheet is immersed in the solution is 5 seconds or more and 200 seconds or less.

[0016]

Moreover, in accordance with another aspect of the present invention

a method for producing anisotropic electrical steel sheet is proposed, in which straightening processing can be performed instead of the above-mentioned shot peening or in addition to shot peening,

and in straightening processing, the number of bending operations of the hot-rolled steel sheet is two or more, the bending angle is 10 degrees or more and 90 degrees or less, and the bending radius is 10 mm or more and 200 mm or less.

[0017]

Moreover, in accordance with another aspect of the present invention

A method for producing an anisotropic electrical steel sheet is proposed in which, when the temperature is rapidly increased during primary recrystallization annealing, the average temperature increase rate in the temperature range of 550-700°C is 100°C/s or more and 3000°C/s or less.

[0018]

Moreover, in accordance with another aspect of the present invention

A method for producing an anisotropic electrical steel sheet is proposed, in which the slab contains, instead of a portion of Fe, one or more elements selected from the group consisting of Cu: 1.0% or less, Sn: 1.0% or less, Ni: 1.0% or less, Cr: 1.0% or less, Sb: 1.0% or less, and Bi: 1.0% or less.

[0019]

Moreover, in accordance with another aspect of the present invention

A method for producing an anisotropic electrical steel sheet is proposed, in which the primary recrystallization annealing includes a temperature raising process, an intermediate processing process from temperature raising to decarburization annealing, and a decarburization annealing process,

in the intermediate treatment, the atmospheric dew point is -40°C or more and 0°C or less, and the residence time of the steel sheet at a temperature of 700°C or more and 950°C or less is 1 s or more and 20 s or less, and

in decarburization annealing, the oxygen partial pressure fraction (P _H2O /P _H2 ) in the atmosphere is 0.35 or more and 0.60 or less.

USEFUL EFFECTS OF THE INVENTION

[0020]

In accordance with the present invention, a solution containing one or more of the elements Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni (in this description they will sometimes be referred to as "Cu, etc."), and electrical steel sheets are in contact with each other. The electrical steel sheet includes MnS, MnSe and MnTe as inclusions (in this description, they will sometimes be referred to as "MnS, etc."). MnS and other inclusions act as inhibitors. In the present invention, if MnS, etc. contact with a solution containing Cu, etc., part of the Mn in MnS, etc., in particular the Mn of the surface layers of MnS, etc., is replaced by Cu, etc. By using this phenomenon to improve the heat resistance of precipitates, the inhibitor strength of anisotropic electrical steel sheet can be improved. Through this mechanism of action, it is possible to provide a new and improved method for producing anisotropic electrical steel sheet, which can produce anisotropic electrical steel sheet with high magnetic flux density and excellent magnetic characteristics.

[0021]

In accordance with another aspect of the present invention, it is possible to further increase the magnetic flux density by combining the technology of increasing grains in the Goss orientation near the surface layer due to rapid heat treatment during the process of increasing the temperature of the primary recrystallization annealing.

[0022]

Moreover, in accordance with another aspect of the present invention, it is possible to further increase the magnetic flux density by adding additional elements to the slab to stabilize secondary recrystallization.

[0023]

In addition, the inventors of the present invention have discovered that the phenomenon of Mn replacing the surface layer of MnS, etc. on Cu, etc. sometimes causes uneven color in the final product, but this can be eliminated by controlling the atmospheric and temperature conditions during intermediate processing and the atmospheric conditions during decarburization annealing in primary recrystallization annealing (rapid heat treatment and intermediate processing and decarburization annealing). Based on this discovery, it is possible to suppress color unevenness using another aspect of the present invention.

DESCRIPTION OF IMPLEMENTATION OPTIONS

[0024]

Next, preferred embodiments of the present invention will be explained in detail. It should be noted that, unless otherwise stated, for numerical values A and B, the expression "from A to B" will mean "A or more and B or less." In such an expression, when units are specified only for value B, the same units apply to value A.

[0025]

Method for producing anisotropic electrical steel sheet

As a result of intensive study of a method for producing anisotropic electrical steel sheet to improve its magnetic characteristics, the present inventors have discovered the following.

[0026]

In particular, when contacting an electrical steel sheet including MnS, etc., with a solution containing Cu, etc., to improve the heat resistance of MnS, etc., a portion of Mn in MnS, etc., in particular The Mn of the surface layers of MnS, etc., is replaced by Cu, etc., and by using this phenomenon, the inhibitor strength can be increased and the magnetic characteristics can be improved. In addition to this, they discovered that it was possible to further improve the magnetic performance by modifying the pre-shot blasting or straightening treatment so as to control the inhibitors in the thickness direction of the steel sheet when the solution contacts the sheet.

In addition, they found that by increasing the Goss-oriented grains near the surface layer through rapid heat treatment during the temperature rise process of primary recrystallization annealing, the magnetic performance could be further improved.

They also discovered that by adding additional elements to the slab to stabilize secondary crystallization, the magnetic performance could be further improved.

In addition, they found that the phenomenon of Mn replacing surface layers with MnS, etc. on Cu, etc. sometimes causes uneven color in the final product, but this can be eliminated by controlling and improving the atmospheric and temperature conditions during intermediate processing and the atmospheric conditions during decarburization annealing in primary recrystallization annealing (rapid heat treatment and intermediate processing and decarburization annealing).

[0027]

The inventors of the present invention have considered the above observations and carried out the present invention. One embodiment of the present invention is a method for producing an anisotropic electrical steel sheet, comprising the following.

[0028]

a process of heating and hot rolling a slab containing, in mass%, C: 0.01% or more and 0.10% or less, Si: 2.5% or more and 4.5% or less, Mn: 0, 01% or more and 0.50% or less, the total amount of one or more of S, Se and Te: 0.001% or more and 0.050% or less, acid-soluble Al: more than 0% and 0.05% or less, and N : more than 0% and 0.015% or less, with the remainder of iron and impurities, to obtain hot-rolled steel sheet or annealing of hot-rolled steel sheet to obtain annealed hot-rolled steel sheet,

cold rolling process of hot-rolled steel sheet or annealed hot-rolled sheet to obtain cold-rolled steel sheet,

annealing process of cold rolled steel sheet for primary recrystallization to obtain primary recrystallized annealed sheet,

the process of coating the surface of a primary recrystallized annealed sheet with an annealing separator including MgO, and then finishing annealing it to obtain a finish annealed sheet,

the process of covering a finished annealed sheet with an insulating coating and then annealing it to level it,

wherein at least one steel sheet of hot-rolled steel sheet, annealed hot-rolled sheet, cold-rolled steel sheet and primary recrystallized annealed sheet is shot peened and also solution contact processed, and

wherein in shot blasting the average particle size of the shot is 0.1 mm or more and 5.0 mm or less, and their speed is 10 m/s or more and 150 m/s or less,

wherein the solution contains one or more of the elements Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni, has a total element concentration of 0.00001% or more and 1.0000% or less, a pH value of -1.5 or more and less than 7 and the solution temperature is 15°C or more and 100°C or less, and the time during which the steel sheet is immersed in the solution is 5 seconds or more and 200 seconds or less.

[0029]

It is also possible to perform straightening treatment instead of or in addition to the above-mentioned shot peening. In straightening processing, the number of bending operations of the steel sheet is two or more, the bending angle is 10 degrees or more and 90 degrees or less, and the bending radius is 10 mm or more and 200 mm or less.

[0030]

In addition, the temperature raising process in primary recrystallization annealing can also be made rapid. When the temperature rises rapidly, the average temperature rise rate in the temperature region of 550-700°C is 100°C/s or more and 3000°C/s or less.

[0031]

In addition, the primary recrystallization annealing may also include a temperature raising process, an intermediate processing process from temperature raising to decarburization annealing, and a decarburization annealing process,

in the intermediate treatment, the atmospheric dew point is -40°C or more and 0°C or less, and the residence time of the steel sheet at a temperature of 700°C or more and 950°C or less is 1 s or more and 20 s or less, and

in decarburization annealing, the oxygen partial pressure fraction (P _H2O /P _H2 ) in the atmosphere is 0.35 or more and 0.60 or less.

[0032]

Next, a method for producing an anisotropic electrical steel sheet according to the present embodiment will be explained in detail.

[0033]

Chemical composition of the slab

First, the chemical composition of the slab used for the anisotropic electrical steel sheet according to the present embodiment will be explained. It should be noted that in the following, unless expressly stated otherwise, the expression "%" means "wt.%". In addition, the remainder in the slab composition, in addition to the elements described below, consists of Fe and impurities. Here, "impurities" means elements that are contained in raw materials or that enter the manufacturing process, and refer to components that are not intentionally included in the steel sheet. In addition, the chemical composition of the slab of anisotropic electrical steel sheet material is mainly based on the composition of the anisotropic electrical steel sheet. However, in the production of a conventional anisotropic electrical steel sheet, some of the contained elements are removed from the system due to decarburization annealing and purification annealing in the production process, so that the chemical composition of the slab material and the final product of the anisotropic electrical steel sheet become different. The composition of the slab can be appropriately adjusted taking into account the influence of decarburization annealing and cleaning annealing in the production process so that the characteristics of the anisotropic electrical steel sheet are desired.

[0034]

The C (carbon) content is 0.01% or more and 0.10% or less. C plays various roles, but if the C content is less than 0.01%, during heating of the slab, the grain size becomes excessively large, causing the core loss value of the final anisotropic electrical steel sheet to increase, and therefore it is undesirable. If the C content is more than 0.10%, during decarburization after cold rolling, the decarburization time increases and production costs increase accordingly, and therefore is undesirable. In addition, if the C content is more than 0.10%, decarburization easily becomes incomplete, and magnetic aging is likely to occur in the final anisotropic electrical steel sheet, and therefore is undesirable. Therefore, the C content is 0.01% or more and 0.10% or less, preferably 0.05% or more and 0.09% or less.

[0035]

The Si (silicon) content is 2.5% or more and 4.5% or less. Si increases the electrical resistance of the steel sheet, thereby reducing losses due to Foucault currents, which are one of the causes of magnetic losses. If the Si content is less than 2.5%, it becomes difficult to sufficiently suppress Foucault current losses in the final anisotropic electrical steel sheet, and therefore it is undesirable. If the Si content is more than 4.5%, the machinability of the anisotropic electrical steel sheet is deteriorated, and therefore it is undesirable. Therefore, the Si content is 2.5% or more and 4.5% or less, preferably 2.7% or more and 4.0% or less.

[0036]

The Mn (manganese) content is 0.01% or more and 0.50% or less. Mn forms inhibitors MnS, MnSe, MnTe, etc., controlling secondary recrystallization. If the Mn content is less than 0.01%, the absolute amount of MnS, MnSe and MnTe causing secondary recrystallization becomes insufficient, and therefore it is undesirable. If the Mn content is more than 0.50%, dissolution of Mn during heating of the slab is difficult and therefore undesirable. In addition, if the Mn content is more than 0.15%, the precipitate size of the inhibitors MnS, MnSe and MnTe easily becomes coarser, and the optimal size distribution of the inhibitors is disturbed, so it is undesirable. Therefore, the Mn content is 0.01% or more and 0.50% or less, preferably 0.01% or more and 0.30% or less, and more preferably 0.03% or more and 0.15% or less .

[0037]

The total content of one or more of S (sulfur), Se (selenium) and Te is 0.001% or more and 0.050% or less. S, Se and Te form inhibitors together with the aforementioned Mn. Two or more of S, Se and Te may be included in the slab, but it is sufficient that at least one of them is contained. If the total content of S, Se and Te falls outside the above range, a sufficient inhibitor effect cannot be obtained, so it is undesirable. Therefore, the contents of S, Se and Te are in total 0.001% or more and 0.050% or less, preferably 0.002% or more and 0.040% or less.

[0038]

The content of acid-soluble Al is more than 0% and 0.05% or less. Acid-soluble Al forms the inhibitors required to produce high magnetic flux density anisotropic electrical steel sheet. If the content of acid-soluble Al is 0, sometimes AlN is missing, the inhibitor strength becomes insufficient, and good magnetic performance cannot be obtained, so this is undesirable. If the content of acid-soluble Al is more than 0.05%, AlN released as an inhibitor becomes coarser, resulting in a decrease in inhibitor strength, so that it is undesirable. Therefore, the acid-soluble Al content is greater than 0% and 0.05% or less, preferably greater than 0% and 0.04% or less.

[0039]

The N (nitrogen) content is more than 0% and 0.015% or less. N forms an inhibitor AlN with the above acid-soluble Al. If the N content is outside the above range, a sufficient inhibitor effect cannot be obtained, so it is undesirable. Therefore, the N content is greater than 0% and 0.015% or less, preferably greater than 0% and 0.012% or less.

[0040]

P (phosphorus) may be contained in an amount greater than 0% and 1.0% or less. P increases strength without causing a decrease in magnetic flux density. However, excessive P content causes the toughness of steel to deteriorate, and the steel sheet is easy to break. For this reason, the upper limit of P content is set to 1.0%. Preferably, it is 0.150% or less, more preferably 0.120% or less. The lower limit of the P content is not particularly limited, but taking production costs into account, it is 0.001% or more.

[0041]

Moreover, the slab used to produce the anisotropic electrical steel sheet according to the present embodiment may contain, in addition to the above-mentioned elements, one or more elements of Cu, Sn, Ni, Cr, Sb or Bi as secondary recrystallization stabilizing elements. If the slab contains the above-mentioned elements, the magnetic flux density of the produced anisotropic electrical steel sheet can be further improved.

[0042]

The slab is formed by casting molten steel with the chemical composition described above. It should be noted that the slab casting method is not particularly limited. Moreover, in research work, even if a steel ingot is formed in a vacuum melting furnace, etc., an effect similar to the case where a slab is formed from the above components can be confirmed.

[0043]

Hot rolled steel sheet forming process

The slab is then heated and hot rolled to produce hot rolled steel sheet. The heating temperature of the slab is not particularly limited. When the inhibitor elements are completely dissolved in the slab, it can be heated, for example, to 1280°C or more. It should be noted that the upper limit value of the slab heating temperature is not particularly specified, but from the point of view of equipment protection, it is preferably 1450°C. For example, the heating temperature of the slab may be 1280°C or more and 1450°C or less. On the other hand, if the inhibitor elements are not completely dissolved in the slab, the heating temperature of the slab may be, for example, less than 1280°C. In this case, in the hot rolling process or in any process from the hot-rolled sheet annealing process to the finishing annealing process, the steel sheet may also be nitrided.

[0044]

The heated slab is then hot rolled to produce hot rolled steel sheet. The thickness of the processed hot-rolled steel sheet may be, for example, 1.8 mm or more and 3.5 mm or less. If the thickness of the hot-rolled steel sheet is less than 1.8 mm, sometimes the shape of the steel sheet after hot rolling becomes unsatisfactory, which is undesirable. If the thickness of the hot-rolled steel sheet is more than 3.5 mm, the rolling pressure in the cold rolling process becomes larger, which is undesirable.

The hot rolled steel sheet can also be annealed to produce annealed hot rolled sheet. By annealing the hot-rolled sheet, the shape of the steel sheet becomes better, so that the probability of the steel sheet breaking during cold rolling can be reduced.

[0045]

Cold rolled steel sheet forming process

Then, the resulting hot rolled steel sheet or hot rolled annealed sheet is processed into cold rolled sheet by one or more cold rolling passes with intermediate annealing in between. It should be noted that if several cold rolling passes are performed with intermediate annealing and/or pickling between them, it is also possible to omit the previous hot rolled sheet annealing step. From the point of view of reducing roll wear during cold rolling, pickling is preferably carried out before the individual cold rolling passes. In addition, both hot-rolled sheet annealing and intermediate annealing can be performed.

[0046]

In addition, the steel sheet may be heat treated at a temperature of 300° C. or lower between cold rolling passes, between rolling stands, or during rolling. In such a case, the magnetic characteristics of the final anisotropic electrical steel sheet can be improved. It should be noted that the hot-rolled steel sheet can be cold-rolled three times or more, but this increases production costs, so the hot-rolled steel sheet is preferably cold-rolled once or twice. When cold rolling is carried out in a reverse manner, for example in the Sendzimir mill, the number of cold rolling passes is not particularly limited, but from the point of view of production costs it is preferably nine or less.

[0047]

Primary recrystallization annealing process

Then, the cold rolled steel sheet is heated and subjected to decarburization annealing. These processes are called "primary recrystallization annealing" and are preferably carried out sequentially. Increasing the temperature in the primary recrystallization annealing can be carried out quickly, whereby it becomes possible to enlarge the Goss-oriented grains in the cold-rolled steel sheet before secondary recrystallization, and in the secondary recrystallization process, the grains oriented close to the ideal Goss orientation are recrystallized a second time.

[0048]

Temperature rise process

In the present invention, in the temperature raising process of primary recrystallization annealing, the average rate of temperature increase from 550°C to 700°C can be 100°C/s or more and 3000°C/s or less. By this means, the Goss-oriented grains can be increased before secondary recrystallization of the cold-rolled steel sheet, and the magnetic flux density of the final anisotropic electrical steel sheet can be improved. The rapid rise temperature range is 550°C - 700°C. If the rapid heating start temperature exceeds 550° C., the recovery of dislocations in the steel sheet is greatly accelerated, and the primary recrystallization of grains with an orientation other than the Goss orientation does not begin, so the effect of increasing the Goss-oriented grains is reduced, which is undesirable. If the rapid temperature rise end temperature is less than 700° C., the primary recrystallization of grains with an orientation other than the Goss orientation is completed before the primary recrystallization of the Goss-oriented grains is completed, so that the enlargement effect of the Goss-oriented grains is reduced, which is undesirable.

[0049]

In addition, if the average temperature increase rate from 550°C to 700°C is made to be 400°C/s or more, the oriented Goss grains before secondary recrystallization can be further increased and the magnetic flux density in the final anisotropic electrical steel sheet can be further improved, so that this is preferable. By making the average temperature increase rate from 550° C. to 700° C. equal to 700° C./s or more, the magnetic flux density in the anisotropic electrical steel sheet can be further improved, so this is highly preferable. If the average rate of temperature increase from 550°C to 700°C is less than 100°C/s, secondary recrystallization does not produce enough Goss grains to improve the magnetic properties, which is undesirable. On the other hand, the upper limit of the average rate of temperature rise from 550°C to 700°C is not particularly regulated, but from the point of view of equipment and production costs it can be set, for example, to 3000°C/s. It should be noted that the initial temperature rise of the primary recrystallization annealing, as well as the heating pattern and peak temperature other than a rapid temperature rise from 550° C. to 700° C. are not particularly limited.

[0050]

The increase in inhibitor strength on the surface of the steel sheet and in a certain depth range of the surface layer of the steel sheet due to solution treatment, which is explained later, and the increase in Goss-oriented grains due to the rapid increase in temperature during primary recrystallization annealing have a synergistic effect on improving the magnetic performance. The mechanism for this may be that the strength of the inhibitor is increased, so that in the process of increasing the finishing annealing temperature, the abnormal growth of grains other than Goss grains near the surface layer is suppressed, and as a result, the abnormal growth of a large number of Goss grains is maintained.

[0051]

Such a rapid temperature increase can be obtained, for example, using a resistance heating method or an induction heating method.

[0052]

Here, the process of raising the temperature can be carried out by several devices. For example, restoring the steel sheet, that is, keeping it at a temperature below 550° C., at which the dislocation density of the steel decreases, or gradually cooling, can also improve the temperature uniformity of the steel sheet before increasing the temperature, so that this can be accomplished. In addition, the process of raising the temperature from 550°C to 700°C can also be performed by one or more devices.

[0053]

The point at which the temperature starts to rise is the transition point on the low temperature side at 550°C or less from a state in which the temperature of the steel sheet falls to a state in which the temperature of the steel sheet rises (ie, a local minimum temperature point). In addition, the point at which the temperature rise ends is the transition point on the high temperature side at 700°C or higher from the state in which the temperature of the steel sheet rises to the state in which the temperature of the steel sheet drops (that is, the local maximum temperature point) .

[0054]

However, due to the provision of a variety of temperature raising devices, on the high temperature side of the temperature raising process including 700°C, there is a possibility that the temperature of the steel sheet will continue to rise. In such a case, for example, the end point of a rapid temperature rise may be made to be 700° C. or more, or a point at which the temperature rise rate becomes a local minimum with a negative value.

[0055]

Here, the method for estimating the starting point of temperature increase and the end point of rapid temperature increase is not particularly limited, but, for example, evaluation can be performed using a remote thermometer, etc. for measuring the temperature of a steel sheet. It should be noted that the method for measuring the temperature of a steel sheet is not particularly limited. In addition, regardless of whether the final temperature of the primary recrystallization temperature increase is lower or higher than the subsequent decarburization annealing temperature, the effect of the present invention is not impaired. If the final temperature of the primary recrystallization temperature rise is lower than the decarburization annealing temperature, the steel sheet can also be heated in the decarburization annealing process. If the final temperature of the primary recrystallization temperature rise becomes higher than the decarburization annealing temperature, the steel sheet may also be treated to dissipate heat or treated with cooling gas, etc., to reduce the temperature of the steel sheet. In addition, the steel sheet can be cooled to a temperature below the decarburization annealing temperature and then reheated in a decarburization annealing process.

[0056]

However, if measuring the temperature of the steel sheet is difficult, and estimating the exact positions of the temperature rise start point and the rapid temperature rise end point is difficult, it is also possible to estimate these positions by evaluating the thermal profiles of the temperature rise process and the cooling process. In addition, the temperature of the steel sheet at the inlet and outlet of the temperature raising device in the temperature raising process can also be considered as the starting point of temperature raising and the ending point of rapid temperature raising.

[0057]

Intermediate processing

Moreover, in another aspect of the present invention, the intermediate treatment process may be provided between the temperature raising process and the decarburization annealing process in the primary recrystallization annealing, the dew point of the atmosphere in the intermediate treatment process may be -40°C or more and 0°C or less, and the residence time of the steel sheet at a temperature of 700°C or more and 950°C or less may be 1 s or more and 20 s or less.

[0058]

As will be explained in detail below, by changing the solution contact processing conditions, the amount of inhibitors in the thickness direction of the steel sheet can be adjusted to improve the magnetic characteristics. On the other hand, when the solution contact processing conditions are modified, the disadvantage of uneven color of the steel sheet sometimes reappears. The uneven color of the steel sheet is due to the formation state of the oxide film after decarburization annealing. More specifically, uneven color occurs when internal oxidation becomes uneven. The inventors of the present invention have discovered that it is possible to suppress the formation of uneven color by controlling the atmospheric and temperature conditions before the decarburization annealing, that is, the intermediate treatment.

[0059]

If the dew point of the atmosphere in the intermediate treatment process is less than -40°C, then in the subsequent decarburization annealing, the oxide film is formed unevenly, and the appearance of the anisotropic electrical steel sheet obtained as the final product has an uneven color, so this is undesirable. Even if the dew point of the atmosphere in the intermediate treatment process is more than 0°C, in the subsequent decarburization annealing, an oxide film is formed unevenly, and the appearance of the anisotropic electrical steel sheet obtained as a final product has an uneven color, so this is undesirable.

If the residence time of a steel sheet at a temperature of 700°C or more and 950°C or less in intermediate processing is less than 1 second, an oxide film is formed unevenly during subsequent decarburization annealing, and the anisotropic electrical steel sheet produced as a final product becomes uneven in color. , so this is undesirable. The upper limit of the residence time of the steel sheet at a temperature of 700°C or more and 950°C or less in intermediate processing is not particularly limited, but if it is more than 20 seconds, the equipment becomes long and large so that it is undesirable.

[0060]

The mechanism by which intermediate treatment affects oxide film formation during subsequent decarburization annealing is not entirely clear, but is thought to be as follows. When performing processing by bringing a solution containing one or more of the elements Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni (Cu, etc.) into contact with a steel sheet (solution contact processing) Mn in part MnS, MnSe or MnTe on the surface of the steel sheet is replaced by these elements. Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni are not uniformly distributed on the surface of the steel sheet, but are locally present in places where MnS is present, etc., therefore, in places where these elements are locally present, internal oxidation during subsequent decarburization annealing is difficult , and eventually there is a difference in the amount of internal oxidation from places where Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni are absent. Moreover, if before decarburizing annealing a given amount of oxide film is formed due to intermediate processing, then areas of internal oxidation during subsequent decarburizing annealing are formed over the entire surface of the steel sheet, therefore it is believed that internal oxidation proceeds relatively uniformly.

If the dew point of the intermediate treatment is less than -40°C, particularly in areas where Cu, Hg, Ag, Pb, Cd, Co, Zn or Ni are locally present, the degree of oxide film formation during the intermediate treatment becomes insufficient, so that this is undesirable . On the other hand, if the dew point of the intermediate treatment is more than 0°C, then the intermediate treatment will eventually form a silica film by external oxidation, and after that, with decarburization annealing, the development of internal oxidation is suppressed and the oxide film will eventually become thinner, it is therefore expected that there will be a deficiency in the amount of oxidation in areas where Cu, Hg, Ag, Pb, Cd, Co, Zn or Ni are locally present, resulting in uneven color remaining in the final product.

Even if the residence time of the steel sheet at a temperature of 700°C or more and 950°C or less in the intermediate treatment is less than 1 second, the amount of oxide film generated in the intermediate treatment becomes insufficient, so it is undesirable. If this residence time is more than 20 seconds, the equipment becomes long and large, so this is undesirable.

[0061]

Decarburizing annealing

The cold rolled steel sheet is then annealed for decarburization. From the point of view of decarburization ability, decarburization annealing can be performed in a humid atmosphere containing hydrogen and nitrogen at a temperature of 900°C or less. Here, in order not to inhibit decarburization, the oxygen partial pressure ratio in decarburization annealing, that is, the ratio P _H2O /P _H2 of the partial pressure of water vapor P _H2O to the partial pressure of hydrogen P _H2 in the atmosphere, can be made to be 0.35 or more.

[0062]

In addition, from the viewpoint of suppressing the formation of uneven color, the ratio P _H2O /P _H2 of the partial pressure of water vapor P _H2O to the partial pressure of hydrogen P _H2 in the atmosphere can be made to be 0.35 or more and 0.60 or less. If the proportion of oxygen partial pressure in the atmosphere during decarburization annealing is less than 0.35, the oxide film becomes thinner, and oxygen deficiency occurs at the places where Cu, Hg, Ag, Pb, Cd, Co, Zn or Ni are present, and uneven color remains in end product, so this is undesirable. If the oxygen partial pressure ratio of the atmosphere during decarburization annealing is more than 0.60, the magnetic performance deteriorates so that it is undesirable. Therefore, the oxygen partial pressure ratio in decarburization annealing is 0.35 or more and 0.60 or less.

[0063]

It should be noted that in the primary recrystallization annealing process, recovery annealing can be performed after decarburization annealing to improve the magnetic and coating characteristics of the cold-rolled steel sheet.

[0064]

Finish annealing process

After this, the cold-rolled steel sheet, after initial recrystallization annealing, is subjected to finishing annealing. In this case, an annealing separator containing MgO as the main component can be applied before finishing annealing to prevent the steel sheets from sticking together, forming a primary coating, controlling the secondary recrystallization behavior, etc. The annealing separator is usually applied to the surface of the steel sheet as a water slurry and dried, but electrostatic coating method, etc. can also be used.

[0065]

Finish annealing is then performed to form a primary coating and secondary recrystallization. Finish annealing can be performed, for example, by heat treating the steel sheet in a coiled state using a batch heating furnace, etc. In addition, to further reduce the core loss value of the final anisotropic electrical steel sheet, cleaning can be performed by raising the temperature of the steel sheet in the coiled state to about 1200° C. and then holding it at that temperature.

[0066]

During finishing annealing, the temperature usually rises from about room temperature. In addition, there are different rates of temperature rise during finishing annealing, but this rate is not particularly limited in the present invention. Conventional finishing annealing conditions may be used. For example, from a performance point of view and normal equipment limitations, speeds of 5-100°C/hour are also possible. Additionally, this process can be performed using other known heating models. During the cooling process, the thermal profile is also not particularly limited.

[0067]

The composition of the atmospheric gas during finishing annealing is not particularly limited. During the development of secondary recrystallization, this may be a gas mixture of nitrogen and hydrogen. This atmosphere can be dry or humid. Cleaning annealing can be performed in dry hydrogen gas.

[0068]

Leveling Annealing Process

Then, in order to impart insulating ability and tension to the steel sheet, after finishing annealing, an insulating coating containing aluminum phosphate or colloidal silica, etc., is applied to the surface of the steel sheet, for example. as its main component. After this, leveling annealing is carried out to bake the insulating coating and level the shape of the steel sheet resulting from the finishing annealing. It should be noted that the components of the insulating coating are not particularly limited as long as insulating ability and tension are imparted to the finished annealed sheet. It should be noted that in the present embodiment, depending on the purpose of the user, the anisotropic electrical steel sheet can also be processed to control magnetic domains.

[0069]

The process of treating a steel sheet by shot blasting and/or straightening and contacting with mortar

In the present process, at least one steel sheet of hot-rolled steel sheet, annealed hot-rolled sheet, cold-rolled steel sheet and primary recrystallized annealed sheet is processed by shot peening and/or straightening, and then immersed in a solution. Solution contact processing (sometimes called “solution contact processing”) is performed at least once after hot rolling and before finish annealing to control the amount of inhibitors in the thickness direction, which will be explained later. It should be noted that the shot peening and/or straightening process and solution contact may be performed in separate processes.

[0070]

Treatment by contact with solution

The order of the procedure may vary, but first the solution contact treatment will be explained. The solution contains one or more of the elements Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni (in this description they will sometimes be referred to as "Cu, etc."). The sum of the concentrations of these elements is, in wt.%, 0.00001% or more and 1.0000% or less, the pH value is -1.5 or more and less than 7, the solution temperature is 15°C or more and 100° C or less, and the time during which the steel sheet is immersed in the solution is 5 s or more and 200 s or less.

If the sum of the concentrations of one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni in the solution is less than 0.00001%, the effect of controlling the amount of inhibitors in the thickness direction becomes insufficient, so it is undesirable. If the sum of the concentrations of one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni in the solution is more than 1.0000%, the magnetism improving effect is saturated and the cost of the solution is also increased so that it is undesirable. Therefore, the sum of the concentrations of one or more of the elements Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni in solution is 0.00001% or more and 1.0000% or less.

In addition, if the pH value of the solution is less than
-1.5, the acidity becomes too strong and the solution becomes difficult to handle, so this is undesirable. If the pH value of the solution is 7 or more, the effect of controlling the amount of inhibitors in the thickness direction by solution treatment becomes insufficient, so it is undesirable. Therefore, the pH value of the solution is -1.5 or greater and less than 7.

Moreover, if the solution temperature is less than 15°C, the effect of controlling the amount of inhibitors in the thickness direction by solution treatment becomes insufficient, so it is undesirable. If the temperature of the solution is more than 100°C, handling of the solution becomes difficult, so this is undesirable. Therefore, the solution temperature is 15°C or more and 100°C or less.

Moreover, in solution processing, if the time during which the steel sheet is immersed in the solution is less than 5 seconds, the effect of controlling the amount of inhibitors in the thickness direction by solution contact processing becomes insufficient, so it is undesirable. If the time during which the steel sheet is immersed in the solution is more than 200 seconds, the equipment becomes long and large, so this is undesirable. Therefore, the time for which the steel sheet is immersed in the solution is 5 seconds or more and 200 seconds or less.

[0071]

It is proposed that the mechanism by which control of the amount of inhibitors in the thickness direction becomes possible during solution treatment is as follows: If the solution contains one or more of the elements Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni (“ Cu, etc."), since the affinity of these elements in solution with S, Se and Te is extremely high, they replace Mn in MnS, MnSe and MnTe inclusions ("MnS, etc.") on the surface of the steel sheet, forming compounds. This reaction occurs easily on surfaces in contact with the solution, in particular in MnS and other inclusions. If Mn is replaced by other metal elements (Cu, etc.) on the surfaces of MnS and other inclusions, these surface compounds become barriers to inhibit the dissolution of Mn and S, Se and Te on the central sides of MnS and other inclusions in steel, so it is believed that Ostwald ripening of MnS, etc. during the finishing annealing process is suppressed, and the thermal stability, that is, the strength of the inhibitor, MnS and other precipitates is increased. This reaction occurs when a solution containing one or more of the elements Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni (Cu, etc.) comes into contact with MnS, MnSe or MnTe (MnS, etc. .). Therefore, if cracks, voids and other defects are present on the surface of the steel sheet due to shot blasting and straightening treatment, the solution passes through these places to penetrate into the steel sheet, causing the solution to react not only with MnS, etc. on most of the surface of the steel sheet, but also with MnS, etc. to a certain depth of the surface layer of the steel sheet, and as a result, the strength of the inhibitor is increased.

[0072]

Shot blasting

Due to shot blasting and other processing, cracks, voids and other defects appear on the surface of the steel sheet. Subsequently, in the solution contact treatment, the solution passes through these places, penetrating into the steel sheet, resulting in the solution not only reaching most of the surface of the steel sheet, but also penetrating to some depth. Through the above solution treatment, it is possible to improve the heat resistance of Mn inhibitors on the surface of MnS, MnSe and MnTe precipitates (“MnS, etc.”) acting as inhibitors by replacing it with Cu, etc. Therefore, through shot peening, it is possible to force the solution to penetrate not only into the uppermost layer of the steel sheet, but also into the interior to some depth, and increase the strength of the MnS and other inhibitors present in it.

[0073]

The shot blasting conditions include an average shot particle size of 0.1 mm or more and 5.0 mm or less and a shot blast speed of 10 m/s or more and 150 m/s or less. Thanks to this, microcracks are introduced into the surface of the steel sheet, allowing infiltration of the solution. Ordinary material can be used as the shot material. Steel balls with a hardness of approximately HV 500 can be used. If the average shot size is less than 0.1 mm, microcracks cannot be produced to a sufficient extent. If the average shot size is more than 5.0mm, the steel sheet is deformed, uniform deformation by cold rolling becomes difficult, and good magnetic performance cannot be obtained. In addition, if the shot blast speed is less than 10 m/s, microcracks cannot be produced to a sufficient extent. If the shot blast speed is more than 150 m/s, the steel sheet will be deformed, uniform deformation by cold rolling becomes difficult, and good magnetic performance cannot be obtained. Shot shapes are usually roughly classified into spherical and angular shapes. As a rule, angular shaped shot blasting material has a high abrasive ability and ensures the rapid appearance of cracks on the surface of the steel sheet. In the present invention, a shot blasting material with an angular shape or a spherical shape can be used. Angular and spherical shaped shot blasting materials can also be used in mixture with each other.

[0074]

Processing for editing

As a method of introducing cracks, voids or other defects into the surface of a steel sheet, in addition to shot peening, straightening processing can be used. Straightening treatment can also be used instead of shot peening. In addition, shot blasting and straightening can be used together. Straightening maintains the flatness of the steel sheet by applying stress to the steel sheet as it bends and re-bends along the straightening roller. By bending and re-bending, this straightening can introduce cracks, voids and other defects into the surface of the steel sheet. Therefore, in the subsequent solution contact treatment, the solution can pass through cracks, voids and other places to penetrate the steel sheet, so that the solution reaches not only the most superficial layer of the steel sheet, but also a certain depth of the steel sheet.

[0075]

The straightening conditions include the bending number of the steel sheet is two or more, the bending angle is 10 degrees or more and 90 degrees or less, and the bending radius is 10 mm or more and 200 mm or less. Thanks to this, microcracks are introduced into the surface of the steel sheet, through which the solution can penetrate. If the number of bends is less than two, microcracks cannot be produced sufficiently. In addition, if the bending angle is less than 10°, microcracks cannot be produced sufficiently. If the bending angle is more than 90°, the steel sheet is deformed, uniform deformation by cold rolling becomes difficult, and good magnetic performance cannot be obtained. In addition, if the bending radius is less than 10 mm, the steel sheet is deformed, uniform deformation by cold rolling becomes difficult, and good magnetic performance cannot be obtained. If the bending radius is more than 200mm, microcracks cannot be produced sufficiently.

[0076]

A method for confirming that the surfaces of inclusions “MnS, etc.” replaced by "Cu, etc."

Next, a method for confirming that the surfaces of the "MnS, etc." precipitates will be explained. replaced by "Cu, etc." First, a sample of steel sheet to be confirmed is polished to a mirror finish and examined using SEM-EDX. The observed SEM image can confirm the presence of MnS and other inclusions. The image in question is overlaid with EDX mapping of elements Cu, etc., such as Mn, S and Cu, and force relationships. Thanks to this, the constituent elements of the inclusion particles can be confirmed. In a typical example, when examining inclusion particles and their surroundings, the ratio of Mn to S mapping strength increases for parts of the inclusion particles, so the particles can be confirmed to be MnS particles. In addition, if the mapping force ratio of Cu also increases at the parts near the surface of the particles, the surface of the inclusions is considered to be replaced by Cu.

[0077]

In addition, the distribution state of elements in inclusion particles is confirmed using Auger electron spectroscopy. More specifically, by sputtering the surface layers of MnS and other inclusions with argon, a few nm (usually 1 nm) Auger electron spectroscopy with elemental analysis can confirm the distribution of constituent elements from parts of the surface layer of the inclusion particles in an inward direction. If Cu etc. are found in high concentration only in parts of the surface layer of MnS or other inclusions, and the concentration of Cu, etc. decreases inside the inclusions, we can assume that the surfaces of the inclusions are replaced by Cu, etc.

[0078]

Moreover, in the present embodiment, it is considered that cracks, voids, etc. are formed in the surface layer of the steel sheet as a result of shot blasting or straightening treatment, so that the solution passes through these places, penetrating the steel sheet and reacting not only with MnS, etc. in the topmost layer of the steel sheet, but also with MnS, etc. to a certain depth of the surface layer of the steel sheet. Using the above method, it can be confirmed to what depth from the surface layer of the steel sheet the surface of inclusions "MnS, etc." replaced by "Cu, etc." From the point of view of increasing the strength of inhibitors, it is preferable that the surfaces of inclusions “MnS, etc.” were replaced by "Cu, etc." up to a fairly large depth. Generally, they are preferably replaced within a depth range of 10-500 µm from the surface of the steel sheet.

[0079]

The devices and measurement conditions used for SEM, EDS and Auger electron spectroscopy can be suitably selected according to the object being measured. In this specification, the SEM device used is the FE-SEM model JEOL7001F from JEOL with a WD of 10 mm and an acceleration voltage of 15 kV. For Auger electron spectroscopy, the FE-AES PHI-700 analyzer manufactured by PHI with an electron beam: 10 kV, 10 nA, and an ion beam: Ar/2 kV is used.

[0080]

In most cases, in the steel sheet manufacturing process, pickling is carried out before subsequent processes to remove scale, clean the surface of the steel sheet, etc. Generally, from the point of view of reducing roll wear during cold rolling, pickling treatment can also be carried out before the individual cold rolling processes. In addition, from the point of view of controlling the surface oxidation of the steel sheet during primary recrystallization annealing, etching can also be performed before primary recrystallization annealing. In addition, from the point of view of improving the plating ability of the annealing separator, etching can also be performed before finishing annealing. These types of etching can also be used in combination.

Along with this, solution contact treatment can be included in the steel sheet pickling process. The above pH value, solution temperature and contact time (etching time) can be used as etching conditions. It should be noted that the effect of improving the heat resistance of inhibitors (precipitates) due to existing technology, etc. can also be obtained when applied to other types of steel. For example, they can also be applied to isotropic electrical steel sheet. When applied to other types of steel, the slab components and process conditions are not limited to those described above.

[0081]

Using the above processes, a final sheet of anisotropic electrical steel can be produced. According to the production method of the present embodiment, an anisotropic electrical steel sheet with excellent magnetic characteristics can be produced.

[0082]

Moreover, in the anisotropic electrical steel sheet according to the present embodiment, the magnetic flux density value B8 can also be controlled. Particularly, in the anisotropic electrical steel sheet according to the present embodiment, the magnetic flux density value B8 can be made equal to 1.91 T or more, preferably 1.92 T or more, more preferably 1.93 T or more, even more preferably 1.94 Tesla or greater, and even more preferably 1.95 Tesla or greater. Here, the magnetic flux density value B8 is the magnetic flux density when a magnetic field of 800 A/m and a frequency of 50 Hz is applied to the anisotropic electrical steel sheet. If the magnetic flux density value B8 is low, the loss value of the anisotropic electrical steel sheet core (particularly hysteresis loss) becomes larger, so that it is undesirable. The upper limit value B8 of the magnetic flux density is not particularly limited, but in practice may be, for example, 2.0 Tesla. It should be noted that the magnetic flux density and other magnetic properties of the anisotropic electrical steel sheet can be measured by known methods. For example, the magnetic properties of an anisotropic electrical steel sheet can be measured using an Epstein test-based method in accordance with JIS C2550, a Single Sheet Tester (SST) method in accordance with JIS C 2556, etc. It should be noted that in research work, if the steel ingot is formed in a vacuum melting furnace, etc., it becomes difficult to obtain a test sample equivalent in size to the actual production. In this case, for example, it is also possible to obtain a test piece of 60 mm wide × 300 mm long and measure the characteristics based on the single-sheet tester method. In addition, the obtained result can be multiplied by a correction factor so that the same measurement value can be obtained as in the method based on the Epstein test. In the present embodiment, the measurement is performed in accordance with the single-sheet tester method.

[0083]

The anisotropic electrical steel sheet thus obtained is processed into a strip core or stacked core in the production of a transformer. Here, the uniform appearance of the anisotropic electrical steel sheet without uneven color, etc. becomes an important factor in gaining the trust of users. In one embodiment of the present invention, color uniformity can be judged by preparing color samples by dividing the color levels from white to black into eight equal parts, dividing the area of the steel sheet into 50 mm x 50 mm samples, and rating the color levels of the divided areas on an eight-level color scale samples, and if the color difference between these areas is two or more levels, color unevenness can be concluded. For example, color samples can be prepared by simultaneously scanning steel sheet samples with different tones and white and black samples and using commercially available image processing software to classify the samples by evenly dividing the brightness from white to black into eight equal levels. By comparing these color samples and the steel sheet, it can be analyzed whether the color difference is two or more levels in a 50x50 mm area of the steel sheet.

[0084]

The anisotropic electrical steel sheet according to the present embodiment has been explained above. The anisotropic electrical steel sheet according to the present embodiment can be produced by the anisotropic electrical steel sheet manufacturing method of the present embodiment. However, the present invention is not limited to this method.

EXAMPLES

[0085]

Next, a method for producing anisotropic electrical steel sheet and anisotropic electrical steel sheet according to embodiments of the present invention will be explained in more detail by means of examples. It should be noted that the examples shown below are merely illustrations of the anisotropic electrical steel sheet according to the embodiments. The anisotropic electrical steel sheet according to the present embodiment is not limited to the examples shown below.

[0086]

Example 1

Production of anisotropic electrical steel sheets

First, a steel ingot was produced containing C: 0.04%, Si: 3.3%, Mn: 0.09%, S: 0.002%, Se: 0.001%, Te: 0.001%, acid soluble Al: 0.005%, and N: 0.003%, with the remainder of Fe and impurities. The steel ingot was annealed at 1200°C for 1 hour and then hot rolled to thereby obtain hot rolled steel sheets with a thickness of 2.3 mm. The resulting hot-rolled steel sheets were annealed at a peak temperature of 1000°C for 140 s, pickled, then annealed and shot-peened, and solution-contacted between two cold rolling processes to thereby obtain cold-rolled steel sheets with a thickness of 0.23 mm. The shot peening conditions and the solution contact processing conditions after intermediate annealing are shown in Table 1.

[0087]

The resulting cold-rolled steel sheets were then annealed for primary recrystallization in a humid hydrogen atmosphere at 850°C for 180 s. The temperature rise rates are shown in Table 1. Then, the surfaces of the steel sheets after primary recrystallization annealing were coated with an annealing separator containing MgO as an aqueous slurry and then dried. After this, they were subjected to finishing annealing, and the annealed steel sheets were washed. After this, the surfaces of the steel sheets were coated with an insulating coating containing aluminum phosphate and colloidal silica as the main components, then leveling annealing was carried out to bake the insulating coating and level the steel sheets.

[0088]

Samples of the obtained anisotropic electrical steel sheets after leveling annealing were cut and stress-relieving annealed, then a method for measuring the magnetic properties of a single sheet for a sample with a size of 60mm x 300mm (based on the method described in JIS C2556) was used to measure the magnetic flux density value B8 anisotropic electrical steel sheets according to the examples of the present invention and comparative examples. Here, the value of B8 represents the magnetic flux density in the steel sheet when the anisotropic electrical steel sheet is excited at 50 Hz and 800 A/m. In the present invention, the average value of five samples was used.

[0089]

Here, the state in which the magnetic flux density value B8 of the anisotropic electrical steel sheet is 1.91T or more was judged to be good (B), the state where B8 is 1.92T or more was judged to be even better (A) , and a condition in which B8 is 1.93 T or greater was rated as very good (S). In addition, conditions other than those listed above were rated as unsatisfactory (C).

[0090]

The production conditions, measurement and evaluation results of the above examples of the present invention and comparative examples are shown in Table 1.

[0091]

[Table 1] Condition Shot blasting conditions Conditions for treatment by contact with solution Rapid Temperature Rise Rate (°C/s) Magnetic flux density
B8 value (T) Grade Notes Average particle size Shot blowing speed Form Metal type Metal concentration (%) Solution (base) pH Solution temperature
(ºC) Contact time between solution and steel sheet (s) A1 2 50 Angular Cu 0.000005 Hydrochloric acid 3 70 thirty 20 1.895 C Comparative example A2 2 50 Angular Cu 0.000010 Hydrochloric acid 3 70 thirty 20 1,910 B Real example A3 2 50 Angular Cu 0.00010 Hydrochloric acid 3 70 thirty 20 1.916 B Real example A4 2 50 Angular Cu 0.01000 Hydrochloric acid 3 70 thirty 20 1,918 B Real example A5 2 50 Angular Cu 0.10000 Hydrochloric acid 3 70 thirty 20 1,919 B Real example A6 2 50 Angular Cu 0.00100 Hydrochloric acid 0 70 thirty 20 1,919 B Real example A7 2 50 Angular Cu 0.00100 Hydrochloric acid 3 70 thirty 20 1,919 B Real example A8 2 50 Angular Cu 0.00100 Hydrochloric acid 5 70 thirty 20 1.917 B Real example A9 2 50 Angular Cu 0.00100 Hydrochloric acid 6 70 thirty 20 1.916 B Real example A10 2 50 Angular Cu 0.00100 Hydrochloric acid 7 70 thirty 20 1,902 C Comparative example A11 2 50 Angular Cu 0.00100 Hydrochloric acid 3 10 thirty 20 1,903 C Comparative example A12 2 50 Angular Cu 0.00100 Hydrochloric acid 3 15 thirty 20 1.915 B Real example A13 2 50 Angular Cu 0.00100 Hydrochloric acid 3 50 thirty 20 1.917 B Real example A14 2 50 Angular Cu 0.00100 Hydrochloric acid 3 100 thirty 20 1,919 B Real example A15 2 50 Angular Cu 0.00100 Hydrochloric acid 3 70 3 20 1,903 C Comparative example A16 2 50 Angular Cu 0.00100 Hydrochloric acid 3 70 5 20 1.915 B Real example A17 2 50 Angular Cu 0.00100 Hydrochloric acid 3 70 10 20 1.917 B Real example A18 2 50 Angular Cu 0.00100 Hydrochloric acid 3 70 100 20 1,919 B Real example A19 2 50 Angular Cu 0.00100 Hydrochloric acid 3 70 200 20 1,919 B Real example A20 2 50 Angular Hg 0.00100 Hydrochloric acid 3 70 thirty 20 1,919 B Real example A21 2 50 Angular Ag 0.00100 Hydrochloric acid 3 70 thirty 20 1,919 B Real example A22 2 50 Angular Pb 0.00100 Hydrochloric acid 3 70 thirty 20 1,919 B Real example A23 2 50 Angular Cd 0.00100 Hydrochloric acid 3 70 thirty 20 1,918 B Real example A24 2 50 Angular Co 0.00100 Hydrochloric acid 3 70 thirty 20 1,919 B Real example A25 2 50 Angular Zn 0.00100 Hydrochloric acid 3 70 thirty 20 1,918 B Real example A26 2 50 Angular Ni 0.00100 Hydrochloric acid 3 70 thirty 20 1,918 B Real example A27 2 50 Angular Cu+Ni 0.00100 Hydrochloric acid 3 70 thirty 20 1,918 B Real example A28 2 50 Angular Ag+Co+Zn 0.00100 Hydrochloric acid 3 70 thirty 20 1,919 B Real example A29 2 50 Angular Cu 1.00000 Sulfuric acid 2.5 70 thirty 20 1,919 B Real example A30 2 50 Angular Cu 1.00000 Nitric acid 2.5 70 thirty 20 1,918 B Real example A31 2 50 Angular Cu 1.00000 Phosphoric acid 2.5 70 thirty 20 1,918 B Real example A32 0.05 50 Angular Cu 0.00100 Hydrochloric acid 3 70 thirty 20 1,902 C Comparative example A33 0.1 50 Angular Cu 0.00100 Hydrochloric acid 3 70 thirty 20 1,919 B Real example A34 5 50 Angular Cu 0.00100 Hydrochloric acid 3 70 thirty 20 1,919 B Real example A35 10 50 Angular Cu 0.00100 Hydrochloric acid 3 70 thirty 20 1,904 C Comparative example A36 2 5 Angular Cu 0.00100 Hydrochloric acid 3 70 thirty 20 1,903 C Comparative example A37 2 10 Angular Cu 0.00100 Hydrochloric acid 3 70 thirty 20 1,919 B Real example A38 2 150 Angular Cu 0.00100 Hydrochloric acid 3 70 thirty 20 1,919 B Real example A39 2 200 Angular Cu 0.00100 Hydrochloric acid 3 70 thirty 20 1,904 C Comparative example A40 2 50 Round Cu 0.00100 Hydrochloric acid 3 70 thirty 20 1,919 B Real example A41 2 50 Angular Cu 0.00100 Hydrochloric acid 3 70 thirty 100 1.926 A Real example A42 2 50 Angular Cu 0.00100 Hydrochloric acid 3 70 thirty 400 1,929 A Real example A43 2 50 Angular Cu 0.00100 Hydrochloric acid 3 70 thirty 700 1.936 S Real example A44 2 50 Angular Cu 0.00100 Hydrochloric acid 3 70 thirty 1500 1.938 S Real example

[0092]

From the results of Table 1, it can be seen that the anisotropic electrical steel sheets satisfying the conditions of the present embodiment were rated as good.

[0093]

Example 2

First, a steel ingot was produced containing C: 0.08%, Si: 3.2%, Mn: 0.08%, S: 0.024%, acid-soluble Al: 0.03%, and N: 0.008%, with the balance from Fe and impurities. The steel ingot was annealed at 1350°C for 1 hour and then hot rolled to thereby obtain hot rolled steel sheets with a thickness of 2.3 mm. The resulting hot-rolled steel sheets were annealed at a peak temperature of 1100°C for 140 s, leveled and solution-treated, and then cold-rolled to thereby obtain cold-rolled steel sheets with a thickness of 0.23 mm. The straightening conditions and solution contact processing conditions after annealing of hot-rolled sheets are shown in Table 2.

[0094]

The resulting cold-rolled steel sheets were then annealed for primary recrystallization in a humid hydrogen atmosphere at 850°C for 180 s. The temperature rise rates are shown in Table 2. Then, the surfaces of the steel sheets after primary recrystallization annealing were coated with an annealing separator containing MgO as an aqueous slurry and then dried. After this, they were subjected to finishing annealing, and the annealed steel sheets were washed. After this, they were subjected to finishing annealing, and the annealed steel sheets were washed. After this, the surfaces of the steel sheets were coated with an insulating coating containing aluminum phosphate and colloidal silica as the main components, then leveling annealing was carried out to bake the insulating coating and level the steel sheets.

[0095]

Samples of the obtained anisotropic electrical steel sheets after leveling annealing were cut and stress-relieving annealed, then a method for measuring the magnetic properties of a single sheet for a sample with a size of 60mm x 300mm (based on the method described in JIS C2556) was used to measure the magnetic flux density value B8 anisotropic electrical steel sheets according to the examples of the present invention and comparative examples. Here, the value of B8 represents the magnetic flux density in the steel sheet when the anisotropic electrical steel sheet is excited at 50 Hz and 800 A/m. In the present invention, the average value of five samples was used.

[0096]

Here, the state in which the magnetic flux density value B8 of the anisotropic electrical steel sheet is 1.92T or more was judged to be good (B), the state where B8 is 1.93T or more was judged to be even better (A) , and a condition in which B8 is 1.94 T or greater was rated as very good (S).

[0097]

The production conditions, measurement and evaluation results of the above examples of the present invention and comparative examples are shown in Table 2.

[0098]

[Table 2] Condition Edit Conditions for treatment by contact with solution Rapid Temperature Rise Rate (°C/s) Magnetic flux density
B8 value (T) Grade Notes Number of times Bend angle Bend radius Metal type Metal concentration (%) Solution
(the basis) pH Solution temperature (°C) Contact time between solution and steel sheet (s) B1 2 60 100 Cu 0.000005 Hydrochloric acid 3 70 thirty 20 1,905 C Comparative example B2 2 60 100 Cu 0.000010 Hydrochloric acid 3 70 thirty 20 1,920 B Real example B3 2 60 100 Cu 0.00010 Hydrochloric acid 3 70 thirty 20 1.924 B Real example B4 2 60 100 Cu 0.01000 Hydrochloric acid 3 70 thirty 20 1.928 B Real example B5 2 60 100 Cu 0.10000 Hydrochloric acid 3 70 thirty 20 1.928 B Real example B6 2 60 100 Cu 0.00100 Hydrochloric acid 0 70 thirty 20 1,929 B Real example B7 2 60 100 Cu 0.00100 Hydrochloric acid 3 70 thirty 20 1.928 B Real example B8 2 60 100 Cu 0.00100 Hydrochloric acid 5 70 thirty 20 1.925 B Real example B9 2 60 100 Cu 0.00100 Hydrochloric acid 6 70 thirty 20 1.925 B Real example B10 2 60 100 Cu 0.00100 Hydrochloric acid 7 70 thirty 20 1.912 C Comparative example B11 2 60 100 Cu 0.00100 Hydrochloric acid 3 10 thirty 20 1.912 C Comparative example B12 2 60 100 Cu 0.00100 Hydrochloric acid 3 15 thirty 20 1.924 B Real example B13 2 60 100 Cu 0.00100 Hydrochloric acid 3 50 thirty 20 1.927 B Real example B14 2 60 100 Cu 0.00100 Hydrochloric acid 3 100 thirty 20 1.928 B Real example B15 2 60 100 Cu 0.00100 Hydrochloric acid 3 70 3 20 1,913 C Comparative example B16 2 60 100 Cu 0.00100 Hydrochloric acid 3 70 5 20 1.924 B Real example B17 2 60 100 Cu 0.00100 Hydrochloric acid 3 70 10 20 1.926 B Real example B18 2 60 100 Cu 0.00100 Hydrochloric acid 3 70 100 20 1.928 B Real example B19 2 60 100 Cu 0.00100 Hydrochloric acid 3 70 200 20 1,929 B Real example B20 2 60 100 Hg 0.00100 Hydrochloric acid 3 70 thirty 20 1.928 B Real example B21 2 60 100 Ag 0.00100 Hydrochloric acid 3 70 thirty 20 1,929 B Real example B22 2 60 100 Pb 0.00100 Hydrochloric acid 3 70 thirty 20 1,929 B Real example B23 2 60 100 Cd 0.00100 Hydrochloric acid 3 70 thirty 20 1.928 B Real example B24 2 60 100 Co 0.00100 Hydrochloric acid 3 70 thirty 20 1.928 B Real example B25 2 60 100 Zn 0.00100 Hydrochloric acid 3 70 thirty 20 1.928 B Real example B26 2 60 100 Ni 0.00100 Hydrochloric acid 3 70 thirty 20 1.928 B Real example B27 2 60 100 Cu+Ni 0.00100 Hydrochloric acid 3 70 thirty 20 1.928 B Real example B28 2 60 100 Ag+Co+Zn 0.00100 Hydrochloric acid 3 70 thirty 20 1,929 B Real example B29 2 60 100 Cu 1.00000 Sulfuric acid 2.5 70 thirty 20 1,929 B Real example B30 2 60 100 Cu 1.00000 Nitric acid 2.5 70 thirty 20 1.928 B Real example B31 2 60 100 Cu 1.00000 Phosphoric acid 2.5 70 thirty 20 1.927 B Real example B32 2 5 100 Cu 0.00100 Hydrochloric acid 3 70 thirty 20 1,911 C Comparative example B33 2 10 100 Cu 0.00100 Hydrochloric acid 3 70 thirty 20 1.928 B Real example B34 2 90 100 Cu 0.00100 Hydrochloric acid 3 70 thirty 20 1.928 B Real example B35 2 120 100 Cu 0.00100 Hydrochloric acid 3 70 thirty 20 1,913 C Comparative example B36 2 60 7 Cu 0.00100 Hydrochloric acid 3 70 thirty 20 1,911 C Comparative example B37 2 60 10 Cu 0.00100 Hydrochloric acid 3 70 thirty 20 1.928 B Real example B38 2 60 200 Cu 0.00100 Hydrochloric acid 3 70 thirty 20 1.928 B Real example B39 2 60 250 Cu 0.00100 Hydrochloric acid 3 70 thirty 20 1.912 C Comparative example B40 1 60 100 Cu 0.00100 Hydrochloric acid 3 70 thirty 20 1,914 C Comparative example B41 2 60 100 Cu 0.00100 Hydrochloric acid 3 70 thirty 100 1.934 A Real example B42 2 60 100 Cu 0.00100 Hydrochloric acid 3 70 thirty 400 1.938 A Real example B43 2 60 100 Cu 0.00100 Hydrochloric acid 3 70 thirty 700 1,944 S Real example B44 2 60 100 Cu 0.00100 Hydrochloric acid 3 70 thirty 1500 1.945 S Real example

[0099]

From the results of Table 2, it can be seen that the anisotropic electrical steel sheets satisfying the conditions of the present embodiment were rated as good.

[0100]

Example 3

First, a steel ingot was produced containing, in wt.%, C: 0.08%, Si: 3.3%, Mn: 0.08%, S: 0.025%, acid-soluble Al: 0.03%, and N: 0.008%, with the balance from the components shown in Table 3 plus Fe and impurities. The steel ingot was annealed at 1350°C for 1 hour and then hot rolled to thereby obtain hot rolled steel sheets with a thickness of 2.3 mm. The resulting hot-rolled steel sheets were annealed at a peak temperature of 1100°C for 140 s, shot-peened and solution-treated, and then cold-rolled to thereby obtain cold-rolled steel sheets with a thickness of 0.23 mm. The shot blasting conditions and solution treatment conditions after annealing the hot rolled sheets were as follows: average shot size: 2 mm, shot speed: 50 m/s, shape: angular, solution Cu concentration: 0.001%, solution (base): hydrochloric acid, pH of the solution: 3, temperature of the solution: 70°C, and contact time of the solution and the steel sheet: 30 s.

[0101]

The resulting cold-rolled steel sheets were then annealed for primary recrystallization in a humid hydrogen atmosphere at 850°C for 180 s. The temperature rise rates are shown in Table 3. Then, the surfaces of the steel sheets after primary recrystallization annealing were coated with an annealing separator containing MgO as an aqueous slurry, and then dried. After this, they were subjected to finishing annealing, and the annealed steel sheets were washed. After this, the surfaces of the steel sheets were coated with an insulating coating containing aluminum phosphate and colloidal silica as the main components, then leveling annealing was carried out to bake the insulating coating and level the steel sheets.

[0102]

Samples of the obtained anisotropic electrical steel sheets after leveling annealing were cut and stress-relieving annealed, then a method for measuring the magnetic properties of a single sheet for a sample with a size of 60mm x 300mm (based on the method described in JIS C2556) was used to measure the magnetic flux density value B8 anisotropic electrical steel sheets according to the examples of the present invention and comparative examples. Here, the value of B8 represents the magnetic flux density in the steel sheet when the anisotropic electrical steel sheet is excited at 50 Hz and 800 A/m. In the present invention, the average value of five samples was used.

[0103]

Here, the state in which the magnetic flux density value B8 of the anisotropic electrical steel sheet is 1.92T or more was judged to be good (B), the state where B8 is 1.93T or more was judged to be even better (A) , a condition in which B8 is equal to 1.94 T or more was rated as very good (S), and a condition in which B8 is 1.95 T or more was rated as the best (SS).

[0104]

The production conditions, measurement and evaluation results of the above examples of the present invention and comparative examples are shown in Table 3.

[0105]

[Table 3] Condition Slab components Rapid Heating Rate (°C/s) Magnetic Flux Density B8 (T) Grade Notes Cu content (%) Sn content (%) Ni content (%) Cr content (%) Sb content (%) Bi content (%) C1 0.0005 0 0 0 0 0 20 1.936 A Real example C2 0.3000 0 0 0 0 0 20 1.937 A Real example C3 1.0000 0 0 0 0 0 20 1.938 A Real example C4 0 0.0005 0 0 0 0 20 1.936 A Real example C5 0 0.3000 0 0 0 0 20 1.938 A Real example C6 0 1.0000 0 0 0 0 20 1.939 A Real example C7 0 0 0.0005 0 0 0 20 1.936 A Real example C8 0 0 0.3000 0 0 0 20 1.937 A Real example C9 0 0 1.0000 0 0 0 20 1.938 A Real example C10 0 0 0 0.0005 0 0 20 1.936 A Real example C11 0 0 0 0.3000 0 0 20 1.937 A Real example C12 0 0 0 1.0000 0 0 20 1.937 A Real example C13 0 0 0 0 0.0005 0 20 1.936 A Real example C14 0 0 0 0 0.3000 0 20 1.938 A Real example C15 0 0 0 0 1.0000 0 20 1.939 A Real example C16 0 0 0 0 0 0.0005 20 1,941 S Real example C17 0 0 0 0 0 0.3000 20 1,943 S Real example C18 0 0 0 0 0 1.0000 20 1,943 S Real example C19 0.1 0.1 0 0 0 0 20 1.937 A Real example C20 0.1 0 0.1 0.1 0 0 20 1.938 A Real example C21 0 0.1 0 0 0.1 0.1 20 1,943 S Real example C22 0 0 0 0.1 0.1 0.1 20 1,943 S Real example C23 0.1 0.1 0.1 0.1 0.1 0.1 20 1,943 S Real example C24 0.0005 0 0 0 0 0 100 1.951 SS Real example C25 0.3000 0 0 0 0 0 100 1.953 SS Real example C26 1.0000 0 0 0 0 0 100 1.953 SS Real example C27 0 0.0005 0 0 0 0 100 1.953 SS Real example C28 0 0.3000 0 0 0 0 100 1.952 SS Real example C29 0 1.0000 0 0 0 0 100 1.953 SS Real example C30 0 0 0.0005 0 0 0 100 1.951 SS Real example C31 0 0 0.3000 0 0 0 100 1.953 SS Real example C32 0 0 1.0000 0 0 0 100 1.954 SS Real example C33 0 0 0 0.0005 0 0 100 1.951 SS Real example C34 0 0 0 0.3000 0 0 100 1.952 SS Real example C35 0 0 0 1.0000 0 0 100 1.952 SS Real example C36 0 0 0 0 0.0005 0 100 1.951 SS Real example C37 0 0 0 0 0.3000 0 100 1.953 SS Real example C38 0 0 0 0 1.0000 0 100 1.954 SS Real example C39 0 0 0 0 0 0.0005 100 1.956 SS Real example C40 0 0 0 0 0 0.3000 100 1.957 SS Real example C41 0 0 0 0 0 1.0000 100 1.958 SS Real example C42 0.1 0.1 0 0 0 0 100 1.952 SS Real example C43 0.1 0 0.1 0.1 0 0 100 1.952 SS Real example C44 0 0.1 0 0 0.1 0.1 100 1.957 SS Real example C45 0 0 0 0.1 0.1 0.1 100 1.957 SS Real example C46 0.1 0.1 0.1 0.1 0.1 0.1 100 1.958 SS Real example C47 0 0.3000 0 0 0 0 400 1.954 SS Real example C48 0 0.3000 0 0 0 0 700 1.955 SS Real example C49 0 0.3000 0 0 0 0 1500 1.957 SS Real example C50 0 0 0 0 0 0.3000 400 1.959 SS Real example C51 0 0 0 0 0 0.3000 700 1,961 SS Real example C52 0 0 0 0 0 0.3000 1500 1,962 SS Real example

[0106]

From the results of Table 3, it can be seen that the anisotropic electrical steel sheets satisfying the conditions of the present embodiment were rated as good.

[0107]

Example 4

Except for performing intermediate processing from temperature rise in primary recrystallization annealing to decarburization annealing (atmospheric dew point and time of steel sheet at a temperature of 700°C or more and 950°C or less) and decarburization annealing (fraction of partial pressure of oxygen in the atmosphere) at different conditions, anisotropic electrical steel sheets were produced under conditions similar to Examples 1-3 of the present invention.

[0108]

The anisotropic electrical steel sheet samples obtained above were cut and evaluated for the presence of two or more levels of color difference over an area of 50×50 mm on an eight-level brightness scale from white to black. For color differences of one level or less, the sample was considered good for color uniformity, and for two levels or more, the sample was considered poor for color uniformity.

[0109]

Samples of the obtained anisotropic electrical steel sheets after leveling annealing were cut and stress-relieving annealed, then a method for measuring the magnetic properties of a single sheet for a sample with a size of 60mm x 300mm (based on the method described in JIS C2556) was used to measure the magnetic flux density value B8 anisotropic electrical steel sheets according to the examples of the present invention and comparative examples. Here, the value of B8 represents the magnetic flux density in the steel sheet when the anisotropic electrical steel sheet is excited at 50 Hz and 800 A/m. In the present invention, the average value of five samples was used.

[0110]

Here, the state in which the color differences were less than two levels and the magnetic flux density value B8 of the anisotropic electrical steel sheet was 1.91 T or more was judged to be the best (B). All other conditions were rated as unsatisfactory (C).

[0111]

It was found that if, in the intermediate treatment, the atmospheric dew point was -40°C or more and 0°C or less, and the residence time of the steel sheet at a temperature of 700°C or more and 950°C or less was 1 s or more and 20 s or less, and when decarburizing annealing, the oxygen partial pressure fraction (P _H2O /P _H2 ) in the atmosphere was 0.35 or more and 0.60 or less, then the color differences were less than two levels, and the sheet magnetic flux density value B8 anisotropic electrical steel was 1.91 T or more, resulting in a “good” result (B).

Claims (23)

1. A method for producing anisotropic electrical steel sheet, containing: the process of heating a slab containing, wt. %, C: 0.01 or more and 0.10 or less, Si: 2.5 or more and 4.5 or less, Mn: 0.01 or more and 0.50 or less, the total amount of one or more of S, Se and Te: 0.001 or more and 0.050 or less, acid-soluble Al: greater than 0 and 0.05 or less, and N: greater than 0 and 0.015 or less, optionally one or more elements selected from the group, containing Cu: 0-1.0, Sn: 0-1.0, Ni: 0-1.0, Cr: 0-1.0, Sb: 0-1.0, and Bi: 0-1.0, with a residue of iron and impurities, hot rolling it and, if necessary, annealing it to obtain hot rolled steel sheet or annealed hot rolled steel sheet, cold rolling process of hot-rolled steel sheet or annealed hot-rolled sheet to produce cold-rolled steel sheet, annealing process of cold rolled steel sheet for primary recrystallization to obtain primary recrystallized annealed sheet, the process of coating the surface of a primary recrystallized annealed sheet with an annealing separator including MgO, and then finishing annealing it to obtain a finish annealed sheet, the process of coating a finished annealed sheet with an insulating coating and then annealing it to smooth it, wherein at least one steel sheet of hot-rolled steel sheet, annealed hot-rolled sheet, cold-rolled steel sheet and primary recrystallized annealed sheet is shot peened and also solution contact processed, wherein in shot blasting the average particle size of the shot is 0.1 mm or more and 5.0 mm or less, and their speed is 10 m/s or more and 150 m/s or less, wherein the solution contains one or more elements from Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni, has a total element concentration of 0.00001% or more and 1.0000% or less, a pH value of 1.5 or greater and less than 7 and has a solution temperature of 15°C or more and 100°C or less, and the time for which the steel sheet is immersed in the solution is 5 seconds or more and 200 seconds or less. 2. A method for producing anisotropic electrical steel sheet, containing: the process of heating a slab containing, wt. %, C: 0.01 or more and 0.10 or less, Si: 2.5 or more and 4.5 or less, Mn: 0.01 or more and 0.50 or less, the total amount of one or more of S, Se and Te: 0.001 or more and 0.050 or less, acid-soluble Al: greater than 0 and 0.05 or less, and N: greater than 0 and 0.015 or less, optionally one or more elements selected from the group, containing Cu: 0-1.0, Sn: 0-1.0, Ni: 0-1.0, Cr: 0-1.0, Sb: 0-1.0, and Bi: 0-1.0, with a residue of iron and impurities, hot rolling it and, if necessary, annealing it to obtain hot rolled steel sheet or annealed hot rolled steel sheet, cold rolling process of hot-rolled steel sheet or annealed hot-rolled sheet to produce cold-rolled steel sheet, annealing process of cold rolled steel sheet for primary recrystallization to obtain primary recrystallized annealed sheet, a process of coating the surface of the primary recrystallized annealed sheet with an annealing separator including MgO, and then finishing annealing it to obtain a finish annealed sheet, and the process of coating a finished annealed sheet with an insulating coating and then annealing it to smooth it, wherein at least one steel sheet of hot-rolled steel sheet, annealed hot-rolled sheet, cold-rolled steel sheet and primary recrystallized annealed sheet is processed for straightening, and also processed by contacting with a solution, in straightening processing, the number of bending operations of the steel sheet is two or more, the bending angle is 10 degrees or more and 90 degrees or less, and the bending radius is 10 mm or more and 200 mm or less, wherein the solution contains one or more elements from Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni, has a total element concentration of 0.00001% or more and 1.0000% or less, a pH value of 1.5 or greater and less than 7 and has a solution temperature of 15°C or more and 100°C or less, and the time for which the steel sheet is immersed in the solution is 5 seconds or more and 200 seconds or less. 3. The method according to claim 1 or 2, in which when the temperature is rapidly increased during primary recrystallization annealing, the average rate of temperature increase in the temperature range of 550-700°C is 100°C/s or more and 3000°C/s or less. 4. Method according to any one of paragraphs. 1-3, in which primary recrystallization annealing includes a temperature rise process, an intermediate processing process from temperature rise to decarburization annealing, and a decarburization annealing process, in the intermediate treatment, the dew point of the atmosphere is -40°C or more and 0°C or less, and the residence time of the steel sheet at a temperature of 700°C or more and 950°C or less is 1 s or more and 20 s or less, and in decarburization annealing, the oxygen partial pressure fraction (P _H2O /P _H2 ) in the atmosphere is 0.35 or more and 0.60 or less.